Light-Responsive Biopolymeric Films Embedded with Natural Polyphenols: ROS-Mediated Suppression of Postharvest Microbial Decay in Perishable Fruits

The development of advanced antimicrobial packaging is crucial for ensuring food safety. This paper reports a novel photodynamic antibacterial film (PVA-CM@TFQ) that effectively combats microbial contamination, delays food spoilage and minimizes the risk of foodborne diseases transmission. Quercetin (Que) was encapsulated within a tannic acid-ferric ion (TA–Fe 3+ ) coordination network and embedded into a biodegradable polymer matrix composed of polyvinyl alcohol (PVA) and carboxymethyl chitosan (CM). The TA-Fe 3+ network significantly improved the stability of Que, while the resulting PVA-CM@TFQ demonstrated excellent mechanical properties, barrier performance, and biocompatibility. Upon light irradiation, the film produced reactive oxygen species (ROS), exhibiting potent photodynamic antibacterial activity, with inhibition rates of 99.83%, 99.42%, 100%, and 100% against Escherichia . coli, Staphylococcus . aureus , Candida. albicans , and Saccharomyces cerevisiae , respectively. When applied to raspberries, hawthorn, goldenberries, and lime, the film effectively prolonged shelf life by suppressing microbial proliferation, minimizing weight loss, and maintaining fruit firmness. These findings highlight a sustainable, light-responsive strategy for fruit preservation with significant potential in enhancing food safety.