Supercritical carbon dioxide extraction of cuphea seed oil

Authors: Eller, Fred; Cermak, Steven - Steve; Taylor, Scott

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2010
Publication Date: 1/5/2011
Citation: Eller, F.J., Cermak, S.C., Taylor, S.L. 2011. Supercritical carbon dioxide extraction of cuphea seed oil. Industrial Crops and Products. 33:554-557.

Interpretive Summary: This research determined that carbon dioxide extraction is an effective means to extract medium chain fatty acids from cuphea seeds. Medium chain fatty acids are important in the manufacture of detergents, shampoos and lubricants. Currently, these medium chain fatty acids are either derived from imported palm and coconut oil or from petroleum. Cuphea seed oil is being investigated as a potential renewable domestic source of these medium chain fatty acids. Although cuphea seed oil can be obtained using either solvent extraction or screw pressing, both methods suffer the dark color of the resulting oils which require subsequent refining before the oil can used. Carbon dioxide extraction is a very effective means to extract vegetable oils and generally gives oils which are much lighter in color. This research compared carbon dioxide and organic solvent extraction for obtaining cuphea seed oil. The yield for the carbon dioxide extraction was only slightly less than that for the organic solvent. In addition, the oil obtained by carbon dioxide had much better physical characteristics, including free fatty acid content, acid values and especially color. Carbon dioxide extraction of cuphea seed oil yields a very high quality oil which requires less refining and subsequently reduces costs.

Technical Abstract: Cuphea seed oil is being investigated as a potential domestic source of medium chain fatty acids for several industrial uses. Although the oil from cuphea seeds has been obtained using both solvent extraction and screw pressing, both methods suffer from several disadvantages. Petroleum ether extraction is efficient and relatively inexpensive, however, the solvent is hazardous to both workers and the environment. In addition, the oil obtained by solvent extraction still requires significant refining before it is suitable in subsequent syntheses. Screw pressing has also been studied, and though it is relatively inexpensive, it is not as efficient as solvent extraction and the screw pressed oil contains high amounts of chlorophyll which must be removed using bleaching clay. In addition to the cost of the clay, its disposal costs, oil is retained by the clay resulting in even lower yields. Supercritical carbon dioxide (SC-CO2) extraction is a very effective means to extract vegetable oils and it is non-toxic, non-flammable, easy to separate from the extract (i.e., no solvent residues) and there are no solvent disposal costs. This research compared SC-CO2 and petroleum ether extraction for the extraction of cuphea seed oil. The yield for the petroleum ether soxtec extraction was 29.7% while the SC-CO2 extraction gave a yield of 28.1%. The FFA for the SC-CO2 extract was only 8.8% while the petroleum ether soxtec extract contained 15.0%. The AVs were also much higher for the petroleum ether soxtec extract (i.e., 29.8) than for the SC-CO2 extract (i.e., 17.4). The Gardner color of the SC-CO2 extract was determined to be 2+ while the color of the petroleum ether soxtec extract could not be determined because it was very dark due to the presence of chlorophyll. Although the two extraction methods differed slightly in their individual fatty acid contents, the magnitudes of the differences were inconsequential. This research demonstrated that cuphea seed oil can be effectively extracted using SC-CO2 at relatively low temperatures and pressures and (i.e., 50°C and 20.7 MPa) to give a very high quality oil. Cuphea oil’s status as a specialty oil and its corresponding higher value make its extraction using SC-CO2 an economically viable option.