Cleanability of stainless steel surfaces soiled bybacillus thuringiensisspores under various flow conditions

Abstract

Adhesion of Bacillus thuringiensis spores on stainless steel surfaces has been investigated under various fouling conditions (static and dynamic). The number of adhering spores as well as the removal of adherent spores following a standard cleaning in place (CIP) procedure were analysed. The number of adhering spores was demonstrated to depend on the fouling conditions, with a significant lower level adhering under static conditions (up to 0.6 log). Under dynamic conditions, the initial rate of contamination was found to be more than twice as high as in the turbulent conditions tested, but then appeared to slow down with time. Cleanability assessment of these surfaces revealed a weak attachment of spores adhering under static conditions as well as in turbulent conditions (removal up to 93% compared to 68% under some laminar fouling conditions). Fouling conditions should thus be taken into account as a major concern in risk assessment procedures.