Calcium carbonate will lower acidity. It will reduce the tartaric acid before dropping out malic or citric acid.
Usage: Use before fermentation. 5/8 teaspoon per gallon will lower acidity by about 0.15%. Do not try to reduce acid by more than 0.30% with calcium carbonate.

Calcium Carbonate is used to lower acidity in wine. Use 1/2 teaspoon per gallon to lower acidity 0.1% Use before fermentation. In brewing Calcium Carbonate increases pH. 1 gram per gallon will add approximately 106 ppm of calcium and 158 ppm of carbonate.