Author Topic: Increasing Apparent Attenuation  (Read 3702 times)

Offline HoosierBrew

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Re: Increasing Apparent Attenuation
« Reply #15 on: October 14, 2015, 07:43:35 am »
I agree with Narvin's post - some strains like 1762 can have surprisingly low attenuation (for a Belgian) on the first pitch, but perform substantially better on the second pitch. I usually make a Belgian pale on the first pitch of 1762 and then a dubbel or quad with the slurry.
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Offline hopfenundmalz

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Re: Increasing Apparent Attenuation
« Reply #16 on: October 14, 2015, 08:02:42 am »
Pull up the Greg Doss presentation from 2012. Nice graph of attenuation vs strain on page 18. The Belgian Trappist strains are low 1214 Chimay, to high 1762 Rochefort. None are 88%.

Yet people are getting 88%. That's really the question. How to get those high values.
Because simple sugars are 100% fermentable.

Do a weighted avg of the attenuation on 80% malt and 20% sugar.
« Last Edit: October 14, 2015, 08:04:35 am by hopfenundmalz »
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Re: Increasing Apparent Attenuation
« Reply #17 on: October 14, 2015, 08:29:53 am »
Yet people are getting 88%. That's really the question. How to get those high values.

Brewers control attenuation via a combination of yeast selection and wort composition.  As long as the yeast strain can handle the ethanol stress, a yeast culture will chew through all of the sugars that it can reduce to hexoses (monosaccharides).  The trick is to minimize the amount of dextrin and trisaccharides in the wort.  Yeast cells consume sugars more complex than glucose by breaking something known as glycosidic bonds. They perform this feat by producing enzymes.  Enzymes are reaction catalysts.  A reaction catalyst is a compound that speeds a reaction.

Let's look at how a yeast cell consumes a molecule of the trisaccharide maltotriose.  It starts by splitting it into one maltose molecule and one glucose (monosaccharide) molecule.  It then splits the maltose molecule into two glucose molecule.  The process of splitting more complex sugars into simpler sugars is called hydrolysis.  The roots in hydrolysis are "hydro" and "lysis."  Hydro is from the Greek word "hydros," which means water.  Lysis is Latin for break apart.  Hence, together they mean break apart using water, and that's exactly what happens.  The enzymes merely speed the rate at which the reaction occurs.

The chemical formula for maltotriose is C18H32O16.

C18H32O16 + H2O  → C12H22O11 + C6H12O6


The reaction shown above reads one molecule of maltotriose combined with one molecule of water yields one molecule of maltose and one molecule of glucose.  The yeast cell can use the molecule of glucose directly.

The cell then goes about breaking the bond that holds the two glucose molecules in maltose together.

C12H22O11 + H2O  →  C6H12O6 + C6H12O6

The reaction shown above reads one molecule of maltose combined with one molecule of water yields two molecules of glucose.

If we move up in the process, what do you think mashing is from a biochemical point of view?  Well, it is the hydrolysis of starch.  The hot liquor in a mash provides the water molecules.  The enzymes limit dextrinase, alpha amylase, and beta amylase are the reaction catalysts in the hydrolysis of starch.  Each of these enzymes breaks a different glycosidic bond. We control the effectiveness of each enzyme by controlling the mash temperature.   A lower mash temperature yields a more fermentable wort because it produces a wort with a higher monosaccharide and disaccharide to trisaccharide and dextrin ratio.  It does so by striking a balance between the different enzymes.

Sucrose is a disaccharide that has the same chemical formula as maltose.  However it is composed of one molecule of glucose and one molecule of fructose. We have all more likely heard of something known as invert sugar.  Invert sugar is an integral component in many British beers.  Invert sugar is sucrose with the glycosidic bond that holds the glucose and the fructose molecules together broken, which is why it is more readily fermented than straight table sugar.   Belgian candi sugar is invert sugar.
« Last Edit: October 14, 2015, 08:46:45 am by S. cerevisiae »

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Re: Increasing Apparent Attenuation
« Reply #18 on: October 14, 2015, 08:43:37 am »
All brewers yeast have the potential to attenuate about the same. The biggest differences you tend to see are with highly flocculent strains that drop out before the fermentable sugar has been totally consumed.

Actually, that assertion is not true.  Flocculation and the ability to consume sugar are separate biological functions. Yeast strains only ferment sugars for which their genetic encoding provides the blueprints necessary to encode the enzyme necessary to break a glycosidic bound.  Flocculation is independent of this encoding.  It based on a set of genes that belong to a family known as FLO.  Enzymes are proteins and proteins are assembled via a process known as transcription. Transcription is controlled by DNA, which is why different yeast strains attenuate to different levels.  Most yeast strains can transcribe the enzymes necessary to break the glycosidic bonds that hold dissaccharides together.  The main disaccharide that separates S. cerevisiae (ale yeast) and S. pastorianus (lager yeast) is called melibiose.  S. pastorianus can break the glycosidic bond that binds the glactose molecule and a glucose molecules together.   Lallemand Windsor is an example of a trisaccharide challenged yeast strain.  It cannot break the bond that hold maltotriose together.



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Re: Increasing Apparent Attenuation
« Reply #19 on: October 14, 2015, 09:01:59 am »
Pull up the Greg Doss presentation from 2012. Nice graph of attenuation vs strain on page 18. The Belgian Trappist strains are low 1214 Chimay, to high 1762 Rochefort. None are 88%.

Right. Sorry. This goes right along with Narvin's comments on yeast attenuation specs being for all malt worts. Understood.

The word is you are searching for is "selected." 

Thank you Mark. That's is the word I was driving at.


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Re: Increasing Apparent Attenuation
« Reply #20 on: October 14, 2015, 09:10:01 am »
This may ultimately be it on the homebrew level unless through selection and repitching you can "cultivate" high attenuation. I may be showing my ignorance here.

That's exactly what happens, and you can see it with a fresh pitch of nearly any strain. Attenuation tends to creep upward for the first few pitches before stabilizing.

This is totally independent of the mutations you and Mark were talking about, by the way. It's just a question of the yeast selectively expressing the genes (and therefore metabolic pathways) that are already in their toolkit.
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Re: Increasing Apparent Attenuation
« Reply #21 on: October 14, 2015, 09:36:50 am »
I am aware that different yeasts have the ability to break down different sugars. In addition to being able to metabolize melibiose, most lager yeasts can also metabolize raffinose, another sugar which most ale yeasts can't. Some brett strains can even metabolize some dextrins which neither ale nor lager yeasts can in general.

I included melibiose because it is a disaccharide.  Raffinose is a trisaccharide, and the trisaccharides are were the differences between yeast strains really start to appear.  If we want split hairs, Saccharomyces diastaticus can chew through dextrins as well, which is why the strains in this species along with the strains in the Brettanomyces genus are considered to be spoilage strains in most breweries.

Flocculation is still not an accurate indicator of attenuation.  Flocculation is a measure of aggregation, not attenuation.   The onset of aggregation is controlled by genetics.  I just used a strain (NCYC 1333) that is unbelievably flocculent, but it achieved an AA of 85%.  The cells in NCYC 1333 stick together like velcro.   Windsor is a low attenuator, but it is non-flocculent.

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Re: Increasing Apparent Attenuation
« Reply #22 on: October 14, 2015, 10:09:52 am »
How do you go about increasing the attenuation of a particular yeast?

The reason I ask this is because in reading and re-reading BLAM, I see many of the Trappist examples, notably the Chimay and Westmalle beers, with lower OG than one would expect but with ABV spot on. They are getting there with high levels of attenuation.

I of course understand that the strains available to is are not the yeast used in the Trappist breweries, but am wondering what it might take to reach those levels of AA with commercially available yeast.


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Mash low and long.  Use sugar.  And yes, Trappist strains ARE available to us.  WY1762 is Rochefort.  Wy3787 is Wetmalle.  WY1214 is Chimay.
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Offline denny

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Re: Increasing Apparent Attenuation
« Reply #23 on: October 14, 2015, 10:14:14 am »
Thanks fellas. Again, great round of information.

I was thinking more (I probably could have made it clearer) from the standpoint of modifying the yeast through repitching, etc.

Obviously Chimay, Westmalle, Rochefort and the like have selectively "bred" (for lack of a better word) their yeast over the years to obtain the way above average levels of attenuation they get. I know, for instance, that the CSI recipe for Grand Reserve quotes 1.077 OG/1.009 FG, which by my calcs is ~88% AA!

Unless of course I'm just confused. I realize I could be just neglecting the fact that people are really waiting it out for those few points of attenuation, but there has to be a limit on the commercially available yeast. Are you guys getting >85% with your Belgian brews?

...not allowing temp to drop until its done done.

This may ultimately be it on the homebrew level unless through selection and repitching you can "cultivate" high attenuation. I may be showing my ignorance here.


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I guess I'm must be missing something.  I have no trouble going from 1.077 to 1.009 with something like WY3787.  I don't feel like I take any extraordinary procedures to do that.  As o waiting it out, you must have missed that part in BLAM!  ;)  Stan says that it often takes as long to get the last 10% of attenuation as it does for the first 90%.  As to cultivating higher attenuation, I'd be really surprised if the yeast would mutate that quickly.

So, how many people out there can't achieve that kind of attenuation?  I'm baffled....
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Offline Iliff Ave

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Re: Increasing Apparent Attenuation
« Reply #24 on: October 14, 2015, 10:15:20 am »
Out of curiosity, how low is low and how long is long?

I am assuming in the ball park of 148F for 90 minutes.
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Re: Increasing Apparent Attenuation
« Reply #25 on: October 14, 2015, 10:17:26 am »
Out of curiosity, how low is low and how long is long?

I am assuming in the ball park of 148F for 90 minutes.

Yep, that's my standard.  I've gone as low as 145 for 2 hours, but seldom bother with that.  The last batch of my Westcoastmalle tripel (based on westmalle with 3787) reached 92% AA.
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Re: Increasing Apparent Attenuation
« Reply #26 on: October 14, 2015, 10:18:54 am »
I guess I'm must be missing something.  I have no trouble going from 1.077 to 1.009 with something like WY3787.  I don't feel like I take any extraordinary procedures to do that.  As o waiting it out, you must have missed that part in BLAM!  ;)  Stan says that it often takes as long to get the last 10% of attenuation as it does for the first 90%.  As to cultivating higher attenuation, I'd be really surprised if the yeast would mutate that quickly.

So, how many people out there can't achieve that kind of attenuation?  I'm baffled....

I realized that I was missing the concept that yeast specs are assuming all malt wort. I am getting in the low 80s with 3787 currently.

As for the strains being available, I was simply referring to not having the actual strains as used in the breweries, and in light of the comments I've received about sugars not being factored into manufacturer specs for attenuation, I see now that it is a moot point.

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Re: Increasing Apparent Attenuation
« Reply #27 on: October 14, 2015, 10:20:33 am »
I guess I'm must be missing something.  I have no trouble going from 1.077 to 1.009 with something like WY3787.  I don't feel like I take any extraordinary procedures to do that.  As o waiting it out, you must have missed that part in BLAM!  ;)  Stan says that it often takes as long to get the last 10% of attenuation as it does for the first 90%.  As to cultivating higher attenuation, I'd be really surprised if the yeast would mutate that quickly.

So, how many people out there can't achieve that kind of attenuation?  I'm baffled....

I realized that I was missing the concept that yeast specs are assuming all malt wort. I am getting in the low 80s with 3787 currently.

As for the strains being available, I was simply referring to not having the actual strains as used in the breweries, and in light of the comments I've received about sugars not being factored into manufacturer specs for attenuation, I see now that it is a moot point.

AFAIK, they ARE the actual strains used in the breweries.

Don't get hung up on attenuation ratings.  They're for comparing one strain to another and may have little to do with the attenuation you'll actually get.  Using the same strain, I can get anywhere from 65% to 85% depending on wort composition.
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Re: Increasing Apparent Attenuation
« Reply #28 on: October 14, 2015, 10:28:43 am »
You're correct, and I misspoke when I implied that all highly flocculant strains attenuate less, because it's not what I meant. Yeast have genetic triggers which cause them to flocculate. One common trigger is a low concentration of simple sugars in the wort. This threshold is different for different yeast. Many highly flocculant strains used by homebrewers have a relatively high threshold, causing them to flocculate while there are still significant amounts of fermentable sugar in solution. This is the spirit of what I was getting at. This does not mean that there aren't yeast out there who will attenuate the wort completely and then flocculate hard.

It is not just the simple sugars glucose and mannose that control flocculation when it comes to brewing strains.  Flocculation is also influenced by the disaccharides maltose and sucrose.  The reason being is that most brewing strains exhibit NewFlo flocculation.  The are a few Flo1 brewing strains, but that they are far and few between.