How to make kombucha, the mother of fermented drinks

Everything we eat is either raw, cooked or fermented. The really intriguing food begins with fermentation: bread, cheese, pickles, miso, salami, tempeh, prosciutto and kombucha.

Sandor Katz lives to ferment; it’s his life’s work. He has studied around the globe and has written a definitive book for laymen called The Art of Fermentation: An In-Depth Exploration of Essential Concepts and Processes from Around the World. [Ed note: Read an excerpt from Katz's book here.]

Lynne Rossetto Kasper: What is kombucha?

Sandor Katz (Sean Minteh)

Sandor Katz: Kombucha is sweet tea fermented by a very interesting community of microorganisms that are sometimes referred to as a kombucha mother and sometimes referred to as a SCOBY, which stands for a symbiotic community of bacteria and yeast. This produces a lovely, refreshing beverage. People have begun to incorporate all sorts of other flavorings and ingredients into it -- there is a huge spectrum of different kombuchas that one could create or purchase.

LRK: We can do it at home?

SK: Absolutely. Kombucha is extremely easy to make at home. When kombucha first began growing in popularity in the U.S. -- when I first became aware of it in the mid-’90s -- I don’t believe there was any commercially available kombucha. It was just spreading as a grassroots culture. Because the mother of kombucha grows with each batch that you make, all the people who make it regularly love to find other people who they can give kombucha mothers to. It’s incredibly simple.

LRK: It sounds like the mother is the zucchini of the fermentation world. How would we go about doing this, and where would we get a mother?

SK: There are all sorts of trading posts online where people who are kombucha-making enthusiasts and have more mothers than they know what to do with love to share them with other people. There are also lots of small commercial enterprises that are making kombucha mothers or kombucha kits available to people.

Then basically all you do is brew some tea, sweeten it with sugar to taste, cool it down, put it in a wide-mouth vessel that is not completely full -- you want to maximize surface in relation to volume -- and then just place that kombucha mother on top. Cover the whole thing with a thin cloth to keep flies and dust out, but allow for airflow. Depending on the temperature of your kitchen, wait anywhere from a week to 2 weeks.

Keep tasting it because it will become increasingly acidic as days pass. Most people like to catch it when it is somewhat acidified and still somewhat sweet, but that is really a matter of personal taste.

LRK: Do you remove the mother to stop the process?

The Art of Fermentation (Read an excerpt here)

SK: Removing the mother does not completely stop the process; basically the mother is populating the sweet tea solution with the community organisms that are doing the transformation. Really, if you remove the mother, another mother is going to grow in its place.

I neglected to talk about one ingredient that is also important, which is a little bit of mature kombucha solution in with your sweet tea. What that does is it acidifies the environment. What all ferments amount to at a certain level are creating selective environments to encourage the growth of the organisms that you want, and at the same time discourage the growth of other types of organisms.

LRK: So where do you get this kombucha solution? You just go out and buy a bottle of kombucha?

SK: For your very first batch, yes, you can go buy a bottle of kombucha. Once you are in regular production, you will always have some mature kombucha to add into your next batch. A culture like this that takes on a physical form, a SCOBY, ends up being like a pet in that it requires regular maintenance. You have to keep feeding it. Each time you harvest your mature kombucha, you start a new batch. So it can potentially perpetuate for the rest of your life or beyond.

LRK: There has been controversy over kombucha. What’s the controversy about?

SK: I don’t know which controversy to start with; there have been lots of controversies. The most recent controversy is that a federal regulatory agency tested some bottles a few years ago and found levels of alcohol in excess of 0.5 percent. Yeast is part of the community in kombucha and kombucha generally has some small percentage of alcohol. Typically it’s fleeting because as long as it’s exposed to the air, Acetobacter, which are also part of the community -- these are the bacteria that convert alcohol into acetic acid -- will convert any alcohol into vinegar. But once it’s bottled, there is no longer access to oxygen, so there is the potential for greater accumulation of alcohol.

Many commercial producers have had to alter production methods. Some producers are actually not even using the traditional kombucha SCOBY as a starter, so I would call some of the currently marketed kombuchas simulated kombuchas.

LRK: What are the options for flavoring kombucha?

SK: If you do what I have described as a primary fermentation, after you pour off your mature solution, mix it with some fruit juice, vegetable juice or herbal tea solution. Then you can have a short secondary fermentation that incorporates fruit, vegetable or herbal flavors. I’ve tasted some really exciting flavor combinations that were done in this manner. If you seal them in a bottle, you carbonate them and have a carbonated soft drink.