Food Protection Trends - May 2009 - 272

Copyright© 2009, International Association for Food Protection 6200 Aurora Ave., Suite 200W, Des Moines, IA 50322-2864 Food Protection Trends, Vol. 29, No. 5, Pages 272–278 A Comparison of Hand and Machine Dishwashing from a Hygienic Standpoint MARIE GRöNVALL,1 EVA STåHL WERNERSSON1* and HåKAN HåKANSON2 1 Environmental Laboratory, GS Development AB, Jägershillgatan 15, SE-213 75 Malmö, Sweden; 2 Dept. of Biotechnology, University of Lund, Box 124, SE-221 00 Lund, Sweden INTRODUCTION Dishwashing is one of the oldest activities in kitchens all over the world. The most common way to perform dishwashing is to soak the items in water with detergent, clean them in dishwater together with detergent, and finally put them through a rinsing process. It is tedious work, often performed in odd locations where ergonomics and ventilation are not optimum. Still, this way of cleaning is the most common method in both domestic and professional kitchens. Hygiene is essential for dishwashing in both domestic and professional kitchens (1, 4, 23). In domestic kitchens, a small number of meals are served to a restricted number of persons, so that if cross-contamination occurs, only a relatively small number of individuals are affected. In professional kitchens, there is a chance for numerous people to be infected by foodborne illness caused by, for example, contaminated dishes (7). Foodborne illness can cause a large cost and a burden for society (16, 22). Increased use of dishwashers can improve hygiene through dishwashing at higher temperatures and the use of more effective and aggressive detergents (30). Dishwashers that utilize a combination of chemical and mechanical treatment of dishes are offered on the market in Europe (27). SUMMARy In Europe, the majority of dishwashing is done manually, whereas dishwashing machines are used in approximately onefourth of washing procedures. In this work, we investigated the survival of Enterococcus faecium with machine dishwashing and hand dishwashing. Bacterial counts in the wash tank of the dishwasher were reduced by more than 3 log units within 5 minutes. Bacterial reduction was much slower during hand dishwashing, in which a reduction of 0.7 log units was observed after 43 minutes. It was also observed that the type of soil has little influence on the survival of E. faecium in dishwater during hand dishwashing. The mean numbers of E. faecium on cleaned dishware was 13–26 times higher for items cleaned by hand dishwashing than for those cleaned by machine dishwashing. Plates that were not visually clean after hand dishwashing had higher numbers of surviving E. faecium than plates that were visually clean. From a hygienic point of view, machine dishwashing is superior to hand dishwashing. In the machine, a higher temperature and pH are combined with lower COD (chemical oxygen demand) and faster drying, creating a harsh environment for microorganisms. Machine dishwashing is also more easily replicated than hand dishwashing, since it is controlled by the specifications of the machine. A peer-reviewed article * Author for correspondence: Phone: 46.40.671.5000; Fax: 46.40.215820 E-mail: eva.stahl.wernersson@gs-development.com 272 FOOD PROTECTION TRENDS | MAY 2009

Food Protection Trends - May 2009

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