ABSTRACT
Spray drying is a commonly used encapsulation technique for delivering both hydrophilic and lipophilic bioactives. Recently, new spray drying techniques have been introduced in an attempt to satisfy the specific requirement on the properties of the spray dried particles, such as particle size, morphology, and product stability. Sprayed droplets generated by the conventional spray dryers are normally polydisperse in the micrometer size range. Microfluidic-jet spray drying is one of the novel spray drying techniques, which fabricates monodisperse microparticles with uniform size and morphology. The microencapsulation of bioactive compounds through microfluidic-jet spray drying has enabled the control of droplet size, size distribution, and thereby generating uniform, controllable, and reproducible small droplets with good bioactive retention. Another new development in the encapsulation of bioactive compounds is through nanoencapsulation by a nano spray dryer, which typically produces nanocarriers with dimensions as small as 100–1000 nm. To investigate the drying history of droplets and the particle formation process of the particles during spray drying, single droplet drying has been applied to observe the transition of a single liquid droplet to a dry particle. This chapter discusses the design of the new spray dryers and their underlying principles, the drying mechanism, and the associated effects on the particle properties with regards to wall materials, bioactive compounds, and processing parameters.
