Influence of protein concentration on the physical characteristics and flow properties of milk protein concentrate powders

•As protein content increased, milk protein concentrate powders exhibited altered physical characteristics.•Increased specific surface area with increasing protein content had a strong negative effect on flowability.•Increased interstitial air with increasing protein content resulted in powders with high compressibility values.•High protein powders had poor flowability and significantly different requirements for the design of mass-flow hoppers.

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.