Munehiro Hoshino

Supercritical Carbon Dioxide Extraction of the Volatiles from the Peel of Japanese Citrus Fruits

Abstract 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 a way 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.

Supercritical CO2 extraction of essential oil from Kabosu (Citrus sphaerocarpa Tanaka) peel

BackgroundCitrus sphaerocarpa Hort. ex Tanaka is one of many popular sour citruses in Japan. Its juice processing peel residues contain a lot of useful compounds including essential oil. Our interests mainly focused on the extraction of this essential oil using supercritical carbon dioxide (SC-CO2), an environmentally benign and generally regarded as safe solvent that has many advantages such as low critical temperature, low viscosity, and easy separation from the extract. In this research, essential oil was extracted from Citrus sphaerocarpa Tanaka peel using SC-CO2 at extraction temperatures of 313 to 353 K and pressures of 10 to 30 MPa.ResultsA maximum yield of 1.55% (by weight of wet sample) was obtained at the temperature of 353 K and the pressure of 20 MPa. The yield obtained by SC-CO2 method was over 13 times higher than that of the conventional cold-press method. Extracted essential oil was qualitatively analyzed using GC/MS, identifying 49 compounds including several non-polar and weakly polar hydrocarbons such as terpenoid, free fatty acid, and coumarin. Compared to the extracts obtained by the conventional methods, the extracts by SC-CO2 had lower content of monoterpenes and higher content of oxygenated compounds, sesquiterpenes, which strongly contribute to the aromatic characteristics of the extracts. Auraptene, a bioactive compound was also identified in the SC-CO2 extract.ConclusionsKabosu essential oil with a fresh natural fragrance was effectively extracted using SC-CO2 compared to the conventional extraction method. In addition, it was found that the extract contained higher content of aromatic components that characterize Kabosu. This work provides an important sequential method for the recovery of valuable compounds from citrus fruit waste using an environmentally friendly technique.