Display omitted Spray drying of dairy products consists of spraying droplets of feed solution into a hot air flow to quickly evaporate water and finally to form dried particles. In order to understand the role of the two-major milk protein (whey proteins and micellar caseins) in the mechanisms of particle formation the evaporation of mixtures containing different whey protein to casein ratios the obtained milk protein concentrates was investigated at single droplet and jet monodispersed stages. The results obtained suggest that the evolution of skin mechanical properties with time strongly depends on the composition of the mix and most of all on both size and mechanical characteristics of the colloidal components. Interestingly, the remarkable shape analogies observed in spray dried particles compared to the single droplets suggest that, despite the significant difference in terms of experimental conditions and process characteristic time scale, the ongoing evaporation dynamics are almost equivalent. Moreover, our results showed an overrepresentation of the smaller size whey proteins at the particle surface of dairy colloidal mixes, in agreement with reported results on model colloids.