Effect of common dairy clean-in-place protocols on the surface roughness of stainless steel surfaces

Document Type


Publication Date



American Dairy Science Association


Journal of Dairy Science




Suppl. 1






surface, roughness, biofilm.


Thermoduric spore formers survive heat treatments and lead to the formation of contact surface biofilms. These biofilms are difficult to clean and cause cross-contamination of milk and dairy products during milk processing. When bacteria aggregate on the surfaces, they form resilient biofilms over time that need to be removed and washed by applying harsh CIP chemicals. These typical cleaning and disinfection protocols in dairy plants are vital in ensuring good quality products. It is hypothesized that repeated use of CIP chemicals would alter the surface roughness of native, welded, and polished SS 316 surfaces and support biofilm formation differently. The present study is focused on evaluating the role of repeated CIP process on surface properties and understanding the relationship between surface roughness and biofilm formation. Plate heat exchanger CIP protocol was followed to clean the SS 316 coupons (2X2 cm2) for 10 consecutive cycles after forming biofilms using Geobacillus stearothermophilus. The selected organism was spiked into sterile skim milk samples at 6.0 log cfu/mL. After every CIP cycle, the biofilm counts were taken using standard microbiological techniques. Scanning electron micrographs were also taken to visually observe the developed biofilms. Laser scanning microscope images were taken to observe surface roughness changes pre-and post-CIP treatment. The replicate data from 3 trials for the chosen organism were analyzed and means were compared using Keyence VK Analyzer software. The surfaces roughness measurements (Ra) of pre-CIP treatment of native, welded, and polished surfaces were 0.6μm, 2.06 μm, and 1.01 μm respectively, and the measurements of post-CIP first cycle were 2.3 μm, 6.7 μm, and 2.9 μm after the first cycle. whereas the post tenth-cycle measurements were 3.8 μm, 19.2 and 4.8 μm respectively. These results demonstrate obvious changes in surface roughness after exposure to CIP chemical solutions, highest being on weldments. These observations agree with our hypothesis that repeated exposure to CIP cleaning cycles alters surface roughness and may cause cross-contamination in dairy products processing due to increased biofilm formation.

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