Author Topic: Potential of Hydrogen (Another pH thread)  (Read 995 times)

Offline JT

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Potential of Hydrogen (Another pH thread)
« on: February 19, 2018, 03:02:21 AM »
This contradicts what I thought I knew.  Are we mashing too low?  I have used 5.6 - 5.6 @ room temp as the guideline for years.  Thoughts?
https://byo.com/mr-wizard/setting-record-straight-mash-ph/


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Online Robert

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Re: Potential of Hydrogen (Another pH thread)
« Reply #1 on: February 19, 2018, 03:37:44 AM »
Just a few thoughts.   I've seen several articles lately stating incorrectly that mash pH is to be taken at mash temp.  I honestly don't see where all the confusion comes from. The textbooks all clearly state that the desired pH is 5.2 to 5.5 in the cooled sample, and that the standard is room temp pH because when the optimum was first determined measurement could only be made at room temp.  Some confusion seems to come from the red herring of the supposed -0.35 displacement.  This seems to be based on a single series of tests reported in DeClerck that have proven unrepeatable.  The actual displacement seems closer to -0.2. But again, the original room temp standard has always been maintained for citations in the literature. Maybe there's mass confusion about ATC.   But of course you also want to take your reading at ROOM temp because, well, it's nice not to kill a $60 electrode in just a few batches.
 
 Anywho, all I  can tell is that the prescribed pH always has been 5.2 to 5.5 at ROOM temp, and mass confusion has only recently set in.  I suspect one erroneous article appeared and its effects have reverberated around.

All that said, experience should tell us some things:  Brewing processes and beer quality are clearly optimized as mash pH centers around 5.4; and pH as low as 5.2 was only helpful in the days of protein rests and moderately modified malt.   5.8 to 6.0 range is the DI pH of malt which has always been considered unacceptble, and I don't see how they get that number for an adjusted mash, even with the mythical 0.35 displacement.

I had thought this was all pretty clear, and any article to the contrary would have just brought a correction notice in the next issue.  The confusion is confusing.  Sorry for rambling it's getting late.
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Offline JT

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Re: Potential of Hydrogen (Another pH thread)
« Reply #2 on: February 19, 2018, 10:24:59 AM »
That's exactly where the alleged confusion is though.  I don't own the texts and so have only seen people quoting them or referencing them.  According to the article, the offset to temp variation is understood, but the optimal mash pH is unclear or has been misinterpreted.   


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Offline JT

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Re: Potential of Hydrogen (Another pH thread)
« Reply #3 on: February 19, 2018, 10:59:57 AM »
The author primarily references Malting & Brewing Science. 

"A primary reference on this subject is the textbook Malting and Brewing Science (Briggs, Hough, Stevens, and Young), and in this text there is an oddly worded paragraph that contains the following:"

"The pH of mash or wort alters with the temperature. At 65˚C (149˚F) the pH of mash will be about 0.35 unit less than at 18˚C (65˚F), owing to the greater dissociation of the acidic buffer substances present.
Therefore, enzymes whose pH optima are known from determination at 20˚C (68˚F) appear to have higher pH optima in the mash if this is cooled, as is usual, before pH determination. An infusion mash is best carried at pH 5.2-5.4. Consequently, the pH in the cooled wort [from this mash] will be 5.5-5.8."



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Offline BrewBama

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Re: Potential of Hydrogen (Another pH thread)
« Reply #4 on: February 19, 2018, 12:49:04 PM »
I understand that the sample should be cooled to room temp. But that begs the question: if a room temp sample is a prerequisite to taking a reading, why have an auto temp compensation feature build into the pH meter?


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Online Robert

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Re: Potential of Hydrogen (Another pH thread)
« Reply #5 on: February 19, 2018, 01:20:31 PM »
I understand that the sample should be cooled to room temp. But that begs the question: if a room temp sample is a prerequisite to taking a reading, why have an auto temp compensation feature build into the pH meter?


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Be sure mash is unique.  The electrode needs to compensate for temperature no matter what it's measuring. If you don't have ATC, to calibrate manually there are tables telling you what the BUFFER SOLUTIONS will read at different temps.  It's just that conductivity will be measured differently with temp, so even distilled water would show differently.   But mash ACTUALLY DOES change it's pH with temperature, unlike water or buffer solutions,  it's not a measurement phenomenon.  ATC just makes calibrating the instrument easier.
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Re: Potential of Hydrogen (Another pH thread)
« Reply #6 on: February 19, 2018, 01:37:27 PM »
As to the Briggs quote:  that textbook addresses solely British brewing.  So two things come to mind:  1) They never needed a protein rest, so a pH of 5.2 would not have beeen really beneficial at any point. But above 5.5 is still detrimental in any case.  2) So I wonder about the declaration that the displacement is -0.35.  Did they somehow just ASSUME this and add it to a room temperature value?  Because, again, that figure is in error, though it has long been accepted as gospel.  That might mean that what they assume would read 5.5-5.8 would actually be nearer 5.3-5.6.

I would just ignore a false debate about a nonexistent problem based on an muddled passage in a potentially outdated and erroneous text dealing with a nonstandard procedure.  Did trolls start this?  Probably not, but then they missed an opportunity.
Rob Stein
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Offline Big Monk

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Re: Potential of Hydrogen (Another pH thread)
« Reply #7 on: February 19, 2018, 01:51:41 PM »
De Clerck states all the way back in the late 40s that pH should be measured in a cooled sample. pH optima as often quoted are for cooled samples, i.e. room temp.

This is a topic I’m surprised is still discussed.
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Offline mabrungard

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Re: Potential of Hydrogen (Another pH thread)
« Reply #8 on: February 19, 2018, 04:42:09 PM »
Sadly the article cited above, set the state of brewing water chemistry back a step. While there are plenty of pH optima that we are forced to compromise on while brewing, the fact of the matter is that tens of thousands of brewers have found that targeting the 5.2 to 5.6 range (room-temperature measurement), produces a better tasting beer than if assuming that range is at mashing temp. There is a spirited discussion of that article and this issue on Bru'n Water's Facebook page.

Do yourself a favor and forget about measuring pH at mashing temperature. It's damaging to your pH probe and it doesn't lead to a better beer. While there are pH probes that are fabricated for high-temperature use, they generally stay at that high temperature throughout their life as part of a process measurement. That's not what happens in brewing where you're taking a room temp probe and plunging it briefly into high temp wort and then back to room temp. That thermal stress does hasten the breakdown of that probe's thin glass membrane.   
« Last Edit: February 19, 2018, 05:39:42 PM by mabrungard »
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Online Robert

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Re: Potential of Hydrogen (Another pH thread)
« Reply #9 on: February 19, 2018, 04:51:18 PM »
The authority has spoken.
Rob Stein
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Offline denny

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Re: Potential of Hydrogen (Another pH thread)
« Reply #10 on: February 19, 2018, 05:23:45 PM »
I understand that the sample should be cooled to room temp. But that begs the question: if a room temp sample is a prerequisite to taking a reading, why have an auto temp compensation feature build into the pH meter?


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It's to correct for the temp of the instrument, not the sample.
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Offline JT

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Re: Potential of Hydrogen (Another pH thread)
« Reply #11 on: February 20, 2018, 01:51:33 AM »
I find the interesting part of the author's response not about ATC or the fact that we should be measuring mash pH at room temp, but rather that the author seemed to double down on optimal mash pH at room temp being between 5.5 and 5.8 and cites Malting & Brewing Science as that reference. 

Does Kunze not reference temperature in Technology Brewing and Malting in regards to mash pH?  Where are the citations from other textbooks that contradict the Malting & Brewing Science citation?


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Offline BrewBama

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Re: Potential of Hydrogen (Another pH thread)
« Reply #12 on: February 20, 2018, 01:53:46 AM »
I understand that the sample should be cooled to room temp. But that begs the question: if a room temp sample is a prerequisite to taking a reading, why have an auto temp compensation feature build into the pH meter?


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It's to correct for the temp of the instrument, not the sample.

Ahhhhhh. Thx.


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Offline Big Monk

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Re: Potential of Hydrogen (Another pH thread)
« Reply #13 on: February 20, 2018, 01:55:28 AM »
I find the interesting part of the author's response not about ATC or the fact that we should be measuring mash pH at room temp, but rather that the author seemed to double down on optimal mash pH at room temp being between 5.5 and 5.8 and cites Malting & Brewing Science as that reference. 

Does Kunze not reference temperature in Technology Brewing and Malting in regards to mash pH?  Where are the citations from other textbooks that contradict the Malting & Brewing Science citation?


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I’ve been down this road before and I have sections jotted down from at least 6 texts. I’ll try to dig those quotes out and post them here. The oldest is DeClerck in “ATOB”. He very clearly states cooled pH samples as the benchmark. That was almost 70 years ago.
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Offline JT

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Re: Potential of Hydrogen (Another pH thread)
« Reply #14 on: February 20, 2018, 02:02:15 AM »
I find the interesting part of the author's response not about ATC or the fact that we should be measuring mash pH at room temp, but rather that the author seemed to double down on optimal mash pH at room temp being between 5.5 and 5.8 and cites Malting & Brewing Science as that reference. 

Does Kunze not reference temperature in Technology Brewing and Malting in regards to mash pH?  Where are the citations from other textbooks that contradict the Malting & Brewing Science citation?


  "If more of us valued food and cheer and song above hoarded gold, it would be a merrier world."

I’ve been down this road before and I have sections jotted down from at least 6 texts. I’ll try to dig those quotes out and post them here.
Thanks.  It's not that I believe the article over all the expertise on this forum, it's more that I can't believe that ALL of the texts are as vague or confusing as indicated in the article. 

I really need to drop some cash on a good brewing text.  I have lots of books on brewing, but I'd like to have a serious "school worthy" text.

Any recommendations or warnings?  I'm leaning Kunze. 

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