Numerous food-borne outbreaks of Escherichia coli O157:H7 have been linked to leafy greens in recent years. An overwhelming amount of lettuce and spinach on the market is sold in modified atmosphere packaging as ready to eat salad mixes. The objectives of this study were to determine the effects of modified atmosphere, storage temperature, and inoculum size on survival of E. coli O157:H7 on cut and whole leaf lettuce and spinach. E. coli O157:H7 H1730 was inoculated onto cut and whole leaves of leaf lettuce and spinach. Samples were held under normal atmospheric conditions or in a modified atmosphere package at either 4ºC or 10ºC to simulate display and abuse temperatures. Leaves were sampled at Days 0, 1 and every other day until visual spoilage occurred (7 days for lettuce, 9 days for spinach). E. coli O157:H7 was able to survive at 4° and 10°C regardless of atmosphere and inoculum size for 7 days on cut and whole lettuce and 9 days on cut and whole spinach. Overall, numbers of E. coli O157:H7 increased (1 log) throughout the storage period on spinach, and decreased on lettuce (1-1.5 log). Significantly higher (P < 0.05) numbers of E. coli O157:H7 were found on lettuce and spinach stored at 10ºC than when stored at 4ºC. There were no significant differences (P > 0.05) in Numbers of E. coli O157:H7 with respect to atmosphere, leaf type or inoculum size. If contamination of lettuce or spinach with E. coli O157:H7 occurred, the pathogen may survive well under typical packaging and storage conditions. / Master of Science in Life Sciences
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/34925 |
| Date | 10 October 2008 |
| Creators | Davis, Marjorie Lynn |
| Contributors | Food Science and Technology, Boyer, Renee R., Williams, Robert C., Ponder, Monica A. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | THESIS2.pdf |
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