Proteomic profiling of the coagulation of soymilk proteins induced by magnesium chloride

The coagulation of soymilk proteins induced by magnesium chloride at 30 °C was investigated using the SDS-PAGE and two-dimensional electrophoresis. Approximately 88.4% of the soymilk proteins were coagulated into the soymilk pellet fraction (SPF) by 5 mM magnesium chloride, and the total protein in the soymilk supernatant fraction (SSF) decreased from 7.80 ± 0.12 mg mL−1 to 0.90 ± 0.18 mg mL−1. SDS-PAGE showed that the total intensities of the protein bands corresponding to the 7S α′ subunit, the 7S α subunit, the 7S β subunit and the 11S A3 subunit were decreased to 10.5 ± 0.3%, 11.8 ± 1.1%, 6.6 ± 0.2% and 15.1 ± 2.2%, respectively. Two-dimensional electrophoresis indicated that most of the soymilk proteins in the SSF, including the 7S subunits, 11S subunits, β-amylase, sucrose binding protein 2, Bd 30K, lectin and trypsin inhibitor A, were coagulated into the SPF by 5 mM magnesium chloride.