The synergistic bactericidal effect of simultaneous 222 nm krypton-chlorine excilamp and 307 nm UVB light treatment on sliced cheese and its mechanisms

In this study, we investigated the combined effect of 222 nm krypton-chlorine excilamp (EX) and 307 nm ultraviolet-B (UVB) light on the inactivation of Salmonella Typhimurium and Listeria monocytogenes on sliced cheese. The data confirmed that simultaneous exposure to EX and UVB irradiation for 80 s reduced S. Typhimurium and L. monocytogenes population by 3.50 and 3.20 log CFU/g, respectively, on sliced cheese. The synergistic cell count reductions in S. Typhimurium and L. monocytogenes in the combined treatment group were 0.88 and 0.59 log units, respectively. The inactivation mechanism underlying the EX and UVB combination treatment was evaluated using fluorescent staining. The combination of EX and UVB light induced the inactivation of reactive oxygen species (ROS) defense enzymes (superoxide dismutase) and synergistic ROS generation, resulting in synergistic lipid peroxidation and destruction of the cell membrane. There were no significant (P > 0.05) differences in the color, texture, or sensory attributes of sliced cheese between the combination treatment and control groups. These results demonstrate that combined treatment with EX and UVB light is a potential alternative strategy for inactivating foodborne pathogens in dairy products without affecting their quality.