Purple potatoes contain a lot of anthocyanins, purple potato soup turns green, because anthocyanins are an unstable water-soluble pigment, will change color because of the degree of acidity and alkalinity, that is to say, when the anthocyanins encountered in acidity will become red; encountered in alkalinity will become green, alkaline weaker will become blue; neutral will remain the original purple.

This phenomenon is the reason for the water, because different regions of the tap water acidity and alkalinity is different, so it will also affect the simmering out of the color of purple potato soup.

Expanded:

Purple potato nutritional value

1, antioxidant "strength". Japanese scholars Ikuo Suda and others compared the free radical scavenging effect of sweet potatoes of different flesh colors, and found that compared with white, yellow and orange flesh sweet potatoes, purple potatoes have the strongest ability, and it is the anthocyanins that play an important role.

2, regulating intestinal flora "new bear". Research has found that anthocyanins in purple potatoes can change the composition of microorganisms in the colon, significantly increasing the intestinal bifidobacteria, lactobacilli and enterococci and other "good bacteria". Researchers believe that consumption of anthocyanin-rich purple potatoes may be beneficial to the gut microbial environment and human health.

3, vision protection "potential stock". When it comes to the protective effect of anthocyanins on eyesight, people can easily associate them with blueberries. Researchers have found that anthocyanins in purple potatoes have the same effect on the growth of retinal pigment epithelial cells, suggesting that it may also have a potential role in the protection of eyesight. Moreover, both in terms of price and anthocyanin content, purple potatoes are more cost-effective and a good choice.

People's Daily News - Why is soup made from purple potatoes green?

People's Daily Online-Purple potato nutrition is not simple