Does kombucha expire?
How long does homemade kombucha keep once chilled? Pretty much indefinitely, if properly brewed and stored — whether you'll want to drink it after a year is another question (hello, vinegar).
Does kombucha expire? · Watch on YouTube
What cold does to yeast and bacteria
Homemade kombucha is a live, real, natural product. It has no yeast inhibitors and hasn't been pasteurized or watered down the way much mass-produced, shelf-stable kombucha is.
Your home brew's live yeast and bacteria go into a state of dormancy when chilled — but refrigerated kombucha still continues to ferment, just very slowly. It keeps getting a little more carbonated and a little more acidic in the fridge as the yeasts keep eating the sugars. Not as rapidly as at room temperature, but fermenting nonetheless.
Pro-tip: age kombucha for complex flavors
You can use that slow, cold fermentation to your advantage if you like dry kombucha. Depending on the fruit flavorings, aged kombucha can develop wonderfully complex flavors akin to dry cider, champagne, or sour/wild beers. Ange purposefully ages bottles of her apple or passionfruit kombucha for 4–5 months to develop a delicious complexity — and aging raspberry or cherry kombucha lands you somewhere near a traditional Belgian lambic or kriek!
Eventually, though, any kombucha reaches the point of acidity where it just tastes like vinegar. At that point: marinades and vinaigrettes. Nothing wasted.
Storing long-term? Burp occasionally
Ange is typically not an advocate of burping bottles during second fermentation — but aging is the exception. When you're keeping bottles for months, release the excess pressure every 1–2 months so they don't over-carbonate and make a mess (or worse) when you finally open them.