Examination of Different Drying Methods in Sultana Seedless Grapes in Terms of Drying Kinetics, Energy Consumption and Product Quality

Sultana Seedless grape samples were dried using hot air and microwave methods in different temperature and power levels with untreated conditions and drying kinetics and energy consumption values based on method were revealed in this study. Hot air drying experiments in electric forced convection oven were conducted in temperatures of 50, 60 and 70 degrees C with 1 m s(-1) air velocity. Microwave drying experiments were conducted in 180 and 270 W power levels. Wang and Singh, Henderson-Pabis, Newton and Logaritmik thin layer drying methods offered in the literature were used to evaluate experimental values and it was determined that Wang and Singh model represents the drying characteristics of Sultana seedless grape as the best for both methods. Phenolic content and browning index increased with temperature rise in hot air method. Minimum drying time was obtained as 10 hours in 70 degrees C hot air drying and 35 minutes in 270 W microwave power level for decreasing moisture content of 200 g grape samples from 75 % (w.b.) to 20 % (w.b.). Minimum specific energy consumption was determined as 19,15 kWh kg(-1) in 70 degrees C hot air drying and 1,52 kWh kg(-1) in 270 W microwave power level.