TA and pH Relation

[musty]

Hi all!

I have a pretty solid chemistry background, but from the reading I've done I have yet to learn how TA and pH are related. Is it a linear correlation? In making wines, I measure the TA, but I don't take pH readings (unless pH is directly related to TA sans a mathematical translation).

Piggy-backing: if pH and TA are not directly related, is it possible to adjust the pH without affecting the TA content?

Bonsai!

 

[pbjosh]

TA and pH are related but do not track together strictly. There is no firm conversion. Most winemakers, over time, dealing with the same fruit from the same vineyards in the same ways, come to be able to predict the interaction year after year. It literally varies with variety, clone, ripeness, site, etc.

TA generally impacts taste / balance more, and pH is more important to microbial stability (most folks aim for 3.75 or lower finished pH), for a couple of reasons including the fact that sulfur becomes less effective at higher pHs, and does so exponentially.

As far as adjusting them independently of each other, you can monkey a little by acidulating with tartaric vs. l-malic vs. d-malic. Both will move, but not the same relative to each other with each acid. It will also depend on if your wine is going to go through malo.

I assume you're trying to lower your pH without getting too much TA?

 

[musty]

Thanks so much!

Yes, I was curious about lowering the pH without bringing up the TA. Is this a common adjustment for the home-winemaker, or does TA adjustment suffice?

 

[pbjosh]

What exactly are you planning on fermenting and what is your starting chemistry like?

I'm not sure what is prevalent among home winemakers, but I can say that acidulating to keep the finished pH under about 3.7-3.8, where possible, is commonplace in the wine industry.

One aside- if you can sterile filter, you can be sloppier with your pH and be safe w.r.t. microbial contamination, but ageability and balance will still suffer.

BTW, Tomato wine? Really?

 

[gregbathurst]

TA and pH would generally follow each other in the same wine but in comparing different wines it would vary a lot. TA is more important for flavour, this is the part you taste, while pH is important for SO2 additions and stability of the wine. Winemakers aim for a pH around 3.4 because that makes SO2 work better. TA drops as fruit ripens and will lead to a "flabby" taste especially in white wine if allowed to fall too low. how do you measure TA? do you do a titration? and what units do you use - I remember something about 0.1M HCl but haven't done this for a while.

 

[musty]

@pbjosh

Tomato wine: yes! I modified the recipe from the Home Winemakers Companion:

4 lbs organic tomatoes
.5 lbs raisins
~1 gal water
1.5 lbs sugar
1/4 ts grape tannin
1 ts acid blend
1 ts yeast nutrient
1 package Red Star Premier Cuvee yeast

Using this recipe, I had a starting must with a TA of .2% and a Brix of 15, which I adjusted--using acid blend and sugar--to .65% and 21 respectively.

@gregbathurst

I use the Brewcraft Cellar Pro acid testing kit (can't find it online to link, but was purchased from local brew store). It's a titration kit with NaOH @ .2N and phenolphthalein indicator solution @ .5%. NaOH is added 1cc at a time, which represents .1% acidity. When the solution turns pink, I check the amount of NaOH used and multiply cubic centimeters used by .1% to give an acid reading.

I don't test the pH, so I've been going by the TA for acidity, and I haven't been too picky with Campden usage (.5 pills / gal). Does this methodology seem sound? Should the pH be tested as well or does my x% above provide me with info needed? I guess this is my main question.