A grape berry is, by weight, approximately 75% pulp, 20% skin, and 5% seeds. Pulp, the soft, juicy center of the grape consists mostly of water, then sugar, followed by a miniscule amount of acids, minerals, pectin, and vitamins. The skins are responsible for the wine’s aroma and flavor, as well as the color and tannin.

The components of wine provide clues about where the wine was grown and how it was made. They also affect qualities such as taste and mouthfeel.

Acid

Acidis the most important element in the pulp other than water and sugar. As a grape ripens its sugar content increases and its acid content decreases; the challenge is to harvest precisely when optimal balance is struck.

  • Acid balances alcohol and sweetness and sometimes adds a crisp, refreshing sensation
  • It may cause your mouth to pucker (like if you were biting into a lemon wedge)
  • Many wines undergo malolactic fermentation, which transforms hard, malic acid into softer lactic acid
  • Grapes grown in cooler regions tend to have higher levels of acidity

Alcohol

Alcohol­ is produced during fermentation when yeasts come in contact with the natural grape sugar in the grape pulp.

  • High-alcohol wines are full-bodied with a richer mouthfeel
  • Alcohol generally has a sweet flavor
  • A wine with high levels of alcohol sometimes gives-off a hot, burning sensation that you can smell and taste
  • High levels of alcohol indicate that the grapes were very ripe at harvest

Sugar

Sugar comes from ripe grapes (although some grape varieties naturally contain more sugar than others). It is mostly converted into alcohol during fermentation. Any remaining sugar is called “residual sugar” (called r.s. for short).

  • A wine with high levels of residual sugar generally tastes sweet, has a richer mouthfeel and fuller body
  • Grapes grown in warmer climates tend to get riper and contain more sugar
  • Wines with no apparent sweetness (or low levels of sugar) are referred to as “dry”

Tannin

Tannin belongs to a class of compounds called phenols and comes from grape skins and seeds; it is mostly found in red wines but can be found in some white wines.

  • Tannin is an important compound that plays a role in the aging of wine; therefore high-tannic red wines such as Cabernet Sauvignon and Nebbiolo are those that can be aged longest
  • An easy way to understand the effect of tannin is to think of a cup of hot tea in which the tea bag has steeped for too long; the tea will have a very strong, harsh, almost bitter (tannic) flavor that can only be softened by the addition of milk. This same concept applies to wine, that is why cheese and wine is a classic pairing (the protein in cheese neutralizes or balances the tannins in wine)

Water

Water pressed from the grape’s pulp, constitutes the single largest element of wine.

Source: spiritswinecellar.com