How are Oils Refined and Deodorized?

Once extracted, the oil 'needs' to be refined, which involves the treatment of the crude oil with a lye solution to reduce the free fatty acid (FFA) content to 0.05 percent. This is done primarily to prevent spoilage—to help the oil last an eternity on the grocer's shelf. However, free fatty acids are not necessarily bad: conjugated linoleic acid (found in meat and dairy products), for example, is a naturally occurring free fatty acid that has been shown to improve nutrient usage, promote muscle tone, significantly reduce body fat, and have anti-tumor properties. But why in the world would we want something like that in our vegetable oil?

In addition, other impurities in the oil, such as gums, phosphatides, pigments, and other oxidation products, which would 'impair' the taste, odor, shelf life, and other 'desired' properties of the oil are likewise removed. This degumming and neutralization process is accomplished by means of phosphoric acid and more lye.

The now 'neutral' oil is mixed with bleaching earth (a type of clay) and activated carbon to give the oil a lighter color. Final purification is accomplished using filters, presses, and polishing filters. At which point, the oil is pumped into storage tanks.

Deodorizing
All edible oils and fats contain certain compounds that give the particular oil its identifiable taste and smell. In all commercial oils, these compounds are removed to make the oil as neutral tasting as possible (after all, who wants to eat anything that has any flavor?). This process is called deodorization, and because of the high temperatures involved, it is extremely damaging to the oil.

Refined bleached oil from refining is first transferred to a de-aerator operating under a vacuum for removal of any air in the oil. The oil then passes through a series of heaters, where the temperature is raised high enough for efficient steam distillation and deodorization—upwards of 200°C (450°F). At these temperatures, the fundamental structure of many oils is changed into a different form of fatty acid through a process called isomerization. These new forms are not beneficial to the human body. The high heat also causes a small amount of trans fatty acids to be formed. Finally, steam is blown through the oil to vaporize those components of the oil that actually give it any lingering odor or taste. The fully deodorized, tasteless, and refined oil then passes through a cooler and polishing filter basket for removal of any fine suspension before being finally pumped to the storage tank.

What's left is an oil that is virtually colorless, odorless, and tasteless, which can last for years in a bottle with no danger of spoilage. On the other hand, it has no connection with the beneficial oil that was originally contained in the seed or nut. It is now a 'plastic fat,' fundamentally changed in structure, that offers no benefits to the human body—a plastic fat that is actually quite harmful. In addition, all of the beneficial phytochemicals (such as the lignans,which are an integral part of the oil complex and play a key anti-cancer role) have been removed."

Reference: www.Johnbarron.org