Focusing on the mechanism of glycinin-soybean lipophilic protein hybrid gels: Effect of ultrasonic, subunit interactions, and formation process analysis

Heat facilitates aggregation and gel formation of soybean proteins. Ultrasonic reduces the size of protein aggregates. This study examined the impact of glycinin (11S) subunits on soybean lipophilic proteins (SLPs) gel formation and underlying mechanisms. Effects of protein dispersion pretreatment with 400 W ultrasonic and associated mechanisms were assessed. Addition of the A- and B-subunits before and after ultrasonic minimally affected SLP secondary structure. A-subunit addition before ultrasonic negligibly affected SLP tertiary structure. Addition of the B-subunit after ultrasonic reduced hydrophobic thermal aggregation. However, the small B-subunit size was unfavorable for the formation of a gel matrix, which led to poor gel properties. In contrast, solubility of the A-subunit after ultrasonic was increased to 31.06 ± 1.62 %). Particle size was decreased to 43.33 ± 1.36 nm for A:SLP (1:2). Endogenous fluorescence spectroscopy demonstrated increased protein unfolding after ultrasonic and decreased disulfide bonds. These changes improved the gel state. Rheological and microstructural analyses revealed increased energy storage modulus and yield strain, accompanied by a more homogeneous microstructure following ultrasonic. Microscopic improvement resulted in increased encapsulated water within interstitial spaces of the A-SLP gel matrix. This enhanced water mobility in B-SLP gels, in turn weakening gel stability. The changes observed in B-SLP were primarily due to reduced hydrophobic interactions between the proteins. The findings clarify the effect of ultrasonic treatment on the formation of soybean globulin-SLP hybrid gels at the subunit level. The data provide a theoretical basis for the synergistic utilization of soybean proteins among different components.