The process of hydrogenation converts a liquid vegetable oil into a more solid state. This occurs through forcing hydrogen atoms into a vegetable oil under high pressure and high temperatures (120 to 210 degrees Celsius). A metal catalyst is used; it may be nickel, copper or platinum, and the process takes six to eight hours. Hydrogenation may be complete or partial.
Complete hydrogenation is where this process continues until all the double bonds in the oil are saturated with hydrogen. In effect this creates a fully saturated fat which is now very hard at room temperature. Because there are no more double bonds, there are no trans fatty acids in this type of fat. This means that the fat is not as harmful to health as partially hydrogenated oil; however all essential fatty acids in the oil have been destroyed. Commonly tropical fats such as coconut fat and palm oil undergo this process, to make them more useful to food manufacturers. This is the type of vegetable fat that is often used in chocolate to make sure it melts at mouth temperature.
Partial hydrogenation is where the process is halted before the oil is totally saturated. This means the resulting fat is not as hard; it has a semi solid, spreadable texture. Many trans fatty acids are present in partially hydrogenated vegetable oil. The essential fatty acids in the oil are also damaged. The word “partially hydrogenated vegetable oil” is present on the label of very many processed foods. This type of fat is present in most margarines, vegetable shortening and processed food such as cakes, biscuits, donuts, crisps and hot chips.
Are there any benefits of hydrogenated oils?
These types of fats benefit the food industry greatly, but our health suffers as a consequence. Usually cheap oils are used for this purpose, such as canola, cottonseed, soy or corn oil, which generally do not have health benefits. It is usually too expensive to use olive oil in manufacturing processed food. Hydrogenated fats, being solid give some foods the required consistency; biscuits for instance are usually made from a solid fat like butter or margarine. Butter is more expensive to use than margarine, and it spoils much faster. Basically hydrogenated vegetable oil is used by the food industry because it is cheap, and gives the foods containing it a longer shelf life.
McDonalds replaced beef tallow with partially hydrogenated soybean oil in 1990. In September 2002 McDonalds promised to use healthier oil in its US stores by February 2003. However, nothing has been done so far: there are still six grams îf trans fat in a large serve of fries. In September 2004, McDonalds Australia began using a canola oil blend. This oil is 75 percent lower in saturated fat than their previous oil, but the trans fat content is not mentioned, and there are other potential problems with canola oil. The canola oil blend McDonalds use contains an antifoam agent called dimethyl polysiloxane.
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