α-Lactalbumin enriched ingredients are being used increasingly in the formulation of nutritional products (e.g., infant formulae). Technologies used to produce such ingredients include selective precipitation, membrane filtration and ion exchange chromatography. The aim of this study was to determine the effects of differences in macro-chemical composition and microstructure of 3 commercially available a-lactalbumin-enriched whey protein ingredients (LAC 1, LAC 2 and LAC 3) on powder flowability and rehydration properties. The protein content was 78.8, 78.2, and 92.5% wt/wt for LAC 1, LAC 2 and LAC 3, respectively. The lipid content was higher in LAC 2 (9.32% wt/wt) than in LAC 1 (0.84% wt/wt) or LAC 3 (0.40% wt/wt). The LAC 1 powder had the largest particles, with a D[4,3] of 159 µm and the lowest specific surface area (SSA); the particles in this powder were observed to have crater-like dents and vacuoles using scanning electron microscopy. The powder particles in LAC 3 were smaller, with a D[4,3] of 36.4 µm, had the highest SSA and were observed to have shell-like, partially fragmented particles. Particles of LAC 2 with a D[4,3] of 72.7 µm were more spherical with smooth surfaces and a SSA similar to LAC 1. The analysis demonstrates that the lipid content influenced powder flow properties, as LAC 2 was very cohesive, with a flow index (i) of 3.29, (where a low value indicates poor flowability). In contrast, LAC 1 and LAC 3 (both with lower fat content) were easy flowing and free flowing, with i values of 6.48 and 11.3, respectively. However, LAC 3 had poor rehydration properties, with contact angle (θ) > 89°, whereas LAC 1 and LAC 2 had similar θ of ~70°. This study clearly shows that flowability was influenced more strongly by composition than the microstructure or particle size of the powders, while the total protein content significantly influenced the rehydration properties of the powders.