Mash pH based on SRM or Grain bill?

[PDevlin75]

Hey everybody!

Okay, so I'm only just beginning to get into treating my water. I know next to nothing about it right now, so please bear with me. I got a water report, and now I'm plugging numbers into Brewer's Friend, getting a feel for how this stuff works. I put in my water report numbers and the grain bill for a Scottish Ale I plan to brew this weekend.

There's an option to determine the mash pH based on the beer color (which, for my recipe is 23 SRM), or my grain bill. If I go by color, the results tell me that my mash pH will be 5.26. But if I go by the grain bill, I get 5.6

For the record, my grain bill has:
15 lb Golden Promise
1 lb 3 oz Crystal 40
10 oz Crystal 120
8 oz Roasted Barley
12 oz Aromatic

Is there a reason to predict the pH based on one method over the other? Is one more reliable than the other? Which would you go by?

Thanks!
-Pete

 

[Silver_Is_Money]

Both are only as reliable as the information they are being fed (by both you and the programmer). Most likely it all comes down to a question of: Do you know how to calculate the percentage of the SRM color that the roasted portion is contributing? I calculate this (using the method of Kai Troester, the guy who developed Brewers Friends calculator) at 68.2%. What % roasted figure did you use? I get this batch mashing into DI water at a pH of 5.39 via SRM color and % roasted. No way to tell what your mash pH might be without full water details. Try running Brewers Friend again using 68.2% roasted and let us know what you get.

To compute % roasted, add up all of the lovibond x quantity (weight) values for only the crystal and roasted pounds of grains, and then divide the roasted color/pounds by the total of roasted plus crystal color/pounds. Aromatic and Golden Promise are excluded from this calculation.

1.1875 x 40 = 48
0.625 x 120 = 75
0.5 x 525 = 263

263/(48 +75 + 263) = 68.2% roasted

 

[PDevlin75]

Wow, okay! Learning something new here! Thank you!

For the % roasted, I had 2.8% as the roasted barley only accounts for that much of the total grain bill. I did not factor in the Crystal malts (although I was wondering if that affects it), nor did I know about the equation you just showed me... So right on, there!

Your value of 68.2% gives me a mash pH of 5.44... I had put in a value of 300 for the roasted barley. But even if I change the math based on that, I'm still getting 55% and ultimately a pH value of 5.40.

I also made the mistake of adding the Aromatic malt as a crystal under the grain list. Now when I fix that, the discrepancy between basing the pH on color vs grain is 5.40 vs 5.58

I'm still not sure why that is, but at least now I'm a little closer!

Thanks for taking the time to show me that!
-Pete

 

[ajdelange]

Never rely on beer color for anything relating to the mash as beer color from a given grain bill can vary considerably depending on things like how long you boil, whether you do decoctions or not, how long your rests are the actual colors of the actual grains you are using (or it assumes you are using) and the amount of color the yeast strip out.

You must know the DI mash pH for each grain and the buffering capacity of the grain in the vicinity of the DI mash pH. The DI mash pH is the more important but it turns out that for many cases you can simply assume the buffering is -40 mEq/kg•pH and get a pretty good answer if you have fed the program the correct DI mash pH's. It is therefore essential that you get those as closely as you can. Many of the programs estimate this from the color of the malt. Some of them allow you to enter a DI mash pH and you should use one of those. Get the pH DI data from the maltsters spec sheet (if it is listed). If not, make a small mash with warm DI water, let it sit half an hour, cool to room temperature and measure pH (with a properly calibrated meter that is known to be stable). Use that number in the program.

As mash is predominantly base malt with relatively small additions of colored malts it is OK to use DI mash pH derived from the color for the specialties. Exceptions arise when the alkalinity of the base malt is being completely offset by the acidity of the specialty malts as in this case the protons supplied by those malts of the same, or greater because of water alkalinity, the the proton deficits of the base malts.

 

[Silver_Is_Money]

I had put in a value of 300 for the roasted barley. But even if I change the math based on that, I'm still getting 55% and ultimately a pH value of 5.40.

I also made the mistake of adding the Aromatic malt as a crystal under the grain list. Now when I fix that, the discrepancy between basing the pH on color vs grain is 5.40 vs 5.58

I'm still not sure why that is, but at least now I'm a little closer!

Thanks for taking the time to show me that!
-Pete

Thank you Pete. You are indeed correct in that Roasted Barley is only 300 Lovibond. Aromatic has some remaining diastatic power (about 30 as I recall), so it is closer to being a base malt, and it is not considered a crystal malt. I believe it has sufficient enzymes to convert itself, but not sufficient to convert any non-diastatic mash components, so it needs to be used in conjunction with a high diastatic malt as you are doing with the golden promise (unless you make a batch with a 100% Aromatic grain bill, in which case this can be done with perhaps a 90 to 120 minute mash, and in theory it has just barely enough disatatic enzyme presence to completely convert itself, but I'm not recommending it).

 

[Silver_Is_Money]

Pete, try it in Brewers Friend again, but this time using DI Mash pH values instead of Lovibond colors, and let us know what the calculated mash pH is. AJ is 100% right about this. The road to accurate mash pH predictions travels through the individual malts DI mash pH's. Use these (my best initial DI mash pH guesses). For real accuracy you will need to pH test each malt in DI water.

DI Mash pH values:
-------------------------
Golden Promise: 5.59
Aromatic: 5.00
Crystal 40: 4.83
Crystal 120: 4.58
Roasted Barley: 4.78

 

[PDevlin75]

Again, thank you for taking the time to give me the info on this! Like I said, I'm just beginning to learn about water chemistry, so you're giving me some good info to work with!

Also, thank you, AJ! More good information! At first this all just seemed way over my head, but I'm starting to pick up little bits at a time. Thanks!

Unfortunately however, I already brewed the beer, and according to your numbers, I may have wound up adding more phosphoric acid than I should have

Ahhh, whatever - I'm sure it'll be fine!

 

[Silver_Is_Money]

You are fine down to pH 5.2, and some even say pH 5.0. What did Brewers Friend say for the pH? Just curious, as I did give you some rather low (vs. more commonly accepted) DI mash pH values, and the reality is that you probably mashed in at a higher pH.

Despite the values I gave you being low vs. accepted norms, they did come from my regression of a large US maltsters data, and they do closely reflect the data which I was given by said maltster.

 

[PDevlin75]

You are fine down to pH 5.2, and some even say pH 5.0. What did Brewers Friend say for the pH?

Awesome! The numbers you provided gave me a pH of 5.5. That is without any additions to my mash water

Based on numbers I was working with previously, I added about 7 tsp (35 ml) of phosphoric acid, aiming for a pH of 5.4. With the numbers you gave me, combined with the same amount of acid, that brought brewer's friend's calculation down to a pH of 5.34... So I guess that ought to be just fine then!

 

[Silver_Is_Money]

5.34 is nigh on perfect! I would draw the line at pH 5.2 and adjust only if software goes below 5.2. Use that as your floor.

 

[Silver_Is_Money]

This web link was just posted in another thread, but has great relevance here:

http://brulosophy.com/2017/01/30/wa...he-impact-of-low-mash-ph-exbeeriment-results/

I'm shocked! Panelists could not distinguish a beer intentionally and massively over-acidified and then mashed at pH 4.45 from an identical beer mashed at pH 5.33. And on top of this, the panalists could not tell that lactic acid had been used, despite the common logic that too much of it will taint the beer with an undesired and pronounced flavor contribution.

The amount of 88% lactic acid intentionally added to hit 4.45 pH is ballpark the equivalent of adding about 200 ml of 10% phosphoric acid. And these were 5.5 gallon batches.

And the most amazing thing is that the batch came out fine despite this abuse.

 

[Silver_Is_Money]

It turns out after some checking that the color-pound contributions of the various base malts are not to be excluded.

 

[jmark]

This web link was just posted in another thread, but has great relevance here:

http://brulosophy.com/2017/01/30/wa...he-impact-of-low-mash-ph-exbeeriment-results/

I'm shocked! Panelists could not distinguish a beer intentionally and massively over-acidified and then mashed at pH 4.45 from an identical beer mashed at pH 5.33. And on top of this, the panalists could not tell that lactic acid had been used, despite the common logic that too much of it will taint the beer with an undesired and pronounced flavor contribution.

The amount of 88% lactic acid intentionally added to hit 4.45 pH is ballpark the equivalent of adding about 200 ml of 10% phosphoric acid. And these were 5.5 gallon batches.

And the most amazing thing is that the batch came out fine despite this abuse.

I'm glad that's just one data point!!! That seems incredibly difficult to believe.

 

[Silver_Is_Money]

I'm glad that's just one data point!!! That seems incredibly difficult to believe.

I'm glad that it shows that low mash pH is not likely going to ruin a batch. I'm now leaning toward the opinion that high mash pH can be more detrimental than low mash pH. Particularly after RPIScotty (www.********************) has stated that he targets his mash pH at 5.2 for all styles, and then adjusts to hit 5.2 for all batches, and with great results.

 

[ajdelange]

Most people feel that lowering pH makes 'all the flavors brighter'. Some feel that if pH is lowered too much the flavors become too bright. These are mostly those trying to advocate tight control around a favorite pH. I roundly applaud the brighter flavor observation but have never explored mash pH as low as 5.2 in order to see if they are 'too bright'. 5.4 - 5.5 works for me but I won't opine that 5.35 might not work even better.