Why is wine not vegan?
Such animal products are used, for example, in fining - after fermentation and ageing of the wine - to remove lees from the wine. Such lees are residues from winemaking and can be bound by proteins. These proteins are usually obtained from chicken eggs (egg white), milk(casein), animal bones, cartilage and skins(gelatine) or the swim bladders of fish(isinglass).
The proteins are aids in winemaking and are filtered out of the wine after fining together with the bound lees. However, since they come into contact with the wine and react with it, residues cannot be completely ruled out. Therefore, a wine is usually not vegan and may not then be called so.
Vegan wines are and are called wines that have been fined with, for example, mineral earth(bentonite) instead of protein. In the case of vegetarian wine, only the use of gelatine and fish bladder as fining agents is dispensed with