Food residuals on the food-contacting surfaces of stainless steel and polypropylene influence the efficacy of ultraviolet light in killing foodborne pathogens

Abstract

This study was conducted to examine effects of food residues on the survivals of pathogens on stainless steel (SSS) and polypropylene (PPP) after ultraviolet-radiation (UVR) surface decontamination. Cultures of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Listeria monocytogenes were inoculated on coupons containing deionized water, tryptic soy broth, pork, chicken, cabbage, and milk, respectively. The surface coupons were incubated at 100% relative humidity (RH) and 25 degrees C for 24hr to produce their own biofilms. UVR (=254 nm) surface decontamination for 120 min resulted in bacterial reductions in the levels of 2.5 log(10) cfu/coupon. Populations of S. Typhimurium and L. monocytogenes within biofilms declined on SSS harboring chicken juice after UVR for 120min, showing by <1.5 log(10)-reductions. The presence of food residues on the food-contacting surfaces would facilitate the strong adhesion of these organisms, indicating that bacteria enclosed in biofilms were more resistant to UVR sanitization. Practical applicationsIn this study, it seemed to indicate that the incidence of varying food residues such as deionized water, tryptic soy broth, pork, chicken, cabbage, and milk could affect bacterial adhesion-attachment to the food-contacting surfaces significantly. At least, some food residues such as pork, chicken, and milk would be supposed to provide a favorable environment where major foodborne pathogens are able to grow and produce their biofilms strongly. Especially, it was determined that the gram-negative bacteria such as Escherichia coli O157:H7 and Salmonella typhimurium showed the higher sensitivity on coupons against ultraviolet-radiation surface decontamination.