This indicates the build up of toxic gases inside the can, possibly from the interaction between the metal and the food
These are signs of botulism, a rare but dangerous bacterial strain which attacks the nervous system. Botulism thrives in anaerobic environments
Rust is a chemical reaction that erodes metal, so if you notice some on your canned goods, it's time to throw it out
Dangerous foods may be looking at the expiration date, but don't throw out your canned food just because the date is off
The canning process creates a sanitary environment to reduce or even eliminate the chance of dangerous bacteria spoiling the contents
There is a science to where you store your canned goods—it should be neither too hot nor too cold, and should never fluctuate between the two
This goes without saying, but if you see mold in your canned goods, throw them out! Mold is an indication that the can was compromised
Sometimes discoloration is an indication of a reaction between the can's contents and the metal, but at the very least, a change in color
If there's a particularly unpleasant smell when you open the can, don't chance it. Bad odor is one of the most obvious signs
If you notice a leak in your canned food, the container has been compromised, and the food is not suitable for consumption