Author Topic: Reusing yeast  (Read 4959 times)

Offline gmac

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Re: Reusing yeast
« Reply #15 on: October 02, 2012, 08:27:03 AM »
Like Joe said, you may try washing the yeast.  I just started doing this and have had great results.  Here's a link I used to get me going:  http://billybrew.com/yeast-washing
 

I read the link and it mentions that washed yeast can be used a few weeks up to maybe a few months after washing. Is this a reasonable estimate? I'm going to bottling a belgian golden strong in the next week or two, and probably won't make another Belgian until next January/February. Would I be better off just getting a fresh vial after that long?

After a couple weeks, it's good practice to make a starter. I'd make a good sized starter or step it up after it's been sitting for a couple months.  You're gonna lose viability after a while so a 2L starter would be wise.  Watch the starter and see how it goes.  If it takes off fast, it's probably enough but if it takes a few days to get to krausen and seems sluggish, you may want to step it once more to make sure you've got enough fresh new yeast.
There's nothing wrong with the yeast after a couple months (assuming good sanitation) but you may not have enough to go right into a new beer.

Offline Joe Sr.

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Re: Reusing yeast
« Reply #16 on: October 02, 2012, 08:31:32 AM »
Like Joe said, you may try washing the yeast.  I just started doing this and have had great results.  Here's a link I used to get me going:  http://billybrew.com/yeast-washing
 

I read the link and it mentions that washed yeast can be used a few weeks up to maybe a few months after washing. Is this a reasonable estimate? I'm going to bottling a belgian golden strong in the next week or two, and probably won't make another Belgian until next January/February. Would I be better off just getting a fresh vial after that long?

I've reused yeast 3-4 months plus with no problems.  Just make a starter.

Dave

Me, too.  But be aware that you don't really have a pure culture anymore.

I've not noted any significant flavor changes in re-using yeast, but I have on occasion noted that after a generation or two the yeast does not flocc out as well.  YMMV.
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Re: Reusing yeast
« Reply #17 on: October 02, 2012, 08:42:27 AM »
Me, too.  But be aware that you don't really have a pure culture anymore.

How does that follow? Are you saying that there will be some (minimal, hopefully) contamination? Obviously that's true, but it's also true when pitching from the initial pack/vial.

I've not noted any significant flavor changes in re-using yeast, but I have on occasion noted that after a generation or two the yeast does not flocc out as well.  YMMV.

I think that's most likely due to harvesting process, getting the least flocculent top layer of sedimented yeast.

FWIW, I've built up 12-18 month old slurries on several occasions.
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Re: Reusing yeast
« Reply #18 on: October 02, 2012, 08:49:00 AM »
When making a starter from old yeast, my recommendation is to take a sample (1 tsp, for example) and step it up from there. First ~200 - 300 ml then 1000 ml for ale and 2000 ml or more for lager.

The reasoning behind this is that there is a lot of dead yeast stuff in that old slurry that you don't want in your beer. You want healthy young cells.

This will not clean up any infection. For that you would have to plate the yeast, pick a single growth colony and step up from there.

Kai

Offline Joe Sr.

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Re: Reusing yeast
« Reply #19 on: October 02, 2012, 08:54:06 AM »
Me, too.  But be aware that you don't really have a pure culture anymore.

How does that follow? Are you saying that there will be some (minimal, hopefully) contamination? Obviously that's true, but it's also true when pitching from the initial pack/vial.

Yes.  Hopefully minimal contamination.  Whatever mutation there may be (probably more on later generations).  You're correct that it's also true with the initial pitch, but there are more intermediary steps once you're re-using yeast.  Nothing I'm worried about, but others may be.  I think the only way you'd have a pure culture is using slants, correct?

I've not noted any significant flavor changes in re-using yeast, but I have on occasion noted that after a generation or two the yeast does not flocc out as well.  YMMV.

I think that's most likely due to harvesting process, getting the least flocculent top layer of sedimented yeast.

FWIW, I've built up 12-18 month old slurries on several occasions.

I agree with this also, as the logic seems airtight.  My only conundrum is the Ardennes I repitched where I used the entire amount of slurry I harvested and it simply would not drop out without fining.  Typically, I swirl the carboy to get everything mixed up and pour out the slurry into containers.  This would seem to mix it well, but maybe I did not agitate enough.  Who knows?
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Re: Reusing yeast
« Reply #20 on: October 02, 2012, 09:13:35 AM »
My only conundrum is the Ardennes I repitched where I used the entire amount of slurry I harvested and it simply would not drop out without fining.

Are you sure it was the yeast that didn't want to drop out? I have a problem with Maris Otter malt in that it always leaves my beer cloudy and I have to use finings. I know its not yeast that's causing the haze b/c I checked it under the microscope.

Kai

Offline Joe Sr.

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Re: Reusing yeast
« Reply #21 on: October 02, 2012, 09:27:51 AM »
My only conundrum is the Ardennes I repitched where I used the entire amount of slurry I harvested and it simply would not drop out without fining.

Are you sure it was the yeast that didn't want to drop out? I have a problem with Maris Otter malt in that it always leaves my beer cloudy and I have to use finings. I know its not yeast that's causing the haze b/c I checked it under the microscope.

Kai

I assumed, but I can't say I'm sure.  Thinking about it now, I had two batches of dubbel that I needed to fine and my quad took FOREVER to drop clear, but eventually did.  Three different yeasts, all repitched (Chimay, Ardennes, and Trappist High Gravity).  I'd have to check if they all had the same base malt, which is possible.  It would have been Pilsner malt, though, not MO.  Also, I only do a partial mash of 5lbs and the balance comes from DME.

I did have the same problem with a stout, but I cultured up the yeast from the dregs in a bottle so that definitely had selection for the least flocculent.

I've not had the problem with my English ales (using MO as a base).  I'm on gen 3 or 4 of London ESB yeast right now so I'll check the two batches of porter this week and see how it looks. That yeast typically floccs like crazy and did so in the starters.
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Re: Reusing yeast
« Reply #22 on: October 02, 2012, 10:44:23 AM »
Yes.  Hopefully minimal contamination.  Whatever mutation there may be (probably more on later generations).

I don't think mutation is going to be an issue under brewery conditions (no intense radiation, mutagenic chemicals, etc.). The yeast labs are starting from a single cell at least occasionally - to build that to 100 billion you've already propagated through 36 generations. Even if you go another hundred or so, which wouldn't be atypical in a brewery, it just isn't enough time for normal genetic drift to become perceptible.

Of course sanitation is always key. If you can't manage that there's no point re-pitching yeast.

I think the only way you'd have a pure culture is using slants, correct?

If we're talking about cell-to-cell genetic variations, even that wouldn't be enough. You'd have to plate the yeast and culture from a single cell. For all practical purposes, though, any yeast propagated from a yeast bank's master culture can be considered "pure", IMO.
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Offline tschmidlin

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Re: Reusing yeast
« Reply #23 on: October 02, 2012, 01:28:46 PM »
I think the only way you'd have a pure culture is using slants, correct?

If we're talking about cell-to-cell genetic variations, even that wouldn't be enough. You'd have to plate the yeast and culture from a single cell.
But if we're talking cell to cell genetic variations, even going from a single cell would introduce mutations. ;)

For all practical purposes, though, any yeast propagated from a yeast bank's master culture can be considered "pure", IMO.
I agree.  If the strain is so unstable that simply growing a culture gives you a lot of variation, I think it is too unreliable to use for brewing.
Tom Schmidlin

Offline davidgzach

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Re: Reusing yeast
« Reply #24 on: October 02, 2012, 01:48:12 PM »
The reasoning behind this is that there is a lot of dead yeast stuff in that old slurry that you don't want in your beer. You want healthy young cells.

Kai,

How much does "old yeast stuff" effect the flavor of a new beer if repitched?  I repitched slurry from lager yeast cakes several times without noticing anything peculiar.  Could be my tastebuds, but am really interested in this as I reuse often.

Dave
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Re: Reusing yeast
« Reply #25 on: October 02, 2012, 02:23:38 PM »
But if we're talking cell to cell genetic variations, even going from a single cell would introduce mutations. ;)

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Offline Joe Sr.

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Re: Reusing yeast
« Reply #26 on: October 02, 2012, 02:36:46 PM »
For all practical purposes, though, any yeast propagated from a yeast bank's master culture can be considered "pure", IMO.
I agree.  If the strain is so unstable that simply growing a culture gives you a lot of variation, I think it is too unreliable to use for brewing.

I don't know that the jars of slurry in my fridge qualify as a "master culture."  I do my best, but in my experience I've noted differences in performance from generation to generation.  This may well simply be an artifact of my harvesting procedures.

I certainly don't want my perhaps poorly worded statement about pure cultures to dissuade the OP from harvesting and reusing yeast.

I have and will continue to harvest and reuse yeast and it has and will continue to make tasty beer.
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Re: Reusing yeast
« Reply #27 on: October 03, 2012, 10:57:02 AM »
How much does "old yeast stuff" effect the flavor of a new beer if repitched?  I repitched slurry from lager yeast cakes several times without noticing anything peculiar.  Could be my tastebuds, but am really interested in this as I reuse often.

I actually don’t know how much the old stuff affects taste. And I’m sure many brewers do this w/o problems.

This is one of the cases where I believe, w/o having strong evidence, that it should be good practice to minimize old yeast in the fermenter. Maybe I’m just used enough to growing yeast all the time that it’s easy for me to avoid using old yeast. I don’t know if it affects flavor in a noticeable way, but there many ways in which old yeast can be detrimental.

Interested brewers may try re-growing yeast from small old slurry samples and try this for a while compared to using all the old slurry. If it doesn’t make a difference and just adds work, you can always switch back.

On the topic of performance changes for repitched yeast, keep in mind that under oxygenation, for example may not show up until the yeast is reused since in the previous batch it was actually living on sterol reserves from the yeast manufacturing.

Kai

Offline tubercle

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Re: Reusing yeast
« Reply #28 on: October 03, 2012, 04:27:38 PM »
I think the only way you'd have a pure culture is using slants, correct?

If we're talking about cell-to-cell genetic variations, even that wouldn't be enough. You'd have to plate the yeast and culture from a single cell.
But if we're talking cell to cell genetic variations, even going from a single cell would introduce mutations. ;)

For all practical purposes, though, any yeast propagated from a yeast bank's master culture can be considered "pure", IMO.
I agree.  If the strain is so unstable that simply growing a culture gives you a lot of variation, I think it is too unreliable to use for brewing.

 Y'all are talking like all variations are bad. Compared to what? Commercially produced yeast? I have a Frankenyeast I have used for years..I forget how many now, at least 10...and it produces very good beer. I'm sure the number of mutations has many zeros but Ol' Frankie is doing well.

 Frankie lives in the back of the fridge in a mason jar but ocassionally I let him out to play. A couple of tablespoons in a starter and he is as happy as can be.

 There is a finite number of commercial yeast but an infinate number of mutations available.

 WARNING: Do not try this if you locked into "making to style", of which there is a finite number also.

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Offline tschmidlin

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Re: Reusing yeast
« Reply #29 on: October 03, 2012, 11:27:40 PM »
Y'all are talking like all variations are bad. Compared to what? Commercially produced yeast?
You're right, we are talking about trying to stick to a style or an expected flavor profile.  If you're more flexible, have at it.  Grow it forever, as long as you like the end result.
Tom Schmidlin