These are of two types—monounsaturated and polyunsaturated. If a fatty acid has one double bond between the carbons, it is monounsaturated (Figure B). Olive and canola oils contain a high percentage of monounsaturated fatty acids. If a fatty acid contains two or more double bonds, the fatty acid is polyunsaturated (Figure C and D). Linoleic acid, an essential fatty acid found in safflower oil, soybean oil, and other vegetable oils, is an example of a polyunsaturated fat. Other oils of this category include groundnut oil, corn oil, and cottonseed oil.
Monounsaturated Fatty Acid: A fatty acid containing one double bond.
Polyunsaturated Fatty Acid: Fatty acid containing two or more double bonds.
The point at which the double bonds begin in the fatty acid is important. Counting from the end with a CH3 group if these double bonds start after the third carbon, it is an omega -3 (?-3) fatty acid. If these double bonds start after the sixth carbon, it is omega-6 (?-6) fatty acid, and so on.
Unsaturated fats are unstable at room temperature and sensitive to interaction with oxygen, light, and heat. This is why storage in dark glass containers/bottles or cans and/or under refrigeration is ideal. Besides refrigeration rancidity of an oil can be prevented by 1) use of antioxidants which bind the points of unsaturation i.e the weak spots in the fatty acid, which can be “attacked” by oxygen and protect the molecules from oxidation.) Vitamin E is a common antioxidant; beta-carotene and the chemicals Butylated Hydroxy Anisole (BHA) and Butylated Hydroxy Toluene (BHT) are other antioxidants and 2) hydrogenation.