Potatoes turning green is a common phenomenon in life. As for the green potatoes, it is often said that they can't be eaten when they turn green. When the potato skin turns green, it will produce a toxin called solanine, which will be poisoned if eaten. For this statement, some people think that it is really inedible, while others think that if the green area is small, it can still be eaten. To this end, the reporter of CCTV's "Is it true" column came to the potato crop research institute of Yunnan Agricultural University, an authoritative potato crop testing institution, to verify with experts.

Guo Huachun, a post expert of national potato system and director of potato crops research institute of Yunnan Agricultural University, explained: "Solanum nigrum, also called glycoside alkaloid, is a secondary metabolite existing in potato plants. The content in flowers is the highest, followed by stems and leaves, and then in tubers, but the content is relatively low. According to the national variety approval standards, the content of more than 20 mg per 100 grams may be toxic to people and animals. "

Experts tell us that Solanum nigrum is a kind of substance with bitter taste, which mainly exists in the flowers and leaves of potato plants and can play a role in preventing pests. However, the content of solanine in potato pieces is very small, so it is usually safe for us to eat potatoes. However, if the content of solanine in potato pieces exceeds 20mg/ 100g, it will be harmful to human health.

Then, will the solanine content exceed the standard after the potato turns green? The reporter decided to test the solanine content of green potatoes. The reporter selected a small part of green potatoes as the No.1 sample, and a large area of green potatoes as the No.2 sample, and took off the green skin with a peeler for testing.

After testing, the content of solanine in the green epidermis of sample No.1 was 34. 12mg/ 100g. The content of solanine in the green epidermis of the second sample is112.56 mg/100g. From this point of view, although the green areas of the two samples of potatoes are different, the content of solanine in the epidermis exceeds the limit, which means that the epidermis is inedible. However, when we eat potatoes, we usually peel them first. Then, after peeling off the skin, can potatoes be eaten? This time, the reporter used a peeler to sample the outermost cortex. Then cut the potato with a horizontal knife and sample the central part of the potato. The content of solanine was detected in the cortex and center of the sample respectively.

After testing, the content of solanine in the green cortex of sample No.1 was 23.36mg/ 100g, and that in the green cortex of sample No.2 was 27. 12mg/ 100g. That is to say, after cutting off the green epidermis, the content of solanine in the slightly green cortex has decreased, but it is still higher than the edible amount.

So there is no green central part at all, and what is the content of solanine? After testing, the content of solanine in the central part of sample No.1 was 4.85mg/ 100g, and that in the central part of sample No.2 was 7.5 1mg/ 100g, both of which were far below the limit of 20mg/ 100g. So does this mean that potatoes can be eaten after cutting off the green skin and green cortex?

Guo Huachun said: "Without the green part, the content of solanine should be relatively low and safe, so it is edible to remove the green part."

In potato tubers, solanin itself is mainly concentrated in the epidermis. However, experts also reminded that if potatoes turn green seriously and penetrate deep into the interior, it is best not to eat them. For some potatoes that turn green, we can cut off all the green parts before eating.

But why is the content of solanine in the green part high? Is it because Solanum nigrum is green in potatoes?

Guo Huachun added: "If it turns green, it is chlorophyll, not solanine, but we see that the greening of potatoes is highly correlated with the increase of solanine content. It is influenced by light and then synthesized in situ."

According to the Life Times, He Hongju, director of the Nutrition Quality Laboratory of the National Vegetable Engineering Technology Research Center, once reminded the public that solanine is the most abundant in potato skins that are green or sprout in the sun. Some people are too lazy to peel potatoes, or they don't pay attention to the potato skin turning green or sprouting, so even if cooked, solanine will still remain in the potato skin. Generally speaking, potatoes with little germination can be eaten by thoroughly digging out the buds and the parts around the bud eyes and removing the green parts. If the green area of potatoes is large and there are many sprouting parts, they should be thrown away. It is best to soak potatoes in water for a while after cutting, and pour some vinegar when cooking to avoid poisoning.

He Li, director of the Science and Technology Department of the Institute of Nutrition and Health, China Center for Disease Control and Prevention, also taught you three ways to identify refurbished old potatoes: First, look at the holes, and be careful with potatoes with deep holes; The second is to pinch the meat, and hard potatoes can't be bought; The third is to rub the skin, and potatoes that don't peel off are also more dangerous.

It seems that when buying potatoes, it is best not to buy green potatoes, and when storing potatoes, we must also pay attention to avoiding light. Because everyone's physique is different, if the potatoes at home turn green, if you are really not sure, you should throw them away. (Xiao Jinbo Yang Sixuan finishing)