If you ever see a watermelon with white foam or bubbles oozing from the stem, it’s a strong indicator that something has gone wrong inside the fruit. While it might look like a harmless reaction, this is a clear warning sign that the watermelon is unsafe to eat.
What the Foam Means
This foaming is caused by fermentation happening inside the watermelon. When bacteria or fungi invade the fruit—often through tiny cracks or bruises—it starts to ferment. As the sugars break down, gases like carbon dioxide are released, creating pressure. Eventually, that pressure forces the juices to bubble out of the stem, resulting in the visible foaming.
Why It’s Dangerous
Fermented watermelon is not just spoiled—it can be dangerous. Unlike safely fermented foods like yogurt or kimchi, this type of spoilage is uncontrolled and unsanitary. The risk of foodborne illness from eating fermented or rotting watermelon includes:
- Stomach cramps
- Nausea and vomiting
- Diarrhea
- Exposure to harmful bacteria like Salmonella or E. coli
Other Signs of Spoiled Watermelon
Besides foaming, look out for these signs of spoilage:
- A sour or alcohol-like smell
- A mushy, overly soft texture
- Unnatural bulging or swelling
- Mold or slime on the skin
- Leaking fluid without being cut
What to Do
If you notice any of these symptoms—especially bubbling foam—do not taste the watermelon. Discard it right away, preferably in a sealed bag to prevent contamination. Clean any surfaces it touched with soap or disinfectant.
Conclusion
A foaming watermelon is not a rare curiosity—it’s a clear sign of internal spoilage and fermentation. Always inspect your fruit carefully, and when in doubt, throw it out. Eating spoiled watermelon is simply not worth the risk to your health.