Energy saving in the supercritical carbon dioxide extraction of essential oils from species of the Lamiaceae family

The reduction of energy consumption in the supercritical carbon dioxide extraction of essential oils from leaves of species of the Lamiaceae family due to the optimal pretreatment of herbaceous material was studied in the present work. Essential oils of species of the Lamiaceae family are stored in peltate glandular trichomes on the leaf surface, and the optimal pretreatment for this type of secretory structure should include grinding followed by supercritical carbon dioxide batch (non-flow) pretreatment under extraction conditions prior to continuous flow extraction. Supercritical fluid extractions of peppermint (Mentha piperita), wild thyme (Thymus serpyllum) and hyssop (Hyssopus officinalis) leaves were performed including only grinding pretreatment as well as optimal pretreatment. The experimentally determined reductions of supercritical carbon dioxide consumption, for the observed extraction yields, ranged from 0.250 to 0.889 kg CO2 per gram of produced essential oil extract, while the corresponding reductions of energy consumption were in the range 48-170.7 kJ per gram of produced essential oil extract.