What VA is
Volatile acidity is mostly acetic acid, reported in g/L as acetic. It is usually accompanied by ethyl acetate, which is responsible for the nail-polish note people often blame on "VA". A little is made by yeast in every ferment; larger amounts nearly always mean bacteria (especially Acetobacter and some Lactobacillus) or stressed yeast.
Reading the number
| VA (g/L as acetic) | What it usually means |
|---|---|
| Below 0.4 | Normal for a clean ferment |
| 0.4–0.6 | Usually unnoticeable; watch it if it is climbing |
| 0.6–0.8 | Around the range many people start to notice it, depending on style and alcohol |
| Above 0.8 | Increasingly likely to read as a fault; act and find the cause |
The trend matters more than any single number. A wine sitting stable at 0.5 g/L is in a better place than one that went from 0.3 to 0.45 in a month.
Export limitsMany markets set a legal maximum. The EU, for example, caps VA at 18 meq/L (about 1.08 g/L as acetic) for most white and rosé wines and 20 meq/L (about 1.2 g/L) for most reds. Check current rules for every market you sell into.
Where it comes from
- Damaged or botrytised fruit carrying acetic acid bacteria into the winery.
- Slow or stuck ferments that leave sugar and time for bacteria.
- Oxygen exposure: ullaged barrels and tanks, where Acetobacter thrives.
- Low SO₂ and high pH, which let bacteria grow.
- Stressed yeast in high-sugar or low-nutrient musts.
Keeping it down
- Sort damaged fruit and get ferments started promptly.
- Keep vessels topped and use inert gas in headspace.
- Hold molecular SO₂ at target once fermentations are finished (SO₂ guide).
- Control fruit flies around the winery.
- Test VA alongside free SO₂ during maturation; if it rises, an Acetobacter qPCR count tells you whether it is still being made.
VA can be reduced by specialist treatments, but they are costly and not always appropriate. Preventing the rise is far easier than reversing it.
Seeing VA climb?
Find the right testsFermLabs guide · general information only — your own wine's analysis and trials come first.