Cleaning and disinfection of knives in the meat industry.

The effect of disinfection of knives with water of 82 degrees C (180 degrees F) strongly depends on the amounts of protein and fat present on the tools. When fats or proteins are absent, even a high bacterial contamination on a stainless steel plate will be completely eliminated by immersion in water of 82 degrees C during 1 s, whereas even after 10 s immersion does not give satisfactory results if a high degree of fat and protein contamination is present. By adding lactic acid to hot water the bactericidal effect may be improved, although the results are far from optimal. Apparently, optimal disinfection of contaminated knives is extremely difficult to attain without the use of mechanical forces such as a high pressure water jet to remove the dirt. Therefore a special disinfection unit was designed in which apart from the factors cleaning time and temperature, the effects of mechanical forces could be determined. By increasing water pressure the cleaning effect was improved. Adding lactic acid to the spraying water made it possible to lower water temperature and water pressure, which, among other things, resulted in a lower climatological strain at the place of work. The thermodisinfector (a modified dish-washer) appear to be a good alternative for cleaning and disinfection of tools if the requirement is dropped that every worker had to have a disinfection facility within his immediate reach. The practical application of such equipment is discussed.