Influence of substrate nature and β-lactoglobulin on cleanability after soiling by suspension spraying and drying

Glass and stainless steel(StSteel,AISI304-2R),previously cleaned with ethanol(-Eth)or with ethanol and UV–Ozone treatment(-UVO),were soiled with quartz suspensions in water and in a β-lactoglobulin (β-LGB) solution,and dried. The cleanability(ease of quartz particle detachment)in water was evaluated using a radial flow-cell. The soiling suspension containing β-LGB was used as such or after heating for 4h at 75°C, which provoked coagulation of about75% of β-LGB. The substrate–solution interfaces were characterized by X-ray photoelectron spectroscopy(XPS)analysis of conditioned substrates and by contact angle measurements. The substrate surfaces are covered by a layer of organic contaminants which are not removed by pre-cleaning or a readsorbed from the surroundings.The presence of β-LGB in the soiling suspension leads to protein adsorption,but a significant amount of contaminants remains at the surface. For three of the substrates tested(Glass-Eth,Glass-UVO,StSteel-UVO)the increase of cleanability when the soiling suspension contained β-LGB may be explained by lower capillary forces acting upon drying. Capillary forces are proportional to the liquid surface tension and depend in a less important way on substrate contact angle.However the order of cleanability observed for the substrates soiled with a suspension of quartz particles in water(Glass-Eth =~Glass-UVO