Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2005
Publication Date: 12/1/2005
Citation: Kuk, M.S., Tetlow, R.R. 2005. Gossypol removal by adsorption from cottonseed miscella. Journal of the American Oil Chemists' Society. 8(12):905-909.
Interpretive Summary: Cottonseed oil and meal are produced from cottonseed by extracting the seed with a chemical solvent. A refining step of cottonseed crude oil, 'caustic refining,' removes by a chemical reaction undesirable chemical compounds such as free fatty acids and gossypol, producing a byproduct, soapstock. Most gossypol is left in soapstock. Gossypol is a toxic chemical in its pure form, but its toxicity is reduced to an extent after this refining step. This caustic refining step neutralizes the acidity of fatty acids. Because of the nutritional value of fatty acids, however, soapstock is added back to animal feed within the allowed limit. If an alternative process to the current caustic refining is available, thereby producing soapstock with a negligible amount of toxic gossypol, this alternative process would help produce cottonseed meal with the increased commercial value. As one of the alternative processes to the caustic refining, SRRC scientists tested a few minerals to remove gossypol by adsorption, a chemical unit operation step, from cottonseed crude oil. This new process would produce cottonseed meal with much less gossypol even with the addition of soapstock compared to those produced by the present method, because the new process produces soapstock with little or a negligible amount of gossypol. The SRRC scientists found that a type of tested adsorbents removed more than 95% of gossypol by adsorption from the tested crude oil. The test results and possible regenerating methods of the used adsorbents are presented. This research directly benefits the U.S. farmers who grow cotton, and indirectly U.S. industries which are involved in producing cottonseed meal and edible oil.
Technical Abstract: A variety of alumina (acidic, basic and neutral), silica and synthetic magnesium silicates were screened to evaluate the potential use of adsorbents for reducing gossypol and related compounds from hexane-based cottonseed miscella. Among the tested adsorbents, a type of silica and a couple of magnesium silicates with a relatively high Brunauer-Emmet-Teller (BET) surface area ('240 M 2/g) showed a superior adsorption capacity in reducing gossypol from hexane miscella. To search for possible regenerating methods for the spent-adsorbents, washing with acetone was tested. The effect of pH in the washing solvent was also tested. Adsorbents which were regenerated by washing with acetone at pH values between 7 and 7.5 performed better than those at pH between 6.5 and 7. The pH values of washing solvent were adjusted by using a small amount of caustics and 1N HCl.