IF you use ascorbic acid in wine, please note that it reacts with the SO2. Test the SO2 level and adjust as needed, otherwise the wine will oxidize. Even though Ascorbic acid is an anti-oxidant in wines with SO2, it can cause oxidation!  

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.                    

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. 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.     

Do a bench test first to determine the need and or the dose for ascorbic acid.   http://www.bcawa.ca/winemaking/h2s.htm    MORE, read this page!  This article explains the connection of ascorbic acid use with this treatment, as some instructions will indicate to add it after treatment and some before!

Some sources recommend always adding the ascorbic acid first!  SO do Bench test first to determine the need for ascorbic acid  and the dose.  

Other sources recommend treating first with Copper Sulfate but if the problem persists, then treatment with Ascorbic Acid will be necessary.

Use 0.25 grams of ascorbic acid per gallon.   You can use your grain scale to determine different rates for your bench test. 

So,  saying it again as there is always more than meets the eye:  IF you use ascorbic acid in wine, it reacts with the SO2.  Test the SO2 level and adjust as needed, otherwise the wine will oxidize.  Even though Ascorbic acid is an anti-oxidant in wines with SO2, it can cause oxidation!