Soy protein gels based on ultrasonic treatment: Effects of Ca2+ and 11S/7S ratio on gel structures and digestive properties

Abstract

This study aimed to explore the impact of varying Ca²⁺ concentrations and 11S/7S ratios on the gel performance of soybean protein gels (SPGs) under ultrasonication (400 W, 15 min) and to clarify the mechanisms involved. Results showed Ca²⁺ addition altered the structure of soybean 11S/7S protein gels. Low Ca²⁺ levels increased the turbidity, hardness, and water retention of the gels, whereas high levels disrupted the orderly aggregation of 11S/7S proteins, creating a rough, porous network. The effect of Ca²⁺ was more pronounced with a higher 11S ratio, significantly influencing turbidity, disulfide bonding, and gel hardness. Conversely, 7S-rich gels showed reduced sensitivity to Ca²⁺. In vitro digestion and SDS-PAGE results indicated that 7S globulin’s α, α’, and β subunits were more digestible than the A and B subunits of 11S globulin. In conclusion, ultrasound combined with Ca²⁺ can enhance the cross-linking degree between 11S and 7S globulin, forming a dense network structure.