How to Spot Unsafe Cans Even though many canned foods are safe past their “Best By” date, you should always check the condition of the can before eating. Throw it away immediately if you notice any of the following warning signs: Bulging or swollen lid Rust or corrosion Leaks or deep dents A sour or strange odor after opening These signs could mean the food inside has spoiled and is no longer safe to consume. Storage Tips to Maximize Freshness To keep canned goods safe for as long as possible: