Kinetic study of microwave extraction of essential oil of Nigella sativa L. seeds

The Nigella sativa L. is widely cultivated in the Algerian Sahara and primarily used for its health benefits. Extraction experiments were carried out by a microwave energy, performed at atmospheric pressure with a small quantity of water for 10 min. This method enabled a best yield (0.54-0.57%) and a high amount of the volatile fraction with a shorter extraction time and a reduction of energy consumption. The kinetic study of essential oils extraction was quantitatively studied. Thus, the qualitative and quantitative composition of the essential oils extracted for 10 min and in different periods was examined by capillary gas chromatography and by gas chromatography-mass spectrometry. The percentage of the main constituents such as p-cymene, thymoquinone, alpha-thujene, 4-terpineol and carvacrol was reported. The family classes present a significant variation according to the extraction time. Kinetic and extraction rate profile of microwave process (yield) showed that it is possible to reduce the extraction time.