What Are Fermented Drinks? Definition, Ingredients, and How They’re Made

Definition and core ingredients

Kombucha is produced when sweetened tea is fermented by a SCOBY (a symbiotic culture of bacteria and yeast). Fermentation is the key mechanism: it drives the formation of organic acids (which contribute tartness), produces carbon dioxide (which creates fizz), and can generate small amounts of ethanol as a normal byproduct of yeast activity.

Most kombucha is built on the same foundation:

• Tea (often black, green, or a blend) – provides flavor compounds and a base for fermentation.
• Sugar (commonly sucrose) – the main substrate that microbes metabolize during fermentation.
• SCOBY – the mixed community of yeasts and bacteria that runs the fermentation.
• Starter liquid (previously fermented kombucha) – helps inoculate the new batch and supports early acidification.

About SCOBY: people often use the word to describe the visible “mat,” but it helps to separate the culture (the microbes) from the pellicle (a cellulose layer that can form on the surface during fermentation). Different cultures behave differently, which is one reason kombucha can vary a lot between brands.

How it’s made and what changes during fermentation

Exact recipes vary, but the production logic is consistent. Kombucha begins as sweetened tea, then fermentation runs for days. Producers may add secondary steps (like blending or controlled carbonation) depending on the desired style and stability for distribution.

A simple high-level flow:

1. Brew tea + dissolve sugar, then cool to a fermentation-safe range.
2. Add starter liquid + culture to begin fermentation in a more controlled, stable environment.
3. Primary fermentation runs for days, building acidity and natural carbonation.
4. Optional finishing steps may adjust clarity, flavor, and carbonation for consistency.

During fermentation, two groups do most of the work:

Yeasts ferment sugars and produce CO₂ (carbonation) and ethanol (a normal byproduct). Acetic acid bacteria can then oxidize ethanol into organic acids (including acetic acid), which contributes to kombucha’s characteristic tang.

In practical terms, fermentation shifts the drink’s balance in three noticeable ways:

• Sweetness perception usually drops as part of the sugar is metabolized.
• Acidity rises as organic acids accumulate.
• Fizz increases as CO₂ is produced and retained.

Those outcomes depend on multiple variables—tea choice, culture composition, time, temperature, oxygen exposure, and post-fermentation handling—which is why “kombucha” is a category with many styles rather than one fixed taste.

Acidity, alcohol, and responsible communication

Acidity and pH: kombucha is acidic by nature, and producers monitor acidity as part of process control and product stability. You’ll often see pH 4.6 referenced as a benchmark used in food microbiology and food processing contexts, but it should not be treated as a single-number guarantee. Growth limits for microorganisms depend on more than pH alone (for example, the food matrix and available nutrients), and documented exceptions exist under certain conditions. In practice, safe production relies on overall hygiene and validated process control—not a single parameter.

Alcohol: kombucha can contain alcohol because yeast fermentation produces ethanol. The amount can vary based on fermentation conditions and what happens after packaging. That’s why many producers and regulators focus on measurement: ethanol in kombucha is commonly quantified using validated laboratory methods (for example, headspace gas chromatography in published validation work).

Health claims: kombucha is often marketed with broad wellness messaging. When writing about benefits, it’s important to separate what is well-established about fermentation chemistry and composition from claims about human outcomes. Reviews of human-subject evidence have emphasized that clinical research is limited compared with how widely kombucha is promoted.