Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2014
Publication Date: 6/13/2014
Citation: Cheng, H.N., Rau, M.W., Dowd, M.K., Easson, M.W., Condon, B.D. 2014. Comparison of soybean and cottonseed oils upon hydrogenation with nickel, palladium and platinum catalysts. Journal of the American Oil Chemists' Society. 91:1461-1469.
Interpretive Summary: For different food uses, edible oils are often hydrogenated. Typically this process involves reacting the oil with hydrogen at high temperature and pressure in the presence of a nickel-based catalyst. Unsaturation in the edible oil is partly hydrogenated, leading to oils of higher melting points, increased resistance to oxidation, and/or improved physical characteristics. However, a side effect of partial hydrogenation is the formation of trans fatty acids (TFA), which have been linked to increased serum cholesterol content. There has been a lot of recent interest in decreasing TFA content in oils, with most of the efforts devoted to soybean oil. In this work, we did a side-by-side comparison of the hydrogenation behavior of soybean oil and cottonseed oil using three commercially available catalysts based on Ni, Pd, and Pt under experimental conditions similar to commercial processes. Under the experimental conditions tested, hydrogenated cottonseed oil was shown consistently to contain lesser amounts of TFA relative to hydrogenated soybean oil in the range of unsaturation of interest. Thus, hydrogenated cottonseed oil can be a viable alternative to hydrogenated soybean oil for food applications.
Technical Abstract: There is current interest in reducing the trans fatty acids (TFA) in hydrogenated vegetable oils because consumption of foods high in TFA has been linked to increased serum cholesterol content. In this work, hydrogenation was carried out on soybean oil and cottonseed oil at two pressures (2 and 5 bars) and 100 ºC using commercially available Ni, Pd, and Pt catalysts. The TFA levels and the fatty acid profiles were analyzed by gas chromatography. In all cases, higher hydrogen pressures produced lower levels of TFA. In the range of 70-95 iodine values, the Pt catalyst gave the least TFA, followed by Ni, and then Pd, for both oils. For all three catalysts at 2-bar and 5-bar pressures and 70-95 iodine values, cottonseed oil contained noticeably less TFA than soybean oil. Kinetic modeling was done on the hydrogenation data that provided additional information on the reaction mechanisms.