Long-term effects of drying conditions on the essential oil and color of tarragon leaves during storage

The effect of storage on the essential oil content and color of French Tarragon (Artemisia dracunculus L.) leaves is studied. Tarragon leaves were dried at temperatures 45, 60 and 90 °C with, respectively, the relative humidity levels 17%, 7% and 2.5%. At 60 °C also a relative humidity level of 18% was applied. The air velocity was constant at 0.6 m/s. Oil content and color were measured for the fresh and dried leaves just after drying as well as after storage during 15, 30, 60 and 120 days. The essential oil compounds of the material were isolated by the hydro-distillation method and analyzed by GC–FID as well as GC–MS. A Chroma meter was used to measure the color of the samples. The results showed a reduction of the oil content and changed color parameters during the storage period. The largest changes of the essential oil content (about 50% after 30 days) and color expressed by the hue value was found for the material dried at 90 °C. Drying at 45 °C resulted in the smallest quality changes.