ARS | Publication request: The composition of corn oil produced after fermentation via centrifugation in a commercial dry grind ethanol process

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 2, 2010
Publication Date: July 26, 2010
Citation: Moreau, R.A., Hicks, K.B., Johnston, D., Laun, N.P. 2010. The composition of corn oil produced after fermentation via centrifugation from a commercial dry grind ethanol process. Journal of the American Oil Chemists' Society, 87:895-902.

Interpretive Summary: In 2008 approximately 9 billion gallons of fuel ethanol were produced in the US. When corn is fermented to produce alcohol, only the starch is used, so other kernel components such as the protein and corn oil can potentially be recovered and used for other food and feed applications. Today, most of the fuel ethanol in the US is being made in "dry grind" ethanol plants, where the whole corn kernels are ground and fermented to ethanol, and the nonfermentable parts of the kernel are combined into a feed coproduct called DDGS, distillers dried grains with solubles. Several dry grind fuel ethanol plants are now utilizing processes to produce corn oil via centrifugation after fermentation. In this study we compared the chemical composition of conventional corn oil with that obtained via centrifugation in a post fermentation process. The main difference in the two oils was that the post-fermentation oil contained high levels of free fatty acids (13-16%). The levels of phytosterols, lutein and zeaxanthin (the latter two are important for eye health) were higher in post-fermentation corn oil than in commercial corn oil and were comparable to the levels in corn oil obtained by extracting ground corn with ethanol. The levels of vitamin E derivatives, tocopherols and tocotrienols, were lower in post-fermentation corn oil than in either commercial corn oil or ethanol-extracted corn kernel oil. These results indicate that post-fermentation corn oil may be a valuable new source of phytosterols, lutein and zeaxanthin.

Technical Abstract: A study was conducted to examine the chemical composition of corn oil obtained via centrifugation after fermentation of corn to make fuel ethanol, and compare its composition to that of corn germ oil (commercial corn oil) and experimental corn oils. The levels of free fatty acids in the post fermentation corn oil were high (13-16%), as previously reported. The levels of free phytosterols and hydroxycinnamate steryl esters (similar to oryzanol in rice bran oil) were higher than those of corn germ oil and were comparable to those of ethanol extracted corn kernel oil. The levels of tocopherols and tocotrienols were lower in post-fermentation oil than in either corn germ oil or ethanol extracted corn kernel oil. The levels of lutein and zeaxanthin in post-fermentation were much higher than those in corn germ oil and were comparable to those in ethanol extracted corn kernel oil. Overall, exposure to all upstream processes of a fuel ethanol plant, including high-temperature liquefaction, saccharification and fermentation appeared to have the greatest effect on tocopherols and tocotrienols, but it had little effect on the levels of free phytosterols, hydroxycinnamate steryl esters, lutein and zeaxanthin. It may be desirable to recover these valuable functional lipids prior to using the post-fermentation corn oil for industrial applications such as for making biodiesel if a cost-effective recovery process can be developed.