Vitis Vinifera is the ancient Latin term for vines whose grapes produce juice that ferments into wine. Vitis Vinifera originated in the Near East when man domesticated wild vines, but its numerous varieties and clones are most widely diffused in Europe, where four-fifths of the world's wine is produced.
Such vines are grown in the temperate climate zones, generally between the 30th and 50th parallels in the northern hemisphere, or between the 30th and 40th parallels in the southern hemisphere. Altitude is a key factor. In most countries, vines thrive at 300 to 600 meters above sea level. Vineyards are rarely planted higher than 800 meters, but there are exceptions, such as Italy's alpine Valle d'Aosta and parts of Chile where vines are regularly cultivated at 1,300 meters.
Soil composition and texture influence the character and quality of wines. Grapes from vineyards in sandy or siliceous terrains often produce wines of fresh flavors and aromas to be drunk young, while those from calcareous clay soils make wines that are richer in body and better suited to aging.
Vineyard positions are important. For most Italian wines of quality, hillsides are better than plains, since day-night temperature variations essential to developing aromas are greater at the heights. In cool zones, vines on south facing slopes benefit from full exposure to the sun, so grapes ripen earlier. They also need to be well ventilated to prevent mold. The fruit of the vine is the grape, which grows in bunches of varying size, consistency and color. The grape has four essential parts:
The stalk (3 to 5 percent of total weight) Each bunch has a stalk that is discarded at the beginning of the wine making process.
The skin (6 to 10 percent) The skins or peels of grapes contain coloring substances, as well as tannins and yeasts, which enable the juice to ferment. Red wines are made from dark-skinned grapes. White wines usually derive from light-skinned grapes, but they can also be made from dark varieties if the skins are separated immediately from the pulp after pressing.
The pulp (82 to 90 percent) The pulpy interior of the grape, source of its juice, consists of water, sugars, acids, mineral substances and vitamins.
The seeds (2 to 4 percent) These are rich in tannins and oils.
