Uncovering the truth and myth about the correlation between the disinfection efficiency of food-associated microorganisms and the oxidation-reduction potential of the aqueous medium

For decades now, there has been the assumption that the oxidation-reduction potential (ORP) can be used as a single value assessment of the quantity of antimicrobial potential of a chemical oxidant in water, not in the least by the post-harvest processing industry. This has predominately been stated for the chemical oxidant chlorine, but has by extension been supposed by some companies to be valid for some other chemical oxidants, such as chlorine dioxide. Some older work hints at the validity of the correlation between inactivation potential and ORP but more recent work makes this statement questionable: Treating ORP as a single value assessment without considering the pH leads to situations where a similar ORP results in large differences in the concentration of the chemical oxidant. Whether this large difference in sanitizer concentration results in a similar inactivation potential has never been studied in a rigorous experimental setup.

A representative set of microorganisms (vegetative Gram- and Gram+, bacterial spores, yeasts and molds) will be isolated from fresh produce and identified using DNA sequencing. Representative microorganisms will be disinfected while changing: i) chemical oxidant (chlorine, chlorine dioxide, hydrogen peroxide, peracetic acid), ii) chemical oxidant concentration, iii) pH, iv) ORP, and the response (microbial reduction) will be measured. Based on these numerous trials, statistical analysis and modelling can be used to draw rigid conclusions concerning the correlation between ORP and antimicrobial potential; which have not been published before in a specific and controlled setup before.