Supercritical carbon dioxide extraction of the volatiles from the peel of Japanese citrus fruits

Citrus volatiles were extracted from the peel of yuzu and kabosu (Citrus junos Sieb. ex Tanaka and Citrus sphaerocarpa Hort. ex Tanaka) which are typical citrus fruits in Japan, with supercritical carbon dioxide in a semi-continuous flow extractor. The peel of citrus fruits containing oil, water, and solid cellulose materials was used as a feed material in this work. Extraction was carried out at 313-333 K and 10-30 MPa with supercritical CO2 in order to optimize the extraction conditions and to compare the compositions of extracted oils from these fruits. The volatiles were also extracted using hexane (as the solvent) at atmospheric conditions to compare the efficiency of supercritical CO2 extraction. Among the studied conditions, the highest extraction efficiency was observed for both yuzu and kabosu peel at a pressure of 10 MPa and temperature of 333 K that was about 91% and 85%, respectively. The compositions of extracts differed qualitatively and quantitatively from each other in such away that the monoterpene (C10H16) content obtained was 89.9% in yuzu and 92.5% in kabosu; limonene was the major compound from both fruits. Oxygenated compounds in these oils represented 7.7%, and 4.6% in yuzu and kabosu peel, respectively.