Efficiency of manual dishwashing conditions on bacterial survival on eating utensils

This study evaluated the sanitization efficacies of manual three-compartment dishwashing processes as a function of washing temperature/time, contaminating organic matter, sanitizing condition, and bacterial type. Ceramic plates, drinking glasses, stainless-steel forks, spoons and knives and plastic serving trays were contaminated with egg, cheese, jelly, lipstick and milk. Each was inoculated with E. coli and L. innocua. Greater than 5-log bacterial reductions were achieved for all samples after washing at the combination of low washing temperature (24 °C) and minimal sanitizer concentration (150 ppm), except for bacteria on the milk-contaminated regular glasses. The viability of the bacterial species was affected by both organic matter types and the washing water temperature. Although E. coli showed better survival when compared with L. innocua for jellied utensils, there was no significant difference in survival between them for all other washing conditions. The use of quaternary ammonium compounds had similar killing effect against both bacteria.