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United States Department of Agriculture

Agricultural Research Service

Research Project: MICROBIAL FOOD SAFETY OF FRESH AND FRESH-CUT PRODUCE Title: Growth of E.coli O157:H7 on Commercially Packaged Fresh-cut Salads As Impacted by Storage Temperature and Time

item Luo, Yaguang
item McEvoy, James
item He, Qiang - SICHUAN UNIV, CHINA
item Shen, Lin - BEJING AG UNIV, CHIN

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: June 5, 2008
Publication Date: August 3, 2008
Citation: Luo, Y., Mcevoy, J.L., He, Q., Shen, L., Vico, I. 2008. Growth of E.coli O157:H7 on Commercially Packaged Fresh-cut Salads As Impacted by Storage Temperature and Time. [abstract]. International Association for Food Protection. .

Technical Abstract: An increasing number of food-borne illness outbreaks have been associated with the consumption of packaged fresh-cut lettuce and baby spinach contaminated with E.coli O157:H7. Since fresh produce grows in open fields, pathogen contamination can occur anywhere from farm to table. Moreover, fresh-cut products are marketed as ready-to-eat without a further microbial killing step. Therefore, preventing pathogen contamination, and limiting its growth are critical measures to ensure fresh-cut produce safety. The main objective of this study was to understand the ecology of E.coli O157:H7 on commercially packaged fresh-cut lettuce and baby spinach and to investigate the effect of storage temperature on the growth of E.coli O157:H7 and other background microorganisms as well as product quality. Recently delivered commercially packaged fresh-cut lettuce salad and baby spinach were obtained from retail stores. The packages were cut at the four corners and sprayed with E.coli O157:H7 inoculum. The packages were re-sealed and stored at 5 and 12 °C until the expiration of their marked shelf life. E.coli O157:H7 and various background microorganisms were enumerated on selective media and product quality was evaluated by a trained panel. Data were analyzed with the General Linear Model Procedure using SAS. Significant growth of E.coli O157:H7 was noted on packaged lettuce salad stored at 12 °C in which the population increased by more than 2 log cfu/g within 3 days. Aerobic mesophillic bacteria, yeast and mold populations also increased significantly while the visual quality of the product remained fully acceptable. No growth of E.coli O157:H7 was noted on packaged products held at 5 oC throughout the entire storage period. These data suggest that E.coli O157:H7 can grow significantly on commercially packaged fresh-cut products when temperature abuse occurs in the supply chain. Maintaining fresh-cut products at 5 °C or below can help mitigate food safety risks if pathogen contamination does occur.

Last Modified: 11/26/2015
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