Reduction of Escherichia coli and Salmonella senftenberg on pork skin and pork muscle using ultraviolet light

The objective of this study was to evaluate the effect of ultraviolet (UV) light on the reduction of Escherichia coli and Salmonella senftenberg. Microbial reduction was measured by determining total reduction and inactivation rates of surviving bacteria after exposure to different UV treatments. Surfaces of tryptic soy agar, pork skin and pork muscle were inoculated with either E, coli or S. senftenberg and exposed to 20, 50, 80, 100, 500 and 1000 microwatts per square centimeter (mu W cm(-2)) of UV light. On the agar surface after 120 s, a >5-log reduction of E. coli on agar was obtained at intensities of 100 mu W cm(-2) or greater and, after 960s, a > 7-log reduction was observed at intensities of 80 mu W cm(-2) or greater for S. senftenberg. For fresh pork muscle and after 1920-s exposure, greatest logarithmic reductions (P < 0.05) were achieved at intensities of 100 mu W cm(-2) or greater for E, coli and at intensities of 80 mu W cm(-2) or greater for S. senftenberg where a 1.5- and 2-log reduction was observed, respectively. For pork skin exposed at 1920 s, maximum logarithmic reductions for S, senftenberg were observed at intensities of 100 mu W cm(-2). However, greatest logarithmic reduction of E. coli on pork skin was not observed until UV intensity reached 1000 mu W cm(-2). After exposure to 100 mu W cm(-2), UV D-values for E. coli were 1370 s for pork muscle, 1282 s for pork skin, and 242 s for agar. When S, senftenberg was exposed to 100 mu W cm(-2), UV D-values were 1163 s for pork muscle, 595 s for pork skin, and 15s for agar. When surfaces were inoculated with E. coli and exposed to 1000 mu W cm(-2), UV D-values on muscle, pork skin and agar surfaces were 1205 s, 592 s, and 177 s, respectively. When surfaces inoculated with S, seftenberg were exposed to 1000 mu W cm(-2), UV D-values were 1064 s, 490 s, and 21 s on muscle, skin and agar, respectively, in all cases, E. coli appeared to be more resistant to UV treatment compared to S. senftenberg. This study demonstrates that UV light can be used to reduce certain pathogens on pork meat surfaces. More research is needed to determine the antimicrobial activity of UV light exposure to meat carcasses or meat cuts in a food-processing environment. (C) 1998 Academic Press.