Identification of residual nano-scale foulant material on stainless steel using atomic force microscopy after clean in place

Abstract

During clean-in-place (CIP), solutions are pumped through process equipment to remove soils having adverse effects on production. In order to validate reductions in CIP inputs, foulants need to be detectable and quantifiable on smaller scales than current industrial practices. In this study, fluorescent microscopy was used for quantifying macroscopic cleanliness of a soiled stainless steel coupon after CIP. An asymptotic model was used to describe the removal of soil as a function of the coupon exposure time and cleaning solution temperature. From these models, cleaning parameters were determined and used to generate coupons predicted to be 99.0 and 99.9% clean. This cleanliness was verified using atomic force microscopy (AFM). AFM identified foulant on the order of 5 μm 2 on a 1.0 x 10 4 μm 2 area. AFM showed cleanliness ranging from 99.41 to 99.94 %. Differences between predicted and actual cleanliness suggest a change in cleaning mechanism at different scales.

Molecular Understanding of Fouling Induction and Removal: Effect of the Interface Temperature on Milk Deposits

“…Subsequently, they were rinsed with a 1.0% (vol/vol) HCl solution, soaked in hexane (5 min) and acetone (5 min) before being dried by an air stream. 24 All solvents used were of HPLC grade.…”

“…They were cleaned using a 2.0% (wt/wt) NaOH aqueous solution at 80°C under stirring for an hour and cooled down to room temperature using a water bath. Subsequently, they were rinsed with a 1.0% (vol/vol) HCl solution, soaked in hexane (5 min) and acetone (5 min) before being dried by an air stream . All solvents used were of HPLC grade.…”

Effect of surface roughness and temperature on stainless steel - Whey protein interfacial interactions under pasteurisation conditions

“…Stainless steel coupons were cleaned by the method detailed in Phinney et al, (2017): 2.0% (wt./wt.) NaOH aqueous solution at 80°C under stirring for 1 h to achieve complete removal of potential contaminants, and cooled to room temperature using a water bath.…”

“…The model solution was prepared by mixing the WPC powder with de-ionised water at room temperature for an hour. Attention was paid to minimise aeration, foam formation, and proteins denaturation of the solution following the procedure developed in Phinney et al, (2017). To mimic relevant industrial conditions (pasteurisation temperatures, protein denaturation and surface contact time allowing ageing of the deposit), 1 ml of the prepared solution was placed on the cleaned coupons (temperature kept at 25°C before deposition, unless otherwise stated) and maintained at 75°C for 1 h in an oven, and then cooled.…”

Comparison of spindle and stomacher efficacy for detaching biofilms from stainless steel, PVC, and green leafy vegetable surfaces

“…As fluid has high Re , the flow become more instable and this indicates that fluid applies higher mechanical forces to surface (Meyer, 1982; Timperley and Smeulders, 1987). Phinney et al (2017) confirmed that fluid with higher impeller Re had larger shear stress. Also, it was reported that foulant removal efficiency was proportional to Reynold number of flow (Fan et al , 2018).…”