General Remarks on Microencapsulation

After the drying process, the food powder of low moisture content and, usually, glassy state is stored at room temperature. In these glassy states, flavor release and the stability of flavor depend on kinetics rather than on thermodynamic mechanisms. 

The respective kinetics correlates with and can be predicted from the glass transition temperature of the carrier materials. Plasticization by water absorption under conditions of high humidity may cause reduction of the glass transition temperature below room temperature. Then, the structural change in the wall material leads to collapse of the food powder, resulting in flavor release from the rubber state of the carrier matrices (Ubbink and Schoonman, 2003). 

In the following sections, encapsulation of flavor by means of spray drying will be discussed. We will focus on flavor retention during spray drying, stability of the encapsulated flavor on the basis of emulsion properties, and on the release and oxidation rates in the spray-dried powder. 

---