Synergistic inhibition of lipid and protein oxidation in refrigerated pork by a chitosan-based composite film incorporated with ZnO and lysine-modified walnut melanin.

Abstract

This study aimed to develop a biodegradable active film to address the environmental and health challenges posed by petroleum-based plastics, as well as to meet the urgent demand for food preservation. Chitosan (CS)-based films (CS/ZnO/L-WFM) loaded with Lysine-modified walnut flower melanin (L-WFM) and ZnO were prepared using the solvent casting method. The films were characterized by ATR-FTIR, TG-DSC, XRD, and SEM to determine their functional groups, thermal stability, crystal structure, and surface morphology. Furthermore, the physical, barrier, antioxidant, and antibacterial properties of the films were determined, and their application in preserving refrigerated pork was evaluated. The results indicated that ZnO and L-WFM were incorporated into the CS matrix primarily through hydrogen bonding. These interactions effectively resulted in a smoother and denser surface morphology while simultaneously significantly enhancing the thermal stability and crystallinity of the CS-based films. Among the formulations, CS/ZnO/L-WFM-2 (with 0.02% L-WFM) exhibited the optimal balance of mechanical strength, water resistance, UV barrier, antioxidant (DPPH radical scavenging of 77.36%, ABTS radical scavenging of 75.08%), and antibacterial properties, whereas further increasing L-WFM to 0.03% (CS/ZnO/L-WFM-3) did not yield significant additional improvements due to saturation in interfacial interactions and functional efficacy. Meanwhile, the optimized film also demonstrated excellent biodegradability and effectively delayed microbial growth, lipid and protein oxidation in refrigerated pork, extending its shelf life by 5 days. In conclusion, the CS/ZnO/L-WFM-2 multifunctional biodegradable packaging film prepared in this study has broad application prospects in meat preservation and environmental sustainability.