Abstract
Onion slices were dried using two different drying techniques, convective and microwave drying. Convective drying treatments were carried out at different temperatures (50, 60 and 70 °C). Three different microwave output powers 328, 447 and 557 W were used in microwave drying. In convective drying, effective moisture diffusivity was estimated to be between 3.49 × 10−8 and 9.44 × 10−8 m2 s−1 within the temperature range studied. The effect of temperature on the diffusivity was described by the Arrhenius equation with an activation energy of 45.60 kJ mol−1. At increasing microwave power values, the effective moisture diffusivity values ranged from 2.59 × 10−7 and 5.08 × 10−8 m2 s−1. The activation energy for microwave drying of samples was calculated using an exponential expression based on Arrhenius equation. Among of the models proposed, Page’s model gave a better fit for all drying conditions used.
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Abbreviations
- a, b, c, n :
-
Constants of models
- D eff :
-
Effective diffusivity (m2 s−1)
- D 0 :
-
Pre-exponential factor of the Arrhenius equation (m2 s−1)
- E a :
-
Activation energy (kJ mol−1 or Wg−1)
- k :
-
Rate constants in models (min−1)
- k 0 :
-
Pre-exponential constant (min−1)
- L :
-
Thickness of the slab (m)
- m :
-
Raw of weight of sample (g)
- M:
-
Moisture content (kg water/kg dry matter)
- M e :
-
Equilibrium moisture content (kg water/kg dry matter)
- M 0 :
-
Initial moisture content (kg water/kg dry matter)
- MR:
-
Moisture ratio
- N :
-
Number of observations
- P :
-
Microwave output power (W)
- R 2 :
-
Determination coefficient
- RMSE:
-
Root mean square error
- T :
-
Temperature (°C)
- t :
-
Drying time (min)
- χ 2 :
-
Reduced Chi square
- z :
-
Number of constants in models
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Demiray, E., Seker, A. & Tulek, Y. Drying kinetics of onion (Allium cepa L.) slices with convective and microwave drying. Heat Mass Transfer 53, 1817–1827 (2017). https://doi.org/10.1007/s00231-016-1943-x
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DOI: https://doi.org/10.1007/s00231-016-1943-x