title: Internalization of Listeria monocytogenes in Whole Avocado.
abstract: In recent years, tree fruits have emerged as a new concern for Listeria monocytogenes contamination. The objective of the current study was to evaluate the potential internalization of L. monocytogenes from the surface of avocados into the edible portions of the fruit during certain postharvest practices simulated in a laboratory setting. One set of intact avocados was spot inoculated with L. monocytogenes on the stem scar, and the second set was hydrocooled in water contaminated with L. monocytogenes. Under these experimental conditions, L. monocytogenes internalized into the avocado pulp through the stem or stem scar after both spot inoculation and hydrocooling. In avocados spot inoculated with 50, 130, 500, and 1,300 CFU per fruit, bacteria were detected in the edible portion adjacent to the stem scar within 15 days postinoculation during storage at 4°C. In avocados hydrocooled in water containing L. monocytogenes at 10(6) and 10(8) CFU/ml, bacteria reached the bottom end of the fruit, and the populations in the edible portion adjacent to the stem scar reached up to 5.90 to 7.19 log CFU/g within 10 to 15 days during storage at 4°C. Dye mixed with inoculum was useful for guiding subsequent sampling, but dye penetration patterns were not always consistent with bacterial penetration.
authors: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA. yi.chen@fda.hhs.gov.
authors: Yi
authors: Y
authors: Chen
authors: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA.
authors: Peter
authors: P
authors: Evans
authors: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA.
authors: Thomas S
authors: TS
authors: Hammack
authors: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA.
authors: Eric W
authors: EW
authors: Brown
authors: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, 5100 Paint Branch Parkway, College Park, Maryland 20740, USA. dumitru.macarisin@fda.hhs.gov.
authors: Dumitru
authors: D
authors: Macarisin
mesh_terms: D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D005511:Food Handling; D005516:Food Microbiology; D005519:Food Preservation; D008089:Listeria monocytogenes; D027421:Persea; D013696:Temperature; D013997:Time Factors