[johnf]

While it might be true that sugars (or their absence) act as a signal for flocculation to occur, but it doesn't explain the pronounced differences between strains.  I think that is something that is bred into the strain via selection.

Seems like temperature would also be a factor, although I suppose the temp simply follows the sugar levels inasmuch as rapid fermentation (and the heat it generates) slows at the time the most abundant and most fermentable sugars become depleted.

I don't believe there is a pronounced difference among the strains, especially if you don't exceed their alcohol tolerance.

English ale yeast will produce a higher AA in a tripel wort than trappist yeast will in a mild wort.

[Kaiser]

Flocculation is just one aspect and WLP002, for example, is a very stubborn flocculator where even the presence of maltose doesn't easily revert flocculation.

I learned this the hard way. Normally when I have flocculant yeasts and want to count them I need to unflocculate them. This is best done in brewing wort and I would put the yeast with a liter or two of fresh wort on the stir plate. After a while all clumps are broken up and the yeast is evenly distributed which allows a sample for counting to be drawn.

Not so with WLP002. Even after an hour on the stir plate it won’t de flocculate. Maybe the wort was too cold since the yeast did deflocculate while being grown. But I ended up pitching it w/o being able to count the cells. No real loss here since I was still able to weigh the sediment but I was really surprised how strong of a flocculator WLP002 is.

Some yeast also flocculate in the presence of alcohol or the absence of glucose.  The motivation for the yeast is simple: low nutrients and/or toxic environment -> let’s clump together to protect at least some of us.

The ideal brewer’s yeast, at least for many of the big guys, ferments all fermentable sugars and then flocculates to provide for easy separation between yeast and beer.  If they flocculate too early or too late it becomes a problem for the brewery. I’d imagine that flocculating too early is more of a problem than flocculating too late. And based on what I have read yeasts are more likely to lose their flocculation ability over time than being able to gain this ability. I think they say that the yeast is becoming dusty and it is a sign of genetic drift.

Kai

[denny]

This might be a good time to mention that Chris White and Jamil Zainisheff are this month's guests in "Ask the Experts".  You guys might want to try directing some of these questions to them for their take on it.

[tomsawyer]

I don't believe there is a pronounced difference among the strains, especially if you don't exceed their alcohol tolerance.

English ale yeast will produce a higher AA in a tripel wort than trappist yeast will in a mild wort.

I am not sure I understand.  You are saying there is not a big difference in flocculation characteristics between yesat strains?  Or that there isn't a difference between them in terms of their reaction to running out of sugar?  Your example seems to indicate that there either isn't a strict relationship between flocculation and attenuation, or that there isn't a difference in flocculation and attenuation is in fact closely coupled to floc.

I do think a yeast cake is still metabolically active for some time, so maybe flocculation doesn't completely determine attenuation.

[tomsawyer]

This might be a good time to mention that Chris White and Jamil Zainisheff are this month's guests in "Ask the Experts".  You guys might want to try directing some of these questions to them for their take on it.

I already submitted two Denny, I don't want to pester them to death.

[denny]

This might be a good time to mention that Chris White and Jamil Zainisheff are this month's guests in "Ask the Experts".  You guys might want to try directing some of these questions to them for their take on it.

I already submitted two Denny, I don't want to pester them to death.

Pester away, man.  If they don't want to answer them, they won't! 

[Kaiser]

I do think a yeast cake is still metabolically active for some time, so maybe flocculation doesn't completely determine attenuation.

Yes, that is correct. Flocculation just reduces the amount of yeast cells that are actively metabolizing the wort.

The rate at which the yeast can metabolize the resulting maltotriose also matters. I think that for a regular gravity beer, where yeast death is not as fast, yeast will slowly keep fermenting the beer until the attenuation limit is reached even if the yeast is deemed a low attenuator. But this process may be so slow that it appears as if the fermentation is complete.

Maybe Chris and Jamil should join in on the discussion


Kai

[kerneldustjacket]

For my current Doppelbock I want to try Kraeusening with non flocculating lager yeast (WY2042 – Danish Lager) after a primary fermentation with WLP833. I want to see if that can speed up the maturation phase.

Kai, this is another example of an "advanced application" of yeast and yeast management. Someday it would be nice to have a manual or write-up of such advanced techniques available.
The process of "keeving" that is used to make French cider is another example of altering fermentation conditions to "exploit" yeast biology -- they deliberatly lower vital yeast nutrients to encourage a long, slow fermentation that results in higher residual sewwtness.

Let me ask this (to anyone who may know, and maybe I should submit it to "Ask the Experts"): I have pitched two yeasts to start fermentation in a beer -- one very flocculent yeast (S-04) and one that attenuates well (US-05). Will this beer ferment to the extent of the US-05, and then clump up and flocculate as well as S-04? Seems to...but I just might be biased on that opinion.
Multistrain fermentations are not new, in fact they used to be the norm until yeast strains were isolated. But to what extent can we regress and use two or more strains to acheive particular results?

[kerneldustjacket]

This might be a good time to mention that Chris White and Jamil Zainisheff are this month's guests in "Ask the Experts".  You guys might want to try directing some of these questions to them for their take on it.

I already submitted two Denny, I don't want to pester them to death.

Pester away, man.  If they don't want to answer them, they won't! 

To a man with 3600+ posts, a few extra questions is far short of pestering!!!!

[denny]

Maybe Chris and Jamil should join in on the discussion

That would be great, but I don't think we can realistically expect it to happen.  I'm grateful that they can make the time to answer questions via email.

[tomsawyer]

Let me ask this (to anyone who may know, and maybe I should submit it to "Ask the Experts"): I have pitched two yeasts to start fermentation in a beer -- one very flocculent yeast (S-04) and one that attenuates well (US-05). Will this beer ferment to the extent of the US-05, and then clump up and flocculate as well as S-04? Seems to...but I just might be biased on that opinion.
Multistrain fermentations are not new, in fact they used to be the norm until yeast strains were isolated. But to what extent can we regress and use two or more strains to acheive particular results?

If the whole premise of attenuation is based on the ability for a good portion of the yeast to stay suspended, then you'd think a good-floccing yeast like S04 would drag down its better-attenuating counterpart when it went and give you the attenuation of S04, just maybe with a lower ester level.

It'd be a good question to ask Chris White, they are selling more and more yeast blends these days and its not strictly a Sacch and a Brett combo.

[Kaiser]

Strictly based on my understanding of flocculation the non flocculent yeast would not be able to attach itsef to the flocculent yeast since both cells need to have the flocculation receptors. So I’d expect the non flocculent yeast to remain in suspension.

But keep in mind that flocculation is only one reason why yeast settles, the other is that the beer movement stops when the production of CO2 stops. Even non-flocculent yeast settles fairly quickly in our barely 2 ft high fermenters.

This would be the first time that I kraeusen with a non flocculent yeast. I have read that poorly flocculent yeast is preferred for long and cold lagering/maturation whereas well flocculating yeast is better for the warmer and shorter maturation that is commonly used for lagers these days.

Kai

[kerneldustjacket]

Strictly based on my understanding of flocculation the non flocculent yeast would not be able to attach itsef to the flocculent yeast since both cells need to have the flocculation receptors. So I’d expect the non flocculent yeast to remain in suspension.
But keep in mind that flocculation is only one reason why yeast settles, the other is that the beer movement stops when the production of CO2 stops. Even non-flocculent yeast settles fairly quickly in our barely 2 ft high fermenters.

{my emphasis added jw}

All this is what I would expect as well. The key effect I was looking for is the dense, stable yeast cake that forms on the bottom of the fermenter with S-04. Maybe S-04 will form clumps that include the US-05?

I have an APA that is approaching the two-week mark this Friday, and it has both S-04 and US-05 pitched right after cooling. I'll start taking pictures of it daily, just to see how flocculation progresses,

This would be the first time that I kraeusen with a non flocculent yeast. I have read that poorly flocculent yeast is preferred for long and cold lagering/maturation whereas well flocculating yeast is better for the warmer and shorter maturation that is commonly used for lagers these days.

Kai

Kai, this seems like a very sound idea -- the "kraeusen" yeast would become the dominant yeast and it's Characteristics would be the ones that matter from then on. It's like employing yeasts as "specialists."

[UnequivocalBrewing]

Just reading through this thread.  I know the consensus is that a lower mash PH with a lower attenuating yeast should be sweeter than a higher mash PH with a higher attenuating yeast. 

The question I have is using the same lower attenuating yeast (say Wyeast London III 1318), what is going to create a sweeter finish...a higher mash temp or lower mash temp?  Conventional wisdom is that the higher mash temp would create the sweeter finish.  However, I'm wondering if the higher mash PH creates more body but actually a drier perception?

[dmtaylor]

Just reading through this thread.  I know the consensus is that a lower mash PH with a lower attenuating yeast should be sweeter than a higher mash PH with a higher attenuating yeast. 

The question I have is using the same lower attenuating yeast (say Wyeast London III 1318), what is going to create a sweeter finish...a higher mash temp or lower mash temp?  Conventional wisdom is that the higher mash temp would create the sweeter finish.  However, I'm wondering if the higher mash PH creates more body but actually a drier perception?

(*Hijack alert*)

I guess I've arrived to this thread late!

I, for one, will answer your question by not answering your question.

I think we all tend to forget that temperature is not the only variable.  If you vary also the mash TIME (e.g., not every beer has to be mashed for exactly 60 minutes), then you may get the result you wish by mashing for, say, 30 minutes instead of 60 or 90 minutes or longer.

If you want "sweeter" or "more body", I do think mashing for just 30 minutes, or maybe even just 20 or 25 minutes, might get you the result you seek.

On the other end of the spectrum, it's been proven by many that if you want a "drier" beer, mashing for 90 minutes, or 120 minutes, or (gasp!) overnight will get you a very dry beer indeed.  All using the same old yeast as you would normally use after mashing for just 60 minutes.

I say these terms like "sweeter" in quotations because it does, in fact, mean different things to different people, regardless of the previous technical discussions.  We are all human; however, we cannot all be scientists who give a crap about the "proper" terminology.

Cheers and hope this helps.