As your interest in wine progresses, it can be helpful
to understand a bit about the basic chemical components of winegrapes and
Sugar - Obviously, grapes
are sweet. When the grape's natural sugars are fermented into alcohol, you get wine. In some
cases, fermentation stops early, and residual sugar can be left behind. This can vary from trace
quanities to slightly higher levels such as in 'off-dry' wines, or the high residual
sugars in dessert wine.
Alcohol - In winemaking, sugar is converted to alcohol. Typically, red wines have
more alcohol than whites, since red grapes are harvested later when grapes are
riper. Wines from warm, sunny regions also tend to have more alcohol. Alcohol
percentages can range from 8% to as much as 16-17%.
Acid - Tartaric acid and malic acid are the most important acids in grapes.
Tartaric acid is rarely found in other fruit, and gives grapes and wine their 'tart'ness. Malic
acid can be found in other fruit, especially green apples. Many wines go through a
secondary 'malolactic' fermentation (ML), where malic acid is converted to lactic
acid. Lactic acid is softer and has a creamy texture (it is found in milk).
Almost all reds go through this process, but some white wines have no ML -
they will have a bright crispness and green apple flavor - or with 100% ML -
they will be creamy and buttery. You can also find whites with varying degrees of partial ML
that will have qualities of both.
Tannin - Bitter and astringent, tannins are found in plants, typically in
leaves, stems, seeds or fruit skins. During production of white wines, grapes are immediately
pressed after harvesting, removing the juice from the other parts of the grape bunch, so white
wines have little to no tannins. However, during red wine production, grapes are fermented
together with skins, seeds and sometimes stems, and tannins are extracted into the wine. This is
why red wines give you more bitter flavors and oftentimes that drying, puckering texture on
Next Article: Wine Pairing Chemistry
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