Impact of formulation adjustment, microfiltration, and spray drying on physicochemical, functional, and microstructural attributes of dairy mixes and powders

This study investigated how the composition of liquid dairy mixes, formulated from microfiltration-derived fractions (retentate and permeate), affects the physicochemical and functional properties of spray‑dried powders and reconstituted mixes. Microfiltration of skim milk through 0.1 μm ceramic membranes was used to produce two fractions: a permeate enriched in soluble proteins and minerals, and a retentate enriched in caseins and colloidal minerals. Different dairy mixes were prepared by blending these fractions in various proportions at a constant dry matter content. One mix corresponded to a recombined milk obtained by mixing retentate and permeate, enabling the specific effect of microfiltration to be assessed. Compared with unprocessed skim milk, microfiltration significantly modified the mineral balance, pH, viscosity, and casein micelle size of the mix, leading to powders with altered gelation capacity, gel morphology, true density, particle surface structure, and improved reconstitution behavior. Additional mixes were formulated by further enriching the skim milk with retentate, thereby increasing the contents of caseins and colloidal minerals. This enrichment resulted in higher viscosity, modified zeta potential and micelle size, as well as changes in flowability, color, and reconstitution properties of the powders. It also enhanced the gelation properties of the reconstituted systems, producing stronger and more fibrous gels that aggregated faster and exhibited increased gelation pH and buffering capacity. These findings highlight the potential of tailoring liquid dairy mix composition through microfiltration to fine‑tune the physicochemical, functional, and microstructural attributes of spray‑dried dairy powders for diverse industrial applications.