@Dear parents, "reused cooking oil" is toxic and carcinogenic, so don't use it to cook!

The Chinese New Year is a time for families to gather together and enjoy delicious food. Fried meatballs, fried hairtail, fried rice cakes and other delicacies are indispensable.

When making these delicacies, a lot of cooking oil is often used. Frugal parents will save the oil used for frying and use it again when cooking.

However, if the oil used for frying food is reused for repeated high-temperature cooking, it is called "recycled oil". Eating such oil frequently can cause great harm to the body.

What are the hazards of “recycled cooking oil”?

Produce harmful substances

Repeated heating of cooking oil at high temperatures will produce harmful substances, such as carcinogens acrylamide and polycyclic aromatic hydrocarbons, etc. These substances can cause potential harm to human health and increase the risk of diseases such as cancer.

Low nutritional value

Repeated heating of cooking oil will lead to the loss of nutrients, such as vitamin E. Long-term consumption of oils with reduced nutritional value may affect the body's nutritional intake, leading to malnutrition or health problems.

Increased risk of cardiovascular disease

Repeated use of cooking oil can easily oxidize the unsaturated fatty acids in it and form trans fatty acids. Trans fatty acids are a type of fat that is not good for health and is related to the occurrence of cardiovascular disease and other health problems, increasing the risk of cardiovascular disease, such as high blood pressure and arteriosclerosis.

Causes digestive problems

After being heated and used multiple times, edible oil may produce fat decomposition products and substances that are difficult to digest. Long-term consumption may cause indigestion, gastrointestinal discomfort and other problems.

Why does oil deteriorate after repeated use?

Oxidation reaction occurs

When cooking oil comes into contact with air at high temperature, oxidation reaction will occur, producing harmful substances such as oxidized lipids and free radicals. These oxidation products will change the chemical structure and properties of the oil, causing the oil to deteriorate.

Effects of moisture and impurities

During repeated use, oil is often affected by moisture, residues and other impurities in the food. These moisture and impurities will accelerate the oxidation of the oil, causing the oil to deteriorate faster.

High temperature damage

Repeated heating will cause the oil to be continuously exposed to high temperatures, destroying the fatty acids and other components in the oil and producing harmful substances. High temperature damage will also reduce the smoke point of the oil, making it easy to produce smoke and odor, which will affect the quality of the oil.

Microbial contamination

Used oil may be contaminated with microorganisms and bacteria, especially when the temperature of the oil in the food is not high enough or it is not stored properly. The microorganisms will multiply rapidly and produce harmful metabolites, causing the oil to deteriorate.

Lighting Effect

Exposure of oil to sunlight will accelerate oxidation and increase the degree of deterioration of the oil. Therefore, if the oil is exposed to light for a long time, the quality of the oil will also deteriorate.

In summary, the main reason for the deterioration of oil due to repeated frying is the combined effect of oxidation, the influence of moisture and impurities, high temperature damage, microbial contamination and light effects. Therefore, in order to maintain the quality and health of the oil, it is recommended to avoid repeated use of cooking oil, replace it with new oil in time, and store it properly.

Eat less fried skewers and chicken cutlets from roadside stalls!

In addition to not reusing oil that has been used for repeated frying at home, we should also pay attention to the use of oil in roadside food stalls when consuming food outside.

In order to save costs, many roadside fried skewers stalls and chicken chop snack bars often reuse the oil many times, sometimes even without changing it for a long time.

But why do fried skewers and chicken steaks from roadside stalls taste more delicious?

This is mainly because the stall owners have done some special processing in the oil. They often add some special ingredients or spices to the oil, such as pepper, onion, ginger, etc., to enhance the aroma and taste of the oil, making the fried skewers more fragrant. More importantly, with repeated use, some aroma and seasonings of the ingredients may remain in the oil. These ingredients will gradually concentrate over time, making the fried food more fragrant and unforgettable.

However, despite their appealing taste, we still need to be wary of their potential health effects.

Long-term high-temperature heating and repeated use of oil will lead to the continuous accumulation of harmful substances in the oil, which will significantly reduce the quality of the oil and even cause it to deteriorate. Especially in the case of poor environmental hygiene conditions, the oil is also susceptible to microbial contamination, increasing the health risks that may be caused after consumption.

Therefore, although fried skewers are delicious, you should eat as little as possible to prevent "diseases from the mouth".

References:

[1] Ge Jiachen, Li Pengyan, Deng Ruijue, et al. Evolution and formation mechanism of aldehydes in high oleic oils during storage and heating [J/OL]. China Oils and Fats, 1-12 [2024-02-09]

[2] Jiang Xin. Formation mechanism of aldehydes and ketones during thermal processing of edible oils[D]. Hainan University, 2021. DOI: 10.27073/d.cnki.ghadu.2019.000834.

[3] Zhang Qing. Study on the changes of characteristic physical and chemical properties of soybean oil in different frying systems[D]. China Agricultural University, 2014.

[4] Li Jing, Wang Chengtao, Liu Guorong, et al. Rapid detection of frying oil quality by electronic nose[J]. Food Science, 2013, 34(08): 236-239.

[5] Mu Zhao, Liu Yuanfa, Wang Xingguo. Chromatographic analysis of polar substances after frying oil heating[J]. Food Industry Science and Technology, 2008(09):118-121.DOI:10.13386/j.issn1002-0306.2008.09.025.

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Author: Xiaojuan is not a volume

Master of Food Science and Engineering, Henan University of Technology