Efficacy of Ultraviolet Treatments for the Inhibition of Pathogens on the Surface of Fresh Fruits and Vegetables

Abstract

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.