The first thing you do when you lift the cloth from the jar is to put your nose to it, breathe in, and sometimes… gasp. Kombucha doesn’t smell like iced tea, and its aromas can be disconcerting, especially at first. A strong vinegary smell, a hint of yeast, a slightly ‘wild’ fragrance: where’s the borderline between normal and worrying?
The good news is that a strong smell doesn’t always mean your kombucha is a failure. In fact, the opposite is often true: as fermentation progresses, the aromas develop. But there are also some really problematic smells that should alert you, such as musty, rotten egg or chemical.
In this guide, we will :
Whether you use a SCOBY passed on by a friend or a live, ready-to-use SCOBY like those offered by Natural Probio, the aim is the same: to have a pleasant, safe drink that you’ll enjoy drinking every day.
Before talking about bad smells, you need to know what you’re supposed to smell. Kombucha doesn’t have the discreet scent of a simple sweet tea. It’s a fermented beverage, so it’s alive, with aromas that evolve day by day.
For the first few days (around D+1 to D+3), your jar will smell mainly of :
Nothing too aggressive. It’s like an iced tea with a hint of ferment.
As the harvest progresses (D+4 to D+8 as a guide, depending on the temperature and the amount of sugar), the smell changes markedly:
Many beginners find the smell a little strong, but it’s still pleasant, tangy, fruity, identifiable as food fermentation.
If you leave the kombucha in for a long time (D+10, D+15 and more, especially in hot weather), the smell can become downright vinegary.
This is not necessarily a problem:
In this case, kombucha is ‘too advanced’ to drink as it is, but it’s still healthy. You can use it in cooking, as a marinade or as the base for a drink mixed with sparkling water or juice.
Many of the smells that worry beginners are in fact typical of fermentation. The important thing is to understand them so that you don’t throw away perfectly healthy kombucha.
A strong vinegar smell usually means that :
It’s not a contamination, just a thorough fermentation. If the taste follows the same trend (very acidic, almost sugar-free), you have two options:
To avoid this in future, simply shorten the fermentation time or test the taste a little earlier.
Some kombuchas smell :
This comes from the yeasts present in the SCOBY and in the liquid. They produce alcohol and CO₂, which gives this aromatic signature. As long as:
… this smell is normal. Some people even appreciate the “alcohol-free beer” aspect once the drink has been carbonated during secondary fermentation.
Occasionally, your kombucha may smell strongly of acid, without any marked fruity notes. This may be the case:
As long as the smell is reminiscent of vinegar, lemon, green apple or highly acidic yoghurt, you’re still in the realms of normal fermentation.
Now for the warning signs. Some smells are a clear indication that something is wrong in the jar. In these cases, it’s not a question of “giving the kombucha a chance”, but of protecting your health.
If when you open your jar you immediately think :
… there is probably a development of mould or undesirable micro-organisms.
Even if you can’t see any coloured stains yet, a strong musty smell should alert you. Remain cautious, observe the surface very carefully and don’t hesitate to throw it away if in doubt.
The smell of rotten eggs, gas or sulphur is a very bad sign. It can come from :
In this case, the rule is simple: don’t taste it, don’t “try it”. Throw away everything (SCOBY + liquid) and clean the equipment thoroughly.
If your kombucha smells :
… this is not normal fermentation. Kombucha is not cheese, and this type of aroma indicates undesirable bacteria. Once again, throw everything away.
A scent reminiscent of :
indicates either a chemical attack (product residue in the jar) or a completely unbalanced fermentation.
Perhaps the jar has not been rinsed sufficiently, or a cleaning product has got stuck in a corner of the glass. In any case, the drink is not drinkable.
Understanding the source of the problem will help you to prevent it recurring and to get back to having great-smelling kombucha.
Kombucha is an ecosystem where yeast and bacteria have to coexist. If the yeasts take over too much, you can have :
If, on the other hand, bacteria run riot in an unsuitable environment, certain undesirable strains can appear and produce strange smells.
Poor hygiene is a common cause of smelly kombucha:
Because kombucha is an acidic beverage, it can withstand quite a lot. But if bacteria or mould find a way in, they can take hold.
Some ingredients are problematic:
Good quality tea, simple sugar (white, cane or blond sugar) and properly filtered drinking water are the basis of a healthy kombucha.
Where you leave your jar to ferment also counts:
The ideal place is a quiet kitchen area, away from direct sunlight, clean and airy, but without cold draughts.
5. 4-step checklist when your kombucha smells bad
Before making a radical decision, there is a simple method you can follow to help you see things more clearly.
Gently lift the cloth and look at the surface of the kombucha:
Fluffy, coloured spots are typical of mould. In this case, the decision is made: throw it all out.
If the surface looks normal, look at the SCOBY :
A SCOBY at the end of its life can contribute to strange smells. Sometimes, simply starting with a younger nappy or a fresh SCOBY solves the problem.
Keep your nose to the ground, but know what you’re looking for:
As soon as you smell something disgusting and not food-related, it’s best not to go any further.
This test is only performed if :
In this case, take a teaspoon of liquid:
Now that you know how to distinguish between odour profiles, let’s look at what to do in each case.
Does your kombucha sting your nose like cider vinegar? Not a disaster, on the contrary.
What to do:
You can then start a new batch with a well-balanced live SCOBY, such as Natural Probio live kombucha SCOBY, and adjust the fermentation time to suit your tastes.
If the smell is more reminiscent of beer, yeast or fermented bread, a few simple adjustments can help:
You can also, from time to time, remove the large yeast deposits at the bottom of the jar to maintain a more stable balance.
If the smell is clearly musty and you identify mould on the surface :
To start again, use a healthy culture and a very acidic starter liquid, following precisely the instructions supplied with your SCOBY.
No rescue attempt is recommended here:
These smells are indicative of micro-organisms that have no business being in domestic kombucha.
If the smell is reminiscent of a cleaning product:
For the next batch, always rinse more than you think is necessary, especially if you are using a scented washing-up liquid.
Once the problem has been solved, the aim is to secure your routine so that you don’t have to go through the same situation again.
It all starts with the quality of the SCOBY and the starter fluid:
If you’ve ever experienced contamination or strange smells, starting with a reliable, controlled culture is often the easiest thing to do, for example with a live SCOBY that’s ready to use and guaranteed.
You don’t need to sterilise your entire flat, but a few simple steps will do the trick:
The aim is to prevent mould or troublesome bacteria from taking over the kombucha culture.
To avoid unpleasant surprises:
By combining a quality SCOBY with simple ingredients, you give your kombucha a stable base that will smell good most of the time.
A happy kombucha is a kombucha that lives in a place :
A clean, out-of-the-way corner of the worktop works just fine.
So you don’t get caught out by the smells:
Eventually you’ll recognise “your” successful kombucha smell, which will make deviations much more obvious.
Yes. Heat accelerates fermentation, which :
In summer, it is often necessary to shorten the fermentation time a little to maintain a balanced smell and taste.
If the smell is vinegary but clean, with no hint of mould or chemicals, and :
So yes, you can eat it, possibly dilute it, or keep it for cooking. The smell of vinegar alone is not a sign of danger.
Not necessarily. Some kombuchas, especially at the start of fermentation, have a fairly discreet smell. It’s the evolution that counts:
Kombucha that is a little too vinegary can be sprinkled with fruit, herbs or spices during the second fermentation. But be careful:
We only flavour healthy kombucha, not dodgy kombucha.
If problems recur:
A good starting point, with a healthy living culture and clear instructions, will often make you forget about these odour problems in the long term.
When you’re just starting out, there’s often a tendency to think that “it smells strong, so it’s a failure”. But a strong smell of vinegar or yeast is often a sign of active fermentation, not a disaster.
What should really alert you are :
In these cases, there are no half-measures: throw everything away, clean up, and start afresh on a healthy footing.
By taking the time to observe, smell and taste carefully, you’ll learn to trust your senses and your SCOBY. Your kombucha will then become a stable, aromatic and pleasant daily companion, rather than a source of anxiety.
And if you’re looking for a reliable starting point, with a young, balanced SCOBY alive and well, along with its starter liquid, quality cultivation and clear advice will help you say goodbye to smelly kombucha, and hello to a drink that makes you want to drink it as soon as you lift the fabric of the jar.
