A micro-fluidic-jet spray dryer was used to fabricate spray freeze dried (SED) and spray dried (SD) uniform microparticles with feed solid content >30 wt% of reconstituted skim milk. The effects of feed solid content on the particle size, morphology, surface composition, wettability and solubility were investigated. The surface composition of SFD and SD sample was characterized via an X-ray photoelectron spectroscopy. Fat and protein was found to be over-represented on the SD particle surface, while lactose significantly declined. Such ingredient segregation was quantitatively shown to occur during atomization and continue within the drying process, i.e. atomization-induced ingredient segregation (AIIS) and drying-induced ingredient segregation (DIIS). The wettability and solubility of the spray dried samples were quantified using scaled-down GEA Niro Methods in relation to the feed solid contents. (C) 2013 Published by Elsevier Ltd.