Drying-induced mechanisms of skin formation in mixtures of high protein dairy powders
Résumé
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.