Influence of drying conditions on the effective moisture diffusivity and energy requirements during the drying of pretreated and untreated pumpkin

Pumpkin as a fruit is consumed by both animals and humans. Its high moisture content makes it perishable and thus there is a need for drying as a means of preservation. Thin-layer drying characteristics for the samples dried using a hot-air dryer were obtained from the experiment data. The drying was observed to take place in the falling rate drying period. Ficks law was used to determine the moisture diffusivity which varied from a minimum of 1.19 x 10(-9) m(2)/s for untreated pumpkin samples dried at 40 degrees C to a maximum value of 4.27 x 10(-9) m(2)/s for steam blanched samples dried at 80 degrees C. The value of the energy of activation varied from 21.44 to 28.67 kJ/mol. The input energy values and specific energy requirement for thin-drying of pumpkin samples were found to be in the range of 317.8-458.1 kW h and 1588.8-2290.3 kW h/kg from 40 degrees C to 80 degrees C with a drying air velocity of 1.5 m/s respectively. (C) 2010 Elsevier Ltd. All rights reserved.