Extraction of citrus flavonoids from peel of Citrus junos using supercritical carbon dioxide with polar solvent

Citrus juice processing residues are mainly composed of peel, juice sack and seed. The peel, especially, consists of bioactive compounds such as flavones. Supercritical carbon dioxide (SC-CO2) extraction of flavonoid was carried out at a pressure of 30 MPa and temperature ranging from 80 to 160°C. Ratio of water and ethanol as a co-solvent was varied from 0 to 100%. Flavonoids such as naringin and hesperidin have glycoside group, thus water was a good solvent for extraction of these compounds. Extraction behavior of tangeretin was quite different, the yield of tangeretin tended to increase with ethanol concentration.