Comparison of fouling of raw milk and whey protein solution on stainless steel and fluorocarbon coated surfaces: Effects on fouling performance, deposit structure and composition

• Published in: Chemical engineering science Vol. 195; pp. 423 - 432
• Main Authors: Magens, Ole M., Hofmans, Jurgen F.A., Adriaenssens, Yves, Ian Wilson, D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 23.02.2019
• Subjects: Beta-lactoglobulin; Calcium phosphate; Coating; Fluoropolymer; Milk fouling; Pasteurisation; Calcium phosphate; Pasteurisation; Beta-lactoglobulin; Coating; Fluoropolymer; Milk fouling
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2018.09.039

•A microfluidic and a bench scale heat exchanger tested deposition from raw milk on different surfaces.•A fluorinated ethylene propylene coating gave the best performance of those tested.•Fouling behaviour of raw milk differs from that of whey protein solution.•The microstructure and composition of deposits on fluoropolymers differed from those on stainless steel.•The results can be explained by considering the interfacial free energies of the materials in an aqueous environment. Fouling from raw milk and from whey protein solutions mimicking the protein content of milk have been performed at two length scales, using a microfluidic heat transfer cell and a bench-scale device with hydraulic diameters 1.0 mm and 16.1 mm, respectively. The microfluidic cell allows raw milk to be studied in once-through mode and was used to identify polymer coated surfaces to test against stainless steel. Several of the fluorocarbon coated surfaces reduced the mass deposition but the pressure drop and thermal resistance did not match these directly, indicating that the nature and structure of the deposit is affected by the surface. A fluorinated ethylene propylene coating was identified as a promising candidate for large scale tests. At the interface with apolar surfaces, raw milk fouling layers were high in protein whereas a strongly attached mineral-rich layer was present at the interface with steel. The attraction of denatured protein towards apolar surfaces and the formation of a calcium phosphate layer on steel at later stages of fouling are explained with arguments based on the interfacial free energy of these materials in water.