this post was submitted on 09 May 2026

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Trying to capture wild yeast (discuss.tchncs.de)

submitted 4 days ago by Aarkon@discuss.tchncs.de to c/homebrewing@sopuli.xyz

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Soaked some decomposing oak leaves for 36 hours in preboiled water with some yeast flakes. Stirred, put 1-2 ml into test tubes with 5 ml of malt beer ("Karamalz", I just picked a random brand), filled up with equal amounts of 5 % vinegar and whisky (didn’t have any vodka at hand). Put a thin layer of neutral vegetable oil on top.

Should keep out the vast majority of bad microbes and provide a mostly oxygen free environment for yeast.

IIRC, I’ve also read on suigeneris brewing that oak leaf litter has a 50 - 80 % chance of catching bretanomyce, which I’d be thrilled to find.

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[–] robsteranium@lemmy.world 3 points 4 days ago (1 children)

Interesting idea. I'd heard of just putting oak bark in beer as that essentially confirms that the yeast can survive in those conditions!

What's the thinking behind the yeast flakes? I presume you mean the Hefeflocken you get in German grocery shops? IIUC this is baked yeast cake so shouldn't have live yeast to compete with the wild ones but perhaps provides nutrients?

I can see how the oil might help stave off kahm yeast but won't you need oxygen at first to help the wild yeast multiply?

[–] Aarkon@discuss.tchncs.de 2 points 4 days ago

Depending on the brand, ready made beer can be pretty high on hops, inhibiting some desirable microorganism growth, and pretty low on easily accessible sugars. I think it can still work, but the success rate will probably be low.
Here, I provide a medium rich in sugars, low on hops, with some acetic acid and alcohol - all selecting against the majority of stuff that I don’t want.

I’m not the expert here, but from what I gather the yeast flakes provide amino acids and such. Yeast nutrient would have been better but that I also did not have on hand. And yes, it’s Hefeflocken, exactly.

The oil on top is there too inhibit mold. Yes, for multiplying, yeast needs oxygen, but there will be some dissolved already I guess. After all though, this is more of a selection than multiplication step.

[–] plactagonic@sopuli.xyz 1 points 3 days ago (1 children)

Have a good time playing with that ;-)

Microbiology is fun but bit too time consuming, I like it but it's not for everyone.

Btw if you want to make your own agar plates I have good results with classic agar with wort, it has to be ~8°Bx and don't need any more nutrients added. I still have some left in jars that got through pressure cooker.

[–] Aarkon@discuss.tchncs.de 2 points 1 day ago (1 children)

Thanks!

So long, I find that it's doable since it can be broken down into chunks and I can fit most of those into my everyday life a lot easier than, say, a full 5 - 8 hour brew day. :)

[–] plactagonic@sopuli.xyz 2 points 1 day ago

Yes it can be split somehow, but if you have to do lot of samples it can get quite long even at home.

I stored few strains of yeasts in fridge and when I had to reinoculate them on fresh plates to keep them alive for bit longer, I had work for few hours bit time sensitively split across 2 weeks.

[–] dumples@piefed.social 1 points 4 days ago (1 children)

If you are really interested in capturing wild yeast I would recommend reading Wild Crafting Brewer. There's a ton of information on great wild yeast sources.

I don't think oak leaves were a specific example but it's everywhere. He recommend flowers, fruit and pinecones as great sources

[–] Aarkon@discuss.tchncs.de 3 points 3 days ago* (last edited 3 days ago) (1 children)

Thanks for the hint! I don’t see myself having time for an entire book anytime soon, but I’ll certainly put it on my list.

The oak litter idea stems from more recent studies where IIRC they found that brettanomyce is rarely found on the skins of fruit, only in vineyards where they dump their pomace (?) below the actual tendrils, but in forest floors and most particularly in oak litter.
If you’re interested, I posted a link to a video by suigeneris brewing where Bryan explains just the above somewhere here in the thread.

[–] dumples@piefed.social 1 points 3 days ago

I'm sure it's going to work great. Wild yeasts are everywhere.

I recommend that book because it's all about brewing with things you forage using simple brewing methods. So you won't find a recipe for a traditional "beer" but lots of things like lemon and mugwort "beer". I got it this winter and can't wait to try it out

[–] portnull@lemmy.dbzer0.com 1 points 4 days ago (1 children)

I did this a few years ago. Dissolved some spray malt in hot water with some hop pellets. Placed in a jar and covered with muslin fabric and a rubber band. Left overnight. Brought them in and put an airlock on. Few days a yeast cake started forming

The hops already help prevent some nasties and boiling the water first helps clear out anything that may have been in there.

[–] Aarkon@discuss.tchncs.de 2 points 4 days ago (1 children)

I'll probably do that as well at some point. In my research though, I've come across the suspicion that hops would hinder the growth of Brettanomyces, so I deliberately left them out here. For whom it may concern, here is one of my sources: https://www.youtube.com/watch?v=G2nhUM5PIrg

[–] portnull@lemmy.dbzer0.com 1 points 3 days ago

I don't know this, but it's interesting. I guess it depends how wild you want to go with your yeast too :)