Synergistic inactivation of foodborne pathogens and biofilm cells using plasma-activated water combined with mild heat

Biofilms formed by foodborne pathogens such as Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes pose significant challenges in the food industry due to their enhanced resistance to sanitizing agents and their ability to cause cross-contamination on food contact surfaces. While chemical or hot water treatments can be used, there is a need for alternatives that do not generate harmful by-products or cause thermal damage. The objective of this study was to evaluate the efficacy of the combination of plasma-activated water with mild heat (PAW-MH) for microbial inactivation and eradiation of biofilms on high-density polyethylene surfaces, a material commonly used in the food industry. In this study, while no significant difference in pH or oxidation reduction potential was observed in PAW-MH at 50 °C, synergistic inactivation of planktonic cells was observed without inducing sublethally injured cells. To elucidate the underlying mechanism of the enhanced efficacy of the combined treatment, intracellular alterations were investigated. Cell membrane permeability and intermembrane enzymatic activity revealed significant damage in the cell envelope. Additionally, an increase in intracellular reactive oxygen species was observed due to damage of cell membrane and inhibition of antioxidant enzyme activity. Furthermore, PAW-MH effectively inactivated biofilm-embedded pathogens, achieving greater than 5 orders magnitude after 5 min of treatment. This result is linked with removal of biofilm biomass, suggesting PAW-MH as a potential method for overcoming the protective extracellular polymeric substance barrier. Our study proposes PAW-MH as an effective antibacterial and anti -biofilm treatment, suggesting its application for the decontamination of food contact surfaces. • Combined treatment of plasma-activated water and 50 °C mild heat (PAW-MH) was applied. • PAW-MH synergistically inactivated foodborne pathogens without causing injured cells. • Cell membrane and antioxidant enzymes were significantly ( P < 0.05) damaged by PAW-MH. • PAW-MH for 5 min reduced the biofilm cells formed on HDPE by more than 5 log CFU/cm 2 .