How many times can I use a yeast cake?

I made an all grain SN Pale Ale clone 2 weeks ago and last night I made an extract SN Celebration Ale clone. I poured the chilled wort directly on top of the yeast cake and I used Wyeast 1056. The yeast started the next morning and are working like crazy. Good thing I used a blow off tube.

What is the most number of times you have reused the yeast cake?

You probably could use it endlessly and still come out with beer, but at some point it starts to mutate. I think a lot of the pros stop at around a dozen generations or so. Usually I plan on 3 or 4 reuses of a cake, moving from low gravity lighter color to higher grav darker. By that time theres a good bit of trub anyway. Also I dump out some of the yeast each time to avoid over pitching.

I've always heard/read about 5 times with the same yeast, then they start mutating. Obviously not immediately after the 5th time you get a crazy different yeast, but could start to be slightly different.

Does it always mutate in a bad way, or different way? How do they keep yeast the same over generations?

Pick said:

Does it always mutate in a bad way, or different way? How do they keep yeast the same over generations?

Click to expand...

Exactly. What the pros don't tell you is that the yeast could mutate into something really special. Take this example from Wikipedia

Also isn't all of the yeast we use today a mutation of an earlier yeast? I mean yeast are one cell organisms that have been around since the beginning of time. They have mutated and adapted to survive. I am sure there are homebrewers out there that pitch 100's of generations with no noticeable ill effects. Remember its in the financial interest of yeast companies such as Wyeast and White Labs to say that you shouldn't reuse yeast past 7 generations or whatever that number is. After all how would they stay in business?

Yeast mutation is often cited as the principal problem, however, yeast age is the real question and live to dead cell ratio. Some people buy off on the one, or two use max yeast and discard the yeast after only a couple of uses. Here are the rules:

1. Continue using your yeast as long as it is separate from contaminants.

2. Low pitching rates will increase reproduction and thus increase potentially viable yeast.

3. High pitching rates invariably lead to old yeast that might not produce vigorous fermentation.

4. Once the yeast are old or you have a lot of dead yeast you can wash, which is easy or you can pour a plate and plate a sample. Once the colonies start to appear, look at the yeast under a scope and choose one that looks healthy. Take a loop and pick off some cells from that colony inoculate a vial and start a fermentation viability test. If it works you are good to go for another year or so.


Edit: A friend that worked at Molson once told me (years ago) that they would go 30 brews before clean up.
m.

9-12



10 char

All of my yeast cakes are reused 3 times. But sure you can use it 300.
Maybe you need to do that to get the best yeast ever.

It would be interesting to see some empirical data on this. Perhaps a poll is in order? I'm also interested in redalert's comments. Personally, I would like to see how many homebrewers have reused their yeast cakes time and time again, and how many of those have actually experienced yeast mutation to the point where a mutation is evident....or even how many have experienced a problem with having reused the yeast cake 5, 10, 15 times...??

I personally wouldn't repitch on a full yeast cake; that's a major overpitch. But you should be able to reuse part of the cake for at least 4-5 generations no problem; if you divide each cake into 5 parts, that gives you

5 brews from first cake
25 brews from second generation cakes
125 brews from third generation cakes
625 brews from fourth generation cakes
3125 brews from 5th generation takes

Or, more realistically, more brews than you can possibly do at home. The only issue is long-term storage if you don't use the same strain every time (see the frozen yeast bank thread for a solution to that).

Even just storing washed yeast in mason jars, you can keep one for a couple of months and then make a starter and brew with it and then harvest that cake for 5 (or more) new jars of washed yeast.

The most I've done is 10. The 10th was better than the first.

I have been re using safale us05 for awhile but I usually wash and divide the first batch into 5 and store in jars. I have recently had a weird taste on my beer. Like strong lemon taste. It might be time to dump it. It must be 5 generations old.

There are other factors that would affect the yeast and the flavors it produces.

For instance, if you brew a normal brew and strain the kettle hops from it prior to racking it to the primary then wash the yeast from the primary it is in about it's purest (cleanest) form. (FWIW, this is my practice).

If you dry hop in the primary and use the slurry directly from it the flavor/aroma will also added to the next brew's flavor/aroma. I would think washing this slurry would clean it up to some point, but not completely strip the dry hop flavor/aroma.

FWIW: I do not dry hop beers (even for the ones that list it in the recipe). Reason: I taste nothing but GREEN.

My normal process is to make a large starter and pull some of it off for a starter for another batch. (I saved a couple dozen of the old WLP vials).

As long as you start with a yeast that is not a blend of two yeasts reuse should be good for a reasonable number of generations.

The collecting and washing could accidentally cause some selection bias favouring poor floculating yeast cells if you are not careful and at some point that could become a problem.

Yeah I did another batch on top of the same yeast that gave the strong lemon taste and it turned out fine. Must be some thing else.

I've reused a yeast cake as much as 12 times. I usually wash the first batch and split it into 4 or 5 jars that I then pitch into separate batches. I pick the lowest gravity batch and wash the yeast from that and continue that way (after the first wash). I've had my best results with S-04 and Conan.

Old thread alert!

What people call "mutations" are probably wild yeast contamination.

This thread is a perfect example:
https://www.homebrewtalk.com/forum/threads/wlp029-gone-bad.648042/

So the question becomes: How many times can you repitch before getting a contamination large enough to influence flavor?
This will be wildly unpredictable.