Structure–functionality impact of heat treatment on the interfacial adsorption of whey proteins at millisecond time scales

Depending on the heating conditions, we found structural changes at the level of individual protein molecules, as well as protein aggregation taking place. Firstly, when using real-time heating, the interfacial tension decreased faster with increasing temperature due to enhanced mass transfer, and even to moderate changes (unfolding) in protein structure. The time needed to lower the interfacial tension by 1 mN/m reduced from about 22 to 2.5 ms as the temperature increased from 20 to 70 °C. Additionally, high (pre- and real-time) heating temperatures and long heating times may facilitate protein aggregation in the continuous phase. These aggregates may diffuse and adsorb slower, but exhibit improved interfacial interactions at (sub)second time scales. These insights strengthen our understanding of the correlation between protein structure and heating-related protein functionality at time scales that closely resemble those encountered in large scale emulsion production, which connects emulsion formulation with process design.