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I'd like to stop buying yeast all the time, especially when I use the same strain repeatedly.

This is especially a problem when it comes to seasonal strains. I'd like to brew with WLP351 Bavarian Weizen Yeast whenever I'd like, but it's only available around March and April.

It would also be nice for our brewing friends in the southern hemisphere that would like to brew with the seasons, but can't because the current seasonals are in sync with the northern hemisphere seasons.

Clarification: I'm looking for a way to keep the strain indefinitely without potentially changing the strain due to factors like contamination and genetic drift. More of a solution where it would be a one-to-many situation. I'm looking for steps that would show me how to keep a culture from changing over time. Be that using petri dishes or test tubes with agar or whatever.

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5 Answers 5

up vote 3 down vote accepted

You might also consider culturing yeast on slants. I do this and currently have around 15 different yeast strains in stock that can be ready to go within a week.

This site explains a very similar process to the one that I use:

http://www.tigereye.net.au/bluedog/slants.html

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404 code on that link –  Jon Jan 27 at 16:46

A friend of mine took the yeast cake from a batch he brewed and used that to make a starter for his next batch. Granted, he didn't keep it long term, but I would think that if you got the yeast cake and kept it in the fridge, it would last awhile.

It would only need to last until you brew again, then you can grab the "fresher" yeast cake and store that in the fridge again.

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What I do is sort of like the previous answer, but it is a bit of a more long term solution. Basically this is the process - I create a yeast starter - 1000 ml of yeast, whether pitching a dry or wet yeast.

I then sterilize (by cooking it in a pressure cooker) a test tube and cap. Before I pitch the yeast into the wort, I pour a test tube or two. I keep these in the fridge, and up to 6 months later, you can then create a starter from one of these. That way you can recycle your yeast.

As long as you're careful and take precautions to keep a sterile work area when creating the test tubes, you shouldn't have any problem. This isn't as long term a solution as creating slants, but it is much easier.

Basically the day before I brew, I take one of the test tubes out of the fridge, create 1000 ml of wort, pitch the yeast to create my starter, and begin the process all over again. As long as you use the year fairly often - perhaps every couple of months, you should be fine.

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I've been keeping my yeast for well past three months in the fridge with no problems.

This is what I've been doing.

Prior to brewing, I sterilize about a dozen jelly jars (Bell brand) in boiling water. Once they have been boiled for at least 10 minutes, I quickly remove and drain them (using a boiled set of tongs). I set them upright on a cooling rack and place the lids and screw caps on top (also boiled). I then use oven mitts to tighten the screw caps down. Let them cool and you will hear them all 'pop' as the air shrinks and forms a vacuum and the lid tightens down.

Now store all those jars in a cool, dry, and dark location.

Whenever you rack a beer from primary to secondary, and you want to keep some of that yeast strain, just leave a little beer in the bottom of the bucket with the yeast cake. Swirl it all around to create some mud. Then pop open a jelly jar and quickly pour the mud into the jar (straight from the bucket, no utensils). Cap the jar again with the same lid and put the screw cap on it. Place it in the fridge.

Now, when you are ready to start a new batch, use it just like it was a vial you bought at the store. Let it warm to room temp. Pitch it into a yeast starter. You don't need the whole amount of yeast in there. About the same amount you would use from a vial. Throw the rest out.

Beware that there will be CO2 in the jelly jar so when you uncap it, you may get quite a bit of foam.

Again, this is not a perfect way to do this. But I have had success with this method. I have repitched my yeast up to six generations with no noticeable issues. About three to four months in the fridge has never been an issue.

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I'm not sure I want to continually use yeast from a yeast cake. I'm more looking for a way to keep the strain indefinitely without potentially changing the strain due to factors like contamination and genetic drift. More of a solution where it would be a one-to-many situation. I'm looking for steps that would show me how to keep a culture from changing over time. Be that using petri dishes or test tubes with agar or whatever. Sorry for the confusion, I'll clarify the question. Thank you for the answer! –  chrislarson Nov 9 '10 at 16:17
3  
No problem. Don't worry about genetic drift in beer yeast. As I understand it Saccharomyces cerevisiae does not drift much. You're main worry as a homebrewer is contamination. As to how to store it longer than a few months? I don't know. I've never tried. My experience is mainly with making the same recipes repeatedly and trying to save money. Also, don't underestimate the yeast colony's ability to 'learn' a beer. Often times, your beer will improve noticeably after the yeasts have fed on the same recipe a couple of times. –  thebeav Nov 9 '10 at 18:45
    
I've kept started yeast in a capped growler (previously sani'd etc) in a fridge for over 6 months and restarted it fine. –  Keith Hoffman Oct 10 '12 at 20:45

This is one of my favorite topics on HomebrewTalk that describes the process of washing and storing yeast.

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