The samples are uniformed and thinly distributed on the drying rack of the drying chamber [23,24]. The mass of product used in drying experiments was (25.0 ± 0.1) g by tray. The heated air enters the drying cabinet below the trays and flowed upwards trough the samples. The auxiliary heater was used for controlling the drying air temperature in order to keep the
drying air temperature constant. A digital weighing apparatus (±0.001 g) measures the mass loss of the product during the drying process. During each drying experiment, the weight of the product on the tray was measured by removing it from the drying cabinet
for approximately 15e20 s. These measuresMh (t) were undertaken
each 5 min until the weight became stable. The difference of mass
before (Mh) and after drying (Md) in the oven at 105 C for 24 h
gives the moisture content. The dry base moisture content at time t
is defined by (Eq. (1)):