Author Topic: Yeast cake rehydration  (Read 2627 times)

Offline tygo

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Re: Yeast cake rehydration
« Reply #15 on: April 05, 2011, 07:43:59 PM »
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. 
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Offline denny

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Re: Yeast cake rehydration
« Reply #16 on: April 06, 2011, 08:01:59 AM »
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
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Offline tschmidlin

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Re: Yeast cake rehydration
« Reply #17 on: April 06, 2011, 10:11:56 AM »
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
Tom Schmidlin

Offline denny

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Re: Yeast cake rehydration
« Reply #18 on: April 06, 2011, 10:29:54 AM »
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.
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Offline tschmidlin

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Re: Yeast cake rehydration
« Reply #19 on: April 06, 2011, 10:56:20 AM »
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 :) ).
Tom Schmidlin

Offline benamcg

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Re: Yeast cake rehydration
« Reply #20 on: April 06, 2011, 11:02:21 AM »
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.

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Re: Yeast cake rehydration
« Reply #21 on: April 06, 2011, 11:06:16 AM »
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.
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Offline gordonstrong

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Re: Yeast cake rehydration
« Reply #22 on: April 06, 2011, 11:09:47 AM »
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.
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Offline denny

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Re: Yeast cake rehydration
« Reply #23 on: April 06, 2011, 11:31:56 AM »
Caveat: except for weizenbiers.  Higher temps = skanky results, not more esters.

Not a style I have much experience with!   ;D
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Offline bluesman

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Re: Yeast cake rehydration
« Reply #24 on: April 06, 2011, 11:42:30 AM »
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.

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Offline tschmidlin

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Re: Yeast cake rehydration
« Reply #25 on: April 06, 2011, 12:12:16 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.
Tom Schmidlin

Offline pyrite

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Re: Yeast cake rehydration
« Reply #26 on: April 06, 2011, 08:03:42 PM »
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?
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Offline tschmidlin

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Re: Yeast cake rehydration
« Reply #27 on: April 06, 2011, 08:28:00 PM »
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.
Tom Schmidlin