Author Topic: Reusing lager yeast  (Read 3349 times)

Offline kcjaz

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Reusing lager yeast
« on: February 16, 2011, 10:00:12 PM »
I generally don't try to keep my yeast cultures going and just buy new smack packs each time I brew.  That made sense to me when I was brewing only ales, and only brewing once every 3 to 4 months.  Now though, after getting my brewery set up in a dedicated space in my basement, I'm brewing more often.  I've brewed 4, 10 gallon batches since November and trying to get the cost down by repitching yeast seems like a good idea. 

My basic question is how long can you store yeast?  Is the amount of time the yeast has been stored the big factor or is it the number of batches that the yeast has been used for?  I have some lager yeast that I used for a batch I brewed on Thanksgiving.  I've kegged half the batch but I still have the other 5 gallons in a carboy (secondary) lagering away, with a thin layer of yeast on the bottom.  Could I just transfer the beer off of it and repitch the yeast into my next lager batch?  Should I "wake up" the yeast by feeding it a DME starter and then repitch it?  Does it matter that this is yeast from a secondary not a primary?  I also saved some of the yeast from the primary.  I've been feeding it about once a month by pouring off the beer and giving it fresh wort made from DME.  I was just doing this to experiment and see how much yeast sediment I could get by keeping it active.  Is feeding it periodically necessary or can I just let it sit in the fridge for several months and repitch it into a new batch?

I would appreciate any words of wisdom on this.

Jason Zoller

Offline ndcube

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Re: Reusing lager yeast
« Reply #1 on: February 17, 2011, 05:00:01 AM »
I don't pitch from a secondary container, the theory being that the least is less flocculent.  It's also been sitting around for a while.

I'll reuse yeast saved from a primary up to two weeks.  After that I make a starter from a scoop of the slurry.  I generally keep yeast for about 6 months for making starters before I pitch it (although I rarely end up using it).  I usually plan a string of batches to keep repitching fresh yeast.

It takes a lot of yeast for a lager and there might not be enough cells left in a yeast cake after a long period of time (especially since Thanksgiving).

I'm not sure about the yeast feeding thing.  I would think that it's dying off at the same rate it's growing, Plus there is the higher risk of contamination.

Offline Kaiser

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Re: Reusing lager yeast
« Reply #2 on: February 17, 2011, 05:36:56 AM »
I see a fairly significant decline in fermentation performance when the yeast has been sitting dormant for more than just a few (2-3) days. As a result I avoid keeping it in the fridge for longer than that. If it is older I would at least make a small starter with it so the yeast can get replenish its resources even though there won't be much growth.

Kai

Offline ndcube

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Re: Reusing lager yeast
« Reply #3 on: February 17, 2011, 06:02:07 AM »
I see a fairly significant decline in fermentation performance when the yeast has been sitting dormant for more than just a few (2-3) days. As a result I avoid keeping it in the fridge for longer than that. If it is older I would at least make a small starter with it so the yeast can get replenish its resources even though there won't be much growth.

Kai

This may be slight off topic...
If (for example) fermentation ends after 2 weeks but you leave the beer in the primary for 3 is that considered to already be past your 2-3 day mark?

Offline Kaiser

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Re: Reusing lager yeast
« Reply #4 on: February 17, 2011, 06:40:43 AM »
If (for example) fermentation ends after 2 weeks but you leave the beer in the primary for 3 is that considered to already be past your 2-3 day mark?

It's actually not that much off-topic.

I would consider this yeast 1 week old since the active part of fermentation stopped a week ago.

While I have been seeing better fermentation times and oftentimes also better attenuation with fresh yeast compared to older yeast I have brewed lagers with slightly older (3-7 days) slurries and they have been fine. I don't have data that actually compares the taste of a beer brewed with fresh yeast to one brewed with older yeast while everything else has been the same.

On a recent Munch Helles life got in the way of brewing the 2nd batch and the yeast sat in the fridge for 4 days, compared to 2 days for the first batch, after propagation was done. The result was that the beer fermented slightly slower and that it had a harder time reaching final gravity. The 2nd batch left an attenuation to attenuation limit difference of 2% while the first batch had only 1% difference. This makes the 2nd beer slightly sweeter. While this works well for a Helles, I wouldn't like this to happen in a Pilsner where the goal is to get attenuation to the attenuation limit.

In the end it comes down to taking good notes. Try to keep track of the age of the yeast and keep track of the fermentation time. For lagers, I take a gravity reading 7 days after pitching and divide the difference between the OG and that reading by 7 to get the average gravity drop during the first 7 days. I also know the attenuation limit from the fast ferment test which allows me to track how well the yeast is able to reach that limit. In most cases getting to the desired attenuation to attenuation limit difference is the hardest part for me. Warm maturation rests, which speed yeast activity, greatly help with that.

Kai

Offline bluesman

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Re: Reusing lager yeast
« Reply #5 on: February 17, 2011, 07:46:52 AM »
I almost always make a starter with lager yeast slurries. I am continually harvesting lager yeast.

I recently made an Ofest using 4th generation lager yeast slurry but I made a starter with it and it fully attenuated as expected down from 1.054 to 1.012. The yeast used was WLP830.

I am going to determine how long (generations) I can actually go with this yeast. My plan is to continue to make lagers with it about once every three months or so. I haven't noticed any detrimental effects from the taste of the beer as of yet. In fact the current beer quality is fantastic. I'll keep you posted as time goes by.
Ron Price

Offline hamiltont

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Re: Reusing lager yeast
« Reply #6 on: February 17, 2011, 08:43:02 AM »
I recently brewed a string of Lagers starting with dry yeast & then pitching fresh, thick slurries less than a day old.  Basically kegging the night before, storing in the fridge and pitching the next afternoon.

Here's data:
10 gallons of American Lager - pitched 3 packs of 34/70 rehydrated yeast. OG 1.054 FG 1.010. Attenuation 81.5%
10 gallons of Vienna Lager - Pitched 1 pint of slurry. OG 1.058 FG 1.012. Attenuation 79.3%
5 gallons of Bock - Pitched 1/2 pint of slurry. OG 1.076 FG 1.015. Attenuation 80.3%
5 gallons of Dopplebock - Pitched 1 pint of slurry. OG 1.110 FG 1.023. Attenuation 79%

All were fermented under the same temperature controlled conditions.  If I didn't pitch within a couple days as Kai mentioned I would have done a starter, but timing it this way eliminated that step.  Cheers!!!
« Last Edit: February 17, 2011, 08:59:42 AM by hamiltont »
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Offline denny

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Re: Reusing lager yeast
« Reply #7 on: February 17, 2011, 08:47:53 AM »
I also saved some of the yeast from the primary.  I've been feeding it about once a month by pouring off the beer and giving it fresh wort made from DME.

My understanding is that this is not a good idea.  You want the yeast to be dormant.
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Offline Thirsty_Monk

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Re: Reusing lager yeast
« Reply #8 on: February 19, 2011, 05:44:46 PM »
I also saved some of the yeast from the primary.  I've been feeding it about once a month by pouring off the beer and giving it fresh wort made from DME.

My understanding is that this is not a good idea.  You want the yeast to be dormant.
BSI actually recommends feeding yeast.
http://www.brewingscience.com/yeast_care.htm
Check the point #3.
I did not see any other yeast house talk about it.
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Offline kcjaz

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Re: Reusing lager yeast
« Reply #9 on: February 22, 2011, 07:53:44 PM »
Thanks, that's pretty interesting.  I wonder if the cleaning/feeding kits can be scaled down to 10 gallon batches.  In reality though, the ecomonics of keeping a yeat culture viable for several months seems sketchy compared to just buying another smack pack. 

I decided to try an experiment with the yeast I have stored and fed for 2 months.  Last Friday I brewed an 11 gallon batch of a wheat lager.  I put it in two 5 gallon carboys and put them in the fridge to cool down to 50F and settle over night.  I made one starter out of 1/2 gallon of the same wort and pitched a new smack pack of Wyeast 2035.  I took my 2 month old 2035 yeast and made another started with another 1/2 gallon of the same wort. 

The old yeast started bubbling in about 20 minutes while the new yeast took about 90 minutes to start going.  The next morning I racked the wort off the trub and pitched each starter.  After 24 hours each carboy was going pretty good, each with a nice krausen on top.  The new yeast was producing airlock bubbles at about 1 per 6 seconds and the old yeast was making bubbles faster at about 1 per 3 seconds.

Now they seem to both be going at about the same rate.  I'll rack to secondary on Friday and take a gravity reading and taste test.  So far though, I don't see any ill affect from my old yeast.  The proof though will be in the gravity numbers and the taste.

Jason Zoller

Offline Kaiser

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Re: Reusing lager yeast
« Reply #10 on: February 22, 2011, 08:23:22 PM »
Jason,

How much difference was there in the initial yeast amount between both the starters?

Kai

Offline kcjaz

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Re: Reusing lager yeast
« Reply #11 on: February 22, 2011, 09:07:35 PM »
My old yeast was waht I collected from my last batche's primary and I had fed a couple times so there was a lot of yeast cake. I don't know how much of it was still alive but there was a lot of thick slurry.  The new yeast I pitched was a large activator pack, so a billion cells or whatever it is.  I believe that explains why the old yeast seemed to get going faster.
Jason Zoller

Offline Kaiser

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Re: Reusing lager yeast
« Reply #12 on: February 23, 2011, 07:04:09 AM »
I believe that explains why the old yeast seemed to get going faster.

Yes, that would be my conclusion as well.

Kai

Offline Kirk

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Re: Reusing lager yeast
« Reply #13 on: February 23, 2011, 02:01:58 PM »
Aren't the vials and smack packs we buy similar to the harvested yeast we store in the fridge?  They're just sitting there in the LHBS fridge.   Are they not becoming less viable with time in the same manner as our home harvested?
Kirk Howell

Offline Thirsty_Monk

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Re: Reusing lager yeast
« Reply #14 on: February 23, 2011, 04:04:24 PM »
Yes,
You do not have a growth but you have cels that die.
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On Tap At The TapRoom:
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Smoked Bock
MaiBock
American Brown Ale
Marzen
Root beer