Chapter 5 - Spray-Drying and Non-Equilibrium States/Glass Transition

Abstract

In this chapter, the fundamental characteristics of spray drying are described with regards to its applications to alter the structure of food powders (crystalline or amorphous). Unlike amorphous powders which are in thermodynamically non-equilibrium state and tend to experience many phase transitions to obtain the lowest energy state, crystalline powders are stable and an alteration of its structure using spray drying involves two steps, disruption of the molecular order in crystal lattice and fast solidification to prevent molecules from orderly arrangement. As compared to other approaches, spray drying is the most effective technique to prepare amorphous powders due to its unique characteristics (fast and continuous process, diversity in capacity and designs, and ability to control crystallinity of produced powders). In the last part, differences about characteristics of crystalline and spray-dried amorphous alpha-cyclodextrin powders are shown as a case study of application of spray drying to change powder structure.