The relationship between substratum surface roughness and microbiological and organic soiling: A review

Substratum surface roughness has a well documented effect on the retention of microorganisms. Implications of this encompass problems in hygiene, infection, fouling, equipment function, corrosion and cleanabil‐ity. This paper reviews methods used for visualising surface topography and measuring roughness which are pertinent to microbiologists, and notes limitations of some of the descriptors of surface roughness. A major issue is the scale on which the surface defects are examined: measurements may now be made in nanometers, but the significance of surface texture at this scale in terms of microbial retention has yet to be investigated in detail. Stainless steel and ceramics are commonly used as hygienic food preparation surfaces. Their wear has been visualised, with roughness measured on a nanometer scale using the atomic force microscope (AFM), and the effect on surface wear of cleanability using microbial and organic soil investigated. Surface analytical methods such as X‐ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectroscopy (ToFSIMS) provided information on the chemical structure at the uppermost atomic layer and demonstrate that microorganisms were removed more rapidly than organic material from the worn surfaces, and that organic soil conditioned the surfaces prior to microbial contamination. On this scale, the dimensions of surface defects were more suited to soil retention than to microbial cell retention. Traditional microscopic methods were not able to differentiate adequately between soil and microbial removal. Surface analytical techniques provide the opportunity to measure and visualise surface roughness and its effect on microbial and organic soiling on a hitherto unavailable level of detection.

Key words:

• surface roughness
• microbial adhesion
• biofouling

Notes

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