When cooking dal (lentils), the foam that forms on the top is a result of the starch and proteins present in the lentils. This phenomenon is known as "scum" or "foam formation."
The foam occurs due to the release of soluble proteins and starches from the dal as it cooks. These substances interact with heat and water, causing them to denature and form bubbles of trapped air. As the water boils, the foam rises to the surface.
The foam is harmless and can be skimmed off the top of the cooking liquid if desired. Some people prefer to remove it as it can make the dal look less visually appealing. Additionally, removing the foam can help prevent the liquid from boiling over during the cooking process.
It's important to note that the formation of foam varies depending on the type of dal being cooked. Lentils with higher starch content tend to produce more foam. To minimize foam formation, you can try the following tips:
Pre-soaking: Soaking the dal for a few hours or overnight can help reduce the foam formation.
Adding oil: Adding a small amount of oil (such as vegetable oil or ghee) to the cooking water can help prevent excessive foam.
Gentle stirring: Stirring the dal gently during cooking can help break up the foam and prevent it from overflowing.
By employing these techniques, you can control the foam formation to some extent while cooking dal.