Illustration by Alyssa Nassner
Often referred to as VA, volatile acidity is a measure of a wine’s gaseous acids. The amount of VA in wine is often considered an indicator of spoilage.
A wide range of acids contributes to a wine’s total VA content, but most winemakers are concerned with acetic acid, which is associated with the smell and taste of vinegar, and ethyl acetate, which causes off-flavors like nail polish or nail polish remover.
Excessive amounts of VA are associated with “unhealthy grapes, poor winery hygiene, oxidative processes or a combination of all of the above,” says Eduardo Soler, winemaker at Ver Sacrum Wines. However, “wine [is] a living thing, and due to its microbiological nature, there is always some degree of VA present in it.”
By law, red and white wine can contain up to 1.4 grams per liter and 1.2 grams per liter (g/L) respectively, yet VA-derived off-flavors are detectable at a much lower threshold, between .6 g/L and .9 g/L.
Detection thresholds may vary from person to person but are also affected by the wine’s style. High sugar content, for instance, can mask VA-derived smells, despite VA being normally present more in sweet wines than in drier styles.
Soler explains that “some wines… made with grapes affected by noble rot…are aged under flor [the layer of dead yeasts that forms on top of sherry] and fermented or aged in an oxidative manner, will have naturally a higher level of VA, which is considered an important part of their heritage and character,” hinting at appellations such as Sauternes, Port, Tokaji and Sherry.
While detection levels might depend on styles and on one’s own sense of smell, what’s an acceptable amount of VA-derived flavors is up for debate.