Something about Tartaric acid
Acids are very important structural components of wine. If a wine is too low in acid, it tastes flat and dull. If a wine is too high in acid, it tastes too tart and sour. Usually, the winemaker can easily manipulate the acidity.
The principal acids found in wine
The principal acids found in grapes, and therefore wine, are tartaric acid, potassium hydrogen tartrate, malic acid and potassium hydrogen malate. Since potassium hydrogen tartrate and potassium hydrogen malate are derivatives of DL-tartaric acid and malic acids, respectively, only tartaric and malic acids will be discussed with the understanding that their derivatives are also present in wine. The relative amounts of tartaric and malic acids vary depending on the grape variety and on where the grapes are grown. For example, in Burgundy, the Chardonnay has a lower concentration of malic acid than the Chardonnay grown in the Napa Valley of California. We will come back to that later.
Volatile acidity
Both D- tartaric acid and malic acids are nonvolatile which means that they do not evaporate or boil off when the wine is heated. This is to be distinguished from volatile acidity (VA) in wine that represents acetic acid (vinegar). Acetic acid does boil off when heated and high VA is undesirable in a wine. A VA of 0.03-0.06% is produced during fermentation and is considered a normal level.
Climate: acid VS sugar
L- Tartaric acid and malic acids are produced by the grape as it develops. In warm climates, these acids are lost through the biochemical process of respiration. Therefore, grapes grown in warmer climates have lower acidity than grapes grown in cooler climates. For example, Chablis (France) produces grapes with high acid because the climate is very cool, while Napa Valley produces grapes with lower acidity because the climate is warmer.