Bacterial re-contamination of surfaces of food processing lines during cleaning in place procedures Original Research Article

The possible contamination of surfaces of food processing lines during cleaning in place (CIP) procedures was investigated. Experiments were focused on surface contamination of straight pipes and a two-way valve, chosen as an example of complex pieces of equipment. Pipes and a two-way valve were inserted into a CIP rig, at the same time as a series of pipes highly contaminated with spores of three Bacillus cereus strains, with various surfaces properties. Following a CIP procedure, performed in conditions close to those encountered in food industries, the contamination level of the various items was estimated. A significant surface contamination occurring during CIP was evidenced, depending on the spore surface properties. Similarly to previously reported observations, when spores were suspended in optimal adhesion conditions (suspension in water at 20 °C), the re-adhesion phenomenon was controlled by the flow pattern and contamination levels inside the valve were significantly higher than in tubes. Cleaning strategies should therefore take into account the re-adhesion phenomenon to limit the risk of contamination by the process line.