Generally 15-20 minutes. To determine whether the purple potatoes are cooked, you can use chopsticks to poke, if it is easy to poke in that means it is cooked. Otherwise, keep steaming.

Purple potatoes have a good antioxidant effect, often eat purple potatoes, can be anti-aging, improve skin texture, endocrine regulation effect. Purple potatoes are rich in fiber, can promote gastrointestinal peristalsis, clean up the intestinal lumen stagnant mucus, stagnant gas and corruption, eliminate toxic substances in the feces, to maintain smooth stools, improve the environment of the digestive tract, to prevent gastrointestinal diseases.

Expanded Information:

Purple potatoes are high in carbohydrates, so it's best not to consume more than 200 grams at a time.

Purple potatoes should not be eaten on an empty stomach, it is easy to feel heartburn, it is recommended that can be eaten with food rich in fat protein, such as eggs, or with other vegetables.

Sprouted purple potatoes have toxins. Sprouting purple potatoes, starch and sugar will be degraded into nutrients needed for sprouting, the degradation process of purple potatoes will release some toxins.

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