A. As with most foods, the nose knows. If your flour smells rancid and sour, throw it out — it affects the flavor of what you make it, and the last thing you want to do is suffer from a hard-earned carb instead of enjoying it. And of course, if you find weevils, larvae, moths or other types of chicks there, it's time to stock up. You can kill eggs and insects by freezing flour to reduce the risk of infestation in the trash, but the waste is where it belongs.