Effect of heat treatment on nutritional quality of germinated legume seeds

The effect of heat treatment of germinated soybean, lupin, and black bean o n chemical composition and protein utilization in rats was evaluated. Heat treatment caused complete inactivation of trypsin inhibitors whereas it did not affect phytic acid levels. Proximate components, minerals, and amino a cids did not change, but low molecular weight sugars were affected by heat treatment differently for each germinated legume. The sugar digestibility r atio (total digestible sugars/total nondigestible sugars) in germinated bla ck beans doubled after heat treatment. True protein digestibility (TD) incr eased with heat treatment only in germinated soybean. Net protein utilizati on was markedly improved (20%) with heat treatment in germinated soybean an d lupin. Utilizable protein of heat-treated germinated legumes was 289, 236 , and 132 g/kg of legume dry weight for soybean, lupin, and black bean, res pectively. Supplementation with methionine did not alter TD but improved al l other indices of protein utilization in the germinated legumes, particula rly in black bean. All three germinated legumes become equivalent in protei n quality when heating and supplementation with methionine are combined wit h germination. The use of germinated heat-treated soybean, lupin, and black bean on their own and/or as food ingredients is nutritionally advantageous due to the low content of nondigestible oligosaccharides and the high prot ein utilization.