pH Temperature Compensation

[cooper]

When we take a pH reading during the mash we always cool the sample to whatever ambient temperature the calibration solution is, then take the reading. Do we want to adjust that reading to what the pH reading would be at mash temperature and adjust accordingly? I was under the impression that we want to shoot for a pH reading of around 5.20 for the mash and I've always assumed that was after the wort was cooled to room/ambient temperature.

So if I take a sample about 15 minutes into the mash, cool it to room temp, then take a reading and it's 5.43, does that mean that my mash pH is actually 5.08 and therefore too low if my goal is 5.20?

I ask because that was mentioned in this article (https://byo.com/article/the-principles-of-ph/) so I figured I'd see what you guys thought.

"Since pH changes with temperature, you need to compensate for this change. At room temperature, the pH of the cooled sample will be around 0.35 units higher than the pH at mash temperature. Thus, if you get a reading of pH 5.60 for your cooled sample, your corrected reading would be pH 5.25. (You need to do this even if your meter has temperature correction.)"

If this is the case then I've been doing it wrong!

 

[Silver_Is_Money]

The ideal mash pH target range shifts downward by the same degree for mash temp readings vs. room temperature readings. So its pretty much a moot point.

But in my opinion, if you intend to take precision pH readings at mash temp, you had best calibrate your meter at mash temp also. I.E., heat the two standardized pH calibrants to 150-156 degrees F.

 

[cooper]

The ideal mash pH target range shifts downward by the same degree for mash temp readings vs. room temperature readings. So its pretty much a moot point.

But in my opinion, if you intend to take precision pH readings at mash temp, you had best calibrate your meter at mash temp also. I.E., heat the two standardized pH calibrants to 150-156 degrees F.

Thanks for the reply!

Like most I have no intentions of taking pH readings at mash temps. The advice to make the temp compensation from the article just threw me off as he’s recommending adjusting the reading and I don’t know anyone who actually does that unless they take a reading at mash temp.

So it makes sense that one would not have to make the adjustment if they calibrate their meter at mash temps.

 

[stickyfinger]

Yeah, I always heard 0.3-0.35 units is the room temp to mash temp shift. I also used to target 5.2 and so tried to hit 5.55 at RT. I don't know if it makes that much difference honestly. I just shoot for 5.4-5.5 at RT now and it seems to work. I remember reading something where someone tested the pH shift with a meter used at RT and at mash temp. They found the shift wasn't as large as 0.35 units. It's a faint memory though.

When we take a pH reading during the mash we always cool the sample to whatever ambient temperature the calibration solution is, then take the reading. Do we want to adjust that reading to what the pH reading would be at mash temperature and adjust accordingly? I was under the impression that we want to shoot for a pH reading of around 5.20 for the mash and I've always assumed that was after the wort was cooled to room/ambient temperature.

So if I take a sample about 15 minutes into the mash, cool it to room temp, then take a reading and it's 5.43, does that mean that my mash pH is actually 5.08 and therefore too low if my goal is 5.20?

I ask because that was mentioned in this article (https://byo.com/article/the-principles-of-ph/) so I figured I'd see what you guys thought.

"Since pH changes with temperature, you need to compensate for this change. At room temperature, the pH of the cooled sample will be around 0.35 units higher than the pH at mash temperature. Thus, if you get a reading of pH 5.60 for your cooled sample, your corrected reading would be pH 5.25. (You need to do this even if your meter has temperature correction.)"

If this is the case then I've been doing it wrong!

 

[ajdelange]

When we take a pH reading during the mash we always cool the sample to whatever ambient temperature the calibration solution is, then take the reading. Do we want to adjust that reading to what the pH reading would be at mash temperature and adjust accordingly? I was under the impression that we want to shoot for a pH reading of around 5.20 for the mash and I've always assumed that was after the wort was cooled to room/ambient temperature.

We want to shoot for the room temperature (because that's where we want to measure it) mash pH that makes the best beer. This is generally 5.4- 5.6. We don't really care about what the actual mash pH is unless we are scientists studying the efficacy of enzymes. That will depend on the grains mashed (grains have different pH vs temperature slopes) and the mash temperature (do you dough in in the cold, at a ß- glucan rest temperature, protein rest temperature, saccharification rest...?).

So if I take a sample about 15 minutes into the mash, cool it to room temp, then take a reading and it's 5.43, does that mean that my mash pH is actually 5.08 and therefore too low if my goal is 5.20?

Probably not but it will be lower than 5.43. If you get 5.43 at room temperature you are in good shape.

I ask because that was mentioned in this article (https://byo.com/article/the-principles-of-ph/) so I figured I'd see what you guys thought.

I think you ought not to take that article too seriously. For example, they seem to think that a pH electrode is powered and that the power should be turned off before removing it from a solution. The electrode itself is, in fact, completely passive. No power is supplied to it (though in modern, fancy meters there may be powered electronics in the head to which the electrode is mounted).

"Since pH changes with temperature, you need to compensate for this change. At room temperature, the pH of the cooled sample will be around 0.35 units higher than the pH at mash temperature. Thus, if you get a reading of pH 5.60 for your cooled sample, your corrected reading would be pH 5.25. (You need to do this even if your meter has temperature correction.)"

Another example. Your pH difference could be between 0.2 and 0.5 depending on the malts and the mash temperature. And you don't need to know what it is as mash temperature anyway.

If this is the case then I've been doing it wrong!

If you have been getting room temperature readings between 5.4 and 5.6 you have been doing nothing wrong.

 

[cooper]

Thanks AJ! The article just threw me for a loop when it suggested we all should be subtracting .35 from our cooled samples in order to get the actual pH reading. Which is why I came back to you guys for clarification.

 

[Silver_Is_Money]

Thanks AJ! The article just threw me for a loop when it suggested we all should be subtracting .35 from our cooled samples in order to get the actual pH reading. Which is why I came back to you guys for clarification.

I believe that what the article is trying to say (rather confusingly perhaps) is that the actual pH reading is what you will get only when you read pH at mash temperature (or alternately, if you subtract ~0.35 from room temperature pH readings you can ballpark approximate actual pH values), but we aren't (and our software isn't) really interested in determining the actual (mash temperature) pH reading. Rather, we (and our software) are only interested in adjusting for and ultimately seeing a reading that falls between 5.2 and 5.6 pH when measured at room temperature.

For those who do read mash pH directly at mash temperature, the ideal target range is closer to 4.9 to 5.3 pH. But you can't 'directly' use software pH adjustment guidance if you choose to take this route.