Changes in nutrient composition, phytate and cyanide contents and alpha-amylase activity during cereal malting in small production units in Ouagadougou (Burkina Faso)

The different traditional processes used in cereal malting were characterised and some biochemical modifications occurring in seeds during malting were studied to examine the possibility of using malted cereal flours to reduce the viscosity of gruels prepared from infant flours. Five production units (PU) of malted red sorghum seeds, two PU of malted millet seeds and one PU of malted maize seeds were selected as a function of the ability of the malt flours to fluidify high energy density gruels. Each of the 8 PU were monitored throughout the malt production process in order to describe rigorously the different steps in their malting process and to establish a detailed general production diagram. Samples were collected after soaking, germination, maturation, drying, and degerming and at the final product. They were analysed for nutrient, phytate and cyanide contents and alpha-amylase activity. For the 3 types of cereals, malting increased protein content while it decreased lipid and ash contents. A significant increase was observed in sucrose, glucose and fructose contents during malting, in particular during the germination step. The decrease in phytate content during malting was more obvious in millet seeds than in red sorghum and maize seeds. alpha-amylase activity increased during malting in all 3 types of cereals but more in red sorghum seeds than in millet and maize seeds. Cyanide content considerably increased during malting, particularly in red sorghum seeds. Sucrose content decreased during maturation while glucose and fructose contents increased. Traditional manual degerming reduced fibre and ash contents in all 3 types of cereals. Degerming had little effect on phytate content but reduced cyanide content to an acceptable level for human consumption even if it did not allow the complete elimination of cyanide. Unfortunately, degerming was accompanied by a decrease in alpha-amylase activity. The maturation step should be eliminated from the malting process (biochemical characteristics were not much affected as a result) and degerming of the seeds has to be systematically conducted after sun drying to achieve a significant reduction in cyanide content. Flours from malted red sorghum or millet seeds presented useful characteristics (alpha-amylase activity and nutrient contents) for incorporation in infant flours to improve the energy and nutrient density of gruels.