How To Make Dosa

Troubleshooting · fermentation

Dosa batter not rising? Check these, in this order.

A batter that has not doubled in 24 hours almost always has one of seven problems. They are listed here from most to least common, each with a test that takes under a minute. Work down the list and stop at the first one that fails.

First, is it actually flat?

Fermented batter does not always look dramatic. Before you diagnose anything, check these three signs:

  • Volume: put a strip of tape on the outside of the vessel at the starting level. Doubled means twice the height.
  • Texture: stir it gently with a spoon. A fermented batter is full of small bubbles and feels light, almost spongy.
  • Smell: pleasantly sour, like yogurt. No sourness at all means fermentation has not started.

If it smells sour and has bubbles but has risen only half its height, it has fermented. The batter just could not hold the gas, which points to causes 2, 3 and 4 below.

The seven causes

  1. The kitchen is too cold

    The most common cause by far, especially outside India. The bacteria and yeasts that leaven the batter slow sharply below 24 °C (75 °F) and nearly stop below 18 °C (64 °F). A recipe written in Chennai assumes 30 °C.

    Test · put a thermometer next to the batter for 10 minutes
    Under 24 °C · expect 15–26 hours, not overnight
    Under 20 °C · move it somewhere warm

    The fix, from an oven with the light on to an Instant Pot, is on fermenting dosa batter in a cold kitchen.

  2. The urad dal is old

    Urad dal is what traps the gas. The protein that does this weakens as the dal ages, and dal more than about a year old often will not hold a rise however long it ferments.

    Float testDrop half a teaspoon of freshly ground dal paste into a glass of water. Fresh, well-ground dal floats. If it sinks after thorough grinding, the dal is the problem. Buy a new pack, and check the packing date if it is printed.

    Whole skinned urad dal (sold as gota or whole white urad) usually holds its rise better than split dal.

  3. The dal was ground too little, or too hot

    Dal needs to be ground alone until it is white, fluffy and roughly doubled. Mixer grinders heat the batter; above about 35 °C, the batter starts to lose its ability to rise.

    Wet grinder · 20–25 min for 100 g of dal
    Mixer grinder · bursts of 90 s with 60 s rests, ice-cold water
    Paste temperature · under 30 °C when you finish

  4. Too much water

    A thin batter lets the gas escape as fast as it forms. The combined batter should fall off a ladle in a thick ribbon, not pour like cream. If you need extra water to get the grinder to turn, add it to the rice, not the dal.

    The ratio325 ml of water for 500 g of dry grain (400 g rice, 100 g dal) is the upper limit. Thin the batter only after it has fermented, just before cooking.

  5. The fenugreek is missing

    Fenugreek seeds, soaked with the dal, help the rise and give dosas their colour. 5 g per 500 g of grain is enough. Leaving them out slows fermentation noticeably, especially in cool kitchens.

  6. Too much salt, or added too early in the cold

    Salt slows fermentation. 10 g per 500 g of dry grain (2%) is the working amount. In a kitchen under 22 °C, try mixing the salt in after fermentation rather than before.

  7. The vessel is wrong

    A wide, shallow bowl spreads the rise out so you cannot see it, and a sealed lid can stop it. Use a straight-sided container filled halfway, with the lid resting on top.

Rescuing a flat batter

Do not throw it away.

  • No sourness at all after 24 hours: it has not started. Move it to 28–32 °C and give it 8 more hours.
  • Sour, bubbly, but only a little risen: it has fermented as much as it will. Make rava dosa-style thin dosas or uttapam with it. It will be less crisp but fine to eat.
  • Last resort for lift: stir in 2 g of baking soda per 500 g of batter just before cooking. It adds air but not flavour, so the dosas will taste flat.

How long should dosa batter take to ferment?

It depends on the kitchen temperature: about 22–26 hours at 20 °C (68 °F), 15–18 hours at 24 °C (75 °F), 10–12 hours at 28 °C (82 °F) and 7–8 hours at 32 °C (90 °F). Go by the rise, not the clock.

Can I ferment dosa batter in the oven?

Yes. Put it in the oven with only the light on, which usually holds 27–32 °C. Check the temperature first with a thermometer, because LED oven bulbs give off almost no heat.

Does iodised salt stop dosa batter fermenting?

At normal amounts it makes little difference. The amount of salt matters more than the type: keep it at 2% of the dry grain weight.

Can I use dosa batter that did not rise?

Yes, if it smells pleasantly sour and not rotten. Dosas from it will be thinner and less crisp. If it smells foul or has pink or grey patches, throw it out.

Keep going