(1) Background: Optimization of production and evaluation of the quality of preparations containing milk proteins facilitates their use in various branches of the food industry. The aim of this study was to produce and characterize high-protein milk powders (MCC, SPC) obtained by membrane techniques, and to compare them with industrially produced powders (WPC, CH, WPH, WPI). (2) Methods: The composition, reconstitution and flow properties, particle size, and microstructure of milk powders were determined, and fractal analysis was performed. (3) Results: MCC and SPC produced by the membrane separation of skim milk and industrially produced powders were characterized by a wettability of >180 s and a high solubility (0.10–0.85 cm³), excluding MCC (10.75 cm³ of insoluble particles). Flowability expressed as the Carr index was very good in CH (<15%), good in MCC (15–20%), and fairly good in the remaining powders (20–25%). All powders were moderately cohesive, excluding CH, which was characterized by low cohesiveness. The analyzed preparations differed in the values of fractal dimension. (4) Conclusions: The reconstitution and rheological properties of high-protein milk powders were affected by their composition, particle size, porosity, and surface properties. The fractal approach to the microstructure of milk particles enabled the unambiguous detection of subtle differences in the microstructure of the analyzed samples, which could not be identified during a visual assessment.

(1) Background: The impact of different drying methods on the functional properties and microstructure of milk powders was analyzed in this study. (2) Methods: Whole milk, skim milk, and buttermilk powders were obtained by freeze drying, spray drying, and roller drying. (3) Results: The examined powders differed in chemical composition, and these differences were attributed mainly to their fat content. The functional properties of the studied powders were determined mainly by the drying method and were less influenced by their composition. Loose and tapped bulk density was highest in roller-dried powders and lowest in freeze-dried powders. The flowability of milk powders was determined by calculating the Carr index and the Hausner ratio, and the results were used to classify the analyzed powders into the following groups: poorly flowing and cohesive (spray-dried samples), passable (roller-dried samples), and fair (freeze-dried samples). The volume of insoluble particles was highest in roller-dried powders and much lower in spray-dried powders, whereas freeze-dried powders were 99.8–99.9% soluble in water. Whole milk powder was characterized by low wettability (>180 s) regardless of the drying method. Powder morphology was influenced mainly by the drying method. (4) Conclusions: The fractal analysis demonstrated that spray-dried powders had the smallest fractal dimensions, which implies that their surface was least complex (most uniform). Regardless of the drying method, fractal dimensions were highest in whole milk powder, which could suggest that fat affects the microstructure of powders. The color parameters of milk powders were determined mainly by the drying method and were less influenced by the type of raw material used in powder production.