Fouling is an unsolved and costly question for the dairy industry and consists in the gradual deposit of the solid fraction of a liquid stream on stainless-steel surfaces due to the combined action of thermal and concentration gradients. Understanding this phenomenon and preventing its consequences is of paramount relevance to optimize the operation unit efficiency and to improve the quality of the products. Until now, most of the studies available in the literature focused on the fouling dynamics in heat exchangers and led to contradictory results based on the off-line analysis of the solid layers. Conversely, the fouling mechanisms have been rarely explored in vacuum evaporators despite their systematic use in dairy industry (e.g., infant formula production) nowadays. In this work, we show that the initiation of the fouling process is not exclusively linked to protein thermal denaturation above a critical temperature (T>65 °C), as usually assumed, but also to the high shear rates in proximity of the equipment walls. Dispersions of whey proteins with different overall concentrations were processed by a rheometer, undergoing the range of shear rates (100-200 s-1) typical of falling film evaporators at fixed temperature (65 °C) and shearing time (10 min). The combined effect of heat and shear on the different stages of protein accumulation was evaluated on glass surfaces, by observing the development of the deposits (density, size, shape) using optical and digital microscopy. Our outcomes highlighted the formation of complex structures at the surface with increasing shear strength and protein concentration, characterized by a fractal arborescence. The morphology of the deposits was further characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which allowed to hypothesize possible mechanisms of initiation and propagation of protein layers. On the basis of these promising results, we also performed preliminary tests by microfluidic devices with the aim of providing a direct observation of the fouling dynamics in dairy mixes. The challenging question is to discriminate the mechanisms governing protein denaturation and aggregation in the bulk solution and those occurring at the surface and leading to growing deposits.