Each type of oil its burning temperature. As soon as the oil reaches this temperature, it produces carcinogens. Moreover, in such numbers that even inhalation of fumes can lead to cancer.
Crude oil for frying the most inopportune. For example, the sunflower starts to burn after 105 degrees, and the olive – at 190. And this despite the fact that the temperature of the pan could easily reach 270 degrees. Therefore, any unrefined oil is better to use for salads or add to hot dishes after cooking to give them flavor.
Fry better on refined vegetable oils – they can withstand higher temperatures. For example, refined sunflower oil is not a terrible temperature to 230 degrees. Palm oil is the most resistant to heat of those that are popular in Russia, and even deep-fried forms a minimum of harmful substances.
But what about butter? Conventional oil barely withstands temperatures to 150 degrees. Have melted butter a higher stability, but there is very little nutrients and burn while cooking, it will still be. Butter can be used as “additive” for flavor in cooking, or add at the very end, before you remove the dish from the pan.
Any oil should not be reused. It is not only dangerous to health but also spoil the flavour of your dish.