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.

Click on the following topics for more information on chemical components of grapes and wine.

Topics Within This Chapter:

  • Sugars
  • Residual Sugars
  • Polysaccharides
  • Pectins
  • Glucans
  • Acids
  • Acids Found in Wine Grapes
  • Vineyard Acid Management
  • Winery Acid Management
  • Acids Produced During Fermentation
  • Acidity and pH Relationships
  • Potassium
  • Tartaric:Malic Acid Ratio
  • Vineyard Management
  • Winery Treatment
  • Phenolic Compounds
  • Flavonoids
  • Flavanols
  • Flavonols
  • Anthocyanins
  • Tannins
  • Non-Flavonoids
  • Phenolic Concentration
  • The Role of Oxygen
  • Extraction of Phenolic Compounds
  • Phenolic Management Strategies
  • Managing Phenolics in the Vineyard
  • Managing Phenolics in the Winery
  • Alcohols
  • Ethanol
  • Glycerol
  • Wine Aroma Compounds
  • Primary Aroma Compounds
  • Methoxypyrazines
  • Norisoprenoids
  • Terpenes
  • Varietal Thiols
  • Secondary and Tertiary Aroma Compounds
  • Acetaldehyde
  • Esters
  • Ketones
  • Oak Volatile Compounds
  • Nitrogen Compounds
  • Protein Stability
  • Volatile Sufur Compounds
  • Hydrogen Sulfide
  • Dimethyl Sulfide
  • Mercaptans
  • Disulfides
  • Volatile Phenols
  • Smoke Taint
  • Microbial
  • Oak Maturation