Freeze Drying
Experiments were performed in a pilot scale freeze
dryer (Armfield, FT 33 Vacuum Freeze Drier,
England). The pumpkin puree were frozen in a
layer of 3 mm in the petri dishes at - 40 °C in an
air blast freezer for two hours, then freeze dried
under vacuum (13.33 Pa absolute pressure), at
- 48 °C condenser temperature for nine hours.
The temperature of the heating plate was set to
+30 °C which accelerated the sublimation process
and it was constant during the drying process.