3.2. Effect of drying methods on the essential oil yield
All essential oils extracted from the aerial parts of two landraces of basil dried under different conditions produced a clear, yellow liquid. An analysis of variance indicated that the drying method had a significant effect on oil yield of both landraces (p < 0.01), with the highest essential oil yields (v/w on dry weight basis) obtained by shade-drying in both landraces. The lowest essential oil yields occurred with sun-drying from the green landrace and microwave-drying for the purple landrace (Fig. 1). In the purple landrace, no significant differences were observed among oil yields obtained from plant materials dried in shade, oven at 40 C, and freeze-dried. In the green landrace, no significant differences were observed among oil yields obtained from fresh plant materials and those dried in shade or freeze-dried. Distillation of the test samples dried by the different methods resulted in both increased and reduced essential oil yields, depending on the drying method, duration and temperature (Rahimmalek & Goli, 2013). The essential oil yield from the green landrace was lower than that from the purple landrace. The green landrace was more sensitive to increased drying temperatures, especially when aerial parts were dried at 60 C or microwaved.
Increasing the drying temperature significantly decreased the