In addition to the preparation and provision of meals, the services in the catering trade also include the reprocess-ing of used working materials, tableware including glass-es and cutleries by using commercial dishwashing machines.

In order to keep the consumption of water, energy and cleaning products in dishwashing processes low and to avoid bad washing results, it is advisable to tailor the dishwashing processes individually to the requirements of the respective operator as well as to the requirements of modern dishwashers operating with the lowest possible consumption values. Operator specific requirements include the amount and type of tableware, the amount and type of dirt, drying time etc. Bad washing results are always associated with a hygiene risk.

Against this background, an electronic performance indicator was developed at wfk-Institute in cooperation with the Fraunhofer Institute for Microelectronic Circuits and Systems, which consist of a non conductive carrier material (ceramics) on which electrode areas with application specific geometry are located.

The electrode area is contaminated with a test organism (e. g. E. faecium, M. luteus) to evaluate the disinfection performance and with a test contamination (e. g. ketchup, egg yolk, starch) to evaluate the cleaning performance.

An uncontaminated electrode area on the electronic performance indicator serves to record the residual moisture or to evaluate the drying capacity, which is moistened and dried by the rinsing process.

Measurement and evaluation methods were developed for the impedimetric analysis of contamination and residual moisture on the electrode area. For this purpose, measuring parameters were defined and models were created to describe the functional relationship between the amount of contamination or residual moisture on the electrode area and the impedance.

In addition, a humidity correction model was created for the respective contamination. The models enable an automated evaluation of the performance indicator.

Restaurant and catering companies, other food preparation and processing companies, manufacturers of dishwashing machines and detergents as well as the predominantly small and medium-sized cleaning and hygiene service providers can use the electronic performance indicator to check and optimize the dishwashing processes they use.

The research report is available on request from FRT.