Plasmonic bismuth-modified gelatin-based photothermal antimicrobial edible films for enhanced tomato preservation

The increasing demand for healthy and safe food with minimal use of non-degradable chemical preservatives facilitates the development of safe and efficient food packaging materials. Near-infrared (NIR) responsive materials, with advantages of remote control and strong penetration, show great potential in food preservation. In this work, NIR-responsive composite films for active food packaging were developed based on Bi-PVP nanoparticles and fish scale gelatin (FSG). Spherical Bi-PVP nanoparticles (5 nm in size) were incorporated into the FSG film matrix to construct the FSG/Bi-PVP antimicrobial nanocomposite edible film. The surface plasmon resonance (SPR) effect of metallic Bi nanoparticles enhanced the photogenerated carrier separation and extended the light absorption range of the composites, resulting in high antimicrobial activity (antibacterial rate of 97.68 % against E. coli and 99.99 % against S. aureus) under NIR light irradiation at 808 nm. Subsequent preservation experiments confirmed that the shelf-life of tomatoes was apparently extended by the combination of the film and near-infrared light. In addition, the FSG/Bi-PVP films also exhibited good biocompatibility with human immortalised epidermal cells (HaCaT), indicating their biosafety. Overall, this study provides a promising approach for innovative packaging strategies and holds great potential for application in the food packaging industry.