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.
Me? Low long mash, subbing at least 10% of the OG from grain with sugar, oxygenation, slow steady ramping fermentation temp as krausen falls, not allowing temp to drop until its done done.
All great info but a bit like basic Belgian brewing 101. Those are all things aimed at achieving the maximum attenuation from a given yeast’s manufacturers specs.
I’m talking getting 85+ %AA. I’ve gotten in the high 70s, low 80s with WY 3787 using all the above referenced methods.
What more advance techniques can get me higher? Obviously repitching from a strong fermentation is a must but are there ways to selectively increase the ability for a yeast to attenuate?
If you really want to jack 'er up, then pitch a pack of Belle Saison yeast after the first 2 days of primary fermentation with your other yeast. The Belle Saison will eat up everything that the first yeast won’t. I’ve never done this but it should work. Final gravity will be about 1.002 – no exaggeration.
You can give it just about any wort you can make and ferment somewhere between 64F and 84F and you will get 90%+ attenuation. I recently brewed a beer with this yeast that had a 1.042 starting gravity and 5.5% abv.
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?
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.
I wouldn’t focus on strain mutations. They were using their yeasts for years by the time the yeast banks got them.
The first generation of yeast grown up from laboratory media just isn’t going to perform as well. Many of the Trapppists repitch from smaller beers into bigger beers. Westmalle top crops very active yeast. I’ve experienced this most with the Rochefort strain, where anything above 1.070 for a first generation yeast is going to be an under attenuated disappointment by Trappist standards.
With 15-20% sugar, there’s nothing that makes 88% attenuation unattainable. The yeast company guidelines are for an all-malt wort. If you’re having trouble with first generation yeast, you can use incremental sugar feedings.
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%.
The word is you are searching for is “selected.” These strains have been selected over the years via selective pressure. In a nutshell, one can think of selective pressure as the result of serial repitching in a specific environment. It is basically Darwinism applied to yeast. The fittest cells for the environment live, and those that cannot hack it die off.
All yeast strains drift genetically over time, which is why most breweries that have one or more house strains keep seed cultures. A seed culture can be thought of as a cell that was selected for its performance at a specific point in time. That cell’s off-spring become the house strain. Seed cultures are usually keep in cryostorage at at least -80C. If a brewing company has deep pockets or uses an organization such as the NCYC in the UK or the ATCC in the United States as a culture repository, it will choose to store its seed cultures under liquid nitrogen at 77 Kelvin (-196C/-321F). Cultures can be maintained indefinitely at 77 Kelvin.
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.
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.
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.