How long does it take to brew a batch of kombucha?

Apr 21

It depends! The type of tea makes a difference, as does the fermentation vessel. When we first started, it took about a month to brew a batch of black tea kombucha, and the better part of three weeks to brew a batch of green tea kombucha. But thanks to some interesting science and innovative design, we’ve cut that in half and have improved the quality of our kombucha, too!

First, different types of teas take different amount of times to ferment, but it’s based on their oxidation. Black teas are fully oxidized, meaning they’ve been exposed to oxygen, and without getting into too much of that science, it means that they don’t have as many of the nutrients that the SCOBY (Symbiotic Culture of Bacteria and Yeast) needs to grow. Green teas, which are unoxidized, tend to take less time to ferment because they have more of the nutrients the SCOBY needs, so the SCOBY grows and ferments the tea faster.

Along with the inherent chemistry of the tea, something else makes a big difference to the fermentation process: surface area. The more room there is for the SCOBY to grow across the surface of a brew, the “happier” the SCOBY will be; and happier SCOBY means it turns the sugar to alcohol to acetic acid faster, thus speeding up fermentation.

The brewing process for kombucha is similar to brewing any other beverage that uses yeast for fermentation: for kombucha, yeast (the ‘Y’ in SCOBY) convert sugar into alcohol, and then the bacteria (the ‘B’ in SCOBY) convert the alcohol into acetic acid. However, unlike brewing alcohol, which is a fully anaerobic process (i.e. oxygen is not part of the process), brewing kombucha is anaerobic and aerobic: the yeast don’t need oxygen, but the bacteria do!

Since brewing beer is far more common, most fermentation vessels are designed to minimize the amount of oxygen in a brew. Like Fall City Kombucha when we started, most kombucha brewers use fermentation vessels that are designed for brewing beer (see the picture on top). These vessels are typically tall and cylindrical to minimize the surface area of the liquid touching air and oxidizing. When brewing kombucha, that means the yeast in the SCOBY will grow faster than the bacteria in the culture. Thus, to speed the process and brew large batches, a lot of commercial kombucha brewers have to add oxygen to oxidize their brews during the process so that the SCOBY can continue to grow, consume the alcohol, and turn it into acetic acid.

Inefficient, right? Because we’re a small craft brewery, we were able to do something pretty cool to improve this process: we custom designed and fabricated fermentation trays. Instead of being tall and narrow, they’re more shallow and wide. They maximize the surface area and oxidation process needed by the SCOBY for the fermentation cycle. The byproduct of this different vessel size is happy, fast-growing SCOBY, which is great for us because it cut our production cycle by almost half. Black tea now takes about two weeks to brew, and we can get a batch of green tea fermented in about eight days! But there’s a benefit for you, too: In the smaller vessels, the lack of surface area in the liquid limits how quickly the SCOBY can grow. With more surface area in our trays, the SCOBY can ferment the tea and sugar as fast as it can, and that gives us extra assurance that, as the yeast is converting the sugar into alcohol, the SCOBY is able to convert it into acetic acid — extra confidence that our kombucha won’t be over the legal limit for residual alcohol content (0.5%).

Happy well-balanced SCOBY means better brews coming faster to you!