Oil separation from wet milled corn germ dispersions as part of aqueous oil extraction and aqueous enzymatic oil extraction

Authors: Dickey, Leland; Kurantz, Michael; Parris, Nicholas

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2007
Publication Date: 3/17/2008
Citation: Dickey, L.C., Kurantz, M.J., Parris, N. Oil separation from wet milled corn germ dispersions by aqueous oil extraction and aqueous enzymatic oil extraction. 2008. Industrial Crops and Products 27(3):303-307.

Interpretive Summary: Dry grind production of ethanol from corn creates a byproduct, distillers' dried grains, contains the embryo of the kernel, also called the germ. The germ contains > 90% of all the oil in the kernel and can be separated from the corn prior to fermentation by several new processes. Corn oil can then be separated from the germ and made available to consumers, keeping the vegetable oil price stable despite likely increased use for biodiesel production. Sale of germ as a byproduct, in place of some of the distillers' dried grains, should significantly reduce the overall cost of producing ethanol and benefit this industry. More dry-grind ethanol production will bolster the U.S. corn market, reduce petroleum imports and slow depletion of world petroleum reserves. The germ price and its impact on dry grind profitability will increase if the cost of removing the oil from the germ can be reduced. This study shows that 37% of the oil can be extracted from 100 g batches of germ as obtained earlier at the 6 gm scale, using slight modifications to an inexpensive aqueous process. Optimum conditions for the germ milling and oil collection were identified. These conditions and the process used will be the starting point for the next larger scale up to commercial trials.

Technical Abstract: Oil was obtained from corn germ by aqueous extraction (AE). 100 g batches of germ were mixed with a buffer solution to a mass concentration of 5 to 20% germ, preheated under 2 atm. pressure (120oC), milled in a blender and then churned in an incubator/shaker to coalesce and float oil droplets. The oil yield increased with germ content of the slurry milled up to a mass fraction of 0.16. A maximum yield of 14 g was obtained when the milled germ mass was churned at a loading between 0.8 and 1.1 g/cm2 of beaker cross section, sufficient to produce a high rate of particle collisions. For aqueous enzymatic extraction (AEE) runs, a solution of enzymes was added to the milled germ suspension prior to churning. The AEE runs exhibited oil yields of 29 g, about twice those of otherwise similar AE runs.