Split moong develops an odor in jars primarily due to moisture and the presence of naturally occurring oils that can turn rancid over time, especially if not stored properly.
Split moong, like other legumes, contains a small amount of oil. When exposed to air, light, and especially moisture, these oils can oxidize and become rancid. This rancidity is what causes the unpleasant odor. The presence of even a small amount of moisture in the jar can accelerate this process, creating a favorable environment for mold and bacterial growth, further contributing to the odor. Improperly dried moong before storage, or condensation forming inside the jar due to temperature fluctuations, are common culprits. The type of jar and lid also play a role; airtight containers are essential to minimize exposure to air and moisture.
Before storing split moong, ensure it is completely dry. You can dry roast it lightly in a pan for a few minutes to remove any residual moisture. Let it cool completely before transferring it to an airtight container.