Supercritical carbon dioxide extraction and fractionation of fennel oil

Ground fennel seeds were extracted with supercritical carbon dioxide. Small -scale subsequent extractions of the same sample showed that the compositio n of volatile compounds was changed with the extension of extraction time a nd only principal volatile components (limonene, fenchone, methylchavicol, and anethole) were present in the last-extracted sample. Fennel oil was suc cessfully fractionated into the essential oil rich and fatty oil rich produ cts in pilot-scale apparatus using two separators in series. Designed exper iments were carried out to map the effects of pressure and temperature in t he first separator on the yields and compositions of the products. The mini mum level of the total undesired components in both essential oil rich and fatty oil rich products appeared at a pressure of 80-84 bar and a temperatu re of 31-35 degrees C in the first separator. Supercritical CO2 extraction of fennel seeds resulted in higher yield (10.0%) than steam distillation (3 .0%), almost the same yield as hexane extraction (10.6%), and lower yield t han alcohol extraction (15.4%). Analysis of the volatile compounds revealed the significant difference of the composition in distilled oil and oleores ins prepared by CO2 and solvent extractions. Sensory evaluation showed that the CO2 extraction product and distilled oil were more intense in odor and taste than alcohol and hexane extracts.