Continuous subcritical water extraction as a useful tool for isolation of edible essential oils

A method for extraction of oregano oil based on the use of subcritical wate r is proposed. Ground oregano (ca. 1.8 g accurately weighed) was extracted with water at 2.0 MPa, 125 degreesC and 1 ml min(-1) for 24 min. The extrac ted compounds were removed from the aqueous extract by a single extraction with 4 ml hexane, determined by gas-chromatography-flame ionisation (GC-FID ) and identified by mass spectrometry (MS). Hydrodistillation was performed on 30 g of ground oregano with 500 ml water for 3 h for comparison of the results with those provided by the proposed method. The subcritical water e xtraction-based method is clearly quicker and more efficient than the conve ntional: yields from the former for eight of the 11 major compounds in the extract are higher after 15-min extraction than after hydrodistillation for 3 h. This enables substantial cost savings of both energy and raw material . In addition, the proposed method has the possibility of manipulating the composition of the oil and thus its quality. The aqueous-oil extract was in vestigated for essential oil preparative purposes and several last, cheap a nd clean alternatives for breaking the emulsion and separating the phases a re proposed. (C) 2001 Elsevier Science Ltd. All rights reserved.