Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2010
Publication Date: May 30, 2010
Citation: Evangelista, R.L., Cermak, S.C., Isbell, T. 2010. Dehulling of Cuphea PSR23 Seeds to Reduce Color of the Extracted Oil. Industrial Crops and Products. 31(3):437-443. Interpretive Summary: Cuphea is being developed as a domestic source of tropical oils and an alternative to imported coconut and palm oils. These oils are used in the manufacture of soap and detergent and other industrial products. The seed oil has an undesirable dark green color due to the high levels of chlorophyll in the seed coat. Considerably more bleaching is needed to remove the green color, compared to those of light colored oil like soybeans or sunflower. As a consequence, the cost of refining cuphea oil is higher because of the added costs of using more bleaching clay, disposing spent clay, and higher oil losses because of the oil absorbed by the clay. This study has shown that removing the seed coat will reduce the chlorophyll level by as much as 87%. This will greatly reduce the cost associated with cuphea oil refining.
Technical Abstract: Oil extracted from the seeds Cuphea PSR23, a semi-domesticated, high-capric acid hybrid from C. viscosissima x C. lanceolata, by screw-pressing contained 200-360 ppm of chlorophyll. A high amount of bleaching clay was needed during refining to remove the chlorophyll in the oil. In this paper, dehulling of the seed using an impact huller was investigated to determine the extent of reduction of chlorophyll in the extracted oil. The effect of seed moisture content, huller’s impeller speed and feed rate to the huller on dehulling of the seeds were determined. The hulls were separated from the cotyledons by screening and using a vacuum gravity separator. The oils extracted from the cotyledon-rich fraction were analyzed for chlorophyll content and color. The hulls in cuphea seeds accounted for 44.6% (w/w) of the whole seed. If seeds were dried to 3.5% moisture content (MC) before dehulling, 37% of the dehulled seed with 8.8% oil can be removed by screening. This discard fraction has similar oil content to those of press cakes. The remaining cotyledon-rich fraction contained 39.2% oil, a 38% increase over that of whole seeds. Hexane-extracted oil from the cotyledon-rich fraction contained 70% less chlorophyll content. The minimum chlorophyll content achievable was 15 ppm from almost pure cotyledons and extracted by hydraulic pressing. Dehulling cuphea seed can greatly decrease the amount of bleaching clay in oil refining and the costs associated with its disposal. This will also reduce the size of the filter needed to remove the clay from the bleached oil.