METHOD FOR PRODUCING DEMINERALIZED MILK POWDER

Description

FIELD OF THE INVENTION

[0001] The invention is in the field of dairy farming and relates to processes for producing demineralized milk powders. TECHNOLOGICAL BACKGROUND

[0002] Milk powder is generally understood to be a dry matter obtained by removing the water content from milk. Whole milk, for example, has a water content of approximately 87.5 percent. This is reduced to approximately 3 percent to produce whole milk powder. About six to seven liters of milk are required to produce one kilogram of dry milk powder. Before the drying step, the dry matter content is usually increased in evaporators. The finished product contains approximately 26 percent fat, 25 percent protein, and 38 percent lactose.

[0003] Skimmed milk powder, on the other hand, is a dry milk product made from skimmed milk by drying (residual water content about 4 percent). Skimmed milk powder contains about 36 percent protein and 52 percent lactose. RELEVANT STATE OF THE ART

[0004] A wide variety of processes for producing milk powders are known from the prior art. US5503865 discloses the production of a dried milk composition based on the natural constituents of milk, characterized in that the milk composition contains, based on the weight of the non-fat dry matter, 33 to 36% protein, 48 to 58% lactose, and 3 to 5% minerals, and that the milk composition has, with regard to minerals, a calcium content of 75 to 100% of that of milk, a phosphorus content of 50 to 75% of that of milk, a sodium and potassium content of 5 to 20% of those of milk, and a citrate content of 10 to 30% of that of milk. In the process, skimmed milk is concentrated by ultrafiltration or microfiltration to between one-third and one-sixth of its volume. Optionally, diafiltration of the retentate can be carried out before further processing.

[0005] EP 2679098 B1 discloses a process for producing milk powders with a low bacterial content and a whey protein nitrogen index (WPNI) of at least 2, in which (a) solids are removed from raw milk in a process known per se, then the cream is separated, (b) the skimmed milk thus obtained is subjected to microfiltration, (c) the permeate thus obtained is pasteurized, (d) the pasteurized permeate thus obtained is concentrated to a dry matter content of 30 to 50 wt.% and the retentate is disposed of, (e) the concentrate thus obtained is subjected to a thermal treatment for a period of at least 15 seconds at a temperature of at least 72 degrees Celsius and (f) the thermally treated product is processed into a dry powder.

[0006] EP 2732706 B1 proposes a process for producing low-germ milk powder with a whey protein index (MPI) of at least 2, in which (a) raw milk is freed from solids in a manner known per se, the cream is separated, (b) the skimmed milk thus obtained is subjected to infusion heating, (c) the heated milk is concentrated to a dry matter content of 30 to 50% by weight, (d) optionally the concentrate thus obtained is subjected to a temperature treatment for a period of at least 15 seconds at at least 72 °C, and (e) the temperature-treated product thus obtained is processed to a dry powder.

[0007] Milk powders with improved sensory properties are known from EP 2946669 B1 (DMK). The powders are obtainable by (a) producing a mixture of a milk product and sugar, (b) subjecting the mixture to a first temperature treatment and simultaneously sterilizing and concentrating it, (c) subjecting the concentrate thus obtained to a second temperature treatment during which caramelization takes place, (d) subjecting the caramelized product thus obtained to a first cooling step, (e) germinating the first cooled product thus obtained with carbohydrate crystals, (f) subjecting the germinated product thus obtained to a second cooling step, (g) subjecting the second cooled product thus obtained to drying on a vacuum belt dryer with subsequent comminution, and finally (h) discharging the dry powder.

[0008] The subject of WO 2016 016397 A1, for example, is a process for producing a lactose-containing milk powder. The process comprises the successive steps of: a) concentrating a lactose-containing liquid to obtain a concentrated liquid with a dry matter content of 55 percent to 65 percent, wherein the concentration step a) lasts between 10 and 20 minutes; b) overconcentrating the concentrate obtained from step a) to obtain an overconcentrated material with a dry matter content of 75 percent to 80 percent, wherein the overconcentration step b) lasts between 2 and 10 minutes; c) granulating the overconcentrate obtained from step b) by mixing the overconcentrate with a lactose-containing powder with a dry matter content of at least 95 percent until a granulated powder with a dry matter content of at least 85 percent dry extract is obtained;and d) drying the granulated powder obtained from step c) to obtain a lactose-containing powder having a dry matter content of at least 95 percent.; TASK OF THE INVENTION

[0009] The object of the present invention was therefore to provide an alternative process for the production of demineralised milk powder specifically for the nutrition of young children, which is free from the disadvantages described and in particular leads to products with a higher protein content. DESCRIPTION OF THE INVENTION

[0010] The invention relates to corresponding processes for producing whole milk or skimmed milk powder. The two variants differ essentially only in the selection of whole milk or skimmed milk as starting materials, so that they are two alternatives linked by the same inventive concept.

[0011] The milk powders produced have a protein content of at least 24% by weight, and in particular from about 34 to about 50% by weight. The mineral content is typically below 4% by weight, preferably below 3% by weight, and the residual moisture content is below 5% by weight.

[0012] In the first embodiment, a process for producing a demineralized whole milk powder is disclosed, comprising or consisting of the following steps: (a) providing whole milk, (b) pasteurising the whole milk and subsequent or simultaneous separation of the pasteurisation product into a skimmed milk fraction and a cream fraction, (c) thermal treatment of the cream fraction from step (b), (d) ultrafiltration or diafiltration of the skimmed milk fraction from step (b) to obtain a first protein-rich retentate R1 and a first permeate P1; (e) nanofiltration of the permeate P1 from step (d) to obtain a second retentate R2 containing lactose and minerals and a second permeate P2, wherein the nanofiltration is carried out using a membrane having an average pore diameter of from about 100 to about 2.000 Daltons; (f) temperature treatment of the retentate R2 from step (e); (g) filtration or separation of the temperature-treated product from step (f) to obtain a third calcium phosphate-containing retentate R3 and a third permeate P3; (h) mixing the third permeate P3 from step (g) with the protein-rich retentate R1 from step (b) and at least part of the temperature-treated cream fraction from step (c); and (i) dewatering the mixture from step (h).

[0013] In the second embodiment, a process for producing a demineralized skimmed milk powder is disclosed, comprising or consisting of the following steps: (a) Providing skimmed milk, (b) Ultrafiltration or diafiltration of the skimmed milk to obtain a first protein-rich retentate R1 and a first permeate P1; (c) Nanofiltration of the permeate P1 from step (b) to obtain a second retentate R2 containing lactose and minerals and a second permeate P2, wherein the nanofiltration is carried out using a membrane having an average pore diameter of about 100 to about 2,000 Daltons; (d) Thermal treatment of the retentate R2 from step (c); (e) Filtration or separation of the thermally treated product from step (d) to obtain a third calcium phosphate-containing retentate R3 and a third permeate P3; (f) Mixing the third permeate P3 from step (e) with the protein-rich retentate R1 from step (b); and (g) Dewatering the mixture from step (f).

[0014] Surprisingly, it was discovered that demineralized milk powder can be produced in this way. FILTRATION PROCESS

[0015] The two alternative production processes involve various filtration steps: ultrafiltration in step (d or b), nanofiltration in step (e or c), and a further ultrafiltration or microfiltration in step (g or e). The first filtration step involves separating large and particularly temperature-sensitive proteins from the milk as retentate, and only later adding this fraction back in. During the subsequent nanofiltration of the permeate, monovalent cations, primarily sodium and potassium, are separated via the permeate, which would otherwise impart an undesirable metallic aftertaste to the powder. Furthermore, the lactose is concentrated in the retentate; the corresponding side stream can then be processed separately. After the temperature treatment, divalent ions, particularly calcium phosphate, are separated by a second ultrafiltration or microfiltration.

[0016] Ultrafiltration and nanofiltration are filtration processes in the field of membrane technology that allow macromolecular substances and small particles to be separated and concentrated from a medium. Microfiltration, ultrafiltration, and nanofiltration are differentiated by the degree of separation. If the exclusion limit (or " Cutoff") at 100 nm or above, this is referred to as microfiltration. If the exclusion limit is in the range between 2-100 nm, this is referred to as ultrafiltration. In nanofiltration, the exclusion limit is below 2 nm. In both cases, these are purely physical, i.e. mechanical, membrane separation processes that work according to the principle of mechanical size exclusion: all particles in the fluids that are larger than the membrane pores are retained by the membrane. The driving force in both separation processes is the differential pressure between the inlet and outlet of the filter surface, which lies between 0.1 and 120 bar.

[0017] The exclusion limits of ultrafiltration membranes are also given in the form of NMWC (English: Nominal Molecular Weight Cut-Off, also MWCO,Molecular Weight Cut Off (MWC, unit: Dalton). It is defined as the minimum molecular mass of globular molecules that are 90% retained by the membrane. In practice, the NMWC should be at least 20% lower than the molecular mass of the molecule to be separated. Further qualitative statements about the filtration can be made using the Flux (Water value) (transmembrane flux or permeation rate). Ideally, this is proportional to the transmembrane pressure and inversely to the membrane resistance. These quantities are determined by the properties of the membrane used, as well as by concentration polarization and any fouling that may occur. The permeation rate is based on 1 m² < membrane area. Its unit is l / (m² < h bar).

[0018] Membranes with pore diameters in the range of approximately 1,000 to approximately 50,000, and preferably approximately 5,000 to approximately 25,000, Daltons have proven particularly suitable for ultrafiltration. Nanofiltration prefers pore diameters in the range of approximately 150 to 1,000 Daltons.

[0019] Alternatively, diafiltration or a combination of both can be performed instead of ultrafiltration. The advantage is that more lactose and minerals are washed out of the retentate, resulting in higher purity. Furthermore, more monovalent ions are removed during the subsequent nanofiltration.

[0020] The material of the filter surface—both in ultrafiltration and nanofiltration—can be stainless steel, polymer materials, ceramic, aluminum oxide, or textile fabric. Filter elements come in various forms: candle filters, flat membranes, spiral-wound membranes, pocket filters, and hollow-fiber modules, all of which are generally suitable for the purposes of the present invention. However, spiral-wound membranes made of polymer materials or candle filters made of ceramic or aluminum oxide are preferably used, with the first embodiment proving particularly preferred for ultrafiltration and the second for nanofiltration.

[0021] Microfiltration is also a membrane separation process. The key difference from ultrafiltration and nanofiltration is its larger pore diameters of more than 0.1 µm, specifically from approximately 0.1 to 1.4 µm, corresponding to approximately 100,000 to approximately 800,000 Daltons.

[0022] The cut-off values overlap in the borderline range, so that, for example, a membrane with a pore diameter of about 2,000 Daltons can be suitable for both ultrafiltration and nanofiltration.

[0023] All of the filtration processes mentioned can be carried out independently of one another in the context of the present invention "hot" or "cold" mode, i.e., in the temperature range from about 10 to about 60 °C. However, it is preferred to operate at temperatures in the range from about 50 to about 60 °C, since this avoids re-dissolving effects. TEMPERATURE TREATMENT

[0024] Following nanofiltration, the resulting retentate is subjected to a thermal treatment to precipitate the calcium phosphate. The thermal treatment involves high heating, typically at approximately 70 to approximately 90 °C for a period of approximately 10 to approximately 30 minutes, and more preferably approximately 20 to approximately 25 minutes.

[0025] The same conditions shall apply to the cream fraction which is subsequently re-introduced, in whole or in part, during the production of whole milk powder. DRYING

[0026] The temperature-treated product is subjected to microfiltration or ultrafiltration as described, and any calcium phosphate present is removed. The phosphate-free product is combined with the retentate from step (a), which contained the large and particularly temperature-sensitive proteins, as described above. In this case, a skimmed milk powder is obtained. If whole milk powder is desired, the cream fraction previously separated from the whole milk and subsequently temperature-treated is also added at this point, in whole or in part, for example, in an amount of 10 to 90% of the total. The mixture(s) are then dried.

[0027] Spray drying is preferably used, with the temperature at the inlet typically being approximately 180 to approximately 260 °C and at the outlet approximately 80 to approximately 105 °C. Therefore, the fraction does not require cooling before entering the spray tower. Temperatures of 60 to 70 °C are actually preferred, as this reduces the risk of protein denaturation. Alternatively, the products can also be dehydrated by freeze-drying. The residual water content is a maximum of 5 wt.% and preferably approximately 3 to approximately 4 wt.%.

[0028] Other additives, such as lactoferrin, lecithins, vitamins, or food emulsifiers [EP 1314367 A1, NESTLE], etc., can be added to the product before, but preferably after, spraying. The final product is demineralized milk powders having a protein content of approximately 24 to approximately 50 wt.%, preferably approximately 28 to approximately 40 wt.%.

[0029] The process according to the invention is also described in the flow diagrams according to the Figures 1 and 2 explained in more detail. P = Pasteurization, S = Separation, UF = Ultrafiltration, NF = Nanofiltration, UHT = Ultra-High Temperature Treatment, MF = Microfiltration, MX = Mixing, and ST = Spray Drying. EXAMPLES EXAMPLE 1 Production of a demineralized whole milk powder according to the invention

[0030] In the pilot plant, 1,000 liters of whole milk and 1,000 liters of dialysis water were pasteurized and skimmed in a plate heat exchanger. The resulting skimmed milk was passed through an ultrafiltration unit equipped with a ceramic membrane with an average pore diameter of 25,000 Daltons at 10 °C. A protein-rich retentate R1 and a depleted permeate P1 were obtained. The permeate P1 was fed at constant temperature to a nanofiltration system equipped with a spiral-wound membrane with an average pore diameter of 700 Daltons. A lactose- and mineral-containing retentate R2 and a permeate P2 were obtained. The retentate R2 was heated to 80 °C for 20 seconds in a flash heater and kept at this temperature for 20 minutes in a stirred tank and then applied to a microfiltration unit equipped with a ceramic membrane with an average pore diameter of 50,000 Dalton.At approximately 55 °C, a phosphate-containing third retentate R3 and a third permeate P3 were obtained. Fractions P3 and R1, as well as the previously separated and subsequently pasteurized cream fraction, were combined in a mixing unit, preheated to approximately 65 °C via a heat exchanger, and then sprayed through a tower at a head temperature of 240 °C. The resulting powder had a protein content of 28.4 wt.%, a fat content of 26.3 wt.%, an ash content of 1.8 wt.%, and a residual moisture content of less than 1 wt.%. COMPARATIVE EXAMPLE V1 (NOT ACCORDING TO THE INVENTION) Production of a demineralized whole milk powder according to the state of the art

[0031] Analogous to Example 1, 1,000 liters of whole milk and 1,000 liters of dialysis water were pasteurized and skimmed, and the resulting skimmed milk was then fed at 10°C into a nanofiltration system equipped with a spiral-wound membrane with an average pore diameter of 700 Daltons. The permeate, containing lactose and minerals, was separated and processed separately. The retentate was evaporated to a dry matter content of approximately 50 wt.%, combined with the previously separated and pasteurized cream fraction, preheated to approximately 80°C via a heat exchanger, and then sprayed through a tower at a head temperature of 240°C. The resulting powder had a significantly lower protein content of 26.2 wt.%, a fat content of 26.8 wt.%, an ash content of 4.6 wt.%, and a residual moisture content of less than 1 wt.%. EXAMPLE 2 Production of a demineralized skimmed milk powder according to the invention

[0032] In the pilot plant, 1,000 liters of skimmed milk and 1,000 liters of dialysis water were passed through an ultrafiltration unit equipped with a ceramic membrane with an average pore diameter of 25,000 Daltons at 10°C. This resulted in a protein-rich retentate R1 and a depleted permeate P1. Permeate P1 was fed at constant temperature to a nanofiltration system equipped with a spiral-wound membrane with an average pore diameter of 700 Daltons. This resulted in a retentate R2 containing lactose and minerals, as well as a permeate P2. Retentate R2 was heated to 80°C for 20 seconds in a flash pasteurizer and held at this temperature for 20 minutes in a stirred tank. The retentate R2 was then fed to a microfiltration unit equipped with a ceramic membrane with an average pore diameter of 50,000 Daltons. At about 55 °C, a phosphate-containing third retentate R3 and a third permeate P3 were obtained.Fractions P3 and R1, as well as the previously separated and subsequently pasteurized cream fraction, were combined in a mixing unit, preheated to approximately 65 °C via a heat exchanger, and then sprayed through a tower at a head temperature of 240 °C. The resulting powder had a protein content of 28.4 wt.%, an ash content of 1.9 wt.%, and a residual moisture content of 3.9 wt.%. COMPARATIVE EXAMPLE V2 (NOT ACCORDING TO THE INVENTION) Production of demineralized skimmed milk powder according to the state of the art

[0033] Analogous to Example 2, 1,000 liters of skimmed milk and 1,000 liters of dialysis water were fed at 10 °C into a nanofiltration system equipped with a spiral-wound membrane with an average pore diameter of 700 Daltons. The retentate containing the monovalent ions was separated and processed separately. The retentate was evaporated to a dry matter content of approximately 50 wt.%, preheated to approximately 80 °C via a heat exchanger, and then sprayed over a tower at a head temperature of 240 °C. The resulting powder had a protein content of 36.1 wt.%, an ash content of 5.1 wt.%, and a residual moisture content of 4.3 wt.%.

Claims

1. A method for producing a demineralized milk powder, comprising or consisting of the following steps: (a) providing whole milk, (b) pasteurizing the whole milk and subsequently or simultaneously separating the pasteurized product into a skim milk fraction and a cream fraction, (c subjecting the cream fraction from step (b) to a heat treatment, (d) subjecting the skim milk fraction from step (b) to ultrafiltration or diafiltration to obtain a first protein-rich retentate R1 and a first permeate P1, (e) subjecting the permeate P1 from step (d) to nanofiltration to obtain a second retentate R2 containing lactose and minerals and a second permeate P2, wherein the nanofiltration is carried out using a membrane having an average pore size of about 100 to about 2,000 Dalton, (f) subjecting the retentate R2 from step (e) to a heat treatment, (g) filtering or separating the heat-treated product from step (f) to obtain a third retentate R3 containing calcium phosphate and a third permeate P3, (h) mixing the third permeate P3 from step (g) with the protein-rich retentate R1 from step (d) and at least a portion of the heat-treated cream fraction from step (c), and (i) dehydrating the mixture from step (h).

2. A method for producing a demineralized milk powder, comprising or consisting of the following steps: (a) providing skim milk, (b) subjecting the skim milk to ultrafiltration or diafiltration to obtain a first protein-rich retentate R1 and a first permeate P1, (c) subjecting the permeate P1 from step (b) to nanofiltration to obtain a second retentate R2 containing lactose and minerals and a second permeate P2, wherein the nanofiltration is carried out using a membrane having an average pore size of about 100 to about 2,000 Dalton, (d) subjecting the retentate R2 from step (c) to a heat treatment, (e) filtering or separating the heat-treated product from step (d) to obtain a third retentate R3 containing calcium phosphate and a third permeate P3, (f) mixing the third permeate P3 from step (e) with the protein-rich retentate R1 from step (b), and (g) dehydrating the mixture from step (f).

3. The method according to claim 1 and / or 2, characterized in that the ultrafiltration according to step (b) is carried out using a membrane having an average pore size of about 5,000 to about 50,000 Dalton.

4. The method according to at least one of claims 1 to 3, characterized in that the nanofiltration is carried out using a membrane having an average pore size of about 150 to about 1,000 Dalton.

5. The method according to at least one of claims 1 to 4, characterized in that the ultrafiltration according to step (b) and / or the nanofiltration according to step (c) are each independently carried out at a temperature in the range of about 10 to about 60°C.

6. The method according to at least one of claims 1 to 5, characterized in that the heat treatment according to step (d) is carried out at a temperature in the range of about 70 to about 90°C.

7. The method according to at least one of claims 1 to 6, characterized in that the heat treatment according to step (d) is carried out over a period of about 10 to about 30 minutes.

8. The method according to at least one of claims 1 to 7, characterized in that the heat-treated product from step (d) is subjected to ultrafiltration or microfiltration.

9. The method according to claim 8, characterized in that the ultrafiltration or microfiltration according to step (e) is carried out using a membrane having an average pore size of about 300,000 to about 800,000 Dalton.

10. The method according to claim 8 and / or 9, characterized in that the ultrafiltration or microfiltration according to step (e) is carried out at a temperature in the range of about 10 to about 60°C.

11. The method according to at least one of claims 1 to 10, characterized in that a demineralized milk powder is produced having an ash content of at most 3 wt.%.