Effect of Immersing Temperature on the Behavior of Exuding Components from Soybean

Abstract

The saponins and flavonoids responsible for undesirable taste are associated with proteins or carbohydrates at a lower temperature, but they are liberated from these proteins or carbohydrates at a higher temperature. The effects of immersing temperature on the swelling behavior of soybean, on the exuding components from soybean into water and on the lipoxygenase activities of swelled soybean were studied. The swelling time of soybean was reduced with elevation of the temperature, but the solid materials exuded from soybean into water was increased. The solid materials exuded from whole soybean into water, which were 2-8% of whole soybean as dry matter, contained 60-77% carbohydrate and 8-14% crude protein. The main component of this crude protein was identified as basic 7S globulin. On the other hand, the solid materials exuded from soybean cotyledon, which were 8-13% of soybean cotyledon, as dry matter, contained 57-65% carbohydrate and 11-22% crude protein. Further, saponin A group which was the most undesirable component of soybean and many other unidentfied components were observed in an exuding solution from whole soybean immersed over 50°C.The lipoxygenase activities contained in soybean swelled at 60°C were 50% lower than those in soybean swelled at20°C, and any activity could not be detected in a sample prepared at 70°C.