The shallots bought by Chongqing citizens have a layer of blue. What is this?

Onion, ginger and garlic can be regarded as the three main ingredients in the seasoning industry. If the food you want to cook loves essence and all three are indispensable, what are these blue substances? Can such onions still be eaten?

When the staff of a restaurant was selecting vegetables, they found that there were many blue substances on the outermost leaves of onion. The restaurant owner said I don't know what it is, and neither do I. The reporter said, are you nervous when you see a blue substance on the onion? The owner of the restaurant said it would be a little nervous, so we soaked them in water and washed them with clean water.

After wiping the onion with a wet paper towel, the reporter found that there would be light blue marks on the white paper towel. Onions are used in restaurants every day, and the employee who picks vegetables said that this situation can often be seen. Many businessmen and citizens selling vegetables said that they would see this kind of onion on weekdays. Some vegetable vendors say that we generally don't choose that kind of onion because it can't be sold and it seems to be drugged.

The reporter went to the nearby vegetable market and bought a small amount of onions at three stalls. A small amount of blue substance was also found on the onion head of a bag of onions. Feng Shuangqing, a professor of food science at China Agricultural University, said that in order to prevent vegetable diseases, some inorganic fungicides and pesticides, namely copper sulfate, are often used. After use, copper sulfate will exist in leaves, such as gaps in onion leaves. Experts say that copper sulfate is a common pesticide, and it is also very convenient to clean copper sulfate, so people don't have to worry when buying onions with blue substances. It's just copper sulfate. Copper sulfate is blue due to copper ions and is easily soluble in water. If it is used by the human body, it will have no effect. After buying it back, the public only needs to wash the vegetables with blue substances carefully.

Food safety has always been a widespread concern of people, so we must pay attention to food safety when eating on weekdays.