Acidity is an essential constituent of wine. This is what gives the impression of freshness and the sour or tangy side of a white, a rosé or even a red wine. And we know it perhaps less, but the acidity also contributes to slow down the process of deterioration of the wine. Explanations.
Just bite into a lemon to take full measure of the acidity contained in citrus fruit. The reaction is so strong that it triggers excessive salivation sometimes just thinking about it. Acidity is measured as a function of pH. In the case of wine, this oscillates between 3 and 4. By comparison, the pH of water is 7, and that of lemon is 2.6. The lower the pH, the stronger the acidity.
So, for chemistry fanatics, a pH of 3 is 10 times greater than a pH of 4. Whereas a pH of 4 is 10 times greater than a pH of 5. But I’m digressing…
So back to our acids in wine. Mainly, there is tartaric acid (sweeter like in banana), malic acid (fruity like a green apple) and citric acid (like in lemon).
Acidity in the vineyard
The longer a winemaker leaves the grapes to ripen in the vineyard, the more the acidity in the berry will decrease (from 1 to 3%), and the more the sugar level will increase (from 4 to 25%). This allows the producer to “play” with the harvest date depending on the year, whether hot or cold. If he picks early, the grape will be more acidic. If he picks later, the sugar level will be higher. It is a choice that must be made according to many parameters.
Acidity during vinification
When the grapes arrive at the estate for vinification, again, the winemaker has some power over the acidity of his finished product. If he wants to reduce the biting malic acid (this impression of biting into a green apple) he can adjust everything with malolactic fermentation which aims to transform malic acid into lactic acid in order to soften the wine. This is the case for red wines but also for certain white wines.
If the acidity is too low (especially in warmer countries), the winemaker can add tartaric acid to acidify the wine. If the wine is really too acidic, it may be possible to deacidify it with calcium or potassium bicarbonate, but this is more rare.
Acidity in sweet wines
It is important to mention that sweet and mellow wines with a high level of residual sugar, such as Sauternes, for example, have a fairly high acidity. Just feel the salivation when you drink them. This is precisely what allows you to have a balance with the sugar so that wine does not become heavy and flat. And above all, it allows you to hold on for the long term.
Because yes, acids remain in any case an essential and natural antioxidant so that the wine can be kept for several years. A flat, low-acid wine will not last long in your cellar. And remember, it’s like in all kinds of wine, balance is above all to be sought…