This feels like it should be an easy question to find an answer to, but all I'm finding are unreliable sources saying both yes and no.

I'm referring specifically to any kind of store-bought flour used for cooking or baking.


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    Welcome to SA! Can you clarify what you're asking? Are you asking if store-bought wheat flour has naturally occuring yeast, or if flour has yeast added to it?
    – FuzzyChef
    Commented Jan 16, 2023 at 18:57
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    Also, it would help if you explained what you're trying to accomplish.
    – FuzzyChef
    Commented Jan 16, 2023 at 19:15
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    Suggestion to responders: include additives to 'self-raising' flour in your answers. I'd expect this to be the biggest source of confusion. (PS: No, it has baking powder and salt added, not yeast)
    – mcalex
    Commented Jan 19, 2023 at 5:09

3 Answers 3


Flour “contains yeast” in the sense that it is not a sterilised product and contains impurities such as wild yeast cells. The yeast and bacteria contained in flour, in fact, are the genesis of “sourdough starters“.

Flour does not “contain yeast”, in the sense it has nowhere near enough yeast cells to use to make a risen dough. Yeast (or an established sourdough starter) must be added to make dough rise.

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    … and the amount of viable wild yeasts can vary depending on a lot of factors. (May be worth keeping in mind when starting a sourdough.)
    – Stephie
    Commented Jan 16, 2023 at 19:54
  • I gather there are many wild yeasts of interest to the sourdough community. They are biologically different species, which explains why German sourdough is not the same as English.
    – RedSonja
    Commented Jan 17, 2023 at 7:28
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    @RedSonja basically just saccharomyces cerevisiae, actually. Sourdough starters are distinguished potentially by the particular yeast strain, but primarily by the bacteria.
    – Sneftel
    Commented Jan 17, 2023 at 7:49
  • Might add that flour under normal circumstances (in the bag you bought it in) is very dry, so that yeast cells and bacteria in the flour can not really grow. Of course this changes if there is a source for water, wet flour will grow mold quickly.
    – eagle275
    Commented Jan 18, 2023 at 15:01
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    @dan04 This is true, but a thing to remember. Humans doing so also didn't expect their bread to rise in an hour.. Hence unleavened bread was a thing. Without concentrated yeast cultures it takes time for the flour to properly leaven and begin to rise.
    – Questor
    Commented Jan 19, 2023 at 21:40

This may surprise you, but there are arguments for both a "yes" and a "no" answer, and both are right. My personal preference is on the "no" side.

The arguments for "flour does not contain yeast" are:

  • yeast is not an ingredient that goes into the making of flour
  • functionally, if you want to make a yeast dough, you have to add yeast to the flour

The argument for "flour does contain yeast" is that technically, there are yeast spores in flour. So, in a very literal sense, flour contains yeast. But if choose to use this to say "flour contains yeast", then you have to concede that everything contains yeast - flour, sugar, the meadow outside, your own hair, and the very air you breathe in. The statement would be irrelevant, which is a very damning thing to say about a statement!

Possible sources of confusion

The first one is unlikely, but I'd like to get it out of the way: Bread mix. These mixes work analogously to cake box mixes - the producer put in everything needed to bake bread, beside the stuff that would make it wet, perishable dough. This includes both flour and yeast, and the package can look deceptively similar to flour.

The second is much more interesting. When you make a sourdough starter, you put a mixture of flour and water at room temperature, and soon you have a thriving colony with lots of yeast inside. Where did that yeast come from? There is a lot of lore among bakers that it (= the yeast that won the "race" and became dominant in the starter) came from the grains of wheat, and stayed on in the flour.

Personally, I prefer to believe the second theory - that the dominant strain more likely came from the air. The air certainly carries a lot of yeast spores, which seems to not be widely known among non-biologists. Also, I remember reading somewhere in the nerdier books on baking that the fact that you tend to get different types of sourdough in different locales is not due to the local yeast strains (as claimed in bakers' lore) but due to the exact starter recipe, including proportions, add-ins and feeding schedule (which, traditionally, were just as regional as recipes) plus the environmental conditions, mostly the circadian temperature cycle in the kitchen.

This does not exclude the presence of yeast within the flour. When you have yeast in the air, you have it sticking to everything that comes in contact with it, including the wheat-grains pre-milling, and the flour post-milling. But when your starter colony has equal chances to stem from your open window as from the wheat (or larger, because nowadays wheat gets fumigated with all kinds of stuff), and when the final taste of the bread turns out to not be dependent on the terroir of your favorite wheat grower, but on what selection pressure you apply during the starter process, then the discussions and fretting about breeding your starter from a flour with the perfect yeast pedigree start looking rather unnecessary.

So, in the end: If you want to be technically right, you can say that "flour contains yeast". If you want to bake something tasty, disregard it and follow a good recipe.

  • 3
    you can create a sourdough starter in an airtight container, so either the yeasts are in the flour, or the small amount of air it gets exposed to each time you open it to feed is enough to populate the sample with yeasts. Also, there are many strains of yeasts and bacteria in flour, and which ones live and become dominant depends on environmental factors (temp/humidity, feeding schedule, etc). See this article by a microbiologist who researched sourdough and the follow-up articles linked
    – Esther
    Commented Jan 17, 2023 at 19:04
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    "Flour contains yeast" is the same type of statement as "tomatoes are botanically a fruit": while these things are true, they are also culinarily completely and utterly useless.
    – Marti
    Commented Jan 17, 2023 at 19:45
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    @Marti tomatoes being fruit helps one understand how they ripen and how to handle them. Flour containing yeast helps one understand sourdough starters.
    – Sneftel
    Commented Jan 18, 2023 at 9:05
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    I think the (incorrect?) assumption/lore that sourdough yeast comes from the wheat grains is probably extrapolated from the (correct) knowledge that wine yeast does naturally grow on grape skins. It's also possible that historical methods of processing wheat were more likely to carry yeast spores through from the unprocessed grain to the finished product. Commented Jan 19, 2023 at 15:42
  • The bread mixes I use do not contain the yeast. I have to add that seperately. Commented Jan 19, 2023 at 16:51

based on does-flour-contain-yeast - it does, but it can be without too (there are alternatives) .

Based on a simple google search it does contain it. So yes, fluor contains yeast.





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    please this is the first day I am here, so I try to be short. Is there anything I can edit to make it more clear?
    – nnihadana
    Commented Jan 17, 2023 at 17:07
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    Welcome! For all new users we recommend to take the tour and browse through the help center. Especially How to Answer would be helpful for you. In short, you are technically answering the question, but you are not saying more than “flour contains yeast”. Compared to the other answers, you see that yours is lacking the “why” and the “context” - and the community tends to disapprove of parroting google results without explaining why these sources are particularly helpful. As a matter of fact, we strive to be the result when people are googling a question, not a collection of search results.
    – Stephie
    Commented Jan 17, 2023 at 19:33
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    And on a more content-oriented note: the information in both of your blog links is pretty low quality - they are phrased quite confusingly, contain technical errors and even contradict themselves within the article. If you really want to learn about flour and baking, I would not recommend them.
    – Stephie
    Commented Jan 17, 2023 at 19:42
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    Generally, Google and DuckDuckGo aren't sources; they're ways of finding sources. If you do a Google search, and that search leads you to the LEAFtv website, and you get information off that website, then Google isn't your source; the LEAFtv website is your source. Commented Jan 17, 2023 at 22:11

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