Antibacterial mechanism of non-thermal treatments against Pseudomonas putida and their application in tilapia fillets.

Pseudomonas putida is a common spoilage organism in food. This study investigated the inhibitory effects of plasma-activated water (PAW), ozone water (OW), and slightly acidic electrolyzed water (SAEW) on P. putida by examining bacterial morphology, membrane structure, redox balance, metabolic activity, and molecular mechanisms. The bactericidal effects of these compounds in real food systems of tilapia fillets were verified. PAW and SAEW caused bacterial rupture and leakage, whereas OW induced plasmolysis. The saturated fatty acid content of the cell membrane increased from 67.93 % in the control group to 86.94 % in the SAEW group. Compared with those in the control group, the intracellular reactive oxygen species (ROS) levels in the PAW group were increased by sixfold. The enzyme activities of superoxide dismutase (SOD), catalase (CAT), respiratory chain dehydrogenase (RCD), and alkaline phosphatase (AKP) were inhibited by the modification of their active sites and metal ligands. The three treatments altered the microbial diversity, total viable count, and abundance of P. putida in tilapia fillets. In summary, the three treatments effectively sterilized P. putida in food by destroying the structure and metabolism of the bacteria, with PAW exhibiting the most potent bactericidal effect on P. putida in tilapia fillets.