Kombucha Copilot

🧽 Wash the jar before you reuse it

Before every batch wash the jar with hot water (no scented or antibacterial soap, or rinse very well), then rinse it with a little vinegar or kombucha. Clean hands and utensils. While you wash, keep the SCOBY on a clean plate with a little kombucha.

🫙 Glass is best

Use a wide glass jar (surface area matters more than height). Lead-free ceramic and food-grade plastic are fine too; no aluminium, iron, copper or brass. Utensils in plastic, wood or stainless steel.

🌡️ Sweet tea at room temperature

Dissolve the sugar in the hot tea, then add cold water and wait until it's below 30 °C before adding the SCOBY and starter: heat damages them. Per litre: 2 tea bags (5 g), 70 g sugar, 100 ml starter.

🥄 Starter: at least 10%

Add sour, ready-made kombucha from the previous batch (or the liquid that came with the SCOBY): at least 100 ml per litre. It acidifies the tea straight away and protects against mould. Don't use vinegar instead of starter.

🧺 Cover with a cloth and a clip

In the first fermentation the jar has to breathe: cover it with a tightly woven cloth (or kitchen paper) held firmly with a rubber band or a clip, so fruit flies can't get in. Never an airtight lid in the first fermentation.

🏠 The right spot

A quiet corner between 22 and 27 °C, in the shade, away from direct sun, the stove, fruit and rubbish. In the settings say where it is (indoors, cool room or outside): it's used for the estimate.

✋ Don't move it

Leave the jar still: the new SCOBY forms on the surface and shaking it breaks it. Lifting the cloth to look is fine.

👃 Smell it every day

Lean in, lift the cloth for a moment and smell: it goes from sweet tea to a light note of vinegar and apple. Look at the surface too, without touching: a pale layer is fine, fuzzy spots are not.

🥤 Taste with a straw

As it gets close, taste a sip: slide a clean straw down the side, under the SCOBY, or use the tap. Never with your fingers. It should be a little sweet and a little sour: when you like it, it's ready. Note how it tastes: the app learns.

🔁 Keep starter for the next batch

When it's ready, lift out the SCOBY with clean hands and set aside, with the SCOBY, about 10% of the kombucha taken from the top: that's the starter for the next batch.

🏨 The SCOBY hotel

If you take a break, keep the SCOBYs in a jar of sour kombucha, covered with a cloth, at room temperature (not in the fridge). Add sweet tea every 4-6 weeks. That kombucha becomes a very strong starter.

🍾 Bottle for the second fermentation

Put the recipe ingredients into the bottles (thick glass with swing tops), then the kombucha through a funnel, leaving 2-3 cm of air. Close them tightly: now the bubbles stay inside. Keep them at room temperature, in the dark.

💨 Burp the bottles

Every day open each bottle for a moment over the sink and close it again: the excess gas escapes. It matters most with fruit and when it's warm.

🧴 Test bottle

Fill a small plastic bottle too: when it's hard to squeeze, the glass bottles are just fizzy enough.

❄️ Into the fridge

When it's as fizzy as you like, put the bottles in the fridge: the cold almost stops fermentation. It keeps for a few weeks; strain out fruit and ginger as you pour.

🚰 Open slowly

Open the bottles cold, slowly, over the sink and away from your face, holding the cap with your hand: the pressure can make the cap fly off.

❓ When in doubt, throw it out

If something doesn't seem right (look, smell, taste), don't drink it. Compare with the assistant's problem cards, but safety comes first.

🧼 Hygiene

Washed hands, clean and well-rinsed utensils and bottles, a clean work surface. No contact with raw meat or other ferments. That keeps the kombucha sound and tasty.

🍷 It contains a little alcohol

Fermentation always produces a little alcohol: usually not much, but more when it's warm, with lots of fruit and with a long second fermentation. Anyone who must avoid alcohol completely shouldn't drink it.

🩺 Ask your doctor first

Pregnant or breastfeeding women, children, people with a weakened immune system or health problems: ask a doctor before drinking homemade kombucha.

🧪 pH strips (optional)

If you want to be extra sure, use pH strips: after adding the starter it should be below 4.5; ready kombucha is usually between 2.5 and 3.5.

ℹ️ A guide, not a doctor

Kombucha Copilot is a guide and a log for brewing kombucha at home: it doesn't promise any health benefits and doesn't replace a doctor's advice. Estimates are approximate: your own tasting is what counts.

⚪ Flat white film

A white, flat, slightly wrinkled film that isn't fuzzy is usually kahm yeast: it isn't mould, but it spoils the taste. Skim it off with a clean spoon and add a little sour starter. If the spots are fuzzy or coloured, it's mould: throw everything away.

➖ No new layer

Still no new layer after a week? It's usually too cold, or there was too little or too weak starter. Move the jar somewhere warmer (22-27 °C) and wait a few days; next time use more sour starter.

🪰 Fruit flies

Fruit flies are drawn to the sour smell. Use a tightly woven cloth (or kitchen paper) pulled taut and held with a rubber band or clip, and keep the jar away from fruit and rubbish. If you see larvae or flies in the liquid, throw everything away.

👃 Strong vinegar smell

A light vinegar smell is normal towards the end. If it's strong in the first days, it's usually warm: taste it now, and if it's already sour, bottle it. Kombucha that's too sour is fine as starter or as kitchen vinegar.

🤢 Odd or rotten smell

Kombucha smells of vinegar, apple or yeast. A rotten, strong cheesy or sewage smell isn't normal: if something on the surface also looks odd, throw everything away. When in doubt, don't drink it.

🥶 Too cold

Below 20 °C fermentation slows right down, and below 18 °C mould has more of a chance. Find a warmer spot (near a warm appliance, never on the radiator) or wrap the jar in a towel. The app lengthens the estimate by itself.

🥵 Too warm

Above 29-30 °C kombucha races ahead and turns sour within a few days. Move it somewhere cooler and out of the sun, and check it every day. In the second fermentation heat builds pressure fast: burp the bottles.

🔩 Contact with metal

Kombucha is acidic and can attack metals such as aluminium, iron, copper or brass: keep it in glass (or food-grade ceramic or plastic). A stainless steel ladle or funnel for a few minutes is fine. If it sat for a long time in a non-stainless metal container, throw it away.

🫧 Not fizzy enough

Not fizzy in the second fermentation: bottles that don't seal well, too little sugar or fruit, too much air above the liquid, or too cold. Use swing-top bottles, leave 2-3 cm of air, add a teaspoon of sugar per litre and leave them a day or two longer somewhere warm.

💥 Bottles too pressurised

Cap pushing up, plastic bottle rock hard or foam gushing out as soon as you open: there's too much pressure. Put the bottles in the fridge straight away, open them cold, slowly, over the sink and away from your face. On warm days burp them daily. Only use bottles made for fizzy drinks.

😖 Too sour (vinegar)

It has gone too far. Bottle it now (the second fermentation makes it nicer) or dilute it with a little cold sweet tea. Keep very sour kombucha as starter for the next batch or use it as vinegar. Next time the app will warn you sooner: it learns from your batches.

🍋 Lemon and ginger

Citrusy and fizzy, a classic.

Per litre

• Lemon juice: 20 ml
• Fresh ginger: 8 g
• Honey: 1 tsp (optional)

Use freshly squeezed lemon juice; a teaspoon of honey or sugar per litre helps the fizz.

🍓 Strawberry and basil

Sweet and fragrant, with a pink colour.

Per litre

• Strawberries: 60 g
• Basil: 4 leaves

Cut the strawberries into small pieces or crush them lightly. Fruit makes bubbles fast: burp every day.

🫐 Mixed berries

Blueberries, raspberries and blackberries: purple colour, full flavour.

Per litre

• Mixed berries: 60 g

Frozen berries (thawed) work too. Crush them a little to release the juice.

🍎 Apple and cinnamon

Mellow and spiced, perfect in autumn.

Per litre

• Apple juice: 100 ml
• Cinnamon stick: ½ piece

Use 100% apple juice without preservatives; half a cinnamon stick per litre, broken up.

🍑 Peach

Summery and delicate.

Per litre

• Peach: 70 g

Ripe peaches in small pieces, peeled if you want a softer taste.

🍍 Pineapple and mint

Tropical and very fizzy.

Per litre

• Pineapple: 60 g
• Mint: 4 leaves (optional)

Pineapple makes lots of bubbles: check the bottles every day, especially when it's warm.

🫧 Plain

Just kombucha and a little sugar: to taste the kombucha itself and get the bubbles.

Per litre

• Sugar: 1 tsp

One teaspoon of sugar per litre is enough. It's also the base for trying your own recipes.