Decontamination of knives used in the meat industry: effect of different water temperature and treatment time combinations on the reduction of bacterial numbers on knife surfaces.

Previous regulations in Australia and internationally required that knives used during the slaughter and dressing of carcasses be sanitized by brief submersion in water at 82 degrees C. Many current international regulations allow science-based equivalent alternative procedures to be used. However, limited time-temperature data are available on the response of bacteria to hot-water treatment on knives. The present study was undertaken to determine the effect of combinations of time and temperature ranging from 1 to 60 s and 60 to 82 degrees C on the disinfection of knives artificially contaminated with Escherichia coli and Listeria monocytogenes. In addition, the effect of a prerinse at 40 degrees C on the disinfection of artificially contaminated knives treated under the same controlled conditions as above was established. The experiments, which were carried out with knives in a meat matrix at each of 42 time and temperature combinations, with and without the prerinse, were performed in a laboratory water bath. Bacterial reductions were established by plate counts from the knife blade before and after immersion. Mean log reductions were subjected to statistical analysis, and basic models were generated from the results. The results demonstrated that dipping knives in water for shorter times at higher temperatures, for example, 82 degrees C for 1 s, or longer times at lower temperatures can produce equivalent inactivation of bacteria. Prerinsing knives at 40 degrees C increases the performance of the subsequent dipping step. Models produced from the data in this study can be used to predict suitable combinations of time and temperature to achieve a desired bacterial reduction.