Any pointers on how best to utilize a pH meter?

[Gavin C]

My first brew using a pH meter was this morning.Hach Pro+. This is one of the pH meters @AJDelange has recommended in various posts in the brew science forum.

In addition to the meter I purchased the following

From hach.com
Buffer solution pH 7.00 in pillow form
Buffer solution pH 4.01 in pillow form

From amazon.com
Storage solution
Cleaning solution
Small borosilicate beakers in which to mix

From thermoworks.com
A green Thermapen on sale for Paddy's Day

pH Meter and associates


Being new to the meter and not thoroughly doing my homework I was unsure of the steps involved but assume prerequisites are an accurate water report; I got a Ward Labs report a few weeks ago, and a water chemistry tool; I used Bru'n Water.

The pH meter was easily calibrated using the two solutions.

Calibrating the meter with pH 4.01 solution

A mash sample was taken 5 minutes into the mash and read 5.5. This was inline with what Bru'n water had predicted.

Using the software tool I calculated a required addition of lactic acid targeting a pH of 5.3-5.4 (seems to be a decent target for a blonde ale but I am a novice so am open to corrections)and checked the mash 5 mins after its addition. The pH was a hair under 5.3 so some work is needed on my part.

Adjusted mash pH


Perhaps the timing of my tests is off. I was keen to take an early reading as this was to be a 40 minute mash and I figured if I waited too long conversion may well have taken place before the addition of the acid. Based on some recent posts by @RM-MN it very well may have.

My mash efficiency was my highest to date at a hair over 92% and ensuing BH efficiency of 83% (rounding to nearest point)

I had chosen a light beer, Biermuncher's Centenial Blonde so as to allow for a possible higher efficiency than my estimated 75%. The result will still hopefully be a tasty easy drinking blonde ale with an OG just a little higher than planned at 1.045

Any pointers in how to improve the process and eliminate any glaring errors to which I am ignorant of would be greatly appreciated.

 

[ajdelange]

A mash sample was taken 5 minutes into the mash and read 5.5. This was inline with what Bru'n water had predicted.

Mash pH's tend to drift (usually upward if no acids have been added to mash or water) for 15 - 30 minutes) so the tip here would be to keep checking to see what happens.

Using the software tool I calculated a required addition of lactic acid targeting a pH of 5.3-5.4 (seems to be a decent target for a blonde ale but I am a novice so am open to corrections)and checked the mash 5 mins after its addition. The pH was a hair under 5.3 so some work is needed on my part.

It is difficult to thoroughly mix acids (or anything else) into a mash so try to avoid that if you can. The best way to do that is to do what you did with the full size mash with a small (1 lb) test mash. Dough in with warm water, wait, check pH, adjust with acid if too high, mix thoroughly and wait, check again. When you get the test mash pH to your liking note the amount of acid it took and scale that up for the full brew length. You should be pretty close in the mash tun. If within 0.1 or better of target in a mash don't try to correct on the fly but rather make a note that you will need a bit more or less of acid next time you brew this beer. The amount required to be added is approximately ∆pH*(W/2.2)*40/12 mL of lactic acid where ∆pH is the desired pH reduction (negative sign if pH is to be increased) and W is the weight of the grain in pounds.

Perhaps the timing of my tests is off.

When you add acid the pH tends to shoot downwards and then inch up for 15 - 30 minutes as it is absorbed by the grains and reacts. Had you waited longer (or, better yet, taken additional readings) you might well have seen the pH creep up over 5.3 after the acid addition.

 

[Gavin C]

Mash pH's tend to drift (usually upward if no acids have been added to mash or water) for 15 - 30 minutes) so the tip here would be to keep checking to see what happens.

It is difficult to thoroughly mix acids (or anything else) into a mash so try to avoid that if you can. The best way to do that is to do what you did with the full size mash with a small (1 lb) test mash. Dough in with warm water, wait, check pH, adjust with acid if too high, mix thoroughly and wait, check again. When you get the test mash pH to your liking note the amount of acid it took and scale that up for the full brew length. You should be pretty close in the mash tun. If within 0.1 or better of target in a mash don't try to correct on the fly but rather make a note that you will need a bit more or less of acid next time you brew this beer. The amount required to be added is approximately ∆pH*2.2*W*40/12 mL of lactic acid where ∆pH is the desired pH reduction (negative sign if pH is to be increased) and W is the weight of the grain in pounds.



When you add acid the pH tends to increase upwards for 15 - 30 minutes as it is absorbed by the grains and reacts. Had you waited longer (or, better yet, taken additional readings) you might well have seen the pH creep up over 5.3 after the acid addition.

Thanks so much. I will do this for my next brew. Never thought of a scaled minimash. The equation will help enormously. Searched to no avail for something comparable.

Good to know I may not have undershot my target mash by too much.

Does a thinner mash facilitate easier homogenization with regard to mash pH adjustment and subsequent measures? I BIAB; 7.38 gallons for 8.5 lbs of grain this last mash.

Thanks again for the continuing education. It is truly appreciated.

 

[eric19312]

The amount required to be added is approximately ∆pH*2.2*W*40/12 mL of lactic acid where ∆pH is the desired pH reduction (negative sign if pH is to be increased) and W is the weight of the grain in pounds.

I am just starting my second cup of coffee and seem to be math impaired this morning. Yesterday I measured pH of 5.6 and added 1/2 tsp lactic which took me to 5.3.

I just tried the calculation above to see what I should of added to get to 5.4...

(5.6-5.4) x 2.2 x 23.5 x 40/12 = 34.5mL = about 7 tsp

Glad I didnt do that...am I doing the equation wrong?

 

[ajdelange]

I am just starting my second cup of coffee and seem to be math impaired this morning.

It isn't you.

Yesterday I measured pH of 5.6 and added 1/2 tsp lactic which took me to 5.3.

I just tried the calculation above to see what I should of added to get to 5.4...

(5.6-5.4) x 2.2 x 23.5 x 40/12 = 34.5mL = about 7 tsp

Glad I didnt do that...am I doing the equation wrong?

Nope. I had you multiply to convert lbs to kg when I should have had you divide. The formula is

(5.6-5.4) x (23.5/2.2) x 40/12 = 7.1 cc which is about 1.4 tsp

The 40 mEq/kg•pH is fairly typical for base malts. Some have higher (46) and some lower (31) but your observed ∆pH = 0.3 for 1/2 tsp (2.5 mL) just doesn't make sense implying buffering of 12*2.5/(23.5/2.2)/0.3 = 9.4.

No malt has buffering that low so it is probable you took the pH reading too soon after adding the acid (it can take up to 30 minutes to react completely). Nevertheless prudence dictates that one shouldn't blindly plug into the formula, even as corrected, and just dump that amount of acid into one's next mash. Perhaps one half of it would be a better idea. Depending on how far that goes towards closing the gap one can decide to use the full amount or 3/4 or whatever on the next brew.

 

[ajdelange]

Does a thinner mash facilitate easier homogenization with regard to mash pH adjustment and subsequent measures?

Yes, it should.