ABSTRACT
Spray drying is a well-established process to encapsulate volatile, sensitive, and functional ingredients. The transformation from a liquid medium into a dry powder stabilizes the sensitive core materials in a closed matrix of the shell material. Since the core material is homogeneously distributed within the encapsulating matrix, the resulting type of capsule is usually referred to as matrix capsule. Air inclusion may occur in the particle in the form of a central void (Figure 3.1). With respect to applications in the food or pharmaceutical sector, spray drying of an emulsion is performed to encapsulate non-water-soluble core materials such as oils, vitamins, or avors. Depending on the type of avor, the process results in a high avor retention above 95%,1-5 and a similar retention for encapsulation of nutritional oils.6-8
Encapsulation by spray drying offers protection to adverse environmental conditions such as oxygen or light as well as protection against undesired reactions with other constituents or ingredients.1,9,10 For this purpose, a carbohydrate-based matrix is usually used. A critical issue related to the process is to preserve the physical properties of the emulsion during drying. Since microcapsules are frequently redissolved before ingestion, the dried emulsions need to be physically stable after dissolution. To create a certain functionality, more sophisticated structures may be build up in the emulsion-like bilayer formation at the interface11,12 or creation of brillar structures,13 and these structures should not be negatively affected during spray drying.
