Salvaging acetefied wine

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Salvaging acetefied wine

Postby tonyhibbett » Thu Sep 21, 2017 12:24

I had 9 litres of a country red wine in a cask. I don't usually add sulphite but clearly this was a serious omission in this case, as was leaving it for 11 months in such a small cask. Tasting it left an unpleasant burning sensation in the mouth, indicating acetification. While not quite at the vinegar stage, it was nonetheless unpalatable. Although the pH was 3.9, titration indicated a massive 14 ppt (t), just about double the maximum. I added about 30 g of potassium carbonate, which reduced this to 9 ppt. I also added a bottle of good wine, some sulphite and removed the sediment from the cask. The result was a significant improvement and behind the acetic acid there was still a good wine. I will leave it to settle for a while and then add more potassium carbonate until the wine becomes palatable. Curiously the pH is now 4.4, but then acetic acid is far more powerful than the usual acids in wine.
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Re: Salvaging acetefied wine

Postby jkp » Thu Sep 21, 2017 16:51

Why not just let it go to vinegar? I know 9L is a lot of vinegar, but so is 9L of not great wine.

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Re: Salvaging acetefied wine

Postby tonyhibbett » Fri Sep 22, 2017 10:33

The addition of another 20 g of potassium carbonate completely solved the problem. Alkaline substances react with acids and neutralise them but they have preferences. In grape juice, they initially work on tartaric acid. This has no harmful side effect but once all that acid has been neutralised, they get to work on the malic acid, which can produce off flavours. Fortunately in this case it seems to have targeted the acetic acid, because that unpleasant taste and smell has completely disappeared, while leaving the 'good' acids, including tannic acid, alone. The wine now tastes and smells really good. The only side effect is a darkening of the wine, but as it is a red, this is actually an advantage. Acetification converts alcohol into acetic acid. When all of the alcohol has been converted, the result is vinegar, hence cider vinegar, for example, is 5% acetic acid.
My wine had a total acidity of 14 ppt (t). It is now 7 ppt with no detectable trace of acetic acid. This implies that the process was caught at an early stage and less than 1% abv. However, during the 11 months in cask, 1 litre of the volume was lost due to evaporation. Almost all of that is water. This concentrated the alcohol (and acidity etc.) by about 10% (1% abv), therefore the loss of alcohol by acetification (0.7%) is of no significance. The vinometer now reads 12% abv, which was what I intended.
I wish I had known about this cure before, but I have found no documentation, other than adding lead (which didn't work) or re-fermenting the wine, which I did not attempt. Fortunately the problem has not occurred and I will make sure it never happens again by ensuring that all wild fruit, such as blackberries and elderberries, is treated with sulphite at an early stage and that all wine made from such ingredients is also sulphited at the maturation stage.
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