Preparation of soy protein isolate-naringin-chitosan protein gel: Synergistic effect of ohmic heating pre-treatment and chitosan addition

Soybean protein isolate (SPI)-Naringin (Nar) complex pre-aggregates were prepared by ohmic heating (OH) and protein gels were formed by adding chitosan (CS). The properties of the pre-aggregate, gel rheological properties, texture, and water holding capacity (WHC) were evaluated. For the properties of the SPI-Nar pre-aggregate, under an OH treatment of 6 V/cm, the α-helix and β-turn structures of the SPI-Nar pre-aggregate were found to be 17.72% and 15.30%, respectively, with a uniform particle size distribution. The surface hydrophobicity, total free sulfhydryl, and turbidity were measured to be 794, 6.54 μmol SH/g, and 0.364, respectively. Atomic force microscopy images showed an Rq value of 3.63 and a height of 14.5 nm. Regarding the properties of the SPI-Nar-CS protein gel, when the CS addition level was 3%, the gel (SPI-Nar-CS 3) exhibited the best rheological properties, with hardness, springiness, and cohesiveness values of 10.17 g, 0.79 mm, and 0.31, respectively. The WHC and LF-NMR analysis of the protein gel revealed that SPI-Nar-CS 3 exhibited a WHC of 90.67% and optimal LF-NMR imaging and apparent state. SEM images showed the best microstructure at this CS addition level. In addition, the synergistic mechanism between the OH treatment and CS addition in protein gel formation was discussed, providing a theoretical foundation for future applications in the food industry.