Microbiological and Chemical Analyses of Stainless Steel and Ceramics Subjected to Repeated Soiling and Cleaning Treatments

Abstract

Stainless steel and ceramic surfaces were subjected to repeated soiling and cleaning procedures, using a milk powder soil inoculated with Pseudomonas aeruginosa and Staphylococcus aureus, followed by spraying with water with or without 0.1% (vol/vol) nonionic detergent. Test surfaces were removed after 1, 5, 10, and 20 soiling-cleaning cycles and were analyzed for attached microorganisms (total viable count of bacteria removed by swabbing and percentage of coverage of cells plus soil stained with acridine orange). Surfaces were additionally examined using a range of analytical techniques: X-ray photoelectron spectroscopy (XPS), dynamic and imaging secondary ion mass spectroscopy (SIMS), and time-of-flight SIMS. Both microbiological and chemical analyses revealed an accumulation of material over the cycles to a maximum level. Surfaces were conditioned rapidly to saturation with organic material within one cycle (XPS), whereas fouling by microorganisms was less rapid (five cycles). Cleaning with detergent tended to retard the cumulative fouling process when compared with spray cleaning using water alone. The methods described provide a more realistic scenario for testing the cleanability of surfaces routinely found in food processing locations and for screening novel cleaning regimens and/or surface materials. The analytical techniques provide additional information on the kinetics of soiling, which complement the more familiar microbiological methods.

Assessment of interplay between UV wavelengths, material surfaces and food residues in open surface hygiene validation

“…It is rare to find microorganisms on surfaces in absence of organic materials; however accumulated residue has a major influence on microbial retention afterwards (Verran et al 2001;Verran et al 2010). …”

“…They are a source of nutrients and afford the bacteria protection from disinfection, in addition to being indicative of poor hygiene processes (Holah 1995;Verran et al 2001). Their presence also makes adhered bacteria difficult to detach from the surfaces (Abban et al 2012).…”

Evaluation of a bioluminescence method, contact angle measurements and topography for testing the cleanability of plastic surfaces under laboratory conditions

“…ATP can be measured either indirectly by swabbing the surface and analysing the swab or directly from the surface, thus avoiding the inaccuracy caused by swabbing [9,12]. Results from the same room area are normally compared when evaluating hygiene.…”

Efficacy of low-pressure foam cleaning compared to conventional cleaning methods in the removal of bacteria from surfaces associated with convenience food

“…This may indicate insufficient cleaning and disinfection, since effective cleaning processes should yield a significantly reduced or zero TPC. 30,47 Table 2 presents a summary of the total samples taken and shows the compliance with the legal limit (< 100 cfu.cm -2 for TPC). 43 Overall, 84 of the 205 TPC samples (41%) complied with the legal requirement, whereas 121 of the 205 samples (59%) did not comply.…”

“…The various food manufacturers used different chemical suppliers and the chemical companies had different levels of cleaning technology, therefore, different levels of cleaning methods were applied. 47 Fifty percent of the outlets used traditional methods such as manual cleaning (brush and bucket) and were supplied by local chemical manufacturers. The brush and bucket method refers to physical energy being carried out by people, using pressure and movement on surfaces.…”