Efficacy of Pre-harvest Applications of Electrolysed Water and Other Chemical Sanitisers in inactivating Foodborne Pathogens on Leafy Green Vegetables

This thesis aims to develop pre-harvest control strategies against foodborne pathogens in order to improve leafy green vegetables (LGV) safety. To do this a series of experiments were carried out. 1) The efficacy of the pre-harvest use of electrolysed water (E-water), 1-Bromo-3-chloro-5,5-dimethylhydantoin (BCDMH) and peroxyacetic acid (PAA) against plant microbiota, non-pathogenic Escherichia coli M23, Listeria innocua, and the spoilage microorganism Pseudomonas fluorescens on commercial LGVs was assessed in a greenhouse trial. (2) Sanitation efficacy by E-water, BCDMH and PAA against LGV-associated microflora and Listeria innocua on LGVs was evaluated within a commercial setting. (3) Microbiological and sensorial analyses were performed to assess their downstream effects on LGV quality and shelf-life during storage. (4) 16S rRNA gene-based amplicon sequencing was used to determine how sanitiser treatments effects LGV bacterial communities. The results from the greenhouse trial showed that pre-harvest sanitiser treatments have potential usefulness to reduce the microbial loads, foodborne pathogens and spoilage microorganisms on LGVs. It was also found that E-water has a similar microbial inactivation efficacy to BCDMH and PAA. Therefore, E-water can be used as an alternative to chemical sanitisers in reducing pathogen contamination on LGVs. These findings were further validated in the field trial, where in-field use of E-water and others sanitisers on LGVs was shown to be a viable disinfection tool for reducing pathogens on LGVs and slowing down microbial growth during cold storage. Pre-harvest treatments are feasible and effective intervention strategies that can reduce the presence of bacterial contamination on LGVs as well as achieve better assurance of delivering microbiologically safe products to the consumer