Antimicrobial activity and preservation efficiency of TEMPO-oxidized chitin/5-aminolevulinic acid films mediated by photodynamic inactivation against salmon fillets

A novel photodynamic inactivation (PDI)-mediated antimicrobial packaging film (APF) was successfully fabricated by covalently grafting 5-aminolevulinic acid (ALA) onto the surface of TEMPO-oxidized chitin film (O-CT). The O-CT/ALA films exhibited good mechanical strength, remarkable UV-blocking capacity, high thermal stability, and chemical stability. Notably, the grafted ALA induced the generation of endogenous protoporphyrin IX in bacterial cells, and they were excited to produce ROS under the irradiation of blue light. Consequently, the films inactivated > 7.00 log CFU/mL of Vibrio parahaemolyticus and 3.29 log CFU/mL of Staphylococcus aureus , as well as efficiently eradicated the bacterial biofilms by disrupting their architectural structures. More importantly, the films inhibited the growth of native bacteria in salmon during storage at 4 °C and 25 °C. Therefore, the PDI-mediated APF is valid in inactivating bacteria and ensuring food quality in the food industry.