Add salt before or after grinding batter?

Should you add salt before or after grinding batter for idli, vadas and chutneys? Let’s find out.

I tested this theory out by grinding 2 identical batches of soaked urad dal and rice, both with and without salt. The conventional wisdom is that salt draws out the water and makes the batter watery. That’s exactly what happened here. Both the batters with added salt ended up being more watery in consistency.

Why is this happening? The soaked urad dal and rice are swollen and plump with water. Because water molecules are polar, if they were trapped inside, they would have formed tight connections with the protein (also charged) and formed a thick batter.

But what happens if you add salt before grinding? This is due to the principle of osmosis. Nature hates an imbalance when there is higher salt concentration on one side of the cell and water on the other. Let’s look at an everyday example to understand this - if you salt your chopped veggies, it will start leaking water almost immediately due to osmosis. Like a pied piper, the salt leads the water towards itself and away from other ingredients.

Adding salt before grinding will release the "bound water," where water molecules are tightly attached to other substances due to their polar nature, making them less mobile than free water. Without the polar water molecules, you cannot get strong, interlocking connections. Hence the batter becomes watery.

So, should you add salt before or after? If the viscosity of the batter matters - which it does for idli and vada batters, then add salt at the end. If you are making a watery chutney using a powerful blender, then it does not matter when you add the salt.