Opened canned tomatoes and saw bubbles rising immediately. Is that fermentation or spoilage

The smell test is a reliable method to assess the safety of canned tomatoes. A fresh can of tomatoes should have a clean, slightly acidic tomato aroma. If you detect sour, yeasty, or otherwise off odors, this could indicate spoilage or fermentation.

Sour or pungent smells can be indicative of lactic acid bacteria activity, while a yeasty smell might suggest the presence of yeast fermentation. Both are signs that the product may not be safe to consume.

Spoilage can also be detected through changes in texture and color. Tomatoes that appear mushy, slimy, or have an off-color could be spoiled. The liquid may appear cloudy or have an unusual hue.

These changes can be caused by enzymatic breakdown or microbial activity, both of which compromise the integrity of the tomatoes and render them unsafe for consumption.

Botulism is a rare but serious concern when it comes to canned foods. It is caused by the bacteria Clostridium botulinum, which can thrive in low-acid environments and produce a potent toxin.