Yeast Attenuation - Alcohol Percentage

[jezter6]

Say you've got a yeast, which you want to use for flavor, but has a rather low attenuation, but you really want a little bit more alcohol out of that yeast, and a little less malty in the end.

Aside from buying the 1% booster, what can you do to increase the attenuation of a low attenuation yeast in a bigger brew?

 

[Blender]

I don't really know if there is way to increase yeast attenuation by adding an ingredient other than a fermentable. I would think about all you could do is try to ensure that you get the most out of type that you are using. In other words give the yeast all it needs to perform at its peak, make sure there is plenty (make a starter) of viable yeast when you pitch, and make your recipe based on it's attenuation.

 

[jezter6]

What about repitching?

If the attenuation is 70%, and you attenuate half-way of that and repitch, shouldn't the 'new' yeast attenuate at 70% of whatever's left? Giving you a lower FG?

 

[Blender]

What about repitching?

If the attenuation is 70%, and you attenuate half-way of that and repitch, shouldn't the 'new' yeast attenuate at 70% of whatever's left? Giving you a lower FG?

Well I wouldn't know about that but if you pitch enough yeast the first time there will be no need to repitch. I would think that after the initial ferment that O2 levels would be low for the repitched yeast to use and attenuation would suffer accordingly. Them yeast need oxygen to work thier magic the best.

 

[Kaiser]

There are 2 forms of attenuation for beer. The first is the limit of attenuation and it is set by the wort composition and the species of yeast (s. uvarum (lager) vs. s. cerveciae (ale) or however you spell this) but not the strain of yeast. This limit of attenuation indicates how much of the extract (which is sugars, proteins and compounds other than water) can be fermented by the yeast. The limit of attenuation can be determined with a forced ferment test where a large amount of yeast is pitched, kept in suspension (shaking or stir plate) and fermented warm.

The actual attenuation depends on the strain, health, fermentation conditions, temperature ..... The more flocculant the yeast, the bigger the difference between actual and limit of attenuation will be because the yeast drops out before the job is done. The lack of significant circulation also helps dropping out the yeast.

The bigger the difference between actual and limit of attenuation, the sweeter the beer will be and the smaller the difference the drier it will be. If you want to get closer to the limit of attenuation you can:
- pitch more but you may get the problems associated with over pitching
- rouse the yeast toward the end of fermentation
- pitch a less flocculant yeast at the end

The latter is best done with a large starter (keep some wort from brew day) since there won't be much yeast growth in the beer due to the lack of nutrients (amino acids, O2, Zink ...) Don't worry about getting much flavor from the second yeast since the main profile has already been set by the 1st yeast.

German Lager brewers may do this by adding some less flocculant yeast when racking the beer into the lagering vessels to make sure that they get the a dry finish in the beer if they haven't fermented with a "dusty" yeast in the first place.

Kai

 

[RichBrewer]

I would add some honey to the batch. For me it always seems to attenuate out and it doesn't create cidery flavors. I swear honey is the most fermentable substance on the earth.