Do you continue to cook with the oil that has been used for frying? It will pose a health hazard!

In daily life

Some friends want to save money

Reuse leftover oil from frying food

But this is not scientific

Zhu Yi, associate professor at the College of Food Science and Nutritional Engineering of China Agricultural University, introduced that during the repeated frying process of edible oil, hundreds or even thousands of very complex oxidized substances will be produced, some of which are harmful to the human body.

Today we will study:

What harmful substances will be produced by repeated heating of cooking oil?

What other oils are not recommended?

How to eat cooking oil in a healthy way?

The dangers of repeatedly heating oil

Many families have the habit of using the remaining oil to fry food or cook dishes after frying. However , repeated frying of oil can easily produce carcinogens, such as benzopyrene, acrylamide, heterocyclic amines, etc. Long-term consumption will pose a health hazard .

In addition, repeated use of cooking oil will produce a large amount of trans fatty acids, which will not only cause weight gain, but also increase the probability of cardiovascular disease, Alzheimer's disease, etc.

The chemical composition of edible oil is mainly triglyceride. After hydrolysis, triglyceride becomes glycerol (about 10%) and fatty acids (about 90%). When frying, the temperature of edible oil rises to 180-200℃. Under high temperature, edible oil will "deteriorate".

1. Oxidation reaction occurs

Oxidation reactions produce many volatile substances, including saturated and unsaturated aldehydes and ketones, polycyclic aromatic hydrocarbons, etc. Many of them are volatile and toxic substances. In particular, acrolein is the most dangerous inducer of lung cancer in oil smoke.

2. Hydrolysis reaction occurs

Fried foods release water at high temperatures, which causes the edible oil to hydrolyze and produce fatty acids, causing the edible oil to quickly become rancid and spoil.

3. Isomerization reaction occurs

Under high temperature, cis fatty acids in edible oil are isomerized into trans fatty acids. Trans fatty acids enter the human body and can cause chronic diseases such as obesity, heart disease, diabetes, and Alzheimer's disease.

These types of oils are not recommended

1. Informal “self-pressed oil”

Many families like to eat self-pressed oil, thinking that this kind of cooking oil will have a stronger taste and more fragrant taste. In fact, some self-pressed oils have safety risks.

Because "earth-pressed" edible oils are not refined and impurities are removed, they contain more impurities that are not suitable for human consumption and are more likely to deteriorate. Therefore, it is recommended that consumers try to buy edible oils produced by regular manufacturers, which is healthier.

2. Oil that has been opened for more than 3 months

Many people think that no matter how long the cooking oil has been opened, it can be eaten as long as it is within the shelf life. In fact, this perception is wrong.

Although the cooking oil has not exceeded its shelf life, if it is opened for too long, the risk of the oil being infected with mold will increase. Moreover, if it is not properly sealed, the oil will come into contact with the oxygen in the air, an oxidation reaction will occur, and some oxidation products will be produced.

Eating cooking oil that contains excessive microorganisms, aflatoxins, and some oxidation products can easily cause poisoning reactions such as nausea, vomiting, and diarrhea , and in severe cases, it may be life-threatening. Therefore, try not to eat cooking oil that has been opened for more than 3 months. You can usually buy small bottles of oil.

Healthy Oil

Too much fat can lead to obesity, high blood pressure, high blood lipids, etc. In fact, some small changes in cooking can help you reduce oil.

1. Use blanching instead of frying

You can change the process of frying to blanching, use boiling water to quickly blanch the meat, and then add the vegetables to stir-fry. Because meat is rich in fat, as long as it is heated quickly, the taste will be very good. Moreover, after blanching, there is a layer of water on the surface of the ingredients, which isolates the penetration of oil and makes the dishes much fresher.

2. Steam or dry-fry the rapeseed first

For vegetables like eggplant that absorb a lot of oil, in order to avoid consuming too much oil, you can steam the eggplant before cooking; or when stir-frying the eggplant, do not add oil first, but stir-fry it over low heat, and wait until the moisture in the eggplant is fried away and the eggplant flesh becomes soft, then add oil to cook.

3. Stir-fry the meat with higher fat content first

For meats with high fat content such as streaky pork and fatty beef, you can stir-fry the meat for two or three minutes to allow the fat in the meat to fully release, and then add other ingredients to stir-fry. This method is similar to the traditional method of refining lard, which saves oil and is not greasy.

4. Marinate the meat before frying

We can achieve the effect of enhancing the flavor and taste of ingredients by marinating them in advance, so that the dishes will be fragrant even with little oil. In addition, when steaming or stewing meat, add some shiitake mushrooms to enhance the flavor, and add some cumin, fennel, and pepper powder before grilling fish. Even if you use half the oil, the taste will still be fragrant.

5. Control the oil before serving

Don't rush to serve the fried dishes. Place the pan at an angle for two or three minutes to allow the oil in the dishes to flow out before serving. Vegetables such as green peppers, beans, water chestnuts, and lettuce absorb less oil. This method can effectively prevent food from being soaked in oil and can also help us reduce fat intake without realizing it.