Should You Discard the Soaking Water from Beans?

During soaking, legumes do not only absorb water; they also release some of their compounds into it. This water collects compounds dissolved from the skins, dust and soil residue on the surface, and some of the sugars associated with gas production from legumes. The color of the water shows this: water that starts clear becomes cloudy and foamy within a few hours. This water carries away what the legumes have released. So if you use a clear soaking container, you can watch how cloudy the water gets. The same cloudiness can also be seen in the thin foam that collects on the water’s surface.

That is why you discard the soaking water from dried beans and chickpeas. Put the legumes in a colander, rinse them under running water for a while, and add them to the pot with fresh water. Check the rinse visually and continue until the water running through the colander is clear. This step cleans up the flavor of the dish, reduces foam during cooking, and lowers the risk of the pot boiling over. Stir the legumes by hand while rinsing so those at the bottom also come into contact with the running water.

For a long soak, you can change the water once. During a soak lasting 8 to 12 hours, discarding the water and replacing it around the midpoint reduces cloudiness and prevents the legumes from souring in hot weather. This is not necessary if you put the soaking container in the refrigerator. In all cases, choose a wide container and add enough water to cover the legumes by a few finger-widths. On hot summer days, soak them directly in the refrigerator; legumes left on the counter may sour. Cover the container, too; water left uncovered collects dust and develops a film on its surface.

Lectins must also be considered in dried beans; levels can be particularly high in raw or undercooked red kidney beans. Changing the water alone is not enough; the FDA recommends soaking the beans for at least 5 hours, discarding that water, and boiling them in fresh water for at least 30 minutes. Do not cook raw dried red kidney beans directly in a slow cooker; do not add the soaking water to the dish.

There are exceptions. Red lentils, mung beans, and dried peas are not soaked, so no soaking water is produced; simply rinse them and cook them directly. Some recipes keep black-bean soaking water to preserve the color, but that is a matter of preference. With dried beans, there is no choice: the water is always discarded. Even in recipes where color matters, this exception does not apply to dried beans; change the water. Any recipe that keeps soaking water is referring to other legumes, not dried beans.