This is the browning of starch. On the one hand, sweet potato contains oxidase, which will change color when exposed to oxygen. On the other hand, starch will turn black when exposed to iron, so it will appear green. However, this discoloration does not affect eating. It is normal that porridge cooked with white sweet potatoes will show a faint green color. If you make sure that the ingredients are not contaminated and do not rot before cooking, there should be no problem to eat.

after the skin of sweet potato is peeled off, the water will be lost, the sweet potato will become dry, and the sweet potato exposed to the air will be oxidized. If the sweet potato is cut into small pieces, the water will be greatly lost, the exposed area will increase, and the oxidized part will naturally increase.

Extended information:

Precautions:

1. It is not advisable to eat raw sweet potatoes: because the cell membrane in raw sweet potatoes has not been destroyed by high temperature, starch is difficult to digest.

2. Don't eat too much at a time: Because sweet potatoes contain gasification enzymes, after eating too much, it is easy to produce a lot of carbon dioxide gas in the gastrointestinal tract, causing discomfort such as abdominal distension, heartburn, burping, acid regurgitation and exhaust. Can be eaten with Chinese cabbage and radish.

3. It is not suitable to eat with persimmon: because the sugar in sweet potato is fermented in the stomach, it will increase the secretion of gastric acid, and react with tannin and pectin in persimmon to precipitate and condense, resulting in lumps.

4. Don't eat sweet potatoes with black spots: sweet potatoes with brown or black spots are polluted by black spot bacteria. The toxin discharged by Alternaria alternata contains phanone and sweet potato ketone alcohol, which can cause poisoning after people eat it.

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