Influence of different drying methods on drying period, essential oil content and composition of Lippia citriodora Kunth

• Vacuum drying at 60 °C had the lowest drying time.
• Minimal damages of glandular trichomes were observed in shade and freeze drying.
• With increasing the temperature in vacuum drying, essential oil content (ml/100 g D.M.) improved.
• Freeze drying preserved the highest amount of citral.

The influence of four drying methods (shade drying, freeze drying, oven drying and vacuum drying at 40, 50 and 60 °C) on the essential oil content and composition of lemon verbena (Lippia citriodora Kunth.) was evaluated. The essential oil content and composition of dried samples were determined by hydro-distillation using a Clevenger apparatus and gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) respectively. Results showed the highest and lowest drying times belonged to shade drying (53 h) and vacuum drying at 60 °C (3 h) respectively. Glandular trichomes were vulnerable to oven whereas vacuum drying and freeze drying preserved them. The maximum essential oil content (1.0 ml/100 g D.M.) obtained from vacuum-dried (60 °C) and oven-dried (40 °C) samples. Freeze drying preserved the highest amount of oxygenated monoterpenes, especially citral (64.7%) but the highest amounts of limonene and 1,8-cineole (8.2 and 7.2% respectively) were determined in vacuum-dried (60 °C) leaves. Apart from the standard oven drying at 40 °C, vacuum drying at 60 °C can be considered as an alternative approach to dry lemon verbena in a significantly shorter drying time.

Figure optionsDownload as PowerPoint slide