Originally Posted by Guts
it will decompose and turn to a mush, open it up and look.
That is absolutely, positively, & DANGEROUSLY UNTRUE!!! Food infiltrated with deadly botulism can look absolutely pristine & have no terribly off smell, taste, or texture. That is what makes it so deadly.
If you have a can of food that's bulging - no matter how slight - or open a jar of something, homecanned or not, that appears suspect in any way, you need to throw it out immediately. In the case of a bulging can, absolutely DO NOT attempt to open it up!!! It could easily burp open in your face, splattering you with its poisonous contents. Just THROW. IT. OUT.