Determination of method and optimum conditions for saffron stigmas drying producted in Kurdistan

Drying process has a major effect on the color, odor and taste of fresh saffron. In this research, effect of traditional including sun and shadow drying and industrial drying methods such as electrical oven at 50 and 80 oC and microwave at 300 and 800 watt on the saffron of Kurdistan province for reaching the optimal condition, was investigated. Results showed that the drying methods had significant effects (p <0.01) on the physiochemical, microbial and sensory properties of saffron.  Crocin content for dried saffron with microwave at 800watt  that was about 171 and for 300 watt was 263.5 and with electric oven at 80 oC  was about 220.5,  respectively, not only were higher than the acceptable level according to national standard of Iran (220), but also they were significantly higher than other methods (p <0.01). The highest level of picrocrocin and safranal content were measured in samples dried with microwave at 800 watt (113.75, 30.25), electronic oven at 80 oC (115.5, 29.05), and shadow (105, 29.35), respectively. The lowest levels of crocin (146.5), picrocrocin (86.7) and safranal (23.4) were measured in sundried saffron. As microwave power level and electronic oven temperature increase, the crosin and picrocrocin contents of saffron increase significantly (p <0.01).  The lowest microbial load was found in saffron dried with microwave at 800 W and then sunlight (p <0.01). Overall, sensory attributes were ranked highest for the samples dried with microwave at 800 W and electronic oven at 80 oC, respectively. However, microwave drying at high power at 800 watt in comparison to other methods, could be the best drying method for saffron due to several advantages including reducing the drying time, keeping qualitative characteristics, decreasing microbial contamination and obtaining the highest score in organoleptic evaluation of dried saffron.