Microwave drying of TURKISH red meat (watermelon) radish (RAPHANUS SATIVUSl.): effect of osmotic dehydration, pre-treatment and slice thickness

Abstract

The major target of this study was to investigate the influences of osmotic dehydration, microwave power and slice thickness on drying phenomena of Turkish red meat (watermelon) radish. Two different thin layer thicknesses were used as 3 and 6 mm and samples dried at 72, 269 and 356 W real microwave powers. NaCl was osmotic solution at a concentration of 6% and slices were waited during 120 min at 25 degrees C for the pre-treatment. The drying data was fitted to 24 mathematical models available in literature and best equations were determined. The results indicated that, pre-treatment application shortened processing time remarkably. Sigmoid, cubic and rational models showed the best performances in all experiments for describing drying kinetics. The estimated effective moisture diffusivities were ranged between 4.44 x 10(-7)-5.56 x 10(-6)and 3.86 x 10(-7)-2.52 x 10(-6) m(2) s(-1)for 3 and 6 mm slices respectively. The activation energies were calculated as in the gap of 2.77 and 10.61 W g(-1)and increased with decreasing slice thickness, however enhanced in presence of osmotic application. The suggested process conditions are 72 W and 6 mm slice thickness without any pre-treatment in order to obtain a well-qualified product.