Uh-oh …
You opened your canning jar, and there are black spots on the underside of the lid.
What is it? More importantly, is your canned food still safe to eat?
You might have cause for concern … or it might be a normal case of “pinholing.”
What Is Pinholing?
Pinholing occurs when certain acidic foods or meats react with the metal on a canning lid.
This causes the metal to corrode, producing black material as a byproduct.
You might notice black spots—or what looks like black soot—on the underside of the lid when you open a canning jar.
Common culprits for pinholing include tomatoes, meats, and rhubarb, as they are acidic and can react with metal. When you clean the lid after discovering pinholing, you will be left with spots of corrosion.
To ensure the safety of canned food, always familiarize yourself with the signs that your canned food has gone bad.
If you find pinholing but no other signs of spoilage, your food is likely safe to eat.
