29G-33 |
Growth, survival and penetration of E. coli O157:H7 within apple puncture, skin and fresh-cut surface |
P. FATEMI1, J. Patton1, L. F. LaBorde1, S. J. Knabel1, and B. A. Annous2. (1) Dept. of Food Science, Pennsylvania State Univ., 118 Borland Lab., University Park, PA 16802-2504, (2) Food Safety Intervention Technologies Research Unit, USDA-ARS-Eastern Regional Research Center, 600 E. Mermaid Ln., Wyndmoor, PA 19038-8598 Outbreaks associated with fresh cut fruits and vegetables have increased in the last twenty years. A distinction needs to be made between surface contamination of the fruit due to fecal contact and internal contamination of the fruit flesh due to penetration and growth of pathogens. Once inside the apple puncture or on the fresh-cut surface, pathogens such as E. coli O157:H7 have the potential to penetrate, grow and survive within the disrupted apple tissue, making decontamination much more difficult. To study the depth of penetration, growth and survival of E. coli O157:H7 on the surface and within the internal structure of unwaxed apple fruit. Punctured (4x5 mm) or fresh cut Golden Delicious apples at 21oC were spot or dip inoculated with 4.3 log cfu/ml of three-strain culture of ampicillin resistant E. coli O157:H7. Apples were allowed to incubate at 21oC or 7oC for up to 6 days. Cut surfaces were then sectioned (2.1 mm increments, to evaluate vertical penetration) and cut with concentric cork borers (1.3 and 3 mm increments, to evaluate horizontal penetration). Samples were plated on TSAYE+Amp. E. coli O157:H7 penetrated at least 4 mm radially and 3 mm vertically away from the boundaries of the fresh puncture. This phenomenon was not observed within 48-h old punctures. Overall, onset of growth occurred within 4-8 hours within fresh puncture and fresh cut surfaces (21oC) and cells grew to nearly 7.1 log cfu/g after 48-h. Bacterial concentrations within 48-h old punctures increased by 1 log cfu/g after 48-h. Dip inoculating the apples resulted in deeper penetration of the cells within fresh punctures, compared to spot inoculation. Understanding the effect of surface damage on the location and concentration of pathogens in/on apples, may aid the development of more effective decontamination treatments.
Session 29G, Food Microbiology: General
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