Changes in the Essential Oil Content and Composition of Lippia citriodora under Vacuum Oven-drying and Pre-drying Operation

Pre-drying operations and drying methods have a significant effect on the quantity and quality of plants essential oils.

In this study, the effect of pre-drying operation and vacuum oven-drying was investigated on the essential oil content and composition of Lippia citriodora.

This research was conducted as a factorial experiment in a completely randomized design (CRD) with three replications. The two studied factors were (1) pre-drying operations in two levels including pre-drying and without pre-drying operation, and also (2) drying methods in 5 levels including fresh plant, shade drying and vacuum oven-drying at 35, 45 and 55°C at 0.5 bar atmospheric pressure.  In this study, the amount of pigments and essential oil content and composition were measured.

The results indicated that the highest chlorophyll content was related to treatment of vacuum oven-drying at 55 °C with a pre-drying treatment, while the highest amount of essential oil was obtained by vacuum oven-drying at 45 °C without a pre-drying operation. The highest amounts of monoterpene hydrocarbons, oxygenated monoterpenes, and geranial were obtained by drying at 55 °C, while the highest content of sesquiterpene hydrocarbons, oxygenated sesquiterpenes and neral were observed in Low-temperature drying.

In general, this study indicated that vacuum oven-drying at 45 °C was the best drying method for obtaining maximum content of essential oil and active components.