Relationship between protein composition and coagulation reactivity, particulate formation, and incorporation of lipids in soymilk

Abstract

Many studies have suggested that the 11S/7S ratio in soybeans affects the coagulation reaction at the first step. In this study, the 11S/7S ratio in soybeans showed significantly negative correlation with MgCl2 concentrations for the maximum breaking stress of tofu for six Japanese varieties. To determine the effect of the 11S/7S ratio, soymilk was fractionated by centrifugation after the addition of MgCl2, and the distribution of lipids and proteins was studied. The amount of precipitate increased as the MgCl2 concentration or the 11S/7S ratio increased. More triglyceride was incorporated into the precipitate as the MgCl2 concentration or the 11S/7S ratio increased. The stain intensity of bands after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that the ratio of oleosin, a membrane protein of the oil body, increased in the precipitate as the MgCl2 concentration or the 11S/7S ratio increased, while the ratios of glycinin and β-conglycinin were less variable. These results indicate that the 11S/7S ratio and coagulant concentration may have an effect on the amount of coagulum and the concentration of oil globules in the coagulum at the beginning of coagulation.