Mash pH over time - does it drop?

[MNDan]

Hi all - I've been trying to get the land of pH in my brewing process dialed in. Using a new and freshly calibrated sensor on my pH56, I'm getting a mash pH of 5.25@70F after 45 minutes of mashing. My target mash pH is around 5.5@70F via the water spreadsheet 3.0, so I'm surprised I missed it by this much. Below is what my recipe looks like - according to the spreadsheet my mineral additions into RO water look right?

Style: American Pale Ale
TYPE: All Grain
Taste: (35.0)

Recipe Specifications
--------------------------
Boil Size: 14.35 gal
Post Boil Volume: 12.48 gal
Batch Size (fermenter): 12.00 gal
Bottling Volume: 12.00 gal
Estimated OG: 13.308 Plato
Estimated Color: 7.5 SRM
Estimated IBU: 39.5 IBUs
Brewhouse Efficiency: 75.00 %
Est Mash Efficiency: 75.0 %
Boil Time: 90 Minutes

Ingredients:
------------
Amt Name Type # %/IBU
18.00 g Calcium Chloride (Mash 60.0 mins) Water Agent 1 -
11.00 g Gypsum (Calcium Sulfate) (Mash 60.0 mins Water Agent 2 -
21 lbs Pale Malt (2 Row) US (2.0 SRM) Grain 3 87.5 %
1 lbs Biscuit Malt (23.0 SRM) Grain 4 4.2 %
1 lbs Cara-Pils/Dextrine (2.0 SRM) Grain 5 4.2 %
1 lbs Caramel/Crystal Malt - 60L (60.0 SRM) Grain 6 4.2 %
1.50 oz Cascade [7.30 %] - First Wort 90.0 min Hop 7 21.2 IBUs
1.00 oz Centennial [11.10 %] - Boil 60.0 min Hop 8 18.3 IBUs
1.50 oz Citra [14.10 %] - Steep/Whirlpool 0.0 m Hop 9 0.0 IBUs
1.0 pkg Safale American (DCL/Fermentis #US-05) Yeast 10 -


Mash Schedule: My Mash
Total Grain Weight: 24 lbs
----------------------------
Name Description Step Temperat Step Time
Step Add 31.99 qt of water at 165.1 F 152.0 F 40 min

 

[ajdelange]

In cases like these where the specialty malts are only about 13% of the grist it should not be surprising that the mash pH depends mostly on the base malt. If the base malt has DI mash pH of 5.6 and nominal (31 mEq/kg-pH) buffering you would expect, assuming 1.25 qts/Lb a mash pH of about 5.5 without the incredible 15.9 mEq/L (318 mg/L) Ca++ you have added. That is enough calcium to drop the pH by almost 0.3 (assuming Kohlbach's rule of thumb applies at this level) to 5.29. Thus, under these assumptions, it is perhaps not so surprising that you measured 5.25. Nonetheless, as it is a new sensor, you should do the cal/stability check described at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/.

OTOH if you used a base malt with a higher DI mash pH, your reading would be expected to be higher. A malt with DI mash pHof 5.86 and buffering 31.3 mEq/kg-pH would be expected, with the calcium, to produce mash pH of around 5.38.

It appears that "the water spreadsheet 3.0" isn't modeling the malts or the calcium effect very well but I hasten to point out that the malt model I am using is based on malts that I have measured that may be appreciably different from the ones you are using. I am modeling calcium based on Kohlbach's observation that 3.5 mEq Ca++ produces 1 mEq protons.

You never asked the question included in the title of your post. Mash pH does change over time. It usually goes up but it can also drop.

 

[mabrungard]

+1 for the mash pH more typically rising very slightly during the course of the mashing period. I typically observe a few hundredths rise in pH.

 

[MNDan]

One thing I forgot - I swapped out 6 lbs of two row for Maris Otter. Doesn't seem to make too much difference. I'm wondering about the "incredible" amount of calcium added? It looks like it is well within the recommended amounts. I am using my RO water, but I put in 95% since it may not be eliminating ALL of the solids I would expect - didn't seem to matter too much.

BTW - thanks for the great response, AJ!

 

[MNDan]

BTW - I am really chasing this due to this last PA that really got weird. Very sour - not undrinkable, but definitely unlike any PA I've made.

https://www.homebrewtalk.com/f14/help-me-my-pa-really-sour-weird-hop-flavor-w-amarillo-citra-480750/

 

[ajdelange]

I checked the other thread and a measured pH of 3.75 for the finished beer puts it in Lambic/Berliner Weiße territory and thus probably infected.

As to the large calcium amount: If those amounts of the salts give you the flavor profile you want then they are not inordinate but that level of calcium, it would seem to me, would give a pretty mineralized beer.

 

[Yooper]

One thing I noticed is that looks like EZ water calculator? My experience with it is that it is always higher than the actual mash pH- always. Often much higher, like in your case.

I'd suggest trying another water spreadsheet to see if the prediction in Brewer's Friend or in Bru'nwater (link to that one above in mabrungard's signature) is more accurate.

Also, the water information in bru'nwater is valuable as it explains the additions and what they do, even if you don't use the spreadsheet. It's not as, well, easy, to use as EZ water, but it is more accurate in my experience.

 

[MNDan]

Thanks! This has been VERY helpful! I plugged in my numbers for the original sour PA, and it said my mash pH was probably 4.9@room temp - obviously a big problem.

I'll have to wait to brew again, but I'm excited to back off on the minerals and work in some of my regular hard water into my mash to see if I can't start hitting my marks. The Bru'nwater sheet is very nice, though it estimates that my mash pH would have been 5.0 instead of around 5.25. I'll have to play around with it some more to see what is up. Not sure if it is happy that I only want to add salts to the mash water and leave the sparge water as pure RO.

thanks again!
dan

 

[ajdelange]

Try the Brewer's Friend one too. It will probably be closer than the other two (it seems to be the most robust but this is based on my impression from what little I can garner about the actual algorithms used as opposed to data from many test cases).

 

[MNDan]

Nice - the Brewer's Friend gets me to an estimated 5.29 for yesterday's mash that measured 5.25, so it's definitely the closest of the three.

thanks!
dan