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Are fermented foods halal? Four fermentations, four answers

Fermentation is not one process but a family of them. Only one member turns a food into an intoxicant, and most of the fermented things on the shelf do not belong to it.

Published 20 September 2026

Sauerkraut, yoghurt, soy sauce, salami and beer have one thing in common: in all five, microorganisms worked before the product reached the pack. That easily becomes a blanket suspicion, and the suspicion misses the point. What decides is not whether something was fermented, but which organism worked and what it left behind.

What happens in a fermentation

Fermentation means that bacteria, yeasts or moulds rebuild the sugar and protein of a food with little oxygen around. What they leave behind depends on the organism. Some make acid, some break protein down into flavour compounds, and some make ethanol.

Only the last group touches the prohibition of khamr, and even there only where an intoxicating drink actually stands at the end. So the question cannot be answered by one word on a pack, but it can be answered in four cases.

The four fermentations

Lactic fermentation. Lactic acid bacteria turn sugar into lactic acid, which makes the food sour and keeps it. This is how sauerkraut, kimchi, yoghurt, sourdough, pickled cucumbers and olives are made, and it is how cured sausage ripens. Ethanol is not what the process is for.

Acetic fermentation. Acetic acid bacteria turn alcohol into acetic acid. What comes out is vinegar and no longer an intoxicant, even where it was made from wine. Why it is judged that way is set out at length under alcohol in food.

Mould and bacterial cultures. Here the organism works on protein rather than on sugar. The koji mould Aspergillus oryzae opens up soybeans and rice for soy sauce and miso, Rhizopus grows through cooked soybeans into tempeh, Bacillus subtilis turns them into natto, and cheese cultures rebuild milk protein. No animal, no intoxication.

Alcoholic fermentation. Yeasts turn sugar into ethanol. That is the road to beer and wine, and it is the only one of the four at whose end khamr can stand.

The residue no pack names

This is where it gets honestly untidy, which is why it belongs here. Even where nobody is trying to make alcohol, a small residue of it often appears, because yeasts take part in almost every fermentation. Kefir, kombucha, sourdough bread and ripe fruit juice all contain traces of ethanol.

None of that is on the pack, and there is a comprehensible reason: an ingredient list names ingredients, that is, what somebody added. What forms by itself during fermentation is not an ingredient. A drink only has to state its alcoholic strength from 1.2 per cent by volume upwards, under Article 9 of the EU food information regulation.

For the ruling the measure is not the number but the effect. What is forbidden is what intoxicates. A milk kefir at a fraction of a per cent intoxicates nobody and was never an intoxicating drink, and the OIC and SMIIC standards treat non-intoxicating alcohol that forms by itself in the fermentation of a permitted food differently from added ethanol. Tayyib therefore does not flag kefir, kombucha or sourdough.

The limit of that statement belongs with it. In water kefir and in a kombucha left to ferment on, the residue can run considerably higher, and individual surveys of retail products found values above one per cent. A drink sold as an alcoholic drink, or one that has to state its strength, is no longer a question of traces but a different question.

Soy sauce: the one declaration that matters

Soy sauce is the case where this distinction is decided in practice, and it is often described wrongly.

Traditionally brewed soy sauce matures for months with koji and with yeasts, and in the process 1.5 to 2 per cent ethanol usually forms. That is more than a trace. It is still not a drink anyone drinks in order to be intoxicated, and nobody is intoxicated by a spoonful of soy sauce. The Hanafi school reaches the same result by way of origin: khamr in the narrow sense is to it wine fermented from grapes and dates, and everything else is measured by its intoxicating effect. The majority of scholars measure all intoxicating drinks by the same yardstick, but likewise do not hold the non-intoxicating residue from the fermentation of a permitted food to be khamr. Large certifiers such as JAKIM in Malaysia and MUI in Indonesia certify brewed soy sauce accordingly, while others advise against it.

Beside that there is a second case, and unlike the first it is on the pack: some manufacturers add alcohol as a preservative so that the bottle does not ferment on after opening. Added alcohol is an ingredient and has to be declared.

That is what the app hangs on. Where the ingredient list names alcohol or ethanol, Tayyib flags it as doubtful. Where it names only water, soybeans, wheat and salt, Tayyib flags nothing, because then the pack simply says nothing about the fermentation residue. Anyone to whom that residue matters will also find brewed soy sauces carrying a halal mark.

Fermented sausage: the question is the meat

Salami, sucuk, Mettwurst and pepperoni are not cooked but soured with starter cultures and dried. The ripening itself raises no halal question. Everything there is to settle here would have to be settled without it too.

Pork, bacon or pork casing in the list: not halal, and the ripening changes nothing about that.
Beef, lamb, poultry or sucuk with no halal statement: doubtful, because an ingredient list does not show the slaughter. Why the cut and not the species decides is under beef gelatine.
Halal beside the meat, as in "beef (halal)": the question is answered and the flag drops out.
Natural casing on its own does not say which animal the skin came from, and Tayyib does not flag the word. Where it is pork casing, it says so plainly.

One note on precision: where a list carries only the word salami with no ingredients behind it, the meat question is not answered but merely not asked. Tayyib reads the ingredient list, and a list can only prove what it names.

Cheese belongs here too

Cheese is a fermented food, and the cultures in it are unproblematic. The question sits not in the ripening but in the coagulant, and it is important enough for a page of its own: is cheese halal, and why it all hangs on the rennet.

What you can do in the shop

Do not ask whether it was fermented. Ask what the ingredient list says.
With soy sauce, read to the end. Four ingredients are four ingredients, a named ethanol is a statement.
With cured sausage the meat counts, and the statement beside it, not the words starter cultures.
On a drink the percentage helps. Where it is given, the content is above 1.2 per cent by volume and is no longer a question of traces.
Cultures, lactic acid bacteria and koji are no reason to put a product back.

In short

Fermented does not mean alcoholic. Only yeast fermentation is aimed at ethanol.
Sauerkraut, kimchi, yoghurt, kefir, sourdough, tempeh, miso and natto: Tayyib flags none of them.
Traces of ethanol form by themselves in many fermentations, appear on no pack and do not intoxicate.
Brewed soy sauce contains around 1.5 to 2 per cent ethanol from the fermentation, which is not declared.
Alcohol or ethanol named in the ingredient list: doubtful, because added it is an ingredient.
With salami and sucuk the meat decides: pork red, other land meat with no halal statement doubtful.
With cheese the rennet decides, and with vinegar the question was settled long ago.

Common questions

Is sauerkraut halal?

Yes. Sauerkraut is made by lactic acid bacteria turning the sugar in the cabbage into lactic acid. Ethanol is not the aim and appears at most in traces. Cabbage, salt and lactic acid bacteria raise no question, and Tayyib flags nothing on a list like that. The same goes for kimchi and for pickled cucumbers and olives.

Does kefir contain alcohol, and is it halal?

Milk kefir contains a very small residue of ethanol, because yeasts work alongside the bacteria. The amounts are of the same order as in bread or ripe juice, they do not intoxicate, and the kefir never became an intoxicating drink. Tayyib does not flag kefir. In water kefir and kombucha the residue can run higher, and from 1.2 per cent by volume a drink has to state its alcoholic strength.

Is soy sauce halal?

That hangs on the ingredient list. Traditionally brewed soy sauce contains around 1.5 to 2 per cent ethanol as a by-product of the fermentation, which does not have to be declared because it was not added. Some manufacturers additionally add alcohol to keep the bottle, and that does appear in the list. Where the pack names alcohol or ethanol, Tayyib flags it as doubtful. Where it names only water, soybeans, wheat and salt, Tayyib flags nothing.

Is salami halal if it is fermented?

The ripening is not the question, the meat is. Where pork or bacon stands in the list, the result is red. Where beef or sucuk stands there with no halal statement, it is doubtful, because the ingredient list does not show the slaughter. Where halal stands beside the meat, the question is answered.

Is tempeh halal?

Yes. Tempeh is made when a mould grows through cooked soybeans and binds them into a firm block. No animal is involved and no intoxicant is produced. The same goes for miso and for natto, which is made by a bacterium rather than a fungus.