15D-16 |
Growth of Escherichia coli O157:H7 on minimally processed produce pieces and produce exudate |
G. E. SKINNER, National Center for Food Safety & Technology, U.S. Food & Drug Administration, 6502 S. Archer Rd., Summit-Argo, IL 60501, T. C. Boersma, National Center for Food Safety & Technology, Illinois Institute of Technology, 6502 S. Archer Rd., Summit-Argo, IL 60501, R. C. Whiting, Center for Food Safety & Applied Nutrition, U.S. Food & Drug Adminstration, 200 C St. S.W., Washington, DC 20204, M. C. Cirigliano, Lipton, 800 Sylvan Ave., Englewood Cliffs, NJ 07632, J. T. C. Yuan, American Air liquide - Chicago Research Center, 5230 South East Avenue, Countryside, IL 60525, A. Paradis, Praxair, Inc., 7000 High Grove Boulevard, Burr Ridge, IL 60521, and C. L. Napier, NCFST/FDA, 6502 South Archer Road, Summit-Argo, IL 60501. Experimental data is necessary to determine how processing and storage temperature affect E. coli O157:H7 that may be present during manufacturing of minimally processed fresh produce. The objective of this study was to obtain experimental laboratory data for the behavior of E. coli O157:H7 on produce pieces and exudate at various temperatures that may be experienced during the processing and storage of minimally processed produce. Baby carrots, cabbage, iceberg lettuce, romaine lettuce, broccoli, cauliflower, spinach and radishes were evaluated. Produce was cut into 3 +/- 0.2 g pieces, soaked in sterile water, drained and inoculated. Pieces and exudates (50g prepared produce blended in 600g sterile distilled water) were inoculated with a dihydrostreptomycin (DHS) resistant strain of E. coli O157:H7 at levels of 103-6cfu/g or ml. Inoculated produce pieces were put in WhirlpakTM bags inside jars containing water saturated paper towels. Pieces and exudate were stored aerobically at 25, 20, 15 and 5oC for up to 2 weeks. E. coli behavior was modeled using the Gompertz and logistic equations and the square root model. Growth was rapid on produce pieces incubated aerobically at 25 and 20oC, increasing 2 to 3 logs within 24 to 48 hours. Growth was slightly slower at 15oC, increasing 1 to 3 logs in 48 to 72 hours, depending on the produce. E. coli O157:H7 grew equally well in exudates, except for cabbage and cauliflower where the initial population decreased 2 to 4 logs during the first 4 to 6 days of incubation at 25 and 20oC. The decrease was slower and slightly less at 15oC. Results show that intact and/or processed produce may support outgrowth of pathogenic E. coli O157:H7. The Gompertz and logistic models were most useful in modeling E. coli O157:H7 growth in produce and exudate. Adherence to Good Agricultural Practices (GAPs) on the farm and Good Manufacturing Principles (GMPs) along with good temperature control in the processing area can limit the spread and outgrowth of E. coli O157.
Session 15D, Food Microbiology: Fruits and vegetables
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