Author Topic: Important Note on pH Model in BeerSmith  (Read 5403 times)

Offline Oginme

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Important Note on pH Model in BeerSmith
« on: February 04, 2019, 05:59:18 AM »
I've been following the discussion on various mash pH models on several forums.  Mark Riffe posted the following note on HBT regarding his model and acid additions (Mark's comment and thread link):


The mash pH estimates used in Beer Smith (at least v2, if not also v3) are based on a couple of papers I wrote in 2013, which can be found on my blog (listed below in my signature). The papers report on my analysis of Kai Troesters work that he wrote up in his 2009 paper "The Effect of Brewing Water and Grist Composition on the pH of the Mash." I wrote these papers mostly for myself in an attempt to understand mash chemistry, which I was beginning to study at the time.

While I believe my analysis of Kai's data to be accurate, it did not go far enough in that I never tested it against real, work homebrewer mashes.

Personally, I used these equations to come up with my own pH calculator, MpH (v. 3.0 at present). Sometime in the past Brad Smith contacted me to ask if he could use my work to incorporate such calculations in bs. I said yes, and so that is where we are with all of that.

Here is the bottom line on the errors in acid additions: equation (6) in my second paper (... Mash pH II...) appears to overestimate the buffering capacity of a typical grist. Hence, the amount of acid required to hit a target pH is overestimated.

Consistent with your (and others) observations, recent preliminary analysis (of actual mash pH measurements) by me indicates the buffering capacity is overestimated by a factor of about 1.65. Thus the observation that changing concentration from 88% to about 140% -- 150% in the bs software (more-or-less) fixes this issue when working with bs.

Towards the end of nailing all of this down, I urge you to add your own data to the thread I recently started -- https://www.homebrewtalk.com/forum/threads/wanted-mash-ph-measurements.661544/ . As you can see there, I have asked that actual mash pH data be posted so that anyone interested in mash pH developing software has a chance of making it accurate.

Just in case you might be interested, I am currently updating MpH (although I have no idea when it will be ready for prime time). The underlying mathematical model will be entirely new (for MpH); it will be based on the water-chemistry ideas that A.J. deLange has discusses at length on this forum.

Cheers!

https://www.homebrewtalk.com/forum/threads/beersmith-3-ph-tool.653778/page-2#post-8512571

Addenda:  Oginme here with additional comments.  I have not used the acid additions from BeerSmith, as I prefer to use acidulated malt instead to make subtle pH adjustments.  The interesting aspect of this is that I increased the acid content of the acidulated malt profile by 60% (pretty close to the factor that Mark stated above) to get agreement of the model in BeerSmith with my actual results.  While not perfect, it does correlate extremely well to the point of matching within .05 pH units of the model to reality.
« Last Edit: February 04, 2019, 06:30:07 AM by Oginme »
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Offline shaunpycroft

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Re: Important Note on pH Model in BeerSmith
« Reply #1 on: February 10, 2019, 11:21:53 AM »
Interesting. I use brunwater for approximate acid additions to try to get correct mash ph. I add the advised acid amount to my strike water and nearly always have to add more to get to the required ph. I guess thats ok as Im always over and can add small amount more as needed? anyway just wondered if his spreadsheet also overestimated the buffering capabilities of most malts?

Offline jomebrew

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Re: Important Note on pH Model in BeerSmith
« Reply #2 on: March 02, 2019, 09:54:43 AM »



 

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