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.