Lecture-04 11 19

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Tartrate precipitation:
Tartrate crystallization and precipitation
Stability tests
Stabilization treatments
Sofia Catarino
Harvest
Crushing and Destemming
Alcoholic Fermentation with Maceration and Pumping over
Running off and Pressing
Sedimentation
Racking
Malolactic Fermentation
Racking (SO2 correction)
Storage in Vats
Oak Barrel Aging
Clarification/Stabilization
by Fining
(Blending)
Tartaric
Stabilization/Filtration
Bottling
Bottle Aging
Schematic representation of the Production of Red Wine
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TARTARIC PRECIPITATION
 One of the most common causes of bottled wines unstability is the appearance of
sediments of K bitartrate, and in a less extent, Ca tartrate
 Tartrate precipitation is a natural phenomenon of wine evolution, occurring during
vinification and conservation
 Although these sediments possess no problems concerning human health, they can lead
to important economic losses because it may change consumer’s perception on wine
quality
 Tartaric stabilization, before bottling, became almost mandatory
Tartaric acid is specific to grapes (“wine acid”)
One of the most prevalent acids in unripe grapes and musts
Concentrations in musts: 2-3 g/l (southern vineyards) – 6 g/l (north)
K and Ca contents in wines
TARTRATE PRECIPITATION
In wine, simple salts are dissociated into hydrogen tartrate (TH-) and tartrate (T2-) ions, 
according to its dissociation balances: 
H2T H
+ + TH- and TH- H+ + T2-
Total molar concentration of tartaric acid: C = [[[[H2T]]]] + [[[[TH
-]]]] + [[[[T2-]]]]
pH 3.0
[H2T] = 0.5126 C
[TH-] = 0.4675 C
[T2-] = 0.0199 C
(acid dissociation contants: pK1 = 3.04; pK2 = 4.37)
pH 3.5
[H2T] = 0.234 C
[TH-] = 0.6749 C
[T2-] = 0.091 C
Free forms
Combined forms
Combined forms
Considering 100 molecules of H2T, at pH 3.5, 23.4 are free, 67.49 semi-combined and 9.1 totally combined
K1 = ([TH
-] × [H+]) / [H2T]
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TARTRATE PRECIPITATION
Potassium bitartrate (KHT) Potassium tartrate (K2T) Calcium tartrate (CaT: CaC4H4O6.4H2O)
Double Potassium calcium tartrate
(highly soluble)
Calcium tartromalate
(relatively insoluble, crystallizes in needles)
At wine pH, and in the presence of K+ and Ca2+ cations, tartaric acid (H2T) is mainly salified in 
5 forms:
Fig. Structure of tartaric acid salts
 Double potassium calcium tartrate
and calcium tartromalate (complex
salts of tartaric acid) show the
property of forming and remaining
stable at a pH over 4.5
TARTRATE PRECIPITATION
Tartaric acid Potassium bitartrate Neutral calcium tartrate
L(+)-C4H6O6
4.9 g/l
KHC4H4O6
5.7 g/l
CaC4H4O6.4H2O
0.53 g/l
Solubility in H2O at 20 °°°°C in g/l of tartaric acid, KHT and CaT
 KHT is perfectly soluble in H2O, but relatively insoluble in alcohol: S=2.9 g/l (10% vol, 20 °C)
 [[[[K]]]] in wine is high enough to exceed the solubility of potassium bitartrate (1183 mg/l of K –
5.7 g/l of KHT)
POTASSIUM BITARTRATE and CALCIUM TARTRATE show special enological importance: 
low soluble salts, causing the most problems in terms of crystalline deposits in wine
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Crystalline deposits
KHT – needle shaped crystals; acid taste
CaT – high risk of occurrence: 80 mg/l 
(white wines); 60 mg/l (red wines) 
Attention: these are empiric limits!
KHT crystallization in wine involves the following sequence
of phenomena:
1. Supersaturation
2. Nucleation
3. Growth
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1.SUPERSATURATION PHASE:
KHT TH- + K+
solid In solution
Solubility balance
CP = [[[[TH-]]]]r [[[[K
+]]]]r Concentration Product (CP) of the real concentrations (r)
SP = [[[[TH-]]]]e[[[[K
+]]]]e Solubility Product (SP)
The concentrations (e) of hydrogen tartrate (TH-) anions and K+ cations are theoretically
obtained at the thermodynamic equilibrium of the KHT/dissolved KHT system, under the T
and P conditions of the wine
SUPERSATURATION PHASE
The wine is supersaturated if, at under a defined T, the Concentration Product is higher than
the Solubility Product:
PC > SP →→→→ Supersaturated wine
i.e. if the the amount of dissolved solute exceeds the allowable (thermodynamic point of view)
Precipitation of the excess salt until equilibrium is reached (PC = SP)
SUPERSATURATION PHASE
 Supersaturation is necessary, but not sufficient, for primary nucleation phenomena and
spontaneous crystallization to occur in a wine
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B A
A and B define 3 fields of states:
(1) - Stable zone (CP < SP) (Added KHT is
immediatly dissolved)
(2) – Supersaturation zone (the probability
of spontaneous occurrence of crystals is low, 
growing of crystals already formed)
States of KHT in a system correlating T/Conc. axes with conductivity
3
2
1
(3) - Unstable zone (spontaneous formation
of crystals)
Curve A - obtained by adding 4 g/l of KHT to wine and by recording
the conductivity according to T;
Curve B – obtained by linking the spontaneous crystallization
T points of a wine brought to various states of supersaturation
by completely dissolving added KHT and then reducing T until
crystallization is observed
Curve A represents
the boundary
between 2 possible
states of KHT 
according to T
A – Solubility (or saturation) curve
B - Hypersolubility (or crystallization) curve
From solubility (A) and hypersolubility (B) curves, it is
possible to determine the state of the wine at a known T
Tsat 1.1 - Saturation T of a wine in which
1.1. g/l KHT have been dissolved
NUCLEATION PHASE
2. NUCLEATION PHASE 
The formation of a small crystal, known as nucleous, in a liquid phase corresponds to the
creation of an interface between liquid and solid phases, requiring a great deal of energy
(interfacial surface energy)
Types of nucleation:
a) Primary or spontaneous nucleation
b) Secondary or induced nucleation
a) Primary or spontaneous nucleation –
under natural conditions, it is an unreliable, unpredictable phenomenon. Corresponds to
spontaneous emergence of nucleous. It takes an induction time, and the presence of TH- and
K+ at the limit of supersaturation.
(traditional stabilization process is based on it)
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NUCLEATION PHASE
b) Induced or secondary nucleation –
Formation of crystallization nucleous induced by the presence of very small particles in the
wine (related to the rupture of pre-existing crystals)
(rapid stabilization processes are based on homogenous induced nucleation)
Homogenous nucleation (salts only) – originated by the presence of crystals (endogenous, or
by addition) of the same chemical nature of the salt. The addition can result in a strong
decrease of the induction time (nucleation phase becomes less limiting)
Heterogenous nucleation (involves impurities, rugosities) – promoted by the presence of other
particules than the salt. The number of formed nuclei is independent of the concentratioin of
TH- and K+
GROWTH PHASE
 Once the formed nuclei are stable, crystals can growth, by incorporating TH- and K+ in
the active points of nuclei surfaces
 The association of K+ and TH- is not stoichiometric. There is more K+ ions on the
crystal surface, that becomes positively charged (negatively charged colloids may be
adsorbed, blocking the crystal growth)
 Binding between TH- and proteins (positively charged) may difficult crystal growth
 K+ and TH- may bind with tannins (crystalization in red wines takes more time than in
white wines)
The width of the saturation field (DS), expressed in °°°°C, is increased by the presence of
macromolecules that inhibit the growth of nuclei and crystallization of KTH:
Proteins and condensed tannins, glucide polymers (from grape and of yeast origin)
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CRYSTALLIZATION KINETICS
• Crystallization kinetics: involves nucleation speed and crystal growth speed
• Crystal growth speed is controled by: 1) transport of the solute to crystal surface; 2)
movement of the solute on surface/surface integration (the slower reaction determines
the crystallizationrate)
Diagram ilustrating the importance of the diffusion speed of THK
aggregates (X) towards the solid/liquid adsorption interface for the
growth of nuclei.
FA, adsorption film; X, molecular aggregate of THK diffusing towards
the interface; IS/L, solid/liquid interface; N, nuclei; C, THK
concentration in the liquid phase; C1, THK concentration at the
solid/liquid interface; S, theoretical solubility of THK; C-S,
supersaturation of the wine; C>C1>S
(Ribéreau-Gayon et al., 2006)
The crystallization rate is directly proportional to the surface
area of the liquid/solid interface represented by the nuclei:
INFLUENCE FACTORS ON KHT CRYSTALLIZATION
pH KHT solubility depends on the concentration product of TH- and K+ and on
wine pH (that influences tartaric acid dissociation).
The proportion of TH- ions is maximal between 3.5 and 4.0 (facilitating KHT
formation)
Temperature T strongly influences the KHT solubility balance. T decrease promotes
insolubilization. Some stabilization techniques explore this effect
Alcoholic
strength
KHT solubility is inversely proportional to alcoholic strength. KHT solubility
decreases during AF
Ionic
strenght
KHT solubility is proporcional to ionic strenght
Stirring Increases the crystallization rate (promotes nucleation speed)
Colloidal
composition
of wine
KHT highly depends on wine composition. The inhibition effect is more important in
red wines. Presence of protective colloids: macromolecules e.g. polyphenols,
polyssacharides (RGI, AGP and mannoproteins) and proteins
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CALCIUM TARTRATE
The crystallization of CaT is a similar phenomenon to KHT
CaT instability is more difficult to control than KHT. Its precipitation tends to occur later,
usually after botling. Very difficult to predict and avoid
Ca origin in must and wine: endogenous, addition of CaCO3 (deacidification), Ca bentonite,
accidental contaminations
SP = [[[[T2-]]]]e[[[[Ca
2+]]]]e
CaT T2- + Ca2+ Solubility balance
Solid In solution
Concentration Product (CP) of the real concentrations (r)CP = [[[[T2-]]]]r [[[[Ca
2+]]]]r
Solubility Product (SP)
If CP > SP, the wine is supersatured
The concentrations (e) of T2- anions and Ca2+ cations are theoretically
obtained at the thermodynamic equilibrium of the CaT/dissolved CaT
system, under the T and P conditions of the wine
CALCIUM TARTRATE – crystallization kinetics
 Nucleation of CaT is more difficult than KHT. Temperature decrease (and
consequently increase of supersaturation) is not enough to induct spontaneous
nucleation
 The induction time required for spontaneous nucleation is much higher than
KHT (CaT precipitation usually occurs later)
 CaT crystallization is a slow and random phenomenon. Wine stabilization on
KHT is not enough to promote the secondary nucleation of CaT
• CaT precipitation is much more slower than KHT 
• CaT is the least soluble salt of wine (~10 fold less than KHT)
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INFLUENCE FACTORS ON CaT CRYSTALLIZATION
pH CaT solubility strongly depends on the pH, varying inversely
Temperature CaT solubility is less dependent on T than KHT solubility. The decrease of CaT
solubility with T is deep related to pH
(T decrease to values close to freezing point is not effective to CaT
precipitation)
Alcoholic
strength
CaT solubility is inversely proportional to alcoholic strength
Ionic
strenght
CaT solubility is proporcional to ionic strenght. Organic acids present
inhibitory effect on precipitation (citric > malic > lactic > succinic)
Colloidal
composition
of wine
CaT highly depends on wine composition. Polyphenols, polyssacharides (RGI, AGP
and mannoproteins) and proteins may acct as inhibitors, affecting the energy barrier
to crystal grow. Their linkage to CaT reduces its concentration in solution (thus its
supersaturation degree), or blocking the nuclei formation
Mestrado em Viticultura e Enologia
Tartrate precipitation:
Stability tests
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Tests for predicting wine tartaric stability
The wine tartaric stability should be evaluate in order to:
 To decide on wine treatment
 To define the treatment intensity (conditions)
 To evaluate the stability of the wine after treatment
Tests for predicting wine tartaric stability
1.Cold test
Traditional and empirical test
 Consists in the storage of the wine (100 ml), taken before or after cold stabilization, in a 
refrigerator for 8-10 days at a temperature close to its freezing point (-4, -5 °°°°C) and then
inspected for crystals. If crystals are observed the wine is considered unstable.
Tfreezing ≅≅≅≅ (1-alcoholic strength)/2
Advantages: simple, practical, requires no special equipment
Disadvantages: mainly qualitative; does not provide accurate indication on the wine´s degree
of instability. It takes a long time (incompatible with short contact stabilization technologies,
where rapid results are essential to assess the treatment’s effectiveness in real time)
• Not reliable, nor easily repeatable, as it is based on the phenomenon of spontaneous
crystallization – a slow and unreliable process
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Tests for predicting wine tartaric stability
2.“Mini-contact” test (Müller-Spath)
 Consists in the maintainance of the wine, after addition of 4 g/l potassium bitartrate, at a
temperature of 0°°°° C for 2 h, and constantly agitated. Assessment of the weight increase
of the KHT (precipitate) collected (exogeneous KHT ++++ wine KHT)
 The test is based on homogeneous induced nucleation, which is faster than primary
nucleation. However the test does not take into account the particle size of the seed
tartrate, although its importance on the crystallization rate
 The test defines the stability of the wine at 0°°°° C and in its colloidal state at the time of
testing (colloidal reorganization during storage and wine aging is not considered)
 The test tends to overestimate the wine’s stability. It was observed that after 2 hours’
contact, only 60-70% of the endogeneous tartrate has crystallized (Boulton, 1982)
Simple, moderately reliable, relatively long
Tests for predicting wine tartaric stability
3. Adapted mini-contact test (associated to conductivity measurements)
In order to make the mini-contact test faster, more reliable:
Seeding the wine with 10 g/l of KHT and measuring the drop in conductivity at 0 °°°°C:
- If, in the 5-10 min after seeding, the drop in conductivity is no more than 5% of the wine’s
initial conductivity, the wine may be considered to be stabilized;
- If the drop in conductivity is over 5%, the wine is considered unstable (3% for white
wines). Alternative criterion: decrease of conductivity (>40-45 µS/cm – high risk of precipitation)
 The test is based on measuring the electrical conductivity, no need to collect the
precipitate
 Much faster (5-10 min, instead of 2 h)
 The state of supersaturation of the wine is multiplied by 2.5 (adding 10 g/l instead of 4
g/l), giving more accurate assessment of a wine’s stability
Disadvantages: does not take into consideration the effect of particle size, is based on
excessively small variations in conductivity and too short contact time
During the crystal growth, the conductivity
decreases due to K+ integration within the
crystal lattice
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Applied to wines to be treated by electrodialysis (Escudier et al., 1993)
Evaluation of the conductivity of a wine at -4 °°°°C, under stirring, during 4 hours, after filtration
(0.65 µµµµm) and addition of 4 g/l KHT
The kinetics of decrease in conductivity is modeled to calculate the conductivity by an infinite 
time: 
If IDT(%) < 5%, stable wine
If 5% < IDT (%) < 10%, slightly unstable wine, the decision to treat is economical
If IDT (%) > 10%, unstable wine
Ci – Cf (inf)
Ci
×××× 100IDT (%) =
Deionization rate (electrodialysis treatment) = IDT % 
4. Instability Degree Test (I.D. Test) 
Tests for predicting wine tartaric stability
5. Saturation temperature (Wurdig Test) 
Reasoning: the more KHT a wineis capable of dissolving at low temperature, the less
supersaturated it is with the salt, therefore, the more stable it should be in terms of bitartrate
precipitation
Saturation temperature concept:
The saturation temperature of a wine is the lowest temperature at which
it is capable of dissolving (exogeneous) potassium bitartrate
Temperature is used as a means of estimating the bitartrate stability of a wine
Tests for predicting wine tartaric stability
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Experimental determination of the saturation temperature of a wine
The saturation temperature is determined by measuring electrical conductivity in a two-step
experiment:
1st experiment: the wine is cooled to a temperature of approximately 0 °°°°C in a thermostat-
controlled bath equipped with sources of heat and cold. The T is then raised to 20 °°°°C in 0.5
°°°°C increments and the wine’s conductivity measured after each temperature change
2nd experiment: the wine is brought to a temperature close to 0 °°°°C, 4 g/l of KHT crystals are
added and the temperature is raised to 20 °°°°C in 0.5 °°°°C increments and the wine’s
conductivity measured after each temperature change
Determination of the saturation temperature of a wine by the gradient temperature method
(Wurdig et al., 1982). Supersaturated wine; crystallization occurs immediately after KHT addition
“with added KHT curve” – the
wine’s conductivity at T around 0
°C was below that of the wine
without addition, indicating that at
low T, crystal addition induces
crystallization, revealing a state of
supersaturation. Its conductivity
increased in a linear manner until
TA; then KHT started to dissolve.
At TB, the exponencial solubility
curve crossed the line of the wine
alone
Curve A and curve B intersection
corresponds to the wine true
saturation temperature (Tsat)
Example of a highly supersaturated wine:
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Saturation temperature of a wine
On the industrial scale (where rapid stabilizations are used), experimental determination of
the saturation temperature by the temperature gradient method is incompatible with the
rapid response required.
Based on statistical studies of several hundreds of wines, a linear correlation was
established Wurdig et al. (1982):
∆∆∆∆L 20 °°°°C – variation in the conductivity of a wine at 20 °°°°C before and after the addition of 4
g/l of KHT
The pratical advantage of using this equation is that the saturation temperature may be
determined in a few minutes, using only two measurements
Only applicable to wines where the solubilization temperature of KHT is between 7 and 20 °°°°C
Tsat = 20 -
(∆∆∆∆L) at 20 °C
29.3
Saturation temperature of a wine
Rosé and red wines most common show high saturation temperature. Samples are heated to 
30 °°°°C. KHT is added ant the increase on conductivity at this temperature is measured.
(Maujean et al., 1985)
• The higher the saturation temperature, greater the risk of crystallization due to a
decrease of temperature (storage conditions)
• The lower the saturation temperature, higher the wine tartaric stability
Tsat = 29.91 -
(∆∆∆∆L) at 30 °C
58.3
Remind Saturation temperature concept:
The saturation temperature of a wine is the lowest temperature at which
it is capable of dissolving (exogeneous) potassium bitartrate
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Relation between saturation temperature and stabilization temperature
In practice the knowledge of the T below which there is a risk of tartrate instability is the
most important
• Relationship between saturation temperature and stability temperature (Maujean et al., 1985,
1986):
This equation ignores protective colloids…
If stability is required at -4° C, the saturation temperature should not exceed 11° C
A red wine with IPT = 50, will be stable if
Tsat < 25.6 °C (test at -2 °C)
Tstab= Tsat – 15 °°°°C
Tsat < (10.81 + 0.297 IPT) °°°°C
• Relationship between tartaric stability of red wines with saturation temperature and total 
phenols index (Gaillard et al., 1990):
White wines
(alcoholic strength < 11.0 % vol)
Relation between saturation temperature and stabilization temperature
Stability is achieved if:
White wine is stable if: Tsat <<<< 12.5 °°°°C
Rose wine is stable if: Tsat <<<< 14 °°°°C, TPI >>>> 10
Red wine is stable if: Tsat <<<< 22 °°°°C, TPI <<<< 50
Red wine is stable if: Tsat <<<< 24 °°°°C, TPI >>>> 50
(by reference to a test of 15 days at -2 °C)
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Tartrate precipitation:
Stabilization treatments
Harvest
Crushing and Destemming
Alcoholic Fermentation with Maceration and Pumping over
Running off and Pressing
Sedimentation
Racking
Malolactic Fermentation
Racking (SO2 correction)
Storage in Vats
Oak Barrel Aging
Blending
Clarification/Stabilization
by Fining
Tartaric
Stabilization/Filtration
Bottling
Bottle Aging
Schematic representation of the Production of Red Wine
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Stabilization treatments / processes
To be done if the wine is unstable!
Several methods to perform a wine stabilization aiming to prevent this instability, based on
different principles:
 The removal of some tartaric acid (cold stabilization)
 The removal of the cations K+ and Ca2+, necessary to the precipitation of the tartaric
acid in the form of crystals of KHT and CaT (electrodialysis and ion exchange)
 Using additives (metatartaric acid, mannoproteins or carboxymethylcellulose) to 
prevent the crystals to be formed
Physical methods
Chemical methods
Stability
Cristalization
Temperature
COLD STABILIZATION  The principle common to all cold stabilization
techniques consists of cooling the wine at a T near the
freezing point, to induce crystallization (preventive)
and consequent separation of formed crystals
 At a constant concentration (or conductivity),
when the T of the wine decreases, KHT
changes from state 2 where it is
supersaturated, to state 3, i.e. where the
spontaneous formation of crystals occurs
(unstable zone)
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Stabilization treatments / processes
COLD STABILIZATION 
 The principle common to all stabilization techniques consists of cooling the wine at a T near the
freezing point, to induce crystallization and consequent separation of formed crystals (preventive
action)
 For most successful stabilization, the wine should be previously clarified (e.g. coarse filtration), to
eliminate protective colloids
1. Slow cold stabilization, without tartrate crystal seeding
2. Rapid cold stabilization with tartrate crystal seeding: static contact process
3. Rapid cold stabilization: dynamic continous contact process
Stabilization treatments / processes
 1. Slow cold stabilization, without tartrate crystal seeding (traditional technology for KHT
stabilization of wine)
 Consists of cooling the wine at a T near the freezing point, to induce spontaneous nucleation
(endogenous KHT nucleous) and then the crystallization. Followed by filtration at the treatment
T. Faster cooling promotes more complete precipitation in the form of small crystals (more difficult to separate by
filtration. Can rapidly redissolve if T increases)
Freezing temperature of the wine is empirically determined according to the expression:
Freezing T (°°°° C) = (1-alcoholic strength) / 2
 Very slow process: 2-3 weeks to achieve the tartaric stabilization. Its effectiveness depends on wine
composition (colloidal content plays an important role)
 There is risk of excessive oxidation as oxigen dissolves more rapidly at low T (oxigen: 11 mg/l at 0
°C, 8 mg/l at 15 °C). Decrease on colour intensity (precipitation of phenols together with KHT salts).
Time and energy consuming. Not effective for CaT. It takes refrigeration equipment, isothermal vats
Treatment T °°°°C = [[[[1 - (% vol. / 2)]]]]
Usual T ~ -4, -5 °°°°C
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Schematic diagram of a cold stabilization installation
Untreated wine Treated wine
Wine during
stabilization
Filter
Refrigeration
system
Heat exchanger for precooling wine to be
treated using it to warmtreated wine
Stabilization treatments / processes
 2. Rapid cold stabilization with tartrate crystal seeding: static contact process
 Consists of cooling the wine at a T near 0 °°°°C, seeding 400 g/hl of KHT crystals, in
continous agitation. The addition of crystallization nuclei at low T promotes homogenous
induced nucleation
 After a contact time for crystal growth, the KHT (added and surplus) is separated by settling,
centrifugation or filtration
 Seeding with KHT does not induce CaT crystallization (while seeding with CaT induces KHT
crystallization)
Advantages: reduction of treatment time (to a few hours) and of energy consume. It is possible
to run 2-3 cycles per days (v = 50-100 hl /bach)
Disadvantage: Price of KHT. Costs may be reduced, by recycling the crystals (white wines) using
devices for KHT separation (hydrociclone)
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Stabilization treatments / processes
 3. Rapid cold stabilization stabilization: dynamic continous contact process
 Continous KHT stabilization process. The contact time of crystals (400 g/hl) with wine
(under agitation), is regulated by the volumetric flow rate of the crystallizer, and by the
supersaturation state of wine.
e.g. throughput = 60 hl/h; volume of crystallizer = 90 hl; treatment time = 1 h 30 min
 Continous treatment is more demanding than the other processes in terms of operational
control:
- Particle size of contact tartrate and the level in the crystallizer must be monitored by sampling
after a few hours;
- Need for a method of monitoring effectiveness with a very short response time (if the treatment
is insufficiently effective, wine can be recycled through crystallizer)
It requires close monitoring, but it is also more efficient
After cooled (near to freezing point), the wine is sent to an isolated crystallization tank,
where due to supersaturation and turbulence, rapid cristallization occurs. Following, the
wine is immediatly filtred to avoid the redissolution of KHT.
Fig. Schematic diagram of a continous cold stabilization system: 1-intake of wine to be treated; 2-heat 
exchanger; 3-refrigeration system; 4-insulation; 5-mechanical agitator; 6-recycling circuit (optional); 7-outlet of 
treated wine; 8-filter (earth); 9-drain; 10-overflow. 
(Ribéreau-Gayon et al., 2006)
 3. Rapid cold stabilization stabilization: dynamic continous contact process
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Stabilization treatments / processes
Advantages Disadvantages
• Well-known (experienced) technique • Requires previous filtrations
• Stabilization with regards to colloidal
colourant matter precipitation (red
wines)
• Requires an additional filtration for 
crystals removal
• Recovery of tartrates • The effectiveness is not always very
good (in special for red wines)
• High energy consume
COLD STABILIZATION TREATMENTS 
Cold stabilization in wine clarification/stabilization line
(example of a schematic diagram) 
Wine
Fining
Settling/racking
Rough filtration
(e.g. with coarse diatomaceous earth)
Filtration
Cold treatment
Low temperature filtration
Sterile filtration (microfiltration: 0.1 -10 µm) / heat treatments
Additives
Bottling / Packaging
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Stabilization treatments / processes
Physical method for the extraction of ions in super-saturation in the wine under the
action of an electric field with the help of membranes permeable only of anions on the
one hand, and membranes permeable only to cations on the other hand
Electrodialysis (ED)
• ED is an energy-efficient alternative to
cold stabilization
• With ED, the wine passes through an
electrical field. Charged ions are removed
as the wine passes through anionic and
cationic membranes
• Wine is circulated from bulk storage
tanks through the ED unit until desired
conductivity levels are reached
Driving force allowing the transfer: Electric field E
Electrodialysis (ED)
Theoretically, all cations and anions can be affected by electrodialysis
However, ions and anions exhibit different behaviours depending on:
- Ion mobilities (charge/mass ratio)
- Ion dimensions
- The membrane
The membrane pair must allow the removal of TH-, T2-;
K+, and Ca2+
The membrane pair must allow the transference of
organic anions:
If K+ removal is excessive in comparison with TH-
removal, the pH change can be unacceptable
Consequences: alcoholic strength decrease (≤≤≤≤0.1 % vol.); pH decrease (≤≤≤≤0.25); volatile
acidity decrease (<<<< 0.09 g/l H2SO4)
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CM – cation exchange membrane; AM – anion exchange membrane; D – diluate chamber;
K – concentrate chamber; e1, e2 – electrode chambers
Fig. Schematic representation of electrodialysis process
Wine to be treated
 ED modules have two electrodes placed at the ends of stacking chambers; are
hydraulically separated by sets of anionic and cationic membranes, respectively
preferentially permeable to anions (HT- and T2-) and cations (K+, Ca2+)
CM – cation exchange membrane;
AM – anion exchange membrane;
D – diluate chamber;
K – concentrate chamber
e1, e2 – electrode chambers
Fig. Schematic representation of electrodialysis process
Wine to be treated
 Ion transport is promoted by a continuous electric field applied between the two electrodes
 An ED module is composed by a large number of cells (basic units). Each cell comprises a
diluate chamber and a concentrate chamber
 The wine flows parallel to the membrane in the dilution chambers, and the ions contained are
moved into the adjacent chambers (concentrate), where are retained.
 Thus, progressively, the wine as it flows in the diluate chambers gets depleted in K ions,
whereas in the concentrate chamber, the concentration increases
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CM – cation exchange membrane;
AM – anion exchange membrane;
D – diluate chamber;
K – concentrate chamber
e1, e2 – electrode chambers
Fig. Schematic representation of electrodialysis process
Wine to be treated
• The selectivity of the membranes means that, under the action of an electric field,
increase of ion concentration in one of the chambers (concentrate chamber), while
decreases in the next chamber (diluate chamber)
The intensity of the treatment depends on wine instability
Affecting factors: speed, P, T
Fig. Schematic representation of electrodialysis process
• The wine is admitted in the ED tank and circulates in the electrodialysis stacks untill the
final conductivity is reached
• The treatment is based on the stability test TID (%)
• This test can be integrated in the ED unit
• Average rate of treatment = 15% (maximum rate 30%)
• Once achieved the extraction rate the treated wine is released and a new bach is admitted
(the control is carried out by a integrated condutivimeter)
• Periodicaly, whashing of the system with acid and alkaline solutions
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Operating limitations
• Solubility of tartrates with Ca2+, K+ in the concentrate – risk of cristallization
• Temperature effect (operating temperature ~~ 9-10 °°°°C)
! Water addition is required to dilute the concentrate percluding cristallization
(conductivity <<<< 7 mS)
! Nitric acid addition to maintain pH between 3 and 3.5
! Water consumption (1 hl/10 hl of wine), high volume of effluents
Stabilization treatments - Electrodialysis
Tartrate stabilization of wines by different treatments – effect on conductivity
(Cameira dos Santos et al., 2000)
Cold treatmentControl Electrodialysis
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Stabilization treatments - Electrodialysis
Tartrate stabilization of wines by different treatments – effect on cations and anions concentrations
(Cameira dos Santos et al., 2000)
Sensory analysis:
No significantly differences
were found between control
and ED treated wines
Control Cold treatment Electrodialysis
Stabilization treatments – Ion exchange
Ion Exchange (Reg EC 606/2009)
 The principle of this technique is the use of a cation-exchange resin in the protonated
form, where ions in the wine are replaced by the protons (e.g. H+, Na+, Mg2+) from the
resin.Typically, this operation involves mixing a certain amount of wine treated with the
rest of the untreated wine
 Insoluble polymer resins, activated with various funcional groups. The polymerized material is
usual based on a mixture of styrene and vinyl benzene. The active radical of cation exchangers
are generally sulfonic acid (-SO3H)
 Ion exchange phenomena are stoichiometric (i.e., 37 mg of K are exchanged by 23 mg of Na)
 Ion exchange rate depends on the type of exchanger: grain size, porosity and
distensibility
Resins criteria for winemaking use:
Mechanical strength, total insolubility in wine and the absence of off-flavors
Must also be capable of being regenerated many times
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Stabilization treatments / processes
Ion exchange resins Equipment StabyMatic 500 (AEB group)
An exchanger generally has a specific affinity for
different ions. In the case of cations, the affinity laws
indicate:
 The ease of exchange increases with the valence of
the exchanger ion: Na+ < Ca2+ < Al3+. Divalent ions are
fixed on the resin in preference to monovalent Na and K ions.
 If two ions have the same valence, the ease of
exchange increases with the atomic number. K is
fixed in preference to Na and Ca in preference to Mg
(Ribérau-Gayoin et al., 1977)
Cation exchangers are likely to improve tartrate stability
by removing K+ and Ca2+, acidify wine by releasing H+, and
possibly, prevent ferric casse by reducing Fe3+
C – Control
AMT – Metatartaric acid
RTI – Cation exchange resin
F – Cold stabilization
(Cabrita et al., 2014)
Effect of different stabilization treatments on wine composition
Total acidity
Tartaric acid
Total phenols
Color intensity
Red wines White wines
Different white and red wines
pH
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(Cabrita et al., 2014)
C – Control
AMT – Metatartaric acid
RTI – Cation exchange resin
F – Cold stabilization
Results on tartaric stability after treatment
Decrease in conductivity (Mc)
• Mc > 40-45 µS cm-1
High risk of KHT 
sedimentation
• Mc < 20-25 µS cm-1
Stable wines
Red wines White wines
Percentage of treated wines:
VT2 – 12.5%; other red wines
and VB2 – 15%; VB1 – 10%
of wine treated by resin
Preventive treatment - Addition of Metatartaric acid
Tartrate stabilization can be achieved by the addition of substances that prevent crystal
precipitation, either by inhibiting their formation or by the modifying their properties and
making them soluble at a lower T
MTA acts by opposing the growth of submicroscopic nuclei around
which crystals are formed:
The large uncrystallizable molecules of MTA are in the way during
the tartrate crystal building process, blocking the “feeding”
phenomenon (crystal growth)
MTA is produced by fusion (170 °C) of tartaric acid powder under controlled conditions. This process
creates internal esterification within the tartaric acid structure, at a legally imposed minimum rate of
40%.
This reaction is reversible as tartaric acid may be formed again by hydrolysis
Metatartaric acid (MTA) is the product most widely used for this purpose
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Stabilization treatments - Metartaric acid
 Up to 10 g/hl to make the wine stable against KHT and CaT precipitations (maximum dose)
 The duration of the protecting effect depends on the quality of MTA (higher sterification
rate gives a longer period of protection) and the T at which the wine is stored (lower
storage temperature increases the period of protection):
Several years at 0 °C
Over 2 years at 10-12 °C
3 months at 25 °C
1 week at 30 °C 
MTA main drawback: low stability in wine, as it hydrolyses over time generating tartaric acid,
losing its protector effect and enhancing tartrate unstability
An alternative when there is no refrigeration equipment; lightly unstable wines
Only on wines to be sold and consumed rapidly
• Available in crystalline form or in 
powder with white or yellow color
• High solubility in water and alcohol
• Highly hygroscopic – should be stored
in dry conditions
• Generally applied after fining operation. Recommended before the final clarification (as a 
slight oplalescence may be observed after MTA treatement)
Stabilization treatments - Yeast mannoproteins
(OIV Oeno 4/01; 15/05)
The traditional practice of barrel-aging white wines on yeast lees for several months often gives
them a high level of tartrate stability, so that cold stabilization is not necessary
 Mannoproteins (MP) are one of the major polysaccharide groups present in wine, having
origin in S. cerevisiae yeast. The 2nd most abundant polysaccharides in wine, after GP. Up to
200 mg/l; > 30% of total polysaccharides of wine
 MP can exhibit a negative charge at wine pH – capacity to establish electrostatic and ionic
interactions with other wine compounds
 MP properties in wines (according to their differences in terms of composition): to
adsorb ochratoxin A; to enhance malolactic bacteria growth; to inhibit tartaric salts
crystallization; to prevent protein haze; to enhance and interact with some wine aromas;
soften astringency by combining phenolic compounds from grape and wood, stabilizing
tannins
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Stabilization treatments - Yeast mannoproteins
Key-steps of the treatment with MP (diagram proposal)
Laffort Oenologie
 Application doses should be
established by lab trials (15-25 g/hl)
Initially applyed only in white wines
(MP can interact with tannins and precipitate) 
MP prevent KHT precipitation by inhibiting
its crystallization, since it affects the rate
of crystal growth by binding to nucleation
points and preventing expansion of the
crystal structure
MP stabilizing effect is stronger than that
of MTA
 These glycoproteins can be
added directly to wine as
commercial preparations
Racking after finning
Stabilization treatments - Carboxymethylcellulose
OIV Oeno 2/08
Carboxymethyl-cellulose (CMC) is a polysaccharide. Like MTA and MP its polymer structure
gives it “protective colloid” characteristics
Derived from cellulose (β-(1→4)-D-glucopiranose polymer). E466, additive widely used in food
industry, mainly because of its emulsifier properties
DS - Degree of substitution (degree of etherification of its alcohol functions)
DP – Degree of polymerization (average number of glucopyranose units per polymer unit)
These characteristics deeply influence CMC effectiveness
DS values (OIV regulations): 0.60-0.95
CMC effectiveness as protective colloid increases with DS values
CMC viscosity (afftecting its facility of use) is determined by the DP, increasing with MW
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Stabilization treatments - Carboxymethylcellulose
• Application doses should be established by laboratorial trials
Maximum dose (OIV regulations) - 100 mg/l
Molecular weight: 17-300 kDa; negative charge at wine pH 
 Only allowed on white and sparkling wines
interacts with phenolic compounds of red wines (can promote colorant matter precipitation);
requires protein stability (CMC can interact with proteins)
Resistant at high T (55-60 °°°°C)
• CMC inhibits tartaric precipitation: it acts as a negatively charged polymer at wine pH
interacting with the electropositive surface of KHT crystals, reducing their growth rate and
modifying the shape of KHT crystals
• It was claimed that the effectiveness of CMC at a dose of 2 g/hl is equivalent to 10 g/hl MTA
treatment
Available in the form of
granules/fibrous powder or in
the form of a concentrate for
solution in wine prior to use.
Solutions must contain at least
3.5% CMC
Effect of enological additives on wine tartaric stability of a white Vinho Verde
CMCs
a – solution at 20%
b – solution at 4%
c – solution at 5%
d – solid power
1 – medium concentration (50 mg/l)
2 – high concentration (100 mg/l)
Arabic gums:
AGA (solid) – 550 mg/l
AGB (liquid) – 650 mg/l
MP:
MPA – 27.5 mg/l
MPB – 225 mg/l
MTA – 50 mg/l
(Guise et al., 2014)Decrease in conductivity (Adapted mini-contact test)
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Effect of enologicaladditives on wine tartaric stability of a white Douro wine
CMCs
a – solution at 20%
b – solution at 4%
c – solution at 5%
d – solid power
1 – medium concentration (50 mg/l)
2 – high concentration (100 mg/l)
Arabic gums:
AGA (solid) – 550 mg/l
AGB (liquid) – 650 mg/l
MP:
MPA – 27.5 mg/l
MPB – 225 mg/l
MTA – 50 mg/l
Decrease in conductivity (Adapted mini-contact test)
Treatment Monomeric 
flavanols
Oligomeric 
proanthocyanidins
Polymeric 
proanthocyanidins
Total tannins
Control 21 ± 3 ns 57 ± 3 a 972 ± 29 ab 1050 ± 31 ab
CMC1 22.7 ± 0.5 ns 57 ± 1 ab 893 ± 22 a 973 ± 23 a
CMC2 23.8 ± 0.6 ns 73.4 ± 0.8 c 922 ± 15 ab 1019 ± 16 ab
CMC3 20.6 ± 0.5 ns 56.2 ± 0.9 a 957 ± 22 ab 1034 ± 21 ab
CMC4 21 ± 1 ns 71 ± 2 b 978 ± 13 ab 1070 ± 12 ab
CMC5 21 ± 2 ns 72 ± 2 c 907 ± 40 ab 1000 ± 39 a
Effect of carboxymethylcelluloses (CMC) on monomeric flavanols, oligomeric and polymeric 
proanthocyanidins of the red wine 
Mean values and corresponding standard deviation values, from 4 analytical replicates, are expressed in mg/L. In each column, means followed by the 
same letter are not significantly different at a 0.05 level of significance; ns – without significant difference. 
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Treatment Colour intensity (u.a.) Tonality
Control 7.77 ± 0.02 a 0.665 ± 0.001 ab
CMC1 8.08 ± 0.01 b 0.679 ± 0.002 b
CMC2 8.18 ± 0.01 c 0.687 ± 0.001 d
CMC3 9.11 ± 0.03 e 0.659 ± 0.001 a
CMC4 8.11 ± 0.01 b 0.6962 ± 0.0004 e
CMC5 9.00 ± 0.01 d 0.671 ± 0.002 b
Effect of carboxymethylcelluloses (CMC) on wine colour intensity and tonality
Treatment Total 
anthocyanins
(mg/L of 
malvidin 3-
glucoside)
Ionization 
index (%)
Coloured 
anthocyanins
(mg/L of 
malvidin 3-
glucoside)
Total pigments
(u.a.)
Polymerization 
index (%)
Polymerized pigments
(u.a.)
Control 389 ± 22 bc 11.0 42.9 ± 0.3 a 23 ± 1 bc 8.9 2.00 ± 0.02 a
CMC1 389 ± 5 bc 11.7 45.5 ± 0.3 b 22.8 ± 0.2 bc 8.9 2.00 ± 0.02 a
CMC2 381 ± 7 b 12.0 45.7 ± 0.2 b 22.5 ± 0.3 b 9.2 2.03 ± 0.01 ab
CMC3 381 ± 1 b 14.6 55.7 ± 0.2 d 22.59 ± 0.06 b 9.4 2.10 ± 0.01 c
CMC4 419 ± 11 c 10.8 45.2 ± 0.5 b 24.3 ± 0.6 c 8.3 1.98 ± 0.02 a
CMC5 343 ± 4 a 15.6 53.7 ± 0.6 c 20.7 ± 0.2 a 10.3 2.11 ± 0.01 c
Effect of carboxymethylcelluloses (CMC) on total and coloured anthocyanins, total and polymerized pigments
The results represent mean values and corresponding standard deviation values from three analytical replicates. In each column, means followed by the same letter are not significantly 
different at a 0.05 level of significance. 
The results represent mean values and corresponding standard deviation values from three analytical
replicates. In each column, means followed by the same letter are not significantly different at a 0.05 level
of significance.
 Several technologies to ensure wine stability regarding tartaric stability (in special KHT)
 Choise is dependent on wine characteristics, on company specificities and on the market
Costs of tartrate stabilization
(10 years)
Cheapest technology – ion exchange
Most expensive – electrodialysis
(Lasanta and Gómez, 2012)
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Polyaspartate - the most recent additive
Resolution OIV-OENO 543-2016
Up to 10 g/hl