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Fluidizing infant gruels with amylase to improve their nutritional value

November 12, 2003

The growth problems which affect the children of the countries of the South are attributable, among other causes, to insufficient and inappropriate complementary feeds. Such supplements are mainly composed of gruels made with flour from locally grown cereals mixed with water. Rich in starch, these gruels thicken and swell when cooked. Mothers therefore reduce the quantity of flour in the mixtures to obtain a more fluid consistency, more palatable for the infants. This reduces significantly the gruel's energy and nutrient content, making it difficult to ensure the children receive their nutritional needs and consequently is detrimental to their growth.

Scientists from the IRD research unit "Nutrition, Food and Societies" have advanced the hypothesis that making available flours which, when cooked, would produce gruels of the appropriate consistency with high energy density and nutritional value, would lead to an increase in energy and nutrient intake and help growth. Their investigation focused on the effect of adding-in a fluidizing enzyme, amylase, to the preparations. This enzyme hydrolyses starch into simpler sugars, maltose and dextrines, thus reducing the gruel viscosity which increases the mixture's energy and nutrient density. A randomized controlled trial conducted in Brazzaville (Republic of the Congo) took two groups of children being fed by their mothers, one with gruels enriched with amylase (the intervention group), the other with identical gruels but without amylase (control group) (1).

The energy intake from the amylase-supplemented gruels conformed with WHO recommendations and exceeded that of control gruels (2). The viscosity-reducing action of amylase led mothers instinctively to add flour during gruel preparation, until they obtained the consistency they judged suitable for their infants. In doing this they naturally increased the food's energy density.
There was clear evidence that consumption of high-energy density gruels can increase the overall energy and nutrient intake provided by such gruels and benefits infant growth at between 6 and 8 months old. Those fed amylase-enriched gruels showed greater monthly growth rate than infants in the control group (3). Feeding with these gruels moreover appears not to disturb breast-feeding, in terms of frequency, duration, or daily energy intake from maternal milk (4).

This trial was conducted in the usual living conditions. In other words, the timing of complementary feed introduction proper to each child was respected, as were the mothers' habitual preparation methods and practices. When mothers had the means available for making enriched gruels in such a way that final consistency was not significantly modified, the children had higher energy and nutrient intakes, beneficial for growth. Unlike powdered milk, nutritionally rich but costly and often difficult to obtain, amylase as an additive to the complementary feed remains an appropriate solution for improving infant nutrition in poor populations. In any case, amylase can be obtained naturally on germination of cereal and leguminous plant seeds. It can therefore be obtained locally as a directly usable product. Other techniques for making low-viscosity complement feeds are being studied, such as fermentation methods. Some have even been developed on an industrial scale, as is the case in Viet Nam of an inexpensive cooking and extrusion process.

Marie Guillaume, DIC

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(1) This trial was set up between June 1995 and February 1996 and involved 80 infants aged between 4 and 8 months, in a district of Brazzaville.
(2) For children of average age of 6 months: the energy densities of the gruels with or without amylase are respectively 565 kJ/100g and 297 kJ/100g.
(3) The infants fed on enriched gruels have an average growth rate 0.51 cm per month higher than those of the control group. There is a statistically significant difference in linear growth between the two groups.
(4) About 134 kJ/kg/day for infants in the intervention group and 130 kj/kg/day for those in the control group.

Institut de Recherche pour le Développement, Paris (IRD)