Effect of Modification Treatment on the Properties of Soy Protein Isolate/Chitosan/Auricularia auricular Polysaccharide Composite Film

Chitosan-based composite film incorporated with soybean protein isolate and Auricularia auricular polysaccharide (SPI/CS/AAP) was modified by ultrasonic, microwave, ultraviolet (UV) or their combination to evaluate the effect of different modification methods on the film’s properties. The results showed that the mechanical properties and barrier properties of the film were improved by ultrasonic, microwave and UV modification treatments. Among them, the effect of ultrasonic-microwave synergistic modification was the most pronounced, resulting in the highest tensile strength (TS) and elongation at break (EAB) (21.67 MPa and 78.02%, respectively) and lowest water vapor permeability (WVP) and oxygen permeability (OP) (1.34 × 10^-12 g/(cm·s·Pa) and 0.47 × 10^-2 g/(m²·d), respectively). Furthermore, the synergistic modification could significantly increase the brightness, whiteness and light transmittance of the film. The composite film was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), revealing that the hydrogen bonding between the film matrix molecules was strengthened by ultrasonic, microwave and UV treatments, and the modified film exhibited a dense and stable network structure and improved thermal stability.