PREDIGESTION OF SOYBEAN PROTEINS WITH IMMOBILIZED TRYPSIN FOR INFANT FORMULA

Soybean protein isolates of low soybean trypsin inhibitor (STI) residu e were prepared by acidic precipitation of soybean flour water extract s (0.8-1.2%) at pH 5.0, followed by acidic washing at this PH and affi nity adsorption of residual STI with immobilized trypsin on polystyren e anion-exchange resin GM 201. After heat treatment, soybean protein i solates were subjected to controlled hydrolysis with the immobilized t rypsin. Then, the predigested soybean protein was prepared. The predig ested soybean protein was free of STI activity, and its solubility at acidic pH range was greatly increased. Sedimentation test showed that it formed a much finer clot at PH 4.5 than that of untreated soybean p rotein. The pepsin digestibility index at pH 4.0 and chymotrypsin dige stibility index at pH 8.0 were obviously improved. These results sugge sted that the predigested soybean protein prepared by this method may be used in infant formulas.