David’s article as prepared for the Duluth News Tribune for the article which ran on 4/1/2015:
Acidity is the essential component for a wine to have good structure. It is what gives wine its balance and its thirst-quenching refreshment. It lifts the pallet by cleansing fats from the mouth and if it was absent, wine would taste cloyingly sweet and clingy. This is called flabby and no one has ever said flabby tastes good.
When you take a sip of wine, acidity is noticeable as the “pucker” effect. The left and right sides of the tongue will tingle and in particularly acidic wines you’ll notice your mouth feels wetter. This is because acids stimulate your salivary glands and you salivate more. This doesn’t sound very appetizing but in the early years of food and wine pairing theory, it was thought that stimulation of the digestive juices would be beneficial to your health. Thus meals were often started with high acid wines to stimulate salivation because it is the very first bodily fluid used in digestion. Classic examples of a high acid wines are Brut Champagne or Fino Sherry, both of which are still generally served before a meal or with the first course.
There are six principal acids found in wine. Three are from the grape: tartaric, malic and citric; and three are from the process of fermentation: lactic, acetic and succinic. Each of these acids imparts a different quality to the wine.
Tartaric acid is the most prevalent acid. It produces most of the total pH in a wine and it has a strange propensity to form crystals when exposed to low temperature. Once these are formed they will not redissolve in the liquid. You might have noticed this on the wet end of a cork or lurking at the bottom of the bottle. While formation of the crystals isn’t considered a fault it does lower the overall acidity. This is also the same substance that bakers would recognize as cream of tartar.
Malic acid is sharp tasting and has the flavor of a green apple. In properly balanced wines, such as German rieslings, the taste and aroma is of a Granny Smith apple rather than an unripe green apple. This acid is produced by the grape to prevent underripe picking of its fruit by predators. As the fruit matures, the acidity falls and the sugars increase.
Citric acid is found in very small quantities. But in a batch of grapes that were left to ripen too much, thus their acidity is reduced and their sugar levels are high, winemakers will use commercially available citric acid to try and balance a wine that is overly sweet. This leads to a citrus-like flavor and this is unsuitable for most quality wines.
Lactic acid is the byproduct of a bacterial fermentation. This is known as malolactic fermentation. During this fermentation, malic acid (tart, green apple) is converted into lactic acid (creamy texture and buttery aroma). This can be done by placing the wine in a barrel where the process was previously performed and the bacteria is still present or by inoculating the must (unfermented grape juice) with a commercially obtained strain. Most often winemakers don’t need to do anything as the winery’s atmosphere is suitably inoculated to start the fermentation. Every red wine goes through malolactic fermentation, but in white wines where crisp fruitiness is desired the winemakers may prevent the process by using SO2 (sulfites). A good example of malolactic fermentation is a buttery California chardonnay.
Acetic acid is the acid found in most types of vinegar. A small amount of this acid is created during fermentation but it is very unstable and it readily evaporates. This can add to the aroma of a wine and at low levels can be very pleasing. However at higher concentrations, which occurs when alcohol and oxygen are employed by the bacteria acetobacter to create vinegar, the aroma can be so unpleasant that it makes the wine undrinkable.
Succinic acid is a minor component and a by-product of alcoholic fermentation. This acid has a sharp, slightly bitter and slightly salty flavor.
Next time we will discuss the difference between dry and sweet and how that relates to our next key component: sugar.
David Devere is a certified specialist of wine. He teaches wine classes mainly in the Duluth, MN area. Contact him at firstname.lastname@example.org.