Brewed my own somewhat robust Stout today to check its mash pH

[Silver_Is_Money]

Just got done cooling the 30 minutes into the mash sample to 68 degrees F. and taking the pH with a well calibrated meter, and after a few minutes it stabilized at 5.13. Re-calibrated and then checked again and this time it stabilized at 5.14. Gotta go, I just hit the 60 minute mark in the mash. Details of the recipe to follow.

 

[Rev2010]

Pretty cool of you to brew one up to check on this. I'm very curious to know what your Calc and the others, if you checked any others, estimated before you took your reading. I appreciate the work all of you have done to bring forth a selection of calcs to choose from and work with. I'd hope that anything learned from this goes to help to making things even more accurate.


Rev.

 

[dmtaylor]

 

[Silver_Is_Money]

60 minute mash pH was a stable 5.22 at 66 degrees F.

BIAB, no-sparge, 9.3 gal. RO water
Minerals added:
5.2 grams CaCl2 (freshly opened pack, est. ~94% pure)
3.5 grams NaCl
0.3 grams potassium metabisulfite
2.3 grams baking soda

Grist:
9 lbs. Swaen Pilsner, 1.9L
1 lb. Briess Victory, 28L
2 lbs. Flaked Oats, 2.5L
0.5 lbs. Briess White Wheat, 2.5L
0.75 lb. 80L Briess Caramel, 80L
0.25 lb. 40L Briess Caramel 40L
0.8 lbs. Briess Chocolate, 350L
0.5 lbs. Briess Roast Barley, 300L
0.25 lbs. Carafa III Special, 525L

Note, the 2.3 grams of baking soda was added up front to the mash water, and not in an attempt to raise the pH. It was thus in there for both pH readings.

 

[dmtaylor]

Just ran the numbers.... My estimate would have been 5.2. RO water with base malt gives a mash pH of approximately 5.8. Salts lowered this to 5.7. Dark roasted malts comprising 17% of the grist takes this down another 0.5 to 5.2. Increasing dark malts to about 20-22% would take this down to 5.1. Adding more salts like gypsum or whatever would take this down to 5.0 or maybe even 4.9.

 

[Silver_Is_Money]

Mash Made Easy test version 5.00 predicted 5.32 pH. It's guess was 5.21 with the baking soda left out, but it wasn't left out, so even my test version didn't hit a low enough pH prediction to account for what I measured for this batch. But overall, 5.00 test version was much closer than the current release MME version 4.33.

 

[Silver_Is_Money]

Just ran the numbers.... My estimate would have been 5.2. RO water with base malt gives a mash pH of approximately 5.8. Salts lowered this to 5.7. Dark roasted malts comprising 17% of the grist takes this down another 0.5 to 5.2. Increasing dark malts to about 20-22% would take this down to 5.1. Adding more salts like gypsum or whatever would take this down to 5.0 or maybe even 4.9.

Whatever method you used to come up with 5.2, it was clearly the winner here. You should be making it into a spreadsheet.

 

[dmtaylor]

Oh, you edited above to add the baking soda. In that case my estimate would have been 5.3 instead of 5.2. Personally I often reserve the baking soda for the boil, if pH gets too low.

 

[dmtaylor]

Whatever method you used to come up with 5.2, it was clearly the winner here. You should be making it into a spreadsheet.

If I did, it would be version infinity, never gets revised, and I never argue about the bases for it. My method is like totally old wifey taley.

 

[Silver_Is_Money]

Looks like I should have added about 5.5 - 6 grams of baking soda instead of the 2.3 that I added.

Not that it matters here, but I added 1 pack each of Danstar Windsor and Fermentis S-04 to the fermenter for this batch. First time ever that I've blended these two. I have my fridge set up to maintain it at 63 degrees F. during the ferment.

 

[Silver_Is_Money]

Mere speculation here, but based upon the progression from 5.13/5.14 pH at 30 minutes into the mash to 5.22 pH at 60 minutes into the mash, if this trend was to be reversed, it is possible that a 10 minute sample may have come in at right close to 5.05.

More off topic stuff of potential interest: This is the first time I ever did a no sparge batch. I had been doing batch sparging, and my no-sparge conversion efficiency was about 6% below what I would have expected for this recipe if batch sparging with a single batch sparge.

Also off topic: Already bubbling nicely this morning at 63 degrees F. I must mention that per the latest advice from Lallemand (and from the testimony of a forum member who directly consulted Fermentis regarding this issue) I didn't apply any aeration at all prior to adding the two dry yeasts. I did rehydrate them though.

 

[Silver_Is_Money]

Conclusions drawn from a single batch are clearly not to be taken as gospel, but from this experience combined with the recent experiences of several other stout brewing forum members, it certainly appears that when Martin Brungard shockingly announced on this forum roughly 2 years ago that dark roasted malts have far more acidity than previously presumed, and that he had significantly modified Bru'n Water accordingly, he was spot on.

 

[Silver_Is_Money]

The one thing that I left unconsidered was the downward pH shift contributed by the 0.3 grams of K-Meta that I added to the 9.3 gallons of RO water. @RPIScotty has published quite detailed data on this, but I currently can't find it. If he is watching, perhaps he can lend guidance here. If the impact of the K-Meta I added is significant enough, then perhaps MME test version 5.00 was closer in its mash pH prediction than I had initially presumed.

 

[dmtaylor]

The one thing that I left unconsidered was the downward pH shift contributed by the 0.3 grams of K-Meta that I added to the 9.3 gallons of RO water. @RPIScotty has published quite detailed data on this, but I currently can't find it. If he is watching, perhaps he can lend guidance here. If the impact of the K-Meta I added is significant enough, then perhaps MME test version 5.00 was closer in its mash pH prediction than I had initially presumed.

I didn't even consider the K-Meta, not knowing what it does. If it reduces pH in a very significant way, then yes, that might explain even better what you experienced. Why did you use K-Meta anyway? LODO-ish brewing?

 

[Silver_Is_Money]

I didn't even consider the K-Meta, not knowing what it does. If it reduces pH in a very significant way, then yes, that might explain even better what you experienced. Why did you use K-Meta anyway? LODO-ish brewing?

Yes, K-Meta was used in an attempt to reduce the adverse effect of oxygen. And it does drop mash pH to some degree.

 

[ajdelange]

Metabite, S2O5-2 has two negative charges so that for a redox reaction in which 2SO4-2 are produced we need 3H2O to get the 3 oxygens we need and we need 2 electrons. The 6 oxygens in the water keep the hydrogen atoms's electrons so 6 H+ are released. Two of the 6 electrons carried by the oxygen atoms are required the get the charge on 2SO4-2 to -4 and so 4 electrons are left over to reduce something. In the case of chlorine, for example, the reaction would be S2O5-2 + 3H2O + 4Cl --> 2SO4-2 + 4Cl- + 6H+. But consider chloramine where the reaction is S2O5-2 + 2NH2Cl + 3H2O --> 2SO4-2 + 2Cl- + 2NH4+ + 2H+. In this case we can think of the chlorine atom being pulled off the substituted ammonia molecule taking an electron with it and leaving NH2+ with 6 electrons in the outer shell. It readily grabs two of those available electrons to give NH2- and each of the unbonded pairs grabs an H+ ion rendering NH4+. Thus two of the 6 protons are taken by each of the nitrogens leaving two left over. In scavenging oxygen the reaction is S2O5-2 + O2 + H2O --> 2SO4-2 + 2H+

Thus the pH reducing effect of metabite depends on the nature of the redox reaction in which it participates. Each mmol of metabite produces from 2 - 6 mEq of protons. 300 mg of meatabite is 300/222 = 1.35 mmol and can produce, at most, 8.1 mEq of protons and on average about 4. A mash like the one under discussion here has buffering of about -0.0021 pH/mEq and so the maximum shift in pH we would expect from 300 mg of K meta is -0.017 pH and we would, more reasonably, expect half or a third of that.

As to a pH prediction - I know nothing about many of the malts used and so really can't come up with a reasonable calculation. Putting in WAGs as to what these might resemble that I do know something about I get 5.34.

 

[ajdelange]

Conclusions drawn from a single batch are clearly not to be taken as gospel, but from this experience combined with the recent experiences of several other stout brewing forum members, it certainly appears that when Martin Brungard shockingly announced on this forum roughly 2 years ago that dark roasted malts have far more acidity than previously presumed, and that he had significantly modified Bru'n Water accordingly, he was spot on.

One would certainly be ill advised to draw such a conclusion from home brewers' reports of low mash pH. Before drawing such a conclusion a reasonable man would want to see measurements on some malts that show more acidity than Kai, Joe or I found.

 

[Silver_Is_Money]

Thanks much A.J.! Is there any way to ballpark how much SO4-- I added to my batch via the 300 mg. of K-Meta? I added zero gypsum knowing in advance that there would be some quantity of SO4 generated as a consequence of my adding the K-Meta, but I didn't have a clue as to how much.

 

[ajdelange]

Assuming all you added scavenges O2 the reaction is, from No. 16: S2O5-2 + O2 + H2O --> 2SO4-2 + 2H+. Thus each mmol of bisulfite you add (you added 1.35) produces 2 mmol of sulfate so you have 2.7 mmol of sulfate at 96 mg per for a total of 259.2 mg. Distributed over the 35.2 L mash water that's 7.4 mg/L.

 

[Big Monk]

Thanks much A.J.! Is there any way to ballpark how much SO4-- I added to my batch via the 300 mg. of K-Meta? I added zero gypsum knowing in advance that there would be some quantity of SO4 generated as a consequence of my adding the K-Meta, but I didn't have a clue as to how much.

@ajdelange hits on the more detailed calculation that he helped me work through.

The "back of the envelope" estimation we have always used is:

-0.1 pH/100 ppm of Metabisulfite

0.3 g/9.3 gal = 300 mg/35.2 l = ~8.5 ppm

-0.1 pH * (8.5/100) = -0.008 pH units

This is pretty much inline with A.J.'s assessment.

Side Note: I wouldn't bother using Metabisulfite for oxygen protection unless you plan on pre-treating your water (pre-boiling, etc.). It's a waste otherwise. I had removed the Meta calculations in the recent edition of Brewing Engine Lite. I'll throw it back in this week for those who may experiment with it.

 

[Silver_Is_Money]

I ran my above listed recipe through Brewer's Friend today, and via the default Lovibond colors mode it predicted a mash pH of 5.48, but when the Advanced Water Calculator was set to its DI_pH mode it came back with a mash pH prediction of 5.63.

This vs. my readings of 5.14 pH at 30 minutes, and 5.22 pH at 60 minutes of mashing.

The now retired Mash Made Easy version 4.33 predicted a 5.53 mash pH, and the new (and now released) Mash Made Easy version 5.00 predicts a mash pH of 5.32. With both of these results acquired for the case of the base malt set at the DI_pH range suggested for Pilsner base malt.

 

[dmtaylor]

Does anybody else notice that when the pH sample is constantly stirred, the pH continues to fall, fall, fall? I believe due to CO2 from the ambient air dissolving into the beer? It is for this reason that I limit stirring as soon as the reading seems reasonably stable. @Silver_Is_Money, could this possibly explain your low reading? Did you stir the sample a lot? This would add CO2 to solution, not present in the original sample itself, if my understanding is correct.

 

[Rev2010]

Does anybody else notice that when the pH sample is constantly stirred, the pH continues to fall, fall, fall?

My new Apera pH meter does not do this, it stays stable, but my previous Milwaukee pH56 did that and it was really annoying. I hated that meter and am glad to be rid of it. Which meter are you using?


Rev.

 

[Silver_Is_Money]

Does anybody else notice that when the pH sample is constantly stirred, the pH continues to fall, fall, fall? I believe due to CO2 from the ambient air dissolving into the beer? It is for this reason that I limit stirring as soon as the reading seems reasonably stable. @Silver_Is_Money, could this possibly explain your low reading? Did you stir the sample a lot? This would add CO2 to solution, not present in the original sample itself, if my understanding is correct.

After rinsing the probe in distilled water, and then damping the probe dry with a tissue, I merely gently swirled the probe in the beer samples for a few seconds, as per the instructions with my meter. Then I let it sit and do its thing. Both times the meter reading rose slowly after swirling was ended until reaching full stability after perhaps a minute or so and then not changing any longer.

I would guess that most people do not give their meters sufficient time in the sample to reach a truly stable reading, and in doing this they get a false low reading to some extent. The meter I have has an indicator that informs when it believes it is stable, and it is always highly incorrect in that regard. The stability signal comes on way too early.

For me, stability in the calibrant buffers always comes quicker than it does for the sampling of water or beer pH's.

 

[dmtaylor]

My new Apera pH meter does not do this, it stays stable, but my previous Milwaukee pH56 did that and it was really annoying. I hated that meter and am glad to be rid of it. Which meter are you using?

I use el cheapo $10 gauge from Amazon. It's good enough.

 

[Silver_Is_Money]

My current meter is an Apera pH60.

 

[ajdelange]

I use el cheapo $10 gauge from Amazon. It's good enough.

How does it fare in a stabilty check?

 

[ajdelange]

My current meter is an Apera pH60.

And how does it do in a stability test?

 

[Silver_Is_Money]

And how does it do in a stability test?

It sat rock solid at 4.01 while sitting in that buffer. I did not extend the test for hours though.

 

[ScrewyBrewer]

My Hanna meter instructions said to never touch or attempt to wipe the sensor bulb as it would damage the coating on it. So I've always soaked the bulb in the cleaning solution and rinsed it with RO water.