Ergosterol Modulates Physicochemical Properties and Conformational Changes in High-Moisture Soy-Wheat Protein Extrudates

This work explores the impact of ergosterol (ERG) addition (0%, 0.5%, 1.0%, 1.5%, and 2.0%) on the physicochemical properties, conformational changes, and digestive characteristics of soy protein isolate (SPI) and wheat gluten (WG) processed by high-moisture extrusion. The results demonstrated that the incorporation of ERG significantly reduced the apparent viscosity and dynamic moduli of the feedstock system, enhancing melt fluidity and consequently reducing extrusion torque, die pressure, and specific mechanical energy. An appropriate amount of ERG (1.0%) effectively facilitated the development of a distinct fibrous morphology, increased the fibrous degree, lightened the color, and softened the texture. However, excessive addition weakened the fibrous structure due to excessively high fluidity. ERG influenced protein aggregation behavior through hydrophobic interactions, reduced thermal stability, and induced a transition in secondary structure from β-turns to α-helices. The in vitro digestibility initially decreased and then increased, with the lowest value observed at 1.0% ERG. This study indicates that ERG can elevate the performance and value of extruded products by modulating protein structure and rheological behavior, providing a theoretical basis for its application in plant-based meat analogue products.