High Attenuation

[apeltes]

My all-grain brews tend to reach attenuation levels that are significantly higher than the published ranges. I keep aiming for lower ABV, and I always miss the mark. For example, I just used Wyeast American Ale yeast for a blonde ale and got 82% (should be 73-77).

Here are the details. Please let me know if you see anything. Thanks!

9lb Maris Otter
1lb 10L Crystal
60 minute mash at 150F
Mash thickness 1.5
Fermented at approx 73F
OG 1.045
FG 1.008

 

[motobrewer]

low mash temp, thin mash, high temp.

try mashing at 152-154 at 1.25 qt/lb and fermenting at 68F

for a 1.045 beer i'd stay above 153 for mash temp.

 

[CaptYesterday]

Moto nailed it.

Mashing at 150 favors beta amylase which will leave you with more short chain dextrins for the yeast to ferment. You might want to check the temp of the mash after the hour as well. Just because you started at 150 doesn't mean you ended there. If you lose a couple of degrees over the course of the hour you will wind up with a more fermentable wort than if the temp hadstayed constant

Fermenting at 73 is a bit on the high side for ale yeast. You might see a slight decrease in attenuation if you kept it closer to 68 F.

 

[ian-atx]

Bump up your mash temps and also verify that the thermometer you're using is accurate. Also verify that the mash tun you have maintains the temp and isn't losing temp (Especially with lower grainbill brews that may not have quite the thermal mass).

 

[apeltes]

I keep track of the mash temperature, and it's very stable. I use a round cooler with the lid filled with foam insulation. It works great. What I'll do is aim for a higher mash temperature to reduce the proportion of fermentable sugars.

I don't have many options with fermentation temperature, though. I'm in central Florida, so there's no basement or cool place. Air conditioning sets the temperature, and the wife will certainly not agree to lowering the house temperature below 70 for brewing! I've tried the "swamp" method before, and maybe I'll give it another go.

 

[Calder]

I don't know that lower ferment temps will reduce attenuation, but it will improve the beer.

Even if you don't use ice bottles in a swamp cooler to keep the temperature down, having a large water mass will prevent the fermenter temperature from taking off. It will reduce the ferment temp by 5 to 10 degrees and reduce the esters and fusel alcohols.

 

[Ichthy]

I had the same problem of 80%+ AA and it didn't matter what my mash temp was. The problem, I never mashed out. Now, I heat my first runnings while I'm adding water for next infusion. Wait till the first runnings are nearly boiling and make sure your second infusion can get the grainbed to mashout temps (168F). My last few beer have all finished where they should be.

And re fermentation temps. Put your fermenters in an ice chest with a water bath. Add one or two bottles per day to maintain appropriate temps. It's pretty easy and makes a huge difference.