Definition - What does Tartaric Acid mean?
Tartaric acid is one of the three naturally occurring acids in wine grapes (the other two are Malic and Citric acids). Tartaric is the most important acid, as it plays a prominent role in the stability, color and feel of a wine. It is also the subtlest acid to taste in a wine; tartaric acid presents very little “flavor” but contributes significantly to the “tart” sensation on the tongue.
Tartaric acid is also the source of “wine diamonds”, crystallized deposits of potassium acid salt that can be found in the bottom of wine bottles or on the corks if the winemaker has not allowed them to precipitate out during bottling.
WineFrog explains Tartaric Acid
Tartaric acid lowers wine’s pH level, killing harmful bacteria and creating a safe, healthy wine. It stabilizes the chemical balance of a wine, allowing for longer aging. When a wine has appropriate levels of tartaric acid, it will be a deep, clear color; without the correct levels the color will fade and be muddy.
Tasting tartaric acid is a bit more challenging. Unlike other acids, Tartaric acid doesn’t have a specific “flavor”. Instead, it has a more tactile effect. It contributes significantly to the tartness of a wine – that mouth puckering sensation that means high acidity.
Tartaric acid starts in the grape. The levels are consistent from flowering to ripening, right through to harvest. However, the overall pH level of the grape will increase as it ripens. The strength of tartaric acid is significantly reduced by dilution within the berries. As the grape ripens, juice and sugars mix with the acid.
Winemakers are tasked with picking the grapes at the appropriate moment, when the tartaric acid strength is ideal for creating a balanced, quality wine. In cooler climates, this is easier, since ripening is slowed by the cold temperatures; warmer climates tends to have a more challenging time, since high temperatures increase the speed of the ripening (which is one of the reasons why warm climate wines tend to have higher sugar and alcohol levels).
Another factor is the natural predisposition of a variety to contain Tartaric acid. Some grapes, like Palomino, produce high levels of tartaric acid; while others, like Pinot Noir, produce lower levels.
If the grapes are harvested too late and the tartaric levels (or overall acid levels) are too low, winemakers will add tartaric acid crystals to the fermenting juice to balance the sugars and alcohol. These crystals are naturally occurring precipitates from previous wines.