Effect of spraying on chemical properties and bactericidal efficacy of electrolysed oxidizing water

A three-factor, three-by-three-by-two-level factorial designs were used for studying the effects of air pressure, sprayer orifice size and electrostatic charge of a spray gun on pH, oxidation-reduction potential (ORP), electric conductivity and residual chlorine of electrolysed oxidizing (EO) waters with either low (9 mg L-1) or high concentration (88 mg L-1) of chlorine. Results indicated that a smaller orifice produced higher reduction in ORP and chlorine concentration than larger orifices. Electrostatic charge, in general, did not cause a significant reduction in chlorine concentration. High air pressure spray retained more chlorine and gave a higher ORP than low air pressure. EO water with high initial chlorine concentration achieved at least a 3-4 log(10) CFU mL(-1) reduction in Listeria monocytogenes populations when sprayed with the spray gun, while spraying with a commercial backpack sprayer or a poly-tank sprayer eliminated Listeria population (9.4 log(10) CFU mL(-1) reductions) completely. These results demonstrated that although spraying reduced the chlorine in EO water by 20-97%, application of EO water through spraying has potential for reducing bacteria in food-processing operations.