Enhancement of riboflavin-mediated photodynamic inactivation against Salmonella on tuna fillets coupled with slightly basic electrolyzed water

This study aimed to develop an efficient PDI system to kill Salmonella in solution or on tuna fillets under 455 nm blue light-emitting diodes (LED) irradiation, by selecting slightly basic electrolyzed water (SBEW) as the solvent. Results showed that the solvent of SBEW increased the solubility of riboflavin, and notably strengthened the production of ROS compared to normal saline solution. On this basis, the riboflavin-mediated PDI coupled with SBEW enhanced the inactivation of Salmonella, supported by that the viability of Salmonella was significantly (P < 0.05) inactivated by 5.02 Log10 CFU/mL with 9.36 J/cm2 irradiation and 80 μM riboflavin, and no viable cells were detected when the irradiation dose was increased to 12.48 J/cm2. The action mechanisms showed that this novel PDI damaged the cell membrane causing the leakage of cellular contents, degraded the genomic DNA and enhanced the lipid peroxidation in Salmonella. In addition, the PDI system efficiently killed >4.0 Log10 CFU/g of Salmonella on tuna fillets with 120 μM riboflavin and 18.72 J/cm2 irradiation. Furthermore, the PDI system decelerated the proliferation of Salmonella, the changes of electrical conductivity, pH and color, and lipid oxidation in tuna fillets during the storage. This study provides a promising PDI system to control food pathogen contamination and preserve the storage quality of seafood.