Quick Reference Guide

Reducing Acid In Juices Using Calcium Carbonate

Grapes grown in cool-climate regions such as the Finger Lakes frequently have high acid levels—with titratable acidity (TA) values significantly above the recommended 0.65% to 0.70% (in metric 6.5 to 7.0 grams/liter). Winemakers faced with such juices who don’t want to add water or sugar to ameliorate the acid can follow a chemical de-acidification process utilizing calcium carbonate (CaCO₃), which is explained below.

BEFORE YOU START: 

You will need to know the initial TA% (not grams/liter) and the desired % reduction in TA. If the starting pH of the juice is 3.3 or higher, do not try to reduce TA more than 0.2% with this technique to avoid raising the pH of the juice too high or giving the wine a salty taste. If the starting pH of the juice is 3.2 or lower, a TA reduction as large as 0.4% is acceptable.

STEP 1:

Figure out how much CaCO₃ is required to reduce the TA by the desired amount in the entire amount of juice (the 25 in the formula below is the grams of CaCO₃ will completely neutralize 1 gallon of juice containing 1% tartaric acid):

Total CaCO₃ required = (# of gallons) * (% reduction in TA) * 25

STEP 2:

Figure out how much of the juice to use for the de-acidification:

Volume = [(% reduction in TA) / (initial TA%)] * (total volume of juice)

STEP 3:

Place the amount of CaCO₃ calculated in Step 1 in a container large enough to easily hold the volume calculated in Step 2. 

STEP 4:

While stirring continuously, slowly add the volume of juice calculated in Step 2 to the CaCO₃; there will be some foaming as the reaction proceeds. After all the juice has been added, continue stirring for a couple of minutes.

STEP 5:

Stir thoroughly every 15 minutes or so for a couple of hours, or until there is no foaming noted during stirring.

STEP 6:

Filter or decant the juice away from the precipitate; a coffee filter works pretty well. Return the de-acidified juice to the untreated portion and dispose of the precipitate somewhere other than by flushing it down the drain—it is reported that it turns to concrete!

An example

 Let’s assume that we have 5 gallons of juice that has a TA of 1.1% and we want to de-acidify it to a TA of 0.8%. From Step 1 above, we find that we need:

(5 gallons) * (1.1% - 0.8%) * 25 = 37.5 grams of CaCO₃.

Now, from Step 2 above, we calculate the quantity of juice to use for the treatment:

[(0.3%) / (1.1%)] * (5 gallons) = 1.36 gallons of the juice

Now it’s just a matter of following Steps 3-6 above: we add the 37.5 grams of CaCO₃ powder to a container with a capacity sufficient to contain at least 1.5 gallons, and slowly add the 1.36 gallons of juice to the powdered CaCO₃ while stirring with a spoon. After all the juice has been added, continue stirring for a couple minutes. Then periodically (every 15 minutes) stir the slurry over the next couple hours to make sure you give the reaction a chance to complete.

After a couple of hours, carefully decant the clear liquid away from the precipitate which settles to the bottom of the container. Don’t panic if a bit of the precipitate gets through or if you can’t quite get all the clear liquid; however, a coffee filter can be used to adequately separate the last of the liquid from the slurry. Finally, pour the treated clear liquid portion back into the container with the untreated portion of the juice and proceed with your winemaking process. Discard the precipitate into a trash receptacle or into the ground outside; do not pour it down the drain.

This procedure is based on Presque Isle Wine Cellars’ brochure entitled “Optimal Tartaric Acid Retention When Using Calcium Carbonate to Reduce Titratable (Total) Acidity”. For more about the chemistry involved please see the research article “How to Reduce Acid in Juices Using Calcium Carbonate”.

Back to top