The influence of genotypic variation in protein composition on emulsifying properties of soy proteins

Abstract

This study describes the relationship between the emulsifying properties of soybean proteins and their composition, i.e., glycinin (11S) and beta-conglycinin (7S). Twelve investigated soybean genotypes showed significant differences in storage protein composition. The beta-conglycinin concentration positively correlated with extractable soluble protein content, which was positively correlated with protein extractability. These data suggest that the level of beta-conglycinin has a positive influence on protein extractability. The emulsion activity index (EAI) was strongly and positively correlated with the 11S:7S ratio and strongly and negatively correlated with the concentration of beta-conglycinin. The emulsion stability index (ESI) showed a moderate positive correlation with the monomeric form of glycinin and a strong positive correlation with the ratio of the monomeric to dimeric form of glycinin. No association was evident between ESI and EAI Also, no relationship was found between ESI or EAI and extractability. Based on these data, it appears that the 11 S:7S ratio strongly reflects the ability of soybean proteins to form emulsions, whereas the ratio of the two different forms of glycinin may be crucial factors for the stability of soybean protein emulsions. Thus, understanding the relationship between protein composition and functionality could be useful for further improvement of functional behavior of soy proteins in food systems.