We all know that purple potato is a kind of sweet potato, but it contains a lot of anthocyanins, so it appears purple. In fact, this anthocyanin is a water-soluble pigment, which can be dissolved in water. In the process of boiling purple potato, this pigment will also be dissolved in water. If the water is acidic, it will appear purple-red, while if the water is alkaline, it will appear blue-green, and the tap water we usually use is mostly alkaline, which is why the water for boiling purple potato is blue.

Purple potato contains anthocyanins, which will change color according to the acidity and alkalinity of the environment. If it is acidic, it is purple, neutral environment is purple and alkaline environment is blue. Your problem may be due to the change of acidity and alkalinity of water or the addition of other things when cooking glutinous rice balls. If you want to cook purple, just add a little white vinegar or lemon juice to the water.

Purple sweet potatoes are rich in anthocyanins, which will change color when exposed to acid and alkali, purple when exposed to acid, and blue-green when exposed to alkali. Tap water is generally alkaline, which is normal, so eat with confidence.

Health care function of purple sweet potato;

1, rich in anthocyanins, preventing many diseases, with high health efficacy and no side effects. The color of purple sweet potato comes from anthocyanin, which is a natural and powerful free radical scavenger. A large number of studies have confirmed that anthocyanins have preventive and therapeutic effects on 100 diseases, and their ability to scavenge free radicals is 20 times that of vitamin C and 50 times that of vitamin E. Anthocyanins can scavenge free radicals through the blood-brain barrier, thus protecting brain tissue and reducing the side effects of antibiotics on human body. 　　

2, high content of selenium and zinc, anti-oxidation, cancer prevention. Zinc is also a component or activator of many antioxidant enzymes, which can prevent free radical damage and maintain normal immune function. Zinc can also maintain the stability of cell membrane and reduce toxin absorption and tissue damage. The regulatory function of zinc in tissue metabolism can regulate the synthesis and metabolism of protein, regulate immune function, and regulate hormones, such as participating in the synthesis and release of insulin and the secretion of prostaglandin. Zinc is also an essential factor in DNA synthesis, participating in the division and proliferation of all cells and promoting growth and tissue regeneration.

3, the cellulose content is high, which can promote the digestion of purple sweet potatoes. These substances can increase the volume of feces, promote gastrointestinal peristalsis, clean up the mucus, gas accumulation and putrefaction retained in the intestinal cavity, discharge toxic substances and carcinogens in feces, keep the stool smooth, improve the digestive tract environment, and prevent the occurrence of gastrointestinal diseases. 　　

4, rich in vitamins, bodybuilding, fitness purple sweet potato stem tip leaves are rich in vitamins, protein, trace elements, edible fiber and soluble non-oxidizing substances, which have the functions of weight loss, bodybuilding, fitness and cancer prevention if eaten frequently. 　　

5, rich in potassium and iron, for the body to send oxygen, stable blood pressure.