Validation of Post-Harvest Wash Process to Prevent Cross-Contamination in Leafy Green Processing

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Aldossari, Huda
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University of Guelph

There is a reliance on the post-harvest wash in leafy green processing to remove field-acquired contamination. However, the post-harvest wash is limited in its ability to remove common human pathogens (Salmonella, Shiga Toxin Escherichia coli O157:H7, and Listeria monocytogenes) from fresh produce. Additionally, cross-contamination events during the washing process can threaten food safety. The following study evaluated the efficacy of a range of sanitizers (sodium hypochlorite 200-ppm total chlorine, chlorine dioxide50 ppm, peracetic acid70 ppm, and Food Freshly 50-500 to prevent cross-contamination during leafy green wash process. From the range of sanitizers tested it was found that peracetic acid or chlorine dioxide reduced cross-contamination between batches with Hypochlorite being effective if free chlorine levels were maintained above 2ppm. In commercial trials it was found that Oxidation Reduction Potential (ORP) was an unreliable reporter of free-chlorine concentration given that the applied concentration of the sanitizer was below the chlorine-demand of the wash water. Yet, cross-contamination of contamination between batches could be reduced if the chlorine demand was satisfied or reactive species in water were maintained at a low level.

wash water, leafy greens-pathogen