Intervention Technologies to Enhance the Microbiological Safety of Fresh Produce

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The number of recalls and foodborne illness outbreaks linked to fresh fruit and vegetables continues to increase. Most noteworthy have been outbreaks of foodborne illness linked to lettuce and cantaloupes which appear especially susceptible to contamination. To date, the main approach has been to focus food safety initiatives at the primary production stage and also at the post-harvest wash stage that is designed to remove field acquired contamination. Although primary production initiatives such as the leafy greens agreement have enhanced food safety standards the open nature of crop production makes it impossible to prevent contamination. In a similar manner, it is well established that post-harvest washing is limited (1-2 log cfu reduction at best) and poses a greater risk of cross-contaminating produce rather than decontamination. The proposed research program will be directed towards developing post-harvest interventions to enhance the microbiological safety of fresh produce through decontamination and prevention of cross-contamination thereby meeting a Food Safety Objective of a 5 log cfu reduction of relevant pathogens. The first stage will reduce contamination of produce during holding and transport by introducing antimicrobial hydroxyl radicals into the headspace. Hydroxy radicals generated do not have strong antimicrobial activity but can inactivate pathogens over long exposure periods hence compatible with storage and transport of fresh produce. Cross-contamination events up to the wash step will minimized through in-process decontamination technologies using electrolyzed water or UV:hydrogen peroxide (Advanced Oxidative Process). Both approaches have the benefits of potent antimicrobial activity without producing significant disinfection byproducts. The surfaces will focus on conveyors and slicing units which are established cross-contamination sites. Although a degree of decontamination is expected in the wash water the main aim is to reduce cross-contamination events through using a novel acidified chitosan based sanitizer that will inactivate pathogens and also coagulate organic loading. Finally, a post-wash decontamination step based on using Advanced Oxidative Process will be applied to remove residual pathogen levels. Here, the research will be directed towards developing a continuous AOP treatment unit to build on the success achieved using a batch reactor. The reactor will be based on a UV tunnel with hydrogen peroxide mist being introduced into the headspace. Each intervention will be optimized in terms of pathogen (five stain cocktail of Salmonella, Shiga Toxin Producing Escherichia coli and Listeria monocytogenes) reduction whilst maintaining product quality (visual, texture). Each intervention will be optimized in terms of maximal log count reduction with no detrimental effects on product quality. The research will benefit the industry by reducing the incidence of pathogens on fresh produce. Although the current study will focus on lettuce and cantaloupes it can be envisaged that the same approach could be applied to other produce types. Moreover, the intervention steps will be optimized and critical limits established to facilitate a true HACCP system. The technologies being applied are currently available or near market so can be readily implemented by the fresh produce industry.