Dehulling of Cuphea PSR23 seeds to reduce color of the extracted oil

Oil extracted by screw pressing seeds of Cuphea PSR23 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, we investigated the dehulling of the seed as a method of reducing the chlorophyll content in oil extracted from cuphea seeds. The effects 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 accounted for 44.6% (w/w) of the whole cuphea seed. When seeds were dried to 3.5% moisture content (MC) before dehulling, 37% of the dehulled seed (containing 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, which is 38% greater than that of whole cuphea seeds. Hexane-extracted oil from the cotyledon-rich fraction contained 70% less chlorophyll content compared with similarly extracted whole seed oil. The minimum chlorophyll content achievable was 15 ppm from almost pure cotyledons and extracted by hydraulic pressing. Dehulling cuphea seed before oil extraction effectively reduced chlorophyll content in the oil, which can greatly decrease the amount of bleaching clay in oil refining and the cost associated with its handling and disposal.