Last week I discussed the process of testing the acid level of your juice. Should your juice not have the acid level you desire, there are several products that can be used to adjust it.
If you want to raise your total acidity, 4.1 grams of tartaric acid will raise one gallon by .10. If you want to lower your acidity, this is actually quite a bit more complicated. You can use either calcium carbonate or potassium bicarbonate. Calcium carbonate is a good option because you can lower your acid further without raising the pH of the wine as much as Potassium Bicarbonate would. However, Calcium carbonate should only be used early in the process on juice or very new wine because it takes a long time to completely fall out of the wine and it is possible that you could have some precipitate in your bottled wine. Potassium Bicarbonate, conversely, cannot not be used for large adjustments to acidity because it has a larger impact on pH. However, it can be added to your wine much later in the process as long as you cold stabilize the wine afterwards.
Calcium Carbonate: 2.5 grams per gallon will lower acidity by .1. 3.8 grams is equal to one teaspoon. Decide how much you want to lower the acid, but no more than .4, and measure your calcium carbonate for the entire batch of juice. Calcium carbonate is tartaric acid preferential, meaning, if you don’t use it properly, it will take out all or most of your tartaric acid, leaving the wine unstable. To avoid this, draw off about ¼ of the juice to be treated and mix all of the calcium carbonate into only that juice. After the calcium carbonate settles out, rack the juice off of it back into the main portion and mix well. This way, the calcium carbonate will react with all the of tartaric acid and then remove the other acids in the smaller portion because when it runs out of tartaric acid to neutralize it looks for other acids. Then when you return the treated portion to the untreated portion, you will have retained the tartaric acid in the untreated portion while lowering the overall acidity of the total batch.
Potassium Bicarbonate: This product can be mixed directly into the juice or wine. It reacts partially right away and finishes its job when the wine is cold stabilized. 3.4 grams per gallon will lower acid .10. 4.8 grams equals one teaspoon. Because Potassium Bicarbonate will raise the pH of your juice/wine (as will Calcium Carbonate) it is not recommended for use in juice or wine that is above 3.5 pH. NOTE: Make sure you leave plenty of head space when mixing these products in as they can foam…think Alka-seltzer.