Question

Foam accumulates on a the surface of dal kept for a long time in summer. Why?

Answer 1

There are two theories regarding the appearance of foam when
lentils are cooked.



1. Saponins - Lentils contain glycosides called Saponins. When they come in contact with water, they get dissolved. These saponins are substances which have properties similar to soap, which when boiled trap the air in them forming a foam.



2. Protein Denaturation - Another theory is that the proteins in the lentils are released when boiled. The air particles which hold more dissolved gases than the hot water leech out forming a foam on the surface.



Since it is harmful to
consume any denatured protein or a substance whose natural structure has been
damaged, it is advisable to remove the foam from the surface before consuming
them