My neighbor who also bakes has run out of yeast and can't find any in the store. We went shopping this afternoon and couldn't find any either.

I have a fair-sized jar of the stuff in my fridge, but I'm also baking a lot. I'm worried about it running out, plus I'd like to share with my neighbor.

Is there a recommended technique for propagating it myself so I don't run out, and have enough to share?


Absolutely there is a way to propagate yeast, it's as simple as making a starter with it. Most of the time these days people create starters for sourdough using natural yeasts, but you can use them to feed any kind of yeast. All you would do is put flour and water in a container with some yeast, let it get to work and once you start to get bubbles put it in the fridge to slow it down. You would then use half of it for every batch of bread you make, replacing the flour and water to keep it at the same quantity.

If you don't use any of it for a few days you'd want to throw half away and refill in order to give the yeast a fresh supply of food. You can share this with as many people as you like, just split it into two, give each a fresh supply of flour and water, and repeat as many times as necessary. Using this technique a small amount of yeast could theoretically supply the entire planet.

NOTE: During the Coronavirus outbreak it's worth noting that corona can survive on surfaces for quite some time, so you should take great care to ensure that your yeast propagation does not lead to virus propagation!

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    Thanks for the inspiration to do a bit of kitchen alchemy! chat.stackexchange.com/transcript/message/53887068#53887068 – Stephie Mar 24 '20 at 15:50
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    If recipe says 7gr instant yeast, how much of this starter should I use, or how can I calculate this? – Davy Landman Mar 31 '20 at 13:38
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    That's a good question I don't have an answer to @DavyLandman. It depends on how much starter you use in your recipe. I'm having trouble finding yeast at the moment so I'm using this method, I'm using about 120g of starter and finding it takes about double the time to get started then when I use 7g of yeast, so I'd say 200-250g of starter is probably equivalent. I'm going to be upping my starter proportion to this myself as it's a pain to wait. – GdD Mar 31 '20 at 14:31
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    I'm gonna go out on a limb and say that although the yeast mixture might become contaminated with Corona; I doubt that the virus will actually propagate that way. In fact, I expect it to die out over time just it normally does. – Edward Falk Apr 1 '20 at 23:41
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    Corona has been shown to live quite some time on plastic and other surfaces @EdwardFalk, it's surviveability is one of the reasons it spreads so easily. A quick wipe of the container surface with some sort of soap will kill it. – GdD Apr 2 '20 at 7:12

Because I have been home brewing for about 30 years, I do it a different way. I sterilize sugar and water by boiling, cool to room temperature, pour into a sterilized 1 gallon jug, put a little bread yeast in it, and put a rubber stopper w an airlock on top. When it’s done, I pour off most of the nasty beer (sugar only with bread yeast makes a nasty brew though ymmv), I swirl the remainder to mix it and then pour it into very small containers, at the bottom of which will settle good yeast. The alcohol will keep it good for months in the fridge. No bacteria, no wild yeast, no off flavors. No need to feed the starter. When ready to use a little yeast, just pour off the alcohol and put the yeast where It needs to go.

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