Vinegar is generally *not* added to idli or dosa batter. It can inhibit fermentation and negatively impact the texture and flavor.
Idli and dosa batters rely on a natural fermentation process driven by microorganisms like bacteria and yeast. These microorganisms consume the carbohydrates in the rice and lentils, producing lactic acid and carbon dioxide. The lactic acid contributes to the characteristic sour taste, while the carbon dioxide creates air pockets, resulting in a light and fluffy texture.
Vinegar, being an acidic substance (acetic acid), can interfere with this delicate fermentation process. Adding vinegar can:
Instead of vinegar, the fermentation process itself should provide the necessary sourness and leavening. Factors like temperature, humidity, and the quality of ingredients play a significant role in successful fermentation.
If your idli or dosa batter isn't fermenting properly, try placing it in a warmer location (around 80-85°F or 27-29°C). A slightly warmer environment encourages microbial activity and promotes fermentation. Avoid adding vinegar as a shortcut.