Thyme essential oil enhanced chitosan/zein composite films: Antioxidant properties, antibacterial mechanism and...

Fresh fruits are highly perishable due to their high-water content and rapid respiration rates, which result in a limited shelf life. Consequently, the development of films composed of natural ingredients with high safety and antibacterial properties is essential for improving fruit preservation and mitigating microbial contamination. This study focuses on the preparation of a thyme essential oil (TEO)-based chitosan-zein composite film. The film's physicochemical properties, antioxidant capacity, antibacterial activity, and cytocompatibility were systematically evaluated. The results showed that the film containing 1.2% TEO exhibited the lowest water vapor permeability (0.39 mm·g·m^-2·h^-1·kPa^-1). The incorporation of TEO significantly enhanced the antibacterial performance of the films; in particular, the film with 2.4% TEO produced inhibition zone diameters of 17.17 ± 0.29 mm against S. aureus and 15.5 ± 0.5 mm against E. coli. The antibacterial mechanism was mainly associated with the induction of oxidative stress, promotion of lipid peroxidation, and disruption of bacterial cell membrane integrity. Cytotoxicity assays demonstrated that the viability of L-02 cells remained above 60% after 24 h of exposure to the films, indicating low cytotoxicity and good cytocompatibility. In strawberry preservation tests, the TEO-incorporated chitosan-zein composite films effectively inhibited microbial growth, reduced weight loss and firmness decline, and delayed the degradation of total soluble solids, thereby extending the shelf life of strawberries by approximately 2-3 days compared with the control. Overall, the TEO-chitosan-zein composite films exhibit promising potential for applications in food packaging and fruit preservation.