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Minimally processed vegetables and fruits are become established as a significant vehicle for foodborne pathogens. Due to the open nature of the fresh produce chain, contamination of the product can occur at any point during cultivation and post-harvest handling. Because bacteria (including human pathogens) can become located within sub-surface structures of plants (stomata, cut- edges) simply washing produce is inadequate even when chemical sanitizers such as hypochlorite are used.
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In this study the efficacy of applying a combination of Ultra Violet (UV)/hydrogen peroxide (H2O2) in decontaminating produce will be evaluated. When H2O2 (<2% v/v) is illuminated with UV light highly anti-microbial, but short-lived, hydroxyl radicals are formed. This provides a greater kill effect than when either UV or hydrogen peroxide is applied alone. Although the combination of UV and hydrogen peroxide have been used for over 20 years for sterilizing carton packaging it has not been fully evaluated as a method for decontaminating fruit or salad vegetables.
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In the proposed project a treatment chamber will be constructed with the capacity to decontaminate 3 kg batches of produce. Optimization of operating conditions will be performed to maximize the generation of hydroxy radicals from H2O2 (0.2-1%). The kinetics and mode by which UV/ H2O2 inactivates a range of pathogenic (E. coli O157, Salmonella, L. monocytogenes, Aeromonas hydrophilia) and spoilage (Pseudomonas fluorescens and Erwinia carotovara) bacteria, in addition to MS2 coliphage (enteric virus surrogate), will be undertaken. The efficacy by which the treatment can decontaminate a diverse range of product types (lettuce, red cabbage, spring mix, spinach, red onion, carrot, tomatoes, cantaloupes, strawberries, raspberries and apples) will be evaluated. A 5-log reduction in bacteria/bacteriophage numbers without adversely affecting product quality will be used as the criteria for success.
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The project brings together Elopak (specialists in UV: H2O2 decontamination technology), Pride Pak Salads (major fresh cut producer within Ontario) food microbiologists and engineers.
Expected Impact of Project Outcomes on Food Safety in Ontario:
The fresh-cut industry represents a significant sector of the Ontario economy with an estimated Farm Gate Value of $224 M per annum. Although foodborne outbreaks linked to fruit and vegetables are rare within Ontario there is a need to take a pro-active approach with respect to ensuring high food safety standards within the industry.
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Currently there is no intervention step within the fresh cut chain that can ensure the removal of field acquired contamination. It is widely acknowledged that aqueous wash-based systems have limited ability to effectively penetrate pathogens present in sub-surface locations. The proposed approach of using UV/ H2O2 is specifically aimed at inactivating pathogens located in such protective sites. The method is based on generating an intense burst of anti-microbial hydroxyl radicals that rapidly inactivate microbes located on the surface and sub-surface of produce. Because of the transient nature of the radicals it is envisaged no bleaching of the product will occur.
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The project will provide a viable, cost effective, alternative to current produce decontamination methods. If successful, the UV/ H2O2 based decontamination system will significantly enhance the safety of minimally processed fruit and vegetables. The method will also find utility in other sectors especially in relation to meat processing where virulent pathogens such as E. coli O157 are an obvious concern. <P> For more information, please visit the <a href="http://www.omafra.gov.on.ca/english/research/foodsafety/index.html" target="_blank">Ontario Ministry of Agriculture, Food & Rural Affairs (OMAFRA) Food Safety Research Program</a>.