Bubbles in Canned Tomatoes: Fermentation or Spoilage? How to Tell the Difference

You open a can of tomatoes, ready to start cooking—and suddenly notice bubbles rising to the surface. Is this normal? Or is it a sign the product has spoiled?

Canned tomatoes are a kitchen staple, prized for their convenience and rich flavor. But unexpected bubbling can raise legitimate concerns about food safety. The good news? Not all bubbles are cause for alarm. Understanding what’s harmless—and what’s hazardous—is key to protecting your health and reducing unnecessary waste.

Here’s how to tell the difference between natural gas release and dangerous spoilage.

1. Why Bubbles Appear When You Open the Can
The moment you crack open a can, you may see small bubbles rising through the liquid. This is often completely normal.