Structure modulation and physicochemical regulation: study on the structure-function relationship of soy protein isolate regulated by Coprinus comatus by-products in high-moisture extrusion.

High-moisture extrusion is an effective technique for structuring plant proteins into fibrous meat analogs. This study investigated the regulatory mechanism of the Coprinus comatus by-products on soy protein isolate conformational rearrangement and physicochemical properties during high-moisture extrusion. At addition levels ≤20%, the by-products directed SPI molecular alignment and ordered aggregation, promoting β-sheet formation, enhancing fiber formation in the extrudates, and improving elasticity and chewiness. In contrast, additions ≥30% induced excessive phase separation and steric hindrance, disrupting the protein matrix continuity and causing disrupted fibrous structures, textural hardening, and discoloration. Mechanistic analysis demonstrated that the by-products facilitated the formation of ordered, stable fibrous structures by modulating system rheological behavior, inhibiting random protein aggregation, directing polypeptide chain assembly along the shear direction, and optimizing water distribution. This work provides a theoretical basis for the high-value utilization of Coprinus comatus by-products and the regulation of fibrous structures in plant-based protein products.