Geek Flight Part Deux: Volatile Acidity

Apologies for the delay in getting Geek Flight out this week!

As stated in our last geeky article (here) the discussion this week revolves around volatile acidity:

Occasionally while tasting through wines we will open a bottle and find that it tastes different than others of the same bottling.  The bottle in question often does not smell mouldy or cardboardy in the way a bottle affected by TCA typically would. Further, the hints that something may be awry are very subtle:  an increased fruitiness on the nose, a little extra twinge of acid on the palate, a few unusual flavors, or maybe a slight sense of imbalance on the tongue.  The culprit in such a mystery case is likely volatile acidity.

Acetic acid is primary in the small group (lactic, succinic, formic, propionic, acetic) of acids associated with VA.  Noticeable quantities of these acids in wine result from acetobacter, a gaggle of bacteria that consume oxygen and react with alcohol to produce volatile acids.  The quantity at which VA is generally considered to begin affecting the flavor, feel, and smell of a wine is 0.2 grams per liter.  At 1.5 grams per liter a noticeable, lingering, and generally off-putting tartness (think vinegar) results. The controversy with volatile acidity as a flaw is that at certain levels it can enhance the flavor and aroma of a wine rather than outright spoiling it.

The still pictured above is the primary means by which our winemaking staff separates and measures the amount of volatile acid in our wines.  This process is ongoing and takes place while the grapes are undergoing secondary fermentation (see Geek Flight #1).  When we discover undesirable levels of volatile acid in a wine we begin removing portions of the batch in question, separating them in to smaller groups.  We then measure the amount of VA in each piece and again remove the most affected portion.  By this process of isolation we essentially quarantine the most actively volatile wine, keeping the overall batch more stable.

A few tips on spotting VA:

-as a flaw VA is rarely as openly evident as TCA. We typically notice it as a result of increased fruitiness on the nose and palate, often followed by a lingering gummy feel on the tongue.  Occasionally, likely as a result of higher concentration, tartness or ‘vinegary’ qualities are readily evident.

-high levels of acohol and/or residual sugar tend to mask the sensory effects of volatile acidity, so wines with higher alcohol tend to be at higher risk and may hide the indicators more than wines at lower alcohol levels.

As always, thank you for reading and we’d love to pick your brain(s) on this topic so feel free to contribute questions or comments!


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