g/L= (target TA − current TA) × equivalent weight of the acid /75 g = g/L × volume_L
TA is reported as tartaric, so a gram of tartaric acid per litre raises TA by
one gram per litre and the factor is 1. Malic and citric have lower
equivalent weights (67 and 64, against tartaric's 75), so a gram of either
carries more acidity and you need less of them for the same change. That's
the only correction, and it's why a recipe that says "add 2 g/L of acid"
without naming the acid is under-specified.
Lowering acidity
A target below the current figure returns zero. Taking acid out is
deacidification (potassium bicarbonate, calcium carbonate, or a malolactic
fermentation), and each of those changes the drink in ways an addition
doesn't. Carbonate removes potassium and tartrate together and moves the pH
much further than the TA, and malolactic converts the malic acid instead of
removing it. A negative weight would describe an operation that doesn't
exist.
Acid to raise a titratable acidity to a target.
TA is reported as tartaric, so a gram of tartaric acid per litre raises TA by one gram per litre and the factor is 1. Malic and citric have lower equivalent weights (67 and 64, against tartaric's 75), so a gram of either carries more acidity and you need less of them for the same change. That's the only correction, and it's why a recipe that says "add 2 g/L of acid" without naming the acid is under-specified.
Lowering acidity
A target below the current figure returns zero. Taking acid out is deacidification (potassium bicarbonate, calcium carbonate, or a malolactic fermentation), and each of those changes the drink in ways an addition doesn't. Carbonate removes potassium and tartrate together and moves the pH much further than the TA, and malolactic converts the malic acid instead of removing it. A negative weight would describe an operation that doesn't exist.