With so many choices of oils that can be used for cooking, it’s hard to know which one is best. A number of factors need to be taken into account, including cooking temperature, nutrient content, and taste. In a recent study published in the Journal of Agricultural and Food Chemistry, researchers tested four different refined oils: olive, corn, soybean, and sunflower. After heating and using the oil ten times, they found that olive oil performed best against the others in stability and nutrition. Olive oil was the most stable oil when fried at 320 and 374 degrees while sunflower oil degraded most rapidly at 356 degrees.
Due to the chemical structure of oils, they degrade at different rates. Some oils are more stable than others. When oils reach a certain temperature, known as their smoke point, they begin to break down, giving off new chemicals including harmful free radicals.
Olive oil is a monounsaturated oil, which means that it only has one (“mono”) unsaturated bond in its structure. Unsaturated bonds are not as stable as saturated bonds, which is why saturated fats tend to be the most stable. Corn, soybean, and sunflower oils are polyunsaturated oils, which means that they are structurally less stable than olive oil.
Because they didn’t test extra virgin or virgin olive oils, which may have differing stabilities, refined olive oil, which will be labeled as “extra light olive oil,” is recommended based on the results of this study.