Corn oil

Corn oil, in a 5 liter plastic bottle

Corn oil, plastic jugs in cardboard boxes, 33 lbs. each

Corn oil (maize oil) is oil extracted from the germ of corn (maize). Its main use is in cooking, where its high smoke point makes refined corn oil a valuable frying oil. It is also a key ingredient in some margarines. Corn oil is generally less expensive than most other types of vegetable oils. One bushel of corn contains 1.55 pounds of corn oil (2.8% by weight). Corn agronomists have developed high-oil varieties; however, these varieties tend to show lower field yields, so they are not universally accepted by growers.

Corn oil is also a feedstock used for biodiesel. Other industrial uses for corn oil include soap, salve, paint, rustproofing for metal surfaces, inks, textiles, nitroglycerin, and insecticides. It is sometimes used as a carrier for drug molecules in pharmaceutical preparations.

Production

Almost all corn oil is expeller pressed, then solvent extracted using hexane or isohexane.^[1] The solvent is evaporated from the corn oil, recovered, and re-used. After extraction, the corn oil is then refined by degumming and/or alkali treatment, both of which remove phosphatides. Alkali treatment also neutralizes free fatty acids and removes color (bleaching). Final steps in refining include winterization (the removal of waxes), and deodorization by steam distillation of the oil at 232 - 260C (450 - 500F) under a high vacuum.^[1]

Some specialty oil producers manufacture unrefined, 100% expeller pressed corn oil. This is a more expensive product since it has a much lower yield than the combination expeller and solvent process, as well as smaller market share.

Constituents

Refined corn oil is 99% triglyceride, with proportions of approximately 55% polyunsaturated fatty acid, 30% monounsaturated fatty acid, and 15% saturated fatty acid.^[2]

• Of the saturated fatty acids, 80% are palmitic acid (lipid number of C16:0), 14% stearic acid (C18:0), and 3% arachidic acid (C20:0).
• Over 99% of the monounsaturated fatty acids are oleic acid (C18:1 c)
• 98% of the polyunsaturated fatty acids are the omega-6 linoleic acid (C18:2 n-6 c,c) with the 2% remainder being the omega-3 alpha-linolenic acid (C18:3 n-3 c,c,c).^[2]

Negative health effects

Some medical research suggests that excessive levels of omega-6 fatty acids, relative to omega-3 fatty acids, may increase the probability of a number of diseases and depression.^[3][4][5] Modern Western diets typically have ratios of omega-6 to omega-3 in excess of 10 to 1, some as high as 30 to 1, partly due to corn oil which has an omega-6 to omega-3 ratio of 49:1. The optimal ratio is thought to be 4 to 1 or lower.^[6][7]

A high intake of omega-6 fatty acids may increase the likelihood that postmenopausal women will develop breast cancer.^[8] Similar effect were observed on prostate cancer.^[9] Other analysis suggested an inverse association between total polyunsaturated fatty acids and breast cancer risk.^[10]

References

1. ^ ^{a b} http://www.corn.org/CornOil.pdf
2. ^ ^{a b} U.S. Department of Agriculture, Agricultural Research Service. 2007. USDA National Nutrient Database for Standard Reference, Release 20. Nutrient Data Laboratory Home Page, listed under "Oil, corn, industrial and retail, all purpose salad or cooking"
3. ^ Lands, William E.M. (December 2005). "Dietary fat and health: the evidence and the politics of prevention: careful use of dietary fats can improve life and prevent disease". Annals of the New York Academy of Sciences (Blackwell) 1055: 179–192. doi:10.1196/annals.1323.028. PMID 16387724. 
4. ^ Hibbeln, Joseph R.; N; B; R; L; Nieminen, Levi R.G.; Blasbalg, Tanya L.; Riggs, Jessica A.; and Lands, William E.M. (June 1, 2006). "Healthy intakes of n−3 and n−6 fatty acids: estimations considering worldwide diversity". American Journal of Clinical Nutrition (American Society for Nutrition) 83 (6, supplement): 1483S–1493S. PMID 16841858. http://www.ajcn.org/cgi/content/full/83/6/S1483. 
5. ^ Okuyama, Hirohmi; Ichikawa, Yuko; Sun, Yueji; Hamazaki, Tomohito; Lands, William E.M. (2007). "ω3 fatty acids effectively prevent coronary heart disease and other late-onset diseases: the excessive linoleic acid syndrome". World Review of Nutritional Dietetics. World Review of Nutrition and Dietetics (Karger) 96 (Prevention of Coronary Heart Disease): 83–103. doi:10.1159/000097809. ISBN 3-8055-8179-3. PMID 17167282. 
6. ^ Daley, C.A.; Abbott, A.; Doyle, P.; Nader, G.; and Larson, S. (2004). A literature review of the value-added nutrients found in grass-fed beef products. California State University, Chico (College of Agriculture). http://www.csuchico.edu/agr/grassfedbeef/health-benefits/index.html. Retrieved 2008-03-23. 
7. ^ Simopoulos, Artemis P. (October 2002). "The importance of the ratio of omega-6/omega-3 essential fatty acids". Biomedicine & Pharmacotherapy 56 (8): 365–379. doi:10.1016/S0753-3322(02)00253-6. PMID 12442909. 
8. ^ Emily Sonestedt, Ulrika Ericson, Bo Gullberg, Kerstin Skog, Håkan Olsson, Elisabet Wirfält (2008). "Do both heterocyclic amines and omega-6 polyunsaturated fatty acids contribute to the incidence of breast cancer in postmenopausal women of the Malmö diet and cancer cohort?". The International Journal of Cancer (UICC International Union Against Cancer) 123 (7): 1637–1643. doi:10.1002/ijc.23394. PMID 10970215. http://www3.interscience.wiley.com/journal/120780752/abstract. Retrieved 2008-11-30. 
9. ^ Yong Q. Chen, at al (2007). "Modulation of prostate cancer genetic risk by omega-3 and omega-6 fatty acids". The Journal of Clinical Investigation 117 (7): 1866–1875. doi:10.1172/JCI31494. PMC 1890998. PMID 17607361. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1890998. 
10. ^ Valeria Pala, Vittorio Krogh, Paola Muti, Véronique Chajès, Elio Riboli, Andrea Micheli, Mitra Saadatian, Sabina Sieri, Franco Berrino (18 July 2001). "Erythrocyte Membrane Fatty Acids and Subsequent Breast Cancer: a Prospective Italian Study". JNCL 93 (14): 1088–95. doi:10.1093/jnci/93.14.1088. PMID 11459870. http://jnci.oxfordjournals.org/cgi/content/full/93/14/1088. Retrieved 2008-11-30. 

Further reading

• Dupont J, PJ White, MP Carpenter, EJ Schaefer, SN Meydani, CE Elson, M Woods, and SL Gorbach (October 1990). "Food uses and health effects of corn oil". J Am Coll Nutr 9 (5): 438–470. PMID 2258533. 

External links

• Institute of Shortening and Edible Oils
• The Maize Page