High pH rise during mash

[Chris-18]

Hey all

I have been brewing some NEIPA's for a while now, and I have been observing some strange problems in my mash. I get a fairly high pH rise throughout the mash, and I need to keep adding acid to knock down the pH to the proper range.

So the grain bill contrains:
Maris Otter
Pale ale malt
Wheat malt
Flaked oats

So after adding all the minerals and treating the water with CaSO4 and a tiny bit of lactic acid, the pH settles at 5,2 after mashing in.
However throughout the mash, the pH looks like this:

10 min = 5,2
20 min =5,29
30 min = 5,32
40 min = 5.37
50 min = 5,41
60 min = 5,5

I have a hard time explaining why this happens. My theory is that some of the buffering capacity is lost and the effect of the lactic acid is broken down during the mash, but I have no idea why this happens.
I use 80% lactic a few ml at a time, I usually use a maximum of 5 ml for the entire batch of 20 L.

I use a digital pH meter and it has been calibrated recently and it has ATC, so it's not a pH meter error, it seems to be a real effect in the mash.

Do any of you have any idea why this happens? I have a very hard time getting a stable mash pH.

 

[ajdelange]

In a situation like this the early suspicion focuses on the pH meter. It is not sufficient that you have calibrated it sucessfully/ It must be able to hold that calibration. To insure that it does perform the stability test described at https://www.homebrewtalk.com/showthread.php?t=302256. When your meter passes that you can be sure that the pH changes you have observed are real. If the stability test exhibits drift in buffer that is a good sign that your elecctrode's junction is blocked or that the electrode is at end of life and needs to be replaced.

Now drift of pH during the mash is normal. Think about what happens here. You make an acidic solution (by adding lactic acid to your mash water) and then dump basic malt, in the form of ground particles, into it. When you present that to your pH meter it initially sees the acid in the mash water and the reading is low. As time progresses the water permeates the malt particles, hydrates and bursts the starch granules and their contents (and the basic substances in them) begin to pass into solution. This takes time and so we see a rise in pH as the mash progresses. Usually, however, it stabilizes (or largely stabilizes by which I mean creeps up 0.01 or 0.02 pH over 5 minutes) by the end of the first half hour. Your data for the first half hour look perfectly normal to me. The pH rising by more in the second half hour than the first does not look normal and that's what makes me suspect your electrode stability.

 

[Chris-18]

Ah yes, that late rise makes sense if the pH meter isn't up to the job!
I will give that a check for sure.

If I were to make an imperial stout for example, where you use a lot of roast malts, which contribute a lot of acidity, and I still observe the same rise at the end of the mash, would that also confirm the pH meter suspision? I only ask since I have an imperial stout planned for next week.

Also I have read a lot of your work on water chemistry AJ, and I must say I really appreciate all the effort you have made! It really helped me understand water chemistry a lot better. So thanks for that as well