Wine grapes naturally produce organic acids, including tartaric, malic and citric acid (in smaller quantities). Other acids, such as lactic acid, are produced during fermentation.
In the proper amounts they give a pleasing and refreshing taste to the wines.When excessive acid is present the wine is tart or sour. This can also be a cause of “unbalanced” wines; when the acidity, sweetness and/or alcohol and tannin are not in harmony.
Acidity, measured by pH value, is also necessary for the conservation of wine (the color in red wine is also stabilized by acidity).
Lack of acidity results in flat “flabby” wines. If a wine has insufficient acidity then “acid adjustment” (the addition of tartaric, citric or other acids) is recommended.