Investigating the Synergistic Bactericidal Effects of Cold Plasma and Ultraviolet Radiation on Pseudomonas fragi

Cold plasma is a novel non-thermal processing technology with broad application prospects in food preservation. When combined with other physical sterilization technologies, it enhances sterilization efficiency and broadens its application scope, providing a safe and effective alternative to traditional sterilization methods. In this paper, the sterilization effect of surface dielectric barrier discharge (SDBD) plasma combined with 222 nm ultraviolet (UV) irradiation against Pseudomonas fragi (P. fragi) was explored for the first time. The sterilization process parameters of SDBD + UV were optimized using the response surface methodology. And the sterilization mechanism of SDBD + UV was preliminary elucidated. The results indicated that the SDBD + UV treatment was highly effective against P. fragi. It could eliminate 6.35 Log CFU/g of P. fragi within 150 s, establishing optimal sterilization parameters: a radiation distance of 16.4 cm and a saving time (a period of preservation in which the samples were retained in the device after the treatment) of 120 s. Furthermore, the treatment caused significant damage to the cell membrane of P. fragi, leading to membrane perforation and content leakage. It also induced oxidative stress, as evidenced by membrane lipid peroxidation, alterations in intracellular reactive oxygen species (ROS) content, and a decrease in antioxidant enzyme activity. This study provides a theoretical basis for the application of cold plasma combined with 222 nm UV treatment in the meat industry.