4. Conclusions
Sliced kale could be successively dried in a connective
air dryer in thin layers ranging from 10 mm to 50 mm
although the drying time considerably increased when
the layer thickness exceed 20 mm. Increasing the temperature
of drying air from 30 to 50 C reduced the drying
time by half for all drying depths. All the drying models
considered in this study could adequately represent the
drying behaviour of kale, although the Modified Page
model was better than the other three models. The moisture
diffusivity of kale was found to range between
14.9 · 1010 and 55.9 · 1010 m2/s within the temperature
range of 30–60 C and it could be represented in
an Arrhenius-type relationship with good accuracy.
The activation energy was also found to be 36.115 kJ/
mol.