Experiments were carried out in the new hybrid dryer. Ultrasounds with frequency
25 kHz were generated constantly using Airborne Ultrasound System (AUS),
produced by Pusonics S.L. (Spain). The hybrid dryer was equipped with a pyrometer,
which measured temperature of the material during the process, with accuracy of 0.1
C. The initial moisture content in potatoes was determined on the basis of a moisture
analyzer model XM120 PrecisaGravimetrics AG, CH – Dietikon (Switzerland).
For each experiment six slices were cut and placed concentrically on the tray in the
dryer. The tray was situated on the rotary shaft, which was attached to the balance
(Radwag PS 6000.R2). The accuracy of weight loss measurements was at 0.01 g. The
measurements were read-out and saved automatically every minute by the computer.
Each experiment was conducted twice, to check if the result is recurrent. The scheme
of the experimental setup is shown in Fig. 1.