Investigating the Influence of Drying Temperature and Air Flow Velocity on Some Qualitative Specifications of the Sliced Pear During Drying and Employment of Image Processing Technique

Drying of agricultural and horticultural crops is one of the most important processes for their long term storage. Therefore, in this study, the influence of drying temperature and air flow velocity on the variation of color, shrinkage and pH were investigated during the drying process of thin-sliced Dargazi pear varieties. Drying air temperature varied in four levels of 50, 60, 70 and 80 °C and the air flow velocity at three levels of 0.5, 1 and 1.5 m/s. The image processing results indicated that maximum variation of the sample’ color (30.78) occurred at drying temperature of 80°C and air velocity of 1.5 m/s. In contrast, the minimum variation of the color (14.38) occurred at drying temperature of 50 °C and air velocity of 0.5 m/s. The results indicated that PH of the examined samples increases during the drying process. The maximum value of pH (4.49) was obtained at drying temperature of 50 °C and air velocity of 0.5 m/s, whereas the minimum value (3.93) was measured at 80 °C and air velocity of 1.5 m/s. Given the overall results obtained in this study, minimum drying time with minimum variation of qualitative specifications occurred at drying temperature of 70 °C and air flow velocity of 0.5 m/s; therefore, this condition could be suggested as the best combination for drying of thin-sliced pears.