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General Category => Yeast and Fermentation => Topic started by: kcjaz on February 17, 2011, 05:00:12 AM

Title: Reusing lager yeast
Post by: kcjaz on February 17, 2011, 05:00:12 AM
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.

Title: Re: Reusing lager yeast
Post by: ndcube on February 17, 2011, 12:00:01 PM
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.
Title: Re: Reusing lager yeast
Post by: Kaiser on February 17, 2011, 12:36:56 PM
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
Title: Re: Reusing lager yeast
Post by: ndcube on February 17, 2011, 01:02:07 PM
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?
Title: Re: Reusing lager yeast
Post by: Kaiser on February 17, 2011, 01:40:43 PM
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
Title: Re: Reusing lager yeast
Post by: bluesman on February 17, 2011, 02:46:52 PM
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.
Title: Re: Reusing lager yeast
Post by: hamiltont on February 17, 2011, 03:43:02 PM
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!!!
Title: Re: Reusing lager yeast
Post by: denny on February 17, 2011, 03:47:53 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.
Title: Re: Reusing lager yeast
Post by: Thirsty_Monk on February 20, 2011, 12:44:46 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.
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.
Title: Re: Reusing lager yeast
Post by: kcjaz on February 23, 2011, 02:53:44 AM
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.

Title: Re: Reusing lager yeast
Post by: Kaiser on February 23, 2011, 03:23:22 AM
Jason,

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

Kai
Title: Re: Reusing lager yeast
Post by: kcjaz on February 23, 2011, 04:07:35 AM
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.
Title: Re: Reusing lager yeast
Post by: Kaiser on February 23, 2011, 02:04:09 PM
I believe that explains why the old yeast seemed to get going faster.

Yes, that would be my conclusion as well.

Kai
Title: Re: Reusing lager yeast
Post by: Kirk on February 23, 2011, 09:01:58 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?
Title: Re: Reusing lager yeast
Post by: Thirsty_Monk on February 23, 2011, 11:04:24 PM
Yes,
You do not have a growth but you have cels that die.
Title: Re: Reusing lager yeast
Post by: 1vertical on February 24, 2011, 05:37:41 PM
I just re-used some S-189 and the thing is that on the second usage, I forgot to add
the yeast nutrient to the BK.  I pitched the cooled wert onto the 1 inch of slurry that
was left in the fermenter after 2 weeks of sitting in the cold 40 deg f garage. Fermentation
took off nicely with a 24 hour lag from start.  The beer was at O.G. 1.050 and the F.G.
was only 1.018 so it did not really attenuate well...The 1st beer seemed to attenuate
much better with O.G 1.060 and F.G. 1.014.  I prolly would have gotten better results
had I not forgotten to add the nutrients.  Livin...learnin  :P
Title: Re: Reusing lager yeast
Post by: denny on February 24, 2011, 06:01:04 PM
Even though I use nutrient myself, I'm not sure I'd attribute the poorer attenuation to not using it.
Title: Re: Reusing lager yeast
Post by: 1vertical on February 24, 2011, 06:50:21 PM
If that is the case Denny, I am wondering what in the heck did cause the difference.
I pitched a lower gravity wert onto a Massive yeast slurry. I pampered that yeast
kept it cool...in the dark in the bottom of the bucket blanketed in CO2.  Fermented
it well within the parameters and gave it a week and a half at warmer temps to finish
prolly was around 60-62 ish for the long d-rest.  It tastes a bit sweet not cloying, but
sweetish. ???

And Oxygen, yep I shoot the ox to it with the ability to use medical tank and a couple
of minutes of fine 2 micron mesh bubbles....LOTS of oxygen.
Title: Re: Reusing lager yeast
Post by: Kaiser on February 25, 2011, 02:06:29 AM
could it be that the yeast sat dormant for too long?

Kai
Title: Re: Reusing lager yeast
Post by: 1vertical on February 25, 2011, 05:48:54 AM
could it be that the yeast sat dormant for too long?

Kai
Kai, I cannot rule that possibility out since I did no testing fast ferment or anything.
It was sitting about a week and a half.  I thought It would just have been the
equivalent of a huge starter but not sure. It just had enough. Consequently, instead
of brewing with that again, I will start with fresh yeast It must be stressed somehow.
Title: Re: Reusing lager yeast
Post by: blatz on February 25, 2011, 03:10:56 PM
could it be that the yeast sat dormant for too long?

Kai

I go back and forth on this a lot - recently, I pitched a helles with yeast that sat in a jar for 3 weeks since racking pils off the top and collecting.  I pitched about 50% more than mrmalty.com recommended and although it took about 36-48 hours to show airlock activity, it fell from 1.050 to 1.012 in less than 2 weeks.  I did not have a chance to do FFT on this one.

point is, sometimes it seems extended dormancy is a major factor, other times its irrelevant.

Title: Re: Reusing lager yeast
Post by: Kaiser on February 25, 2011, 03:32:27 PM
Quote from: blatz link=topic=5994.msg73461#msg73461 date=1298646656
point is, sometimes it seems extended dormancy is a major factor, other times its irrelevant.
[/quote

I agree that this is a subject that may warrant more investigation. In the end it is not just about how fast and how well the beer attenuates but it is also important how the final product tastes. My recommendations are largely based on what I have observed. Records of measured values, like gravity and attenuation, are always better than recollection of taste.

Kai
Title: Re: Reusing lager yeast
Post by: kcjaz on February 26, 2011, 05:44:19 AM
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.

OK, its Friday now and I racked both carboys to secondary carboys, 6.5 days after pitching (I pitched the yeast last Saturday morning). Gravity data is this:

Old yeast:1.014
New yeast: 1.013

Both were in the same fridge held at 50F.  While it's tempting to say the new yeast did better, I'd say 0.001 difference in gravity after 6.5 days is really, in practical terms, pretty much the same.  The taste between the two was very similar.  I'd say the old yeast was a tad sweater but I think that is just because I knew the gravity was higher.  In a blind test, I don't think I could tell the difference.  There was nothing funky with the old yeast.  Now I'll drop the temp a couple degrees each day down to 36 or so and lager until the gravity levels out.  This is a new recipe so I'm not sure where it will end up but I'm hoping for 1.008 or so.  I'll post the final results when I have then.
Title: Re: Reusing lager yeast
Post by: johnf on February 26, 2011, 06:01:37 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?

I think the conditions in the white labs or wyeast package are a bit more optimal but yes it is similar to stored slurry. That's one reason I wouldn't ask these companies to package large quantities of yeast. If I can't get it within a couple of days (I sometimes can but I cannot count on that) I would want to use a smaller quantity and a starter anyway.
Title: Re: Reusing lager yeast - Update
Post by: kcjaz on March 22, 2011, 01:41:40 AM
OK, here are the final numbers.  To remind everybody, on February 18, I brewed an 11 gal batch of wheat beer.  OG = 1.044.  I had some old yeast slurry saved from a previous lager batch that was brewed on Thanksgiving (Wyeast 2035).  I had periodically been "feeding" this yeast with shots of DME wort.  On brewday, I took this old yeast and made a new starter from a 1/2 gal of my new wheat beer.  I also did the same thing with a brand new smack pack of 2035.  I let the starters do their thing over night while I let the remaining 10 gal of wort chill and settle in the fridge.  The next morning, I racked the work of the trub into new carboys and pitched each starter into the wort at 50F.

Both took off pretty quickly. 7 days later on 2/25 the gravities were:

New yeast = 1.013
Old yeast  = 1.014

Today (3/21/2011), after lagering at 33F since 2/25 the gravities are:

New yeast = 1.010-
Old yeast  = 1.010

I put the minus sign after the 1.010 for the new yeast because it was a slightly lower reading than the 1.010 for the old yeast. 

I can't say that I can detect any real flavor difference between the two half batches.  The "old yeast" may be a little sweater but it is barely perceptible, I may even be imagining it.  Both taste really good.  I am certain that any taste difference could only be noticed by tasting each beer side by side.  Tasted months apart, with different batches, you could never tell, there are many more other factors that could cause "identical" homebrew batches to be different (that is part of the fun). 

My conclusion is that the "old yeast" was just fine to use and conversley, the "new yeast" provided no real advantage in the end product.  The only advantage I see for the "new yeast" would be a higher chance of success and and lower chance of something bad happening.