AgNPs@cellulose reinforced gelatin/dialdehyde alginate photothermal composite film with enhanced barrier, antioxidant and antibacterial performance for perishable food preservation

The widespread use of petroleum-based plastics has raised increasing environmental concerns, driving the demand for biodegradable alternatives. In this study, a multifunctional bio-based composite film was developed via cross-linking of fish scale gelatin (FSG) and dialdehyde alginate (DAA), with AgNPs-loaded pomelo peel cellulose (AgNPs@PC) incorporated as an active filler. The synergistic effect of FSG/DAA cross-linking and AgNPs@PC reinforcement enhanced intermolecular interactions and formed a compact network, resulting in remarkable improvement in UV blocking (shielding rate > 90%), mechanical properties (tensile strength increased by 168.62%), gas barrier (water vapor and oxygen decreased by 61.67% and 65.36%, respectively), and thermal stability. Moreover, the composite film displayed excellent antioxidant (radical scavenging rate > 90%) and antibacterial efficiencies exceeding 99% against S. aureus and E. coli , attributed to the synergistic effects of AgNPs-mediated antibacterial activity and NIR-triggered photothermal inactivation. Soil burial and migration tests further confirmed the film's rapid biodegradability within 14 days and its compliance with food-contact safety standards. Packaging tests demonstrated its effectiveness in maintaining the post-harvest quality of strawberries and preserving the freshness of pork. Overall, this work provides a green strategy for developing multifunctional active films and demonstrates their strong potential for preserving perishable foods and extending shelf life.