Improving nutritional quality

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No one legume or cereal can provide adequate amounts of all nutrients to meet the nutritional requirements of a child. However, even before knowledge on protein content, protein quality, digestibility and the nutrient requirements of humans became available, it was recognized that mixing legumes with cereals in the diet could improve overall nutrition. The present and newly derived knowledge in these areas makes it possible to blend, mix or fortify one food material with others so that the resulting fortified mix has not only better nutritional quality but also the necessary attributes for consumer acceptance.

The nutritional quality of sorghum and millets, especially the former, is poor. Therefore attempts have been made to fortify these cereals with legumes or other cereals to make nutritionally superior and acceptable products. Cost, availability of ingredients and marketability must be taken into consideration if fortification is to be implemented successfully on a sustained basis.

Sorghum and pearl millet have been successfully used in feeding programmes after fortification with legumes. Vimala, Kaur and Hymavati (1990) described various infant mixes based on sorghum and pearl millet and fortified with soybean, green gram, red gram or Bengal gram flour (Table 36). They were evaluated through rat feeding trials and nitrogen balance studies in children.

It is possible to fortify malted finger millet (rug)) weaning food with green gram. The food has the advantage of having low cooked paste viscosity and has high energy density when mixed in the proportion of 70 percent malted ragi flour and 30 percent green gram flour. The NPU of this food was observed to be 52 percent and was comparable to that of a commercially available weaning food (Malleshi, Desikachar and Venkat Rao, 1986).

Okeiyi and Futrell ( 1983) evaluated the protein quality of various combinations of sorghum with cereals and legumes. These included (dehulled) sorghum, wheat and soy flours; sorghum, wheat, cowpea and soy flours; sorghum, wheat and cowpea flours plus peanut butter; sorghum and wheat flours plus peanut butter; and sorghum, wheat and soy flours plus peanut butter. A diet of sorghum, wheat and soy flours met the FAO recommendations for required amino acids. Over 25 percent of the energy of this diet was provided by fat and 10 percent of the energy was provided by protein as recommended by the United Nations Protein Advisory Group for the formulation of high-protein foods for children. The diet had the same high PER as casein.

TABLE 36: Formulations tested and developed for adoption in feeding programme (millet and pulse mixes)

Ingredients Proportion
Sorghum rawa (semolina): soybean flour: skim milk powder 70:25:5
Sorghum rawa: soybean flour: sugar 70:10:20
Sorghum flour: pigeon pea flour 80:20
Pearl millet flour: green gram flour 70:30
Pearl millet flour: black gram flour 70:30
Pearl millet flour: Bengal gram flour 70:30

Source: Vimala, Kaur and Hymavati, 1990.

Brookwalter, Warner and Anderson (1977) evaluated the stability of sorghum fortified with soy and cottonseed flour in different proportions. The various formulations were stored at -18C (control), 49C for two months, 37C for six months and 25C for 12 months. All combinations displayed adequate stability as measured by change in available lysine, stat, acidity and flavour. The flavour of all blends was acceptable.

In Burundi, sorghum fortified with maize and soy flours, locally known as musalac, has been used as a baby and adult food. It has the following composition: 35 percent sorghum flour, 30 percent maize flour, 20 percent soybean flour, 10 percent sugar and 5 percent milk powder. This combination has about 16 percent protein, with 3.76 percent of protein contributed by lysine and 440 kcal per 100 g of product. Musalac is very popular; 60 l/month were sold commercially in 1989, and production is expected to reach 9 000 tonnes by the year 2000.

TABLE 37: Mean protein intake and net available protein in children on different diets

Diet

Protein intake

Net available protein

FAO reference protein requirementsa
  (g) (g/kg) (g) (g/kg)  
Finger millet 29.7 1.31 13.5 0.60 0.72
Finger millet + L-lysine 29.9 1.32 15.8 0.70 0.72
Finger millet + L-lysine  
+ DL-threonine 30.4 1.35 18.0 0.80 0.72
Skim milk powder 28.3 1.25 21.2 0.94 0.72

a From FA0, 1965.
Source: Daniel et al., 1965.

The quality of a ragi diet was evaluated by feeding it to eight 11 - to 12-yearold girls in Mysore, India (Daniel et al., 1965). In addition to ragi, the diet included peanut oil, red gram dhal, condiments and skim milk powder. After the diet was followed for four days as acclimatization period, material was collected for analysis during the next four days. The retention of nitrogen on the finger millet diet was very low (6.1 percent of intake) and the biological value (BV) and net protein utilization (NPU) were 67.0 and 45.5 percent respectively (Table 37). Supplementation of the finger millet diet with L-lysine caused a significant improvement in nitrogen retention (13.6 percent of intake), BV (75.9 percent) and NPU (52.7 percent). When the ragi diet was supplemented with both L-lysine and DL-threonine, highly significant improvements in the nitrogen retention (21.3 percent of intake), BV (8 1.2 percent) and NPU (59.3 percent) were observed. The corresponding values obtained for skim milk powder were 33.2,85.3 and 74.8 percent, respectively. Net available protein showed good improvement on supplementation with Iysine and threonine.

Supplementing various types of millets with chickpea has shown good improvement in the protein efficiency ratio as shown in Table 38 (Casey and Lorenz, 1977).

TABLE 38: PER of diets based on millets or blends of millet and chickpea a

Protein source PER
Foxtail millet 0.80
Proso millet 1.10
Proso millet + chickpea 1.80
Pearl millet 1.60
Pearl millet + chickpea 2.16
Finger millet 2.00
Finger millet + chickpea 2.10
Rice 2.09
Whole wheat 1.30

a Protein content in diet: 10 percent. As a supplemental protein source. chickpea provided 40 percent of protein
Source: Casey and Lorenz, 1977.

Composite flours

Composite flour technology initially referred to the process of mixing wheat flour with cereal and legume flours for making bread and biscuits. However, the term can also be used in regard to mixing of non-wheat flours, roots and tubers, legumes or other raw materials (Dendy, 1992). One example is the mixture of sorghum and maize flour for tortillas.

Diluting wheat flour with locally available cereals and root crops was found to be desirable to encourage the agricultural sector and reduce wheat imports in many developing countries. In Africa there has been an ever-increasing demand for wheat products such as bread. Africa is not a major wheat-growing region, but it produces large quantities of other cereals such as sorghum and millets. It has been reported that replacing wheat with 20 percent non-wheat flour for the manufacture of bakery products would result in an estimated savings in foreign currency of US$320 million annually (FAO, 1982). At 30 percent substitution the savings would be US$480 million annually. Thus composite flour technology holds excellent promise for developing countries. Although actual consumer trials have been rare, products made with composite flour have been well accepted in Colombia, Kenya, Nigeria, Senegal, Sri Lanka and the Sudan (Dendy, 1992).

When sorghum or millets are used for bread-making, addition of bread improvers or modification of the bread-making process is needed. A higher level of substitution is possible with hard than with soft wheat flour (United Nations Economic Commission for Africa, 1985). For the production of biscuits from composite flours, the fat content of the non-wheat flour should be kept as low as possible to promote a longer shelf-life.

Crabtree and Dendy (1979) reported that bread could be produced from composite flour made by co-milling wheat with pearl, prove, barnyard or finger millets. The proportion of millet in the flour can be up to 15 percent. Potassium bromate treatment of the dough tends to improve the loaf volume. Bread containing I 0 percent pearl millet flour had an excellent texture and flavour similar to that of whole-wheat bread (Bad), Hoseney and Finney, 1976; see also Perten, 1972).

Sorghum flour milled at 80 percent extraction rate could be blended with white wheat flour for bread-making without any adverse effect (Rao and Shurpalekar, 1976). Acceptability studies conducted at the Food Research Centre in Khartoum, the Sudan, indicated that breads made with composite flour of 70 percent wheat and 30 percent sorghum were acceptable. Milling at 72 to 75 percent extraction rate yielded fine sorghum flour that is more suitable for bread-making. Consumer acceptance trials in Nigeria indicated that breads made with 30 percent sorghum flour were comparable to 100 percent wheat bread (Aluko and Olugbemi, 1989; Olatunji, Adesina and Koleoso, 1989). The protein content of composite flour was lower than that of wheat flour, while its crude fibre was higher. Addition of pentosan improved the quality of bread made with composite flour. The Institute of Food Technology in Dakar, Senegal, prepared a bread consisting of 30 percent millet and 70 percent wheat using the popular millet varieties Souna and Sanio (Thiam,1981). Another bread, called panble, was prepared with 15 percent millet and 85 percent wheat. Bread with 30 percent sorghum and 70 percent wheat was also prepared in Senegal (Thiam and Ndoye, 1977). Breads with up to 15 percent prove millet were acceptable and comparable to white wheat bread (Lorenz and Dilsaver, 1980).

A combination of 80 percent non-wheat cereal and 20 percent wheat can be used to produce biscuits with acceptable quality. Sorghum and pearl millet flour blended with wheat flour can be used to make biscuits (Badi and Hoseney, 1976, 1977). Olatunji, Adesina and Koleoso ( 1989) reported that a proportion of 55 percent sorghum could be used for biscuits without adversely affecting biscuit quality. Proso millet was found suitable for making biscuits; biscuit spread and quality score increased with increased levels of prove millet flour because of its high fat content (Lorenz and Dilsaver, 1980). Millet flour imparted a slight grittiness, however. Pearl millet could replace 50 percent of the wheat for cake and 80 percent for biscuits (Thiam, 1981). In Senegal, traditional foods such as faux, conus conus and beignets (fritters) are prepared by mixing millet flour with rice, maize or wheat flour (Thiam, 1981).

Alternative uses of sorghum and millet

Sorghum and pearl millet production has considerably increased in several countries during the past few years. With the simultaneous increase in the production of wheat and rice and the available surplus in storage, millets face competition from the utilization point of view. There is already an increasing trend of using wheat or rice in place of sorghum even in those regions where sorghum has been the traditional staple grain in the past.

Sorghum and millets will continue to be major food crops in several countries, especially in Africa (and in particular in Nigeria and the Sudan, which together account for about 63 percent of Africa's sorghum production). These grains will be used for traditional as well as novel foods. However, there is a need to look into the possibilities of alternative uses. Though sorghum and millets have good potential for industrial uses, they have to compete with wheat, rice and maize. Sorghum in particular could be in great demand in the future if the technology for specific industrial end uses is developed. Although pearl millet has some potential for industrial use, other millets have limited potential because of their small grain size and the associated difficulties of adopting a suitable dehulling technology. However, they can be considered for animal and poultry feed. There is a need to compare their performance as feed in comparison with maize.

Sorghum and millets can be adopted for other food products by using appropriate processing methods. Dehulling and milling practices to improve the quality of foods made from sorghum and millets have been described in Chapter 3. It may be possible to select grain types with improved milling quality that will make these crops competitive with other cereals in terms of utilization. Wheat milling technology with suitable modification can be effectively used for grinding sorghum and millets. Although bread can be produced from whole sorghum flour, the quality of the bread can be improved by using sorghum flour from which the bran fraction has been removed by passage through sieves (Caster et al., 1977). Kulkarni, Parlikar and Bhagwat ( 1987) reported that sorghum malt could be used to make biscuits, weaning foods and beer wort. Addition of up to 40 percent sorghum malt in biscuits caused reduction in stack height and increase in spread because of increased water absorption.

The use of sorghum in common foods such as idli (a steamed product), dosa (a leavened product) end ponganum (a shallow-fat-fried product) can be popularized for wider use in sorghum-growing areas (Subramanian and Jambunathan, 1980). A few important sun-dried or extruded and sun-dried products from sorghum are papad, badi and kurdigai. These products usually have a shelf-life of over one year. They can be popularized through marketing channels similar to those used for rice products. A wide range of bakery and snack products prepared with dehulled sorghum were accepted by consumers in Andhra Pradesh, India (Andhra Pradesh Agricultural University, 1991). It was indicated that these foods should be marketed commercially to make them reach more people and become more popular.


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