Development of a Photothermal Antibacterial Film using Purple Corncob Anthocyanin and Its Application in Cherry Tomato Preservation

Food packaging not only conveys information about the food but also protects it from environmental pollution during processing and storage. Traditional photothermal materials, often reliant on costly precious metals and inorganic nanoparticles, face limitations in costs and safety. This study develops a cost-effective, sustainable photothermal packaging solution using agricultural waste-derived purple corn cob extract (PCCE), naturally occurring iron ions, and biodegradable chitosan (CS). A simple one-pot method was employed to create PCCE/Fe-chitosan composite films that exhibit high photothermal efficiency and antibacterial properties. The PCCE/Fe composite was prepared by mixing PCCE containing anthocyanins with iron ions, and then the PCCE/Fe composite was mixed with chitosan to prepare the PCCE/Fe-CS composite membrane. Microstructural analysis revealed that the PCCE/Fe complexes were uniformly dispersed in the CS matrix, enhancing the films’ tensile strength, water vapor barrier properties, and thermal stability. In vitro tests showed potent antibacterial activity against Escherichia coli and Staphylococcus aureus . A 24-day storage trial demonstrated that cherry tomatoes wrapped in the PCCE/Fe-CS photothermal film had significantly less weight loss, pH change, and hardness reduction compared to those wrapped in polyethylene (PE) and CS films, indicating superior quality preservation. These results suggest that the PCCE/Fe-CS composite film offers a promising, environmentally friendly solution for food packaging with enhanced thermal sterilization and improved shelf-life extension.