Recently it has been recognized that the action of the enzymes contain
ed in soybeans has negative effects on the qualities of soybean protei
n foods. Based upon these findings, new manufacturing techniques for h
igh quality soybean protein foods have been developed through the cont
rol of such enzyme action. For instance, new soybean seeds lacking lip
oxygenases have been developed which reduce the production of grassy-b
eany flavors. The gel hardness of tofu can also be controlled through
the action of the lipoxygenases contained in soybeans. In addition obj
ectionable after-tastes develop through the hydrolysis of soybean isof
lavones by the beta-glucosidases which are found in soybeans. Genetic
engineering of soybean proteins made a great progress in improving the
ir functional and nutritional qualities through the modifications of g
enes encoding for soybean storage proteins. The application of a biore
actor for soy sauce is also described as an example of the progress on
the biotechnology.