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I'm interested in learning about brewing using wild yeast, but I wonder what is the best method to catch a strain that would produce good results in homebrewing. And of course how to ensure that it wins over all the other wild microorganisms.

No need to explain how to keep it going, as that shouldn't be different from store bought yeast.

I 've baked bread with wild yeast before, but one thing I learned is that it turns sour very soon, which is not something you want in drinks.

Note that this is not a subjective question, the best method is one that scores the lowest in the following benchmarks:

  • Availability of ingredients (0 Air - Belgian Cave 10) * Wherever the cave is, we assume the judge lives in the other side of the planet
  • Ease of culture (0 Pot - Laboratory equipment 10)
  • Dedication (0 Leave it alone - Stir it each minute for two weeks 10)
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6  
Good question. What's the point of surviving a zombie apocalypse if you can't get a decent drink? –  robaker Nov 9 '10 at 16:16
    
The best place to hunt for interesting yeast is John Maier's Beard. <rogue.com/store/products/The-Beard-Beer.html/>; –  dana Aug 31 '13 at 20:47

3 Answers 3

It's a bit involved, but I've done it with good results. The hardest thing to do is to separate the yeast from any other wild molds.

What you need.

  1. Wild fruit. I have a peach tree and plum tree so it worked out well for me.
  2. 2lbs. DME
  3. Gelatin
  4. 3 Petri Dishes
  5. Hops
  6. Conical flask w/ airlock

Take 1 lb. of the DME and dissolve into warm water. You're shooting for a gravity of 1.020 and an IBU of around 20. Add hops and boil. Strain into conical flask. Cover immediately and let cool.

Wash and sanitize your hands as well as possible. Peel the skin off of whatever fruit your using and add to the flask. Attach airlock and let alone. In about 3 days you should begin to see fermentation. The hops help inhibit bacterial growth and you should mostly get saccharomyces (brewing yeast).

With your petri dishes you want to take the rest of your DME and gelatin and make an agar plate. Agar agar works best, but you can use your gelatin. And obviously the DME is used in place of the sugar.

Take some of the yeast that has begun to settle on your conical flask and streak with a needle on your agar plates. After a few days you will be able to identify individual growths. These are colonies from individual cells. This makes it easier to separate your saccharomyces from any other odd bacteria.

From here you gently remove the culture from the agar agar and make small starters. I will typically take two or three of the cultures I find and make starters from those. Start small and then build up from there. I typically do three to four starters in graduated steps before I have a culture that is ready to be pitched into beer.

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In this answer, for example, there are hops which is an ingredient that is easy to buy in most countries, but doesn't grow wild on most places. Still as it is used here for its anti-bacterial properties, it might have local replacements. And for beer you are using hops anyways. Petri dishes are relatively easy to get but nobody has them at home and a good culture medium is a bit harder. –  qpr Nov 10 '10 at 13:33

The most obvious place to gather wild yeasts consistently to me is on the surface of fresh picked fruit. Get a few non-waxed apples (i.e. not the ones in the typical grocery store), mash 'em up, add some water and you'll get a yeast feast going.

That is basically what wild-fermented cider is and I've got a batch of fresh-pressed cider that I'm letting ferment using the wild yeast from the apples. I'm planning on harvesting that yeast and culturing it to see what I get.

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I really don't recommend this. Fruit from a grocery store has god knows what from god knows where on it. When using wild yeast go local. –  Matt Utley Nov 10 '10 at 1:17
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Umm. I specifically said not the ones in the grocery store. –  J Wynia Nov 10 '10 at 3:20
    
It doesn't seem to me that you'd get "colonies from individual cells" from your method without the use of a microscope or an acid wash. Can you help me understand why I couldn't just use yeast from the fermenting fruit peels –  danafr4 Nov 21 '10 at 11:55

The method that I have used successfully is to go pick some wild fruit (apples) that have not been sprayed and throw them in the wort (unwashed). After they have been washed by the wort remove apples and watch the yeast grow.

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