Title page for ETD etd-06182002-123842

Type of Document Master's Thesis
Author Yaun, Brian Robert
URN etd-06182002-123842
Title Efficacy of Ultraviolet Treatments for the Inhibition of Pathogens on the Surface of Fresh Fruits and Vegetables
Degree Master of Science
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Sumner, Susan S. Committee Chair
Eifert, Joseph D. Committee Member
Marcy, Joseph E. Committee Member
  • Ultraviolet light
  • E. coli O157:H7
  • Salmonella
Date of Defense 2002-06-07
Availability unrestricted
Two studies investigating the use ultraviolet light at a wavelength of 253.7nm (UVC) into the inhibition of Salmonella spp. and Escherichia coli O157:H7 were conducted. The objectives of these studies were: to determine the rates for the destruction of Salmonella and Escherichia coli O157:H7 on the surface of agar and to investigate its effectiveness on the surface of fresh produce. Multiple replications of different doses and cocktail concentrations were performed and resulted in a 5 log reduction of Escherichia coli O157:H7 at doses exceeding 8.4 mW / cm2, while a 5 log reduction for Salmonella spp. was observed at doses exceeding 14.5 mW / cm2. Samples of Red Delicious apples, green leaf lettuce and tomatoes were subjected to different doses ranging from 1.5 – 24 mW / cm2 of UVC to determine effective log reductions of microbial populations. UVC applied to apples inoculated with E. coli O157:H7 resulted in the highest log reductions of approximately 3.3 logs at 24 mW/cm2. Lower log reductions (2.19 logs) were seen on tomatoes inoculated with Salmonella spp. and leaf lettuce (2.65 and 2.79) inoculated with both Salmonella spp. and E. coli O157:H7 respectfully. Due to the low capital involved in initiating a UVC system, the use of ultraviolet energy may prove to be a beneficial mechanism to decrease pathogens on fresh produce if used in conjunction with strict adherence to a sanitation program, Good Manufacturing Practices and Good Agricultural Practices in ensuring the safety of fresh produce.
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