Supercritical CO2 extraction of essential oil from orange peel. Effect of operation conditions on the extract composition

The supercritical fluid extraction (SFE) of orange essential oil was studie d using dehydrated orange peel (0.0538 kg H2O/kg dm) from naveline cultivar s as raw material and CO2 as solvent. The effect of operation conditions wa s analyzed in a series of experiments at temperatures between 293 and 323 K and pressures between 8 and 28 MPa. The collected extracts were analyzed a nd the relative composition of the essential oil was determined. Limonene w as the principal component extracted, the optimum conditions for limonene e xtraction were 12.5 MPa and 308 K, in these conditions limonene represents more than 99.5% of the essential oil. Within the operating range conditions , the optimum for extracting linalool was found at 80 bar and 35 degrees C, conditions which coincide, in quite an approximate way, with those in the bibliography (F. Temelli et al., Food Technol. 42 (1988) 1451). Furthermore , the effect of CO2 flow rate and particle size of orange peel was studied in the range of 0.5 to 3.5 kg h(-1) and 0.1 to 10 mm, respectively. For a r apid extraction, particle sizes lower than 2 mm are adequate. For particle size of 0.3 mm and any CO2 mass flow, approximately 75% of the total conten t of essential oil was extracted using a solvent ratio of 6 kg of CO2 per k g of orange peel. A model based on the assumption of plug flow of a solvent through a fixed bed of milled material was applied to analyze the experime ntal results. The model successfully fitted the kinetic extraction of the e ssential oil. (C) 1999 Elsevier Science B.V. All rights reserved.