Selective Proteolysis of the Glycinin and β‐Conglycinin Fractions in a Soy Protein Isolate by Pepsin and Papain with Controlled pH and Temperature

Proteolysis of soy protein isolates (SPI) was investigated by using pepsin with a pH of 1.5 to 4.0 at 37°C and papain at a temperature of 37°C to 80°C with pH 7.0. The glycinin fraction in native SPI was selectively hydrolyzed by pepsin in the pH 1.5 to 2.5 range. On the other hand, the p‐conglycinin fraction in native SPI was selectively hydrolyzed by papain at 70°C. This selective proteolysis would be significantly correlated with the denaturation of glycinin and β‐conglycinin in SPI. A protocol for preparing hydrolysates selectively enriched with glycinin or β‐conglycinin was proposed.