Effectiveness of commercial household steam cleaning systems in reducing the populations of Listeria monocytogenes and spoilage bacteria on inoculated pork skin surfaces

In a previous study conducted in our laboratory, a commercial household steam cleaner was found to be effective in reducing the naturally occurring bacterial populations on 72 beef and 72 hog carcasses processed by four small and very small meat processing plants. The goals of this study were to determine the maximum levels of bacterial reduction caused by treatments using the steam cleaner, and to compare the efficacy of this cleaner with the efficacies of two other commercial household steam cleaning systems in reducing bacterial populations on the surface of pork skin artificially inoculated with ca. 7.61 or 5.75 log(10) CFU/cm(2) of Listeria monocytogenes. The contaminated pork skin samples were treated with the three stream cleaners for 30-180 s in 30 s intervals, and assayed for the populations of L. monocytogenes as well as total aerobic and thermoduric bacteria. The application of steam significantly reduced the population of L. monocytogenes (7.61-3.23 log(10) CFU/cm(2)), as well as total aerobic (5.68-4.04 log(10) CFU/cm(2)) and thermoduric (6.12-2.57 log(10) CFU/cm(2)) bacteria on the surface of pork skin (P <= 0.05). Significant differences in microbial reductions were observed between different inoculation levels, treatment times, and types of cleaning systems used in the study (P <= 0.05). (C) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.