*3.3. Particle Morphology*

Spray-dried particles are usually spherical with varying diameters and concavities, regardless of the choice of coating material [17]. Mean size range of such particles range from 10 μm to 100 μm [25]. The formation of concavities is associated with shrinkage of the particles due to dramatic loss of moisture after cooling. On the other hand, powders obtained by freeze-drying have a flake-like structure or one that resemble broken glass. The reason could be the low temperature of the process which results in the absence of forces to break the frozen liquid into droplets. Differences in surface morphology of freeze-dried powders could be due to different coating agents. For example, powder with soybean protein and maltodextrin as coating materials had a spherical porous structure, while powders with only maltodextrin lost their porous structure [17]. The final particle size of freeze-dried powders depends on the grinding procedure, not on the drying process [31].
