Bamboo Shoot Shell Powder-Regulated High-Moisture Extruded Soy Protein Isolate: Improving Fibrous Structure and Physicochemical Properties

Textured vegetable proteins produced by high-moisture extrusion often exhibit limited controllability of fibrous structure, restricting their utilization in plant-based meat analogues. In this work, bamboo shoot shell powder (BSSP) was incorporated during the high-moisture extrusion of soy protein isolate (SPI) to modulate the multiscale structure and functionality of the resulting extrudates. During high-moisture extrusion, the incorporation of 5–10% BSSP promoted the evolution of extrudate microstructures into channel-like pores aligned along the extrusion direction. Moderate BSSP addition (~15%) increased β-sheet and β-turn contents while decreasing α-helix and random coil fractions. These conformational transitions, linked to enhanced hydrogen bonding and weakened hydrophobic interactions, generated extrudates with improved thermal stability. Moreover, the addition of 15~20% BSSP increased the hardness and chewiness of the extrudates, as revealed by texture profile analysis. BSSP incorporation also enhanced the freeze–thaw stability of the extrudates while reducing bitterness. These findings suggested that BSSP acted as a functional structural regulator, offering an approach for tailoring plant-based meat analogues with improved microstructural organization and textural properties.