Just soak for about an hour and a half. It is necessary to peel the mung bean dumplings. The peeling method is as follows: Wash the mung bean, put it in a pot, add appropriate amount of water, heat it until it boils, and soak it for about ten minutes. You can peel the mung bean by rubbing it with your hands, and then wash it with water to separate the skins. Purchase of mung beans: distinguish whether mung beans are fresh or not. When selecting mung beans, we must pay attention to selecting mung beans without mildew, insects and deterioration. Fresh mung beans should be bright green, and old mung beans will turn yellow. Distinguish whether mung beans are polluted. To see whether mung beans are polluted, one is to see whether mung beans are dry and wrinkled, and the other is to see whether mung beans have irritating chemical odor.