Limited hydrolysis of soy proteins with endo‐ and exoproteases

Abstract

AbstractChanges in the native state and functional properties of soy protein achieved by limited proteolysis of soy flour were investigated. Different enzyme‐to‐substrate ratios (E/S) were used to obtain low (3–5%) and medium (5–10%) degrees of hydrolysis (DH). Six protease preparations (three with predominately exopeptidase activities and three with predominately endopeptidase activities) were evaluated, and their effects on solubility, emulsification capacity, SDS‐PAGE profiles, and denaturation enthalpies were characterized. Endoproteases (Multifect® Neutral, Protex™ 6L, and Multifect® P‐3000) and exoproteases (Fungal Protease Concentrate, Experimental Fungal Protease #1, and Experimental Fungal Protease #2) yielded similar increases in soy protein solubility. The modifications to the soy peptide profile were similar for the three exoprotease mixtures at a 1% E/S ratio, whereas the extent of hydrolysis with Protex™ 6L was more pronounced than with the two other endoproteases (Multifect® Neutral and Multifect® P‐3000). The emulsification capacity of protease‐modified soy flour declined regardless of DH and enzyme type (exo‐ or endoprotease). After hydrolysis to >4% DH, denaturation enthalpies of glycinin and β‐conglycinin decreased significantly, whereas hydrolysis to lower DH did not affect these values.