Light-responsive Cu₂O-tannic acid nanoparticles enhance the fruit preservation performance of pectin films

Pectin, a natural polysaccharide, has attracted considerable attention as a sustainable packaging material owing to its biocompatibility, biodegradability, and film-forming ability. However, its practical applications are hindered by brittleness, moisture sensitivity, and limited functionality. In this work, Cu₂O-tannic acid (TA) nanoparticles, prepared by coating Cu₂O with TA, were incorporated into pectin (PE) to fill nanoscale voids and establish hydrogen bonding between TA and pectin. The resulting Cu₂O-TA-PE films exhibited outstanding mechanical and functional properties. Compared with pristine PE films, the Cu₂O-TA-PE film effectively blocked ultraviolet light in the 200-300 nm range. Moreover, the 2,2-Diphenyl-1-picrylhydrazyl radical scavenging rate increased markedly from 18.46 % to 91.68 %, while tensile strength improved by 1.2-fold. The films also showed excellent photothermal conversion capability, maintaining a temperature above 51.0 °C after five cycles of light irradiation, along with strong antibacterial activity against Escherichia coli, Staphylococcus aureus, and Botrytis cinerea. Cytotoxicity and migration tests confirmed the films' biocompatibility, while strawberry preservation experiments demonstrated effective shelf-life extension. Notably, the casting solution also functioned as an efficient fruit-coating preservative. Collectively, these findings underscore the multifunctional potential of the composite films, highlighting their promise as sustainable materials for food preservation.