How do I keep yeast from a strain that I've bought?

Question

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.

Answer 1

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://web.archive.org/web/20120708055744/http://www.tigereye.net.au/bluedog/slants.html

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

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

Answer 6

I like the idea of wild yeasts & bacteria, sourdough cultures and genetic drift. What better way to discover new and original beer flavors. The yeasts may adapt in time to the particular type of ingredients people use in their brewing. I've been using my own sourdough yeast culture to brew beer for years...just prepared by taking wild yeasts and bacteria at random out of the air into a flour and water mixture, which begins to ferment after about a week and can be kept in a fridge for months or years by feeding weekly with a tablespoon of wholegrain flour and a little freshly squeezed lemon juice plus a little yeast nutrient occasionally. I like to add some of the spent yeast from the previous brew to the culture to keep it stronger and livelier. I also use this yeast for baking bread. Just recently I did try a commercial ale yeast called Nottingham to see how it would compare. I have to admit, the Nottingham yeast did give a more rapid (3-4 days) and complete fermentation, right down to 1.004 SG. My own yeast is slower (about 7-10 days) and gets down to about 1.008. I have kept a culture of the Nottingham yeast in my fridge for future experimentation. I can see why the faster yeasts would be an advantage for commercial beer brewing.

Answer 7

There are sourdough yeast strains that are decades old and they just store them in a cooler