value addition of convenience food using processed millet...
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VALUE ADDITION OF CONVENIENCE FOOD
USING PROCESSED MILLET POWDER
A Thesis submitted to the Pondicherry University in partial fulfillment of the
requirement for the Degree of
DOCTOR OF PHILOSOPHY
IN
FOOD SCIENCE AND NUTRITION
Submitted by
M. Pushpa Devi
R22951
DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY
SCHOOL OF LIFE SCIENCES
PONDICHERRY UNIVERSITY
PUDUCHERRY- 605 014
INDIA
August – 201
CERTIFICATE
Certified that this thesis entitled “VALUE ADDITION OF CONVENIENCE
FOOD USING PROCESSED MILLET POWDER” is a record of research work
done by the candidate Mrs. M. Pushpa Devi during the period of her study in the
Department of Food Science and Technology, School of Life Sciences,
Pondicherry University, Puducherry, under my supervision and that it has not
previously formed the basis for the award of any
Degree/Diploma/Associateship/Fellowship of any other University or Institute.
Place: Puducherry
Date:
DECLARATION
I hereby declare that the work presented in the thesis entitled “VALUE ADDITION
OF CONVENIENCE FOOD USING PROCESSED MILLET POWDER” is the
result of investigation carried out by me in the Department of Food Science and
Technology, School of Life Sciences, Pondicherry University, Puducherry under the
guidance of Dr. Narayanasamy Sangeetha, Assistant Professor, Department of Food
Science and Technology, School of Life Sciences, Pondicherry University,
Puducherry, and it has not been submitted for the award of any
Degree/Diploma/Associateship/Fellowship of any other University or Institute.
Place : Puducherry
Date : (M. Pushpa Devi)
R22951
ACKNOWLEDGEMENT
I am extremely indebted to Prof. (Dr.) CHANDRA KRISHNAMOORTHY,
Vice Chancellor, Pondicherry University, Puducherry, and
Shri RAAJIV YADUVANSHI, IAS, Registrar, Pondicherry University, Puducherry,
for not only providing opportunity to pursue doctorate program and infrastructural
facilities in this esteemed university but also afforded with scholarship which helped
and fueled my financial needs towards my research.
I take this opportunity to sincerely acknowledge and thank Dr. J. SAMPATH,
Controller of Examinations, Pondicherry University, Puducherry, for having
rendered academic guidelines for smooth conduct of research throughout the study
period. I would like to express my profound gratitude to Prof. ANISA BASHEER
KHAN, Dean, School of Life Sciences, Pondicherry University, Puducherry, for
providing academic support at various phases of the Ph.D. program.
I owe a great deal of appreciation, profound gratitude and sincere thanks to
Dr. H. PRATHAP KUMAR SHETTY, Associate Professor, Head i/c. , Department
of Food Science and Technology, Pondicherry University, Puducherry, for his
valuable advice, constructive criticism and his extensive discussions around my work.
At this moment of accomplishment, I pay homage to my beloved and energetic
guide, Dr. NARAYANASAMY SANGEETHA, Assistant Professor, Department of
Food Science and Technology, Pondicherry University, Puducherry. This work
would not have been possible without her guidance, support and encouragement. She
patiently provided the vision, encouragement and advice necessary for me to proceed
through the doctorial program and complete my thesis. She has been a strong and
supportive adviser to me throughout my career. She has always given me great
freedom to pursue independent work. Under her guidance I successfully came over
many difficulties and learnt a lot. I can’t forget her hard times. Despite of her ill
health she used to review my thesis progress. Her unflinching courage and conviction
will always inspire me, and I hope to continue to work with her noble thoughts. I can
only say a proper thanks to her through my future accomplishments.
I gratefully acknowledge my Doctoral Committee Member (External)
Dr. Anil Jacob Purty MD, DNB, MNAMS, Registrar, Professor & Dean (PG),
Department of community Medicine, Pondicherry Institute of Medical Science,
Puducherry, for his understanding and encouragement which provided good and
smooth basis for my Ph.D. tenure.
My heartfelt thanks to Doctoral Committee Member (Internal),
Dr. S. HARIPRIYA, Assistant Professor, Department of Food Science and
Technology, Pondicherry University, Puducherry, who always triggered my
knowledge, boosted my interest and supported towards the progress of my research.
I am also thankful to Dr. JOHN DON BOSCO, Associate Professor,
Department of Food Science and Technology, Pondicherry University, Puducherry,
for his guidance, technical support, ideas and positive comments to complete my work
successfully.
I thank Dr. K.V. SUNOOJ, Assistant Professor, Department of Food Science
and Technology, Pondicherry University, Puducherry, for his valuable censure
during my study and also facilitated me in operating texture analyzer and
Dr. G. SEGHAL KIRAN, Assistant Professor, Department of Food Science and
Technology, Pondicherry University, Puducherry, for her encouragement in
completion of my research work.
I express my gratitude to Mrs. ANUSUYA and Mr. GANESH, Guest Faculty,
Department of Food Science and Technology, Pondicherry University, Puducherry,
who supported and provided immense help in statistical interpretation.
I thank Indian Institute of Crop Processing and Technology (IICPT),
Thanjavur and Anna University, Chennai for providing additional equipment to
pursue my experiment work for the extrusion and for their encouragement and
support in the formulation of products.
Most of the results described in this thesis would not have been obtained
without the help rendered by Central Instrumentation Facility (CIF), Pondicherry
University to utilize few of major equipments.
I am much indebted to Dr. K. SUNDAR, Young Scientist DST, for his
inspiration given to complete my research. I am indebted to my many scholar
colleagues for providing a stimulating and fun filled environment to complete the
Ph.D. programme. A special thanks to Ms.P.Vasantha Kumari who has been very
supportive of my decision to relate to the academics and she helped me during
writing, and incented me to strive towards my goal. I render my profound thanks to
other scholars S. Uma Maheswari, D. Sumitha, C. Saravanan, Sanjay Prathap Singh,
K. Devi, S. J. Cynthia, Soumya Bhol, Ravindra Kumar Agarwal, Ch. Koteeswara
Reddy, K. Kumarakuru, Shabir Ahmed Mir, P.Vandarkuzhali, Mansoor ahmed shah,
S.Santhalakshmi, G.Venkadesaperumal, K.Ragul, Amritha Balagopal, Ankitha Lakede
and Mudhasir Bashir Mir for their help offered during my research period and for the
moral support given.
I also thank G. RAMYA, S. KAMASHI AND M. SURYA, Research Assistants
who willingly devoted so much time during the inevitable ups and downs in conduct of
my research.
I extend my thanks to the non-teaching staffs Mrs. GOMATHI,
Mr. CHAKRAVARTHY, Mrs. KOLANCHIAMMAL, Mrs. CHANDRA,
Mrs. VALLIAMMAL, Mr. PRADEEP Mr. ANGAPPAN and Mr. SITHANANDHA
BARATHI for helping me with the needed amenities.
Last but not the least, I would like to pay high regards to my MOTHER and
FATHER and my BROTHER for their sincere encouragement and inspiration
throughout my research work and lifting me uphill in this phase of life as well. I owe
everything to them. I would like to thank my HUSBAND for his support,
encouragement and help. Besides this, several people have knowingly and
unknowingly helped me in the successful completion of this project. Thanks to all!
I surrender my thesis which is the end result of hard work and endurance to
the Almighty, for His showers of blessings throughout my research and my dear
Mam Late. JACQUELINE ELIZABETH.
(M. Pushpa Devi)
ABBREVIATIONS
FF&V - Fresh Fruits and Vegetables
FAO - Food and Agriculture Organization
WHO - World Health Organization
AOAC - Association of Official Analytical Chemists
AACC - American Association of Cereal Chemists
HPLC - High Performance Liquid Chromatography
GC-MS - Gas Chromatography-Mass Spectroscopy
ANOVA - Analysis of Variance
DMRT - Duncan‟s Multiple Range Test
DPPH - Diphenyal Picrylhydrazyl
FAO - Food and Agriculture Organization
LSD - Least Significant Difference
SPSS - Statistical Package for Social Sciences
CVD - Cardiovascular Diseases
USSR - Union of Soviet Socialist Republics
FAOSTAT - Food and Agriculture Organization Statistical Databases
ATP - Adenosine Tri-Phosphate
LDL - Low Density Lipoprotein
HDL - High Density Lipoprotein
LP -Linear Programming
IVPD -In Vitro Protein Digestibility
EFA - Essential Fatty Acids
UNU - United Nations University
SEM - Scanning Electron Microscope
RTE - Ready To Eat
LDPE - Low Density Poly Ethylene
CFU - Colony-forming unit
MAP - Modified Atmospheric Package
PHLSG - Public Health Laboratory Service Guidelines
ICMSF - International Commission on Microbiological Specifications
IU - International Unit
EFA - Essential Fatty Acid
FM - Finger Millet
PM - Pearl Millet
KM - Kodo Millet
LM - Little Millet
FOM - Foxtail Millet
CM - Composite Millet Powder
FCTD - Forced Convection Tray Drying
SD - Sun Drying
FD - Freeze Drying
TPC - Total Plate Count
PAG - Protein Advisory Group
WAC -Water Absorption Capacity
BD -Bulk Density
ABSTRACT
Millet is an underutilized species holding great genetic diversity and
consumed by the people of low socio economic status. Despite their nutritional
superiority, utilization of millets is restricted due to non-availability of refined and
processed millets in ready to eat form. Therefore, it is necessary to optimize a
processed composite millet powder for the development of convenience food with
application of processing and drying methods. The techniques used for processing
millets are soaking, preparation of slurry from millets, dehydration and milling were
carried out for development of millet powder. The selected raw materials were
weighed and soaked for a period of 6 hours, after which the excess water was drained.
The processed millet grains were ground into fine slurry using wet grinding
technique. The obtained millet slurry was subjected to drying methods namely sun
drying (T0:18 hours), forced convection tray drying (T1: 60ºC-70°C, 15-16 hours) and
freeze drying (T2: –50°C to 30°C, 14-16 hours). The dried millet powder was milled
in stone miller to obtain fine powder which was packed in LDPE and stored in air
tight container for the development of convenience foods. Convenience foods namely
pasta and extrudates were formulated and evaluated for their physical, nutritional,
functional and shelf life characteristics. The results indicate that in general the drying
methods adopted did not influence the proximate principles, nutrient content but the
physical characteristics of composite millet powder were altered slightly. However,
the slight change observed in the nutritional profile of composite millet powder could
be attributed to the natural existence of the nutrients present in the selected millets.
After several permutation and combination, 70 % composite millet powder and 30%
of refined wheat flour (70:30) has proved to improve the nutritional and sensory
property of pasta where a significant increment (p≤0.05) in the protein, fat, minerals
and vitamin content was observed. The incorporation of egg white powder in pasta
formulated using composite millet powder caused a significant reduction in cooking
loss showed an increase in phytochemicals and essential amino acid profile which are
considered as desirable qualities of pasta. The extrudates obtained from the composite
millet powder exhibited significant difference (p≤0.05) in the protein, carbohydrate,
vitamins, minerals and essential amino acid profile when compared to control.
Among the drying methods adopted, the composite millet powder subjected to freeze
drying and thereby the products developed had better retention of nutrients,
phytochemical, essential fatty acid and essential amino acids exhibited better
antioxidant activity (p<0.05) when compared to forced convection tray drying. As the
products were heat treated, the storage study revealed that the convenience food
developed was found to hold good shelf life in terms of total plate count and sensory
parameters up to six months. Hence, consumption of millets in the daily diet would
benefit the health and wellbeing of the people and moreover is receiving tremendous
attention among the vulnerable population.
CONTENTS
CHAPTE
R NO.
TITLE PAG
E NO.
LIST OF TABLES
LIST OF FIGURES
LIST OF PLATES
ABBREVIATIONS 1. INTRODUCTION 1-3
2. REVIEW OF LITERATURE 4
2.1. Production, cultivation and consumption of millet grains
2.2. Therapeutic significance of millet grains
2.3. Nutritional and functional properties of millet grains
2.4. Effect of different processing methods on millet grains
2.5. Utilization of millet grains in the preparation of value
added products
4
7
10
15
20
3. METHODOLOGY
3.1. Selection and pre-processing of raw materials
3.2. Steps involved in preparation of processed millet powder
3.3. Optimization of composite millet powder
3.4. Finalized parameters for further analysis and product
development
3.5. Process involved in development of convenience food
3.6. Quality analysis of developed convenience food and the
powder
3.7. Statistical interpretation of the data
26
27
31
32
32
36
37
4. RESULTS AND DISCUSSION 38
4.1. Effect of drying methods on the quality characteristics of
processed millet powder
4.2. Effect of drying methods on the physic-chemical
properties of composite millet powder (CM)
4.3. Evaluation of quality characteristics of convenience food
developed using composite millet powder
4.4. Functional characterization of protein in the convenience
food developed using composite millet powder exposed to
freeze drying
38
55
71
117
5. SUMMARY AND CONCLUSION 120
6. BIBLIOGRAPHY
LIST OF TABLES
TABLE
NO. TITLE
PAGE
NO.
1. Optimization of composite millet powder (%) 31
2. Composition of raw material for formulation of pasta 33
3. Analysis of quality characteristics of developed composite millet
powder and convenience food 36
4. Proximate principles of processed millet powder 40
5. Mineral (mg/100g) content of processed millet powder 45
6. Bulk density (g/cm3) of the processed millet powder 47
7. Swelling index (%) of the processed millet powder 48
8a. Foam capacity (ml) of the processed millet powder 49
8b. Foam stability (ml) of the processed millet powder 49
9. Water absorption capacity (ml/g) of the processed millet powder 50
10. Color values of the processed millet powder 54
11. Total microbial count (cfu/g) of processed millet powder 55
12. Physico-chemical properties of composite millet powder 56
13. Color values of composite millet powder 61
14. Pasting properties of the composite millet powder 62
15.
Essential amino acids (mg/100g) profile of composite millet
powder 64
16. Vitamin content of the composite millet powder 66
17. Essential fatty acids (mg/100g) composition of composite millet
powder 67
18. Phytochemical profile of composite millet powder 68
19. DPPH scavenging activity of composite millet powder 70
20. Reducing power of composite millet powder 71
21. Nutritional properties of pasta 72
22. Physical properties of pasta 75
23. Essential amino acid (mg/100g) profile of pasta 77
24. Vitamin content of pasta 78
25. Essential fatty acid (mg/100g) composition of pasta 79
26. DPPH scavenging activity of pasta 80
27. Reducing power of pasta 81
28. Color values of pasta 82
29. Textural profile of pasta 84
30. Sensory properties of pasta 91
31. Effect of storage on overall acceptability of pasta 93
32. Total plate count (cfu/g) of pasta during storage 94
33. Nutritional properties of extrudates 95
34. Physical properties of extrudates 98
35. Essential amino acid (mg/100g) profile of extrudates 100
36. Vitamin content of extrudates 101
37. Essential fatty acid (mg/100g) composition of extrudates 102
38. DPPH scavenging activity of extrudates 103
39. Reducing power of extrudates 104
40. Color values of extrudates 105
41. Textural profile of extrudates 106
42. Sensory properties of extrudates (plain) 112
43. Sensory properties of extrudates with choco milk 112
44. Sensory properties of extrudates - spice mix 113
45. Effect of storage on the overall acceptability of extrudates 115
46. Effect of storage on total plate count of extrudates 116
47. Protein fraction of composite millet powder and products 118
LIST OF PLATES
PLATE
NO. TITLE
PAGE
NO.
1. Raw materials selected for processing and product
development
26
2. Process of soaking involved in the preparation of millet
powder
27
3. Process involved in the preparation of slurry from processed
millets
28
4. Millet slurry exposed to sun drying 29
5. Millet slurry exposed to forced convection tray drying 29
6. Millet slurry exposed to freeze drying 30
7. Processed millet powder in LDPE pouch 30
8. Pastas obtained from composite millet powder 34
9. Extrudates obtained from composite millet powder 35
LIST OF FIGURES
FIGURE
NO. TITLE
PAGE
NO.
1. Process involved in the preparation of millet powder 31
2. Process involved in the formulation of pasta 34
3. Steps involved in the formulation of extrudates 35
4. Proximate principles of processed millet powder 42
5. Mineral content of processed millet powder 46
6. Physical properties of processed millet powder 52
7. Color values of processed millet powder 54
8. Physico-chemical properties of composite millet powder 60
9. Colour values of composite millet powder 61
10. Pasting properties of composite millet powder 63
11. Morphological structure of composite millet powder 64
12. Essential amino acids (mg/100g) profile of composite millet
powder
65
13. Vitamin content of the composite millet powder 66
14. Essential fatty acid (mg/100g) composition of composite millet
powder
67
15. Phytochemical profile of composite millet powder 68
16. DPPH scavenging activity of composite millet powder 70
17. Reducing power of composite millet powder 71
18. Nutritional properties of pasta 74
19. Physical properties of pasta 76
20. Essential amino acid (mg/100g) profile of pasta 78
21. Vitamin content of pasta 79
22. Essential fatty acid (mg/100g) composition of pasta 80
23. DPPH scavenging activity of pasta 81
24. Reducing power of pasta 81
25. Color values of pasta 83
26. Textural profile of pasta 86
27. Morphological structure of pasta 88
28. Pasting properties of pasta 90
29. Sensory properties of Pasta 92
30. Effect of storage on overall acceptability of pasta 94
31. Nutritional properties of extrudates 97
32. Physical properties of extrudates 99
33. Essential amino acid (mg/100g) profile of extrudates 101
34. Vitamin content of extrudates 102
35. Essential fatty acid (mg/100g) composition of extrudates 103
36. DPPH scavenging activity of extrudates 103
37. Reducing power of extrudates 104
38. Color values of extrudates 106
39. Textural properties of extrudate 107
40. Morphological structure of extrudates 109
41a. X-ray diffractograms of composite millet powder 109
41b. X-ray diffractograms of extrudates 109
42. Pasting properties of extrudates 111
43a. Sensory properties of extrudates (plain) 115
43b. Sensory properties of extrudates (choco mix) 115
43c. Sensory properties of extrudates (Spice mix) 115
44. Effect of storage on the overall acceptability of extrudates 116
45. Protein solubility of composite millet powder and products 117
1. INTRODUCTION
Millet is one of the indigenous foods known to human and has been widely
used in India as a staple food for thousands of years. Millet, a versatile grain is highly
nutritious, non-glutinous and non-acid forming food. It contains high amount of
macro as well as micro nutrients and also rich in phytochemicals including lignans,
phenolic acids and phytosterols. Minor millets in particular are used as food sources
mainly in arid and semiarid regions of the world. They play an important role in the
food and nutritional security of the poor.
Millet is gluten free and therefore an excellent option for anyone suffering
with bowel diseases. The phytochemicals present in millets lowers cholesterol level,
helps to prevent colon cancer, aid in elimination and improves insulin sensitivity. It
has relatively higher proportion of non-starchy polysaccharides, dietary fiber and low
glycemic index which helps to reduce the risk of degenerative diseases both in urban
and rural population. The nutritional factors and also the ease of digestion of millet
are the basis for their recommended use for pregnant women, nursing mothers,
children and the elderly. The health status of the targeted population will be improved
through millet foods consumption keeping many deficiencies (nutrient) and diseases
at bay. The most popular millet produced in India are pearl millet/spiked millet
(Bajra), finger millet (Ragi), great millet/sorghum (Jowar), foxtail millet (Kheri), little
millet (Samai) and barnyard millet (Jhungori).
However, their presence in the Indian food basket has been declining over the
years. The major reason for this decline is the increased availability of rice, wheat and
maize. In addition, the lack of modern technologies for their effective processing and
utilization is another important reason for their decline. On the other hand, increasing
urbanization and decreasing time for domestic chores in rural households are
discouraging traditional processing of millets. In addition with the increasing
availability of other cereals, minor millet consumption in Asia is getting restricted to
the poorest of the poor and to those having traditional affinity. In order to overcome
this problem, suitable processing techniques should be adopted to utilize millets as
one of the major ingredients in food preparations. Millets are largely consumed as
traditional preparations like conjee (porridge) or as fermented food (koozhu) for
consumption. They would probably be more widely used if processing was improved
and sufficient good-quality flour was made available to meet the demand. Traditional
processing techniques that are commonly used for cereals include decorticating,
malting, fermentation, roasting, flaking and grinding. The processing of millets
enhances the flavor and palatability of foods, increases the bioavailability of nutrients
by reducing the anti-nutritional factors, growth inhibitors and heam-agglutins and also
helps in new food formulations.
While formulating new foods, ultimate emphasis should be given to the food
trends and food transitions which are being strongly bonded with modern society that
has moved towards designer foods, convenience foods, ready-to-eat breakfast cereals
and ready-to-eat snack foods. Convenience foods are defined as fully or partially
prepared foods in which a significant amount of preparation time, cooking skills or
energy inputs that has been transferred from home kitchen to the food processor and
distributor (Candel, 2001 and Costa et al., 2001). These types of foods require
minimum preparation and are packaged for a long shelf life with little loss of flavor
and nutrients over time. In the preparation of convenience foods, extrusion technique
has become more popular which has dramatically transformed the cereal industry, the
key thing being quality extruded products offered to consumer at competitive price.
They also bring more choices for the quick consumers who want to eat a good meal,
thus offering a good business opportunity for food product developers, service and
retail providers (Sloan, 1999). Ready-to-eat extruded products is an ideal food for
people in modern-day lifestyle, where speed and convenience, as well as complete
nutritional values are desirable food characteristics for ready-to-eat millet based
products that gives a healthful addition for a better lifestyle.
Though several snack foods of different cereals including wheat, rice,
barley etc., are being prepared and marketed to the public using varying type of
traditional processing techniques, snack foods prepared by incorporating processed
millets would probably be an effective way to motivate the preparation of gluten free
ready-to-eat snack food. Hence, an attempt is taken to explore on the preparation of
convenience foods using processed composite millet powder possessing immense
nutritional and functional properties by different drying methods which would help in
increasing the consumption of millets among non-millet consumers and production of
novel food product. With this background, the following objectives were framed.
Studying the effect of processing methods on the quality characteristics of
processed millet powder.
Optimization and process development of convenience foods using composite
millet powder and its evaluation of quality characteristics.
2. REVIEW OF LITERATURE
The functional foods has been used for foods that promote health through
prevention of specific degenerative diseases like diabetes, CVD, cancer, Parkinson‟s
disease, cataract etc. This effect is due to the presence of health-promoting and
bioactive phytochemicals in plant foods. Some of the known nutrients like
vitamins, minerals, essential fatty acids also have benefits in terms of prevention of
degenerative diseases, besides their known functions of preventing nutritional
deficiency diseases. Millets which are a treasure hunt of health-promotive
phytochemicals have received attention for their potential role as functional foods.
Being non-glutinous, millets are safe for people suffering from gluten allergy and
celiac disease. Hence their importance in terms of nutritional composition, health
benefits, processing and utilization for the food product development was reviewed in
detail. The literature pertaining to the present study entitled, “Value addition of
convenience food using processed millet powder” is presented under the following
heads.
2.1. Production, cultivation and consumption of millet grains
2.2. Therapeutic significance of millet grains
2.3. Nutritional and functional properties of millet grains
2.4. Effect of different processing methods on millet grains
2.5. Utilization of millet grains in the preparation of value added products
2.1. Production, cultivation and consumption of millet grains
In India, the last land production was reported as 9, 26, 10,000 hectares in
2010 according to a World Bank report published in 2012. The production of cereal
was found throughout the history and which is the most important sources of plant
food for human‟s and livestock. Millets are one of the oldest foods known to
humans & possibly the first cereal grain to be used for domestic purposes. Millets
are small seeded cereal grains consumed as food by millions of people throughout the
world. They are often referred to as „poor man‟s cereal, because people with a choice
prefer other cereals such as wheat or rice. But recently Prof. M. S. Swaminathan
designated millets as „nutritious millets‟ and it deserves to be reclassified because of
its nutritive properties. The millet is considered as a crop for poor people, it is grown
mainly in china, Bangladesh and India. In the world level, most of the millet grains
are cultivated and grown in Asia, Africa and USSR. In India, cereal security is very
important, because it was characterized by history of drought and famines, vast and
expanding population and social structure still not fully evolved up to the expectation
of our civil society. The increase in productivity during the last four decades has been
accompanied by increase in personal income. The total millet production in the world
is around 31,875,597 tonnes. In 2007, the top ten millet producing (Tonnes) countries
were found to be India (10,610,000), Nigeria (7,700,000), Niger (2,781,928), China
(2,101,000), Burkina Faso (1,104,010), Mali (1,074,440) Sudan (792,000), Uganda
(732,000), Chad (550,000) and Ethiopia (500,000).
India is the biggest producer of millets in the world and millets remain a
staple crop for numerous households. In India, eight millets species sorghum
(Sorghum bicolor), finger millet (Eleusine coracana), pearl millet
(Pennisetum glaucum), foxtail millet (Setaria italica), barnyard millet
(Echinochloa crus-galli), proso millet (Panicum miliaceum), kodo millet
(Paspalum scrobiculatum) and little millet (Panicum sumatrense) are commonly
cultivated under rain fed conditions. The pearl millet and sorghum is primary crop and
allied crops respectively in the desert regions and eastern parts of Rajasthan and
Gujarat. Likewise, Finger millet is a primary crop in Tamil Nadu and Gharwal, while
the same is a minor crop in Telangana. Hence, the spatial distribution of millets either
as a primary crop or as allied crops largely depends on the growing habitat and the
amount of rainfall the region receives. Similarly, sorghum is sown as major crop
in the Telangana (Andhra Pradesh), Maharashtra and parts of Central India, while it
is considered as fodder crop in some of the Southern regions. While sorghum
predominates in areas receiving annual rainfall beyond 400 mm, pearl millet
rivals it in areas with annual rainfall of 350 mm. Further, the small millets like
finger millet, foxtail millet, barnyard millet, little millet and proso millet are found in
most of the southern and central states in India especially wherever annual rainfall is
below 350 mm, perhaps where no other cereal crop can grow under such moisture
stress. However, in spite of a rich inter/intra-species diversity and wider climatic
adaptability cultivation of diverse millet species/varieties is gradually narrowing in
the recent past. In a way, a lack of institutional support for millet crops in contrast to
the institutional promotion of rice and wheat continue to shrink the millet-growing
region.
Over the last 50 years, the share of „Coarse grains‟, which include pearl
millet, sorghum, maize, finger millet, barley and 5 other millet species known as
„Small Millets‟, in terms of total area has registered 25.3% decline from 38.83 Mha.
(1949-50) to 29.03 Mha. (2004-05). It requires warm weather and matures quickly in
the hot summer months. In India, states namely Andhra Pradesh, Karnataka, &
Tamilnadu are the major millet growing state which contributes to about 90% of the
total area under cultivation. Andhra Pradesh is a major part for foxtail millet growing
state contributing about 79% of the total area (Anju et al., 2010). Millets plays an
important role in biodervisity components in agriculture and food security system in
millions of poor farmer area of Sub-Saharan Africa. The production of pearl millet is
largest in India and food to be found across the Sahel. In food industry the plant
nutrients are larger and also the cereals grain constitutes the major sources of dietary
fiber (Izadi et al., 2012).
FAO (2005) found that pearl millet production attained approximately 54% of
the global production in 2004. In emerging trends, the production and exploration of
plant foods is the basic need for the world to feed its growing population, in these
cases millets are plant foods that are grown locally and it is also consumed by low
income household‟s places like India and in the Sahel Zones (Obilana, 2003).
According to FAOSTAT 2005, the global consumption of millet for an
average of five years was found to be highest in India (9,041,765), followed by
Nigeria (4,299,211), Niger (1,733,793), China (1,116,505), Burkina Faso (856,337),
Mali (701,701), Sudan (560,548) and Uganda (408,137). India and China rank as the
1st and 4
th consumer of millet but due to their population size they rank 11
th and 38
th in
per capita consumption. The consumption of millets as rice or flour in the daily
routine food has several advantages; since the millet grains may not be available
in all places, due to its increased price and decreased marketing strategy. The
traditional way of consumption of millets has been restricted to remote and
rural population, especially during certain festivals. The health promoting factors of
millets need awareness among mass and made available as ready to eat or semi
processed millet products for health benefits. Millets based food beverage is a known
food product worldwide and still is a part of major diet in most of African countries.
Generally, the finger millet are consumed in the form of kozhu and congee
(Amadou et al., 2011). Lei and Michalsen (2006) investigated an intervention study
in Northern Ghana traditionally used fermented millet product as a natural probiotic
for the treatment of diarrheoa in young children. Lei and Jacobsen (2004)
characterized that millet koko is an African products which is frequently used as a
fermented millet porridge and drink. In Africa there are two different varieties of
beers produced traditionally such as Burukulu and pito which differ from western
beer types in several ways (Anukam and Reid, 2009; Amadou et al., 2011a).
Regular consumption of finger millet is one of the basic ingredients upto
15-20% (w/w) along with other essential ingredients such as black or green gram, rice
and spices which has become a tradition in millet growing areas of south India.
According to Begum et al., (2007) the addition of finger millet up to 60% is possible
and it practiced in some part of Karnataka. Inspite of this, several communities in the
dry/rain fed regions have known to possess food-qualities of millets over generations
continue to include a range of millets in the traditional cropping patterns, which
recognize millets as an essential part of the local diet.
2.2. Therapeutic Significance of millet grains
Food provides not only essential nutrients for life but also it gives other
bioactive compounds for health promotion in prevention of diseases. Regular
consumption of plant foods helps to reduce the risk of chronic degenerative diseases
and biological ageing. A recent research indicates that the nutritional guidance of
grains and grain products based on food guide pyramid emphasizes the importance of
the consumption of grains and grain products as part of a normal diet for optimal
health (USDA 2000, 2005; Singh and Sharma, 2009). The epidemiological evidence
from recent research showed that the plant foods protect against several degenerative
diseases, metabolic syndrome and Parkinson‟s disease (Gupta et al., 2012). Millets
are traditionally accepted as functional and nutraceutical foods for more than four
decades since they provide dietary fiber, protein, energy, minerals, vitamins and
necessary benefits for human health. It gives several potential health benefits such as
preventing cancer, cardiovascular diseases, reducing incidence of tumor, lowering
blood pressure, delaying gastric emptying etc. The consumption of whole millets have
health promoting effects which is equal to or even in higher amount when compared
to fruits and vegetables and it has the potential to protect against insulin resistance,
heart diseases, diabetes, ischemic stroke, obesity, breast cancer, childhood asthma and
premature death (Cade et al., 2007). Among the millets, the minor millets possess
several health benefits which could be attributed to their presence of low carbohydrate
content, low digestibility and water soluble gum content as it improves the glucose
metabolism there by release sugar slowly to the blood and also diminish the
absorption of glucose. The dietary fiber and resistant starch present in minor millets
have been endorsed to exhibit hypoglycemic and hypolipidemic effects and it also
contains the anti-oxidant properties phytochemicals like phenolics, tannins, phytates,
micro minerals etc., which help to prevent against hyperglycemia and oxidative stress
(Anderson et al., 1991; Ranhotra et al., 1991; Srivastava et al., 1998).
Millets are good sources of minerals especially magnesium and phosphorus.
Intake of magnesium helps to reduce the effects of migraine also lowers high blood
pressure. The phosphorus present in millets also is essential component of Adenosine
TriPhosphate (ATP) that acts as a precursor to energy in the body. Niacin helps to
reduce the high cholesterol levels in the body (Guigliano et al.,2011;
Badau et al., 2005; Liang et al., 2010; Devi et al., 2011; Shashi et al., 2007).
Viswanath et al., 2009 and Xu et al., 2011 reported that the extract from millet
seed coat had shown high antibacterial and antifungal activity when compared to
extract from wheat flour due to high polyphenols content in seed coat and also rich in
phytochemical including phytic acid, thereby helps to lower cholesterol and phytate
levels which is associated with reduced cancer risk (Coulibaly et al., 2011;
Izadi et al., 2012). An interesting information in the study revealed that the different
millet like kodo millet, finger millet, little millet, foxtail millet, barnyard millet have
higher free radical quenching potential (Devi et al., 2011; Quesada et al., 2011;
Kamara et al., 2012). Millet is found to be gluten-free which helps in treatment of
people suffering from cealic diseases and also wheat intolerance (Gelinas et al., 2008;
Krishnakumari et al., 1997).
In recent scenario, the changes in utilization pattern of processed products and
awareness of the consumers about the health benefits which is associated with regular
intake of millet foods, the important application which the finger millet possesses are
antibiotics, anti-inflammatory agents and its functional components such as slowly
digestible starch and resistant starch. It has high proportion of complex carbohydrates
in the form of non-starchy polysaccharides and dietary fiber in grains which helps in
reducing cholesterol and regulates the glucose to the blood stream during digestion. It
was found to be good source of micronutrients, which helps to lessen the wide, spread
micronutrient malnutrition among the vulnerable segments in the developing country
(Wadikar et al., 2007; Shobana, and Malleshi 2007; Subba Rao and
Muralikrishna, 2002; Samantray, 1989). The presence of tannin and phytic acid are
responsible for the highest free - radical quenching activity in non-processed brown
finger millet than the processed finger millet (Devi et al., 2011; Quesada et al., 2011;
Kamara et al., 2012; Chandrasekhar and Shahidi 2010; Wisker et al., 1985;
Gopalan et al., 1981; Kang et al., 2008). It reduced the level of total serum
cholesterol, LDL by 9%, triglycerides by 15% and increased HDL level. The soluble
dietary fiber in finger millet is the important fractions in foods because they trap fatty
substances in the gastro-intestinal tract and therefore reduced cholesterol levels in the
blood and lower the risk of heart disease (Kurup et al., 1993).
The pearl millet provides a low-cost solution to combating malnutrition due to
micronutrient deficiency. Pearl millet provides an additional health-related advantage
because of their higher level of insoluble dietary fiber and more balanced amino acid
profile. The kodo millet have therapeutic effect on lowering post prandial blood
glucose response is possibly due to lowering of viscous soluble fiber. Among the
millets kodo millet contains natural antioxidant and high soluble dietary fiber for
maintaining the low blood glucose and inhibits LDL cholesterol oxidations which
play a vital role in the prevention of atherosclerosis and related heart diseases.
Soluble fiber present in kodo millet has gelling properties that could delay the
intestinal absorption (Sharma 2003 and Jenkkins et al., 1986).
The protein present in the proso millet could show a therapeutic effect in Type
2 diabetes. The presence of polyphenols and dietary fiber in proso millet is considered
to be gluten free and it can be used for development of products to the celiac patients.
The starch present in millet is the resistant starch which escapes from digestion in
small intestine and helps in lowering caloric density and low glycemic response
(Choi et al., 2005; Park et al., 2008; Hegde et al., 2005)
The foxtail millet has good nutritional profile when compared to cereals such
as rice and wheat in terms of protein, fiber, minerals and vitamins which has a
potential role as lower gastrointestinal food. It is found to be highly nutritious, easy to
digest, non-glutinous and is not an acid forming food. Millet is considered to be one
of the least allergenic and most digestible grains and it helps to give heat to the body
in cold or rainy seasons hence it is called as a worming grains. Antioxidants and
polyphenols in foxtail millet appear to be beneficial for preventing CVD, cancer and
obesity – related disorder. Pawar et al., (2006) found that foxtail millet contain higher
amount of bioactive compound which possess many health benefits mainly in the
treatment of improving cholesterol metabolism (Zhou et al., 2009; Anu et al., 2010).
Anju et al., (2006) formulated biscuits prepared from foxtail millet powder showed a
significant decrease in serum glucose, serum lipids, glycosylated hemoglobin in
type 2 diabetes. The proteins present in the foxtail millet have a potential role to fight
against type 2 diabetes among women & cardiovascular disease
(Krishnakumari et al., 1997; Sivakumar et al., 2006; Abdel et al., 2006).
2.3. Nutritional and functional properties of millet grains
Nutritional properties of food play a vital constituent in maintaining the
overall physical well-being of human health, because the nutritional properties act as
a sustainable force for health and development which helps to maximizes the human
genetic potential of the body, thereby for solving the problem such as food insecurity,
malnutrition and dietary quality. Cereal grains occupies a significant place in human
nutrition particularly in the dietary pattern of low income people of developing
countries and are considered to be a best way for delivering good nutrients. Among
the cereals, millets is referred to as poor man‟s cereals and is considered to be a minor
grains and also found to be higher in their nutritional properties when compared to
other major cereal crops such as wheat and rice (Singh and Raghuvanshi, 2012;
Parameswaran and Sadasivan, 1994). The millet grains such as finger millet, pearl
millet, kodo millet, foxtail millet and little millet are unique among the minor cereal
grains since it is superior in nutritional qualities and possess several health benefits
with nutraceutical potential for human health (Malleshi and Hadimani et al., 1993).
Millets have good source of carbohydrates (67.0g/100g), protein (7.7g -12g/100g),
and fat (4.5-7.6g/100g) and also contains higher proportion of vitamins and minerals.
The seed coat fractions enclosed comparatively higher level of fat, protein, calcium,
phosphorus and iron. The dietary fiber was the highest in seed coat followed by whole
powder (Malleshi and Hadimani et al., 1993; Mbithi-Mwikya et al., 2000).
Among vitamins, the B group vitamins were found to be important sources of
millets and it possess higher amount of ash, iron, phosphorus, dietary fiber and amino
acids was higher than the rice or wheat (FAO 1995; Ganapati et al., 2008;
Rao,1986). The presence of natural antioxidant like vitamin C, tocopherol,
carotenoids and polyphenol helps to prevent the free radical damage in the body
(Vithal et al., 2006; Abdel-Aal et al., 2006; Malleshi et al., 1993;
Sri Devi et al., 2008). Among the whole grain foods the millets shows higher
antioxidants activity due to presence of minerals (Ca, Mg, K. P, Na and Fe) and
phytochemicals (phytates and phenolic compounds) which play major role in body
immune system. The moisture content of finger millet range from 7.7 to 9.7%. In
addition, one cup of cooked millets provides 26.4% daily value for magnesium and
24% daily value for phosphorus (Chandrasekara and Shahidi, 2010;
Lakshmi et al., 2002). The total lipid content in the foxtail, proso and finger millet
range from 5.2 to 11.0% whereas in the little, kodo and barnyard millets it ranges
from 5.1 to 8.3%. Hence the overall qualities of all millets possess good protein and
carbohydrate and with immense nutritional properties helps to promote the human
health. Recommendation of combined millets in the form of ready to eat, ready to
cook, health mix and other supplementary products would be highly beneficiary.
The combinations of different millets are being introduced for the
development of products by different processing method to retain and enrich the
nutritional properties of products. Whereas during processing like malting and
hydrothermally treated, the seed coat of native millet contain 9.5-12% protein, 2.6-3.7
fat and 40-48% dietary fiber and in addition it also contains 3-5% polyphenols and
700-860mg/100g of calcium. Malting usually hydrolysis some protein of the starch
and increases the activity of amylases in finger millet. During processing the changes
in protein is observed usually by physical, chemical and biological such as
fermentation or enzymatic treatment and also changes in structure and consequently
in physicochemical and functional properties (Amadou et al., 2011b and
Saldivar, 2003).
The finger millet is a wealthy source of macro and micro nutrients. The
nutritional properties of finger millet revealed that it contains higher amount of
carbohydrate (81.5%), protein (9.8%), crude fiber (4.37%) and minerals (2.7%) which
is comparable to other cereals and millet. The seed coat of finger millet fraction
contain 13.1% protein, 3.3% fat, 5.6% ash and 43.8% dietary fiber and these values
were significantly higher than those for the whole meal millet. In addition, it contains
1.25% calcium where 50% of the calcium content of the whole grain is concentrated
in the seed coat (Kurien et al., 1959). The crude fiber and minerals content was
obviously found to be higher than wheat (1.2% fibers, 1.5% minerals). The finger
millet has a high content of dietary fiber-19.1g, calcium-334g, phytate-209mg.
tannins-360g, iron- 2.4-6.4mg, beta-caroteine-42µg and total minerals-2.7%. Protein
is comparatively better in finger millet; it contains more lysine, threonine and valine
than other millet and also it is a good source of methionine, an essential amino acid. It
also contains many micro nutrients like calcium, iron, and phosphorus, sodium, zinc
and potassium. The calcium content is superior to all cereals and iodine content is said
to be maximum among all the food grains (Upadhya et al., 2006; Duke 1979;
Gopalan et al., 2000; Gopalan et al., 2004).
The nutritional compositions of pearl millet indicate that it is a good source of
energy and protein. On a dry weight basis, it contains 7.4% protein, 6.3% fat,
2.8% fiber and 2.2% ash. Linoleic acid (44.8%), oleic acid (23.2%) and palmitic acid
(22.3%) are the prevailing fatty acids in millet oil followed by stearic acid (4.0%) and
linolenic acid (2.9%). The results are associated with the Kamara et al., (2009) that
pearl millet contains 12.3% crude protein, 3.3% minerals and 72% carbohydrates
which include the main components such as starch, protein, lipid, vitamins &
minerals. It is considered to be the cheapest source of energy, protein, iron and zinc
when compared to other cereals and pulses. Essential amino acid profile of pearl
millet contains about 40% of lysine and methionine and it contains 30% of threonine
when compared to protein present in corn (Burton et al., 1972; FAO/WHO, 1995;
Gopalan et al., 2000; Klopfenstein and Hosney et al., 1995).
The foxtail millet holds nearly 15% protein, 70-80% of carbohydrates and fair
amount of fiber, methionine, lecithin, vitamin E and B- complex vitamin which
includes niacin, thiamin and riboflavin. It also contains good amount of chromium
with an account of 0.03mg per 100g (Bahadursingh et al., 2011). In foxtail millet 79%
of edible portion which indicates the presence of high amount of fiber and it typically
contains higher quantities of essential amino acids (methionine and cysteine) and it is
superior in fat content than maize, rice, sorghum (Gopalan et al., 1987;
Kamara et al., 2009).
When compared to other major cereals, the nutritional composition of little
millet and kodo millet possess 65–72 % carbohydrate, 8–9 % protein, 1–2 % fat,
2–3 % minerals and 9 % fiber. The little millet contains 4.79g/100g of fat
(Nirmala kumari et al., 2010; Ramanathan et al., 1957). Starch content account of
79 % that favours extrusion process in developing the expanded snack
(Geervani et al., 1989).
The physical properties of cereals and millets are essential for the formulation
of the products which plays a vital role in the final output of the product. The physical
properties of millet grains and other cereals along with millets were carried to analyze
the functionality of the millets and its products. Studying the functional properties like
bulk density, swelling power, water absorption capacity, foam capacity and foam
stability and oil absorption capacity of millets would have helped to enhance the
quality as well as shelf life of the food products prepared from millet grains.
The increased swelling power reflects the susceptibility for hydration and
better gelatinization. The behavior of starch in flour reacts on water and its
concentration and temperature. Generally, the starch absorbs very little water at room
temperature; hence, it leads to low swelling capacity. The swelling power of finger
millet flour was higher than composite flours. This difference could be explained by
the high content of starch, low contents of protein and fat into the millet flour in
contrary to composite flour. Wang and Seib (1996) have reported that the amount of
protein and fat could inhibit swelling of the starch granules. These findings were
recently confirmed by those of Hathaichanock and Masubon (2007) who have shown
that the presence of protein in the flour could reduce or inhibit swelling of the starch
granules. Similarly swelling power of the flour is also affected by the processing
methods. Swelling capacity decreased with increasing the fermentation period.
Values of swelling capacity for non-fermented sorghum, pearl millet and maize flour
was 0.29, 0.14 and 0.21 % respectively which reduced up to 0.18, 0.10 and 0.10 %
respectively after 36 hours of fermentation. Adebowale and Maliki (2004) reported
that fermentation was found to reduce the swelling capacity of pigeon pea flour.
Increase in the swelling power on chemical modification might be due to the
weakening of the intragranular binding forces within the starch granule, which offered
less restriction to swelling of the modified starches. Solubility increased as the
temperature increased because of increase in mobility of the starch granules, which
facilitated dispersion of starch molecules in water.
The bulk density is a reflection of the load that the flour samples can carry, if
allowed to rest directly on one another. The density of processed products dictate
the characteristics of its container or package product. Density influences the
amount and strength of packaging material, texture or mouth feel. The bulk density
was found to be higher in sorghum (0.75g/mL) followed by maize (0.72g/mL) and
pearl millet (0.71g/mL) respectively. Bulk density depends on interrelated factors
including intensity of attractive inter particle forces, particle size and number of
contact points. Bulk density values decreased gradually with increase in fermentation
periods. Fermentation of sorghum flour for 24 h decreased the bulk density of the
sorghum flour by about 10%. The decrease in bulk density of fermented flour would
be an advantage in the preparation of infant foods. Fermentation has been reported as
a useful and traditional method for the preparation of low bulk weaning foods. A
higher BD is desirable, since it helps to reduce the paste thickness which is an
important factor in convalescent and child feeding (Peleg et al., 1983). The bulk
densities of blends are lower compared to durum wheat blends (0.80-0.82 g/ml)
(Amajeet et al., 1993) thereby making the blend suitable for the formulation of
nutrient dense weaning food (Desikachar, 1980).
Water absorption capacity gives an indication of the amount of water
available for gelatinization. Lower absorption capacity is desirable for making
thinner gruels. The water absorption capacity (WAC) of pearl millet was improved to
143 ml H2O/100 g, 163 ml H2O/100g and 180 ml H2O/100 g with increasing the level
of soybean supplementation to 5%, 10% and 15% respectively.
Narayana and Narasinga Rao (1992) reported that soya flour had WAC of 310 g/100 g
flour, while Kinsella (1976), reported a value of 275g/100 g flour. The results
obtained indicated that soybean flour had high WAC which contributed to the
improvement of WAC of pearl millet. WAC is considered a critical function of
protein in viscous foods, like soups, gravies, dough and baked products
(Sosulski, 1976).
Foaming properties are dependent on the proteins, as well as on other
components, such as carbohydrates present in the flour. Brou et al., (2013) reported
increasing foaming stability with increasing protein content while characterizing
complementary food made from maize, millet, beans and soybeans. They further
reported higher protein stability for native proteins. The increase in foaming stability
observed for sample that germinated for 48 h might have been as a result of
bioavailability of inherent proteins which were probably bound by antinutritional
factors such as phytin in the sample. Singh and Raghuvanshi (2012) reported that
antinutritional factors in cereals bind to both exogenous and endogenous proteins
including enzymes of the digestive tract affecting utilization of proteins. The
reduction in stability observed for sample that germinated for 72 h could have been
due to denaturation of protein (Brou et al., 2013).
The low foam capacity may be attributed to the low protein content of
the flour since foamability is related to the amount of solubilized protein
(Narayana and Narasinga Rao, 1982) and the amount of polar and non-polar
lipids in a sample (Nwokolo, 1985). Cowpea flour showed markedly higher foam
stability after 30 min than did chickpea and horse gram flours. Foaming capacity was
increased significantly at p<0.05 while increasing the pH of the sample which
was likely due to increased net charge on the protein. These results indicate that the
proteins and other components of cowpea flour have greater ability to form a strong
and cohesive film around air bubbles and greater resistance of air diffusion from the
bubbles. In general, all three legume flours depicted high foam stability and may find
application in baked and confectionery products (Kanu et al., 2007).
2.4. Effect of different processing methods on millet grains
The cereals and millet possess higher levels of anti-nutritional factors. In order
to include the cereal and millet in diet it is necessary to process before incorporating
in the food products to increase the acceptable of products among the consumers
(Hajos and Osagie, 2004). FAO (1990) and Singh et al., (2000) stated that millets are
minor cereals and form the staple food for a large segment of the population in India.
Utilization of millet as food is still mostly confined to the traditional consumers and
population in lower economic strata, partly because of non–availability of
ready–to–eat forms. Several researches evidenced that traditional method of food
processing namely threshing, cleaning, washing, dehulling, soaking, germination,
hydrothermal treatment, decortications, dehulling, depigmentation and fermentation
increases the bioavailability of the millets.
In processing methods the sprouting improves the nutritional quality of millet
seeds by increasing the availability of essential nutrients which helps to decrease the
levels of anti-nutrients (Chavan and Kadam 1989; Nkama and Ikwelle et al., 1998;
Kadam et al., 1989). In many developing countries there are three main operations
namely soaking, germination and drying for the process of traditional malting. For
each operation, the duration and conditions are different which resulted in highly
variable malt and good quality product (Mbithi-Mwikya et al., 2000;
Badau et al., 2005). Taur et al., (1984) reported that in malting process the finger
millet improves the calcium, phosphorus and vitamin C content. Whereas in case of
protein and fat content there was not much difference. In finger millet, the malting
process increases the bio availability and digestibility of nutrients, nutritional quality
and it helps to improve the sensory characteristics of product.
Marero et al., (1989a) stated that to improve the nutritive composition of
cereals and millet, germination was one of the processing methods adopted. The
germination helps to decrease the level of anti-nutrient present in cereals and millets
which increases the availability of nutrients. According to WHO (1998) during
germination there was an increase in protein which could be attributed due to net
synthesis of enzyme protein. During germination of pearl millet, the protein content
increase and the reason behind the enhancement in protein content of the germinated
grains may be the decreased levels of anti-nutritional factors such as polyphenols and
phytic acid. Germination for 48hours at 30ºC reduced phytic acid and also enhances
the level of invitro protein digestibility (IVPD) and HCL- extractability of P, Ca, Fe
and Zn (Hassen et al., 2006; Kumar et al., 1993).
One of the traditional methods of food processing which is used extensively in
Asia and Africa for the process of cereals and millets is fermentation. Generally
fermentation does not affect the total protein contents but will enhance nutritional
properties of millets. The increased protein availability resulted from increased
extractability of protein in the form of albumin and globulin fraction. The
fermentation process resulted in breakdown of tannins and phytases and increased
microbial protease action. Chung et al., (1981) investigated that during fermentation it
has been found to increase pepsin digestibility of millet protein, and it helps to
decreases the concentration of phytic acid and polyphenols thereby improving the
availability of minerals. WHO (1998) stated that there was some physical
characteristics modification during fermentation which will increases the level of
nutrients, digestibility and bioavailability of food grains and also reduces the level of
anti-nutrients and imparts some anti-microbial property. Fermentation process has
inhibitory effects on the microorganism that can be cause spoilage and eventually
improving the shelf life of product (Odumadu et al., 2006). Whereas in the
fermentation process, the millet flour was observed to contain high carbohydrate
content which may be associated with increased water absorption capacity (260%)
because the millet flour undergoes gelatinization and swelling when heated
(Shulka et al., 1986, Bishoni et al.,1994 and Shinde et al., 1991).
One of the modern technologies in the fermentation is that the pearl millet was
fermented with lactobacilli or yeasts with natural microflora with combination of
different processing pre-treatments such as soaking, grinding, debranning, dry heat
treatment, autoclaving and germination resulted in lower anti-nutritional properties. In
order to reduce the anti-nutritional factors, the whole pearl millet grains were soaked
for 24hours at room temperature until the millet seeds reached 30±2% moisture and it
was steamed at 1.05Kg/CM2
for 15 minutes in order to reduce the anti-nutritional
properties and it helps to improve the acceptability of product among consumers and
it helps to increase utilization of pearl millet (Kapoor et al., 1996, Shobhana and
Malleshi et al., 2007). Fermentation and germination enhance the nutritional quality
of millets, protein availability, and in vitro protein digestibility of millets by causing
significant changes in chemical properties thereby decreases the level of anti-
nutritional factors (Usha et al., 1995; Sugel et al., 1978; Sripriya, Usha Antony and
Chandra, 1997).
Roasting is the ancient method of processing of the cereals and legume based
grains. The advantage of roasting process is that it shows the reduction in microbial
content leading to loss of nutrient, while heating at high temperature and it decrease
the level of anti-nutritional factors. The total phenols and tannins are reduced during
roasting could be attributed due to heating at high temperature. During roasting
process the antioxidant activity was found to increase (Marwin et al., 2011).
The studies related to cereals based food grains investigated that thermal
treatment which helps to decrease or increase the phenolic content and their
antioxidant activity depends on the severity of heat treatments, time exposure and
type of cereals used for research (Hedge and Chandra et al., 2005). According to
Ramanath et al., (1957) reported that the pulversing effect of seed coat matter was
minimized by tempering or moistening of the millets which can be evident as dark
color, high yield of powder when compared to refined powder. In addition the nutrient
composition of the whole powder was found to be higher than the refined powder
except the starch.
Dehulling and decortications is a traditional method of processing that
decreases the levels of phytic acid content of millet. On the other hand, dehulling
increases starch content and in vitro protein digestibility of pearl and finger millet
(Almeida-Domingueze et al.,1993; Monawar,1983). Dehulling process decreases the
polyphenols content to the extent of 41.49% to 50.92%. The leaching out of
polyphenols in concentrated form was found in soaking medium and destruction
during cooking process and also by removal of pericarp (Maxson et al.,1972).
Decortication is one of process that has been found to decrease the level of total
polyphenols, phytic acid of anti-nutrients of pearl millet, and increases the starch
content and in vitro protein digestibility (IVPD) (Almeida et al., 1993).
One of the effective processing techniques used in preparation of pasta using
pearl millet is depigmentation. This process resulted in acceptable in vitro protein and
starch digestibility. Depigmentation of pearl millet was carried out to use in
preparation of pasta (Rathi et al., 2004). Their results indicated that depigmentation
was an effective processing technique to develop acceptable in vitro protein and
starch digestibility. Millet samples having higher malt fraction had a higher WSI as
compared to those having lesser malt. Increase in WSI due to malting in pearl millet
was also reported by Pelembe et al., (2003).
In order to improve the acceptability of the grains for consumption among
consumers the grains were subjected to some processing method such as milling, heat
extraction cooking and parboiling. Most of the commercial products in cereals grains
are available in the form of extruded, puffed, flaked without altering their desirable
quality and also extrusion does not remove the biological important components of
wholegrain (Slavin et al., 2001a). The analysis result of processed bread and cereal
products indicates that they are rich sources of antioxidant (Miller et al., 2002).
Dehydration plays a vital role in processing of food products to increase the
quality and extend the shelf life of the products. Dehydration techniques inactivate all
kinds of anti-nutritional enzymes and improves flavor and overall acceptability of the
food. Dehydration is one of the heat processing methods to remove the moisture from
the slurry to make powder. During dehydration process, the reduction of moisture
content makes the product shelf life stable for an extended period of time. It also
contains other benefits like weight reduction and reduction in volume of product
which minimizes the packaging cost for storage and also reduce the transportation
cost (Domanz, 2004, 2007). Dehydration of foods helps to control the effects and
preserve the structure and create a new one that serves for functional purposes. In
addition, these foods present the following advantages: maximum microbiology
security soft and homogenous texture, prolonged preservation time, lesser production
of food by products, easy use and storage food (Aguilera et al., 2003).
In traditional processing the food products were dried using open sun drying
method. Since, this drying is common for non-commercial purposes. It is necessary to
improve the dehydrated foods to make products of high commercial value which
resulted in modification of various dryers for food applications. The other drying
techniques such as solar cabinet dryers, tray dryers, fluid bed dryers, vaccum freeze
dryers had resulted in better product quality than that of open sun drying
(Mujumdar et al., 2008; Chen et al., 2008; Jangam et al., 2010). Bozyma and
Kutovoy (2005) reported that preservation of cereal, millet grains, fruits and
vegetables by drying were practiced many centuries back and it is based on sun and
solar drying techniques. Due to improper drying, poor quality and product
contamination led to the development of different drying technologies. In common,
the drying of fruits, vegetables, cereals and millets includes freeze drying, forced
convection tray drying, vaccum, osmotic, cabinet or tray, sprouted bed, ohmic, heat
pump and microwave drying and their combinations.
In recent research the open sun drying is used for many non-commercial
applications but it resulted in very poor properties of most dried products. For drying,
food products mainly depends on the type of the feed, the amount of moisture and
type of moisture drying kinetics, heat sensitivity, physical structure of the material to
be dried and quality required for dried food products.
In different drying methods, freeze drying offers good color retention and also
increases the functionality of foods (Soong and Barlow, 2004). In recent research the
juices developed by freeze dehydration have indicated its feasibility of technology in
developing high quality shelf-stable products (Ammu et al., 1977;
Jayathilakan et al., 2003; Mujumdar et al., 2008).
Advances in drying techniques and growth of novel drying techniques have in
current years facilitated the research of a wide range of dehydrated products and
convenient processed foods. Combination of millet based products was found to be a
best option for improving the consumption of millet among non-millet consumer.
Hence formulation of products in combination of millets would give overall essential
amino acid balance and complex carbohydrate which in turn pave way to ruin the
world from protein calorie malnutrition problem and helps to reduce the level of
glucose. (Livingstone et al., 1993) Breakfast products and other snack products with
the combination of millets fits today‟s life style because of their convenience,
economical and nutritious attributes.
2.5. Utilization of millet grains in the preparation of value added
products
In the forthcoming review of the present section, some of the value added
products and possibilities of utilizing different variety of millet as one of the basic
ingredients are discussed below. Millet can be used in a variety of ways and is a great
substitute for other grains such as rice and other starchy grains. Since the seed coat of
millets were normally dark color, cherry texture and nasty odors the food products
prepared from that millet had an effect on their acceptability. Hence to increase the
consumption of millets, it was further processed to remove the seed coat which
improves the acceptability of the products.
These products are either in practice or have been demonstrated as avenue for
enhanced consumption of millets among the consumers since millets are considered to
be nutritionally superior when compared to rice or wheat. The presence of required
nutrients in millets are suitable in the production of food products like snacks foods,
baby foods and dietary foods (Bahadur et al., 2011). In the traditional preparation, the
millets were consumed in the form of thick porridge (mudde or dumpling), thin
fermented porridge (ambali) fried or baked pancake (roti,dosa), and beverage. Finger
millet are fermented naturally for the preparation of a product using traditional
method of called „Ambali‟. Millet are brewed and consumed as „chang‟
(Malleshi and Hadimani, 1991). The pulverized millet powder and whole meal is used
to prepare traditional foods such as unleaded pancakes, stiff porridge or dumpling and
thin porridge.
Generally the millets were used for preparation of pudding, porridge and roti.
In emerging trends the millets are used as a raw material in industrial purposes for the
production of biscuits and confectionery, beverages, weaning foods and beers
(Laminu et al., 2011; Anukam and Reid, 2009). A weaning diet was processed from
pearl millet, conophor nut flour was found to promote growth in children. Hence the
malted and fermented millet powder are usually used in preparation of weaning food,
instant mixes and beverages in pharmaceutical products. (Gomez et al., 1993;
Rao et al., 2001). The most popular weaning foods blends prepared from fermented
pearl millet/ cowpea in 70:30 and 60:40 ratios were found to have resulted in lowering
the levels of phytic acids and also increased in vitro protein digestibility of the
weaning food blends.(Laminu et al., 2011). In order to improve the utilization of
millets among the consumers the modern methods of preparation was developed for
incorporation of millet powder in wheat flour with different ratio for development of
bread, biscuit and other snacks helps to improve the nutritive value of the foods
(Mridula et al., 2007; Akeredolu et al., 2005). Soft biscuits and cookies are developed
using sorghum, maize and wheat composites. (Akeredolu et al., 2005,
Hama et al., 2011, Laminu et al., 2011).
In recent days, extrusion technology has become popular among food
industries and consumers. Because this method satisfies not only the consumer
demand but also helps to meet the necessary requirement for people suffering from
wheat in tolerances such as celiac disease (Sabanins and Tzia 2009;
Faller et al., 1999). Due to the economic and nutritional consideration it is desirable to
replace wheat flour with other locally available non-gluten flours to develop a
product. Some of the alternative cereals like barley, sorghum, millet, amaranth and
also the grains like flaxseed, quinoa are used for extrusion processes
(Plahar et al., 2003; Arya 1990). Ready to eat extruded breakfast cereal products were
prepared by using millet, amaranth and buckwheat as replacement for wheat and
maize flour. The result shows that there was an alteration in physical and nutritional
quality of extruded breakfast cereal. The pasta is well known ancient and versatile
dish for both nutritive and gastronomic point. It was found to be consumed in large by
people all over the world. This had a significant quality of complex carbohydrates,
protein, B-Vitamin and iron and is low in sodium, amino acids and total fats.
(Antognelli 1980 and Breman et al., 2012.). Pasta prepared from millets had a rich
sources of carbohydrates (74.77%) and had low glycemic index. (Monge et al., 1990).
The inclusion of pseudo cereals showed a significant reduction in readily digestible
carbohydrates and slowly digestible carbohydrates when compared to the control
products.
The composite flour containing finger millet and wheat flour in the ratio of
60:40 and 70:30 (w/w) were used in the formulation of biscuits and the quality
characteristic were evaluated for dough and biscuits. The results indicated that the
biscuit prepared from composite flour in the ratio of 60:40 was found to be the best.
The effect of replacement of wheat flour with different percent from 0% - 100% was
studied in which 100% finger millet flour was replaced for development of muffins.
The muffin prepared from the combination of 60% finger millet flour was found to be
significantly increased in volume and in quality characteristic. (Rajiv et al., 2011,
Saha et al., 2011). In addition, as a new technology, the incorporation of finger millet
powder with refined wheat flour in the different proportion (30%-50%) was used for
the preparation of noodles for diabetic patients. The results of sensory evaluation
showed that 30% of finger millet incorporated noodles was found to be acceptable
and it was evaluated for glycemic response. The results revealed that 30% finger
millet incorporated noodles had significantly lower glycemic index when compared to
control noodles (Shukla and Srivastava, 2011).
The blanched and malted pearl millet flour were used to develop a biscuit in
combination with soybean flour with equal proportion of milk powder, fat, sugar and
other minor additives. The products developed from combination of pearl millet had
higher mineral content and improves the digestibility. Pearl millet flour was used for
formulation of cookies which do not spread during baking, and had poor top grain
character and it looks dense and compact. The fermented foods like rabadi used pearl
millet had shelf life for 7 days. Another combination of pearl millet, finger and
decorticated soybean blends were used for extrudates for which was carried out by a
linear programming (LP) model since it was used to minimize the total cost of the
finished product. Ready to eat dessert like kheer was formulated using pearl millet
flour and it was reported to be acceptable among the consumers
(Abdel Rahaman et al., 2005; Balasubramanian et al., 2012; Singh et al., 2000;
Badi et al., 1976; Modha and Pal et al., 2011; Jha et al. 2011). Popped pearl millet
rich in fiber, carbohydrates and energy are used for developing weaning foods or food
supplements (Bhaskaran et al., 1990). Pearl millet was used to prepare the flakes
which are rich in fiber and an ideal snack for the obese and for calorie consumers
(Hadimani and Malleshi, 1993).
The foxtail millet and barnyard millet was used to prepare biscuit from where
sensory analysis was carried out and it was found to be acceptable among the diabetic
subjects. Bread was prepared using millet based composite flours using barnyard
millet and wheat composite flours with proportion of 61.8g/100g of barnyard millet,
31.4g/100g of wheat and 6.8g/100g of gluten. The results of the sensory analysis were
found to be acceptable among the consumers (Anju et al., 2010; Singh et al., 2012).
The weaning foods and thinner gruel by low viscosity was prepared using millet flour
such as kodo millet and barnyard millet and also other flour namely wheat flour and
soy flour were used for preparation of products and it was found to increase in the
level of syneresis that may improve the resistant starch content on storage
(Vijayakumar and Mohanakumar, 2009).
One of the traditional and highly popular cereal based product is pasta. It was
highly acceptable among the consumers because of its convenience, nutritional
quality and palatability of the products and it became one of the popular foods with a
high acceptability scores among the population groups. In order to increase the
acceptability of products it can be readily incorporated with new ingredients in large
scale utilization of the industry for production of pasta (Cubadda et al., 2007;
Goni and Valentine-Gamazo, 2003).
In food industry, the extrusion technology has been commercially stable for a
long time. The convectional ingredients used for extrusion processing are starch based
food materials like corn, rice and semolina. Extrusion process involves high
temperature short time process and simultaneous thermal and pressure treatment and
also mechanical shearing takes place. As a result, the extrudates had several changes
such as gelatinization of starch, denaturation of protein and even complete cooking
takes place for the final product. For popular breakfast cereals in commercialized
industry, the extrudates was developed using corn and oatmeal
(Sefa-Dedeh et al., 2003; Rossen and Miller, 1973). The commonly used ingredients
for the development of extrudate products are corn flour which is rich in carbohydrate
and fibers but they are relatively low in protein content. In the large scale industry, the
extrudate products usually contain high quality protein mix which is formulated using
local ingredients. In present scenario, the food processing industry has a challenge of
developing convenience foods such as breakfast cereals and snacks with high
nutritional value. Popular extrudate products which are consumed worldwide are
spaghetti, macaroni, vermicelli and noodles. The main ingredient for preparation of
pasta is durum wheat (Frame 1994, Muhungu et al., 1999, Warren et al., 1983).
Extrusion plays a vital role in modern technology. Extrusion cooking had
significant effect in the development of the products. Extruded products not only
enhance the acceptability of the products but also help to improve its appearances,
taste and texture. The effect of extrusion on their nutritive value had limited studies
(Castello et al., 1998 and Noguchi et al., 1982). The extruded product are developed
from the rice flour or starch, was found to be low in protein and have low biological
value as they have a lower content of amino acids. So in order to improve the
nutritional contents of the extruded products, the fortification was carried out with
cereals and high protein foods and lysine foods to improve the amino acids content
(Baskaran and Bhattacharya, 2004). The products prepared using millet and legume
flours blends are being carried out in India to form nutritionally balanced foods that
can be used as supplementary food products for malnourished children. Soy fortified
millet based products was prepared from sorghum blended with soy, millet and rice.
(Seth et al., 2012; NRC, 1996). Malleshi et al., (1996) reported that the millet grits
and flour are used to prepare the ready to eat products. Soya or protein rich
ingredients namely legumes or groundnuts cakes blended with pearl millet are for
extrusion. Extrusion cooking have the potential to inactivate the anti-nutritional
factors such as lysine inhibitors and urease activity and it reduce the growth of the
fungal pathogen fusarium and increases the shelf life of the product as well. The
extruded products were prepared in order to improve the nutritive value of developed
supplementary foods with the addition of soy to corn extruded products which serves
as a tool to produce healthy foods.
3. METHODOLOGY
The methodology pertaining to the study entitled, “Value addition of convenience
food using processed millet powder” is discussed under the following heads.
3.1. Selection and pre-processing of raw materials
3.2. Steps involved in the preparation of processed millet powder
3.3. Optimization of composite millet powder
3.4. Finalized parameters for further analysis and product development
3.5. Process involved in the development of convenience food
3.6. Quality analysis of developed convenience food and the powder
3.7. Statistical interpretation of the data
3.1. Selection and pre-processing of raw materials
The millet grains are unique among the minor cereal grains due to its superior
nutritional qualities and possess several health benefits as well. The five dehulled
millets such as finger millet (Eleusine coracana), pearl millet (Pennisetum glaucum),
kodo millet (Paspalum scrobiculatum), little millet (Panicum miliare) and foxtail
millet (Setaria italica) were procured from supermarket of Puducherry. The selected
millets were cleaned to remove dust, other foreign materials and stored in plastic
container for further processing. The raw materials selected for processing and
product development are shown in Plate 1.
Plate 1. Raw materials selected for processing and product development
Pearl millet
Foxtail millet
Little millet
Kodo millet
Finger millet
3.2. Steps involved in the preparation of processed millet powder
Millet and other coarse grains were dehulled and subjected to different
treatments before consumption to improve their sensory and edible quality
(Liu et al., 2012). There are some traditional processing technologies namely thermal
processing, mechanical processing, soaking, fermentation, germination and malting
which helps to improve the nutritional characteristics, sensory properties of the
developed food products and also enhances the bioavailability of micronutrients in
plant-based diets (Hotz and Gibson, 2007). Dehydration techniques facilitate the
reduction of moisture content making the product shelf life stable for extended period
of time (Doymaz, 2004, 2007). In the present study, the processing methods namely
soaking, preparation of slurry and dehydration were carried out for the development
of millet powder. The steps involved in the preparation of processed millet powder are
shown in Figure 1.
3.2.1. Soaking
Soaking of grains is a popular technique in food preparation for reducing the
anti nutritional compounds namely phytic acid and helps to improve bioavailability of
minerals. The deprivation and leaching of phytates, phytase activity increases the iron
and zinc concentrations after soaking of whole seeds, dehulled seeds and flours of
millet (Lestienne et al., 2007).
Soaking is a simple prolongation of the obligatory washing of the seeds and
also has other advantages, such as facilitating dehulling or swelling of seeds. After
preprocessing, the selected millets were soaked in water. Based on their
morphological characteristics, the finger millet and pearl millet were soaked for
8 hours whereas kodo millet, little millet and foxtail millet were soaked for 6 hours in
ambient temperature. Process of soaking involved in preparation of millet powder is
shown in Plate 2.
Plate 2. Process of soaking involved in preparation of millet powder
3.2.2. Preparation of slurry from processed millets
After soaking process, the water was drained from millets and then it was
ground to fine slurry by using wet grinding techniques. After grinding, the slurry was
filtered using muslin cloth and the filtrate was dehydrated by three different drying
techniques to obtain fine powder. Process involved in preparation of slurry from
processed millets is shown in Plate 3.
Plate 3. Process involved in preparation of slurry from processed millets
3.2.3. Dehydration of slurry
Dehydration is one of the processes of food preservation that completely
remove the water from foods and it is used to increase the shelf life of the products.
The processed foods were dehydrated to remove the moisture content. Further in
present study, the obtained millet slurry was subjected to three types of drying
methods namely sun drying (T0-18 hours), forced convection tray drying
(T1- 60ºC-70°C for 15-16 hours) and freeze drying (T2- –50°C to 30°C for
14-16 hours).
3.2.3.1. Sun Drying
The oldest and traditional methods carried for food preservation is sun drying.
Adequate care is required against contamination and also damage from insects and
birds. The ground millet slurry was subjected to sun drying by covering the slurry
using net so that the sunlight can pass through. However, improper removal of
moisture was observed in sundried powder which limits the shelf life of product.
Millet slurry exposed to sun drying is shown in Plate 4.
Plate 4. Millet slurry exposed to sun drying
3.2.3.2. Forced convection tray drying
In forced convection tray drying, the required moisture content can be attained
by removal of moisture from the slurry up to 2-3%. The temperature was standardized
to 70oC for 12 hours which is highly dependent on the nature of the product. Millet
slurry exposed to forced convection tray drying is shown in Plate 5.
Plate 5. Millet slurry exposed to forced convection tray drying
3.2.3.3. Freeze drying
The process of freeze drying produce excellent structural retention suitable for
high-value products (Flink, 1975). In spite of its high instrumentation cost, it finds
wider application in improving the mass transfer kinetics of foods such as higher
uptake of solutes in shorter period of time, better retention on color, taste and texture
of the products. The physico-chemical, nutritional and sensory traits of the food
products affect with respect to the type of packaging materials used during storage
(Marques et al., 2007).
Plate 6. Millet slurry exposed to freeze drying
The millet slurry were dehydrated using freeze dryer (Model:Del Vac) by
spreading the samples uniformly in the trays and kept inside the chamber where all
the valves are closed and checked under vaccum condition. The low temperature
–50°C to +30oC was applied for a period of 16-18 hours, which facilitates to preserve
the color and texture of the samples through thermostat adjustment. The instrument
work under an automatic mode with respect to vaccum and temperature. As soon as
the drying process is completed, the instrument is switched off and a slow release of
vacuum was ensured. Finally the samples were collected. Millet slurry exposed to
freeze drying is shown in Plate 6.
The dehydrated millet powder obtained from the three drying methods were
packed in aluminium foil laminated LDPE pouches and stored at refrigerator
temperature (4oC) for further analysis and product development. The processed millet
powder packed in the aluminium foil laminated LDPE pouches is shown in Plate 7.
Plate 7. Processed millet powder in LDPE pouch
3.3. Optimization of composite millet powder
After several permutation and combination, equal proportions of millet
powder obtained from the selected millets were optimized to produce the composite
millet powder. The optimization of composite millet powder is given in Table 1.
Table 1. Optimization of composite millet powder (%)
Samples (%)
Sample A - Finger millet (Eleusine coracana ) powder 20
Sample B- Pearl millet (Pennisetum glaucum) powder 20
Sample C- Kodo millet (Paspalum scrobiculatum) powder 20
Sample D- Little millet (Panicum sumatrense) powder 20
Sample E- Foxtail millet (Setaria italica) powder 20
Total 100
The obtained composite millet powder was used for the development of
convenience food.
Selection of raw materials
Finger millet, Pearl millet, Kodo millet, Little millet, Foxtail millet
Washed with water
Kodo millet
Little millet 6 hours
Foxtail millet 8 hrs
Finger millet
Pearl millet 8 hours Soaked
Drained excess water
Ground to fine slurry
Filtered using muslin cloth
Filtrate was dehydrated
1. Sun drying 2. Forced convection tray drying 3. Freeze drying
Figure 1. Process involved in the preparation of millet powder
Millet powder (212 microns)
3.4. Finalized parameters for further analysis and product
development
Millet contains a high amount of protein and a great source of dietary fiber. It
is also a good source of essential amino acids except lysine and threonine but it is
relatively high in methionine, phytochemicals and micronutrients. The sundried
processed millet powder produced off flavor which is considered to be an undesirable
property for development of products. Hence, in-depth analysis was carried out for
composite millet powder obtained from drying methods namely forced convection
tray drying (T1) and freeze drying (T2).
The composite millet powder subjected to FCTD (CM-T1) and FD (CM-T2)
were further utilized for the development of convenience foods namely ready to cook
product (pasta) and ready to eat product (extrudates).
3.5. Process involved in the development of convenience food
Extrusion cooking is a vital processing technique in food production as it is
considered as a proficient manufacturing process (White, 1994). The Food extruders
afford thermo-mechanical and mechanical energy (shear) which is necessary to cause
physicochemical changes of raw materials with an extreme mixing for spreading and
homogenization of ingredients which includes conveying, incorporation, shearing,
heating or cooling, shaping, flavor generation, encapsulation, and sterilization
(Linko et al., 1981,Wiedman and Strobel,1987). The advantage of extruder process is
that it can operate at relatively low temperatures and produce pasta (Harper, 1981). In
the present study, the composite millet powder was used for developing convenience
foods namely ready to cook (pasta) and ready to eat (extrudates) products.
3.5.1. Process involved in formulation of pasta
Pasta is one of the popular products in modern lifestyle because they are
healthy, tasty and convenient for preparation and transportation
(Cubadda, 1994). The pastas in general are developed using refined wheat flour. To
provide nutritious pasta, millets have received the interest for preparation of
diversified and value added food products which are considered to be indigenous and
low cost as well.
The pasta was developed using cold extrusion with single screw extruder
(La Monferrinsrl Model dolly) at a pressure of 400 rpm. Extrusion is a process used to
create objects of a fix cross-sectional profile. A material is pushed or drawn through a
die of the desired cross-section. The process steps involved in formulation of pasta is
shown in Figure 2 and Plate 8.
In the present study, the replacement method was carried out to develop pasta
with the refined wheat flour and composite millet powder as the major raw materials.
After several permutations and combinations with a trial ratio from 10% to 100% of
raw materials, the 70% of composite millet powder and 30% of refined wheat flour
were found to be the acceptable combination for the extrusion of pasta (70:30). Since
millet is gluten free, it is required to incorporate an ingredient which has the binding
property to obtain the desirable color and firm texture during cooking that is
associated with good quality pasta. Therefore, the egg white powder was chosen as an
additional ingredient for making pasta in order to enhance the functional, nutritional
as well sensorial properties. So the pasta was developed by replacing the 15% of egg
white powder in 30% of refined wheat flour (70:15:15). Hence 100% refined wheat
flour serves as the control. The ratio of composite millet powder, refined wheat flour
and egg white powder is given in Table 2.
Table 2. Composition of raw material for formulation of pasta
Raw Material (%) Control CM-T1/CM-T2 CM-T1E/CM-T2E
Processed composite millet powder - 70 70
Refined wheat flour 100 30 15
Egg white powder - - 15
CM-Composite millet powder; T1-Forced convection tray drying; T2-Freeze drying; E- Egg white powder.
Figure 2. Process involved in the formulation of pasta
1. Raw pasta 2. Cooked pasta CM-T1-Pasta prepared using composite millet powder exposed to forced convection tray drying. CM-T2- Pasta prepared
using composite millet powder exposed to freeze drying. CM-T1-E-Pasta prepared with incorporation of egg white powder,
CM-T2-E- Pasta prepared with incorporation of egg white powder.
Plate 8. Pastas obtained from composite millet powder
3.5.2. Process involved in formulation of extrudates
The extrudates are developed using the extrusion cooking process. In the
modern days, millets have received attention among the people. This is mainly because
of their high nutritional properties and health benefits. Efforts are taken under way to
1 2 1 2
1 2 1 2
1 2
Control CM-T1
CM-T2 CM-T1E
CM-T2E
provide it to consumers in convenient forms. The process involved in preparation of
extrudates is shown in Figure 3.
In the present work, the development of extrudates was performed in a
laboratory using high shear twin screw food extruder (syslg30-iv). The temperature of
the barrel of extruder was set at 140°C. Screw speed was set up at 130 r min -1
and
equipped with 3 mm restriction die or nozzle. Constant feeding rate was kept
throughout the experiments. 100% of composite millet powder was taken for the
development of extrudates. Three replicate samples were extruded and dried to about
6% -7% moisture levels. In order to improve the acceptability of the extrudate two
different variations namely spice mix and milk with and without addition of choco mix
were studied. The extrudates obtained from composite millet powder are shown in
Plate 9.
Figure 3. Steps involved in the formulation of extrudates
Plate 9. Extrudates obtained from composite millet powder
Step 3: Extrusion of
the final product
Step 2: Addition of flour (1 Kg)
Step 1: Setting of temperature
and screw speed
Screw speed: 2040 rpm
Temperature: 120-140oC
3.6. Quality analysis of developed convenience food and the powder
After the finalization of processing techniques and the development of
convenience food from composite millet powder, various quality characteristics have
been analyzed in terms of nutritional, physico-chemical, functional and shelf-life as
per standard reference methods as represented in the Table 3.
Table 3. Analysis of quality characteristics of developed composite millet powder
and convenience food
pppp Physical properties References and methods
Buvc Bulk density Okka Akpapunam, M.A. and Markakis, P. (1981)
Fdkfd Swelling power Leach Leach et al,(1959)
Water Water holding capacity (1977 Beuchat (1977)
Foam stability and Foam capacity Naray Narayana and Narasinga rao (1982)
Color Colou Hunter Laboratory Instrument Model CIE, Olajide, (2010)
Cooking time AACC (2005)
Cooking Loss AACC (1976)
Expansion Ratio Chakraborty et al., (2004)
Water absorption and solubility index Hanwu et al., (2005); Kurt et al., (2009)
Morphological structure Scanning electron micrograph
X–ray diffraction pattern X–ray diffractometer
Texture Texture Analyzer, Anton, A.A., and Liciano, F.B. (2007)
Nutritional properties
Energy Bomb Calorimetric method
Carbohydrates Anthrone method and AOAC (1995)
Protein Kjeldhal method and Raghuramalu et al., (2005)
Fat Soxhlet method and Ranganna (2000)
Moisture Hot air oven method and AOAC (1990)
Ash AACC method and AOAC (1999)
Minerals X–ray fluorescence
Functional properties
Protein solubility Araba, M. and N. Dale (1990)
Protein fraction Landry J, Moureaux T (1970)
Protein Digestibility Elkhalil et al.,(2001)
Fatty acids GC–MS, Pharmacopeial forum (2007)
Amino acids HPLC, Pharmacopeial forum (2007)
Vitamins HPLC, Pharmacopeial forum (2007)
Phytochemicals HPLC, Pharmacopeial forum (2007)
Shelf life study
Microbial count Total plate count, Banwart, G. J. (1989)
Sensory analysis 9 point hedonic scale, Meilgaard et al., (2006) References: AOAC. (1995&1999)
3.7. Statistical interpretation of the data
The analyses of physical, chemical, functional, phytochemical and shelf-life
characteristics were done using triplicate samples. The data on the experimental
results were subjected to Analysis of Variance (ANOVA) and differences between
means were assessed by DMRT (Duncan‟s Multiple Range Test) and sensory analysis
was carried out by applying non parametric test using kruskal wallis test with help of
statistical package SPSS (20 version) in order to compare the means and determine
the most acceptable treatment where the means was compared (p≤0.05).
4. RESULTS AND DISCUSSION
The results of the study entitled “Value addition of convenience food using
processed millet powder” are presented and discussed under the following heads.
4.1. Effect of drying methods on the quality characteristics of processed millet powder
4.2. Effect of drying methods on the physic-chemical properties of the composite
millet powder (CM)
4.3. Evaluation of quality characteristics of convenience food developed using
composite millet powder
4.4. Functional characterization of protein in the convenience food developed using
composite millet powder exposed to freeze drying
4.1. Effect of drying methods on the quality characteristics of
processed millet powder
The quality characteristics namely proximate principles, mineral content,
physical properties and microbial analysis were studied for the processed millet powder
and results of the same are discussed below.
4.1.1. Proximate principles of processed millet powder
The proximate principles of the processed millet powder in terms of
carbohydrates (g/100g), protein (g/100g), fat (g/100g), energy (Kcal/100g), ash
(g/100g) and moisture (g/100g) are discussed in the Table 4 and Figure 4.
The proximate principles of the processed millet powder did not show any
effect on the drying methods adopted namely sun drying (T0), forced convection tray
drying (T1) and freeze drying (T2). However, the varying change in the nutritional
profile could be attributed to the natural existence of the nutrients present in the
individual millets as supported by Joshi et al., (2011).
Moisture content of powder is very important for determining the shelf life.
Lesser moisture content will lead to better storage stability. The moisture content of all
the samples subjected to sun drying (T0-10.20% to 12.02%) and freeze drying
(T2-9.17% to 10.30%) was found to be slightly higher (p≤0.05) when compared to
forced convection tray drying (T1-8.13% to 10.30%). The mean increments in the
moisture content of the sundried millet powder could be due to improper removal of
water during drying process and hydroscopic nature of the flour. Similarly the reduction
in moisture content of the T1 samples is due to the temperature (70ºC) maintained
uniformly during the drying process. The findings of the present study goes in par with
the results of King and Parwastin (1987) who stated that higher temperature resulted in
vaporization of water in the flour thereby reducing the moisture content. However on
comparing the moisture content between the millet powders there was not much
significant difference (p>0.05).
The amount of ash present in food indicates a rough estimation of the mineral
content of the product (Fasai Olufunmilayo Sade, 2009). The existence of ash in the
finger millet powder (T0A-2.27, T1A-2.20, T2A-2.20), kodo millet powder (T0C-2.43,
T1C-2.30, T2C-2.63) and foxtail millet powder (T0E-2.37, T1E-2.23, T2E-2.40) was
greater (p≤0.05) thereby their inorganic minerals would also be higher. Whereas the ash
content in pearl millet powder (T0B-1.70, T1B-1.60,T2B-1.80) and little millet powder
(T0D-0.53, T1D-0.83, T2D-0.63) were comparatively lesser due to leaching out of solid
matter during pre-germination and soaking process which could be the reason for
significant reduction (p≤0.05) of mineral content. Further decrease of ash could be due
to dehulling, grinding process and removal of hull. In the present study, the leaching of
ash content in the millet powder was observed during processing namely soaking,
extraction of slurry and dehydration. However, the ash content of processed millet
powder was found to be slightly higher when compared to refined wheat flour and rice
flour hence considered as mineral dense and can be utilized in development of the
products.
Cereals and millets are the richest sources of carbohydrate and serve as
a main source of energy for human being (FAO, 2006). The variation in
carbohydrate content may be attributed due to alteration that had occurred as a result of
soaking and germination. The concentration of carbohydrate in the processed millet
powder exposed to different drying methods were almost found to be similar, however
there exhibited a significant difference (p≤0.05). The carbohydrate content was
significantly higher (p≤0.05) in finger millet powder (T0A-72.60 g/100g,
T1A-72.17 g/100g, T2A-72.67 g/100g), little millet powder (T0D-72.17 g/100g,
T1D-74.30 g/100g, T2D-75.13 g/100g) and foxtail millet powder (T0E-72.10 g/100g,
T1E-74.30 g/100g, T2E-75.33 g/100g). The increase in carbohydrate content is due to
presence of starch and free sugars, cellulose and pentosans in the selected millet
powder. Least concentration of carbohydrate content was observed in the kodo millet
powder (T0C-56.0 g/100g, T1C-58.03 g/100g, T2C-58.27 g/100g) and pearl millet
powder (T0B-65.03 g/100g, T1B-64.03 g/100g, T2B-71.20 g/100g). According to Ross
Brand (1987), the composition of carbohydrates was found to be 69% in millet and
maize comprising of complex carbohydrates. Moreover, high GI value was found in
white rice (87) and extruded wheat flour products (80) whereas the glycemic index
reponses was lesser in the millet flour due to the presence of complex carbohydrates
(Foster-Powell et al., 2002).
Table 4. Proximate principles of processed millet powder
Proximate
principles
Treatments Sample
p -
value A B C D E
Moisture
(g/100)
T0 12.02 ± 0.03 11.02± 0.02 10.30 ± 0.20 10.20 ± 0.20 11.10 ± 0.10
p≤0.05*
T1 10.30 ± 0.20 9.43 ± 0.25 8.37 ± 0.31 8.13 ± 0.15 9.40 ± 0.30
T2 10.37 ± 0.25 9.17 ± 0.21 9.17 ± 0.21 9.23 ± 0.15 10.17 ± 0.21
p-value p≤0.05* p≤0.05
* p≤0.05
* p≤0.05
* p≤0.05
*
Ash (g/100)
T0 2.27 ± 0.15 1.70 ± 0.20 2.43 ± 0.25 0.53 ± 0.31 2.37 ± 0.25
p≤0.05*
T1 2.20 ± 0.20 1.60 ± 0.20 2.30 ± 0.20 0.83 ± 0.02 2.23 ± 0.25
T2 2.20 ± 0.20 1.80 ± 0.20 2.63 ± 0.25 0.63 ± 0.25 2.40 ± 0.20
p-value p≤0.05* p>0.05
NS p≤0.05
* p≤0.05
* p≤0.05
*
Carbohydrates
(g/100)
T0 72.60 ± 0.20 65.03±0.03 56.00±0.20 72.17±0.21 72.10±0.10
p≤0.05*
T1 72.17 ± 0.21 64.03 ± 0.03 58.03 ± 0.15 74.30±0.20 74.30±0.20
T2 72.67±0.55 71.20 ± 0.02 58.27±0.25 75.13±0.25 75.33±0.31
p-value p≤0.05* p>0.05
* p≤0.05
* p≤0.05
* p>0.05
*
Protein (g/100)
T0 10.28 ± 0.45 10.11 ± 0.09 9.85 ± 0.03 9.47 ± 0.21 10.28 ± 0.23
p≤0.05*
T1 9.81 ± 0.02 10.05 ± 0.03 9.67 ± 0.06 9.50 ± 0.20 10.10 ± 0.10
T2 10.14 ± 0.02 10.21 ± 0.03 9.76 ± 0.02 9.57 ± 0.15 10.60 ± 0.02
p-value p≤0.05* p>0.05
* p≤0.05
* p≤0.05
* p≤0.05
*
Fat (g/100)
T0 1.92 ± 0.02 6.67 ± 0.25 3.94 ± 0.12 2.77 ± 0.66 3.03 ± 0.72
p≤0.05*
T1 1.47 ± 0.15 5.20 ± 0.20 3.70 ± 0.20 3.10 ± 0.20 3.13 ± 0.15
T2 1.40 ± 0.20 5.20 ± 0.20 4.20 ± 0.20 3.07 ± 0.21 3.02 ± 0.03
p-value
p≤0.05* p≤0.05
* p≤0.05
* p>0.05
* p>0.05
*
Energy(K/cal)
T0 352 ± 2.00 353 ± 3.06 322± 2.08 293 ± 2.52 323± 2.52
p≤0.05*
T1 352 ± 2.08 334± 3.61 321 ± 3.22 287± 2.00 314± 2.00
T2 355 ± 2.52 355 ± 1.53 323 ± 2.52 295± 2.52 323± 2.52
p-value p≤0.05* p≤0.05
* p≤0.05
* p≤0.05
* p≤0.05
*
All values are means of triplicate determinations ± standard deviation (S.D); SD-Sun Drying (T0),
FCTD-Forced Convection Tray Drying (T1), FD-Freeze Drying (T2). Sample A-Finger millet powder, Sample B-Pearl millet powder, Sample C-Kodo millet powder, Sample D-Little millet powder,
Sample E-Foxtail millet powder.* Significantly different (p≤0.05) by ANOVA, NS- Not Significant.
The protein is considered to be the second major component in the millets.
The protein content was observed to be maximum in pearl millet powder
(T0B-10.11 g/100g, T1B,-10.05 g/100g, T2B-10.21 g/100g) and foxtail millet powder
(T0E-10.28 g/100g, T1E-10.10 g/100g, T2E-10.60 g/100g) and minimum in little
millet powder (T0D-9.47 g/100g, T1D-9.50 g/100g, T2D-9.57 g/100g). The protein
content of processed millet powder obtained from different drying techniques was
found to be increased significantly when compared to refined flour (10g/100g). The
quality of protein was found to be higher in the minor millets when compared to the
major millet (Kalinova and Moudry, 2006). The protein loss may be ascribed due to
the removal of hull and elimination of some of the protein rich aleurone cells during
processing (Abdalla et al., 1998). However on comparing the dehydration methods,
the protein content was found to slightly decline in the millet slurry subjected to
forced convection tray drying than sun drying and freeze drying. Perera(2005)
reported that during drying process, the protein present in food undergoes oxidation
reactions which cause protein loss and changes in color, texture, taste and flavor of
foods.
Crude fat provides the essential fatty acids (EFA) that cannot be synthesized in
the body. The cereal grains are generally considered to be negligible in fat content.
However pearl millet powder posses slightly higher amount
(T0B-6.67 g/100g, T1B-5.20 g/100g, T2B-5.20 g/100g) of fat when compared with the
other millet powders such as finger millet powder (T0A-1.92 g/100g, T1A-1.47
g/100g, T2A-1.40 g/100g), kodo millet powder (T0C-3.94, T1C-3.70, T2C-4.20), little
millet powder (T0D-2.77 g/100g, T1D-3.10 g/100g, T2D-3.07 g/100g) and foxtail
millet powder (T0E-3.03 g/100g, T1E-3.13 g/100g, T2E-3.02 g/100g). Among the
millets, the pearl millet posses higher fat content due to presence of unsaturated fatty
acids in germ layer thereby increasing the concentration of fat to about
1.5%-6.8% (Abdelrahman, Hoseney and varriano-Marston, 2005; Taylor, 2004).
The energy content is the reflection of the presence of carbohydrate, protein
and fat. In the present study, the energy values were found to be more or less similar
in all the processed millet powder ranging from 293 kcal to 355 kcal and it is greater
than recommendation of WHO (2003) for an infant complementary food in
developing countries which range from 200 to 300 kcal/day. The results revealed
that the drying methods adopted did not show any significant difference (p≥0.05)
among the selected millet powders.
Sun drying (T0)
Forced convection tray drying (T1)
Freeze drying (T2)
Figure 4. Proximate principles of processed millet powder
0
2
4
6
8
10
12
14
A B C D E
(g
/ 1
00
g)
Samples
Moisture (g/100g)
0
0.5
1
1.5
2
2.5
3
A B C D E
(g
/10
0g
)
Samples
Ash (g/100g)
0
20
40
60
80
100
A B C D E
(g/1
00
g)
Samples
Carbohydrate (g/100g)
0
2
4
6
8
10
12
A B C D E
(g/1
00
g)
Samples
Protein (g/100g)
0
1
2
3
4
5
6
7
8
A B C D E
(g/1
00
g)
Samples
Fat (g/100g)
0
50
100
150
200
250
300
350
400
A B C D E
(K
/ca
l)/1
00
g
Samples
Energy (K/cal)
4.1.2. Mineral content of the processed millet powder
The total mineral (ash) content of all millets is often higher
(Klopfenstein et al., 1995). Mardia et al., (2002) reported that dehulling of the seeds
significantly reduced the dry matter and especially ash content of the seeds of millet
cultivars. The concentrations of minerals in sample increased upon soaking and
germination (Sushma et al., 2008). It was also observed that minor millets
quantitatively provide more total minerals than the common cereals like maize,
sorghum, rice and wheat with a range of 0.6 to 2.5 per cent (Narasing Rao, 1992).
The minerals namely calcium, phosphorus, iron, magnesium and zinc were
studied for the processed millet powder and results of the same are discussed below in
Table 5 and Figure 5.
The calcium content of all the millet powder subjected to freeze drying
was in the range of 8.60mg/100g-212.93mg/100g which was higher (p≤0.05) when
compared with other drying methods adopted (T0-8.43-211.83mg/100g and
T18.10-211.00 mg/100g). Among different samples, calcium content of finger millet
powder (Sample A-211.00-212.93 mg/100g) was found to be the highest when
compared to other samples. The presence of calcium in finger millet powder
(Sample A) shows the abundant nature of mineral present. The results were in
accordance with the findings of Bhatt, Singh, Shrotria and Baskheti (2003) who
stated that among the cereals, the finger millet has the highest calcium content
(344 mg/100g). The minimal losses in calcium content of other minor millets may
be due to leaching of mineral during soaking (Singh et al., 2006).
The phosphorus content of all the samples subjected to different drying
methods was in the range of 121.67-179.77 mg/100g in sample subjected to sun
drying, 120.0-182.00 mg/100g in sample subjected to forced convection tray drying
and 125.20 - 183.33 mg/100g in sample subjected to freeze drying. However slight
increase in phosphorus content was noted in all samples subjected to freeze drying
(T2) which was significant at p≤0.05 when compared to other two drying methods.
The slight reduction in phosphorus content was observed in the samples exposed to
forced convection tray drying. The reduction in the mineral content could be
attributed due to heating of millets at high temperature. There existed a significance
difference (p≤0.05) between the samples and drying method adopted.
The iron content of the sample subjected to different drying methods namely
sun drying (T0), forced convection tray drying (T1) and freeze drying (T2) was in the
range of 0.13-9.27 mg/100g, 0.13-9.30 mg/100g and 0.57-9.43 mg/100g
respectively. Among the processed samples, the little millet powder (sample D)
possess high iron content (p≤0.05) when compared to other samples due to natural
existence of iron present and thereby soaking and germination which significantly
improves and enhanced the bioavailability of iron and zinc (Afify et al., 2011a).
The magnesium content of the samples were in the range of
78.13-101.33 mg/100g in T0 samples, 76.40 - 99.80 mg/100g in T1 samples and
78.93-101.70 mg/100g in T2 samples respectively which showed a significant
difference at p≤0.05 to all the samples exposed to different drying methods.
Magnesium has been revealed to be capable of reducing the severity of asthma and
the frequency of migraine attack as well as lowering the high blood pressure
(Ensminger et al., 1986).
In the present study, a significant increment of zinc content was noted in
freeze dried samples (T2) than forced convection tray dried (T1) and sun dried (T0)
samples which is highly dependent on the heat maintained during processing of
powder. The analysis of variance of processing on zinc content of the selected millet
powder revealed significant effects (p≤0.05) during drying.
The potassium content of all the selected samples subjected to different
drying methods namely sun drying (T0), forced convection tray drying (T1) and
freeze drying (T2) was in the range of 97.17-242.67 mg/100g, 97.67-243.33
mg/100g and 98.00 - 246.33 mg/100g respectively. The potassium content of all
the samples subjected to sun drying (T0), forced convection tray drying (T1) and
freeze drying (T2) were observed to be slightly varied which showed a significant
difference at p≤0.05. However higher potassium content was noted in finger millet
(Sample A) exposed to freeze drying (246.33 mg/100g) which showed significant
difference at p≤0.05 when compared to other samples. It has been observed that
finger millet is the richest sources of potassium, magnesium, phosphorus and
calcium (Obilana and Manyasa, 2002).
Table 5. Mineral (mg/100g) content of processed millet powder
Mineral content Treatments Samples
p -value A B C D E
Calcium
(mg/100g)
T0 211.83 ± 1.27 31.07 ± 0.91 20.90 ± 0.27 8.43 ± 0.25 25.23 ± 0.21
p≤0.05* T1 211.00 ± 1.00 29.87 ± 0.21 19.77 ± 0.21 8.10 ± 0.10 24.83 ± 0.15
T2 212.93 ± 0.32 31.50 ± 0.27 22.23 ± 0.59 8.60 ± 0.44 25.60 ± 0.44
p-value p≤0.05*
Phosphorus
(mg/100g)
T0 179.77 ± 0.21 133.00 ± 1.00 121.67 ± 2.08 162.00 ± 2.00 170.47 ± 0.42
p≤0.05* T1 182.00 ± 2.00 130.13 ± 0.15 120.13 ± 0.15 162.93 ± 0.15 169.07 ± 0.15
T2 183.33 ± 1.53 134.70 ± 0.62 125.20 ± 0.53 165.20 ± 0.20 170.87 ± 0.76
p-value p≤0.05*
Iron
(mg/100g)
T0 2.67 ± 0.15 6.13 ± 0.15 0.13 ± 0.06 9.27 ± 0.06 1.63 ± 0.15
p≤0.05* T1 2.63 ± 0.06 6.13 ± 0.15 0.13 ± 0.06 9.30 ± 0.10 1.30 ± 0.10
T2 2.57 ± 0.15 6.50 ± 0.36 0.57 ± 0.25 9.43 ± 0.15 1.80 ± 0.10
p-value p≤0.05*
Magnesium
(mg/100g)
T0 97.13 ± 0.15 99.00 ± 0.70 93.13 ± 0.15 101.33 ± 0.21 78.13 ± 0.15
p≤0.05* T1 96.43 ± 0.25 96.43 ± 0.25 92.93 ± 0.12 99.80 ± 1.13 76.40 ± 0.20
T2 97.63 ± 0.57 99.40 ± 0.20 93.60 ± 0.20 101.70 ± 0.10 78.93 ± 0.15
p-value p≤0.05*
Zinc
(mg/100g)
T0 0.90 ± 0.10 1.30 ± 0.52 0.90 ± 0.10 0.90 ± 0.10 0.20 ± 0.10
p≤0.05* T1 1.13 ± 0.15 0.13 ± 0.06 1.40 ± 0.20 1.40 ± 0.20 0.57 ± 0.15
T2 1.40± 0.10 1.73 ± 0.15 1.83 ± 0.06 0.43± 0.15 0.90 ± 0.10
p-value p≤0.05*
Potassium
(mg/100g)
T0 242.67 ± 1.53 209.33 ± 0.57 97.17 ± 0.15 98.10 ± 0.10 121.07 ± 0.25
p≤0.05* T1 243.33 ± 1.53 211.67 ± 1.53 97.67 ± 0.58 98.00 ± 1.00 122.67 ± 2.52
T2 246.33 ± 1.53 215.00 ± 1.00 98.00 ± 1.00 99.57 ± 0.25 123.00 ± 2.00
p-value p≤0.05*
All values are means of triplicate determinations ± standard deviation (S.D); SD-Sun Drying (T0), FCTD-Forced Convection Tray Drying (T1), FD-Freeze Drying (T2). Sample A-Finger millet
powder, Sample B-Pearl millet powder, Sample C-Kodo millet powder, Sample D-Little millet powder, Sample E-Foxtail millet powder. * Significantly different (p≤0.05) by ANOVA.
Sun drying (T0)
Forced convection tray drying (T1)
Freeze drying (T2)
Figure 5. Mineral content of processed millet powder
0
50
100
150
200
250
A B C D E
(mg
/10
0g
)
Samples
Calcium (mg/100g)
0
50
100
150
200
250
A B C D E
(m
g/1
10
0g
)
Samples
Phosphorus (mg/100g)
0
2
4
6
8
10
12
A B C D E
(mg
/10
0g
)
Samples
Iron (mg/100g)
0
0.5
1
1.5
2
2.5
A B C D E
(m
g/1
00
g)
Samples
Zinc (mg/100g)
0
50
100
150
200
250
300
A B C D E
(m
g/1
00
g)
Samples
Pottasium (mg/100g)
0
20
40
60
80
100
120
A B C D E
(mg
/10
0g
)
Samples
Magnesium (mg/100g)
4.1.3. Physical properties of the processed millet powder
4.1.3.1. Bulk density (g/cm3) of the processed millet powder
Table 6 and Figure 6 depicts the bulk density of the processed millet powder.
Table 6. Bulk density (g/cm3) of the processed millet powder
Samples SD (T0) FCTD (T1) F D(T2) p-value
A 0.55 ± 0.01 0.66 ± 0.01 0.61 ± 0.02
p≤0.05*
B 0.70 ± 0.01 0.62 ± 0.01 0.72 ± 0.01
C 1.01 ± 0.01 1.03 ± 0.01 0.94 ± 0.01
D 0.98 ± 0.01 0.95 ± 0.01 0.92 ± 0.01
E 0.97 ± 0.01 0.94 ± 0.01 0.84 ± 0.01
p-value p≤0.05*
All values are means of triplicate determinations± standard deviation (S.D), SD-Sun Drying (T0),
FCTD-Forced Convection Tray Drying (T1), FD-Freeze Drying (T2). Sample A-Finger millet powder,
Sample B-Pearl millet powder, Sample C-Kodo millet powder, Sample D-Little millet powder, Sample E-Foxtail millet
powder, * Significantly different (p≤0.05) by ANOVA.
Bulk density is a measure of heaviness and porosity of a flour sample. This
influences package design and could be used in determining the type of packaging
material required and application in wet processing in the food industry
(Iwe and Onalope, 2001).
The bulk density of kodo millet powder (Sample T0C-1.01 g/cm3,
T1C-1.03 g/cm3, T2C-0.94 g/cm
3), little millet powder (T0D-0.98 g/cm
3, T1D-0.95
g/cm3, T2D-0.92 g/cm
3) and foxtail millet powder (T0E-0.97 g/cm
3, T1E-0.94 g/cm
3,
T2E-0.84 g/cm3) exposed to different drying methods were found to be slightly higher
when compared to finger millet powder (T0A-0.55 g/cm3, T1A-0.66 g/cm
3,
T2A-0.61 g/cm3) and pearl millet powder (T0B-0.70 g/cm
3, T1B-0.62 g/cm
3,
T2B-0.72 g/cm3). This may be due to high amount of small sized particle found in
millet flour and greater starch content. The bulk density (g/cm3)of all the samples
subjected to sun drying (T0), forced convection tray drying (T1) and freeze drying (T2)
range between 0.55 to 1.01 g/cm3, 0.62 to 1.03 g/cm
3 and 0.61 to 0.94 g/cm
3
respectively. There was a slight decrease (p≤0.05) in the bulk density of the sun dried
samples when compared to the other two drying methods. The decrease in bulk
density may be associated with the extent of starch gelatinization and the destruction
of crystalline structure. High Bulk density is a desirable characteristic for powdered
food materials of high nutrient content packed in a limited space (Hassan et al., 2013).
Hence, the processed millet powder subjected to forced convection tray drying and
freeze drying possess slightly higher bulk density which would be beneficial for
development of convenience foods.
4.1.3.2. Swelling power (%) of the processed millet powder
The Table 7 and Figure 6 depict the swelling index of the processed millet powder.
Table 7. Swelling power (%) of the processed millet powder
Samples SD (T0) FCTD (T1) FD (T2) p-value
A 8.31 ± 0.01 6.28 ± 0.01 7.03 ± 0.01
p≤0.05*
B 9.03 ± 0.01 7.11 ± 0.01 9.31 ± 0.01
C 7.06 ± 0.01 9.37 ± 0.01 9.54 ± 0.01
D 7.16 ± 0.01 8.83 ± 0.01 9.27 ± 0.01
E 7.47 ± 0.01 9.53 ± 0.01 9.34 ± 0.01
p-value p≤0.05*
All values are means of triplicate determinations± standard deviation (S.D), SD-Sun Drying (T0),
FCTD-Forced Convection Tray Drying (T1), FD-Freeze Drying (T2). Sample A-Finger millet powder,
Sample B-Pearl millet powder, Sample C-Kodo millet powder, Sample D-Little millet powder, Sample E-Foxtail millet
powder, * Significantly different (p≤0.05) by ANOVA.
Swelling pattern of the flour suggests the level of crystalline packing of the
starch granules present in the flour (Billiadaris, 1982). In flour granules the swelling
power is the indication of the extent of associative forces within the granules
(Moorthy et al., 1986).
The swelling power (%) of processed millet powder was almost similar and
there was not much significant difference between the processed millet powder. The
swelling power of millet powder subjected to sun drying (T0), forced convection tray
drying (T1) and freeze drying (T2) range from 7.06 to 9 .03%, 6.28 to 9.53% and 7.03
to 9.54 % respectively. Among the drying method adopted, there was a slight decrease
in the level of swelling power in the sun dried samples. The alteration in the swelling
power is observed due to the starch content (amylose and amylopecin chains) in the
processed millet powder. The difference in the swelling power indicates the degree of
exposure of the internal structure of the starch present in the flour to the action of
water (Ruales, 1993). Moreover, the swelling capacity of flours depends on size of
particles, variety of flour and type of processing methods adopted. As per literature,
the flour of parboiled rice and millet has more swelling capacity which contributes to
the quality of product in terms of uniform texture and expansion of better disperability
and solubility.
4.1.3.3. Foam capacity (ml/g) and foam stability (ml/g) of the processed millet
powder
The Table 8 (a, b) and Figure 6 depicts the foam capacity (ml) and foam
stability of the processed millet powder.
Table 8a. Foam capacity (ml/g) of the processed millet powder
Samples SD (T0) FCTD (T1) FD (T2) p-value
A 38.27 ± 0.06 37.33 ± 0.01 40.46 ± 0.01
p≤0.05*
B 39.03 ± 0.06 36.96 ± 0.01 39.47 ± 0.01
C 34.47 ± 0.12 32.07 ± 0.01 35.30 ± 0.10
D 35.02 ± 0.01 35.10 ± 0.06 36.13 ± 0.01
E 40.13 ± 0.06 38.36 ± 0.01 41.18 ± 0.01
p-value p≤0.05*
All values are means of triplicate determinations ± standard deviation (S.D), SD-Sun Drying (T0),
FCTD-Forced Convection Tray Drying (T1), FD-Freeze Drying (T2). Sample A-Finger millet powder,
Sample B-Pearl millet powder, Sample C-Kodo millet powder, Sample D-little millet powder, Sample E-Foxtail millet
powder, * Significantly different (p≤0.05) by ANOVA.
Table 8b. Foam stability (ml/g) of the processed millet powder
Samples SD (T0) FCTD (T1) FD (T2) p-value
A 27.33 ± 0.06 26.23 ± 0.06 29.67 ± 0.15
p≤0.05*
B 32.13 ± 0.01 33.33 ± 0.01 38.22 ± 0.01
C 35.13 ± 0.01 36.23 ± 0.06 39.21 ± 0.01
D 29.13 ± 0.01 28.14 ± 0.01 33.57 ± 0.06
E 32.26 ± 0.02 31.17 ± 0.06 30.60 ± 0.10
p-value p≤0.05*
All values are means of triplicate determinations ± standard deviation (S.D), SD-Sun Drying (T0), FCTD-
Forced Convection Tray Drying (T1), FD-Freeze Drying (T2). Sample A-Finger millet powder, Sample B-Pearl millet
powder, Sample C-Kodo millet powder, Sample D-Little millet powder, Sample E-Foxtail millet powder. * Significantly
different (p≤0.05) by ANOVA.
The development of protein based foam involves the diffusion of soluble
protein towards the air water interface and the rapid conformational change and
rearrangement at the interface. For the stable foam formation it requires thick,
cohesive and viscoelastic film around each gas bubble (Kinsella, 1979). Among the
processed millet powder, finger millet powder (Sample A), pearl millet powder
(Sample B) and foxtail millet powder (Sample E) had the highest foam capacity
ranging from 38.27 to 40.13 ml/g, 36.96 to 38.36 ml/g, 39.47 to 41.18 ml/g
respectively when compared to kodo millet powder (Sample C: 32.07 to 35.30 ml/g)
and little millet powder (Sample D: 35.02 to 36.13 ml/g). The reason being denser
concentration of protein. However, on comparing the drying methods, freeze dried
samples had slightly increased foam capacity when compared to other two drying
methods. Akubor and Badifu et al, (2012) observed that the thermal processing
decreased the foam capacity of the flour. Application of heat treatment reduced
solubility of nitrogen proteins by denaturation and reduced their foaming capacity
(Akubor and Eze, 2012; Sathe et al., 1982).
Foam formation and foam stability are determinants of the type of protein, pH,
processing methods, viscosity and surface tension. Foam stability is affected by
protein denaturation, with native protein giving higher foam stability than denatured
proteins (Sosulski et al., 1976; Sathe et al., 1982). Foams are used to improve texture,
consistency and appearance of foods. All the treated flours may find applications in
bakery and confectionery products. The results of foam stability was found to be more
or less similar in all the selected millet powder as there was greatest stability due to
increased thickness of interfacial films. The foam capacity and stability was found to
be higher in the millet powder when compared to rice flour which is mainly due to its
natural existence of protein present in the millets.
4.1.3.4. Water absorption capacity (ml/g) of the processed millet powder
The Table 9 and Figure 6 depicts the water absorption capacity (ml/g) of the
processed millet powder.
Table 9. Water absorption capacity (ml/g) of the processed millet powder
Samples SD (T0) FCTD (T1) FD (T2) p-value
A 0.86 ± 0.01 0.75 ± 0.01 0.91 ± 0.01
p≤0.05*
B 0.82 ± 0.01 0.84 ± 0.01 0.81 ± 0.01
C 1.24 ± 0.01 1.21 ± 0.01 1.26 ± 0.01
D 0.63 ± 0.01 0.57 ± 0.01 0.75 ± 0.01
E 1.23 ± 0.01 1.21 ± 0.01 1.24 ± 0.01
p-value p≤0.05*
All values are means of triplicate determinations ± standard deviation (S.D), SD-Sun Drying (T0),
FCTD-Forced Convection Tray Drying (T1), FD-Freeze Drying(T2). Sample A-Finger millet powder,
Sample B-Pearl millet powder, Sample C-Kodo millet powder, Sample D-Little millet powder, Sample E-Foxtail millet
powder. *Significantly different (p≤0.05) by ANOVA.
The water absorption is dependent mainly on the nature of hydrophilic
constituents and protein to some extent on the pH
(Onimawo and Akubor, 2012). The highest water absorption capacity was found in
freeze dried millet powder (T2) when compared to sun dried (T0) and forced
convection tray dried powders (T1). The analysis of variance showed significant effect
(p≤0.05) on the water absorption capacity during drying process. Among the samples,
the kodo millet powder (Sample C: 1.21-1.26 ml/g) and foxtail millet powder
(Sample E :1.21 - 1.24 ml/g) showed significantly higher water absorption capacity
(p≤0.05) when compared to other millet powder namely finger millet powder
(Sample A- 0.75 to 0.91 ml/g), pearl millet powder (Sample B-0.81 to 0.84 ml/g) and
little millet powder (Sample D-0.57 to 0.75 ml/g) which may be due to nature of
starch and possible contribution of water absorption by the cell wall materials which
was not completely removed. The highest WAC could be attributed due to the
presence of greater amount of carbohydrates (starch) and fiber present in the
powder. During heating, gelatinization of carbohydrates and swelling of crude fiber
may have enhanced the water absorption. Water absorption capacity describes the
water association of the flour with the limited amount of water present. The rice flour
and processed millet powder does not contain fiber, hence similar water absorption
was observed however both posses good amount of starch which would also helps in
enhancing the water absorption (Adeyeye and Aye, 2005). Millets starch show
higher water binding capacity and gelatinization temperatures than the wheat
starch (Leach et al., 1959).
Sun drying (T0)
Forced convection tray drying (T1)
Freeze drying (T2)
Figure 6. Physical properties of processed millet powder
0
0.2
0.4
0.6
0.8
1
1.2
A B C D E
(g/m
l)
Samples
Bulk density (g/ml)
0
2
4
6
8
10
12
A B C D E
(%)
Samples
Swelling power (%/g)
05
101520253035404550
A B C D E
(ml/
g)
Samples
Foam capacity (ml/g)
0
5
10
15
20
25
30
35
40
45
A B C D E
(ml/
g)
Samples
Foam stability (ml/g)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
A B C D E
(ml/
g)
Samples
Water absorption capacity (ml/g)
4.1.3.5. Color values of the processed millet powder
The Table 10 and Figure 7 reveal the color values of the processed millet
powder.
Color is an important quality parameter in foods. The units within the L*, a*
and b* system gives equal perception of the color difference to a human observer. The
L* measures the brightness (lightness) from black (0) to white (100). The a* is the
measure of function of difference in the red-green where positive a* indicates redness
and negative a* indicates greenness. The b* is the function of the green blue
difference, where positive values indicates the yellowness and negative values
represent the blueness. During processing, the color of the seed coat in grains were
changed while grinding which eventually resulted in alteration of the L*, a* and b*
values.
The L*(lightness) was observed to be higher in kodo millet powder
(T0C-88.26, T1C-91.32, T2C-87.75), little millet powder (T0D-87.55, T1D-92.16,
T2D-89.85) and foxtail millet powder (T0E-91.14, T1E-88.52, T2E- 86.85). When
compared with the other millet powders namely finger millet powder (Sample A) and
pearl millet powder (Sample B). This could be due to natural color present in the
processed millets.
The a* (greenish-red) was found to be higher (p≤0.05) in finger millet powder
(T0A-3.42, T1A-2.52, T2A-2.51) and pearl millet powder (T0B-1.76, T1B-1.41,
T2B-0.11). This was due to the presence of seed coat that was found to be more
towards the red and green shades. In the case of b* (blue-yellowish) values, pearl
millet powder subjected to sun drying (T0) was observed to be 12.45 followed by the
sample subjected to forced convection tray drying (T1) was 11.83 and freeze drying
(T2) was 12.13. The b* value of foxtail millet powder (T0E-8.92, T1E-10.34 and
T2E-9.76) powder were observed to be higher (p≤0.05) which might be due to the
presence of yellow color in the millet. During the process of heat, the overall color
change takes places due to maillard reaction (Ibanoglu, 2002).
Table 10. Color values of the processed millet powder
Color
Values Samples SD (T0) FCTD (T1) FD (T2) p-value
L*
A 82.43 ± 0.03 85.17 ± 0.02 82.43 ± 0.03
p≤0.05*
B 78.41 ± 0.02 81.53 ± 0.02 81.02 ± 0.02
C 88.26 ± 0.02 91.32 ± 0.02 87.75 ± 0.03
D 87.55 ± 0.03 92.16 ± 0.02 89.85 ± 0.05
E 91.14 ± 0.02 88.53 ± 0.02 86.85 ± 0.02
p-value p≤0.05*
a*
A 3.42 ± 0.03 2.52 ± 0.02 2.51 ± 0.02
p≤0.05*
B 1.76 ± 0.02 1.41 ± 0.01 0.11 ± 0.01
C 1.18 ± 0.02 0.12 ± 0.01 0.21 ± 0.02
D 0.55 ± 0.03 0.07 ± 0.02 0.26 ± 0.02
E 0.10 ± 0.01 0.32 ± 0.02 0.21 ± 0.02
p-value p≤0.05*
b*
A 11.04 ± 0.04 9.21 ± 0.02 8.33 ± 0.02
p≤0.05*
B 12.45 ± 0.03 11.83 ± 0.02 12.13 ± 0.02
C 7.463 ± 0.03 6.84 ± 0.02 6.62 ± 0.02
D 8.43 ± 0.02 5.43 ± 0.02 7.94 ± 0.02
E 8.92 ± 0.02 10.34 ± 0.02 9.76 ± 0.02
p-value p≤0.05*
All values are means of triplicate determinations ± standard deviation (S.D), SD-Sun Drying (T0),
FCTD- Forced Convection Tray Drying (T1), FD -Freeze Drying (T2). Sample A-Finger millet powder,
Sample B-Pearl millet powder, Sample C-Kodo millet powder, Sample D-Little millet powder, Sample E-Foxtail millet
powder. * Significantly different (p≤0.05) by ANOVA.
\
Sun drying (T0)
Forced convection tray drying (T1)
Freeze drying (T2)
Figure 7. Color values of processed millet powder
0
100
200
A B C D E
L*
Samples
L* values of processed millet
powder
0
2
4
A B C D E
a*
Samples
a*values of processed millet
powder
0
5
10
15
A B C D E
b*
Samples
b* values of processed millet powder
4.1.3.6. Total microbial count (cfu/g) of the processed millet powder
Table 11 explains the total microbial count of the processed millet powder.
Table 11. Total microbial count (cfu/g) of processed millet powder
Samples T0 T1 T2
A 1.7x102 1.2x10
2 1.4x10
2
B 1.6x102 1.4x10
2 1.6x10
2
C 1.7x102 1.2x10
2 1.4x10
2
D 1.5x102 1.1x10
2 1.3x10
2
E 1.3x102 1.0x10
2 1.1x10
2
T0-Millet powder exposed to Sun Drying, T1- millet powder exposed to forced convection tray drying,
T2-Millet powder exposed to freeze drying. Sample A-Finger millet powder, Sample B-Pearl millet powder,
Sample C-Kodo millet powder, Sample D-Little millet powder, Sample E-Foxtail millet powder.
Microbial load of the processed millet powder obtained from different drying
methods were done using aerobic plate count. The aerobic plate count of the
processed millet powder subjected to sun drying showed maximum colony forming
unit (cfu/g) than freeze drying and forced convection tray drying methods. The results
showed that the products which were exposed to natural environments (sun drying)
were easily contaminated but under the oven drying chamber, the products were
covered and therefore were protected to some extent from contamination.
Draft Kenya standard (2009) reported that the maximum permissible level of TVC is
105 per gram and Y& M count is 10
4 per gram. In the present study the total microbial
count of processed millet powder was well within the permissible level
(102 per gram). Compaore et al., (2011) observed nil growth of coliform in pearl
millet and maize based composite flour subjected to forced convection tray drying.
4.2. Effect of drying methods on the physicochemical properties of
the composite millet powder (CM)
After several permutation and combination 20% of the different processed
millet powders were optimized and finalized to produce the composite millet powder.
The ratio of optimized composite millet powder is given in table 1. As far as the
drying methods are concerned, sun drying was removed as it produced off flavor
which is considered to be an undesirable property for development of products.
Hence, in-depth analysis was carried out for composite millet powder (CM) obtained
from forced convection tray drying (T1) and freeze drying (T2).
4.2.1. Physico-chemical properties of composite millet powder
The physico-chemical properties of composite millet powder were carried out
in terms of nutritional properties, physical properties and microbial analysis.
Table 12. Physico-chemical properties of composite millet powder
Physico-chemical properties CM-T1 CM-T2 p-values
Nutritional properties
Moisture (g) 8.53±0.41 10.50±0.30 p≤0.05*
Ash (g) 3.27±0.25 3.47±0.25 p≤0.05*
Carbohydrate (g) 76.03±0.02 76.21±0.02 p≤0.05*
Protein (g) 11.90±0.01 11.82±0.02 p>0.05NS
Fat (g) 3.30±0.20 3.43±0.25 p>0.05NS
Energy (Kcal) 362±2.52 363±2.00 p>0.05NS
Mineral content
Calcium (mg) 74.93±0.25 79.27±0.76
p≤0.05*
Phosphorus (mg) 163.13±0.15 168.13±0.83
Iron (mg) 1.20±0.20 2.03±0.15
Magnesium (mg) 99.70±0.58 111.83±0.47
Zinc (mg) 1.37±0.15 1.27±0.06
Pottasium (mg) 150.43±0.59 151.27±0.15
Physical properties
Bulk Density (g/ml) 0.62±0.01 0.62±0.01
p≤0.05* Swelling Index (%) 9.62±0.01 9.33±0.01
Foam capacity (ml) 41.17±0.06 45.53±0.01 p>0.05*
Foam Stability (ml) 36.3±0.06 39.23±0.01 p≤0.05*
Water absorption capacity (ml) 1.7±0.01 1.7±0.01 p≤0.05*
Microbial count 1.1X102 1.6X10
2
All values are means of triplicate determinations ± standard deviation (S.D); CM-T1- Composite millet powder
exposed to Forced convection tray drying, CM- T2 –Composite millet powder exposed to Freeze drying.
* Significantly different (p≤0.05) by ANOVA, NS-Not significant.
As far as the moisture content is concerned, the composite millet powder
subjected to forced convection tray drying (CM-T1) was found to be slightly lower
when compared to freeze drying (CM-T2). Sanni et al., (2006) reported that lower
the moisture content of a product better the shelf stability of such products. Since
moisture content of ingredients affects gelatinization process, lower moisture
content indicates better gelatinization process (Miller, 1985 and Santosa et al., 2005)
which further results in better swelling of the extrudate (Foubion et al., 1982). In the
present study, the moisture content of composite millet powder subjected to both
drying methods showed significant difference. Whereas the moisture content of
composite millet powder exposed to forced convection tray drying showed slightly
lesser when compared to sun drying and freeze drying methods.
The ash content was observed to be more or less similar in the composite
millet powder exposed to forced convection tray drying (CM-T1)-3.27 g/100g and
freeze drying (CM-T1)- 3.47 g/100g which is the reflection of the ash content
present in the selected minor millets namely finger millet, pearl millet, kodo millet,
little millet and foxtail millet. Among the different millets, kodo millet had the
highest proportion of total minerals (4.9%) and lowest was recorded in foxtail millet
(1.4%) Kulkarni et al., 1992; Hadimani and Malleshi, 1993 and Veena et al., 2012).
The carbohydrate content of composite millet powder subjected to different
drying methods namely forced convection tray drying (T1) and freeze drying (T0) was
found to be more or less similar (p≤0.05). The values were observed to be
76.03 g/100g in the composed millet powder exposed to forced convection tray drying
(CM-T1) and 76.21 g/100g in freeze drying (CM-T2). Sahu (1987) reported that
little millet possess highest carbohydrate content (73.40 g/100g) when compared
to kodo millet, foxtail millet and other millets. Hence in the present investigation,
the increase in carbohydrate content of the composite millet powder is attributed
mainly due to the presence of carbohydrate in the little millet. Similar results were
seen in little millet based composite mix which range from 69.09 to 71.44 g/100g.
The protein content of composite millet powder exposed to forced convection
tray drying (CM-T1) and freeze drying (CM-T2) was found to be 11.90 and
11.82 g/100g respectively. The slight variation was found in the sample subjected to
forced convection tray drying which might be due to higher temperature used during
dehydration (p≤0.05). The protein content increased significantly (p≤0.05) in the
composite millet powder. Similar results was noted by Singh et al., (2005),
Premavalli et al., (2005) who stated that by increasing the levels of foxtail millet in
formulation of composite millet powder led to increase in the concentration of
protein. The protein content of composite millet powder is almost similar to the
average protein content in little millet, kodo millet and foxtail millet which
contain 9.5, 8.8 and 11.07% of protein respectively with varietal differences
within species as reported by several investigators
(Malleshi and Desikachar, 1985; Monteiro et al.,2000;
Hadimani and Malleshi, 1993 and Veena et al., 2005).
The fat content of composite millet powder was found to be almost similar in
the samples subjected to freeze drying (CM-T2-3.43 g/100g and forced convection
tray drying (CM-T1-3.30 g/100g). The fat content in cereals is generally
insignificant. However the fat content observed in the composite millet powder is
due to the natural existence of fat in the selected minor millets. Hence there existed
no significant difference (p>0.05). Several researcher reported that foxtail millet
recorded a fat content ranging from 2.3 to 5.9 %, followed by proso millet
(2.1 to 5.2%), little millet (3.10 to 3.7%) and kodo millet (1.1 to 3.3%)
(Malleshi and Desikachar, 1985; Sahu, 1987).
The energy level was more or less similar in composite millet powder obtained
from both dehydration techniques which was found to be CM-T1-362 k/cal and
CM-T2-363 k/cal respectively, since the application of heat does not alter any change
in the energy values. There was no significant difference among drying method
(p>0.05). As per PAG recommendation, a composite mix should provide more
than 360 Kcal of energy (Anonymous, 1975) and 300 - 400 Kcal according to
BIS specifications (Anon,2008). In the present study, the composite millet powder
subjected to different drying methods observed to provide 362 - 363 Kcal, which
agrees with the recommendations of PAG and BIS.
The composite millet powder subjected to freeze drying possess to contain
more or less similar amount of calcium (79.27 mg/100g), phosphorus
(168 mg/100g), iron (2.03 mg/100g), magnesium (111.83 mg/100g), potassium
(151.27 mg/100g) and zinc (1.27 mg/100g) when compared to composite millet
powder exposed to forced convection tray drying. The increase is mainly due to the
drying techniques adopted for processing of millet. Similar report was observed in
the study conducted by National Institute of Nutrition on mineral and trace elements
where relatively higher concentration of zinc, copper and chromium was observed in
little millet, while concentration of calcium, phosphorous, manganese and
magnesium was greater in barnyard millet (Anon.,2008). A significant variation in
calcium content of five minor millets (proso millet, kodo millet, foxtail millet, little
millet and barnyard millet) was recorded with values ranging from
12.36 to 29.17 mg/100 g (Kulkarni et al., 1992). The ionisable iron content was
1.47, 1.50, 0.55, 10.76 and 1.38 mg in proso millet, kodo millet, foxtail millet, little
millet and barnyard millet respectively (Veena et al., 2012). Hence, composite
millet powder is a nut shell of minerals holding therapeutic significance.
The physical properties of composite millet powder were studied in terms of
bulk density (g/ml), swelling index (%), foam capacity (ml), foam stability (ml) and
water absorption capacity (ml).
Irrespective of drying methods adopted, the bulk density of composite millet
powder did not show much difference between drying methods. The values of bulk
density are relatively high for the composite millet powder when compared to refined
flour or 100% wheat flour and thereby facilitates quick reconstitution to give fine
constituent dough during mixing followed by extrusion. (Adebowale et al., 2008).
The swelling capacity of composite millet powder was noted to be 9.62% in
CM-T1 and 9.33% in CM-T2, which is almost similar. Swelling behavior of cereal
starches was mainly correlated to the amylopectin content where amylose acts as an
inhibitor of swelling. The distribution of amylose in starch granule was not uniform
(Seguchi et al., 2003) which also affect the swelling power of starch.
The foamability of the flour depends on the presence of the flexible protein
molecules which may decrease the surface tension of water (Sathe et al., 1982). It was
observed from table that the foam capacity and foam stability of the composite millet
powder obtained from two drying techniques were found to be 41.17 ml and 36.3 ml
for CM-T1 and 45.53 ml and 39.23 ml for CM-T2 respectively. The results revealed
that maximum foaming capacity and foaming stability was observed in composite
millet powder subjected to freeze drying. The low foamability of flour indicates the
presence of highly ordered globular protein molecules which increase the surface
tension. Graham and Phillips (1976) linked good foamability with flexible protein
molecules which reduces surface tension of water thereby favoring better expansion
of the product.
Water absorption capacity is useful in structure interaction in food especially
in flavor retention, improvement of palatability and extension of shelf life
(Adebowale, 2004). The water absorption of composite millet powder was found to be
more or less similar in both the drying techniques.
The total microbial counts (cfu/g) of composite millet powder subjected to
both drying methods were studied. The composite millet powder subjected to freeze
drying showed a slight increase in microbial growth due to improper removal of
moisture during drying and handling as well.
The composite millet powder possess an average of the nutrients present in the
processed millet powder obtained from selected minor millet namely finger millet,
pearl millet, kodo millet, little millet and foxtail millet. In order to bridge the existing
gap of the deficit in nutrients and physical qualities by the use of single millet, there is
a need to combine millet to produce composite mix for the development of value
added products which will help in alleviating the problems of malnutrition in general
and evolution of specific novel products.
Figure 8. Physico-chemical properties of composite millet powder
300
350
400
CM-T1 CM-T2
Energy (Kcal)
0
5
10
15
Protein (g) Fat (g) Ash (g) Moisture (g)
0
50
100
150
200
Calcium
(mg)
Phosphorus
(mg)
Iron (mg) Magnesium
(mg)
Zinc (mg) Pottasium
(mg)
0
20
40
60
Bulk Density (g/ml) Swelling Index(%) Foam capacity (ml) Foam Stability(ml) Waterabsorption
capacity (ml)
CM- T1 CM- T2
CM-T1
CM-T2
4.2.2. Color values of composite millet powder
The color values of composite millet powder are shown in Table 13 and
Figure 9.
Table 13. Color values of composite millet powder
Color values CM-T1 CM-T2 p - value
L* 84.84±0.03 83.96±0.02 p≤0.05
*
a* 2.70±0.01 1.94±0.02
b* 8.80±0.015 10.38±0.02 All values are means of triplicate determinations± standard deviation (S.D); CM-T1-composed millet power exposed to
forced convection tray drying, CM-T2- composed millet power exposed to freeze drying,
* Significantly different (p≤0.05) by ANOVA.
The color of the composite millet powder is the reflections of natural color
present in the millet and represented as L*, a* and b*. The L* (Lightness) value was
found to be more or less similar in composite millet powder subjected to both the
drying methods. The L* values of composite millet powder was towards the dark
shades due to addition of millets for the formulation of composite millet powder. The
a* value indicates the redness of sample which was also found to higher in composite
millet powder exposed to both drying methods. The b* value indicates the yellowish
shades of sample which was found to be lower for the composite millet powder
subjected to both the drying methods.
Figure 9. Color values of composite millet powder
4.2.3. Pasting properties of the composite millet powder
The pasting characteristics of the composite millet powder are shown in
Table 14 and Figure 10.
0
10
20
30
40
50
60
70
80
90
100
L* a* b*
Color values CM-T1
CM-T2
CM-T1
CM-T2
Table 14. Pasting properties of the composite millet powder
Pasting properties Raw flour CM-T1 CM-T2 P-
value
Pasting Temp. (°C) 77.67a ± 1.53 88.50
d ± .20 81.27
b ± 0.06
p≤0.05*
Peak time (mins) 3.15a ± 0.03 4.13
d ± 0.03 3.33
b ± 0.01
Peak viscosity(cP) 2629.00c ± 1.00 1865.67
a ± 3.05 2742.00
d ± 1.00
Hold viscosity(cP) 2507.00b ± 9.50 1762.00
a ± 2.00 2302.33
b ± 2.52
Final viscosity (cP) 3191.67c ± 1.53 2021.33
a ± 1.53 3534.33
d ± 1.53
Breakdown(cP) 253.67c ± 1.53 107.67
b ± 1.53 436.67
d ± 2.08
Setback (cP) 816.33c ± 1.53 261.33
a ± 1.53 1230.33
d ± 1.53
All values are means of triplicate determinations ± standard deviation (S.D), CM-T1- Composite millet powder
exposed to forced convection tray drying , CM-T2- Composite millet powder exposed to freeze drying , The same
superscripts in row indicate the same to each other and different superscripts in row indicates different to each other are
significant different (p≤0.05) by DMRT. * Significantly different (p≤0.05) by ANOVA.
The pasting properties varied significantly with different processing conditions
of the composite millet powder. There was a significant difference (P≤0.05) in pasting
temperature between the raw and composite millet powder. The pasting temperature
of composite millet powder exposed to forced convection tray drying was 88.50°C
and freeze drying was 81.27°C. The pasting temperature reflects the cooking time of
the food samples, which is a measure of the minimum temperature required to
cook a given food sample (Sandhu et al., 2008). The peak time of the composite
millet powder range from 3.33 to 4.13 min for the processed composite millet powder
and 3.15 min for the raw millet powder.
Peak viscosity indicates the water-holding capacity of the starch or flour
samples and is often correlated with final product quality. Peak viscosity of processed
composite millet powder subjected to forced convection tray drying and freeze drying
range between 1865.67 and 2742.00 cP respectively and for the raw powder the
pasting property was 2629.00 cP. The peak viscosity was highest (p≤0.05) for the
raw sample (2629.00 cP) and composite millet powder exposed to freeze drying was
2742.00 cP and decreased peak viscosity was observed in composite millet powder
exposed to forced convection tray drying (1865.67 cP). A decrease in peak viscosity
was due to its loss of water-binding capacity as a result of partial gelatinization taken
place during the drying process. A rise in peak viscosity is an indication of increased
swelling index of the powder samples due to higher solubility as a result of starch
degradation of the flour (Shittu et al., 2001). The interaction of other components like
protein, fiber and the degree of starch damage during processing could affect the peak
viscosity of flours. The holding viscosity (2507 cP) and final viscosity (3191 cP) were
observed to be highest in raw composite powder followed by freeze dried composite
millet powder. The lowest value for holding viscosity (1762 cP) and final viscosity
(2021 cP) were seen in forced convection tray dried sample. The highest breakdown
viscosity is greater in freeze dried sample (436 cP). The setback values were noted to
be higher in composite millet powder exposed to freeze drying (1230 cP) and in raw
samples (816 cP), whereas composite millet powder subjected to forced convection
tray drying exhibited lower set back values (261 cP) which indicates lower tendency
of retro gradation of starch during cooling of hot paste.
In general, the changes in the pasting properties observed in the composite
millet powder exposed to forced convection tray drying (CM-T1) and freeze drying
(CM-T2) could be suitable for the extrusion process.
Figure 10. Pasting properties of the composite millet powder
4.2.4. Morphological structure of composite millet powder
The Figure 11 shows the morphological structure of composite millet powder.
The morphology of starch granules depends on the biochemistry of the
chloroplast or amyloplast as well as physiology of the plant (Badenhuizen, 1969). A
heterogeneous combination of composite millet powder can be observed in the
micrographs (Figures 11) with irregular structures having indefinite shapes, rich in
spongy-aspect material with cavities and structural gaps of varied sizes. The starch
granules are either oval or round in shape with smooth surfaces with little variation
and some bulges, probably resulting due to great strength of starch–protein
interactions. The microstructure of composite millet powder shows a disturbed
structure and protein matrix applies pressure on some starch granules leading to small
structural deformations. Starch granules seem to be surrounded by other materials like
fibers and proteins giving a „„raising dust” appearance that may contribute to those
0
20
40
60
80
100
120
0
1000
2000
3000
4000
00:00:00 00:07:12 00:14:24
Tem
per
atu
re
Time(mins)
RAW
T0
T1
T2
TEMP
T
0
T
characteristics. The drying method showed a structural change in the composite millet
powder by affecting their starch, protein and fat bodies. The structural damage was
more in the sample exposed to forced convection tray drying (CM-T1) when
compared to freeze drying (CM-T2).
CM-T1 CM-T2
PM-Protein matrix, PB-Protein bodies, SG-Starch granules
Figure 11. Morphological structure of composite millet powder
4.2.5. Functional properties of composite millet powder
4.2.5.1. Essential amino acid (mg/100g) profile of composite millet powder
The Table 15 and Figure 12 show the essential amino acid (mg/100g) profile
of composite millet powder.
Table 15. Essential amino acid (mg/100g) profile of composite millet powder
Essential
amino acids
(mg/100g) CM-T1 CM-T2
FAO/WHO/UNU 2007
g/kg/d p-value
Histidine 0.487±0.006 0.583±0.006 0.14
p≤0.05 *
Valine 0.207±0.006 0.227±0.006 0.19
Methionine 0.310±0.006 0.319±0.006 0.42
Iso-leucine 0.230±0.006 0.219±0.006 0.38
Phenylalanine 0.790±0.006 0.797±0.006 0.15
Leucine 0.294±0.006 0.294±0.006 0.25
Lysine 0.415±0.006 0.399±0.006 0.02
Proline 0.028±0.006 0.136±0.058 0.05
Tryptophan 0.345±0.006 0.347±0.006 0.24 All values are means of triplicate determinations± standard deviation (S.D), CM-T1 – Composite millet powder
exposed to forced convection tray drying, CM-T2 - Composite millet powder exposed to freeze drying,
* Significantly different (p≤0.05) by ANOVA.
Results in Tables 15 show the effect of processing on the total amino acid
profile of composite millet powder. The results shows significant changes (P≤0.05) in
the two drying techniques; forced convection tray drying and freeze drying of
PB
P
M SG
P
M
PB
SG
composite millet powder. As far as the essential amino acids are concerned, slight
changes (P≤0.05) were recorded for all amino acids in both the drying methods. The
total amount of essential amino acid composition was in the range of
0.028-0.790g/100g in CM-T1 and 0.136-0.797g/100 g in CM-T2. The highest
concentration of conditionally essential amino acids for the composite millet powder
was phenylalanine while the least was proline (CM-T1-0.028 and CM-T2-0.136) in the
both drying techniques. Among the cereals, millet is considered to be the rich source
of leucine, which is found to contain twice the amount of other cereals except
sorghum and corn. Tryptophan is usually considered as the second most deficient
amino acid in cereals but it is found to be higher in finger millet (Lupien, 1990).
Among the millets, finger millet is relatively better balanced in essential amino acids
because it contains more lysine, thereonine and valine (FAO/WHO/UNU, 2007). The
albumin and globulin fractions contain a good compliment of essential amino acids.
The prolamin fraction contains higher proportion of glutamic acid, theronine,
isoleucine, leucine and phenylalanine but low in valine and glycine (Cardoso, 2014).
The isoleucine content of finger millet is also high. The mean values of the amino
acid profile from this study revealed that most of the essential amino acids are present
in adequate amount when compared with the recommended values of
FAO/WHO/UNU (2007).
Figure 12. Essential amino acid (mg/100g) profile of composite millet powder
4.2.5.2. Vitamin content of composite millet powder
The mean value of vitamin content of composite millet powder is presented in
Table 16 and Figure 13.
0
0.2
0.4
0.6
0.8
1
Histidine Valine Methionine Iso-leucine Phenylalanine Leucine Lysine Proline Tryptophan
mg
/10
0g
Essential amino acids (mg/100g) CM-T1
CM-T2CM- T1
CM- T2
Table 16. Vitamin content of the composite millet powder
Vitamins CM-T1 CM-T2 P- value
Vitamin A(IU) 94.48±0.06 95.01±0.06
p≤0.05*
Vitamin D (mg) 3.45±0.01 3.47±0.01
Vitamin E (mg) 1.36±0.01 1.39±0.01
Vitamin B6 (mg) 3.48±0.01 3.48±0.01
Vitamin B12 (mg) 0.40±0.001 0.40±0.01 All values are means of triplicate determinations± standard deviation (S.D), CM-T1 – Composite millet powder
exposed to forced convection tray drying, CM-T2 – Composite millet powder freeze drying ,
* Significantly different (p≤0.05) by ANOVA.
Vitamin content of the composite millet powder subjected to both drying
methods was found to have almost similar values with slight significant difference
(p≤0.05).Vitamin A was found to be slightly higher in composite millet powder
subjected to freeze drying when compared to forced convection tray drying. Vitamin
A plays a major role in specialized function such as in vision and ascorbate in distinct
hydroxylation reactions. The vitamin D, vitamin E, vitamin B6, vitamin B12 and
vitamin C content of the sample CM-T1 and sample CM-T2 were found to be
significantly more or less similar.
Figure 13. Vitamin content of the composite millet powder
4.2.5.3. Essential fatty acid (mg/100g) composition of composite millet powder
The mean value of essential fatty acid composition of the composite millet
powder is presented in Table 17 and Figure 14.
0
20
40
60
80
100
120
Vitamin
A(IU)
Vitamin D
(mg)
Vitamin E
(mg)
Vitamin B6
(mg)
Vitamin
B12 (mg)
Vitamin/100g CM-T1
CM-T2CM- T1
CM- T2
Table 17. Essential fatty acid (mg/100g) composition of composite millet powder
Essential fatty acids
(mg/100g) CM-T1 CM-T2 p-value
Palmitic acid 0.99±0.000 0.99±0.000
(p≤0.05)*
Stearic acid 0.034±0.000 0.34±0.000
Oleic acid 0.80±0.006 0.80±0.000
Linoleic acid 1.35±0.006 1.38±0.006
Alpha linolenic acid 0.79±0.000 0.79±0.000 All values are means of triplicate determinations± standard deviation (S.D). CM-T1 – Composite millet powder
exposed to forced convection tray drying, CM-T2 – Composite millet powder exposed to freeze drying,
* Significantly different (p≤0.05) by ANOVA.
The essential fatty acid composition of composite millet powder shows the
presence of saturated and unsaturated fatty acids. The essential fatty acids namely
palmitic acid, stearic acid, oleic acid, linoleic acid, alpha linolenic acid were found to
be highly proportionate in the composite millet powder obtained from both
dehydration techniques and found to be significant at p≤0.05. The overall dominant
fatty acids in the composite millet powder are linoleic acid (1.35 to 1.38 mg/100g)
and palmitic acid (0.99mg/100g). The dominant polyunsaturated fatty acid is linoleic
acid which was slightly higher in composite millet powder.
Figure 14. Essential fatty acid (mg/100g) composition of composite millet
powder
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Palmitic
acids
Stearic acis Oleic acids Linoleic Alpha
linolenic
acid
(mg
/10
0g
)
Essential fatty acids (mg/100g) CM-T1
CM-T2
CM- T1
CM- T2
4.2.5.4. Phytochemical profile of composite millet powder
The Table 18 and Figure 15 discusses on the phytochemical profile of
composite millet powder.
Table 18. Phytochemical profile of composite millet powder
Phytochemicals profile CM-T1 CM-T2 p-value
Phenols 0.95±0.01 0.96±0.01 0.492NS
Alkaloids 1.33±0.01 1.34±0.02 0.275NS
Terpenoids 0.44±0.00 0.44±0.00 0.374NS
Tannins 0.11±0.00 0.12±0.00 0.016 NS
Anthraquinines 3.48±0.01 3.51±0.02 0.034 NS
Glycosides 12.31±0.01 12.33±0.01 0.189NS
All values are means of triplicate determinations± standard deviation (S.D), CM-T1- Composite millet powder exposed to
forced convection tray drying, CM-T2- Composite millet powder exposed to freeze drying.
*Significantly difference (p≤0.05) by ANOVA, NS-No significantly difference.
Nutrition and health care research substantiates the potential of
phytochemicals such as polyphenols, alkaloids, terpenoids, tannins, anthraquinines,
glycosides and dietary fiber on the health beneficial properties (Devi et al., 2011). The
degradation of phenols (mg) is observed at temperature beyond 50-60ºC of heat
treatments in foods. The phenol content of composite millet powder subjected to
freeze drying (CM-T2-0.96) showed an increment when compared with forced
convection tray drying (CM-T1-0.95) samples which was statistically significant at
p≤0.05. Similar result was observed by Zhu et al., (2011) who reported that total
phenolic contents were found significantly higher in freeze dried food samples than
forced convection tray dried samples.
Alkaloids have different structures and a range of pharmacological actions
including antimicrobial activity (Herraiz and Galisteo, 2003). On comparing between
the drying techniques, the processed composite millet powder obtained from freeze
drying (CM-T2-1.34) shows slightly higher concentration than the samples subjected
to forced convection tray drying (CM-T1-1.33). There was not much significant
difference observed at p>0.05 among the samples subjected to forced convection tray
drying and freeze drying.
Terpenoids are used as protective substances in storing agriculture products as
they are known to have insecticidal properties. Theis et al., (2003); Shah et al., (2009)
observed antimicrobial, antifungal, antiparasitic, antiviral, anti-allergenic, anti-
spasmodic, anti-hyperglycemic, anti-inflammatory, and immunomodulatory
properties in terpenoids. It was observed that there was no reduction in terpenoids
when the composite millet slurry was subjected to forced convection tray drying and
freeze drying.
The tannin content of composite millet powder obtained from freeze drying
(CM-T2-0.12) showed high values when compared to forced convection tray dried
(CM-T1-0.11) samples which was statistically significant at p≤0.05.
Ferreira et al., (2004) examined higher amounts of condensed tannins in freeze dried
samples than oven-dried samples from Sericacea lespedeza. Nevertheless, these
outcomes are in accordance with those obtained by Palmer et al., (2000) who
observed a reduction in condensed contents of oven-dried samples when compared
with freeze-dried ones.
The anthraquinine and glycoside content of composite millet powder obtained
from freeze drying (CM-T2-3.51, 12.33) had greater content when compared to the
composite millet powder dehydrated using forced convection tray drying
(CM-T1 -3.48, 12.31), which was found to be statistically significant at p<0.05.
Figure 15. Phytochemical profile of composite millet powder
4.2.6. Antioxidant activity of composite millet powder
4.2.6.1. DPPH Radical-scavenging activity of composite millet powder
DPPH is a stable free radical widely used in evaluating the antioxidant
activities in a relatively short time as compared with other methods. The color of
DPPH in methanol changes from violet to yellow upon reduction, which is
demonstrated by the decrease in absorbance at 517nm. Pradeep et al., (2006) reported
0
2
4
6
8
10
12
14
Phenols Alkaloids Terpenoids Tannins Anthraquinines Glycosides
(µg
/10
0g
)
Phytochemical (µg/100g) CM-T1
CM-T2CM- T1
CM- T2
that in the DPPH method, the color stability of DPPH radical is reduced in the
presence of an antioxidant which donates hydrogen to non-radical DPH-H.
The DPPH scavenging activity of composite millet powder was observed
by the extracts of composite millet powder exposed to both drying methods is
illustrated in the Figure 16 and Table 19.
Table 19. DPPH scavenging activity of
composite millet powder
Figure 16. DPPH scavenging activity of
composite millet powder
DPPH free radical scavenging activity was studied at different
concentrations from 20µg to 150µg. Radical scavenging activities slightly varied with
the processing methods and concentration used. The greatest activity was obtained at
a higher concentration when it falls above 100µg in the processed composite millet
powder extracts. The antioxidant activity of standard ascorbic acid increases as the
concentration increases. The percentage of inhibition was found to be 18.14µg/ml and
21.05µg/ml during initial concentration and 75.16µg/ml and 73.73µg/ml in the final
concentration. Similar findings were reported by Pradeep et al., (2011) for roasted
little millet which showed enhanced radical scavenging activity (95.5%) than
germinated (91.7%) and steamed (93.4%) millets.
Figure 16 shows IC50 values of the extracts of processed composite millet
powder prepared by subjecting to different drying methods. It was found that the IC50
values of composite millet powder exposed to forced convection tray drying and
freeze drying was found to be 36.31mg/ml and was 45.57 mg/ml extract respectively.
4.2.6.2. Reducing power of composite millet powder
Reducing power measures the reductive ability of antioxidant, and it is
evaluated by the transformation or reduction of Fe3+
ferricyanide complex to Fe2+
by
CMT1- y = 0.666x + 9.115
R² = 0.991
IC50-36.31
CMT2- y = 0.723x + 3.2
R² = 0.993
IC50-45.57 0
50
100
0 50 100 150P
erce
nta
ge
of
Inh
ibit
ion
Concentration (µg/ml)
DPPH radical scavenging activity
Ascorbic acid
CM-T1
CM-T2
Concentration
(µg/ml)
Percentage of Inhibition
Ascorbic
acid CM-T1 CM-T2
20 31.14 18.14 21.05
40 50.19 32.69 37.23
60 69.89 43.7 48.34
80 74.86 63.33 65.16
100 95.21 75.16 73.73
CM-T1- Composite millet powder exposed to forced
convention tray drying; CM-T2 Composite millet
powder exposed to -freeze drying
CM-T1
CM-T2
using the sample extracts (Gülçin et al., 2003). The methanolic extracts of composite
millet powder and its products were analysed at 20 to 50 mg/ml of concentrations.
The Fe 2+ was then monitored by measuring the formation of Perl‟s Prussian blue at
700nm (Oyaizu, 1986).
The Table 20 and Figure 17 show the reducing power of processed composite
millet powder.
Table 20. Reducing power of composite
millet powder
Figure 17. Reducing power of composite
millet powder
The reducing power of composite millet powder was studied at the
concentration of 20-100mg/ml and its results vary from 0.12-0.68mg/ml in CM-T1
and CM-T2 samples. The reducing powder of composite millet powder subjected to
forced convection tray drying range from 0.12 to 0.68mg /ml and for freeze drying
about 0.12 to 0.68mg/ml. There was a significant (p≤0.05) variation in reducing
power activity of the extracts of composite millet powder subjected to both the drying
methods.
4.3.Evaluation of quality characteristics of convenience food
developed using composite millet powder
4.3.1. Quality characteristics of pasta
The quality characteristics of the convenience foods namely ready to cook
(pasta) product were studied in terms of nutritional, physical, functional, instrumental
and sensory properties including shelf life studies and are discussed below.
0
0.5
1
1.5
2
0 0.05 0.1 0.15A
bso
rban
ce 7
00
nm
Concentration (mg/ml)
Ascorbic acid
CM-T1
CM-T2
Concentration
(mg/ml)
Absorbance of 700nm
Ascorbic
acid CM-T1 CM-T2
0.02 0.39 0.12 0.12
0.04 0.66 0.26 0.26
0.06 1.05 0.39 0.38
0.08 1.34 0.47 0.49
.1 1.45 0.66 0.68
CM-T1-Composite millet powder exposed to
forced convention tray drying;
CM-T2- Composite millet powder exposed to
freeze drying
CM-T1
CM-T2
4.3.1.1. Nutritional properties of pasta
The Table 21 and Figure 18 represent the nutritional properties of pasta.
The nutritional properties of pasta are noted in terms moisture, ash,
carbohydrates, protein, fat and energy.
Table 21. Nutritional properties of pasta
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05)
by ANOVA. The same superscripts in row indicate the same to each other and different superscripts in row indicates
different to each other are significantly different (p≤0.05) by DMRT. CM-T1 –Pasta formulated using composite millet
powder exposed to forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder exposed to
freeze drying, CM- T1E - Pasta formulated using composite millet powder exposed to forced convection tray drying with
addition of egg white powder. CM- T2E- Pasta formulated using composite millet powder exposed to freeze drying with
addition of egg white powder.
The moisture content of all the pasta developed from composite millet powder
subjected to forced convection tray drying and freeze drying range between 2.28 %
and 2.78% respectively either with or without addition of egg white powder. The
pasta developed from 100% of maida (control) had significantly (p≤0.05) lesser
moisture content (2.25%). Whereas desirable moisture was obtained for all the pastas
developed in order to maintain the shelf life of the product.
From the Table 21, it was observed that the ash content of the pasta ranged
from 1.37g to 2.25 g and found to be significant at p≤0.05. The highest ash content
was observed in the pasta formulated using composite millet powder subjected to
forced convection tray drying and freeze drying with addition of egg white power
(CM-T1E-2.01 g/100g and CM-T2E-2.25g/100g) followed by CM-T1-1.67g/100g and
CM-T2-1.87 g/100g and the least was observed in the control (1.37g/100g). A similar
study conducted by Prasad et al., (2007) on millet-sorghum soy based extruded
snacks, reported about 2.9 % of the ash content. This could be attributed to the fact
that multimillets and egg white powder contains high amount of minerals. The results
showed significant difference in ash content of the pasta incorporated with egg white
powder (p≤0.05).
Nutritional
properties Control CM-T1 CM-T2 CM- T1 E CM- T2 E p-value
Moisture (g) 2.25a ± 0.01 2.75
b ± 0.01 2.74
b ± 0.01 2.78
c ± 0.01 2.77
c ± 0.01
p≤0.05*
Ash (g) 1.37a ± 0.06 1.67
b ± 0.06 1.87
c ± 0.06 2.01
d ± 0.01 2.25
e ± 0.01
Carbohydrate(g) 82.00a ± 0.01 74.47
b ± 0.06 75.00
c ± 0.01 75.87
d ± 0.06 76.13
e ± 0.06
Protein (g) 11.21a ± 0.01 11.95
b ± 0.01 12.56
c ± 0.01 21.23
d ± 0.06 21.87
e ± 0.06
Fat (g) 0.30a ± 0.01 0.77
b ± 0.06 0.82
c ± 0.03 0.98
d ± 0.01 0.98
d ± 0.01
Energy (Kcal) 404.00a ± 0.58 387.00
b ± 0.58 398.00
c ± 0.58 407.00
d ± 0.58 409.00
e ± 0.58
The extruded pasta obtained from 100% refined wheat flour (control)
possesses higher carbohydrate content (82 g). The carbohydrate content of the pasta
incorporated with 15% egg white powder subjected to forced convection tray drying
and freeze drying was 75.87g and 76.13g respectively. The carbohydrate content was
found to be lower in pasta developed from composite millet powder either with or
without addition of egg white powder when compared to control pasta which
exhibited significant difference (p≤0.05) among the pasta. This is due to the fact that
refined wheat flour possess abundant amount of starch and carbohydrate.
Irrespective of drying methods adopted, the total protein content of the pasta
formulated from composite millet powder with addition of 15% egg white powder was
found to be highest (p≤0.05) due to natural existence of protein in the egg.
(CM-T1E-21.23 and CM-T2E-21.87) than the pasta formulated from composite millet
powder without addition of egg white powder (CM-T1-11.95, CM-T2-12.56). According
to Priyanka et al., (2012), the incorporation of concentrated sources of proteins like egg
albumin powder and cheese powder resulted in the increased protein content in the
noodles. The control pasta showed a decrease in the protein content (11.21g).
The fat content of the control pasta, CM-T1, CM-T2, CM-T1E and CM-T2E
was found to be 0.30g, 0.77g, 0.82g, 0.98g and 0.98g respectively. The pasta
formulated using composite millet powder in both drying techniques was found to be
slightly higher than the control. Among the selected millets, the fat present in pearl
millet tends to increase the fat content of pasta prepared from composite millet powder.
The energy level of the pasta formulated from composite millet powder
obtained from forced convection tray drying and freeze drying with incorporation of
15% egg white powder was found to be 407kcal and 409kcal respectively. However the
energy level of the control pasta was almost similar to the pasta prepared with addition
of egg white powder. The pasta formulated without addition of egg white powder was
found to be CM-T1-387kcal, CM-T2-398kcal respectively which was comparatively
lesser than the control pasta (404kcal).
Figure 18. Nutritional properties of pasta
4.3.1.2. Physical properties of pasta
Table 22 and Figure 19 depicts the cooking quality of pasta. The quality of
pasta is influenced by cooking characteristics which includes cooking time, cooking
weight and cooking loss (Tudorica et al.,2002).
0
0.5
1
1.5
2
2.5
3
3.5
Control CM-T1 CM-T2 CM- T1 E CM- T2 E
(g/1
00
g)
Moisture (g/100g)
0
0.5
1
1.5
2
2.5
Control CM-T1 CM-T2 CM- T1 ECM- T2 E
(g
/10
0g)
Ash (g/100g)
0
10
20
30
40
50
60
70
80
90
100
Control CM-T1 CM-T2 CM- T1 ECM- T2 E
(g/1
00
g)
Carbohydrate (g/100g)
0
5
10
15
20
25
Control CM-T1 CM-T2 CM- T1 E CM- T2 E
(g/1
00
g)
Protein (g/100g)
0
0.2
0.4
0.6
0.8
1
1.2
Control CM-T1 CM-T2 CM- T1 E CM- T2 E
(g/1
00
g)
Fat (g/100g)
360
370
380
390
400
410
420
Control CM-T1 CM-T2 CM- T1 ECM- T2 E
(Kca
l/1
00g)
Energy (Kcal/100g)
CM-T1 CM-T2 CM-T2 E CM-T2 E CM-T1 CM-T2 CM-T2 E CM-T2 E CM-T1 CM-T2 CM-T2 E CM-T2 E
CM-T1 CM-T CM-T2 E CM-T2E
CM-T1 CM-T2 CM-T2 E CM-T2 E CM-T1 CM-T2 CM-T2 E CM-T2 E
CM-T1 CM-T2 CM-T2 E CM-T2 E Control CM-T1 CM-T2 CM-T2 E CM-T2 E
Table 22. Physical properties of pasta
Samples Cooking time (min) Cooking weight (g) Cooking loss (g)
Control 6.33a± 0.58 21.13
c±0.61 3.00
b±0.20
CM-T1 7.67a,b
± 0.58 20.25b±0.64 7.07
c±0.21
CM-T1E 7.67a,b
± 0.58 22.41d± 0.35 0.00
a±0.00
CM-T2 7.00a,b
±1.00 19.43a±0.08 6.97
c±0.21
CM-T2E 8.00c ±1.00 22.98
e±0.04 0.00
a±0.00
p-value 0.139NS
p≤0.05* p≤0.05*
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05)
by ANOVA. The same superscripts in row indicate the same to each other and different superscripts in row indicates
different to each other are significantly different (p≤0.05) by DMRT. NS-Not Significant. CM-T1 –Pasta formulated using
composite millet powder exposed to forced convection tray drying. CM-T2 - Pasta formulated using composite millet
powder exposed to freeze drying, CM- T1E - Pasta formulated using composite millet powder exposed to forced
convection tray drying with addition of egg white powder. CM- T2E- Pasta formulated using composite millet powder
exposed to freeze drying with addition of egg white powder.
In the present study, it was observed that cooking loss was higher in pasta
developed from composite millet powder and lowest for control pasta. The cooking
loss was found to be zero percent in the pasta developed from composite millet
powder with addition of egg white powder. The increase in cooking loss may be due
to weakening of gluten network as millets are free of gluten. In addition, the protein
present in egg helps to bind the structure of the pasta hence it decreases the cooking
loss. Similar finding was observed in gluten-free pasta, where solid loss during
cooking is mostly due to solubilization of loosely bound gelatinized starch at surface
of the product. This phenomenon depends mainly on the degree of starch
gelatinization and the strength of the retrograded starch network surrounding the
gelatinized starch (Marti et al., 2010). The lack of gluten in the millets might have led
to the increased solid loss. Similar trend of increased solid loss was observed in
proso millet incorporated noodles (Lorenz and Dilsaver,1980b).
Milatovic and Mondelli (1990) found that egg albumin contribute to the
formation of a protein network and improves the retention of the starch, which avoids
the leaching of starch in the cooking water. The highest cooking time was observed
for pasta developed from composite millet powder and egg white powder. This could
be attributed to the hydration level which is more for millet based pasta than pasta
made from refined wheat flour. Pasta prepared from composite millet powder with
addition of egg white powder showed higher cooking weight (CM-T1E-22.40,
CM-T2E-22.97) when compared to pasta prepared from composite millet powder and
control pasta. This might be due to addition of egg white powder which helps to bind
the structure of pasta. Matsuo and Irvine (1970) reported that addition of egg albumin
and wheat protein improved the cooking quality of pasta. The decrease in the cooked
weight was apparently due to increase in cooking loss or gruel loss in the pasta
without addition of egg white powder.
Figure 19. Physical properties of pasta
4.3.1.3. Functional properties of pasta
In the present study, the functional properties such as amino acids profile,
fatty acids, vitamins, phytochemical and antioxidant activity were carried out for the
developed products and their heat stability was assessed for the processed composite
millet powder after the application of dehydration techniques namely forced
convection tray drying and freeze drying.
4.3.1.3.1. Essential Amino acid (mg/100g) profile of pasta
Table 23 and Figure 20 shows the essential amino acids profile of pasta.
0
2
4
6
8
10
Control CM-T1 CM-T1E CM-T2 CM-T2E
(min
s)
Cooking time (mins)
0
2
4
6
8
Control CM-T1 CM-T1E CM-T2 CM-T2E
(%)
Cooking loss (%)
0
5
10
15
20
25
30
Control CM-T1 CM-T1E CM-T2 CM-T2E
(g)
Cooking weight (g)
CM-T1 CM-T2 CM-T2 E CM-T2 E CM-T1 CM-T2 CM-T2 E CM-T2E
CM-T1 CM-T2 CM-T2 E CM-T2 E
Table 23. Essential amino acid (mg/100g) profile of pasta
Essential
amino acids
(mg/100g) Control CM-T1 CM-T2 Egg White Powder p-value
Histidine 0.25a±0.01 0.48
b±0.01 0.47
b±0.01 1.77
c±0.06
p≤0.05*
Valine 0.58b±0.01 0.20
a±0.01 0.21
a±0.01 6.13
c±0.06
Methionine 0.31a±0.01 0.31
a±0.01 0.32
a±0.01 3.17
b±0.06
Iso-leucine 0.47b±0.01 0.23
a±0.01 0.22
a±0.01 4.97
c±0.06
Phenylalanine 0.68a±0.01 0.78
b±0.01 0.80
b±0.01 5.07
c±0.06
Leucine 1.54b±0.01 0.29
a±0.01 0.29
a±0.01 7.07
c±0.06
Lysine 0.14a±0.01 0.41
b±0.01 0.40
b±0.01 4.97
c±0.06
Proline 0.91c±0.01 0.02
a±0.01 0.13
b±0.06 3.33
d±0.06
Tryptophan 0.17a±0.01 0.34
b±0.01 0.34
b±0.01 1.27
c±0.06
All values are means of triplicate determinations ± standard deviation (S.D), * Significantly different (p≤0.05) by
ANOVA. The same superscripts in row indicate the same to each other and different superscripts in row indicates
different to each other are significantly different (p≤0.05) by DMRT. CM-T1 –Pasta formulated using composite millet
powder exposed to forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder exposed to
freeze drying, CM- T1E - Pasta formulated using composite millet powder exposed to forced convection tray drying with
addition of egg white powder. CM- T2E- Pasta formulated using composite millet powder exposed to freeze drying with
addition of egg white powder.
The essential amino acid composition of processed composite millet powder
of exposed to both the drying was carried out. The major cereal foods of the world
and their mutant types have basically similar amino acid profiles except for lysine,
tyrosine, leucine, isoleucine, and tryptophan. The total essential amino acid profile of
pasta prepared from composite millet powder range from 0.023mg/100g to
0.797mg/100g. The protein present in control pasta which is produced from refined
flour was considered to be incomplete because it lacks in one or more essential amino
acids. A protein that presents a chemical score higher than 1.0 for all amino acids is
considered to have high nutritional value, while amino acids with chemical score
lower than 1.0 are considered as limiting amino acids (Pires et al., 2006). The total
amount of essential amino acid composition was found to be similar in the pasta
prepared from the composite millet powder subjected to both drying methods. The
highest concentration of conditionally essential amino acids for the composite millet
powder was histidine, methionine, phenylalanine, lysine and tryptophan while the
least was proline and valine when compared with their references values. The
essential amino acid content of egg white powder was significantly higher (p≤0.05)
(Shivendra et al., 2007). During drying process of pasta, the reducing sugar generally
decreases due to the browning reaction (Maillard reaction), which tends to increase
the total essential amino acids. The mean values of essential amino acid profile
observed in the study revealed that most of the essential amino acids are present in
adequate amount when compared with the recommended values of FAO/WHO/UNO
(2007).
Figure 20. Essential amino acid (mg/100g) profile of pasta
4.3.1.3.2. Vitamin content of pasta
The vitamin content of pasta is discussed in the Tables 24 and Figure 21.
Table 24. Vitamin content of pasta
Vitamins Control CM-T1 CM-T2 Egg white powder p- value
Vitamin A 2.03a±0.06 94.43
b±0.06 94.83
c±0.06 -ND-
p>0.05*
Vitamin D -ND-a±0.00 3.44
b±0.01 3.46
c±0.01 -ND-
Vitamin E 0.23a±0.06 1.34
b±0.01 1.38
c±0.01 -ND-
Vitamin B6 -ND-a±0.00 3.45
b±0.01 3.47
c±0.02 -ND-
Vitamin B12 -ND-a±0.00 0.35
b±0.01 0.35
c±0.01 0.40
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA,
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1 –Pasta formulated using composite millet powder exposed to
forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder exposed to freeze drying,
CM-T1 - Pasta formulated using composite millet powder exposed to forced convection tray drying with addition of egg
white powder. CM-T2- Pasta formulated using composite millet powder exposed to freeze drying with addition of egg
white powder. ND-Not Detected.
The vitamins are sensitive to physical and chemical treatments. Vitamin
stability depends on the chemical structure and can be decreased due to exposure to
heat, light, oxygen, moisture and minerals (Singh et al., 2007). The percent gain of
vitamin A was found to be higher (CM-T1-94.43, CM-T2-94.83) in pasta formulated
using composite millet powder exposed to both drying methods when compared to
control pasta. As in the case of vitamin D, vitamin B6 and vitamin B12, the control
pasta made up of 100% refined flour was found to be lacking when compared to the
pasta formulated using the composite millet powder. In control pasta and pasta with
0
1
2
3
4
5
6
7
8
Histidine Valine Methionine Iso-leucine Phenylalanine Leucine Lysine Proline Tryptophan
(mg
.10
0g
)
Essential amino acids (mg/100g) Control
CM-T1
CM-T2
Egg White Powder
T1
T2
addition of egg white powder pasta were found to be deficit in most of the vitamins.
On comparing between the drying methods, the vitamin content does not show any
significant difference (p>0.05).
Figure 21. Vitamin content of pasta
4.3.1.3.3. Essential fatty acid (mg/100g) composition of pasta
Table 25 and Figure 22 presents the essential fatty acid composition of pasta
developed from composite millet powder either with or without addition of egg white
powder and the control pasta formulated using refined wheat flour were analyzed and
presented below.
Table 25. Essential fatty acid (mg/100g) composition of pasta
Essential fatty acids
(mg/100g) Control CM-T1 CM-T2
Egg white
powder p-value
Palmitic acids 0.147a±0.012 0.993
b±0.000 0.993
b±0.000 -ND-
p≤0.05*
Stearic acids 0.072b±0.001 0.034
a±0.000 0.336
c±0.000 -ND-
Oleic acids 0.083a±0.006 0.785
b±0.006 0.789
b±0.000 -ND-
Linoleic 0.057a±0.006 1.343
b±0.006 1.377
c±0.006 -ND-
Alpha linolenic acid 0.000a±0.000 0.783
b±0.000 0.784
c ±0.000 -ND-
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significantly different (p≤0.05) by DMRT. CM-T1 –Pasta formulated using composite millet powder exposed to
forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder exposed to freeze drying,
CM- T1E- Pasta formulated using composite millet powder exposed to forced convection tray drying with addition of egg
white powder. CM- T2E- Pasta formulated using composite millet powder exposed to freeze drying with addition of egg
white powder.
The pasta developed using composite millet powder with addition of egg
white powder did not show any increment in the fatty acid composition. On
comparing between the drying techniques the pasta developed from composite millet
powder subjected to both the drying techniques did not show much significant
0
20
40
60
80
100
120
Vitamin A
(IU)
Vitamin D
(mg)
Vitamin E
(mg)
Vitamin B6
(mg)
Vitamin B12
(mg)
Vit
am
in/1
00
g
Vitamins/100g Control
CM-T1
CM-T2
Egg white powder
CM-T1
CM-T2
difference (p>0.05). The mean increment was observed in pasta formulated using
composite millet powder when compared to the control pasta. The pasta prepared
from composite millet powder showed slightly higher values in stearic acids, oleic
acids, palmitic acids, linoleic acids and alpha linoleic acids. Yoshida et al., (1988)
reported that the level of moisture present in raw food material provides protection
against losses of unsaturated fatty acids during thermal heating.
Figure 22. Essential fatty acid (mg/100g) composition of pasta
4.3.1.4. Antioxidant activity of pasta
4.3.1.4.1. DPPH scavenging activity of pasta
Table 26 and Figure 23 illustrates the DPPH scavenging activity of pasta
developed from composite millet powder either with or without addition of egg white
powder obtained from both dehydration techniques was observed in the concentration
of 20-100mg/ml.
Table 26. DPPH scavenging activity of pasta
Concentration
(µg/ml)
Percentage of Inhibition (%)
Ascorbic
acid CM-T1 CM-T2 CM-T1E CM-T2E
20 31.14 15.89 11.01 15.14 12.19
40 50.19 29.91 17.18 28.69 20.71
60 69.89 37.17 30.13 39.13 31.98
80 82.86 49.21 43.21 48.41 44.21
100 99.21 60.01 53.22 59.42 56.13 CM-T1 –Pasta formulated using composite millet powder exposed to forced convection tray drying. CM-T2 - Pasta
formulated using composite millet powder exposed to freeze drying, CM- T1E- Pasta formulated using composite millet
powder exposed to forced convection tray drying with addition of egg white powder. CM- T2E- Pasta formulated using
composite millet powder exposed to freeze drying with addition of egg white powder.
0
0.5
1
1.5
2
Palmitic acid Stearic acid Oleic acid Linoleic acid Alpha linoleic
acid
mg
/10
0g
Essential fatty acids(mg/100g) Control
CM-T1
CM-T2
Egg whitepowder
CM-T1
CM-T2
Figure 23. DPPH scavenging activity of pasta
The results indicated that the scavenging activity was lesser in pasta
without incorporation of egg white powder which range between 15.89% (20mg/ml)
and 60.01% (100mg/ml), whereas in case of pasta with addition egg white powder it
was found to be 12.19% (20mg/ml) and 56.12% (100mg/ml) respectively. IC50
values of the extracts of pasta prepared from composite millet powder subjected to
both the drying methods either with or without incorporation of egg white powder
exhibited significant (p≤0.05) increase.
4.3.1.4.2. Reducing power of pasta
Table 27 and Figure 24 shows the reducing power of pasta developed from
composite millet powder either with or without addition of egg white powder.
Table 27. Reducing power of pasta
Concentration
(mg/ml)
Absorbance of 700nm
Ascorbic
acid CM-T1 CM-T2 CM- T1E CM-T2 E
0.02 0.39 0.07 0.13 0.11 0.17
0.04 0.66 0.16 0.27 0.22 0.32
0.06 1.05 0.29 0.40 0.39 0.41
0.08 1.34 0.41 0.47 0.43 0.59
0.1 1.45 0.59 0.72 0.67 0.76 CM-T1 –Pasta formulated using composite millet powder exposed to forced convection tray drying. CM-T2 - Pasta
formulated using composite millet powder exposed to freeze drying, CM- T1E- Pasta formulated using composite millet
powder exposed to forced convection tray drying with addition of egg white powder. CM- T2E- Pasta formulated using
composite millet powder exposed to freeze drying with addition of egg white powder.
Figure 24. Reducing power of pasta
CM T2-y = 0.552x - 2.185
R² = 0.988
IC50=46.041
CM T1-y = 0.541x + 5.674
R² = 0.995
IC50=39.512
CMT1E-y = 0.541x + 5.674
R² = 0.995
IC50=39.512
CM T2E-y = 0.556x - 0.37
R² = 0.995
IC50=89.262
0
20
40
60
80
100
120
0 20 40 60 80 100 120
Per
cen
tag
e (%
) in
hib
itio
n
Concentration (µg/ml)
DPPH radical scavenging activity
Ascorbic acid
CM-T1
CM-T2
CM-T1E
CM-T2E
0
2
0 0.1 0.2
Ab
sorb
an
ce
70
0n
m
Concentration (µg/ml)
Reducing powder
Ascorbic acids
CM-T1
CM- T1Egg
CM-T2
CM-T2 Egg
CM-T1
CM-T2
CM-T1E
CM-T2E
CM-T1
CM-T2
CM-T1E
CM-T2E
The reducing power of the extracts of pasta increased with increase in
concentration. The absorbance was studied in five different concentrations ranging
from 0.05 to 1.00mg/ml for the pasta formulated using composite millet powder
obtained from both drying techniques either with or without addition of egg white
powder. The absorbance of CM-T1 was found to be 0.07-0.59 mg/ml and CM-T2 was
0.13-0.72 mg/ml. However, the reducing power of all the pasta were lesser than that
of ascorbic acid at the same concentration. The drying methods adopted did not have
any effect on antioxidant property.
4.3.1.4. Instrumental analysis of pasta developed from composite millet powder
4.3.1.4.1. Color values of pasta
The most accepted criteria to estimate the quality of cooked pasta are based
mainly on color and texture assessment (Brennan Tudorica, 2007). In fact, color,
firmness and lack of stickiness are the most desired characteristics to define the
overall quality of pasta products. The color value of pasta is given Table 28 and
Figure 25.
Table 28. Color values of pasta
Color values Control CM-T1 CM-T2 CM-T1E CM-T1E p- values
L*- Raw 56.46 ±.01 40.25±.02 40.28±.01 40.31±.02 40.34±.01
p≤0.05*
L* - Cooked 55.73±.03 44.04±0.03 44.06±.01 35.45±.03 35.67±.29
a* - Raw 2.52±.02 5.06±0.02 5.08±.01 2.93±.02 2.89±.02
a* - Cooked 0.10±0.01 5.67±0.02 5.68±.01 6.17±.02 6.11±.01
b* - Raw 20.93±.02 13.31±0.02 13.34±.01 15.05±.03 15.02±.01
b* - Cooked 14.01±0.02 14.62±0.02 14.62±.02 14.62±.02 14.59±.01
Delta E 18.53±0.03 22.53±.02 20.30±.02 22.58±.02
13.42±0.02 23.11±.01 13.43±.01 24.71±.01 All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1 –Pasta formulated using composite millet powder exposed to
forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder exposed to freeze drying,
CM- T1E - Pasta formulated using composite millet powder exposed to forced convection tray drying with addition of egg
white powder. CM- T2E- Pasta formulated using composite millet powder exposed to freeze drying with addition of egg
white powder.
The color is the important quality attribute of pasta
(Rayas-Duarte et al., 1996). The Luminosity (L*) values of the raw pasta prepared
from composite millet powder prior to cooking varied from 40.25 to 40.34 and for
the control pasta it was found to be 56.46. The slight decrement in the luminosity
(p≤0.05) of pasta formulated using composite millet powder was due to the darker
color of the millet seed coat (more brown) when compared to refined flour (maida).
Similar results were observed by Gallegos-Infante et al., (2010) and
Howard et al., (2011) in the formulation of pasta using bean flour or peanut flour.
The decrease in the L* values resulted in increased a* and b* values of pasta
formulated from composite millet powder when compared to control pasta. During
cooking process, the changes occurred in the structure and color of the pasta is mainly
due to flour composition and addition of egg white powder. Hence, it resulted in
declined brightness in pasta and increase in redness which may be associated to the
progression of maillard reaction. Irrespective of the drying methods adopted, the
cooked pasta resulted in less bright (L*), more red (a*) and more yellow (b*) than the
control pasta (p≤0.05).
Figure 25. Color values of pasta
0
20
40
60
80
Control CM-T1 CM-T2 CM-T1E CM-T1E
L*
L* values of ready to cook pasta Raw
Cooked
0
2
4
6
8
Control CM-T1 CM-T2 CM-T1E CM-T1E
a*
a* values of ready to cook pasta
Raw
Cooked
0
5
10
15
20
25
Control CM-T1 CM-T2 CM-T1E CM-T1E
b*
b* values of ready cook pasta Raw Cooked
CM-T1 CM-T2 CM-T1E CM-T2E
CM-T1 CM-T2 CM-T1E CM-T2E
CM-T1 CM-T2 CM-T1E CM-T2E
4.3.1.4.2. Textural profile of pasta
Table 29 and Figure 26 show the textural profile of pasta.
Table 29.Textural profile of pasta
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significantly different (p≤0.05) by DMRT. CM-T1 –Pasta formulated using composite millet powder exposed to
forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder exposed to freeze drying,
CM- T1E- Pasta formulated using composite millet powder exposed to forced convection tray drying with addition of egg
white powder, CM- T2E- Pasta formulated using composite millet powder exposed to freeze drying with addition of egg
white powder.
The textural characteristics of pasta play a vital role in determining the final
acceptance and also show the preference for pasta by the consumer, which retains the
texture characteristics not only with normal cooking time but also with overcooking.
Results revealed that the textural characteristics of the pasta like pasta firmness,
elasticity, adhesiveness, and stickiness are presented in Table 29.
The hardness values of composite millet pasta were higher than the control
pasta. However, it did not make so much difference between the pasta either with or
without incorporation of egg white powder. The firmness was found to be higher in
pasta incorporated with egg white powder than the control pasta and the pasta without
incorporation of egg white powder. Differences in firmness values mainly arise due to
protein present in egg white powder. Increasing the amount of gluten in spaghetti
decreased the amount of residue in the cooking water and increases the force required
to produce a given extension in cooked spaghetti a report by Matsuo and Irvine, 1970
supports the present study. The parameters like adhesiveness or stickiness is related
with the amount of starch and starch gelatinization taking place during processing.
Textural
profile Control CM-T1 CM-T2 CM-T1E CM-T2E p -value
Hardness 1033.4a ± 105.30 1050.5
a ± 108.258 1026.3
a ± 62.508 1298.4
b ± 32.113 1165.4
a,b ± 120.405 0.019*
Adhesiveness -0.732b ± 9.51 -14.04
a ± 1.892 -15.997
a ± 0.802 0.004
b ± 1.060 0.007
b ± 1.076 p≤0.05*
Springiness 0.90b,c
± 0.10 0.79a ± 0.031 0.823
a,b ± 0.031 0.903
b,c ± 0.045 0.960
c ± 0.010 0.017*
Cohesiveness 0.79b,c
± 0.06 0.53a ± 0.044 0.523
a ± 0.025 0.720
b ± 0.035 0.823
c ± 0.059 p≤0.05*
Resilience 0.51a ± 0.08 0.65
b ± 0.072 0.623
b ± 0.021 0.480
a ± 0.030 0.640
b ± 0.036 p≤0.05*
Stringiness 5.92a,b
± 0.48 6.37b,c
± 0.201 6.483c ± 0.146 5.533
a ± 0.115 5.800
a ± 0.100 p≤0.05*
Gumminess 787.83b ± 79.69 591.77
a ± 78.164 559.570
a ± 60.751 1179.957
c ± 30.754 1296.567
c ± 72.857 p≤0.05*
Chewiness 644.25b,c
± 63.59 456.35a ± 107.870 561.3
a,b ± 0.839 924.680
c ± 74.997 720.067
d ± 36.143 p≤0.05*
The adhesiveness values were found to be higher in the early stages of
cooking and it starts to decrease as cooking time proceeds. Water cannot diffuse into
inner layers up to optimum cooking time and protein network does not develop, as a
result starch leaches into cooking water easily. The adhesiveness or stickiness was
found to be higher in pasta without incorporation of egg white powder. This could be
attributed due to nonexistence of gluten in millet which increases the stickiness and
leads to increase in the residue loss of pasta during cooking process.
Cohesiveness is the good indicator to know how the sample holds together
upon cooking. Cohesiveness values of control pasta and pasta either with egg white
powder was higher in their holding properties of structure together since the control
pasta was developed using refined wheat flour which contain high gluten content
whereas in the case of egg white powder incorporated pasta, the protein present in the
egg helps to holds the structure of pasta and prevent the loss of residue.
Chewiness which is associated with the elastic strength of the protein matrix
was highest for control pasta and pasta incorporated with egg white powder. As
cooking time proceeded chewiness of all pasta decreased significantly due to possible
leaching of starch to cooking water (Sozer, 2007). However, the parameters such as
springiness, resilience and stringiness do not show much significant difference
(p>0.05) among the pastas.
Figure 26.Textural profile of pasta
4.3.1.4.3. Morphological structure of pasta
Microscopy internal structure of dry and cooked pasta made from composite
millet powder is shown in Figure 27. Microscopy techniques is used to explore the
information about size, shape, and arrangement of the particles of pastas which can
be further correlated with other characteristics such as texture, cooking
behavior, and digestibility (Fardet et al.,1998). The changes in many physical
uniqueness of food during drying are due to changes in the product microstructure
(Mercier et al., 2011). Microstructure studies revealed significant difference in the
structure of the raw flour, uncooked pasta and cooked pasta of control and composite
millet powder either with or without addition of egg white powder.
Control CM-T1 CM-
CM-T1E
CM-T2E
CM-
The morphological structure of raw flour, uncooked pasta and cooked pasta of
the SEM specimens were examined both at the surface and within the transverse
section of pasta. The starch granules within the pasta appear to be slightly swollen and
irregular in size and shape which indicates the level of gelatinization during the
extrusion process (Tudorica et al., 2007). In control pasta, the structure exhibits a
good network formation which is due to presence of gluten matrix in the maida. A
heterogeneous combination of composite millet powder can be observed in the
micrographs, featuring irregular structures with indefinite shapes, rich in spongy-
aspect material, with cavities and structural gaps of varied sizes. Pagani et al., (1986)
reported a homogeneous and porous structure where starch granules were deeply
embedded in a protein matrix.
In pasta, numerous starch granules of varying sizes were visible on the
structure of uncooked pasta. The numerous minute holes and cracks would facilitate
rapid water penetration during cooking. In addition, many cracks and minute holes
were evident in the protein matrix at the surface. This was partly due to both
shrinkage during sample preparation and surface tension in spaghetti dough during
drying (Alirezasadeghi et al., 2008). As reported in the previous study, the uncooked
spaghetti appears to be coated with smooth protein film (Evans et al., 1975). Whereas
in cooked pasta, the starch granules possessed disturbed structure and the protein
matrix which applies pressure on some starch granules lead to small structural
deformations which indicates the level of gelatinization during cooking process.
During cooking process, the surface of pasta is smooth and the volume of
pasta expanded by imparting the stress on the enveloping protein films. Addition of
egg white powder in pasta showed changes in the outside and inside structure of pasta
products. The uncooked pasta prepared with incorporation of egg white powder was
observed to be quite smooth and regular surface. The inside structure was also
regular, compact with single air bubble on protein matrix and starch granules
attached. In case of cooked pasta egg white powder incorporated, exhibited
gelatinized starch granules and protein matrix with irregular shapes and size.
Flour Raw pasta Cooked pasta
Pasta incorporated with egg white powder
CM-T1-Pasta formulated using composite millet powder exposed to forced convection tray drying;
CM-T2-Pasta formulated using composite millet powder exposed to freeze drying
Figure 27. Morphological structure of pasta
1 2 3
4 5 6
8 9
1
0
1
1
7
Control
CM-T1
CM-T2
4.3.1.4.4. Pasting properties of pasta
The pasting characteristics of the ground pasta samples were studied using a
Rapid Visco Analyzer (Figure 28). The pasting properties of control pasta and the
pasta prepared from composite millet powder is shown in Figure 28. The control pasta
and pasta prepared from composite millet powder subjected to freeze drying was
observed with higher pasting temperature followed by pasta prepared from composite
millet powder subjected to forced convection tray drying. The pasta incorporated with
egg white powder indicates lower pasting temperature which is comparable to those
of pasta without egg white powder.
The pasting temperature is related to breakdown of the hydrogen bonds
between the molecules of starch and swelling of starch granules in the presence of
heat and water. Differences in onset pasting temperature are due to the strength of
bonding of the miscellar network of individual starch granules present in refined
maida flour and millet powder. It is known from the previous literature (Kulp, 1973;
Eliasson and Karlsson, 1983) that small wheat starch granules gelatinize at higher
temperatures than the larger granules. On the other hand, the lower pasting
temperature was noted in egg incorporated pasta which was due to lower starch
content present in millet.
The highest peak viscosity was observed in control pasta when compared to
other pasta. It has been investigated that higher content of starch in flours, to some
extent, may contribute to higher pasting viscosity (Ragaee and Abdel-Aal, 2006).
Therefore, lower protein content in the control pasta might have resulted in higher
starch concentration and hence higher peak viscosity. Higher peak viscosity may also
be due to the ability of starch granules to swell more. Whereas, pasta observed lower
pasting temperature which is due to the presence of protein in millet and egg white
powder. Differences in protein composition are also known to affect pasting
viscosities and properties (Batey and Curtin, 2000). Breakdown values for control
pasta was significantly higher than the pasta prepared from composite millet powder.
Breakdown viscosity reflects the fragility of the swollen granules which first swell
and then breakdown under the continuous stirring action of the amylograph.
Therefore, these values indicate that starch from pasta were more fragile and hence
had less ability to withstand heating at high temperature and the shear stress. Sissons
and Batey (2003) pointed out that high values for breakdown are usually correlated
with high peak viscosity. In the present study, significant difference but not much
variation was found for the setback viscosity values among the pasta. Setback
viscosity that relates to the tendency of the starch to retrograde was significantly
higher in pasta prepared from composite millet powder.
Figure 28. Pasting properties of pasta
4.3.1.5. Sensory characteristics of the pasta developed from composite millet
powder
Sensory evaluation is the primary function of sensory testing conducted to
provide data on which sound decision is taken. It is defined as specific discipline used
to evoke, measure, analyze and interpret the characteristics of food materials as they
are perceived by the senses of sight, smell, taste, touch, and hearing
(Meilgaard et al., 2000). Sensory characteristics like appearance, texture, colour,
taste, flavor, mouthfeel and acceptability were analyzed for the pasta developed from
composite millet powder by formulating score card.
A scorecard is a visual display of the most significant information needed to
accomplish one or more objectives, combined and arranged on a single screen so the
information could be observed at a glance (Stone et al., 2004).
4.3.1.5.2. Evaluation of the product
The two different products namely pasta and extrudates developed from
composite millet powder were subjected to 15 panel members. Based on the
treatments both products were coded commonly as CM-T1 and CM-T2 and was
displayed on a desk. The panel members were asked to examine the products carefully
0
20
40
60
80
100
120
-500
0
500
1000
1500
2000
00:00:00 00:02:53 00:05:46 00:08:38 00:11:31 00:14:24
Vis
cosi
ty(c
p)
Time (mins)
Pasting properties of pasta Control
CM-T1
CM-T2
CM-T1 E
CM-T2 E
Temp
CM-T1
CM-T2
CM-T1E
CM-T2E
for appearance, flavor, taste, color and overall acceptability using the 9-Point hedonic
scale. Different ratings ranging from “Like extremely" to "dislike extremely" were
given by the judges, specifying the values from 9 (like extremely) to 1 (dislike
extremely) respectively. The average scores were taken for each treatment.
Treatments which gained a mean score of 5 and above are acceptable and the one
which scored below 5 points were rejected. This experiment was conducted under a
controlled environment in cool place. The results of the sensory analysis led way to
select the most acceptable products for further analysis (Meilgaard et al.,2000).
4.3.1.5.3 Sensory properties of pasta
The sensory scores of pasta prepared from composite millet powder either
with or without the incorporation of egg white powder were examined by panelist
using 9 point hedonic scale and the scores were analyzed for significance at p≤0.05.
In the present study, the pasta was developed by composite millet powder which is
obtained from forced convection tray drying and freeze drying and also the control
pasta developed from refined wheat flour were analyzed. The scores given by panel
members were compared with control pasta and presented in Table 30 and Figure 29.
Table 30. Sensory properties of pasta
Sensory
Parameters Control CM-T1 CM-T2 CM-T1-E CM-T2-E p - value
Appearance 9.00±0.00a 8.33±0.58
a 9.00±0.00
a 8.67±0.58
a 9.00±0.00
a 0.171
NS
Texture 8.67±0.58a 8.33±0.58
a 9.00±0.00
a 8.38±0.58
a 9.00±0.00
a 0.233
NS
Color 9.00±0.00c 7.33±0.58
a 8.00±0.00
ab 7.33±0.58
a 8.33±0.58
bc 0.005*
Taste 8.67±0.58a 8.00±0.00
a 8.67±0.58
a 8.00±0.00
a 8.67±0.58
a 0.171
NS
Flavour 8.33±0.58a 7.67±0.58
a 8.33±0.58
a 7.33±0.58
a 8.67±0.5
b 0.092
NS
Mouthfeel 8.67±0.58a 8.33±0.58
a 8.67±0.58
a 7.67±0.58
a 8.33±0.58
a 0.274
NS
Overall
Acceptability 8.67±0.58
a 8.33±0.58
a 9.00±0.00
a 8.33±0.58
a 9.00±0.00
a 0.233
NS
All values are means of triplicate determinations ± standard deviation (S.D), Same capitals superscripts in column
indicate the same to each other and different superscripts in column indicates different to each other are significantly
different (p≤0.05) by applying non parametric test using kruskal wallis test. CM-T1 –Pasta formulated using composite
millet powder exposed to forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder
exposed to freeze drying, CM- T1E - Pasta formulated using composite millet powder exposed to forced convection tray
drying with addition of egg white powder. CM- T2E- Pasta formulated using composite millet powder exposed to freeze
drying with addition of egg white. NS-Not Significant powder.
Figure 29. Sensory properties of Pasta
The best appearance was observed in control pasta and pasta produced from
freeze dried composite millet powder with incorporation of egg white powder.
Whereas the pasta prepared from forced convection tray drying had a dark color
hence showed a decrement in the sensory scores. This indicates that consumers
mostly like yellowish appearance of pasta rather than dark appearance. There was no
significant (p≤0.05) difference between the flavor, mouth feel and overall
acceptability scores of pasta and panelists showed the same preference for texture,
flavor, mouth feel and overall scores of pasta samples. Regarding color, the control
pasta was more acceptable than the other samples and it may be due to the effect of
addition of refined flour which could be significantly (p≤0.05) different from other
pasta developed from composite millet powder. The texture evaluation presented a
good score for all samples, with no significant differences (p>0.05) among the
samples with the exception of the pasta prepared from composite millet powder with
incorporation of egg white powder which had the highest result. The control pasta
had the best result in the color assessment (9.00) with significant differences (p≤0.05)
in relation to the other pasta prepared from composite millet powder.
However, it should be noted that the addition of egg white powder had an
impact on improving scores of color and taste of pasta. In general, the results obtained
for the cooked pasta with egg white powder showed an increase in sensory quality by
increasing the mean scores of overall acceptability.
0
1
2
3
4
5
6
7
8
9
10
Appearance Texture Color Taste Flavour Mouthfeel Overall
Acceptability
Sen
sory
sco
res
Pasta ControlCM-T1CM-T2CM-T1-ECM-T2-E
CM-T1
CM-T2
CM-T1E
CM-T2E
4.3.1.6. Effect of storage on the overall acceptability and total plate count (cfu/g)
of the pasta
4.3.1.6.1. Effect of storage on overall acceptability of pasta
In the processed food, the storage quality is an essential attribute to extend
their utilization and was evaluated by several investigators in terms of sensory
characters and chemical components.
The sensory score on ready to cook pasta either with or without the
incorporation of egg white powder was examined over a storage period of 90 days for
every 15 days interval and the scores were analyzed for significance at p≤0.05. In the
present study, the different dehydrated composite millet powder was used for the
developing the product and their shelf life were studied using the overall acceptability
scores of products among the panelist.
The sensory qualities of ready to cook pasta produced from composite millet
powder were evaluated in terms of overall acceptability (Figure 42). Significant effect
on the overall acceptability of stored pasta was observed up to 90th
day of storage.
Maximum over all acceptability was observed at 0th
day, 15th
day, 30th
day and
45th
day in all the samples beyond which the overall acceptability started to decline
(p≤0.05) significantly. Similar results were reported by Duszkiewicz et al., (1988)
that no significant differences between spaghetti containing concentrates and flour for
mouth feel at zero days and after 6 months of storage and for external appearance and
general acceptability after 3 months.
Table 31. Effect of storage on overall acceptability of pasta
All values are means of triplicate determinations± standard deviation (S.D), Same capitals superscripts in column
indicate the same to each other and different superscripts in column indicates different to each other are significantly
different (p≤0.05) by applying non parametric test using kruskal wallis test. CM-T1 –Pasta formulated using composite
millet powder exposed to forced convection tray drying. CM-T2 - Pasta formulated using composite millet powder
exposed to freeze drying, CM- T1E - Pasta formulated using composite millet powder exposed to forced convection tray
drying with addition of egg white powder. CM- T2E- Pasta formulated using composite millet powder exposed to freeze
drying with addition of egg white powder.
Samples 0 day 15 days 30 days 45day 60 day 75 days 90 days p-
value
Control 8.67±.02aA
8.10±.10aB
7.67±.01aC
7.34±.02aD
6.67±.01aE
6.32±.02aF
5.66 .01aG
p≤0.05*
CM-T1 8.34±.01bA
8.68±.01bB
8.67±.01bB
8.37±.01bA
6.66±.01aC
5.65±.02bD
5.33±.01bE
CM-T2 8.35±.02bA
8.67±.01bB
8.69±.02cB
8.67±.010cB
7.33±.01bC
7.32±.01cC
6.32±.02cD
CM-T1E 8.97±.06cA
8.67±.02bB
8.07±.06dC
8.03±.06dC
7.67±.01cD
7.32±.01cE
6.67±.02dF
CM-T2E 8.97±.06cA
8.93±.06cB
8.87±.16dB
8.10±.10dC
8.10±.10dC
7.67±.01dD
7.34±.01eE
p-value (p≤0.05)*
Figure 30. Effect of storage on overall acceptability of pasta
4.3.1.6.2. Effect of storage on the total plate count (cfu/g) of the pasta
The Table 32 explains the total plate count of the pasta
Table 32. Total plate count (cfu/g) of the pasta during storage
Samples
Storage days (cfu/g)
0 Day 15 Days 30 Days 45 Days 60 Days 75 Days 90 Days
Control 1.1X101 1.3X10
2 1.9X10
2 1.8X10
3 2.1X10
3 1.3X10
4 2.9X10
4
CM-T1 7X101 9X10
1 1.3X10
2 1.2X10
3 1.9X10
3 1.3X10
4 2.3X10
4
CM-T2 3X101 7X10
1 1.5X10
2 1.1X10
3 1.3X10
3 1.0X10
4 2.1X10
4
CM-T1E 6X101 1.1X10
1 1.2X10
2 1.4X10
3 2.1X10
3 1.4X10
4 2.3X10
4
CM-T2E 3X101 9X10
1 1.3X10
2 1.3X10
3 2.0X10
3 9X10
4 1.7X10
4
CM-T1-Pasta developed from composed millet powder exposed to forced convection tray drying ;
CM-T2 - Pasta developed from composed millet powder exposed to freeze drying; E- Egg white powder.
Table 32 shows the results of microbial analysis during the storage period.
Microbial analyses of sample during the storage period were analyzed up to 90 days.
Bacterial count was increased gradually 0-90 days for all the samples, still microbial
load was observed within the limits and the products were stable up to 90 days. The
pasta developed either with or without addition of egg white powder (Control, CM-T1,
CM-T2, CM-T1E, and CM-T2E) was analyzed in 0th
, 15th
, 30th
, 45th
and 60th
days
using nutrient agar. As pasta has relatively low water activity, it is generally regarded
as a microbiologically safe product. The results showed that the aerobic plate count of
pasta formulated using composite millet powder either with or without addition of egg
white powder had lesser count when compared to the control pasta. The less aerobic
plate count was observed in sample followed by the CM-T1 and CM-T1E that might
be due to the effect of heat treatment on the survival of bacteria and the highest level
was observed in control which had no heat treatment during processing. Cereals and
their products are prone to attack by yeast and molds (Onyango Christine
Akoth et al., 2012). Low levels of yeasts and molds were detected in 30 days and
2
4
6
8
10
0 15 30 45 60 75 90
Sen
sory
sco
res
Days
control
CMT1
CMT2
CMT1E
CMT2E
CM-T1
CM-T2
CM-T1E
CM-T2E
increased for the remaining of the storage period. The levels remained within the
acceptable standard till 90 days of storage periods.
4.3.2. Evaluation of quality characteristics of extrudates
The quality characteristics of the convenience foods namely ready to eat
(extrudates) product were studies in terms of nutritional, physical, functional,
instrumental and sensory properties including shelf life studies are discussed below.
4.3.2.1. Nutritional properties of extrudates
Table 33 and Figure 31 show the nutritional properties of extrudates.
Table 33. Nutritional properties of extrudates
Nutritional
properties Control CM-T1 CM-T2 p-value
Moisture (g) 8.60c ± 0.03 4.04
b ± 0.02 3.37
a ± 0.15
p≤0.05*
Ash (g) 0.30a± 0.01 2.78
b ± 0.01 2.81
c ± 0.01
Carbohydrates (g) 90.48c ± 0.61 70.85
ba ± 0.02 72.01
a ± 0.02
Protein (g) 6.53a ± 0.03 11.02
b ± 0.01 11.40
c ± 0.01
Fat (g) 2.23c ± 0.03 0.34
b ± 0.03 0.20
a ± 0.02
Energy (Kcal) 404.33b ± .51 303.00
a ± 3.61 308.67
a ± 3.06
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significantly different (p≤0.05) by DMRT. CM-T1-Extrudates formulated using composite millet powder
exposed to forced convection tray drying, CM-T2- Extrudates formulated using composite millet powder exposed to
Freeze drying.
Moisture is one of the variables that are most significant in modifying the
physical properties of extruded products (Avin et al., 1992). The highest moisture
content was observed for control extrudates (8.60g/100g) while lowest moisture
content was noted in extrudates formulated from composite millet powder subjected
to forced convection tray drying (4.04g/100g) and freeze drying (3.37g/100g). The
moisture content of extruded products depend on factors such as the initial feed
moisture content, water binding capacity and vaporization of heat (Park et al., 1993).
Marzo et al., (2002) reported that less influence of extrusion cooking on the
ash content. The ash content of extrudates increased with increase in multimillets
thereby showed higher ash content which range between 2.78 g/100g and 2.81g/100g.
The least ash content was observed in control extrudates (0.30g) made from rice flour.
High amount of ash content was seen in composite millet powder and this could be
attributed to the fact that millets contains high amount of minerals and fibre. The
observed increase in ash content could also be due to addition of multimillets for
formulation of extrudates whereas ash content in control was lesser due to absence of
minerals in rice. The extrusion cooking does not significantly affect the mineral
composition of pea and kidney beans except for iron. Iron content of the flour is
increased after processing and it is most likely due to the result of the wear of metallic
pieces and screws of the extruder (Alonso et al., 2000).
The carbohydrate content of the control extrudates (90.48g/100g) was
significantly higher (p≤ 0.05) than that of the extrudates formulated using composite
millet powder obtained from both dehydration techniques (CM-T1-70.85g/100g and
CM-T2-72.01g/100g). This difference in the carbohydrate was due to abundant starch
present in the rice flour. It was already established that carbohydrates present in millet
are slowly digested and assimilated than other cereals. Regular consumption of millet
helps to reduce the risk of diabetes (Chethan et al., 2008b).
Protein content of the extrudates obtained from both the drying methods varied
from 6.53 to 11.40 g. The protein content is highest in extrudates made from processed
composite millet powder obtained from forced convection tray drying (11.02g/100g)
and freeze drying (11.40g/100g). The change in protein content was attributed due to
the combination of multimillets for the formulation of products. Pelembe et al., (2003)
reported that the apparent protein content was not affected by extrusion temperature as
nitrogen is not affected by heat treatment.
The fat contents of the extrudates are shown in Table 33. The effects of fat on
extrudate properties are also important and multifaceted. Among the extrudates
developed, lowest fat content was noted in control extrudate (0.30g/100g) which is
developed from rice flour when compared to extrudate developed from composite
millet powder subjected to forced convection tray drying (2.78g/100g) and freeze
drying (2.81g/100g). The increase in the fat content is attributed due to the natural
existance of fat in selected millets. Park et al., (1993) found that the higher fat content
lowers the expansion ratio of the product. The 100% of rice flour extrudate (control)
had the lowest fat content and thereby highest expansion ratio. Extrudates prepared
from blends of multimillets showed significantly increased fat content (p≤0.05).
Regarding energy values, the extrudates formulated using composite millet
powder subjected to forced convection tray drying was found to have 303kcal/100g
and for freeze drying it was observed to be 308kcal/100g. High energy values
(404kcal/100g) were observed in control extrudates made from rice flour. The energy
content increases due to higher concentration in rice flour.
During cooking process, the surface of pasta is smooth and the volume of
pasta expanded by imparting the stress on the enveloping protein films. Addition of
egg white powder in pasta showed changes in the outside and inside structure of pasta
products. The uncooked pasta prepared with incorporation of egg white powder was
observed to be quite smooth and regular surface. The inside structure was also
regular, compact, with single air bubble on protein matrix and starch granules
attached. In case of cooked pasta egg white powder incorporated, exhibited
gelatinized starch granules and protein matrix with irregular shapes and size.
Figure 31. Nutritional properties of extrudates
0
2
4
6
8
10
Control CM-T1 CM-T2
(g/1
00
g)
Moisture (g)
0
1
2
3
4
Control CM-T1 CM-T2
(g/1
00
g)
Ash (g)
0
20
40
60
80
100
Control CM-T1 CM-T2
(g/1
00
g)
Carbohydrates (g)
0
5
10
15
Control CM-T1 CM-T2
(g/1
00
g)
Protein (g)
0
0.5
1
1.5
2
2.5
Control CM-T1 CM-T2
(g/1
00
g)
Fat (g)
0
100
200
300
400
500
Control CM-T1 CM-T2
(Kca
l/1
00
g)
Energy (Kcal)
CM-T1 CM-T2
CM-T1 CM-T2
CM-T1 CM-T2
CM-T1 CM-T2
CM-T1 CM-T2
CM-T1 CM-T2
4.3.2.2. Physical properties of extrudates
Table 34 and Figure 32 represent the physical properties of extrudates.
Table 34. Physical properties of extrudates
Physical properties Control CM-T1 CM-T2 p- value
Expansion Ratio (g/100cc) 3.68a ± 0.03 3.20
b ± 0.02 3.31
a ± 0.202 p≤0.05*
Bulk Density (g/ml) 77.32c ± 0.02 74.18
a ± 0.04 74.32
b ± 0.020
p≤0.05* Water Absorption Index(g/ml) 9.78b ± 0.03 8.09
a ± 0.02 8.09
a ± 0.010
Water Solubility Index (%) 33.02c ± 0.02 31.63
b ± 0.01 31.03
a ± 0.025
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA,
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1 –Extrudates formulated using composite millet powder exposed
to forced convection tray drying, CM-T2- Extrudates formulated using composite millet powder exposed to Freeze drying.
In extrusion cooking process, the expansion ratio is the most important quality
parameter connected with product crispiness, water absorption, water solubility, and
crunchiness. In biopolymers extrusion cooking, the viscoelastic material is forced
through the die as a result of the sudden pressure drop that causes part of the water to
vaporize, giving an expanded porous structure (Sawant et al., 2013). The result of
expansion ratio of extrudates indicates that extrudate made from composite millet
powder showed lower expansion ratio when compared to control extrudate. A high
expansion ratio is desirable in production of expanded snacks. The extrudates
prepared from composite millet powder obtained from two drying methods such as
forced convection tray drying (3.20) and freeze drying (3.31) had lower expansion
ratio as compared with control extrudates prepared from rice flour (3.68). It was due
to the increase in protein and fiber content which resulted in a decrease in expansion
ratio of extrudate. Similar findings were observed by an Jones et al., (2000) where
there was a decrease in expansion ratio of extrudates due to increase in protein and
fiber content Balandrán-quintana et al., (1998) reported that, as the temperature of
extrusion cooking increased, the starch present in extrudates gets completely cooked
and thus resulted in the better expansion of products.
The bulk density (g/ml) was calculated by measuring their actual dimensions
of the extrudate products. Asare et al., (2004) reported that bulk density has been
linked with the expansion ratio in describing the degree of puffing in extrudates. The
bulk density was minimum for control extrudate (73.99 gcm3) and maximum for
extrudate (CM-T1- 74.18, CM-T2 - 74.32) prepared from composite millet powder.
The higher bulk density may be due to the presence of protein in the composite millet
powder which reduces the puffing quality of extrudate. The bulk density was
increased as the quantity of cereals starch increases in extrudates. Similar findings
were observed by Quing et al., (2005).
Water solubility index is the indication of degree of gelatinization.
Gelatinization of starch is associated with the disruption of granular structure causing
starch molecules to disperse in water (Wajira and Jackson, 2006). Water solubility
index was observed to be significantly increased (p≤0.05) in control extrudates
(33.023%) when compared with the extrudates prepared from composite millet
powder obtained from forced convection tray drying (31.63 %) and freeze drying
(31.03%). The increase in the water solubility index shows macromolecular
degradation depending upon the intensity of extrusion process (Sirawdink Fikreyesus
Forsido et al., 2011).
Water absorption index reflects the ability of starch to absorb water and is an
indirect measure of the amount of intact and fully gelatinized starch granules. Water
absorption index was observed to have slight increase in control extrudates (9.73%)
whereas the extrudates developed from composite millet powder obtained from forced
convection tray drying (8.09%) and freeze drying (8.09%) was decreased which showed
significant differences (p≤0.05) between the control and composite millet powder
extrudates. Increased water absorption index in extrudate led to increase in starch
gelatinization (Colonna et al., 1989 and Osman et al., 2000).
Figure 32.Physical properties of extrudates
0
1
2
3
4
5
Control CM-T1 CM-T2
(g/1
00
cc)
Expansion Ratio (g/100cc)
0
20
40
Control CM-T1 CM-T2
(%)
Water Absorption and Solubility Index (%)
Water Absorption
Index %
Water Solubility
Index (%)
CM-T1 CM-T2 CM-T1 CM-T2
Control CM- T1 CM-T2
70
72
74
76
78
80
Control CM-T1 CM-T2
(g/m
l)
Bulk Density (g/ml)
CM-T1 CM-T2
4.3.2.3. Functional properties of extrudates
Functional food is a natural or processed food that contains known
biologically-active compounds and powerful antioxidant nutrients which provides a
clinically proven and documented health benefit. In the present study, the functional
properties such as Essential amino acid profile, Essential fatty acid, vitamins,
phytochemicals and antioxidant activity were carried out for the developed extrudates
4.3.2.3.1. Essential amino acid (mg/100g) profile of extrudates
Table 35 and Figure 33 show the result of essential amino acid profile of the
extrudate.
Table 35. Essential amino acid (mg/100g) profile of extrudates
Essential amino acids
(g/100g)
Control CM-T1 CM-T2 p- value
Histidine 0.14a±0.01 0.45
b±0.01 0.47
c±0.01 0.000*
Valine 0.33c±0.01 0.18
a±0.01 0.20
b±0.01 0.000*
Methionine 0.14a±0.01 0.29
b±0.01 0.31
c±0.01 0.000*
Isoleucine 0.23c±0.01 0.21
a±0.01 0.22
a,b±0.01 0.064
NS
Phenylalanine 0.31a±0.01 0.77
b±0.01 0.89
c±0.01 0.000*
Leucine 0.48c±0.01 0.27
a±0.01 0.29
b±0.01 0.000*
Lysine 0.19a±0.01 0.39
b±0.01 0.40
b±0.01 0.000*
Proline 0.22b±0.01 0.02
a±0.01 0.01
a±0.01 0.000*
Tryptophan 0.07a±0.01 0.31
b±0.01 0.33
c±0.01 0.000*
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1 –Extrudates formulated using composite millet powder exposed
to forced convection tray drying, CM-T2- Extrudates formulated using composite millet powder exposed to Freeze drying.
NS –Not Significant.
The change in amino acid content during the extrusion of extrudates
developed from composite millet powder. Most of the extruded products are made
from durum wheat which contains both protein and gluten. The protein in extruded
product is low to medium depending on the type of powder. The total amount of
essential amino acid composition in both the dried extrudates range between
0.013-0.887g/100 g in composite millet powder and 0.067- 0.477g/100 g in
control (rice flour). The value of valine, metheonine, leucine, tryptophan and
isoleucine, histidine was significantly (p≤0.05) reduced during extrusion cooking.
However, lysine, leucine, threonine and phenylalanine were not significantly (p>0.05)
affected. The highest concentration of conditionally essential amino acids for the
composite millet powder was threonine while the least was valine. Finger millet
contains 44.7% essential amino acids (FAO, 1991) of the total amino acids
which is higher when compared with the reference protein (33.9%) (FAO, 1991).
Tryptophan is usually considered as the second most deficient amino acid in cereals
however it is not deficient in finger millet (Ravindran, 1992). Among the millets,
finger millet is relatively better balanced in essential amino acids because it
contains more lysine, thereonine and valine (Lupien, 1990). The isoleucine content
of finger millet is also high. It is evident that composite flour prepared by blending
multimillets in proportion can provide the required amino acids to the consumer.
Figure 33. Essential amino acid (mg/100g) profile of extrudates
4.3.2.3.2. Vitamin content of extrudates
Table 36 and figure 34 shows the vitamin content of extrudates which are
discussed below.
Table 36. Vitamin content of extrudates
Vitamins Control CM-T1 CM-T2 p –value
Vitamin A 0.00a±0.00 94.17
b±0.06 94.57
c±0.06
p≤0.05*
Vitamin D 0.00a±0.00 3.42
b±0.01 3.44
c±0.01
Vitamin E 0.11a±0.01 1.31
b±0.01 1.36
c±0.01
Vitamin B6 0.44a±0.01 3.44
b±0.01 3.46
c±0.01
Vitamin B12 0.00a±0.01 0.33
b±0.01 0.35
c±0.01
All values are means of triplicate determinations± standard deviation (S.D), * significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1 –Extrudates formulated using composite millet powder exposed
to forced convection tray drying, CM-T2- Extrudates formulated using composite millet powder exposed to Freeze
drying.
When compared with other nutrients, the daily intake of vitamins is comparably
lesser but is essential for good health because of the role of vitamins as coenzymes in
metabolism. The focus is to study the effect of extrusion on the recovery of vitamins
and minerals that are added prior to extrusion. From the above table the vitamin
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Histidine Valine Methionine Isoleucine Phenylalanine Leucine Lysine Proline Tryptophan
(mg
/10
0g
)
Essential amino acids (mg/100g) Control
CM-T1
CM-T2
T1
T2
content of extrudates shows slight decrement during extrusion process. When
compared with control extrudates developed from rice flour, the extrudate prepared
from composite millet powder shows higher vitamin content. This might be due to
multimillets in the composite blends which are used for extrudate development. The
property of extrusion however showed destructive effects for vitamins from the
B-groups, vitamin A and vitamin E and more over no data on the retention for vitamin
D and vitamin K were presented (Killeit, 1994).
Figure 34.Vitamin content of extrudates
4.3.2.3.3. Essential fatty acid (mg/100g) composition of extrudates
The table 37 and figure 35 represents the essential fatty acid composition of
the extrudates.
Table 37. Essential fatty acid (mg/100g) composition of extrudates
Essential fatty acids
(mg/100g) Control CM-T1 CM-T2 p –value
Palmitic acid 0.35a ±0.00 0.99
b±0.00 0.99
b±0.00
p≤0.05*
Stearic acid 0.02a ±0.00 0.03
b±0.00 0.04
c±0.00
Oleic acid 0.44a ±0.00 0.78
b±0.01 0.79
b±0.00
Linoleic acid 0.07a ±0.00 1.34
b±0.01 1.38
c±0.01
Alpha Linoleic acid 0.00a ±0.00 0.78
b±0.00 0.78
c±0.00
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1 –Extrudates formulated using composite millet powder exposed
to forced convection tray drying, CM-T2- Extrudates formulated using composite millet powder exposed to Freeze
drying.
The palmitic, stearic, oleic, linoleic and α-linolenic acids found in control
extrudates were 0.346%, 0.023%, 0.437%, 0.067%, and 0.00% respectively. The
essential fatty acid composition of extrudates prepared from composite millet powder
from both the drying techniques is depicted in Table 37.
0
20
40
60
80
100
120
Vitamin A
(IU)
Vitamin D (mg) Vitamin E (mg) Vitamin B6
(mg)
Vitamin B12
(mg)
Vitamin (g/100g) Control
CM-T1
CM-T2
T1
T2
The results revealed that extrusion conditions did not significantly affect the
composition of essential fatty acid content. The concentration of linoleic acid was
observed to be maximum for both the drying methods (CM-T1-1.34%, CM-T2-1.38%)
when compared to other fatty acids. The palmitic acid concentration range from a
minimum value of 0.99% to a maximum value of 0.99% as a result of different type
of dehydration observed in extrusion. The stearic acid was almost similar in both the
drying methods. Camire (2001) reported that during extrusion process the loss of fatty
acid content in the extrudates can be attributed due to the formation of complexes
between lipid and protein. These values are in line with the values of the fatty acids
distribution of lipid fractions extracted from corn meal samples as reported by
Guzman et al., (1992).
Figure 35. Essential fatty acid (mg/100g) composition of extrudates
4.3.2.3.4. Antioxidant activity of extrudates
4.3.2.3.4.1. DPPH scavenging activity of extrudates
Table 38 and Figure 36 shows the DPPH activity of extrudates.
Table 38. DPPH scavenging activity of extrudates
Figure36. DPPH scavenging activity of extrudates
Radical-scavenging activity, employing DPPH, has been extensively used in
the field of food processing for screening the antioxidant capacity of products
0
0.5
1
1.5
2
Palmitic
acids
Stearic acis Oleic acids Linoleic acids Alpha
Linoleic acids
(mg
/10
0g
)
Essential fatty acids (mg/100g) Control
CM-T1
CM-T2
CMT1-y = 0.634x + 9.791
R² = 0.982
IC50-63.421 CMT2-y = 0.676x + 1.141
R² = 0.986C
IC50-72.27 0
50
100
0 100 200
Per
cen
tag
e
inh
ibit
ion
Concentration (µg/ml
DPPH radical scavenging activity
Ascorbic acid
CM-T1
CM-T2
Concentration
(µg/ml
Percentage of Inhibition
Ascorbic
acid CM-T1 CM-T2
20 31.14 19.5 14.41
40 50.19 39.16 29.96
60 69.89 47.23 38.15
80 74.86 61.63 58.13
100 95.21 71.68 67.96
CMT1-Composite millet powder; T1- Forced convention tray
drying; T2-Freeze drying.
T
1
T
1
(Robards et al., 1999; Sanchez-Moreno, 2002). In the current study, DPPH was
expressed as mmol Trolox/g in dry sample. The extracts of dry extrudates developed
from composite millet powder at concentration of 20mg/ml scavenged 19.5% and
14.41% DPPH respectively, while a significant (p≤0.05) enhancement in the
scavenging activity was observed when the concentration was increased to
100mg/ml respectively.
When the concentration of the crude extract of sample was increased to
100mg/ml, the extracts of CM-T1 and CM-T2 registered to increase in double the
fold of scavenging activity. Similarly, the estimated IC50 values of extrudates
CM-T1 and CM-T2 were 63.421 and 72.27mg/ml respectively. This was supported by
Brand-Willams et al., (1995) who stated that the method of scavenging stable DPPH
free radicals can be used to evaluate the antioxidant activity of exact compounds. The
low antioxidant content was observed in the extrudates prepared from forced
convection tray drying when compared to freeze drying is due to the fact that the
molecules acting as antioxidants that were present in the raw samples are generally
destroyed during the high temperature used in processing of powder and also by
extrusion cooking.
4.3.2.3.4.2. Reducing power of extrudates
Table 39 and Figure 37 shows the reducing power of extrudates.
Table 39. Reducing power of extrudates
F Figure 37. Reducing power of extrudate
There was no significant difference in the extrudate developed from composite
millet powder obtained from two different drying methods such as forced convection
tray drying and freeze drying. The reducing power of CM-T1 at 0.05-1.00mg/ml of
concentration varies from 0.058-0.56mg/ml and for CM-T2 the range was about
0.08-0.51mg/ml. When comparing between the standard ascorbic acids the reducing
0
2
0 0.05 0.1 0.15
Ab
sorb
an
ce 7
00
nm
Concentration(µg/ml)
Reducing powder
control
CM-T1
CM-T2
Concentration
(mg/ml)
Absorbance of 700nm
Ascorbic
acid CM-T1 CM-T2
0.02 0.39 0.058 0.08
0.04 0.663 0.136 0.17
0.06 1.053 0.279 0.29
0.08 1.341 0.426 0.37
0.1 1.45 0.56 0.51
CM-T1-Extrudates developed using composite millet
powder exposed to forced convention tray drying.
CM-T2-Extrudates developed using composite millet
powder exposed to freeze drying.
powder was found to be lower in extrudate developed from composite millet powder.
The antioxidant activity increased as a function of the development of the reducing
power (Oyaizu, 1986).
4.3.2.4. Instrumental analysis of extrudates
4.3.2.4.1. Color values of extrudates
Table 40 and Figure 38 show the color of extrudates.
Table 40. Color values of extrudates
Color
values Control CM-T1 CM-T2 p –value
L* 84.40c ± 0.30 46.27
a ± 0.025 47.22
b ± 0.015
p≤0.05* a* 3.10a ± 0.10 9.30
b ± 0.015 9.93
c ± 0.392
b* 12.13a ± 0.15 21.08
b ± 0.020 22.19
c ± 0.020
All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1-Extrudates formulated using composite millet powder exposed
to forced convection tray drying; CM-T2-Extrudates formulated using composite millet powder exposed to freeze drying.
Color is an important parameter which directly relates to the acceptability of
food products and also gives the information about the extent of browning reactions
such as caramelization, maillard reaction, degree of cooking and pigment degradation
during the extrusion process (Ilo and Berghofer, 1999). Also, color considers being
essential to attract consumers to increase the product marketing (Finely, 1985).
The extrudates prepared from composite millet powder were darker
(lower „L‟ values) than the control extrudates developed from rice flour. The L*
values were found to be lower in extrudates prepared from composite millet powder
(46.27, 47.22) as compared with control extrudates (84.40). The addition of multi
millets resulted in darker shades of the extrudates and also the extrusion process
would have induced chemical changes on increased addition of millet powder.
The changes in a* values of extrudates were from negative to positive
(green to red). The a* value was high in the extrudates obtained from composite
millet powder (9.30, 9.93) when compared to control extrudates prepared from rice
flour (3.10). Darker color in the products is due to the caramelization of sugar by
maillard reaction. With addition of composite millet powder, the extrudate became
more yellow due to increase in positive b* values. Maillard reaction or non-
enzymatic browning would have resulted in a complex set of reactions initiated by
reactions between amines and carbonyl compounds at elevated temperature would
decompose and eventually condense into insoluble brown pigments known as
melanoidins (Damodaran,1996). The higher protein content of millet powder and
presence of sugars may have enhanced maillard browning of extrudates.
Figure 38. Color values of extrudates
4.3.2.4.2. Textural profile of extrudates
Table 41 and Figure 39 represent the texture profile of extrudates.
Table 41.Textural profile of extrudates
Sample Hardness Crispness
Control 1282.9a ± 2.587 2.03
c ± 0.058
CM-T1 1884.3b ± 1.752 1.71
b ± 0.004
CM-T2 2124.17c ± 1.950 1.11
a ± 0.002
p- value p≤0.05* All values are means of triplicate determinations± standard deviation (S.D), * Significantly different (p≤0.05) by ANOVA.
The same superscripts in row indicate the same to each other and different superscripts in row indicates different to each
other are significant different (p≤0.05) by DMRT. CM-T1-Extrudates formulated using composite millet powder
subjected to forced convection tray drying, CM-T2-Extrudates formulated using composite millet powder subjected to
freeze drying.
In extruded products, the textural profile is considered to be one of the
important parameters which are closely associated with the consumer acceptance. The
quality of processed ready-to eat extruded products should be produced with harder
texture than the commercial snack food, which helps to hydrate more slowly and
retain their desired crispness longer when consumed with milk. In the present study,
the hardness and crispness of ready to eat extrudate was carried out, as they are
closely associated with the expansion and cell structure of the product. The
instrumental method used for the measurement of hardness is the maximum
force required for a probe to penetrate the extrudate. With regard to the hardness
of the extrudates, the composite millet powder extrudates resulted in a significant
increase as shown in Figure 30 when compared with control extrudates developed
from rice flour. Increased fiber and starch content of multi millets resulted in rupture
of gas cells, which reduced overall expansion and increased hardness.
Change in the hardness of extrudates was probably due to cell wall thickness
to make the product less porous. Similar findings were reported by
0
50
100
Control CM-T1 CM-T2C
olo
ur
va
lue
L*,a*,b* value of extrudates L*
a*
b*
CM-T1 CM-T2
Mendonca et al., (2000); Yanniotis et al., (2007) and Ainsworth et al., (2007).
Likewise, increasing the moisture content possibly resulted in a lower degree of starch
gelatinization and lower expansion which showed increasing hardness in extrudates.
Whereas in the case of crispness, the control extrudates (2.03) found to be more crispy
when compared with the extrudates prepared from composite millet powder
formulated using two dryers like forced convection tray drying (1.71) and freeze
drying (1.11). This might be due to reduced starch conversion and compressed bubble
growth eventually resulting in a dense product and reduced crispness (area under the
force-deformation curve) (Ding et al., 2005).
Figure 39. Textural profile of extrudates
4.3.2.4.3. Morphological structure of extrudates
Figure 40 shows the effect of extrusion on extrudates cellular structure. The
scanning electron micrograph (SEM) result shows the inner structure of raw flour
before and after extrusion. Before extrusion, the SEM micrograph indicates the intact
arrangement of starch granules, visible protein matrix and decreased air cell size. The
SEM micrographs indicate that the drastic changes observed in the extrudates after
extrusion process. As a result of high temperature during extrusion, damage of starch
granules and protein matrices has occurred which intern showed large number of
flattened and sheared granules in the extrudates. The partially damage of particles was
highest in the case of extrusion at temperature 120°C. The air cell walls and
honeycomb structure became thinner and collapsed as a result of high temperature.
This may be due to the breaking of hydrogen bonds in starch and their reformation
resulting in grafting of starch. Addition of multimillets decreased the mean air cell
size. Moreover, the number of air cells increased and cell wall thickness decreased
which is associated with protein and starch granules. The collapse of cell walls and
CM-T1
CM-T2
CM-T2
the appearance of large void spaces within the extrudates were observed as the
expansion volume in the control extrudates increases. Whereas, in the case of
composite millet powder extrudates, the air cell walls are composed mainly of
gelatinized starch matrices and cooked proteins. Large air gaps occurred in the control
extrudates which constitutes the starch matrix. Smaller air gaps and smaller pores
(tiny air cells) were observed to be increased in the extrudates developed from
composite millet powder. The tiny air cells were more evident in the gelatinized
starch matrices at high magnification and also observed in the cooked protein
inclusions (Figure 40). However, these tiny air cells were less abundant than those in
the gelatinized starch matrices in control extrudates.
CM-T1 Raw powder CM-T1 Extrudates
CM-T2 Raw powder CM-T2 Extrudates
CM-T1 Cross section CM-T2 Cross section
Figure 40. Morphological structure of extrudates
B
D
a b
c d
A B
The scanning electron microscopy examination for cross section of composite
millet powder extrudates exhibited the presence of small numbers of air cells of
irregular shapes. In extruded product, the starch is gelatinized allowing it to expand
fully and resulted in numerous air bubbles, which differentiate the cell structure
providing a suitable tool to differentiate the level of gelatinization.
4.3.2.4.4. X-ray Diffraction pattern and relative crystallinity of composite millet
powder
The starch structure can be identified at the light microscope level
(Figure 41 a and b) and through characteristic x-ray diffraction patterns. The X-ray
diffractograms of processed composite millet powder is shown in Figure 41a and b.
Figure 41a. X-ray diffractograms of composite millet powder
CM-T1
CM-T2
Figure 41b. X-ray diffractograms of extrudates
The crystalline structure exhibited distinct x-ray diffraction pattern that can be
classified into three categories namely A, B and C type crystal structure. In raw flour
A, B type x ray diffraction patterns are characterized by clear diffraction peaks
(CM-T1-18.33º, and CM-T2-18.33º) and the A-pattern was generally regarded as
cereal starch crystal form. According to Miyoshil, (2002) the raw sample showed a
type A X-ray pattern, typical of cereal starches, with main peaks at 2θ values of ≈
15.1°A, ≈19.2º A, and ≈22.4º A. But during extrusion, the crystalline patterns of
starch get destroyed due to process of gelatinization and the retrogradation lead to the
formation of altered peaks at CM-T1-22.9º A and CM-T2 -23.11° A showed the
V-type pattern. These effects are mainly due to the effect of thermal processing during
extrusion. The formation of V-type pattern was attributed mostly due to the formation
of the amylose-lipid complex in extruded products. The similar pattern has been
observed by Singh et al. (1998), while studying the different extrudates treated with
cereal flours.
4.3.2.4.5. Pasting properties of extrudates
The RVA study of the extrudates showing their peak, hold and final viscosities
along with their breakdown and setback values are shown in Figure 42. The control
extrudate has the highest peak viscosity and final viscosity of 2761cP and 5018cP
respectively and found to be significantly (p≤0.05) higher than the other extrudates.
The extrudate prepared from composite millet powder (CM-T2) has the lowest peak
CM-T1
CM-T2
viscosity of 566 cP and also the lowest final viscosity of 418cP. It was observed that
the pasting temperature was not detectable for extrudate prepared from forced
convection tray dried powder which could be owed to the destruction of starch
granules when subjected to extrusion process. This may be attributed to the higher
degree of gelatinized starch in the extrudate that allowed it to absorb large quantities
of water. According to Liu et al., (2006), starch content in the flour, other components
in the starch-water system and processing of flours are very critical to pasting
properties. The interaction of other components and the degree of starch damage
during extrusion could affect the peak viscosity of extruded flours.
Figure 42. Pasting properties of extrudates
4.3.2.5. Sensory properties of extrudates
Ready-to-eat (RTE) breakfast cereals and snacks are developed for
formulations of suitable products for consumption without any further cooking
process. These are favored by consumers of all ages because of their
convenience, variety and high nutritional value. Most of the breakfast cereals are
made primarily from corn, wheat, oat or rice, usually with added flavor and coated
with sugar and other sweeteners (Muhammad Asif, 2011). In the present study, the
ready to eat extrudates were developed by using the composite millet powder. In order
to improve the acceptability of extrudate the different variations were formulated in
which plain extrudates with milk, extrudates in milk with choco powder and
extrudates with spice mix were carried out.
4.3.2.4.5.1. Sensory properties of extrudates (plain)
Table 42 and Figure 43a shows the sensory analysis of extrudates.
0
20
40
60
80
100
120
0
1000
2000
3000
4000
5000
6000
00:00:00 00:02:53 00:05:46 00:08:38 00:11:31 00:14:24
CM-T1
CM-T2
Control
Temp
Table 42. Sensory properties of extrudates (plain)
Sensory parameters Control CM-T1 CM-T2 p-value
Appearance 8.33±0.58a 8.83±0.28
a 9.00±0.00
a 0.154
NS
Texture 8.67±0.58a 7.17±0.28
b 8.33±0.28
a 0.009
NS
Color 8.83±0.28a 7.83±0.28
a 8.17±0.28
a 0.014
NS
Taste 8.50±0.50a 7.00±0.50
a 7.50±0.50
b 0.027
NS
Flavour 7.83±0.76a 7.33±0.29
a 8.00±0.50
b 0.369
NS
Mouthfeel 8.50±0.50a 7.17±0.29
a 8.33±0.29
a 0.009
NS
Aftertaste 8.00±0.50a 7.50±0.50
b 8.17±.0.29
a 0.422
NS
Overall acceptability 8.00±0.58a 7.50±0.28
a 7.83±0.29
a 0.079
NS
All values are means of triplicate determinations± standard deviation (S.D), CM-T1-Extrudates formulated using
composite millet powder subjected to forced convection tray drying; CM-T2-Extrudates formulated using composite
millet powder subjected to freeze drying. NS-Not Significant. Same capitals superscripts in column indicate the same to
each other and different superscripts in column indicates different to each other are significantly different (p≤0.05) by
applying non parametric test using kruskal wallis test. NS-Not Significant.
The scores sensory evaluation of the extrudates prepared from composite
millet powder is presented in Table 42. The result shows that the control extrudates
were highly rated except the other two extrudates developed from composite millet
powder whose color was darkened due to addition of composite millet. The
extrudates formulated using composite millet flour were not significantly (p>0.05)
different in terms of appearance, texture, color, taste, flavor, aftertaste, mouth feel
and overall acceptability. Whereas, control extrudates was rated highest and
significantly different (p<0.05) in color, taste and flavor.
4.3.2.4.5.2. Sensory properties of extrudates with choco milk
The sensory scores of ready to eat extrudates products with choco milk are
shown in Table 43 and Figure 43b.
Table 43. Sensory properties of extrudates with choco milk
Sensory parameters Control CM-T1 CM-T2 p-value
Appearance 8.50±0.50a,b
8.17±0.29a 9.17±0.29
b 0.042
NS
Texture 8.50±0.50a 7.17±0.29
b 9.17±0.29
a 0.002*
Color 9.17±0.50a 8.17±0.29
b 8.50±0.50
b 0.593
NS
Taste 8.17±0.29a 8.00±0.00
a 9.17±0.29
b 0.002*
Flavour 8.17±0.29a 8.17±0.29
a 9.33±0.29
b 0.004*
Mouthfeel 8.50±0.50a 8.67±0.29
a 9.17±0.29
a 0.154
NS
Aftertaste 8.17±0.58a 9.00±0.00
b 8.17±.0.29
a 0.007
NS
Overall acceptability 8.17±0.58a 8.17±0.28
a 8.83±0.28
a 0.548
NS
All values are means of triplicate determinations± standard deviation (S.D), Same capitals superscripts in column
indicate the same to each other and different superscripts in column indicates different to each other are significantly
different (p≤0.05) by applying non parametric test using kruskal wallis test. CM-T1-Extrudates formulated using
composite millet powder subjected to forced convection tray drying; CM-T2-Extrudates formulated using composite
millet powder subjected to freeze drying. NS-Not Significant.
The mean scores of sensory evaluation showed that the extruded products
soaked in choco milk prepared from composite millet powder were within the
acceptable range and had significantly better appearance (9.17), color (7.9),
flavour (9.33), texture (9.17), taste (9.17) and overall acceptability (8.83) when
compared with the control extrudates. There were no significant differences (p>0.05)
in appearance, mouth feel, aftertaste and overall acceptability among extrudates
formulated using composite millet powder from both drying methods. The CM-T2 had
a higher score in attributes namely appearance, texture, taste, mouth feel and overall
acceptability when compared to the other extrudates. This could be due to lower heat
treatments performed on millet flour during processing. Chen et al., (1991) reported
that during extrusion the color changes to brown, this may be due to
decomposition of pigments, product expansion causing fading and chemical
reactions like caramelization of carbohydrates. Among extrudates the coco blends
formulated products, CM-T2 was found to be acceptable among the panelist.
4.3.2.4.5.3. Sensory analysis of extrudates with spice mix
Table 44 and Figure 43c depicts the extrudates with spice mix
Table 44. Sensory properties of extrudates – spice mix
Sensory parameters Control CM-T1 CM-T2 p-value
Appearance 7.83±0.29a 7.33±0.29
a 8.33±0.29
a 0.016
NS
Texture 7.50±0.50a 6.83±0.29
b 7.17±0.29
a 0.171
NS
Color 7.67±0.58a 7.33±0.58
a 7.17±0.29
a 0.014
NS
Crispness 8.17±0.29 a 8.00±0.00
a 8.33±0.58
a 0.579
NS
Taste 8.50±0.50a 7.00±0.50
a 7.50±0.50
b 0.027
NS
Flavour 7.17±0.29a 7.50±0.50
a 7.33±0.29
b 0.369
NS
Mouthfeel 7.90±0.17a 6.50±0.50
a 6.50±0.29
a 0.009
NS
Aftertaste 7.17±0.29a 6.50±0.50
b 7.33±.0.29
a 0.422
NS
Overall acceptability 8.17±0.29a 8.00±0.50
a 8.67±0.76
a 0.079
NS
All values are means of triplicate determinations± standard deviation (S.D), Same capitals superscripts in column
indicate the same to each other and different superscripts in column indicates different to each other are significantly
different (p≤0.05) by applying non parametric test using kruskal wallis test. CM-T1-Extrudates formulated using
composite millet powder subjected to forced convection tray drying; CM-T2-Extrudates formulated using composite
millet powder subjected to freeze drying. NS-Not Significant.
Results from the panelist for the acceptance of products and the average mean
scores of the sensory parameters namely appearance, taste, texture, flavor, crispness,
mouthfeel, aftertaste and overall acceptability of the extrudates with the spice mix is
presented in Table 44. Significant difference (p≤0.05) was observed between control
extrudates and extrudate formulated using composite millet powder with the sensory
parameters namely appearance, taste, texture, flavor, crispness and surface of the
product. The mean scores of the overall acceptability of the control extrudate (8.17)
and the extrudate formulated using composite millet powder obtained from both
dehydration techniques (8.00-CM-T1 and 8.67-CM-T2) was found to more or less
similar. The addition of composite millet powder has improved the flavor of the
product at the same time the composite millet powder affected the mouth feel of the
product when compared to the control due to characteristics taste of the millet. These
results agree with the findings of Acosta-Sanchez (2003); Perez-Gonzalez (2005),
who mentioned that crunchy texture and gritty appearance of the whole grain sorghum
extrudates were liked by consumer sensory panel.
Figure 43 a. Sensory properties of extrudates (plain) Figure 43 b. Sensory properties of extrudates (choco mix)
Figure 43 c. Sensory properties of extrudates (Spice mix)
0
2
4
6
8
10
Appearance Texture Color Taste Flavour Mouthfeel Aftertaste Overall
accepability
Sen
sory
sco
res
Plain Control
CM-T1
CM-T2
0
2
4
6
8
10
12
Appearance Texture Color Taste Flavour Mouthfeel Aftertaste Overall
accepability
Sen
sory
Sco
res
choco milk
Control
CM-T1
CM-T2
0
2
4
6
8
10
Appearance Texture Color Crispness Taste Flavour Mouthfeel Aftertaste Overall
accepability
Sen
sory
sco
res
Spice mix Control CM-T1
CM-T2
4.3.2.6. Effect of storage on the overall acceptability of extrudates and total plate
count (cfu/g) of extrudates
4.3.2.6.1. Effect of storage on overall acceptability of extrudates
Table 45 and figure 44 depicts the sensory scores of overall acceptability of
extrudates.
Table 45. Effect of storage on overall acceptability of extrudates
Samples 0 days 15 days 30 days 45 days 60 days 75 days 90 days p -value
Control 8.33±.01Aa
8.10±.10aA
7.67±.01aB
7.34±.02aC
5.68±.01aD
5.33±.01aE
3.89±.39aF
p≤0.05* CM-T1 8.67±.02
bA 8.68±.01
bA 8.67±.01
bA 8.34±.01
bB 7.33±.01
bC 7.3700±.06
bC 6.22±.20
bD
CM-T2 8.78±.17bA
8.67±.07Ab
8.69±.02bA
8.67±.01cA
8.34±.02cB
7.3333±.01bC
7.34±.01cC
p- value (p≤0.05)*
All values are means of triplicate determinations± standard deviation (S.D), Same capitals superscripts in column
indicate the same to each other and different superscripts in column indicates different to each other are significantly
different (p≤0.05) by applying non parametric test using kruskal wallis test.CM-T1-Extrudates formulated using
composite millet powder subjected to forced convection tray drying; CM-T2-Extrudates formulated using composite
millet powder subjected to freeze drying.
There was a significant decrease in sensory scores of extrudates during the
storage period from 0th
day to 90th
day. The composite millet powder extrudates were
rated high for over all acceptability of 8.78 in 0th
day and 7.34 in 90th
day when
compared to control extrudates with the sure of 8.33 in 0th
day and 3.89 in 90th
day.
As the duration of storage period increased there was a decrease in the scores of
overall acceptability of the products (P≤0.05). Thus, extrudates prepared from
composite millet powder and control extrudates were found to be acceptable even at
the end of storage period of six months. After 6 months the slight decrement in the
scores of all the extrudates were noted.
Figure 44. Effect of storage on the overall acceptability of extrudates
2
4
6
8
10
0 15 30 45 60 75 90
Sen
sory
sco
res
Days
control
CMT1
CMT2
CMT1E
CMT2E
CM-T1
CM-T2
CM-T1E
CM-T2E
4.3.2.6.2. Effect of storage on total plate count of extrudates
Table 46 explains the microbiological analysis of the extrudates. The
microbiological changes are measured by the total plate count in the extrudate
products formulated from composite millet powder prepared from two drying
methods and it was stored at room temperature.
Table 46. Effect of storage on total plate count of extrudates
Samples Storage days (cfu/g)
0 Day 15 Days 30 Days 45 Days 60 Days 75 Days 90 Days
Control 9x101
1.3x102 1.6x10
2 2.8x10
2 1.3x10
3 1.7x10
3 2.5x10
3
CM-T1 6x101 1.0x10
2 1.4x10
2 2.6x10
2 1.0 x10
3 1.5x10
3 2.2x10
3
CM-T2 5x101 1.1x10
2 1.5x10
2 2.6x10
2 1.2x10
3 1.7x10
3 2.3x10
3
CM-T1-Extrudates formulated using composite millet powder subjected to forced convection tray drying;
CM-T2-Extrudates formulated using composite millet powder subjected to freeze drying.
The microbiological load as measured by the total plate count per gram of
sample was generally low in all the extrudates prepared. This shows that
temperature and drying parameters maintained to have a significant effect on the
growth of micro-organisms. Generally as the storage time increased, the measured
total plate count at room temperature steadily increased for all the extrudates. The
total plate count of the extrudates on 0 day was 5 × 101
to 9×101cfu/g for all the
extrudates. During storage the extrudates were packed in aluminum foil laminated
LDPE pouches (gauge size 0.03 µm) with the application of nitrogen gas under
MAP technology which limited the permeability of air to curtail the growth of
microorganism.
As the storage time further increases to 15 days, there was a continuous
increase in the total plate count particularly at the room temperature. A similar trend
was observed when the extrudates were stored at 30th
and 45th
days. Based on the
above result (Table 46), extrudate had higher microbial load as the day‟s increased
above 45th days to 90th
days. The maximum permissible level of total aerobic colony
of ready-to-eat foods as given by Fylde Borough Council extracted from manual of
PHLSG (2008) was 104to less than 10
6cfu/g for ready-to-eat products. Similar finding
was examined where microbial loads were detected in the white sorghum breakfast
cereal at 10th
week although the levels were low they were well within the
acceptable limits of microbial standards on cereal products (ICMSF, 1996).
4.4. Functional characterization of protein in the convenience food
developed using composite millet powder exposed to freeze
drying
4.4.1. Protein solubility of composite millet powder and products
Protein solubility at different pH will serve as a useful indicator to know how
well the protein concentrate will perform when they are incorporated into food
systems. Protein solubility characteristics are influenced by factors such as origin,
processing conditions, pH, ionic strength and the presence of other ingredients
(Vinay et al., 2008, Elkhalifa et al., 2010). Thus, it is an important characteristic in
the functional behavior of proteins and their potential application to food processing.
The results of the present study showed variation in the flour nitrogen solubility
at different pH levels of processed composite millet powder and products.
Figure 45. Protein solubility of composite millet powder and products
The effects of extruded processing and raw powder on protein solubility were
shown in figure 45. The minimum solubility was found to be at the pH of 4 and pH 5
for processed composite millet powder and its developed products respectively, at pH
4.0 which indicates that the isoelectric point of the flour protein is 4.0. Similar
study was reported by Narayana and Rao, 1991; Carbonaro et al., 1993 that
minimum solubility at pH 4.0 and the increment of it on both sides of this pH. The
incidence of minimum solubility near the isoelectric pH is mainly due to the
lack of electrostatic repulsion, which promotes aggregation and precipitation via
hydrophobic interaction (Fennema, 1996). The solubility of pH was increased up to a
maximum values for all the samples. The high net charge acquired at both acid and
1
3
5
7
9
11
13
15
17
19
2 3 4 5 6 7 8 9 10 11 12
Pro
tein
%
PH
Protein solubility Composite millet
powder
Extrudate product
Pasta
Pasta with egg
white powder
Extrudates
alkaline pH's caused a rise in solubility due to unfolding of the flour protein with the
degree of unfolding being greater at alkaline than the acidic pH (Damodaran, 1996).
The protein solubility showed a gradual increase from pH7 to pH12 in which
extrudate had higher solubility rate. Millets containing higher amount of amino acids
and also the extrusion will increases the solubility is due to cooking of flour during
extrusion process. Similar results was observed by Hathaichanock and Masubon
(2007) that during extrusion the higher temperature denature the starch granules
present in the flour which helps to improve the solubility which is closely related to
amylase from starch granules during the swelling. Selected millet powder showed
good solubility in both acidic and alkaline pH regions which can be considered
as an important characteristic for food formulations. Since protein solubility largely
affect other functionalities like emulsification, foaming and gelation
(Kinsella, 1979), the high solubility of the flours indicated that they could have
promising food applications.
4.4.2. Protein Fraction of composite millet powder and products
Table 47. Protein fraction of composite millet powder and products
Protein fraction CM-T2
(powder)
CM-T2
(Ready to Eat)
CM-T2
(Ready to cook)
Globulin(Nacl) 1.1 1.62 3.36
Albumin(H2O) 2.3 3.74 2.49
Prolamin (Ethanol) 3.03 3.12 2.5
Gultelin (NaOH) 2.1 4.60 4.00
Total Protein 12.04 11.4 12.56
CM-T2-Freeze drying powder;
Table 47 presents the effect of extrusion process on protein fractions based on
solubility for each fraction into globulins, albumins, prolamin and glutelins like
protein. It could be noticed that raw millet powder contain 1.1%, 2.3%, 3.03% and
2.1% of globulins, albumins, glutlines like protein and prolamins respectively.
Distribution of protein in fractions extracted with the different solvents suggested that
the raw flour and developed products had variation in amount of total extractable
protein which is due to the differences in total protein. Glutelin, represented a
considerably greater fraction in developed products when compared to raw powder.
Results are close to Ejeta et al., 1987, who stated that fractionated protein in raw
sorghum range from 10.00 to 24.00%, 6 to 16% and 11.00 to 31.00% for albumins
plus globulins, prolamins and cross linked kafirins respectively. The raw powder had
lower protein in glutelin and higher protein in prolamins. Hence the total protein was
found to be higher in extrudates which is followed by composite millet powder.
5. SUMMARY AND CONCLUSION
Millet is one of the indigenous foods known to human and has been widely
used in India as a staple food for thousands of years. The present study focused on
the use of underexploited millets namely for production of convenience products.
The study emphasis on formulation of convenience processed foods with
application of processing and drying methods using different powder and
combination. The techniques used for processing millets are soaking, extraction of
slurry from millets; dehydration and milling were carried out for development of
millet powder. The selected raw materials were weighed and soaked for a period of
6 hours, after which the excess water was drained. The processed millet grains were
grounded into fine slurry using wet grinding techniques. After which the slurry
were subjected to drying methods namely sun drying (SD for 18 hours), forced
convection tray drying (FCTD (T1): 60ºC-70°C for 15-16 hrs) and freeze drying
(FD (T2): -50°C to 30°C for 14 -16 hrs). All the dried millet powder were milled in
stone miller to obtain fine flour and it is packed in LDPE and stored in air tight
container for the development of convenience processed foods. Convenience foods
namely ready to eat product (extrudates) and ready to cook products (pasta) were
formulated and evaluated for their physical, nutritional, functional and shelf life
characteristics. The findings on the effect of drying methods on the quality
characteristics of processed millet powder and composite millet powder and its
products are discussed below
The nutritional properties of the processed millet powder does not show any
effect on the drying methods adopted namely sun drying (T0), Forced convection
tray drying (T1 ) and Freeze drying (T2). However, the varying change in the
nutritional profile could be attributed to the natural existence of the nutrients
present in the selected millets. The carbohydrate content (g) was significantly
higher in finger millet powder (72.17-72.67), little millet powder (72.17 -75.13)
and foxtail millet powder (72.1 -75.33). It is interesting to note that the starch
content (g) was found to be higher in kodo millet powder (56.0-58.27). The
protein content was observed to be higher in finger millet powder (9.31-10.14),
pearl millet powder (10.05-10.21), and foxtail millet powder (10.28-10.60). The
cereal grains are generally considered to be negligible in fat content. However
pearl millet powder (5.2-6.67) posses slightly higher amount of fat when
compared with the other millet powders. The energy content which is the
reflection of the presence of carbohydrate, protein and fat was found to be more
or less similar in all the processed millet powder ranging from
293 to 355 (p≥0.05).
The existence of ash in the finger millet powder (2.2 -2.26), kodo millet powder
(2.3 – 2.63) and foxtail millet powder (2.2 -2.4) was greater thereby their
inorganic minerals would also be higher. The finger millet powders possess to
contain higher amount of calcium (211-212.93), sodium (8.9-9.5), phosphorus
(179.77-183.33) and zinc (1.1-1.16). The minerals namely sodium (9.2-9.8) and
iron (6.13-6.5) were present abundantly in pearl millet powder which is
significantly higher (p≤0.05). Phosphorus (162-165.2) and iron (9.3-9.44)
content was found to be higher in little millet powder. Zinc content was higher
(1.4) in kodo millet and foxtail millet powder when compared to other minerals.
This increasing tendency illustrates the affluent nature of minerals present in the
plant produce. The moisture (g) content of the samples subjected to sun drying
showed slightly higher values (p≤0.05) when compared with the other two
drying methods. The mean increments in the moisture content of the sundried
millet powder could be due to its improper removal of water during drying
process.
Irrespective of drying methods adopted, there was a slight increase in the level of
bulk density (g/ml) of the samples exposed to sun drying when compared to the
other two drying methods. This was statistically significant at p≤0.05 among the
selected millet powders. As in the case of swelling power (%), there was a slight
decrease in the sun dried samples. The alteration in the swelling power is observed
due to the starch content (amylose and amylopectin chains) in different processed
millets powders. Among the selected millet powders, the finger millet powder,
pearl millet powder and foxtail millet powder had the highest foam capacity when
compared to kodo millet powder and little millet powder which is due to
concentration of protein. The foam stability was found to be more or less similar
in all the selected millet powders as there was greatest stability due to increased
thickness of interfacial films. Irrespective of drying methods adopted, there was
not much significant difference in the water absorption capacity (p>0.05) between
the processed millets powders.
Color is an important quality parameter of the processed millet powder. The units
within the L*, a*, b* system give equal perception of the color difference to a
human observer. The L* values (brightness) were significantly higher (p≤0.05) in
the kodo millet powder, little millet powder and foxtail millet powder when
compared with the other millet powders. This could be due to natural color present
in the selected processed millets. Whereas the a* (greenish-bluesish) was found
to be higher in finger millet and pearl millet powder because the seed coat was
more towards the red and green shades. In the cases of b* (reddish -yellowish)
values, pearl millet powder and foxtail millet powder were observed to be higher
which might be due to the presence of yellow color in the millet.
On comparing the pasting properties of raw millet powder (control) with
processed millet powders obtained by three drying methods, there was a
noticeable change in their peak viscosity and final viscosity. The pasting
properties were higher in the raw millet powder when compared to the processed
powders which is due to break down of starch during application of heat while
processing the millet powders.
The total microbial counts (cfu/grams) of processed millet powders treated with
three different drying methods was studied. The processed millet powders
subjected to sun drying showed a slight increase in microbial growth. This might
be due to improper removal of moisture during drying and handling as well as.
After several permutation and combination, equal proportions of selected millet
powders were optimized to produce the composite millet powder. In-depth
analysis was carried for composite millet powder obtained from both the drying
methods namely forced convection tray drying (CM-T1) and freeze drying
(CM-T2). The sundried processed millet powder produced off flavor which is
considered to be an undesirable property for development of products. Hence it
was removed for further analysis and product development.
The carbohydrate content of composite millet powder in both the treatments
(T1-76.03, T2-76.21) was found to be more or less similar, however it does not
show any significant difference (p>0.05). The pasta prepared from 100% of maida
which is considered to be the control possess higher carbohydrate content when
compared to pasta developed from a mixture of composite millet powder and egg
white powder. The carbohydrate level relatively remained high in the control
extrudate when compared to extrudate prepared from composite millet powder.
This could be probably because rice flour has more amount of carbohydrate
content when compared to composite millet powder.
The energy level was found to be more or less similar in composite millet powder
in both drying methods since the application of heat does not alter any nutrient
content of processed millet powder. The energy values (Kcal) of the pasta
developed from a mixture of composite millet powder and egg white powder was
found to be significantly (p≤0.05) higher when compared to other pasta‟s. The
data revealed that the energy value of the extrudate of rice flour (control) was
found to be significantly higher than the extrudate of composite millet powder.
The drying methods did not affect the protein content of composite millet powder
(p>0.05). The total protein (g) content of pasta made from a mixture of composite
millet powder and egg white powder showed a significant increase (p≤0.05) when
compared to other pasta‟s. The mean increment in the total protein content may be
due to protein present abundantly in the egg. From the result, it shows that the
mean increament of protein in the extrudate prepared from composite millet
powder ranged from 6.53 to 11.4 g which may be attributed due to their inherent
protein content of millets.
There was not much difference in the fat content of composite millet powder
obtained from both drying methods. The slight increase in the fat content was
observed because of the incorporation of egg white powder in the pasta. Fat
content was found to be decreased in extrudate which ranged from 0.2 to 2.23%
indicating the fact that extrusion process plays a role in fat reduction.
As far as the moisture content is concerned, the composite millet powder
subjected to forced convection tray drying was found to be slightly higher when
compared to freeze drying. The moisture content of all the pasta varied from 2.25
to 2.78%, which is the desired level for pasta in order to maintain the cooking
quality of the product. Moisture content of extrudate of control and extrudate
prepared from composite millet powder (4 to 8%) were within the desirable level.
Ash content of extrudate prepared from composite millet powder was higher when
compared to control. High amount of ash content (p≤0.05) was observed in egg
white powder incorporated pasta, and this could be attributed to the fact that
multimillets and egg white powder contains high amount of minerals.
Irrespective of drying methods adopted, there was not much difference in the
physical properties namely bulk density, swelling index, water absorption
capacity, foam capacity and foam stability of the composite millet powder.
It was observed that cooking loss was higher in pasta developed from composite
millet powder and lowest for control pasta. The cooking loss was found to be zero
percent in the pasta developed from composite millet powder with addition of egg
white powder. The increase in cooking loss may be due to weakening of gluten
network, since millet was found be gluten free. Whereas decrease in cooking loss
is due to high protein in egg which helps to bind the structure of the pasta. The
highest cooking time was observed for pasta developed from a mixture composite
millet powder and egg white powder. This could be attributed to the hydration
level, which is more for millet based pasta than refined maida pasta. Pasta
prepared from composite millet powder with addition of egg white powder
showed higher cooking weight (CM-T1-22.78, CM-T2-22.97) when compared to
pasta prepared from composite millet powder and control pasta. The decrease in
the cooked weight was apparently due to increase in cooking losses or gruel
losses. This might be due to addition of egg white powder which helps to bind the
structure of pasta.
A high expansion ratio is desirable in production of expanded snacks. It was
observed that the extrudate made from composite millet powder showed lower
expansion ratio when compared to control extrudate. It was due to the increase in
protein and fiber content which resulted in a decrease in expansion ratio of
extrudate. The bulk density was minimum for control extrudate (73.99 gcm3) and
maximum for extrudate (CM-T1, CM-T2) prepared from composite millet powder.
The higher bulk density may be due to presence of protein in the composite millet
powder which reduces the puffing quality of extrudate. The water solubility was
more for the extrudate made from composite millet powder and it was found to be
lesser for the extrudate prepared from rice flour. The increase in water solubility
index was due to addition of millets in the extrudate. The water absorption index
was found to be more for extrudate made from composite millet powder when
compared to control extrudate.
The pasting properties of composite millet powder concluded that peak viscosity
and final viscosity were found to be increased when compared to individual
processed millet powder. In ready to cook pasta, the pasting characteristics of all
pasta samples were studied. The pasta prepared from purely processed composite
millet powder and with a mixture of egg white powder in composite millet powder
had lower peak viscosity and final viscosity when compared with the control. This
can be correlated to its higher protein content and comparatively lower starch
levels. The extrudates prepared from processed composite millet powder had
lowest pasting viscosity because of their destructurized and gelatinized starch
during extrusion process. Whereas, the extrudate made from rice flour showed
slightly higher viscosity because of the existence of starch in rice.
The crystalline structure exhibited distinct x-ray diffraction pattern that can be
classified in to three categories namely A, B and C type crystal structure. In raw
flour A, B type x ray diffraction patterns are characterized by clear diffraction
peaks (CMT1-18.33, 22.9 and CM-T2-18.33, 23.11) and the A-pattern was
generally regarded as cereal starch crystal form. But during extrusion, the
crystalline patterns of starch get destroyed due to process of gelatinization, so it
showed V-type pattern in extrudate product.
Color of the products is the reflections of natural existence of color in millet and
it is represented by L*, a*, b*. L*(Lightness) value was found to be higher in
control pasta developed from refined maida, when compared with other pastas
prepared from composite millet powder and addition of egg white powder in
composite millet powder. The redness “a” values of pasta prepared from
composite millet powder was indicating green tinge (-a), which was higher than
those of control pasta. The yellowish “b*” value was found to be slightly higher
in pasta prepared from composite millet powder with addition of egg white
powder. The lightness value (p≤0.05) was more for the extrudate made from rice
flour.
Textural parameters, especially hardness and adhesiveness are important for
cooking quality of pasta. The hardness values of pasta prepared from composite
millet powder and addition of egg white powder in composite millet powder were
higher than the control. In case of adhesiveness, the control pasta prepared from
refined flour was found to be higher which might due to lower protein content.
Low protein content tends to absorb more water which leads to high stickiness
and low firmness. There was not so much difference between the cohesiveness
values of control pasta and composite millet powder pasta. The results showed
that the pasta had the capacity to hold the structure together as cooking time
proceeded. However the parameters such as springiness, resilience and
stringiness do not show much significant difference among the pastas. The
hardness was found to be increased in control extrudate. It was due to higher
expansion with the increase in moisture content. There was no significant
difference observed in the crispness of control extrudate and composite millet
powder extrudate.
A heterogeneous combination of composite millet powder can be observed in the
micrographs, featuring irregular structures with indefinite shapes, rich in spongy-
aspect material, with cavities and structural gaps of varied sizes. In ready to cook
pasta, the numerous starch granules of varying sizes were visible on the structure
of uncooked pasta. Whereas in cooked pasta, the starch granules possessed
disturbed structure and the protein matrix which applies pressure on some starch
granules lead to small structural deformations which indicates the level of
gelatinization during cooking process. The pasta incorporated with egg white
powder indicated more protein matrix attached to the starch granules. The
micrographs of the extrudate revealed that the surface of the flour is embedded
with starch granules, protein matrix and also fat particles with regular shapes. But
after extrusion the starch granules were disrupted because of gelatinization
occurring at high temperature during extrusion.
The internal cross sectional structure of the extrudate prepared from processed
composite millet powder subjected to both the drying methods was studied.
Large air cells space was observed in extrudate obtained from freeze drying. In
contrary the extrudate produced from composite millet powder exposed to forced
convection tray drying had smaller air cell spaces.
The total essential amino acid profile of composite millet powder ranged from
0.01 mg/100 g to 0.79 mg/100g. The results showed that the composite millet
powder showed higher amount of essential amino acids namely phenynlalanine
(0.7873mg/g), histidine (0.48mg/100g), and lysine (0.40mg/100g) while proline
was found to be least in composite millet powder. The essential amino acid
profile of the composite millet powder was higher than the reference values of
FAO/WHO/UNO (2007). The highest concentration of conditionally essential
amino acids for the pasta prepared from processed composite millet powder was
histidine, methionine, phenyl alanine, lysine and tryptophan while the least was
proline and valine when compared with their references values. Whereas the
essential amino acids content of egg white powder was significantly higher
(p≤0.05), therefore the pasta formulated using processed composite millet
powder and egg white powder was higher when compared to control pasta.
Extrusion adversely affected the contents of the amino acids namely histidine,
methionine, phenylalanine, lysine, tryptophan (p≤0.05) especially in extrudate.
There was no any alteration in the content of valine, iso-leucine, leucine and
proline of the control extrudate made from rice flour. Among essential amino
acid which is presented, leucine was the most affected, moreover valine also
underwent a high percent loss during extrusion process. The reason for reduction
perhaps extrusion at low moisture and high temperature led to starch degradation.
The essential fatty acid composition of processed composite millet powder shows
the presence of saturated and unsaturated fatty acids. The overall dominant fatty
acids in the processed composite millet powder are linoleic acid (1.34 mg/100g)
and palmitic acid (0.99mg/100g). The dominant polyunsaturated fatty acid is
linoleic acid which was slightly higher in composite millet powder. The highest
concentration of palmitic acid, linoleic acid and alpha linolenic acid was
observed in pasta prepared from processed composite millet powder when
compared to control pasta. The essential fatty acids of extrudate prepared from
processed composite millet powder was found to be significantly higher (p≤0.05)
than the control extrudate.
The composite millet powder contains about 94.4IU of Vitamin A, 345 mg of
Vitamin B12, 3.46 mg of vitamin B6 and 20.33 mg of vitamin C. The percent
gain of vitamin A, Vitamin D, vitamin E and vitamin B6 among the pasta and
extrudate prepared from composite millet powder was greater when compared to
control pasta. The decrement in the vitamins levels of the control was mainly due
to the lack vitamins.
The antioxidant activity was determined for composite millet powder in both
drying method was carried by two assays. The DPPH radical scavenging activity
and reducing power of composite millet powder was higher when compared to
standard ascorbic acids. This indicates the presence of scavenging activity in
millet powder which reflects on the product as well as.
The presence of phytochemical in the composite millet powder, pasta and
extrudate prepared from processed composite millet powder were found to be
higher (p<0.05) in phenols, alkaloids, terpenoids, tannin, anthaquanines and
glycosides.
The sensory scores of products developed from processed composite millet
powder among the panel members were found to be acceptable as per 9 point
hedonic scale. The pasta prepared from composite millet powder with addition of
egg white powder revealed the highest overall acceptability scores when
compared with other pasta. In order to improve the acceptability of the extrudate
two different variations namely spice mix and milk with and without addition of
choco powder were carried out. The sensory scores showed a significant increase
in spice mix extrudate made from composite millet powder when compared with
control in terms of texture, taste, crispness, flavor and overall acceptability. The
extrudate prepared with milk and choco mix had significantly better appearance,
colour, flavor, taste, overall acceptability it was revealed from the scores of the
overall acceptability that the millet can be successfully replaced with refined flour
to produce a better acceptable product.
The storage study was carried out for the products. The products were packed in
aluminum foil laminated LDPE pouches with the application of nitrogen gas
under MAP technology to limit the permeability of air to curtail the growth of
microorganism. It was stored for 90 days at room temperature. The shelf life study
was carried for all the pasta developed. The scores of pasta were evaluated for
overall acceptability using 9 point hedonic scale at the regular intervals of 15
days. There was no significant difference in overall acceptability of pasta up to 60
days. The scores of pasta decreased significantly from 60 days till the end of the
storage.
The results revealed that there were no significant difference (p>0.05) in terms of
colour, texture, taste, flavor, and overall acceptability for the extrudates. There
were also no significant difference (p>0.05) between the control and extrudates
prepared from millet powder. The overall acceptability for all extrudate after 60
days storage was similar. The flavor and taste had slightly low rating for all
products after 90 days.
The microbial analysis was carried to study the shelf life of the product. The total
plate count was done at every 15 days interval. There was no significant
difference among the pasta till 60 days. The total microbial count (cfu/grams) of
pasta prepared from composite millet powder subjected to forced convection tray
drying as well as freeze drying were shown with slight progress in microbial
growth but was found safe till three months of storage period with good sensory
acceptability scores as suggested by panelists. After 60 days there was progression
of microbial growth in all the pastas.
Total plate count assay was carried for extrudate in which limited level of
microbial growth was detected up to 90 days. This is due to high processing
temperature (90-120°C) which favored in decreasing the growth of micro
organism present. So the extrudate product was acceptable till 3 months.
The product produced from the freeze drying had better retention of nutrients as
evidenced by few studies. Hence the protein solubility and protein fraction were
studied for developed products from composite millet powder exposed to freeze
drying.
The protein solubility for the processed composite millet powder and convenience
food were studied. The protein solubility showed a gradual increase from pH7 to
Ph12 in which extrudate had higher solubility rate. The lowest solubility was
observed in the processed composite millet powder between pH 4 and 5 for all the
samples.
The protein fractions of processed composite millet powder and convenience food
were studied. The globulin fraction of pasta increased significantly (p<0.05) when
compared to processed millet powder and extrudate. The albumin fraction was
observed to be more in pasta incorporated with egg white powder. The protein
fraction such as prolamin and glutenin were found to be more or less similar in
other samples.
CONCLUSION
Millets are claimed to be the future foods for better health and nutrition security.
Nutritionally, millet is a good source of macronutrients, micronutrients and
nutraceutical components. In present research, steps were taken to increase the
utilization of millet powder and development of convenience products which is
superior to the products formulated using refined flours. In comparison to rice and
wheat, the exploitation of the millet for value addition will helps to widen the scope of
their utilization. The processed millet powder formulated using different drying
methods had desirable nutritional quality, physical properties as well as functional
properties. Among the drying methods adopted, the composite millet powder
subjected to freeze drying and thereby the products developed had better retention of
nutrients, phytochemical, essential fatty acids and essential amino acids, exhibited
better antioxidant activity (p<0.05) when compared to forced convection tray drying.
Feasibilities for production of convenience foods would pave the way for
commercial-scale processing and their utilization even by the non-millet consumers.
Hence, there is a great scope for utilization of the millets in variety of foods and value
added products in the years to come.
Future Recommendations
To study the impact of formulated products on the target groups such as gluten
intolerances and undernourshied population.
To develop entrepreneurship, and appropriate strategies to promote and
popularize multi millets product for commercialization through value-addition
and branding as health foods.
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Details of Publication
International
1. M.Pushpa Devi., Narayanasamy Sangeetha ;(2013);Extraction and
dehydration of millet milk powder for formulation of extruded product ;
Journal Of Environmental Science, Toxicology And Food Technology ,. 7(1),
63-70,e-ISSN: 2319-2402,p- ISSN: 2319-2399,Impact factor : 1.3.
2. Narayanasamy Sangeetha., Pushpa Devi.M, (2012);Effect of Dehydration on
the quality characeteristics of extruded pasta using millet milk powder ;
Journal Of Nutrition and Food Science, 2(10), e-ISSN: 2155-9600, Impact
factor : 0.923.
3. Pushpa Devi.M, Narayanasamy Sangeetha ;(2012); Processing and quality
evaluation of extruded pasta using millet milk powder. Bioactive Natural
Compounds from Plant Food in Nutrition and Health; ISBN: 978-81-923850-
5-1,pp:39-45.(Conference Proceedings)
National
4. Pushpa Devi.M., Narayanasamy Sangeetha ; (2012) ;Process development of
ready to cook health mix by extracting milk from finger millet(Eleusine
coracana), ISBN: 81-87299-57-6, pp: 106-112. (BOOK CHAPTER)
5. Pushpa Devi.M., Narayanasamy Sangeetha;(2011),Processing and quality
evaluation of milk extracted from sprouted finger millet (Eleusine coracana),
ISBN: 978-9331-1737-7, pp: 205-211. (BOOK CHAPTER)
APPENDIX I
Determination of Bulk Density
A 50 g flour sample was put into a 100 ml measuring cylinder. The cylinder was tapped
continuously until a constant volume was obtained. The bulk density (g cm-3) was
calculated as weight of flour (g) divided by flour volume (cm3) (Okaka and Potter, 1979).
Bulk density: weight of flour/flour volume
A 5-cm long cylindrical section of extrudate was weighed and the diameter measured using a
vernier calliper. The bulk density was then calculated as the ratio of the weight of the
extrudate to the volume of extrudate (Barret & Peleg, 1992).
Determination of water absorption capacities
Water absorption capacities of the flour samples were determined by Beuchat (1977)
methods. One gram of the flour was mixed with 10 ml of water or oil in a centrifuge tube and
allowed to stand at room temperature (30 ± 2°C) for 1 h. It was then centrifuged at 200 x g for
30 min. The volume of water on the sediment water measured. Water and oil absorption
capacities were calculated as ml of water absorbed per gram of flour. Water and absortion
capacities: ml of water absorbed /gm of flour
Determination of foaming capacity (FC) and foam stability (FS)
The method of Narayana and Narasinga Rao (1982) was used to determine the foam capacity
and stability of flaxseed flours. Fifty mL water was taken in a cylinder, into which two grams
of flour samples were mixed keeping the temperature at 30± 2 0C. The suspension was
properly shaken to foam, and the volume of the foam after 30 seconds was recorded in mL as
foam capacity while the foam volume (mL) recorded after 1 h of whipping was recorded as
foam stability.
Procedure for In vitro digestibility
In vitro digestibility was carried out according to the method described by Elkhalil et al. with
slight modifications. Twenty mg of protein concentrate samples were digested in triplicate in
10 mL of trypsin (0.2 mg/mL in 100 mM Tris–HCl buffer, pH 7.6). The suspension was
incubated at 37 °C for 2 hours. Hydrolysis was stopped by adding 5 mL 50% trichloroacetic
acid (TCA).The mixture was allowed to stand for 30 min at 4 °C and was then centrifuged at
9,500 × g for 30 min using a D-3756 Osterode AM Harz Model 4515 Centrifuge (Sigma,
Germany). The resultant precipitate was dissolved in 5 mL of NaOH and protein concentrate
was measured using the Kjeldahl method.
Determination of protein Solubility
One hundred mg of millet protein concentrates and soy protein concentrate were dispersed in
10 mL of distilled de ionized water. The suspensions were adjusted to pH 2.0 up to pH 12.0
using either 0.1 M HCl or 0.1 M NaOH. These suspensions were shaken (Lab-Line Environ-
Shaker; Lab-Line Instrument, In c., Melrose Park, IL, USA) for 30 min at room temperature
(approximately 25°C) and centrifuged at 4000 × g for 30 min. The protein content of the
supernatant was determined by the Kjeldahl method.
Determination of protein Fractionation
Proteins were extracted from defatted fox tail millet flour based on their solubility at room
temperature (25o
C) in water. 5% NaCl. 0.1M NaOH and 70% ethanol using the procedure of
Osborne (1909) with minor modifications. The defatted flour was extracted with 400mL
distilled water with stirring for 4h and centrifuged at 3000 x g for 30 min to obtain the
albumin fraction (supernatant). The residue from this step was then similarly extracted with
400mL of 5% NaCl to obtain the globulin fraction. The residue after extraction of globulin
was extracted with 0.1 M NaOH (1h) to obtain the glutelin fraction, while the residue after
glutelin extraction was extracted with 70% ethanol to obtain the prolamin fraction. All the
extractions were carried out twice. The albumin, globulin, glutelin and prolamin fractions
were then purified by isoelectric precipitation at pH 4.0, 4.0, 4.1 and 2.5 respectively and
washed with distilled water. All fractions were freeze dried using a Christ-Alphaa 1-4 freeze
dryer (Biotech International Germany). The determination of the various protein fractions and
concentrates (N H 6.25) was done with a Micro- Kjeldahl method.
Procedure for Texture Analysis
Texture analysis of the sample was performed with a 5mm HDP-CFS cylindrical ball
probe by Texture Analyzer (Model No.: 5197, stable Micro Systems HD Plus, Goldalming,
Surrey, GU71YL, UK) (Plate IIIa,b). Each sample was placed on the heavy duty platform and
the test speed was set to 1mm/sec and the probe compressed 50% of the sample to measure
the hardness. Recording of maximum force is calculated as the hardness of the sample.
Maximum breaking force (N) and deformation were measured from the force-deformation
curve.
Procedure for Color measurement
Color of the sample including 5 or 6 pieces from each set were selected to determine
using the Hunter‟s Lab Colorimeter (Model: CX2748, Easy Match QC, Software Version 4.0,
Hunter Lab, USA) with spectral reflectance (Plate IV). The Hunter Labs color space is a 3-
dimensional rectangular color space based on the opponent-colors theory. One by one sample
were kept in the glass dish of 9 cm internal diameter and color difference readings were taken
with a black plate on top of the dish. The samples were rotated over the instrument and 4
readings were measured in one. The instrument was first calibrated with black plate followed
by white plate. The color determinations were reported as L*, a*, b*, whereas (lightness)
axis - 0 is black, 100 is white, a*(redness-greenness) axis -positive values are red; negative
values are green and 0 is neutral, b* (yellowness-blueness) - positive values are yellow;
negative values are blue and 0 is neutral values and ΔE indicates the overall average colour
according to Olajide (2010).
The hue angles were calculated as the arctangent of b*/a* expressed as degrees and
the chroma values were also calculated as the square root of the sum of the squared values of
both CIE a* and CIE b* as suggested by Ronald and Daniel (1998). The chroma and Hue
angle were calculated by the formulas given below.
Determination of Expansion ratio
Expansion ratio was measured as the ratio of crosssectional area of the dried cylindrical
extrudate to that of the die (Chakraborty et al., 2009). The diameter of the extrudate was the
average of ten random measurements. This index describes the degree of puffing undergone
by the sample as it exits the extruder.
Procedure for X-ray diffraction and crystallinity
X-ray diffraction analysis was performed using an X-ray diffractometer (Shimadzu
XRD 7000) with Cu Kα value of 1.54060 radiation at a speed of 2º/min, diffraction angle of
2θ at 4º and 50º at 40 kV and 30 mA. The total area under the curve and the area under each
prominent peak was determined using OriginPro software package and the percentage
crystallinity was estimated by using the following formula:
Procedure for X-ray fluorescence
The analysis of minerals was performed using WD-XRF (Bruker, Germany). Two
grams of sample was crushed and mixed with 0.5 grams boric acid (granulated) with a mortar
and pestle. The prepared sample was then made into a 34 mm diameter pellet with the help of
a 40 ton hydraulic press machine (10 ton pressure, 20 min. pressing time). The pellets were
then introduced in the sample slots of WD-XRF and analyzed for the composition of elements
in the samples.
Determination of cooking Time.
The cooking time for pasta was determined by adding a 25g portion of the sample into a
beaked of 250 ml boiling water. A stopwatch was used and the pieces of pasta were stirred to
separate while maintaining a rolling boil. The cooking water was maintained to at least 90%
of its original volume. A piece of pasta was removed from the cooking water at 30-s interval
and squeezed between two pieces of clear plastic. The time when the white centre of the
sample just disappeared was designated as “cooking time”. Cooking time was carried out in
triplicate and the mean values were reported.
Determination of cooking loss and water Absorption
A 20 ml of gruel was pipetted out into a pre weighed petri dish stirring well to give an even
distribution of the solid content. It was evaporated to dryness on a water bath. The petri dishes
were transferred to a hot air oven maintained at 105±2ºC and dried to constant mass. It was
then cooled to room temperature in a desiccators and the final weight was noted. Water
absorption was calculated according to the increase in weight and expressed as % of the
sample weight before cooking. The average means of triplicates were reported in percentage.
Determination of Carbohydrate content
The amount of carbohydrate present in the sample was determined by Anthrone
method using glucose as standard. Carbohydrates are first hydrolyzed into simple sugars
using dilute Hcl. In hot acidic medium glucose is dehydrated to hydroxymethyl furfural.
This compound forms with anthrone as green colored product with an absorption
maximum at 630 nm (AOAC, 1990). The presence of total sugar in samples was
estimated by determining sugars before and after inversion by copper reduction methods
(AOAC, 1990).
Determination of protein content
Protein was calculated by converting the nitrogen content (% N X 6.25) as
determined by Kjeldhal‟s method (AOAC,1990).The principle used in the estimation of
nitrogen is described, where the given sample is digested with concentrated sulphuric acid in
a Macro kjeldhal flask when nitrogen gets converted to ammonium sulphate. Ammonia is
liberated by the action of strong alkali in a macro kjeldhal steam distillation apparatus. This
nitrogenous substances are converted to ammonium borate by absorbing 2% boric acid and is
titrated against N/70 H2SO4. The volume of acid required to bring the test sample to the
colour of the blank gives the acid equivalent to the ammonia.
Determination of total fat content
The fat content of the osmotic dehydrated, hot air and freeze dried coconut based
snack was extracted using petroleum ether (40-60°C ) and determined using soxhlet
apparatus AOAC (1990).The dry sample (2-5 g) is weighed accurately into a thimble. The
thimble is then placed in a soxhlet apparatus and extracted with petroleum ether for about
2hours. The ether extract is filtered into a weighed beaker. The ether is then removed by
evaporation and the beaker with the residue is dried in an oven at 80 to100º c, cooled in a
desiccator and weighed.
Determination of the moisture content
The moisture content was calculated using oven-dry method to a temperature of 105
°C to 110 °C until reaching constant weight approximately within 16-17 hours (AOAC,
1990). The major purposes of determining moisture content in foods comprised of assessment
of quality, quality assurance, quality control, and detection of adulteration, assessment of
stability and shelf life during storage period.
Determination of ash content
To determine ash content, about 5 g of samples was incinerated in a muffle furnace
(Gelman, Germany) at about 550 °C for 8 h. The total ash content was expressed in dry
weight percentage (method no. 940.26, AOAC 1990).
Determination of the total dietary fibre
Total dietary fibre was determined in dried, low-fat or fat-free sample which was
homogenised and dried overnight in 70°C vacuum oven. The loss of weight due to fat was
recorded (Asp et al., 1989).
Determination of The energy value
The energy value of the samples was estimated using bomb calorimeter. The principle
behind the working of bomb calorimeter is based on the fact that a known weight of the
sample completely burnt in the apparatus permits the heat developed by the combustion to be
absorbed by a definite weight of water. By determining the rise in temperature, it is possible
to calculate within close limits, the number of heat units liberated.
Determination of Calcium
Calcium was estimated using titrimetric method, the principle behind the estimation
involved precipitation of calcium oxalate and titrating the oxalate solution in dilute sulphuric
acid against standard potassium permanganate, Raghuramulu et al., (2005).
Determination of the potassium, zinc, chromium and selenium
Potassium, zinc, selenium and chromium were determined by using atomic
absorption spectrophotometer (Unicam Analytical system, Model 919, Cambridge, UK.) by
dissolving the incinerated ash (3 h at 550 °C) in 2 mL of filtered HCl (Whatman no. 1;
Maidestone, U.K.), and brought up to 100 mL with water (HPLC grade) (Pharmacopeial
Forum, 2007).
Determination of the phosphorus
Phosphorus was determined spectrophotometrically, the principle used in phosphorus
estimation, Where the ash solution is treated with ammonium molybdate, phosphomolybdic
acid is formed. Phosphomolybdic acid is reduced by the addition of 1,2,4 amino
naphtholsulphonic acid reagent to produce a blue colour which is apparently a mixture of
oxides of molybdenum. The intensity of thecolour developed is the measure of phosphorus
present, Raghuramulu et al., (2003).
Determination of the iron
Iron is determined calorimetrically with ferric iron which gives a blood red color with
potassium thiocyanate, Raghuramulu et al., (2003).
Determination of the Vitamin A
Vitamin A was determined by HPLC using standard procedures given in the
Lawrence Evans Pharmacopeial Forum. The determination of vitamin A by the liquid
Chromatographic system is equipped with a 325-nm detector and a 4.6-mm × 15-cm column
that contains 3-µm packing L8. The flow rate is about 1 mL per minute. The mobile phase
used was n-hexane. Procedure: the peak responses were observed in the chromatographic
system with resolution, R, between retinyl acetate and retinyl palmitate is not less than 10;
and the relative standard deviation for replicate injections is not more than 3.0%.
Determination of the Vitamin E
Vitamin E was determined by HPLC using standard procedures given in the
Lawrence Evans Pharmacopeial Forum. HPLC protocol consisted of the mobile phase,
composed of 10 ml of phosphoric acid with the dilution of 1000 ml of distilled water,
termed as solution A. A degassed and filtered mixture of methanol and Solution A (95:5)
was prepared. Standard preparation involves dissolving accurately weighed quantity of USP
Alpha Tocopherol RS, USP Alpha Tocopheryl Acetate RS, or USP Alpha Tocopheryl Acid
Succinate RS in methanol, and dilution made quantitatively with methanol to obtain a
solution having a known concentration of about 2 mg per mL.Chromatographic system. The
liquid chromatography is equipped with a 254-nm detector and an 8-mm × 10-cm column
that contains 5-µm packing L1. The flow rate is about 2 mL per minute.
Determination of the Vitamin C
Ascorbic acid of the sample was determined by the by visual titration with
2,6dichlorophenol solution. Solution of the sample equivalent to 0.2 mg ascorbic acid/ml was
prepared using water containing 3% (w/v) metaphosphoric acid. It was titrated against
standard 2, 6 dichlorophenol indophenol solution of 0.5 mg/ml concentration until the the
development of pink colorimetrically. The process was repeated with a blank (Ranganna,
2000).
Determination of the fatty acids
Fattyacid content was determined by GC-MS protocol.In the GC-MS protocol, the
Column used was fused silica, size ofl = 30 m, Ø = 0.25 mm, and the stationary phase was
macrogol 20 000 R (film thickness 0.25 µm). The Carrier gas hydrogen was used for
chromatography R or helium for chromatography R, where oxygen scrubber was applied and
the Split ratio was1:200. The temperature used for Column was 170-225°C, Injection port -
250°C, Detector - 280°C respectively. Detection was enabled through flame ionisation with
aninjection of1 µl, twice. The fatty acids are tested with system suitabilityidentified from the
chromatogram with the injection of a mixture of equal amounts of methyl palmitate R, methyl
stearate R, methyl arachidate R, and methyl behenate R respectively (Pharmacopeial Forum,
2007).
Determination of the tannins
Colorimetric estimation of tannins is based on the measurement of blue colour
formed by the reduction of phosphotungsto molybdic acid by tannin like compounds in
alkaline solution (Ranganna, 2000). A known amount of extract was mixed with 5.0 ml
of Folin- Denis reagent (FD) and Na2Co3 solution and made up to 100 ml, mixed
well and absorbance was read at 760 nm after 30 min using spectrophotometer. Total tannin
content as expressed as mg tannic acid equivalent /100 g of sample.
Determination of the steroids
About 5g dried samples were extracted with 250 ml of acetone for 24 hr. For sterol
analysis, acetone extracts were used frequently as explaind by Stedman and Rusaniwskyj
(1959). Gas chromatography was used to separate individual sterols by 1.80-m column, 6 mm
id., packed with 5z OV-101 on Anakrom ABS 80- to 90-mesh (Grunwald, 1969). The
temperature of the column was 250°C and the temperature of flash heater was kept 50°C
above that of the column. The temperature of flame ionization detector was 275°C.The
carrier gas was Helium at a flow rate of 100 ml/min (Pharmacopeial forum, 2007).
Determination of the alkaloids
The determination of alkaloids by HPLC consisted of mobile phase by dissolving
9.93 g of monobasic potassium phosphate in 730 mL of distilled water. About 270 mL of
acetonitrile was mixed and filtered. The liquid chromatography was equipped with a 235-nm
detector and a 4.6-mm × 150-mm column that contains packing L1. The flow rate was about
1.8 mL per minute (Pharmacopeial forum, 2007).
Determination of the saponins
Saponins were extracted according to the method of Huhman et al., (2005). The
samples were extracted using extraction solvent methanol prepared with a mixture of water
and centrifuged 2200 rpm for 20 min at 4 °C prior to liquid chromatographic analysis. HPLC
separation was achieved using a 250 4.6 mm i.d., 5 ím, reverse-phase, C18 column. Samples
were eluted with H2O.
Determination of the totalflavonoids
Flavonoids were extracted according to methods of Crozier, Lean, McDonald,and
Black (1997). Extraction solvent was prepared with a mixture of alcohol, water, and
hydrochloric acid (50:20:8) and the mobile phase constituted a mixture of methanol, water,
and phosphoric acid (100:100:1). Standard solution was prepared using Quercetin RS,
kaempferol, myricetin, apigenin, luteolin, hesperidin and isorhamnetin by dissolving it in
methanol. About 10 g of the sample was extracted using the extraction solvent in a hot water
bath for 135 minutes and allowed to cool at ambient temperature. Chromatographic system
was equipped with a 270-nm detector and a 4.6-mm × 25-cm column that contains packing
L1. The flow rate was about 1.5 mL per minute. The flavonoid in the samples was identified
by comparison made between retention times and spectral characteristics of their peaks with
standards.
Determination of the total phenols
The TPP content was determined according to the procedure of Folin–Ciocalteu
method (Sellappan & Akoh, 2002a, 2002b) with slight modifications. Food extracts (0.5 ml)
or standard solutions prepared with gallic acid were mixed with 2.5 ml of Folin–Ciocalteu‟s
Reagent (FCR-1:10 dilution) and allowed to stand for 8 min at ambient temperature to let for
the FCR to react completely with the phenolates. 2.0 ml of Na2CO3 (7.5% solution in water).
The absorbances were measured at 760 nm using a Cintra 5 UV–vis Spectrophotometer after
incubating at ambient temperature for a period of 2 h. Results were expressed as milligrams
of gallic acid equivalents (GAE) per 100 g fresh weights.
Determination of the antioxidant activity (µg FeSO4 equivalents)
The antioxidant power represents the total antioxidant potential of the samples
determined by ferric reducing antioxidant power (FRAP) assay according to the procedure of
Benzie and Strain (1996). FRAP assay is used to measure the change in absorbance at 593
nm, which results in the formation of a blue colorcompound II -tripyridyltriazine from
colourless oxidized Fe III due to the presence of antioxidants which are electrons donators.
FRAP reagent was composed of a mixture of 10 vol of 300-mmol/L acetate buffer, pH 3.6, 1
vol of 10-mmol/L TPTZ (2,4,6-tripyridyl-s-triazine) in 40-mmol/L hydrochloric acid and 1
vol of 20-mmol/L ferric chloride.10 vol of 300-mmol/L acetate buffer, pH 3.6, 1 vol of 10-
mmol/L TPTZ (2,4,6-tripyridyl-s-triazine) in 40-mmol/L hydrochloric acid and 1 vol of 20-
mmol/L ferric chloride. To the freshly prepared FRAP reagent (3 ml), extract (100-mL) was
added and thoroughlymixed and reading taken at 593 nm. Standard curve was made using
various concentrations (100–1000 mmol/L) of FeSO4.7H2O.The results were represented in
micromole Trolox equivalents per gram fresh weight.
Sensory analysis
Sensory evaluation is defined as specific discipline used to evoke, measure, analyze
and interpret the characteristics of food and materials as they are perceived by the senses of
sight,smell, taste, touch, and hearing. The primary function of sensory testing is conducted
valid andreliable tests to provide data on which sound decision may be made (Meilgaard et
al., 1999).
Selection of the panel member
Fifteen research scholars of the department of Food Science and Technology were requested
to take up threshold sensitivity test using salt, sweet, sour and bitter as suggested by
(Meilgaard et al., 1999). They were mixed in the different composition with the code
numbers and the subjects were asked to identify the sequence of the concentration from low
to high. Essentially the threshold test determines the sensitivity of the panellist to a particular
test.
Formulation of score card for sensory evaluation
A scorecard is a visual exhibit of the most significant information needed to accomplish oneor
more objectives, combined and arranged on a single screen so the information could be
observed at a glance. The score card is prepared suspiciously and it is clearly printed (Stone et
al., 2004).
Determination of the storage and keeping quality
Storage plays an important role in the safety and the quality of the product. Thirty gram of the
sample was packed in Aluminium Foil Laminated LDPE pouches with composition of 100%
nitrogen gas and stored in ambient temperatures. Care was taken to see that the snack was
stored in clean and dry place which was away from sunlight and pests. Sensory evaluation of
the snack was done once in 15days and microbial testing once in 30 days over a period of 90
days to analyse the extent of storage.
Determination of the amino acid
About 1g of the sample should be treated with phosphate buffer at pH 7.0 and centrifuged at
2000rpm for 20min. at 4ºC. The supernatant of the centrifuged sample is precipitated with
equal volumes of 10% sulfosalicyclic acid and centrifuged at 2500rpm for 15 min. The
centrifuged deposits were dissolved in 6ml of 6N HCl and were subjected to hydrolysis in
boiling water bath for a period of 24 hrs. The tubes were cyclomixed for every 1hr. for proper
hydrolysis to take place. After 24 hrs of hydrolysis, the tubes were centrifuged at 3500rpm for
15 minutes. The supernatant was filtered and was neutralized with 1N NaOH. Then the
filtered solution was diluted to 1:100 of 109 the volume (1ml diluted to 100ml) with milli-Q
water and was proceeded for estimation of protein amino acids in HPLC (Grafts field-
Huesgen method, 1998).
Determination of the preparation of sample for microbial analysis
Specific agar medium was prepared and poured in the petri plates and kept aside for
setting. 1g of the sample was weighed in aseptic condition and mixed in 10 ml of saline
solution.Then the mixture is streaked in the agar medium and incubated. After 48 hours the
number ofcolonies was counted.
Determination of the evaluation of the product
Sensory evaluation of hot air oven and freeze dried sample prepared under
different treatments was carried by a panel of fifteen judges. The various products were
displayed on a desk and random numbers were consigned to the judges. The judges were
asked to examine the samples carefully for appearance, flavor, taste and color using the 9-
Point Hedonic scale. Here, different ratings, ranging from "Like extremely" to "dislike
extremely" were given by the judges, specifying the values from 9 (like extremely) to
1(dislike extremely), respectively. Later on, the scores were averaged for each sample.
Treatments which gained a mean score of 5 and above are acceptable and the one's which
score below 5 points were rejected. This experiment was conducted under a controlled
environment in cool place. The results of the sensory analysis led way to select the most
acceptable products prior to further analysis (Meilgaard et al., 1999).
Procedure for scanning electron microscope
The morphology of multi cereal composite mix and maida granules was evaluated by
scanning electron microscope (SEM) (QUANTA FEG 250 ESEM). Samples were mounted
on circular aluminium stubs with double-sided sticky tape. The starch granules were evenly
distributed on the surface of the tape. The samples were then coated with 12 nm gold,
examined and photographed at an accelerating voltage of 5 kv with a magnification of
x1000 and x5000.
APPENDIX II
Acceptability and Sensory Evaluation of tertiary products
Name:
Date:
9 = Extremely acceptable, 8= Very much acceptable, 7= Moderately acceptable,6 = Slightly
acceptable, 5= Neither acceptable nor unacceptable, 4 = Slightly unacceptable, 3 =
Moderately unacceptable, 2=Very much unacceptable1= Extremely unacceptable
Place a number in the appropriate box that best describes your response to the following
attributes
Characteristics A B
Appearance
Texture
Color
Taste
Mouth feel
Flavor
Aftertaste
Overall
Comments: