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General Category => Yeast and Fermentation => Topic started by: pyrite on March 31, 2011, 01:22:30 PM

Title: Yeast cake rehydration
Post by: pyrite on March 31, 2011, 01:22:30 PM
What method do you use to rehydrate a yeast cake and prepare it for pitching?

I'll be transferring a 6% lager from primary to the secondary this weekend, and wanted to use the yeast cake right away in another lager.  What method would you suggest to get that yeast healthy for next pitch?   
Title: Re: Yeast cake rehydration
Post by: Hokerer on March 31, 2011, 02:16:48 PM
What method do you use to rehydrate a yeast cake and prepare it for pitching?

I'll be transferring a 6% lager from primary to the secondary this weekend, and wanted to use the yeast cake right away in another lager.  What method would you suggest to get that yeast healthy for next pitch?   

Wouldn't think you'd need to do anything.  Just rack the new batch into the fermenter right on top of the cake.
Title: Re: Yeast cake rehydration
Post by: denny on March 31, 2011, 02:36:03 PM
Wouldn't think you'd need to do anything.  Just rack the new batch into the fermenter right on top of the cake.

If you were using an ale yeast, I'd suggest using only part of the slurry.  But since you're doing a lager, I'd go with the advice above.
Title: Re: Yeast cake rehydration
Post by: tschmidlin on March 31, 2011, 04:11:31 PM
How long has it been sitting, and what is the gravity of the new batch?
Title: Re: Yeast cake rehydration
Post by: bluesman on March 31, 2011, 05:05:41 PM
Yeast cakes should be used within a week or two otherwise I would suggest making a starter from it. Go to mrmalty.com and estimate the quantity of slurry required and pitch on that ideally within a day or two.
Title: Re: Yeast cake rehydration
Post by: pyrite on March 31, 2011, 06:23:37 PM
How long has it been sitting, and what is the gravity of the new batch?

So from what you guys are saying, the yeast cake is ready to go to work again with out any nutrients or any type of help?

The lager has been in primary fermentation for 25 days @ 48F, with an included D-rest for 3 days @ 65F.. The new humulus lager hoppy lager batch will have an expected O.G. of  1.060. 
Title: Re: Yeast cake rehydration
Post by: tschmidlin on March 31, 2011, 06:36:54 PM
I think it will be fine, there should be plenty of viable yeast there to finish the new batch if you just rack on top of the cake like hokerer/Denny were saying.  I use nutrients in all of my batches, but other than that I don't think you need to do anything special for this yeast cake.
Title: Re: Yeast cake rehydration
Post by: Kirk on March 31, 2011, 07:44:10 PM
+1 to all, only to say that if you want to use a clean container, just swirl it (after racking your beer of course) and pour it into the new one.
Title: Re: Yeast cake rehydration
Post by: jeffy on March 31, 2011, 07:50:29 PM
You could pour it into a sanitized jar and let it settle.  That'll give you time to clean the fermenter and let you use the MrMalty site to actually measure the amount to use.
That said, when I brew back to back batches I often syphon the finished batch out of the primary and then fill it with the new wort right onto the yeast.
Title: Re: Yeast cake rehydration
Post by: pyrite on March 31, 2011, 09:41:48 PM
Thanks all, for the suggestions.

I will pitch the yeast cake as is.
Title: Re: Yeast cake rehydration
Post by: Will's Swill on April 02, 2011, 05:14:33 PM
Probably a stupid question, but is it preferable to use the yeast cake from the primary or the secondary (assuming a secondary is used of course)?  I would think the yeast population would be higher from the primary, but in the secondary I would think the yeast sediment would be "cleaner" (i.e. less unwanted trub).
Title: Re: Yeast cake rehydration
Post by: denny on April 02, 2011, 05:16:00 PM
OTOH, if you use the secondary, you're selecting the less flocculant yeast.  All if which is a way of saying it doesn't really matter all that much.
Title: Re: Yeast cake rehydration
Post by: pyrite on April 06, 2011, 02:11:50 AM
Update: Less than one hour after pouring the new wort right on top of the lager yeast cake, the violent fermentation created enough force to pop the blow off tube right off the carboy.  I've never seen that before, especially since it's fermenting at a constant 43F.  Only 3 full days since the inoculation and it seems to be almost done.   
Title: Re: Yeast cake rehydration
Post by: bluesman on April 06, 2011, 02:16:38 AM
Update: Less than one hour after pouring the new wort right on top of the lager yeast cake, the violent fermentation created enough force to pop the blow off tube right off the carboy.  I've never seen that before, especially since it's fermenting at a constant 43F.  Only 3 full days since the inoculation and it seems to be almost done.   

Sounds like your making beer. ;)

Congrats. Hope it turns out well for you.  :)
Title: Re: Yeast cake rehydration
Post by: gmac on April 06, 2011, 02:30:41 AM
If you were using an ale yeast, I'd suggest using only part of the slurry.  But since you're doing a lager, I'd go with the advice above.
What's the rationale for only using part of the yeast cake for an ale?  I know lager need larger starters but what's the downside to using a large starter for an ale?
Title: Re: Yeast cake rehydration
Post by: tygo on April 06, 2011, 02:43:59 AM
If you were using an ale yeast, I'd suggest using only part of the slurry.  But since you're doing a lager, I'd go with the advice above.
What's the rationale for only using part of the yeast cake for an ale?  I know lager need larger starters but what's the downside to using a large starter for an ale?

The growth phase of the yeast produces esters which add to the characteristic ale flavor.  Overpitching will reduce those. 
Title: Re: Yeast cake rehydration
Post by: denny on April 06, 2011, 03:01:59 PM
The growth phase of the yeast produces esters which add to the characteristic ale flavor.  Overpitching will reduce those. 

Or, as I often point out, according to Dr. Clayton Cone of Danstar/Lallemand, yeast growth will reduce esters.  That's been my experience with slurries.

http://www.danstaryeast.com/library/yeast-growth
Title: Re: Yeast cake rehydration
Post by: tschmidlin on April 06, 2011, 05:11:56 PM
The growth phase of the yeast produces esters which add to the characteristic ale flavor.  Overpitching will reduce those. 

Or, as I often point out, according to Dr. Clayton Cone of Danstar/Lallemand, yeast growth will reduce esters.  That's been my experience with slurries.

http://www.danstaryeast.com/library/yeast-growth
Thanks for the link Denny.

My take on it . . . this is an important sentence.  "Ester and other flavor component production or synthesis is a complex subject because there are so many variables taking place at the same time" ;)  It's very complex, and because of that I am not convinced that the effects he mentions can be entirely put into growth+/growth- bins.

I think this is important too: "I am also sure that there are beer makers that have experienced the very opposite with each of the variables."  Several of the conditions that he says "inhibits or slows down yeast growth" I call "stressing your yeast", for example "low nutrient, low O2", and we both agree that it will increase ester production.

There is plenty of evidence that ester formation increases with temperature, but I don't know that those studies differentiated between high start vs high finish temperatures so I'm not going to comment on that.

I think the problem I'm having with his statement is that we know that ester production comes after glycolysis, but we also know that glycolysis is an important part of amino acid synthesis, for example valine and leucine.  Those are required for all protein synthesis.  You can supply them to the yeast, which explains why nutrients reduce ester formation.  So inhibiting amino acid production reduces ester formation, however, that doesn't mean that growth is inhibiting ester formation.  One could just as easily argue the other side of the coin: since growth requires proteins, and protein synthesis requires amino acids, and amino acid synthesis produces esters, growth produces esters.

I think the reality is that "growth" is too macro of a level to discuss ester formation.

I refer you back to his first sentence: "Ester and other flavor component production or synthesis is a complex subject because there are so many variables taking place at the same time" ;) ;D
Title: Re: Yeast cake rehydration
Post by: denny on April 06, 2011, 05:29:54 PM
Tom, I really appreciate your take on this.  And I agree that the first sentence is kind of a CYA statement!  But to me, it shows that it isn't as cut and dried and some people would have you believe.  The fact that my own experience pitching less slurry led to cleaner beers shows that.
Title: Re: Yeast cake rehydration
Post by: tschmidlin on April 06, 2011, 05:56:20 PM
Tom, I really appreciate your take on this.  And I agree that the first sentence is kind of a CYA statement!  But to me, it shows that it isn't as cut and dried and some people would have you believe.  The fact that my own experience pitching less slurry led to cleaner beers shows that.
As always Denny, trust your empirical results over experiments done under conditions that are not the same as your beer making. ;)

Because of the complexities, I think you're right, it is not as cut and dried as some people say (including me sometimes :) ).
Title: Re: Yeast cake rehydration
Post by: benamcg on April 06, 2011, 06:02:21 PM
So, given this information would overpitching be OK for styles where you dont want an estery, fruity taste?   I make a lot of IPAs with higher amounts (than recommended according to the Mr. Malty calculator) of washed California Ale yeast slurry - and I dont want a high amount of esters in flavor.
Title: Re: Yeast cake rehydration
Post by: denny on April 06, 2011, 06:06:16 PM
So, given this information would overpitching be OK for styles where you dont want an estery, fruity taste?   I make a lot of IPAs with higher amounts (than recommended according to the Mr. Malty calculator) of washed California Ale yeast slurry - and I dont want a high amount of esters in flavor.

Based on my own experience, you'd want to pitch less yeast, not more, for that to happen.  YMMV.  Pitching rate is a very difficult, inexact way to control ester production.  IMO, you're better off doing that with temp.
Title: Re: Yeast cake rehydration
Post by: gordonstrong on April 06, 2011, 06:09:47 PM
So, given this information would overpitching be OK for styles where you dont want an estery, fruity taste?   I make a lot of IPAs with higher amounts (than recommended according to the Mr. Malty calculator) of washed California Ale yeast slurry - and I dont want a high amount of esters in flavor.

Based on my own experience, you'd want to pitch less yeast, not more, for that to happen.  YMMV.  Pitching rate is a very difficult, inexact way to control ester production.  IMO, you're better off doing that with temp.

In general, +1.  Caveat: except for weizenbiers.  Higher temps = skanky results, not more esters.
Title: Re: Yeast cake rehydration
Post by: denny on April 06, 2011, 06:31:56 PM
Caveat: except for weizenbiers.  Higher temps = skanky results, not more esters.

Not a style I have much experience with!   ;D
Title: Re: Yeast cake rehydration
Post by: bluesman on April 06, 2011, 06:42:30 PM
In general my experience has shown high ester levels are a product of the yeast strain, fermentation temperature and high gravity worts. I haven't experimented with yeast pitching rates and its effect on the production of esters, but it makes sense that if there is more yeast there's potentially more budding and therefore more ester production.

By George I think we've got it!  ;D

Title: Re: Yeast cake rehydration
Post by: tschmidlin on April 06, 2011, 07:12:16 PM
I agree it is better to control esters through fermentation temperature.  I would also make sure you have sufficient yeast nutrients, O2, and healthy yeast.
Title: Re: Yeast cake rehydration
Post by: pyrite on April 07, 2011, 03:03:42 AM
I would also make sure you have sufficient yeast nutrients, O2, and healthy yeast.

How do big breweries reuse yeast cakes?  I assume they're into saving money, and so they reuse their yeast. 
So do they re-energize their yeast, and if so how?
Title: Re: Yeast cake rehydration
Post by: tschmidlin on April 07, 2011, 03:28:00 AM
I would also make sure you have sufficient yeast nutrients, O2, and healthy yeast.

How do big breweries reuse yeast cakes?  I assume they're into saving money, and so they reuse their yeast. 
So do they re-energize their yeast, and if so how?
I don't know for certain.  I am quite sure they have their own labs and yeast management facilities, and make sure that they pitch plenty of healthy yeast.  But I don't know the details of their processes.