Yes, pakora batter can be made ahead of time, but it's best used within a few hours to maintain its leavening and prevent it from becoming too dense.
Making pakora batter ahead of time can be a convenient way to streamline the cooking process. The key is understanding how the ingredients interact over time. When you mix gram flour (besan) with water and spices, gluten development begins, albeit less than with wheat flour. Letting the batter rest for a short period (30 minutes to an hour) allows the gluten to relax, resulting in a slightly lighter pakora. However, if the batter sits for too long (several hours or overnight), the gluten can over-develop, leading to a denser, chewier pakora. Additionally, if you've added any leavening agents like baking soda or baking powder, their effectiveness diminishes over time as they react with the moisture in the batter. Therefore, it's best to prepare the batter a few hours before frying and store it in the refrigerator. Before frying, give it a good stir and add a tablespoon or two of water if it has thickened too much.
If you must make the batter further in advance, consider adding the leavening agent (baking soda or baking powder) just before frying to ensure maximum lift and a light, crispy texture.