Novel double cross-linked gels of soybean protein isolates and soluble dietary fiber from soybean coats with their functionalities

Traditional hydrocolloids made by materials of soybeans is mainly composed by soy protein isolated (SPI) with ions. Another main component of the resource of soybean coats, the soluble dietary fiber (SDF), was firstly added to SPI gels to form double cross-linked network by using calcium ions and transglutaminase (TGase), which was called as M-TG-Ca. Rheological, microstructure, mechanical, thermodynamic and hydration properties of composite gels were investigated. Rheological studies proved that the addition of SDF, Ca2+ and TGase could significantly improve the G′ value of SPI gel. M-TG-Ca had the highest hardness value and the densest network. The thermal analysis found that gels cross-linked by TGase showed different thermodynamic properties compared to those only added with Ca2+. In addition, M-TG-Ca exhibited the lowest pH sensitivity and the highest bile acid binding capacity, which was indicated that it had potential to prevent the chronic disease. The research on novel double cross-linked gels may provide an idea to the utilization of soybean resources. In addition, the composite gels of protein and soluble dietary fibers of soybeans can be developed as functional additives in food industry.