The Role of Tannins in Wine, Wine Taste and Winemaking
Tannins occur when various phenols polymerize, or join together. On the palate, tannins give a sensation opposite of acidity. Unlike acid which makes the mouth salivate, tannins will give the mouth a sensation of dryness, or astringency. High tannin concentration tends to give the sensation of bitterness and roughness.
Within reason, tannins give wine very desirable characteristics. Because they are a preservative, wines that are tannic in their youth often have the ability to age and become more complex when stored at the correct wine storage temperature.
They also are helpful during the clarification process; tannins naturally bond to proteins and can then be removed with other solid matter to make a wine visually brilliant. Fining agents such as egg whites can be used to induce this process.
White wines generally pick up tannins from being aged in wooden barrels. The younger the barrel, the more tannins it will impart in a wine. Additionally, it is very important that the tannins in grapes are fully ripe before they are harvested. “Green” tannins are rough and undesirable.
This should be a primary focus of the vineyard manager’s decision to harvest. While sugar and acidity readings are extremely important, nothing can substitute actually tasting the grapes to ensure that tannins are ripe and the phenolics are fully developed.
If grapes are harvested before the tannins are fully ripe, this can be remedied to a certain extent by a skilled winemaker. Tannin molecules will soften if the grape must is heated. This process is known as polymerizing the tannins.
The results are smoother, more graceful sensation on the palate. This process is also known as hot maceration and will also give the must added pigments and flavor characteristics. Hot maceration is often used so the winemaker can remove the skins and solids during the alcoholic fermentation process. This results in a less tannic wine that still has desired pigment and flavor characteristics.
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