Opened Canned Tomatoes and Saw Bubbles Rising? Here’s What It Means
Nora PatelYou pop open a can of tomatoes—ready to make sauce, soup, or chili—and bubbles immediately rise to the surface, like a gentle fizz. No shaking. No stirring. Just… bubbling.
Your stomach drops.
Is this fermentation? Or is it spoiled?
The short answer: This is likely spoilage—not safe fermentation—and the tomatoes should be discarded.
Here’s why—and what to look for next time.
🚩 Why Bubbling in Canned Tomatoes Is a Red Flag
Commercially canned foods (like store-bought tomatoes) are heat-sterilized and hermetically sealed to kill all microbes and prevent recontamination. In a properly processed can, nothing should be alive inside—so no gas should form.
If you see bubbles rising immediately upon opening, it means:
Microorganisms (bacteria or yeast) got inside after canning
They’ve been fermenting sugars in the tomatoes
They’re producing carbon dioxide gas as a byproduct
This is uncontrolled spoilage—not intentional fermentation.
❗ Important: A sealed metal can on your pantry shelf is not a fermentation vessel. True fermentation requires controlled conditions, specific cultures, and oxygen management. This is not that.
🍅 But Aren’t Tomatoes Acidic? Doesn’t That Make Them Safe?