Heat and Mass Transfer

, Volume 53, Issue 5, pp 1817–1827 | Cite as

Drying kinetics of onion (Allium cepa L.) slices with convective and microwave drying

  • Engin Demiray
  • Anıl Seker
  • Yahya Tulek


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.


Root Mean Square Error Microwave Power Effective Diffusivity Moisture Diffusivity Apple Pomace 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

a, b, c, n

Constants of models


Effective diffusivity (m2 s−1)


Pre-exponential factor of the Arrhenius equation (m2 s−1)


Activation energy (kJ mol−1 or Wg−1)


Rate constants in models (min−1)


Pre-exponential constant (min−1)


Thickness of the slab (m)


Raw of weight of sample (g)


Moisture content (kg water/kg dry matter)


Equilibrium moisture content (kg water/kg dry matter)


Initial moisture content (kg water/kg dry matter)


Moisture ratio


Number of observations


Microwave output power (W)


Determination coefficient


Root mean square error


Temperature (°C)


Drying time (min)


Reduced Chi square


Number of constants in models


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.Department of Food EngineeringPamukkale UniversityDenizliTurkey

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