Attenuation Factors

[Brody]

To not further derail the Helles Recipe thread I wanted to start a topic on attenuation. I’m guessing most of you have read Kai’s article, “Evaluation of the Effect of mash parameters on the limit of attenuation and conversion efficiency in single infusion mashing”. In it he outlines a few things concentrating on attenuation potential.

Factors that increase attenuation:

Lower temperature: Has anyone experimented with different Beta rests? Looks like 140f to 145f is the normal range?

Time: I used 30m as a baseline Beta, I imagine this could be increased to an hour easily? Has anyone gone longer?

Mash pH: 5.4 to 5.6 was cited as optimum for attenuation with pH’s outside of that range to the lower end hurting efficiency more. This clashes with the 5.2 to 5.3 optimum for yield.

Grind: It seemed grind didn’t affect attenuation much in Kai’s experiment but it did impact efficiency a good bit. Has anyone noticed negative effects from grinding to fine?

Water to Grist: This seemed to be a wash with attenuation but improved efficiency.

Grain Composition: High Diastic power malts = higher efficiency. Has anyone noticed an effect on large amounts of Chit or Unmalted Grains affecting EVG?

[Techbrau]

30 min is the minimum amount of time you want to spend at the beta rest. 62c is the temperature optimum here.

30 minutes is also the minimum amount of time I would spend at an alpha rest. 72c is the temperature optimum here. However, you may get a 0.5 Plato or so lower limit of attenuation by using a 70c rest, because beta will still be active for 10 to 15 minutes at this temperature whereas it is gone at 72c. This means it will have a few
minutes to work on new starch branches exposed by alpha. A slow temperature ramp between 62c and 72c should in theory have the same effect.

Alpha amylase works rather quickly and conversion should be finished within 30 minutes at the alpha rest. However, full bodied Bavarian beers benefit from a 60 minute rest.

5.4 is a compromise pH that works well for both enzymes. Beta would be happier a bit lower and alpha a bit higher, but 5.3-5.4 is what I shoot for.

Recirculation or agitation of the mash, especially during the beta rest, has proved essential for me in order to get a high fermentability.

With mash recirculation, a 60 minute beta rest, and a 60 minute alpha rest, I can achieve a limit of attenuation of 2 Plato for a 12 plato wort. This corresponds to a limit of 83.33% EVG.

Getting the beer to actually attenuate to or near this limit is a separate matter. Yeast should be freshly propagated with plenty of access to oxygen. Fresh yeast with a proper pitch rate and level of wort aeration should get you close to the attenuation limit.

I have 13.5 liters of helles in my fermenter now. The original extract was 12 Plato, and the limit of attenuation 2 plato. I pitched approximately 300 billion cells of freshly grown WLP838 and aerated to 9ppm oxygen. Fermenting at 11.5c, the beer reached 2.25 Plato within 6 days from pitching, resulting in an EVG of 81.25%.

[lhommedieu]

What's a ball park figure for aerating 13 gallons of wort with one of those little red oxygen canisters for welding? Two minutes?

[Techbrau]

Depends on the flow rate, size of the stone, how well you distribute the o2...there's no way to know without measuring.

[lhommedieu]

OK - so I guess a dissolved oxygen meter is the way to go. That's a fairly expensive toy considering that there are formulas for determing ppm based on stone size, volume of wort and rate of flow. I am wondering if purchasing an oxygen tank and a regulator would be cheaper in the long run?

[Brandon]

[Bryan R]

It's far from a toy, infact it's more important than a pH meter imo.

[narcout]

[Bryan R]

I have 2. A Milwaukee(mw600) and an extech(do600). They do alright for how cheap they are.

[Bryan R]