Acidity adjustments that hold: tartaric acid, deacidification and pH

Acidity holds a wine together — its freshness, its colour, its microbial stability and how well SO₂ works all track with it. Warm vintages leave musts flat and high in pH; cool ones leave them sharp. Correcting acidity is routine, but doing it so it "holds" through fermentation and cold means understanding the difference between TA and pH.

TA and pH are not the same thing

• Titratable acidity (TA) — the total acid available to neutralise, reported as g/L tartaric. It tracks perceived sourness.
• pH — the strength of the free acidity, and the number that governs colour, SO₂ efficiency and microbial risk. A wine can have "enough" TA and still sit at a dangerous pH.
• Adjust with both in view: you are usually chasing a pH target, using TA as the lever.

Acidifying with tartaric

Tartaric acid is the acid of choice because it is the grape’s own strongest acid, it is not metabolised by bacteria (unlike malic), and it drives pH down efficiently. As a first approximation, adding 1 g/L of tartaric raises TA by about 1 g/L, though part of it later precipitates as tartrate salts during cold, softening the net effect. Add before or early in fermentation for the best integration.

Legal and practical limits apply. Over-acidifying is hard to undo, and much of a large tartaric addition can drop out in cold stabilisation — bench-trial to the pH you actually want.

Deacidifying with carbonates

When TA is too high, calcium carbonate (CaCO₃) or potassium bicarbonate (KHCO₃) neutralises acid and raises pH. Roughly, ~0.67 g/L of CaCO₃ lowers TA by about 1 g/L. Carbonates preferentially remove tartaric acid and can leave residual calcium that precipitates slowly later, so go gently and let the wine stabilise before the final trim.

Every acid or carbonate addition in GrapeFlow is tied to the lot with the before/after numbers, so the correction is traceable and repeatable next vintage.

Confirm with bench trials and your local limits on acidification and deacidification before treating a tank.