Experimental study on drying of pear slices in a convective dryer

Abstract

The experiments were conducted on pear slices with thickness of 5mm at temperatures of 50, 57, 64 and 71 degrees C with an air velocity of 2.0ms(-1). Prior to drying, pear slices were pretreated with citric acid solution (0.5% w/w, 1min, 20 degrees C) or blanched in hot water (1min, 85 degrees C). Also, the untreated samples were dried as control. The shortest drying time of pear slices was obtained with pretreatment with citric acid solution. It was observed that whole drying process of pear slices took place in a falling rate period. Four mathematical models were tested to fit drying data of pear slices. According to the statistical criteria (R-2, (2) and RMSE), the Midilli etal. model was found to be the best model to describe the drying behaviour of pear slices. The effective diffusivity of moisture transfer during drying process varied between 8.56x10(-11) and 2.25x10(-10)m(2)s(-1), while the activation energy of moisture diffusion in pear slices was found to be 34.95-41.00kJmol(-1).