Stability of electrolyzed oxidizing water and its efficacy against cell suspensions of Salmonella Typhimurium and Listeria monocytogenes

Electrolyzed oxidizing (EO) water has proved to be effective against foodborne pathogens attached to cutting boards and poultry surfaces and against spoilage organisms on vegetables; however, its levels of effectiveness against Listeria monocytogenes and Salmonella Typhimurium in cell suspensions have not been compared with those of other treatments. In this study, the oxidation reduction potentials (ORPs), chlorine concentrations, and pHs of acidic and basic EO water were monitored for 3 days at 4 and 25°C after generation. There were no differences between the pHs or ORPs of acidic and basic EO waters stored at 4 or 25°C. However, the free chlorine concentration in acidic EO water stored at 4°C increased after 24 h. In contrast, the free chlorine concentration in acidic EO water stored at 25°C decreased after one day. Cell suspensions of Salmonella Typhimurium and L. monocytogenes were treated with distilled water, chlorinated water (20 ppm), acidified chlorinated water (20 ppm, 4.5 pH), acidic EO water (EOA), basic EO water (EOB), or acidic EO water that was "aged" at 4°C for 24 h (AEOA) for up to 15 min at either 4 or 25°C. The largest reductions observed were those following treatments carried out at 25°C. EOA and AEOA treatments at both temperatures significantly reduced Salmonella Typhimurium populations by >8 log₁₀ CFU/ml. EOA and AEOA treatments effectively reduced L. monocytogenes populations by >8 log₁₀ CFU/ml at 25°C. These results demonstrate the stability of EO water under different conditions and that EO water effectively reduced Salmonella Typhimurium and L. monocytogenes populations in cell suspensions.