Kombucha: SCOBY Fermentation
Kombucha — sweetened tea fermented by a SCOBY (Symbiotic Culture Of Bacteria and Yeast) — is one of the fastest fermentations that produces a complex product. The SCOBY's yeast component converts sugar to alcohol; the acetic acid bacteria convert the alcohol to acetic acid; the overall result is a slightly alcoholic, lightly carbonated, pleasantly sour beverage. Noma's documentation provides the technical parameters that home brewers typically manage by intuition.
- **The SCOBY:** A cellulose matrix produced by Acetobacter and Gluconobacter bacteria — the structure that houses the fermentation community. Each batch produces a new SCOBY layer on top of the previous one. - **Tea:** The substrate. Black, green, or herbal — the polyphenols in the tea are food for the SCOBY community. [VERIFY] Noma's tea specification. - **Sugar concentration:** 5–7% of the tea volume. Enough to fuel fermentation; not so much that the result is unpleasantly sweet after fermentation. - **Temperature:** 22–28°C. The acetic acid bacteria are aerobic — the SCOBY sits on top of the liquid, requiring air contact. - **pH:** Starting at 6.5–7.0 (neutral), falling to 3.0–3.5 by completion. - **Time:** 7–14 days for the primary fermentation; 2–3 days for secondary fermentation (with additional fruit/juice in a sealed bottle, producing the carbonation).
Noma Fermentation