Identification of surface characteristics relevant to the hygienic status of stainless steel for the food industry Original Research Article

The hygienic status of stainless steels used for food equipment was investigated by means of the number of residual adhering Bacillus cereus spores after a complete run of soiling and cleaning in place procedure. The 14 materials tested (304, 316 and 430 grades; pickling (2B), bright annealed (2R), and electropolished finishes) were shown to be highly hygienic with slight differences in the number of residual adhering spores. Nevertheless, they could be grouped into different classes according to their hygienic status. Grade, and to a lesser extent finish, were found to be related to the hygienic status. Among the stainless steel surface free energies, only γ+ could be slightly related to the hygienic character. Moreover, surface topography by means of the RPK parameter, corresponding to the height of the top portion of the surface profile, was also shown to control the hygiene of stainless steel surfaces.