Acids in Wine - in Winemaking

In Winemaking

Acidity is highest in wine grapes just before the start of veraison, which ushers in the ripening period of the annual cycle of grape vines. As the grapes ripen, their sugar levels increase and their acidity levels decrease. Through the process of respiration, malic acid is metabolized by the grape vine. Grapes from cooler climate wine regions generally have higher levels of acidity due to the slower ripening process. The level of acidity still present in the grape is an important consideration for winemakers in deciding when to begin harvest. For wines such as Champagne and other sparkling wines, having high levels of acidity is even more vital to the winemaking process, so grapes are often picked under-ripe and at higher acid levels.

In the winemaking process, acids aid in enhancing the effectiveness of sulfur dioxide to protect the wines from spoilage and can also protect the wine from bacteria due to the inability of most bacteria to survive in low pH solutions. Two notable exceptions to this are Acetobacter and the lactic acid bacteria. In red wines, acidity helps preserve and stabilize the color of the wine. The ionization of anthocyanins is affected by pH, so wines with lower pH (such as Sangiovese-based wines) have redder, more stable colors. Wines with higher pH (such as Syrah-based wines) have higher levels of less stable blue pigments, eventually taking on a muddy grey hue. These wines can also develop a brownish tinge. In white wines, higher pH (lower acidity) causes the phenolics in the wine to darken and eventually polymerize as brown deposits.

Winemakers will sometimes add acids to the wine (acidification) to make the wine more acidic, most commonly in warm climate regions where grapes are often harvested at advanced stages of ripeness with high levels of sugars, but very low levels of acid. Tartaric acid is most often added, but winemakers will sometimes add citric or malic acid. Acids can be added either before or after primary fermentation. They can be added during blending or aging, but the increased acidity will become more noticeable to wine tasters if added at this point.

Read more about this topic:  Acids In Wine

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