IMPROVED CORN AND MILLET BASED WEANING FOODS: FORMULATION, VISCOSITY, AND NUTRITIONAL AND MICROBIAL QUALITY

IMPROVED CORN AND MILLET BASED WEANING FOODS: FORMULATION, VISCOSITY, AND NUTRITIONAL AND

MICROBIAL QUALITY

DOROTHY M. GIMBI

Department of Food Science and Technology Sokoine University of Agriculture

P. 0. Box 3045, Morogoro, Tanzania

DAVID KAMAU

Coca-Cola Northern Africa

P. 0. Box 30134, Nairobi, Kenya

AND

AUREA M. ALMAZAN'

George Washington Carver Agricultural Experiment Station College of Agricultural, Environmental and Natural Sciences

Tuskegee University Tuskegee, AL 36088

ABSTRACT

In Tanzania, germinated cerealflour is added to weaning foods consisting of ungerminated cereal or root crop flour and sometimes legumes to reduce bulk and viscosity, and increase nutrient density. However, there is no standard pro- cedure for germinated cereal flour preparation and addition to gruels. This study was conducted to improve the chemical, physical and microbiological quality of millet and corn gruels based on protein and energy requirements for infants. Ger- minated millet flour (GMF) was more eficient than germinated cornflour in reducing gruel viscosity to < 3 Pascal s in 5 min. Washing before germination did not significantly reduce the microbial levels in GMF. Formulations consisting of millet, corn or combinations with soybean or peanut at a cereal: legume ratio of 7:3, and GMF were prepared by traditional and improved methods, In the lat-

'Author to whom correspondence should be addressed.

Journal of Food Processing and Preservation 21 (1997) 507-524. All Rights Reserved 0 Copyright 1997 by Food & Nutrition Press, Inc., Trumbull, Connecticut. 507

508 D.M. GIMBI, D . KAMAU and A.M. ALMAZAN

ter, pasteurization for 10 min at 95C reduced bacteria, yeast and mold counts to undetectable levels even after 6 duys storage at 20.5C. Without pasteurization, the gruels had > 9 log CFU/mL within 24 h. Corn and millet gruelsfor- tijied with peanut or soybean can supply the RDA for protein but not the RDA for energy if children aged 6 months to 2 years are fed three servings only daily.

INTRODUCTION

In developing countries, children aged 4 months to 2.5 years usually suffer from protein energy malnutrition while being weaned, partly due to insufficient consumption of microbiologically safe and high nutrient density weaning foods (Gordon et al. 1967; UNICEF 1987). Gruels or porridge prepared with cereals or root crops, sometimes supplemented with legumes, must be diluted to attain viscosities < 3.0 Pascal s, the consistency suitable for feeding children younger than 3 years (Kanashiro et al. 1991; Kingamkono et al. 1984; Martines et al. 1994). Dilution decreased nutrient density and increased the necessary bulk or volume intake to meet recommended dietary allowances (RDA) for protein and energy (FNJ3 1989). The use of germinated cereals and legumes only, or addition of germinated cereal flour to the gruel before or after cooking reduced viscosity to acceptable levels because of their amylolytic activities. Energy and nutrient density either increased or were minimally affected (Gahlawat and Sehgal 1992; Hansen et al. 1989; Karlsson et al. 1982; Kibona et al. 1995; Marero et al. 1988a,b, 1990; Mosha and Svanberg 1983). Depending on the preparation method for the germinated flour, the gruel may be contaminated with spoilage and pathogenic microorganisms at a level that can cause health problems such as diarrhea.

This study was conducted to improve the chemical, physical and microbiological quality of corn and millet based weaning foods supplemented with soybean or peanut to meet the infant protein and energy requirements. Germination times that produced the highest amylolytic activities in the cereals, and microorganism levels during preparation of the more efficient germinated millet flour (GMF) were monitored to standardize GMF preparation. Viscosity, nutrient composition, and bacteria, mold and yeast counts of the gruels prepared by the traditional and improved methods were compared.

MATERIALS AND METHODS Materials

White corn and dried shelled peanuts were purchased from a seed and a grocery store, respectively, in Tuskegee, Alabama. Pearl millet (variety HGM-100) was

CORN AND MILLET BASED WE4NING FOODS 509

obtained from Forage and Turf Research Unit, Agricultural Research Service, USDA, Tifton, Georgia. Defatted soybean flour was manufactured by Cargill, Inc. (Minneapolis, Minnesota) and had minimum concentrations of 50% crude protein, 0.5% crude fat and 3.5% crude fiber.

To prepare the ungerminated corn or millet flour, the seeds were washed, oven dried at 55-60C for 3 h, cooled and milled using a Cross Beater Mill with a screen diameter of 0.5 mm. Each flour sample was stored in a sealed polyethylene bag (0.1 mm thick) at 2 4 C . The dried shelled peanuts were dehulled, then ground to a paste using a blender and a rolling pin.

Preparation of Germinated Corn and Millet Flour

Tanzanian traditional germination techniques were adapted to laboratory con- ditions, Corn or millet (1.5 kg) was winnowed to remove fluffs, washed, and soaked in 4 L tap water in the dark for 12 h at 2 1-24C. After draining, the grains were spread between wet cotton cloths and allowed to germinate for 24,48,72, and 96 h. Millet started sprouting after 18 h while corn began germinating after 30 h. After each germination period, 300 g sprouted seeds were oven dried at 55-60C for 10-12 h, cooled, and milled using a Cross Beater Mill with a screen diameter of 0.5 mm. Each flour sample was stored in a sealed polyethylene bag at 2 4 C . Moisture content of germinated flour ranged from 7.0 to 8.1 %.

Amylolytic Activity of Germinated Millet and Corn Flour

The amylolytic activity of germinated corn (GCF) and millet flour (GMF) was indirectly determined by measuring the viscosity of the gruels before and after its addition. Flowwater (weightlweight) ratio was 1 5 for millet and 1.5: 10 for corn. The ratio for corn was lowered to obtain a gruel with an initial viscosity that can be measured by the Brookfield viscometer. Each gruel was prepared by mixing ungerminated flour with cold deionized water in a beaker, and cooking on a hot plate with intermittent stirring until the temperature reached 95C. It was transferred into a hot water bath (95-97C) and cooked with stirring for 15 min more. After cooling to 40C, the initial viscosity was measured with a Brookfield viscometer Model LVTDV-I with spindle number 4 (for thick fluid) at a shear rate of 6 rpm. GCF (10% of total flour) was added to corn gruel while the same amount of GMF was used for millet gruel. Viscosity was measured again after 5 min. There were three replicates for each gruel type.

Time for Viscosity Reduction by GMF

Only GMF was used to determine the minimum time required to reduce gruel viscosity to < 3.0 Pascal s because preliminary experiments showed that GCF’s

510 D.M. GIMBI, D. KAMAU and A.M. ALMAZAN

amylolytic activity was already very low after three weeks storage even at 2 4 2 . GMF concentration was reduced from 10% to 5% of total flour because the lesser amount was sufficient to reduce viscosity to < 3.0 Pascal s in 5 min. Three replicates each of formulations consisting of millet, corn, or combinations with soybean or peanut at a cerea1:legume (weight/weight) ratio of 7:3 and at 95% of total flour were tested.

The flowwater ratio of 1:5 for millet gruel and 1.5:lO for corn gruel were maintained. Gruels were prepared as above, and viscosity was measured at one min interval from 3 to 7 min after addition of GMF. For the millet gruel, 20.0 g millet flour, 100 mL water and 1.05 g GMF were used. For the corn gruel, 15 g corn flour, 100 mL water and 0.79 g GMF were used.

Microbiological Quality of GMF

Water is not readily available in some rural areas in Tanzania especially during the dry season. Thus, the effect of washing millet before germination on the microbial levels in GMF was determined. Millet was either washed or not washed prior to germination. In the prewashed batch, the grains were washed with tap water at least four times until the water was colorless. Three replicates each of prewashed and unwashed millet were soaked, germinated for 72 h, dried and milled as described above. GMF were divided into two groups with one set stored at 19-22C and the second set stored at 2 4 2 .

Microbiological assays for total bacteria, yeast and mold counts were done after each step in the preparation and after two weeks storage of GMF. Samples (10 g) were placed in sterile sample bags (0.1 mm thick) and rinsed with 90 mL 1 % sterile peptone by shaking. An aliquot of the peptone rinse (1 mL) was serially diluted with 9 mL sterile peptone to obtain less than 300 colony forming units (CFU) per plate. Standard methods for aerobic plate count (APC) on agar, and for yeast and mold counts (YM) on acidified potato dextrose agar (pH 3.5) were used (FDA 1992). The plated petri dishes were incubated at 34-36C for 48 h for bacteria and at 20-22C for five days for yeast and molds, and the colonies were counted using a Quebec colony counter.

Amylolytic Activity of GMF

The amylolytic activities of unwashed and prewashed GMF after storage at room or cold temperature were monitored at weekly intervals for one month. Corn and millet gruels were prepared, and viscosity was measured before and 5 min after addition of GMF as above.

CORN AND MILLET BASED WEANING FOODS 511

Pasteurization of and Inactivation of Amylolytic Activity in Gruels

The gruel preparation method used in the above experiments were based on the traditional method. As an improvement, a pasteurization step after viscosity reduction by GMF was added to inactivate the starch hydrolytic enzymes and to eliminate or minimize contaminating microorganisms. Five min after addition of GMF, the gruel was rapidly reheated in a water bath at 95-97C for 10 min. It took about 7 min for the gruel to reach 95C. The gruels were cooled to 40C, and viscosity and microbial counts were determined.

Comparison of Traditional and Improved Gruel Formulations

Gruels consisting of millet, corn, or combinations with soybean or peanut at a cerea1:legume (weight/weight) ratio of 7:3 and GMF were prepared in the traditional way as described above, packed in sterile bags and stored at ambient temperature. Microbiological and viscosity changes were monitored every 6 h for 24 h. Only combinations of millet or corn with soybean or peanut were used to prepare gruels by the modified method which included a pasteurization step. Likewise, the improved gruels were packed immediately in sterile plastic bags and stored at room temperature. Changes in microbiological counts and viscosity were monitored every 24 h for 6 days.

Nutrient Analyses of Gruels

Gruels prepared by the traditional method were analyzed before and after storage for 24 h while those prepared by the modified method were analyzed before and after storage for six days using standard procedures (AOAC 1990). Moisture content was determined by drying 5 g gruel at lOlC for 12 h. Total nitrogen was determined by digesting 0.05 g oven dried gruel in a Tecator Digestion System, distilling the digest in a Kjeltec 1002 distilling unit (Tecator AB, Hogans, Sweden) and titrating the distilate with standardized 0.02N HC1. Crude protein was obtained by multiplying Kjeldahl nitrogen by 6.25. Fat was extracted with petroleum ether using the Soxhlet method (AOAC 963.15). To determine ash content, 10 g gruel were dried in the crucible at lOlC to 12 to 15% moisture to prevent spat- tering, then ashed at 550C for at least 10 h until white or light gray in color (AOAC 942.05). Total solid concentration was obtained by subtracting % moisture from 100. Carbohydrate content was calculated as the difference between % total solid and the sum of % protein, % fat and % ash.


Statistical Analysis

There were three replicates each for viscosity, microbiological count and nutrient concentration determinations. Means and standard errors of means (SE) were determined by StatView 4.01 (Abacus Concepts, Inc., Berkeley, CA). Means were compared by analysis of variance (ANOVA) and tested by Fisher’s p r e tected least significant difference (PLSD) at 5 % level, or by unpaired comparison and t-test at 5% significant level.

Computation of Gruel Volume that Meets 1/3 RDA

The volume of gruel that should be fed to infants and children younger than 3 years to reduce or prevent protein energy malnutrition was calculated based on the RDA for protein and energy (FNB 1989) and on the fact that children are generally fed three meals per day in Tanzania (Machunda 1990). For infants, 1/3 RDA for protein is 4.67 g and for energy is 1185.3 KJ (283.3 Kcal). For children aged 1-3 years, 1 /3 RDA for protein is 5.33 g and for energy is 18 13 .O KJ (433.3 Kcal). It was assumed that gruel volume is the same as the volume of water used, yielding densities of 1.16 g/mL for corn based gruels and 1.21 g/mL for millet based gruels. Gruel energy densities were estimated by multiplying carbohydrate, protein and fat concentrations by 17, 17 and 38 KJ/g (Brody 1994). Protein and energy values used were those of stored corn and millet gruels prepared using the traditional method, and those of the stored supplemented gruels prepared using the modified method.

RESULTS AND DISCUSSION

Germination Time for Optimum Amylolytic Activity

Millet germination at 72 h had the highest amylotic activity as indicated by its ability to reduce the viscosity of millet gruel (Fig. 1). Percent reduction in viscosity increased up to 72 h, then declined. Corn started sprouting after 30 h, and its amylolytic activity in corn gruels increased linearly with time indicating that the germination time for optimum activity is longer than 96 h. Marero et al. (1988a) reported that the germination period which yielded acceptable changes in viscosity for corn and rice was 72 h. Mosha and Svanberg (1983) germinated improved white sorghum varieties and corn for 48 h, and improved brown sorghum varieties for 96 h. However, they did not indicate that the times used were optimum for amylolytic activity. It appears that germinated cereals have different starch hydrolytic enzymes activity depending on the specie, variety and germination temperature and time. In this study, germinated millet was more efficient


100 1

L

20 40 60 80 100

Germination Time (h)

FIG. 1. GERMINATION TIME FOR OPTIMUM AMYLOLYTIC ACTIVITY OF CORN IN CORN GRUEL (0) AND OF MILLET IN

MILLET GRUEL (0)

than germinated corn in reducing gruel viscosity based on the shorter germination time for high amylolytic activity.

Time for Viscosity Reduction by GMF

Initial viscosities were 65.90-68.90 Pascal s (cps/1OOO) for millet based gruels and 9.97-11.40 Pascal s for corn based gruels. When 5% GMF was added, viscosities dropped to 1 .O-2.0 Pascal s after 5 min. Similarly, Mosha and Svanberg (1983) showed that addition of germinated sorghum flour at the same level to sorghum gruel led to a viscosity drop from 10.0 Pascal s to 1.0 Psacal s at 40C after 5 min.

Microbiological Counts during Preparation and Storage of GMF

Table 1 shows that washing the millet grains before germination significantly reduced the number of bacteria (P < 0.005) but not the yeast and mold counts. After germination, there was an increase of 9 log CFU/g (as is) in the bacterial alevels but the amounts in the prewashed and unwashed grains were not significantly different. The yeast and mold counts increased by 3 log CFUlg (as is), and the value for prewashed grains was significantly lower than that for the unwash-


TABLE 1.

MICROBIAL LEVELS (CFU/G, AS IS) DURING PROCESSING AND

STORAGE OF GERMINATED MILLET FLOUR a*b

Preparation step GMF typeC Bacterial counts Yeast and mold counts

Before germination Unwashed 7.33 x 1621.09 x 1 6 d 97.0219.1

Rewashed 1.20 x ld+O.lO x l d e 48.3+1.70

After germination Unwashed 2.47 x 101420.24 x 1014 d 4.03 x 1&~0.27 x 1&

3.03 x 104k0.07 x 104 Rewashed 2.50 x 101420.36 x lot4 d

After drying Unwashed 13.00 x l@+l.oOX 108d 2.07 x 102+0.35 x l@d

Rewashed 9.70 x 10820.30 x l 08e 1.50 x 1@~0.10 x 102

Milled and stored for 2 weeks at

3.0 2 1.0 C Unwashed 14.33 x 10820.88 x 108 <lo0

Rewashed 11.67 x 109~0.sS x 108 <lo0

20.5 2 1.5 C Unwashed 43.33 x 10825.24 x 108 <lo0

Rewashed 33.67 x 108~6.77 x 108 d <lo0

a Means 2 SE for tiipiicates.

Values in the same column with the same treatment and different letters are significantly

different at P<0.05.

Millet was either washed or unwashed before germination.

ed grains (P < 0.05). The high moisture content and temperature of 21-24C during germination were favorable for bacteria, yeast and mold growth leading to an increase in microbial levels (Jay 1992). Drying reduced the bacterial load by 6 log CFU/g (as is) with the value for the unwashed grains significantly higher


TABLE 2.

EFFECT O F STORAGE TEMPERATURE AND TIME. AND OF PREWASHING

ON THE AMYLOLYTIC ACTlVITY OFGERMINATED MILLET FLOUR

IN CORN GRUEL

Storage Storage time Final gruel viscosity (Pascal s)a temperature (weeks)

Unwashed GMF (OC) Rewashed GMFb

3 . 0 ~ 1.0 1 1.47 2 0.09 1.63 2 0.03

3.02 1.0 2 1.27 2 0.07 1.57 2 0.07

3.0 2 1.0 3 1.23 20.12 1.47 2 0.03

3.0 2 1.0 4 1.30 5 0.06 1.53 0.03

20.5 2 1.5 1 1.47 2 0.09 1.63 2 0.03

20.5 2 1 .5 2 1.63 0.03 1.73 2 0.03

20.5 2 1.5 3 1.67 2 0.07 1.73 2 0.09

20.5 & 1.5 4 1.81 2 0.03 2.07 2 0.09

Analysis of variancec P - value

Storage time (S time) <0.005

Storage temperature ( S temp) <0.0001

Prewashing t0.0001

S time x S temp <o.ooo 1

a Means 2 SE for triplicates. Initial viscosities were 10.00+0.43, 1 1.4-0.21,

11.2720.45 and 11.30+0.12 Pascal s for 1, 2. 3, and 4 weeks, respectively.

Millet was either washed or unwashed before germination.

P - value > 0.05 or not significant for for S time X Prewashing, S temp x Prewashing,

and S temp x S time x Prewashing.


than that of the prewashed grains (P < 0.05). There was also a decrease of 2 log CFUlg for yeast and mold counts but the amounts for both grains were not significantly different. After two weeks storage, GMF had an increased bacterial level at the higher temperature only and had yeast and mold counts < 100 CFU/g. Thus, addition of GMF can adversely affect the microbial quality of the gruel because of its high bacterial count.

Amylolytic Activity of GMF'

Prewashing millet apparently increased germination and amylolytic activity resulting to lower final corn gruel viscosities (P < 0.0001) (Table 2). Storing GMF at room temperature decreased its activity leading to higher corn gruel viscosities especially after four weeks (P < 0.OOOl). However, no prewashing and room storage of GMF still reduced gruel viscosities to < 3.0 Pascal s in 5 min. When stored GMF was added to millet gruels, the final gruel viscosities were similarly affected by prewashing, storage temperature and time even though the initial viscosities were higher (Unpublished data). Thus, it appears practical to prepare GMF without prewashing especially in areas where water supply is critical since the bacteria, yeast and mold counts were similar for both prewashed and unwashed GMF. GMF can also be stored at room temperature for at least 4 weeks.

Gruels Prepared by Traditional Method

Corn and millet gruels with or without soybean or peanut were prepared by the traditional method and stored at 19-22C. Microbial quality and viscosity changes in the gruels were monitored for 24 h at 6 h interval (Fig. 2). Bacterial counts increased significantly (P < 0.05) and final viscosity decreased significantly (P < 0.05) in both corn and millet based gruels within 24 h. Yeast and mold were either not detected or minimal (0-1.5 CFU/mL) probably because of the low initial concentrations which were outgrown by the bacteria.

Final viscosities 5 min after addition of GMF were 1.27-1.67 Pascal s for corn based gruels and 1.27-1.60 Pascal s for millet based gruels. Six hours later, the viscosities dropped to < 1 .O Pascal s and continued decreasing to 0.20-0.27 Pascal s for corn based gruels and to 0.27-0.67 Pascal s for millet based gruels at 24 h. These values are lower than the gruel consistency preferred by most children aged 6 to 36 months which is 1.0-3.0 Pascal s (Mosha and Svanberg 1983). Thus, if the gruel is not reheated to inactivate enzymes, the viscosity would continue to drop to an undesirable level and affect acceptability. Bacteria will also increase to unsafe levels creating a health hazard for the children.

CORN AND MILLET BASED WEANING FOODS 5 17

0

2.0 1

10 20 30 0 1 0 2 0 30

1.6 - u1 -

1.2

P,

g 0.8 > .= 0

> .-

0.4

2'ol 1.6

1.2

0.8

0.4

0.0 I 0.0 I 0 1 0 20 30 0 1 0 2 0 30

Storage Time (h) Storage Time (h)

FIG. 2. BACTERIAL COUNTS AND FINAL VISCOSITIES IN CORN (A), CORN AND SOY- BEAN (0) CORN AND PEANUT (O), MILLET (A), MILLET AND SOYBEAN (D),

MILLET AND PEANUT (0) DURING STORAGE

Gruels Prepared by Modified Method

Only corn and millet gruels supplemented with soybean or peanut were prepared by the modified method. After pasteurization, microbial contamination was not observed except in a few bags ( out of 72) which may have been contaminated


during packaging. Bacterial, and yeast and mold counts were 0-20 CFU/mL only even after 6 days at ambient temperature, indicating that the gruels can be pasteurized by reheating to 95C for 10 min.

Gruel viscosities 5 min after addition of GMF were 1.23-1.50 Pascal s (Table 3). After pasteurization, viscosities dropped slightly, except for corn with soybean, probably due to continued starch hydrolysis during reheating before the inactivation temperature was reached. During storage, viscosities remained essen- tially the same for 5 days. After 6 days, the values were slightly higher than those before storage, perhaps due to starch retrogradation (Whistler and Daniel 1985). In spite of the slight changes during pasteurization and storage, the gruel texture was not affected because viscosity levels were still acceptable (1 .O-3.0 Pascal s). Thus, gruels prepared by the modified method had better shelf life due to minimal microbial contamination and to retention of desirable viscosity.

Nutrient Quality of Gruels

In Tanzania, weaning foods traditionally consist of ungerminated millet and corn. The nutrient quality of the gruels was improved in this study by supplementa- tion with ungerminated soybean or peanut. The improved formulations were based mainly on the work of Marero et al. (1988a) who showed that gruels prepared

TABLE 3.

VISCOSITY (PASCAL S) OF CORN AND MILLET GRUELS PREPARED

USING THE MODIRED METHOD^,^

Measurement Corn Millet

time + Soybean + Peanut + Soybean + Peanut

Before

pasteurization I .23 2 0.09b 1.40 2 0.06a 1.60 F 0.06b 1.37 F 0.03a

After

pasteurization 1.60 2 O.Ma 1.20 O.Mb 1.27 2 0.03c 1.17 0.09b

After 6 days

storage 1.57 2 0.03a 1.53 2 0.03a 1.77 2 0.03a 1.43 2 0.03a

a Means SE for triplicates.

Values in the same column with different letters are significantly different at P < 0.05.


with germinated rice or corn and germinated mungbean or cowpea at a cereal: legume (weightlweight) ratio of 7:3 adequately supplied 1/3 RDA for protein and energy in a child’s meal consisting mainly of gruel, and also contained the energy density of 0.7-1 .O Kcallg (2 .934.18 KJ/g) recommended by Svanberg (1987).

Percent moistures for the traditional corn gruels (Table 4) were similar to the calculated values based on the materials used (84.25 W ) while those for the traditional millet gruels (Table 5) were higher than the estimated value (79.0%). Moisture content in the pasteurized gruels (Table 6) were generally lower than

TABLE 4.

PERCENT PROXIMATE COMPOSITION OF CORN GRUELS PREPARED BY THE

TRADITIONAL HOD BEFORE AND AFTER STORAGE^,^.

Component StorageTime ( h ) Corn Corn + Soybean Corn + Peanut

Moisture 0

24

Fat

Ash

0

24

0

24

Rotein 0

24

Carbohydrate 0

84.0950.34

g5.+-0.52

0.9950.04

0.9620.02

0.20+0.00c

0. m0.01d

1.5220.1 1

1.3 120.09

13.2020.27

83.92kO.46

84.719.27

1.76-0.10

1.69~0.07

0.439.02

0.40+_0.0 1

3.0150.08

2.7050.09

10.E2320.33

83 .3950.26d

84.8020.16C

2.7eO. 1 1

2.63~0.19

0.1950.0 1

0.1250.04

2.2k0.16

1.99+0.07

1 1.4320.12

24 12.129.46 10.57+0.13 10.47+0.36

a Means 2 SE for triplicates.

Concentrations of the various components before and after storage for 24 h were not

significantly different at P < 0.05 except where indicated by c and d.


TABLE 5.

PERCENT PROXIMATE COMPOSITION OF MILLET GRUELS PREPARED BY

THETRADITIONAL METHOD BEFORE AND AFER STORAGE^.^.

Component Storage Time (h) Millet Millet + Soybean Millet + Peanut

Moisture 0

24

Fat

Ash

0

24

0

24

Protein 0

24

Carbohydrate 0

81.7320.26

83.73~0.67

0.99+0.06

0.922+0.04

0.3 1-0.02

0.2720.0 1

1 .95+_O0.O5C

1.69~0.06d

15.0220.26

81 .12~0.27~

83.03+0.49

2.04t0.13

1.9720.04

0.56L0.2 I C

0.5020 .o 1 d

4.0250.27

3.6720.06

12.26~0.16~

79.3 1+0.3Sd

84.8020. 16c

3.6550.06

3.6120.08

0.38~0.02

0.3220.02

3.38-0.14

2.7820.18

13 .2820.3sc

24 13.3820.67 10.82kO .44d 10.77+0.2sd

a Means SE for triplicates.

Concentrations of the various components before and after storage for 24 h were not

significantly different at P c 0.05 except where indicated by c and d.

those in the traditional gruels perhaps due to evaporation during pasteurization. Supplemented millet gruels (Tables 4-6) had higher fat and protein than the

modified corn gruels due to the higher flour:water ratio and the higher cereal protein content (14.5% for millet, 9% for corn) (Dupont and Osman 1987) in the former. Protein content of the gruels also depended on the legume with soybean increasing the values more than peanut because of its higher protein content (40% for soybean, 19-23% for peanut). Gruels supplemented with peanut paste had higher fat content because peanut contains > 40% fat (Dupont and Osman 1987) while the defatted soybean had 0.5% crude fat only.

CORN AND MILLET BASED WEANING FOODS 52 1

TABLE 6.

PERCENT PROXIMATE COMPOSITION OF CORN AND MILLET GRUELS

PREPARED BY THE MODIRED METHOD BEFORE AND AFTER STORAGE^.^

~~ ~

Storage Corn Millet

Component time(d) + Soybean i Peanut + Soybean + Peanut

Moisture 0 83.17+0.09 83.38+0.44 79.8920.14c 79.76+0.I4C

6 83.3120.15 82.96+_0.51 78.t3f&0.14d 78.88~0.14~

Fat 0 1.68+0.12 2.7840.07 1.9&0.03 3.a-0.08

6 1.6720.1 4 2.79~0.05 2.00+0.05 3.6920.05

Ash 0 0.42+0.01 0.37+0.01 0.5920.02 0.40+0.01

6 0.41+0.01 0.35+0.01 0.60+0.02 0.39+0.01

Protein 0 3.2220.07 2.05e0.04 4.234.24 3.1720.08d

6 3.0720.04 2.00+0.07 4.4820.06 3.4320.05C

Carbohydrate 0 I1.51+0.17 11.42k0.50 13.3*0.Ibd 13.W-O.05d

6 11.54+0.24 11.90+0.54 14.06+0.07c 13.6220.2oC

a Means 2 SE for triplicates.

Concentrations of the various components before and after storage for 6 days were not

significantly different at P < 0.05 except where indicated by c and d.

Concentrations of the various nutrients in the traditional gruels (Tables 43) generally did not change after 24 h storage. A few exceptions were noted, with concentrations lower after storage, probably due to the metabolic activity of microorganisms, mainly bacteria, which increased in 24 h (Jay 1992). Gas pro- duction, indicated by bubbles and probably caused by fermentation, was observed within 12 h in most gruels. Thus, the higher moisture content after storage could be due to a decrease in the total solids which were utilized by the microorganisms.

In the modified method, there was good nutrient retention even after six days


storage at room temperature (Tabte 6). Percent moistures in the millet based gruels decreased resulting in slightly higher carbohydrate and protein concentrations.

Gruel Volume Supplying 1/3 RDA for Protein and Energy

The ideal weaning food formula should supply a child with at least 113 RDA for protein and energy per meal since most families in Tanzania feed their children three times per day (Machunda 1990). One third RDAs for protein for infants (6-1 1 months) and for children aged 12-24 months are 4.67 g and 5.33 g, respectively (FNB 1989). Marero et al. (1988a) reported that infants can consume 249-285 mL gruels with viscosity of 1 .O-3.0 Pascal s while the older children can take 305-327 mL. To obtain at least 1/3 RDA for protein, an infant must take 295.6 mL corn, 127.9 mL corn with soybean, 193.0 mL corn with peanut, 238.3 mL millet, 89.8 mL millet with soybean or 117.3 mL millet with peanut gruel. Older children must consume 337.3 mL corn, 146.0 mL corn with soybean, 220.2 mL corn with peanut, 271.9 mL millet, 102.5 mL millet with soybean or 133.9 mL millet with peanut gruel. Thus, children can obtain the RDA for protein if they are fed with the gruels three times per day except for the corn gruel which is not sufficiently protein dense.

Only gruels supplemented with legumes contained 2 . 9 3 4 18 KJ/g (0.7-1 .O Kcallg), the amount required in weaning foods by Svanberg (1987). One third RDA for energy for infants is 1185.3 KJ and for older children is 1813 KJ (FNB 1989). Based on the gruel energy densities, infants need to consume 370.4 mL corn, 314.4 mL corn with soybean, 286.3 mL corn with peanut, 350.7 mL millet, 261.1 mL millet with soybean or 237.5 mL millet with peanut gruel per meal. Older children would require 566.6 mL corn, 480.9 mL corn with soybean, 437.9 mL corn with peanut, 536.4 mL millet, 399.3 mL millet with soybean or 363.3 mL millet with peanut gruel. Except for the volumes for millet with legume gruels for infants, these amounts are higher than those that can be consumed by the children per meal.

Even though corn and millet gruels fortified with peanut or soybean can supply enough protein to meet one third RDA per meal, more frequent feeding is essen- tial to meet the RDA for energy. Since 80% of the infants are breast fed from birth to 12 months and 40% up to 24 months (Machunda 1990), use of the improved weaning foods at lesser volumes can supplement the required calories. For a better nutrient balance especially with respect to vitamins, minerals and dietary fiber, inclusion of some fruits and vegetables is recommended as the child grows older.


ACKNOWLEDGMENT

This paper is contribution no. 253 of the George Washington Carver Agricultural Experiment Station. The study was supported by the US Agency for International Development (Grant #%23-OOOO-A-OO-OO32-U€)). Any opinions, findings, conclu- sions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of USAID.

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IMPROVED CORN AND MILLET BASED WEANING FOODS: FORMULATION, VISCOSITY, AND NUTRITIONAL AND MICROBIAL QUALITY