Because titratable acidity (TA) and pH both measure acidity, they tend to move together. Higher TA usually means lower pH and vice versa. Sometimes that relationship breaks down, and that can drive winemakers and meadmakers crazy.
How are pH and titratable acidity different?
TA and pH are two different ways of measuring how acidic your wine is. Because they each measure acidity in a different way, they tell you about different effects that acid will have on your wine. Without getting into the chemistry, TA tells you how acidity will affect the taste. Does a wine taste tart? That’s high TA your tasting. Too flabby? That would be low TA.
What about pH? It most directly measures how the acidity will affect your wine’s microbial stability. As pH rises above 3.5, microcritters have an easier time taking up residence in your wine. Below 3.5, and the wine becomes much more stable. Cultured wine yeasts have an advantage over many other molds, bacteria, and fungi in that they can thrive as long as the pH remains above 3.0, so keeping fermenting wine at a pH between 3.0 and 3.5 goes a long way towards preventing spoilage.
If pH is too high, you can push it down by adding acid. To low, and you can neutralize acid. TA corrections are similarly straightforward, but what do you do when TA and pH need adjustment in opposite directions? A high pH and high TA can mean a tart wine that is vulnerable to spoilage. Try to fix one problem and you’ll make the other one worse. Low pH and low TA is easier to deal with, but both cases need special handling.
Using sugar to balance a high TA wine
I had a high TA – high pH problem with my cherry wine, and I just recently noticed it in my Merlot. The way I handled it was to leave the acidity alone and address the harsh taste by balancing the wine with sugar. It’s not a perfect solution, but it let me address the tart taste without making the pH even worse. I’ve done some more research since then and have another idea that might work: treat with phosphoric acid to push down the pH.
Using phosphoric acid to lower pH
Adding most any acid will usually push the pH down, but phosphoric acid gives you much more bang for the buck than the acids we normally use (citric, malic, and tartaric). This gives us the ability to lower a wine’s pH with only a negligible impact on it’s TA. Now we can tackle a high TA – high pH wine by first neutralizing enough acid to get the TA where we want it, then adding phosphoric acid to push the pH down. You will have to conduct trials on precisely measured amounts of wine to know how much a given amount of phosphoric acid will move the pH.
You’ll also have to be careful! While this stuff is non toxic, it can be very dangerous to handle. If you’re not qualified to handle corrosive chemicals, then you shouldn’t use this option.
Low TA – low pH in mead
If you run into high TA – high pH, it’s probably in a wine. You’ll see the flip side of that coin in mead. You can tackle that by adding cream of tartar before pitching the yeast and delaying any acid additions until after it has fermented out.
So if the mead is too flabby for your taste, you can improve it by adding acid. To avoid pushing down the pH so much that your yeast can’t ferment, adjust the TA after the mead has fermented to dryness. A low pH won’t matter nearly as much, then, and can keep your mead stable for extended aging.
You can also a teaspoon of potassium bitartrate (cream of tartar) to each gallon of must. This will improve the buffering capacity of the fermenting mead and keep the pH from dropping so much. It’s still a good idea to delay any acid additions until after the yeast have done their work.