Measuring Acidity

[scbeec]

I understand from reading The Compleat Meadmaker (which has been sitting within arm's reach for the last year), that Dan McFeeley has a method of measuring acidity that is more accurate than titration (which doesn't work with mead because of the fading endpoint reaction). I wasn't able to find this info by using the search and was hoping someone could point me in the right direction. Thanks.

 

[Dan McFeeley]

I understand from reading The Compleat Meadmaker (which has been sitting within arm's reach for the last year), that Dan McFeeley has a method of measuring acidity that is more accurate than titration (which doesn't work with mead because of the fading endpoint reaction). I wasn't able to find this info by using the search and was hoping someone could point me in the right direction. Thanks.

Hello Scbeec --

There's two ways to go with this, simple and complicated.

The simple way is use a pH meter to give you an idea of the acidity of the honey must. It won't give you grams/liter of of gluconic acid, but in meadmaking that's really not necessary. Gluconic acid, the primary acid in honey, has a much different effect on the overall flavor profile of a finished mead, as compared to the other organic acids found in wines, tartaric, malic and citric. Because of this, acid additives in mead act more as flavor adjuncts, as compared to their use in winemaking to adjust balance.

In other words, check the pH of the must to make sure it's in a good range (3.7 to 4.0, or even a little higher is ok). After that, leave it alone. Finish out the mead, taste, and add acid if you like but only to taste, and as though you were making a metheglin.

The more complicated way was developed by John W. White jr. in 1958, and became a standardized means of measuring he acid content in honey. Since the gluconic/lactone reaction persists in mead, I'm assuming the method is equally valid in mead.

I can list the method if you like, but it's long and complicated, and will require familiarity with analytical procedures in chemistry. Believe me, you're better off working with a pH meter. ;D

I had an article published in the September/October 2007 issue of Zymurgy that lists fuller details on all thisk inclduding John W. White jr.'s method. It's fairly lengthy, but if you locate it (check a local homebrew shop, sometimes book stores like Barnes and Noble will carry Zymurgy), it should answer a lot of your questions.

Aside from that, feel free to ask any other questions here!

 

[scbeec]

Thanks for your response, Dan. I'm using a pH meter, but want to know what's happening - really happening - in the mead. I've done titrations before so I'm comfortable with that and while I didn't get great marks in organic chem, I did eventually pass. I wouldn't mind knowing the procedure if possible. I'll have a look for your article next time I'm in the LHBS.

In my first batch, which is 24 days old, I found the pH dropped to 3.39 on the 2nd day after pitching, but the fermentation was still fine. It's just slowing now. I don't understand why the low pH didn't affect it - I'm using K1-V1116. Here's what I did:

9.36 L (12 kg) Allspice-Infused Wildflower Honey
36 L Spring Water
12 g Fermaid
10 Campden Tablets
11 g K1-V1116 - rehydrated in 110 g water for 20 minutes at 35-40 degrees C
OG 1.090
Room Temp is about 22 deg C
initial pH 5.24

This low pH is part of why I want to find out TA, plus I'd like to learn about how it affects the taste - that way, I'll know how to adjust it if necessary. Thanks for any :help: .

 

[Dan McFeeley]

Here's the procedure:

A 10 gram sample of honey is diluted with 75 mg CO2 free distilled water and the initial pH recorded. The solution is titrated to pH 8.5 with 0.05N NaOH from a 10 ml microburet at a rate of 5 ml/minute. Once the pH reaches 8.5, 10 ml of 0.05N NaOH is added to the solution, then, without delay, is back titrated to pH 8.3 with 0.05N HCL from a 10 ml microburet.

From this procedure, free acidity, lactone content and total acidity in miliequivalents can be determined. Free acidiity is the amount of NaOH from the buret minus the blank correction. Lactone content is the amount of HCL subtracted from 10 ml. Total acidity is free acidity plus lactone content.

Some time back, some one whose name I can't recall, posted some info on the Mead Lovers Digest on relations of taste and pH. Sorry, I can't recall anything more than that, and to the best of my knowledge, there hasn't beeen similar info posted or published elsewhere.

 

[Dan McFeeley]

This might be helpful -- take a look here:

http://www.meadmadecomplicated.org/science/pH_acidity.html

 

[Dan McFeeley]

Some time back, some one whose name I can't recall, posted some info on the Mead Lovers Digest on relations of taste and pH. Sorry, I can't recall anything more than that, and to the best of my knowledge, there hasn't beeen similar info posted or published elsewhere.

Just had a memory jog -- it was Micah Millspaw. I tried doing a search for his post, sorry, couldn't find it.

 

[scbeec]

Thanks so much Dan - much appreciated.