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Post-harvest conservation food
Development of weaning foods with high caloric
density and low hot-paste viscosity using traditional
technologies
Human
nutrition and gossypol
H.S.R. Desikachar
Central Food Technological Research Institute, Mysore, India
The usefulness of weaning foods to meet the needs of children being weaned from a liquid, milk-based diet to a solid or semi-solid diet is now well recognized, and several weaning foods have been developed in different parts of the world. Such foods should be nutritionally well balanced, and should have a soft texture with a very low fibre content. Most of them are pre-cooked, roller-dried mixtures based on blends of cereals, legumes, or other protein-rich foods with varying proportions of milk solids, and they are fortified with vitamins and minerals.
A weaning-food requirement now being emphasized is a high caloric density per unit volume of food. This can be effected by reducing the viscosity of the product being fed to children. Customary weaning foods are starchy and gelatinized and have a high paste viscosity when mixed with cold or hot water prior to feeding. Modifications of starch-paste viscosity can be accomplished by suitable adjustment of the processing conditions, or by enzymatic modification of the starch.
In formulating such weaning foods for use in the developing countries, the processing modification for reducing viscosity of the starch-base mix should be simple and cheap, and should fit into the traditional culinary and child-feeding practices of the region. In this context, a preliminary study was made on the effects of different traditional heat-processing operations on the paste viscosity of cereal flours. As malting or germination is well known to have both saccharifying and dextrinogenic (viscosity-reducing) effects on starch, this process was also included for comparison. The heat-processing operations included toasting, sand roasting, parboiling, steaming under pressure, and flaking. Commonly used cereals and millets as well as a typical legume were used in the study.
EFFECT OF MALTING AND TRADITIONAL HEAT PROCESSING ON PASTE VISCOSITY
The results of this study, presented in figure 1, show that heat treatment of cereal grains/legumes reduces hot-paste viscosity. Gelatinization of starch during heating increased the cold-paste viscosity. The more severe the heat treatment the greater the effect on starch viscosity. Maximum reduction in hot-paste (slurry) viscosity was effected by cooking under pressure, or puffing for a short time (1 to 2 minutes) at high temperature (200° to 250°C). Maximum reduction, both in hot or cold-paste viscosity, was achieved by malting of the grains.
FORMULATION OF A WEANING-FOOD MIX AND ITS VISCOSITY PROPERTIES
As malting was found to be the most effective method for reducing paste viscosity, and because it is a simple, traditional practice, it was utilized in the formulation of a basic weaning-food mix. Among the grains studied, ragi (finger millet- Eleusine coracana) developed the amylase to a large extent within 48 hours compared with maize or sorghum, and had certain advantages over pearl millet, particularly in terms of flavour and storage stability of the malted product. Among the legumes needed for balancing of the protein content and amino acid profile, green gram (Phaseolus radiatus) was chosen because of its relative freedom from toxic factors, flatus-producing components, and trypsin inhibitors.
The components, after germination for 24 to 48 hours, were dried, and the vegetative portion was removed by gentle abrasion. The materials were kilned by toasting to 70°C. The bran was removed after appropriate moist conditioning and milling of the ragi and simple, abrasive rubbing of the green gram. The malted flours were mixed in a proportion of two parts of cereal flour to one part of legume flour, thus constituting the basic weaning-food mix. It was fortified with synthetic vitamins.
The effect of malting on the reduction in viscosity of flour slurries at different concentrations is presented in figure 2. The paste viscosity of conventional commercial weaning food is also shown for comparison. It can be seen that malting considerably reduces the slurry viscosity. Weaning food based on malted grains also has a much lower viscosity (higher caloric density) than conventional, roller-dried weaning food.
Apart from low viscosity, the malted weaning food can be expected to permit better digestibility of the starch, as partial starch breakdown to dextrins occurs during malting. Lowered starch complexity and partial pre-digestion by enzymes during malting should help in its utilization by a child being weaned from a lactose-based milk diet to a starch-based cereal diet.
Preliminary feeding studies in children 1 - 3 1/2 years old in a village, in a hospital, in a children's home, and in a labour crèche indicated that it was well tolerated, and confirmed the adaptability of the process of malting for preparing the weaning food using the simple facilities available in the village. Its advantages over the commercial weaning food are: (i) low bulk (higher caloric density); (ii) better digestibility; (iii) much lower cost (Rs 5 per kg compared to Rs 25 per kg of commercially marketed weaning foods), and (iv), most important, its adaptability to preparation at any level of technology. It can be prepared not only in remote villages or communities lacking sophisticated processing facilities, but can also be manufactured by a modern food industry. By malting, it has also been possible to effect a considerable viscosity reduction in commercial weaning foods.
Further studies are in progress to apply the malting technique to other cereal/legume grains, and also to develop easily digested foods suitable for elderly people.
