How to Detect Spoiled Foods
No one can promise you that your home-canned foods will always be free from spoilage, but you can rest assured that your chances for spoiled food are greatly reduced when you follow the precise guidelines for each preserving method.
If you suspect, for any reason, that your food is spoiled or just isn’t right, don’t taste it.
Just because your food doesn’t look spoiled, doesn’t mean that it’s not. Signs of spoilage are
Bulging or loosened lids on canned jars
Weeping or leakage from under a previously sealed jar
Bubbly or foamy contents of canned food
Visible mold or mildew on the lid, inside the jar, or on the food itself.