In winemaking citric acid is reduced during normal fermentation and all but disappears.
it can be added to acidify wines and will give a freshness to the wine, HOWEVER it is important to note that it will give an artificial freshness if overused. Because Citric Acid has a high degree of instability when added to wine, Tartaric acid is the preferred choice of additional acid in winemaking.
Citric acid is more commonly used as a final rinse aid after sterilising equipment. As a final rinse add add 50gm to 10 litres of water and rinse barrels, equipment in this solution.