Technical field

The present invention relates to a method for separating one or more agents from a medium, and a filtration device.

Background

Separation or filtration processes are used to either remove an agent from a medium, and/or to enrich or upconcentrate an agent within a medium. The processes are particularly relevant in industries with high standards of hygiene, cleanliness, and product standards, such as the dairy, beverage, food, and pharmaceutical industry.

For example, water, salts, bacteria, spores, and impurities are typically removed from a raw milk, whereas nutritional agents such as fats and proteins are recovered and upconcentrated in the filtered product. This way, the taste and health benefits of the milk may be improved, and the use of inhibitors and related treatment steps may be avoided, thereby obtaining preservative-free or -reduced milk. Further, a standardized and uniform milk product may be obtained, irrespective of the breed of cow and season.

Filtration may also be used in the dairy and pharmaceutical production, where the fluids used for cleaning the production equipment (CIP or clean-in-place fluids) are filtered to remove toxic or active chemical agents before the fluids are discharged to the sewage system, and/or filtered to remedy chemical agents, which may be recycled. This way, the environmental impact of the production may be reduced. Further, the CIP fluids may be filtered to recover or reclaim agents, which may be re-used or recycled.

Filtration, in particularly the dairy industry, has traditionally been obtained by centrifugal separation. However, membrane filtration is receiving increasing interest. A sketch of a membrane filtration or separation process is shown in Figure 1. The membrane 4 may be in the form of a layer or a cylindrical wall surrounding a lumen, as shown in Figure 1 in cross-sectional view. A feed medium 1 flows in parallel or tangentially to a surface of the semi-permeable membrane, e.g. within the lumen of the cylindrical wall, also referred to as a monotube. Thus, the configuration is also referred to as cross-flow or tangential flow, in contrast to dead-end flow where the medium flows perpendicular to the surface of the membrane. Due to the pressurization, the feed is separated into two streams or fractions: a permeate fraction 2 passing through the membrane, and a retentate fraction 3 rejected by the membrane. For example, the feed medium may be a raw milk, where the permeate includes the undesired dissolved parts (water, salt, lactose, nonprotein nitrogen (NPN), whey proteins), and the retentate includes the desired insoluble agents (fats, insoluble proteins, such as casein). Hence, the undesired first agents are removed with permeate, and the desired second agents are recovered or upconcentrated in the retentate. It follows that the membrane performance is determined by the filtration efficiency, i.e. the capable filtration flux rates and the separation efficiency and selectivity towards the desired agents in either the permeate or retentate. However, other parameters also affect the membrane performance, such as the stability of the membrane (e.g. the strength, chemical resistance, thermal and hydrothermal resistance), the durability and operational lifetime (e.g. fouling resistance, cleanability), and the environmental impact of the membrane materials (e.g. the carbon footprint of the membrane production.

There is a need for membranes and membrane filtration methods with improved membrane performance. Summary

It is an object of the present invention to solve the need for membranes and membrane filtration methods with improved membrane performance. Particularly, the need for membranes and methods for separating dairy products, such as cream cheese, cheese milk, milk, whey, and/or fresh cheese, as well as CIP fluids from diary production and similar productions such as pharmaceutical and beverage production.

The object can be achieved by means of a membrane comprising silicon carbide. Said membranes provide surprisingly improved filtration efficiency, durability and operational lifetime, particularly for CIP fluids and dairy products. For example, improved filtration efficiency towards fats and eatable oils, is obtained, as well as high efficiency and selectivity towards certain proteins, such as casein within the rententate. Further, permeates with surprisingly reduced contents of Total-N, Total-P, oxygen, fats, and/or oils are obtained. The membranes may further provide an improvement in the environmental impact. A first aspect of the invention relates to a method for separating one or more agents from a medium, comprising the steps of: a) providing a feed of the medium, b) separating the feed by use of a membrane, wherein the membrane comprises silicon carbide, whereby a permeate comprising at least a first agent, and a retentate comprising at least a second agent is obtained.

In a preferred embodiment, the invention relates to a method for separating a dairy product, comprising the steps of: a) providing a feed of the dairy product, b) separating the feed by use of a membrane, wherein the membrane comprises silicon carbide, whereby a permeate and a retentate is obtained, wherein the retentate comprises one or more recovered agents selected from the group of: dairy fats, milk fats, proteins, casein, and combinations thereof.

The method surprisingly facilitates that the retentate may recover essentially all of dairy fats present within the feed, such that a fat up-concentration above 250 % may be obtained. Further surprisingly, the method enables, a casein recovery between 65- 99% from the feed, as well as 25-75% recovery of other soluble proteins (SP).

A second aspect of the invention relates to a filtration device, comprising:

- at least one tubular membrane structure comprising silicon carbide,

- at least one temperature controlling element in thermal communication with the membrane, and configured to a temperature of between 50-90 °C.

Advantageously, the device according to the second aspect is configured for carrying out the method according to the first aspect. Further advantageously, the method according to the first aspect is configured for being carried out in a device according to the second aspect.

Description of Drawings

The invention will in the following be described in greater detail with reference to the accompanying drawings. Figure 1 shows an embodiment of a membrane filtration or separation process using cross-flow configuration.

Figure 2 shows an embodiment of a membrane filtration device according to the present disclosure, where (A) shows a top view of the device in cross-section, and (B) shows a side view of the device in cross-section.

Figure 3 shows an embodiment of a membrane filtration device according to the present disclosure.

Figure 4 shows the results from a separation process. Figure 4A shows a cream cheese feed (indicated as (1) on the bottle cap) that was separated into a permeate (indicated as (2) on the bottle cap), and a concentrate of fat and protein (indicated as (3) on the bottle cap). Figure 4B shows a synthetic milk feed (1) that was separated into a permeate (2), and further into a protein concentrate, such as a casein concentrate (3). Figure 5 shows the results from a separation process, where a feed of CIP fluid from a pharmaceutical production (1) was separated into a permeate (2), and a concentrate of protein (3).

Detailed description The invention is described below with the help of the accompanying figures. It would be appreciated by the people skilled in the art that the same feature or component of the device are referred with the same reference numeral in different figures. A list of the reference numbers can be found at the end of the detailed description section.

Silicon carbide

Surprisingly high membrane performances were observed for membranes comprising silicon carbide (SiC), and particularly ceramic SiC formed by sintering. SiC has a relatively low environmental impact, and e.g. the carbon footprint of a ceramic membrane is lower than for a polymeric membrane. The material further provides durability and long operational lifetime to the membrane, because the material has a high fouling resistance, hence e.g. the growth of thermophilic bacteria may be suppressed. Further, SiC surfaces have a high cleanability in many fluids, due to the negative surface charge or zeta potential when exposed to the fluids, and ceramic SiC membranes are easily shaped into structures with a high cleanability. The longer lifetime of the SiC based membranes further contributes to the low environmental impact.

Furthermore, SiC provides high stability and robustness to a membrane, because SiC is a rigid and strong material with high chemical-, thermal-, and hydrothermal resistance. The ceramic based SiC membranes are further easily shaped by ceramic processing techniques into structures with specific dimensions and flow channels for the medium to be separated, and with tailored porosity, and pore size distribution. Hence, the membranes are capable of high filtration flux rates.

Membranes comprising SiC were further found to provide surprisingly efficient separation and high separation selectivity. Particularly for dairy related mediums, such as dairy products and CIP fluids from dairy production (i.e waste waters, and/or process waters from dairy production), high filtration efficiency and selectivity towards second agents, including fats and eatable oils, particularly dairy fats and milk fats, and certain proteins, such as casein, may be obtained. Hence, retentates with high recovery concentrations or upconcentrations of dairy fats, milk fats, and proteins, such as casein, may be obtained. Correspondingly, permeates with surprisingly reduced contents of Total-N, Total-P, oxygen, fats, and/or oils (i.e. the second agents), and high contents of the first agents, including water, salt, lactose, nonprotein nitrogen (NPN), whey proteins, may be obtained.

The high efficiency and selectivity towards these agents may be due to the SiC surface properties, particularly the surface charge and hydrophilicity. Further, the SiC based membranes with high fluxes have the advantage of providing a less energy intensive separation, and retentates with surprisingly high quality fats/oils, dairy fats/milk fats, and proteins may be obtained, because the upconcentrated agents have not been damaged by e.g. an energy intensive centrifugal process.

In an embodiment of the disclosure, the medium is a dairy product, selected from the group of: milk, concentrated milk, raw milk, whey, concentrated whey, cream, cream cheese, cheese milk, fresh cheese, waste waters and/or process waters from dairy production, and combinations thereof. In a further embodiment, the second agents are selected from the group of: nutritional components. In a further embodiment, the second agents are selected from the group of: dairy fats, milk fats, proteins, casein, and combinations thereof. In a further embodiment, the first agents are selected from the group of: water, salt, lactose, nonprotein nitrogen (NPN), whey proteins, and combinations thereof. To simplify the ceramic processing, and to enhance the membrane performance, particularly the stability and robustness, the membrane advantageously comprises a high mass fraction of silicon carbide, and preferably essentially consists of silicon carbide. In an embodiment of the disclosure, the membrane comprises between 50-100 wt% silicon carbide, such as essentially consists of silicon carbide, more preferably comprises between 70-99.9 wt% or 80-99.5 wt% silicon carbide, and most preferably comprises between 90-99 wt%, 92-98 wt%, or 94-96 wt% silicon carbide, such as 95 wt% silicon carbide.

To further enhance the membrane performance, particularly the chemical resistance towards the medium to be separated, the membrane advantageously comprises a ceramic metal oxide, such as zirconia (ZrC>2), doped zirconia and/or stabilised zirconia, such as yttria- and/or ceria stabilised zirconia, titanium dioxide (T1O ₂ ), alumina (AI ₂ O ₃ ), more preferably zirconia (ZrC>2) or stabilised zirconia. Advantageously, the stabilized zirconia is tetragonal stabilized zirconia, for example zirconia doped with 40 mol% T1O ₂ or 8 mol% Y ₂ O ₃ . The ceramic metal oxide may further improve the chemical resistance of the membrane, and e.g. making it resistant to mediums and cleaning fluids with pH values between 0-14. Even relatively small amounts of the metal oxide between 0.1-50 wt% may improve the resistance. It was further surprisingly found that membranes comprising a combination of SiC and a metal oxide may facilitate particularly high separation efficiency, and/or a high separation selectivity of second agents selected from the group of fats, diary fats, milk fats, casein, and soluble proteins. Specifically, it was found that membranes comprising zirconia may facilitate high separation efficiency and/or selectivity of fats, casein and other soluble proteins.

In an embodiment of the disclosure, the membrane further comprises a metal oxide, selected from the group of: zirconia, stabilised zirconia, titanium dioxide, alumina, and any combinations thereof, and preferably is zirconia (ZrC>2) and/or stabilised zirconia. In a further embodiment, the membrane comprises between 0.1-50 wt% zirconia, more preferably between 0.5-20 wt% zirconia, and most preferably between 1-10 wt%, 2-8 wt%, or 4-6 wt% zirconia, such as 5 wt% zirconia.

Advantageously, the metal oxide is coating the silicon carbide, at least in a part of the surface in contact with the medium to be separated. For example, the metal oxide may be in the form of a layer coating one or more surfaces of the support, e.g. partly or fully coating the lumen surfaces, and also be referred to as an intermediate layer. For example, advantageously, the metal oxide layer may be coating the lumen of the monotube or multichannel tube. Hence, when a feed is flown through the lumens, the permeate will pass through the membrane, the intermediate layer, and to the surroundings. This is also referred to as inside-out filtration.

Hence, the intermediate layer may be coating the silicon carbide. Particularly, the intermediate layer may be configured to provide a high mechanical stability of the membrane by having a strong physical attachment to the membrane. The strength and degree of attachment will depend on the material and pore size distribution of the intermediate layer. For example, a composite layer comprising silicon carbide and a metal oxide may facilitate a high attachment degree between the support and the membrane. Also, a zirconia layer with meso porosity may facilitate a high attachment degree.

In an embodiment of the disclosure, the metal oxide is coating the silicon carbide. In a further embodiment, the membrane comprises a metal oxide coating, such as a metal oxide layer comprising mesoporous zirconia. In a further embodiment, the metal oxide coating is mesoporous with an average pore size of between 10-70 nm, such as 30 or 60 nm.

Membrane porosity

The permeate is transferred through the pores within the membrane. Hence, the membrane performance, and particularly the possible permeate flux, will increase with increasing porosity. In addition to the porosity, the surface area of the membrane, also influences on the possible permeate flux. Advantageously, the membrane porosity is between 35-70 vol% and the absolute surface area between 0.05-10 m ² to provide a high flux and sufficient mechanical strength. By the term porosity is meant the void fraction present within the membrane structure, which is accessible to a measurement technique. Advantageously, the porosity is the open porosity measured by capillarity porosimetry, capillary flow porometry, and/or mercury porosimetry, and preferably by capillary flow porometry due to the simple and environmental friendly technique.

By the term absolute surface area is meant the absolute surface area of the actual membrane structure, as measured by gas adsorption, such as nitrogen BET. Advantageously, the absolute surface area is based on a membrane structure, such as multichannel tubular membrane, with a length of 1 m and with a diameter of 30 mm.

In an embodiment of the disclosure, the membrane has a porosity of between 35-70 vol%, more preferably between 40-65 vol%, and most preferably between 45-60 vol%, such as 50 or 55 vol%. In a further embodiment, the membrane has an absolute surface area between 0.05-10 m ² more preferably between 0.06-5 m ² , and most preferably between 0.07-1 m ² , such as 0.09, 0.28, or 0.33 m ² .

The membrane performance, and especially the separation efficiency and selectivity towards certain agents, will also depend on the average pore size and pore size distribution of the membrane. For example, fats and certain proteins, have larger molecule size, or form molecule structures or micelles, which may not be transferred through the average pore size within the membrane, such as an average pore size of 0.3 or 0.33 pm. Also certain proteins, such as casein, may have a molecule size or form micelles, which may not be transferred through an average pore size of ca. 0.06 pm or 60 nm of the membrane. In contrast, salts and lactose may be completely dissolved within the medium, and hence easily transferred through pores with these average pore sizes. Hence, advantageously the membrane comprises one or more average pore sizes to facilitate separation of one or more selected agents. For example, the membrane advantageously comprise a bimodal or trimodal pore size distributions, whereby fats and casein may be separated, recovered and upconcentrated in the retentate.

By the term average pore size is advantageously meant the average pore size or median pore size as measured and calculated by capillary flow porositmetry, mercury porosimetry or gas adsorption, such as nitrogen BET. Preferably the average pore size is measured by capillary flow porometry due to the simple and environmental friendly technique. A pore is typically not spherically shaped, and unambiguously defined by its diameter or radius. In most cases, the pore is not spherical, and will instead form an irregular, interconnected network with neighbouring pores. Thus, when applying the common techniques as known to the skilled person for evaluating pore sizes, the pore size is often quantified in terms of a representative pore diameter or pore cylinder diameter, such as the average pore/cylinder diameter. For example, the size of non- spherical pore may be quantified as the diameter of an equivalent sphere or cylinder, such as the sphere/cylinder having the same volume or surface area as the non- spherical pore. Alternatively, the pore size may be measured indirectly by the gas pressure required to displace a liquid within a pore, as measured by capillary flow porosimetry and Young-Laplace formula. Despite this is not a proper quantification from a geometrical point of view, it is applied to provide a quantitative description of the characteristic sizes.

In an embodiment of the disclosure, the membrane has an average pore size of between 0.05-5 pm, such as 0.06 pm, more preferably between 0.1-3 pm, such as 1 or 1.2 pm, and most preferably between 0.2-0.8 pm, such as 0.3 or 0.6 pm. In a further embodiment, the membrane comprises a bimodal ortrimodal pore size distribution. In a further embodiment, the first peak has an average pore size of between 0.05-0.5 pm, such as 0.06 pm, the second peak has an average pore size of between 0.1 -0.5 pm, such as 0.3 or 1 pm, and the third peak has an average pore size of above 1 pm, such as 1.5, 2, or 5 pm. Geometrical structure

The geometrical bulk structure of the membrane advantageously is a tubular structure, such as a monotube, which a single flow channel as illustrated in Figure 1, or a multichanneled tube with multiple channels 4.1 e.g. 5 channels, as illustrated in Figure 2, which are geometrically robust and simple to manufacture, and which may enable a large contact surface area between the medium to be separated and the membrane. Hence, the membrane comprises one or more lumens for flowing the medium to be separated, and the permeate is efficiently transferred and discharged via the membrane wall surrounding the lumens. In an embodiment of the disclosure, the membrane comprises one or more lumens for the medium, and preferably is a monotube and/or a multichannel tubular membrane.

Advantageously, the monotube and/or multichanneled membrane is not a monolith supported membrane. A monolith is an extruded structure with typically thousands of parallel channels or holes defined by thin walls in a honeycomb structures. The monotube or multichanneled membrane according to the disclosure facilitates a more efficient separation and/or a higher selectivity of the separation, especially for dairy products due to the rheology of dairy fluids and a more efficient transport of the permeate.

In an embodiment of the disclosure, the membrane is not a monolith supported membrane. For simple membrane manufacture and simple filtration systems, the membrane is advantageously a monotube. Further, to reduce the material costs associated with the manufacture, the monotube advantageously has a thin wall thickness, and may be mechanically supported by a cheaper support structure, such as an alumina support or stainless steel support.

In an embodiment of the disclosure, the monotube has a wall thickness of between 5- 50 pm, more preferably between 7-40 pm or 9-30 pm, and most preferably between 10-20 pm. In a further embodiment, the monotube further comprises a supporting structure.

To improve the separation rate and medium flux through the membrane, particular for viscous media such as dairy products, the membrane is advantageously a multichannel tubular membrane, comprising 3 or more lumens. The lumens may have any shape and orientation, but for simple processing and geometrical stability, the lumens are preferably cylindrical, extending in parallel to each other, and/or arranged in a symmetrical pattern.

In an embodiment of the disclosure, the multichannel tubular membrane comprise 3 or more lumens, more preferably 4, 5, or 6 lumens, and most preferably 7 or more lumens, such as 8, 9, or 10 lumens. In a further embodiment, the lumens have a cross-sectional shape selected from the group of: circular, ovalic, squared, and polygonal, such as hexagonal, octagonal, decagonal, dedecagonal, and preferably wherein the lumens are cylindrical. In a further embodiment, the lumens extend in parallel to each other. In a further embodiment, the lumens are arranged mirror symmetrical and/or rotation symmetrical as seen in top view in cross-section.

To further improve the separation rate and medium flux through the membrane, particular for viscous media such as dairy products, the lumens and geometrical bulk dimensions of the membrane, advantageously are within certain limits.

In an embodiment of the disclosure, the lumens have a diameter of between 1-15 mm, more preferably between 2-10 mm, and most preferably between 2.5-5 mm, such as 3 or 4 mm. In a further embodiment, the tubular membrane has a length of between 50- 500 mm, more preferably between 70-400 mm, and most preferably between 90-350 mm, such as 100 mm or 305 mm. In a further embodiment, the tubular membrane has a diameter of between 5-70 mm, more preferably between 10-50 mm, and most preferably between 20-40 mm, such as 25 mm or 30 mm.

As described earlier, the membrane filtration efficiency and the chemical resistance towards the medium to be separated, may be improved by a metal oxide, such as zirconia, coating at the part of the membrane surface in contact with the medium to be separated. Hence, advantageously, the lumen surfaces are partly or fully coated by a metal oxide, such as zirconia. In an embodiment of the disclosure, the lumens comprise a coating selected from the group of: zirconia, doped zirconia, stabilized zirconia, titania, alumina, and any combinations thereof.

Operation conditions In addition to the geometrical bulk structure of the membrane, the medium flow pattern affects the contact surface area between the medium to be separated and the membrane. For an efficient and continuous process, facilitating a large contact surface area, the separation is advantageously carried out in a cross-flow configuration. In an embodiment of the disclosure, the separation is carried out in a cross-flow configuration, and/or dead-end configuration.

The medium flow pattern and flux is also dependent on the medium viscosity. For viscous media, such as dairy related products, sufficient and optimized flow and flux of the medium may be obtained by adjusting the temperature at which the separation is carried out, and/or the viscosity of the medium.

By the term viscosity is meant the medium’s resistance to deformation, as measured by viscometers and rheometers under defined conditions. Advantageously, the viscosity is measured by a viscometer configured to measure at a predetermined temperature.

In an embodiment of the disclosure, the separation is carried out at a temperature of between 35-90 °C, more preferably between 40-85 °C, such as 50 or 60 °C, and most preferably between 70-75 °C. In a further embodiment, the medium is adjusted to have a viscosity at the operational temperature of between 10-60 CP, more preferably between 20-50 CP, and most preferably between 25-40 CP, such as 30 CP at 70-75 °C. To improve the cost- and energy efficiency of the separation or filtration process, and to ensure an low energy filtration, where e.g. the dairy fats and casein is minimally affected, the process is advantageously carried out at a low pressure, and/or with a certain medium load rate, and permeate flux. In an embodiment of the disclosure, the medium is adjusted to have a pressure of between 0.2-10 bar, more preferably between 0.4-5 bar, and most preferably between 0.5-1 bar. In a further embodiment, the medium load is between 5-30 kg/h, more preferably between 10-20 kg/h, such as 14 kg/h. In a further embodiment, the permeate flux is between 2-20 L/h-m ² , more preferably between 3-15 L/h-m ² ,, such as 4 or 11 L/h-m ² . In a further embodiment, the process is carried out at a trans-membrane pressure (TMP) of between 0.2-1.5 bar, more preferably between 0.3-1 bar, such as 0.5 bar.

To further improve the cost- and energy efficiency of the separation process, the retentate and/or permeate is advantageously recycled in a feed and bleed step. For example, the retentate obtained after a first separation step within the membrane, may be collected and recycled as medium in a second separation step. This way, retentates with surprisingly high fat concentrations may e.g. be obtained. Optionally, a step of centrifugation may be included to further increase the retentate concentration.

In an embodiment of the disclosure, the retentate is recycled in a feed and bleed step. In a further embodiment, the process further comprises a step of centrifugation.

Filtration device The separation process according to the present disclosure is advantageously carried out in a filtration device configured for the process. For example, the filtration device may be adapted for separating dairy products media, such as cream cheese, cheese milk, milk, whey, fresh cheese, waste waters and/or process waters from dairy production, and combinations thereof. This may be obtained by the filtration device being configured to operate at predefined temperature ranges and pressure ranges, which facilitates sufficient flow patterns, fluxes, and viscosity of dairy products. Further, membranes comprising silicon carbide are particularly suitable for efficient temperature and pressure control, due to the thermal conductivity and surface energy properties of the silicon carbide.

In an embodiment of the disclosure, the filtration device comprises at least one temperature controlling element in thermal communication with the membrane, and configured to a temperature of between 50-90 °C. In a further embodiment, the temperature controlling element is a jacket.

In an embodiment of the disclosure, the filtration device comprises a pressure controlling element. In a further embodiment, the pressure controlling element is a pump, more preferably a positive displacement pump comprising pressure controllers. In a further embodiment, the pressure controlling element is configured to provide a trans-membrane pressure (TMP) of between 0.2-1.5 bar, more preferably between 0.3- 1 bar, such as 0.5 bar.

Reference numbers

1 - Feed 2 - Permeate or filtrate 3 - Retentate or concentrate

4 - Membrane 4.1 - Channels Examples

The invention is further described by the examples provided below.

The experiments were conducted at Liqtech Water in Hobro, Denmark.

Example 1 - Cream cheese filtration SiC based membranes are used to filter different types of dairy applications, for example the dairy product cream cheese. The separation process may be continuous, or batch wise. In an example, a batch process was carried out using a 7 kg or 14 kg feed of cream cheese with originally ca. 9, 11 , 18, or 40 wt% fat. Different types of membranes comprising silicon carbide were tested. Specifically, four types of SiC based membranes with the characteristics as summarized in Table 1 below were tested.

Table 1. Characteristics of different types of membranes comprising SiC.

The porosity and average pore size of the membrane are easily and advantageously determined by capillarity porosimetry or capillary flow porometry. The absolute surface area of the membranes is advantageously evaluated based on BET gas adsorption. The separation was carried out using cross-flow configuration using a set-up similar to the set-up shown in Figure 3. The trans-membrane pressure (TMP) was regulated to ca. 0.5 bar. During the separation, the feed was exposed to temperature regulation, such that a temperature of 50-55 °C or around 70 °C was obtained. The temperature was regulated depending on the viscosity of the raw feed, such that the resulting feed viscosity is around 30 CP at the determined temperature, as measured by a rheometer or viscometer e.g. from Anton Paar. Hence, the cream cheese feed with 40 wt% fat was regulated to a temperature of ca. 70 °C, whereby a viscosity of 30 CP at 70 °C was obtained as measured by viscosimeter. Correspondingly, for a milk feed a temperature of ca. 50-55 °C may be used to obtain a viscosity of 30 CP at 50-55 °C.

The separation process was controlled by the valve on the permeate outlet being closed, when the cream cheese was added, and then slowly opening the valve to regulate the permeate flux. In the examples, the permeate flux was regulated to be between 4-11 L/h-m ² .

The permeate and retentate was subsequently visually observed and analysed with regards to fat, lactose, oxygen and protein content. The concentrations of fat, lactose, protein, and particularly casein are measured by use of FTIR (Fourier Transform Infrared) spectroscopy analysis for food products, such as by use of a Milkoscan instrument. The concentrations of the compounds may also be determined by use of light scattering particle sizing, such as by use of a laser particle sizer, e.g. a Malvern Mastersizer instrument type 1000, 2000, or 3000, due to the different particle size, agglomerate size, and/or micelle size of the compounds.

Figure 4A shows the results from a cream cheese separation process, where the feed (indicated as (1) on the bottle cap), was separated into a permeate (indicated as (2) on the bottle cap), and a concentrate of fat and protein (indicated as (3) on the bottle cap).

Table 2 below summarizes the resulting concentrations of fat, and protein, such as casein, which was obtained based on an original feed having a fat concentration of 40 wt% and a protein concentration of below. Table 2. Fat and protein concentrations in the retentate and permeate.

A higher separation efficiency for membranes of types 2-3 were seen, and from this it appears that a higher separation efficiency may be obtained for membranes with an average pore size below 1 pm, such as 0.3 pm or 0.06 pm.

Further, higher separation efficiency for the type 2 membrane compared to type 3, indicating that membranes with a multi-channel configuration are more efficient compared to monotube configuration.

Further tests indicate that a higher separation efficiency may be obtained for membranes comprising a mixture of SiC and a metal oxide, such as a coating of ZrC>2, corresponding to the type 4 membrane.

Further testing shows that a fat up-concentration above 250 % may be obtained. In addition, a casein recovery between 65- 99% and 25-75% recovery of other soluble proteins (SP) may be obtained.

In addition to the fat and protein concentrations indicated in Table 2, the retentate and permeate may further be analysed with respect to casein, lactose, and oxygen concentration, as mentioned above, and an upconcentration of casein in the retentate may be observed. In addition, the physicochemical properties such as viscosity (rheology), fat globule integrity (confocal microscopy), emulsion stability (Lumifuge), protein denaturation and aggregation and protein-milk fat interaction (SDS-PAGE) and phospholipid composition (HPLC) may be evaluated, and differ from the a dairy product obtained by other separation methods, such as centrifugation.

Example 2 - Synthetic milk filtration and casein separation

Example 1 is repeated with a feed of synthetic milk comprising casein, and a type 4 membrane. Figure 4B shows the feed (indicated as 1) that was separated into a permeate (indicated as 2) essentially free of casein, and a retentate with a surprisingly high concentration of casein (indicated as 3), corresponding to a casein recovery of approximately 99%. Example 3 - Full fat milk filtration

Example 1 is repeated with a feed comprising full fat milk, and a type 2, 3, or 4 membrane. Similar results as in Example 1 may be obtained.

Example 4 - Pharmaceutical CIP water separation Example 1 is repeated with a feed comprising proteins from CIP fluids from pharmaceutical productions, and a type 4 membrane. Figure 5 shows the feed (indicated as 1) that was separated into a permeate (indicated as 2), and a retentate (indicated as 3) with a surprisingly high recovery of the proteins, such as a protein recovery of between 65-99%.

Example 5 - Beverage CIP water separation

Example 1 is repeated with a feed comprising proteins from CIP fluids from a beverage production. Surprisingly high recovery or reclamation of the proteins into the retentate may be obtained.