To study the potential of three bacterial pathogens to cross-contaminate orange juice during extraction, normal operation conditions during juice preparation at food service establishments were simulated.
The spread of Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes from inoculated oranges to work surfaces and to the final product was determined. The transference
of these three bacterial pathogens to orange juice made from uninoculated oranges with the use of contaminated utensils was also studied. Fresh oranges were inoculated with a marker strain of rifampicin-resistant
Salmonella Typhimurium, E. coli O157:H7, or L. monocytogenes. Final pathogen levels in juice were compared as a function of the use of electric or mechanical juice extractors to squeeze
orange juice from inoculated oranges. Pathogen populations on different contact surfaces during orange juice extraction were determined on sulfite-phenol redrifampicin plates for Salmonella Typhimurium
and E. coli O157:H7 and on tryptic soy agar supplemented with 0.1 g of rifampicin per liter for L. monocytogenes. After inoculation, the average pathogen counts for the orange rind surface were 2.3
log10 CFU/cm2 for Salmonella Typhimurium, 3.6 log10 CFU/cm2 for E. coli O157:H7, and 4.4 log10 CFU/cm2 for L. monocytogenes.
This contamination was spread over all utensils used in orange juice squeezing. Mean pathogen counts for the cutting board, the knife, and the extractor ranged from-0.3 to 2.1 log10 CFU/cm2,
and the juice contained 1.0 log10 CFU of Salmonella Typhimurium per ml, 2.3 log10 CFU of E. coli O157:H7 per ml, and 2.7 log10 CFU of L. monocytogenes
per ml. Contact with contaminated surfaces resulted in the presence of all pathogens in orange juice made from uninoculated oranges. These results give emphasis to the importance of fresh oranges as a source
of pathogens in orange juice.
Document Type: Miscellaneous
Department of Biology and Pharmacy, University of Guadalajara, Guadalajara, Jalisco 44340, Mexico 2:
Department of Microbiology, National Polytechnic Institute, Mexico City, 11340, México
Publication date: August 1, 2003
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