ACIDS [home] [topic page]
"Organic" acids - carbon compound based acids are all defined by the structure called the carboxyl group.
The acid properties come from the proton ( H+ ) being donated from the hydroxyl group.
All fruits are acidic .
The main acids in the grape are tartaric acid and malic acid. Malic acid is associated more with apples and does give a sharp "appley" taste. Tartaric acid is closely associated with grapes and wine.
Citric acid is relatively small in percentage and disappears during fermentations.
Malic acid level is generally modified through a secondary fermentation using Leuconostoc enos in the barrel to lactic acid which has a softer taste. ( See earlier ). The molecular conversion is one malic acid molecule to one lactic acid molecule plus carbon dioxide.
The lactic acid, the result of the secondary fermentation, giving a "milky" or "buttery" taste ( it is present in milk ) to the wine.
Tiny amounts of acetic acid ( the basis of vinegar) are a feature of the second fermentation, not of the fruit. If acetic acid is too high in concentration, the wine does indeed, taste of vinegar.
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Another significant acid in wine is succinic acid, a byproduct of the yeast fermentation. It gives a slight acid, salt and bitter taste.
Wine acidity offsets the sugars residing in the wines from the fruit.
Insufficient sugars leaves the wine tasting "sharp" and acidic whereas too much sugar to acid can be oversweet with no "cut" to it.
Tastes are, however, very personal and most experience a drift in preferred wine tastes with time. ( Return to "Barreling" )
