the impacts of fluidized and static bed drying methods on bio-active compounds and antioxidant properties of saffron petal

Saffron petal was dried from 85% to 10% moisture content with fixed layer bed (flb), semi fluidized bed (sfb) and fully fluidized bed (ffb) at temperatures (t) of 35, 45 and 55 °c. the airflow (v) of flb, sfb and ffb were 0.2, 0.7 and 1.7 ms-1, respectively. when the t/v ratio increased in each method, the dehydration time decreased considerably. the dehydration times and drying rates of saffron petal for flb (v = 0.2 ms-1 t = 35 °c) and ffb (v = 1.7 ms-1 t = 55 °c) were “570 30 min” and “0.13 2.50 gh2o/min”, respectively. when the airflow increased from 0.2 to 0.7 and then to 1.7 ms-1, the phenolic, anthocyanin antioxidant contents of dried saffron petal improved to about 6, 15 15% and then to 15, 20 42%, respectively.  however, by increasing air temperature from 35 to 45°, their phenolic and anthocyanin contents did not change significantly. however, sharp reductions of 20, 23 and 41% respectively were noticed in phenolic and anthocyanin contents and antioxidant activities of saffron petal when the drying temperature exceeded 45 and reached to 55 °c. overall, the fresh saffron petal dehydrated at 45 °c with ffb had the highest phenolic and anthocyanin contents and antioxidant activities.