Spray-freeze drying (SFD) is a relatively new technique for microencapsulation of heat sensitive products. In SFD process, the solution is sprayed in a cryogenic medium such as liquid nitrogen to form frozen fine droplets. Then, the droplets subjected to freeze-drying under vacuum. The freeze-drying time is comparatively short due to the relatively large surface area achieved by the SFD. In this study, frequently used microencapsulation agents namely maltodextrin, inulin and gum arabic were sprayfreeze dried both individual and in the form of mixtures and the resulting powders were characterized with respect to particle morphologies. Morphology of the particles were observed using Scanning Electron Microscopy (SEM). All the spray-freeze dried particles showed spherical shape, sometimes being slightly aggregated. Regular pore structures originating from the formation of crystals were observed on the surface of the maltodextrin particles, while the gum arabic particles were found to have more irregular and small pores. However, inulin particles were found to have a smoother surface form than others. 204 | P a g e www.iiste.org
ConclusionIn this study, maltodextrin, inulin and gum arabic, which are frequently used as microencapsulation agents, were dried by SFD method and the particle morphologies were examined. As a result, all the samples were observed to be in a spherical shape. It was observed that gum arabic particles were larger in size due to higher viscosity of gum arabic, and inulin molecules were smaller and more prone to aggregation. Although different forms of porous structures were observed on the surfaces of maltodextrin and gum arabic particles, inulin particles were found to be smoother. The surface porosity aids in solubilization for rehydration during end use. However, it may not be desirable in the case of protection of a biological activity. Therefore, the microencapsulation agent or mixture to be used should be selected according to the desired final product property.