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CONSUMER ACCEPTABILITY OF DRY MEDIUM-ROASTED ALMONDS
STORED UNDER VARYING STORAGE CONDITIONS
by
ANNA NICOLE CHEELY
(Under the Direction of Ruthann Swanson)
ABSTRACT
Consumers reject roasted almonds primarily due to rancidity development during
storage. Dry medium-roasted Nonpareil almonds were stored in polypropylene (PP) bags
at 15, 25, 35 °C and 50 or 65% relative humidity (RH) or at 4 °C without RH control,
and in high barrier bags (HBB) at 4, 15, 25, and 35 °C without RH control.
Chemical/instrumental analyses and descriptive and consumer sensory testing were
conducted over 16 months. Three PP and one HBB samples, held at higher RH and/or
temperatures, were rejected by consumers. Descriptive panelists found increases in
rancidity and hardness reflective of chemical/instrumental data in rejected PP but not
HHB samples. For the rejected HHB sample, consumer comments suggest deterioration
of characteristic flavor attributes rather than presence of flavor notes related to rancidity.
Overall, storage in HBB rather than PP resulted in better quality retention over the
storage period, especially when held under more abusive conditions.
INDEX WORDS: shelf-life, storage study, roasted almonds, rancidity, texture, sensory,
acceptability
CONSUMER ACCEPTABILITY OF DRY MEDIUM-ROASTED ALMONDS
STORED UNDER VARYING STORAGE CONDITIONS
by
ANNA NICOLE CHEELY
B.S., Augusta State University, 2008
A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial
Fulfillment of the Requirements for the Degree
MASTER OF SCIENCE
ATHENS, GEORGIA
2014
© 2014
Anna Nicole Cheely
All Rights Reserved
CONSUMER ACCEPTABILITY OF DRY MEDIUM-ROASTED ALMONDS
STORED UNDER VARYING STORAGE CONDITIONS
by
ANNA NICOLE CHEELY
Major Professor: Ruthann Swanson
Committee: Ronald Pegg
William Kerr
Electronic Version Approved:
Julie Coffield
Interim Dean of the Graduate School
The University of Georgia
December 2014
iv
TABLE OF CONTENTS
LIST OF TABLES ................................................................................................................... vii
LIST OF FIGURES ...................................................................................................................i x
CHAPTER
1 INTRODUCTION ..................................................................................................... 1
Nutrient and health benefits of almonds ............................................................... 2
United States almond production, harvesting, and grading.................................... 5
Almond shelf-life ................................................................................................ 7
References .......................................................................................................... 8
2 LITERATURE REVIEW......................................................................................... 13
Processing of roasted almonds ........................................................................... 14
Shelf-life of food products ................................................................................. 15
Shelf-life of nuts ............................................................................................... 17
Rancidity ........................................................................................................... 19
Textural changes ................................................................................................ 21
Control of lipid oxidation and textural changes .................................................. 23
Methods for assessing shelf-life ......................................................................... 28
Reference ........................................................................................................... 40
3 METHODS AND MATERIALS ............................................................................. 46
Characterization of the product .......................................................................... 46
Overall study design........................................................................................... 47
v
Descriptive panel ............................................................................................... 52
Consumer panel ................................................................................................. 69
Non-sensory tests ............................................................................................... 71
References ........................................................................................................ 73
4 POLYPROPYLENE BAG STORAGE RESULTS .................................................. 75
Non-sensory results ............................................................................................ 76
Descriptive sensory results ................................................................................. 78
Consumer sensory results ................................................................................... 81
Acceptability of the roasted almonds at baseline ................................................ 82
Conclusion ......................................................................................................... 87
References ........................................................................................................ 88
5 HIGH BARRIER BAG STORAGE RESULTS........................................................ 90
Non-sensory results ............................................................................................ 91
Descriptive sensory results ................................................................................. 93
Consumer sensory results ................................................................................... 96
Acceptability of the roasted almonds at baseline ................................................ 97
Conclusion ....................................................................................................... 100
References ...................................................................................................... 101
6 CONCLUSION ..................................................................................................... 103
References ...................................................................................................... 106
REFERENCES ....................................................................................................................... 108
APPENDICES
A INFORMATIONAL LETTER ............................................................................... 117
vi
B DESCRIPTIVE SENSORY PANEL: PRESCREENING QUESTIONNAIRE ....... 119
C REFERENCE CARDS .......................................................................................... 122
D ALMOND DESCRIPTIVE SCORECARD (1/2) ................................................... 124
E ALMOND DESCRIPTIVE SCORECARD (2/2) ................................................... 127
F CONSENT FORMS .............................................................................................. 130
G CONSUMER SCORECARD ................................................................................. 133
H CONSUMER QUESTIONNAIRE ......................................................................... 136
I APPENDIX I CHEMICAL/INSTRUMENTAL ANAYLSES BY FOODS AND
SCIENCE DEPARTMENT AT THE UNIVERSITY OF GEORGIA ..................... 138
J DEMOGRAPHIC INFORMATION ON POLYPROPYLENE BAG CONSUMER
PANELS ............................................................................................................... 144
K WEAK AND STRONG POINTS FROM POLYPROPYLENE BAG CONSUMER
PANELS ................................................................................................................ 148
L DEMOGRAPHIC INFORMATION ON HIGH BARRIER BAG CONSUMER
PANELS ................................................................................................................ 154
M WEAK AND STRONG POINTS FROM HIGH BARRIER BAG CONSUMER
PANELS ................................................................................................................ 156
vii
LIST OF TABLES
Page
Table 2.1: Fatty acid profile of Nonpareil almondsa (n=18) (Sathe and others 2008) .................. 18
Table 2.2: Descriptive sensory lexicon of almonds (Civille and others 2009)............................. 31
Table 3.1: Anchors for hardnessa (15-point scale) ...................................................................... 54
Table 3.2: Five basic taste anchorsa ........................................................................................... 56
Table 3.3: Calibration of the panel during evaluation of hardnessa (session 3—9/21/2012 and
session 4—9/28/2012) ................................................................................................... 59
Table 3.4: Anchors for crunchiness/fracturabilitya (15-point scale) ............................................ 60
Table 3.5: Crunchiness calibration check—Session 6 (10/5/2012) ............................................. 60
Table 3.6: Anchors for Spectrum™ intensity scale (Universal Intensity Scale)ab
(15-point) ....... 62
Table 3.7: Anchorsa for oxidized oils......................................................................................... 63
Table 3.8: Peroxide values of Crisco canola oila ........................................................................ 63
Table 3.9: Dry medium-roasted NP almond samples stored by Almond Board of California ..... 64
Table 3.10: Flavor, odor, and texture attributes, definitions, and references used by trained panel
to evaluate dry medium-roasted NP almond samples ..................................................... 67
Table 4.1: Dry medium-roasted almonds in polypropylene bags: Sensory rejection and non-
sensory tests .................................................................................................................. 77
Table 4.2: Consumer sensory resultsa for roasted almonds at baseline and after 16 months storage
in polypropylene bagsb of each sample at 4 different temperatures: rejection rates and
contribution of each attribute to overall acceptability ..................................................... 83
viii
Table 4.3: Consumer sensory panel scorecard responsesa for samples stored in polypropylene
bagsb .......................................................................................................................... 85
Table 5.1: Dry medium-roasted almonds stored in high barrier bagsa after 16 months storage:
Sensory rejection and non-sensory tests ......................................................................... 92
Table 5.2: Descriptive sensory panel results (means±SD)a of dry medium-roasted almonds stored
in high barrier bagsb ....................................................................................................... 95
Table 5.3: Consumer sensory resultsa for roasted almonds at baseline and after 16 months storage
in high barrier bagsb at 4 different temperatures: reflection rates and contribution of each
attribute to overall acceptabilityc of each sample ............................................................ 98
Table 5.4: Consumer sensory panel scorecard responsesa after 16 months storage for samples
stored at 4 temperatures in high barrier bagsb ............................................................... 100
ix
LIST OF FIGURES
Page
Figure 2.1: Mechanism of Autoxidation (Richards 2007) .......................................................... 21
Figure 2.2: Antioxidant species clinching free-radical (deMan 2007) ........................................ 24
Figure 2.3: Managing humidity and temperature in almonds to ensure shelf-life (adapted from
Almond Board of California 2010) ............................................................................... 27
Figure 2.4: Decision and process flow for multi-point shelf-life study ....................................... 35
Figure 3.1: Packaging plana for dry medium-roasted Nonpareil almonds ................................... 49
Figure 3.2: Decision tree for chemical/instrumental and sensory testing .................................... 51
Figure 4.1: Trained panel results for baseline (0 months) and samples with significant differences
at final testing point.. ..................................................................................................... 80
Figure 4.2: Almond Acceptability: baseline sensory panel (n=119) ........................................... 83
Figure 5.1: Descriptive sensory results at baseline (n=6) on a 15-point intensity scale where
0=“not perceptible” and 15=“high intensity”.................................................................. 96
Figure 5.2: Almond acceptability: baseline sensory panel (n=119) ............................................ 98
1
CHAPTER 1
INTRODUCTION
According to data analysis by the Centers for Disease Control and Prevention
(CDC), as of 2012, 117 million Americans had at least one chronic disease and chronic
diseases accounted for seven out of ten deaths (Ward and others 2012). Similarly on a
worldwide basis, more people die from chronic diseases than from infectious diseases,
maternal and peri-natal conditions, and nutritional deficiencies combined (WHO 2005a;
WHO 2005b). Current dietary guidance emphasizes the role of a healthy diet in reducing
chronic disease risk, specifically the risk for cardiovascular disease, cancer, diabetes and
obesity (ADA 2012; AICR 2012; WHO 2005ab). Nuts, due to their composition, when
incorporated into the diet, are likely to positively impact health outcomes (Ros 2010).
Nut consumption in general has long been linked to a decreased risk of sudden
cardiac death (Albert and others 2002; Kelly and Sabaté 2006; Kris-Etherton and others
2008). More recent evidence reveals an inverse relationship between nuts and obesity
and metabolic syndrome independent of demographic, lifestyle, and dietary factors
(Jaceldo-Siegl and others 2014). Benefits of nut consumption also have been found in
established diabetics (Lovejoy and others 2002), although Kochar and others (2010)
report the lack of a relationship between nut consumption and incidence of type 2
diabetes. Further, an inverse relationship between nut consumption and prostate (Chen
and others 2006) and pancreatic (Bao and others 2013a) cancer has been
reported. Finally, Bao and others (2013b) found that independent of other predictors of
2
death, frequency of nut consumption was inversely associated with total and cause-
specific mortality (heart disease, cancer and respiratory diseases). Similar results were
found for tree nuts as well as peanuts across all population subgroups.
Nutrient and health benefits of almonds
Almonds (Prunus dulcis) are a popular tree nut, with 1.8 pounds consumed per
person in the United States. In comparison, less than 0.5 pounds each of walnuts, pecans,
and pistachios are consumed each year. Forms of almonds available in the marketplace
include whole, slices or flakes, slivers or halves, diced or chopped, meal or flour, milk,
paste or butter, almond oil, and green almonds. Whole almonds are available raw,
blanched, and roasted (Almonds Board of California 2013). Of the California almond
production consumed by Americans, 60-70% is consumed roasted (Huang 2014). Health
benefits of almond consumption have been attributed to their nutrient profile,
specifically their high content of monounsaturated fats and bioactive compounds (Chen
and others 2006).
Like other nuts, almonds are a high-fat food with a fat content that is 49.4% by
weight (Chen and others 2006). However, monounsaturated fats make-up nearly 66% of
this total fat and 26% of the fat is polyunsaturated (United States Department of
Agriculture 2011). Although there may be an assumption that almond consumption
would contribute to obesity and obesity-related diseases due to the high fat content of the
nuts, a meta- analysis reveals no association between nut consumption, including
almonds, and a higher body mass index (Flores-Mateo and others 2013; Sabaté and others
2003). This lack of association has been attributed to the displacement of energy from
other foods, the satiating property of almonds (Hollis and Mattes 2007), and the
3
incomplete absorption of the fat present. The incomplete fat absorption is thought to be
because the cell walls of the almond limit the bioaccessibility of the fat present to the
physical and chemical actions of the gastrointestinal tract (Zemaitis and Sabaté 2001;
Ellis and others 2004). Almonds are also a good source of protein, with one serving (28g)
containing 12.1% of the U.S. Daily Value (DV) and fiber present at 13.2% of the DV.
Among the micronutrients, almonds are an excellent source of manganese
(containing >20% Daily Value) and a good source of magnesium, copper, phosphorus,
and riboflavin (containing 10-20% DV) (Chen and others 2006). Almonds are also an
excellent source of antioxidants. In addition, to being an excellent source of vitamin E
(36.4% of DV) (Chen and others 2006), 100g of almonds also contain 2 micrograms of
carotenoids, 261 mg of gallic acid equivalents of total phenolics, 25.01 mg of
flavonoids, 184.02 mg of anthocyanidins, and 595.63 micrograms of lignans (Boiling
and others 2010). It is important to note that this almond profile is affected by cultivar,
harvest year, orchard location, processing and storage (Boiling and others 2010; Yada
and others 2013).
Evidence is continuing to emerge that almonds and other nuts may decrease the
risk for type 2 diabetes (Mori and others 2011; Cohen and Johnson 2011; Li and others
2010). When patients with type 2 diabetes or metabolic syndrome were fed an almond-
based high fat diet versus a contemporary American Heart Association diet, there were
reductions in weight, triglycerides, fasting glucose, and low density lipoprotein (Lovejoy
and others 2002).
In multiple studies (Albert and others 2002; Hyson and others 2002; Jenkins and
others 2002; Spiller and others 1998), almond consumption has been associated with
4
decreased low-density lipoprotein cholesterol (LDL), as well as decreased total
cholesterol (TC). Studies suggest these cardiovascular benefits of almonds reside
primarily in their high content of monounsaturated fatty acids (Kamil and Chen
2012). Jenkins and others (2002) found a linear dose-response relationship with the
addition of 28 and 56 g of almonds daily to an isoenergetic diet, lowering LDL-C by 4.7
and 9.9% respectively. These researchers suggested that consumption of 28 or 56 g per
day of almonds would reduce the 10-year risk of CVD by 7.1 and 9%, respectively.
In 2003, the FDA concluded that there was sufficient evidence for a qualified B-
level health claim and that eating 42 grams daily of almonds and other nuts (excluding
Brazil, cashew, macadamia, and some pine nuts) “as part of a diet low in saturated fat
and cholesterol may reduce the risk of heart disease” (Food and Drug Administration
2003). More recently, The American Heart Association certified almonds with its
Heart-Check mark to signify that almonds are a heart healthy food; this is one of the
most consumer-trusted icons that can appear on packaged food (Almond Board
of California 2013).
The role of phenolic acids and polyphenols role in promoting health and
preventing chronic diseases is subject to a growing body of research (Kroon and
Williamson 2005), and at least some of the positive effects of almond consumption on
CVD may be attributed to the high levels of these antioxidants present. Flavonoid-
containing almond skin extracts can inhibit LDL-oxidation and DNA damage in vitro
(Wijeratne and others 2006). In a hamster model, flavonols and flavanols have been
shown to be bioavailable and to grant antioxidant protection against LDL-C oxidation.
At physiological concentrations, almond skin-derived flavonoids and phenolic acids
5
have been found to enhance the resistance of LDL-C to oxidation in a dose-dependent
manner (Chen and others 2005). In vitro, these phenolic compounds have also been
found to act synergistically on LDL-C oxidisability with vitamins C and E, suggesting
that foods containing all of these nutrients may provide greater than the predicted
antioxidant activity (Chen and others 2005). Further, polyphenols extracted from almonds
have strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (Sang
and others 2002).
Human studies suggest almonds and other nuts can modulate inflammation,
particularly among those with enhanced inflammatory status (Estruch and others 2006;
Salas-Salvadó and others 2007; Mena and others 2009). Inflammation plays an important
part in the risk and progression of cardiovascular disease and type two diabetes. The
biomarkers C-reactive protein and interleukin-6 are independent predictors of their
pathology. The anti-inflammatory effect of increased consumption of almonds and other
nuts is consistent with an inverse association with both of these biomarkers (Kamil and
Chen 2012). The chemoprotective effects of almonds using a human model, as opposed
to animal or in-vitro models, and the mechanistic effect of almonds on inflammation
(Chen and others 2006; Kamil and Chen 2012) are continuing to be investigated. Long-
term studies also are needed to examine health benefits of nut incorporation in the diets
of free-living individuals and in the diets of those individuals who are not at increased
risk for chronic health problems (Kamil and Chen 2012).
United States almond production, harvesting, and grading
The average life of an almond tree is 20 to 25 years with nut production beginning
3 to 4 years after planting (Boriss and others 2013). Almond trees lay dormant November
6
through February. Between late February and early March, buds start to blossom. From
March to June as the almonds continue to mature, their shells harden and a kernel, the
part of the almond that is typically consumed, forms. In July and early August almond
hulls begin to split, exposing the shell and allowing the almond to dry. From mid-August
through October, the almonds are harvested and the harvested almonds are then sent to a
huller/sheller where the kernels pass through a roller to remove the hull, shell, and any
other remaining debris. After sizing, the kernels are kept in controlled storage conditions
before being shipped or further processed (Almond Board of California 2014a).
Recommended storage conditions for roasted almonds include: cool and dry conditions in
vacuum-packed foil bags at <10 °C and <65% relative humidity (Almond Board of
California 2014b).
The USDA has established grading standards for all whole shelled almonds.
Although not widely used, “US Fancy” is the highest quality standard. Additional grades
in order of decreasing quality are “US Extra No. 1,” “US No. 1,” “US Select Sheller
Run,” “US Standard Sheller Run,” “US No. 1 Whole and Broken,” “US No. 1 Pieces,”
and “Mixed varieties.” Almonds graded as “US No. 1” are typically used for roasting
and blanching, and this grade is often referred to in the almond industry as “Supreme.”
As the grade moves down the scale from “US Fancy” to “US No. 1 Pieces”, the
percentage of defects and foreign material increases (United States Department of
Agriculture 2007). All grades of almonds, with the exception of “US No. 1 Pieces” and
“Mixed varieties,” consist of almonds with similar varietal characteristics. Further, bitter
almonds are not found in “US No. 1 Pieces” and can comprise no more than 1 percent of
the almonds designated as “Mixed varieties” (USDA 2007).
7
Almond shelf-life
Because almonds are a low-moisture food with high levels of antioxidants
(Almond Board of California 2010), they have a relatively long shelf-life. However,
almond shelf-life is affected by environmental factors, such as humidity and temperature
which impact quality of the product. Because almonds are only harvested once per year,
maintenance of quality during storage is very important in the delivery of a uniform
quality product to the consumer over time. Rancidity is the limiting factor in consumer
acceptability, regardless of product form (Garcia-Pascual and others 2003). Development
of rancidity is attributable most often to suboptimal storage conditions and/or lengthy
storage (Shahidi and John 2010). Rancid almonds are generally described as having an
“off” flavor with the kernel being noticeably rancid (Harris and others 1972).
There is currently a lack of detailed information on factors that affect the shelf-
life of almonds in general and roasted almonds specifically (Almond Board of California
2010; Garcia-Pascual and others 2003). More specific guidelines are needed to assure a
consistent quality product throughout the storage period. Because almonds are high in
unsaturated fatty acids and are prone to oxidation and deterioration, controlling these
changes and extending the shelf-life of almond products is one of the biggest challenges
of the food industry (Shahidi and John 2010). Improved and consistent quality will
increase consumer acceptability, and therefore, increase the likelihood that consumers
will realize the health benefits associated with almond consumption.
The research question was “how does consumer acceptability of dry medium-
roasted almonds change when the almonds are held under varying storage conditions?”
The overall hypothesis was that the most acceptable dry medium-roasted almonds would
8
be stored in high barrier bags (Almond Board of California 2010), which had been held in
the least humid conditions and at the lowest temperature.
There were 3 objectives for this research project:
1. to determine how attributes of dry medium-roasted almonds held under different
storage conditions are perceived by a trained descriptive panel over time.
2. to determine if there is a relationship between chemical results, and perceived
intensity of sensory attributes by trained descriptive panelists, and almond
acceptability and/or rejection rate as determined by a consumer sensory panel.
3. to identify relationships between instrumental/chemical testing of quality and the
data obtained from trained descriptive and consumer acceptability sensory panels.
References:
[AICR] American Institute for Cancer Research. 2012. AICR’s Foods that Fight Cancer.
Washington, DC.: American Institute for Cancer Research. Available at:
www.aicr.org/foods-that-fight-cancer/. Accessed September 15, 2014.
Albert CM, Gaziano JM, Willett WC, Manson JE. 2002. Nut consumption and decreased
risk of sudden cardiac death in the Physicians’ Health Study. Arch Intern Med.
162:1382–1387
Almond Board of California. 2013. Almond Almanac. Modesto, CA: Almond Board of
California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/2013_almanac.pdf.
Accessed September 15, 2014.
Almond Board of California. 2014a. Almond Lifecycle. Modesto, CA: Almond Board of
California. Available from:
http://www.almonds.com/consumers/about-almonds/almond-lifecycle. Accessed
September 15, 2014.
9
Almond Board of California. 2014b. Almond Shelf Life Factors. Modesto, CA.: Almond
Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/2014aq0007_shelf_life_f
actors.pdf. Accessed September 21, 2014.
Almond Board of California. 2010. Background information on almond shelf life
research. Modesto, CA.
[ADA] American Diabetes Association. 2012. Standards of Medical Care in Diabetes—
2012. Alexandria, VA: American Diabetes Association. Available
from: http://care.diabetesjournals.org/content/35/Supplement_1/S11.full. Accessed
September 22, 2014.
Bao Y, Hu FB, Giovannucci EL, Wolpin BM, Stampfer MJ, Willett WC, Fuchs CS.
2013a. Nut consumption and risk of pancreatic cancer in women. Br J Cancer.
109(11):2911-2916.
Bao Y, Han J, Hu FB, Giovannucci EL, Stampfer MJ, Willett WC, Fuchs CS. 2013b.
Association of nut consumption with total and cause-specific mortality. N Engl J Med.
369(21):2001-2011.
Boiling BW, McKay DL, Blumberg JB. 2010. The phytochemical composition and
antioxidant actions of tree nuts. Asia Pac J Clin Nutr. 19(1):117-123.
Boriss H, Brunke H, Huntrods D. 2013. Almond profile. Ames, IA.: Agricultural
Marketing and Resource Center. Iowa State University. Available from:
http://www.agmrc.org/commodities__products/nuts/almond-profile/. Accessed October
8, 2014.
Chen CY, Lapsley K, Blumberg J. 2006. A nutrition and health perspective on
almonds. J Sci Food Agric. 86:2245-2250.
Chen CY, Milbury PE, Lapsley K, Blumberg JB. 2005. Flavonoids from almond skins
are bioavailable and act synergistically with vitamins C and E to enhance hamster and
human LDL resistance to oxidation. J Nutr. 135:1366-1373.
Cohen AE, Johnson CS. 2011. Almond ingestion at mealtime reduces postprandial
glycemia and chronic ingestion reduces hemoglobin A1c in individuals with well-
controlled type 2 diabetes mellitus. Metabolism. 30:1312-1317.
Ellis PR, Kendall CW, Ren Y, Parker C, Pacy JF, Waldron KW. 2004. Role of cell walls
in the bioaccessibility of lipids in almond seeds. Am J Clin Nutr. 80:604-613.
10
Estruch R, Martinez-Gonzalez, MA, Corella D, Salas-Salvado J, Ruiz-Gutiérrez, Covas
MI, Fiol M, Gómez-Garcia E, López-Sabater MC, Viñoles E, Arós F, Conde M, Lahoz C,
Lapetra J, Sáez G, Ros E. 2006. Effects of a Mediterranean-style diet on cardiovascular
risk factors. Ann Intern Med. 145(1):1-11.
Flores-Mateo G, Rojas-Rueda D, Basora J, Ros E, Salas-Salvadó J. 2013. Nut intake and
adiposity: meta-analysis of clinical trials. Am J Clin Nutr. 97(6):1346-1355.
[FDA] Food and Drug Administration. 2003. Summary of Qualified Health Claims
Subject to Enforcement Discretion. Silver Spring, MD.: U.S. Food and Drug
Administration. Available from:
http://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm073992.h
tm. Accessed September 20, 2014.
Garcıa-Pascual P, Mateos M, Carbonell V, Salazar DM. 2003. Influence of storage
conditions on the quality of shelled and roasted almonds. Biosyst Eng. 84(2):201–209.
Harris NE, Westcott DE, Henick AS. 1972. Rancidity in almonds: shelf life studies. J
Food Sci. 37(6):824–827.
Hollis J, Mattes R. 2007. Effect of chronic consumption of almonds on body weight in
healthy humans. Br J Nutr. 98(03):651-656.
Huang G. October 8, 2014. Personal communication (email). Almond Board of
California, Modesto CA.
Hyson DA, Schneeman DO, Davis PA. 2002. Almond and almond oil have similar
effects on plasma lipids and LDL oxidation in healthy men and women. J Nutri. 132:703-
707.
Jaceldo-Siegl K, Haddad E, Oda K, Fraser GE, Sabaté J. 2014. Tree nuts are inversely
associated with metabolic syndrome and obesity: the Adventist health study-2. PLoS One
9(1).
Jenkins DJ, Kendall CW, Marchie A, Parker TL, Connelly PW, Qian W. 2002. Dose
response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-
density lipoproteins, lipoproteins(a), homocysteine, and pulmonary nitric oxide: a
randomized controlled, crossover trial. Circulation 106:1327-1332.
Kamil A, Chen CYO. 2012. Health benefits of almonds beyond cholesterol reduction. J
Agric Food Chem. 60:6694-6702.
Kelly JH, Sabaté J. 2006. Nuts and coronary heart disease: an epidemiological
perspective. Br J Nutr. 96(2):S61-S67.
11
Kochar J, Gaziano JM, Djoussé L. 2010. Nut consumption and risk of type II diabetes in
the Physicians' Health Study. Eur J Clin Nutr. 64(1):75-79.
Kris-Etherton PM, Hu FB, Ros E, Sabaté J. 2008. The role of tree nuts and peanuts in the
prevention of coronary heart disease: multiple potential mechanisms. J Nutr.
138(9):1746S-1751S.
Kroon P, Williamson G. 2005. Polyphenols: dietary components with established benefits
to health. J Sci Food Agric. 85:1239-1240.
Li SC, Liu YH, Liu JF, Chang WH, Chen CM, Chen CYO. 2010. Almond consumption
improved glycemic control and lipid profiles with type 2 diabetes. Metabolism. 6(4):474-
479.
Lovejoy JC, Most MM, Lefevre M, Greenway FL, Rood JC. 2002. Effect of diets
enriched in almonds on insulin action and serum lipids in adults with normal glucose
tolerance or type 2 diabetes. Am J Clin Nutr. 76:1000-1006.
Mena MP, Sacanella E, Vazquez-Agell M, Morales M, Fitó M, Escoda R, Serrano-
Martinez M, Salas-Salvadó J, Beneages N, Casas R, Lamuela-Raventós RM, Masanes F,
Ros E, Estruch R. 2009. Inhibition of circulating immune cell activation: a molecule anti-
inflammatory effect of the Mediterranean diet. Am J Clin. 89(1): 248-256.
Mori AM, Considine RV, Mattes RD. 2011. Acute and second-meal effects of almond
form in impaired glucose tolerant adults: a randomized crossover trial. Nutr Metab.
8(1):6.
Ros E. 2010. Health benefits of nut consumption. Nutrients. 2(7):652-682.
Sabaté J, Haddad E, Tanzman JS, Jambazian P, Rajaram S. 2003. Serum lipid response to
the graduated enrichment of a Step I diet with almonds: a randomized feeding trial. Am J
Clin Nutr. 77(6):1379-1384.
Salas-Salvadó J, Garcia-Arellano A, Estruch R, Marquez-Sandoval F, Corella D, Fiol M,
Gómez-Garcia E, Viñoles E, Arós F, Herrera C, Lahoz C, Lapetra J, Perona JS, Muñoz-
Aguado D, Martínez-González MA, Ros E. 2007. Components of the Mediterranean-type
food pattern and serum inflammatory markers among patients at high risk for
cardiovascular disease. Eur J Clin Nutr. 62(5):651-659.
Sang S, Lapsley K, Jeong WS, Lachance PA, Ho CT, Rosen RT. 2002. Antioxidative
phenolic compounds isolated from almond skins (Prunus amygdalus Batsch). J Agric
Food Chem. 50:2459-2463.
Shahidi F, John JA. 2010. Oxidation and protection of nuts and nut oils. 2nd. vol. In:
Decker EA, Elias RJ, McClements DJ, editors. Oxidation in foods and beverages and
antioxidant applications. Cambridge, UK.: Woodhead Publishing Ltd. p 274-305.
12
Spiller GA, Jenkins DA, Bosello O, Gates JE, Cragen LN, Bruce B. 1998. Nuts and
plasma lipids: an almond-based diet lowers LDL-C while preserving HDL-C. J Am Coll
Nutr. 11:126-130.
[USDA] United States Department of Agriculture. 2011. Basic Report: 12565, Nuts,
almonds, oil roasted, with salt added in National Nutrient Database for Standard
Reference. Washington, D.C.: U.S. Dept. of Agriculture. Available:
http://ndb.nal.usda.gov/ndb/foods/show/3753?fg=&man=&lfacet=&format=&count=&m
ax=25&offset=&sort=&qlookup=almonds. Accessed October 9, 2014.
[USDA] United States Department of Agriculture. 2007. United States Standards for
Grades of Shelled Almonds. Washington, D.C.: U.S. Dept. of Agriculture. Available
from: http://www.almondboard.com/Handlers/Documents/USDA-Standards-Shelled-
Almonds.pdf. Accessed October 28, 2014.
Ward BW, Schiller JS, Goodman RA. Multiple chronic conditions among US adults: a
2012 update. Prev Chronic Dis. 2014;11:130389. DOI: Available from:
http://dx.doi.org/10.5888/pcd11.130389. Accessed November 11, 2014.
Wijeratne S, Abou-Zaid M, Shahidi F. 2006. Antioxidant polyphenols in almond and its
coproducts. J Agri Food Chem. 54(2):312–318.
[WHO] World Health Organization 2005a. Chronic diseases and their common risk
factors. Geneva, Switzerland: World Health Organization.
http://www.who.int/Chp/chronic-disease-report/media /Factsheet1.pdf. Accessed October
9, 2014.
[WHO] World Health Organization 2005b. Solving the chronic disease problem. Geneva,
Switzerland: World Health Organization. http://www.who.int/Chp/chronic-disease-
report/media /Factsheet5.pdf. Accessed October 9, 2014.
Yada S, Huang GW, Lapsley K. 2013. Natural variability in the nutrient composition of
California-grown almonds. J Food Compos and Anal. 30:80-85.
Zemaitis J, Sabaté J. 2001. Effect of almond consumption on stool weight and stool fat.
FASEB J. 15:A602.
13
CHAPTER 2
LITERATURE REVIEW
California produced over 2.02 billion pounds of almonds in the 2011/12 crop
year, representing over 80% of the global almond production and virtually 100% of the
domestic supply (Almond Board of California 2012). The major varieties of almonds
produced in California include Nonpareil, Monterey, Carmel, and Butte, which accounted
for approximately 36.2%, 13.0%, 9.1%, and 7.8% of the entire 2012/13 crop, respectively
(Almond Board of California 2013). Nonpareil, due to its tree and nut characteristics, is
the most important variety. Almond varieties differ in kernel size, shape, blanchability
(ease of skin removal), and composition (Yada and others 2013).
Of the total California production, it is estimated that 60 to 70% of the domestic
shipment is roasted or consumed roasted (Huang 2014). Almonds graded “US No. 1” are
typically used for roasting. These almonds are relatively free from decay, rancidity, insect
injury, foreign material, particles and dust, and exhibit limited injury caused by chipped
and scratched kernels; few doubles, split, or broken kernels are present (United States
Department of Agriculture 2007). Roasting is done to not only create desirable
sensory/textural features but also to inactivate enzymes, destroy microorganisms, and
reduce water activity (Özdemir and others 2001). However, thermal processing or
roasting also contributes to a shorter shelf-life because deterioration of the nuts begins
immediately after roasting (Shahidi and John 2013).
14
Processing of roasted almonds
The roasting of nuts has been taking place for a very long time, although the
process has been fine-tuned over the past few decades. Roasting is a thermal process. It
creates the expected roasted flavors, develops roasted color characterized by a yellowish-
brown hue, and it changes the texture of the raw nut from hard or rubbery to crunchy.
Roasting always involves dehydration and the extent to which dehydration occurs
depends on the variety of nut and the desired sensory properties in the final product.
Unlike the typical uses of dehydration, this step in the nut roasting process does not help
produce a more stable product. The roasted end-product is actually less stable than its raw
counterpart. Roasting processes have been designed and tweaked through the
manipulation of the temperature and time to minimize lipid oxidation as much as possible
(Shahidi and John 2013).
There are two types of roasting processes—hot-air and oil roasting. Most
manufacturers use hot-air roasters that transfer heat by convection. Air is heated in a
combustion burner then is conveyed through the load of nuts to each individual kernel.
The load is typically agitated during the roasting process so that heat is spread evenly
across the kernels. In the final stage of hot-air roasting, temperatures are between 120 and
180 ºC. The final target moisture content is approximately 2.5g/100g wet basis. The
determination of the final moisture content is not defined by the lipid stability in
almonds, but instead by the crispness/crunchiness of the final roasted product (Shahidi
and John 2013).
In the industry there are two types of roasting systems—batch and continuous.
Batch roasters are either the traditional ball and drum roasters or semi-fluidized roasters,
15
with modern control systems. The semi-fluidized systems can be run in a quasi-
continuous manner. Continuous roasters include single belt line, vertical continuous
roasters, and continuous drum roasters.
Both roasting systems have limitations. In drum-type roasters, the nuts are
agitated constantly, which can cause potential damage to the surface structure of the
kernel, resulting in a release of oil and/or a damaged appearance. With use of a
continuous belt-roaster, although the overall roasting conditions may remain constant, the
heat transfer can be problematic with larger product loads. In addition, continuous
roasters typically have a limited range of roasting times and temperatures.
At the conclusion of the roasting step, a fast air-cooling system is essential in
order to stop the heat transfer and reduce the extent of lipid oxidation during subsequent
storage. The product should be cooled to temperatures below 30-35 ºC, and then
packaged so that no risk of moisture condensation is present on the inner surface of the
packaging (Shahidi and John 2013).
Shelf-life of food products
Sensory attributes are a key factor in consumer acceptability of food products.
Changes in sensory attributes occur with storage. Labuza and Szybist (2001) state that
shelf-life is a function of time, environmental factors, and susceptibility of the product to
changes in quality. This includes the physical, chemical, and biological changes that
occur through time and lead to product deterioration and therefore compromised
nutritional, microbiological or sensory quality. In recent years, interest in shelf-
life evaluation of food and beverage products has increased due to technological
16
developments and the increase in consumer interest in eating fresh, safe and high
quality products (Giménez and others 2012). Often the consumer’s negative reactions
to changes in product sensory characteristics precede any risk to health (Lawless
and Heymann 2010).
Shelf-life is defined by the Institute of Food Science and Technology (1993) as
“the time in which a food product remains safe, complies with label description of
nutritional data, and retains desired sensory, chemical, physical, and microbiological
characteristics when stored under the recommended conditions.” Traditionally, shelf-life
determination only focused on the food itself. Interaction with the consumer was not
considered. For example, an estimation of shelf-life has been determined based on
changes in flavor and texture as measured by a trained descriptive panel only. However,
Griffiths (1985) found that the significant differences found in descriptive sensory work
do not always translate to differences in consumer acceptability ratings. This suggests the
importance of the consumer perspective, rather than relying on measurable changes
detected by trained descriptive panelists alone. Knowing which sensory changes occur
and how those changes affect acceptability is very valuable information for
manufacturers that requires input from trained descriptive panelists.
Hough and others (2003) express more specifically that shelf-life should be
examined from a consumer sensory point-of-view. They contend that a food product
does not have a shelf-life of its own but rather its shelf-life depends on the interaction
between the food product and the consumer. Hough and others (2003) define this
consumer and food interaction through a “rejection” test. With this test, the time point
17
at which a consumer rejects a product rather than the characterization of the deterioration
of a food product through the use of instrumental, chemical, or descriptive sensory
evaluation is determined.
Changes over a storage period are often monitored using analytical methods.
Often these tests are conducted independent of one another, and any sensory testing. In
actuality, these results may complement one another and together can help elucidate the
changes that occur and their relationship with sensory quality (Giménez and others 2012).
Shelf-life of nuts
Almonds, like other tree nuts, are a low-moisture (3-6%) microbiologically stable
food (Almond Board of California 2014a); therefore, shelf-life is determined by changes
in sensory attributes (Hough and others 2003). Almond shelf-life is typically limited by
the rancid flavors that are imparted by lipid oxidation (Lin and others 2012).
Susceptibility to oxidation is influenced by total fat content, the fatty acid profile, and
presence of antioxidants.
Composition of Nonpareil almonds sampled across three harvest years and three
California production regions was: 3.9±0.6% water, 20.2±0.9% protein, 12.9±1.2%
dietary fiber and 49.6±1.9% total fat. Saturated fatty acids accounted for nearly 8% of the
total lipid present, with monounsaturated and polyunsaturated fatty acids accounting for
63 and 24%, respectively (Yada and others 2013). Sathe and others (2008) reported that
oleic and linoleic acid were the two most abundant fatty acids in almond lipids in general
and in Nonpareil lipids specifically. The fatty acid profile of Nonpareil almonds across
two harvest years is found in Table 2.1 (Sathe and others, 2008). Almonds are not a
source of linolenic acid (Robbins and others 2011; Sathe and others, 2008; Yada and
18
others 2013). Across seven almond varieties (including Nonpareil), negligible amounts of
alpha-linolenic acid and no gamma-linolenic acid were found (Yada and others 2013).
Table 2.1: Fatty acid profile of Nonpareil almondsa (n=18)
(Sathe and others 2008)
Fatty acid Average grams per 100 g lipid
C14:0 0
C16:0 5.91
C16:1 0.43
C18:0 0.603
C18:1 66.99
C18:2 25.96
C18:3 0.069
C20:0 0.46
Grams per 100 g lipid
Oleic:Linoleic 2.62
Oleic+Linoleic 94.65 aSamples provided from the two crop years by the Almond
Board of California (Modesto, California)
In addition to exhibiting Vitamin E activity, tocopherols are important naturally
occurring antioxidants in fats and oils. When compared to other nuts, almonds are
naturally high in alpha-tocopherol, although differences due to variety have been noted
(Fourie and Basson 1989; Garcıa-Pascual and others 2003; Yada and others 2013).
Across 7 varieties, levels ranged from 18.2 to 32.9 mg/100g almonds, with alpha-
tocopherol levels in the Nonpareil variety equal to 26.0±1.9mg/100g almonds (Yada and
others 2013). Decreases in total tocopherol content were found when almonds were
stored in double plastic bags at 30 ºC for 16 months. Development of rancidity when
exposed to O2 is related to the rate at which the antioxidants present are destroyed under
the conditions of storage (Fourie and Basson 1989).
19
Changes in texture may also determine shelf-life. The importance of texture in
consumer acceptability is indicated by the use of crispness/crunchiness as the indicator of
the appropriate moisture content in the roasted product (Shahidi and John 2013). When
almonds gain moisture (absorption), they may lose some the characteristic crunchiness or
crispness. This migration of moisture may affect not only texture, but also microbial
stability, and the rate of various chemical reactions, including those related to oxidation
(Fontana 2000). Exposure of almonds to the immediate environment means time,
temperature, relative humidity, light, and packaging continuously influence changes in
moisture content. (Garcıa-Pascual and others 2003; Almond Board of California 2010).
Rancidity
Rancidity is caused by two pathways—oxidative and hydrolytic. Oxidative
rancidity involves oxygen (fat oxidation). This process is initiated by heat, pro-oxidants,
certain enzymes, or light. Oxidative rancidity can be suppressed by minimizing light or
oxygen exposure, high temperatures, trace metals, or by the addition or natural
occurrence of antioxidants. Indeed in the absence of oxygen, oxidative rancidity would be
prevented, as oxygen is essential to propagate the reaction (Velasco 2010). Hydrolytic
rancidity occurs by hydrolysis and involves a chemical (generally requiring high
temperatures) or enzymatic (involving lipase) process to detach fatty acids from the
glycerol molecule. Hydrolytic rancidity can be suppressed by low temperatures and
moisture content, and the deactivation of lipases. Consumers perceive products as rancid
or spoiled even when low levels of free fatty acids are present (Richards 2007).
Rancidity, which causes negatively perceived flavors, may be retarded in various
ways, including preventing oxygen from coming in contact with the product, lowering
20
storage temperatures, inactivation of enzymes that typically catalyze oxidation, and
selection of appropriate packaging (Pokorny 2001; Shahidi and John 2013). Simply
delaying the onset of rancidity will extend the shelf-life and available market period
of food products.
Lipid oxidation
Lipid oxidation is the oxidative deterioration of lipids containing carbon-carbon
double bonds. It is a large problem with the storage of high-fat foods, and these changes
can result in negative flavors, and a loss of valuable nutrients (Kanner and Rosenthal
1992; Shahidi and John 2010). Lipid oxidation, which results in oxidative rancidity,
can be sub-divided into three types—autoxidation, photo-oxidation and enzyme-
catalyzed oxidation.
Autoxidation is a reaction that involves molecular oxygen and lipids. The overall
mechanism consists of three phases—initiation, propagation, and termination (Figure
2.1). In the initiation phase, a hydrogen atom is removed from an unsaturated fatty acid to
form a fatty acid free radical (alkyl free radical). This free radical formation is influenced
by temperature, light, or metal ions. In the propagation phase, the fatty acid free radical
readily reacts with oxygen, forming a peroxyl radical. The peroxyl radical becomes an
initiator and reacts with new lipid molecules, beginning another chain reaction, as well as
further producing hydroperoxides. In the termination phase, radicals react with one
another to yield relatively stable non-radical molecules (Shahidi and John 2013).
21
Initiation
LH + I → IH + L
Propagation
L + O2 → LOO
LOO + LH → LOOH + L
Termination
LOO + LOO → LOOL + O2
LOO + L → LOOL
L + L → LL
Figure 2.1: Mechanism of Autoxidation (Richards 2007)
The rate of oxidation of fatty acids increases as their level of unsaturation
increases. The state of conjugation also affects the rate of oxidation; conjugated
unsaturated fatty acids are less likely to oxidize than are nonconjugated fatty acids
(Richards 2007). Nonconjugated polyunsaturated fatty acids oxidize more rapidly than
monounsaturated fatty acids.
The primary oxidation products are the hydroperoxides formed during
propagation. These compounds are unstable and decompose into secondary oxidation
products. Effects on flavor are caused by secondary oxidation products, and include
alcohols, aldehydes, and ketones (deMan 1999; Richards 2007).
Textural Changes
Texture, which is multidimensional, is derived from the structure of the food
(molecular, microscopic, or macroscopic) and is detected by the senses—most
importantly touch and pressure. Textural perception by consumers, which is generated by
structural breakdown during mastication, is closely related to acceptability. Szczesniak
22
(2002) defines texture as “the sensory and functional manifestation of the structural,
mechanical, and surface properties of foods detected through the senses of vision,
hearing, touch, and kinesthetics.”
Consumer attitudes towards texture also can be affected and shaped by
physiological factors, socially and culturally learned expectations, and psychological
factors (Szczesniak and Kahn 1971). Previous experiences, the age of the consumer, as
well as the socioeconomic status and education level have an influence on textural
preferences. In general, consumer attitudes indicate texture is typically taken for granted
unless there is an inappropriate or off texture present and textural expectations are
violated. Texture tolerance, or how far a textural characteristic can deviate from the
anticipated norm, depends on the category of food product, and its principal
characteristics. Crispness and crunchiness are two of the generally favored textural
characteristics (Szczesniak and Kahn 1971) and for products that are valued for their
crispness or crunchiness, less variation is tolerated. Sound emissions of crisp and crunchy
foods also have been shown to influence the perception of the texture (Kilcast 2000).
Consumers generally expect roasted almonds to be crunchy rather than soft, mealy, or
chewy (Varela and others 2008a).
The textural properties of food also have an effect on the perception of flavor.
Changes to the structure of the food during mastication affect the way in which tastants
and odorants are released from the food. Perceptions of flavor and texture, and
perception of food product as a whole can be changed drastically if changes in food
23
structure occur during storage (Kilcast 2000). Due to the complex interaction of texture
with perceived flavor, storage conditions and time could result in the quality change in
the product (Kilcast 2000).
Control of lipid oxidation and textural changes
Rancidity is the reported limiting factor in consumer acceptability of nuts when
measured over time (Garcıa-Pascual and others 2003). The development of an
unacceptable flavor due to rancidity can be a result of poorly stored nuts or nuts stored
for too long (Shahidi and John 2010). Because of these effects, the inhibition of oxidative
reactions is important to the producer, manufacturer, and the consumer.
Lipid oxidation is a multifactorial process, and many of these events occur
simultaneously and are inter-related making it difficult to analyze one process or evaluate
a single factor in the overall oxidation process (Velasco and others 2010). Oxygen
content, relative humidity, moisture content of nuts, temperature, light, physical
characteristics of the nuts, fatty acid composition and antioxidant content, and previous
processing all affect the rate of oxidation during storage.
Effects of shelling and product form: Any damage caused during the shelling
process expedites the onset of oxidation and decreases shelf-life of the almonds. In-shell
almonds can typically be stored twice as long as those without shells, and the storage
period is further reduced when the shelled almonds are stored as pieces rather than as
intact kernels. The outer skin of the almond kernel also protects the kernel from
penetration from atmospheric oxygen, thus peeled almonds are more susceptible to the
effects of oxidation. In addition, transportation and/or further storage also has the
24
capability of damaging the nut or the structure of the kernel, further creating additional
opportunities for oxidation and off-flavor development (Shahidi and John 2013).
Effects of roasting: After roasting there is a loss of compartmentalization in
almonds, along with an increase in porosity, which accelerates mass transfer, making the
nut tissue more susceptible to oxygen (Perren and Escher 2013). This tissue breakdown is
a major factor affecting the extent of lipid oxidation in roasted nuts, with roasting
temperature being more important than roasting time. For almonds, it is advised to keep
roasting temperatures as low as possible, while increasing the time for which they are
roasted in order to achieve the desired sensory characteristics. This will minimize the
cascade of events that lead to lipid oxidation (Perren and Escher 2013).
Effect of fatty aid composition and antioxidants: Fatty acid composition and
antioxidant content affect rates of oxidation. While the consumption of unsaturated fatty
acids is associated with many health benefits, this unsaturated quality of the fatty acid
chain causes the lipid to be more vulnerable to oxidation. The susceptibility of PUFAs to
oxidation exceeds that of MUFAs. Antioxidants naturally present in nuts interfere with
the chain reaction of oxidation, reducing the number of free radicals (Figure 2.2), which
slows down the oxidation process (Fourie and Basson, 1989). Examples include
tocopherols (Richards 2007).
AH + R → RH + A
AH +RO2 → RO2H + A
Figure 2.2: Antioxidant species clinching free-radical (deMan 2007)
[A denotes antioxidant and R denotes free radical species]
25
Effects of temperature and light: Storage temperature, in particular, seems to have
a major influence on quality and therefore on shelf-life of nuts when measured affectively
(Shahidi and John 2010; Garcıa-Pascual and others 2003). The rate of oxidation increases
exponentially with increases in temperature (Shahidi and John 2013). In almonds, as well
as pistachios, peanuts and walnuts, higher storage temperatures (30, 36 and 40 ºC vs 8,
10, 20, 25 ºC) were associated with increased rancidity when nuts were stored over the
same period of time under the same conditions (Garcıa-Pascual and others 2003). There
is a strong indirect correlation between oxygen and temperature, because oxygen
solubility decreases as temperature increases. At temperatures higher than 130-140 ºC,
the hydroperoxides, because of their instability, decompose at a rate higher than their
formation. These higher temperatures are found in roasting (Velasco 2010).
Light favors the formation of free radicals in the initiation phase of lipid
oxidation, where it acts as a catalyst for hydrogen abstraction and the decomposition of
hydroperoxides. In a study by Jensen and others (2001), when walnuts were stored under
light at 21 ºC, pronounced oxidative changes occurred, however, when the walnuts were
stored in the dark at 21 ºC, no rancid taste was noted during a 25-week storage study
under accelerated conditions (50% oxygen).
Effects of final moisture content and relative humidity: In nuts, the recommended
final moisture content is based on stability of the lipid fraction (Calvaletto 1981),
assuming desirable textural characteristics are present (Shahidi and John 2013). Final
moisture content is influenced by maturity as well as harvest and storage conditions.
Unlike some other nuts, almonds are not typically subjected to mechanical drying post-
harvest. For almonds (raw, blanched, cut), three to six percent final moisture content
26
is the industry standard. When roasted, The Almond Board of California (2014a)
recommends that almonds have a final moisture content below 3%.
Studies involving the effects of relative humidity (RH) on nut stability have been
reported (Shahidi and John 2013). During storage, almonds will absorb and lose moisture
to reach equilibrium when held under varying humidities (moisture migration). As
moisture increases, hydrolytic oxidation may occur (Lin and others 2012). Further,
increases in moisture levels or water activity, may be associated with bacteria and mold
growth on almonds. Conversely, when almonds are stored under high temperatures and
low relative humidity they may lose moisture (Garcıa-Pascual and others 2003; Almond
Board of California 2010). The relationship between moisture or relative humidity and
water activity of almonds can be seen in Figure 2.3. Equilibrium is important and requires
moisture-barrier packaging and/or reducing the humidity in the environment (Almond
Board of California 2014a).
27
Figure 2.3: Managing humidity and temperatures in almonds to ensure shelf-life (adapted
from Almond Board of California 2010)
Effect of packaging material: Foil and polyethylene bags are often used by
the almond industry for packaging various forms of almonds (Almond Board of
California 2010, 2014bc). Both polyethylene and polypropylene are flexible, strong,
lightweight, stable, moisture and chemical resistant. They also have easy
processability. Polypropylene is harder, more dense, and more transparent than
polyethylene. Both polyethylene and polypropylene are also relatively inexpensive
(Marsh and Bugusu 2007).
In laminated packaging, thin-gauge aluminum foil is bound to paper or plastic,
whereas metallized films are plastics that contain a thin layer of aluminum metal. A
metallized film is the more inexpensive option. Both processes have an improved barrier
to light, moisture, oils, air, and odors when compared to polyolefins but the seal may not
28
completely bar moisture and air. A huge drawback of the use of aluminum materials is its
high cost compared to other materials (Marsh and Bugusu 2007). When selecting among
alternatives, performance properties and economics should be evaluated (Butler and
Morris 2010).
Packaging material for the roasted almonds should be chosen to restrict air or
oxygen exposure to the product, with an overall goal of preventing or slowing down lipid
oxidation (Almond Board of California 2010). Appropriate packaging is made from
nontransparent material that protects the nuts from light. The material should be firm but
also have elasticity and tensile strength to prevent the almond tips from piercing the bag.
Packaging should allow oxygen and water vapor exchange with the environment. Use of
modified atmosphere and vacuum packaging also decreases oxidation during subsequent
storage (Richards 2007; Shahidi and John 2013).
The Almond Board of California (2014a) recommends that almonds should
generally be stored under cool and dry conditions, specifically at 10 °C and at less than
65% relative humidity. Because roasted almonds need to be protected from oxygen due to
their exposure to high temperatures during the roasting process, it is recommended that
they be vacuum-packaged with nitrogen flushing (Almond Board of California 2014c).
Thus, roasted almonds are commonly packaged and shipped in cartons (25 lb or 11.3 kg)
with vacuum-packed foil bags as the primary packaging.
Methods for assessing shelf-life
Current methods used in shelf-life studies
Most of the studies found in the literature examine the influence of different
factors such as packaging material, temperature, time, roasting, light or irradiation, trace
29
metals, and antioxidants over a defined storage period on physical, sensory, and chemical
parameters of nuts (Shahidi and John 2010). Techniques employed included sensory
evaluation by consumer panels (Guadagni and others 1978, Harris and others 1972,
Mexis and others 2009, Varela and others 2008a, Varela and others 2009; Vickers and
others 2014) and trained descriptive panels (Vickers and others 2014; Varela and others
2006; Varela and others 2008a).
The chemical testing used includes but is not limited to: determination of free
fatty acid content (Harris and others 1972; Lin and others 2012), tocopherols (Garcıa-
Pascual and others 2003), and fat content (Garcıa-Pascual and others 2003; Varela and
others 2006) as well as hexanal-SPME procedure (Mexis and others 2009), and the
determination of 2-Thiobarbitruric acid (Mexis and others 2009), iodine value (Harris and
others 1972; Lin and others 2012), lipase activity (Lin and others 2012), and peroxide
value (Mexis and others 2009; Garcıa-Pascual and others 2003; Lin and others 2012). In
addition to sensory and chemical studies, texture can be quantified and assessed by
fracture pattern quantification (Varela and others 2008a; Varela and others 2008b) and
instrumental texture analysis of hardness and fracturaiblity (Varela and others 2008a;
Varela and others 2008b; Varela and others 2009).
Other analyses that have been performed include water activity (Vickers and
others 2014; Varela and others 2009) and moisture determination (Garcıa-Pascual and
others 2003; Lin and others 2012; Vickers and others 2014; Varela and others 2006).
Many studies employ multiple assessments of shelf-life (chemical, instrumental and
sensory) (Garcıa-Pascual and others 2003; Vickers and others 2014; Reed and others
2002), but the linkage with consumer assessment is often lacking.
30
Sensory assessments of almond quality and acceptability
A key to understanding consumer acceptability ratings is to measure sensory
attributes on an objective scale. A descriptive trained panel can provide a profile of
product sensory properties. Descriptive data collected can help in the design of
questionnaires and in identifying attributes of importance for individual products or
storage conditions. In addition, descriptive data can help in the interpretation of the data
collected in consumer testing. By relating these two types of data, the researcher can
discover relationships between product attributes and consumer acceptability (Meilgaard
and others 1991).
Descriptive sensory tests involve the detection and description of both qualitative
and quantitative measures to help judge product characteristics. Qualitative components
include aroma, appearance, after-taste, texture, sound, and flavor. Descriptive panelists
quantify the intensity of the individual product attributes. An advantage of descriptive
sensory tests is that a product can be assessed over a period of time, allowing product
changes or packaging effects on shelf-life to be tracked (Murray and others 2001).
A trained descriptive panel which typically consist of 6-12 members (Meilgaard
and others 1991 completes descriptive sensory tests. Panelists are typically screened prior
to joining the panel to assure they have a reasonable level of sensory acuity. When
undertaking the profiling of a new product, the panel generally develops a lexicon, which
is a comprehensive vocabulary of terms that describe the product of interest.
Alternatively, because of the complexity and time needed for development, existing
lexicons from the literature may be used by descriptive panels to analyze and compare
different samples. A lexicon has been developed by a trained sensory panel for describing
31
the appearance, aroma, flavor, and texture attributes of raw almonds (Civille and others
2009). Some of the descriptors from Civille and others (2009) can be seen in Table 2.2.
Several of these descriptors are related to rancidity. To date however, a similar lexicon
has not been developed for roasted almonds, although Vickers and others (2014) used
some of the attributes and associated definitions in the evaluation of different forms of
almonds, including roasted almonds.
Table 2.2: Descriptive sensory lexicon of almonds (Civille and others 2009)
Descriptor Definition
Appearance
Color hue Actual color name
Aroma
Cardboardy Aroma compounds associated with
partially oxidized oil; reminiscent of
cardboard boxes
Woody/tea Associated with the general category of
wood and/or dried tea leaves
Flavor
Roasted Aroma associated with almonds that have
been roasted
Painty Associated with linseed oil or oil-based
paint
Earthy/dry dirt Associated with clean dry earth or potting
soil
Basic tastes
Sweet Taste on the tongue simulated by sucrose
and other sugars
Bitter Taste associated with caffeine and other
bitter substances
Texture
Toothpack Amount of product packed in teeth surfaces
after expectoration
Crunch Force with which sample breaks or
fractures, rather than deforming when
chewed with the molars
32
Once a lexicon has been established, the panel uses “frames of reference” to
define the individual attributes and their intensity in the product of interest. These
references, which are used to define the “measuring stick” used to assess attribute
intensity, are constantly reinforced during training of the panel (Murray and others 2001).
The Modified Spectrum Descriptive (Meilgaard and others 1991; Murray and
others 2001) technique can be used if a lexicon has already been established and there is
no need to further establish terms of interest. Munoz and others (1992) explains two
applications—Comprehensive Descriptive procedure and a Difference-from-Control
procedure. In the Comprehensive Descriptive procedure, a reduced set of attributes is
selected by testing the variability in production and choosing characteristics whose
variability most affects consumer acceptance. This technique can be applied to manage
quality control, processing batches of food products, or incoming materials. Difference-
from-Control testing occurs when a trained panel assesses how key attributes of the
product being evaluated differ from the control/standard product. In this test, the
magnitude of the difference between the sample and the standard (control) product is
measured (Meilgaard and others 1991).
Discrimination tests may also be used. During discrimination tests, panelists are
asked if there is a perceived difference between two products or conversely, if the
products are the same. The former is used much more often than the latter (Kilcast 2000).
An example of a discrimination test is the triangle test, where three samples, two of
which are identical, are coded and presented to a panelist. The panelist then chooses the
sample that is different from the other two (Kilcast 2000). However, discrimination
33
tests are limited because they can only establish if a difference exists between two
samples. If any additional acceptability or scaling of intensities is needed, other types of
sensory testing must be implemented (Kilcast 2000; Meilgaard and others 1991; Stone
and Sidel 2004).
Consumer sensory testing is performed to assess preference for or acceptability of
a product (Stone and Sidel 2004). These tests can provide a direct measure of liking,
allowing shelf-life to be directly estimated. In the process of evaluating products,
consumer sensory testing usually, but not always follows descriptive and discrimination
tests (Stone and Sidel 2004). Preferably 100 or more panelists are used in the assessment
of acceptability, but smaller numbers of panelists have also been found to be effective in
determining shelf-life (ASTM 2011; Kilcast 2000; Meilgaard and others 1991). The 9-
point hedonic scale, where 1 equals extremely disliked and 9 equals extremely liked, is
frequently used. This scale is easily understood by consumers, requires minimal
instruction and results are stable and reproducible with different groups of subjects (Stone
and Sidel 2004). Additional information including the acceptability of appearance, odor,
flavor, and/or texture can also be obtained (Kilcast 2000).
Consumer sensory testing is a highly effective tool used by manufacturers in
designing products or maintaining product quality (Meilgaard and others 1991). These
tests alone do not guarantee success of a product in the marketplace, as other factors that
reach beyond the scope of the sensory scientist also need to be taken into consideration.
In addition, acceptability results may not be indicative of a population’s intent to
purchase. One way to obtain more action-oriented information on consumers is to use a
food action rating scale or FACT. This asks a consumer to estimate the frequency of
34
consumption or purchase of a specific food or product (Stone and Sidel 2004). More
recently, Hough and others (2003), who have employed a survival analysis to assess
shelf-life of food products, have addressed the intent to consume question by asking the
consumer panelist if he/she would consume the product—“yes” or “no” if the product
had already been purchased or if it was being served to them at their homes. This
question focuses on product rejection rather than the deterioration of product
characteristics (Hough and others 2003).
The ASTM (2011) protocol for shelf-life determination outlines the use of
sensory evaluation in determining shelf-life of food products. Approaches using
discrimination, descriptive, and affective testing are described. Regardless of the sensory
method employed, the end-point criteria should be established prior to beginning the test.
The use of both multi-point and single-point evaluations are addressed in the
ASTM (2011) method for shelf-life studies. In the single-point evaluation protocol,
products are collected from different lots over the expected shelf-life of the product and
then products representative of all time-points are evaluated at once. Single-point
evaluations minimize variation often observed in consumer response because the testing
is done at one time. Conversely, multi-point evaluation (Figure 2.4) occurs when a single
product lot is tested after being held under specified conditions over a period of time.
Samples are pulled and evaluated at predetermined time points throughout the study.
Large quantities of the control and test samples are needed for the multiple evaluations.
The amount of sample required in multi-point testing can take-up space, use more labor,
and therefore be a financial burden. However, multi-point evaluations can provide an
35
early indication of product change that can be tracked until the change impacts consumer
use of the product. Often data collected at baseline are used as the control sample.
Figure 2.4: Decision and process flow for multi-point shelf-life study
Figure adapted from ASTM 2011 a Screening tests can include analytical measures, bench top evaluation, or sensory
discrimination testing. These should be sufficiently rigorous to avoid passing a product
that should be failed. b Confirmatory tests may include discrimination testing, descriptive sensory analysis, or
consumer testing, as determined by your pre-established end point criteria.
Implementing a pass/fail test in conjunction with the specific criteria previously
set for acceptability ratings or significant differences from a standard or control can be
useful (ASTM 2011) and has been employed by a number of researchers (Curia and
others 2005; Hough and others 2003; Salvador and others 2005). An answer of “no” to
Testing Phase
Confirmatory testb Screening testa
Pull samples
Store samples
End point established:
Shelf-life = The last
point at which the
product is passed.
Pass or Fail? Pass or Fail?
36
the intent to consume question is defined as rejection. A 25% rejection rate (percentage
of consumers rejecting sample after testing) has been used to define the endpoint for the
shelf-life of yogurt (Curia and others 2005; Salvador and others 2005). Ares and others
(2006) and Gámbaro and others (2006) both used the 25% rejection rate to define the
shelf-life for shiitake mushrooms and apple-baby food respectively. Giménez and others
(2007) also used a 25% rejection rate during a shelf-life study on brown pan bread. Based
on preliminary studies, a 25% rejection rate was found to be much more practical and a
better reflection of consumer behavior than the 50% rejection rate used in earlier studies
(Hough and others 2003).
Consumer identification of strong and weak points coupled with an assessment of
acceptability has been used to gain insight into the reasons for the acceptability ratings.
This approach overcomes the limitations associated with the use of consumers to rate
intensity of identified product attributes. The frequency at which terms are listed can be
analyzed using a correspondence analysis (Rousset and Martin 2001). Previous studies
indicated that consumers focused on the most noticeable popular and unpopular attributes
or traits of the product when listing strong and weak points whereas trained assessors
focused on the greatest sensory differences (Rousset and Martin 2001). Rousset and
Martin (2001) concluded that the number of strong points attributed to the sample was
indicative of its acceptability. In addition, this assessment allowed the main reasons for
the panelists’ ratings to be identified. When coupled with a rejection test, it also allows
the reason(s) for consumer rejection to be identified.
37
Non-sensory assessments of almond quality
Chemical assessments, water activity, moisture determination, and instrumental
texture analysis are useful tools in assessing chemical and/or physical changes in
almonds. Levels of both peroxides and free fatty acids are commonly used in the nut
industry to describe product quality and serve as the basis of recommendations designed
to conserve almond quality (Garcıa-Pascual and others 2003). Changes in water activity
are associated with changes in the rate of lipid oxidation (Fontana 2000). Additionally,
changes in almond texture during storage are reflected in changes in water activity,
moisture content and instrumental assessment of texture (Vickers and others 2014). Thus,
water activity may be an indicator of textural changes as well as the presence of chemical
changes that result in rancidity and by extension product acceptability or rejection.
Determination of peroxide values is a simple test that measures the amount of
hydroperoxides in fat or oil; it is a test of primary lipid oxidation products (Shahidi and
John 2013). Fourie and Basson (1989) showed that changes in peroxide levels could be
used to predict oxidation and peroxides values are the most performed measure of
oxidation in almonds (Garcıa-Pascual and others 2003). Because fatty acids are cleaved
from the glycerol backbone during the oxidation process, levels of free fatty acids present
also serve as a chemical indicator of rancidity (Lin and others 2012). Industry
recommendations are free fatty acid levels of less than 1.5% and peroxide values of less
than 5.0 meq. active O2/kg oil (Almond Board of California 2014c).
In hydrolytic oxidation, moisture facilitates the enzyme-catalyzed hydrolytic
cleavage and the resulting free fatty acids can further oxidize and give rise to rancidity.
38
An increase in moisture content combined with heat can further intensify the enzyme-
catalyzed hydrolytic reactions, creating a chain-reaction (Lin and others 2012). Thus
moisture content of almonds is often determined.
Water activity is related to lipid oxidation, as well as textural properties of food.
Lipid oxidation reaction rates generally decrease as water activity decreases, but as water
activity drops below 0.4 lipid oxidation rates begin to drastically increase. Further,
almond texture is affected by moisture content and water activity levels. Low-moisture
foods are often described as hard and/or crunchy and as the water activity increases their
textural attributes can change undesirably to soggy or chewy (Fontana 2000). Texture
perception by consumers, which is generated by the breakdown of a roasted almond
during mastication, is closely related to its acceptability.
Varela and others (2008b) used a TAXT.2 Plus Texture Analyzer for fracture
analysis of Marcona almonds, which had been subjected to different roasting times. Six
replications were performed on each lot. This compression test successfully detected
differences in the fracturability or crunchiness of the roasted almonds. The longer the
roasting time for the sample, the more brittle it was, resulting in deformation and
increased fracturing with a lower application of force.
Combined sensory and non-sensory methods
Sensory measures have been used in combination with chemical and instrumental
techniques in shelf-life studies (Giménez and others 2012). Chemical and instrumental
testing can help explain the results found in sensory work and vice versa. Off-flavors that
develop during storage (Hough and others 2003; Garcıa-Pascual and others 2003; Shahidi
and John 2010; Almond Board of California 2010) can be identified and quantified with
39
descriptive sensory analysis (Murray and others 2001). Chemical compounds responsible
for these off-flavors can be determined with headspace analysis (Velasco and others
2010). In some cases, the products associated with the chemical reactions during storage,
such as peroxide and free fatty acid values, can be quantified through chemical testing
(Lin and others 2012). When coupled with consumer sensory testing, levels of the
compounds or the extent to which the intensity of an attribute deviates from baseline
allows the effect of these changes on acceptability to be determined.
In a 9-month storage study conducted by Garcıa-Pascual and others (2003),
different varieties of almonds (raw and roasted) were held under different conditions
(temperature, atmosphere, and raw and roasted). Peroxide values were higher in the
roasted than the raw almonds throughout the study. Nonpareil almonds consistently
exhibited the highest peroxide values, while Marcona almonds, despite having a higher
fat content, had the lowest peroxide values. Further, a significant inverse relationship was
found between an increase in peroxide values and a decrease in tocopherol content. No
significant effect of packaging the almonds in air versus a nitrogen environment was
found. Although higher peroxide values were correlated with increases in rancid flavor, a
significant relationship was not found when overall acceptability was assessed by an
untrained sensory panel (Garcıa-Pascual 2003). The lack of a peroxide-acceptability
relationship suggests that thresholds for rancidity as reflected in peroxide values and their
relationship with acceptability should be determined. A trained descriptive panel can
facilitate the identification of these relationships (Garcıa-Pascual and others 2003;
Gonzalez and others 2001).
40
In multiple-year shelf-life studies commissioned by the Almond Board of
California, the relationship found between peroxide values and consumer acceptability
for almonds stored under differing conditions resulted in an industry recommendation
that roasted almonds should be stored at temperatures between 4 ºC and 21 ºC and at a
relative humidity between 45%-70%. Packaging was not specified (Almond Board of
California 2012). It is unclear if the currently recommended conditions are the optimal
ones. Further, packaging is likely to affect the extent to which environmental conditions
are influential.
Changes in almond texture that help explain consumer acceptability can be related
to the instrumental assessment of textural parameters. However, textural parameters
detected and quantified instrumentally must eventually be interpreted in terms of sensory
perception (Szczesniak 2002). Vickers and others (2014) performed a study analyzing the
impact of almond form and water activity on textural attributes and consumer
acceptability. An increase in water activity was associated with decreases in sensory and
instrumental crispness/crunchiness measures. It was concluded that water activity levels
above 0.3 - 0.4 can be detrimental to almond crispness/crunchiness.
References:
Almond Board of California. 2012. Request for proposals: Shelflife of whole almonds in
retail and bulk packages. Modesto, CA.
Almond Board of California. 2013. Almond Almanac. Modesto, CA.: Almond Board of
California. Available from:
http://www.almondboard.com/AboutTheAlmondBoard/Documents/2012%20Almond%2
0Almanac_FINAL.pdf. Accessed October 28, 2014.
Almond Board of California. 2010. Background information on almond shelf life
research. Modesto, CA.
41
Almond Board of California. 2014a. Almond Shelf Life Factors. Modesto, CA.: Almond
Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/2014aq0007_shelf_life_f
actors.pdf. Accessed September 21, 2014.
Almond Board of California. 2014b. Long-Term Storage Study of Raw and Blanched
Almonds. Modesto, CA.: Almond Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/aq0105_lin_summary_re
port_july_2014_final.pdf. Accessed November 2, 2014.
Almond Board of California. 2014c. Technical Information Kit and Poster. Modesto, CA:
Almond Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/english_technical_kit.pdf
. Accessed October 30, 2014.
Ares G, Parentelli C, Gámbaro A, Laeo C, Lema P. 2006. Sensory shelf life of shiitake
mushrooms stored under passive modified atmosphere. Postharvest Biology and
Technology. 41:191-197.
ASTM Standard E2454-05. 2011. Standard evaluations methods to determine the sensory
shelf life of consumer products. West Conshohocken, PA.
Butler TI, Morris BA. 2010. PE based multilayer film structures. In: Wagner JR, editor.
Multilayer Flexible Packaging: Technology and Application for the Food, Personal Care,
and Over-The-Counter Pharmaceutical Industries. Burlington, MA.: Elsevier. p 205-230.
Calvaletto CG. 1981. Quality evaluation of macadamia nuts. In: Charalambous G, Inglett,
editors. The Quality of Food and Beverages: Chemistry and Technology. New York:
Academic Press. p 71-82.
Civille GC, Lapsley K, Huang G, Yada S, Seltsam J. 2009. Development of an almond
lexicon to assess the sensory properties of almond varieties. J Sen Stud. 25:146-162.
Curia A, Aguerrido M, Langohr K, Hough G. 2005. Survival analysis applied to sensory
shelf life of yogurts–I: Argentine formulations. J Food Sci. 70(7):442-445.
deMan J. 2007. Principles of Food Chemistry. 3rd ed. New York: Kluwer Academic
Publishers. 520 p.
Fontana AJ. 2000. Understanding the importance of water activity in food. Cereal Foods
World. 45(1):7-10.
Fourie PC, Basson DS. 1989. Predicting rancidity in stored nuts by means of chemical
analyses. Lebensmittel Wissenschaft und Technologie. 22:251-253.
42
Gámbaro A, Ares G, Giménez A. 2006. Shelf-life estimation of apple-baby food. J Sen
Stud. 21:101-111.
Garcıa-Pascual P, Mateos M, Carbonell V, Salazar DM. 2003. Influence of storage
conditions on the quality of shelled and roasted almonds. Biosyst Eng. 84(2):201–209.
Giménez A, Verla P, Salvador A, Ares G, Fisman S, Garitta L. 2007. Shelf life estimation
of brown pan bread: a consumer approach. Food Qual Prefer. 18:196-204.
Giménez A, Ares F, Ares G. 2012. Sensory shelf-life estimation: a review of current
methodological approaches. Food Res Int. 49:311-325.
Gonzalez R, Benedito J, Carcel JA, Mulet A. 2001. Cheese hardness assessment by
experts and untrained judges. J Sen Stud. 16:277-285.
Griffiths N. 1985. Sensory analysis in measuring shelf-life. Food, Flavours, Ingredients,
Packaging and Processing. 7(9):47-48.
Guadagni DG, Soderstrom EL, Storey CL. 1978. Effect of controlled atmosphere on
flavor stability of almonds. J Food Sci. 43:1077-1080
Harris NE, Westcott DE, Henick AS. 1972. Rancidity in almonds: shelf life studies. J
Food Sci. 37(6):824–827.
Hough G, Langohr K, Gomez G, Curia A. 2003. Survival analysis applied to sensory
shelf life of foods. J Food Sci. 68(1):359-362.
Huang G. October 8, 2014. Personal communication (email). Almond Board of
California, Modesto, CA.
IFST. 1993. Shelf life of foods – guidelines for its determination and prediction. London:
Institute of Food Science & Technology.
Jensen PN, Sørenson G, Engelsen SB, Bertelsen G. 2001. Evaluation of quality changes
in walnut kernels (Juglans regia L.) by vis/NIR spectroscopy. J Agri Food Chem.
49(12):5790-5796.
Kanner J, Rosenthal I. 1992. An assessment of lipid oxidation in foods. Institute of Pure
and Applied Chemistry. 64(12):i959-i964.
Kilcast D. 2000. Sensory evaluation methods for shelf-life assessment. In: Kilcast D,
Subramaniam P, editors. The Stability and Shelf-life of Food. Cambridge, UK:
Woodhead Publishing Ltd. p 79-105.
Labuza TP and Szybist LM. 2001. Open Dating of Foods. Connecticut: Food and
Nutrition Press. 239 p.
43
Lawless HT and Heymann H. 2010. Sensory Evaluation of Food. 2nd ed. New York:
Chapman & Hall. 596 p.
Lin X, Wu J, Rongbi Z, Chen P, Huang G, Li Y, Ye N, Nanhui Y. 2012. California
almond shelf life: Lipid deterioration during storage. Inst Food Tech. 77(6):C583-C593.
Marsh K, Bugusu B. 2007. Food packaging—roles, materials, and environmental issues.
J Food Sci. 72(3):R39-R55.
Meilgaard M, Civille GV, Carr BT. 1991. Sensory Evaluation Techniques. 2nd ed.
Florida: CRC Press. 354 p.
Mexis SF, Badeka AV, Riganakos KA, Karakostas KX, Kontominas MG. 2009. Effect of
packaging and storage conditions on quality of shelled walnuts. Food Control. 20:743-
751.
Munoz A, Civille GV, Carr BT. 1992. Sensory Evaluation in Quality Control. New York:
Chapman & Hall. 240 p.
Murray JM, Delahunty CM, Baxter IA. 2001. Descriptive sensory analysis: past, present,
and future. Food Res Int. 34:461-471.
Özdemir M, Ackurt F, Yilldiz M, Biringen G, Gürcan T, Löker M. 2001. Effect of
roasting on some nutrients of hazelnuts (Corylus Avellana L.). Food Chem 73:185-190.
Perren R and Escher F. 2013. Impact of roasting on nut quality. In: Harris LJ, editor.
Improving the Safety and Quality of Nuts. Cambridge, UK.: Woodhead Publishing Ltd. p
173-197.
Pokorny J. 2001. Natural antioxidant functionality during food processing. In: Pokorny J,
Yanishlieva N, Gordon M, editors. Antioxidants in Food, Practical Applications.
Cambridge, UK.: Woodhead Publishing Ltd. p 335-351.
Reed KA, Sims CA, Gorbet DW, O’Keefe SF. 2002. Storage water activity affects
flavour fade in high and normal oleic peanuts. Food Res Int. 35:769-774.
Richards MP. 2007. Lipids: functional properties. 2nd ed. ln: Hui YH, editor. Food
Chemistry: Principles and Applications. Sacramento, CA: Science Technology System. p
71-720.
Robbins KS, Shin EC, Shewfelt RL, Eitenmiller RR, Pegg RB. 2011. Update on the
healthful lipid constituents of commercially important tree nuts. J Agri Food Chem.
59(22):12083-12092.
44
Rousset S, Martin JF. 2001. An effective hedonic analysis tool: weak/strong points. J Sen
Stud. 16:643-661.
Salvador A, Fizman SM, Curia A, Hough G. 2005. Survival analysis applied to sensory
shelf life of yogurts–II: Argentine formulations. J Food Sci. 70(7):446-449.
Sathe SK, Seeram NP, Kshirsagar HH, Heber D, Lapsley KA. 2008. Fatty acid
composition of California grown almonds. J Food Sci. 73(9):C607-614.
Shahidi F, John JA. 2010. Oxidation and protection of nuts and nut oils. 2nd. vol. In:
Decker EA, Elias RJ, McClements DJ, editors. Oxidation in Foods and Beverages and
Antioxidant Applications. Cambridge, UK.: Woodhead Publishing Ltd. p 274-305.
Shahidi F, John JA. 2013. Oxidative rancidity in nuts. In: Harris LJ, editor. Improving the
Safety and Quality of Nuts. Cambridge, UK.: Woodhead Publishing Ltd. p 199-229.
Stone H, Sidel JL. 2004. Sensory Evaluation Practices. 3rd ed. London: Elsevier. 408 p.
Szczesniak AS and Kahn EE 1971. Consumer awareness and attitudes towards food
texture I: adults. Journal of Texture Studies. 2:280-295.
Szczesniak AS. 2002. Texture is a sensory property. Food Qual Prefer. 13:215-225.
[USDA] United States Department of Agriculture. 2007. United States Standards for
Grades of Shelled Almonds. Washington, D.C.: U.S. Dept. of Agriculture. Available
from: http://www.almondboard.com/Handlers/Documents/USDA-Standards-Shelled-
Almonds.pdf. Accessed October 28, 2014.
Varela P, Chen K, Fiszman S, Povey MJW. 2006. Crispness assessment of roasted
almonds by an integrated approach to texture description: texture, acoustics, sensory, and
structure. J Chemometr. 20:311-320.
Varela P, Salvador A, Fiszman S. 2008a. On assessment of fracture in brittle foods.
Biting or chewing? Food Research International 41:544-551.
Varela P, Aguilera JM, Fiszman S. 2008b. Quantification of fracture properties and
microstructural features of roasted Marcona almonds by image analysis. LWT - Food Sci
Technol. 41(1):10-17.
Varela P, Salvador A, Fiszman S. 2009. On assessment of fracture in brittle foods II.
Biting or chewing? Food Research International. 42:1468-1474.
Velasco J, Dobarganes C, Màrquez-Ruiz G. 2010. Oxidative rancidity in foods and food
quality. In: Skibsted LH, Risbo J, Andersen ML, editors. Chemical Deterioration and
Physical Instability of Food and Beverages. Cambridge, UK.: Woodhead Publishing Ltd.
p 3-32.
45
Vickers Z, Peck A, Labuza T, Huang G. 2014. Impact of almond form and moisture
content on texture attributes and acceptability. J Food Sci. 79(7):S1399-S1406.
Yada S, Huang GW, Lapsley K. 2013. Natural variability in the nutrient composition of
California-grown almonds. J Food Compos and Anal. 30:80-85.
46
CHAPTER 3
METHODS AND MATERIALS
16-month study— December 2013 through February 2014
This project was a collaboration between the Foods and Nutrition and Food
Science and Technology departments at the University of Georgia. The Food Science
department conducted chemical and instrumental testing at 2-month intervals throughout
the 16 month duration of the study and the Department of Foods and Nutrition was
responsible for all sensory tests and the non-sensory tests performed on the day of
sensory evaluation. All sensory procedures were approved by the University of Georgia
Institutional Review Board.
Characterization of the product
The raw Nonpareil (NP) almonds were from the 2012 crop and were a composite
lot harvested from different orchards during September and October of 2012. They were
sized at 27/30 kernels per ounce and graded Supreme. The almonds were pasteurized by
propylene oxide fumigation (PPO) and roasted for 68 minutes at 122 °C (dry medium-
roasted, no salt). The final moisture content was 2.0%. Before being shipped to Athens,
the roasted almonds were packaged in high barrier bags (ABC Packaging, Cleveland,
Ohio, U.S.A.) on 307th day of 2012 and were flushed with nitrogen prior to being sealed.
The shipment of almonds arrived to the University of Georgia on November 14, 2012 via
47
commercial carrier and were placed in a refrigerated room (4 °C) until packaging began
on November 15, 2012. Almonds were packaged for storage under specified conditions
over a 23-day period.
Almonds were packaged in either Uline S-17960 (100µm, clean polypropylene
(PP) bags (Uline, Waukegon, IL) or ABC 5 x 8 x 3 metallized film laminate (100 µm
PET, 100 µm Al, 75 µm PE) high barrier bags (StandUpPouches, Avon, Ohio). The
polypropylene material had water vapor transmission rates (WVTR) of 8 g m-2
d-1
and
oxygen transmission (OT) of 860 cm3 m
-2d
-1. The laminate material (PET/Al/PE) had a
WVTR <0.5 g m-2
d-1
and OT < 1 cm3
m-2
d-1. Bags were vacuumed using a Henkelman
600 vacuum packaging system (Henkelman bv, Netherlands), flushed with food-grade
N2, and sealed, providing a sufficient pillow. Thirty bags per treatment were packaged.
Each bag contained 300±5 g of roasted almonds. Initial oxygen level was below 0.5%.
Overall study design
The effects of storage conditions on almond quality characteristics were
investigated with an incomplete factorial design. The dry medium-roasted Nonpareil
almonds were divided into eleven lots according to predetermined combinations of
temperatures (n=3), humidity levels (n=3), and packaging materials (n=2) (Figure 3.1).
The almonds as received from the Almond Board of California served as the control. Six
(35°C/65% relative humidity (RH); 35°C/50%RH; 25°C/65%RH; 25°C/50%RH;
15°C/65%RH; 15°C/50%RH) samples that were repackaged in polypropylene bags were
stored in HotPack (SP Industries, Warminster, PA) environmental chambers, 2 high
barrier bag (15°C and 25°C without humidity control) samples were stored in Thermo
Scientific Incubators (Thermo Fisher Scientific Inc., Waltham, MA), 1 (35°C without
48
humidity control) high barrier bag sample was stored in Thelco Precision Scientific
Model 6 Incubator (Thermo Fisher Scientific Inc., Waltham, MA), and 2 (4°C PEB and
4°C HBB without humidity control ) samples were stored in a Norlake Listed Walk-in
(Nor-Lake, Inc., Hudson, WI). Temperature and relative humidity of each chamber were
recorded every hour throughout the study with an Extech RHT-10 temperature/humidity
probe (Extech Instruments Corporation, Nashua, NH). Samples were loaded so that the
stored samples could be pulled every 2 days for chemical, instrumental, and sensory
testing, if appropriate.
The protocol for sensory evaluation outlined by the ASTM (2011b) was followed.
Almonds were assessed at baseline by a consumer (n=119) sensory panel and the 6-
member descriptive sensory panel. These results served as the control throughout the
study. In addition baseline assessments were completed for all non-sensory analyses.
For all quality assessments, almonds assessed were similar to “good” quality
almonds, as defined by USDA grading standards (USDA 2007), broken pieces, pinched
kernels, and almonds with visual defects were removed prior to sensory evaluation.
49
Relative Humidity (RH) and
Temperature (polypropylene bags)b
No RH control 4 °C
Temperature (high barrier bags)b at
no RH control
15 °C 50%RH 25 °C
35 °C
15 °C 65%RH 25 °C
35 °C
4 °C
15 °C
25 °C
35 °C
Figure 3.1: Packaging plana for dry medium-roasted Nonpareil almonds
a Divided into 11 lots
b Flushed with N2; initial O2 level <0.5%
The eleven samples were assessed every 2 months over a 16-month time frame
for chemical, instrumental, and qualitative sensory triggers of descriptive sensory
evaluation (Figure 3.2). Peroxide values of 2.0 meq. active O2/kg oil or greater, or the
detection of sensory notes (ASTM 2011a) typical of degradation in nuts were triggers of
further evaluation after each 2-month period. This procedure was followed to ensure that
evaluation occurred during the potential rejection window. Three experienced sensory
analysts evaluated textural and flavor notes for degradation. When triggered, sensory
evaluation was completed by the trained sensory panel (n=5-6 in duplicate), followed by
a subsequent comparison of the descriptive sensory results to baseline measures. When
the stored sample differed significantly (p<0.05) from the baseline sample in the sensory
50
attributes associated with oxidation, a consumer screening panel was triggered (n=~35).
If 25% of these consumer panelists rejected the sample, a larger confirmatory panel was
triggered (n=~100-120); rejection by 25% of the consumer panelists on the confirmatory
panel was required to confirm rejection and the elimination of the sample from
additional testing. When the confirmatory panel did not reject the sample, the descriptive,
consumer screening, and consumer confirmatory panels were repeated at subsequent 2-
month intervals, until 25% of the panelists on the confirmatory panel “rejected” the
sample. Beginning at month 10 of storage, all samples not previously rejected, were
evaluated by both descriptive sensory as well as the non-sensory tests. At 16 months of
storage, all samples remaining in storage were evaluated by all 3 sensory panels, and the
study was terminated.
51
Figure 3.2: Decision tree for chemical/instrumental and sensory testing a Tests administered were headspace analysis, moisture analysis, water activity, texture
analysis, peroxide values, free fatty acids, conjugated dienes, and TBARS b PV of 2.0 meq. active O2/kg oil, or detection of off-sensory notes by 3 experienced
sensory analysts (ASTM 2011a). c Beginning at 10-mos storage, all samples subjected to all sensory tests even in absence
of a chemical/instrumental trigger. d Significant differences in oxidation attributes versus baseline measures
e “If you had purchased this product would you eat it?” (yes or no) (Hough and others
2003) f Once triggered if the sample was not rejected by a consumer confirmatory panel,
reevaluation, occurred during the next pull 2 months later g Water activity, moisture content, and instrumental texture were assessed at each time
point that a sensory panel was conducted
52
Descriptive trained panelists evaluated samples in duplicate. No more than 9 days
passed between completion of the instrumental/chemical tests by the Food Science and
Technology department and the completion of the associated sensory testing—
descriptive, consumer (screening and if appropriate, confirmatory panels). Non-sensory
tests [instrumental texture (n=36 assessments per sample), moisture (n=6 assessments per
sample), and water activity (n=6 assessments per sample)] also were completed in
conjunction with the sensory panels on the day of testing.
Descriptive panel
Criteria for acceptance as a descriptive panelist
Six panelists served on the descriptive sensory panel. The panelists were trained
for approximately 25 contact hours. Training sessions focused on quality attributes of
almonds that are related to shelf-life (Civille and others 2009). Panelist inclusion criteria
were: at least 18 years old, not allergic to any tree nut or peanuts; and a consumer of nuts
or nut products at least once per month. Potential panelists were screened for smell and
taste sensitivity, the lack of dental appliances that prohibit assessments of texture, and
their availability over the duration of the study. All panelists selected responded similarly
on texture and flavor screening quizzes/tasks.
Recruitment and screening of potential descriptive panelists
Informational letters (Appendix A) on the “Almond Acceptability Study” were
sent-out on the University of Georgia Department of Foods and Nutrition and Food
Science listservs. Interested participants completed a prescreening questionnaire that
included questions pertaining to food allergies, time availability during the study, current
food habits, health, and awareness of texture and flavor of food products. Texture and
53
flavor questions were used to assess current knowledge on these topics. Questions
included, “Describe some noticeable flavors in Ritz crackers?” and “What are some
textural properties of potato chips?” After review of the completed questionnaire
(Appendix B), thirteen respondents were asked to participate in a screening visit. During
this visit, potential respondents completed an odor identification test, a texture ranking
test, and a triangle test which assessed each panelist’s ability to discriminate between two
products. For all sensory assessments used in the screening process, samples presented
were coded with 3-digit random numbers.
Screening Odor Assessment
For the odor identification test, 2 cotton balls placed in 4-ounce screw-closed
glass jars (Wheaton, Millville, NJ) carried 3 drops of an extract—orange, cinnamon,
coconut, or almond (McCormick & Company, Inc., Sparks, MD). The prepared
containers were capped and held at room temperature for 2 hours before evaluation. The
panelist was asked to sniff the sample and identify the odor detected.
Screening Texture Assessment
A texture test was created using the “hardness scale” (Meilgaard and others
1991). Four products located at positions 1.0, 4.5, 9.5 and 11.0 on the 15-point scale
(Table 3.1) were presented in a random order to each panelist. The panelist ordered the
samples from “least hard” to “most hard.” This test was completed to assess the panelist’s
ability to judge the relative intensity of one textural attribute—hardness— in the four
products presented.
54
Table 3.1: Anchors for hardnessa (15-point scale)
Scale value Product Sample size
1.0 Kraft/Philadelphia cream cheesebc
½ in. slice
4.5 Land O’Lakes American Cheesedc
½ in. slice
6.0 Goya Foods/giant sized, stuffed olivesbe 1 olive pimiento
removed
7.0 Hebrew national, large, cooked 5 minutes
Frankfurterf
½ in. slice
9.5 Cocktail style peanuts, in vacuum tinbc
1 nut, whole
11.0 uncooked, fresh, unpeeled carrots ½ in. slice
11.0 shelled planters almondsc
1 nut
14.5 Life Savers hard candybg 3 pieces, one
colora Meilgaard and others 1991
b Products choosen for reference card
c Kraft Foods North America, Tarrytown, NY
d Land O’ Lakes, inc., Arden Hills, MN
e Goya Foods, Inc., Seacacus, NJ
f ConAgra Foods, Inc., St. Paul, MN
g Wm. Wrigley Jr. Company, Peoria, IL
Triangle test
The triangle test (Meilgaard and others 1991) included two unroasted slivered
almond (Kroger Co., Cincinnati, OH) samples which had been baked at 185°C for 1
minute and 185°C for 6 minutes. Samples were held at room temperature for 1 hour
before being presented to each panelist seated in individual booths under red lighting.
Each potential panelist evaluated the samples coded with 3-digit random codes. Three
triangles were evaluated during the session with each sample serving as the odd sample.
In addition to the screening tests, personality traits (group interaction, ability to make
independent decisions, ability to convey opinions, willingness to come to consensus)
that indicated that a potential panelist was not well-suited for a role as a descriptive
sensory panelist were noted. Individual panelists’ responses were compared to those of
the entire screening group (n=13). Potential panelists who struggled with fluency in
55
English, who had difficulty completing the screening tests or could not make the
necessary time commitment were excluded from consideration. A panel of 8 was
selected. Two of these panelists were subsequently dropped because of complications
with the time commitment.
Training of descriptive panelists
Twelve sessions were held during the initial phase of panelist training. Panelists
received monetary, as well as food-based rewards for attending training sessions.
Training sessions ranged from 1.5 hours to 3 hours. Breaks were included during longer
review sessions, and when practice samples were evaluated in the sensory booths. During
evaluation and discussion times, panelists were offered still and seltzer water (Kroger
Co., Cincinnati, OH), unsalted top saltines (Kroger Co., Cincinnati, OH), and baby
carrots for cleansing purposes.
Training: Overview, procedures, and basic tastes introduction
During the introductory training session, expectations of a descriptive sensory
panelist were explained and sensory attributes including odor, taste, mouthfeel
sensations, texture, and flavor were introduced. The 5 basic tastes also were presented to
the panel (Table 3.2). Each panelist was supplied with water, crackers/carrots, and an
expectorant cup.
56
The differences between taste and flavor were discussed, as were the relationships
with texture and mouthfeel sensations. Flavor was described as a combination of basic
taste, odor, and overall mouthfeel sensation. Mouthfeel sensation was described to the
panel as sensations perceived by the nerves in the skin of the mouth cavity—thermal
(cold from ice cubes), chemical (warmness from wine), burning (jalapeno pepper), and
astringent (unsweetened hot tea). Mouthfeel sensations evoked by frozen fruit punch
concentrate reconstituted with seltzer water were provided and discussed.
The difference between perception of basic tastes and aromatics and their
contribution to flavor was introduced. A covered small glass vial (1 dram) filled with
cinnamon sugar (1 teaspoon per 1 cup of sugar) was given to each panelist. Panelists
were asked to note the taste of the sample with their noses pinched shut, and again after
releasing their noses and inhaling and exhaling. This exercise illustrated detection of the
basic taste via the gustatory system, and that inputs (aromatics) from the olfactory system
were necessary for the detection of flavor.
Sensory attributes of food products which were defined as a property or trait were
then discussed and defined as “a quality or feature regarded as a characteristic or inherent
Table 3.2: Five basic taste anchorsa
Taste Product and preparation
Salty Sodium chloride at 1.2g/500ml water
Sweet Sucrose at 12g/500ml water
Bitter Caffeine at 0.2g/500ml water; prepare with
boiling water and bring back to boil after
adding.
Sour Citric acid at 0.4g/500ml water
Umami Miso soupb prepared from package
a Meilgaard and others 1991
b Trader Joe’s, Monrovia, CA
57
part of something.” The attributes of dry medium-roasted almonds specifically important
to the study were also explained—textural attributes of hardness and crunchiness; levels
of sweetness; and oxidized odors and flavors.
During the initial introductory session, an overview of the training process was
provided. The protocol to be followed during each sensory session was reviewed, this
included an encouragement to observe/play with the food product by smelling, tasting,
and manipulating the food inside the mouth and the importance of expectoration of the
samples. The idea that evaluation did not mean eating was repeatedly emphasized, as
was the need to develop a sensory testing technique and consistently use the technique.
Scaling was introduced and the use of anchors was discussed. All scales ranged from 0 to
15 (15-centimeters), where “0” was labeled as “not perceptible” and “15” was labeled
as “high intensity.”
Training: Texture attributes
Texture evaluation was the main focus during sessions 2, 3, and 4. The Standard
Hardness Scale (Meilgaard and others 1991) was first explained, followed by a Standard
Crunchiness Scale (described by “Standard Fracturability Scale” in Meilgaard and others
1991). During these sessions, panelists were continuously supplied with cleansers—
still and seltzer water, carrots, and unsalted-top saltines (Mondelēz International, Inc.,
Deerfield, IL). They were also given pencils, scratch paper, and practice scales, and
encouraged to make notes.
During the practice and training for the hardness scale (Table 3.1), products that
were not on the scale were introduced to the panelists as a group, and where the newly
introduced sample fell on the scale was discussed. These products included Kroger
58
oatmeal cookies (Kroger Co., Cincinnati, OH), Kroger butter crackers (Kroger Co.,
Cincinnati, OH), Pringles (Kellogg Company, Battle Creek, MI), and Corn Nuts (Kraft
Foods North America, Tarrytown, NY).
Once the group began to align their values for commercially available products
similarly, panelists while seated in individual sensory booths were given two different
potato chips—Pringles (Kellogg Company, Battle Creek, MI) and Kettle brand (Kettle
Foods, Inc., Salem, OR), and asked to rate them on the hardness scale. The 4 anchors, as
well as a reference scale were available for use when evaluating these chip samples. Both
potato chip samples were cut into ½ inch pieces, put in 2-ounce plastic cups with lids and
coded with a 3-digit random number for evaluation. After a short break, the panelists
discussed the results as a group. Table 3.3 shows two of the products that were evaluated
during two of the sessions, first in session 3, then in session 4. The second time that the
samples were evaluated, standard deviations decreased, indicating increased uniformity
in the group response.
59
Table 3.3: Calibration of the panel during evaluation of hardnessa (session 3—9/21/2012
and session 4—9/28/2012)
Session 3
Sample Panelists Mean±SD
501 502 503 504 509 511 513
Kroger butter
crackerb
6 3.5 4.5 5.2 1.8 6.3 5.5 4.6±1.6
Kroger oatmeal
cookieb
4.5 4.2 6 7 2.5 7.3 8.2 5.7±2.0
Session 4
Kroger butter
crackerb
4.5 5.4 5.3 5.5 5.6 4.8 3.6 4.9±0.7
Kroger oatmeal
cookieb
5.4 6.8 5.8 6.6 6.5 5.1 5.7 6.0±0.7
a Samples were evaluated in sensory booths according to previously set standards;
reference cards were used. b Kroger Co., Cincinnati, OH
In the next phase of training the focus on hardness continued, and the testing of
nuts were introduced. Hardness in a raw pecan versus a roasted pecan was discussed.
This introduction of nuts and other nut products helped to familiarize the panelists with a
product similar to almonds.
During the practice and training for the crunchiness scale (Table 3.4), products
including Ritz salted crackers (Mondelēz International, Inc., Deerfield, IL) and Wheat-
thin, original flavored crackers (Mondelēz International, Inc., Deerfield, IL) were
evaluated. Other commercially available products used for training and to practice
scaling techniques included: Lay’s Potato Chips (Frito-Lay North America, Inc., Dallas,
TX Potato Chips), Kroger butter crackers (Kroger Co., Cincinnati, OH), Corn nuts (Kraft
Foods North America, Tarrytown, NY).
60
Once panelists began to improve their texture scaling techniques, raw and roasted
nuts, both salted and unsalted, were introduced to allow them to become more familiar
with the product class. Table 3.5 presents the panelists’ evaluation of crunchiness of raw
and roasted almonds.
Table 3.4: Anchors for crunchiness/fracturabilitya (15-point scale)
Scale value Product Sample size
1.0 corn muffinbc
½ in. cube
4.2 Nabisco Graham
crackersbd
½ in. square
6.7 plain Melba toaste
½ in. square
8.0 Nabisco Ginger
snapsbd
½ in. square
14.5 Life Savers hard
candybf
1 piece
a Meilgaard and others 1991
b Products chosen for reference card
c Kroger Co., Cincinnati, OH
d Mondelēz International, Inc., Deerfield, IL
e B&G Foods, Inc., Parsippany, NJ
f Wm. Wrigley Jr. Company, Peoria, IL
Table 3.5: Crunchiness calibration check—Session 6 (10/5/2012)
Sample Panelists Mean±SD
501 502 503 504 511 513
Raw almondsa
8 7.4 9.2 7.6 6 6.4 7.4±1.1
Roasted almondsa
10.3 9.5 10.8 9.4 8 8 9.3±1.2 a Earth Fare, Asheville, NC
61
Training: Flavor attributes
Flavor attributes were addressed in sessions 5, 6, and 7 beginning with the
sweetness intensity scale. Five sucrose solutions differing in concentration (Meilgaard
and others 1991) were presented. Still and seltzer water, as well as unsalted-top saltine
crackers (Mondelēz International, Inc., Deerfield, IL) served as palate cleansers.
After becoming familiar with the sweetness scale, three lemonade flavored
Kool-Aid (Kraft Foods North America, Tarrytown, NY) samples prepared with 1 cup of
sugar, 1/3 cup sugar and 2/3 cup of sugar per 2 quarts of product were assessed for
sweetness intensity.
Various peanut butter spreads including Kroger natural (Kroger Co., Cincinnati,
OH), Peter Pan (ConAgra Foods, Inc., Omaha, NE) and Earth Fare Natural (Earth Fare,
Asheville, NC) were also used for evaluation of sweetness. These peanut butters were
selected because of the “nutty” flavor similar to almonds and almond products, and
because their use reinforced the importance of sweetness as an important attribute in the
almonds. Initially, the spreads were evaluated with the sucrose reference solutions. In
later sessions, the spreads were evaluated without references present.
The “Universal Intensity Scale” or Spectrum™ intensity scale (Meilgaard and
others 1991) was next introduced to the panel. The products that serve as anchors on the
15-point scale (Table 3.6) were presented to panelists and the specific flavor notes and
their intensities were discussed. A universal intensity reference card was created for use
inside of the individual booths (Table 3.6; Appendix C).
62
Table 3.6: Anchors for Spectrum™ intensity scale (Universal Intensity Scale)ab
(15-point)
Scale value Product
2 Soda note in Nabisco Premium, unsalted, Saltine
crackerscd
4.5 Grape note in prepared grape Kool-Aidce
4.5 Potato note in Pringles potato chipsf
5 Cooked orange note in Frozen orange concentrate
(Minute Maid)—reconstitutedcg
10 Welch’s grape juicech
12 Big Red gum (Wrigley)ci
a Meilgaard and others 1991
b Derived from repeated tests with trained panels at Hill Top Research, Inc.,
Cincinnati, Ohio c Products choosen for reference card
d Mondelēz International, Inc., Deerfield, IL
e Kraft Foods North America, Tarrytown, NY
f Kellogg Company, Battle Creek, MI
g The Coca-Cola Company, Atlanta, GA
h Welch Foods, Inc., Westfield, NY
I Wm. Wrigley Jr. Company, Peoria, IL
The concept of oxidization was introduced to the panel by presenting rancid
potato chips. Rancid samples were prepared by exposing a single layer of Lay’s Original
potato chips (Frito-Lay North America, Inc., Dallas, TX) to incandescent lighting (75
watts) for 24 hours. The exposed chips were then double-bagged in Ziploc freezer bags
and placed in a dark refrigerator to halt oxidation. These chips along with a newly opened
bag of Lay’s Original potato chips were assessed with a triangle test. Panelists were
asked to pick the odd sample. After the individual evaluation, the group met to sample
the chips and discuss the results. A brief explanation of oxidation was presented with
emphasis on odor and overall flavor. Cardboardy, rancid, and painty were the specific
notes of interest. Anchors for these attributes as defined in the ASTM (2011a) method
63
were introduced and evaluated (Table 3.7). Panelists were given Crisco canola oils with
increasing peroxide levels as training references (Table 3.8).
Table 3.7: Anchorsa for oxidized oils
Attribute Technique/Anchor Definition
Cardboard (odor) 4x4 square of corrugated cardboard
steeped in filtered water overnight
Aromatic associated with
slightly oxidized fats and
oils, reminiscent of wet
cardboard packaging
Rancid (taste and
odor)
Oil stored for 4 days at 60 °C or until
peroxide value is 5.0
Aromatic associated with
oxidized fats and oils,
often described as on
“off” note, in between
cardboard and painty
Painty (taste and
odor)
Canola oil aged 4-6 days at 60 °C or
until peroxide value is 10.
Linseed oil (odor only)
Aromatic associated with
oxidized oil; similar to
the aromatic of linseed
oil and oil based paint a ASTM 2011a
Table 3.8: Peroxide values of canola oila
Timeb
Peroxide values
Baseline 0.25
Day 1 1.76
Day 2 2.32
Day 3 6.93
Day 4 27.8
Day 5 47.5 a J.M. Smucker Co., Orrville, OH
b Prepared by heating at 60 °C in oven in 24-hour
increments (ASTM 2011a)
To facilitate identification of these oxidation attributes in nuts, the panel initially
evaluated nut samples for texture and sweetness and then responded to the question—
“Oxidation note present? Please check one of the following: Yes or No.” Once the panel
64
was consistent in identifying the presence or absence of an oxidation note, assessment of
the three oxidation attributes (cardboardy, rancid, painty) was refined. Stored almond
samples were provided by the Almond Board of California for panel training; peroxide
values for these almond samples are found in Table 3.9.
After all sensory attributes were consistently assessed singly, multiple attributes
were evaluated in different combinations (ex. hardness and sweetness; oxidation odor,
flavor and crunchiness, etc.), followed by assessment of all of the attributes introduced
(all textural, sweetness, and oxidation flavor and odor attributes). The trained panel was
monitored to ensure no loss of calibration throughout the 16-month study and
recalibration sessions were conducted throughout the study, when appropriate. These
sessions were conducted when increases in standard deviations associated with individual
attributes were noted.
Table 3.9: Dry medium-roasted NP almond samples stored by
Almond Board of California
Harvest year Peroxide valuesa (meq. active O2/kg oil)
2006 85.7
2010 6.92 a Determined 8/5/2012 by Department of Food Science at the
University of Georgia; method in Appendix I
65
Descriptive panel evaluation of almonds
Evaluation of each sample took 10-15 minutes. Each evaluation session was
preceded by a warm-up sample. This roasted/unsalted almond sample was obtained from
The Fresh Market, Inc. (Greensboro, NC). It was found to be most consistent with the
least amount of variation in locally available roasted/unsalted almond samples throughout
the duration of the study. No more than 4 samples, including warm-up samples, were
evaluated during one testing session and no more than two sampling sessions were
completed within a day. When multiple sessions occurred within a single day, there was
at least a 1-hour break between sessions.
Samples pre-coded with a 3-digit random number were evaluated under white
light by panelists seated in individual booths. The tray presented through a sensory pass-
thru window included a napkin, water, expectorate cup, a palate cleanser (baby carrots),
scorecard, reference scales, and the almond sample.
Each almond sample (example, 35°C/65%RH in polypropylene bags) s evaluated
in two separate phases. In phase 1, texture—attributes included hardness and
crunchiness as defined by Meillgard and others (1991) and sweetness as defined by
Meillgard and others (1991) were assessed. Each panelist received 4 almonds and
evaluated the samples according to scorecard instructions (Appendix D), and then
returned the tray along with the completed scorecard. There was a break of approximately
one minute before the second tray with the same almond sample was presented for
evaluation of odor and flavor rancidity attributes.
66
The second set of samples included 5 almonds along with 3 odor reference
samples and a scorecard for evaluating rancidity attributes. The Universal Intensity Scale
was used for reference when evaluating these samples (Appendix C) (Meillgard
and others 1991).
Odor reference samples were prepared as follows: Whole roasted almonds were
placed into a mini-food processor (Proctor Silex 1.5C Mini Food Chopper, Hamilton
Beach Brand, Inc., Southern Pines, NC) and pulsed while shaking vigorously for 10
seconds. Chopped almonds were then sifted through a 2-mm sieve to get rid of the very
fine almond dust. The remaining chopped almonds were then separated by another sieve
with 5-mm holes, and these almond pieces that measured between 2 and 5-mm were used
for the odor samples. The larger almond pieces were placed in the mini food processor to
be chopped again. Three ounce plastic cups were filled with 15.0 grams of chopped
almonds and closed with a lid. Cups sat at least 2 hours but no longer than 6 hours for
volatiles to accumulate in headspace. Three odor samples are presented with each group
of almonds, one cup for each oxidation factor evaluated (Appendix E). Before the next
almond sample was presented to the panelist, there was a 7-minute break.
Two repetitions were completed for each triggered almond sample at each time
point. References and definitions for textural, taste, flavor, and odor anchors are found
in Table 3.10.
67
Table 3.10: Flavor, odor, and texture attributes, definitions, and references used by trained panel to evaluate dry medium-roasted NP
almond samples
Term Definition References/anchors
|---------------------------------------------------------------|
0 15
not perceptible high intensity
I. Texturea
Hardness The force required to chew
through the sample using the
molars; force required to
compress through food
cream cheesec (1)---green olive
d (6)---peanut
c (9.5)---Life saver
e (15)
Crunchiness The force at which the sample
breaks or fractures when
chewed with the molars
corn muffinf (1)--graham cracker
g (4.2)--ginger snap
g (8)--Life saver
e (15)
III. Odorb
The following was the Universal Scale, which applied to all of the
flavor/odor attributes:
Soda: saltineg (2)
Grape: grape Kool-aidc (5)---Welch’s grape juice
h (10)
Orange: Minute Maid orange juice from concentratei (7)
Cinnamon: Big Red Gume (12)
Cardboard odor Aromatic associated with
slightly oxidized fats and oils,
reminiscent of wet cardboard
packaging
Rancid odor Aromatic associated with
oxidized fats and oils
Painty odor Aromatic associated with
oxidized oil; similar to the
aromatic of linseed oil and oil
based paint
II. Flavor/basic tasteb
Cardboard flavor Flavor associated with slightly
oxidized fats and oils,
reminiscent of wet cardboard
packaging
68
Rancid flavor Flavor associated with oxidized
fats and oils
Painty flavor Flavor associated with oxidized
oil; similar to the aromatic of
linseed oil and oil-based paint
Sweeta Basic taste on the tongue
stimulated by sugars and high
potency sweeteners
Surcose solution in water
2.0% (2)---5.0% (5)-----10.0% (10)------15.0% (15)
a Meilgaard and others 1991
b ASTM 2011a
c Kraft Foods North America, Tarrytown, NY
d Goya Foods, Inc., Seacacus, NJ
e Wm. Wrigley Jr. Company, Peoria, IL
f Kroger Co., Cincinnati, OH
g Mondelēz International, Inc., Deerfield, IL
h Welch Foods, Inc., Westfield, NY
i The Coca-Cola Company, Atlanta, GA
69
The trained panelists received monetary and dietary rewards throughout their
participation in the study. Panelists received $25 for each of the 12 training sessions and
$25 for every two testing sessions during training and product evaluation.
Statistics
Data were analyzed using SAS (SAS version 9.4, SAS Institute Inc., Cary North
Carolina). Proc TTest was used to identify significant differences between sample
oxidation factors at 2-month time points versus baseline data (p < 0.05). Proc TTest also
was performed between repetitions for each sample tested, to check variability in
response by each panelist at each time point (p < 0.05). Proc ANOVA (p < 0.05) was also
run at the conclusion of the study to identify significant differences between samples at
rejection; Student-Newman-Kuels (SNK) was used for means separation when
appropriate. Proc Corr (p< 0.1) was used to find correlations between descriptive panel
parameters and instrumental textural assessments.
Consumer panel
All consumer sensory panelists provided informed consent (Appendix F). All
protocols followed were the same for the screening and confirmatory panels. Criteria for
inclusion as a sensory panelist were: at least 18 years old; absence of allergies to any tree
nut or peanuts; and consumes nuts or nut products at least once per month.
Consumer panelists evaluated no more than 3 samples per session. Each sample
consisted of three almonds presented to panelists seated in individual sensory booths
equipped with white lighting. Up to 3 samples were presented monadically in a single
session. Presentation order was randomized and samples were coded with 3-digit random
70
numbers. Palate cleansers provided were water and baby carrots and unsalted top saltine
crackers. Using a 9-point hedonic scale ranging from “Extremely Dislike” (1) to
“Extremely Like” (9) panelists rated each almond sample on 4 acceptability attributes-
odor, texture, flavor, and overall (Appendix G). Each panelist also indicated what he/she
liked or disliked (in words) about each sample (Rousset and Martin 2001). Lastly, the
panelist responded to “If you had purchased this product would you eat it?” (yes or no)
(Hough and others 2003). Post-sample evaluation, panelists completed a general
questionnaire (Appendix H) that allowed the panel as a whole, including their
consumption of nuts, to be profiled.
At 11 months of storage a “fresh” sample was evaluated (n=60) to counter any
expectation by panelists of decreased almond quality with the progression of the study
(ASTM 2011b). This “fresh” sample had been held since 0-months at 0C in a
polypropylene bag, which had been flushed with food grade nitrogen prior to sealing.
A screening consumer panel was triggered when the descriptive panel found the
sample differed significantly from this baseline assessment for one or more of the
oxidation factors—cardboardy, rancid, painty odor and flavor. This sensory panel
consists of 35 to 40 consumers. If 25% of the screening panelists answered “No” to the
rejection question (Appendix G) (Hough and others 2003), a larger confirmatory panel
(n=100-120) was then triggered. Testing ended when 25% of the panelists on the
confirmatory rejected the sample. At 16-months, all samples that had not been rejected
were evaluated by the descriptive, screening and confirmatory panels.
71
Statistics
Data were analyzed using SAS (SAS version 9.4, SAS Institute Inc., Cary, North
Carolina). Proc Means was run for every screening and confirmatory panel to gather
means and standard deviations. Proc ANOVA (SNK) (p < 0.05) was also run at the
conclusion of the study to identify significant differences versus baseline. Stepwise
multiple regression analyses were completed using Proc Stepwise to find the best-fit
variables (odor, texture and flavor acceptability) with the overall acceptability attribute (p
< 0.05). Demographic information was summarized with Proc Freq, and a panel profile
was generated.
Non-sensory tests
Water activity, moisture content, and instrumental assessment of textural hardness
and crunchiness were determined in conjunction with sensory testing. All non-sensory
tests were completed on the same day as sensory testing, beginning 2 hours after the
sample was removed from the storage chamber.
Texture analysis
Instrumental texture, specifically hardness and fracturability or crunchiness was
assessed using a TAXT.2 Plus Texture Analyzer (50 kg load cell) equipped with Texture
Exponent 32 software (Texture Technologies, Scarsdale, NY) by employing the
methodology outlined by Varela and others (2008). A 40-mm diameter cylinder probe
was used to compress a single almond at a test speed of 1 mm/s to a distance of 5 mm
from the baseplate; a trigger of 10 g was employed. The compression distance was the
maximum possible to fully fracture the sample but not to overload the instrument. Six
replications were performed on each sample at each time-point (36 almonds total).
72
Water activity and moisture determination
Samples were ground (10 seconds while shaking vigorously) in a mini-food
processor (Proctor Silex 1.5C Mini Food Chopper, Hamilton Beach Brand, Inc., Southern
Pines, NC) to final size of 2-mm or smaller for use in water activity and moisture
determination. An Aqualab Dew Point Water Activity Meter 4TE (Decagon Devices,
Inc., Pullman, WA) was used to determine water activity on 6 aliquots taken from the
composite ground sample. Temperature was 25.0±0.06.
The one-step protocol outlined in AACC Method 44-15A was followed to
determine moisture content in 6 aliquots taken from the composite ground almond
sample. Samples were weighed at 0 minutes and then again at 60 minutes. Preliminary
testing revealed a constant weight was reached by 60 minutes of drying under these
conditions. Weighed samples were dried at 135 °C in a Fisher Scientific Isotemp
Premium Lab forced-air convection oven (Thermo Fisher Scientific Inc., Waltham,
MA). Samples, held in a desiccator, were cooled completely before the final weight
was obtained.
Statistics
Data were analyzed using SAS (SAS version 9.3, SAS Institute Inc., Cary North
Carolina). Proc Means was run for every set of non-sensory data at each time point to
gather means and standard deviations. Proc ANOVA (p < 0.05) was used to determine
significant differences versus baseline, as well as other time points; SNK was used for
means separation when appropriate. Proc Corr was used to find correlations between
descriptive panel and instrumental textural assessments.
73
Chemical and instrumental tests performed by food science and technology partners
The analyses that triggered sensory testing were conducted following
standardized protocols in the Department of Food Science and Technology. These
chemical analyses and other instrumental tests included peroxide values, water activity,
and texture analysis for fracturability. Additional potential chemical measures related to
oxidation were also conducted to further characterize the changes that occurred during
storage. These assessments which were performed at month 0 and then at 2-month
intervals throughout 16-month duration of the study included: free-fatty acid values,
conjugated dienoic acid values, 2-Thiobarbituric acid values,
SPME values, water activity, moisture content, and texture analysis. Beginning at 8
months, samples were also evaluated for vitamin E. The methodology employed for these
analyses is found in Appendix I.
References:
AACC. 2000. Approved Methods for Moisture— Air-Oven Methods. 10th ed. St. Paul,
MN.: Method 44-15A.
ASTM Stock DS72. 2011a. Lexicon for Sensory Evaluation: Aroma, Flavor, Texture, and
Appearance. ASTM International. West Conshohocken, PA.
ASTM Standard E2454. 2011b. Standard Guide for Sensory Evaluation Methods to
Determine the Sensory Shelf Life of Consumer Products. ASTM International. West
Conshohocken, PA.
Civille GC, Lapsley K, Huang G, Yada S, Seltsam J. 2009. Development of an almond
lexicon to assess the sensory properties of almond varieties. J Sens Stud. 25:146-162.
Hough G, Langohr K, Gomez G, Curia A. 2003. Survival analysis applied to sensory
shelf life of foods. J Food Sci. 68(1):359-362.
74
Meilgaard M, Civille GV, Carr BT. 1991. Sensory Evaluation Techniques. 2nd ed.
Florida: CRC Press. 354 p.
Rousset S, Martin JF. 2001. An effective hedonic analysis tool: weak/strong points. J
Sens Stud. 16:643-661.
[USDA] United States Department of Agriculture. 2007. United States Standards for
Grades of Shelled Almonds. Washington, D.C.: U.S. Dept. of Agriculture. Available at:
http://www.almondboard.com/Handlers/Documents/USDA-Standards-Shelled-
Almonds.pdf Accessed July 28, 2014.
Varela P, Aguilera JM, Fiszman S. 2008. Quantification of fracture properties and
microstructural features of roasted Marcona almonds by image analysis. LWT - Food Sci
Technol. 41(1):10-17.
75
CHAPTER 4
POLYPROPYLENE BAG STORAGE RESULTS AND DISCUSSION
In this multi-point shelf-life study (ASTM 2011), seven almond samples (initial
O2 level <0.5%) were stored in sealed polypropylene (PP) bags at 15, 25, and 35 °C and a
relative humidity (RH) of 50 or 65% and at 4 °C without relative humidity (RH) control.
The chamber humidity in which the 4 °C was held was monitored throughout the study.
The bags were clear polypropylene (100µm, Uline S-17960, Waukegon, IL); the material
had a water vapor transmission rate (WVTR) of 8 cm3m
-2d
-1 and oxygen transmission
(OT) of 860 cm3m
-2d
-1.
Descriptive and consumer sensory assessments were conducted at baseline (0
months storage). Descriptive panel assessments were conducted bi-monthly beginning at
10 months of storage and consumer sensory panels assessed samples once triggered by
the descriptive panelists. Consumer panels continued bi-monthly until either the sample
was rejected or the study was concluded; a negative response by 25% of the consumer
sensory panelists (n=94-119) to “If you had purchased this product, would you eat it?”
signified end of shelf-life. The samples stored at 35 °C/65%RH, 35 °C/50%RH, 25
°C/65%RH were rejected by consumer panelists after 12, 14, and 16 months of storage
respectively. The study concluded after 16 months of storage. Changes during storage
also were monitored bimonthly with chemical and instrumental tests.
76
Non-sensory results
Non-sensory assessments as well as descriptive sensory evaluation of quality
attributes can document differences between samples and aid in determining if the change
impacts consumer acceptability (Giménez and others 2012). Moisture content, water
activity, force and the large number of fractures obtained when assessed instrumentally
(Table 4.1) suggest these almonds at baseline were hard and crunchy. Although the water
activity levels fall within the range where lipid oxidation is a concern (Almond Board of
California 2010), peroxide levels (<0.01 meq active O2/kg oil) suggest oxidized lipids
were not present in this sample at baseline, although conditions were present for the
development of rancidity with storage.
77
Table 4.1: Dry medium-roasted almonds in polypropylene bags: Sensory rejection and non-sensory tests
Storage
conditions n
%
panelists
rejectinga
Moisture
(%)b
Water
activityc
Peroxide
value
(meq. active
O2/kg oil)
Peaks
(number)d
Force (g)d
-----------------------------------------means±SDe---------------------------------------
Baseline 119 4 1.98±0.77d 0.20±0.02f < 0.01e 17.49±5.13a 42143±7181c
35°C /65%RH
12 mo 101 30 4.80±0.41a 0.50±0.01a 1.89±0.048d 5.62±2.63f 77616±9090a
35°C /50%RH
14 mo 94 25 3.72±0.52b 0.34±0.03d 3.22±0.53b 9.41±4.61e 45006±6817bc
25°C /65%RH
16 mo 102 35 3.34±0.23bc 0.41±0.00b 2.85±0.26b 11.87±4.19d 45925±6582bc
25°C /50%RH
16 mo 102 19 3.37±0.33bc 0.34±0.01d 3.67± 0.20a 13.66±4.02cd 44386±6982bc
15°C /65%RH
16 mo 102 21 3.29±0.51bc 0.36±0.05cd 2.42±0.14c 13.47±5.48cd 42008±7578c
15°C /50%RH
16 mo 102 10 3.25±0.38bc 0.38±0.01c 1.54±0.23d 15.05±3.93bc 43489±6293bc
4°C
16 mo 102 10 2.56±0.57c 0.31±0.01e 0.368±0.07e 16.18±4.81ab 47565±9619b a negative response to “If you had purchased this product would you eat it?” (yes or no)
(Hough and others 2003) b n=6 (AACC Method 44-15A 2000)
c n=6 (Aqualab Dew Point Water Activity Meter 4TE)
d n=36 (TAXT.2 Plus Texture Analyzer equipped with Texture Exponent 32 and a 50 kg
load cell as described by Varela and others 2008a) e means±SD, followed by different letters within a column differ significantly (p<0.05),
according to ANOVA and SNK means separation test
78
All rejected samples (Table 4.1) exhibited a significant increase in peroxide
values, water activity, moisture content, and a significant decrease in the number of
fractures when compared to the baseline sample (rejection % ≥ 25). Few differences in
force were noted except for the sample stored at 35 °C/65%RH, which required nearly
twice the force to compress as was found for all remaining samples. All peroxide values
were below the 5 meq. active O2/kg oil recommended as the cutoff by the Almond Board
of California. However, increases ranged from 189 to 322 times over the baseline values
at the rejection time point. The general trend shows that when the number of fractures
was at least 1/3 less than the number found at baseline, the sample was rejected. These
samples also exhibited an increase in water activity, with values above 0.4 found all
rejected samples except for 35 °C/50%RH. Previously, Vickers and others (2014)
reported that water activity values above 0.4 were associated with detrimental effects on
almond textural quality. The sample with the chemical and instrumental characteristics
most like baseline after 16 months of storage was stored at 4 °C without RH control.
Recorded humidity levels for this sample were 95±3%. Moisture content for this sample
differed significantly when compared to the sample at baseline. These results suggest a
protective effect of low temperature when humidity levels are high when roasted almonds
are stored in polypropylene bags.
Descriptive sensory results
Descriptive profiles for all of the samples where significant differences were
found are shown in Figure 4.1. The intensity of texture, flavor, and odor attributes
changed over the storage period. For all rejected samples as well as the sample stored at
25 °C/50%RH, descriptive panelists perceived an increase in the flavor note rancid. The
79
later suggests that descriptive panelists perceive an increase in rancidity before the note is
intense enough to result in rejection by the consumer panelists. A significant increase in
hardness, but no change in crunchiness, was found for all rejected samples with the
exception of 35 °C/50% RH, although p-values (0.14) suggest a trend in increased
hardness for this sample as well. These textural results differ from those found when
texture was assessed instrumentally (Table 4.1) and the lack of a significant correlation
between the descriptive sensory and instrumental assessments (P>0.1) suggest that these
two techniques are assessing different aspects of texture. The sample stored for 14
months at 35 °C/50% RH also developed a rancid odor note that was significantly more
intense than was found in the control. For the samples not rejected by the consumer
panel (Table 4.2), with the exception of the 25 °C/50%RH sample which was rejected by
a screening panel at 16 months (n=35; 28% rejection) but not the follow-up confirmatory
consumer panel (n=102; 19% rejection), the descriptive panel found no significant
difference between baseline and any sensory attribute.
80
Figure 4.1: Trained panel results for baseline (0 months) and samples with significant
differences at final testing point. a Rated on 15-point scale were 0 was “Not perceptible” and 15 “High intensity”
(Meilgaard and others 1991)
81
Consumer Sensory Results
Volunteers who served on the consumer sensory panel were recruited from
faculty, staff, students and visitors at the University of Georgia. Twenty-nine consumer
panels [screening, n=16 and confirmatory including the baseline panel which served as
the control, n=13) (ASTM 2011)] were run. Demographics of each panel differed
slightly, although trends were similar. These panelists were mostly female (76 to 87%)
(Appendix J) and approximately 80% were 18-27 years old. At least 85 percent of the
panelists consumed nuts (including peanuts) at least several times per month; all were
consumers of nuts.
In addition to responding to the intent to consume question, which focused on
consumer response to the product rather than the deterioration of product attributes
(Hough and others 2003), the consumer sensory panelists rated the appearance, flavor,
texture, and overall acceptability of the roasted almonds on a 9-point hedonic scale.
Panelists also indicated what they liked or disliked in particular about each sample
(Appendix K). These qualitative responses help to explain consumer acceptability of the
samples and aid in the identification of storage conditions that minimize detrimental
effects on almond quality, without asking the consumer panelists to quantify the
differences found. These panelists stated less specific reasons for liking than for disliking
particular samples. In general, when consumers respond to this query they tend to focus
on the most noticeable popular and unpopular attributes or traits of the product (Rousset
and Martin 2001).
82
Acceptability of the roasted almonds at baseline
Panelists rated acceptability of all sensory attributes of the roasted almonds at
baseline above 7 on the 9-point scale, where 9 is like extremely and 1 is dislike extremely
(Figure 4.2); approximately 4% of these consumer panelists rejected this sample.
Stepwise regression (Table 4.2) revealed that flavor and texture were significant
predictors of overall acceptability (R2 = 0.81), with percentage contribution to overall
acceptability equal to 70 and 11, respectively. Odor was not a significant predictor of
overall acceptability at 0 months storage. When asked to identify what they liked about
the samples, panelists’ responses related to texture in general and crunchiness and
fracturability, specifically, dominated (Appendix K). In regards to flavor, the generic
responses flavor or taste were the most frequent responses, with roasted, nutty, and sweet
the most specific responses. Interestingly, odor also was indicated as a reason for liking,
nearly equaling the total number of responses related to flavor. For those that chose to
reject the sample at baseline, texture (67%) and odor (29%) but not flavor were
significant predictors of overall acceptability (R2= 0.95). Few reasons for dislike were
given, however, dryness, toothpack and bland were most commonly cited (Appendix K).
83
Figure 4.2: Almond Acceptability: baseline sensory panel (n=119)
Series1, Odor, 7.546218487
Series1, Texture , 7.302521008
Series1, Flavor , 7.403361345
Series1, Overall acceptability, 7.571428571
Hed
on
ic s
cale
Attributes
Table 4.2: Consumer sensory resultsa for roasted almonds at baseline and after 16
months storage in polypropylene bagsb of each sample at 4 different temperatures:
rejection rates and contribution of each attribute to overall acceptability
n
% panelists
rejectingc R
2 Odor
d Texture
d Flavor
d
Baseline 119 4 0.81 X 0.1126 0.7011
35°C /65%RH
12 mo 106 30 0.87 0.0080 0.0733 0.7902
35°C /50%RH
14 mo 94 25 0.83 0.019 0.0431 0.7781
25°C /65%RH
16 mo 102 35 0.85 0.0103 0.0457 0.7979
25°C /50%RH
16 mo 102 19 0.89 0.0240 0.0183 0.8483
15°C /65%RH
16 mo 102 21 0.85 0.0141 0.0275 0.8095
15°C /50%RH
16 mo 102 10 0.90 0.0095 0.0869 0.8084
4°C
16 mo 102 10 0.86 X 0.0390 0.8223 a X in column indicates attribute was not a significant predictor, therefore it was
excluded from model b Uline, Waukegon, WI, U.S.A.
c negative response to “If you had purchased this product would you eat it?” (yes or no)
(Hough and others 2003) d determined with proc stepwise (p ≤ 0.05)
84
All samples stored at 65% RH, with the exception of the sample stored at 15 °C,
were rejected. Shelf-life was increased as storage temperature decreased, suggesting a
protective effect of temperature reduction when the roasted almonds are stored under
high humidity conditions as previously suggested by Garcia-Pascual and others (2003).
These high humidity conditions were associated with higher water activities, suggesting a
potential impact on both texture and rancidity, which indeed were reflected in the
increase in peroxide values and decrease in number of fractures (Table 4.1). It is
noteworthy that among the rejected samples, the sample (35 °C/65%RH) with the lowest
number of fractures was rejected (30%) at the lowest peroxide levels. All acceptability
values were at 6 or below for this sample and all made a contribution to overall
acceptability (Tables 4.2 and 4.3). The most cited reasons for dislike were related to
flavor with the generic taste/flavor accounting for approximately one-third of the
responses. However an equal number of responses were bland or stale (Appendix K).
These responses suggest that rancidity was not the major reason for the difference from
the control in flavor acceptability. In addition to the generic descriptor texture, the
specific texture-related responses soft and chewy dominated. These responses for strong
and weak points are supported by the non-sensory data (Table 4.1). Previously, Varela
and others (2008b) indicated that consumers expect roasted almonds to be crunchy rather
than soft, mealy, or chewy. According to Szczesniak and Kahn (1971) when products
are expected to be crunchy, consumers have limited tolerance for deviations from
expected texture.
85
Table 4.3: Consumer sensory panel scorecard responsesa for samples stored in
polypropylene bagsb
n
%
panelists
rejectingc Odor Texture Flavor
Overall
Acceptability
-----------------------------means±SDe-------------------------
Baseline 119 4 7.6±1.5a 7.3±1.6a 7.4±1.6a 7.6±1.4a
35 °C /65%RH
12 mo 101 30 5.9±1.9d 6.1±2.1b 5.5±2.1c 5.8±2.0d
35 °C /50%RH
14 mo 94 25 5.9±1.9d 6.9±1.8a 5.9±2.0b 6.2±1.8bc
25 °C /65%RH
16 mo 102 35 6.1±1.7d 6.7±1.8a 5.3±2.0c 5.8±1.9cd
25 °C /50%RH
16 mo 102 19 6.0±1.6d 6.7±1.7a 6.1±1.8b 6.3±1.6bc
15 °C /65%RH
16 mo 102 21 6.4±1.6cd 6.8±1.6a 6.2±1.7b 6.5±1.5b
15 °C /50%RH
16 mo 102 10 7.0±1.6b 7.3±1.6a 6.9±1.7a 7.1±1.6a
4 °C
16 mo 102 10 6.7±1.7bc 7.1±1.5a 6.9±1.8a 7.1±1.5a a hedonic scale where 1 is “extremely dislike” and 9 is “extremely like”
b Uline, Waukegon, WI, U.S.A.
c negative response to “If you had purchased this product would you eat it?” (yes or no)
(Hough and others 2003) d means±SD, followed by different letters within a column differ significantly (p<0.05),
according to ANOVA and SNK means separation tests.
86
When stored at the highest temperature, 35 °C, reducing the humidity level was
somewhat protective. When relative humidity level was reduced from 65 to 50%, these
almonds were not rejected until tested at 14 as opposed to 12 months of storage.
Although water activity was significantly increased relative to the baseline sample, it is
within the water activity range where texture of roasted almonds has been found to be
acceptable (Vickers and others 2014). The consumer panelists did not find the
acceptability of the texture to be significantly less than was found for the control (Table
4.3). Peroxide values however were increased and are reflected in the acceptability
assessment, with significant decreases found in odor, flavor, and overall acceptability.
When compared to the 35 °C/65% RH sample, fewer consumers indicated textural
reasons for dislike, although when listed, chewy and no crunch dominated (Appendix K).
The most common flavor-related reasons for disliking this sample included stale, old, and
rancid in addition to the less specific terms taste and flavor. Further, unlike the sample
stored at 35 °C/65% RH, odor was listed as a reason for dislike. Descriptive panelists
detected an increase in the rancid odor note in the sample stored at 35 °C/50%RH but not
35 °C, 65% RH (Figure 4.1).
When the samples stored at 25 °C were compared, the rejection rate at study
conclusion (16 months) was 35 and 19% for the samples stored at 65 and 50% RH
respectively. Similar but delayed trends as those observed for the samples stored at 35
°C and 65 and 50% RH were observed for water activity, number of fractures, and
peroxide values.
87
Consumer panelists rated all samples at the time of rejection or after 16 months of
storage if not rejected earlier, above midpoint on the acceptability scale for all attributes.
Despite these acceptability ratings, storage regardless of conditions, produced significant
decreases in odor, flavor, and overall acceptability ratings; in addition, all samples stored
at 65%RH also differed significantly in texture when compared to the control. All also
exhibited significant increases in water activity. Even though the samples stored at 25
°C/50% RH, and 15 °C/65%RH were significantly less acceptable than the control in
overall, as well as flavor and odor acceptability (Table 4.3), these samples were not
rejected by 25% or more of the consumer panelists. Overall these samples were more
likely to be described as bland rather than rancid, oxidized, or cardboardy (Appendix K).
Previously, Garcia-Pascual and others (2003) reported that a reduction in storage
temperature was protective against development of rancidity during storage. However,
when any acceptability attribute was below 6 on the hedonic scale, the sample was
rejected (Table 4.3). With storage, stepwise regressions revealed that a greater
percentage of the variability in overall acceptability was explained when compared to the
control with flavor explaining an increased percentage of the variability in overall
acceptability (Table 4.2).
Conclusion
Out of the 7 samples stored in polypropylene bags, 3 failed over the 16-month
study (35 °C/65%RH, 35 °C/50%RH, and 25 °C/65%RH). Lower temperatures,
especially when employed in combination with lower humidity levels resulted in
increased acceptability of the dry medium-roasted almonds over the 16-month storage
period. In the rejected samples, the descriptive panelists found increases in rancidity and
88
that were also detected in non-sensory assessments of the rejected samples. It is
important to note that texture-related comments of “soft, chewy, and/or no crunch”
appeared to have a negative effect on acceptability and were associated with the rejection
of the almond samples. These consumer comments support the contention that when
foods that are expected to be crunchy are not, consumer tolerance for this deviation from
the expectation is low (Szczesniak and Kahn 1971). Flavor was very important in all
samples tested whether or not the sample was rejected. In all samples, flavor explained
more than 70% of the variability in overall acceptability. In all rejected samples,
consumer panelists noted deleterious effects on flavor during the storage period.
Rejection by consumers appears to be more complex than a single chemical indicator or
sensory attribute and is associated with a broader set of parameters. When stored in PP
bags, reduction of temperature and/or humidity increases shelf-life. Samples stored at 25
°C /50%RH, 15 °C /65%RH, 15 °C /50%RH, and 4 °C/no RH control remained
acceptable after 16 months of storage. Indicators of rancidity or textural deterioration
were not present in the samples that were not rejected.
References:
AACC. 2000. Approved Methods for Moisture— Air-Oven Methods. 10th ed. St. Paul,
MN.: Method 44-15A.
Almond Board of California. 2010. Background information on almond shelf life
research. Modesto, CA.
ASTM Standard E2454-05. 2011. Standard evaluations methods to determine the sensory
shelf life of consumer products. West Conshohocken, PA.
Garcıa-Pascual P, Mateos M, Carbonell V, Salazar DM. 2003. Influence of storage
conditions on the quality of shelled and roasted almonds. Biosyst Eng. 84(2):201–209.
89
Giménez A, Ares F, Ares G. 2012. Sensory shelf-life estimation: a review of current
methodological approaches. Food Res Int. 49:311-325.
Hough G, Langohr K, Gomez G, Curia A. 2003. Survival analysis applied to sensory
shelf life of foods. J Food Sci. 68(1):359-362.
Meilgaard M, Civille GV, Carr BT. 1991. Sensory Evaluation Techniques. 2nd ed.
Florida: CRC Press. 354 p.
Rousset S, Martin JF. 2001. An effective hedonic analysis tool: weak/strong points. J Sen
Stud. 16:643-661.
Szczesniak AS. 2002. Texture is a sensory property. Food Qual Prefer. 13:215-225.
Varela P, Aguilera JM, Fiszman S. 2008a. Quantification of fracture properties and
microstructural features of roasted Marcona almonds by image analysis. LWT - Food Sci
Technol. 41(1):10-17.
Varela P, Salvador A, Fiszman S. 2008b. On assessment of fracture in brittle foods.
Biting or chewing? Food Research International 41:544-551.
Vickers Z, Peck A, Labuza T, Huang G. 2014. Impact of almond form and moisture
content on texture attributes and acceptability. J Food Sci. 79(7):S1399-S1406.
90
CHAPTER 5
HIGH BARRIER BAG STORAGE RESULTS AND DISCUSSION
In this multi-point shelf-life study (ASTM 2011), four almond samples (initial O2
level <0.5%) were stored in heat-sealed high barrier bags at 4, 15, 25, and 35 °C without
relative humidity (RH) control. RH in each storage chamber which was monitored
throughout the study differed. When stored at 4 °C, RH was 95±3%, at 15 °C, RH was
15±1%, at 25 °C, RH was 53±1% and samples stored at 35 °C were held at 30±1% RH.
The bags (ABC, Avon, OH) were a metallized film laminate (100 µm PET, 100 µm Al,
75µm PE). The laminate material affords chemical protection that minimizes
compositional changes triggered by environmental exposure to: gases, including oxygen
(OT < 1 cm3
m-2
d-1
); moisture, both loss and gain (WVTR <0.5 g m-2
d-1
); and/or to
visible, infrared or ultraviolet light (Marsh and Bugusu 2007). Minimization of these
compositional changes is protective against rancidity and the textural changes associated
with deterioration of almond quality during storage (Garcıa-Pascual and others 2003;
Shadidi and John, 2010; Varela and others 2008a; Velasco and others 2010).
Descriptive and consumer sensory assessments were conducted at baseline (0
month storage). Descriptive panel assessments were conducted bi-monthly beginning at
10 months of storage. Both descriptive and consumer panels were conducted at study
conclusion. A negative response by 25% of the consumer sensory panelists (n=102-119)
to “If you had purchased this product, would you eat it?” signified rejection or end of
91
shelf-life. Only the sample stored at 35 °C was rejected by consumer panelists after 16
months of storage. Changes during the 16-month storage period were monitored
bimonthly with chemical and instrumental tests.
Non-sensory results
Non-sensory assessments as well as descriptive sensory evaluation of quality
attributes can document differences between samples and aid in determining if the change
impacts consumer acceptability (Giménez and others 2012) . Moisture content, water
activity, force and the large number of fractures obtained when assessed instrumentally
(Table 5.1) suggest these almonds at baseline were hard and crunchy. Although the water
activity levels are within the range where lipid oxidation is a concern (Almond Board of
California 2010), peroxide levels (<0.01 meq active O2/kg oil) suggest oxidized lipids
were not present in this sample at baseline. These water activity levels, however, are
conducive for the development of rancidity with storage.
92
Table 5.1: Dry medium-roasted almonds stored in high barrier bagsa after 16 months storage: Sensory
rejection and non-sensory tests
Storage
conditions n
%
panelists
rejectingb
Moisture
(%)c
Water
activityd
Peroxide
value
(meq. active
O2/kg oil)
Peaks
(number)e
Force (g)f
-------------------------------------means±SDe------------------------------------
Baseline 119 4 1.98±0.77 0.20±0.02a <0.01a 17.49±5.13 42143±7181b
35 °C 102 26 2.23±0.27 0.31±0.02b 1.25±0.29b 17.13±5.05 46600±7068a
25 °C 102 3 2.31±0.42 0.25±0.02c 1.41±0.14b 16.68±5.35 38155±5823c
15 °C 102 8 2.20±0.41 0.33±0.05b 0.93±0.016b 16.82±5.10 42520±6215b
4 °C 102 7 2.15±0.58 0.30±0.01b 1.00±0.83b 16.39±4.24 46695±8242a a ABC, Avon, OH
b Negative response to “If you had purchased this product would you eat it?” (yes or no) (Hough and others
2003) c n=6 (AACC Method 44-15A 2000)
d n=6 (Aqualab Dew Point Water Activity Meter 4TE)
e n=36 (TAXT.2 Plus Texture Analyzer equipped with Texture Exponent 32 and a 50 kg load cell as described
by Varela and others 2008b) f means±SD, followed by different letters within a column differ significantly (p<0.05), according to ANOVA
and SNK means separation test.
93
All samples (Table 5.1) exhibited significant increases in peroxide values and
water activity over baseline after 16 months of storage. Although there was no
significant difference in moisture level for samples stored at any temperature when
compared to the baseline sample, the change in water activity suggests the migration of
water within the sample. All peroxide values were below the 5 meq. active O2/kg oil
recommended as the cutoff by the Almond Board of California (2010). Moisture content
also remained below the 3% level recommended by the industry (Almond Board of
California 2014) throughout the storage period. Although these samples exhibited an
increase in water activity, levels remained below 0.35. Previously Vickers and others
(2014) reported that water activity values in the 0.3-0.4 range were associated with
desirable textural attributes in roasted almonds. No significant difference in number of
fractures occurred over the storage period. In 3 of the 4 samples, a significant difference
in force versus baseline was present, although there is no consistent trend and standard
deviations within each storage condition are relatively large.
Descriptive sensory results
Descriptive sensory results for the almonds evaluated at baseline are found in
Figure 5.1. Descriptive sensory panelists found no significant differences in any texture,
flavor, or odor attribute evaluated over the storage period regardless of temperature
(Table 5.2); data were obtained at 10, 12, 14 and 16 months of storage. Panelists
employed a Spectrum®-like Short-Version for Shelf-life Studies standardized protocol,
which targets attributes known to be of concern in the shelf-life of a given product, in
this case nuts (Meilgaard and others 1991). For this product, the focus was on attributes
94
associated with rancidity (cardboardy, rancid, painty) and texture (hardness and
crunchiness), therefore a full product descriptive profile was not obtained and any
additional changes were not captured.
95
Table 5.2: Descriptive sensory panel results (means±SD)a of dry medium-roasted almonds stored in high barrier bags
b
Texture Basic taste Oxidation odor Oxidation flavor
°C Month Hardness Crunchiness Sweet Cardboardy Rancid Painty Cardboardy Rancid Painty
0 9.33±1.48 6.98±2.58 1.67±1.06 1.68±2.29 2.25±1.03 0.63±1.17 2.35±2.39 1.85±1.01 1.07±1.95
35 10 10.79±0.67 6.65±1.01 0.49±0.30 1.25±1.92 2.15±1.98 0.85±0.94 1.87±1.35 2.47±1.50 1.01±1.30
12 9.68±1.04 6.53±0.62 1.50±1.17 0.84±0.56 1.36±1.03 0.2±0.16 1.15±0.79 1.82±1.56 0.21±0.19
14 10.47±0.71 6.43±1.52 1.60±1.77 0.89±1.31 1.20±0.90 0.19±0.24 1.39±1.55 1.99±1.88 0.14±0.13
16 10.74±0.56 6.27±0.63 1.33±1.77 1.02±1.26 1.91±1.64 0.30±0.23 1.82±1.79 2.20±1.82 0.26±0.28
25 10 10.42±1.02 7.52±1.43 1.03±1.10 0.97±0.69 1.90±1.45 0.58±0.94 1.57±1.98 2.58±1.56 0.95±2.02
12 10.25±0.84 5.80±0.83 0.84±1.14 0.71±0.54 2.38±1.08 0.2±0.17 1.07±1.03 1.89±1.43 0.35±0.52
14 10.84±0.89 5.97±1.19 1.80±1.54 1.28±1.39 1.49±1.43 0.44±0.35 1.13±0.83 2.12±1.86 0.26±0.37
16 10.71±1.03 6.09±0.79 1.43±1.34 1.62±1.79 0.51±0.70 1.78±1.69 2.02±1.19 2.02±1.19 0.15±0.18
15 10 10.30±0.75 6.48±0.71 1.02±0.61 1.34±1.51 1.15±0.87 0.73±1.29 1.66±1.41 1.57±1.31 1.24±2.42
12 10.70±1.06 6.17±.86 1.45±1.74 0.68±0.48 1.82±0.87 0.21±0.26 0.85±0.54 2.13±1.31 0.21±0.14
14 10.43±0.61 6.18±0.85 2.43±1.77 0.49±0.28 0.84±1.00 0.3±0.32 0.48±0.38 1.56±1.65 0.20±0.30
16 9.89±1.22 5.99±0.96 1.78±1.52 1.16±1.57 2.34±1.97 0.32±0.27 1.06±1.46 2.44±2.02 0.35±0.79
4 10 10.33±0.69 6.65±1.07 1.53±1.55 0.82±0.58 1.67±1.37 0.3±0.27 1.41±1.31 2.47±1.78 0.33±0.46
12 10.41±0.68 6.25±0.86 1.34±0.95 0.54±0.38 2.19±1.98 0.17±0.13 1.31±1.21 2.03±1.54 0.18±0.18
14 10.5±0.87 6.36±.075 1.09±0.96 0.71±0.93 1.68±1.86 0.18±0.22 1.29±1.73 1.00±1.11 0.11±0.15
16 10.55±0.77 6.12±0.53 1.23±1.12 0.92±0.97 2.06±1.78 0.33±0.60 1.33±1.47 2.25±1.74 0.55±1.15 a means±SD, p ≥ 0.05 according to ANOVA
b ABC, Avon, OH
96
Figure 5.1: Descriptive sensory results at baseline (n=6) on a 15-point intensity scale
where 0=“not perceptible” and 15=“high intensity”
Consumer Sensory Results
Volunteers who served on the consumer sensory panel were recruited from faculty,
staff, students and visitors at the University of Georgia. Demographics of each panel
differed slightly, although trends were similar. These panelists were mostly were female
(74 to 91%) (Appendix L) and approximately 80% were 18-27 years old. At least 89
percent of the panelists consumed nuts (including peanuts) at least several times per
month. All were nut consumers.
In addition to responding to the intent to consume question, which focused on
consumer response to the product rather than the deterioration of product attributes
(Hough and others 2003), the consumer sensory panelists rated the appearance, flavor,
texture, and overall acceptability of the roasted almonds on a 9-point hedonic scale.
Panelists also indicated what they liked or disliked in particular about each sample
(Appendix M). These qualitative responses help to explain consumer acceptability of the
Series1, Hardness,
9.933333333
Series1, Sweetness,
1.666666667
Series1, Crunchiness, 6.983333333
Series1, Cardboard
odor, 1.683333333
Series1, Rancid odor, 2.25 Series1, Painty
Odor, 0.633333333
Series1, Cardboard flavor, 2.35 Series1, Rancid
flavor, 1.85 Series1, Painty
flavor, 1.066666667
Inte
nsi
tie
s
Attibutes
97
samples and aid in the identification of storage conditions that minimize detrimental
effects on almond quality, without asking the consumer panelists to quantify the
differences found. In general, when consumers respond to this query they tend to focus
on the most noticeable popular and unpopular attributes or traits of the product (Rousset
and Martin 2001).
Acceptability of the roasted almonds at baseline
Panelists rated acceptability of all sensory attributes of the roasted almonds at
baseline above 7 on the 9-point scale, where 9 is like extremely and 1 is dislike extremely
(Figure 5.2); approximately 4% of these consumer panelists rejected this sample.
Stepwise regression (Table 5.3) revealed that flavor and texture were significant
predictors of overall acceptability (R2 = 0.81), with percentage contribution to overall
acceptability equal to 70 and 11, respectively. Odor was not a significant predictor of
overall acceptability at 0 months storage. When asked to identify what they liked about
the samples, panelists’ responses related to texture in general and crunchiness and
fracturability, specifically, dominated (Appendix K). In regards to flavor, the generic
responses flavor or taste were the most frequent responses, with roasted, nutty, and sweet
the most specific responses. Interestingly, odor also was indicated as a reason for liking,
nearly equaling the total number of responses related to flavor. Few reasons for dislike
were given, however, dryness, toothpack and bland were most commonly cited. For
those that chose to reject the sample at baseline, texture (67%), and odor (29%) but not
flavor were significant predictors of overall acceptability (R2= 0.95). Few reasons for
dislike were given, however, dryness, toothpack and bland were most commonly
cited (Appendix K)
98
Figure 5.2: Almond acceptability: baseline sensory panel (n=119)
Series1, Odor, 7.546218487
Series1, Texture , 7.302521008
Series1, Flavor , 7.403361345
Series1, Overall acceptability, 7.571428571
Hed
on
ic s
cale
Attributes
Table 5.3: Consumer sensory resultsa for roasted almonds at baseline and after 16 months
storage in high barrier bagsb at 4 different temperatures: reflection rates and contribution of
each attribute to overall acceptabilityc of each sample
Storage
conditions n
% panelists
rejectingc R
2 Odor
d Texture
d Flavor
d
Baseline 119 4 0.814 X 0.1126 0.7011
35 °C 102 26 0.870 0.0077 0.0272 0.8354
25 °C 102 3 0.894 0.0171 0.0914 0.7853
15 °C 102 8 0.920 0.0102 0.0793 0.8301
4 °C 102 7 0.853 0.0229 0.0636 0.7662 a X in column indicates attribute was not a significant predictor, therefore it was excluded from
model b ABC, Avon, OH
c negative response to “If you had purchased this product would you eat it?” (yes or no)
(Hough and others 2003) d determined with Proc Stepwise (p ≤ 0.05)
99
After 16 months of storage, only the sample stored at the highest temperature,
35 °C, had been rejected. Higher storage temperatures have been associated with
development of increased rancidity levels during almond storage (Garcia-Pascual and
others 2003). Acceptability values for this sample ranged from 5.9 to 6.8 with odor,
flavor, and texture making a significant contribution to overall acceptability (R2=0.87)
(Tables 5.3 and 5.4). Overall acceptability as well as the acceptability ratings for odor
and flavor were significantly lower for the sample stored at 35 °C than was found at
baseline and for all samples stored at lower temperatures (Table 5.4). Conversely, the
descriptive panelists found no significant differences between this sample and the
remaining samples evaluated for any of the shelf-life related attributes assessed (Table
5.2).
Examination of the strong and weak points provided by the consumer panelists,
suggest that flavor of this sample was an issue (Appendix M). For this sample, the
number of like responses related to generic descriptor flavor/taste was approximately half
the number reported for all other samples. Rousset and Martin (2001) have linked the
number of “like” responses to overall acceptability ratings. The number of more specific
responses related to taste/flavor, which were less numerous than found for all other
samples, did not compensate for the reduced number of generic taste and flavor
responses. Similar patterns were found for odor. When queried regarding reasons for
dislike, the most common responses were flavor, taste and odor, with the most prevalent
specific responses being bitter and woody. In addition the aftertaste was regarded as a
negative. These specific attributes were not evaluated by the descriptive panel (Table
5.2; Figure 5.1), nor were they reflected in the non-sensory assessments reported here
100
(Table 5.1). These results suggest a protective effect of temperature reduction even when
roasted almonds are stored in high barrier bags. Permeability rates for high barrier films
increase with temperature and follow the Arrhenius equation (Butler and Morris 2010).
Conclusion
Out of the 4 samples stored in HHB, one, stored at 35 °C, failed over the 16-
month study. Based on descriptive sensory evaluation, the rejection of this sample cannot
be attributed to the development of rancidity or changes in texture. Similarly, these
consumer sensory results cannot be explained by the chemical/instrumental results
obtained. These results suggest the importance of the consumer evaluation when
determining acceptability and rejection rather than relying on significant differences in
Table 5.4: Consumer sensory panel scorecard responsesa after 16 months storage for samples stored at 4 temperatures in high barrier bagsb
Storage conditions n
%
panelists
rejectingc Odor Texture Flavor Overall
Acceptability -----------------------------means±SD
d-------------------------
Baseline 119 4 7.6±1.5a 7.3±1.6ab 7.4±1.6a 7.6±1.4a 35 °C/ 30%RH 102 26 6.2±1.9c 6.8±1.9a 5.9±2.1b 6.3±1.9b 25 °C/ 53%RH 102 3 7.4±1.5ab 7.3±1.6ab 7.2±1.7a 7.4±1.4a 15 °C/ 15% RH 102 8 7.5±1.3a 7.6±1.5a 7.3±1.7a 7.4±1.5a 4 °C/ 95%RH 102 7 7.0±1.5b 7.3±1.4ab 7.2±1.5a 7.3±1.3a a hedonic scale where 1 is “extremely dislike” and 9 is “extremely like”
b ABC, Avon, OH
c negative response to “If you had purchased this product would you eat it?” (yes or no)
(Hough and others 2003)d means±SD, followed by different letters within a column differ significantly (p<0.05),
according to ANOVA and SNK means separation tests.
101
attribute intensity or a chemical/instrumental test alone. Although it is more typical that
descriptive panels will detect differences before they actually impact consumer
acceptability, in this case, only a limited number of attributes were evaluated. Overall,
rejection by consumers appears to be more complex than a single chemical indicator or
textural parameter and is associated with a significant decrease in all acceptability
attributes. In addition to the acceptability and rejection tests, consumer provided strong
and weak points for each sample were helpful in identifying the degradation of the
characteristic flavor as a major factor influencing rejection.
Little evidence of degradation was found with storage in high barrier bags,
suggesting these bags are protective against light, moisture, humidity, and oxygen.
However when stored at high temperatures, the protective effects afforded by these bags
was reduced and the associated deleterious effects on the sample resulted in sample
rejection by consumers, even in the absence of rancid-flavor notes.
References:
AACC. 2000. Approved Methods for Moisture— Air-Oven Methods. 10th ed. St. Paul,
MN.: Method 44-15A.
Almond Board of California. 2010. Background information on almond shelf life
research. Modesto, CA.
Almond Board of California. 2014. Almond Shelf Life Factors. Modesto, CA.: Almond
Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/2014aq0007_shelf_life_f
actors.pdf. Accessed September 21, 2014.
Butler TI, Morris BA. 2010. PE based multilayer film structures. In: Wagner JR, editor.
Multilayer Flexible Packaging: Technology and Application for the Food, Personal Care,
and Over-The-Counter Pharmaceutical Industries. Burlington, MA.: Elsevier. p 205-230.
102
Garcıa-Pascual P, Mateos M, Carbonell V, Salazar DM. 2003. Influence of storage
conditions on the quality of shelled and roasted almonds. Biosyst Eng. 84(2):201–209.
Giménez A, Ares F, Ares G. 2012. Sensory shelf-life estimation: a review of current
methodological approaches. Food Res Int. 49:311-325.
Griffiths N. 1985. Sensory analysis in measuring shelf-life. Food, Flavours, Ingredients,
Packaging and Processing. 7(9):47-48.
Hough G, Langohr K, Gomez G, Curia A. 2003. Survival analysis applied to sensory
shelf life of foods. J Food Sci. 68(1):359-362.
Marsh K, Bugusu B. 2007. Food packaging—roles, materials, and environmental issues.
J Food Sci. 72(3):R39-R55.
Meilgaard M, Civille GV, Carr BT. 1991. Sensory Evaluation Techniques. 2nd ed.
Florida: CRC Press. 354 p.
Rousset S, Martin JF. 2001. An effective hedonic analysis tool: weak/strong points. J Sen
Stud. 16:643-661.
Shahidi F, John JA. 2010. Oxidation and protection of nuts and nut oils. 2nd. vol. In:
Decker EA, Elias RJ, McClements DJ, editors. Oxidation in Foods and Beverages and
Antioxidant Applications. Cambridge, UK.: Woodhead Publishing Ltd. p 274-305.
Varela P, Salvador A, Fiszman S. 2008a. On assessment of fracture in brittle foods.
Biting or chewing? Food Research International 41:544-551.
Varela P, Aguilera JM, Fiszman S. 2008b. Quantification of fracture properties and
microstructural features of roasted Marcona almonds by image analysis. LWT - Food Sci
Technol. 41(1):10-17.
Velasco J, Dobarganes C, Màrquez-Ruiz G. 2010. Oxidative rancidity in foods and food
quality. In: Skibsted LH, Risbo J, Andersen ML, editors. Chemical Deterioration and
Physical Instability of Food and Beverages. Cambridge, UK.: Woodhead Publishing Ltd.
p 3-32.
Vickers Z, Peck A, Labuza T, Huang G. 2014. Impact of almond form and moisture
content on texture attributes and acceptability. J Food Sci. 79(7):S1399-S1406.
103
CHAPTER 5
CONCLUSION
Almonds are the largest US specialty crop export. California produced over 2.02
billion pounds of almonds in the 2011/12 crop year, representing over 80% of the global
almond production and virtually 100% of the domestic supply (Almond Board of
California 2012). They are available in many different forms (raw, roasted, blanched,
sliced, slivered) (Almond Board of California 2013). Because almonds are a low-
moisture food with high levels of antioxidants (Almond Board of California 2010), they
have a relatively long shelf-life. Of the California almond production consumed by
Americans, 60-70% is consumed roasted (Huang 2014). Health benefits of almond
consumption have been attributed to their nutrient profile, specifically their high content
of monounsaturated fats (MUFA) and bioactive compounds (Chen and others
2006). However, because of their unsaturated fat content, almonds are prone to oxidation
and deterioration during storage. Rancidity is the limiting factor consumer acceptability,
regardless of product form (Garcia-Pascual and others 2003).
Maintenance of quality of stored almonds is very important because they are only
harvested once per year (Almond Board of California 2013). There is currently a lack of
detailed information on factors that affect the shelf-life of almonds in general and roasted
almonds specifically (Almond Board of California 2010; Garcia-Pascual and others
2003). More specific guidelines are needed to assure a consistent quality product
throughout the storage period. Recommended storage conditions that currently exist for
104
roasted almonds include: cool and dry conditions in vacuum-packed foil bags at < 10 °C
and < 65% relative humidity (Almond Board of California 2014). Improved and
consistent quality will increase consumer acceptability, and therefore, increase the
likelihood that consumers will realize the health benefits associated with almond
consumption. The purpose of this study was to determine the acceptability of dry
medium-roasted Nonpareil almonds stored in 2 types of packaging at different
temperature and humidity levels over a 16 month period. Almonds that were received had
been packaged in bulk in high barrier bags (ABC Packaging, Cleveland, Ohio, U.S.A.)
and flushed with nitrogen prior to being sealed. The almonds were evaluated upon receipt
with chemical and instrumental tests, descriptive sensory, and consumer sensory
assessments. These data collected at baseline served as the control.
Eleven almond samples were packaged in polypropylene (PP) and high barrier
bags (HBB). Four samples were packaged in high barrier bags (Stand Up Pouches, Avon,
OH) (initial O2 level <0.5%) without relative humidity (RH) control at 4, 15, 25, and 35
°C, and 7 samples were stored in clear polypropylene bags (Uline, Waukegon, IL) (initial
O2 level <0.5%) at 15, 25, and 35°C with a relative humidity (RH) of 50 or 65% and at 4
°C without RH control. A 6-member descriptive panel, using a Spectrum®-like protocol
for shelf-life studies, assessed intensity of odor (cardboardy, rancid, painty), flavor
(sweet, cardboardy, rancid, painty), and texture (hard and crunchy) attributes, in duplicate
on 15-point scales at baseline and at 2-mo intervals, beginning with the tenth month of
storage. Peroxide values, moisture content, water activity, and instrumental textural
assessments were conducted. Consumer assessment of acceptability was triggered when
the descriptive panel found significant differences in oxidation-related attributes versus
105
the control sample. Consumer panelists assessed odor, flavor, texture, and overall
acceptability on 9-point hedonic scales. Rejection by 25% of the members of a consumer
screening panel (n=33-39) triggered a larger consumer sensory panel (n=94-119) for
confirmation. Baseline (0-mo storage) acceptability assessments (n=119; means±SD)
were: odor=7.6±1.45, texture=7.3±1.59, flavor=7.4±1.64, overall=7.6±1.36; “will not
consume”=4.0%.
Sample degradation that leads to consumer rejection is associated with storage.
Four of eleven samples tested were rejected over the 16-month study (35 °C/65%RH, 35
°C/50% RH and 25 °C/65%RH in PP bags and 35 °C in HBB). When stored in
polypropylene bags, rancidity and hardness increased as shown by descriptive sensory
results. Non-sensory results generally supported the results found by the descriptive
panel, although instrumental and descriptive assessments of texture appear to be
assessing different aspects of texture. In rejected samples, consumer panelists
commented the texture was “soft, chewy and or had no crunch.” A negative effect on
flavor was also noted by consumers in rejected samples. Flavor was very important in all
samples tested, explaining more than 70% of the variability in overall acceptability. For
those samples stored in polypropylene bags, lower temperatures especially when
combined with lower humidity levels resulted in increased shelf-life of the almonds and
the maintenance of their acceptability by consumers. Controlled storage conditions are
important to quality retention when polypropylene bags are the packaging choice.
Of the 4 samples rejected by consumers, only one was packaged in the high
barrier bags, suggesting the use of these bags adds an additional level of quality
protection not offered by the PP bags over the 16-month storage period. When stored in
106
high barrier bags, sample rejection was not due to rancidity or changes in texture. This
surprising result suggest the importance of consumer evaluation of acceptability and
determination of sample rejection rather than relying exclusively on trained descriptive
panelists who measure changes in attribute intensity or chemical/instrumental tests
(Griffiths 1985). Consumer provided strong/weak points for each sample were helpful in
identifying degradation of the characteristic flavor as a major factor that influenced
rejection of the high barrier bag sample.
In conclusion, dry medium- roasted Nonpareil almonds can be stored for up to 16
months in clear polypropylene bags if the temperature is below 25 °C and RH is 50% or
below. When RH cannot be controlled, storage at low temperatures (4 °C) or in high
barrier bags at temperatures below 35 °C is recommended. Regardless of bag type,
storage at 35 °C is not recommended. Although high barrier bags are a better packaging
material when only quality retention is considered, there are other factors that must be
taken into consideration when choosing both storage conditions and packaging materials.
These factors include cost as well as availability and maintenance of warehouse space
and storage chambers, and cost of electricity as well as packaging. It also is important to
consider that according to online sources high barrier bags (0.28) (StockBag Depot 2014)
cost significantly more than the clear polypropylene bags (0.087) (Uline 2014) per piece.
References:
Almond Board of California. 2012. Request for proposals: Shelflife of whole almonds in
retail and bulk packages. Modesto, CA.
Almond Board of California. 2013. Almond Almanac. Modesto, CA.: Almond Board of
California. Available from:
107
http://www.almondboard.com/AboutTheAlmondBoard/Documents/2012%20Almond%2
0Almanac_FINAL.pdf. Accessed October 28, 2014.
Almond Board of California. 2010. Background information on almond shelf life
research. Modesto, CA.
Almond Board of California. 2014. Long-Term Storage Study of Raw and Blanched
Almonds. Modesto, CA.: Almond Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/aq0105_lin_summary_re
port_july_2014_final.pdf. Accessed November 2, 2014.
Chen CY, Lapsley K, Blumberg J. 2006. A nutrition and health perspective on
almonds. J Sci Food Agric. 86:2245-2250.
Garcıa-Pascual P, Mateos M, Carbonell V, Salazar DM. 2003. Influence of storage
conditions on the quality of shelled and roasted almonds. Biosyst Eng. 84(2):201–209.
Griffiths N. 1985. Sensory analysis in measuring shelf-life. Food, Flavours, Ingredients,
Packaging and Processing. 7(9):47-48.
Huang G. October 8, 2014. Personal communication (email). Almond Board of
California, Modesto, CA.
StockBag Depot. 2014. 12 oz. Foil Stand Up Zip Pouch. City of Industry, CA.: StockBag
Depot.
Available from: http://www.stockbagdepot.com/stand-up-pouches/plain-foil/12-oz-
gold.html. Accessed on November 9, 2014.
Uline. 2014. Uline.com Reclosable Polypropylene Bags. Waukegon, IL.: Uline.
Available from: http://www.uline.com/BL_5562/Reclosable-Polypropylene-Bags.
Accessed on November 9, 2014.
108
REFERENCES
AACC. 2000. Approved Methods for Moisture— Air-Oven Methods. 10th ed. St. Paul,
MN.: Method 44-15A.
[AICR] American Institute for Cancer Research. 2012. AICR’s Foods that Fight Cancer.
Washington, DC.: American Institute for Cancer Research. Available at:
www.aicr.org/foods-that-fight-cancer/. Accessed September 15, 2014.
Albert CM, Gaziano JM, Willett WC, Manson JE. 2002. Nut consumption and decreased
risk of sudden cardiac death in the Physicians’ Health Study. Arch Intern Med.
162:1382–1387
Almond Board of California. 2012. Request for proposals: Shelflife of whole almonds in
retail and bulk packages. Modesto, CA.
Almond Board of California. 2013. Almond Almanac. Modesto, CA.: Almond Board of
California. Available from:
http://www.almondboard.com/AboutTheAlmondBoard/Documents/2012%20Almond%2
0Almanac_FINAL.pdf. Accessed October 28, 2014.
Almond Board of California. 2010. Background information on almond shelf life
research. Modesto, CA.
Almond Board of California. 2014a. Almond Shelf Life Factors. Modesto, CA.: Almond
Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/2014aq0007_shelf_life_f
actors.pdf. Accessed September 21, 2014.
Almond Board of California. 2014b. Long-Term Storage Study of Raw and Blanched
Almonds. Modesto, CA.: Almond Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/aq0105_lin_summary_re
port_july_2014_final.pdf. Accessed November 2, 2014.
Almond Board of California. 2014c. Technical Information Kit and Poster. Modesto, CA:
Almond Board of California. Available from:
http://www.almonds.com/sites/default/files/content/attachments/english_technical_kit.pdf
. Accessed October 30, 2014.
[ADA] American Diabetes Association. 2012. Standards of Medical Care in Diabetes—
2012. Alexandria, VA: American Diabetes Association. Available
109
from: http://care.diabetesjournals.org/content/35/Supplement_1/S11.full. Accessed
September 22, 2014.
Ares G, Parentelli C, Gámbaro A, Laeo C, Lema P. 2006. Sensory shelf life of shiitake
mushrooms stored under passive modified atmosphere. Postharvest Biology and
Technology. 41:191-197.
ASTM Stock DS72. 2011a. Lexicon for Sensory Evaluation: Aroma, Flavor, Texture, and
Appearance. ASTM International. West Conshohocken, PA.
ASTM Standard E2454-05. 2011. Standard evaluations methods to determine the sensory
shelf life of consumer products. West Conshohocken, PA.
Bao Y, Hu FB, Giovannucci EL, Wolpin BM, Stampfer MJ, Willett WC, Fuchs CS.
2013a. Nut consumption and risk of pancreatic cancer in women. Br J Cancer.
109(11):2911-2916.
Bao Y, Han J, Hu FB, Giovannucci EL, Stampfer MJ, Willett WC, Fuchs CS. 2013b.
Association of nut consumption with total and cause-specific mortality. N Engl J Med.
369(21):2001-2011.
Boiling BW, McKay DL, Blumberg JB. 2010. The phytochemical composition and
antioxidant actions of tree nuts. Asia Pac J Clin Nutr. 19(1):117-123.
Boriss H, Brunke H, Huntrods D. 2013. Almond profile. Ames, IA.: Agricultural
Marketing and Resource Center. Iowa State University. Available from:
http://www.agmrc.org/commodities__products/nuts/almond-profile/. Accessed October
8, 2014.
Butler TI, Morris BA. 2010. PE based multilayer film structures. In: Wagner JR, editor.
Multilayer Flexible Packaging: Technology and Application for the Food, Personal Care,
and Over-The-Counter Pharmaceutical Industries. Burlington, MA.: Elsevier. p 205-230.
Calvaletto CG. 1981. Quality evaluation of macadamia nuts. In: Charalambous G, Inglett,
editors. The Quality of Food and Beverages: Chemistry and Technology. New York:
Academic Press. p 71-82.
Chen CY, Lapsley K, Blumberg J. 2006. A nutrition and health perspective on
almonds. J Sci Food Agric. 86:2245-2250.
Chen CY, Milbury PE, Lapsley K, Blumberg JB. 2005. Flavonoids from almond skins
are bioavailable and act synergistically with vitamins C and E to enhance hamster and
human LDL resistance to oxidation. J Nutr. 135:1366-1373.
Civille GC, Lapsley K, Huang G, Yada S, Seltsam J. 2009. Development of an almond
lexicon to assess the sensory properties of almond varieties. J Sen Stud. 25:146-162.
110
Cohen AE, Johnson CS. 2011. Almond ingestion at mealtime reduces postprandial
glycemia and chronic ingestion reduces hemoglobin A1c in individuals with well-
controlled type 2 diabetes mellitus. Metabolism. 30:1312-1317.
Curia A, Aguerrido M, Langohr K, Hough G. 2005. Survival analysis applied to sensory
shelf life of yogurts–I: Argentine formulations. J Food Sci. 70(7):442-445.
deMan J. 2007. Principles of Food Chemistry. 3rd ed. New York: Kluwer Academic
Publishers. 520 p.
Ellis PR, Kendall CW, Ren Y, Parker C, Pacy JF, Waldron KW. 2004. Role of cell walls
in the bioaccessibility of lipids in almond seeds. Am J Clin Nutr. 80:604-613.
Estruch R, Martinez-Gonzalez, MA, Corella D, Salas-Salvado J, Ruiz-Gutiérrez, Covas
MI, Fiol M, Gómez-Garcia E, López-Sabater MC, Viñoles E, Arós F, Conde M, Lahoz C,
Lapetra J, Sáez G, Ros E. 2006. Effects of a Mediterranean-style diet on cardiovascular
risk factors. Ann Intern Med. 145(1):1-11.
Flores-Mateo G, Rojas-Rueda D, Basora J, Ros E, Salas-Salvadó J. 2013. Nut intake and
adiposity: meta-analysis of clinical trials. Am J Clin Nutr. 97(6):1346-1355.
Fontana AJ. 2000. Understanding the importance of water activity in food. Cereal Foods
World. 45(1):7-10.
[FDA] Food and Drug Administration. 2003. Summary of Qualified Health Claims
Subject to Enforcement Discretion. Silver Spring, MD.: U.S. Food and Drug
Administration. Available from:
http://www.fda.gov/Food/IngredientsPackagingLabeling/LabelingNutrition/ucm073992.h
tm. Accessed September 20, 2014.
Fourie PC, Basson DS. 1989. Predicting rancidity in stored nuts by means of chemical
analyses. Lebensmittel Wissenschaft und Technologie. 22:251-253.
Gámbaro A, Ares G, Giménez A. 2006. Shelf-life estimation of apple-baby food. J Sen
Stud. 21:101-111.
Garcıa-Pascual P, Mateos M, Carbonell V, Salazar DM. 2003. Influence of storage
conditions on the quality of shelled and roasted almonds. Biosyst Eng. 84(2):201–209.
Giménez A, Verla P, Salvador A, Ares G, Fisman S, Garitta L. 2007. Shelf life estimation
of brown pan bread: a consumer approach. Food Qual Prefer. 18:196-204.
Giménez A, Ares F, Ares G. 2012. Sensory shelf-life estimation: a review of current
methodological approaches. Food Res Int. 49:311-325.
111
Gonzalez R, Benedito J, Carcel JA, Mulet A. 2001. Cheese hardness assessment by
experts and untrained judges. J Sen Stud. 16:277-285.
Griffiths N. 1985. Sensory analysis in measuring shelf-life. Food, Flavours, Ingredients,
Packaging and Processing. 7(9):47-48.
Guadagni DG, Soderstrom EL, Storey CL. 1978. Effect of controlled atmosphere on
flavor stability of almonds. J Food Sci. 43:1077-1080
Harris NE, Westcott DE, Henick AS. 1972. Rancidity in almonds: shelf life studies. J
Food Sci. 37(6):824–827.
Hollis J, Mattes R. 2007. Effect of chronic consumption of almonds on body weight in
healthy humans. Br J Nutr. 98(03):651-656.
Hough G, Langohr K, Gomez G, Curia A. 2003. Survival analysis applied to sensory
shelf life of foods. J Food Sci. 68(1):359-362.
Huang G. October 8, 2014. Personal communication (email). Almond Board of
California, Modesto, CA.
Hyson DA, Schneeman DO, Davis PA. 2002. Almond and almond oil have similar
effects on plasma lipids and LDL oxidation in healthy men and women. J Nutri. 132:703-
707.
IFST. 1993. Shelf life of foods – guidelines for its determination and prediction. London:
Institute of Food Science & Technology.
Jaceldo-Siegl K, Haddad E, Oda K, Fraser GE, Sabaté J. 2014. Tree nuts are inversely
associated with metabolic syndrome and obesity: the Adventist health study-2. PLoS One
9(1).
Jenkins DJ, Kendall CW, Marchie A, Parker TL, Connelly PW, Qian W. 2002. Dose
response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-
density lipoproteins, lipoproteins(a), homocysteine, and pulmonary nitric oxide: a
randomized controlled, crossover trial. Circulation 106:1327-1332.
Jensen PN, Sørenson G, Engelsen SB, Bertelsen G. 2001. Evaluation of quality changes
in walnut kernels (Juglans regia L.) by vis/NIR spectroscopy. J Agri Food Chem.
49(12):5790-5796.
Kamil A, Chen CYO. 2012. Health benefits of almonds beyond cholesterol reduction. J
Agric Food Chem. 60:6694-6702.
Kanner J, Rosenthal I. 1992. An assessment of lipid oxidation in foods. Institute of Pure
and Applied Chemistry. 64(12):i959-i964.
112
Kelly JH, Sabaté J. 2006. Nuts and coronary heart disease: an epidemiological
perspective. Br J Nutr. 96(2):S61-S67.
Kilcast D. 2000. Sensory evaluation methods for shelf-life assessment. In: Kilcast D,
Subramaniam P, editors. The Stability and Shelf-life of Food. Cambridge, UK:
Woodhead Publishing Ltd. p 79-105.
Kochar J, Gaziano JM, Djoussé L. 2010. Nut consumption and risk of type II diabetes in
the Physicians' Health Study. Eur J Clin Nutr. 64(1):75-79.
Kris-Etherton PM, Hu FB, Ros E, Sabaté J. 2008. The role of tree nuts and peanuts in the
prevention of coronary heart disease: multiple potential mechanisms. J Nutr.
138(9):1746S-1751S.
Kroon P, Williamson G. 2005. Polyphenols: dietary components with established benefits
to health. J Sci Food Agric. 85:1239-1240.
Labuza TP and Szybist LM. 2001. Open Dating of Foods. Connecticut: Food and
Nutrition Press. 239 p.
Lawless HT and Heymann H. 2010. Sensory Evaluation of Food. 2nd ed. New York:
Chapman & Hall. 596 p.
Li SC, Liu YH, Liu JF, Chang WH, Chen CM, Chen CYO. 2010. Almond consumption
improved glycemic control and lipid profiles with type 2 diabetes. Metabolism. 6(4):474-
479.
Lin X, Wu J, Rongbi Z, Chen P, Huang G, Li Y, Ye N, Nanhui Y. 2012. California
almond shelf life: Lipid deterioration during storage. Inst Food Tech. 77(6):C583-C593.
Lovejoy JC, Most MM, Lefevre M, Greenway FL, Rood JC. 2002. Effect of diets
enriched in almonds on insulin action and serum lipids in adults with normal glucose
tolerance or type 2 diabetes. Am J Clin Nutr. 76:1000-1006.
Marsh K, Bugusu B. 2007. Food packaging—roles, materials, and environmental issues.
J Food Sci. 72(3):R39-R55.
Meilgaard M, Civille GV, Carr BT. 1991. Sensory Evaluation Techniques. 2nd ed.
Florida: CRC Press. 354 p.
Mena MP, Sacanella E, Vazquez-Agell M, Morales M, Fitó M, Escoda R, Serrano-
Martinez M, Salas-Salvadó J, Beneages N, Casas R, Lamuela-Raventós RM, Masanes F,
Ros E, Estruch R. 2009. Inhibition of circulating immune cell activation: a molecule anti-
inflammatory effect of the Mediterranean diet. Am J Clin. 89(1): 248-256.
113
Mexis SF, Badeka AV, Riganakos KA, Karakostas KX, Kontominas MG. 2009. Effect of
packaging and storage conditions on quality of shelled walnuts. Food Control. 20:743-
751.
Mori AM, Considine RV, Mattes RD. 2011. Acute and second-meal effects of almond
form in impaired glucose tolerant adults: a randomized crossover trial. Nutr Metab.
8(1):6.
Munoz A, Civille GV, Carr BT. 1992. Sensory Evaluation in Quality Control. New York:
Chapman & Hall. 240 p.
Murray JM, Delahunty CM, Baxter IA. 2001. Descriptive sensory analysis: past, present,
and future. Food Res Int. 34:461-471.
Özdemir M, Ackurt F, Yilldiz M, Biringen G, Gürcan T, Löker M. 2001. Effect of
roasting on some nutrients of hazelnuts (Corylus Avellana L.). Food Chem 73:185-190.
Perren R and Escher F. 2013. Impact of roasting on nut quality. In: Harris LJ, editor.
Improving the Safety and Quality of Nuts. Cambridge, UK.: Woodhead Publishing Ltd. p
173-197.
Pokorny J. 2001. Natural antioxidant functionality during food processing. In: Pokorny J,
Yanishlieva N, Gordon M, editors. Antioxidants in Food, Practical Applications.
Cambridge, UK.: Woodhead Publishing Ltd. p 335-351.
Reed KA, Sims CA, Gorbet DW, O’Keefe SF. 2002. Storage water activity affects
flavour fade in high and normal oleic peanuts. Food Res Int. 35:769-774.
Richards MP. 2007. Lipids: functional properties. 2nd ed. ln: Hui YH, editor. Food
Chemistry: Principles and Applications. Sacramento, CA: Science Technology System. p
71-720.
Robbins KS, Shin EC, Shewfelt RL, Eitenmiller RR, Pegg RB. 2011. Update on the
healthful lipid constituents of commercially important tree nuts. J Agri Food Chem.
59(22):12083-12092.
Ros E. 2010. Health benefits of nut consumption. Nutrients. 2(7):652-682.
Rousset S, Martin JF. 2001. An effective hedonic analysis tool: weak/strong points. J Sen
Stud. 16:643-661.
Sabaté J, Haddad E, Tanzman JS, Jambazian P, Rajaram S. 2003. Serum lipid response to
the graduated enrichment of a Step I diet with almonds: a randomized feeding trial. Am J
Clin Nutr. 77(6):1379-1384.
114
Salas-Salvadó J, Garcia-Arellano A, Estruch R, Marquez-Sandoval F, Corella D, Fiol M,
Gómez-Garcia E, Viñoles E, Arós F, Herrera C, Lahoz C, Lapetra J, Perona JS, Muñoz-
Aguado D, Martínez-González MA, Ros E. 2007. Components of the Mediterranean-type
food pattern and serum inflammatory markers among patients at high risk for
cardiovascular disease. Eur J Clin Nutr. 62(5):651-659.
Salvador A, Fizman SM, Curia A, Hough G. 2005. Survival analysis applied to sensory
shelf life of yogurts–II: Argentine formulations. J Food Sci. 70(7):446-449.
Sang S, Lapsley K, Jeong WS, Lachance PA, Ho CT, Rosen RT. 2002. Antioxidative
phenolic compounds isolated from almond skins (Prunus amygdalus Batsch). J Agric
Food Chem. 50:2459-2463.
Sathe SK, Seeram NP, Kshirsagar HH, Heber D, Lapsley KA. 2008. Fatty acid
composition of California grown almonds. J Food Sci. 73(9):C607-614.
Shahidi F, John JA. 2010. Oxidation and protection of nuts and nut oils. 2nd. vol. In:
Decker EA, Elias RJ, McClements DJ, editors. Oxidation in Foods and Beverages and
Antioxidant Applications. Cambridge, UK.: Woodhead Publishing Ltd. p 274-305.
Shahidi F, John JA. 2013. Oxidative rancidity in nuts. In: Harris LJ, editor. Improving the
Safety and Quality of Nuts. Cambridge, UK.: Woodhead Publishing Ltd. p 199-229.
Spiller GA, Jenkins DA, Bosello O, Gates JE, Cragen LN, Bruce B. 1998. Nuts and
plasma lipids: an almond-based diet lowers LDL-C while preserving HDL-C. J Am Coll
Nutr. 11:126-130.
StockBag Depot. 2014. 12 oz. Foil Stand Up Zip Pouch. City of Industry, CA.: StockBag
Depot.
Available from: http://www.stockbagdepot.com/stand-up-pouches/plain-foil/12-oz-
gold.html. Accessed on November 9, 2014.
Stone H, Sidel JL. 2004. Sensory Evaluation Practices. 3rd ed. London: Elsevier. 408 p.
Szczesniak AS and Kahn EE 1971. Consumer awareness and attitudes towards food
texture I: adults. Journal of Texture Studies. 2:280-295.
Szczesniak AS. 2002. Texture is a sensory property. Food Qual Prefer. 13:215-225.
Uline. 2014. Uline.com Reclosable Polypropylene Bags. Waukegon, IL.: Uline.
Available from: http://www.uline.com/BL_5562/Reclosable-Polypropylene-Bags.
Accessed on November 9, 2014.
115
[USDA] United States Department of Agriculture. 2011. Basic Report: 12565, Nuts,
almonds, oil roasted, with salt added in National Nutrient Database for Standard
Reference. Washington, D.C.: U.S. Dept. of Agriculture. Available:
http://ndb.nal.usda.gov/ndb/foods/show/3753?fg=&man=&lfacet=&format=&count=&m
ax=25&offset=&sort=&qlookup=almonds. Accessed October 9, 2014.
[USDA] United States Department of Agriculture. 2007. United States Standards for
Grades of Shelled Almonds. Washington, D.C.: U.S. Dept. of Agriculture. Available
from: http://www.almondboard.com/Handlers/Documents/USDA-Standards-Shelled-
Almonds.pdf. Accessed October 28, 2014.
Varela P, Chen K, Fiszman S, Povey MJW. 2006. Crispness assessment of roasted
almonds by an integrated approach to texture description: texture, acoustics, sensory, and
structure. J Chemometr. 20:311-320.
Varela P, Salvador A, Fiszman S. 2008a. On assessment of fracture in brittle foods.
Biting or chewing? Food Research International 41:544-551.
Varela P, Aguilera JM, Fiszman S. 2008b. Quantification of fracture properties and
microstructural features of roasted Marcona almonds by image analysis. LWT - Food Sci
Technol. 41(1):10-17.
Varela P, Salvador A, Fiszman S. 2009. On assessment of fracture in brittle foods II.
Biting or chewing? Food Research International. 42:1468-1474.
Velasco J, Dobarganes C, Màrquez-Ruiz G. 2010. Oxidative rancidity in foods and food
quality. In: Skibsted LH, Risbo J, Andersen ML, editors. Chemical Deterioration and
Physical Instability of Food and Beverages. Cambridge, UK.: Woodhead Publishing Ltd.
p 3-32.
Vickers Z, Peck A, Labuza T, Huang G. 2014. Impact of almond form and moisture
content on texture attributes and acceptability. J Food Sci. 79(7):S1399-S1406.
Ward BW, Schiller JS, Goodman RA. Multiple chronic conditions among US adults: a
2012 update. Prev Chronic Dis. 2014;11:130389. DOI: Available from:
http://dx.doi.org/10.5888/pcd11.130389. Accessed November 11, 2014.
Wijeratne S, Abou-Zaid M, Shahidi F. 2006. Antioxidant polyphenols in almond and its
coproducts. J Agri Food Chem. 54(2):312–318.
[WHO] World Health Organization 2005a. Chronic diseases and their common risk
factors. Geneva, Switzerland: World Health Organization.
http://www.who.int/Chp/chronic-disease-report/media /Factsheet1.pdf. Accessed October
9, 2014.
116
[WHO] World Health Organization 2005b. Solving the chronic disease problem. Geneva,
Switzerland: World Health Organization. http://www.who.int/Chp/chronic-disease-
report/media /Factsheet5.pdf. Accessed October 9, 2014.
Yada S, Huang GW, Lapsley K. 2013. Natural variability in the nutrient composition of
California-grown almonds. J Food Compos and Anal. 30:80-85.
Zemaitis J, Sabaté J. 2001. Effect of almond consumption on stool weight and stool fat.
FASEB J. 15:A602.
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APPENDIX A
INFORMATIONAL LETTER
118
Dear __________:
I am a graduate student under the direction of Dr. Ruthann Swanson in the Department of Foods and
Nutrition at The University of Georgia. I invite you to participate in a research study entitled
Acceptability of Almonds that is being conducted jointly with faculty in the Department of Food Science
and Technology at the University of Georgia. The purpose of this study is to identify optimal conditions for
storing almonds, ensuring that a quality product is available to consumers in the marketplace.
To participate, you must be at least 18 years of age or older and available to serve as a sensory panelist
multiple times over the next 14 months. You will also participate in several training session prior to serving
as a sensory panelist. You must be a nut consumer (any type of nut), and must be sensitive to smells and
tastes so that you can detect and rate the intensity of the odor, flavor and texture characteristics of almonds.
As a panelist, you will asked to evaluate almonds using s standard procedure and form. Each evaluation session will last about 15 minutes. Although training sessions may vary somewhat in length, on average it is anticipated the training session will last about 90 minutes; it is expected that there will be 6 to 8 training sessions.
Your involvement in the study is voluntary, and you may choose not to participate or to stop at any time
without penalty or loss of benefits to which you are otherwise entitled. This study is confidential. You will be assigned an identifying code and this code will be used on all questionnaires and evaluation forms that
you fill-out. It will be possible to link specific individuals with specific responses. However, no
individually identifiable information about you, or provided by you during the research, will be shared with
others without your written permission, except if it is necessary to protect your welfare (for example, if you
were injured and need physician care) or if required by law. The results of the research study may be
published, but your name will not be used. In fact, the published results will be presented in summary form
only. Your identity will not be associated with your responses in any published format.
The findings from this project may provide information on factors that affect quality of the roasted almonds
available to consumers. An expected benefit is the increased availability nutritious foods that are
acceptable to consumers; their availability will empower consumers to improve their dietary choices. In
addition, participation in this hands-on experience may enhance discussions in the classroom, facilitating a
better understanding of the process and limitations associated with development/ and market success of products available to consumers. There are no known risks or discomforts associated with this research.
Panelists will be paid $25 for each training session and will also receive compensation for the evaluation
sessions; amount will vary with number of samples but will average $25 per 12 samples evaluated for all
attributes on the scorecard.
If you have any questions about this research project, please feel free to call Dr. Ruthann Swanson at 706-
542-4834 or send an e-mail to [email protected]. Questions or concerns about your rights as a research
participant should be directed to The Chairperson, University of Georgia Institutional Review Board, 629
Boyd GSRC, Athens, Georgia 30602; telephone (706) 542-3199; email address [email protected].
By completing and returning this questionnaire in the envelope provided, you are agreeing to participate in
the screening process for the above described research project and to participate in the training sessions and sensory evaluation sessions if selected as a participant. We will contact you to schedule your prescreening.
Thank you for your consideration! Please keep this letter for your records.
Sincerely,
Anna Cheely Graduate Student
Department of Foods and Nutrition, UGA
119
APPENDIX B
DESCRIPTIVE SENSORY PANEL: PRESCREENING QUESTIONNAIRE
120
1. Name:_______________________________
2. Address: _________________________________________
3. Phone:_________________________ Email:______________________________
Time availability:
1. Are there any days that you will not be available on a regular basis?
2. Will you be available during the summer ? _____yes _____no
Health:
Do you have any of the following:
1. Dentures _____yes _____no
2. Diabetes _____yes _____no
3. Oral or gum disease _____yes _____no
4. Food allergies _____yes _____no
If yes, please list foods you are allergic to:
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Do you take any medications which affect your sense of taste or smell? ____yes _____no
Food habits:
1. What is your favorite food?
2. What is your least favorite food?
3. What foods can you not eat?
4. What foods do you not like to eat?
5. Is your ability to distinguish smells and tastes:
Smell Taste
Better than average ________ _______
Average ________ _______
Worse than average ________ _______
6. Is your sensitivity to textural characteristics in foods:
Better than average ________
Average ________
Worse than average ________
Texture and Flavor Quiz:
121
1. How would you describe the difference between flavor and texture?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
2. How would you describe the difference between flavor and aroma?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
3. Describe some of the properties which are apparent when one chews a food.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
4. What are some textural properties of potato chips?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
5. Describe some noticeable flavors in Ritz crackers?
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
Scaling Exercise:
1. On a 15-point hardness scale, cocktail peanuts are a 9.5. Please place a mark across
the line below to indicate where the hardness rating of peanuts falls.
_________________________________________________________________
0 15
Not perceptible High Intensity
122
APPENDIX C
REFERENCE CARDS
123
124
APPENDIX D
ALMOND DESCRIPTIVE SCORECARD (1/2)
125
Almond Scorecard
PANELIST #: _____________
Date:__________________
Directions: 1. Place one almond at a time between the molars; bite through once; evaluate for
hardness. Continue to chew sample and evaluate for sweetness.
2. Mark an X on scale along with product number.
Hardness- use hardness reference card
0 15
Not High
Perceptible Intensity
Sweetness- no reference needed
0 15
Not High
Perceptible Intensity
PLEASE FLIP OVER SCORECARD
126
Directions: 1. Place one almond at a time between the molars; bite through once; evaluate for
crunchiness.
2. Mark an X on scale along with product number.
Crunchiness- use crunchiness reference card
0 15
Not High
Perceptible Intensity
127
APPENDIX E
ALMOND DESCRIPTIVE SCORECARD (2/2)
128
Almond Scorecard
PANELIST #: _____________
Date:__________________
Directions: 1. Quickly open lid and take 3 short sniffs of the sample, through the nose; close
lid and evaluate for presence of a cardboardy, rancidity, and/or painty note.Then rate its intensity. Between each sample wait 30 seconds and continue.
2. Mark an X on scale.
Cardboardy- use Universal Intensity scale
0 15
Not High
Perceptible Intensity
Rancid- use Universal Intensity scale
0 15
Not High
Perceptible Intensity
Painty- use Universal Intensity scale
0 15
Not High
Perceptible Intensity
129
Directions: 1. Taste one almond and evaluate for presence of a cardboard, rancid, and/or painty note.
Then rate its intensity. Wait 30 seconds between almonds.
2. Mark an X on scale.
Cardboardy- use Universal Intensity scale
0 15
Not High
Perceptible Intensity
Rancid- use Universal Intensity scale
0 15
Not High
Perceptible Intensity
Painty- use Universal Intensity scale
0 15
Not High
Perceptible Intensity
Send tray and scorecard through window and wait for next sample
130
APPENDIX F
CONSENT FORM
131
The product today is roasted almonds
Consent Form
I, _____________________, agree to participate in a research study titled Sensory Evaluation of Almonds
conducted by Dr. Ruthann Swanson (706-542-4843) and graduate student Anna Cheely, Department of
Foods and Nutrition, University of Georgia. I am at least 18 years of age or older. I understand my
participation is voluntary. I can refuse to participate or stop taking part without giving any reason and without penalty or loss of benefits to which I am otherwise entitled. I can ask to have all of the information
about me returned to me, removed from the research records, or destroyed immediately after my
participation as a sensory panelist. The purpose of this study is to investigate the quality and acceptability
of almonds. All products were handled in facilities in which ServSafe or appropriate GMP procedures
were followed. If I volunteer to take part in this study, I will be asked to do the following things:
- Read and sign the consent form (1-2 minutes)
- Complete the demographic and food choices questionnaire (5-8 minutes)
- Evaluate almonds according to directions on the sensory scorecard (4-6 minutes)
Students who have selected participation on this sensory panel as an extra credit option will receive class
credit. In classes where extra credit is offered, other options are available, however these options vary with
class and are determined by the instructor in the class. Optional commercially prepared snacks will be made available following the participant’s involvement in the research study.
Food allergies that I have include:
______________________________________________________________________________________
______________________________________________________________________________________
____________________________________________
This study is confidential. I will be assigned an identifying number and this number will be used on all
questionnaires and evaluation forms that I fill-out. It will be possible to link specific individuals with
specific responses during the evaluation of the product. However, there is no way to connect specific
responses with a specific individual once the test is completed. No individually identifiable information
about me, or provided by me during the research, will be shared with others without my written permission,
except if it is necessary to protect my welfare (for example, if I were injured and need physician care) or if required by law. An expected benefit is the production of healthier products that are acceptable to
consumers; their availability will empower consumers to improve their dietary choices. My participation in
this hands-on experience may enhance discussions in the classroom, facilitating a better understanding of
the process and limitations associated with development/success of products available to consumers. There
are no expected risks or discomforts associated with participation for any person who does not have
allergies to almonds. In the event I suffer a research-related injury, I will seek treatment at an appropriate
medical facility. However, my medical expenses will be my responsibility or that of my third-party payer,
although I am not precluded from seeking to collect compensation for injury related to malpractice, fault, or
blame on the part of those involved in the research. As a participant, I do not give up or waive any of my
legal rights.
If I have further questions about this study, I can call Dr. Ruthann Swanson at (706) 542-4834.
I understand the procedures described above and my additional questions have been answered to my satisfaction. I agree to participate in this research study, and I have received a copy of this consent form for
my records.
Ruthann Swanson___ ________________________ _________
132
Name of Researcher Signature Date
Anna Cheely ________________________ _________
Name of Researcher Signature Date
__________________ ________________________ _________
Name of Participant Signature Date
Please sign both copies, keep one and return one to the researcher.
Additional questions or problems regarding your rights as a research participant should be addressed to
Chairperson, Institutional Review Board, University of Georgia, 629 Boyd Graduate Studies Research
Center, Athens, Georgia 30602-7411; Telephone (706)542-3100; Email address [email protected].
133
APPENDIX G
CONSUMER SCORECARD
134
Product Code Number: P anelist Number:
________________ ______________
Almond Sensory Scorecard
You will evaluate XX samples today, each presented in a closed container. Please check
the box (□) that best reflects your opinion of this sample
Before tasting, evaluate the odor of the product. Hold the cup close to your nose and
gently lift the lid as you take three short sniffs.
Odor
□ □ □ □ □ □ □ □ □ Extremely Extremely
Dislike L ike
Eat the almonds and evaluate texture, flavor and overall acceptability by marking the box
(□) that best reflects how much you like this product
Texture
□ □ □ □ □ □ □ □ □ Extremely E xtremely
Dislike Like
Flavor
□ □ □ □ □ □ □ □ □ Extremely Extremely
Dislike L ike
Overall Acceptability
□ □ □ □ □ □ □ □ □ Extremely Extremely
Dislike L ike
Please drink water and eat some crackers and/or carrot to cleanse you mouth
Turn-overandcompletetheback
135
.Comments: Please indicate WHAT in particular you liked or disliked
about this almond sample (Use WORDS not SENTENCES)
LIKED DISLIKED
If you had purchased this product, would you eat it?
_______yes _______no
Please place your tray in the hatch in front of you and close
the hatch. You will receive another sample in a moment.
If this was your last sample, you will receive a short questionnaire.
136
APPENDIX H
CONSUMER QUESTIONNAIRE
137
Panelist _________________
Almond Questionnaire
Now, we would like to know a little more about you.
Please check the best response for each item below.
1. Your gender: Male ________ or Female __________
2. Please check your age category:
_______18-27 _______44-51
_______28-35 _______52-61
_______36-43 _______62 and above
3. How often do you eat nuts, including peanuts? (check 1)
_______Daily
_______Several times a week
_______Several times a month
_______Once a month
_______Several times a year
_______Never
4. How often do you eat almonds? (check 1)
_______Daily
_______Several times a week
_______Several times a month
_______Once a month
_______Several times a year
_______Never
Please return your completed questionnaire and pull the hatch closed.
Thank you for making our study a success!
138
APPENDIX I
CHEMICAL/INSTRUMENTAL ANAYLSES BY FOODS AND SCIENCE
DEPARTMENT AT THE UNIVERSITY OF GEORGIA
139
Texture analysis
Almond samples were assessed with 10 replications at each 2-month interval.
Almonds were sorted to have similar sizes and appearances. Texture analyses were
measured using a Texture Technologies TA-XT2i texture analyzer (Texture Technologies
Corp., Scarsdale, NY, U.S.A.) loaded with a 25 kg ± 1g electronic load cell. The load cell
was equipped with a TA-94 40mm diameter compression disc. Data was recorded on a
computer loaded with Texture Expert Exceed 2.64 software (Stable Micro Systems,
Haslemere, Surry, England). The force was graphed as N/time. The test speed 1.0 mm/s
with trigger of 0.1N, which compressed to a distance of 50% strain. Area under the curve,
force required for compression, number of fracture points, the gradient of the force curve,
the average drop-off between peaks, the linear distance of the curve, the average gradient
between peeks, the force to the first fracture point, and the distance of compression of the
first fracture point were all calculated from the compression test.
Texture was monitored for any changes due to storage conditions, and how it
affects the overall acceptability of the almond sample. Texture was also analyzed as a
possible trigger for panels.
Water activity
Water Activity was assessed for each sample in a calibrated Aqua Lab CX-2
water activity meter (Decagon Devices, Inc., Pullman, WA). Each sample was evaluated
in triplicate and reported as a partial pressure of water in the sample compared to distilled
water at the same temperature.
Samples were removed from the environmental chambers and “cold- pressed” in a
Carver hydraulic press using a Carver 2.25” ID Stainless steel test cylinder and pellet
140
mold (Carver, Inc, Wabash, IN, U.S.A.). The oil was then transferred into a 2-ounce
amber colored screw-cap vial (Fisher Scientific, Suwanee, GA) and flushed with
nitrogen. Once the vials were capped, they were placed in a dark refrigerator at 4 oC
overnight until the analyses were performed. For vitamin E analysis, oil samples were
frozen at -80 oC until analyzed.
Water activity was measured due to the possiblibilty of it being an indicator of
textural changes and presence of chemical changes resulting in rancidity (Fontana 2000;
Vickers and others 2014.
Peroxide
Peroxide values (PV) were assessed in triplicate using a modified AOAC Method
965.33 (AOAC International, Gaithersburg, MD). A PV of 2.0 meq. active O2/kg oil
triggered evaluation by the descriptive sensory panel.
Measuring peroxide values is the most popular measure (Shahidi and John 2013)
to indicate quality of nuts. It is a simple test and is a good predictor oxidation (Fourie and
Basson 1999; Garcıa-Pascual and others 2003).
Free Fatty Acids
Free Fatty Acid values were assessed in triplicate using a modified version of
AOCS Official Method Ca 5a-40 (AOCS, Urbana, IL) by weighing 1±0.1g of oil into a
25mL Erlenmeyer flask. 95% ethanol was neutralized with 0.005N NaOH and 2.5mL
was added to each flask with 0.1mL of 1% Phenolphthalein in 80EtOH:20 H2O (v/v).
Samples were heated to 70 oC and agitated by a stir bar and titrated with 0.005N NaOH
until the solution turned slightly pink color and continued for 30 seconds.
141
Free fatty acids are a popular chemical measure to describe nut quality, serving as
an indicator of rancidity (Garcıa-Pascual and others 2003; Lin and others 2012).
Conjugated Dienoic Acid
Conjugated dienoic acid values were assessed in triplicate using IUPAC Official
Method 2.505 (IUPAC, Research Triangle Park, NC). For each sample, 25±5mg of the
pressed oil was dissolved in 10mL hexane. Each sample was mixed using a vortex mixer
for 10 seconds to ensure proper dilution. The absorptivity was measured at 233 nm in a
10mm quartz cuvette with pure solvent in the reference cuvette.
Conjugated dienoic acid values are used for measuring primary oxidation
factors—the formation of hydroperoxides from polyunsaturated fatty acids. This occurs
in the beginning of the oxidation process (Esteves and others 2009).
2-Thiobarbituric Acid Value
2-Thiobarbituric acid values were assessed in triplicate using a modified version
of AOCS Official Method Cd 19-90 (AOCS, Urbana, IL) by weighing 40mg of the
pressed oil in 5mL 1-butanol and 5mL TBA reagent (200 mg 2-thiobarbituric in 100 mL
1-butanol). Samples were then placed in a water bath at 95 oC for 120 minutes, then
cooled to room temperature under running water. Using distilled water as the reference,
sample absorbance was measured at 530nm in a 10mm quartz cuvette.
This test is a convenient method for measuring secondary oxidation products—
those responsible for flavor compounds (Shahidi and John 2013).
Headspace Volatiles
Headspace volatiles were assessed using an Agilent 1890A GC-FID using a
SPME fiber using a 60mx0.25mm DB-5 non-polar column with a film thickness of
142
25µm. The gradient run had an initial temperature of 38 oC, which was held for 1 minute
followed by an increase in temperature at the rate of 2.5 oC/min to 175
oC. The
temperature was then increased 50 oC/min to 220
oC, and held for 2 min. The injector
port was held constant at 250 oC. Split ratio was 1:40 and split flow was 40.3 mL min
-1,
column head pressure was 132.8 kpa, and the flow rate was 1.0 mL min-1
. The carrier gas
was helium. The chromatographs were compared with standards and correlated
with sensory data.
Vitamin E
At 8 months, the pressed oil samples were analyzed for vitamin E content using
normal phase HPLC with a flow rate 0.85 mL/min. The mobile phase was 0.85%
isopropanol in hexanes using a Phenomenex C18; 250x4 column. Samples were prepared
in triplicate by dissolving 1g of oil in mobile phase + 0.01% (v/w) BHT. Each sample
was prepared by adding 1g of oil in a 5 mL volumetric flask. The flasks were then filled
to mark and mixed thoroughly. Next, the samples were filtered through a 0.45 µm
membrane filter and stored in amber glass until being manually injected into a 20µL
Rheodyne Fixed Loop. Total tocopherols were calculated based on standard curves
created using the same method. Vitamin E was calculated and evaluated to analyze the
free radical quenching capabitities of the different almond samples.
References:
AOAC International. 1999. Method 965.33. In: P Cunniff, ed. Official Methods of
Analysis of AOAC International, 16th ed., 5th revision. Gaithersburg, MD.: AOAC
International.
AOCS. 1989. Official Methods and Recommended Practices of the American Oil
Chemists’ Society, 4th ed., edited by D. Firestone. Champaign, IL. Ca 5a-40.
143
AOCS. 1995. Method Cd 19-90. Official Methods and Recommended Practices of the
American Oil Chemists’ Society. Champaign, IL.: AOCS Press.
Esteves M, Morcuende D, Ventanas S. 2009. Determination of oxidation. In: Nollet
LML, Toldrá F, editors. Handbook of Muscle Food Analysis. Florida: CRC Press. p 221-
240.
Fontana AJ. 2000. Understanding the importance of water activity in food. Cereal Food
World. 45(1):7-10.
Fourie PC, Basson DS. 1989. Predicting rancidity in stored nuts by means of chemical
analyses. Lebensmittel Wissenschaft und Technologie. 22:251-253.
Garcıa-Pascual P, Mateos M, Carbonell V, Salazar DM. 2003. Influence of storage
conditions on the quality of shelled and roasted almonds. Biosyst Eng. 84(2):201–209.
Lin X, Wu J, Rongbi Z, Chen P, Huang G, Li Y, Ye N, Nanhui Y. 2012. California
almond shelf life: Lipid deterioration during storage. Inst Food Tech. 77(6):C583-C593.
Shahidi F and John JA. 2013. Oxidative rancidity in nuts. In: Harris LJ, editor. Improving
the Safety and Quality of Nuts. Cambridge, UK.: Woodhead Publishing Ltd. p 199-229.
Vickers Z, Peck A, Labuza T, Huang G. 2014. Impact of almond form and moisture
content on texture attributes and acceptability. J Food Sci. 79(7):S1399-S1406.
IUPAC Official Method 2.505. 1987. Standard Methods for the Analysis of Oils, Fats
and Derivatives. 7th ed. 1st revision. Blackwell Scienfic. Paolo Alto, CA.
144
APPENDIX J
DEMOGRAPHIC INFORMATION ON POLYPROPYLENE BAG CONSUMER
PANELS
145
Demographic profile for consumer panels assessing roasted almond samples stored in polypropylene bags
Storage conditions
Consumption Daily
Several
times a
week
Several
times a
month
Once a
month
Several
times a
year Never
--------------------------------Frequency %---------------------------------
Baseline/0-month (n= 119; 77.3 % female; 74.8 % 18-27 years)
Nuts 17.7 32.8 34.5 8.4 8.4 5.9
Almonds 5.0 22.7 38.7 15.1 16.8 1.7
10 month screen (n=35; 87.9% female; 97.0% 18-27 years)
35°C /65%RH Nuts 0 51.5 36.4 6.1 0 6.1
Almonds 3.0 27.3 20.2 21.2 12.1 6.1
10 month confirm (n=106; 76.5% female; 83.5% aged 18-27 years)
Nuts 83.5 7.8 1.0 1.9 1.0 4.9
Almonds 12.6 40.8 34.0 5.8 5.8 1.0
12 month screen (n=36; 85.7% female; 97.1% 18-27 years)
Nuts 14.3 60.0 22.9 2.9 0 0
Almonds 11.4 25.7 54.3 5.7 2.9 0
12 month confirm (n=101; 85% female; 97% 18-27 years)
Nuts 9.0 40.0 34.0 9.0 7.0 1.0
Almonds 3.0 26.0 42.0 14.0 12.0 3.0
10 month screen (n=35; 87.9% female; 97.0% 18-27 years)
35°C /50%RH Nuts 0 51.5 36.4 6.1 0 6.1
Almonds 3.0 27.3 30.3 21.2 12.1 6.1
12 month screen (n=35; 66.7% female; 47.1% 18-27 years)
Nuts 17.7 47.1 20.6 5.9 8.8 0
Almonds 5.9 41.2 26.5 2.9 17.7 5.9
14 month screen (n=39; 84.6% female; 76.9% 18-27 years)
Nuts 18.0 43.6 30.8 5.1 2.6 0
Almonds 5.1 30.8 41.0 10.3 12.8 0
14 month confirm (n=94; 80.0% female; 83% 18-27 years)
Nuts 18.4 41.4 34.5 2.3 3.5 0
Almonds 4.6 28.7 41.4 13.8 6.9 4.6
16 month screen (n=40; 71.8% female; 79.5% 18-27 years)
146
25°C /65%RH Nuts 10.3 30.8 46.2 7.7 5.1 0
Almonds 2.6 23.1 43.6 20.5 10.3 0
16 month confirm (n=102; 86.9% female; 84.9% 18-27 years)
Nuts 16.3 44.9 26.5 4.1 5.1 3.1
Almonds 2.0 41.4 37.4 8.1 7.1 4.0
12 month screen (n=35; 85.7% female; 71.4% 18-27 years)
25°C /50%RH Nuts 10.3 30.8 46.2 7.7 5.1 0
Almonds 2.6 23.1 43.6 20.5 10.3 0
14 month screen (n=36; 85.7% female; 88.6% 18-27 years)
Nuts 16.3 44.9 26.5 4.1 5.1 3.1
Almonds 2.0 41.4 37.4 8.1 7.1 4.0
16 month screen (n= 38; 73.7% female; 79.0% 18-27 years)
Nuts 15.8 44.7 29.0 0 5.3 5.3
Almonds 2.6 29.0 44.7 15.8 2.6 5.3
16 month confirm (n=102; 79.2% female; 83.2% 18-27 years)
Nuts 13.9 46.5 33.7 5.0 1.0 0
Almonds 4.0 35.6 40.6 12.9 6.9 0
16 month screen (n=36; 75% female; 77.8% 18-27 years)
15°C /65%RH Nuts 16.7 44.4 27.8 0 5.6 5.6
Almonds 2.8 30.6 44.4 13.9 2.8 5.6
16 month confirm (n=102; 79.2% female; 83.2% 18-27 years)
Nuts 13.9 46.5 33.7 5.0 1.0 0
Almonds 4.0 35.6 40.6 12.9 6.9 0
147
16 month screen (n=40; 71.8% female; 79.5% 18-27 years)
15°C /50%RH Nuts 10.3 30.8 46.2 7.7 5.1 0
Almonds 2.6 23.1 43.6 20.5 10.3 0
16 month confirm (n=102; 86.9% female; 84.9% 18-27 years)
Nuts 16.3 44.9 26.5 4.1 5.1 3.1
Almonds 2.0 41.4 37.4 8.1 7.1 4.0
16 month screen (n=35; 90.1% female; 75.0% 18-27 years)
4°C Nuts 12.5 53.1 28.1 3.1 3.1 0
Almonds 6.3 37.5 34.4 15.6 6.3 0
16 month confirm (n=102; 73.7% female; 80.8% 18-27 years)
Nuts 14.1 40.4 33.3 8.1 3.0 1.0
Almonds 3.0 33.3 33.3 16.2 11.1 3.0
148
APPENDIX K
WEAK AND STRONG POINTS FROM POLYPROPYLENE BAG CONSUMER PANELS
149
Panelists responses to the open-ended question: Please indicate what in particular you liked and disliked about this almond sample.
Likes presented for samples stored in polypropylene bags.
Baseline
35 °C
/65%RH
at 10 mo
35 °C
/65%RH
at 12 mo
35 °C
/50%RH
at 14 mo
25 °C
/65%RH
at 16 mo
25 °C
/50%RH
at 16 mo
15 °C
/65%RH
at 16 mo
15 °C
/50%RH
at 16 mo
4 °C
at 16
mo
Appearance
Appearance 1 3 6 3 3 1 1
Color 6 2 6 7 1 2 3
Skin 2
Mouthfeel/Texture
Texture 25 24 22 30 34 22 11 27 17
Crunchiness 50 36 34 41 29 28 40 42 38
Crispness 4 1 2 2 2 2 3
Smooth 4 5 3 2 1 4 2 4 1
Soft 2 1 2 1 1 1
Firm 1 2 1 3 2 2
Dry
Chewy 4 6 1
Feel 1
Not dry 1 3
Consistency 1
Fracturable 1
Creamy 1
Grainy 1
Juicy 1
Tender 1 1
Hard 1
Flavor/Taste
Flavor 20 28 14 15 11 12 23 25
Flavor: Almond 1 1 2
Flavor: Natural 1
Flavor: Roast 3 3
150
Flavor: Musty 1
Flavor: Nutty 2
Flavor: Light/not
offensive/ low
1
Taste 17 13 5 9 8 13 17 23
Taste: Natural 1
Odor 30 22 15 10 12 16 17 20 18
Odor: Strong 1
Odor: Roast 1 2
Odor: Nutty 2 2
Odor: Woody 1
Roasted 12 5 2 6 3
Sweet 8 2 2 2 4 3 4 3 3
Nutty 11 3 5 5 3 4 4 7 5
Buttery
Salty 6 1 1 1
Aftertaste 4 5 2 2 2 2 2 2
Smokey 5 1 2 1
Mild 1 1 2
Woody 1
Not too salty 4
Bitter 1 1
Savory 2 1
Chewable 5
Pleasant 2
Light/mild 3 2 4 1
Sharp 1
Floral 1
Moist 1
Other
Earthy 2 2 1 3 1 1 1 1
Fresh 4 2 3 1
151
Healthy 1 1 1 1
Simple 1
Robust 1
Natural 3
Dense 1
Brisk 1
Panelists responses to the open-ended question: Please indicate what in particular you liked and disliked about this almond sample.
Dislikes presented for samples stored in polyethylene bags.
Baseline
35 °C
/65%RH
at 10 mo
35 °C
/65%RH
at 12 mo
35 °C
/50%RH
at 16 mo
25 °C
/65%RH
at 16 mo
25 °C
/50%RH
at 16 mo
15 °C
/65%RH
at 16 mo
15 °C
/50%RH
at 16 mo
4 °C
at 16
mo
Appearance
Appearance 1 1 1 1 2 1 1
Color 2 1 1
Inconsistent color 1 1
Skin 2 1
Bruised 1
Papery outside 1
Dark 1
Mouthfeel/Texture
Texture 3 6 6 4 10 7 3 4 4
Coarse 1
Chalkiness 1
Soft 1 2 9 4 4 1 5 1
Dry 7 7 7 7 2 5 3 4 3
Grainy 2 4 1
Flakey 1 2 3
Crumbly 4 2
Brittle 1 1
Crunchy 1 3 3 1 2
No crunch 1 8 1 2 1
152
Mealy 2 1 1 3
Chewy 8 9 6 4 3 2 2
Hard to chew 2
Mushy/soggy 1 1
Gummy 2 1
Tough 1
Oily 1
Toothpack 4 4 1 1
Inconsistent texture 1
Hard 1 2 2 2 2 1 2
Papery outerfeel 2
Moist 2 1 1
Waxy 1
Pasty 1
Squeeky 1
Gritty 1
Not smooth 2
Flavor/Taste
Taste 1 2 10 5 11 9 5 5
Taste: Old/rancid/
strong/off
7 2
Taste: Oxidized 1
Taste: Chemical 1
Taste: Bitter 1
Flavor 2 8 9 6 13 9 4 3 4
Flavor: Off 2 1
Flavor: Musky 1
Flavor: Burnt 4
Flavor: Chemical 1
Flavor: Woody 1
Flavor: Rancid/off 1 1 1
Flavor: Strong roast 1
153
Flavor: Strong 1
Odor 13 9 18 11 9 3 6
No odor 5 5 3 4 6
Odor: Strong 1
Odor: old 4
Odor: Industrial 1
Not salty 1
Not roasted 2
Bland 7 13 18 8 21 10 26 17 15
Aftertaste 7 10 6 7 3 5 5 5 5
Not sweet 1 1 1
Sweet 2
Woody 2
Smokey burned oils 1
Burnt 1 3 2 1 1
Smokey 2 1
Rancid 1 9 2 1 1
Stale 8 10 5 4 3 1 1 1
Old 3 1
Cardboardy 1 2
Bitter 4 1 2 4 3 2 1 1 2
Oxidized 1 1
Greasy/oily 1 1
Tangy 1
Peanutty 1
Other
Not fresh 1
Dense 1
Earthy 2 3 1
154
APPENDIX L
DEMOGRAPHIC INFORMATION ON HIGH BARRIER BAG CONSUMER PANELS
155
Demographic profile for consumer panels assessing roasted almond samples stored in high
barrier bags
Temperature
(°C)
Consumption
question Daily
Several
times a
week
Several
times a
month
Once a
month
Several
times a
year Never
-------------------------------Frequency %----------------------------
Screen (n=35; 90.6% female; 75.0% 18-27 years)
35 Nuts 12.5 53.1 28.1 3.1 3.1 0
Almonds 6.3 37.5 34.4 15.6 6.3 0
Confirm (n=102; 73.7% female; 80.8% 18-27 years)
35 Nuts 14.4 40.4 33.3 8.1 3.0 1.0
Almonds 3.0 33.3 33.3 16.2 11.1 3.0
Screen (n=36; 75% female; 77.8% 18-27 years)
25 Nuts 16.7 44.4 27.8 0 5.6 5.6
Almonds 2.8 30.6 44.4 13.9 2.8 5.6
Confirm (n=102; 79.2% female; 83.2% 18-27 years)
25 Nuts 13.9 46.5 33.7 5.0 1.0 0
Almonds 4.0 35.6 40.6 12.9 6.9 0
Screen (n=40; 71.8% female; 79.5% 18-27 years)
15 Nuts 10.3 30.8 46.2 7.7 5.1 0
Almonds 2.3 23.1 43.6 20.5 10.3 0
Confirm (n=102; 86.9% female; 84.9% 18-27 years)
15 Nuts 16.3 44.9 26.5 4.1 5.1 3.1
Almonds 2.0 41.4 37.4 8.1 7.1 4.0
Screen (n=35; 90.6% female; 75.0% 18-27 years)
4 Nuts 12.5 53.1 28.1 3.1 3.1 0
Almonds 6.3 37.5 34.4 15.6 6.3 0
Confirm (n=102; 73.7% female; 80.8% 18-27 years)
4 Nuts 14.1 20.4 33.3 8.1 3.0 1.0
Almonds 3.0 33.3 33.3 16.2 11.1 3.0
156
APPENDIX M
WEAK AND STRONG POINTS FROM HIGH BARRIER BAG CONSUMER
PANELS
157
Panelists responses to the open-ended question: Please indicate what in particular you
liked and disliked about this almond sample. Likes presented for samples stored in high
barrier bags
4 °C at 16 mo 15 °C at 16
mo
25 °C at 16
mo
35 °C at 16
mo
Appearance
Appearance 3 1 1
Color 1 3 1
Mouthfeel/texture
Texture 23 30 19 22
Crunchiness 37 37 33 37
Crispness 2 2 2
Smooth 5 2 5 2
Soft 1 3 1 2
Firm 1 1
Dry 1 1
Not too crunchy 1 1
Tough 1
Chewy 1
Not too hard 1
No toothpack 1
Hard 1
Flavor/Taste
Flavor 28 23 29 13
Flavor:
Roast/Toast
1 3
Flavor: almond 5
Flavor: Nutty 1
Taste 18 29 16 9
Taste: Smokey 2
Odor 22 32 24 15
No odor 2
Odor: Roast 4
Odor: Floral 1
Odor: Nutty 1
Roasted 7 4 2
Sweet 8 8 2 3
Nutty 5 10 13
Not burned 1
Buttery 1 1
Salty 1 3 1
Aftertaste 2 2 3 3
Light/not 3
158
offensive
Earthy 1 1 1
Smokey 3 4
Savory 1 1
Mild 2
Other
Fresh 3 1 4
Panelists responses to the open-ended question: Please indicate what in particular you
liked and disliked about this almond sample. Dislikes presented for samples stored in
high barrier bags
4 °C at 16 mo 15 °C at 16
mo
25 °C at 16
mo
35 °C at 16
mo
Appearance
Appearance 1 2
Color 1 1
Pale 1 1
Mouthfeel/texture
Texture 4 4 4 3
Chalkiness 1
Slippery 1
Soft 2 4 3
Dry 6 6 3 6
Rough 1
Grainy/gritty 1 1 1 3
Flakey 1
Crumbly 1 1 2 2
Brittle 1
No crunch 1 1
Mealy 1
Hard to chew 1
Chewy 2 2
Toothpack 1
Hard 2 2
Crispy 1
Squeeky 1
Astringent 1
Flavor/Taste
Taste 3 3 7
Taste: Bland 1
Taste: Strong/off 3
Flavor 3 5 2 10
Flavor: floral 1
Flavor: off 1
159
Flavor: Bland 4
Odor 4 4 7 10
No odor 5
Odor: Bland 1
Odor: off 1
Odor: Musty 1
Not salty 1
Not roasted 1
Over roasted 1
Bland 9 11 12
Sweet 2
Green 1
Bitter 1 4 6
Dirty 1
Aftertaste 2 3 4 5
Less sweet 1
Fishy 1
Stale 1
Burnt 1 3
Rancid 1
Woody 4
Cardboardy 1
Chalky 1