Cooking oil is purified fat of plant or animal origin, which is liquid at room temperature. Common plant-derived cooking oils (vegetable oils) are derived from nuts, seeds, grains and beans. Most animal fats are solid at room temperature (and thus not considered oils), but fish, whales and some other cold-climate animals have oils. Cooking oil is most often used to fry or deep-fry food, or to preserve it. Oil can be flavoured by immersing aromatic food stuffs such as fresh herbs, peppers and so forth in the oil for an extended period of time. However, care must be taken when using garlic and onions to prevent the growth of botulism in this medium.

The smoke point refers to the temperature at which an oil begins to smoke, become discolored, and decompose. Cooking oil should never be allowed to heat to the smoking point because this will cause food to burn and will produce an unpleasant taste in the food.

A number of factors may contribute to a decrease in the smoke point of an oil. The length of time the oil has been heated, the number of times the oil has been used, the presence of salt or any other impurities, improper storage, and if the oil is a generic blend of various oils may all contribute to lowering the smoke point.

Unrefined oils (oils obtained from cold extraction methods only) usually have lower smoke points than refined oils (oils obtained through high heat extraction). Generally, an oil that has very little color, aroma, or taste is probably a refined oil. Although it may not be necessary to know the actual temperature of the smoke points of various oils, it is important to know which oils and fats may be safely used for different cooking methods.

Smoke Point of Popular Oils and Fats