Distribution of β-amylase and lipoxygenase in soy protein products obtained during tofu production

Soybean is considered an important source of human food and animal feed. Okara and tofu whey are the main by-products of soymilk and tofu production. The distribution of enzymes ?-amylase and lipoxygenase (Lox) from six soybean genotypes in protein extracts of okara and tofu as well as in soymilk and tofu whey was assessed. SDS-electrophoretic results showed that production process significantly affected high molecular mass protein fractions of soybean by-products. Low amounts of Lox in soymilk were registered, while in okara protein extracts and tofu whey this enzyme was present in trace. In tofu protein extracts, Lox was registered in higher quantity that might be the result of the aggregation process during formation of the tofu gel. Content of ?-amylase in all soy protein products was high and similar to the content in soybean genotype. Content of ?-amylase in okara depended on respective soybean genotype.