Grapes & Wine
So what’s in a grape that makes wine so delicious?
In order to have wine, you need ripe grapes, and the components of a grape lead to specific characteristics in a wine. The grape is made up mostly of four main parts, the seed, stem, pulp, and skin. Each part of the grape plays a role in what we get in a wine, and helps winegrowers determine if a grape is ready for harvest, and how a winemaker will make decisions in their techniques.
The seeds and stems contain tannins. However, these tannins can be bitter. To avoid adding bitterness to a wine, winemakers will destem the grapes and use a gentle pressing technique. This process is more frequently used with producing white wine, since white grapes have more delicate flavors and aromas.
The bitterness of the tannins in the seeds decrease with ripeness. Wine growers use the grape seeds to help determine whether or not a grape is ready to be harvested. They will look at the color and taste of the seed. Green seeds are unripe and will be more bitter. As the grape seed ripens the seed will become smaller, harder and brown. This change helps the winegrower to know when the grape has matured.
The skins are another part of the grape that is important in making wine. The skins provide desirable tannins, color, and characteristic flavors. As the grapes ripen, they will change color from the exposure to sunlight. This process called veraison changes the white grape skins from green into a golden color and more obviously changes red grapes from green into its characteristic purple color.
In addition to the color the skins provide to wine, they also provide the characteristic flavors and tannins. How a winemaker decides to produce their wine determines how much of color and tannin structure is integrated. When producing a white wine with fruity, delicate flavors, the winemaker will press the grapes immediately to extract the juice. This avoids the color and tannins from being part of the wine. However, when producing a red wine, the winemaker will desire the color and tannins. The red grapes will be crushed and then will macerate or sit with the skins and seeds to extract tannin structure and color.
Lastly, the pulp is another aspect of a grape that leads to a wine. This part of the grape is made up of mostly water, sugars, acids, and phenolic and aroma compounds. When determining if a wine grape is ripe for harvest, winegrowers will test for the Brix level (percent sugar), PH and Titratable Acidity. They will also look to see how well the pulp detaches from the skins and will look for expected aromas and flavors. The Brix level helps to determine the final alcohol percentage in a wine. It is determined by multiplying Brix x 0.55%. Winegrowers will look to harvest when PH is around 3.1-3.3 and 0.6%-0.8% TA. The most prevalent acid in a grape is Tartaric acid, followed by malic acid. These acids are an essential component to a wine. Without them the wine will appear flabby.
A delicious wine needs all the components of a grape by helping wine growers know when the grape is matured and ready for harvest. They also lead to the characteristics of flavors, aromas, color, acidity, alcohol, and tannins… all the components of a desirable glass of wine.
Cheers!
