Texture and structure of high-moisture extrudates produced from soybean protein isolates with different 7S/11S globulin ratios

The effects of different 7S/11S ratios of soybean isolate proteins (SPI) on the structure of textured vegetable proteins (TVP) and their formation mechanisms were investigated using a temporal multi-scale approach to understand the formation of fibrous structures throughout the extrusion process. Although the effect of different 7S/11S ratios on the secondary structure of the SPI was less, the water-holding and emulsification properties of the isolated proteins differed significantly. The results of the high-moisture extrusion experiments showed that the hardness, elasticity, and chewiness of TVP increased significantly with higher 7S/11S ratio and that the degree of organization improved by 14.28 %. Correlation analysis showed that proteins with high 7S/11S ratios had higher water-holding and emulsification stability mainly because of improvement in the water-holding property of the SPI, forming more disulfide bonds during extrusion, increasing the hardness, elasticity, and chewiness of TVP. Analysis of the texture formation process showed that the material underwent extrusion in the die zone, where the β-sheet content increased and inter-molecular disulfide bonds and protein aggregates were formed. The material was subjected to a force in the vertical extrusion direction in the molding area, which caused closely aggregated proteins to disperse, which further aggregated and cross-linked, resulting in the formation of fiber structure. Investigations on the formation of TVP from SPI with different 7S/11S ratios provided support for the preparation of suitable SPI for use in high-moisture textured protein processing.