Effect of Eggshell Membrane Enzymatic Hydrolysate on Antibacterial and Antioxidant Properties of Soybean Protein Packaging Film

Soybean protein film has good mechanical properties and is an environment-friendly edible packaging material. However, its antibacterial and antioxidant properties are poor, which limits its application to perishable food packaging. In this study, composite films were prepared from soy protein isolate (SPI) as the film-forming substrate with different amounts of an enzymatic hydrolysate of eggshell membrane (ESM) added, and their physical and functional properties were investigated such as mechanical, barrier and optical properties, contact angle, free radical scavenging capacity and antibacterial zone diameter. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize their structures. Finally, we discussed the effect and mechanism of ESM hydrolysate concentration on the structure and properties of composite films. The results showed that the thickness, tensile strength, elongation at break and contact angle of the composite film with 4 g/100 g enzymatic hydrolysate increased by 115.38%, 100.78%, 57.87% and 110.42% respectively compared with pure SPI film, and the water vapor permeability (WVP) and oxygen permeability (OP) decreased by 63.54% and 84.07%, respectively. The antioxidant and antibacterial properties of composite films increased with increasing hydrolysate concentration, and the surface exhibited a dense network structure, due to the formation of intermolecular hydrogen bonds, and good compatibility between SPI and ESM hydrolysate. The results of this study will provide a theoretical basis and technical support for designing active packaging for perishable foods and comprehensive utilization of egg by-products.