Effect of moisture content on physical and flow properties of milk‐millet powders

Abstract

The physical and flow properties of milk blended barnyard and foxtail millet powders were evaluated at different moisture contents. Particle‐size distribution and span decreased considerably as moisture increased. The d _0.5 increased from 24.769 to 38.642 μm in milk‐barnyard millet powder and from 27.942 to 41.063 μm in milk‐foxtail millet powder as moisture increased from 3 to 9%. The dynamic flow and shear tests revealed the hygroscopic nature of both millet powders, wherein moisture and particle size were found to influence flowability. The basic flow energy and shear tests proved that both millet powders would flow easily at 9% moisture content than at 3% due to agglomeration and reduction in contact surface area of the particles and the magnitude of their interactions. Compressibility and wall friction tests also corroborated the fact that milk‐millet powders were relatively more cohesive at 3% moisture, manifesting difficulties in flow. Between milk‐foxtail millet and milk‐barnyard millet powders, the former had better flowability due to its larger particle size and narrower span than the latter.

Practical Applications

Powders are dynamic systems whose behavior changes drastically with minor changes in the environment or moisture. In this study, the influence of moisture on physical and flow properties of milk‐millet powders were evaluated. The physical and flow properties of milk blended barnyard and foxtail millet powders were influenced by particle size and moisture content. The flow properties could be useful in understanding their behavior during handling, processing, and storage, and thus help in the design and optimization of processing and storage operations.