Most of the world’s cooking oil comes from soybeans and about 13 million tons of the oil is produced annually. It makes up about 55 percent of all vegetable oils produced in the world and 30 percent of all oil consumed. The United States is probably the largest consumer of soybean oil. Thirty million acres of soybeans are grown there and 18 billion pounds of oil are made a year. Because of its wide use in most packaged foods, 80 percent of all the vegetable oil consumed in the United States is soybean oil and it is the main source of fat in the American diet.
The oil is made from cleaned and dehulled soybeans, which contain only about 20 percent oil. One bushel of soybeans makes roughly 11 pounds of soybean oil. The oil is isolated from the dry components of the soybeans, called soybean meal, by a process called solvent extraction. Here a liquid solvent such as hexane is pumped over soybean flakes to isolate the oil, which then goes through several stages of purification. The extraction step also removes about 30 percent of the vitamin E in soybeans, which is often used to make vitamin E supplements. The oil still contains a good amount of vitamin E, and one serving will provide more than 10 percent of the daily recommended amount. It also contains a fair amount of healthy omega-3 fatty acids.
Soybean oil is made up of 61 percent polyunsaturated fatty acids, 24 percent monounsaturated fatty acids, and 15 percent saturated fatty acids. The main type of polyunsaturated fatty acid in the oil is linoleic acid. Soybean oil also contains about 7 to 8 percent linolenic acid, another polyunsaturated fatty acid that is prone to oxidation and spoilage. Most manufacturers increase the shelf life of this oil by hydrogenation. This process reduces the amount of linolenic acid, but it also creates trans fatty acids that are thought to be especially unhealthy. Researchers today are trying to find better ways to stabilize the oil without hydrogenation. One example is a new variety of genetically bred soybean called Soyola that contains oil with much less linolenic acid, helping to increase its shelf life.
Soybean oil is produced in two different forms. The first is a refined, liquid form that can be found in grocery stores. It is commonly used for frying foods because it has a high smoke point of 450 ° F. The other is a partially hydrogenated, solid form that is mainly used commercially. This form is widely used in all kinds of baked goods including cereal, cookies, crackers, and breads. It can also be found in most salad dressings, peanut butter, and margarine. Actually, it is difficult to find a packaged product in the United States that does NOT contain partially hydrogenated soybean oil. If you want to avoid consuming this oil, try looking into organic products. Homemade baked goods such as bread and cookies also will not have partially hydrogenated soybean oil unless certain kinds of margarine or shortening were used to make them.
http://www.wsu.edu/~gmhyde/433_web_pages/433Oil-web-pages/Soy/soybean1.html
http://www.notrans.iastate.edu/
http://www.unitedsoybean.org/
http://www.heartlandfields.com/soy_health/soybean_oil.html