Process for producing a demineralized sweet whey powder

Description

FIELD OF THE INVENTION

[0001] The invention is in the field of dairy farming and relates to a process for producing a demineralized sweet whey powder with a high protein content. TECHNOLOGICAL BACKGROUND

[0002] Whey is the watery, greenish-yellow residual liquid that is produced during cheese production. It is the liquid part that can be separated after the milk has curdled into cheese or curd. There are two types of whey: sweet whey (also rennet whey ), which is produced when milk is thickened with rennet to make cheese, and the sour whey, which is created when milk is fermented by lactic acid bacteria.

[0003] Whey consists of 94% water, 4 to 5% lactose, and is virtually fat-free. It also contains lactic acid, vitamins B1, B2 (which gives it its greenish color), and B6, as well as potassium, calcium, phosphorus, and other minerals, but most importantly, 0.4 to 1% whey protein. Whey contains significantly less protein than milk. In particular, unlike milk, it does not contain casein. In milk, casein is the main protein. Sweet whey is therefore a valuable source of protein. Whey products are sold as powdered concentrates.

[0004] To produce the corresponding sweet whey powder, sweet whey is typically subjected to a three-step process. This consists of nanofiltration followed by electrodialysis and an ion exchanger. A disadvantage is that electrodialysis must be carried out at a temperature in the range of 25 to 40 °C, as this leads to the growth of microorganisms. The ion exchanger's task is to separate bivalent ions that have survived the electrodialysis ("polishing"). This step is also disadvantageous because the ion exchanger has a large surface area that is difficult to clean and also offers space for strong microorganism growth. This can therefore easily lead to recontamination of the product. RELEVANT STATE OF THE ART

[0005] The subject of US 2009 / 142459 A1 is a process for producing a demineralized whey powder, which comprises the following steps: (a) concentrating the whey; (b) demineralizing it using a cation exchanger; (c) electrodialysis; (d) ion exchange treatment ("polisher"), and (e) spray drying.

[0006] WO 2004 057973 A1 discloses a process for producing whey protein concentrates, in which sweet whey is filtered, pasteurized, crystallized and finally dewatered by spray drying.

[0007] The subject of WO 2006 135983 A1 is a process for obtaining a potassium-rich mineral mixture, in which whey is demineralized by filtration and the retentate is subsequently freed from calcium phosphate using an ion exchanger. TASK OF THE INVENTION

[0008] The object of the present invention was therefore to provide an alternative process for the production of demineralized sweet whey powder that is free of the disadvantages described and, in particular, leads to products with an adjustable, preferably higher, protein content. The process should also lead to low-germ or germ-free products with high flavor quality. DESCRIPTION OF THE INVENTION

[0009] The invention relates to a process for producing a demineralized sweet whey powder, comprising or consisting of the following steps: (a) Providing whey, (b) Dia-ultrafiltration of the whey 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) Temperature treatment of the retentate R2 from step (c); (e) Filtration of the temperature-treated product from step (d) to obtain a third 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).

[0010] Surprisingly, it was discovered that the specific sequence of process steps produces a demineralized sweet whey powder with an adjustable protein content without the risk of contamination. By adding more or less retentate R2, protein contents can be adjusted. The product has a mineral content of less than 2% by weight and, in particular, less than 1% by weight, and therefore also meets the taste requirements. FILTRATION PROCESS

[0011] The process according to the invention involves various filtration steps, namely diafiltration or ultrafiltration in step (b), nanofiltration in step (c), and a further ultrafiltration or microfiltration in step (e). The first filtration step involves separating large and particularly temperature-sensitive proteins from the whey as retentate, and adding this fraction back in later. Furthermore, salts can also be washed out during diafiltration. The permeate from the subsequent nanofiltration or water can be used for this purpose. During the subsequent nanofiltration of the permeate, minerals—primarily sodium and potassium—that would otherwise impart an undesirable metallic aftertaste to the powder are separated via the permeate. Lactose is also removed; the corresponding side stream can then be processed separately.After the temperature treatment, the calcium phosphate is separated by a second ultra- or microfiltration.

[0012] Ultrafiltration and nanofiltration are filtration processes in the field of membrane technology, which 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 called microfiltration. If the exclusion limit is in the range between 2 and 100 nm, this is called ultrafiltration. In nanofiltration, the exclusion limit is below 2 nm. In both cases, these are purely physical, i.e. mechanical, membrane separation processes that operate 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 is between 0.1 and 10 bar for ultrafiltration and microfiltration and up to approximately 40 bar for nanofiltration.

[0013] The exclusion limits of ultrafiltration membranes are also expressed 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).

[0014] 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.

[0015] 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 nanofiltration, and the second for microfiltration.

[0016] Microfiltration or diafiltration also belongs to the membrane separation process. The main difference from ultrafiltration and nanofiltration is the larger pore diameters of more than 0.1 µm, specifically from approximately 0.1 to 1.4 µm, corresponding to approximately 10,000 to approximately 800,000 Daltons.

[0017] 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.

[0018] All of the filtration processes mentioned can be carried out independently of one another in the context of the present invention "hot" or "cold," i.e., in the temperature range from about 10 to about 60 °C. However, it is preferred to operate at temperatures in the low range of about 10 to about 20 °C. TEMPERATURE TREATMENT

[0019] Following nanofiltration, the resulting retentate is subjected to a thermal treatment to render the product sterile. Sterile is defined as a product containing fewer than 1,000 (thermophilic and mesophilic) microbes per milliliter. The thermal treatment involves ultrahigh temperature heating, typically carried out at approximately 70 to approximately 90 °C for a period of approximately 10 to approximately 30 minutes, and in particular approximately 15 to approximately 20 minutes. This process leads, among other things, to the precipitation of salts and is preferably carried out in a stirred tank. DRYING

[0020] The heat-treated product is subjected to microfiltration or ultrafiltration as described, removing any magnesium phosphate present. Alternatively, the phosphate can be precipitated and then filtered off. The phosphate-free product is combined with the retentate from step (a), which contained the large and particularly temperature-sensitive proteins, as described. The mixture is then dried.

[0021] 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 2 to approximately 3 wt.%.

[0022] Other additives can be added to the product before, but preferably after, spraying, such as lactoferrin, lecithins, vitamins or food emulsifiers [EP 1314367 A1 ,NESTLE] and the like. A demineralized sweet whey powder is finally obtained which has a protein content of about 50 to about 95% by weight, preferably about 85 to about 92% by weight.

[0023] The process according to the invention is also shown in the flow diagram according to Figure 1 explained in more detail. UF = ultrafiltration, NF = nanofiltration, UHT = ultra-high temperature treatment, MF = microfiltration, MX = mixing, and ST = spray drying. INDUSTRIAL APPLICABILITY

[0024] A further object of the invention relates to the use of the demineralized sweet whey powder according to the invention or the corresponding process product as a food, especially as a protein source for infant nutrition, and for the production of cosmetic products, especially creams and lotions for the care of skin and hair, into which the powders can be easily incorporated. EXAMPLES EXAMPLE 1 Production of a demineralized sweet whey powder according to the invention

[0025] In the pilot plant, 1,000 liters of sweet whey were 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 unit 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 78 °C for approximately 20 minutes and then fed to a microfiltration unit equipped with a ceramic membrane with an average pore diameter of 0.2 µm at 55 °C. At approximately 15 °C, a phosphate-containing third retentate R3 and a third permeate P3 were obtained.Fractions P3 and R1 were combined in a mixing unit, preheated to approximately 80 °C via a heat exchanger, and then sprayed through a tower at a head temperature of 180 °C. The resulting powder had a protein content of 13.7 wt.%, an ash content of 1.2 wt.%, and a residual moisture content of approximately 3 wt.%. COMPARISON EXAMPLE V1 Production of a demineralized sweet whey powder according to the state of the T technology

[0026] Analogous to Example 1, 1,000 liters of sweet whey were fed at 12 °C into a nanofiltration system equipped with a spiral-wound membrane with an average pore diameter of 2,000 Daltons. The retentate, containing lactose and minerals, was warmed to 35 °C and subjected to electrodialysis. It was then cooled to 15 °C, passed over an ion exchanger, and sprayed as in Example 1. The resulting powder had a significantly lower protein content of 11.5 wt.%, an ash content of 1.5 wt.%, and a residual moisture content of approximately 3 wt.%.

Claims

1. Process for producing a demineralized sweet whey powder, comprising or consisting of the following steps: (a) providing whey, (b) diafiltration or ultrafiltration of the whey 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 performed using a membrane with an average pore diameter of approximately 100 to 2,000 Daltons, (d) temperature treatment of the retentate R2 from step (c), (e) filtration of the temperature -treated product from step (d) to obtain a third 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) dehydrating the mixture from step (f).

2. Process according to claim 1, characterized in that the ultrafiltration according to step (b) is carried out with a membrane having an average pore diameter of about 1,000 to 50,000 Daltons.

3. Process according to at least one of claims 1 to 2, characterised in that the ultrafiltration according to step (b) and the nanofiltration according to step (c) are each carried out independently of one another at temperatures in the range from about 10 to about 60°C.

4. Process according to at least one of claims 1 to 3, characterised in that the temperature treatment according to step (d) is carried out at a temperature in the range from about 70 to about 90°C.

5. Method according to at least one of claims 1 to 4, characterised in that the temperature treatment according to step (d) is carried out over a period of about 10 to about 30 minutes.

6. Process according to at least one of claims 1 to 5, characterised in that the temperature-treated product from step (d) is subjected to ultrafiltration or microfiltration.

7. Process according to claim 6, characterised in that the ultrafiltration or microfiltration according to step (e) is carried out with a membrane which has an average pore diameter of about 10,000 to about 800,000 Daltons.

8. Process according to claims 6 and / or 7, characterised in that the ultrafiltration or microfiltration according to step (e) is carried out at a temperature in the range from about 10 to about 60°C.

9. Process according to at least one of claims 1 to 8, characterised in that the mixed product from step (f) is subjected to freeze-drying or spray-drying.

10. Process according to at least one of claims 1 to 9, characterised in that the spray drying according to step (g) is carried out at temperatures of 180 to about 260°C - measured at the feed onto the spray tower.

11. Process according to at least one of claims 1 to 10, characterised in that a demineralised sweet whey powder is produced which has a protein content of about 11 to about 18% by weight and a mineral content of less than 2% by weight.