Fabrication of gelatin-based photodynamic food packaging with dual-antimicrobial activity for enhanced pork preservation

Microbial spoilage is a major reason of global food waste. Photodynamic inactivation (PDI) showed promise as an antimicrobial strategy owing to the reactive oxygen species (ROS) produced by photosensitizer, but the short lifespan of ROS limited its penetration into cells and accordingly hindered its effectiveness against Gram-negative bacteria. In this study, a photodynamic composite film with aggregation-induced emission behavior and dual antimicrobial activity was developed by incorporating natural photosensitizer nanoparticles with ε-Polylysine (PL) into a matrix composed of gelatin and dialdehyde nanocellulose. The advantage of this design lay in the PL's role as a " forward team”, facilitating ROS penetration through perforating the external membrane or cell wall of bacteria, thereby enhancing the PDI efficiency and achieving a 6 log CFU/sample bacterial reduction within 15 min of light exposure. Moreover, the composite film exhibited minimal ultraviolet transmittance, high transparency (exceeding 86.57 %), hydrophobicity, and enhanced mechanical strength. Pilot studies further confirmed the composite film's effectiveness in inhibiting microbial growth, protein oxidation, lipid oxidation, and pH of pork samples, successfully extending the shelf life of fresh pork to 10 days at 4 °C. Therefore, this study proposes a green and efficient synergistic antimicrobial strategy with PDI, demonstrating a potential application for enhanced pork preservation.