Study on effect of air temperature and velocity in drier on quality and quantity of essence of Thymus

Medical herbs with essence have important role in human’s life. Thymus is one of the important ancient medical herbs in Iran.Volatile componds in the essence of herbs is affected by processing methods. In this research, two varieties of Thymus (Thymus transcaspicus, Ziziphora clinopodiodes) oriented to Khorasan province were dried in different temperatures of 30, 45 and 60°C and air flow rate of 1.5, 2.5 and 3 m/s, by using a cabinet drier. After drying, the essence of each sample was extracted with clevenger apparatus, the efficiency of each sample was determined according to volume and weight percentage. The experimental design was factorial in frame of complete randomized was performed in three replications. The quality of essences were analyzed with GC and GC/Mass. The results of the efficiency of essence showed that Ziziphora clinopodiodes in comparison with Thymus transcaspicus and the temperatures of 30 and 45°C and air velocity of 1.5 m/s had a higher effeciancy. The drying air velocity didn’t show any effects on the quantity of essential compounds. In Thymus transcaspicus, the precentage of Thymol and Carvacrol in essence grew higher by increasing temperature. In Ziziphora clinopodiodes by increasing temperature, the amount of Isomenthone increased and Pulegun decreased and Piperitenone and Neo-isomenthol were remained constant and there was no relation between change in drying temperature and other essential compounds.