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.