Supercritical carbon dioxide (SC-CO2) extraction of grapefruit flavedo

Grapefruit flavedo (Citrus paradisi Macf.) was extracted by different methods: hydrodistillation; and solvent extraction using pentane, ethanol and supercritical carbon dioxide (SC-CO2) at two fluid densities. The composition of the distillates and oleoresins were compared. Monoterpene hydrocarbons decrease in SC-CO2 extracts at 87-90% with respect to their quantity in pentane extracts (95%) and in hydrodistillates (97%); these levels in monoterpene hydrocarbons were related to the limonene content, the most representative compound in grapefruit essence. Sesquiterpenes, aldehydes, alcohols and esters increased their GC area percentage in SC-CO2 extract at a high density of the solvent, with respect to the hydrodistillate and the pentane extract. Very interesting was the high increase in nootkatone concentration in the SC-CO2 extracts; this grapefruit essence component was 4.72% in the extract at 8 MPa, and it was 5.19% in that at 25 MPa; the ketone was very low in the hydrodistillates (0.22-0.26%). The monoterpene hydrocarbon concentrations, expressed as g of component in 100 g of extract, showed a decrease in SC-CO2 oleoresins. Oxygenated, sesquiterpenes and particularly nootkatone increase their amount in SC-CO2 extracts. (C) 1998 John Wiley & Sons, Ltd.