Supercritical carbon dioxide extraction of Foeniculum vulgare volatile oil

Supercritical fluid extraction (SFE) with CO2 of the volatile oil from fennel (Foeniculum vulgare ssp. piperitum (Ucria) Coutinho) was carried out at temperatures of 40 and 50 degreesC and pressures of 90 and 100 bar in a flow apparatus using a two-stage fractional separation technique. The best conditions for extraction (pressure P = 90 bar, and temperature, T = 40 degreesC) and separation (P = 80 bar, T = -10 degreesC for the first separator and P = 20 bar, T = -10 degreesC for the second) were used to assess the effect of different mean particle size and flow rate of CO2. The yield of the extraction and composition of the volatile oil were compared with those obtained by hydrodistillation. The study showed that the particle size of the fruits does not practically affect either the yield or the composition of the oil, with the exception of the presence of a small amount of waxes in the volatile oil extracted by SFE from the fruits presenting the highest particle size. Further, increasing of the flow rate of CO2 does not seem to influence the composition, although it increases the rate of extraction, thus leading to a decrease of the extraction time. The fennel oil was analysed by gas chromatography (GC) and chromatography-mass spectrometry (GC-MS). The main compounds identified in the oils were fenchone (17%), estragol (21%) and (E)-anethole (43%). Copyright (C) 2003 John Wiley Sons, Ltd.