Kombucha is fermented sweet tea. One litre of water, 6 to 8 g of tea, 70 to 90 g of sugar, one SCOBY and 150 ml of starter liquid, left seven to twelve days at room temperature. What comes out holds roughly 3 to 5 g of sugar and 10 to 25 mg of caffeine per 100 ml, plus traces of alcohol under 1 per cent. The culture is reused indefinitely. No health claim is made on this page.
Most pages about kombucha lead with what it supposedly does. This one leads with what it is: the ingredients and their purpose, the numbers on the drink, the timeline, and a clear list of what nobody is allowed to promise about it.
Four ingredients and a jar. The tea is not there for flavour alone: it supplies the nitrogen the yeasts need, which is why a kombucha made with herbal infusion instead of real tea weakens over successive batches. The sugar is food for the culture, not sweetening. And the starter liquid, 150 ml of finished kombucha from the last batch, drops the acidity within minutes and is the single best protection against anything going wrong.
A SCOBY is not a mushroom, despite some older names. It is a firm disc of cellulose that the bacteria build themselves, with yeasts and bacteria living inside it. It grows a new layer with every batch.
| Per 100 ml | Kombucha, 8 days | Kombucha, 12 days | Cola |
|---|---|---|---|
| Energy | about 20 to 30 kcal | about 15 kcal | about 42 kcal |
| Sugar | 3 to 5 g | 1 to 2 g | about 10 g |
| Caffeine | 10 to 25 mg | 10 to 25 mg | about 10 mg |
| Alcohol traces | 0.5 to 1 per cent | up to about 1 per cent | none |
| Fibre | 0 g | 0 g | 0 g |
| Live cultures | yes, composition varies | yes | none |
Two rows are worth reading twice. Caffeine is present, which surprises people who treat kombucha as a herbal drink. And fibre is zero, as in every fermented drink, so it does not substitute for vegetables, pulses or wholegrains in that respect.
| Room temperature | First fermentation | Second fermentation |
|---|---|---|
| 18 C | 14 to 21 days | 4 to 6 days |
| 22 C | 9 to 14 days | 3 to 4 days |
| 24 C | 7 to 10 days | 2 to 3 days |
| 28 C | 5 to 7 days | 1 to 2 days |
This is why two people following the same recipe get different results. A kombucha recipe that states ten days without naming a temperature cannot be right in January and in July. Taste from day five and use the table to know roughly when to start.
A kombucha straight out of the jar is tart but flat, because the gas escapes from under a cloth. The bubbles come from the second fermentation, in a sealed bottle.
| Stage | Vessel | Duration | Effect |
|---|---|---|---|
| First fermentation | jar with a cloth | 7 to 12 days | acidity, almost no gas retained |
| Bottling | swing top bottle | 5 minutes | keep 150 ml as starter |
| Second fermentation | bottle sealed | 2 to 4 days | pressure and fine bubbles |
| Chilling | fridge | from 6 hours | fermentation slowed, gas stable |
Watch the pressure. A bottle left four days at 28 C with fruit juice can overflow or force its stopper. Open it briefly over the sink once a day until you know the rhythm of your kitchen.
The origin of kombucha is usually told with a confidence the records do not support. What can be dated begins in the twentieth century; everything before that is oral tradition, and we mark it as such.
| Period | What is claimed | How solid |
|---|---|---|
| Antiquity | origins in north east Asia | tradition, not documented |
| Nineteenth century | spread through Russia and eastern Europe | accounts exist, details vary |
| Early twentieth century | first scientific descriptions in Europe | documented |
| 1990s onwards | commercial production in the United States | documented |
| 2010s onwards | shelf product across Europe | documented |
The practical point behind the history is simple. Fermentation was a way of keeping a drink safe and interesting without refrigeration, and that is a better explanation for the spread of kombucha than any health story attached to it later.
The tea changes the flavour and the pace but not the method. One rule matters: it has to be real tea, from the tea plant, because that is where the nitrogen comes from.
| Tea | Flavour | Pace | For the culture |
|---|---|---|---|
| Black tea | strong, malty | brisk | the safe default |
| Green tea | light, grassy | slightly slower | fine, long term |
| Half black, half green | balanced | brisk | the usual compromise |
| Oolong | floral | medium | occasional |
| Flavoured tea with oils | perfumed | erratic | avoid |
| Herbal infusion, no real tea | very mild | very slow | not as a permanent diet |
A single batch of kombucha on herbal infusion does no harm. Several in a row weaken the culture, because the yeasts run short of the nitrogen that only real tea provides. Alternate with black tea if you want to experiment.
The flavour goes into the second fermentation, and a small amount per litre is enough. The sugar in the fruit is food for the culture rather than an additive, which is the difference between a home batch and a bottle sweetened after the fact.
| Addition | Per litre | Result | Second fermentation |
|---|---|---|---|
| Fresh grated ginger | 1 teaspoon | sharp, strongly fizzy | 2 days |
| Raspberries | a handful | fruity, deep red | 3 days |
| Lemon and mint | 1 slice, 3 leaves | fresh, light | 3 days |
| Apple juice | 50 ml | mild, sweeter | 2 days |
| Dried hibiscus | 1 teaspoon | tart, strongly coloured | 3 days |
Two rules keep it predictable: change one thing at a time, and shorten the second fermentation for sugary additions because the pressure rises faster. A bottle of kombucha with juice should be checked on the first day.
This is the part that decides whether a jar survives past the first month. Kombucha is a weekly commitment rather than a daily one.
| How often | What to do | Time |
|---|---|---|
| Every 7 to 12 days | bottle, keep 150 ml, set up fresh tea | 15 minutes |
| Monthly | remove the spare disc layers | 5 minutes |
| Before a trip | SCOBY into sweet tea in the fridge | 5 minutes |
| After a trip | one batch to restart | 1 fermentation |
| Never | buy the culture again | not applicable |
Fifteen minutes every ten days, and the consumables are tea, sugar and water. The last row is the structural difference from a shop bottle: the culture grows, so it is larger at the end of the year than at the start.
This is not a list of dangers, it is a list of situations where a conversation with a professional comes before an experiment. We give no medical advice.
| Criterion | Kombucha | Water kefir | Milk kefir |
|---|---|---|---|
| Base | sweetened tea | sugared water | milk |
| Culture | firm disc | translucent crystals | white clusters |
| Time | 7 to 12 days | 24 to 48 hours | 18 to 30 hours |
| Caffeine | yes | none | none |
| Effort per week | 15 minutes once | 5 minutes three times | 5 minutes daily |
| Patience needed | more | less | less |
Kombucha is the slowest of the three and the only one with caffeine. It is a weekly project rather than a daily habit, which suits some people considerably better.
Authorised health claims in the European Union are listed by the European Food Safety Authority. There is no authorised claim for kombucha, which is why this page describes a drink rather than a benefit.
Live kombucha SCOBY
Shipped with its own starter liquid, ready for a first batch the day it arrives.
See the SCOBYThe step by step method: how to make kombucha. Shop bottles compared: homemade or industrial.
A fermented drink made from sweetened tea and a live culture called a SCOBY, a firm disc of cellulose housing bacteria and yeasts. It ferments for seven to twelve days at room temperature and ends up tart and lightly fizzy. The culture is reused batch after batch.
Tart, slightly vinegary, with the tea still recognisable underneath. A shorter fermentation leaves it sweeter, a longer one sharper. Fruit added in a second fermentation moves it towards a soft drink without adding anything artificial.
Yes. It is made from tea, and part of the caffeine remains, roughly 10 to 25 mg per 100 ml depending on the tea and the brew. Green tea gives slightly less than black.
About 3 to 5 g per 100 ml after eight days, and 1 to 2 g after twelve. It never reaches zero because the culture lives on it. A flavoured bottle with juice added afterwards can reach 6 to 9 g.
Not entirely. Fermentation produces traces, usually under 1 per cent at home and under 0.5 per cent in commercial products. A long, warm second fermentation raises the figure.
Seven to twelve days at 22 to 24 C, then two to four days in a sealed bottle for the fizz. At 18 C the first phase can take three weeks, at 28 C under a week.
In principle you can grow one from an unpasteurised, unflavoured bottle, but it takes two to four weeks and often fails. A live disc with starter liquid is the reliable route.
That is a question we do not answer, because health claims in the European Union are only permitted when they have been assessed, and there is no authorised claim for kombucha. What we can say is what is in it and how it is made.
