Do you know what is the smoke point? It is the temperature at which smoke appears on the surface of the olive oil when cooking. It shows that the olive oil is very hot and it begins to lose properties.
Olive oil, during the frying, suffers unfavorable transformations. When increasing the temperature the chemical processes are accelerated, making it degrade before. Some of these processes are:
It occurs between the water of the food (or the humidity presents in the olive oil) and the olive oil itself, generating an increase of the free fatty acids that favor the oxidation. It causes an unpleasant smell and taste, as well as reduces its smoke point. Also, it forms methyl ketones and lactones. It is recommended to dry the food as much as possible, before frying it.
The action of the oxygen on fatty acids (mainly polyunsaturated) creates unstable compounds called hydroperoxides and free radicals. The unsaturated fatty acids become saturated, losing the beneficial qualities for health. Also, other elements appear (hydrocarbons, lactose, alcohols, acids, etc.) that create changes in the olive oil, making its flavor worse.
The last chemical reaction that can happen is the polymerization. It generates the appearance of foam and increases the viscosity of the olive oil because the free radicals that are united to each other, or united to the fatty acids, creates compounds of bigger size and molecular weight (polymers) that increases that viscosity, appearing a layer of polymers very difficult to eliminate from the surface of the olive oil and in the container.
Steps to fry with olive oil without risks
It is important to take into account that the smoke point is different in each kind of oil: in an olive of first cold pressure it is about 130º, in the extra virgin olive oil is 160º, in virgin olive oil is 215º, in unrefined sunflower oil is 105º, refined sunflower is at 220º and coconut or palm oil is at 230º.
Olive oil has less double bonds and for this reason, it resists higher temperatures than other oils, being more stable. To summarize, it is better to use olive oil instead of sunflower oil or other oil for frying. We also advise you not mix new oil with the one already used, nor olive oil with seeds oil, because they have different smoke points.
It is also important that the olive oil does not reach the 170-180º. When it overheats, it gets darker and smokes, generating potentially toxic substances. Additionally, if it is burned, we should discard it. Also, before frying, we suggest drying completely the food and do not take it directly from the fridge or freezer because water promotes the decomposition of the olive oil.
After frying, it is necessary to filter the olive oil and removing the burnt food waste that favors its decomposition. The storage of the reusable oil must be in dark container that not let the light pass through the olive oil and without humidity.