Author Topic: pH Estimation: Let's Talk Charge Conservation/Proton Deficit  (Read 348 times)

Offline Big Monk

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Rob and I had some discussion here:

https://www.homebrewersassociation.org/forum/index.php?topic=33615.0

about the proton deficit model for pH estimation.

Here is a screenshot of the troubleshooter I've put together:



Thought I'd spin off a new thread to devote to it.

Feel free to post questions or discuss.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Big Monk

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #1 on: July 05, 2019, 07:15:55 PM »
In a nutshell: The Charge Conservation/Proton Deficit model calculates the charge (protons contributed or absorbed) of the various acid/base components (Q (mEq)) commonly found in the mash and then sums these values.

pH (pHz) is then estimated by minimizing QTotal (mEq) as follows:

QTotal (mEq) = QWater + QAlkalinity + QMalt - QCalcium - QMagnesium + QNaHCO3 + QCaOH2 - QLactic - QPhosphoric = 0

Since many of these charges, and their corresponding charge differences (ΔQ or dQ), have pHz dependence, varying pHz minimizes the charge total.

« Last Edit: July 05, 2019, 07:19:44 PM by Big Monk »
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Robert

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #2 on: July 05, 2019, 08:29:47 PM »
Hate to hog this discussion.  But I deleted my last post over there, it was getting pretty OT.  Thanks for moving.

Anyway, to follow your last post over there.  The more records I go through, the more it looks like total buffering in my mashes, despite different grain bills and even with adjuncts, still gravitates toward 32 mEq/(pH*kg).  Could something be happening in the actual mash as a total system to cause this, which your titrations of different malts isn't showing?  You show a wide range of values in your tables, as I've seen elsewhere in work by AJ and others.  I know I've seen references in various papers to all mashes and worts having similar buffering capacity within certain pH ranges.  Maybe this is related to the simple "flat rate" for acidification given in e.g. Kunze ch. 3?  Does it make a difference that I'm always setting initial conditions and not adjusting after mash in? 

So many questions.  I'm confused.  I wasn't when I just trusted my quick and dirty approximation of this method.  (Which I should probably just do, since it works.)

Well at least I've opened this can of worms.   Think I should give it a rest for now.
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline Big Monk

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #3 on: July 05, 2019, 09:50:54 PM »
Hate to hog this discussion.  But I deleted my last post over there, it was getting pretty OT.  Thanks for moving.

Anyway, to follow your last post over there.  The more records I go through, the more it looks like total buffering in my mashes, despite different grain bills and even with adjuncts, still gravitates toward 32 mEq/(pH*kg).  Could something be happening in the actual mash as a total system to cause this, which your titrations of different malts isn't showing?  You show a wide range of values in your tables, as I've seen elsewhere in work by AJ and others.  I know I've seen references in various papers to all mashes and worts having similar buffering capacity within certain pH ranges.  Maybe this is related to the simple "flat rate" for acidification given in e.g. Kunze ch. 3?  Does it make a difference that I'm always setting initial conditions and not adjusting after mash in? 

So many questions.  I'm confused.  I wasn't when I just trusted my quick and dirty approximation of this method.  (Which I should probably just do, since it works.)

Well at least I've opened this can of worms.   Think I should give it a rest for now.

There are 2 options:

1.) Every malt you use has the exact same buffering characteristics;

2.) You are incredibly consistent, i.e. you use similar base malts for all batches, target the same pH, use only small amounts of specialty malts, similar water profile, similar amounts of acids, consistent grain totals and volumes.

1.) isn’t possible. Knowing your posts and having a general sense of the type of brewer you are, 2.) is certain.

You are my favorite type of person to troubleshoot for. The Beerery is also very consistent and a dream to troubleshoot with/for.

We can go over any/every nut and bolt of the calculations whenever you want to.
« Last Edit: July 05, 2019, 10:17:46 PM by Big Monk »
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Big Monk

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #4 on: July 06, 2019, 05:45:41 PM »
The biggest hurdle with this model is the QMalt component. Without values for a1, a2, and a3 directly from measurement or try maltster, I was forced to try and make a data set out of the available known data.

That data set is actually pretty solid but can’t account for all malt. Linear data around pH DI and a1 sacrifices some accuracy over the polynomial but should be fairly easy to measure.

I’m working on drafting some correspondence to the American and European maltsters to petition them to measure these values as an analysis standard. With that in hand, I see no reason to estimate pH with any other algorithm.

Keep in mind that there are also reasonable assumptions that can be made for a1 for a variety of different malts.
« Last Edit: July 06, 2019, 05:52:18 PM by Big Monk »
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Robert

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #5 on: July 06, 2019, 07:05:33 PM »




Keep in mind that there are also reasonable assumptions that can be made for a1 for a variety of different malts.

I found a brewing record that contained enough information for me to infer an approximation of a1 for a base malt that is well outside my usual repertoire, but was used for a (single malt) seasonal once.   It appears that a1 (what I've always just called buffering capacity) is somewhat greater than -50 for this malt.

Then I determined that using my usual simplified method and my default assumption of -32 for a1 should give an actual result only off by ~pH +0.02 of target.

Even using gross assumptions, and a linear equation, it seems that this method is very robust, obviously because it's grounded in valid science.  Which it seems cannot be said for other models and calculators based on them, IME.
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline Big Monk

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #6 on: July 06, 2019, 07:40:34 PM »




Keep in mind that there are also reasonable assumptions that can be made for a1 for a variety of different malts.

I found a brewing record that contained enough information for me to infer an approximation of a1 for a base malt that is well outside my usual repertoire, but was used for a (single malt) seasonal once.   It appears that a1 (what I've always just called buffering capacity) is somewhat greater than -50 for this malt.

Then I determined that using my usual simplified method and my default assumption of -32 for a1 should give an actual result only off by ~pH +0.02 of target.

Even using gross assumptions, and a linear equation, it seems that this method is very robust, obviously because it's grounded in valid science.  Which it seems cannot be said for other models and calculators based on them, IME.

Absolutely. This is a good model granted you enter good data. We could get into the weeds about how other algorithms do certain portions of what’s presented here but it’s fair to say that there are definitely some shortcuts, proxies for real mEq values, and flat out deletions of certain important factors.

My thought is if you are going to go through the trouble of making a sheet in Excel, which is an incredibly powerful (and readily available) calculation engine, why would you not want to eliminate every possible source of even incremental error?

Make it look as sharp as you can and be as firmly grounded in reality as you can and coach people on the proper data entry. The reward is accurate estimates.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Robert

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #7 on: July 06, 2019, 08:15:51 PM »
Yes, but what I find reassuring is how good an estimate can be made if the only data you have are DIpH and a semi-reasonable proxy for the a1 value.   Still exponentially closer than what's generated  from the actual data in calculations based on color based assumptions of malt acidity etc.   As you said earlier, I see no reason to use any other model, even if not using it to its fullest potential -- which will be necessary until all the data are available to all brewers.  Good luck persuading the maltsters. Too few COAs even include DIpH. Most of us will be willing or able at most to obtain a DIpH and a provisional approximation of a1 -- which fortunately still gives quite serviceable results for the pragmatic brewer.  I hope brewers will not be discouraged from adopting this by the perception that they need to do elaborate titrations or otherwise compile rafts of complex data.  Flexibility of the method is appealing.
Rob Stein
Akron, Ohio

I'd rather have questions I can't answer than answers I can't question.

Offline Big Monk

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #8 on: July 06, 2019, 10:16:37 PM »
Yes, but what I find reassuring is how good an estimate can be made if the only data you have are DIpH and a semi-reasonable proxy for the a1 value.   Still exponentially closer than what's generated  from the actual data in calculations based on color based assumptions of malt acidity etc.   As you said earlier, I see no reason to use any other model, even if not using it to its fullest potential -- which will be necessary until all the data are available to all brewers.  Good luck persuading the maltsters. Too few COAs even include DIpH. Most of us will be willing or able at most to obtain a DIpH and a provisional approximation of a1 -- which fortunately still gives quite serviceable results for the pragmatic brewer.  I hope brewers will not be discouraged from adopting this by the perception that they need to do elaborate titrations or otherwise compile rafts of complex data.  Flexibility of the method is appealing.

I’ll flesh out the discussions on each component in the calculations in the days to come. That may help to offer perspective on how other spreadsheets do what they do, how they differ and agree with this one, and to help people be less scared of what is really a pretty simple topic.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Big Monk

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #9 on: July 08, 2019, 11:42:51 AM »
So let's break this down a bit.

I'll be quoting A.J. deLange liberally here, as he's the one who's been banging this drum for quite some time.

We can break the estimation of pH using the Charge Conservation/Proton Deficit model down into 3 major chunks:

1.) THE SOURCE WATER
2.) THE MALT
3.) THE ADDED MINERALS, ACIDS AND BASES

THE SOURCE WATER

There are a few characteristics of note concerning the source water:

  • The charge on a volume of pure water
  • Charge on carbo
  • The charge due to the water's alkalinity
  • The charge due to the Calcium and Magnesium content of the source water


THE MALT

There are a few characteristics of note concerning the malt used:

  • The distilled water pH (pH DI) of the malt
  • The co-efficients of titration: a1, a2, and a3


THE ADDED MINERALS, ACIDS AND BASES

There are a few characteristics of note concerning the minerals, acids and bases used:

  • The charge due to added Calcium and Magnesium
  • The charge due to Lactic and Phosphoric acid (among others)
  • The charge due to Sodium Bicarbonate (Baking Soda)
  • The charge due to Calcium Hydroxide (Pickling Lime)
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/

Offline Big Monk

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Re: pH Estimation: Let's Talk Charge Conservation/Proton Deficit
« Reply #10 on: July 08, 2019, 01:50:08 PM »
Added some features to the troubleshooter this morning:

brewingtroubleshooter.yolasite.com

Link is always in my signature as well.
“We are what we repeatedly do. Excellence, therefore, is not an act, but a habit.” Aristotle
"Messieurs, c’est les microbes qui auront le dernier mot." Louis Pasteur
Check out The Brewing Troubleshooters at https://brewingtroubleshooter.yolasite.com/