Kombucha Blog: The Importance of a Second Fermentation

Carbonation is part of the magic of kombucha. Without it, you would be drinking half-brewed yeasty vinegar. Simply put, the bubbles are pleasing and we want to keep them. On the other hand, too much carbonation makes for over-bubbled kombucha and a mess in your kitchen. How do you balance the two?

Let me start by saying that I’ve never had problems with carbonation. Some people do, and I would probably recommend that they start over with a fresh mother colony or take a sample from another persons carbonated kombucha to use as starter in your next batch. As an alternative, you could try adding extra sugar to hold a yeast holiday and restore the yeast to prominence. I don’t recommend adding yeast from anything but kombucha as there are many strains of yeast and adding the wrong one might disrupt your colony.

In case you hadn’t guessed, yeast makes the kombucha fizzy. In absence of enough oxygen, yeast cells convert sugar to carbon dioxide which builds up in the liquid. When you are about to bottle your kombucha, you should be able to taste some of that fizzle already in the liquid. From there, getting the right amount of carbonation is a little luch and a little science.

First, you may get inconsistent carbonation from different bottles in the same batch. Why? One bottle may have had more yeast. Gently mixing the kombucha before you bottle it allows the yeast to distribute uniformly and creates a more desirable product.

If the bottles are universally flat, there are a couple options. First, you may not have let them sit out long enough. The longer kombucha sits sealed on the counter at room temperature, the greater the carbonation provided there is sugar for the yeast to consume. That brings us to problem 2. You may not have had enough sugar left over. Kombucha that has sat for a very long time can run low on sugar and they yeast may not have had enough to work with. Another problem is that the bottles you used didn’t seal well enough. Get new washers or bottles and try again.

Some things that have helped some people:

• Add more sugar to each bottle before the secondary fermentation
• Add ginger or something else to the kombucha before the secondary fermentation
• Warm the bottles slightly during the second fermentation
• Let the bottles sit longer

Warning: Don’t let the kombucha bottles sit forever, as they build up CO2 and explode on rare occasion. If you have to let them sit for a long time, refrigerate them after the desired fermentation time to slow down the metabolisms of your yeast cells.