Water kefir
Milk kefir
Kombucha
Ginger beer
Kefir duo
Kefir and kombucha
Starter kit
RennetHomemade kombucha contains traces of alcohol, usually under 1%. The same goes for every drink you ferment at home, water kefir and ginger beer included. Most of it forms in the closed bottle during the second fermentation. With 80 g of sugar per litre, bottling between day 7 and day 10 and moving the bottles to the fridge after 2 to 5 days, you keep the level low.
Is there really alcohol in kombucha?
Yes, in small amounts. It comes with fermentation, just as the fizz does.
Whenever yeasts get hold of sugar, they turn it into gas and a little alcohol. It happens in bread dough rising on the counter, in a carton of apple juice left open too long and in your kombucha jar. In kombucha it stays at traces, because the same jar is home to bacteria that use that alcohol up almost as soon as it appears. Nobody can give you an exact figure for your own batch, since every jar behaves a little differently. What you can control is which way you push it.
One thing worth knowing: homemade kombucha is not alcohol-free in the strict sense that a shop label uses the term. If you are pouring it for someone who does not drink alcohol at all, simply tell them it contains traces, and let them decide.
Who makes the alcohol, and who clears it up?
The yeasts make it; the acetic acid bacteria turn it into acid. To do that, the bacteria need oxygen.
A SCOBY is exactly that partnership: yeasts and bacteria in one rubbery disc. In the open jar, with only a cloth over it, they work like a production line. The yeasts break down sugar, the bacteria pick up the alcohol and turn it into the fresh, tangy taste that makes kombucha what it is. That is why your tea gets a little less sweet and a little sharper every day. For more on what lives in that disc, see What is a kombucha SCOBY?
When does most of the alcohol form?
In the closed bottle. No air gets in, so the bacteria slow right down while the yeasts carry on.
| Stage | What happens | Alcohol |
|---|---|---|
| First fermentation, open jar, 7 to 10 days | Yeasts make alcohol, bacteria use oxygen to turn it into acid | Stays low; the jar mainly gets sourer |
| Second fermentation, closed swing-top, 2 to 5 days | Yeasts feed on leftover sugar and fruit; gas and alcohol stay in the bottle | Rises a little, more when warmer and sweeter |
| Fridge | The yeasts barely work | Stays roughly where it is |
The second fermentation is the step that makes kombucha worth making: without those days in the bottle you have very little fizz. So there is no need to skip it, only to keep it short. How to go about that, with the amount of fruit and the right moment to chill, is in Kombucha: the second fermentation.
The five dials you control
Sugar, time, temperature, fruit and the cover. With these five you keep the level low without giving up any flavour.
- Sugar: 80 g per litre, no more. With 1 SCOBY, 1 cup of starter liquid (about 250 ml) and 3 tea bags or about 8 g of loose tea, that is the basic recipe from How to make kombucha.
- Time in the jar: taste from day 7 with a clean straw. If it still tastes like sweet iced tea, wait another day or two. Bottling too early hands the yeasts in the bottle a lot of sugar.
- Temperature: 20 to 25°C. In a warm spell, when the kitchen climbs towards 28°C, everything speeds up, so chill the bottles sooner.
- Fruit: a small handful of raspberries or a few slices of ginger per litre is plenty. A big splash of apple juice or a lot of ripe mango gives the yeasts extra work.
- The cover: always a cloth and an elastic band during the first fermentation, never a lid. Otherwise the jar is short of the oxygen the bacteria need.
Leave your kombucha too long in the open jar and it does not get stronger, it gets sour, heading for vinegar. That has its own solutions, in Kombucha too sour?
Does the season matter?
Yes. Warmth speeds everything up, the yeasts in the bottle included.
In July a bottle can be properly fizzy after two days. Leave it until the weekend and it becomes drier, with more pressure and a touch more alcohol. Around Christmas, in a kitchen at 18°C, you will more likely need five days, and the first fermentation can run a day over. Tasting works better than following the calendar in every season. More on the cold months is in Fermenting in winter.
Is it different with water kefir and ginger beer?
No. There too it is a question of traces, usually under 1%, and there too the time in the closed bottle counts most.
Water kefir spends 24 hours in the jar and then 24 to 48 hours in a swing-top with fruit; ginger beer spends 48 hours in the bottle. Same logic: short and warm, then cold. How it works for water kefir is in Water kefir: the second fermentation. Making a jug for a bank holiday barbecue or a birthday in the garden? Try the alcohol-free Moscow mule. It is called that because there is no vodka in it; the ginger beer itself still has its traces.
Can you measure it at home?
Not reliably. The hydrometers used for home brewing beer and wine are not made for a drink this low in alcohol and this full of gas and acid, and the readings would tell you very little. The basic recipe is a far better guide: steady sugar, bottling on time and a short, warm second fermentation followed by the fridge.
Frequently asked questions
Is homemade kombucha alcohol-free?
Does kombucha get stronger if I leave it longer?
Do extra sugar or fruit mean more alcohol?
Does the fridge stop the fermentation completely?
With your own SCOBY, you decide how long, how sweet and how warm. Our live kombucha SCOBY with starter liquid costs £16 and, well looked after, keeps going for years. Brewing, bottling and storing are all gathered on the kombucha page.