In the spirit of this fermentation issue, our Homebrew Recipe goes off the beaten path to the land of homemade kombucha
By Michael Dawson
Photos by Emma Christensen
Citizens, like the beer you usually see formulated and brewed in this column, kombucha is a fermented beverage, but instead of malted grain it uses sugar-sweetened tea as a base. Fermentation is carried out by a mixed culture called a SCOBY (Symbiotic Culture Of Bacteria [and] Yeast). A further difference is that the intended outcome of kombucha fermentation is, like kimchi or kefir, more concerned with probiotics and preservation than with ABV: most kombucha does contain alcohol, but usually less than 1% ABV, about as much as a typical non-alcoholic beer.
It’s all about the SCOBY—this mixed culture looks like the love child of a sourdough pancake and a shiitake mushroom and is absolutely iconic to kombucha brewers. During fermentation, SCOBYs form a multi-layered bio-film in the jar that will look a bit familiar to any sour ale brewers who’ve ever waited on a pellicle. A single SCOBY can be cultured for a long time and used to produce many batches of kombucha—in fact, finding a practicing kombucha brewer and cadging a slice of their bio-film pancake is one of the best ways to acquire your own starter SCOBY.
The exact composition of a SCOBY varies widely, but it can include some familiar faces like Saccharomyces and Brettanomyces, as well as acetic acid bacteria of some stripe. These guys are responsible for kombucha’s vinegary twang as well as the crucial acidification of the brew—a low pH is critical for creating an environment that’s favorable to the beneficial native microorganisms and discouraging contamination.
Related Post: Yeast and Fermentation with Dave Hoops
Tea is the base beverage that sets the stage for the prominent fermentation character created by the SCOBY. Any kind of unflavored tea—black, green, white, oolong, etc.—can be used for kombucha; avoid flavored teas or herbal infusions like mint or chamomile. Supermarket tea bags will work fine, but here in the Twin Cities we’re lucky to have access to some truly wonderful tea shops that have a large selection of high-quality loose-leaf teas at reasonable prices if you’d really like to customize it.
Finally, since this is a fermentation, we need a little something sweet for the microorganisms to eat—although at a low ratio to keep the ABV% low. Plain white sugar works just fine, while some kombucha brewers favor brown sugar, agave syrup, honey, or brown rice syrup—just stay away from stevia or artificial sweeteners.
Gear for Kombucha
Pretty short and sweet—if you’re already a homebrewer, you already have the stuff for sanitizing the fermenting jar and for bottling the kombucha (if you care to bottle it).
• A 1-2 gallon glass jar. The most common batch size for homemade kombucha is 1 gallon, although the headspace requirement for a beer primary doesn’t apply here, a bit bigger is better because a wide surface-volume ratio provides more oxygen for the fermentation. A wide mouth is a good thing—using a narrow-necked cider-style jug or growler makes it too difficult to inoculate the brew and to harvest the SCOBY. My wife, the hardcore kombucha brewer of our household, uses a large sun tea jar from one of the aforementioned local tea shops. Four-quart canning jars can be found at hardware stores.
• A porous cloth to cover the jar. Homemade kombucha uses a quasi-open fermentation—covered but not sealed. We need to allow plenty of respiration while keeping flies and mold spores out. A clean towel or a few layers of clean cheesecloth cinched down with a rubber band does the trick.
One gallon kombucha starter kits can be purchased online or at some of our local homebrew shops. These kits also include enough tea and sugar for one batch, plus a coupon that can be redeemed for a SCOBY shipped to you by mail.