Effect of the phosphate/calcium molar ratio on fouling deposits generated by the processing of a whey protein isolate in a plate heat exchanger

Whatever the dairy derived fluids that are heat processed, many studies have demonstrated the key role of beta-lactoglobulin (beta-lg) denaturation in the initiation of a dairy fouling and mentioned that interactions between beta-lg, phosphate and calcium ions are essential in fouling growth. However only few authors have reported the influence of the phosphate/calcium molar ratio on fouling mechanisms. To partly fill this gap, various whey protein solutions (composed mainly of beta-lg) having different phosphate:calcium molar ratios were prepared by rehydrating a whey protein isolate powder and by adding calcium chloride and various amounts of soluble inorganic phosphate (noted PI). Fouling experiments were carried out at pilot scale using a plate heat exchanger (PHE) at a fixed temperature profile and the deposited mass per channel was measured. Finally, the chemical composition and structure of the proteinaceous fouling layer were observed using an Electron Probe Micro Analyser. Results clearly demonstrated that the phosphate:calcium molar ratio modified the deposit structure and influenced substantially the amount of fouling. These results suggest that the relative proportion of calcium phosphate and calcium ions governs the mechanism of fouling build-up and also sets, to a certain extent, the fouling ability of the whey protein solutions. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.