Structural characterization of heat-induced protein particles in soy milk.

This study analyzed the aggregation mode of polypeptides in protein particles of soy milk by using ultracentrifugation, gel filtration, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results show that the protein particles in soy milk were mainly formed by various complex protein aggregates. These protein aggregates were mainly composed of the basic and acidic polypeptides of glycinin (11S), which interact with each other via disulfide bonds, and a very small amount of the disulfide-linked alpha' and alpha subunits of beta-conglycinin (7S). Moreover, the protein aggregates and a part of monomeric subunits of 7S and 11S form protein particles through non-covalent interactions, especially hydrophobic interactions and hydrogen bonds. It is suggested that the polymerized basic polypeptides should be located inside the protein particles, whereas the acidic polypeptides of 11S, alpha' and alpha subunits are located outside them.