The case against "mash pH" prediction, and for "wort pH" prediction based adjustment

[Silver_Is_Money]

Factors that make mash pH adjustment prediction difficult, and seemingly (to me, at least) favor wort pH adjustment (an incomplete list):

1) Crush alone has been documented to have as much as up to a 0.6 pH impact upon measured mash pH.

2) To my knowledge there is no EBC or ASBC defined procedure for mash pH measurement. No one fully agrees as to when to sample, or with regard as to at what temperature to measure the pH of the sample. Time and temperature variabilities both lead to wild swings in mash pH measurement.

3) Variability in mash procedures is high. Some step mash, some decoction mash, and some single infusion mash. Some fly sparge, some batch sparge, and some perform no sparge at all. Temperatures vary measurably across many of these steps.

4) Some mineralize both mash and sparge water, some mineralize only mash water, some only sparge water. Mineral quantities and types also vary wildly.

5) Some utilize local tap water, some use mineral water, and some use RO, and there are an infinite degree of analyticals, as well as potential blends introducing variabilities that involve pH.

6) Some proclaim that the measured downward shift in pH due to calcium and magnesium levels in the mash is 100% of Kolbach's projection, while others proclaim it is only on the order of 50-60% of Kolbach's projection during the mash, and some claim values inbetween. Some agree that Kolbach got it right, and some question that he got it right. Kolbach himself said the measure of downward pH shift was to be assessed at "knock out", well downstream from the mash step.

7) The acidic characteristics of each individual grist component are only ballpark known in most cases. Grist component testing and/or certified grist component analysis is scant. Data when given is generally qualified as wort pH data, and not as mash pH data.

8) Other negative factors??? All thoughts as to identifying more of these factors are welcome.

By taking a pH reading post the mash and also post all stages of lautering, and just pre-boil, and measuring "wort pH" at this juncture in compliance with EBC method 8.17, all of the above variabilities which influence and confound mash pH prediction are bypassed. They are of course replaced by another set of variabilities (known and unknown) to pH adjustment at this juncture which would seemingly be inherently present within the (now divorced from the grist) pre-boil wort regardless of whether or not the mash pH was or was not adjusted aforehand.

 

[bob1852]

8) pH precision (especially down to the hundredth) isn't really that important....

Some may disagree and some may bring some science, but in my experience, trying to accurately hit a pH of, say, 5.56 just isn't that important.....as long as you're in the range of 5.2 to 5.8 (which is easy to hit with most grists, neutral water, and additives based on the many calculators).

Recipe development, yeast management, etc., are far more important that pH in my opinion and experience...

Flame on....

 

[dmtaylor]

8) pH precision (especially down to the hundredth) isn't really that important....

Some may disagree and some may bring some science, but in my experience, trying to accurately hit a pH of, say, 5.56 just isn't that important.....as long as you're in the range of 5.2 to 5.8 (which is easy to hit with most grists, neutral water, and additives based on the many calculators).

Recipe development, yeast management, etc., are far more important that pH in my opinion and experience...

Flame on....

I'll be the one who agrees with you 100%.

However, I'll continue to experiment anyway.

 

[Silver_Is_Money]

One might presume that if the brewing industry at large (not to be confused with home brewers, or books and dissertations oriented toward home brewing) saw merit in mash pH there would be a recognized and well defined industry standard for the taking of a mash pH.

 

[Qhrumphf]

Honestly I think both are important. There are times I'll adjust the kettle pH independently from the mash because the kettle pH I want doesn't flow from my desired mash pH. And when doing a continuous sparge, pH absolutely impacts tannins to a very large degree. I wouldn't disregard those factors at all.

What I *would* do is ignore an arbitrary mash pH target from anyone else due to the factors you list, and use a consistent measurement process and adjust relative to that process to get your desired results.

The same way IBU calculations don't line up to real world IBUs, they're still useful as a metric relative to themselves when one's process and calculations are consistent.

 

[bob1852]

One might presume that if the brewing industry at large (not to be confused with home brewers, or books and dissertations oriented toward home brewing) saw merit in mash pH there would be a recognized and well defined industry standard for the taking of a mash pH.

Or a well defined mash DO target.

 

[Qhrumphf]

there would be a recognized and well defined industry standard for the taking of a mash pH.

Commercial practices vary as much or more than homebrewer practices.

Just saying.

 

[Robert65]

I might add (I'm also in an up-in-the-air state thinking about this) that pH may not be nearly as critical as thought in the mash. Enzymes are happy over a broad range of conditions, and time and temperature have much more influence on their performance than pH or mash viscosity. But kettle pH seems to have a considerably greater effect on hop utilization, break formation, effectiveness of kettle finings, and so on, and perhaps pitching wort pH on yeast performance.

I further wonder how much of the reported benefit (in German papers at least) of a particular mash pH is really due to the resulting kettle pH, since the focus is generally on biological acidification of the mash to control the downstream processes (but we see how unpredictable this is.) That's just off the top of my head.

One thing I can think of where a low pH on the mash may be beneficial is the supposed suppressed activity of LOX below 5.2; but even Kunze is not 100% clear (as I read him) in endorsing such a low mash pH; and other measures can address the risks associated with LOX.

Much to think about. I don't think at this point I'd say we should completely ignore probable mash pH. But maybe empirically derived guidelines for water profiles and RA that generally get a particular beer style into the ballpark is the most that is needed. Which really is where the entire subject began.