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Supercritical CO<inf>2</inf> extraction of essential oil from orange peel. Effect of operation conditions on the extract composition

Abstract:

The supercritical fluid extraction (SFE) of orange essential oil was studied using dehydrated orange peel (0.0538 kg H2O/kg dm) from naveline cultivars as raw material and CO2 as solvent. The effect of operation conditions was 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 and the relative composition of the essential oil was determined. Limonene was the principal component extracted, the optimum conditions for limonene extraction 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°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 kgh-1 and 0.1 to 10mm, respectively. For a rapid 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 content of essential oil was extracted using a solvent ratio of 6 kg of CO2 per kg 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 experimental results. The model successfully fitted the kinetic extraction of the essential oil. © 1999 Elsevier Science B.V. All rights reserved.