Purple potatoes contain a large number of anthocyanins, turning blue and green is caused by them. Anthocyanin is a water-soluble natural pigment, it is characterized by red in acidity, alkaline usually blue, there may also be purple, green and other transitional colors. If the color is darker, it may appear purple-black.

Most of the northern regions of our country water is weakly alkaline, so when boiling purple potatoes, there will be the phenomenon of water and purple potatoes skin turn green. Wash strawberries blue with alkaline water, purple rice flour with baking soda green is also the role of anthocyanins, which are normal phenomena, discolored food can also still eat.

Expanded information:

1, healthy weight loss: purple potatoes and ordinary sweet potatoes, as rich in starch, vitamins and trace elements, coupled with easy to digest, can be used as a side dish or even staple food to eat. What's more, although purple potatoes are rich in starch, but every 100 grams of fresh purple potatoes contain only 0.2 grams of fat, calories produced by only about 1/3 of the rice, so the purple potatoes are low-fat, low-calorie staple food in the best, if you want to lose weight, eat purple potatoes on the right.

2, prevention of constipation: purple potatoes to prevent constipation effect is more significant, it contains cellulose to water-soluble cellulose-based, water-soluble cellulose in the intestinal tract to absorb water expansion, so that the feces soften and increase the volume of feces, and to promote intestinal peristalsis, play a role in the prevention and treatment of constipation.

3, can prevent cancer eye: purple potatoes are purple food, rich in anthocyanin pigments, and anthocyanins are currently found in the most outstanding natural antioxidants, it also has the role of free radicals. Therefore, purple potatoes as a representative of purple food, is the World Health Organization recommended one of the best cancer prevention fruits and vegetables. Anthocyanins in purple potatoes can fight free radicals on eye irritation, is a natural eye protection food.

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