You’ve followed the recipe, prepared the sweet tea, set up your SCOBY, covered the jar… and after several days, still nothing convincing. The kombucha tastes almost exactly the same as when you started, the surface seems frozen, there’s no marked acidity, and sometimes you can’t even see a new disc.
It’s frustrating, especially when you’ve just discovered this drink and wanted to pour your first fizzy bottles. You wonder if you’ve messed up, if SCOBY is dead, if the water is to blame, or if it’s just not for you.
Rest assured: most of the time, a kombucha that ‘doesn’t ferment’ is not a definitive failure, but a problem of conditions. Temperature, proportions, tea, water, quality of SCOBY, starting pH, container… every detail counts.
By understanding how fermentation normally works, you can identify what’s going wrong in your situation, correct it and often get the ball rolling again. If your culture comes from a SCOBY Natural Probio, you already have an advantage: the strain is healthy and balanced. All you have to do is give it the right environment.
What “fermenting” means for kombucha
Before talking about breakdowns, you need to know what you’re supposed to be looking at when things are going well.
Signs of fermentation in progress
A kombucha that ferments over the course of a few days :
a change in taste: from very sweet to increasingly acidic
a slight spiciness on the tongue associated with organic acids
a scent that shifts from simple sweet tea to notes of cider or sweet vinegar
the formation of a new film (a SCOBY baby) on the surface of the liquid
sometimes a few bubbles on the edges of the jar or under the SCOBY
These are not always spectacular signs, but together they indicate that yeast and bacteria are at work.
Signs of stuck fermentation
Conversely, kombucha that doesn’t ferment (or hardly at all) can often be identified by :
a taste almost identical to the original sweet tea
very low acidity after 5, 7, 10 days
total absence of new film on the surface
no smell of kombucha / vinegar, just sugar and tea
sometimes a SCOBY which seems inert, which does not change, without any trace of a new layer
This is not necessarily dangerous (as long as there is no mould), but it indicates that something is blocking the process.
First question: is it really too early to judge?
Many fermentation “breakdowns” are actually… normal impatience.
Kombucha is not an instant soda
If your kitchen is cool, it’s possible that :
at D+3, the taste has changed very little
at D+5, acidity is just beginning to appear
it’s only at D+7 or D+10 that the transformation becomes obvious
The colder the room, the slower the fermentation. Below 20°C, everything slows down. At 17-18°C, kombucha can take much longer to acidify.
Before concluding that it “doesn’t ferment”, ask yourself:
How many days have actually passed?
What is the approximate temperature of your jar?
If you’re at D+3 in a room at 19°C, it’s logical that the drink still seems very sweet. Give it more time.
How to test without upsetting everything
To follow developments :
take a teaspoon of liquid with clean hands, without stirring the jar
taste, then put the jar back without shaking it
If, day after day, you feel a slight drop in sugar and a rise in acidity, fermentation is underway, even if it remains discreet. If after 7 to 10 days there is no change at all, there is probably a problem that needs to be corrected.
Temperature: the number one cause of soft fermentation
Too cold: the SCOBY slows down
Kombucha is a drink that likes moderate to slightly warm temperatures:
ideally around 22-26 °C
acceptable between 20 and 28 °C
Below 20°C, the crop works, but much more slowly. Below 18°C, it can almost go to sleep.
Result:
tea stays very sweet for a long time
no new disc is formed
you have the impression that the SCOBY “does nothing”.
This is common in winter, in kitchens with little heating.
What you can do
Place the jar in the most temperate room in the house (often the living room rather than the kitchen).
Avoid cold windowsills, cellars or garages.
If necessary, place the jar on an insulating surface (wooden board, folded tea towel) rather than directly on an icy work surface.
With SCOBY Natural Probio, simply raising the temperature can be enough to restart fermentation.
Too hot: activity goes haywire
Conversely, above a constant 28-30°C :
fermentation gets out of control
certain micro-organisms take over
the SCOBY may suffer, or even deteriorate
In this case, fermentation can start and then quickly stall or become very unbalanced.
What you can do
Keep the jar away from hotplates, ovens and appliances that heat up.
Protect it from direct sunlight (especially behind glass).
If your home is very hot, opt for the “coolest” place in the house, even if it’s not the kitchen.
Sugar: neither too little nor too much
Sugar isn’t for you, it’s for SCOBY
The reflex to drastically reduce sugar “to make things healthier” is very common… and very problematic.
The SCOBY of kombucha :
needs sugar to work
transforms it into alcohol and then into acids
cannot ferment without a sufficient source of energy
If you start with a tea that is not sweet enough, the :
finds little fuel
gets off to a slow start, if at all
produces a kombucha that remains flat and sweet… but doesn’t protect itself sufficiently against contamination
What problems arise if you cut back on sugar too much?
fermentation stagnates
the pH does not fall very much, so the environment remains fragile
kombucha does not acquire the protected acidic profile that makes it so stable
If you use SCOBY Natural Probio in an almost unsweetened tea, you’re simply preventing it from expressing its potential.
What you can do
Keep to a reasonable proportion of sugar for the first fermentation (for example, the equivalent of around 70-80 g per litre of tea, depending on the recipe you use).
Let the fermentation process do its work: the sugar will be consumed little by little.
If you find the final kombucha too sweet, prolong fermentation for a few days instead of reducing the starting sugar to a ridiculous level.
A sufficiently sweet tea to start with is one of the pillars of a fermentation that gets off to a good start.
Tea, water and kombucha mother: the foundations to check
Even with the right temperature and enough sugar, certain basic elements can block fermentation.
Tea that is unsuitable or too fragile
SCOBY likes :
classic black or green teas
sufficiently rich in tannins and minerals
If you only use :
fruit infusions
caffeine-free herbal teas
teas flavoured with lots of essential oils
fermentation can :
be capricious
start very slowly
or provide an environment that is too poor to sustain the crop over the long term
Essential oils, in particular, can be antimicrobial and disrupt SCOBY.
What you can do
For a healthy crop, always start with a simple, unscented black or green tea.
You can add herbal teas or flavourings later, during the second fermentation, when the kombucha is already acidified.
With a SCOBY Natural Probio, a classic black or green tea puts all the chances on your side.
Problematic water (chlorine, aggressive treatments)
Highly chlorinated water can :
harm some of the micro-organisms in SCOBY
slow down fermentation
even block the start-up, especially if the crop is already a little fragile
What you can do
Leave your tap water in an open carafe for a few hours to allow the chlorine to evaporate.
Or use filtered water (without excess treatment).
Avoid distilled or excessively demineralised water, which lacks minerals useful for fermentation.
Not enough kombucha mother (starter liquid)
Kombucha mother is :
the very acidic liquid supplied with your SCOBY Natural Probio
or a portion of previously fermented kombucha from a previous batch
This liquid is used for :
quickly acidify sweet tea
protect the crop from foreign micro-organisms
create a comfortable environment for acetic bacteria
If you use too little, the starting pH will be too high, the medium will remain vulnerable and fermentation may stall.
What you can do
Make sure you add the right proportion of kombucha mother to each new batch (e.g. 10-20% of the total volume, depending on the concentration).
If you have very acidic kombucha (almost vinegar), a smaller quantity may be enough to acidify it.
With a Natural Probio kit, use all the liquid supplied as the acid base for your first jar.
The jar, the oxygen and the cover: details that count
Kombucha is an aerobic fermentation for some of the people involved (acetic bacteria like oxygen). Access to air is therefore important.
Container too tight: fermentation stifles
If you close your jar :
with a hermetic lid screwed on tightly
without any air exchange
the bacteria that need oxygen are restricted, the formation of the new surface layer is hindered and the process is slowed down.
What you can do
Use a wide-mouth jar.
Cover it with a clean cloth (cotton or linen) held together with an elastic band.
If you’re using a lid, simply fit it on without screwing it down, or pierce it with small holes and keep a cloth underneath to keep out insects.
Jar in the wrong place
There are two areas that often pose problems:
directly onto a very cold surface (which cools the entire jar)
in full sun behind glass (greenhouse effect, excessive heat and UV)
In both cases, thermal stability is compromised, which disrupts the crop.
What you can do
Place the jar on a neutral surface (wood, shelf, unglazed work surface).
Avoid very sunny windowsills.
Choose a quiet spot, not just above the dishwasher or next to the oven.
The SCOBY itself: quality, health and vitality
You may have complied with all the conditions… and still the fermentation doesn’t take. In this case, you need to take a close look at the state of the SCOBY.
SCOBY too young or too thin
A very young SCOBY :
very fine
recently formed on the surface of a batch
used on its own, without the older ‘parent’.
can sometimes have difficulty starting fermentation on a large volume. It does not yet have sufficient microbial density.
What you can do
Combine a young SCOBY with an older coat at first.
Use plenty of highly acidic kombucha mother.
If you’re starting from scratch, a SCOBY of Natural Probio kombucha is already a mature culture, ready to work from the very first batch.
SCOBY weakened by poor conditions
A SCOBY may be alive but weakened by :
very long breaks without food
prolonged refrigerated storage
repeated recipe errors (unsuitable tea, too little sugar, aggressive water)
In this case, fermentation starts very slowly, or remains stuck at a lukewarm level.
What you can do
“Reactivate” the SCOBY in a convalescent bath: sweet tea + a good dose of acidic kombucha, at room temperature, leaving it to work for longer.
Accept that the first batch of stimulus is mainly technical: designed to reinvigorate the crop, not necessarily to be drunk.
If, after one or two attempts, nothing happens, it may be time to start again with a healthy SCOBY (for example a new SCOBY Natural Probio).
SCOBY dead or contaminated
A dead SCOBY no longer ferments. But you have to distinguish between simple weakness and the true end of life.
Alarming signs :
smell of rubbish, rotten eggs, damp mould (not vinegar)
green, blue, black or white fluffy patches: these are moulds
SCOBY which liquefies, disintegrates completely, becomes greyish and crumbly
In these cases :
no attempt is made to restart fermentation
we throw out the whole batch and the SCOBY
carefully clean the jar
we’re starting again with a healthy crop
This is where having a hotel in SCOBY or the option of ordering SCOBY Natural Probio means you don’t have to stop everything.
Special cases: sweeteners, flavourings, secondary fermentation
Certain practices, often inspired by soft drinks or ‘diet’ drinks, can kill off fermentation before it even begins.
Using sweeteners instead of sugar
The SCOBY does not feed:
of stevia
artificial sweeteners
erythritol or other non-fermentable sugars
If you replace sugar with this type of product :
you get a tea that’s sweet for you, but not for the crop
fermentation does not start, or hardly starts at all
kombucha is still a flavoured infusion, without any real processing
What you can do
Keep the classic sugar for the first fermentation.
If you want to limit the sugar in the final drink, let the SCOBY consume a large part of it by prolonging fermentation.
You can add sweeteners later, just before serving, if required.
Add flavourings too early or in too large quantities
Put in from the first fermentation:
fruit juices in large quantities
very strong spices
powerful liquid flavours
essential oils
can upset the balance of SCOBY, or even be downright antibacterial.
What you can do
Keep the first fermentation simple: tea + sugar + SCOBY + kombucha-mother.
Use the second fermentation (in the bottle, after removing the SCOBY) to flavour: a little juice, a few pieces of fruit, etc.
With a SCOBY Natural Probio, this discipline gives you a stable base on which you can then have fun with aromas.
How to revive kombucha that won’t ferment: a practical action plan
If your kombucha seems to be blocked, let’s recap in the form of a simple procedure.
1. Check the time and temperature
Count the number of days that have passed.
Measure or estimate the room temperature.
If you have been below 20°C for less than 5 days, wait a little longer.
If you are 7-10 days out with a temperature of around 22-24°C and nothing is happening, continue with the diagnosis.
2. Taste and smell analysis
Taste: still very sweet, no acidity?
Odour: neutral sweet tea or already a little vinegary?
If everything is completely neutral, fermentation has hardly started. If there is a hint of acidity, fermentation has begun but remains timid.
3. Look at the SCOBY and the surface
Can you see the beginnings of a film on the surface?
Is SCOBY a normal colour (cream to brown)?
Are there any fluffy spots or just smooth/brown spots (yeast)?
If you see mould, throw it out. If not, carry on.
4. Asking the right questions
Did I use enough sugar to start with?
Have I added the kombucha mother or the very acidic liquid?
Was my tea a real black/green tea, or just a fruity herbal tea?
Is my water highly chlorinated? Have I left it to stand?
Is my jar covered in a breathable fabric or enclosed in a hermetically sealed lid?
Each answer can point to a probable cause.
5. Decide to correct or start from scratch
If the SCOBY looks healthy and smells OK:
prepare a new sweet tea
add a generous amount of acidic kombucha (if you have any)
transfer the SCOBY to this new medium, at the correct temperature
If, despite this, fermentation refuses to start after a week:
your culture is probably too weak
the simplest and safest solution will be to start again with a healthy Natural Probio SCOBY, with its mother kombucha, to restart a line in good conditions
In short: kombucha that doesn’t ferment is rarely a fatality
Kombucha that doesn’t ferment (or doesn’t ferment very well) isn’t a condemnation, it’s a signal. It’s telling you:
“I’m cold,
“I don’t have enough to eat”,
“my tea is not suitable”,
“I lack the acidity to protect myself”,
or “my SCOBY is at the end of his rope”.
Reviewing :
the temperature
the amount of sugar
the type of tea
water quality
sufficient presence of mother kombucha
the condition of your SCOBY
In most cases, you can identify the weak link and correct it.
With a healthy, balanced SCOBY, like a Natural Probio culture, every adjustment bears fruit more quickly: fermentation gets off to a clearer start, the kombucha acidifies properly and new discs form with regularity.
If, despite all your care, your current lineage remains capricious or inert, don’t see it as a personal failure. It’s simply the life of a culture. Throw away what needs to be thrown away, clean your jars, start again with a robust SCOBY, adjust your parameters once and for all… and let the magic happen.
The day you finally taste a well-fermented, balanced homemade kombucha from a jar that has long refused to budge, you’ll see that this ‘breakdown’ phase will have taught you one precious thing above all: to listen to what’s really going on in your jar, and to respond to what’s alive with simple, precise gestures.
