Acid is probably the most important component of wine that the casual drinker doesn’t know about. It’s crucial to the wine’s balance and flavor profile throughout the life of the wine, from the time the grapes are ripening on the vine to when you’re picking which wine to go with dinner. (It also impacts how long the wine can age, but that’s another discussion.) You may love the taste of it (like me), or you may prefer less of it. Here’s some basic information that should help you to discover your own wine preferences and match them with food successfully!
Where does it come from?
All grapes naturally contain some amount of acid. As the grapes ripen, sugar levels increase and acid levels decrease. Ideally, the grapes will be harvested at the precise moment when this acid/sugar balance is perfect for winemaking. (Remember that some or all of the sugar will convert to alcohol during fermentation.) In top quality winemaking, nothing is done to change the acid and sugar levels after the harvest. Everywhere else, sugar or acid may be added to correct an imbalance.
The primary acid in grapes is malic acid, which is the same acid found in green apples. Most red wines and some whites go through a process called malolactic fermentation, during which the malic acid is converted to lactic acid. The lactic acid is smoother and less harsh.
How does it impact the wine?
When you taste wine, the acid creates a mouthwatering sensation. If you take a sip of a crisp white wine, swish it around in your mouth, then swallow completely, you will probably notice a sudden rush of saliva in your mouth, particularly under your tongue. This is caused by high acid levels. The more your mouth waters, the more acid is in the wine. Super high acid levels can even make your tongue feel prickly, like you’re drinking soda.
The acid/sugar balance is so important at harvest because it is also key to the final product. Sweetness reduces the perception of acid, and acid reduces the perception of sweetness. In other words, a sweet wine needs strong acidity to balance the sweetness. A highly acidic wine will often benefit from a little extra sugar. The amazing part is that if you compare 2 wines with the same level of sugar, but different acid levels, the 1 with more acid will taste less sweet, while the one with less acid will taste sweeter (maybe even cloying).