Abstract
It was observed that the spray-dried water-soluble protein of soybean meal processed at low temperature has a marked trypsin inhibitor activity and when it was fed to rats, the food intake and growth of rats were depressed.
Since the degree of growth retardation seemed to be related to the amount of trypsin inhibitor, the effect of heating on soybean protein in overcoming antitryptic activity and also availability of heat treated protein and acid-precipitated fraction of native protein for the growth of rats were investigated.
The antitryptic activity test in vitro showed that trypsin inhibitor activity was reduced to a level of 15% of the original protein by mild heating at 90°C, 30 min., pH 6.4, although the rate of inactivation of trypsin inhibitor was higher when heated in an alkaline medium.
As the results of rat growth experiment, the heat treated protein supported the growth of rats, and the acid-precipitated fraction which was actually low in content of trypsin inhibitor showed a higher protein availability.
