3.4 The effect of inlet temperature on the powder recovery
Process yield also can be affected by the inlet temperatures where the higher inlet temperatures, the higher
process yield. Process yield is related to the efficiency of heat and mass transfer processes occurring during the
process spray drying. The higher inlet air temperatures were used, the greater efficiency of heat and mass transfer
processes would be. But sometimes, the increasing of inlet air temperature can reduced the yield due to the melting
of the powder and cohesion wall. Therefore the amount of powder production also reduced (G.R. Chegini, 2007).
Figure 7 shows that the higher the inlet temperature at the same concentration of maltodextrin, the amount of
powder recovery will increase but there are also the amount of powder recovery is reduced as the higher inlet
temperature. It is also shown that, at the constant the concentration of maltodextrin at 20% of maltodextrin, the
powder recovery is reduced.
3.5 The effect of inlet temperature on the particle size of the pineapple powder
Besides that, the inlet temperature can affects the bulk density of powder. The increasing of inlet air temperature
will give a result in a rapid formation of dried layer on the droplet surface. Furthermore, it can cause the particle size
change beside the skinning over or casehardening on the droplets at the higher temperatures. This process leads to
the formation of vapor-impermeable films on the droplet surface followed by the formation of vapor bubbles and the
droplet expansion (Chegini, 2005)