Formation mechanism of yeast-soy protein extrudates during high-moisture extrusion and their digestive properties

Yeast protein (YP) has generated significant interest due to its potential for high production efficiency and nutritional value. This study investigated the effects of YP ratios (0-50%) on the formation mechanism of extrudates prepared by YP and soy protein isolate (SPI) during high-moisture extrusion and their in vitro dynamic digestive properties. Extrudates containing 40% YP had the most abundant fiber structures. Combined segmental sampling and closed cavity rheometer (CCR) simulated the extrusion process (mixing, melting, cooling, and extrudate) found that YP was dispersed throughout the SPI network structure in both the mixing and melting zones, and YP as a separate phase transformed SPI into a "mushy" state, facilitating the development of intermolecular forces and promoting the reconstruction of the protein network in the cooling zone. Additionally, in vitro dynamic gastrointestinal digestion has shown that extrudates with high YP content had higher gastric emptying rates and produced digestates with smaller particles. Extrudates containing 30% YP exhibited the highest essential amino acid index (EAAI). Overall, this finding provides a promising strategy for production of meat analogues with high quality using yeast protein.