Top mistakes kombucha home brewers make
(and how to fix them!)
I’ve found that once you have a good grasp of kombucha science and methodology, it’s pretty intuitive to troubleshoot issues that come up or prevent them from happening in the first place. But, I admit, producing “perfect” kombucha can be tricky task if you don’t have a full understanding of the process or the science behind it.
And because everyone’s unique variables (the makeup of the SCOBY, the tea they’re using, the temperature, their process) will always differ in some ways from everyone else’s, it’s possible to run into some problems every once in a while.
A good place to start out would be to read up on my processes for first and second fermentation. But here are the most common mistakes that I think homebrewers make. Between all the people I interact with online and in my friends and family circles — most of the time, when I’m troubleshooting problems with them, their issues typically root from these errors. So arm yourself with knowledge!
Use these links to jump down to specific sections or just keep scrolling to hit them all:
Mistake #1: Using vinegar in place of starter tea
I go into this in my video here, so do give that a watch. This is a big one for me, and one that really gets under my skin because so many supposedly “reputable” sources recommend that it’s OK to use white vinegar (or worse! apple cider vinegar) in place of starter tea, especially when you’re just starting out. This is false. Vinegar is not a good substitute for starter tea.
While it is true that kombucha is a type of vinegar ferment, I think we can all agree that not all vinegars are the same (balsamic vinegar is not red wine vinegar, etc. etc.) So the best way to acidify kombucha is with acidic kombucha a.k.a. starter tea a.k.a. kombucha vinegar. I avoid using any other vinegar in my kombucha-making processes. It’s just not necessary. Over time, exposure to vinegar can create an imbalance of bacteria and yeast, which could make your brew acidify too much or too fast. It won’t necessarily be harmful to your health, but it definitely doesn’t taste good and could lead to problems like a weakened SCOBY, a SCOBY that produces awful-tasting kombucha, a SCOBY that doesn’t produce carbonation, etc.
I think I know where the rumor started that you can use vinegar as a substitute for starter tea. In my research, I’ve read a lot of books and articles written in the 70s and 80s about brewing kombucha. At the time, it was difficult to find raw, unflavored starter tea in a store. So if you happened to acquire a SCOBY and not enough starter tea to brew a batch, the next best thing was to use vinegar to lower the pH and acidify your brew. It was risky, but better than nothing. Today, we have so much unflavored kombucha available to us that it’s not at all necessary to rely on vinegar as a last resort. If you've already used vinegar and want to know what to do, watch here.
Mistake #2: Not using enough starter tea
In order to get the fermentation process going and make your brew inhospitable to mold, you need to lower the pH of your sweet tea. You do this by adding a SCOBY and some starter tea. That starter tea is crucial to the process, maybe even more so than the SCOBY. And remember, starter tea = plain, unflavored kombucha that’s successfully undergone a first fermentation. In general, I use 2 cups of strong starter tea per gallon batch.
By adding that starter tea to your sweet tea, you inoculate it with good bacteria and yeast. But if you don’t add enough, it may take too long to acidify your brew. If your brew doesn’t acidify fast enough, that’s a cue for mold to come into the picture.
It’s also a good practice to increase the amount of starter tea you add based on changes to other variables in your process. For example, is wintertime coming up and average room temp at you place dropping from mid-70s to mid 60s? Try adding 3 cups of starter tea instead of 2 cups to really make sure your brew is fermenting (to try to accommodate for the drop in temperature which could cause dormancy.)
Mistake #3: Agitating your vessel
...especially during the first few days of first fermentation. I know it’s a fascinating process and it’s hard to leave it alone! I hear ya. But the first few days after you start your first fermentation is the critical period for your SCOBY to to form. If you agitate the vessel (by moving it around, opening the lid and poking at it with a pH meter or thermometer, etc.), this could lead to poor or uneven scoby growth. The best thing you could do for your first fermentation is to leave it alone and just let it do its thing.
I will note that if you do agitate your SCOBY and it does sink or fold over on itself, or if it stops developing altogether, it’s OK (it won’t harm your brew). But I like to use healthy SCOBY growth to indicate that my fermentation is going well. So for new brewers, if you’re unfamiliar with the process, a lack of healthy SCOBY growth may stress you out even further because now it’s harder to tell that your brew is fermenting properly. And it may just be because you “bothered” it and accidentally sunk your SCOBY formation.
If you’re curious about what to expect while your brew is going through first fermentation, you can read about it here.
Mistake #4: Putting your SCOBY or brew vessels in the fridge
Kombucha doesn’t not be refrigerated until it is “finished” or ready to be drunk. Some people like to keep their backup SCOBYs or SCOBY hotels in the fridge, thinking it’ll somehow keep them “fresher.” They’re actually doing the absolute opposite. Cold temperatures put kombucha yeasts and bacteria into a state of dormancy. If they’re dormant, they’re not acidifying the brew. And if they’re not acidifying the brew, that means the environment could be conducive to mold growth. And if you keep your SCOBYs in the fridge, then take them back out, it may be difficult for your bacteria and yeast to wake back up and start acidifying. That puts your brews at risk for developing mold as well.
SCOBYs thrive just fine at room temperature. Between 65 - 85 degrees Fahrenheit is fine, though mid-70s is ideal. There’s no need to ever put your SCOBY or your fermenting kombucha in the fridge. Learn more about SCOBY care here. You can also read my in-depth post on why I'm against refrigerating SCOBY hotels here.
Note: Of course, after you bottle and second ferment your kombucha, you do want to put it in the fridge to halt the fermentation process (since it’s already at a good carbonation level and you don’t want it to over-carbonate, and since you don’t want it to continue acidifying). At that point, after you’ve already gone through a successful first fermentation, and your brew is in a sealed container, your brew will be protected and will have acidified to the point that you don’t need to worry about mold growth.
Mistake #5: Using flavored tea for first fermentation
You should keep flavorings, oils and extracts away from your kombucha SCOBY. This means no flavored or herbal teas during first fermentation. (After all, there are limitless opportunities to flavor during second fermentation anyhow!)
This might be controversial for some home brewers who like to use flavored teas or herbal infusions during first fermentation. But most flavorings (even if they’re “natural”) can degrade and weaken your SCOBY over time. This is why in my Ingredients 101: Tea post, I talk about making sure that you use “real” tea in your first fermentation and don’t use flavored or herbal teas that could contain ingredients like essential oils or non-tea ingredients that your SCOBY can’t properly “digest.”
A lot of people think it’s fine to use flavorings because a flavored batch of first fermented kombucha can often yield good kombucha at least a few times. But it’s the long-term that’s a problem. Sometimes problems won’t manifest immediately. You might be able to make a successful batch of kombucha using peppermint or chamomile tea, for example. You might even be able to make 3 or 4 batches, but at some point down the line, your SCOBY may finally show signs of it being weakened over time and you might start to have problems like lack of fizz, too much yeast or worse: mold. Sometimes problems don’t show up until several SCOBY “generations” later. It’s a pretty common way to weaken your SCOBY and create an imbalance in the culture.
I know, I know, it sounds like I’m a total fun-killer when it comes to experimentation. I promise I’m not! I’m all for experimenting, but when it comes to kombucha, you should know the rules so you know how to best break them. You can still experiment with interesting teas and herbs, but you should know what the risks are so you can accommodate for them!
Mistake #6: Using sugar substitutes or not using enough sugar
The yeast and bacteria in your kombucha depend on cane sugar to survive and thrive. It’s their food source. So using alternate sugars or not using enough sugar basically deprives your culture of its food source. In other words, you’re starving your SCOBY. And if you starve your SCOBY, it can’t turn sweet tea into kombucha. And using artificial substitutes like Splenda or Equal are harmful to kombucha (I’d argue that they’re harmful to humans in general too).
I understand that we live in a sugar-conscious society, and people are understandably concerned about sugar intake. But remember, your yeasts are using that sugar to create kombucha. I do not advise using anything other than plain white cane sugar. I use ¾ cup per gallon batch and that does the trick for me. So it’s actually not that much sugar per bottle if you think about it, and as the brew ferments, a good amount of that sugar gets eaten away anyhow.
You can read more here about why sugar is important, what sugars to avoid and options you can take if you want to limit sugar intake.
Mistake #7: Not stirring your kombucha before bottling
This is an easy one to make. Yeast has this habit of settling down at the bottom of our brew vessels during first fermentation. So if you don’t stir your kombucha liquid before you bottle, that yeast won’t be evenly distributed throughout your liquid or throughout your bottles.
So, some bottles (the ones you fill with liquid from the bottom of the vessel) may have too much yeast. And the bottles you fill with liquid from the top of the vessel may not have enough yeast. This can make it so that some of your bottles don’t develop the same level of carbonation even if they’re from the same batch. Some may be too fizzy and some can even be flat. Stirring before bottling distributes yeast evenly and helps make your kombucha more consistent.
This is especially a problem with people who use the continuous brew (CB) method to make kombucha. (I prefer batch brews and you can read about the differences here.) But with CB, since you use the spigot at the bottom of the vessel (where the yeasties live), you’re pulling very yeasty brew out of your vessel if you don’t stir it before you “harvest” your tea. That could lead to over-carbonated or overly yeasty-tasting brews.
Mistake #8: Not using a proper bottle to get carbonation
For second fermentation, you want good-quality, food-grade glass that’s thick enough to handle high pressure contents. And equally important is the cap. You want a cap that can be secured tightly enough to make an airtight seal. That’s what’ll allow you to trap the carbonation into the liquid as your brew ferments in the bottle.
If your bottle isn’t airtight, it’ll leak carbon dioxide out of the bottle, which means your kombucha will be flat. Flip-top bottles are a great place to start, but you can read my in-depth post on bottles and caps for more details and other options to consider.
On the other hand, many home brewers (accidentally) use poor-quality glass that isn’t intended to handle pressurized contents like kombucha. If your bottle is airtight and poor quality (say it’s made of thin glass, it’s square-shaped, it’s poorly-made like IKEA bottles or if it’s a decorative bottle), then you could put yourself at risk of a bottle breaking or exploding on you. I think this is the leading cause of a lot of unfounded fear with a lot of home brewers. People are so afraid of glass explosions that they take unnecessary “precautions” like burping bottles to prevent bottle explosions. (And some fear-mongering kombucha brewer Facebook groups perpetuate this fear.) But most bottle explosions are the result of using poor-quality bottles or bottles that were never meant to handle pressure in the first place. And now kombucha gets a bad rap for being potentially “dangerous” and people say that the only way to prevent an explosion is to burp your bottles. But burping bottles only releases good carbonation that the yeasts worked so hard to build up. You can read more about why I'm anti-burping here.
The best precaution you can take to prevent an explosion is to just use the right kind of bottle. It’s also a good practice to keep your second fermenting bottles in a cabinet or closed-off vessel like a cooler without ice to contain any potential messes. The most mess I’ve had with a good quality bottle is just the cap unscrewing a bit and the contents leaked out, but by no means did my glass break.
I’ll get off my soap box, but in reality, you don’t need to burp and you don’t need to worry about glass explosions if you’re using good quality bottles.
Mistake #9: Not chilling your kombucha before opening
This one’s not crucial, but it can lead to a lot of messes. Cold temperatures help keep carbonation in liquid better than warmer temperatures. That means if you open up a bottle of kombucha at room temperature, it could fizzy up out of the bottle and all over your countertops and walls. That same bottle of kombucha, if you chilled it, may still be perfectly bubbly — but those bubbles would stay “trapped” in the liquid so you can enjoy it in your beverage as opposed to on your ceiling.
I think a lot of home brewers who like to burp their kombucha bottles run into this problem a lot. (This is yet another reason why I don’t like to burp bottles. Read more about why here.) They try to burp their bottle, then see that the liquid is really aggressive at room temp. It may even make a mess. So they figure, “Hey my kombucha is really carbonated, I better move it to the fridge to stop it from getting over-carbonated!” But then, when they move it to the fridge to chill it, then open it back up, it might be flat or not very carbonated. It’s because firstly, they burped their bottle and released a lot of carbonation, and secondly, the fizz is exaggerated at room temperature. That bottle may not have been “over-carbonated.” It may have been perfectly fizzy, but they released the carbonation through burping so there wasn’t a ton of bubbles left to stay in the liquid itself. Then when they’re ready to drink it, they wonder why the fridge supposedly zapped their bottle of carbonation.
The best way to avoid all this is to have an understanding of how long it takes your particular brew to get fizzy. Then, don’t burp your bottles and use that timeline to second ferment before moving your bottles to the fridge to chill before testing them. If you take one out and it’s still not bubbly enough, you can always bring the whole batch back out to continue fermenting at room temperature to build more carbonation!
Mistake #10: Having unrealistic expectations
I think this last one is more of a mindset thing. Learning how to brew kombucha (or learning anything for that matter) is a process — and you’ll hit challenges and snags that may seem discouraging. But just remember: kombucha is a living thing. It’s not going to be consistent all the time. It’ll change with the seasons. And it’ll take time to get your process down and understand how your particular cultures behave. It may not always be perfectly fizzy or sometimes it’ll be too fizzy. Some fruit flavorings may taste divine and others might taste like crap. If something goes wrong, as long as you learn from it, it wasn’t all for nothing. This is where taking lots of notes really comes in handy!
But all that is part of the beauty of it. This is a real, raw, natural product. And you made it yourself. No one else’s kombucha is like yours. And you have the freedom and power to make it however you want. So don’t stress out if it’s not perfect right away. It’s a process, but it’s rewarding once you get it down. And hopefully You Brew Kombucha can help arm you with the science and info you need to make your brews as amazing as you want them to be.
I should also note that this also applies to having unrealistic expectations about any of kombucha’s supposed health benefits. You can read more about this in my post on “Is kombucha good for you?” but in a nutshell: you should know that like any food we consume, kombucha’s effects on your body will be very unique to you. Kombucha is just a drink. It’s not a cure-all. It’s not a miracle superfood. All foods we consume affect us all differently. The benefits it has for you (if any) may be different than how it affects someone else.
So don’t go into it with too-high expectations. But I’ve found home brewing kombucha to be incredibly rewarding journey, and I hope you do too.
A note about “mistakes” and experimentation...
I know that this list may make it seem like kombucha is such a rigid process. I truly don’t want to be a stickler to the creative process! But here at You Brew Kombucha, my goal is to make home brewing accessible to the masses. That means that my process and methodology are intended to produce the most resilient cultures, the most delicious kombucha and the most consistent carbonation with each bottle.
I do believe that there should be room for experimentation. I fully support thinking outside the box and breaking the rules! But as Pablo Picasso once said, “You should learn the rules like a pro, so you can break them like an artist.” That means that you have to understand the “rules” and understand the science behind what makes this process work. Once you have that foundation, you can get creative and know what fun, experimental risks you can take...and you’ll be able to hypothesize what to do to adjust for them so your experiments turn out successful!
Here, I’ve compiled the foundational guidelines that I believe are the common denominators that produce the type of kombucha I like to drink. And it’s my hope that You Brew Kombucha can be a helpful resource for people who have as many questions as kombucha as I did when I first started this journey.
No one’s going to slap you on the wrist for doing things differently or finding a process that works for you. If you’ve found a way to make your brew work that’s contrary to what’s on this site — that’s fantastic! Your variables are going to be different than mine, so there’ll be infinite possibilities for successful kombucha brewing processes. You do what you’ve gotta do for your ‘bucha! I support you.