"gutter oil" is also called "crude oil" by people in the industry. There are three main sources: one is the oil dumped with leftovers in swill, that is, hogwash fat; The second is the oil used to fry food, that is, the re-fried oil; The third is the oil bottom of cooking and the oil discharged into the sewer with the brush pot water. In addition, there is a kind of "new gutter oil", which is different from the traditional gutter oil. It is mainly produced by simply processing and refining inferior, expired and corrupt animal skins, meat and internal organs.

According to He Dongping, a professor at the School of Food Science and Engineering, Wuhan University of Technology, at present, there are 2-3 million tons of waste oil returning to the table every year in China. According to the proportion, for every 11 meals, there may be 1 meals that meet with gutter oil. Once the waste oil flows into the table, there will be endless troubles. Especially for the "new gutter oil", most of the rotten animals themselves contain germs. After being bitten by mosquitoes and flies and rancid, they contain a lot of toxic ingredients, which directly threaten human health.

The main hazard of "gutter oil" is aflatoxin, which is a strong carcinogen, and its toxicity is about 11 times that of potassium cyanide and about 111 times that of arsenic.

The biggest harm of gutter oil lies not only in the carcinogenic aflatoxin, but also in repeated heating and oxidation. Liquid vegetable oil is not heat-resistant, and the temperature of cooking and frying can be as high as 161℃-311℃. When oil is heated, trans-isomerization, thermal oxidation, thermal cracking, cyclization, etherification, polymerization and other reactions will occur. After cooking oil is repeatedly heated by frying, roasting, frying and frying, polycyclic aromatic hydrocarbons (PAHs) will be produced, which have a strong carcinogenic and DNA mutation hazard to adults and a strong teratogenic effect on fetuses.

refined waste oil is almost pure, which is similar to the principle of refining gasoline from crude oil. At present, no country in the world can accurately detect gutter oil, because gutter oil itself has not found a detectable feature. Food poisoning is basically not a problem of gutter oil, but caused by bacteria. We just can't stand it in ethics and law, so safety will be fine. I hope that regulators will keep their eyes open and protect the table of the people.