Adhesion of bacteria and the development of biofilms can cause serious problems in food industry, such as contamination, resulting in food spoilage or food borne illnesses, increasing energy consumption and corrosion Repeated exposure to sanitizers can even lead to an enhanced resistance of bacteria in biofilms 1 Hence it is evident that biofilms have to be removed entirely from food contact surfaces Even though cleaning and disinfection protocols exist in food industry, biofilms are still present This might be due to the fact that the design of most cleaning protocols is still semi empirical or based on personal knowledge The aim of this work was to establish an optical laboratory method for an online detection of biofilms during the cleaning process in order to understand the removing behaviour of biofilms on surfaces used in food industry.