Natural deep eutectic solvent-extracted propolis bioactives and ZIF-L integrated PVA films for active packaging and oyster preservation

Green NADES extracted propolis bioactives integrated into PVA/ZIF-L films. • Leaf-like ZIF-L nanocarriers enhanced UV shielding and film flexibility. • PVAD/ZIF0.5 exhibited 70.2% DPPH scavenging and strong antibacterial activity. • Composite films effectively inhibited oyster spoilage during 10 d refrigeration. • Synergistic DES–ZIF-L system enabled safe and sustainable active packaging. Active packaging materials with integrated antioxidant and antimicrobial functions offer an effective strategy for extending the shelf life of highly perishable aquatic foods. In this study, a multifunctional composite film was fabricated by incorporating natural deep eutectic solvent (NADES)-extracted propolis bioactives and two-dimensional ZIF-L nanocarriers into a poly(vinyl alcohol) (PVA) matrix. The synthesized ZIF-L exhibited a characteristic leaf-like morphology with an average particle size of 140 nm, facilitating its uniform dispersion within the polymer network. Structural analyses confirmed that ZIF-L and propolis extracts were successfully integrated into the PVA matrix through hydrogen bonding and physical interactions. The resulting PVAD/ZIF composite films displayed enhanced flexibility and improved UV-shielding properties while maintaining good transparency. The optimized PVAD/ZIF0.5 film exhibited the highest antioxidant activity with a DPPH radical scavenging rate of 70.2%, and showed strong antimicrobial activity against Staphylococcus aureus and Escherichia coli . Application tests demonstrated that oysters packaged with PVAD/ZIF0.5 maintained TVB-N values below 30 mg/100 g and a TVC of 5.80 log CFU/g after 10 days of refrigerated storage, whereas control samples exceeded spoilage limits. Furthermore, the PVAD/ZIF0.5 retained good mechanical integrity under high-humidity conditions, while Zn 2+ migration remained well below the regulatory limit for food-contact materials. In addition, cytocompatibility assays showed high cell viability (96.28%) after 24 h incubation. These findings demonstrate that the PVAD/ZIF composite film is a promising biodegradable active packaging material for aquatic food preservation. Download: Download high-res image (113KB) Download: Download full-size image