Sometimes I Blow It: Over Fermented Kombucha

Note from Shannon: Please welcome Julie Feickert, Cultures for Health Founder and Cultured-Kitchen Keeper.

I tend to crave fermented foods in phases. I’ll go months where I can’t seem to drink enough water kefir. Fast forward a bit it’s kombucha, or sauerkraut, or Greek yogurt. A while back I started to crave kombucha again. I dutifully bottled up four dozen bottles of freshly fermented kombucha and organic juice, drank a few bottles and promptly lost my craving. Leaving the bottles to hang out in the increasingly warm garage.

A few months later I found them. Whoops! I grabbed a bottle I placed a towel over the top, applied downward pressure and opened each bottle. Let’s just say the towel and the pressure kept me from having to clean the ceiling multiple times. Four months of fermentation with added juice yielded a few interesting results…


First, I noticed that while all the bottles had developed significant levels of carbonation, whether they were bubbling out (resulting in losing half the contents in many cases) or whether they just had a nice carbonated texture really depended on the juice I’d used.

More specifically, juice with relatively high sugar content produces a lot more bubbles. Not surprising of course since the sugar is consumed by the still active yeast and bacteria (even after the scoby has been removed) and creates carbon dioxide. In particular, the bottles containing 100% cranberry juice (very little sugar) to flavor the kombucha fared the best in terms of not spilling most of their contents into the sink. My favorite flavoring, pineapple juice, didn’t do so well.

Second, I noticed that the bottles with more sugary juice (such as my beloved pineapple) had over-fermented. Apparently I have developed a skill for making something that tastes a whole lot like beer—and not the more pleasant varieties! So down the sink went quite a few bottles.

Now you may be asking yourself why over fermented kombucha in this case tastes like nasty yeasty beer instead of, say, vinegar.

If you leave kombucha on the counter with the scoby too long, you get something that taste like vinegar and can be used to replace vinegar in recipes. But the addition of the juice in this case fed the active yeast and bacteria in the kombucha. Combined with the warm environment, the yeast and bacteria continued to grow out of control with plenty of new sugar to keep them fed and happy. These bottles all contained a ratio of around 1 part juice to 3 parts kombucha.

Juice has a very high concentration of sugar (with the exception of the pure cranberry juice) and that much sugar actually has the ability to form a fairly significant level of alcohol. Frankly though, even if you want to create alcohol, this isn’t the way to do it. Not pleasant tasting at all! Remember, adding juice for a second fermentation won’t produce any significant amount of alcohol if you are consuming them in a reasonable amount of time. In this case I was thinking Eric and I would each drink a bottle a day meaning the four dozen bottles would have been consumed in just a few weeks. Four months in a warm garage is what did us in.


So what should you do if you ever find yourself in this position with bottles of over fermented kombucha?

First, open with care using a towel over the top and downward pressure. Let them bubble over in the sink until they stop. Second, smell them. If they smell like kombucha, great, odds are good they can be consumed. If they smell like yeast or beer, might as well dump them out and get a head start on washing bottles.

We all have a batch of something here and there fail for one reason or another not taste good. It’s okay! These learning experiences only help us figure out better ways to do it next time.

Have you had a batch of cultured food fail? Share it with us!

Julie Feickert

Julie Feickert

Julie Feickert started Cultures for Health in late 2008. She is the mother to three young children and enjoys cooking and reading. Her favorite cultured foods include water kefir and kombucha. Julie lives with her family in Sioux Falls, South Dakota.

More Posts - Website


  1. Leah says

    My kombucha seems to be too sweet and not bubbly or have that slight vinegar taste. I usually leave it for 2 weeks. Is there something to do to help this?

    • Julie Feickert says

      There could be a couple of things going on. I would double check that you used your normal ingredient ratios (I managed to leave the sugar out of one of my batches a few years ago–just not thinking that day). Since it tastes sweet, I’d particularly look at whether you had enough acid (kombucha from a previous batch or vinegar) in this batch.

      If the ingredients aren’t an issue, I’d look at the ambient temperature in your house. This time of year the temperature tends to shift and a cooler temperature could simply be slowing the process down. If I keep my brewing container near a window it can take a full extra week for my kombucha to get to that perfectly brewed point.

  2. Daniel says

    Thanks for posting, I had just come home from a less than successful waste veggie oil processing afternoon. After 15 years of alternative ways of living with little experience when I start, I still get frustrated when things don’t work out well. I need to get after that gallon of Kombucha on the counter too!

  3. Yochannah says

    Is the “over-fermented” kombucha BAD for you? i.e. will it make you sick, or do bad things to you, or…does it just taste bad?

    • Julie Feickert says

      Plain kombucha that has over-fermented isn’t bad for you at all actually. It’s just tough to drink but makes a great vinegar substitute in salad dressings and marinades.

      In this case since I’d added juice, it’s a little different. I wouldn’t say it was likely dangerous to drink but the smell alone told me I shouldn’t try. I suspect I would have had an upset stomach to deal with.

    • Julie Feickert says

      Scoby’s can be used as long as they’ve only been sitting in plain kombucha and they are not grossly discolored (tan and brown are fine, black, green, red, etc. are not). It’s actually pretty rare to have a scoby quit working. It is technically possible to starve a scoby by allowing it to sit in a batch for many months on end but even then, most of the time you can get them to come back by adding fresh sugared tea.

  4. Suzi Peterson says

    I was so glad to read that someone else blows it every once in a while!This is my first try with Kombucha. Because of the hours I work, I am having a hard time keeping up with the fact things are fermenting, and all the time that passes. My poor Kefir went from February to September…it has mercifully recovered. I don’t think I’ll be as blessed with the Kombucha. The idea sounds so wonderful. But, 14-21 days have effortlessly turned into 3+ months. I am ashamed to admit that I have become afraid of the Scoby. Due to severe lack of attention to it, I swear it is threatening to take over our house. (I can hear you saying “what an idiot-who could be that silly???”) I have a literal,whole family of Scobies: a greatgrandmother, grandmother, daughter and child – all growing thickly together in an ever shrinking gallon of sweet tea. I have absolutely no idea what to do about it except sneak it out back and upend the silent monster into the compost and call it a day…

    I really am trying to learn how to do this. I am just not sure about this enormous blob floating on the top…Could someone help? Is this just a matter of “Oh grow up and get over it?” Does anyone else feel this way? And, dare I ask, is the newest Scoby still usable?

    Any advice anyone has for me would be greatly appreciated! Thank you in advance!

  5. Julie Feickert says

    I’ve been there. When I had my last child I ended up with jar of kombucha that brewed for months and I realized I felt a need to avoid it even more as each day passed. It may seem like a weird reaction but I think it’s fairly common. For some reason it can seem overwhelming just to deal with it.

    I would try to salvage the top layer and use it to start a new batch. Odds are excellent it will be just fine. The rest can be turned over into the compost pile where it will be far more useful and unsightly than sitting on the counter.

    A trick I’ve learned too is to get into a habit of drinking kombucha each day and making batches large enough to feed my habit. Then I have to harvest it after 2 or 3 weeks simply because I’ve run out of bottled kombucha to drink.

  6. Annemarie says

    My Kambucha smells very yeasty and tastes that way too. I did the first ferment for 8 days and the second (added raspberries, blackberries, and blueberries) for 3 days. Did I not let it ferment long enough? Or did I let it go too long? I live in CA so it’s always pretty warm although I keep it in a closet inside so it stays around 80 degrees during the day and around 68 at night. My scoby just got much bigger but did not have a baby so hopefully the next batch will give me a baby. Thank you for your help, Annemarie

Leave a Reply

Your email address will not be published. Required fields are marked *