You taste your kombucha: either it takes your mouth away like a very strong vinegar, or it still tastes like sweet tea, almost unchanged. Between the two, there seems to be a ‘perfect point’… but it’s hard to reach when you’re just starting out.
Don’t worry: kombucha that’s too acidic or too sweet is neither a disaster nor a sign that you’re ‘bad at fermentation’. It’s simply proof that your culture is alive and kicking, and that you still need to get to grips with a few parameters: fermentation time, temperature, proportion of sugar, quantity of starting liquid, size of SCOBY, volume of jar, etc.
In this guide, we’ll look at :
why kombucha turns sour or stays sweet
how to make up for a batch that is too acidic or too sweet
how to adjust your next tests so that you regularly find “your” right balance
how healthy cultures (such as a well-balanced live SCOBY, like those offered by Natural Probio) facilitate this adjustment on a daily basis
The aim: to make this drink a steady pleasure, rather than a lottery where each jar is a complete surprise.
1. Understanding the sugar/acidity balance in kombucha
To know what to do, you need to understand what’s really going on in your jar.
1.1. Sugar, fuel for yeast
To start with, you prepare a sweet tea. That sugar isn’t there just for taste; it’s the main food for the yeast in the SCOBY and the starter liquid.
These yeasts :
consume sugar
produce alcohol and CO₂
leave behind compounds that will then be transformed by bacteria
As long as there’s a lot of sugar left, it’s still very much like a sweet iced tea, with fermentation starting slowly.
1.2. Bacteria, the architects of acidity
Bacteria (mainly acetic, sometimes lactic) then take over. They transform :
the alcohol produced by the yeast into organic acids (acetic acid, gluconic acid, etc.)
the jar environment, which gradually becomes more acidic
It is this acidity that :
gives the character “kombucha
protects the beverage against many undesirable micro-organisms
provides a fresh, “fermented drink” sensation
The longer you leave the jar, the more acids accumulate and the more sugar decreases: kombucha goes from being a slightly sweet fizzy tea to a very vinegary drink.
1.3. Your taste lies somewhere in between
There is no universal ‘right’ level of acidity. Some people like their kombucha very sweet, others love it almost like cider vinegar.
Your mission is to find :
at what point in the fermentation process do you like the taste best?
How long do you have to wait to reach this point in the current season?
how to reproduce this result regularly
A kombucha that’s too acidic or too sweet is not a failure: it’s a benchmark for adjusting the next batch.
2. Recognising a kombucha that is too acidic… or simply well fermented
Before trying to ‘correct’ it, you need to be sure that it is really too acidic for you.
2.1. Signs of a kombucha that is simply well acidic
A well-fermented kombucha has :
a vinegary but clean smell (cider vinegar, green apple, white grape)
a clearly acidic taste that makes you salivate, but without burning you
a virtual disappearance of sugar, or just a hint of sweetness
slight heat in the throat, but no pain
If you like it rather soft, this stage may already seem “too advanced”, but that’s not a safety issue: it’s a question of preference.
2.2. Signs that it is too acidic for your use
Kombucha is more likely to be described as “too acidic” if :
you grimace as soon as you take your first sip
you have the impression of drinking almost pure vinegar
you no longer perceive the tea or the original aromas at all
you find it impossible to drink it without diluting or adding flavour
At this stage, the drink is still healthy, but difficult to enjoy as it is. The good news is that it’s not lost.
3. What should I do if my kombucha is too acidic?
Rather than throwing it away, you can give this highly advanced kombucha a second life.
3.1. Turning it into homemade kombucha vinegar
Highly acidic kombucha makes an excellent vinegar:
for salads, as a replacement for cider vinegar
to deglaze a pan
for marinating vegetables or tofu
to spice up a sauce
All you need to do is :
Store in a clean, closed glass bottle at room temperature or slightly cool.
let it age a few more weeks if you want a rounder profile
use it like any other mild vinegar
Many people even deliberately grow highly acidic kombucha for this purpose.
3.2. Dilute it to make a tonic drink
Another option: dilute your overly acidic kombucha in :
still or sparkling water
apple juice, grape juice or a blend of juices
a cooled herbal infusion (mint, verbena, hibiscus, etc.)
For example:
1/3 very acidic kombucha
2/3 sparkling water + lemon juice or a little honey
The result is a tonic drink that is less aggressive but still rich in organic acids.
3.3. Use it as a base for a second flavour fermentation
You can also use this very acidic kombucha as a base for a second fermentation in the bottle, with :
Fruit (raspberries, apple pieces, citrus fruit)
a little sugar, honey or syrup (ginger, agave…)
Spices (fresh ginger, cinnamon, cardamom)
Added sugar :
is not just there to soften
also serves as fuel for the remaining yeasts
gives you more sparkle and aromatic complexity
The final drink will seem less acidic thanks to the added sweetness and fruit flavours.
3.4. Using it in cooking and home care
Highly acidic kombucha can also be used:
to deglaze roasted vegetables
to marinate red onions, radishes and carrots
to replace some of the vinegar in quick pickles
diluted hair rinse (if you’re used to it and your scalp tolerates it)
So you can make the most of every drop, even if the initial jar seemed like a “dud”.
4. How can I prevent it from becoming too acidic in the future?
Once this batch has been recycled, it’s time to focus on prevention.
4.1. Slightly reduce the fermentation time
The easiest lever to adjust is the fermentation time of your next batch.
For example:
If you’ve left it for 12 days and it’s too acidic, try 8-9 days.
If you’re in the middle of summer and it’s 26-28°C in the kitchen, you should know that everything goes faster: a kombucha that took 10 days in winter may be ready in 6-7 days.
The best thing to do is not to wait for the “theoretical date”, but to taste every day from the 5th or 6th day onwards.
4.2 Taste regularly to learn the taste curve
From day 5 :
take a teaspoonful of kombucha
taste and note your impressions (sweet, sour, vinegary…)
repeat every day until you really like the taste
In just 2-3 batches, you’ll have a clear picture of :
how many days it takes to reach equilibrium
how it changes with the season
when to bottle for the second fermentation
4.3. Playing with the quantity of starting liquid
The more acidic the starter liquid (kombucha from a previous batch), the more :
the environment is acid from the start
bacteria are numerous
acidification is rapid
If your kombuchas are systematically too acidic, you can :
remain within the recommended low range (around 10% of total volume)
avoid exceeding 20% unless you deliberately want a very vinegary result
On the other hand, cultures such as those offered by specialists like Natural Probio are supplied with just the right amount of starter liquid, making it easier to get off to a balanced start and limiting excesses.
4.4. Monitoring temperature
Below 20°C, fermentation slows down; above 26-28°C, it goes into overdrive.
For greater control :
keep the jar away from sources of heat (oven, radiator, direct sunlight)
choose a location with a relatively stable temperature
in hot weather, taste earlier and more often: 5-7 days may be enough
5. Kombucha that’s too sweet: understanding what’s going on
On the other hand, :
the kombucha tastes almost exactly like the sweet tea it starts with
you felt only a tiny hint of acid, or nothing at all
the SCOBY doesn’t seem to be working
It’s not just a question of taste: it means that fermentation hasn’t really started or has slowed down considerably.
5.1. Signs of a ‘young’ kombucha
If you taste very early (D+2, D+3), it is normal that :
the sugar is still very present
the acidity is very slight
evolution is discrete
That’s not a problem: just wait a few more days.
5.2. Signs of under-fermented kombucha
If, after 7-10 days :
the taste is almost identical to sweet tea
the liquid is not more acidic
there are no or very few yeast deposits at the bottom
a new surface disc (new SCOBY) does not really form
In this case, there’s a real problem with fermentation, and something needs to be done.
6. How to make up for over-sweetened kombucha?
Fortunately, kombucha that is too sweet still offers plenty of room for manoeuvre.
6.1. Check the basic conditions
First of all, check :
Temperature: if it’s 18°C in the kitchen, fermentation will be slow. In this case, leave for longer, sometimes up to 14-20 days.
The position of the jar: not in the fridge, not in an icy place, not next to a very cold window in winter.
The cover fabric: it must breathe (no airtight cover), while keeping insects out.
Sometimes, simply moving the jar to a warmer spot and waiting a few more days is enough.
6.2. Prolonging fermentation
If all the conditions seem correct, the first solution is simply :
leave to ferment for longer
taste every 2 days to monitor progress
You’ll often find that sugar levels are gradually reduced, until you reach a point of equilibrium.
6.3. Reinforcing the initial acidity
If fermentation is still very slow, it may be that :
you have not added enough acid starter liquid
your starting liquid is itself fairly mild and not very protective
To correct this, you can :
keep a little more acidic kombucha from another batch
use it as a starting liquid (10-20% of the volume) for the next batch
or start with a crop where the SCOBY and the starting liquid have been designed to guarantee sufficient initial acidity.
A healthy, well-acidified base offers a much better chance of fermentation starting quickly.
6.4. Checking the status of the SCOBY
Kombucha that remains sweet despite days and days of fermentation can also be a sign that :
the SCOBY is tired, weak or almost inactive
it has been damaged by cold (refrigeration) or heat
it has been too short of food for too long (batches that are very far apart in time)
In this case, you can :
separate the layers of SCOBY and start again with a younger, lighter, softer layer
run a small relaunch test in a smaller jar to see if it produces a new disc and acidity
or decide to start with a fresh, living SCOBY to save you weeks of trial and error
7. Adjusting future batches: a simple method to avoid making mistakes
Rather than suffer from acidity or sugar, you can put in place a small homemade method.
7.1. Keeping a mini fermentation log
Take a notebook or a note in your phone, and write :
the batch launch date
the approximate temperature of the room (or the season: winter, mid-season, summer)
the type of tea used (black, green, blended)
the amount of sugar (per litre)
the amount of starting liquid (% of volume)
Then, every day from the 5th :
taste a teaspoon
note: very sweet, sweet, semi-sweet/half-sour, very sour, very vinegary
identify the day when, for you, it’s “perfect”.
In just a few batches, you’ll see a pattern emerge: for example, “in summer, I like my kombucha on D+6, in winter on D+9”.
7.2. Choosing an “ideal zone” interval
Instead of aiming for a specific day, give yourself a zone:
For example: “between the 6th and 8th day, it’s perfect for me”.
Bottle inside this window, according to your schedule and your desires.
That way, you won’t be stressed if you can’t bottle on the exact day, and you’ll stay within a range that suits you.
7.3. Adapting the second fermentation time
Don’t forget that :
the first fermentation is used to create the acid base
the second fermentation (in the bottle, with a little sugar or fruit) is used to develop the sparkle and aromas
If you are bottling a kombucha that is still a little sweet, the second fermentation :
will consume this sugar
will produce more gas
will increase complexity
If you are bottling kombucha that is already quite acidic, you can :
add a little sugar, juice or fruit
allow a shorter second fermentation to avoid extreme acidity
8. Special cases: when acidity or sugar seem “capricious
Sometimes, even if you’re careful, the result varies from one batch to the next. Here are a few tips to help you understand.
8.1. Tea or sugar changes
A fuller-bodied, more tannic tea, or a fuller-bodied sugar (muscovado type) can influence the taste:
the speed of fermentation
the perception of acidity
aromas (rounder, more caramelised, more tannic)
If you change your type of tea or sugar, make a note of it in your notebook, and accept a few batches of adjustment.
8.2. Size and vitality of SCOBY
A SCOBY :
very bulky, old and thick
very young, fine and light
… do not work in quite the same way. A big old SCOBY can acidify very quickly; a young SCOBY can take a little longer to set up, especially at the beginning.
To maintain stability, some keep :
a moderate-sized SCOBY
a sort of “SCOBY hotel” next door, where excess records wait in highly acidic kombucha
8.3. Temperature differences between rooms
Simply moving the jar can change a lot of things:
on a work surface close to the oven, it will be warmer
in a corner of the kitchen near a cold window, it will be slowed down
on top of a refrigerator, the heat generated can accelerate the temperature.
Once again, observe and adjust: if a new location consistently produces kombuchas that are too acidic in a short space of time, reduce the time or move to another location.
9. Frequently asked questions: sour, sweet… and everything in between
9.1. Is it dangerous to drink highly acidic kombucha?
As a general rule, a very acidic, clean kombucha with no musty or chemical smell is not dangerous in itself; it is simply very powerful in the mouth. Some people dilute it or consume it in small quantities.
On the other hand, if the acidity is accompanied by :
suspect odours (musty, eggy, chemical)
visible mould on the surface
… throw it out without hesitation.
9.2 Can I add sugar to kombucha that is too acidic to soften it?
Yes, but this won’t ‘remove’ the acidity: it will simply balance it out with more sweetness. You can :
add a little sugar, honey or syrup
mix with fruit juice
start a second fermentation in the bottle with fruit
This often results in a more harmonious drink, especially if you like flavoured kombuchas.
9.3. My kombucha is still sweet after 10 days: should I throw it out?
Not necessarily. Ask yourself these questions first:
Is the temperature very low?
Have I used enough acid starter fluid?
Does my SCOBY seem to be alive (new layer forming, presence of yeast)?
If all is well, leave for a few more days and taste. If nothing really moves after 14-20 days, it may be time to check the condition of the SCOBY and, if necessary, start again with a more vigorous crop.
9.4. Can I mix kombucha that is too acidic with kombucha that is too sweet?
Yes, it’s even a good tip:
mix one part very acidic kombucha with one part still sweet kombucha
taste, adjust the proportion until you find the point you like
bottle, possibly with light aromas (fruit, plants), for a second fermentation
You get a well-balanced drink, while avoiding wastage.
9.5. Does a good quality SCOBY really help to stabilise all this?
A healthy SCOBY, well balanced in yeast and bacteria, accompanied by a good quality acidic starter liquid, makes a huge difference:
fermentation starts faster and more regularly
the evolution of taste is more predictable
you have fewer extreme variations from one batch to the next
That’s why it’s better to start with a serious culture, prepared by specialists, rather than a SCOBY recovered in uncertain conditions. When the base is solid, adjusting the acidity and sugar becomes much simpler.
Conclusion: from a “problem” to a tool for learning your kombucha
Kombucha that is too acidic or too sweet is not an end in itself, it’s a message that your drink is sending you:
too acidic: fermentation time too long for your taste, high temperature, very acidic starter liquid, very active SCOBY
too sweet: slow fermentation, low temperature, lack of acidic starter liquid, weakened SCOBY or less than optimal conditions
By learning to :
taste regularly
record your observations
adjust the time, temperature and quantity of starter fluid
make the most of even “imperfect” batches (dilution, cooking, secondary fermentation, homemade vinegar)
… you turn your mistakes into experience. Batch after batch, you get closer to that moment when you lift the cloth, taste, and say: “Now that’s exactly how I like it”.
With a healthy, robust starter culture, a well-balanced live SCOBY and a clearly acidified starter liquid, such as those offered by specialist artisanal kombucha producers, this learning curve becomes even smoother. You’ll no longer have the impression that your kombucha is ‘doing its thing’ without you, but rather that it responds to your gestures and adjustments, and eventually finds its natural place in your daily routine.
