Physico-chemical and hygienic property modifications of stainless steel surfaces induced by conditioning with food and detergent

Abstract

The effect of repeated conditioning procedures (25 runs), consisting of soiling (milk and meat products) and cleaning steps, on the hygienic status, physico-chemical properties and surface chemical composition of stainless steel (SS) surfaces, was investigated. Five SSs differing in grade and finish were used. Both soiling and surface cleaning/conditioning procedures resulted in a similar increase in the surface contamination with carbon, while the changes in the basic component of the surface free energy depended on the conditioning procedure. The passive film was also affected, the Fe/Cr ratio in particular. The hygienic status was also changed, especially with milk as shown by monitoring the number of residual adhering Bacillus cereus spores after contaminating the surface with spores followed by cleaning. The results show that in food environments, the presence and the nature of conditioning molecules play a major role in the hygienic status of SS surfaces.

Keywords:

• Bacillus spores
• conditioning
• food
• hygiene
• soiling and cleaning runs
• stainless steel

Acknowledgements

This work was supported by a financial grant from the European Coal and Steel Community (Special and Alloy Steels, contract No. 7210-PR/101). Special thanks are due to F. Fontaine, J.F. Migdal, and S. Parent for their valuable technical assistance.