The role of non-covalent interactions in the alkaline dissolution of heat-set whey protein hydrogels made at gelation pH 2–11

The alkaline dissolution of protein hydrogels occurs during the cleaning of protein-rich fouling deposits common in the food industry, as in the cleaning of whey protein deposits in dairy processing. Here we seek to identify which are the dissolution rate limiting mechanisms by systematically studying whey protein isolate (WPI) heat-set gels formed at different gelation pH between 2 and 11. Swelling, which facilitates mechanical erosion, is controlled by the gel microstructure (particulate or stranded), unlike chemical dissolution. Results show that the alkaline dissolution rate of WPI gels is mainly controlled by the breakdown reactions of interprotein non-covalent interactions, particularly hydrophobic ones at gelation pH 4–11, and by hydrogen bonds at pH 2–3. Furthermore, we propose that the very low dissolution rates at very high NaOH concentrations and low temperatures are not only caused by lack of swelling, but are due to the slowing down of these non-covalent breakdown reactions by the NaOH itself.