Inhibitory Effects of UV Treatment and a Combination of UV and Dry Heat against Pathogens on Stainless Steel and Polypropylene Surfaces

Pathogens that contaminate the surfaces of food utensils may contribute to the occurrence of foodborne disease outbreaks. We investigated the efficacy of UV treatment combined with dry heat (50 degrees C) for inhibiting 5 foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Pseudomonas aeruginosa, Listeria monocytogenes, and Staphylococcus aureus) on stainless steel and polypropylene surfaces in this study. We inoculated substrates with each of the 5 foodborne pathogens cultured on agar surface and then UV treatment alone or a combination of both UV and dry heat (50 degrees C) was applied for 30 min, 1 h, 2 h, and 3 h. The initial populations of the 5 pathogens before treatment were 8.02 to 9.18 and 8.73 to 9.16 log(10) CFU/coupon on the surfaces of stainless steel and polypropylene coupons, respectively. UV treatments for 3 h significantly inhibited S. Typhimurium, L. monocytogenes, and S. aureus on the stainless steel by 3.06, 2.18, and 2.70 log(10) CFU/coupon, and S. aureus on the polypropylene by 3.11 log(10) CFU/coupon, respectively. The inhibitory effects of the combined UV and dry heat treatment (50 degrees C) increased as treatment time increased, yielding significant reductions in all samples treated for 3 h, with the exception of S. aureus on polypropylene. The reduction level of E. coli O157:H7 treated for 3 h on the surface of stainless steel and polypropylene treated was approximately 6.00 log(10) CFU/coupon. These results indicate that combined UV and dry heat (50 degrees C) treatments may be effective for controlling microbial contamination on utensils and cooking equipment surfaces as well as in other related environments.