Moisture and thermal diffusivity of seedless grape under infrared drying

Abstract

The values of thermal diffusivity, moisture diffusivity and drying rate under different drying temperatures and moisture contents were determined by using of the data obtained from infrared drying of seedless grape. Thermal and moisture diffusivity values were obtained with a range of 3.34 × 10 −7 − 1.66 × 10 −8 and 5.39 × 10 −10 − 2.09 × 10 −11, respectively. Nine non-linear equations including the effect of initial moisture content and temperature were derived for obtaining equations that can be used in calculation of thermal diffusivity, moisture diffusivity and drying rate. The following equation can be used for prediction of thermal diffusivity, moisture diffusivity for, both with and without pre-treatment, dried seedless grape with a wide range of moisture content and drying temperatures between 50 and 80 °C. α , D eff , d M d t = a + b ⋅ M + c ⋅ T + d ⋅ T ⋅ M + e ⋅ M 2 + f ⋅ T 2 This equation can be also used in prediction of drying rate for cases without pre-treatment of seedless grape. However, in case of pre-treatment seedless grape, equation given below is more suitable for prediction of drying rate. d M d t = a exp ( b ⋅ M c ) ⋅ d T e