Supercritical fluid extraction of Vernonia galamensis seeds
2001
King, J.W. | Mohamed, A. | Taylor, S.L. | Mebrahtu, T. | Paul, C.
Vernonia galamensis is an excellent source of a seed oil rich in vernolic acid. However, the seeds of this plant exhibit a high lipase activity in the dormant state. The activity of this enzyme is apparent as vernonia oil will undergo lipolysis when the seeds are crushed prior to extraction. In this study, supercritical fluid extraction (SFE) utilizing carbon dioxide has been examined as an alternative solvent, at different pressures, temperatures and cosolvent concentrations. The use of supercritical fluid carbon dioxide (SC-CO2) as the extraction fluid under high temperatures and pressures has the potential to inhibit the lipolysis reaction during the extraction by reducing the activity of the enzyme, and hence the production of undesired fatty acids. Vernonia seeds were ground with dry ice prior to extraction to minimize any nascent lipase activity. Selective SFE was conducted at various pressures, temperatures, modifier concentrations, and total CO2 volume used to determine whether the vernolic acid content of the resultant extract could be enriched. An increase in pressure and temperature significantly increased the amount of extracted oil as well as the vernolic acid content. In addition, a significant reduction in the free fatty acid content of the oil from 69 to 8 mg/g oil was present with increasing extraction pressure. Exhaustive extraction of the oil could be attained via SFE with neat CO2 and with ethanol-modified CO2. However, regrinding the matrix after the initial extraction, followed by re-extraction of the seed matrix was necessary in these cases. The resultant oil and extracted meal were characterized with respect to free fatty acid, phospholipid, and percent protein contents.
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