Acid Addition DetailsWhy adjust acid?
Acidity is an essential aspect of wine balance, and is present naturally in grapes as Tartaric acid and Malic acid. Acid is added to musts and wines to correct natural deficiencies, especially in grapes from warm climates.
Tartaric is the most common acid added to musts and wines, and the addition should be made after a bench trial is done to confirm the desired acid level. Tartaric acid contributes to cold instability, so care should be taken when adding Tartaric acid to white wines close to bottling.
Malic acid is also found in grapes, and is typically converted to lactic acid during Malolactic Fermentation. Malic acid additions can contribute to microbial instability if the wine is already ML dry, but it's a good choice for additions being made to already cold-stable whites that will be membrane filtered.
Citric acid is found in trace quantities in grapes and is not typically added to musts or wines, though some winemakers choose to use it. Citric acid is converted into diacetyl by lactic acid bacteria, so elevated levels can result in an increased buttery character if added before MLF. Adding citric acid after MLF can stimulate lactic acid bacteria (it's food to them, after all)... so maintain good SO2 levels and sterile filter, if you can.
In any case, you should always set up and taste bench trials before making an addition to the production lots.