pH-Responsive Chitosan-based Films Incorporated with ZIF-8@ Dihydromyricetin Nanoparticles for Enhanced Grape Preservation

The development of active packaging with sustained antimicrobial and antioxidant functions is crucial for extending the shelf life of highly perishable fruits. In this study, we developed a novel composite film by incorporating dihydromyricetin (DMY)-loaded zeolitic imidazolate framework-8 (ZIF-8) nanoparticles into a chitosan (CS) matrix. Scanning electron microscopy (SEM) confirmed the good compatibility between ZIF-8@DMY and the chitosan matrix at optimal loadings (2.5–15wt%). Importantly, the incorporation of ZIF-8@DMY significantly enhanced the mechanical properties of the composite films, increasing tensile strength by approximately 4.8-fold (from 1.77 to 8.50 MPa). Concurrently, critical physical properties including water vapor permeability, hydrophilicity and UV-vis transmittance were also enhanced. The composite films exhibited intelligent pH-responsive release of DMY. Furthermore, the ZIF-8@DMY/CS films exhibited potent in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus , with the 5% ZIF-8@DMY/CS film reducing E. coli counts by 5.38 log CFU/mL. In the grape preservation test, the 5% ZIF-8@DMY/CS film effectively mitigated weight loss and retained higher levels of total soluble solids (TSS) and ascorbic acid (V C ) over10 days of cold storage. These findings highlight that ZIF-8@DMY/CS composite films are a promising smart active packaging material for preserving the postharvest quality of fresh produce.