The Impacts of Fluidized and Static Bed Drying Methods on Bio-active Compounds and Antioxidant Properties of Saffron Petal

Saffron petal was dried from ۸۵% to ۱۰% moisture content with fixed layer bed (FLB), semi fluidized bed (SFB) and fully fluidized bed (FFB) at temperatures (t) of ۳۵, ۴۵ and ۵۵ °C. The airflow (v) of FLB, SFB and FFB were ۰.۲, ۰.۷ and ۱.۷ ms-۱, 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 = ۰.۲ ms-۱& t = ۳۵ °C) and FFB (v = ۱.۷ ms-۱& t = ۵۵ °C) were “۵۷۰ & ۳۰ min” and “۰.۱۳ & ۲.۵۰ gH۲O/min”, respectively. When the airflow increased from ۰.۲ to ۰.۷ and then to ۱.۷ ms-۱, the phenolic, anthocyanin & antioxidant contents of dried saffron petal improved to about ۶, ۱۵ & ۱۵% and then to ۱۵, ۲۰ & ۴۲%, respectively.  However, by increasing air temperature from ۳۵ to ۴۵°, their phenolic and anthocyanin contents did not change significantly. However, sharp reductions of ۲۰, ۲۳ and ۴۱% respectively were noticed in phenolic and anthocyanin contents and antioxidant activities of saffron petal when the drying temperature exceeded ۴۵ and reached to ۵۵ °C. Overall, the fresh saffron petal dehydrated at ۴۵ °C with FFB had the highest phenolic and anthocyanin contents and antioxidant activities.

Keywords:

Saffron petals , fluidized bed , Drying methods , Phenolic compounds , anthocyanins