Exploring the mechanism of amylose/amylopectin improving formation of yeast-soy protein high-moisture extrudates based on small and large amplitude oscillatory shear rheology

Yeast protein (YP) has high production efficiency and comprehensive nutritional value compared to soy protein isolate (SPI). However, relatively higher proportion of YP replaces SPI seriously affect the structure of extrudates in the production of meat analogues. This study investigated starch addition (amylose/amylopectin) on the structure of YP-SPI extrudates with higher YP proportion and formation mechanism by using closed cavity rheometer simulated the high-moisture extrusion process (mixing, melting, cooling, and extrudates). The proportions of YP:SPI:amylose:amylopectin were set as 5:5:0:0, 5:4:1:0, 5:4:0:1, and 5:4:0.5:0.5. Starch addition could improve the structure formation of extrudes, but the improvement effect varied depending on the type of starch. Compared to amylose, incorporating amylopectin significantly enhanced the fibrous degree of extrudates and improved their tensile resistance. Furthermore, small amplitude oscillatory shear (SAOS) was used to establish texture map. In the mixing and melting zones, amylose decreased the miscibility of protein and starch phase, while amylopectin had positive effect on the integrity and uniformity of protein network. Amylopectin could transform the extrudates into a "mushy" state, contributing to reconstruct protein network. Large amplitude oscillatory shear (LAOS) demonstrated amylopectin had higher energy dissipation ratio in the cooling zone, indicating the uniform "phase separation" facilitated the formation of fiber structure of extrudates. This study provides technical reference for the preparation of high-moisture extrudates using YP as a substitute for SPI based on starch type addition.