The effect of short and medium infrared radiation on some drying and quality characteristics of quince slices under vacuum condition

Infrared assisted vacuum drying technology is a newly emerged strategy, which found its place in the food drying industry. Therefore, in this research, the effectiveness of near infrared (NIR) and medium infrared (MIR) radiation was experimentally investigated on drying kinetics and some quality properties of quince slices under vacuum condition. Experiments were conducted at drying temperatures of 50, 60 and 70 degrees C and absolute pressures of 20, 40 and 60 kPa for NIR and MIR radiations. Drying process in MIR assisted vacuum drying domain lasted about 3 to 28 min lower than NIR one, indicating improved drying process under MIR condition. Effective moisture diffusivity for NIR domain was obtained in the range of 0.17x10(-9) to 0.46x10(-9) m(2)/s while it was between 0.18x10(-9) to 0.46x10(-9) m(2)/s under MIR condition. Minimum specific energy consumption for NIR and MIR radiation was estimated 0.55 and 0.34 kWh, respectively. Total colour difference and sample shrinkage under NIR radiation were calculated within the range of 5.5 to 25.4% and 40.4 to 64.5%, respectively, which were significantly lower the ranges of MIR. Minimum total colour change (5.5%) and shrinkage (40.4%) of quince samples were calculated under NIR condition while, the minimum values for MIR domain were 12.1 and 50%, respectively.