How do I correlate "pHDI" with "Wort pH" for Weyermann malts?

[Silver_Is_Money]

On page 115 of the 2004 published and peer reviewed book titled "Brewing Science And Practice" (by Dennis E. Briggs, Chris A. Boulton, Peter A. Brookes, and Roger Stevens) is found the following statement:

Infusion mashes are best carried out at pH 5.2 - 5.4 (mash temperature), and so will give cooled worts with pH values of about 5.5 - 5.8.

This ought to about seal the case and nail it shut for mashing at 5.5 - 5.8 pH as measured at room temperature. The midrange here is 5.65 pH as measured for mash samples cooled to room temperature (which in the brewing industry means 68 degrees F. or 20 degrees C., per EBC rule 8.17). This documentation would indicate that ~5.65 should be the target pH at which mash pH assistant software is set so as to determine acidification or caustification requirements. We have nearly all apparently been collectively doing mash pH adjustment wrongly for years.

http://vinic.com/files/books/Brewing_Science_and_Practice__2004_.pdf

 

[mabrungard]

This ought to about seal the case and nail it shut for mashing at 5.5 - 5.8 pH as measured at room temperature.

Nope. That is just one source. There are other sources that do cite room-temperature pH measurement. Additionally, I invite any brewer to perform a pale beer mash in that pH range and see if the beer is better than when mashed closer to 5.4. I don't find that its true, in my experience.

The only caveat I can apply is effect of post-boil acidification. While that is a British text, I'm not sure that its common for British brewers to perform any sort of post-boil acidification like the continental Europeans might do.

 

[Silver_Is_Money]

Nope. That is just one source. There are other sources that do cite room-temperature pH measurement. Additionally, I invite any brewer to perform a pale beer mash in that pH range and see if the beer is better than when mashed closer to 5.4. I don't find that its true, in my experience.

I've been searching brewing industry level documents. I grant that many homebrewing oriented dissertations and books insist upon 5.2 to 5.6 mash pH at room temperature, but that is not what I'm focusing upon. That aside, the book I referenced above also gives its expectations as to room temperature mash pH, as can be seen within my quote.

In an admittedly highly limited way I've already tested this. The best infusion mashed Bohemian Pilsner I ever brewed occurred many years ago, and well before most of us were paying much attention (if any) to mash pH. When I run that old recipe through software today I find that it likely mashed at around 5.75 - 5.8 pH for measurement done at room temperature. And I've also referenced a book that indicates that a well renowned Trappist Ale brewery mashes intentionally at 5.8 to 5.9 pH.

 

[Silver_Is_Money]

The problem with available data on mash pH comes down to one of circular reasoning, as can be seen from this Charles W. Bamforth quote taken from his paper titled "pH in Brewing: An Overview":

There have been surprisingly few (if any) detailed studies of the precise impact of pH on mashing performance and wort composition. Textbooks of brewing make reference to “optimum” pH’s for parameters such as extract and “wort filtration”, though they are conspicuous by the lack of references. One textbook refers to a previous textbook! It seems that a largely empirical approach has been employed. How the data has been generated and on what scale (lab mashes are not always good mimics of commercial mashes) is unclear.

Circular reasoning based merely upon empirical guesswork is essentially what we see today. Repetition of what one unreferenced person guessed at some point in the obscure past is repeated until it mystically becomes truth. And this paper admits that this problem exists even at the commercial level, let alone at the homebrew level.

Per Wikipedia: Charles W. Bamforth is the Immediate Past President of the Institute of Brewing and Distilling and Anheuser-Busch Endowed Professor of Malting and Brewing Sciences at University of California, Davis.

 

[eric19312]

The more I search peer reviewed papers, the more I'm discovering that those associated with the brewing industry are not very concerned (if they are concerned at all) with mash pH, and alternately that they appear to be highly concerned with wort pH.

My quick reaction to this idea is that it makes a lot of sense as it would take out all the ambiguity in sampling time introduced by so many possible ways to conduct a mash.

 

[Silver_Is_Money]

My quick reaction to this idea is that it makes a lot of sense as it would take out all the ambiguity in sampling time introduced by so many possible ways to conduct a mash.

Exactly. It greatly demystifies the entire process.

 

[Vale71]

Here is an interesting find. An employee of Rahr states that in 2017 Rahr measured the "Wort pH" of 100 lots of what I must initially presume to be typical Rahr 2-Row, as measured at 20 degrees C. (68 degrees F.) in compliance with EBC rule # 8.17, and the (left unpublished) "wort pH" result was a mind boggling 5.98 pH.

If we back off ~0.23 pH points to arrive at a nominal "mash pH" we get ~5.75 (for the case of measurement at 20 degrees C.). And if we next back off an additional ~0.3 points to see what this mash pH might nominally have looked like if taken at actual mash temperature we arrive at ~5.45 pH.

https://byo.com/mr-wizard/setting-record-straight-mash-ph/

I'm now recommending that manufacturers reported Congress Mash "Wort pH" values be reduced by 0.22 to 0.24 pH points to arrive at a nominal 20 degrees C. measured "DI Mash pH" value.

There's nothing mind boggling about the reported average value. As a matter of fact, between 5.95 and 6.00 is the recommended range for light colored malt. Please bear in mind that this is measured on wort from a standardized Congress Mash wich has a mash thickness of 9:1 (very thin) and is performed with distilled water. Just going from 9:1 to 4:1 will drop the PH by approximately 0.35 which in the case of Rahr would give an average wort PH of 5.63.
I really don't follow your adjustments though and I don't see why Rahr should report a value different from what they have actually measured using the accepted standard methodology.

 

[Robert65]

Please bear in mind that this is measured of wort from a standardized Congress Mash wich has a mash thickness of 9:1 (very thin) and is performed with distilled water. Just going from 9:1 to 4:1 will drop the PH by approximately 0.35....

Thank you. Now I understand why, when I test a sample in distilled water, I get a much lower value than is given on the COA, more in line with the values given by Kai's paper, for example, than data sets I've seen applied in some software; and explains why using those higher values in my own calculations gives very inadequate predictions of real, measired mash pH. I test samples in distilled water, but using a normal grind and mash thickness. I had thought there might be something amiss in my measurement, instead it was something amiss in my understanding.

 

[Vale71]

Now that you mention it, the finer grind of a Congress Mash would also influence PH but in the opposite direction, i.e. lower than with a coarser grind, so in the end you will have two distinct differences acting on mash PH but in opposite directions making accurate predictions even more difficult.

 

[Robert65]

It also puts into perspective a tidbit in Kunze that's confused me. He says that Kolbach found that to reduce mash pH by 0.01 requires something like 60 mEq/kg of acid but to reduce wort requires 30. My experience suggests that the requirement for mash is nearer the 30 figure. If these studies by Kolbach were performed under specific laboratory conditions, our mashes may behave more like his wort.

 

[Silver_Is_Money]

Just going from 9:1 to 4:1 will drop the PH by approximately 0.35 which in the case of Rahr would give an average wort PH of 5.63.

That would only be the case for an unbuffered system, as AJ has reminded me (or rather forcefully chided me) more than once, after I tried to make the same diluted pH argument as you are making.

As AJ has instructed, and also shown via doing the math, in a buffered system there is only a trivial change in DI_pH as the mash thickness is varied, even when appreciably varied.

Here is a snippet of one of such chidings that I received from AJ:

50 grams of 600L chocolate mashed in 150 mL of DI water will come to pH 4.6995 (its DI mash pH) and the same amount of this malt mashed in 1.5 L of water will come to 4.7065 and mashed in 15L of water, to 4.7660.

 

[Silver_Is_Money]

As to mash pH vs. wort pH here is a snapshot of what I presume to be one of their Pilsner malts, as taken from the Weyermann presentation:



The horizontal scale is in half percent of grist weight increments (whereby 12 represents 6% by weight acid malt in the grist).

 

[Silver_Is_Money]

Another way of looking at the Weyermann chart data:

 

[Silver_Is_Money]

Perhaps it all comes down to whether or not AJ is correct in his conclusion that mash thickness has merely a trivial effect upon mash pH. Anyone care to mash 50 grams of their Pilsner malt in 150 mL and likewise in 1,500 mL of DI water (or alternately, distilled if DI is not available) and let us know their measured room temperature mash pH results?

 

[mabrungard]

These are results for Pils malt with about 40 ppm Ca from gypsum in DI water. These are measured at 60 min.

1.33 qts/lb: 5.57
2 qts/lb: 5.60
4 qts/lb: 5.66

Relatively minor pH difference due to mash thickness, but appreciable. The differences in pH are very much more pronounced at the 15 minute mark. This response is relatively consistent for a wide variety of mash grists and mineral/acid additions.

 

[Silver_Is_Money]

These are results for Pils malt with about 40 ppm Ca from gypsum in DI water. These are measured at 60 min.

1.33 qts/lb: 5.57
2 qts/lb: 5.60
4 qts/lb: 5.66

Relatively minor pH difference due to mash thickness, but appreciable. The differences in pH are very much more pronounced at the 15 minute mark. This response is relatively consistent for a wide variety of mash grists and mineral/acid additions.

Thanks Martin! Your measured pH shift for a mere 3X dilution is about on par with AJ's anticipated 100X dilution induced shift.

 

[Silver_Is_Money]

These are results for Pils malt with about 40 ppm Ca from gypsum in DI water. These are measured at 60 min.

1.33 qts/lb: 5.57
2 qts/lb: 5.60
4 qts/lb: 5.66

Relatively minor pH difference due to mash thickness, but appreciable. The differences in pH are very much more pronounced at the 15 minute mark. This response is relatively consistent for a wide variety of mash grists and mineral/acid additions.

Martin, was 40 ppm Ca++ maintained across all of these dilutions?

 

[mabrungard]

The water was created in one batch and split into volumes for the mash trials. Only the amount of grains differed.

 

[Silver_Is_Money]

I've been thinking about the disparity between Martin's measured pH results and AJ's pH theory with respect to dilution impact upon pH drift, as whenever there is a discrepancy, there must be a reason for the discrepancy.

For 1.33 qts of DI water and 1 Lb. of malt, the overall water and malt system has a weight of 1.715 Kg.

For 4.00 qts. of DI water and 1 lb of malt, the overall water and malt system has a weight of 4.237 Kg.

4.237/1.715 = 2.47

40 mg/L Ca ions * 2.47 = 98.8 mg/L Ca ions

Just thinking while I'm typing, and certainly that in itself is rather dangerous and often off base, and therefore the reason for the differences in mash pH that Martin measured clearly may lie elsewhere. But also wondering what the mash pH would be for 98.8 mg/L Calcium ion water used for the case of the 4 quart water and 1 Lb. malt sample alongside of 40 mg/L calcium ion water being used for the case of the 1.33 Qts. of water and 1 Lb. of malt sample. If the 4 Qt mash thereby winds up measuring 5.57 pH, just as for the 1.33 Qt. sample, that might indeed be interesting. And it would likely call for a different model of mash pH prediction software development also.

 

[Vale71]

Where do you get the increased concentration of Ca ions? The water was prepared in a single batch with 40 mg/l and then simply split into two batches of different volume.

The simple answer is that malt brings its own ions (Ca and Mg among them) into the mash and with differing concentrations they will react differently with the water and create PH differences with a proportionality to the mash thickness that is approximately linear (within a reasonable range but nobody mashes 1:100 anyway).

This is what is taught in any professional brewing course and I'd be surprised if that were to be completely wrong. There is certainly some degree of approximation as the mash is a quite complex system from a chemical standpoint but it certainly is not a simple two component buffer and does not behave like one either.

 

[Silver_Is_Money]

Where do you get the increased concentration of Ca ions?

By adding them.

 

[Vale71]

By adding what? That looks like a multiplication to me...

The Ca ions don't get concentrated, they stay at 40 mg/l no matter how much water you use for the mash.

 

[Silver_Is_Money]

By adding what? That looks like a multiplication to me...

The Ca ions don't get concentrated, they stay at 40 mg/l no matter how much water you use for the mash.

For the case of 1.33 Qts. of water and 1 Lb. of malt use water with 40 mg/L Ca++
For the case of 4.00 Qts. of water and 1 Lb. of malt use water with 98.8 mg/L Ca++

Mash each as identically as possible, and take their mash pH's. I don't know how to make this any more clear.

 

[Vale71]

Maybe it's just me but it's never clear to me when you're proposing someone do an experiment...

 

[Silver_Is_Money]

Maybe it's just me but it's never clear to me when you're proposing someone do an experiment...

Apparently I can be that way sometimes, though it is not by intent.

But cutting to the chase, wouldn't it be interesting if both now mash at the same pH? (not saying that they will, just asking if you [and others] would find it interesting if they did)