The mung bean sprouts are placed for too long, and the watercress is easy to turn black, which may be caused by air oxidation. If the mung bean sprouts are only partially black, the rest are still fresh. Generally speaking, eating them has no obvious harm, but the taste may be affected.

However, if the whole mung bean sprout has gone bad, smells bad or has mildew spots, it is not recommended to eat it, because these may lead to food pollution and endanger human health. Therefore, before eating mung bean sprouts, it is best to check carefully to ensure the safety and hygiene of food. In addition, in order to ensure the freshness of food, mung bean sprouts should be cleaned before eating and should not be placed for too long.