In this study, the composition and microstructure of three whey protein ingredient powders enriched in alpha-lactalbumin (LAC 1, 2 and 3), prepared using three different enrichment approaches, were assessed to determine their bulk handling (flowability, wall friction, bulk density and compressibility) and rehydration (wettability and dissolution) properties. The LAC powders had significantly lower bulk density (0.26-0.30 g/cm(3)) than the other powders (0.35-0.51 g/cm(3)) analysed. All powders analysed generally displayed free- or easy-flowing behaviour, with the exception of LAC 2, which was cohesive. This cohesiveness was associated with the significantly (p < 0.05) higher fat content (9.23%) of LAC 2. LAC 3, with highest protein content (92.5%), was the least wettable powder with initial contact angle (theta) of 93.5 degrees. In contrast, while LAC 2 and LAC 3 had almost identical protein content (78.2 and 78.8%, respectively), LAC 2 exhibited significantly faster initial wetting behaviour, due to differences in the concentrations of non-protein constituents. The use of dissolution spectroscopy to measure the rate constant for disapperance of occluded air (i.e., air within powder particles) also demonstrated that the dissolution properties of the LAC ingredients were influenced by differences in powder physical and microstructural properties. The results obtained in this study provide new insights into the complex inter-relationships between composition, microstructure, bulk handling and rehydration properties of value-added whey protein ingredients.