preparation of iron-fortified rice using edible coating materials

Original article

Preparation of iron-fortified rice using edible coating materials

D. Mridula* & Jha Pooja

Food Grains & Oilseeds Processing Division, Central Institute of Post Harvest Engineering and Technology, Ludhiana 141 004, Punjab, India

(Received 9 February 2013; Accepted in revised form 12 July 2013)

Summary Iron-fortified rice premix (IFRP) was prepared using soaking and spraying method followed by coating

with hydroxypropyl methyl cellulose (HPMC), methyl cellulose (MC), combination of HPMC and MC,

zein, palmitic acid (PA) and stearic acid (SA). Steaming caused a reduction in iron content in iron-fortified

rice premix than without steaming treatment. Iron content ranged from 1.33 to 7.11 and 1.61 to

4.49 mg g�1, respectively, in IFRP prepared using soaking and spraying method. Retention of iron in IFRP

samples coated with 9% PA, 7% and 9% SA, and combination of HPMC and MC at 2% level, respec-

tively, after washing twice with distilled water was similar (P > 0.05). Retention of iron in these coated

IFRP ranged from 87.34% to 89.39% (P > 0.05) as compared to 39.12% in uncoated IFRP. Sensory

acceptability indicated the scope for the production of IFRP by spraying of iron solution with iron content

20.1 mg mL�1, 180-min tempering time and coating with 2% HPMC and MC followed by drying.

Keywords Biopolymer coating, ferrous sulphate, fortification, hardness, iron retention, washing losses.

Introduction

India ranks first (about 45 million hectare) in terms ofrice-growing area and second in production next toChina. Rice contributes 43% of total food grain pro-duction and 46% of total cereal production in Indiaand continues to play a vital role in the food grainsupply in India. In Asia, people eat about 150 kgmilled rice annually. However, milling results in theloss of several nutrients that are present in the externallayers of the kernel, contributing to the diminishednutritional quality of white rice (Pedersen & Eggum,1983; Juliano, 1985; Luh, 1991; Dexter, 1998).

Micronutrient malnutrition affects about more thanhalf of the world population, particularly in develop-ing countries. The National Nutrition MonitoringBureau (NNMB) Report of December 2006 indicatedthat the consumption of protective foods such aspulses, green leafy vegetables (GLV), milk and fruitswas grossly inadequate particularly amongst the mostvulnerable population. This report indicated that morethan 70% of preschool children consume <50% RDAof iron, vitamin A and riboflavin. Consequently, theintake of micronutrients such as iron, vitamin A, ribo-flavin and folic acid was far below the recommendedlevels in all the age groups.

Iron fortification of food is considered to be the mostcost-effective (Baltussen et al., 2004), long-term andconvenient approach to provide additional absorbable

iron to populations (Bothwell & McPhail, 1992).Rice represents a perfect food vehicle for fortification,because it is a staple food, cultivated in manycountries, consumed by all population groups (children,elderly, etc.), even by allergic, regardless their income(FAO, 1997; Johnson, 1994; Dexter, 1998). Increasingiron concentration in rice grain is expected to enhanceiron intake by rice consumers and decrease the incidenceof iron deficiency anaemia.Generally two methods of rice fortification are con-

sidered: (i) fortification of intact grains and (ii) fortifi-cation of reconstituted grains through extrusion(Misaki & Yasumatsu, 1985; FAO, 1997; Dexter,1998). In the intact grain method, the nutrients areapplied externally or mixed with rice kernels, while inthe later method, fortificants are added in the riceflour followed by extrusion resulting in fortified prod-uct similar to rice in shape and size. Fortification isusually applied to a limited amount of kernels, whichafterwards are mixed with the normal rice at a desiredratio. As compared to uncoated fortified rice, coatingof fortified rice by edible coating materials may facili-tate enhancing the retention of micronutrients andreducing their leaching losses during washing andcooking as observed in many studies (Cort et al., 1976;Peil et al., 1982; de Ambrosis, 2006). The water-insolu-ble coating materials and polymers have been reportedinclude ethanol or isopropanol solution of zein, pal-mitic or stearic acid and abietic acid (FAO, 1997). Otherreported coating materials are ethyl cellulose (EC), hy-droxypropyl methylcellulose, methylcellulose, pectin,*Correspondent: Fax: +91 161 2308670; e-mail: [email protected]

International Journal of Food Science and Technology 2013

doi:10.1111/ijfs.12305

© 2013 The Authors. International Journal of Food Science and Technology © 2013 Institute of Food Science and Technology

1

methylcellulose (MC) and hydroxypropyl methylcellu-lose (HPMC), locust bean gum (LBG), gum tragacanth,carrageenan, gum guar and low methoxyl pectin, carb-oxymethyl cellulose (CMC), sodium alginate and gumarabic (Shrestha et al., 2003). They may dissolve at theelevated temperatures employed during cooking (Bau-ernfeind & deRitter, 1991) but reduce the losses duringwashing, if practiced before cooking (Peil et al., 1982). Inview of this, the present study was carried out to developiron-fortified rice premix using soaking and sprayingmethod and polymer coatings.

Materials and methods

Preparation of fortified rice

Milled rice, commonly known as pauna rice, procuredfrom the local supplier, Ludhiana, Punjab, was usedfor the preparation of iron-fortified rice. Bio-availableforms of iron compounds recommended for rice fortifi-cation include ferrous citrate, ferrous lactate, ferroussulphate, ferrous pyrophosphate, electrolytic iron,ferrous fumurate and sodium iron EDTA (Flynn &Cashman, 1999; Hurrell, 1999, 2002; Swain et al., 2003;Allen et al., 2006; National Institute of Nutrition,2011). Ferrous sulphate (procured from SD Fine ChemLtd, Mumbai, India), due to good bioavailability, lowcost and good amount of iron content (Flynn & Cash-man, 1999; Hurrell, 1999, 2002; Swain et al., 2003), wasused as a source of iron for the fortification of rice inthe present study. Iron-fortified rice was prepared fol-lowing two methods, that is, soaking and sprayingmethod.

In soaking method, rice (sample size 250 g) wassoaked in iron solution with different levels of iron con-tent (12.06, 16.08 and 20.1 mg mL�1) for three differentsoaking duration, that is, 60, 90 and 120 min. The ratioof rice and iron solution was 1:1.5. Iron solution wasprepared using glass-distilled water with pH 6.9. Duringsoaking, rice samples were kept at 30 °C in an orbitalshaking incubator and agitated for 1 min at 130 rpm atan interval of 15 min. After soaking for a desired per-iod, iron solution was drained using a muslin cloth fol-lowed by steaming at 5 psi (0.409 kgf cm�2) for 5 minusing an autoclave. Control samples, that is, sampleswithout steaming, were also prepared in the similarmanner. Both the samples with and without steamingwere spread evenly in a tray lined with butter paper andkept for drying using a tray dryer at 40 °C to reduce themoisture content up to desired level (8–9%, w.b.).

In spraying method, the prepared iron solution(12.06, 16.08 and 20.1 mg mL�1) was added to rice (atthe rate of 30 mL 100 g�1 of rice) using a sprayer.While spraying, rice samples (sample size 250 g) werealso thoroughly mixed so that iron solution could besprayed on each and every rice kernel. After complet-

ing the spraying, rice samples were kept at 30 °C fortempering purposes at three different tempering dura-tions, that is, 120, 150 and 180 min. Tempered ricesamples were then steamed at 5 psi (0.409 kgf cm�2)for 5 min using a laboratory autoclave. Control iron-fortified sample, that is, sample without steaming, wasalso prepared in the similar manner. Both type of sam-ples, that is, rice samples with and without steaming,were spread evenly in a tray, lined with butter paperand kept for drying using a tray dryer at 40 °C toreduce the moisture content up to desired level.

Coating of iron-fortified rice with edible coating materialsTo reduce the washing losses, iron-fortified rice sam-ples were coated with different biopolymers, namelyhydroxypropyl methyl cellulose (HPMC), methyl cellu-lose (MC), combination of HPMC and MC (3:1) andzein (corn protein), and two fatty acids, namely pal-mitic acid (PA) and stearic acid (SA). Iron-fortifiedrice prepared using iron solution having 20.1 mg ironper mL, spraying method and 180-min tempering time,without steaming, showed the desired iron content;hence, these conditions were followed for further studyto find out the suitable coating material to reduce theleaching losses during washing if practiced beforecooking. To coat the iron-fortified rice with differentcoating material, HPMC (1%, 1.5% and 2%), MC(1%, 1.5% and 2%), zein (5%, 7% and 9%), PA andSA were dissolved in hot water (90 °C), cold water,ethanol (80%) and absolute ethanol, respectively.Combination of HPMC and MC was prepared bytaking HPMC and MC solutions of different concentra-tion and then mixing in the ratio of 3:1. For makingcoated iron-fortified rice premix, desired amount of ironsolution was sprayed on rice, tempered for 180 min andthen partially dried at 40 °C for 1 h to reduce the sur-face moisture. Thereafter, coating solution was sprayedon iron-fortified rice with gentle mixing followed bydrying using a tray dryer in two steps: first at 70 °C for1 h followed by 40 °C for 4–5 h to achieve the desiredmoisture content (Kyritsi et al., 2011).

Quality evaluation of iron-fortified rice premix

Moisture and iron contentMoisture content and iron content in fortified rice pre-mix samples were determined as per AOAC (2000).

Textural propertiesThe textural properties, that is, hardness and tough-ness of the uncooked unfortified and iron-fortified ricepremix, were measured using a Texture Analyzer(TA-Hdi, Stable Micro system, Surrey, UK; equippedwith a 500-N load cell; graph recorder). TA settings werepretest and post-test speed 2 mm s�1, test speed1 mm s�1, distance 0.4 mm and SMS P/5 probe. The

© 2013 The Authors

International Journal of Food Science and Technology © 2013 Institute of Food Science and Technology


Iron fortified rice D. Mridula and J. Pooja2

peak force from the resulting curve was considered ashardness (N), and the area under the peak force onthe graph was considered as toughness (Nmm).

Instrumental colour analysisColour (L, a and b) of iron-fortified rice premix sampleswas measured using Hunter Lab (Hunter Associateslaboratory Inc., Reston, VA, USA) colorimeter (modelno. 45/0L, made in USA). The L value represents thelightness of the product colour from 100 for perfectwhite to 0 for black. The redness/greenness and yellow-ness/blueness are denoted by the ‘a’ and ‘b’ values,respectively. ho (hue angle) and C* (chroma) were com-puted using the following formula.

h� ¼ tan�1ðb=aÞ C� ¼ ½a2 þ b2�1=2,where b = measured b values, a = measured a values

Determining washing lossesIron-fortified rice premix samples were washed as sug-gested by Shrestha et al. (2003) with little variation.For single washing, 20 g of iron-fortified rice premixwas taken in a 200-mL beaker. With this rice premix,1.5 times, that is, 30 mL, of distilled water was addedand swirled for 5 s. For double washing, premix waswashed as in the case of single washing followed byrepeated washing in the same manner using the sameamount of distilled water. The rice premix sampleswere then dried in hot air oven at 40 °C to reduce themoisture content before analysing the iron content inthem.

Sensory characteristics

Eating quality of rice largely depends on the texture ofcooked rice, which is determined by the degree ofcooking and the rice–water ratio (Juliano, 1985). Ricewas cooked in a covered boiling pan for a desired per-iod, using four different ratios of rice and water (1:1.5,1:2, 1:2.5 and 1:3). Based on the eating quality, theoptimum water-to-rice ratio was found as 1:2.5.

Sensory characteristics like appearance and colour,sensory texture, odour, flavour and taste and overallacceptability for all the cooked iron-fortified rice sampleswere assessed using nine-point hedonic scale, with ninefor like extremely and one for dislike extremely (Lawless& Heymann, 1998). For sensory evaluation, iron-forti-fied rice was prepared by mixing coated iron-fortified ricepremix sample with unfortified milled rice at the ratio of1:100, as suggested by National Institute of cooked iron-fortified rice (about 40 °C) was carried out by a group offifteen researchers. The staple diet of most of the panel-lists was rice. Water was provided for mouth rinsing aftertasting the cooked rice to avoid the carryover effect ofthe aftertaste.

Statistical analysis

Data pertaining to all the parameters of the presentstudy were calculated for mean values using MS Excel2003. ANOVA and least significant difference (LSD) werecomputed using AgRes statistical software (1994;version 7.01; Pascal International Software Solution,Boston, MA, USA).

Results and Discussion

Physical properties of dried iron-fortified rice premix

The colour quality of iron-fortified rice premix is givenin Table S1. L (32.03 � 2.74 to 41.88 � 0.79) and bvalues (10.84 � 0.42 to 12.88 � 0.27) of iron-fortifiedrice premix prepared using soaking method were sig-nificantly affected with iron content in soaking solu-tion, soaking time and steaming, while a values(6.45 � 0.31 to 7.41 � 0.17) were affected only withiron content in soaking solution and soaking time(P < 0.05). L, a and b values of iron-fortified rice pre-pared using spraying method varied from 32.45 � 2.74to 39.31 � 0.68, 6.73 � 0.27 to 8.30 � 0.50 and10.92 � 0.69 to 13.01 � 0.42, respectively, which weresignificantly influenced by steaming treatment. Due tovariation in the L, a and b values of different iron-fortified rice premix samples, prepared using soakingand spraying methods, hue and chroma changedaccordingly (P < 0.05). Although hue of iron-fortifiedrice premix was influenced by the level of iron in thesoaking and spraying solutions and soaking or temper-ing time, three-factor ANOVA results indicated no com-bined impact of these factors on hue values. L, a, b,hue and chroma values of unfortified rice were71.02 � 0.48, 2.66 � 0.08, 14.48 � 0.13, 79.59 � 0.22and 14.72 � 0.14, respectively. As compared to unfor-tified rice, the colour of iron-fortified rice premixturned reddish brown due to lower L and b and highera values. Steaming resulted significantly higher avalues of iron fortified rice premix prepared usingspraying method, may be due to the gelatinizationeffect of steaming under pressure that ultimatelyresulted in darker grain. Kyritsi, Tzia & Karathanos(2011) also observed the significant higher colour dif-ference (based on unfortified rice) for white and par-boiled rice after vitamin fortification.The effect of steaming on hardness and toughness of

iron-fortified rice premix is given in Table S2. Hardnessand toughness of iron-fortified rice premix, preparedusing soaking or spraying method, were affected due tosteaming (P < 0.05), but three-factor ANOVA resultsindicated no combined impact of level of iron contentin soaking/spraying solutions, soaking/tempering timeand steaming treatment. Mean comparison by LSDshowed that steaming resulted in harder texture of

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Iron fortified rice D. Mridula and J. Pooja 3

dried iron-fortified rice premix prepared using sprayingas well as soaking method (Table S2). Partial gelatini-sation of rice starch due to steaming treatment mightbe a reason for increased hardness of dried iron-forti-fied rice premix, prepared using both the studied meth-ods of fortification. The magnitude of enhancement inthe hardness of rice premix due to steaming rangedfrom 6.19% to 14.77% in iron-fortified rice premix pre-pared using soaking method, while it was 6.93% to17.60% in rice premix prepared using spraying method.No specific pattern of increment of hardness of iron-fortified rice premix was observed after steaming, maybedue to heterogeneous nature of the samples.

Effect of preparation method on iron content in ricepremix

Moisture content of iron-fortified rice premix, preparedusing fortificant solution having 12.06, 16.08 and20.1 mg mL�1 iron, was 9.08–9.04%, 8.44–8.75%and 7.82–8.83% (w.b.), respectively. Effect of soakingand spraying methods and tempering time on ironcontent is shown in Fig. 1(a–d). Soaking methodresulted in 133.39 � 4.76 to 710.65 � 9.32 and126.03 � 4.49 to 417.15 � 3.75 mg of iron content per100 g of iron-fortified rice premix prepared followingwithout and with steaming, respectively. Iron contentin iron-fortified rice premix, prepared using with andwithout steaming treatment and spraying method, var-

ied from 161.48 � 8.24 to 410.47 � 5.08 and 188.87� 8.98 to 448.74 � 5.87 mg 100 g�1 rice premix,respectively. Iron content increased significantly withincreasing level of iron content in soaking or sprayingsolution, soaking or tempering time, which was obvi-ous (P < 0.05). Although steaming resulted in hardertexture of rice premix, which is desirable to preventfrom breakage during mixing with unfortified rice,steaming lowered the iron content in the rice premix(P < 0.01), which is quite undesirable. The magnitudeof reduction in the iron content due to steaming variedfrom 5.51% to 41.30% in iron-fortified rice premixprepared using soaking method, while it was 5.52% to19.98% in rice premix prepared using sprayingmethod. In general, reduction in iron content due tosteaming was higher at increased soaking period andalso at higher concentration of iron in fortificant solu-tion. But in case of spraying method, no specific trendwas observed in the reduction in iron content in ricepremix due to steaming. Reduction in iron contentfrom iron-fortified rice premix after steaming may bedue to loss of added iron, available at the surface ofthe rice kernel by way of leaching with the steamvapours. Soaking method resulted in higher iron con-tent in the iron-fortified rice premix than sprayingmethod. This may be possibly due to the fact thatsoaking method maximised the diffusion of iron solu-tion towards the centre core of rice kernel than spray-ing method. Although soaking method resulted in

(without steaming)

0100200300400500600700800

Iron content in soaking solution, mg/mL

Iron

con

tent

in ri

ce p

rem

ixm

g/10

0 g

ST, 1 h ST, 1.5 h ST, 2 h

(without steaming)

0

100

200

300

400

500

Iron content in spraying solution, mg/mL

Iron

con

tent

in ri

ce p

rem

ixm

g/10

0 g

TT, 2 h TT, 2.5 h TT 3 h

(with steaming)

050

100150200250300350400450

Iron content in spraying solution, mg/mL

Iron

con

tent

in ri

ce p

rem

ixm

g/10

0 g

TT, 2 h TT, 2.5 h TT, 3 h

(with steaming)

050

100150200250300350400450

12.06 16.08 20.1

12.06 16.08 20.1 12.06 16.08 20.1

12.06 16.08 20.1Iron content in soaking solution, mg/mL

Iron

con

tent

in ri

ce p

rem

ixm

g/10

0 g

ST, 1 h ST, 1.5 h ST, 2 h(a) (b)

(c) (d)

Figure 1 Effect of Soaking (a, b) and spraying method (c, d) on iron content in dried iron fortified rice premix (n = 6).

© 2013 The Authors




higher iron content in premix, spraying method maybeeconomical over soaking method. Moreover, thismethod would also be technically feasible to produceiron-fortified rice premix, which would meet the needof the target consumer in terms of quality and expecta-tions of suggested level of 43 mg kg�1 fortified rice(NIN, 2011). Kyritsi et al. (2011) also recommendedthe spraying method for the preparation of vitaminfortified rice due to being a physical process and easilyapplicable in a conventional rice mill plant.

Physical properties of iron-fortified rice premix preparedusing coating materials

Moisture content of different biopolymer- and fattyacid-coated iron-fortified rice premix samples was8.24 � 0.69–8.56 � 0.44% (w.b.) (P > 0.05). Colourquality of biopolymer- and fatty acid-coated iron-forti-fied rice premix was found dependent on the type ofcoating material as well as their level in coating solu-tion. None of the studied coating solutions were foundsuitable for masking the reddish brown colour of theiron-fortified rice. L (34.38 � 1.66–48.89 � 0.71) anda values (6.01 � 0.29–9.37 � 0.61) were affected bythe type of coating material, but b values (2.27� 0.09–2.75 � 0.75) were influenced by both parame-ters, that is, type of coating material and concentrationof coating material. Mean comparison by LSD resultsshowed that coating of iron-fortified rice premix withMC, HPMC and combination of HPMC and MCresulted in higher a and b values, while L values ofthese premix samples were lower, which ultimatelyindicated the lower hue and higher chroma values ofthese samples (Table S3).

Coating materials also brought a significant impacton hardness and toughness of iron-fortified rice pre-mix. Hardness of different iron-fortified rice premixcoated with MC was found maximum followed byHPMC- and MC-, and zein-coated premix samples.Hardness was increased with increasing concentrationof coating material in coating solution. This might bedue to thick layer of coating material on the surface ofdried rice premix, which was found beneficial in reduc-ing the washing losses, thus enhancing the retentionduring washing. Similarly, toughness of differentcoated iron-fortified rice premix samples was alsochanged accordingly (Table 1).

Effect of coating on iron retention after washing

Iron content in different biopolymer- and fatty acid-coated iron-fortified rice premix samples was 471.79�8.86–494.52 � 6.13 mg 100 g�1 (w.b.). Effect ofwashingof coated iron-fortified rice premix in distilled water (pH6.9) on retention of iron content is given in Fig. 2. Ironcontent in different biopolymer- and fatty acid-coated

iron-fortified rice premix samples after single and doublewashing varied from 335.32 � 7.35 to 462.65� 5.70 mg and 300.62 � 6.60 to 420.67 � 4.55 mg100 g�1, respectively. Iron retention during washing wasfound dependent on the type of coating material, theirconcentration in coating solution and number of wash-ing. Iron retention in different washed, coated iron-forti-fied rice premix samples after single and double washing(with respect to iron content in unwashed sample) rangedfrom 70.65 � 0.47% to 92.54 � 1.44% and 63.91� 0.66% to 89.39 � 1.12%, respectively, while that of inuncoated iron-fortified rice premix was only 65.12% and39.12%, respectively. This showed that coating of iron-fortified rice premix samples with studied coating mate-rial was quite effective in reducing the leaching losses ofiron during washing. Mean comparison by LSD resultsindicated the maximum iron retention after double wash-ing in iron-fortified rice premix coated with SA.Although iron retention after double washing was maxi-mum (89.39%) in iron-fortified rice premix coated withPA at 9% level in coating solution, the premix samplescoated with PA at 9%, SA at 7% and 9%, and combina-tion of HPMC and MC at 2% level in coating solutionwere found statistically similar. Iron retention in thesecoated iron rice premix samples was 87.34–89.39% after

Table 1 Effect of coating material on textural properties of dried

iron-fortified rice premix

Coating solution

Hardness, N

Toughness,

Nmm

Coating

material Concentration,%

MC 1.0 114.01 � 3.90g 17.45 � 0.43bcd

1.5 118.83 � 4.28d 17.79 � 0.42bc

2.0 122.79 � 2.88bc 17.96 � 0.35b

HPMC 1.0 99.74 � 3.32j 16.52 � 0.25gh

1.5 108.52 � 4.38h 16.89 � 0.32efgh

2.0 119.06 � 3.45d 17.31 � 0.33cde

Combination

of HPMC

and MC

1.0 109.93 � 3.42h 15.85 � 0.38i

1.5 114.72 � 4.18fg 16.39 � 0.51i

2.0 119.06 � 3.45a 17.31 � 0.33defgh

Zein 5 105.60 � 4.01i 16.69 � 0.54fgh

7 118.33 � 5.36de 17.26 � 0.23cde

9 124.93 � 5.07ab 19.12 � 0.74a

PA

5 102.35 � 7.69j 17.17 � 2.93def

7 116.00 � 6.68efg 17.37 � 0.74cde

9 126.93 � 5.07a 17.42 � 0.74bcde

SA

5 101.97 � 7.69j 16.92 � 2.93defgh

7 117.12 � 6.68def 17.12 � 0.74def

9 121.92 � 7.20c 17.32 � 0.74cde

F value E 36.21** 18.55**

C 544.28** 32.45**

E 9 C 11.04** 4.66**

**P < 0.01; E, edible coating material; C, concentration in coating

solution; E 9 C-interaction effect of E and C; all values are mean of 30.

Values with different lowercase letters are statistically differ at

P < 0.05.

© 2013 The Authors




double washing (P < 0.05). Peil et al. (1982) alsoobserved the maximum retention of micronutrients (vita-min and minerals) in rice premix coated with combina-tion of HPMC and MC (3:1) and reported 100% ironretention in the rice, cooked in excess water and whichwas drained after cooking.

Sensory characteristics of cooked iron-fortified rice

Iron fortification resulted in dried iron-fortified ricegrains similar to normal unfortified rice in terms ofshape and size although of reddish brown colour andwith hard texture. Sensory characteristics of cookedrice are very important for consumer acceptance, mar-ketability and thus profitability of fortified rice. Sen-sory characteristics of iron-fortified rice, evaluated incooked form, are given in Table S4. Iron-fortifiedcooked rice samples, prepared using coated iron-forti-fied rice premix, were of good sensory acceptabilitywith overall acceptability scores 7.50–7.93, that is, inthe hedonic category of liked very much. During cook-ing, the reddish brown iron-fortified rice premix kernelturned orange yellow, which was quite visible but it didnot diminish the appearance of cooked fortified rice asindicated by good sensory scores. The ratio of iron-for-tified rice premix, mixed with the main batch of whiterice, was 1:100, which seems towards lower side todiminish the aesthetic value of the cooked fortified rice.This may be a reason for good overall sensory accept-ability of cooked fortified rice. Results indicated no sig-nificant variation in the different sensory characteristicsof cooked iron-fortified rice due to type of coatingmaterial. But the scores of fortified rice for different

sensory characteristics were lower than the cookedunfortified rice (P < 0.05). Panellist indicated that ifthey had evaluated the iron-fortified cooked rice sam-ples without tasting the unfortified cooked rice, theywould score them better. During sensory evaluation,panellists reported a slight bitter flavour of cookediron-fortified rice coated with zein, PA and SA at 9%level in coating solution. This indicated that instead ofhigher iron retention of PA- and SA-coated samplesafter washing twice with distilled water, this coatingmay not be feasible for its application at commercialscale and from marketability and thus profitabilitypoint of views. Sensory scores more than seven for dif-ferent sensory characteristics of iron-fortified cookedrice samples, prepared using iron-fortified rice premixcoated with HPMC and MC (3:1; 2% in coating solu-tion), indicated the scope for large-scale production ofcoated iron-fortified rice premix for nutritional benefitof the consumers and thus enhancing the iron intakeamongst the vulnerable population.

Conclusions

Iron-fortified rice premix prepared using spraying andsoaking method, and coating materials resulted in ricegrains of similar in shape and size but of reddish brownin colour. Iron content in dried iron-fortified rice pre-mix increased with increasing level of iron content inthe solution and soaking or tempering time. Althoughsteaming resulted in harder texture of dried iron-forti-fied rice premix, prepared using spraying method, itcaused a reduction in the iron content. Soaking methodproduced the rice premix with higher iron content, but

0

20

40

60

80

100

120M

C-1

MC

-1.5

MC

-2

HPM

C-1

HPM

C-1

.5

HPM

C-2

HPM

C+M

C-1

HPM

C+M

C-1

.5

HPM

C+M

C-2

Zein

-5

Zein

-7

Zein

-9

PA-5

PA-7

PA-9

SA-5

SA-7

SA-9

Coating material, % in coating solution

Ret

entio

n of

iron

in ri

ce p

rem

ix %

Iron retention after first washing Iron retention after second washing

Figure 2 Effect of washing on retention of

iron content in rice premix (n = 3).

© 2013 The Authors




spraying method may be environment friendly and alsoeconomical. Hence, spraying method may be consid-ered for production of iron-fortified rice premix. Theproperties of coated iron-fortified rice premix exhibitedvarying colour, textural properties and washing lossesof iron. Coating of iron-fortified rice premix with dif-ferent coating material was found affective in reducingthe leaching losses of iron in washing water. Iron-forti-fied rice premix samples, coated with PA at 9%, SA at7% and 9%, and combination of HPMC and MC at2% level retained more (87.34–89.39% iron) iron afterwashing twice with distilled water. Iron-fortifiedcooked rice samples, prepared using coated iron-forti-fied rice premix, were well accepted with overall accept-ability scores 7.50–7.93. Although washing losses werelowest in PA-coated rice premix due to good sensoryacceptability of HPMC- and MC-coated rice premix,spraying of solution having iron content as20.1 mg mL�1, 180-min tempering time and coatingwith HPMC and MC (3:1; 2% in coating solution) fol-lowed by drying may be considered for production ofiron-fortified rice premix to enhance the iron intakeamongst rice consumers and reducing the incidence ofiron deficiency anaemia.

Acknowledgments

Authors express sincere thanks to Director, CIPHET,for providing different facilities for conducting thisstudy under the Institute Research Project No. 158.

References

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Supporting Information

Additional Supporting Information may be found inthe online version of this article:Table S1. Effect of steaming on instrumental colour

quality of dried iron-fortified rice premix.Table S2. Effect of steaming on textural properties

of dried iron-fortified rice premix.Table S3. Effect of coating material on colour qual-

ity of dried iron-fortified rice premix.Table S4. Effect of edible material coating on sen-

sory characteristics of cooked iron-fortified rice.

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preparation of iron-fortified rice using edible coating materials

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