why does wine become cloudy?
Answer From Expert Roger Bohmrich MW
The most common cause of cloudiness in a bottled wine is sediment. This applies almost exclusively to red wines that have thrown a deposit over the course of maturing for a number of years. When a bottle of an older red wine is carried or handled, or otherwise agitated, the sediment can be partially dissolved, and the wine can appear cloudy. Leaving this bottle upright and undisturbed for a day or two should result in a (relatively) clear wine with the sediment accumulated at the base.
Cloudiness can also be a sign of trouble in both red and white wines, although this is very uncommon given the techniques and equipment available to a modern winemaker. Cloudiness could be a sign of microbial activity, either yeast or bacteria, and could therefore indicate that the wine is unstable. Or, it might be a sign of protein instability, but this is extremely unusual today.
