Antibacterial potency of riboflavin-mediated photodynamic inactivation against Salmonella and its influences on tuna quality

This study investigated the antibacterial potency of novel riboflavin-medicated blue light-emitting diode (LED) photodynamic inactivation (PDI) against Salmonella and its biofilms, and also evaluated its potency to kill Salmonella on tuna. Results showed that the PDI inactivated >6.0 Log CFU/mL of planktonic Salmonella with 9.36 J/cm2 irradiation dosage and 150 μM riboflavin. Antibacterial analysis indicated that the PDI treatment destroyed the cell wall, degraded the cytoplasmic RNA and disrupted the cell membrane functions, but barely degraded the genomic DNA of Salmonella. Meanwhile, the PDI treatment potently eradicated the biofilms of Salmonella. Additionally, the PDI effectively reduced 2.1 Log CFU/mL of Salmonella on tuna with 93.6 J/cm2 irradiation dosage and 150 μM riboflavin. It was also found that higher irradiation dosage promoted the transition of trapped water to free water in extra myofibrillar space, and collectively accelerated the lipid oxidation, but it had no obviously negative effect on the total protein and the total volatile basic nitrogen content of tuna. Therefore, this study deepens the understanding of the inactivation potency and mechanisms of riboflavin-mediated blue LED PDI against foodborne pathogens, as well as its effects on the food quality.