Does exploding milk kefir mean it's bad? Not necessarily.
posted on
August 22, 2025

We get this question from customers on the regular --> "My kefir exploded. Is that normal? Does that mean it's bad?"
The answer? Bubbly volcanic kefir is 100% ok. Kefir is known as the "champagne of dairy" for a reason!
In case you haven't tried it, milk kefir is a fermented drink made with milk. It's similar in taste to yogurt (a little stronger in my opinion) but has more probiotics.
As I've heard it said, yogurt is good for cleansing the gut. Kefir, on the other hand, adds to the gut. People working to heal or enhance the function of their digestive system often turn to kefir as part of this process.
Even though kefir has been around for thousands of years, it seems that there's still some mystery around it. I mean, it's just not as popular as yogurt, particularly in the US.
Bubbles in kefir are a natural part of the fermentation process.
To make kefir, you need to add culture to milk. Different from yogurt culture, which is strains of probiotic bacteria only, kefir is a symbiotic culture of probiotic bacteria AND yeast.
Once the culture is added, you let it ferment at room temp. The culture eats up the milk sugar (AKA lactose), creates bubbles (AKA CO2), and grows more of the culture.
When you get bubbly kefir, that's a sure sign that it's fermented. It's also a sure sign that it's probiotic. After all, the more CO2, the more eating and duplicating the bacteria and yeast did.
After we make it, kefir will continue to ferment. It will happen more rapidly at room temp and more slowly in the fridge. But, it's still happening. More and more bubbles are created over time. And, if that container is air tight, lots of pressure builds up within the container.
If you don't open the kefir and it's super fermented, there is the potential for lots of bubbles upon opening. Here's a short video of a kefir explosion:
And, here's a little story about the worst kefir explosion I've heard of. Years ago, we used to sell blueberry kefir. With that added sugary fruit in the end, the culture would really take off. A customer sent us a picture of blueberry kefir on her kitchen ceiling!! It really exploded. I wish I could have been there to help her clean it up!
Open slowly or burp kefir to stop it from exploding.
Not a fan of your kefir exploding? Thankfully, there's an easy solution. Open slowly. Simply crack the lid a little, and let the gas escape before opening all the way. You could even burp your kefir every day or two in the fridge to prevent it from getting too bubbly.
The only way to stop kefir from fermenting and creating more bubbles is to freeze it. However, I don't recommend that.
First off, kefir tends to get clumpy when thawed.
Second, there's some probiotic loss when freezing. The longer it's frozen, the more probiotic loss. If you need to freeze kefir for later, I don't recommend freezing it for more than 3 months.
You know kefir really went bad by the smell and look.
When you make kefir with raw milk, it's slowly turning into kefir cheese. So when I say it goes "bad", it's really just knowing when it's too sour or pungent to palate. It's not necessarily a safety issue. Here are two things to look for:
- Putrid Smell: OK, kefir smells funky, even good kefir. But, especially if you've been drinking kefir for a while, you should be able to tell when it smells putrid. Like, you absolutely aren't able to consume it.
- Massive Separation: A little separation in kefir is normal. You will see the whey (a yellowish liquid) separate from the thicker white part. But, if it's all separated, and the white creamy part has turned into a mass of clumps, it's probably not the best to consume anymore. *Side note: I think this is why most kefir comes in a container that's NOT clear.
When you make kefir with pasteurized milk, it's a different story. Since there isn't a natural community of microorganisms that are regulating themselves, it has the potential to go bad in a dangerous way. In addition to the signs listed above, here's one more thing to look for:
- Visible Mold: Especially green, orange, red, or black mold, which is a clear indication that the kefir is bad and should be tossed.
All in all, this is really about trusting your gut and being connected to your food.
How bubbly has your kefir been? Have you ever had it explode? Do you drink kefir for its yumminess or probiotic benefits?
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