Influence of Thin Layer Drying on the Essential Oil Content and Composition of Lavandula officinalis

Abstract

Drying affects essential oil content and composition of aromatic plants. In this study the effect of drying temperature and air velocity on the chemical content and composition of the essential oils of Lavandula officinalis was evaluated. For this purpose aerial parts without inflorescence (just leaves and stems) of this plant were collected at full flowering stage and dried in laboratory dryer. In the experiments, 123.9 g of freshly harvested plant material was spread uniformly as a thin layer on a tray (sample thickness: 1.0±0.2 cm) to obtain 50 g dried sample. Three drying air velocities (0.5, 1.0 and 1.5 m/s) and three drying temperature (30, 45 and 60°C) were used. Essential oil content of dried samples affected significantly and ranged from 0.7 % to 2.34 % (v/w) and overall average of 1.3 % (v/w). Results showed that highest oil content (2.34 % v/w) was obtained when plant dried with air velocity of 1.5 m/s, at 45°C of oven temperature. The essential oils from fresh and dried samples were isolated by hydrodistillation in a Clevenger apparatus and analyzed using gas chromatography-mass spectrometry (GC-MS). Different temperatures and air velocities caused some variation of the relative proportions of the components. The main compounds were 1,8-cineole (ranged from 26.82 to 52.64 %), borneol (ranged from 11.62 to 23.41 %), camphor (ranged from 6.67 to 12.65 %) and caryophyllene oxide (ranged from 1.15 to 3.87 %.) in dried samples. Among groups of the chemical compounds, Oxygenated monoterpenes constituted the principal fraction ranged from 51.07 % to 82.04 % (overall average of 66.7 %).

Key words:

• Lavandula officinalis
• Thin layer drying
• Essential oil
• Air velocity
• Drying temperature