Location: Functional Foods ResearchTitle: Composition and oxidative stability of crude oil extracts of corn germ and distillers grains Author
Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2010
Publication Date: 1/8/2011
Citation: Moser, J.K., Breyer, L. 2011. Composition and oxidative stability of crude oil extracts of corn germ and distillers grains. Industrial Crops and Products. 33:572-578. Interpretive Summary: Post-fermentation corn oil from the dry-grind ethanol process has potential value as a fourth co-product from ethanol production as a rich source for antioxidants and functional lipids, as well as a feedstock for biodiesel production. This research determined that post-fermentation corn oils from the dry grind ethanol process are higher in several antioxidants and functional lipids, and had increased oxidative stability, compared to oil extracted from corn germ. Also, this research demonstrated that post-fermentation corn oil from a raw starch ethanol processing facility has lower free fatty acid content and increased oxidative stability when compared to oil extracted from a conventional dry grind ethanol processing facility. This research may be of interest to ethanol producers that are interested in increasing the number and value of co-products and to biodiesel producers who are interested in low-cost biodiesel feedstock. It is also of national interest to increase the number of fuels obtained from a single feedstock, corn.
Technical Abstract: The fatty acid composition, Acid Value, and the content and composition of tocopherols, tocotrienols, carotenoids, phytosterols, and steryl ferulates were determined in corn germ oil and four post-fermentation corn oils from the ethanol dry grind process. The oxidative stability index at 110ºC was determined for the five oils, and four oils were compared for their stability during storage at 40ºC as determined by peroxide value and hexanal content. The fatty acid composition of all five oils was typical for corn oil. The Acid Value (and percentage of free fatty acids) was highest (28.3 mg KOH/g oil) in corn oil extracted centrifugally from a conventional dry grind ethanol processing facility and for oil extracted, using hexane, from distillers dried grains with solubles (DDGS) from a raw starch ethanol processing facility (20.8 mg KOH/g oil). Acid Value was lowest in two oils extracted centrifugally from thin stillage in a raw starch ethanol facility (5.7 and 6.9 mg KOH/g oil). Tocopherols were highest in corn germ oil (~1400 µg/g), but tocotrienols, phytosterols, steryl ferulates, and carotenoids were higher in all of the post-fermentation corn oils. Hexane extracted oil from DDGS was the most oxidatively stable as evaluated by OSI and storage test at 40ºC, followed by centrifugally extracted thin stillage oil from the raw starch ethanol process, and centrifugally extracted thin stillage oil from the conventional dry grind ethanol process. Corn germ oil was the least oxidatively stable. When stored at room temperature, the peroxide value of centrifugally extracted thin stillage oil from the raw starch ethanol process did not significantly increase until after six weeks of storage, and was less than 2.0 mEq peroxide/kg oil after three months of storage. These results indicate that post-fermentation corn oils have higher content of valuable functional lipids than corn germ oil. Some of these functional lipids have antioxidant activity which increases the oxidative stability of the post-fermentation oils.