Author Topic: Yeast Strain Development with Subsequent Generations  (Read 5197 times)

Offline skyler

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Yeast Strain Development with Subsequent Generations
« on: December 02, 2011, 11:19:20 PM »
So I recently took a smack pack of Pacman through more generations than I typically do - I believe the last beer I made with the Pacman was made with the 5th or sixth generation. And I think I noticed something odd happen - Pacman has gone English. With each subsequent generation, my beers have attenuated less and less (70% on the last beer), and the yeast has become more and more flocculant. The ester profile is still pretty gentle and the yeast has continuously fermented very cool, but the attenuation shift has been pretty surprising. Has anyone seen something like this happen in re-pitching for continuous generations?

Anyway, I have had a pack of 1450 since June that I've been meaning to play with, so I think I will retire this 7th-generation pacman.

Offline rbclay

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Re: Yeast Strain Development with Subsequent Generations
« Reply #1 on: December 02, 2011, 11:31:45 PM »
i'm curious how you harvest your yeast from one gen to the next.

I often pitch on yeast cakes. I know I am overpitching. i've only done it for max of 3 batches. i would think if i kept pitching directly on cakes for more than 3 gens, each one would become less attenuative because I would be pitching an enormous amount of dead and tired yeast. just wondering what you do.
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Offline bo

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Re: Yeast Strain Development with Subsequent Generations
« Reply #2 on: December 03, 2011, 06:07:02 AM »
If you like the results of the Pacman yeast after 5-6 generations, I'd bank that strain for future use. It's not uncommon for breweries to do that same thing until they get what they want.

Offline tschmidlin

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Re: Yeast Strain Development with Subsequent Generations
« Reply #3 on: December 03, 2011, 11:23:30 AM »
The yeast is probably becoming more flocculent because of your harvesting methods.  If you rack to secondary quickly and take what has settled from the primary you are essentially selecting and enriching for the first yeast to settle out every time.  High flocculation could lead to under attenuation, so that may be what you are seeing.
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Offline The Professor

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Re: Yeast Strain Development with Subsequent Generations
« Reply #4 on: December 03, 2011, 11:31:38 AM »
If you like the results of the Pacman yeast after 5-6 generations, I'd bank that strain for future use. It's not uncommon for breweries to do that same thing until they get what they want.

That's pretty much how I arrived at my "house" yeast more than 20  years ago.  I took the yeast I started with (an unknown mix to begin with) through something like 15 generations (and actually, probably more than that) and liked what I was getting,  so I banked it. 
To this day I don't know what it actually is or what I isolated when I saved it  (and it really doesn't matter), but it still works great and I use it for the majority of the beer I make.  Occasionally I'll switch off to some London Ale or Old Newark for a few batches, but my old standby is still my favorite. 
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Offline ynotbrusum

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Re: Yeast Strain Development with Subsequent Generations
« Reply #5 on: December 03, 2011, 03:42:09 PM »
The yeast is probably becoming more flocculent because of your harvesting methods.  If you rack to secondary quickly and take what has settled from the primary you are essentially selecting and enriching for the first yeast to settle out every time.  High flocculation could lead to under attenuation, so that may be what you are seeing.

+1, and I think that would explain it best, but it is possible that the yeast has also changed through mutation or bud scarring.  You don't mention if you have supplemented the yeast with nutrient, which can affect the dynamics, as well, since less robust yeast will typically poop out earlier.

cheers.
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Offline skyler

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Re: Yeast Strain Development with Subsequent Generations
« Reply #6 on: December 03, 2011, 06:42:29 PM »
I typically pitch all of a 5 gal batch's yeast slurry into a 12 gal batch, then I will store subsequent slurries in mason jars and use within one week or make starters with a small amount of the mason-jar slurry if I take longer than that to use the stuff.

I never transfer a beer from primary before the 2-week mark. Usually I give a beer a minimum of one full week at ambient temperature after fermentation has finished, and then another 3 days to a week at 34F before I rack into a keg or (occasionally) a secondary fermenter.

Offline skyler

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Re: Yeast Strain Development with Subsequent Generations
« Reply #7 on: December 04, 2011, 11:28:47 AM »
And I always use wyeast nutrient.

Offline musseldoc

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Re: Yeast Strain Development with Subsequent Generations
« Reply #8 on: December 07, 2011, 07:21:50 AM »
Your method seems well thought out and you shouldn't be selecting for flocculation. 

I have heard on one of the podcasts out there that yeast companies don't always use pure strains with their homebrewer products.  They want to put out a product that has the character they claim, but is also 'foolproof' for the average Joe homebrewer.  They accomplish this by using a blend of a hearty strain, like 1056 or 001, with the desire specialty strain, like the pacman.  This way, no matter how finicky the specialty strain, the beer will work at nearly any temperature, will generally attenuate fully and will represent the company as producing reliable products.  However, this may just be conjecture, as I have not confirmed this with any company myself. 

What you may be observing is the elimination of the secondary strain.  The pacman strain may be outcompeting the 1056 and the ferment is taking on the characteristics of just the pacman strain.  If initially the pac contained 90% pacman and 10% 1056, then the pacman could easily out-compete the 1056 in 4-6 generations. 
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Offline tschmidlin

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Re: Yeast Strain Development with Subsequent Generations
« Reply #9 on: December 07, 2011, 10:49:57 AM »
Your method seems well thought out and you shouldn't be selecting for flocculation. 

I have heard on one of the podcasts out there that yeast companies don't always use pure strains with their homebrewer products.  They want to put out a product that has the character they claim, but is also 'foolproof' for the average Joe homebrewer.  They accomplish this by using a blend of a hearty strain, like 1056 or 001, with the desire specialty strain, like the pacman.  This way, no matter how finicky the specialty strain, the beer will work at nearly any temperature, will generally attenuate fully and will represent the company as producing reliable products.  However, this may just be conjecture, as I have not confirmed this with any company myself. 

What you may be observing is the elimination of the secondary strain.  The pacman strain may be outcompeting the 1056 and the ferment is taking on the characteristics of just the pacman strain.  If initially the pac contained 90% pacman and 10% 1056, then the pacman could easily out-compete the 1056 in 4-6 generations. 
I have never heard of a company selling a blend as a pure strain, and I doubt that it happens.  Also, the only way the pacman would out compete 1056 in a few generations in your scenario is if pacman doubles significantly faster.  This is really unlikely, especially when the alleged origin of pacman is 1056.

Skyler, since you're not obviously selecting for flocculation (you may still be in a way that is not obvious) then I would be worried about the malt and/or yeast health.  There are malt constituents that promote early flocculation, so it may improve if you switch malts.  Poor yeast health will make it flocc early, especially a lack of zinc.  What kind of nutrient are you using?
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Offline skyler

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Re: Yeast Strain Development with Subsequent Generations
« Reply #10 on: December 08, 2011, 12:51:13 AM »
I use Wyeast-branded beer yeast nutrient. I might add that Pacman in particular has always been very flocculant for me after the first generation. In fact, the only time I have had a real clarity issue when brwing with Pacman was with a beer brewed with 30% rye malt. The base malts I use are mostly Great Western (2-row and pale ale) and Gambrinus (Pils, Pale, Munich, and Vienna).

Offline tschmidlin

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Re: Yeast Strain Development with Subsequent Generations
« Reply #11 on: December 08, 2011, 01:43:07 AM »
I use Wyeast-branded beer yeast nutrient. I might add that Pacman in particular has always been very flocculant for me after the first generation. In fact, the only time I have had a real clarity issue when brwing with Pacman was with a beer brewed with 30% rye malt. The base malts I use are mostly Great Western (2-row and pale ale) and Gambrinus (Pils, Pale, Munich, and Vienna).
Crap.  I was hoping this would be easier to diagnose. :-\

Are you using any new bags of malt?  I don't know that any brand is necessarily worse than any other, but it could be bad batch. 

What kind of beers have wound up under attenuated, do they have anything in common?  Has every beer had early floccing after a certain number of generations, or is it just some of them?  If we looked at all of the data maybe we could figure it out.  Maybe not though.

Pacman is a good floccer, but I don't have as much experience with it as you do.
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Offline skyler

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Re: Yeast Strain Development with Subsequent Generations
« Reply #12 on: December 09, 2011, 10:06:29 AM »
The beers with lower attenuation were a brown rye ale, a porter, and a brown ale with D-180. Every beer tasted/tastes good - they just seem as though I made them with 1318 and fermented really cool.

Offline tschmidlin

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Re: Yeast Strain Development with Subsequent Generations
« Reply #13 on: December 09, 2011, 10:31:43 AM »
Those are all darker beers - how much do you control the pH of your mash?  If it gets too low from the darker malts then you could be getting poor conversion which could be causing poor attenuation, so it is not the yeast that is at fault but the mash.

Do you use the same base malt for each?  Have you made any batches following a lower attenuation batch that were lighter in color and attenuated better?  Or a batch from the same yeast cake, where part went in to one batch and part went in to another, and one had low attenuation and the other didn't?
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Offline skyler

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Re: Yeast Strain Development with Subsequent Generations
« Reply #14 on: December 09, 2011, 02:07:18 PM »
Those three beers were brewed with 3 different base malts - one of them made with Great Western Pale Ale Malt, one with Great Western 2-row, and one with Gambrinus Pale Malt. I think it is safe to say that the malt hasn't led to any problem. Also, the mash temps were fairly different. The Mash temps were 150, 152, and 154.

I control the pH by building my water with Bru'n Water. I filter my very soft Berkeley tap water and add salts. I add a small portion of Epsom Salt to every mash because my water is very soft and has nearly no Magnesium. Depending on the style, I also add Calcium Chloride and Gypsum. The salts I use to raise pH are Chalk and Baking Soda. I typically use as little of those salts as necessary to achieve a pH of 5.3 - though in one instance (the Rye Brown Ale), I made a calculation error and the pH was 5.5 - or at least that's what I back-calculated it to be... But I have to trust in Bru'n Water's calculations because I don't measure my pH. The reason being, I don't use pH strips since they are not accurate enough (or so I have read), and I haven't yet purchased a more advanced pH meter.