Inhibitory effects of UV treatment and a combination of UV and dry heat against pathogens on stainless steel and polypropylene surfaces

Abstract: 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 °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 °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 log₁₀ 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 log₁₀ CFU/coupon, and S. aureus on the polypropylene by 3.11 log₁₀ CFU/coupon, respectively. The inhibitory effects of the combined UV and dry heat treatment (50 °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 log₁₀ CFU/coupon. These results indicate that combined UV and dry heat (50 °C) treatments may be effective for controlling microbial contamination on utensils and cooking equipment surfaces as well as in other related environments.