Heat and Mass Transfer Analysis in High-Protein Dairy Fluids During UHT and HTST Processing

High-protein dairy fluids present particular challenges during high-temperature short-time (HTST) and ultra-high-temperature (UHT) processing because thermal exposure interacts with concentration-dependent rheology, protein aggregation and fouling. This narrative critical review examines how heat and mass transfer, reaction kinetics and deposit formation affect the processing of milk protein concentrates, whey protein formulations and related dairy systems. Evidence is considered from dairy experiments and, where relevant, methodological analogues from non-dairy heat-transfer and kinetic-modelling studies. The review discusses shear-thinning and yield-stress behaviour and considers Casson, Williamson and Cross models for describing flow characteristics associated with heat transfer and residence-time distributions. Thermal treatment is examined in relation to protein denaturation, micronutrient stability and the influence of temperature gradients. The kinetic discussion addresses denaturation and aggregation as potentially multistage processes and evaluates the methodological relevance of the Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa approaches without treating non-dairy parameters as dairy-specific estimates. Fouling is discussed in terms of protein deposition, mineral precipitation and the representation of deposits as evolving porous layers. Dynamic-mesh computational fluid dynamics and data-driven prediction are examined as possible approaches for characterising deposit development and exchanger performance. The synthesis identifies limitations in transferring models across formulations and processing conditions. It emphasises the need for dairy-specific measurements and experimental validation before these approaches can be adopted for routine process optimisation.