Tartaric acid is the primary acid found in grapes. In part, tartaric acid is responsible for the vinous character of wine. This acid also lowers the pH (typically pH 3.2) of must and finished wine, to a level that spoilage bacteria cannot live, as well as acting as a preservative after fermentation. Recommended dosage is to taste, beginning with 1/2 tsp. per 5 gallons. It is a good practice to monitor additions of tartaric acid using pH test equipment such as pH strips or a pH meter.