and stored in the refrigerator at 4 C. The moisture content of each
sample was measured using the oven drying method at 103 C for
24 h (AOAC, 1990). Prior to the drying experiments and after 4 h
stabilization at the laboratory temperature (25 C), the samples
were hand peeled and sliced to pieces of 3 mm thick using a sharp
knife on a cut board. In order to select samples of the same stiffness,
Fruits Stiffness Tester (model OSK-10576 Ogawa Seiki, Japan, accuracy
0.01 kg) was used. The samples were weighed rapidly at regular
time intervals using an electronic digital balance (AND, model
GF-400, Japan, accuracy 0.001 g) to determine drying rate. All the
experiments were carried out at the laboratory temperature (25 C)
with a relative humidity of 0.3 g/g. An ultrasonic humidifier
equipped with a microcontroller was used to adjust and control the
relative humidity of the isolated drying room wherein the experiments
were conducted. The ambient relative humidity was
measured by a sensor (Philips H8302 model) with an accuracy and
linearity of 2% full scale for an operating span of 0.2e0.95 g/g RH.