Improving the Foaming Properties of Soy Protein Isolate Through Partial Enzymatic Hydrolysis

Abstract

The effect of partial enzymatic hydrolysis of soy protein isolate (SPI) on its foaming properties is investigated in this study. Enzymes of different origin, including papain, alcalase, and pancreatin, were used. Foaming properties (foaming capacity and foam stability) were measured and their relationships with physicochemical characteristics such as degree of hydrolysis, molecular weight of hydrolysates, and surface tension were investigated. Papain hydrolyzed SPI hydrolysates were found to be the best in terms of improved foaming capacity and foam stability. Molecular weights of SPI hydrolysates obtained by papain and alcalase hydrolysis were mainly in the range of 5 kDa to 30 kDa, while those hydrolyzed by pancreatin had molecular weight above 50 kDa. Foaming capacity was found to correlate well with the relative abundance of hydrolysate in the molecular weight range of 5 kDa to 10 kDa (r = 0.84, p < 0.05). Surface hydrophobicity was found to correlate negatively (r = − 0.89, p < 0.05) with foaming capacity of SPI hydrolysates. Surface tension values of SPI hydrolysates produced by all enzymes were significantly lower than (p < 0.05) compared to that of SPI. The surface tension of pancreatin hydrolyzed SPI hydrolysates was lower than the surface tension of those hydrolyzed by papain and alcalase. The surface tension of pancreatin hydrolyzed SPI hydrolysates decreased more rapidly with time compared to the rest. These findings will provide better understanding of how best to carry out the partial hydrolysis of SPI using various enzymes in order to improve its foaming properties.