When soaking beans, it is a common practice to discard the soaking water and cook the beans in fresh water. Here are a few reasons for this:
Removal of Indigestible Compounds: Beans contain complex carbohydrates called oligosaccharides that our bodies have difficulty digesting. These compounds can cause gas and bloating. Soaking beans helps to break down and leach out some of these indigestible compounds, making the beans easier to digest. Discarding the soaking water removes some of these substances, reducing the likelihood of digestive discomfort.
Removal of Phytic Acid: Beans also contain phytic acid, which is an anti-nutrient that can interfere with the absorption of minerals such as iron, zinc, and calcium. Soaking beans can help reduce the levels of phytic acid. Discarding the soaking water removes some of the phytic acid, allowing for better nutrient absorption when the beans are cooked.
Reduction of Flatulence: Soaking and discarding the water can help reduce the gas-producing properties of beans. While it doesn't eliminate the issue entirely, it can help minimize gas formation by removing some of the substances responsible for it.
Flavor Improvement: Some people believe that soaking and discarding the soaking water can improve the flavor and texture of cooked beans. It helps remove any off-flavors or impurities that may be present in the beans.
However, it's important to note that soaking beans is not always necessary. Some varieties of beans, like lentils and split peas, cook relatively quickly and don't require soaking. Additionally, pre-soaked canned beans can be used directly without discarding the liquid since they have already undergone a cooking process.
If you do choose to soak beans, it's recommended to soak them for several hours or overnight in plenty of water, and then rinse them well before cooking. This process helps ensure that you start with clean, hydrated beans for cooking.