Composite gel based on κ-carrageenan-soybean isolate protein/soy protein fibrils: Focus on structural differences and gel properties

The effects of different concentrations of kappa-carrageenan (kappa C) on the structure and gel properties of soybean protein isolate (SPI) and soybean protein fibrils (SPF) were investigated in this work. The interaction between kappa C and SPI/SPF was explored by SDS-PAGE, FTIR, fluorescence spectroscopy, surface hydrophobicity (H0). Results indicated that the binding of kappa C to SPI and SPF is mainly hydrogen bonding and hydrophobic interactions. With the increase of kappa C concentration, the fluorescence intensity and H0 of SPI/SPF-kappa C decrease. When kappa C was 8 mg/ mL, the H0 of SPI/SPF-kappa C decreased by 53.56 % and 57.23 % respectively. The addition of kappa C increased the particle size and turbidity of SPI, while the opposite results for SPF. The gel properties of SPI/SPF-kappa C were evaluated by texture, rheology and LF-NMR. The results showed that the gel properties of SPF were better than those of SPI, and the addition of kappa C significantly increased the G ', apparent viscosity and resistance to denaturation of the gel. When kappa C concentration was 8 mg/mL, the hardness of SPI/SPF-kappa C was 127.2 +/- 5.82 g and 134.23 +/- 5.89 g, respectively. In conclusion, the fibrillation of proteins and kappa C can effectively improve the gel properties of SPI gels, which provides a theoretical basis for expanding the high-value utilization of SPI and SPF.