Acidification & Deacidification Calculator

Indroduction

The Acidification & Deacidification Calculator determines the amount of a selected acid or deacidifier required to increase or decrease the acidity of a wine from its current value to some target value. If the target acidity is greater than the initial acidity, a list of acids will be shown. If the target acidity is less than the initial acidity, a list of deacidifiers will be shown.

Acid blend is assumed to be a blend of 40% tartaric, 40% malic, and 20% citric acids.

Input Field Definitions

Target Acidity – The desired acidity of the wine.

Initial Acidity – The current acidity of the wine.

Wine Volume – The volume of wine being treated.

Acid Type – The acid to be used to treat the wine. The list of acids will be shown if the target acidity is greater than the initial acidity. Acid blend is assumed to be a blend of 40% tartaric, 40% malic, and 20% citric acids.

Deacidifier Type – The deacidifying agent to be used to treat the wine. The list of deacidifiers will be shown if the target acidity is less than the initial acidity.

Output Field Definitions

Acid Required – The calculated mass of the selected acid required to achieve the target acidity.

Deacidifier Required – The calculated mass of the selected deacidifier required to achieve the target acidity.

Calculation Details

There are two scenarios we need to consider for this calculation.

Initial acidity is less than the target acidity.
Initial acidity is greater than the target acidity.

For the first scenario, FermCalc will calculate the amount of acid required to increase the acidity to the specified target. For the second case FermCalc will calculate the amount of deacidifier to add.

If you are diluting a must with water, blending juices, or blending wines to adjust acidity, use the Blending Calculator to calculate the proportions required to achieve the desired acidity.

Case 1: Initial Acidity is Less Than the Target Acidity

For this case we’ll be adding acid to increase the acidity. FermCalc first converts the initial and target acidity values to the tartaric reference using the conversion factors explained in the Acidity Conversions discussion.

To calculate the required addition of the selected acid we need to write a molar balance equation for the H⁺ ions in the wine. The final (or target) number of H⁺ ions must equal the initial number of H⁺ ions plus the number of H⁺ ions added, or:

i_ta_fv/mw_t = i_ta_iv/mw_t + i_am_a/mw_a

(3-5)

where:

i_t = number of H⁺ ions per molecule for tartaric acid

a_f = target (final) acidity, grams/liter tartaric

a_i = initial acidity, grams/liter tartaric

v = volume of wine, liters

mw_t = molecular weight of tartaric acid, grams/mole

i_a = number of H⁺ ions per molecule for the acid being added

m_a = mass of acid required, grams

mw_a = molecular weight of the acid being added, grams/mole

Rearranging to solve for the mass of acid to add we get:

m_a = v(a_f – a_i)(i_t/mw_t) / (i_a/mw_a)

(3-6)

Values of molecular weight and number of H⁺ ions per molecule are shown in the table below, compiled from Margalit (2004) and Weast (1977).

Acid	Molecular Weight	H⁺ Ions
Tartaric	150.09	2
Malic	134.09	2
Citric	192.12	3

For Acid Blend, the composition is assumed to be 40% tartaric, 40% malic, and 20% citric acids.

Case 2: Initial Acidity is Greater Than the Target Acidity

For this case we’ll need to add a deacidifier such as calcium carbonate (CaCO₃), potassium carbonate (K₂CO₃), potassium bicarbonate (KHCO₃), or potassium hydroxide (KOH) to reduce the acidity. All of these work by neutralizing tartaric acid, or H₂T, where T represents a tartrate ion (C₄H₄O₆). The reaction equations are (Margalit, 2004 and Beelman et al., 1979):

CaCO₃ + H₂T —> CaT + H₂O + CO₂	(3-7)
K₂CO₃ + 2H₂T —> 2KHT + H₂O + CO₂	(3-8)
KHCO₃ + H₂T —> KHT + H₂O + CO₂	(3-9)
KOH + H₂T —> KHT + H₂O	(3-10)

Note that KOH is not authorized by the Alcohol and Tobacco Tax and Trade Bureau (TTB) for treatment of wine or juice, so it cannot be used by commercial wineries. But that shouldn’t stop amateur winemakers from using it.

To calculate the required amount of any of these additives, we need to know their molecular weights as well as the number of H₂T molecules that are neutralized by each molecule of deacidifier. These parameters are tabulated below.

Deacidifier	Molecular Weight	Molecules of H₂T Neutralized
Calcium Carbonate	100.09	1
Potassium Carbonate	138.21	2
Potassium Bicarbonate	100.12	1
Potassium Hydroxide	56.106	1

We can calculate the required mass of deacidifier to add by balancing the initial and final quantities of H₂T molecules present against the number of molecules neutralized, or:

n·m_d/mw_d = v(a_i – a_f)/mw_t

(3-11)

where:

n = molecules of H₂T neutralized per molecule of deacidifier

m_d = mass of deacidifier added, grams

mw_d = molecular weight of the deacidifier being added, grams/mole

v = volume of wine, liters

a_f = target (final) acidity, grams/liter tartaric

a_i = initial acidity, grams/liter tartaric

mw_t = molecular weight of tartaric acid, grams/mole

Solving for the amount of deacidifier we get:

m_d = v(a_i – a_f)mw_d/(n·mw_t)

(3-12)

Based on equation (3-12) above, FermCalc calculates the following addition rates to reduce acidity by 0.1% (1 g/l) tartaric.

Calculated Addition Rates to Reduce Acidity by 0.1% (1 g/l) Tartaric
Deacidifier	grams/liter	grams/gallon(US)
Calcium Carbonate	0.67	2.52
Potassium Carbonate	0.46	1.74
Potassium Bicarbonate	0.67	2.53
Potassium Hydroxide	0.37	1.42

For additional information on using these additives, see this article by Bill Collings.