pH at mash and room temp?

[BrewyRick]

Hi, I just started to use a pH meter and there is something that confuses me… I bought this guy: http://www.milwaukeeinstruments.com/MW101.html

I brewed last night and here’s what I did:
Measure the temperature of the pH buffer, adjust the ATC to the buffer temp and proceed with the calibration.

I cooled a mash sample to 21 degC, I adjusted the ATC and I took a reading. The reading was 5.75.

Now here’s what confuses me. I have read mix thing about taking a reading at mash vs room temp. From my understanding base on what I read in Gordon Strong book, mash pH at room temp is 0.35 higher than mash pH at mash temp. I was shooting for 5.4 (predicted by bru’n water) so base on my understanding I was right on target.

Am I correct?

Thanks.

 

[mchrispen]

https://sites.google.com/site/brunwater/water-knowledge

Scroll down to 2.1 pH section - it details measuring pH in the brew house - and the relationships between pH and temperature and what role ATC plays.

I chill to room temperature (roughtly 20C) for all of my readings, and note the temperature for later estimation.

You may wish to look at the stabilization process found here - https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/

 

[GotPushrods]

The reading was 5.75.
I was shooting for 5.4 (predicted by bru’n water) so base on my understanding I was right on target.

Am I correct?

No, all of the models currently available (that I'm aware of) reference pH at room temperature.

I do suspect the reading though. What is your grain bill?

I pH of 5.75 would come from an all-base malt mash, with low calcium, possibly some alkalinity, and no acid.

 

[ajdelange]

Hi, I just started to use a pH meter and there is something that confuses me… I bought this guy: http://www.milwaukeeinstruments.com/MW101.html

First thing you need to do is check that your meter is OK. Calibrate it and run the stability check described at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/. This page also has the details on things like what ATC is (and isn't) and how to use a meter properly in the brewing application.

I brewed last night and here’s what I did:
Measure the temperature of the pH buffer, adjust the ATC to the buffer temp and proceed with the calibration.

Your meter does not have ATC. That is why you have to measure and dial in termperatures. The 102 does and will handle this for you automatically - within the limitations of ATC (discussed at the referenced page).

Now here’s what confuses me. I have read mix thing about taking a reading at mash vs room temp. From my understanding base on what I read in Gordon Strong book, mash pH at room temp is 0.35 higher than mash pH at mash temp.

What is mash temp? Is it the temperature of a ß - glucan rest, a protein rest, a low saccharification rest or a high saccharification rest? That's one of the problems with referring pH to mash temperature as opposed to room temperature which is what the majority (but not all) authors etc. do.

As a rule of thumb mash pH climbs 0.0055 pH per degree increase in temperature. Thus if you dough in at 50°C (122°F i.e. protein rest) you would expect the actual pH at that temperature to be (50 - 20)*0.0055 = 0.165 lower than what you would measure at room temperature.

I cooled a mash sample to 21 degC, I adjusted the ATC and I took a reading. The reading was 5.75. I was shooting for 5.4 (predicted by bru’n water) so base on my understanding I was right on target.

Bru'n water, as do the vast majority of people, calculates referred to room temperature. Thus if you measure 5.75 at room temperature you are quite high relative to a Bru'n water estimate of 5.4. But check that the 5.75 reading is valid. The MW101 does not enjoy a very good reputation. It seems that about half of the one's they sell are just fine but the other half have serious problems associated with them. We can always hope that as your unit is new these problems have been ironed out but I would definitely want to do a check.

 

[BrewyRick]

No, all of the models currently available (that I'm aware of) reference pH at room temperature.

I do suspect the reading though. What is your grain bill?

I pH of 5.75 would come from an all-base malt mash, with low calcium, possibly some alkalinity, and no acid.

Grain bill was:

3.49 kg Pilsner (2 Row) Ger (2.0 SRM) Grain 2 85.7 %
0.25 kg Wheat Malt, Bel (2.0 SRM) Grain 3 6.1 %
0.17 kg Honey Malt (25.0 SRM) Grain 4 4.1 %
0.17 kg Munich Malt - 10L (10.0 SRM) Grain 5 4.1 %

Starting water was: (ppm)
Calcium (Ca) 32,5
Magnesium (Mg) 8,3
Sodium (Na) 12,9
Bicarbonate (HCO3) 105
Sulfate (SO4) 25,3
Chloride (Cl) 25,3
Total Alkalinity as CaCO3 87
pH 7.5

I added 1.1 grams of gypsum and 1.8 ml of lactic acid

 

[BrewyRick]

What is mash temp?

Mash temp was 149F


Thanks all. Very useful informations.

 

[Wynne-R]

The MW101 does not enjoy a very good reputation.

Evidence?

The only negative thing I have ever heard was on Amazon. Oh wait.

Lots of us have that unit and it works really well.

I talked to an engineer at Milwaukee, and he told me the MW101 and MW102 were basically the same. The 101 is faster and the 102 is slightly more accurate.

 

[ajdelange]

Evidence?

The only negative thing I have ever heard was on Amazon. Oh wait.

Amazon, other sites that sell it and offer reviews and here on HBT.

Lots of us have that unit and it works really well.

Not a formal tally by any means but it seems to be about half.

I talked to an engineer at Milwaukee, and he told me the MW101 and MW102 were basically the same. The 101 is faster and the 102 is slightly more accurate.

Interesting comment as the 101 is clearly an analogue design requiring that temperature be set in with a pot and slope and offset to be adjusted with a pot while the 102 is clearly a digital design with ATC. I'm sure the electrode is the same and probably the instrumentation amp is doubtless the same in both. I suppose they could be using largely identical circuits with the microprocessor 'crippled' in the 101 and the bridge circuitry for the RTD replaced with the gain control elements. Wouldn't know unless I took one of each apart.

Reviews on the 102 do not seem to indicate the level of problems as with the 101.

 

[Dirty]

Bru'n water, as do the vast majority of people, calculates referred to room temperature.


This is an issue I'm having also.

All the given ph reading that we are shooting for as brewers (Mash, Boil, Sparge, ect) are all at room temp.

So if i have a 21 degree cooled mash sample at a ph of 5.4 than the actual ph of the mash at 70 degrees is (70-21)*.0055 or 5.67?

So every recommended ph value for a particular phase in the brewing process is always at room temperature?

Thanks

Chris

 

[ajdelange]

T'other way round. If you measure 5.4 at 21 the pH at 70 is approximately

5.4 - 0.0055*(70 - 21) = 5.13

 

[Veedo]

I use the mw101, its been a good meter although I have had to change the probe after 16ish months. Other than that it cals fine and when compared to a more expensive meter I have at work, it matches.