The prepared mung beans must be cleaned, and then put into a pot and soaked in cold water for 20 hours. If it is made in winter, it is best to soak it in warm water, and the amount of water must be twice that of mung beans. When the soaked mung beans are ground by hand, the bean skin can be ground off. At this time, we add some water to these soaked mung beans and grind them into fine pulp. What we need to do next is filtering, pouring all the ground fine pulp into gauze, filtering out some impurities and bean dregs, and putting these filtered liquids aside for later use.
The filtered liquid can be left for several hours, and then the upper slurry is poured into the container. You can choose a glass container and leave it for 12 hours so that these liquids can ferment. If it is made in winter, the fermentation time will be longer, at least 24 hours, because the temperature in winter is lower and the fermentation speed will be slower. After a period of precipitation, the liquid below is thicker, which is actually raw bean juice. There will be some froth and mud on it. All these froth and pulp should be removed, and then the raw bean juice inside should be scooped out.
Find a pot and add a proper amount of cold water to it, not too much. After the fire boils, pour in the raw bean juice and continue to cook over high fire. After boiling, change it to low heat, and then you can take it out. This is actually the finished bean juice. There are also some tips when cooking bean juice. The first is to master the ratio of mung beans to water, and the second is not to cook bean juice. The fire should not be too big, otherwise it will easily turn into old tofu.