Glass spray-dried powder stickiness

If the glass consists in substantial part of low-molar-mass components, like sugars, the material tends to become quite sticky somewhat above Tg. This can occur with several spray-dried powders that take up water from the air the stickiness then causes the powder particles to form a coherent mass, a phenomenon called caking. On the other hand, powder particles can be... 

Adhikari B, Howes T, Leocomte D, Bhandari BR. 2005. A glass transition temperature approach for the prediction of the surface stickiness of a drying droplet during spray drying. Powder Technology 149 168-179. 

For example, powdered milk products remain dry, free-flowing and stable when maintained below the glass transition temperature. However, if the powder picks up moisture from the air or experiences elevated storage temperatures, it may exceed the glass transition curve and become less stable (mbbery state). In this case, powdered milk would be likely to get sticky, and the powder would cake together. In a spray-dryer, operating parameters have to be chosen to ensure a rapid drying... 

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