Evaluation of Clean-in-Place Agents on the Removal of Thermophilic Biofilms Formed under Partially Simulated Conditions Associated with the Dairy Industry

Abstract

In this study, various clean-in-place agents against thermophilic biofilms were evaluated. Dairy contaminants such as Geobacillus thermodenitrificans, Geobacillus thermoglucosidans, Anoxybacillus flavithermus, and Anoxybacillus kamchatkensis subsp. asaccharedens were sampled under simulated conditions (whole milk, static and dynamic conditions). Biofilm removal strategies were conducted, and agents acting on proteins such as trichloroacetic acid (TCA) and sodium dodecyl sulfate (SDS) were found to be most effective on thermophilic biofilms. It was found that thermophilic strains, especially under dynamic conditions, can form intense biofilms at an early stage (<5 h) and that these biofilms cannot be removed by the previously recommended routine sanitation procedures. In the current study, tandem treatment (SDS after TCA) with chemicals such as TCA and SDS for 30 min gave clear results in removing thermophilic biofilms. Moreover, enzymes such as trypsin and protease were highly effective in removing thermophilic biofilms. It was also found that surface materials used in the dairy industry, such as stainless steel, polypropylene, polyvinyl chloride, and polycarbonate, are not critical for the removal of thermophilic biofilms. Thermophilic biofilms sampled on surfaces under simulated conditions (whole milk, temperature, steady-state, and dynamic conditions) were also evaluated using confocal laser microscopy analysis after sanitary treatment.