Extraction of Helianthus Annuus (sunflower) oil with supercritical carbon dioxide
Wessels, Abraham Albertus
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The principal objective of this study was to extract sunflower (Helianthus annuus) oil from seed with supercritical carbon dioxide (sc-C02) as an alternative to the cold-press method and subsequent 3-stage refining of the acquired crude oil. Extractions were performed on laboratory scale with a commercially available supercritical fluid extractor of the latest design. A minimum number of extraction runs based on a statistical design was performed to establish the conditions (time, pressure, temperature) required for a maximum yield of oil by virtue of surface response analysis and kinetic yield-versus-time data fitting. Several additional extraction runs were performed at randomly selected conditions to properly reveal the temperature, pressure and density dependence of the extraction process and thereby elucidate its mechanism. The physical appearance, chemical quality and composition of the sc-C02 derived sunflower oil were evaluated against the crude and refined oil obtained by the cold-press method as well as a standard specification for commercial sunflower oil. This evaluation was done by chemical analysis performed in the quality control laboratory of a commercial sunflower oil supplier and by GC and GC-MS analysis of samples of both sc-C02 and cold-press obtained sunflower oil. It was concluded that sunflower oil of a superior quality can be obtained by sc-CO2 extraction, especially when de-hulled seed is used to minimise the wax content of the extract. Extraction runs were performed on seed with natural moisture content as well as on oven-dried, freeze-dried and sun-dried seed in order to establish the crucial role played by moisture content as a yield-determining factor. Preliminary results of up scaling on a supercritical pilot-plant suggest that sc-C02 extraction of sunflower oil could be performed on industrial scale should an extruder based continuous feed mechanism and a viable process of de-hulling of seed be implemented.
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