Engineering quercetin assemblies as multifunctional photodynamic nanofillers in gelatin/κ-carrageenan films for postharvest preservation.

Conventional food packaging functions as a passive barrier, failing to dynamically counter microbial contamination that accounts for 30-40% of postharvest losses. Herein, inspired by polyphenol coordination chemistry, a light-driven, metal-phenolic coordination system was engineered with programmable reactive oxygen species (ROS) release for active polysaccharide films. FQM nanoparticles (FQM NPs) were prepared via a one-pot supramolecular assembly of ferrous ions, plant-derived quercetin, and aromatic aldehyde, and subsequently incorporated homogeneously into a gelatin/κ-carrageenan (GCA) matrix. The resulting 0.5 wt% FQM-GCA film exhibits multifunctionality: mechanical reinforcement, enhanced gas barrier, and photodynamic antimicrobial activity via breaking the ROS balance by light irradiation. This system achieved complete inactivation (100%) of Staphylococcus aureus and Escherichia coli and > 99.4% suppression of fungal pathogens (Penicillium expansum and Botrytis cinerea). Comprehensive validation from nanostructure characterization to postharvest preservation of diverse agricultural products demonstrates a significant shelf-life extension. This work establishes a green, precise, and multifunctional platform for next-generation active packaging, aligning with circular economy principles and providing a transformative solution for sustainable food preservation.