Synergistic effect of pressurized water and carbon dioxide on extraction of the valuable compound from byproduct of citrus juice processing Arata Takamizu 1 , Akiko Takahashi 1 , Msahiro Tanaka 2 , Munehiro Hoshino 2 , Mitsuru Sasaki 1 , * Motonobu Goto 3 1 Guraduate school of Science and Technology, Kumanoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan 2 ASCII Co., Ltd., 2425 Tabara, Kawasaki-machi, Tagawa-gun, Fukuoka 827-0004 3c Bioelectorics Research Center, 2-39-1 Kurokami, Kumamoto 860-8555, Japan *Email address; mgoto@kumamoto-u.ac.jp Carbon dioxide and water are nonflammable, non-toxic, environmentally-friendly, and cheap. Solubility of water in supercritical carbon dioxide (SCCO2) is increased with increasing temperature and pressure. These properties enable to give polarity SCCO 2 by adjusting the experimental parameters such as temperature and pressure. On the other hand, solubility of SCCO 2 in subcritical water increased with increasing temperature and pressure above the temperature of 100 o C and pressure of 20 MPa. In this coexistence of supercritical CO 2 condition, the catalytic effect of CO 2 dissolved in water is expected. 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. A semi-continuous flow type extractor was used for extraction combined SCCO 2 and water. Extraction was carried out at temperature of 40-120 o C, pressure of 10, 20 and 30 MPa. Increasing pressure accelerated to the pectin extraction. As a result, 90 % of pectin could be obtained at the temperature of 120 o C and the pressure of 30 MPa. On the other hand, SCCO 2 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.