Kombucha has a lot of things going for it. Many people drink it based on potential boons to health - these can include improvement of digestion, prevention against oxidative stress, activity against acid reflux and inflammation, as well as its richness with probiotics, antioxidants and amino acids - to name a few.
It can be tough to eat or drink something for its health benefits when it's a stretch to find it palatable. I'll wince and bear eating a few oysters (many thanks to Brooklyn Oyster Party's hospitality at Smorgasburg), and though they're starting to taste better, I don't seek them out. Noni is considered a superfood that grows wild in tropical climates that many regard as having a scent and flavor reminiscent of feet and parmesan cheese - not exactly on my snacking radar.
Flip-top bottle, left, alongside a KBBK growler and fresh, carbonated 'buch
I feel like kombucha is similar for a lot of people. One of the big problems is simply that it's difficult to find truly tasty kombucha in a bottle - it's very hit-or-miss. Potentially off-putting aspects of kombucha are easily countered in a home-brewing situation with a little knowledge and instruction, and the effects of carbonation and temperature can greatly increase palatability. For someone new to kombucha, like one of your friends or relatives you'd like to enjoy your home brew, making the best 'buch possible is important - it's powerful to provide a positive kombucha experience to newcomers, and ideally it will keep them coming back for more, or may even start them brewing their own.
Carbonating your kombucha - a 'buch brewer's seal of excellence
I've posted a few blogs that focus on the flavor of kombucha, which is an immensely broad category still open to even more experimentation. There's a measure of success that can be very easy to achieve, and is a milestone for brewers of every size - when you realize your home-brewed kombucha tastes much better than what is available at the store. Many people that have great success with flavoring can have issues with something else that's very important - carbonation - and it can mean the difference between brewing a dud and hitting a homerun.
While carbonation affects the delivery and sensation of flavors, and can possibly even affect our physiology, for the sake of discussion today it's a physical characteristic; there's something very pleasant about a cold carbonated beverage that has me clamoring for 'buch first thing in the morning. In its affiliation with kombucha, carbonation is something that is desirable - but that can cause a multitude of headaches for the home brewer.
As the primary fermentation process for kombucha is essentially open-air (there is a free exchange of gases taking place between the culture and the outside environment), your kombucha will not inherently retain carbonation. The CO2 produced by your SCOBY's yeast will for the most part be released to the environment. That is, until you bottle it.
Bottling your 'buch has the effect of allowing CO2 to build up in a closed environment (provided you've used a vessel with a tight-fitting lid). This will happen to the greatest extent in a warm environment - most simply, for a home brewer, at room temperature. Just like in primary fermentation, during "bottle conditioning" (or what we call secondary fermentation), yeast will continue to consume nutrients - it's the amount of sugar in your brew that has the greatest effect on the production of CO2 during this secondary fermentation. One rule of thumb I like to use is that once your kombucha has achieved a pleasant balance of sweetness and acidity, it's ready to be bottled. You must keep in mind, however, that the residual sweetness of your brew when you bottle it plays a major role in the production of CO2, and thus that delightful effervescence we love in 'buch.
Here's a quick overview of the secondary fermentation process:
- Bottle your kombucha in containers with air-tight lids
- Allow your filled bottles to sit at room temperature, generally for 1-2 weeks*
- Once it's been decided that enough carbonation has built up, place the bottles into the refrigerator and start drinking them as soon as they are cold
*This time frame depends on your room temperature and the tea/sweetener you've used
Left: Lemon and spruce are unsweetened flavorings; Right: mango and elderberry puree are sweet flavorings
Any flavoring you add to your brew during bottling can potentially contribute to the amount of fermentable sugars available to the yeast. As your kombucha is still raw when you bottle it at home (unless you've pasteurized it, but who would do such a thing!?), yeast will still be present in the bottle and still be voracious for more sugar to eat. This is a very important fact to keep in mind - if you are adding a sweetener to your 'buch when you bottle (think fruit juice, but really, anything that is sweet), carbonation will build up more quickly than if you had left that sweetener out. Combined with the leftover residual sugars (primarily fructose) from your primary fermentation, you're potentially creating a very volatile situation. Hungry yeast + sugar = CO2. The buildup of gas in an enclosed space definitely gives our 'buch that delightful effervescence, but can also potentially create volcanic 'buch that erupts when you open it, or in extreme circumstances, can cause bottles to explode from the pressure.
Higher summertime temperatures will speed the buildup of CO2!
If you want to prevent carbonation, place your kombucha directly into the refrigerator after bottling
We've all experienced that excitable bottle of 'buch that can no longer handle being all cooped up -
You've just stepped out of your local natural market with a bottle of your favorite 'buch. You get into your car, roll down the window, and turn on that hot summer track from the week's big artist. Time for 'buch! Only not how you expect. You unscrew the lid, and instead of befriending your belly, your freshly-purchased kombucha instead befriends the totality of the inside of your car.
Sticky 'buch everywhere, not to mention chia seeds, if you're so inclined to enjoy the style. A day-changer, for sure, but not something that can't be changed with a little know-how.
Tips for bottling your kombucha and achieving transcendent effervescence:
1. Bottle when there's a nice balance of sweetness and acidity. This will help to ensure that your 'buch isn't a sugar bomb. I've found that when there is a balance of these two factors, 1-2 weeks is plenty of time to build up a nice amount of carbonation. You will also notice some differences based on the type of tea you used in primary fermentation; take notes when you notice these types of things, it will only improve your brewing skills.
2. Bottle into one plastic bottle at the same time you fill your glass bottles. This will be a model help you to know when a good amount of CO2 has built up, based on your environment (temperature) and the unique qualities of your brew. Your plastic bottle will tell you there's carbonation when it's very tight, and thus clearly pressurized. So, when you know your plastic bottle has carbonation, your glass bottles will too. This will also ensure that you aren't wasting carbonation every time you open a glass bottle to see how much has built up.
3. Don't leave much headroom in your bottles. An inch or so is just fine - you don't want excess oxygen in your bottle, as that takes up space that could otherwise be CO2. It will oxidize your brew, and make it more likely that bacteria are still active, thus creating more acids, potentially contributing off-flavors. It's also important to note that chia seeds expand immensely in the bottle, so you'll want to leave quite a bit more headroom than usual if you're bottling with them.
4. Invest in good bottles. My favorite bottles are the 32 oz Amber Growler available on our website. They're strong, opaque to UV, and have great caps that form an excellent seal, locking in 'buch and your precious carbonation. Keep an eye out for flip-top bottles as well, these can be great for home-brewing escapades and are also very good at holding tight under pressure. We always recommend bottling into glass instead of plastic.
Lids for our growlers: Cone-shaped plug is forced into the neck of the bottle, creating an airtight seal
5. Open any extremely carbonated bottles into a large pitcher. This is especially easy to do with flip-top bottles. Take a large, empty pitcher, slowly invert any bottles you've detected to be highly effervescent, and use both hands to open the cap of the bottle when it's as deep as possible in the pitcher. Your pitcher will quickly fill with 'buch foam (which you will shortly see is still kombucha) and subside within a minute or so. Your 'buch will be delightfully bubbly, and it's now ready for you to drink, or pour back into your bottle and put in the refrigerator. It won't build up pressure like that again, and it's fine to drink without fear of volcanism ;-).
There you have it! This post highlights thoughts from many years of kombucha trial and error, and the techniques will hopefully be easily replicated in your home brew situation. Please feel free to comment and offer any insight, and if you still are wondering why your 'buch just isn't up to your standards, consider visiting the KBBK Learning Center for 'Buch Kamp 1 & 2 to build up your chops and ready yourself for a lifetime of brewing pleasure.