Shelf Life of Homemade Cultures

One of the most frequently asked question is about the shelf life of a particular culture (kefir, kombucha, etc).

There are really two answers to that.

One answer is that it will never really go bad or it will take a very long time.

It is already fully comprised of bacteria and yeast and those good probiotics will fight off mold and spoilage bacteria for a very long time. And even if the probiotics die (which takes a very long time), the fermented drink will be so acidic that it will continue to fight back spoilage bacteria or mold. So essentially, it generally won’t ever go bad or at least for a very long time.

Will store-bought kefir and kombucha go bad?

Homemade cultures that that consist of a scoby (symbiotic culture of bacteria and yeast) such as milk kefir, water kefir, ginger beer plant, kombucha, jun, etc have an extraordinarily long shelf life.

Store-bought kefir or kombucha are different and not in symbiotic environment. They are more like yogurt where the controlled ferment does extend the life, but they are more susceptible to mold and spoilage than a natural scoby environment.

Home made yogurt and room temperature yogurts are also more susceptible to mold and spoilage due to their lack of symbiosis between the bacteria and yeast.

The second answer is that the shelf life really comes down to taste preference.

When the finished drink is stored in the fridge, its still very active and will continue to slowly ferment. Which basically means it becomes less sweet, more acidic and sometime more alcoholic over time. Some cultures like milk kefir are better when its fresh (due to the greater activity and milk content) and others like water kefir are better stored for a while to really get those multi-dimensional flavors.

Here our are recommendations for consumption of home made cultures that are stored in the fridge:

Milk Kefir

Water Kefir

Ginger Beer

Kombucha or Jun

Room temperature yogurts like Viili, Caspian, Fil Mjolk, etc.

*Palatable shelf life refers to the time period where you could still drink it and it will taste okay for some people, but too sour for some. Beyond that time, its likely not spoiled, but you would likely need to mix it with fruit or sugar or juice to make it more drinkable.

Bottom Line

Homemade cultures don't really go bad. If you notice any kind of mold (something usually colorful and fuzzy on the surface), its best to throw away. Or if it just smells and taste bad to you (beyond just being extra sour), then its also best to throw away.

As far as when its best to consume for the best flavor, water kefir can ginger beer tend to taste much better when stored for a few days in the fridge or after a 2nd ferment.

Milk kefir is so active that it can be get really sour and not very tasty even after a couple days in the fridge. So that one is best to drink within 48 hours.

Kombucha or Jun can go either way. Sometimes its best to drink fresh or it can get better with some storage time in the fridge.

For the room temperature yogurts like viili, the fresher the better typically, but its usually tastes pretty good for about a week.

Do you prefer to drink your fermented beverage fresh or store in the fridge for a while?