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.

How to Brew Kombucha - Basics

This post will explain the simplest preparation of kombucha. Feel free to experiment on your own, but start with the original recipe if you are new to this. I assume that you already have a kombucha colony, also called a scoby. If you don’t have one, I’ll be covering that later so stay tuned to the kombucha blog.

1. Start by brewing an entire gallon of tea. You should use about 6 tea bags. Any plain black or green tea is suitable (including decaffeinated tea), but teas with additional ingredients, volatile oils, or herbal infusions should be used with caution. A known colony killer is Earl Grey, which has antimicrobial agents in the bergamot infusion. See the warning below.
2. Let the tea cool to room temperature overnight.
3. Place the tea in a fermenting vessel. Large glass jars are recommended and can be procured from stores like target at minimum cost. Lids are not needed at this stage.
4. Add sugar to the tea. Some recipes call for adding the sugar earlier, but adding sugar before acidifying the tea offers more time for aerial microbes to colonize the tea before the kombucha takes over. Mix until the sugar is dissolved.
5. Add your kombucha colony and starter. Place a significant portion of an active colony (or the entire colony) into the tea along with 1-2 cups of saved plain kombucha from your previous batch.
6. Cover the jar with a cloth to prevent flies from accessing the kombucha and ruining it, secure the cloth with a rubber band, and let it sit in a dark corner of the house.
7. After 6-7 days, you can sample the tea. First observe the kombucha colony. It should be growing a new layer on the surface of the tea which should be free of mold. If that is the case, you can sample your work. Use a plastic spoon or straw, as metals harm the colony on contact. If the kombucha tastes to your liking, it is time to bottle it. Remove your colony and some starter fluid to start a new batch. At this point you can add more flavoring elements if you please (I recommend ginger to start).
8. Bottle the remaining kombucha in sealing containers and let them sit for at least 3 more days at room temperature in order to ensure maximum carbonation.
9. Serve over ice or refrigerate if desired.

WARNING: Kombucha is a living culture of organisms that can be damaged through the addition of foreign substances. If you intend to alter this recipe, be sure to have a spare colony in case the first colony is harmed by the addition of different substances.