A review on the influence of water on food powder flowability

Abstract

AbstractPowder flow behavior is a complex phenomenon in which the physical and chemical properties of powder particles are involved. One of the main features that alter pharmaceutical and food powders flowability is water content. Water content modifies the arrangement and interaction of the powder’s internal particles. A water content increment in powders is generally associated with a flowability decrease. In this paper, the interaction mechanisms between water and powder particles are reviewed. Also, the most used flowing indexes in powders are analyzed, and their relationship with the water content index. Moisture content and water activity effect on powders flowability, described by Carr index, Hausner ratio, angle of repose, and flow factor are examined. Finally, the structural changes within the powder matrix due to water adsorption, agglomeration of particles, and powder caking are discussed. The water content of powders is hard to handle because it is in a dynamic equilibrium under ambient conditions. In this sense, the water content in powders becomes a critical control point to ensure an enhanced flowing capacity. Small changes in water content may lead the powder to flow or not to flow, with its inherent consequences during their storage or transport. Regarding flow factor and moisture content, an individual behavior for each powder is shown. These results could not be extrapolated. On the contrary, water activity data appear interesting due to the linear relationship with flow factor in almost all the reported powders.