At even lower levels, di sulfides often do not produce a specific odor. Sometimes they are not detectable, but minute quantities of di sulfides can kill the normal bouquet of a fine wine. When ascorbic acid is added to wine, it reacts with the di sulfides, and the di sulfides are converted into a material called mercaptan. The copper sulfate removes the mercaptan from the wine. This treatment is only effective when the ascorbic acid is added to the wine several days before the copper sulfate addition.
Many Australian winemakers use ascorbic acid as an anti oxidant when bottling wine.
The ascorbic acid is used in combination with sulfur dioxide. Sometimes, grapes grown in cold climates contain too much acid. Then winemakers often use calcium carbonates to reduce the acid content of juice before fermentation. This material is occasionally used to reduce the acid content of finished wines by small amounts. However, when carbonates are used to reduce the acidity of a finished wine, they can change wine flavors, raise pH and cause other problems.