ABSTRACT
Introduction ........................................................................................................ 513
Materials and Methods ..................................................................................... 514
Results and Discussion ..................................................................................... 514
Conclusions......................................................................................................... 517
Acknowledgments ............................................................................................. 517
References ........................................................................................................... 517
In spray drying, inadequate drying conditions can produce a powder with
nondesirable characteristics. The size distribution of the droplets is the
variable that influences most the properties of final products. Droplet
diameter or particle size is a very important parameter but difficult to
evaluate given the many variables influencing it (Furuta et al., 1994; Kieviet
and Kerhof, 1997; Aguilera and Stanley, 1999; Chanona et al., 2003). At the
same time, phenomena associated with evaporation such as shrinkage,
deformation, expansion, formation of crust, and breakage arise (Liang and
King, 1991; Oakley, 1997; Walton, 2000). The thickness of the crust will
depend on drying velocity. High drying rates tend to produce large particles
with a thin crust and low density, whereas low drying velocity produces
small particles with a thick crust and high density (Masters, 1985; Oakley,
1997). Also, depending on the temperature of the particles, the liquid caught
inside may vaporize and generate pressure. If a portion of the crust is
broken, water vapor will be displaced and hollow spheres or fragments of
spheres will be produced, which may improve rehydration. If the crust is
flexible, particles may expand or collapse depending on drying conditions
(Oakley, 1997; Walton, 2000).
