This study investigated the physical characteristics and flow properties of seven milk protein concentrate (MPC) powders, ranging from 36.6 (MPC35) to 89.6 (MPC90) % (w/w) protein in dry-matter. MPC80, MPC85 and MPC90 had the smallest particle sizes (P < 0.05) and significantly higher (P < 0.05) specific surface areas, as measured using nitrogen adsorption. The bulk density of MPC powders decreased with increasing protein content, due to increased (P < 0.05) levels of interstitial and occluded air. Flow testing indicated that high protein MPC powders were more compressible (P < 0.05), had lower flow index values (P < 0.05) and required larger (P < 0.05) outlet diameters for optimal flow in mass-flow hoppers compared to lower protein MPC powders. (C) 2014 Elsevier Ltd. All rights reserved.