The Refreshing Tartness of Wine.

There are four tastes: sweet, bitter, salty, and sour. Of these four, the sour taste plays the most important role in the sensation of tasting wine. Sweet wines are out of fashion. Wines with a bitter taste are considered flawed. Grapes are never salty, nor are there any salty tasting additives in wine. Grapes, however, are generously endowed with acidity, the class of compounds which causes the sour taste of wine.

We taste acidity at the sides of our tongues. It gives a tingling, almost tactile, sensation. This makes sense since we know that acids are highly reactive compounds. Upon sampling an acidic liquid, a common reflex action is to smack our lips. Certain wines because they are made with grape varieties that naturally have high acid levels almost always give this sensation. Examples of common wine grape varieties with high acid levels are Chenin Blanc, Chardonnay, Riesling, and Cabernet Sauvignon. Generally the cooler the climate that the grapes are grown in, the more acidic the final wine. Hence, even though they are made with the same grape variety, Chablis, a northern white Burgundy, will generally be more acidic than a Pouilly-Fuisse, a southern white Burgundy.

Another factor to take into consideration is that in many countries such as the United States and Australia it is common practice to add acid artificially to wine in order to modify and shape wine taste. This practice is less widespread in Europe and is a reason why European wines are more varied in style than American wines.

There are several different acid compounds in wine. The most important is tartaric acid. Grapes are one of the few fruits to have large amounts of this acid in their chemical composition. This is a strong acid which has a clean, pure taste. Another is malic acid. Though chemically less strong an acid, malic acid has a stronger and coarser taste. We have all bit into an underripe apple and winced at the attack of malic acid on our taste buds. Wines made from less than fully ripe grapes can have give this coarse, acidic sensation.

A third kind of acid common in wines is lactic acid. This acid is not important in fresh grapes. During the wine making process, however, many wines go through a post-yeast fermentation catalyzed by bacteria. This fermentation lowers the overall acidity of the wine and changes the coarse, tart-tasting malic acid into the smoother, softer lactic acid. It reduces some of the fruitiness of wines and adds nutty and buttery nuances. Depending on the wine style desired, some winemakers will encourage malolactic fermentation while others will discourage it

Acidity has an important role in the structure of a wine's taste. Without a generous amount of acidity, most wines would simply not taste good. Acidity not only adds a refreshing quality to wine taste, it balances the rich taste of alcohol and the sweet taste of unfermented fruit sugars. This balancing of acid with rich and sweet tastes is something we experience unconsciously everyday. In salad dressings, vinegar (quite acidic) is used to balance the rich flavor of olive oil. When we bake a fruit pie, we are more likely to add more sugar to a tart base such as rhubarb than a less tart base such as peaches. In cooking, the addition of wine or lemon to sauces serves to lighten the richness of meat fats and dairy fats like butter.

Acidity is a much more important factor in the taste structure of white wines than in red wines. In dry red wines, the balance of tastes depends on three basic elements: Alcohol, tannins, and acids. The tactile effects of tannins make the role of acidity in red wine structure less clear and more complex. Dry white wines have minimal tannins. Hence their balance relies solely on the balance of acid and alcohol. If you would like to experience the difference between high acid and low wines, sample wines in the categories listed below.

Examples of white wines that generally display high natural acidity:

German wines (particularly rieslings) , Northern French white and sparkling wines ( Vouvray, Sancerre, Pouilly-Fume, Champagne, Chablis), New Zealand Sauvignon Blancs

Examples of white wines that generally have low natural acidity and are usually not greatly chemically adjusted in the winery:

Rhone white wines (Condrieu, white Chateauneuf-du-Pape, and white Hermitage), Alsace Gewurztraminer.

We thank Bill Nesto for sharing the knowledge he has gained in the course of becoming a Master of Wine.