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Fermentation Atlas

Soft drinks from worldwide

Kombuchaчайный гриб

Sweetened tea is soured by a SCOBY, a floating cellulose mat full of yeasts and bacteria, plus some liquid from the last batch. Yeasts turn the sugar into alcohol and carbon dioxide and acetic acid bacteria turn the alcohol into acid, so in one to two weeks the tea becomes sour and lightly fizzy. Made in 5 steps over 8 days – 17 days. The longest step, ferment open to the air, takes 7–14 days (Colorado State University Extension (Food Sma…) and runs at 18–26 °C (Colorado State University Extension (Food Sma…). Komagataeibacter, acetic acid bacteria that build the cellulose mat and Brettanomyces yeasts do most of the fermenting.

Key numbers
Main step7–14 daysSet[csu-kombucha]Ferment open to the air
Temperature18–26 °CSet[csu-kombucha]Ferment open to the air
AciditypH 2.5–4.2Set[bccdc][wahealth]Ferment open to the air
Fully documentedSoft drinks8 days – 17 daysMore soft drinksMore from East AsiaMore from Russia

Recipe

Amounts from a sourceColorado State University Extension's 1-gallon home batch. The first culture should come from a commercial source; later batches reuse the SCOBY and some kombucha from the batch before.
1 gallon (about 3.8 L)Filtered water[csu-kombucha]
¼ cup loose, or 4–8 tea bagsGreen and/or black tea[csu-kombucha]
1 cupCane sugar[csu-kombucha]
1–2 cupsStarter liquid from a previous batch · Health guidance asks for at least 10 % of the batch volume[csu-kombucha][bccdc]
1SCOBY[csu-kombucha]
StarterSCOBY plus starter liquid (backslop)

Total time across the recorded steps: 8 days – 17 days

Start
Drag the bar or press Play
100 °C

What changes: Boiling water draws the tea, and the sugar dissolves in it

Step 1 of 5
Brew and sweeten the tea
Time
10 min
Set
Temperature
100 °C
Set
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Komagataeibacter
Acetic acid bacteria
Brettanomyces
Zygosaccharomyces
Yeasts

Output: hot sweet tea, leaves removed.

Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Not documented for this step.

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

What makes this one different

Kombucha ferments open to the air with a SCOBY, so the yeasts' alcohol is turned into acid as in vinegar. Jun is a close relative made with green tea and honey.

Related ferments

Variants

  • Hard kombuchaExtra sugar and yeast for an alcoholic drink (see hard-kombucha).
  • JunGreen tea and honey with its own culture (see jun).

Safety

Add at least 10 % starter liquid so the sweet tea starts at pH 4.6 or lower. Discard the batch, and do not reuse its SCOBY, if the pH has not reached 4.2 within 7 days or fuzzy mould grows on the culture (BCCDC). Refrigerate when the pH nears 2.5, because very acidic kombucha is a risk for some people. Do not brew or store it in glazed earthenware, painted ceramic or metal, which the acid can leach lead from. Alcohol can pass 0.5 % ABV, the US limit for non-alcoholic kombucha.

Hazards the sources name: Moulds on the SCOBY (Penicillium, Aspergillus); Escherichia coli, Salmonella and Listeria monocytogenes, if the pH falls too slowly.

History and sources

Every number is labelled with how it is known. How this atlas is made

Many sources trace kombucha to north-east China. It spread through Russia and Eastern Europe as "tea fungus" (chainyi grib) and is also called Manchurian tea.

  1. [csu-kombucha] Colorado State University Extension (Food Smart Colorado) 2020, Understanding and making kombuchagov
  2. [bccdc] BC Centre for Disease Control, Environmental Health Services 2015 (updated 2020), Food safety assessment of kombucha tea recipe and food safety plangov
  3. [wahealth] Department of Health, Western Australia, Risk assessment and legislative requirements for fermented foods, guide for Food Act 2008 authorised officers (kimchi and kombucha)gov
  4. [kbi] Kombucha Brewers International, Kombucha code of practice, version 3.0 (trade body)other
  5. [uga-c1312] Cullinan S. et al. 2026 (revised), What's the word on homemade kombucha?, UGA Cooperative Extension Circular 1312gov
  6. [harrison2021] Harrison K. and Curtin C. 2021, Microbial composition of SCOBY starter cultures used by commercial kombucha brewers in North America, Microorganisms 9(5), 1060 (103 SCOBYs)paper