What Causes Volatile Acidity
Acetic acid, the primary component of VA, is produced by:
- Acetic acid bacteria (Acetobacter) — these aerobic bacteria convert ethanol to acetic acid in the presence of oxygen. Damaged grapes, poor cellar hygiene, and excessive headspace in barrels are common causes
- Yeast metabolism — all fermentations produce small amounts of acetic acid as a byproduct. Wild yeasts (particularly Brettanomyces) tend to produce more than cultured strains
- Lactic acid bacteria — can produce acetic acid alongside lactic acid during malolactic fermentation if conditions are suboptimal
Legal Limits and Thresholds
EU regulations set maximum VA levels at 1.2 g/L for red wines and 1.08 g/L for whites and rosés. The sensory detection threshold for most tasters is approximately 0.7-0.8 g/L, though sensitivity varies. Wines with VA below 0.5 g/L are generally considered clean.
VA as a Positive Element
In small amounts, volatile acidity contributes to a wine's aromatic lift and perceived complexity. Many prestigious wines — including aged Barolos, Burgundies, and Amarones — carry measurable VA that enhances their bouquet. Some natural wine enthusiasts embrace slightly elevated VA as part of a wine's artisanal character.
Prevention and Management
Winemakers prevent excessive VA through:
- Rigorous grape sorting — removing damaged or botrytised fruit that harbours acetic bacteria
- Minimising oxygen exposure — topping barrels (ouillage), using inert gas, and maintaining full containers
- Sulfite management — SO₂ inhibits Acetobacter and other spoilage organisms
- Temperature control — cool cellar conditions slow bacterial activity
- Hygiene — regular cleaning of all equipment, barrels, and transfer lines