Fermented dosa batter should be stored airtight in the refrigerator to prevent further fermentation and maintain its desired consistency and flavor.
Fermentation is a process where microorganisms, like yeast and bacteria, convert carbohydrates into acids and gases. In dosa batter, this process creates the characteristic sour flavor and airy texture. Once the batter has fermented to your liking, you want to slow down or stop the fermentation process to prevent it from becoming overly sour or developing an undesirable texture. Storing the batter in an airtight container in the refrigerator significantly slows down the activity of these microorganisms. The cold temperature reduces their metabolic rate, and the airtight seal limits the oxygen available, further inhibiting their growth and activity. If the batter is stored loosely, it will continue to ferment at a faster rate, potentially leading to a sour, thin, and unusable batter. Therefore, transferring the fermented dosa batter to an airtight container and refrigerating it is crucial for preserving its quality and extending its shelf life.
When storing dosa batter, leave some headspace in the airtight container as the batter may continue to expand slightly due to residual fermentation. This prevents the container from bursting or leaking.