There are three ways to soak beans before cooking them, whether to allow them to cook properly later, to remove undesirable substances and dirt from their surface, or both. The most classic method used to soak beans is simply to place the beans in a bowl or pan made from a non-reactive material and cover them in cold water, allowing them to soak for several hours or overnight, until they soften. The other two methods used to soak beans involve cooking the beans briefly in boiling water and then allowing them to soak in the warm water for an hour or more. Both methods have been known to work well, although the age and type of beans can drastically affect the amount of soaking and cooking time they will need. It is important to wash the beans thoroughly after they soak and to cook them in a fresh pot of water, because the soaking water will be full of particles of materials that should not be eaten and might affect the taste of the finished beans.
The simplest but most time-consuming way to soak beans is to cover them in cold water and allow them to sit for as long as necessary to make them soft. This method works well and has the benefit of completely removing compounds such as phytic acid, which can prevent mineral absorption, and oligosaccharides, which are sugars that are not properly digested and can cause gas. The slow soaking also gives the beans a chance to absorb the liquid gradually, preventing any chance of the skins splitting or the beans exploding. Additionally, any type of dirt or other residue that is left on the surface from processing will be removed and pass into the water. It is important in some instances to prevent the beans from soaking for too long in warm water when the air is very warm, because there is a slight chance the beans could start to ferment or sprout.
A faster method that can be used to soak beans involves placing the beans in a pot and covering them in cold water. The pan is then heated until the water boils, and the beans are allowed to cook for a few minutes. After boiling, the pan is taken off the heat and the beans are allowed to soak for a few hours. Beans that are prepared in this way do not need to soak overnight but might have a firmer texture when they are cooked. A similar method involves the same process but uses a pressure cooker instead of a simple pot and the pressure is allowed to reduce naturally before the beans are removed, reducing the amount of time the beans need to soak.
No matter which method is used to soak beans, the water that was used should be disposed of when the soaking is done. All the materials in and on the beans will be in the water and could affect the taste. The beans also should be washed after their soaking to remove any materials the water might have left on their surface. When it is time to cook the beans, fresh cold water should be used in the cooking pan.