Fermentation: Strange Ch-Ch-Ch-Changes: SCOBY
This is a part of my series exploring fermentation at the cooking school. To start from the beginning or see a list of previous posts, click here.
SCOBY: Symbiotic Culture of Bacteria and Yeast
With slightly less historical caché than lacto-fermented foods (here in the west), recent trends and a (for some reason only) new concern for probiotic health would indicate that kombucha, it’s jellyfish like SCOBY bobbing on its surface, is the ferment you’re most likely to have on top of your fridge right now (the slightly-warmer-than-room temperature here is ideal for most fermentation). Kombucha is a sugar-sweetened tea fermented over only a week or two to produce a bright, effervescent, and somewhat sour tonic. While most commonly bottled and consumed as a beverage, we’ve recently begun exploring the ways that kombucha might be used as an ingredient in simple-syrups, vinaigrettes, sauces, and more.
As its name implies, a kombucha’s SCOBY or mother, ferments by way of cooperation between yeast and acetic acid bacteria (AABs) - a process which, incidentally, produces the physical raft these microbes live on; that ghastly floating mass, equal parts disturbing and utterly fascinating (SCOBY tastes good on its own, almost like canned litchi). Once added to your sweetened tea (which can be anything you’d like, from standard black, to herbal teas, to fruit juices; we even recently made a batch with kombu), the yeast in the SCOBY begins the fermentation process by consuming the sugars in your liquid and producing ethanol. Then, the AABs jump in, fermenting that ethanol by oxidizing it (kombucha needs access to air!) into acetic acid, lowering the pH, and slowly transforming the once overly-sweet tea into a complex and punchy drink (The Noma Guide to Fermentation).
Taste-tested and having reached your desired level of acidity (generally 10 to 14 days, but begin tasting after about a week), the kombucha is strained from its mother and replaced in a sealed bottle or jar where some remaining strains of yeast work to produce more CO2 and create that effervescent lightness we all love.
The entire process, as easy as it is and taking only a couple of weeks, is definitely a ferment worth playing around with. In fact, during the second fermentation, feel free to add whatever additional flavorings you’d like, including herbs and spices, simple syrups, fruit purees or whole fruits, and more. Far better than commercial booch and a great addition to cocktails or salads.