Yes, appam batter can be stored in the refrigerator after fermenting to slow down the fermentation process and preserve its quality for later use. It's best to use it within 2-3 days for optimal results.
Once your appam batter has fermented to the desired consistency, the fermentation process will continue if left at room temperature. This can lead to an overly sour taste and a batter that is too airy, resulting in appams that are difficult to cook properly. Refrigerating the batter significantly slows down the activity of the yeast and bacteria responsible for fermentation. To store the batter, transfer it to an airtight container. When you're ready to make appams, take the batter out of the refrigerator and let it sit at room temperature for about 30 minutes to an hour. This will allow it to warm up slightly and regain some of its original consistency. You may need to gently stir the batter before using it. Keep in mind that the batter will continue to ferment slowly in the refrigerator, so it's best to use it within 2-3 days for the best flavor and texture.
If you find that your refrigerated appam batter has become too thick after being stored, add a tablespoon or two of water to achieve the desired consistency before cooking. Mix gently to avoid over-stirring.