Tribological properties and interfacial adsorption behavior of milk protein-based formulations: Roles of whey protein type and thermal processing

Whey protein-associated mouthdrying during oral processing is a driving factor for consumers' dislike of high-protein beverages, however, remains mechanistically underexplored in dairy systems. This study investigated the fundamental mechanisms driving powderiness in whey protein-enriched dairy beverages (8 % w/w protein). We conducted a comparative analysis of whey protein concentrate (WPC) versus whey protein isolate (WPI) at various casein-whey ratios (80:20 to 20:80) and evaluated thermal processing effects (63 °C/85 °C for 30 min) from rheological characterization, particle size distribution, tribological properties, and interfacial adsorption kinetics. Results demonstrated that protein composition significantly altered frictional behavior, with WPC-dominated systems (casein-whey protein ratio of 20:80) exhibiting 33.6 % higher friction coefficients versus WPI counterparts at 10 mm/s without heating. Thermal treatment at 85 °C induced substantial aggregation in WPI-dominant systems (hydrodynamic diameter increased from 0.150 μm to 0.167 μm) and reduced adsorption capacity by 30.80 %, correlating with impaired lubrication. Conversely, WPC maintained structural homogeneity and enhanced interfacial coverage post-heating, preserving lubrication functionality. These findings establish composition-specific thermal processing guidelines for optimizing sensory attributes in high-protein dairy beverages.