AU685838B2 - Automatic method and device for tartaric stabilisation of wines - Google Patents

Abstract

The invention relates to a tartaric stabilisation method for wines, comprising the following steps: taking a sample of the wine to be stabilised; determining the specific instability degree of said wine; if the wine is unstable, said wine to be stabilised is treated according to a membrane electrodialysis technique until it becomes stable. The invention also relates to an automatic device for the tartaric stabilisation of wines.

Description

Automatic method and device for tartaric stabilization of wines The invention relates to an automatic method and device for the tartaric stabilization of wines.

It is known that tartaric acid is a characteristic constituent of the grape. These salts are relatively insoluble. As a result of the concentration of tartrate, potassium and calcium ions in wine, potassium hydrogen tartrate (or potassium bitartrate) and calcium tartrate tend to precipitate naturally from wines.

The development of the crystallization depends on various factors, in particular the temperature, pH, ethanol concentration and the presence of constituents inhibiting nucleus formation or preventing crystal growth.

Considering the abundance of tartaric acid, potassium and calcium in grapes, as well as the phenomena which control the ionic equilibria, new wines are naturally in a supersaturated state as regards the potassium and calcium salts of tartaric acid. A high proportion of potassium hydrogen tartrate is deposited in crystalline form, during and after the alcoholic fermentation.

These crystallizations appear as a function of the storage conditions of the wines and the development of their colloidal state. They are generally slow and random, in view 2 of the complexity of the parameters inducing or delaying crystallization.

When precipitations of the crystals take place in the bottle, they are considered as a defect prejudicing the presentation of the wine and the brand image of the marketed product.

Given the demands of an increasingly competitive market, it is essential for wine producers to supply products which are stable over time as regards their tartaric level.

For this reason considerable research has been carried out to characterize the supersaturated state of the wine, to develop tests for measuring the stability and to develop industrial stabilization processes against tartaric precipitations.

The techniques used industrially to guard against the risks of precipitation in the bottle are aimed either at maintaining the supersaturated state, or at inducing precipitation by reduction of the temperature of the wine.

The techniques of the former type use the addition of metatartaric acid. They are designed for young wines, with a short distribution channel.

The other techniques, which make use of refrigeration, are well developed. They are the most widely used and are in addition the only ones authorized in EEC member countries.

These techniques are mainly effective on white wines. For red .000 *4 r dB 3 wines, despite improvements in the equipment used and the development of control methods, the prevention of the precipitation of crystals in the bottle is not conclusively achieved.

In addition, some oenologists consider that the organoleptic qualities of wines can be affected by refrigeration stabilisation treatment. These observations are attributable on the one hand to the filtration techniques which it is necessary to perform before refrigeration to facilitate the crystallisation phenomena, and on the other to the filtrations performed to remove the crystals and clarify the cooled wine.

Work already carried out has also shown the possibility of avoiding the risks of precipitation of *oo e o o :oe *e *e *ee e* I I tartrate by other methods such as inverse osmosis, ion exchange or electrodialysis.

Study of these different techniques shows that electrodialysis and ion exchange are the only two currently able to give a complete guarantee of effective treatment.

The technique of ion exchange on a cationic resin leads to the addition of exogenous ions by exchange with those extracted from the wine, while electrodialysis is a technique which removes ions, anions and cations, across selective membranes, alternatively cationic and anionic.

Thus, the principle of cationic ion exchange potentially induces modifications to the composition of the wine which are more significant than when the electrodialysis technique is used.

In addition, the regeneration of the used ion exchange resins causes polluting effluents.

The application of electrodialysis to the tartaric stabilization of wines has been known for several years. It leads to selective extraction of the anions *and cations in the wine in a quantity which can be controlled and determined in advance. Electrolysis is however not yet used on an industrial scale.

25 Document FR-A-2 574 939 describes a laboratory test for monitoring the effectiveness of a wine treatment method, this treatment resulting in a variation in the concentration of a specified type of ion. The monitoring consists of measuring the conductivity of the wine before and after treatment, then calculating in particular the saturation temperature, to determine if the wine is stable or not.

The document Die Weinwirtschaft (vol. 114, no.

1/2, 1978, pages 28-33) describes an electrodialysis treatment of wine. As a function of the initial potassium concentration -T RA(, P SZ\ IC I I of the wine, or of its initial conductivity, an electrodialysis treatment level is adopted, expressed in potassium elimination and in reduction in conductivity. This treatment is based on the elimination of 100 to 350 mg/l of potassium, considered to be necessary to obtain a stable wine.

However, research has shown that there is no relation between the initial potassium concentration of a wine (or its initial conductivity) and the electrodialysis treatment level necessary to obtain a stable wine.

The object of the invention is thus a method for tartaric stabilization of wines, using an electrodialysis treatment, which guarantees the quality and effectiveness of the treatment.

The invention relates to a regulated tartaric stabilization method for wines, comprising the following steps taking a sample of the wine to be stabilized, 20 determining the specific instability degree of said wine, from a predicted conductivity value corresponding to that which the wine would have if it were stable, if the wine is unstable, said wine to be 25 stabilized is treated according to a membrane electrodialysis technique until it becomes stable.

*According to a preferred embodiment of the invention, the predicted conductivity value is "converted into a reference value corresponding to the 30 fall in conductivity necessary for the stabilization of the wine to be treated, the wine to be stabilized being subjected continuously to electrodialysis treatment until the reference value is attained.

Preferably, the predicted conductivity value is obtained from a model calculation.

~II -r I s*iel 6 The method according to the invention also has the following characteristics, taken singly or in combination the treatment is carried out on the whole of the wine to be stabilized, continuously, in a single cycle, the treatment is carried out continuously, by successive cycles, an intermediate volume being treated in each cycle, until the whole of the wine to be stabilized has been treated, the wine to be stabilized is filtered before the electrodialysis treatment, the treatment is limited to a previously determined maximum deionization level, for example of about the ionic concentration of the concentrate resulting from the electrodialysis treat-ment is maintained below a fixed threshold, the maintenance below said threshold is achieved by regulation of the conductivity of the concentrate by addition of water.

Another object of the invention is an automatic device for the tartaric stabilization of wines.

Thus, the invention relates to an automatic device for the tartaric stabilization of wines comprising 25 a test apparatus to determine the specific 0* instability degree of the wine to be stabilized, from a predicted conductivity value corresponding to the conductivity which the wine would have if it were stable, a treatment device comprising'an electrodialyzer and receiving the wine to be stabilized, a control system to control automatically the treatment device, as a function of the instability degree of the wine to be treated, determined by the test apparatus.

Preferably, the predicted conductivity value is converted into a reference value corresponding to the

I

fall in conductivity necessary for the stabilisation of the wine to be treated.

The stabilisation device according to the invention also has the following characteristics, taken singly or in combination: -the treatment device also comprises a measuring device for measuring the conductivity of the wine on leaving the electrodialyser, the control system ensuring the continuous return of the wine to be stabilised into the electrodialyser by appropriate means, if the reference value is not yet attained, -the control system ensures the evacuation of the wine from the treatment device using appropriate means, once the reference value is attained, the stabilisation device is used between a first vat containing the whole of the wine to be stabilised and a second vat which collects the stabilised wine, -the treatment device is directly linked to said first vat containing the whole of the wine to be stabilised, -the treatment device comprises an intermediate vat linked to the 15 electrodialyser and receiving a volume of wine to be stabilised, '-when the volume of wine present in the intermediate vat at the beginning of the treatment has been evacuated, the control system acts on appropriate means to ensure its filling by a new volume of wine to be stabilised, -the emptying and filling of the intermediate vat are carried out in such a way that the wine is treated continuously in the electrodialyser, -the treatment device also contains a filter situated upstream of the electrodialyser, -the treatment device in addition includes a circuit comprising a loop linking the electrodialyser to a vat receiving the ion concentrate,

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II II IL~ I 'I p ura~ la- l~ glPI~LI~-~-- 8 the treatment device contains means to regulate the conductivity threshold of said concentrate, the test apparatus produces an identification record for the wine, the stabilization device contains a safety device to prevent the treatment of the wine in the electrodialyzer when the characteristics of the wine do not conform to its identification record.

The invention will be better understood and its other aims, advantages and characteristics will emerge more clearly from reading the following description, together with the annexed drawings, in which Figure 1 is a schematic representation of a device for the tartaric stabilization of wines, *15 Figure 2 is a detailed representation of an embodiment of the treatment device according to Figure 1, and Figure 3 illustrates an electrodialysis cell.

The components common to the different figures are designated by the same reference numbers.

20 Referring to Figure 1, the device according to the invention is used between a vat 1 which is filled with the wine to be treated and a vat 5 which receives the stabilized wine. These two vats may in particular be located in the premises where the method is used.

I III~~CI Cll~nal~G*l(rCI*I"~A47* Reference 2 designates a test apparatus. This apparatus is used to determine the specific tartaric instability degree of the wine to be treated, from a sample taken from the vat 1.

As will be seen later, the result supplied by this apparatus will be used during the implementation of the subsequent treatment method.

This apparatus 2 uses a method .comprising the following steps use of a cryogenic stability test using an apparatus of a type known in the state of the art (STABISAT) and specifically adapted to the following step execution of a model calculation, specific to the wine S: to be treated, to calculate precisely the conductivity value of the wine once its stable state is attained and, -conversion of the conductivity value obtained into a reference value to adapt this conductivity value to t.' rest of the stabilization method, which uses the S S electrodialysis technique. The reference value of the conductivity corresponds to the level of deionization or .e the fall in conductivity necessary for the stabilization of the wine to be treated.

Thus, the test apparatus 2 uses a method which is based on the analysis of the variation, over a sufficiently long period, of the conductivity of a sample placed at a controlled

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Liv o&' o~ low temperature and under conditions of seeding of potassium bitartrate of selected quality, under constant agitation.

The method can be used to model refrigeration treatment by contact (addition of seed crystals and agitation). This modeling is designed to reduce the time required to perform the test. Different mathematical models can be used as a function of the temperatures selected (between -4°C and 0°C) and the possible addition of ethanol to accelerate the precipitation.

It is observed that, compared to conventional stability tests, the test used by the apparatus 2 is more precise and enables the stable state of the wine to be characterized by a predicted conductivity value which corresponds to that which .15 the wine would have if it were stable.

It is worth to emphasizing that the first two steps of the method used by the test apparatus 2 are independent of the subsequent treatment method. It is the last step of the method which enables it to be adapted to the technique used during the actual treatment method.

The test apparatus 2 also enables the wine to be identified and recognized by its conductivity as well as by other conventional oenological analytical criteria (for example pH, turbidity, degree of alcohol, etc) before the u, I 11 treatment method is implemented. These latter criteria are determined by devices connected to the test apparatus 2.

These various values are combined together and represent the identification record or signature of the wine. Their advantage will be described later. It can be noted here that the identification record is not essential for the execution of the treatment method.

The result of the test (reference value) and the identification record of the wine are transmitted to a control system which memorizes them.

The analysis of the sample can be performed by the test apparatus 2 in the premises where the stabilization method is S: implemented. It can also, in certain conditions, be carried 15 out in a different location, for example in a laboratory. In this case, the transmission of the test result and the identification record to the control system 3 can be carried out by conventional means, such as diskettes.

As a function of the instability degree of the wine, in 20 other words the value of the level of deionization, the system 3 determines if the wine is stable or not.

If the wine is stable, the treatment method is not performed on the vat 1.

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If, on the other hand, the wine is unstable, the control system 3 authorizes the initiation of the electrodialysis treatment method according to the invention.

The treatment method is performed to obtain the deionization level determined by the control system 3. This deionization level corresponds to the fall in conductivity necessary to obtain stability. It is expressed in with respect to the initial conductivity measured by the test apparatus 2.

The treatment method is thus based on a conductivity measurement. Experiments have in fact shown that the conductivity is linearly related to the potassium concentration. It is in addition easy to regulate the electrodialysis treatment by means of a conductivity value.

5 Reference should more particularly be made to Figure 2 which illustrates the treatment device 4 in more detail.

It should first be noted that in the embodiment of Figure 2, the treatment of the whole of the vat 1 containing the wine p considered to be unstable is performed in cycles. For each 20 cycle, a volume of wine from the vat 1 is transferred into the intermediate or working vat 6 to .be treated there by the electrodialyzer This is particularly advantageous when there is a large volume of wine to be treated.

~-91b ~L3C However, the whole of the wine to be treated may also be treated in a single cycle. In this case, the intermediate vat 6 is not necessary and the electrodialyzer 10 is directly linked to the vat 1.

The volume of wine to be treated is transferred from the vat 1 to the vat 6 by the pipe 7 and by appropriate means represented by a solenoid valve 8. The pump 20 draws the wine to be treated from the vat 1 through a filter 22. The control system 3 controls the filling of the vat 6. The wine contained in the vat 6 is then transmitted by the pipe 9 to the electrodialyzer 10 via a pump 11. In the electrodialyzer the wine undergoes treatment which will be described later. This treatment extracts the potassium and tartrate o S ions from the wine and thus lowers its conductivity. The circuit is completed to the vat 6 by the solenoid valve 15 and S the pipe 14.

The conductivity is measured continuously in the electrodialyzer 10 by the measuring device 21.

o Once the reduction in conductivity necessary to ensure o :20 the stability of the wine treated has been obtained within the loop, the wine contained in the vat. 6 is transferred via the •c o electrodialyzer 10, the pipe 9, the pump 11, the solenoid a.

valve 13 and the pipe 12 into the vat 5, while the return by the pipe 14 is closed by the solenoid valve 15. The control I Le I _I II-J~SISIIO 14 system 3 controls the method until the working vat 6 is completely empty.

After the wine to be stabilized contained in the vat 6 has been transferred to the vat 5 containing the stable wine, the control system 3 again orders the filling of the vat 6.

The electrodialysis treatment can then be carried out on a new volume of wine to be stabilized.

These different cycles are performed until the vat 1 is empty. The treatment of the wine is carried out continuously, in the electrodialyzer It should be noted that the stabilization device according to the invention preferably includes a safety device which closes down the electrodialysis treatment under certain 0 conditions.

ee As has been seen earlier, the test apparatus 2 produces an identification record for the wine to be treated, based on a sample taken from the vat 1.

If the wine is unstable, it is transferred into the e** electrodialyzer 10. The latter contains a conductivity :20 measurement device 25 as well as sensors measuring the same analytical criteria as those given on the identification record. These sensors are not shown on Figure 2.

The results of these measurements are transmitted to the control system 3 which compares them to the identification record of the wine.

0 I I ~s If the relevant analytical criteria do not have the same value, the control system 3 forbids the starting of the electrodialysis treatment method and the wine is evacuated from the device.

As has been indicated earlier, this safety device is not essential for the operation of the stabilization method according to the invention. It is essentially intended to verify that the wine transferred into the electrodialyzer is indeed identical to the wine whose sample was analyzed by the test apparatus 2. It thus acts to prevent any fraud in the treatment of the wines.

The treatment device 4 also contains a circuit for the concentrate (effluent) generated by the electrodialyzer 10, as will be explained later. This circuit comprises a loop 16 which connects the membranes of the electrodialyzer 10 to a S• vat 17 containing the ion concentrate. The concentrate is circulated in this loop by a circulation pump 18, located upstream of the membranes.

The concentrate essentially contains water and KC1 at the beginning of the treatment, then it becomes enriched in K, Na, Ca and tartrates during the treatment. The concentration S progressively increases during the treatment. It is maintained below a threshold determined by regulation of the conductivity. The conductivity of the concentrate is measured by the device 25. The control system 3 regulates the conductivity by additions of water, which are performed by the solenoid valve 19 in communication with a water supply 23.

The pH of the concentrate can advantageously be regulated and maintained at the pH of the treated wine, or at a lower pH, by a dosing-measuring device, so as to prevent precipitation of the extracted salts on the membranes of the electrodialyzer 10 and to limit the volume of the effluent.

This dosing-measuring device is not shown on Figure 2.

The concentrate can be recovered by overflow, at a high and regulated concentration, by means of the pipe 24.

It may be noted that on Figure 1, the logical relationships between the different components of the stabilization device are represented by arrows. They are shown between the control system 3 and on the one hand the S: test apparatus 2, and on the other the treatment device 4.

As an example, Table 1 (see end of description) contains the principal analytical parameters of a wine treated by electrodialysis on a laboratory pilot of membrane area 0.1 m 2 20 at different deionization levels of 0% to 40%. The deionization level necessary and sufficient to obtain the S tartaric stability of this wine was 17%. Its initial conductivity was 3 10 5 uS/cm at 20 0

C.

The analytical parameters of the wine treated to 17% deionization show that for this level of treatment, the I I car 17 variations in pH and in Total Acidity remain within acceptable limits. Compared with the untreated wine (deionization level these two parameters fell by 0.09 units and 0.25 g/1 (H 2 SO4), respectively. The Volatile Acidity was practically unchanged.

However, at 35% deionization, the reduction in pH, Total Acidity and Volatile Acidity were respectively 0.18 units, 0.55 g/l and 0.05 g/1 expressed in H 2

SO

4 These reductions still remain within the limits regarded as oenologically acceptable. However, they are not necessary and thus should be avoided.

For the group of red wines treated by the applicant, it would seem that the reduction in conductivity to be applied to S the wines varies in general between 5 and 20%. It is 15 to 5 20% for the young wines and 5 to 15% for the other wines.

S.

As an example, Tables 2 to 4 (see end of description) Sgive the set of results obtained during a comparative test between the traditional refrigeration method and the controlled membrane electrodialysis method.

The control wine was not stable. The wine treated by electrodialysis was stable with -respect to the normal S oenological tests performed after the treatment.

For white wines and primeur-type wines, these percentage decreases in conductivity could reach 30%. These observations, taken with the corresponding analytical tests, I L I l;r _sl ~IC

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lead to a proposed maximum limit of treatment to deionization. The control system can automatically ensure that any maximum treatment limit is respected.

Thus, the control system 3 automatically controls all the operations of the method carried out by the stabilization device according to the invention (filling of vats, treatment of the wine, emptying, rinsing, management of operational safety features) by acting on the following devices :the solenoid valves 13, 15, 19), the pumps (11, 18, 20) and the regulators.

The control system also controls the collection of information and analog or logical data for control of the method, V regulation, monitoring of the sequence of events in the method.

It may be noted that, in practice, the control system is operated by an interface console (screen/keyboard/peripheral) able to carry out the all aspects of the method (control, 9* monitoring and recording).

20 We will now describe in more detail the electrodialysis treatment method itself, as well as the electrodialyzer used for it.

Electrodialysis is a separation method which can be applied to ionic solutions. It makes use on the one hand of an electric field which constitutes the power source for I ILI transporting the ions in solution, and on the other hand ion-permeable membranes which achieve the selectivity of the ion transport and enable the ions to be separated.

Cationic membranes only allow passage of cations while anionic membranes are only crossed by anions.

Figure 3 illustrates the operational principle of an electrodialysis cell which constitutes an elementary unit of an electrodialyzer. This cell is composed of two compartments 31 and 32 which are alternately bounded by anionic membranes 33 and 34 and a cationic membrane A potential difference applied to the electrode terminals (anode 36 and cathode 37) will cause migration of the ions.

The cations 38 will move towards the cathode 37 while the anions 39 will move towards the anode 36. The cations in the :15 compartment 31 will be able to cross the cationic membrane and will therefore be removed from the compartment 31.

However, they cannot leave the compartment 32 since they are blocked by the anionic membrane 34. Similarly, the anions 39 can leave the compartment 31, via the anionic membrane 33, but they remain in the compartment 32 of the electrodialysis cell since they cannot cross the cationic membrane As a consequence of the alternating anionic and cationic membranes, one of the compartments of the electrodialysis cell exports its ions into the neighboring compartments. Its concentration in ions decreases and this is why this c.

cc cc lsll~ ~C compartment, here 31, is called the "diluate". The compartment 32 is enriched in ions and is normally called the "concentrate".

It should be noted that the ion separation is performed without reaction at the electrodes.

An electrodialyzer is made up of a stacking of electrodialysis unit cells. Between each membrane, a separator frame maintains a constant distance between the membranes. This frame also ensures maintenance of the fluid flow and the rigidity and impermeability of the stacking.

An el-ctrodialyzer can comprise up to 500 pairs of membranes. Their assembly uses a technology similar to that used for filter presses. The thickness of the compartments varies from 0.3 to 0.7 mm depending on the manufacture. An electrodialyzer conventionally contains two hydraulic circuits :0 which feed all the compartments of the same type (diluates and concentrates) in parallel.

It is also fitted with two electrodes (an anode and a cathode) which are placed at the two ends of the stacking.

:20 They are isolated in a compartment in which a saline solution to maintain electrical conduction, is' circulated. This e m compartment has no contact with the product to be treated.

The electrodes supply the operating current of the electrodialyzer. They are fed by a direct electric current.

The electrical potential difference, in general of the order I I L of 1 volt per cell, which is maintained on either side of each membrane, causes the selective i .ssage of the ions.

It is observed that the energetic yield is about The electrodialysis method and the device used for it are known in the state of the art.

To be able to use the electrodialysis method within the scope of a wine stabilization method, it is however necessary to select membranes specifically suited to wines. The electrodialysis must only change the ionic concentration of the treated wines, while retaining the balance between the different ionic species.

Thus, the membranes chosen must have good flow properties with respect to the ionic species to be extracted, in other words the potassium cations and the tartrate anions. They must not affect the nonionic constituents of the wine, in t particular the polyphenols and polysaccharides. They must in addition not allow the diffusion of small molecules such as ethanol. In practice, the maximum decrease in degree of alcohol is fixed at 0.1% vol. Lastly, they must be resistant to clogging and to regular cleaning.

It is desirable to seek the best membrane couple, cationic and anionic, so that the physico-chemical equilibrium of the wine is least changed.

In fact, if the elimination of pota3sium from the wines is favored, the pH is reduced. This occurs when cation

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II/ IYIII\l exchange resins are used. If, on the other hand, tartrate extraction is favored, the other anions (including acetate) are also removed, which leads to a decrease in the volatile acidity of the wines.

In addition, the level of treatment must be controlled and limited. The following limits have been fixed pH reduction less than 0.2 units, reduction of volatile acidity less than 0.09 g/l (expressed as H 2

SO

4 concentration) It may be noted that the maximum change in pH which has been fixed is significantly lower than that obtained by refrigeration treatment (addition of tartaric acid followed by cooling) under the conditions allowed by the regulations.

These limits can be used to make a choice amongst the membranes available on the market.

i The use of the electrodialysis method to treat wines, with a :w to stabilizing them, has several advantages.

Firstly, many tests have been carried out with a view to determining the tartaric stability of wines treated by refrigeration and by the method according to the invention.

The stability tests used are conventional :for the resistance to cold (stabilization in test tubes for 15 days at C) and measurement of the saturation temperature.

-4 0 C) and measurement of the saturation temperature.

I I ~L I ~M These tests have demonstrated the effectiveness of the method according to the invention, both on young wines and on wines of one or more years old.

On the other hand, stability has not always been obtained by the various refrigeration treatments (discontinuous by stabilization or continuous with seeding).

Analytical tests have also been performed based on the following parameters density, total sugars, alcohol concentration by volume, methanol, glycerol, higher alcohols, ethanal, total nitrogen, ammonia, amino acids, total acidity, pH, volatile acidity, organic acids tartaric, malic, lactic, free and total SO 2 Na Ca++, Fe, Cu, Mg, Mn, absorbances at 520, 420 and 280 nm, total polyphenols, state of coloring matter, polysaccharide profile of the wines.

.II I hl~ 1IIII~RP UI~~ I at The various analyses performed clearly show that only the cations and anions of the wine are affected by the electrodialysis treatment and that, in consequence, the other constituents of the wine, such as ethanol, volatile compounds, polyphenols and amino acids are not, or very little, affected by this treatment.

In addition, it has been verified that the method according to the invention causes less significant changes to the coloring matter than the conventional treatments of refrigeration stabilization.

A refrigeration treatment in fact causes not only the precipitation of potassium bitartrate but also the precipitation of coloring matter.

*.e On the contrary, because of the absence of pores in the 9.

electrodialysis membranes (dense membranes), only ions of low S: steric volume are exported. Thus electrodialysis better preserves the colloidal component of the wines compared with refrigeration treatment. Significant differences have been e. observed in the level of the colloidal coloring matter of red 20 wines.

As a result, for some wines, a significant difference may be detectable, in a triangular tasting between the wine treated by refrigeration and the wine treated by the method according to the invention.

,'Ki R~4 K0 *Yr -I IC II "IC311CC~-* II- On the other hand, there do not seem to be any significant differences between wines, before and after treatment in accordance with to the method of the invention.

In fact, the use of the electrodialysis method is very favorable to the preservation of the organoleptic qualities of the wine, since all the transfer conditions are very mild the wine circulates in a thin film in the compartments and in the absence of any contact with air, the speed of the passage of the wine over the membranes is relatively low, of the order of 6 cm per second, the flow is carried out at low pressure (less than 1 bar), at a controlled temperature (20 0 C to 25 0 C) and under the protection of inert gas, the average time that the wine remains in contact with the membranes is relatively short, of the order of seconds.

The wine is not subjected to any electrochemical effect since the electrodes are isolated in a compartment where only a solution of a potassium salt is circulated.

9 In addition, in contrast to the techniques using ion exchangers, an electrodialysis membrane does not have to be be: regenerated. After each cycle of operation, the membranes are S' cleaned with weakly alkaline or acid solutions, as for any membrane technique.

The stabilization process has significant advantages compared to the conventional treatments by refrigeration since it can be adapted to the physico-chemical equilibrium of each wine to be treated, by removing only the quantities of potassium and tartaric acid necessary to obtain stability.

The control system enables the treatment method to be controlled, on the one hand by preventing treatment of a stable wine, and on the other by fixing a maximum treatment level (for example a maximum deionization level). This enables prevention of excessive or unnecessary use of electrodialysis, leading in particular to reduction in pH or in volatile acidity of the treated wine. It also prevents Streatment in the case of a substituted wine.

*o In addition, the electrodialysis treatment method comprises less steps than a refrigeration treatment method.

The filtrations which are necessary downstream and upstream of the refrigeration treatment are reduced to a single prefiltration, for an electrodialysis treatment. This results w 20 in economies in consumable products, such as filtration adjuvants, seeding tartrates and metatartaric acid.

Electrodialysis also results in a reduction in energy consumption. It has in fact been estimated that the energy consumption resulting from refrigeration treatment is at least I I ~I RIeUllUlC C- IICI~-- 27 ten times higher than that resulting from the electrodialysis treatment method.

The automation of the electrodialysis method reduces its operational cost. It has been estimated that, according to the case, the labor cost involved in a tartaric stabilization method for wines can be reduced by a factor of 2 to 8 with the method according to the invention.

Lastly, the electrodialysis concentrate is a liquid effluent, not a significant pollutant, and rich in tartaric o0 acid which can be recovered.

Thus, the method and device for tartaric stabilization of wines in accordance with the invention enable the problems of tartaric precipitations specific to each wine to be resolved in a logical and controlled manner.

15 The test apparatus 2 has been described as a component of S the treatment device according to the invention. It may be noted that this apparatus may be used independently of the treatment device, as a measurement device designed to assess the stability degree of a sample of wine. In this case, the Oe 20 test apparatus can implement only the first two steps of the method described above, since it is not necessary to determine a reference value.

The apparatus can also be used within a treatment method not using the electrodialysis technique.

'/SE R41, 0 I I 2S The reference numbers inserted after the technical character ist iq mentioned in the claims are only intended to facilitate understanding of the latter, and in no way limit their scope.

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S TABLE 1 VARIATION OF THE ANALYTICAL PARAMETERS OF A WINE AS) A FUNCTION OF THE DEIONIZATION LEVEL (Pilot laboratory tests) RED WINE 1992 Deionization level Alcohol concn. by volume (16) at Total acidity

(H

2 S0 4 g/1

PH

volatile acidity

(H

2 S0 4 g/l Tartaric acid g/l Lactic acid g/l Free SO 2 mg/i Total SO 2 mg/l K-1 mg/l1 Ca++ mg/i Na+ mg/i OD 280 nm 0 10 G0 3 .10 3 .84 0.55 2.60 1.40 8 32 1 690 66 21. 7 100- 10 G0 3.00 3.79 0 .53 2 .20 1.40 8 29 1 440 69 20. 0 17%; 200-* 10.60 10.60 2. 85 3.75 0 .54 1.80 1.40 8 31 1 280 67 18.9 2.80 3,.74 0 .54 1.80 1.40 9 30 1 190 67 18 .5 25%li 10.55 2.75 3 .72 0 .54 1.60 1 .4.0 9 26 1 100 68 17 .9 300% 10.50 2.65 3 .71 0 .53 1.40 1.40 10 31 990 67 16.9 3 5% 10.40 2.55 3.66 0.50 1.20 1.30 8 31 860 67 15S. 6 37 .5 10.35 2. 3 .64 0 .52 1.00 1.30 8 29 780 64 14 .7 37.5 40.7 39.7 39.4 39.5 38.9 38.5 TABLE 2 ANALYTICAL RESULTS OF COMPARATIVE TESTS BETWEEN THE TRA0DIbONAL REFRIGER-ATION METHOD AND THE CONTROLLED MEMBRANE ELECTRODIALYSIS METHOD Phvs ico -chemicai-analyae RED BORDEAUX 1988 Control RT ED Density 0.9921 0.)921 0.9920 Sugars Glucose g/l 0.55 0.55 0.55 Fructose g£1 0.25 0.25 0.20 Alcohol vol. 11085 11085 11081 Total acidity H 2 S0 4 g/l 3.45 3.40 3.40 pH 3.58 3.57 3.51 Volatile acidity H 2 S0 4 g/1 0.49 0.49 0.43 Tartaric acid g/l 2.3 2. 2.3 Malic acid 0 0 0 Lactic acid 1.90 1.90 1.85 Free SO 2 22 16 21 Total SO 2 80 70 K+ rng/l 1160 1130 1090 Na+ mg/l 18 18 18 Ca++ mg/l 76 76 G6 Fe rng/l 6.8 6.6 Lead [tg/l 62 58.5 Conductivity Ls at 20'C 2135 2100 J.980 control :filtered wine RT Refrigeration treatment (8 days at -2 0

C)

ED Eetoils treatment TABLE 3 ANALYTICAL RESULTS OF COMPARATIVE TESTS BETWEEN THE TRADITIONAL REFRIGERATION METHOD AND THE CONTROLLED MEMBRANE ELECTRODIALYSIS METHOD Analyses of polyvhenQls color and polvsaccharides Control RT ED Composition in anthocyanins: -Total anthocyanins 332 304 325 -PVP index 44 43 44 -Ionization index 18 21 17 -Free anthocyanins mg/l 185 174 183 -Anthocyanins combined with 147 130 143 tannins -Colored anthocyanins 59.8 63.8 55.4 -Heating index 22 22 -Polymerized pigments 56 55 57 index Composition in tannins -Procyanidins mg/l 2816 2763 2807 -OD 280 (x dil) 45 43.2 44.5 -Folin Ciocalteur 225 218 224 (OD 700 x dil x 100) -Procyanidins/Anthoc. 8.5 9.1 8.6 -Tannins precipitated 21 22 24 by HC1 -Tannins precipitated by gelatin -Tannins precipitated by ethanol 17 1 0 13 -Tannins g/1 n g' 3.60 3.46 3.56 Coloration: -Colorant intensity 0 OD420+OD520+OD620-10mm 6.15 6.07 6.26 bJL->6.15 6 0 G.26 Color OD420/OD520 0.77 0.74 0.76 OD 420 38.70 38.05 38.50 OD 520 51.40 50.40 50.80 OD 620 10.90 10.55 10.70 S Origin of the red color -OD 520 (wine) 1 mm 0.310 0.312 0.318 -OD 520 (Al) 1 mm 0.055 0.057 0.065 -OD 520 (TA) 1 mm OX-149 0.161 0.130 -OD 520 (TAT) 1 mm 0.106 0.094 0.122 -OD 520 (TA)/TA g/l 1.01 1.24 0.91 S-dialysis 19 17 19 Other polymers -Colorless colloids mg/l 686 672 702 -Neutral polysaccharides 284 234 233 mg/1 -Acid polysaccharides mg/l 87 75 96 0 Yz^.

i TABLE 4 ANALYTICAL RESULTS OF COMPA.ATIVE TESTS BETWEEN THE TRADITIONAL REFRIGERATION METHOD AND THE CONTROLLED MEMBRANE ELECTRODIALYSIS METHOD Analyses of amino acids and volatile compounds Control RT ED Nitrogen-containing compounds in nmoles/50 ul wine -Aspartic acid 2.14 2.16 2.69 -Threonine 0.88 0.97 0.98 -Serine 1.60 1.62 1.58 -Glutamic acid 6.69 7.36 6.92 -Proline 376.6 365.9 370.7 -Glycocoll 7.33 7.90 8.36 -Alanine 15.03 17.16 17.12 -Valine 3.98 4.99 2.11 -Cystine -Methionine 0.99 0.92 0.90 -Isoleucine 1.30 1.37 1.48 -Leucine 2.63 2.85 3.14 -Tyrosine 1.24 1.34 1.42 -Phenylalanine 2.30 2.51 2.60 -Aminobutyric acid 2.68 3.10 3.98 -Ethanolamine 9.86 11.87 11.07 -Ornithine 3.03 2.65 2.76 -Lysine 3.70 3.99 4.24 -Histidine 1.84 1.99 1.39 -Arginine 3.71 2.39 4.45 S -NH3 14.73 16.18 22.05 Volatile compounds -Ethanol 11085 11085 11081 -Ethanal 23.60 22.05 25.60 -Ethyl acetate 52.90 57.20 50.85 -Propanol 16.25 16.05 15.45 -Isobutanol 79.85 76.15 76.50 -Isopentanols 331.70 325.70 324.75 S-Methanol mg/l 154 145 149 in g/hl of pure alcohol I, I

Claims (23)

1. Regulated method for the tartaric stabilisation of wines comprising the following steps: taking a sample of the wine to be stabilised, -determining the specific instability degree of said wine, from a predicted conductivity value corresponding to that which the wine would have if it were stable, if the wine is unstable, said wine to be stabilised is treated according to a membrane electrodialysis technique until it becomes stable.

2. Method in accordance with claim 1, according to which the predicted conductivity value is converted into a reference value corresponding to the fall in conductivity necessary for the stabilisation of the wine to be treated, the wine to be stabilised being subjected continuously to electrodialysis treatment until the reference value is attained.

3. Method in accordance with one of claims 1 and 2, according to which the predicted conductivity value is obtained from a model calculation.

4. Method in accordance with one of claims 1 to 3, according to which the treatment is carried out on the whole of the wine to be stabilised, continuously, in a single cycle.

5. Method in accordance with one of claims 1 to 3, according to which the treatment is carried out continuously, by successive cycles, an intermediate volume being treated in each cycle, until the whole of the wine to be stabilised has been treated.

6. Method in accordance with one fo claims 1 to 5, according to which the wine to be stabilised is filtered before the electrodialysis treatment.

7. Method in accordance with one of claims 1 to 6, according to which the treatment is limited to a previously determined maximum deionisation level, for -O I '/VT OA i la I ~I I-i example of about

8. Method in accordance with one of claims 1 to 7, according to which the ionic concentration of the concentrate resulting from the electrodialysis treatment is maintained below a fixed threshold.

9. Method in accordance with claim 8, according to which the maintenance below said threshold is achieved by regulation of the conductivity of the concentrate by addition of water.

Automatic device for the tartaric stabilization of wines comprising a test apparatus to determine the specific instability degree of the wine to be stabilized, from a predicted conductivity value corresponding to the conductivity which the wine would have if it were stable, a treatment device comprising an electrodialyzer (10) and receiving the wine to be stabilized, a control system to control automatically the treatment device as a function of the instability degree of the wine to be treated, determined by the test apparatus

11. Device in accordance with claim 10, according to which the predicted conductivity value is converted into a reference value corresponding to the fall in I conductivity necessary for the stabilization of the wine to be treated.

12. Device in accordance with claim 11, according to which the treatment device also comprises a measuring device (21) for measuring the conductivity of the wine on leaving the electrodialyzer the control S system ensuring the continuous return of the wine to be stabilized into the electrodialyzer (10) by appropriate means (15, 14, 6, 9, 11), if the reference value is not yet attained.

13. Device in accordance with claim 12, according ~LI to which the control system ensures the evacuation of the wine from the treatment device using appropriate means (12, 13), once the reference value is attained.

14. Device in accordance with claims 10 to 13, according to which it is used between a first vat (1) containing the whole of the wine to be stabilized and a second vat which collects the stabilized wine.

Device in accordance with one of claims 10 to 14, according to which the treatment device is directly linked to said first vat containing the whole of the wine to be stabilized.

16. Device in accordance with one of claims 10 to 14, according to which the treatment device comprises an intermediate vat linked to the electrodialyzer and receiving a volume of wine to be stabilized.

17. Device in accordance with claim 16, according to which, when the volume of wine present in the intermediate vat at the beginning of the treatment has been evacuated, the control system acts on appropriate means 20) to ensure its filling by a new volume of wine to be stabilized.

18. Device in accordance with claim 17, characterized in that the emptying and filling of the intermediate vat are carried out in such a way that the wine is treated continuously in the elect.'wodialyzer

19. Device in accordance with claims 10 to 18, according to which the treatment device also contains a filter (22) situated upstream of the electrodialyzer

20. Device in accordance with claims 10 to 19, according to which the treatment device in addition includes a circuit comprising a loop (16) linking the electrodialyzer (10) to a vat (17) receiving the ion concentrate.

21. Device in accordance with claim 20, according I to which the treatment device contains means (23, 19) to regulate the conductivity threshold of said concentrate.

22. Device in accordance with claims 10 to 21, according to which the test apparatus produces an identification record for the wine.

23. Device in accordance with claim 22, according to which it contains a safety device to prevent the treatment of the wine in the electrodialyzer (10) when the characteristics of the wine do not conform to its identification record. DATJED this 26th day of September, 1997. EURODIA U.. WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 SUSTRALIA a.. a a U. IAS/JGC:BA VAX DOC17 PAT 7r97/94.WPC G I