Kombucha is made by fermenting sweet tea with a SCOBY, first to acidify, then to carbonate in bottles.
Kombucha starts as sweet tea and ends as a tart, bubbly drink. The bridge between the two is a living SCOBY—a culture of yeast and bacteria—that turns sugar into acids and a splash of natural sparkle.
How Kombucha Is Made, From Tea To Bottle
Brewers begin with black or green tea, plain sugar, clean water, and a SCOBY with strong starter liquid. The base tea is brewed, the sugar is dissolved, and the liquid cools to room temperature. Starter tea lowers the initial pH to a safer zone so the culture can take hold. The SCOBY goes in, and primary fermentation begins.
Kombucha Production At A Glance
| Stage | Typical Time | Target Sign |
|---|---|---|
| Make Sweet Tea | 15–20 minutes | Sugar fully dissolved |
| Add Starter + SCOBY | Instant | Start pH below ~4.5 |
| Primary Fermentation (F1) | 7–14 days | pH drops; taste turns tart |
| Remove SCOBY | 1–2 minutes | New pellicle formed |
| Flavoring (optional) | 5–10 minutes | Fruit, herbs, or ginger added |
| Bottling | 10 minutes | Tight seal; headspace left |
| Secondary Fermentation (F2) | 1–3 days | Bubbles build; chill to set |
Primary fermentation (often called F1) is where the SCOBY does most of the work. Yeasts eat the sugar and produce CO2 and a small amount of ethanol; bacteria convert much of that into acetic and gluconic acids. The brew turns more acidic, which guards against spoilers and gives that familiar bite.
How Do They Make Kombucha? Step-By-Step At Home
Ingredients And Gear
You’ll need tea (black or green), plain white sugar, a SCOBY with 1–2 cups of strong starter tea per gallon, a 1-gallon glass jar, cloth cover with rubber band, pH strips or meter, bottles rated for pressure, and a funnel.
Step 1: Brew And Cool The Sweet Tea
Brew 10–12 cups of tea and dissolve 1 cup of sugar per gallon. Cool fully; hot liquid can stress the culture.
Step 2: Acidify And Inoculate
Pour the cool tea into the jar, add starter tea to push the mix below pH ~4.5, then slide in the SCOBY. Cover with cloth.
Step 3: Ferment F1
Set the jar in a warm spot (70–80°F/21–27°C). Taste on day 7. When it lands between lightly sweet and tart, and the pH has dropped, it’s ready to bottle or keep fermenting to your taste.
Step 4: Bottle And Flavor
Lift out the SCOBY and reserve 2 cups of finished kombucha as starter for the next batch. Funnel the rest into swing-tops. Add fruit, juice, or ginger if you like.
Step 5: Ferment F2
Leave capped bottles at room temperature 1–3 days to build carbonation, then refrigerate to stop pressure from climbing.
Safety Basics That Keep Batches On Track
Clean gear, strong starter tea, and a low starting pH help keep unwanted microbes out. Many extension and food-code sources point to a pH below about 4.2 in finished kombucha, with a drop below 4 within the first few days of F1. Keep the brew warm—not hot—and out of direct sun. If you ever see fuzzy mold on the surface, toss the batch and start again with fresh culture.
Finished kombucha can carry trace alcohol from fermentation. When sugar and yeast push alcohol above 0.5% ABV, the drink falls under beverage-alcohol rules in the United States. Home batches can vary, so keep F1 temperatures moderate and don’t leave F2 at room temperature for long stretches.
Flavor Paths And Tea Choices
Classic profiles start with black tea for body and tannin, or green tea for a lighter finish. Oolong, white tea, and blends work too. Keep oils and spices modest during F1 so the SCOBY stays happy; add bold flavors in F2 instead. Popular add-ins: ginger, lemon, berries, mango, pineapple, and herbs like mint or basil.
Sugar isn’t a sweetener here so much as fuel. Plain sucrose ferments cleanly and predictably. Raw honey can carry its own microbes; if you want that flavor, add a small amount in F2, not F1. For less sweetness in the glass, let F1 run longer, then bottle without juice and chill sooner.
Benchmarks, pH Targets, And Timing
Brewers aim for a starting mix below pH 4.5 using enough starter tea. During F1, the pH usually falls below 4 within several days and into the 2.5–3.5 range at finish, depending on time and temperature. A warmer room shortens F1; a cooler room stretches it. Taste and measure, then act: bottle sooner for lighter acid and lower fizz, or later for sharper acid.
When you bottle, leave about an inch of headspace. Chill when bubbles meet your goal; cold storage slows yeast, holds carbonation, and steadies flavor.
Science Inside The Jar
During F1, yeasts such as Saccharomyces chew through sucrose and release ethanol and CO2. Acetic acid bacteria like Komagataeibacter then oxidize ethanol into acetic acid and produce gluconic and other organic acids. That shifting balance is why time, temperature, and sugar all change the taste.
People often ask, “how do they make kombucha?” in factories. The core steps are the same, only scaled and monitored: measured starting pH, fermentation logs, tight hygiene, and controlled carbonation. Commercial producers also watch alcohol. In the United States, drinks that hit 0.5% ABV or more fall under beverage-alcohol rules.
Food Safety Notes And Sources
Keep the starting mix acidic. University extensions and food-code digests call for dropping below about pH 4.5 before F1, then finishing near 2.5–3.5. A pH meter or fresh strips makes this easy. See the home-brewing sheet that targets a finishing pH near 2.5–4.2 and warns against long, hot ferments.
If anything grows fuzzy on the surface, bin it. Rare illness reports have been linked to unsanitary, uncontrolled brews during primary fermentation, which is why a low starting pH, clean gear, and steady temperatures matter.
Quality Control Checklist For Every Batch
- Acidify below pH ~4.5 with enough starter tea before adding the SCOBY.
- Hold 70–80°F during F1; colder rooms slow the drop in sugar and acid.
- Taste every couple of days after day 7 and note time, temp, and flavor.
- Finish below pH 4; many bottle between pH 3.0 and 3.6.
- Keep F2 brief, then refrigerate to set bubbles and cap alcohol growth.
- Reserve at least 2 cups as strong starter for the next jar and clean gear well.
Common Mistakes And Simple Fixes
| Issue | Likely Cause | Quick Fix |
|---|---|---|
| No Carbonation | Cold room; weak seal; little sugar in F2 | Warm F2; use tighter bottles; add small sugar source |
| Vinegar Taste | F1 too long or hot | Bottle earlier; lower room temp |
| Surface Mold | High starting pH; weak starter; dusty jar | Discard; sanitize; use stronger starter |
| Yeasty Haze | Excess sediment carried to bottles | Strain through nylon mesh |
| Exploding Bottles | F2 too long warm; thin glass | Check daily; chill sooner; use pressure-rated glass |
| Flat After Fridge | Under-fermented F2 | Leave at room temp one more day, then chill |
| Stalled Ferment | Room too cold; low yeast | Move warmer; feed a little fresh tea and sugar |
Equipment Upgrades That Help
Basic gear gets you far, and a few extras make brewing smoother. A digital scale locks in repeatable sugar and tea ratios. A narrow-range pH meter with storage solution gives steady readings; fresh strips are fine in a pinch. A stick-on thermometer shows when a cool night slowed the culture. For bottling, choose heavy swing-tops with gaskets or pressure-rated soda bottles. A small nylon mesh strainer removes yeast clumps without stripping flavor.
Brewing often? Set a simple loop: one bin for clean bottles, one for “needs washing,” and a no-rinse sanitizer. Label caps with date and flavor. These tidy habits prevent residue, keep carbonation predictable, and steady flavor consistency.
Practical Notes On Caffeine, Alcohol, And Shelf Life
Use both SCOBY and strong starter tea for a reliable start. Caffeine drops from the base tea; green tea is lighter. Alcohol stays low, but long warm F2 raises it, so chill sooner if needed. Store bottles cold; flavor and fizz evolve slowly as yeast settle.
The Method At A Glance You Can Save
- Brew tea and dissolve sugar. Cool fully.
- Add 1–2 cups starter tea per gallon to drop pH.
- Add SCOBY. Cover with cloth.
- Ferment 7–14 days at 70–80°F, tasting along the way.
- Remove SCOBY and reserve starter for next batch.
- Bottle, add flavors if you like, and seal.
- Ferment 1–3 days warm, then chill to set bubbles.
When people ask, “how do they make kombucha,” the real answer is simple: sweet tea, a healthy culture, patient primary fermentation, and a short, cold-finished bottle step. Do that, keep pH in range, and you’ll pour crisp, clean kombucha every time.
