Cleanability of soiled stainless steel as studied by atomic force microscopy and time of flight secondary ion mass spectrometry

The hygienic status of food contact surfaces can deteriorate with wear. Eff ective cleaning regimes must remove any adsorbed organic material as well a s microorganisms. Previous work has determined the extent of surface wear o ccurring on a stainless steel surface within the food industry, and we have reproduced representative samples in vitro. Two surface analytical techniq ues, atomic force microscopy and time of flight secondary ion mass spectrom etry were combined with fluorescence microscopy to give detailed analysis o f stainless steel surfaces fouled with starch and milli powder, then cleane d with water either by a spray or brushing method. It was found that the su rface cleanability is affected by the cleaning regime and the surface rough ness, not only the average vertical roughness but also by the shape of the surface defects, with sharp scratches more difficult to clean than wider su rface defects. Spray cleaning with distilled water was found to be a select ive method by preferentially removing proteinaceous material more easily th an fatty acid ester material. The analytical techniques employed provided i nformation on selective cleanability and surface topography at a hitherto u nexplored level, and the information gained may be of value in the design a nd investigation of novel cleaning regimes and hygienic surfaces.