A photodynamic inactivation-mediated 5-aminolevulinic acid-grafted chitin film for preserving salmon: antibacterial efficiency and storage quality maintenance

A 5-aminolevulinic acid (ALA)-grafted chitin film (O-CT/ALA film) with a photodynamic inactivation (PDI) against bacteria was previously fabricated, and its preservation efficiency and mechanisms against salmon were explored. Results showed that the PDI-mediated O-CT/ALA film exhibited sustained generation capability of ROS, which had potent antibacterial activity in vitro under blue LED irradiation. Moreover, this film significantly inactivated the native bacteria and suppressed their growth in salmon fillets during storage at 4 °C and 25 °C, extending the shelf-life by >2 days compared to commercial polyethylene film. Consequently, the O-CT/ALA film retained the textural integrity of salmon muscle, stabilized the physicochemical properties of pH value, electrical conductivity, color appearance, and reduced the level of protein and lipid oxidation. Notably, it obviously reduced the accumulation of microbial metabolites and oxidation-related volatile compounds in salmon. Therefore, the PDI-mediated film shows a valid ability in preserving the storage quality of aquatic products.