Limited hydrolysis of soy proteins with endo- and exoproteases

Changes in the native state and functional properties of soy protein achieved by limited proteolysis of soy flour were investigated. Different enzyme-to-substrate ratios (US) 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 enclopeptidase activities) were evaluated, and their effects on solubility, emulsification capacity, SDS-PAGE profiles, and denaturation enthalpies were characterized. Endoproteases (Multifect(R) Neutral, ProteX(TM) 6L, and Multifect(R) 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% US ratio, whereas the extent of hydrolysis with Protex(TM) 6L was more pronounced than with the two other endoproteases (Multifect(R) Neutral and Multifecto 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 beta-conglycinin decreased significantly, whereas hydrolysis to lower DH did not affect these values.