PROCESS FOR DEMINERALIZING A MILK PROTEIN COMPOSITION, AND MILK PROTEIN COMPOSITION OBTAINABLE BY SAID PROCESS

Abstract

A process for manufacturing a demineralized milk protein composition, including a step (ii) of electrodialysis of a milk protein composition on an electrodialyzer, the unit cells of which have three compartments, and configured to substitute at least one cation by at least one hydrogen ion H+ in the milk protein composition to obtain an at least partially demineralized and acidified milk protein composition; a step (iii) of electrodialysis of the milk protein composition obtained in step (ii) on an electrodialyzer, the unit cells of which have three compartments, and configured so as to substitute at least one anion by at least one hydroxyl ion OH− in the milk protein composition.

Claims

1. A process for manufacturing a demineralized milk protein composition, the process comprising the steps: (i)—providing a milk protein composition; (ii)—electrodialysis of the milk protein composition on an electrodialyzer, the unit cells of which have three compartments, and configured to substitute at least one cation by at least one hydrogen ion H.sup.+ in the milk protein composition to obtain an at least partially demineralized and acidified milk protein composition; (iii)—electrodialysis of the milk protein composition obtained in step on an electrodialyzer, the unit cells of which have three compartments, and configured to substitute at least one anion by at least one hydroxyl ion OH.sup.− in the milk protein composition; (iv) obtaining the demineralized milk protein composition.

2. The process according to claim 1, comprising a step of treating (v) at least part of the salt(s) selected from the following salts: the salt(s) derived directly from the electrodialysis step (ii), the salt(s) derived indirectly from the electrodialysis step (ii), the salt(s) derived directly from the electrodialysis step (iii), the salt(s) derived indirectly from the electrodialysis step (iii), the salt(s) from a preliminary demineralization step carried out on the milk protein composition in step (i), a mixture of the latter, wherein said treatment step (v) being configured to produce one or more acid(s) from the salt(s) on the one hand, and a base(s) from the salt(s) on the other hand.

3. The process according to claim 2, wherein the treatment step (v) includes an electrodialysis step carried out on a bipolar membrane electrodialyzer.

4. The process according to claim 3, wherein the bipolar membrane electrodialyzer, in step (v), comprises unit cells with three compartments A, B and C, the compartments A and B are supplied with water, and the compartment C, arranged between the compartments A and B, is supplied with one or more salt(s).

5. The process according to claim 2, wherein at least part of the salt(s) obtained during the treatment step (v), is supplied to one of the three compartments of the electrodialyzer in step (ii).

6. The process according to claim 2, wherein at least part of the salt(s) obtained during the treatment step (v), is supplied to one of the three compartments of the electrodialyzer in step (iii).

7. The process according to claim 1, comprising a step of electrodialysis of the at least partially demineralized and acidified milk protein composition obtained in step (ii), and carried out before step (iii), on an electrodialyzer comprising two-compartment unit cells.

8. The process according to claim 1, wherein the electrodialysis step (ii) produces a mixture comprising at least one chloride salt of a monovalent cation and at least one chloride salt of a divalent cation, and the mixture undergoes a separation step (vi) of the chloride salt(s) of a monovalent cation and the chloride salt(s) of a divalent cation.

9. The process according to claim 1, wherein the electrodialysis step (iii) produces a mixture comprising at least one sodium salt of a monovalent anion and at least one sodium salt of a divalent anion, and the mixture undergoes a separation step (vii) of the sodium salt(s) of a monovalent anion and of the sodium salt(s) of a divalent anion.

10. The process according to claim 8, wherein the salt of a monovalent cation collected at the conclusion of one or more of the separation step (vi) and the separation step (vii) is supplied to one or more of the electrodialysis step (ii) and the electrodialysis step (iii).

11. The process according to claim 8, wherein the salt of a monovalent cation collected at the conclusion of one or more of the separation step (vi) and the separation step (vii) undergoes, at least in part, the treatment step (v).

12. The process according to claim 1, wherein the electrodialyzer in step (ii) comprises at least one membrane permselective to monovalent cations.

13. The process according to claim 1, wherein the three-compartment unit cells of the electrodialyzer in step (ii) comprise at least one unit cell comprising: a first compartment delimited between a membrane permselective to monovalent cations and a cationic membrane; a second compartment delimited between two cationic membranes; a third compartment delimited between a cationic membrane and a membrane permselective to monovalent cations.

14. The process according to claim 1, wherein the three-compartment unit cells of the electrodialyzer in step (ii) comprise at least one unit cell comprising: a first compartment delimited between an anionic membrane and a cationic membrane; a second compartment delimited between two cationic membranes; and a third compartment delimited between a cationic membrane and an anionic membrane.

15. The process according to claim 13, wherein the first compartment is supplied with at least one acid salt, the second compartment is supplied with the milk protein composition of step (i), and the third compartment is supplied with at least one chloride salt of a monovalent cation.

16. The process according to claim 1, wherein the electrodialyzer in step (iii) comprises at least one membrane permselective to monovalent anions.

17. The process according to claim 1, wherein the three-compartment unit cells of the electrodialyzer in step (iii) comprise at least one unit cell comprising: a first compartment delimited between a membrane permselective to monovalent anions and an anionic membrane; a second compartment delimited between two anionic membranes; a third compartment delimited between an anionic membrane and a membrane permselective to monovalent anions.

18. The process according to claim 1, wherein the three-compartment unit cells of the electrodialyzer in step (iii) comprise at least one unit cell comprising: a first compartment delimited between a cationic membrane and an anionic membrane; a second compartment delimited between two anionic membranes, and a third compartment delimited between an anionic membrane and a cationic membrane.

19. The process according to claim 17, wherein the first compartment is supplied with at least one basic salt, the second compartment is supplied with the partially demineralized and acidified milk protein composition obtained in step (ii), and the third compartment is supplied with at least one chloride salt of a monovalent cation.

20. The process according to claim 1, comprising a heat treatment step (viii), performed after step (ii) and before step (iii).

21. The process according to claim 1, wherein the milk protein composition in step (i) is whey.

22. The process according to claim 1, wherein the milk protein composition in step (i) is partially demineralized whey and has undergone at least one step selected from: an electrodialysis step, a nanofiltration step, a reverse osmosis step, an evaporation step, and a combination thereof.

23. A demineralized milk protein composition obtained by the process according to claim 1.

24. The process according to claim 14, wherein the first compartment is supplied with at least one acid salt, the second compartment is supplied with the milk protein composition of step (i), and the third compartment is supplied with at least one chloride salt of a monovalent cation.

25. The process according to claim 18, wherein the first compartment is supplied with at least one basic salt, the second compartment is supplied with the partially demineralized and acidified milk protein composition obtained in step (ii), and the third compartment is supplied with at least one chloride salt of a monovalent cation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0125] FIG. 1 schematically represents the various steps of a first example of a process for manufacturing a demineralized milk protein composition;

[0126] FIG. 2 schematically represents an example of the treatment step v) according to the disclosure, in particular a unit cell of the bipolar membrane electrodialyzer implemented in the first and second example processes shown in FIGS. 1 and 3; and

[0127] FIG. 3 schematically represents the various steps of a second example of a process for manufacturing a demineralized milk protein composition.

DETAILED DESCRIPTION

[0128] The first example of a process for manufacturing a demineralized milk protein composition represented in FIG. 1 comprises two electrodialyzers 5 and 10 whose unit cells 15 and 35 have three compartments. A single unit cell 15 of the electrodialyzer 5 is shown in FIG. 1. This unit cell 15 comprises a first compartment 20 delimited between a cationic permselective membrane 22 and a cationic membrane 24, a second compartment 26 delimited between the cationic membrane 24 and the cationic membrane 28, and a third compartment 30 delimited between the cationic membrane 28 and the cationic permselective membrane 32. A single unit cell 35 of the electrodialyzer 10 is shown in FIG. 1. This unit cell 35 comprises a first compartment 39 delimited between an anionic permselective membrane 37 and an anionic membrane 41, a second compartment 43 delimited between the anionic membrane 41 and an anionic membrane 45, and finally a third compartment 47 delimited between the anionic membrane 45 and the anionic permselective membrane 49. The cationic permselective membranes 22 and 32 can only be crossed by monovalent cations, and the permselective membranes 37 and 49 can only be crossed by monovalent anions. The electrodialyzers 5 and 10 each comprise a cathode (80, 88) and an anode (78, 90) generating a current through the conductive solutions passing through the compartments of the unit cells 15 and 35. The process also comprises a first nanofiltration device 50 for performing step vi), a second nanofiltration device 60 for performing step vii), and a three-compartment bipolar membrane electrodialyzer 70, detailed in FIG. 2, for performing step v). This first example process also comprises a heat treatment unit 75 for performing the heat treatment step viii).

[0129] In operation, a milk protein composition MPC, in particular whey demineralized to at least 50%, is supplied in a step i) and then supplied to the second compartment 26 of the electrodialyzer 5. At the same time, acidified salt, in particular a hydrochloric acid solution, is supplied to the first compartment 20, and brine, in particular a sodium chloride salt, is supplied to the third compartment 30. The H.sup.+ ions cross the cationic membrane 24 and are replaced by Nat ions coming from the third compartment 30 and thus passing through the permselective membrane 32 or 22 under the effect of the electric field. The monovalent and/or divalent cations, in particular Na.sup.+ ions and Ca.sup.2+ ions, cross the cationic membrane 28, under the effect of the electric field, in the direction of the cathode 80, and are substituted by H.sup.+ ions coming from the first compartment 20. The milk protein composition obtained MPC1 in step i) is thus partially demineralized, the cations having been substituted by H.sup.+, and acidified. The pH of MPC1 is less than or equal to 4. The third compartment 30 comprises a mixture of chloride salts, in particular a calcium chloride salt (CaCl.sub.2) and a sodium chloride salt (NaCl), derived from the milk protein composition MPC. The monovalent ions (e.g., Na.sup.+; K.sup.+) thus cross the cationic permselective membrane 22 or 32 and supply the first compartment 20 while the divalent ions (e.g., Ca.sup.2+) remain in the third compartment 30.

[0130] The acidified milk protein composition MPC1 undergoes a heat treatment in step viii), (90° C., for a few minutes) to improve its bacteriological stability. Advantageously, as the composition MPC1 is acidified, the heat treatment conditions can be more intense than usual and defined so that the proteins are not altered.

[0131] The mixture of salts derived from the third compartment 30 may undergo a nanofiltration step vi) on the nanofiltration unit 50 in order to increase the purity of the sodium chloride salt derived from the third compartment 30 by retention of divalent salts, such as calcium chloride CaCl.sub.2. The purified sodium chloride salt is thus supplied to the third compartment 30.

[0132] The composition MPC1, in particular pasteurized, undergoes a second electrodialysis step iii) on the electrodialyzer 10. The first compartment 39 is supplied with a basic salt, such as sodium hydroxide, from step v). The mobility of the OH.sup.− ions being greater than the mobility of the Cl.sup.− ions, the OH.sup.− ions cross the anionic membrane 41, and are replaced by Cl.sup.− ions coming from the first compartment 39 and having crossed an anionic permselective membrane 49 or 37 under the effect of the electric field. In the second compartment 43 supplied with the heat-treated and acidified composition MPC1, the residual anions (chlorides, sulfates, phosphates).sup.− cross the anionic membrane 45 under the effect of the electric field in the direction of the anode 90, and are substituted by OH.sup.− ions from the first compartment 39. The composition MPC2 obtained in step iv) is thus demineralized and deacidified. In the third compartment 47, the mixture of sodium chloride and potassium chloride salts (NaCl, KCl) and phosphate salts are derived from MPC1. The chloride ions cross the anionic selective membrane 49 and supply the first compartment 39 while the divalent ions, in particular phosphate ions, are blocked in the third compartment 47 by the anionic permselective membrane 49.

[0133] The salts derived from the third compartment 47 may undergo a nanofiltration step vii) to increase the purity of the sodium chloride salt derived from the third compartment 47 by retention of phosphate ions.

[0134] This first example process also comprises a step v) of treating the sodium chloride salt on a three-compartment bipolar membrane electrodialysis unit 70 allowing regeneration of the acid, mainly HCl, and the base, mainly sodium hydroxide, from the NaCl flows derived from the first compartments 20 and 39 of the cationic and anionic electrodialysis steps ii) and iii), and optionally from the NaCl derived from the pre-demineralization steps carried out upstream on the composition MPC of step i), and/or from food-grade NaCl. The pre-demineralization steps may include a nanofiltration step followed by a two-compartment electrodialysis step applied to the nanofiltration retentate. With the exception of the salt used at the start of step v), the acidic and basic salts used for the implementation of the electrodialysis steps ii) and iii) are derived from the milk protein composition MPC1, which avoids the introduction of exogenous mineral compounds.

[0135] FIG. 2 shows the electrodialyzer 70 and a unit cell 105 thereof comprising a first compartment 110 delimited between a bipolar membrane 112 and an anionic membrane 114, a second compartment 116 delimited between the anionic membrane 114 and a cationic membrane 118, and a third compartment 120 delimited between the cationic membrane 118 and a bipolar membrane 122. The salt, in particular sodium or potassium chloride, is supplied to the second compartment 116. The chloride ions cross the anionic membrane 114 under the effect of the electric field toward the anode 125 while the Na.sup.+, K.sup.+ ions cross the cationic membrane under the effect of the electric field to the cathode 127. This step v) allows regeneration of the acidic and basic salts, in particular hydrochloric acid and sodium hydroxide, which are then supplied for the acidic salt to the first compartment of the unit cell 15 of step ii), and for the basic salt to the first compartment of the unit cell 35 of step iii).

[0136] The second example process for manufacturing a demineralized milk protein composition shown in FIG. 3 comprises two electrodialyzers 200 and 205 whose unit cells (215, 235) have three compartments. A single unit cell 215 of the electrodialyzer 200 is shown in FIG. 3. This unit cell 215 comprises a first compartment 220 delimited between an anionic membrane 222 and a cationic membrane 224, a second compartment 226 delimited between the cationic membrane 224 and the cationic membrane 228, and a third compartment 230 delimited between the cationic membrane 228 and the anionic membrane 232. A single unit cell 235 of the electrodialyzer 205 is also shown in FIG. 3. This unit cell 235 comprises a first compartment 239 delimited between a cationic membrane 237 and an anionic membrane 241, a second compartment 243 delimited between the anionic membrane 241 and an anionic membrane 245, and a third compartment 247 delimited between the anionic membrane 245 and the cationic membrane 249. The electrodialyzers 200 and 205 each comprise an anode (278, 290) and a cathode (280, 288) generating a current through the conductive solutions passing through the compartments of the unit cells 215 and 235. The process also comprises a first nanofiltration device 250 for performing step vi), a second nanofiltration device 260 for performing step vii), and a three-compartment bipolar membrane electrodialyzer 70, detailed in FIG. 2, for performing step v). In addition, the process comprises a heat treatment unit 275 for performing the heat treatment step viii).

[0137] In operation, a milk protein composition MPC, in particular whey demineralized to at least 50%, is supplied to the second compartment 226 of the electrodialyzer 200. At the same time, acidified salt, in particular a hydrochloric acid solution, is supplied to the first compartment 220, and brine, in particular a sodium chloride salt and a potassium chloride salt, is supplied to the third compartment 230. Only H.sup.+ ions cross the cationic membrane 224 to the second compartment 226 toward the cathode 280, and chloride ions cross the anionic membrane 232 to the third compartment 230 toward the anode 278. In the second compartment 226, monovalent or divalent cations, such as Na.sup.+ and Ca.sup.2+, cross the cationic membrane 228 under the effect of the electric field toward the cathode 280, and are substituted by H.sup.+ ions from the first compartment 220. The milk protein composition obtained MPC1 in step ii) is thus partially demineralized, the cations having been substituted by H.sup.+ ions, and acidified. The pH of MPC1 is less than or equal to 4. The third compartment 230 comprises a mixture of CaCl.sub.2 and NaCl derived from the milk protein composition MPC. Chloride ions from the first compartment 220 cross the anionic membrane 222 or 232 and supply the third compartment 230.

[0138] The acidified milk protein composition MPC1 undergoes a heat treatment in step viii), in particular a heat-treatment step (90° C., for a few minutes) in order to improve its bacteriological stability. Advantageously, since the composition MPC1 is acidified, the conditions of the heat treatment can be defined so that the proteins are not altered.

[0139] The salt mixture derived from the third compartment 230 may undergo a nanofiltration step vi) on the nanofiltration unit 250 to increase the purity of the sodium chloride salt derived from the third compartment 230 by removing divalent salts, such as calcium chloride CaCl.sub.2. This step may optionally be followed by a chelating resin run to achieve the 3-5 ppm input specification of step v).

[0140] The composition MPC1, in particular heat-treated, undergoes a second electrodialysis step iii) on the electrodialyzer 205. The first compartment 239 is supplied with a basic salt, such as sodium hydroxide, from step v). OH.sup.− ions cross the anionic membrane 241 toward the second compartment 243, and Na.sup.+ ions cross the cationic membrane 249 toward the third compartment 247. In the second compartment 243, residual anions from the acidified, heat-treated MPC1, such as chlorides and phosphates, cross the anionic membrane 245 under the effect of the electric field toward the anode 290, and are substituted by hydroxyl ions OFF, from the first compartment 239. The composition obtained MPC2 is demineralized and deacidified in step iv). In the third compartment 247, the mixture of chloride salts of monovalent cations, including potassium and sodium chloride salts, phosphate salts, and sulfate salts, are derived from MPC1. The monovalent or divalent anions, such as chlorides, phosphates, sulfates, cross the anionic membrane 245 and supply the third compartment 247.

[0141] The salts from the third compartment 247 may undergo a nanofiltration step vii) to increase the purity of the sodium chloride salt derived from the third compartment 247 by extracting the phosphate ions.

[0142] This second example process also comprises a step v) of treating the sodium chloride salt on a three-compartment bipolar membrane electrodialysis unit 70 allowing regeneration of the acid, mainly HCl, and the base mainly sodium hydroxide, from the NaCl flows derived indirectly from the third compartments 230 and 247 of steps ii) and iii) of cationic and anionic electrodialysis since they have previously undergone the nanofiltration steps of steps vi) and vii). The NaCl flows may optionally come, mixed or not with those derived from steps ii) and iii), from the NaCl from the pre-demineralization steps carried out upstream on the composition MPC of step i), and/or from a food-grade NaCl. The pre-demineralization steps may include a nanofiltration step followed by a two-compartment electrodialysis step applied to the nanofiltration retentate. With the exception of the salts used at the start of steps ii) and iii), thanks to step v), the acidic and basic salts used for the implementation of electrodialysis steps ii) and iii) are derived from the milk protein composition MPC1, which avoids the introduction of exogenous mineral compounds.

[0143] The second example process differs from the first example in that steps ii) and iii) do not comprise permselective membranes, and that the NaCl flows treated by bipolar membrane electrodialysis are not derived directly from the electrodialyzers 200 and 205, but undergo an intermediate nanofiltration step corresponding to step vi) or vii).

[0144] The cationic substitution step ii) can be carried out either on the electrodialyzer 5 (FIG. 1) or 200 (FIG. 3).

[0145] The anionic substitution step iii) can be carried out either on the electrodialyzer 10 (FIG. 1) or 205 (FIG. 3).

[0146] For carrying out the tests described below, a milk protein composition, MPC, was made by preparing a dispersion of sweet whey powder (raw), at 16% dry mass in demineralized water. The dispersion is mechanically stirred until a homogeneous mixture is obtained. MPC thus presents the following parameters: mass rate in dry matter: 15.9% (powder mass/total mass); pH=5.95; initial conductivity: 10.95 mS/cm; ash content by mass: 8.1%; lactose content by mass: 73.5%; cation content by mass (in particular Na, NH.sub.4, K, Ca, Mg): 3.79%; anion content by mass (in particular CI, NO.sub.3, PO.sub.4, SO.sub.4): 3.64%; the various mass rates (except for that in dry matter) are calculated by relating the total mass of one or more compounds to the total mass of the dry matter.

[0147] 1—Cationic Substitution on the Electrodialyzer 200 (FIG. 3)

[0148] The electrodialyzer 200 comprises, for example, from 5 to 15 cells 215. The first compartment 220 is supplied with an HCl solution having a conductivity greater than or equal to 100 mS/cm, in particular greater than or equal to 150 mS/cm. The second compartment 226 is supplied with MPC exemplified above. The third compartment is supplied with a NaCl solution having a conductivity less than or equal to 50 mS/cm, in particular less than or equal to 25 mS/cm, in this specific example less than or equal to 15 mS/cm. A current (I) greater than or equal to 1 ampere, in particular less than or equal to 2 amperes, is applied to the electrodialyzer 200, and the voltage may be left free. During electrodialysis ii), the conductivity of MPC decreases indicating its demineralization, and then it increases because the cations it comprises are substituted by H.sup.+ ions. The pH of MPC1 obtained is of the order of 1, and the conductivity of MPC1 is about 12 mS/cm. The conductivity of the acidic solution, i.e., HCl, at the outlet of the first compartment 220 is lowered by about 74%, and the conductivity of the brine, i.e., NaCl, obtained at the outlet of the third compartment 230, is increased by about 234%. The cation removal is about 84%.

[0149] 2—Cationic Substitution on the Electrodialyzer 5 (FIG. 1)

[0150] The electrodialyzer 5 comprises, for example, from 5 to 15 cells 15. The first compartment 20 is supplied with an HCl solution having a conductivity greater than or equal to 100 mS/cm, in particular greater than or equal to 150 mS/cm. The second compartment 26 is supplied with MPC exemplified above. The third compartment is supplied with a NaCl solution having a conductivity less than or equal to 50 mS/cm, in particular less than or equal to 25 mS/cm, in this specific example less than or equal to 15 mS/cm. A current (I) greater than or equal to 1 ampere, in particular less than or equal to 2 amperes, is applied to the electrodialyzer 5, and the voltage may be left free. At the beginning of electrodialysis ii), the conductivity of MPC decreases, indicating its demineralization, and then it increases because the cations it comprises are substituted by H.sup.+ ions. In the acidic compartment 20, the conductivity decreases due to the depletion of H.sup.+ ions and the production of NaCl, which is less conductive. The cations extracted from MPC migrate into the brine compartment 30, which is enriched in multivalent cations more conductive than NaCl. The pH of MPC1 obtained is of the order of 1, and the conductivity of MPC1 is about 12 mS/cm. The conductivity of the acid solution at the outlet of the first compartment 220 is lowered by about 35%, and the conductivity of the brine obtained at the outlet of the third compartment 30 is increased by about 25%. The cation removal is about 82%.

[0151] For the implementation of step iii), MPC1 used may be either that from electrodialyzer 5 or 200 since the latter have identical performance in terms of cation removal rate.

[0152] 3—Anionic Substitution on the Electrodialyzer 205 (FIG. 3)

[0153] The electrodialyzer 205 comprises, for example, from 5 to 15 cells 235. The first compartment 239 is supplied with a NaOH solution having a conductivity greater than or equal to 30 mS/cm, in particular greater than or equal to 50 mS/cm. The second compartment 243 is supplied with MPC1 obtained above. The third compartment 247 is supplied with a NaCl solution having a conductivity less than or equal to 50 mS/cm, in particular less than or equal to 25 mS/cm, in this specific example less than or equal to 15 mS/cm. A current (I) greater than or equal to 1 ampere, in particular less than or equal to 2 amperes, is applied to the electrodialyzer 205, and the voltage may be left free. During electrodialysis iii), the conductivity of MPC1 decreases indicating its demineralization. The pH of MPC2 obtained is greater than 6, in this specific example of the order of 7.7, and the conductivity of MPC2 is about 1 mS/cm. The conductivity of the basic solution, i.e., NaOH, at the outlet of the first compartment 239 is lowered by about 120%, and the conductivity of the brine obtained at the outlet of the third compartment 247 is increased by about 126%. The anion removal is about 98%. The conductivity reduction of MPC to arrive at MPC2 is 85%.

[0154] 4—Anionic Substitution on the Electrodialyzer 10 (FIG. 1)

[0155] The electrodialyzer 10 comprises, for example, from 5 to 15 cells 35. The first compartment 39 is supplied with a NaOH solution having a conductivity greater than or equal to 30 mS/cm, in particular greater than or equal to 50 mS/cm, in this specific example greater than or equal to 80 mS/cm. The second compartment 43 is supplied with MPC1 obtained above. The third compartment 47 is supplied with a NaCl solution having a conductivity less than or equal to 50 mS/cm, in particular less than or equal to 25 mS/cm, in this specific example less than or equal to 15 mS/cm. A current (I) greater than or equal to 1 ampere, in particular less than or equal to 2 amperes, is applied to the electrodialyzer 10, and the voltage may be left free. During electrodialysis iii), the conductivity of MPC1 decreases, indicating its demineralization. The pH of MPC2 obtained is greater than or equal to 6, of the order of 7, and the conductivity of MPC2 is about 2 mS/cm. The conductivity of the basic solution at the outlet of the first compartment 39 is lowered by about 21%, and the conductivity of the brine obtained at the outlet of the third compartment 47 is lowered by 25%. The anion removal is about 84%. The conductivity reduction of MPC to arrive at MPC2 is 77%.

[0156] Depending on the desired demineralization rate, it is possible starting from the above-exemplified MPC to reach a demineralization rate of 90%, with an ash rate lower than 1.5% on dry matter (DM), for example by combining the cationic substitution according to the above-exemplified point 1 or 2 with the anionic substitution according to the above-exemplified point 3.

[0157] It is also possible that the starting MPC is already partially demineralized, which makes it possible to combine the exemplified anionic substitution according to item 4 above with a cationic substitution according to the disclosure.

[0158] For the tests described below, a milk protein composition, MPC″, was made by preparing a dispersion of sweet whey powder (raw), at 17% dry mass in demineralized water. The dispersion is mechanically stirred until a homogeneous mixture is obtained. MPC″ thus has the following parameters: mass rate of dry matter: 17% (powder mass/total mass); pH=5; initial conductivity: 12 mS/cm; mass rate of ash: 8%; mass rate of lactose: 74%; mass rate of cations (in particular Na, NH.sub.4, K, Ca, Mg): 5%; mass rate of anions (in particular CI, NO.sub.3, PO.sub.4, SO.sub.4): 3%; the various mass rates (with the exception of that in dry matter) are calculated by relating the total mass of one or more compound(s) to the total mass of the dry matter.

[0159] 5. Cationic Substitution on the Electrodialyzer 200 (ESC) (FIG. 3)

[0160] The electrodialyzer 200 comprises, for example, from 5 to 15 cells 215. The first compartment 220 is supplied with an HCl solution having a conductivity greater than or equal to 100 mS/cm, in particular greater than or equal to 150 mS/cm. The second compartment 226 is supplied with above-exemplified MPC″. The third compartment is supplied with a NaCl solution having a conductivity less than or equal to 50 mS/cm, in particular less than or equal to 25 mS/cm, in this specific example less than or equal to 15 mS/cm. A current (I) greater than or equal to 2 amperes, in particular less than or equal to 3 amperes, is applied to the electrodialyzer 200, and the voltage may be left free. During electrodialysis ii), the conductivity of MPC″ decreases indicating its demineralization, and then it increases because the cations it comprises are substituted by H.sup.+ ions. The pH of MPC1″ obtained is about 2, and the conductivity of MPC1″ is about 12 mS/cm. The conductivity of the acid solution, i.e., HCl, at the outlet of the first compartment 220 is lowered by about 53%, and the conductivity of the brine, i.e., NaCl, obtained at the outlet of the third compartment 230, is increased by about 292%. The cation removal (or substitution rate) is about 77%. The anion rate is substantially similar between MPC″ and MPC1″.

[0161] 6. Conventional Two-Compartment Electrodialysis (ED) (Anionic Membrane/Cationic Membrane)

[0162] This electrodialyzer (not shown in the drawings) comprises, for example, from 5 to 15 cells. The first compartment is delimited between a cationic membrane and an anionic membrane, and the second compartment is delimited between an anionic membrane and a cationic membrane. The first compartment is supplied with above-described MPC1″ and the second compartment is supplied with a salt, in particular sodium chloride, having a conductivity greater than or equal to 5 ms/cm and less than or equal to 15 ms/cm. During the test, a voltage greater than or equal to 10 V and less than or equal to 20 V, in particular less than or equal to 15 V, is applied to the two-compartment electrodialyzer, and the current (I) is left free. During the test, the conductivity of MPC1″ decreases, indicating its demineralization. Part of the H.sup.+ ions are extracted in the brine compartment, hence the increase of the pH of MPC1″ (ESC+ED) at the outlet, in particular at a pH greater than or equal to 2.5, in particular greater than or equal to 3. The final conductivity of MPC1″(ESC+ED) is lowered, by about 90% compared with MPC, thanks to this conventional electrodialysis. The cation removal rate (Na, NH.sub.4, K, Ca, Mg) in MPC1″ (ESC+ED) is greater than or equal to 90% (compared with MPC1″ obtained at the outlet of the cation substitution ED, FIG. 3). The anion removal rate (CI, NO.sub.3, PO.sub.4, SO.sub.4) in MPC1″ (ESC+ED) is greater than or equal to about 80% (compared with MPC1″ obtained at the outlet of the cationic substitution ED, FIG. 3).

[0163] 7. Anionic Substitution on the Electrodialyzer 205 (ESA) (FIG. 3)

[0164] The electrodialyzer 205 comprises, for example, from 5 to 10 cells 235. The first compartment 239 is supplied with a NaOH solution having a conductivity comprised between 20 and 35 mS/cm. The second compartment 243 is supplied with MPC1″ (ESC+ED) obtained above. The third compartment 247 is supplied with a NaCl solution having a conductivity less than or equal to 50 mS/cm, in particular less than or equal to 25 mS/cm, in this specific example, less than or equal to 15 mS/cm. A voltage greater than or equal to 10 V and less than or equal to 15 V is applied, and the current (I) may be left free. During electrodialysis iii), the conductivity of MPC1″ (ESC+ED) decreases, indicating its demineralization. The anions extracted from MPC1″ (ESC+ED) migrate to the third compartment containing the brine. The pH of MPC2″ obtained is higher than 4, in this specific example of the order of 5, and the conductivity of MPC2″ is lower than 1. The conductivity of the basic solution, i.e., NaOH, at the outlet of the first compartment 239 is lowered by more than 55%, and the conductivity of the brine at the outlet of the third compartment 247 is increased by more than 35%. The conductivity reduction from MPC″ to arrive at MPC2″ is greater than or equal to 95%. The final reduction rate (between MPC″ and MPC2″), for both anions and cations, is greater than or equal to 95%.