Challenges in the microbiological food safety of fresh produce: Limitations of post-harvest washing and the need for alternative interventions

Fresh produce (processed fruit and vegetables) continues to be the main source of foodborne illness outbreaks implicating pathogens such as Escherichia coli O157:H7, Salmonella, Listeria monocytogenes and human parasites (e.g. hepatitis A, Cyclospora). Previously, outbreaks were primarily limited to leafy greens, tomatoes, and cantaloupes, but more recently there has been a trend of more diverse produce types (e.g. cucumbers and papayas) being implicated. Although on-farm good agriculture practices (GAP) contribute to preventing pathogens entering the fresh produce chain, it cannot be relied upon completely due to the open nature of farming. As a consequence, there is an identified need for interventions that can remove field-acquired contamination, especially given fresh produce is eaten raw. In the following review, an overview of foodborne illness outbreaks linked to contaminated fresh produce will be described along with potential sources of contamination. Post-harvest washing that was once considered decontamination is now viewed as a high-risk cross-contamination point. The challenges in monitoring the post-harvest wash process will be discussed along with processing factors that need to be considered. A range of alternative, or supplemental, non-aqueous interventions will be described including irradiation, ultraviolet light, high hydrostatic pressure, gas phase (ozone and chlorine dioxide), and hydroxyl radicals generated through advanced oxidative process or gas plasma. All have been proved to be effective at pathogen control on the laboratory scale and are poised to enter commercial application. The current status of these alternative interventions along with challenges of integrating into commercial practice will be described.