Investigation of Chemical and Microbiological Residues on Dishes Cleaned by Hand and Machine on the Basis of Specific Examples

New technologies in dishwashing by machine in private homes and new kinds of cleaner have been introduced in the previous years. EN 50242 is the basis for the assessment of dishwashers for the energy label. As invisible residues like chemical and microbiological substances are not covered by the visual examination according to EN 50242, both aspects are objects of this study. Although the penetration of automatic dishwashers is increasing, the manual dishwashing is still very common. Therefore it was another task to compare both processes to each other.Nonionic and anionic surfactants on automatic and manual cleaned dishes were chosen as primary substance for the investigation on chemical residues. The impact of the kind of dishwashing program, the composition and quantity of the cleaning agents onto residual surfactants on plates were investigated. Another method to detect such chemical residues was studied by regarding its applicability and suitability. The reduction of bacterial activity was examined using test microorganisms Geobacillus stearothermophilus, Enterococcus faecium and Staphylococcus aureus on inoculated plates which have been cleaned by hand and machine under various conditions.