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Supercritical CO<inf>2</inf> extraction of essential oils from orange peel

Abstract:

The supercritical fluid extraction of orange essential oil was studied using dehydrated orange peel (0.0538 kg H2O kg-1 dm) from naveline cultivars as raw material and CO2 as solvent. The effect of operation conditions was analyzed in a series of experiments at 313 and 323 K and pressures between 1 and 25 MPa. 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. The subcritical CO2 dissolves hardly any essential oils, however, on reaching the critical point, the amount of essential oils dissolved increased with pressure, within the range of pressures considered in this study. Increasing solvent mass flow decreased the extraction efficiency while increasing particle size of orange peel decreased the extraction rate. For a rapid extraction, particle sizes lower than 2 mm and solvent mass flows lower than 2.5 kg h-1 are adequate. A model based on the assumption of plug flow of a supercritical solvent through a fixed bed of milled material was applied to analyze the experimental results. The model successfully fitted the experimental data. The collected extracts were orange in color due to the carotenoid and flavonoid content. During the process, water was extracted in the final stage of the extraction.