The samples were cleaned with fresh water at room temperature to remove the dirt and other foreign materials deposited over the surface. The excessive water on the surface of the products was gently removed using clean cotton clothes and the bitter gourd was cut into 5–7 mm thick slices. Then the slices were placed on the drying trays in a single layer. Slice diameters were in the range of 43–51 mm (Fig. 3). The weight of the product on each tray was measured by taking out from the drying chamber on hourly basis.