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Title: Growth of Escherichia coli O157:H7 and Its Interaction with Background Microorganisms on Commercially Packaged Baby Spinach as Impacted by Storage Temperature

Author
item Luo, Yaguang - Sunny
item McEvoy, James
item HE, QIANG - SICHUAN UNIV, P.R. CHINA
item Conway, William

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2008
Publication Date: 5/5/2008
Citation: Luo, Y., Mcevoy, J.L., He, Q., Conway, W.S. 2008. Growth of Escherichia coli O157:H7 and Its Interaction with Background Microorganisms on Commercially Packaged Baby Spinach as Impacted by Storage Temperature. [abstract]. United Fresh Produce Association meeting.

Interpretive Summary:

Technical Abstract: An increasing number of food-borne illness outbreaks associated with the consumption of packaged fresh-cut products call attention to the importance of maintaining food safety. Given the fact that there are no effective pathogen killing steps during the preparation of packaged fresh-cut products, prevention of pathogen contamination and reducing the potential for pathogen growth throughout the entire supply chain are critical measures for ensuring produce safety. The main objective of this study was to evaluate the effect of storage temperature on the survival and growth of Escherichia coli O157:H7, the growth of indigenous microorganisms, and the changes in product quality of packaged baby spinach. Commercially packaged spinach leaves were used within 2 days after processing. The packages were cut at one end to allow spinach leaves to be inoculated with E. coli O157:H7 via a fine mist spray, and re-sealed. The prepared packages were then stored at 1, 5, 8 and 12 °C for 12 days and evaluated every three days. E. coli O157:H7 grew significantly when stored at 12 °C for 3 days, and continued to grow through day 9 of storage, while the population decreased when held at 1 and 5 °C. Aerobic mesophilic bacteria, psychrotrophic bacteria, yeast and mold populations increased significantly at all storage temperatures tested, though more significant growth was seen on products stored at higher temperatures. Minimal quality declines were seen on products stored at 1 and 5 °C, with products retaining a score of 8 (like strongly) on a 9-point hedonic scale after 12 days of post-inoculation storage. However, quality decline was seen on products stored at 8 and 12 °C from day 9 through day 12. In conclusion, although all types of microorganisms grew faster at 12 °C than at 1 and 5 °C, E. coli O157:H7 growth benefited from temperature increase more than others. These data suggest that E. coli O157:H7 can grow significantly on packaged fresh-cut products when temperature abuse occurs in the supply chain. Maintaining a temperature of 5 °C or below reduces the potential for pathogen proliferation on packaged fresh-cut products.