Quick question on adjusting mash pH

[eric19312]

Eric, I will use the spreadsheet to note first the estimated target pH and (usually) the acid necessary to achieve that. Working from there, I figure out how much baking soda or pickling lime to raise that 0.1 units and note it... then reverse that out and note the liquid acid addition necessary to move 0.1 unit lower. It is convenient as I use the spreadsheet to plan anyway. Because I use RO, the amounts required are typically small and are based on the buffering of the mash, and from my notes very similar to the amounts in the chart.

Thanks this will work fine. I like your advice about not chasing. One addition and leave it alone will be my plan.

 

[youngdh]

I used my new MW102 meter for the first time yesterday on a Guinness clone 90 min mash with a target pH of 5.2 as calculated by Bru'n Water, at t+20 min my reading was 5.08! Following advice gleaned from this thread I didn't panic and start dumping baking soda into the mash but just made note for next time I brew. As a sanity check I pulled another sample at t+40min and the pH was 5.22. Whew, that's better but fear that during the critical conversion period (first 30 min) my mash pH might have been well below target. I calibrated the meter before each measurement, cooled each sample to 25C, rinsed probe in fresh DI water and blotted dry with clean paper towel. Is it normal for the mash to go below target pH and then move back up and settle at or near the target?

I guess it's not wise to assume Bru'n Water predicted 0.1 points high based on one mash day.

 

[ajdelange]

It is very normal for pH to change over time in the mash and where acid (as from the roast barley in you stout or sauermalz in a lighter beer) is involved for it to increase. I believe the acid gets released rather quickly from the acidic malts and then takes a while to be absorbed by the base malts - just a theory. What does seem strange is a mash pH as low as even 5.22 for a typical dry stout (10% roast barley) in water with any reasonable alkalinity. Most of the reports I have seen here and on other sites indicate that 5.5 is more likely. That, BTW, is what I get every time I brew such a beer. Was there something unusual in your grist such as a high percentage of roast barley (20% gives me pH 5.2 in lab experiments).

 

[youngdh]

It is very normal for pH to change over time in the mash and where acid (as from the roast barley in you stout or sauermalz in a lighter beer) is involved for it to increase. I believe the acid gets released rather quickly from the acidic malts and then takes a while to be absorbed by the base malts - just a theory. What does seem strange is a mash pH as low as even 5.22 for a typical dry stout (10% roast barley) in water with any reasonable alkalinity. Most of the reports I have seen here and on other sites indicate that 5.5 is more likely. That, BTW, is what I get every time I brew such a beer. Was there something unusual in your grist such as a high percentage of roast barley (20% gives me pH 5.2 in lab experiments).

I was purposefully targeting a pH of 5.2 using DI water built up based on Bru'n Water for my mash water volume and grain bill targeting Ireland's Wicklow Mtn water except I went for higher calcium in the profile (46ppm). For more clarity here are my water additions and grain bill for 6G DI mash water (no sparge as doing BIAB). All water amendments were added prior to dough in:

Gypsum: 2.4g
Epsom Salt: 0.6g
NaCl non iodize: 0.6g
Calcium Cl: 1.8g
Phos Acid 10%: 30ml

Grain bill:
5.49# Maris Otter
2.06# Flaked Barley (1.7 SRM)
0.43# Roasted Barley (300 SRM)
0.26# Dehusked Carafe III (677 SRM)

Target mash temp was 152F striking at 158.6F

My plan was to hold back roasted barley and dehusked Carafe III until last 10 min of mash so I could increase final beer color while reducing roast flavor from my first attempt at this recipe. My last Guinness clone (and first attempt at this recipe) the final product was a tad bit roasty'er than I remember the Guinness over in Dublin in June. My first attempt also turned out more of a dark amber vs a very deep almost black ruby, so, replaced some of the roast with dehusked Carafe III and going with a late mash addition or so I'd planned. I'm hoping adding the Carafe III early being dehusked/debittered won't have that big of a flavor impact.

10 min after mashing in Maris Otter and Flaked barley my mash temp was still at 154F. My fear of leaving at 154F for very long would allow the beta amylase a leg up over the alpha amylase. In an attempt to quickly lower temp another degree I decided to dough in the Carafe III at 10 min in. This lowered the temp to 151F. Knowing I had a long mash ahead and would lose 3-4F I put a bit of heat back on the mash getting it to 153F. Good enough, so, covered my kettle with sleeping bag and let it go.

Since I pulled my first pH sample at t+20min the Carafe III had only been in the mash 10 min. I was expecting the reading to be above 5.2 at this point since the Carafe hadn't had a chance to "do it's thing". When the pH reading came in at 5.08 I was very surprised. Based on AJ's response above maybe the Carafe III had done a big acid dump in those 10 min and the pale malts hadn't absorbed it yet?

If that's the case this brings up a questions if one is holding the roasted malts until late in the mash. How should that be accounted for in a tool such as Bru'n Water?

 

[ajdelange]

If I make up a mash like yours (using similar grains but I don't know exactly what yours are and I wouldn't have detailed models for them anyway) and mash with the water as you have treated it except that it has alkalinity of 75 I would expect a mash pH of 5.55 (which is what I get when I male Irish stout with my well water). This includes the dark grains.

If I take away the alkalinity the expected pH drops to 5.40. If I take out the dark grains and add the phosphoric acid it drops further to 5.31. With the dark malts and the acid I'd expect 5.24. Note that while my algorithm may be more robust my malt titration data set isn't so I don't advertise these estimates as being any more accurate than what you got with Bru'n Water.

So apparently the lower pH you saw (relative to what I would expect for Irish Stout) stem from
1) 0 alkalinity
2) The use of phosphoric acid.

It is still weird that the pH was low at t+20 and increased as much as it did 20 min later. Usually things are pretty well settled at t+20.

If you want to withhold the dark malts then you would plan your brew to give the mash pH you want without them but then must consider that they will add extra acid when they are eventually added. What a lot of people don't seem to get is that in an Irish stout they don't add too much. In the case of this mash they estimated pH pull of the dark malts is only 0.06 pH.

Usually 10% roast barley gives plenty of color. I usually realize 60 - 80 SRM with that amount. If you want more color without flavor Sinamar is now sold in small quantities in the US.

 

[youngdh]

I guess the final results of this brew must wait for another 4-6 weeks when I can taste it and compare to batch #1 of my Guinness clone. Of course I dorked with multiple variables on this batch (splitting roasted grains into 2 types, withholding part of roast from full mash, introducing pH measurements vs driving blind trusting spreadsheet output, etc) so will be difficult to determine any cause and effect relationships. Hey, it's all about the journey and discovery .


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[youngdh]

I guess the final results of this brew must wait for another 4-6 weeks when I can taste it and compare to batch #1 of my Guinness clone. Of course I dorked with multiple variables on this batch (splitting roasted grains into 2 types, withholding part of roast from full mash, introducing pH measurements vs driving blind trusting spreadsheet output, etc) so will be difficult to determine any cause and effect relationships. Hey, it's all about the journey and discovery .


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I bottled this on Monday after 4 weeks in fermenter. The beer was a nice dark ruby similar to Dublin Guinness. The green beer was not as roasty tasting as first batch but had enough there to say "Guinness". If the green beer is any indication of the finished product I'll be very happy .


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