Preparation, characterization, and application of gallic acid-mediated photodynamic chitosan-nanocellulose-based films.

In this study, an active film composed of gallic acid (GA), chitosan (CS), and cellulose nanocrystals (CNC) was prepared using a solution casting method and synergistic photodynamic inactivation (PDI) technology. Characterization of the film showed that the CS-CNC-GA composite film had high transparency and UV-blocking ability. The addition of GA (0.2 %-1.0 %) significantly enhanced the mechanical properties, water resistance, and thermal stability of the film. The tensile strength increased up to 46.30 MPa, and the lowest water vapor permeability was 1.16 × e-12 g/(cm·s·Pa). The PDI-treated CS-CNC-GA1.0 composite film exhibited significantly enhanced antibacterial activity, with inhibition zone diameters of 31.83 mm against Staphylococcus aureus and 21.82 mm against Escherichia coli. The CS-CNC-GA composite film also showed good antioxidant activity. Additionally, the CS-CNC-GA1.0 composite film generated a large amount of singlet oxygen under UV-C light irradiation. It was found that using the CS-CNC-GA1.0 composite film for packaging and storage of oysters at 4 °C effectively delayed the increase in pH, total colony count, and lipid oxidation in oysters. In conclusion, the CS-CNC-GA composite film based on PDI technology has great potential for applications in the preservation of aquatic products.