Chapter 1

Chemical Components of Grapes and Wine

(book excerpts)

The quality and style of a wine depends not only on the composition of the juice obtained from healthy ripe grapes, but also other constituents that have roles of varying importance in determining the ultimate flavor and color of the end product. In general, grapes consist of clear juice (80%), skins (8%), seeds (4.5%), pulp (4.5%), and stems (3%). The skins, seeds, pulp and stems are collectively known as pomace. Freshly expressed grape juice consists of 70 to 80 percent water and many dissolved solids. These soluble solids include numerous organic and inorganic compounds. The important group of compounds, from the winemaking point of view, include sugars, organic acids, phenolic compounds, nitrogenous compounds, aroma compounds, minerals, and hundreds or thousands of other compounds. The style and balance of each individual wine is dependent on the components found in the grapes and the various processes that follow used in making wine - destemming/crushing, pre-fermentation treatments, fermentation, malolactic fermentation, maturation, fining, stabilization, filtration, and bottling.

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