Effects of different drying methods (natural method, oven and microwave) on drying time, essential oil content and composition of Savory (Satureja hortensis L.)

Drying is one of the important pre-processing methods of medicinal plants after harvest that has a major role in quantity and quality of their active substances. To determine the effect of different drying methods on drying time, essential oil content and composition of Savory (Satureja hortensis L.), the experiment was carried out during 2008. The experimental design was randomized complete block design with three replications and treatments were: two temperatures: 50°C and 70°C, six microwave powers: 100, 180, 300, 450, 600 and 900 w and drying in shade and under sun light. The drying process was continued until the mass of the sample reduced to a moisture content of about 0.10 on a dry weight basis or 10% on a wet weight basis. Results indicated that different treatments of drying method had significant effects on drying time and essential oil content. The maximum essential oil content (3%) obtained from drying at 70°C and drying in shade while minimum content (0.9%) obtained from drying under sun light. One hundred and 300 w microwave powers had an average content of essential oil (2.3%). Carvacrol content percentage in treatments of microwave drying was more than other methods as maximum percentage (63.9 %) was obtained from 300 w microwave drying with a little difference with 180 w microwave drying treatment. Drying by low microwave powers is recommended for Satureja hortensis L. due to the reduction of drying time and considerable maintenance of essential oil content and composition. Maximum γ-terpinene content (28.2%) obtained from drying at 70°C with a low difference with 50°C, 100 and 300 w microwave.