Does Kefir Go Bad?

So you’ve bought a few bottles of milk kefir to give it a try. The taste was a-okay, but it didn’t rock your world. Now you have the last bottle sitting in the fridge, and it’s nearing the date on the label. That makes you wonder: does kefir go bad?

While kefir is basically fermented milk, you might think that since it’s already “spoiled,” there’s nothing bad that can happen to it. Unfortunately, that’s not true. Like all other dairy products, kefir spoils. And while its shelf life might be a bit longer than of other milk-related products, it’s not that long at all. In this article, we will go through storage, shelf life, and going bad of store-bought milk kefir.

We will touch upon homemade kefir too but won’t go into details of making it. If you’re interested in making your own kefir, many companies sell kefir starter packs and kefir grains. You can easily choose one, buy the ingredients you need and get started.

Homemade kefir
Image used under Creative Commons from David Niergarth

How to Store Kefir?

Similarly to almost all dairy products, you should store kefir in the refrigerator. For it to retain freshness for longest, place it in the far corner of the fridge instead of on the door. That’s because the temperature in the far corner stays more or less the same, while it fluctuates near the door. Once you open the bottle, make sure you always keep it sealed tightly and refrigerated when not in use. Generally, if you won’t finish the bottle or container, pour yourself a glass and put the rest back into the fridge.

Can You Freeze Kefir?

In case you wondered about freezing kefir, you can do it, but many producers advise against it. Like with yogurt or buttermilk, the liquids and solids from kefir often separate after freezing and thawing. While you can blend the thawed kefir, its texture won’t exactly be creamy and delightful as it was before. In other words, you can not turn back time. Because of that, thawed kefir works only in dishes where its consistency doesn’t matter that much, e.g., in smoothies.

When it comes to how to freeze kefir, I recommend freezing it using an ice cube tray. This way you can easily thaw as much as you need without thawing all of it. If the cubes are too small, feel free to use a muffin tin instead. When it comes to thawing, put the cubes to the fridge the night before you need them.

Also, many people who consider freezing kefir worry about the active cultures in the dairy product being killed by freezing. On some websites, you can find people saying that the cultures simply go dormant and get back to life after thawing. Others state that most of them die. Right now the best answer to this question seems to be: we don’t know. I haven’t found any credible research on this topic, and I’m not really sure if anyone capable of doing such a test is interested in doing it. All in all, if you’re drinking kefir for the probiotics and good bacteria, don’t freeze the kefir.

Making kefir
Image used under Creative Commons from David Niergarth

How Long Does Kefir Last

Like other dairy products, kefir comes with a date on the package. Most often it’s a sell-by date, but sometimes it literally says “expiration date”. If it’s a sell-by date, you can assume that the kefir should stay fresh for maybe a week more if unopened. If the label says “expiration,” you can add a few days to that date too. It’s not like the manufacturer tampered with the dairy product for it to go bad the day after the date on the label.

When it comes to how long does the kefir stay fresh after opening, it depends. If you open it soon after buying, it pretty much should last until the date on the label. If, on the other hand, you open it near the date on the label, you shouldn’t expect it to stay tasty for more than 5 days. Obviously, if you open it a couple of days past the date on the label, it’s best if you use it within 24 hours.

When it comes to homemade kefir, it should last for about 2 to 3 weeks if stored properly. For more specific guidelines consult the instructions given in the kefir starter or on the website of the producer of the grains.

Fridge
Kefir (unopened)Sell-by + 1 week
Kefir (opened)Sell-by or 3 – 5 days
Homemade kefir2 -3 weeks

Please note that the periods above are estimates and for best flavor.

How to Tell If Kefir Has Gone Bad?

Fresh store-bought milk kefir usually has a uniform and creamy texture. Its flavor depends on the variety. Plain kefir tastes sweetish-tart, but many brands offer flavored kefir, and each one has its own unique taste. That being said, kefir is a live product, so the taste, texture, and the level of fizz vary from bottle to bottle. Those slight variations are natural and by no means mean the product is bad. That’s just the nature of the beast, especially for preservatives-free kefir. So if you find that a certain bottle seems a bit more tart than what you’re used to, that doesn’t mean it’s spoiled. The same thing when it comes to thickness, as it also varies a bit batch to batch and season to season. Last but not least, lumps can also form, and that’s natural too.

Having said that, there are some obvious signs of kefir that is off. The first is any sign of mold or any other fuzzy growth on the surface or a changed color of the kefir. If that’s the case, throw it out. Same thing if it starts to smell off or really sour. If it already started to separate, it’s your choice if you want to use it or discard for quality purposes. As I mentioned earlier, lumps occur naturally, but if it’s too much for you and you find the kefir gross, just dump it. It makes no sense to force yourself to drink something you find unappealing. If everything seems to be okay, and you don’t already store the kefir for too long, give it a taste. Given that it tastes okay feel free to drink it or use it in any other way. If it tastes sour or just not as good as it should, discard it.