Soaked dals should be stored covered in the refrigerator to prevent contamination and maintain moisture.
When you soak dals, you're essentially rehydrating them and starting the germination process. This makes them more susceptible to bacterial growth and absorbing odors from the surrounding environment. Storing them uncovered allows airborne contaminants to settle in, potentially leading to spoilage. Covering the soaked dals creates a barrier against these contaminants and helps to retain the moisture necessary for proper rehydration. It's best to use an airtight container or cover the bowl tightly with plastic wrap. Make sure to refrigerate the soaked dals promptly, as room temperature encourages bacterial growth. Change the soaking water at least once during the soaking period to further reduce the risk of spoilage.
If you're soaking dals for an extended period (more than 8 hours), change the water every 4-6 hours to prevent fermentation and maintain a fresh taste.