Sustained-Release Chitosan/Gelatin Active Packaging Films Incorporating Quercetin-Loaded Zeolitic Imidazolate Framework-8 for Cherry Tomato and Grape Preservation

Abstract

Biodegradable active packaging films with sustained antioxidant and antibacterial activity are promising for fresh produce preservation, but direct addition of natural active agents often causes poor dispersion, low stability, and burst release. Herein, quercetin-loaded zeolitic imidazolate framework-8 nanoparticles (Qu@ZIF-8) were prepared by a co-precipitation method and incorporated into a chitosan/gelatin (CS/Gel) matrix to fabricate sustained-release active films. Structural analyses confirmed quercetin loading while preserving the crystalline and porous features of ZIF-8. Qu@ZIF-8 improved the water resistance, UV-light shielding, mechanical strength, and water vapor barrier properties of CS/Gel films. At 9 wt% Qu@ZIF-8, tensile strength increased from 5.42 to 11.07 MPa, and water vapor permeability decreased from 5.85 × 10⁻¹¹ to 4.86 × 10⁻¹¹ g m⁻¹ s⁻¹ Pa⁻¹. Release tests in food simulants showed that CS/Gel-Qu@ZIF-8 films reduced initial burst release and produced a more sustained quercetin migration profile than films containing free quercetin. The optimized film showed DPPH and ABTS radical scavenging activities of 77.51% and 70.34%, respectively, and reduced Escherichia coli and Staphylococcus aureus survival to 1.9% and below 1.0%, respectively. The biocompatibility and environmental compatibility of the system were demonstrated by hemolysis, Caco-2 cytotoxicity, and bean sprout growth assays. In storage trials, CS/Gel-Qu@ZIF-8 better maintained the appearance, physicochemical quality, and sensory attributes of both cherry tomatoes and grapes, while reducing yeast and mold growth. This study provides a feasible strategy for biodegradable sustained-release packaging films for fresh produce preservation.