Preparation, properties, and application of soy protein isolate nanofiber-chitosan based films: Focus on the impact of morphologically diverse SPIFs

: This study fabricated soy protein isolate nanofibers (SPIFs) with different morphologies by modulating heat treatment time, then incorporated them into chitosan (CH) to make SPIF-CH composite films. The SPIF morphology’s effects on the film’s physicochemical properties, mechanical performance, and cherry tomato preservation efficacy were systematically evaluated. Results showed that SPIFs enhanced composite film’s mechanical properties via cross-linking and filling, solving pure CH or protein film’s brittleness. The W-12 film which contained medium-length (approximately 1.5 μm) SPIFs formed after a 12-hour fibrillation process had optimal performance: 18.29 MPa tensile strength (a 66.3% increase over pure chitosan film) and 108.04% elongation (71.4% improvement compared to pure chitosan film). Films with SPIFs from 12h or 24h fibrillation had better cherry tomato preservation (suppressed respiration by over 50%) and good stability, degradability and recyclability, providing a new strategy for high-performance sustainable packaging.