ARS | Publication request: Dehulling of cuphea seed for the production of crude oil with low chlorophyll content

Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Abstract
Publication Acceptance Date: August 1, 2008
Publication Date: September 7, 2008
Citation: Evangelista, R.L. 2008. Dehulling of cuphea seed for the production of crude oil with low chlorophyll content [abstract]. Association for the Advancement of Industrial Crops Conference.

Technical Abstract: Cuphea (PSR23) seed oil is rich in medium chain fatty acids (MCFAs). MCFAs are used in soaps, detergents, cosmetics, lubricants, and food applications. Currently, cuphea is being grown to provide oil needed for research. The oil can be extracted effectively by screw pressing flaked whole seeds. Crude oil containing up to 350 ppm of chlorophyll had been observed. Chlorophyll in the oil can act as a prooxidant and has also been found to poison catalysts used in oil processing. In addition, high levels of chlorophyll increases the amount of diatomaceous earth used in the bleaching step in oil refining. This study was conducted to evaluate the feasibility of dehulling the small cuphea seed and to assess its benefit in reducing the chlorophyll level in the crude oil extracted from the dehulled seeds. Preliminary work indicated that the seed can be dehulled using a roller mill and an impact huller. To establish the suitable seed moisture content (MC) and the huller¿s impeller speed for dehulling, 1-kg batches of cuphea seeds with 3.5, 7, 11, and 14% MCs were dehulled at 1150, 1425 and 1700 rpm huller impeller speeds. The dehulled seeds were screened through a stack of U.S. standard sieves (Nos. 12, 16, 25, and 35) and the weight and oil content of each fraction were determined. Fraction 12 was mostly undehulled seeds. Fractions 16 and 25 were a mix of seed meat (cotyledon and germ) and hulls which can be further enriched by aspirating or density grading. Fraction 35 and through 35 were also a mix of hulls and meat and their oil contents were higher than that of the starting seed. Their small particle size, however, made them unsuitable for aspirating or density grading. To maximize meat purity, the amount of fines (fractions 35 and smaller) must be minimized. This can be achieved by dehulling seeds with greater than or equal to 11% MC at huller impeller speed of 1425 rpm. A 60-kg batch of seed was dehulled and the hulls were separated from fractions 16 and 25 by aspirating and density grading. High-purity meat (>98%) was achieved by density grading. The crude oil obtained by hexane extraction had a chlorophyll content of around 20 ppm, an 86% reduction from that of undehulled seeds. The crude oil from the fines fraction had 45 ppm of chlorophyll or a reduction of about 70%.