Slow and Steady: Contrarian Attenuation Advice


So...what's the best mash temperature for increased attenuation?

I was recently lectured on this point pretty aggressively, and every attempt to introduce a touch of empiricism to the discussion resulted in a pretty condescending response.  I don't mind saying, it pissed me off a little, and I hadn't planned on writing about attenuation today but I now feel basically forced into it.

Why?  Because I sincerely believe that lots of homebrewers are walking around with advice on the topic that is, if not wrong, then certainly debatable, and they should maybe knock it off with the aggressive certitude.

Time and Temperature

I mash every beer pretty much the same way.  I'm not a fan of tinkering with mash temperature or density to try to yield a more or less fermentable wort.  If I want more, I add simple sugar.  If I want less, I add dextrine malt.  Why?  Because I know what those will do.  Trying to get there via the mash requires a little too much faith in what playing with mash temperature will do, and mashes aren't uniform.

So, I mash everything at 152F.  

Why that number?  Well, for one, you have to pick something if you're going to do it at the same figure for everything, and lots of brewers seem to agree that 152F lands you nicely in the window of a good ratio of alpha- to beta-amylase activity.  

For another, I do so because of a compelling and convincing argument I heard at the National Homebrewers Conference in Seattle, delivered by one Greg Doss, a microbiologist at Wyeast.  

Greg was intent on getting to the bottom of what made for fermentable wort, along several dimensions of variability.  These included yeast strain, grist, and length and temperature of the mash.  

The short version - following a methodologically rigorous and sound multi-round forced-fermentation test - is this: maximum fermentability was achieved at mashes of 75 minutes in length, at temperatures ranging from 151F-153F.  Outside of that range, fermentability was practically constant as low as 146F and as high as 155.5F. 

So, I mash at 152F for 70 minutes, every time, every beer, with precious few exceptions (mostly going over 156F on some scaled-down session versions).  But I also mention to folks who tell me that "oh, I wanted a super-fermentable wort, so I mashed at 148F" that maybe they want to reconsider that.

Hence the push-back, recently, on this question.

Don't Question Everything - but Ask Questions

I'm not telling you that you should reject out-of-hand all brewing conventions.  There are undoubtedly lessons learned over centuries of a practice that defy easy empirical assessment or verification.  There are also things that may have substantively insignificant benefits/costs that, taken with other minuscule effects, can aggregate into something that is substantively significant, and therefore we might consider keeping around despite their lack of obvious benefit (or continue to limit, despite their lack of obvious cost).  

So, it isn't so much that I'm advocating for a purely empirical approach to what is sometimes best approached as an alcehmic, artistic endeavor.

But I'm definitely advocating that you should be willing to question what you think, do, and advocate for when there's a decent empirical reason to do so.  However you come down on the question, ultimately, be willing to ask it.

Keep it simple.


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