Volatile Acidity (VA) is a measure of the total concentration of 'volatile acids' in wine. While there are a number of wine acids that are volatile, the most serious one is acetic acid, which accounts for over 95% of any VA measurement.
How Volatile Acidity Forms
A small amount of VA is produced during both the alcoholic fermentation and the malolactic fermentation stages of vinification, and this is not necessarily a spoilage problem for a wine. Indeed, small amounts of VA can actually add complexity to both the aroma and taste of a wine.
VA really becomes a problem when its concentation in a wine goes above a certain level, and when it is generated by spoilage yeasts or bacteria (i.e the bad guys that can lurk around a winery) after the wine is made. The most important VA producing 'baddie' is acetobacter. Acetobacter is most known in making vinegar.
In the presence of oxygen acetobacter produces acetic acid, which in the presence of alcohol creates the ester 'ethyl acetate', which is volatile. It is this ester 'ethyl acetate' that ruins wine.
Why Volatile Acidity is Generally Undesirable in Wine
When volatile acidity levels in a wine are excessively high they spoil the aromas and flavors. Volatile acidity destroys the wine's fruitiness and finally makes the wine taste like vinegar.
Preventing Excessive Levels of Volatile Acidity
Within the European Union, levels of VA in wine are regulated and maximum amounts are set for all types of wines. Red wines can tolerate more VA than white wines and sweet botrytis infected wines even more.
Today there are a number of 'technological' ways to treat (i.e. remove) wines with excessive VA. However, it is better to try prevent its occurrence. Winery hygiene, rejecting moldy grapes, managing brettanomyces, managing the wine's exposure to air as well as appropriate QA/QC protocols can go a long way to ensure that spoilage yeasts and bacteria do not produce excessive levels of volatile acidity.
Mary Gorman-McAdams, MW (Master of Wine), is a New York based wine educator, freelance writer and consultant. In 2012 she was honored as a Dame Chevalier de L'Ordre des Coteaux de Champagne
Previous Wine Word: Dry Farmed
(Image: Underlying image by Sadovnikova Olga/Shutterstock)