Ascorbic Acid is an anti-oxidant used as a partial substitute for sulfur dioxide, or used to prevent oxidation, which creates a dull and unpleasant flavor, and to prevent discoloring in the final product. Recommended for wines that discolor easily.
Ascorbic Acid, like Copper Sulfate, is often used to treat hydrogen sulfide (H2S) or ‘mercaptans’, which presents as a rotten egg scent in your wine. Try treating first with Copper Sulfate but if the problem persists, then treatment with Ascorbic Acid will be necessary. If you have advanced H2S ‘disulfide’, the scent could be described as burnt rubber or garlic-like and the wine will not improve with the treatment of Copper Sulfate alone. The use of 0.25gm Ascorbic Acid per gallon will often help by converting the disulfides back to mercaptans. The process may take up to three weeks, after which the wine should be treated with Copper Sulfate.