Hot air-drying (AD) was carried out using Zalmut type S-3
electric laboratory driers (1850 W) adapted for the drying of fruit,
vegetables and mushrooms. Cut kale leaves were dried at a temperature
of 55 C, this being the temperature of air blowing over the
first lower sieve. The position of sieves was changed every 30 min
to prevent crusting at the beginning of the drying process and
roasting at the end. The drying time required to attain the predetermined
humidity level of below 5% was 5.5 h. After drying,
material from different batches was mixed and packed in air-tight
containers (glass twist-off jars 2.0 L in volume