Have you ever heard the term "SMOKE POINT" in reference to oils?
This basically means the point at which the fat starts to break down when exposed to heat. Heat changes the characteristics of oils and fats (including nuts and seeds) and can quickly change a "good fat" into a toxic one (this is why raw nuts are healthy and roasted nuts generally are not). The release of free radicals from over-heating the oil has been directly linked to cancer. So in cooking it becomes important to familiarize yourself with the smoke point of different oils. Extra-virgin olive oil might be perfect on your salad but has a relatively low smoke point. Sunflower, safflower and canola oils are a much better choice if you are going to be frying or using a high temperature.
This is a chart on wikipedia.com
|Type of oil or fat||Saturated||Monounsaturated||Polyunsaturated||Smoke point||Uses|
|Butter||66%||30%||4%||150 °C (302 °F)||Cooking, baking, condiment, sauces, flavoring|
|Ghee, clarified butter||65%||32%||3%||190–250 °C (374–482 °F)||Deep frying, cooking, sautéeing, condiment, flavoring|
|Canola oil||6%||62%||32%||242 °C (468 °F)||Frying, baking, salad dressings|
|Coconut oil||92%||6%||2%||177 °C (351 °F)||Commercial baked goods, candy and sweets, whipped toppings, nondairy coffee creamers, shortening|
|Rice bran oil||20%||47%||33%||254 °C (489 °F)||Cooking, frying, deep frying, salads, dressings. Very clean flavoured & palatable.|
|Corn oil||13%||25%||62%||236 °C (457 °F)||Frying, baking, salad dressings, margarine, shortening|
|Cottonseed oil||24%||26%||50%||216 °C (421 °F)||Margarine, shortening, salad dressings, commercially fried products|
|Grape seed oil||12%||17%||71%||204 °C (399 °F)||Cooking, salad dressings, margarine|
|Lard||41%||47%||2%||138–201 °C (280–394 °F)||Baking, frying|
|Margarine, hard||80%||14%||6%||150 °C (302 °F)||Cooking, baking, condiment|
|Margarine, soft||20%||47%||33%||150–160 °C (302–320 °F)||Cooking, baking, condiment|
|Diacylglycerol (DAG) oil||3.5%||37.95%||59%||215 °C (419 °F)||Frying, baking, salad oil|
|Olive oil (extra virgin)||14%||73%||11%||190 °C (374 °F)||Cooking, salad oils, margarine|
|Olive oil (virgin)||14%||73%||11%||215 °C (419 °F)||Cooking, salad oils, margarine|
|Olive oil (refined)||14%||73%||11%||225 °C (437 °F)||Sautee, stir frying, cooking, salad oils, margarine|
|Olive oil (extra light)||14%||73%||11%||242 °C (468 °F)||Sautee, stir frying, frying, cooking, salad oils, margarine|
|Palm oil||52%||38%||10%||230 °C (446 °F)||Cooking, flavoring, vegetable oil, shortening|
|Peanut oil||18%||49%||33%||231 °C (448 °F)||Frying, cooking, salad oils, margarine|
|Safflower oil||10%||13%||77%||265 °C (509 °F)||Cooking, salad dressings, margarine|
|Sesame oil (Unrefined)||14%||43%||43%||177 °C (351 °F)||Cooking|
|Sesame oil (semi-refined)||14%||43%||43%||232 °C (450 °F)||Cooking, deep frying|
|Soybean oil||15%||24%||61%||241 °C (466 °F)||Cooking, salad dressings, vegetable oil, margarine, shortening|
|Sunflower oil (linoleic)||11%||20%||69%||246 °C (475 °F)||Cooking, salad dressings, margarine, shortening|
|Sunflower oil (high oleic)||9%||82%||9%|
One other important thing to note is whether the oil is refined or unrefined. Refined oils have gone through numerous processes that remove different impurities (and arguably nutrients) that cause the oil to smoke. This means that refined oils have a higher smoke point than their unrefined counterpart.
Years ago I read that coconut oil was preferred for its high smoke point. Although it is high in saturated fat , I opted for this oil instead of olive oil for my high temperature dishes. As it turns out, the coconut oil I was using in fact has a very low smoke point. I also learned that the Extra Light Olive Oil has a relatively high smoke point. From now on I think I will use it, or canola, in my cooking.