[TeeDubb]

I'm planning on trying take myself out the comfort zone and brew a gluten free pale ale for a few friends that have pretty severe gluten sensitivity.  I have been trying to do as much reading on the topic and Denny's podcast (episode 38) earlier this year was a huge help understanding the basics.  I decided to try a modified version of the Ground Breaker Brewing recipe that was posted here:

https://static1.squarespace.com/static/538fa264e4b09eb4feac4903/t/594577a2b6ac50716937d515/1497724834648/GBB+Gluten-Free+Homebrew+Pale+Ale.pdf

My only changes are the hop bill (hop type) using the guidance that James Neumeister from GBB gave in the podcast.  Aim for lower bitterness, focus on late additions - sounds great and a personal preference anyway.

The question I have is on the water for the recipe.  I was not able to find much information on building water for a GF beer.  My gut feel says to do my usual which is: start with RO water, add salts to suit the style. But the unknown is pH. It does not seem that pH is major factor in the mash starch conversion, but there is likely a target range for healthy fermentation, mouthfeel, flavor and preservation.  Right now I'm leaning on taking some measurements during the mash and then adjusting the pH with lactic acid before the boil (I suspect it may need an adjustment down).  Has anyone else worked through this?

[Andy Farke]

In terms of pH, it looks like your grain bill will likely be in the acceptable ballpark, based on two articles I pulled up...

See here: https://krex.k-state.edu/dspace/bitstream/handle/2097/2281/KirstinVeith2009.pdf
(pdf -- p. 132/133 for some numbers and references; it's not peer reviewed, so should be taken with caution in case there are any basic things a reviewer would have flagged)

and here: http://onlinelibrary.wiley.com/doi/10.1002/jib.166/full
(data for buckwheat)

I suspect pH coming off any non-barley malted grain is going to vary a lot depending on variety, etc. I don't get the sense this has had nearly as much research as for malted barley. So yeah, I think your strategy of adjusting pH before the boil would work best.

Also, because you're using extract for much of the fermentables, you may not want or need to do a lot of water building (the extract presumably has the various salts in whatever mash water was used originally). Maybe just a touch of gypsum (or whatever works for your tastes...you know your preferences better than anyone!)?

[TeeDubb]

Andy - thank you for the finding this reference! There is a wealth of great info in there. Your comment made me think back to when I started out and was doing partial mash kits.  I never adjusted water and the beer turned out fine. I did not think to consider that the extract already has most of the necessary salts but that makes complete sense.  Much appreciated.

[Andy Farke]

You're welcome!

Yeah, I only learned about the mineral content in extracts late in the game. Of course, it's largely a mystery, because who knows how the water is in any of the production plants (or how it is modified from the local water).