Calcium Chelation by Phosphate Ions and Its Influence on Fouling Mechanisms of Whey Protein Solutions in a Plate Heat Exchanger

Abstract

Fouling of plate heat exchangers (PHEs) is a recurring problem when pasteurizing whey protein solutions. As Ca2+ is involved in denaturation/aggregation mechanisms of whey proteins, the use of calcium chelators seems to be a way to reduce the fouling of PHEs. Unfortunately, in depth studies investigating the changes of the whey protein fouling mechanism in the presence of calcium chelators are scarce. To improve our knowledge, reconstituted whey protein isolate (WPI) solutions were prepared with increasing amounts of phosphate, expressed in phosphorus (P). The fouling experiments were performed on a pilot-scale PHE, while monitoring the evolution of the pressure drop and heat transfer coefficient. The final deposit mass distribution and structure of the fouling layers were investigated, as well as the whey protein denaturation kinetics. Results suggest the existence of two different fouling mechanisms taking place, depending on the added P concentration in WPI solutions. For added P concentrations lower or equal to 20 mg/L, a spongy fouling layer consists of unfolded protein strands bound by available Ca2+. When the added P concentration is higher than 20 mg/L, a heterogeneously distributed fouling layer formed of calcium phosphate clusters covered by proteins in an arborescence structure is observed.

A critical review on surface modifications mitigating dairy fouling

“…For WPI solutions, when phosphate ions content is low, it seems that free ionic calcium content actively participates in the formation of the fouling layer but calcium carbonate (Jimenez et al., 2013) and calcium phosphate (Blanpain‐Avet et al., 2020; Dupeyrat et al., 1987; Khaldi et al., 2018; Scudeller et al., 2021) have also been mentioned when phosphate ions content increases.…”

“…Consequently, depending on the fluid composition, interactions with surfaces could also differ for a given temperature as shown by and later by Blanpain-Avet et al (2020) and Scudeller et al (2021).…”

“…As shown in Tables 3 and 4 but also the content in carbohydrate (lactose) and lipids is very different. Consequently, depending on the fluid composition, the concentration balance of species (protein and/or mineral) in the bulk can be seriously affected and may significantly alter the fouling layer build-up (Blanpain-Avet et al, 2020;Liu et al, 2020;Scudeller et al, 2021).…”