Anti-foam is used to prevent foam from overflowing containers during active fermentation. This material is completely inert and does not react with the wine in any way. Most of the anti-foam added will disappear when the wine is racked. Even if a few drops remain, they will be removed when the wine is filtered. In larger amounts, di sulfides can smell like a skunk.
Smaller quantities give wine a rubber or garlic smell.
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.