A few days ago, I saw a hot search "an inconspicuous cooking habit causes cancer to the upper body", which refers to the matter of burning oil to smoke when cooking. In fact, this hot search is half right, "cooking the oil to smoke is not healthy", which is the correct advice. However, the hot search said that "high temperature will make unsaturated fatty acids in vegetables undergo oxidative cracking and isomerization, resulting in trans fatty acids with trans configuration", which is the logic of "shooting first and drawing the target", and there is no reason.

Frying the oil until it smokes produces very little trans fatty acid

First of all, the conversion of unsaturated fatty acids into trans fats requires "high temperature + catalyst" to proceed efficiently. If there is no catalyst and only high temperature, it is not easy to produce trans fats. During the refining process of vegetable oil, the temperature is much higher than stir-frying, the duration is also much longer, and the trans fat formed is generally about 2%. Even if the oil is burned to smoke, the trans fat formed is very small and can be ignored.

Cooking fume is an important source of PM2.5 at home

However, "burning oil to smoke" does have considerable harm, but it has nothing to do with trans fats.

There are some impurities in the oil, such as free fatty acids, lecithin and so on. When the oil temperature is high to a certain extent, these substances will generate various volatile substances and become "smoke". These "smoke" particles are small and are a significant source of PM2.5 in the home. If you put an air purifier or PM2.5 detector in the kitchen, you can see that the oil is burned to smoke and stir-fry a dish, PM2.5 will soar from dozens to hundreds. When cooking, oil smoke is equivalent to creating smog in the kitchen.

There are many harmful components in the oil fume, which have different adverse effects on the human body

1. The harmful ingredient acrolein in oil smoke. It has a strong irritating effect on the eyes and respiratory tract, and was even used as a chemical weapon in World War I.

2. There are also polycyclic aromatic hydrocarbons in lampblack, which enter the lungs through breathing and increase the risk of lung cancer like smoking.

Surveys show that cooks and middle-aged and elderly women who are often exposed to soot have significantly higher levels of carcinogens in their blood than those who are not exposed. Even if they do not smoke, the incidence of lung cancer is significantly higher than that of non-exposed people.

3. There are a variety of free radicals in the oil smoke.

Oil smoke contains a large number of free radicals, long-term and frequent contact will accelerate skin aging.

4. The harm of kitchen fumes to pregnant women is particularly obvious, which will affect the development of babies.

Therefore, pregnant women and breastfeeding women need to stay away from oil fumes.

"Self-pressing oil" and "stupid pressing oil" low smoke point will easily produce oil smoke

The temperature at which the oil begins to smoke is called the "smoke point". Smoke points are closely related to impurities in oil. No refined "self-pressed oil", "soil pressed oil" and "stupid pressed oil" are called "gross oil" in the food industry. There are many impurities in the crude oil, so the smoke point is relatively low, for example, the smoke point of earth pressed sunflower oil is less than 110 ° C, the smoke point of earth pressed soybean oil and peanut oil is about 160 ° C, and the smoke point of earth pressed sesame oil is relatively good to be close to 180 ° C.

After refining, various impurities such as free fatty acids and lecithin in vegetable oils are almost removed, and the smoke point is greatly improved. Generally speaking, the smoke point of refined vegetable oils is above 230 ° C.

When cooking, it is usually necessary to burn the oil to "70% heat" and "80% heat", and the corresponding oil temperature is roughly 210 ° C and 240 ° C. That is to say, those who have not refined "self-pressed oil", "soil pressed oil" and "stupid pressed oil", basically can not reach the temperature required for stir-frying will smoke, and refined oil will basically not.

To avoid the harm of oil smoke, you can consider the following three

Stir-frying smoke is harmful to health, and this hazard is mainly for people who cook. To avoid the harm of oil smoke, you can consider the following three:

1. Reduce the cooking methods of frying and stir-frying, and use more cooking methods such as stewing and steaming that do not produce oil smoke.

2. If you want to fry and saute, choose highly refined vegetable oil with a smoke point, and do not use "self-pressed oil", "soil pressed oil" and "stupid pressed oil" with a low smoke point.

3. Install a strong range hood, open it before burning oil, and continue to open it for a while after cooking to fully exhaust the oil smoke.