Shrinkage of potato slice during drying

The effects of drying conditions on shrinkage of potato slices were studied. A thin-layer dryer with machine vision system and image processing software was used. Potato slices were dried at temperatures of 60, 70, 80 °C and air velocities of 0.5 and 1.0 m/s. Changes in area, perimeter, major and minor diameters, diameters parallel and perpendicular to airflow, roundness and elongation of the slice were measured continuously during drying. Shrinkage showed almost linear relation with moisture content. It was found that airflow direction had significant effect on shrinkage of parallel and perpendicular diameters in 60 and 70 °C and no significant effect at 80 °C. Drying took place entirely in the falling rate period. Air velocity had no significant effect on drying time and shrinkage in the rage tested. Slices dried in 80 °C showed more circularity than slices dried in 60 and 70 °C.