Citric Acid

Used mainly for acidifying a new oak barrel or when cleaning a used barrel.  Always dissolve in water before adding.  Use 2 teaspoons for every 5 gallons of barrel capacity.  Can also be added to potassium metabisulfite sanitizing solution to lower pH and make the sanitizing solution more effective.

Occasionally used to acidify white wines for a specific flavor note, but care must be taken as it can be unstable.  Generally, tartaric acid is preferred for acidifying wine.