Heat and Mass Transfer

, Volume 54, Issue 12, pp 3715–3725 | Cite as

Ohmic blanching of white mushroom and its pretreatment during microwave drying

  • Bashir Nouroallahi Soghani
  • Mohsen Azadbakht
  • Hosain Darvishi


The effect of heating duration and applied voltage were investigated on heat and mass transfer of the ohmic blanching mushroom. The drying kinetics and energy consumption of blanched/control samples were studied in a microwave dryer. Results showed that the mass loss during ohmic blanching depended on heating duration and applied voltage. Variation of electrical conductivity of mushroom was calculated using basic model and validated by the first law of thermodynamics (energy balance). The electrical conductivity of mushroom, water, and mixture increased with increasing temperature. At high voltage and longer heating duration, the blanched mushrooms dried faster than un-blanched mushroom while the drying of both samples occurred in a falling rate period. Moisture diffusion for blanched samples varied in the range of 4.23–6.08 × 10−7 m2/s while it was 4.22 × 10−7 m2/s for the control sample. Blanched sample at low voltage and heating duration consumed the minimum total energy during the drying process.



Surface contact between mixture and electrode (m2)


Surface area of convective heat transfer (m2)


Length of a characteristic mushroom (m)


Specific heat capacity (J/kg.K)


Specific heat capacity of mushroom (J/kg.K)


Specific heat capacity of water (J/kg.K)


Effective moisture diffusivity (m2/s)


Microwave energy consumption (J)


Specific energy consumption for ohmic blanching (J/kg fresh sample)


Total specific energy consumption (J/kg fresh sample)


Convective heat transfer coefficient (W/m2.K)


Current (A)


Gap between electrodes (m)


Mass (kg)


Moisture content (%, wet basis)


Mass of fresh mushroom (kg)


Mass of blanched mushroom (kg)


Mass loss of sample (%)


Moisture ratio (−)


Mass of sample at any time (kg water/kg dry matter)


Mass of water in ohmic cell (kg)


Number of observations


Microwave power (W)


Density of power loss (W/m3)


Radius (m)


Coefficient of determination


Root mean square error (−)


Temperature (°C)


Time (s)


Ambient temperature (°C)


Center temperature of the cap or stem mushroom (°C)


Temperature homogeneity (−)


Temperature of mushroom (°C)


Temperature of the ohmic cell


Surface temperature of the cap or stem mushroom (°C)


Water temperature (°C)


Volume (m3)


Volume of the ohmic cell (m3)


Volume of mushroom samples (m3)


Volume of water (m3)


Applied voltage (V)


Initial moisture content (kg water/kg dry matter)


Equilibrium moisture content (kg water/kg dry matter)


Moisture content at any time (kg water/kg dry matter)




Independent variable


ith root of the Bessel function


Mushroom density (kg/m3)


Water density (kg/m3)


Electrical conductivity (S/m)


Experimental electrical conductivity (S/m)


Electrical conductivity of mushroom (S/m)


Electrical conductivity of the mixture (S/m)


Predicted electrical conductivity (S/m)


Electrical conductivity of water (S/m)


Volume fraction of mushroom in the mixture (−)


Electrical field strength (V/m)












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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Bashir Nouroallahi Soghani
    • 1
  • Mohsen Azadbakht
    • 1
  • Hosain Darvishi
    • 2
  1. 1.Department of Bio-systems EngineeringGorgan University of Agricultural Sciences and Natural ResourcesGorganIran
  2. 2.Department of Bio-systems Engineering, Faculty of AgricultureUniversity of KurdistanSanandajIran

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