Short answer
Use about 3 tablespoons of mashed fresh or frozen blueberries per 500 ml bottle, or about 2 to 4 tablespoons of cooked blueberry syrup. Top up with plain kombucha, seal the bottle, and leave it at room temperature for three to five days. Burp it daily.
Two ways to add blueberries
Mashed berries (simplest)
Mash the berries in the bottle with the back of a spoon. This is the quickest method, and it gives a fruity, slightly cloudy drink. Strain it before serving if you want it clear.
Cooked blueberry syrup (smoother)
Cook the berries with a little water and sugar until they burst and thicken slightly. Strain the syrup through a fine sieve and let it cool completely. The syrup gives an even colour and a smooth, clean flavour, and it is easier to strain than mashed fruit.
What you need (per 500 ml bottle)
For mashed berries:
- About 3 tablespoons of blueberries, mashed
- Plain first-ferment kombucha, about 500 ml
- A pressure-rated swing-top bottle and a funnel
For cooked syrup (makes enough for about four bottles):
- About 1/2 cup of blueberries
- About 1/2 cup of water
- About 1 tablespoon of sugar, or honey or maple syrup
- Optional: a squeeze of lemon, or a thin coin of fresh ginger
How to make blueberry kombucha
- For the syrup: put the berries, water and sugar in a small saucepan. Heat until they burst, mash them, and simmer for three to five minutes. Strain through a fine sieve and cool to room temperature.
- Divide the syrup, or the mashed berries, evenly between clean bottles.
- Pour in the plain kombucha through a funnel, leaving about 2.5 cm (1 inch) of headspace.
- Seal the bottles and leave them at room temperature, out of direct sun, for three to five days.
- Burp each bottle once a day over a sink.
- Chill the bottles when they are fizzy enough.
Cool the syrup first. Do not add hot liquid to a living brew. Let the syrup cool fully before it goes into the bottles.
Fizz timing and burping
Blueberries add sugar, so the fizz builds steadily over three to five days. In warm weather, check after two days. Burp daily, and open the bottle slowly. A very hard bottle should be vented over a sink.
Strain or leave the fruit in?
Strain before serving if you want a clear drink. Mashed berries leave bits in the bottle, which settle, and the flavour can change as they sit. Cooked syrup is easier to strain.
Variations: lemon, ginger, mint
- Lemon: a squeeze of lemon brightens the drink and makes the colour more vivid.
- Ginger: a thin coin of fresh ginger adds warmth. See the ginger kombucha recipe.
- Mint: two or three leaves give a fresh, cool finish. Strain them out before serving.
- Lavender: a light floral note pairs well with blueberry. See the lavender kombucha recipe.
Troubleshooting
- Too sweet: use less sugar in the syrup, or dilute with a little plain kombucha.
- Not fizzy: check the seal and the temperature. See why your kombucha is not fizzy.
- Pale colour: add more berries, or use a little more syrup.
For more berry batches, see the raspberry kombucha recipe and the strawberry kombucha recipe. For the full method, see how to flavour kombucha.