Extraction of valuable compounds from byproduct of citrus juice processing utilizing synergistic effect of water and carbon dioxide

Citrus juice processing residues are mainly composed of the part of peel, juice sack and seed. Especially, peel includes polar and non-polar bioactive compounds such as flavones and pectic substances. Sub-critical water extraction was expected to separate the polar substances such as pectic substances effectively adding small amount of carbon dioxide due to addition of acid catalyst effect. A semicontinuous flow type extractor was used for subcritical water extraction with carbon dioxide. Extraction was carried out at temperature of 40-120 o C, pressure of 10, 20 and 30 MPa. Increasing pressure accerated to the pectin extraction. As a result, 90 % of pectin could be obtained at the temperuture of 120 o C and the pressure of 30 MPa. On the other hand, supercritical carbon dioxide (SC-CO2) was suitable for extracting weakly polar substances such as flavones adding small amount of polar cosolvent such as water and ethanol. Some kinds of polymethoxyflavones were extracted with modifier and determined by HPLC.