EP0346426A1

EP0346426A1 - Process for separating the dissolved and undissolved constituents of milk

Info

Publication number: EP0346426A1
Application number: EP89900604A
Authority: EP
Inventors: Kailash Kumar Dr. Prof. Gauri
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-12-21
Filing date: 1988-12-21
Publication date: 1989-12-20
Also published as: DE3743440A1; DK407889A; DK407889D0; AU2826189A; US5028436A; WO1989005586A1; JPH02502517A

Abstract

Selon un procédé de séparation des éléments dissous et non-dissous du lait, on traite au préalable une membrane microporeuse dont les pores ont une grandeur comprise entre 0,1 et 2 mum avec une solution aqueuse, dispersion ou émulsion de lipides ou de peptides, puis on utilise cette membrane traitée au préalable pour séparer le lait.According to a process for separating the dissolved and undissolved elements of milk, a microporous membrane, the pores of which have a size between 0.1 and 2 mum, is first treated with an aqueous solution, dispersion or emulsion of lipids or peptides, then this pre-treated membrane is used to separate the milk.

Description

METHOD FOR SEPARATING THE SOLVED AND UNSOLVED COMPONENTS OF MILK

The invention relates to a method for separating the dissolved and undissolved components of milk.

The composition of mammalian milk has been very well studied. The dry weight of cow's milk is known to be on average about 12.7%, of which about 3.7% are fat components, 3.4% total protein, 4.7% lactose and about 0.7% ash. The protein component consists mainly of caseins and whey proteins. In addition, one speaks of a non-protein nitrogen (non-protein _^ aceous nitrogen) fraction, protease peptones and minor proteins, which are mainly enzymes.

A separation into caseins and whey proteins is usually carried out for milk. This separation is carried out using the so-called rennet, ^(β 30 to 35 C) in which one of heated milk rennet added. The fall

Casein out while the whey proteins remain in solution. The same applies to the so-called acid precipitation of the caseins, which takes place at the isoelectric point (cow's milk pH 4.7). Caseins are heat-stable, while the whey proteins are heat-unstable.

It is also known to concentrate milk by reverse osmosis, which removes practically pure water from the milk, which means that all dissolved and undissolved components of the milk, including the salts dissolved in the milk, remain in the milk Retentate back and the permeate consists essentially of pure water. In this way, so-called condensed milk is obtained today. Reverse osmosis is also used to concentrate whey and for the production of curd cheese, yoghurt and thick milk.

It is also known to subject milk to ultrafiltration. The enrichment of the milk proteins does not pose any difficulties, however, only when using skimmed milk or whey. The ultrafiltration of native whole milk, however, only leads to an incomplete separation. A separation of the milk is not possible with conventional membrane filters.

Obtaining the whey proteins that are particularly desirable in terms of nutritional physiology is relatively complex using the known methods. In addition, the whey proteins obtained by the known processes are generally contaminated with bacteria and contain fat as well as the calcium and phosphate ions released upon separation into caseins and whey proteins.

The invention is therefore based on the object of providing an improved method for separating the milk into soluble and insoluble constituents with the aid of membranes.

Surprisingly, it has now been found that milk can be separated into the dissolved and undissolved components if the milk is passed through a microporous membrane which has been pretreated with lipids and / or peptides. The invention therefore relates to a process for separating the dissolved and undissolved components of milk, which is characterized in that a microporous membrane with a pore size in the range from 0.1 to 2 μm is pretreated with lipids and / or peptides and the Separates milk on the membrane pretreated in this way.

A membrane based on a fluorocarbon polymer is advantageously used. A membrane made of polyvinylidene fluoride, e.g. a so-called "Durapore" membrane from Millipore (e.g. the type designation GVLP or HVLP).

The pore size of the membrane is preferably in the range from 0.1 to 1 μm, in particular 0.1 to 0.6 μm.

The membrane can be pretreated with lipids or peptides alone or first with lipids and then with peptides. With the help of this pretreatment, a membrane is obtained which, in contrast to an untreated membrane, enables the milk to be separated into the dissolved and undissolved components. An explanation for the effect achieved by the pretreatment cannot be given. However, it could be a polarization effect.

The membrane is pretreated in a simple manner by treating it with a solution, emulsion or dispersion of the lipids and / or peptides in water in the flow. It is generally sufficient to use a 0.1 to 10%, preferably 2 to 5%, lipid emulsion or a 0.01 to 10%, preferably 0.1 to 5%, solution of the peptides.

The pretreatment is expediently carried out at a temperature of 8 to 40 ° C., in particular 15 to 35 ° C. The duration of the pretreatment depends on the lipid or peptide used in each case and on the concentration of the emulsion or solution with which the membrane is treated in the flow. In general, a pretreatment of 1 to 8 hours, in particular 2 to 5 hours, is sufficient to obtain a membrane which allows the milk to be separated.

Pretreatment with lipids alone leads to the desired effect, especially with membranes with small pore sizes (e.g. 0.1 to 0.4 μm). If membranes of larger pore size are pretreated with lipids, the milk components cannot be completely separated. In order to achieve complete separation in such a case, it is sufficient to treat the membrane with peptides after the pretreatment with lipids. This stepwise pretreatment has the advantage that the effect achieved is reversible and that the time for the pretreatment (in particular for the treatment with peptides in the second step) is reduced.

Pretreatment with peptides alone leads to the desired effect for each of the membranes mentioned, which is generally permanent.

Unsaturated vegetable oils are preferably used as lipids. Suitable examples are rapeseed oil, sunflower oil, coconut oil, peanut oil, olive oil, corn oil and linseed oil.

The peptides or peptide mixtures used according to the invention are generally short-chain peptides with a molecular weight of up to about 10,000, preferably up to about 5,000 and particularly preferably up to about 2,000. The following peptides are preferred according to the invention:

^a ) peptides, petid fractions and peptide extracts which are obtainable from raw milk, fresh milk or whey proteins (obtained from raw or fresh milk),

b) peptides, peptide fractions and peptide extracts which are obtained from hydrolyzates of raw milk, fresh milk,

Whey proteins, plant proteins (in particular banana proteins), animal proteins (from fish, eggs, meat) or bacterial proteins (in particular yeast proteins) are included, including enzymatically treated (for example with liposes such as pancreatin and proteases such as p-peptide protease) ) Raw milk per se,

c) synthetic peptides, and

d) raw milk.

Peptide fractions which can be isolated from raw milk and the particularly preferred peptide fractions with the arbitrary names A, B and C are obtainable, for example, by:

- Untreated raw milk is subjected to membrane filtration on a 0.1 to 0.6 μ membrane;

the filtrate obtained from a second membrane filtration on a membrane with a separation limit of 6

10,000 MG subjects;

- The filtrate obtained is subjected to a third membrane filtration on a membrane with a separation limit of 1000 MG; - The filtrate obtained is subjected to reverse osmosis on an open or closed membrane;

if an open membrane is used, the filtrate obtained is concentrated to about 20% of the volume used in the reverse osmosis, left to stand in the cold and filtered off from the solid matter which has precipitated out;

the filtrate obtained is further concentrated, adjusted to an ethanol content of about 80% with absolute ethanol and filtered;

- the filtrate obtained is concentrated, the residue is extracted with 90 to 95% ethanol, filtered and the filtrate is concentrated;

- Extract the residue obtained with chloroform or isopropanol;

- The extract solution obtained is evaporated to dryness and the residue is isolated as product A in the form of an almost colorless solid substance;

- In the case of using a closed membrane, the retentate (instead of the filtrate obtained when using an open membrane) is subjected to the specified work-up steps and product A is obtained in the process; and

for the extraction of B and C. - The retentate of the third membrane filtration and / or the retentate IV of the reverse osmosis on the open membrane either concentrated in vacuo and extracted with 80% ethanol or an ethanol content of 80% by adding absolute ethanol, from undissolved portions filtered off, the ethanolic solution is evaporated to dryness and thereby the product C - is obtained as a colorless substance;

- The portions which remained undissolved in the ethanol treatment are extracted with 25% aqueous ethanol, filtered off from undissolved constituents, the filtrate is concentrated to dryness in vacuo and product B is obtained in this way.

Product A is characterized by:

- an HPLC band at RT 4.6; DEAE-5PW column, Waters, .Pak protein, mobile phase: 10 t methanol; 0.5 ml / min;

an HPLC band at RT 26; Pillar J-125, Waters,

Protein Pak, mobile phaset ICH-PO. 0.05 ro; 0.5 ml / min;

- HPLC bands at RT 23.3 (weak); 25.3 <strong); 29.5 (medium); 30.5 (medium) y 34.4 (weak); Column »1-125, Waters, Protein Pak, mobile phase» KH ₂ P0. 0.05 m; 0.5 ml / min;

- ninhydrin positive reaction;

- good solubility in chloroform, isopropanol, ethanol and water » Substance 3 is characterized by:

- HPLC bands at RT 19-20 (strong); 21.6 (shoulder); 24.3 (medium);

Column: 1-125, Waters, Protein Pak, mobile phase: KH ₂ PO. 0.05 m; 0.5 ml / min;

good solubility in 20 to 30% aqueous ethanol,

- ninhydrin positive reaction

Substance C is characterized by:

- HPLC bands at RT 21-22 (weak); 23.4 (strong) and 26.5 (strong) (conditions as for G-a);

- ninhydrin positive reaction

- Good solubility in 70 to 90% aqueous ethanol.

The production of these peptide fractions is described below under FIG. 1, which schematically reproduces the production process.

Fresh, untreated raw milk from a pet, preferably cow's milk, serves as the starting material. It can be done in the usual way, e.g. have been skimmed by centrifugation. However, skimming can also be carried out together with the first membrane filtration described below.

Said raw milk is subjected to a first membrane filtration on a microporous membrane with a pore size in the range from 0.1 to 0.6 μm, preferably 0.2 μm. It is advantageous to use a membrane filter arrangement _that enables filtration in the tangential flow. As part way before ^¬ such as for example, has proven to be a polyvinylidene fluoride membrane, a GVLP or HVLP Durapore membrane from Millipore.

To _d hese way, a clear permeate and a thick ^¬ liquid retentate. The permeate (or filtrate) contains all salts, milk sugar, amino acids, oligopeptides and low molecular weight polypeptides in a genuinely undenatured form. In the retained all the casein and fat ^¬ are virtually ingredients of milk included.

The dry matter of the filtrate (permeate) is about 6% and the nitrogen content of the dry matter is about 1.2%. By concentrating you can get dietary foods and food additives.

The filtrate from the first membrane filtration is subjected to a second membrane filtration on a membrane with a separation limit of 8-10,000 MG. The so-called whey proteins essentially remain in the retentate. The filtrate, which essentially contains NPN compounds, lactose, short fatty acids and some salts, is fed to a third membrane filtration on a membrane with a separation limit of 1,000 MW. The resulting retentate is described below. The filtrate is fed to a reverse osmosis. You can either work with a so-called closed membrane or with a so-called open membrane. A Millipore type Mr-3-NF-40 HF membrane can be used as the open membrane, for example. When using an open membrane, the desired product A is mainly in the filtrate. 10

For working up, it is concentrated to about -20% of the volume used in the reverse osmosis and left to stand for a few hours at the refrigerator temperature. Solids form, in particular crystallized lactose. The solids are suctioned off or filtered off. The mother liquor is again concentrated by a few percent and adjusted to an alcohol content of 80% with ethanol. A precipitate forms again in the cold, which is removed by suction or filtering. The filtrate obtained is evaporated to dryness and then extracted with about 10 times the amount of 90 to 95% ethanol. The extract obtained is evaporated to dryness, and the residue obtained is extracted with isopropanol or chloroform. When the extract is evaporated to dryness, the product A • is obtained as a colorless substance.

Product A is ninhydrin-positive and has good solubility in chloroform, isopropanol and ethanol. and water and shows chemical and chromatographic behaviors of short chain peptides.

When using a closed membrane for the reverse osmosis, product A is obtained from the retentate, while the permeate (filtrate) consists practically only of water, a few salts and a small amount of NPN compounds. Said retentate is worked up in the same way as described above for the filtrate of reverse osmosis on an open membrane. However, somewhat larger amounts of the above-mentioned organic solvents are required, since the retentate contains larger amounts of lactose and salts than the filtrate of the reverse osmosis on an open membrane. In the way already described, product A is also obtained from the retentate of the reverse osmosis on a closed membrane. _{χ χ}

100 milligrams of product A are obtained from one liter of milk.

As already mentioned above, the product B / C is obtained from the retentate III of the third membrane filtration. The

Retentate is extracted with about 10 times the volume of 80% ethanol. The ethanolic extract solution is suctioned off or filtered off and the residue is washed again with a little 80% ethanol. Subsequently, it is extracted with approximately 10 times the amount of 25% aqueous ethanol and also briefly washed again when the extract solution is suctioned off. The extract solutions obtained are each evaporated to dryness in vacuo. In both cases, a colorless solid substance is obtained, referred to here as product / C. The two fractions can be combined or used separately.

The substance obtained from the 25% ethanol extract is ^* B "; the substance obtained from the 80% ethanol extract is." C ^* , also referred to below as Rt-103-25.

Not only the products A, -B and C can be used according to the invention, but also the filtrates, extracts and retentates obtained in the reverse osmosis obtained in the course of the production process.

The products described can be obtained in the same way from so-called fresh milk (in the sense of the milk regulation).

Of course, whey or the NPN fraction of a non-heat-denatured milk can also be used. In this

The 1st or 1st and 2nd membrane filtration are not applicable These cesor-αers preferred peptides according to the invention are genuinely contained in very small amounts in raw milk. It is therefore also possible to pretreat the membrane with raw milk. However, a longer treatment period is then necessary.

Of the protein hydrolyzates described above under point b), those in PCT / EP 86/00016 (corresponding to US application 918 253) are preferred.

The other hydrolysates mentioned under point b) are prepared analogously to the process described in PCT / EP 86/00016.

Show it:

FIG. 1: a photographic illustration of the filtrates obtained according to the example;

FIG. 2: a chromatogram (HPLC) of a filtrate obtained according to the invention;

Figure 3: the image of a membrane pretreated according to the invention after spraying with ninhydrin compared to the untreated membrane. With the aid of the method according to the invention, it is possible to separate the dissolved and undissolved components of milk (in particular in the tangential flow method). A clear filtrate (permeate) and a very viscous retentate are obtained. The filtrate contains the dissolved components, namely all salts, lactose, amino acids and other NPN components as well as oligopeptides and low molecular weight polypeptides (whey proteins). It is bacteria-free, casein-free and fat-free and also contains no calcium and phosphate ions, because in the process according to the invention the casein which binds the calcium and phosphate ions is not denatured.

In the context of the present invention, “raw milk” and “fresh milk” means that fresh untreated raw milk and fresh milk from a pet, preferably cow's milk, are used which do not have any of the heating treatments (pasteurization, ultra-high temperature or sterilization) that are customary in dairies. has been subjected. However, it can be carried out in the usual way, e.g. by centrifugation.

The following examples illustrate the invention.

Example

20 liters of fresh raw milk (cow's milk) are subjected to tangential filtration using a polyvinylidene fluoride membrane with a pore size of 0.2 μm. About 17 liters of filtrate and 3 liters of retentate are obtained. The latter consists essentially of caseins and fat. The filtrate (17 liters), dry matter about 6% and nitrogen content of the dry matter about 1.2%, is fed to a second membrane filtration, in which a membrane with a separation limit of 6-10,000 MG is used. This produces about 1/2 to 1 liter of retentate, which mainly contains the whey proteins and enzymes. The filtrate, about 16 liters, is fed to a third membrane filtration, using a membrane with a separation limit of 1000 MG. Here too, only about 1/2 to 1 liter of retentate is obtained. ProductBy'C is obtained from this retentate in the manner described below.

The filtrate is now fed to reverse osmosis. In Ver¬ application of an open membrane, the filtrate is concentrated to ^"about 3 liters and allowed to stand in the refrigerator a few hours. It crystallize some products insbeson particular lactose aus..Man filtered off from the solids, the filtrate is concentrated to such an extent that an ethanol content of about 80% is formed by adding about 10 times the volume of absolute ethanol in the total mixture, the mixture is mixed vigorously, then the undissolved constituents are filtered off with suction or filtered off, the filtrate is evaporated to dryness, and the residue obtained is extracted with 90-95% ethanol (about 10 times the volume), the extract solution is filtered off or suction filtered and concentrated, the resulting residue is treated with about 10 times the amount of chloroform or about 10 times the amount of isopropanol is evaporated to give the desired product A.

If a closed membrane is used in reverse osmosis, the substance sought is in the retentate and the retentate must be worked up in the manner described above for the filtrate. To obtain the product B / C, the retentate III of the third membrane filtration is mixed with about 5 times the amount of absolute ethanol, so that a mixture is obtained which is about 80% pure in ethanol. The whole is stirred vigorously, left to stand for a few hours, then the undissolved constituents are filtered off, and the filtrate is evaporated to dryness. The

The residue of the extractive treatment is then subjected to an extractive aftertreatment with 25% strength aqueous ethanol (approximately 10 times the volume). The precipitate is filtered or filtered from the un ^¬ dissolved constituents, the filtrate is concentrated to dryness, and receives a second fraction of product B / C The two products may be combined.

Example: 2

A polyvinylidene fluoride membrane with a pore size of 0.2 μm (Durapore from Millipore) was cleaned and rinsed with water for one hour. The membrane is not _. able to filter milk clearly.

The membrane is then treated with a 0.1% solution of fraction A (obtained according to Example 1) for eight or fourteen hours in a flow at room temperature. The membrane is then suitable for separating the dissolved and undissolved components of the milk. A clear filtrate is obtained. The properties of the membrane do not change even after treatment with 0.3 N NaOH.

The same results are obtained when using a 0.6 µm membrane. Example

A Durapore membrane 0.2 μm is cleaned and rinsed as described in Example 2. The membrane is then treated for 3.5 hours at room temperature with a 0.3% solution of Rt-103-25 (obtained according to Example 1) in the flow. After this pretreatment, the membrane is suitable for separating the dissolved and undissolved components of the milk, and a clear filtrate is obtained. Treatment of the pretreated membrane with 0.6% NaOH for one hour does not change the properties of the membrane.

The same results are obtained when using a membrane with a pore size of 1 μm.

Example

Four 0.2 μm Durapore membranes were subjected to the following treatments:

Membrane 1; It was cleaned and rinsed as indicated in Example 2;

Membrane 2 The cleaned membrane was treated for 2 hours at room temperature with a 4% emulsion of rapeseed oil in water in the flow;

Diaphragm 3. The purified membrane was treated for 8 hours at room temperature ^• with a 4% aqueous canola oil emulsion in the effluent;

Membrane 4 It was first treated like membrane 3 and then for 2 hours with an 8% total hydrolyzate from raw milk. These membranes were used to try to separate the dissolved and undissolved components from milk. The filtrates obtained are shown in FIG. 1. It can be seen that the membrane 1 does not allow separation, only a slight separation is possible with membrane 2, an almost complete separation is possible with membrane 3 and the membrane 4 gives a clear separation of the dissolved and undissolved components _Q.

Example 5

A 0.1 μm polyvinylidene fluoride membrane (Durapore) was treated and cleaned as described in Example 2.

The membrane was then treated for 8 hours with a 4% emulsion of sunflower oil in water in the flow at room temperature. The membrane was then suitable for filtering milk clearly.

20th

Example 6

A 0.6 μm polyvinylidene fluoride membrane (Durapore) was treated with an 8% raw milk hydrolyzate at room temperature in the flow. After 8 hours the milk could be filtered clearly.

If you use the same membrane for 3 1/2 hours with a 0.5%

30 solution of Rt-103-25 (prepared according to Example 1) treated, the same result is obtained.

If the membrane pretreated in this way is sprayed with ninhydrin reagent, the pretreated product is obtained

35 part of the membrane a blue color, which indicates the presence of peptide nitrogen (see Figure 3). The untreated parts of the membrane have no color (white stripes in FIG. 3). As mentioned, the filtrate obtained according to the invention contains the dissolved components of the milk, in particular the whey proteins. FIG. 2 representatively shows the composition of the filtrate obtained according to the invention. The chromatogram was obtained under the following conditions:

Column: J - 125 Waters, Protein Pak;

Mobile phase: 10% methanol; 0.5 ml / min;

Extinction: 0 to 0.2; 224 nm;

Sample: 20 μl

Claims

P a t e n t a n s r u c h e

^' ι. Process for separating the dissolved and undissolved components of milk,

Therefore, a microporous membrane with a pore size in the range from 0.1 to 2 μm is pretreated with an aqueous solution, dispersion or emulsion of lipids or peptides and the milk is separated on the pretreated membrane.

2. The method according to claim 1, characterized in that one uses a membrane based on a fluorocarbon polymer.

3. The method according to claim 1, characterized in that one uses a polyvinylidene fluoride membrane.

Process according to Claim 1, characterized in that a membrane with a pore size in the range from 0.1 to 1 µm, in particular 0.1 to 0.6 µm. used.

5. The method according to claim 1, characterized in that one first carries out a pretreatment with an aqueous solution, dispersion or emulsion of lipids and then a pretreatment with an aqueous solution, dispersion or emulsion of peptides.

D. The method according to claim 1, characterized in that unsaturated vegetable oils are used as lipids.

7. The method according to claim 1, characterized in that one uses a lipid which is selected from rapeseed oil, sunflower oil, coconut oil, peanut oil, olive oil, corn oil and linseed oil.

8. The method according to claim 1, characterized in that the peptides used are:

a) peptides, peptide fractions and peptide extracts which are obtainable from raw milk, fresh milk or whey (obtained from raw or fresh milk),

b) peptides, peptide fractions. and peptide extracts which are obtainable from hydrolyzates of raw milk, fresh milk, whey proteins, plant proteins, animal proteins or bacterial proteins, including enzymatically treated raw milk per se, 5 - ^" -

c) synthetic peptides, and

0 d) raw milk.

9. The method according to claim 1, characterized in that the peptides used are the products with the arbitrary designation A, B or C -5, which can be obtained by - Untreated raw milk is subjected to membrane filtration on a 0.1 to 0.6 μ membrane;

10,000 MG subjects;

subjecting the filtrate obtained to a third membrane filtration on a membrane with a separation limit of 1000 MG;

- The filtrate obtained from a reverse osmosis. subject to an open or closed membrane;

- in the case of use of an open membrane, the filtrate is concentrated er¬ maintained at about 20% of the volume used in the reverse osmosis, in the refrigeration s tehen lä _ß t and failed Fes tsubs dance abf iltriert;

the filtrate obtained is further concentrated, the ethanol content is about 80% with absolute ethanol and the mixture is filtered;

the filtrate obtained is concentrated, the residue is extracted with 90 to 95% ethanol, filtered and the filtrate is concentrated;

the residue obtained is extracted with chloroform or isopropanol; - The extract solution obtained is evaporated to dryness and the residue is isolated as product A in the form of an almost colorless solid substance;

for the extraction of B and -C

the retentate of the third membrane filtration and / or the retentate IV of the reverse osmosis on the open membrane is either concentrated in vacuo and extracted with 80% ethanol or an ethanol content of 80% is obtained by adding absolute ethanol, from undissolved portions filtered off, the ethanolic solution is evaporated to dryness and thereby the product C as a colorless substance;

- The portions which remained undissolved during the ethanol treatment are extracted with 25% aqueous ethanol, filtered off from undissolved constituents, the filtrate is evaporated to dryness in vacuo and product B is obtained in this way.

10. Microporous membrane, obtainable by a process as defined in claims 1 to 9.