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Abstract
The use of electrolyzed (EO) water as an effective antimicrobial against pathogens on foods has been well documented in literature. Most challenge studies however, use culturing techniques to enumerate microorganisms after treatment which are unable to detect bacteria that enter the viable but non-culturable (VBNC) state, thus underestimating the actual viable populations of microorganisms present and overstating sanitizer effectiveness. The objective of this project was to evaluate EO water effectiveness as a sanitizer on different foods and investigate VBNC induction when foodborne pathogens are treated with EO water. In the first study, a meta-analysis was conducted to develop an overall estimate of the reductions of Escherichia coli O157:H7, Salmonella and Listeria monocytogenes after EO water treatment of foods. Twenty-seven studies were included and summary effects of 0.66, 1.12, 1.15, 2.41, 4.45 and 5.34 log reductions were estimated for EO water treatments on poultry, fish, meats, lettuce, eggs and tomatoes, respectively. The second study compared culturing and viability data (using flow cytometry) after treatment of E. coli O157:H7 and L. monocytogenes with EO water and revealed that treating the pathogens at low free chlorine concentrations (FCC) of 2.5 and 1.25 mg/L induced the VBNC state. In the third study, the pH and the organic load content of EO water (UV254 as indicator) were determined to be significant in the induction of E. coli O157:H7 and L. monocytogenes into the VBNC state. The presence of organics raised the FCC level of VBNC induction and it was also determined that keeping the residual chlorine concentration in produce wash water at 9 mg/L and above prevented VBNC induction. In the final study, VBNC induction after treatment of E. coli O157:H7 inoculated romaine lettuce with chemicals sanitizers were studied. For all treatments, viable cell reductions were always lower than those from plating, showing that significant portions (1.94 % to 66.72%) of E. coli O157:H7 treated with sanitizers entered the VBNC state. These research findings suggest that combining culturing with viable cells detection of microorganisms represents a more accurate measure of the EO water effectiveness.