Sugar in Wine
Sweetness is one of the primary characteristics of wine that affects taste and balance. Sugars are the main contributors to this, and play a critical role in alcoholic fermentation.
The Role of Sugar in Wine
The sugar in wine plays a major role in its sensory characteristics. It can be as obvious as the difference between a sweet and dry wine; or as subtle as the difference between sugar interactions with different tannins. The relationship between sugars and balance looks like this:
Sweet Taste (sugars + alcohols) <= => Acid Taste (acids) + Bitter Taste (phenols)
Sugar Chemistry
Sugar chemistry helps to explain its role in wine. One of these is fermentation, where yeasts metabolize sugars for energy, yielding alcohol as a major byproduct. In dry wine, yeasts consume almost all of the sugar from the grapes. In sweet wine, the yeasts are killed before all the sugar is used, leaving residual sugars.
Development of Grape Sugar
The sugar used by yeasts in fermentation is developed by the vine and stored in the grape. The development of grape sugar is different for each varietal, and is influenced by environmental and viticultural practices. V. vinifera sugar content can reach 20% or more at maturity. While other species like V. labrusca and V. rotundifolia almost never reach 20%.
Taste Perception of Sugar
The primary sugars in grapes are glucose and fructose. There are other sugars present, but they occur in insignificant quantities. The different sugars and their relative concentration play an important role in the taste perception of sugar. In addition, glucose concentration in grapes is an indication of ripeness to vineyard managers.
Brix Scale
Grape maturity at harvest is critical for fermentation and perceptible sweetness. The Brix scale was developed for this very reason. Vineyard managers use the Brix scale to monitor sugar development and concentration. Brix readings give objective numbers that are used to determine the appropriate time for harvest.
Sugars may very well be the most important class of chemicals in the winemaking process. Enologists must control sugar production in the vineyard to make a balanced wine in the winery.
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