Correlation of Transit Temperatures with the Potential for E. coli O157:H7 Growth On Pre-Cut Greens

Pre-harvest sources for contamination of leafy greens are numerous and extremely varied with no microbial reduction strategies currently available to completely ensure the safety of fresh-cut leafy greens at the time of consumption.  It is therefore imperative that the cold-chain be established and maintained from packaging through retail purchase to minimize exposure to E. coli O157:H7 and other food-borne pathogens.  The specific objectives of this study are to:  (1) measure the temperature of leafy greens during transcontinental transport and distribution using a RFID temperature and positioning sensor, (2) based on microbial studies, develop a series of statistical models from the data that define the least favorable conditions for E. coli O157:H7 growth in leafy greens during transport and distribution, and (3) determine the robustness of these models using various fresh-cut leafy-green salad mixes.  Though collection is on-going, data has shown that temperatures greater than 4.4°C can occur in commercial trailers during transcontinental shipment of leafy greens during summer, or can be less than 0°C in commercial trailers during winter, both situations potentially leading to increased microbial growth on the product.  Based on initial findings, microbial studies and statistical modeling have been initiated.  However, progress has been very slow or even thwarted due to concerns by commercial packer/shippers of unfavorable exposure and liability, and this will be discussed.