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Yeasts are used to produce "alcoholic beverages" / beer / wine, to bake, yogurt/cheese, etc....

Going to a shop and buy some baker's yeast is easy but not a long term solution, at least the ones I know (and have access) have a short expiration date.

In a situation where:

  • going to a shop" is not an option
  • trying to "freeze/preserve" some backup batch is not an option

Is it possible to "obtain/grow" yeasts for this uses at "home" easily? Which kind? And how?

Basically I want to know how easy/hard it is to obtain this kind of yeasts in the "nature" (from "nothing".... )?

Thanks.

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    Perhaps if you could write a little more about why going to the shop and buying some "is not a long-term solution", we can better work out what *is a long-term solution – 410 gone Jan 30 '13 at 7:48
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    Yeast can be frozen - at least I did it and used successfully afterwards. But you have to buy it first. To make bread without continuing buying yeast I think you can keep some of the dough containing yeast as a starter for the next bread. I will take longer and you'll need to put more effort than buying new yeast. Is this the kind of solution you were looking for? – 0ana Jan 30 '13 at 8:14
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    I think this also really depends on what you want to use the yeast for. The type of yeast used in winemaking is very different from yeasts used for beer, which is different from bread yeast. – lemontwist Feb 3 '13 at 19:58
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    Also, for bread, you can get a brick of SAF instant yeast that you can keep in the freezer. If you don't bake terribly often you'll find it lasts almost forever, and you don't have to worry about feeding it like a sourdough starter. – lemontwist Feb 3 '13 at 19:58
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The yeast you are interested in is saccharomyces cerevisiae, also called "baker's yeast" and "ale yeast". The process you are looking for is called "spontaneous fermentation" in the context of brewing.

When brewing beer through spontaneous fermentation, you aren't starting out with yeast so there is no competition for the potentially unsavoury microbes that eat the same food source (sugar). In some styles (e.g. lambics and berliner weisse) this is desirable.

For bread making the turn around time is faster and is definitely worth it. What you are looking to create is a "sour dough starter" which will be a mixture of water, flour, lactobacillus (responsible for the sour flavor in sour dough), and saccharomyces cerevisiae. You set out a certain amount of water and flour, feed it flour and water, and wait. When you make bread, you use just a portion of it so that you can continue your starter.

If you search for instructions on creating a sour dough starter from scratch or from (as they call it) "wild yeast", you will be baking bread in no time.

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As the other answer says, baking with sourdough involves keeping a portion of dough for the next loaf baked.

Whether you create a sourdough culture from scratch or get one from a friend, once you've got a culture that works for you, you can thinly spread some fermented dough onto some waxed paper (or perhaps a greased tray, if you prefer something you don't have to buy) and let it dry. Once dry, you can break it into flakes and freeze it. Use the flakes to kick off your next batch of dough.

I'm not sure how long exactly the flakes will last, but it's helpful to have some stored that way in case you forget to keep some starter or neglect the fresh starter to the point that it grows some nasty mould.

There's no reason why you couldn't use the same technique to preserve other yeasts too, so you could avoid needing to buy more.

I've had a few tries at creating a sourdough starter from scratch, without much success. If I persisted, perhaps I could've managed it, but didn't seem easy by any means. I was given some sourdough starter from a friend eventually that worked better.

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    Since with a sourdough culture you're trying to capture yeasts in the air, it's much easier to capture benevolent yeasts in an environment with fresh air. All our fermented foods taste much, much better since we moved to the countryside. In a big city, receiving a good starter culture is much more likely to be successful. – Earthliŋ Jul 1 '14 at 0:10
  • There was a series of talks on the radio here recently by a sourdough artisan baker in Auckland, NZ. They go through the process of baking sourdough, and should be available for free for quite some time, so here's the link: radionz.co.nz/national/programmes/thiswayup/collections/… – Highly Irregular Aug 2 '14 at 8:48
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Note that these aren't all or nothing. You can help with spontaneous fermentation by proper harvesting of wild yeasts but this isn't strictly speaking necessary.

One thing you can do is make a starter with store-bought yeast and once it is at concentration keep it in the fridge.

When doing this it is important to practice good asceptic techniques (less important for bread than beer, if things go sour you might accidently get sourdough but with beer you can get lots of unpleasant tastes).

I would also suggest checking out homebrew as yeast harvesting and re-use is a perpetual topic there. You may find out that with a bit of research, most of your questions may have already be answered there.

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I never had any luck in creating a sourdough starter, but the dried flakes I got from Friends of Carl served me well for a year. I dried it into flakes when I temporarily stopped baking, and was not able to revive the starter, though that may have been due to the whole-house heat treatment for bedbugs. Note that sourdough starter can contain several species of yeasts (not just Saccharomyces cerevisiae) and Lactobacillus.

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  • Please try to edit your answer to make it less conversational and more of a clear specific answer to the question, avoiding irrelevant detail that do not directly answer the question being asked. – WilliamKF Aug 3 '14 at 0:39
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In traditional homebrewing, the yeast was derived from natural sources, such as the unwashed fruit rinds or skins. Since store-bought fruit comes pre-washed, this won't work quite as well today.

Another source of yeast for homebrewing is simply using a starter. After a batch has finished fermenting, transfer about half a cup of the (unsterilized, undistilled) completed batch to the next batch. If you have a bad batch, obviously, don't try to re-use it as a starter; discard the whole batch.

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