Impedanzspektroskopische Messung bei der Reinigung von Belägen in der Lebensmitteltechnologie

Problem: During the heat processing of liquid food (milk, beer, juice) layers are formed on the surface of the production lines. Usually these layers were removied whith the CIP (cleaning in place) technology with a combination of alkaline and acid. A measurement method for inline monitoring of the cleaning process is not avail-able up to now. Therefore the duration of the CIP process has a certain excess time to assure the cleanliness of the production unit. Solution A planar capacitive sensor, incorporated in the tubes and tanks can measure the cleaning process. The sensor is a interdigitated capacitor (IDC) with a raster of some 10 µm. The Au-electrodes are coated with a thin and corrosion resistant SiC coating. For experimental purposes a conventional flange is the housing of the sensor. The sensor is measured with a impedimetric technique(impedance spectroscopy, 100 Hz 1 MHz). The spectra were evaluated with a multivariate tech-nique (principal component analysis), which results in an cleaning indicator.