Ultrasonic methodology coupled to ATP bioluminescence for the non-invasivedetection of fouling in food processing equipment - validation and application to a dairy factory

The use of an ultrasonic apparatus (40 kHz) for the non-destructive, rapid and reproducible removal of biofilm from standard materials (stainless stee l and polypropylene) in a dairy factory was investigated. The application o f ultrasound with the tested conditions (10 s and 40 kHz) was found not to be detrimental for standard ATP (concentration ranging between 5 x 10(-9) a nd 10(-5) mol l(-1)) and for prokaryotic cells, including both rods and coc coid-shaped bacteria (Escherichia coli and Staphylococcus aureus). It allow ed the use of the ATP bioluminescence measurement for quantifying the biofi lm removal. The repeatability of industrial milk removal was determined on fouled stainless steel and polypropylene sheets. The variability of the res ults with the sonication method was constant, +/-24% (coefficient of variat ion) for both surfaces, and was variable with the swabbing method, +/-42% f or the stainless steel sheet and +/-74% for the polypropylene sheet. The ul trasonic apparatus removed twice the amount of industrial milk biofilm comp ared with the swabbing method in the case of the polypropylene sheets. The apparatus was used to validate the industrial cleaning protocols of a milk factory.