Investigation of chemical and microbiological residues on dishes cleaned by hand and machine on the basis of specific examples

This thesis examines how new technologies in machine dishwashing in private homes and new kinds of cleaner have been introduced in previous years. Both machine and manual dishwashing were studied. Nonionic and anionic surfactants were chosen for investigation of chemical residues on plates after washing, and the impact of dishwashing program, composition and quantity of cleaning agents was investigated. The reduction of bacterial contamination was examined using Geobacillus stearothermophilus, E. faecium and S. aureus was determined. A high degree in transfer of test microorganisms from inoculated plates into dishwashing water and onto clean plates and sponges is observed. High temperatures, use of cleaning agents and changes of water results in higher reduction of test organisms in automatic dishwashing. In manual dishwashing the reduction of test microorganisms is less because of the lower wash temperature, the short contact time between water and microorganisms and use of cleaning liquids with only marginal biocide impact. The thesis was published in 2006 and can be ordered online from: http://www.shaker.de/de/content/catalogue/index.asp?lang=de&ID=8&ISBN=978-3-8322-5410-0