MILK PROTEIN CONCENTRATES WITH A REDUCED ASH CONTENT

Abstract

A milk protein concentrate is suggested, obtainable or obtained by: (i) skimming the cream from raw milk, obtaining a skimmed milk fraction having a dry matter content of about 5 to about 15% by weight, and particularly about 10% by weight; (ii) concentrating the skimmed milk fraction of step (i) to a dry matter content of about 45 to about 60% by weight; (iii) standardising the skimmed milk concentrate of step (ii) by adding a milk fraction; and (iv) drying the standardised skimmed milk concentrate to a powder having a dry matter content of at least 95% by weight,
with the proviso that a milk permeate is employed for standardisation, which was previously subjected to electrodialysis.

Claims

1. A milk protein concentrate, obtained the steps of: (i) separating raw milk, and obtaining a skimmed milk fraction having a dry matter content of about 5 to about 15% by weight, and particularly about 10% by weight; (ii) concentrating the skimmed milk fraction of step (i) to a dry matter content of about 45 to about 60% by weight; (iii) standardising the skimmed milk concentrate of step (ii) by adding a milk fraction; and (iv) drying the standardised skimmed milk concentrate to a powder having a dry matter content of at least 95% by weight, wherein a milk permeate is used for standardisation, which was previously subjected to electrodialysis.

2. The concentrate of claim 1, having a protein content of at least 34% by weight in the non-fat dry matter.

3. The concentrate of claim 2, having a lactose content of about 45 to about 60% by weight, based on dry matter.

4. The concentrate of claim 1, having an ash content of a maximum of 7.5% by weight.

5. A process for the production of skimmed milk protein, comprising the following steps: (i) providing a skimmed milk with a dry matter content of about 5 to about 15% by weight, and particularly about 10% by weight; (ii) concentrating the skimmed milk of step (a) to a dry matter content of about 45 to about 60% by weight; (iii) standardising the skimmed milk concentrate of step (ii) with a milk fraction; and (iv) drying the standardised skimmed milk concentrate of step (iii), obtaining a skimmed milk protein concentrate with a dry matter content of at least 95% by weight, wherein a milk permeate is used for standardisation, which was previously subjected to electrodialysis.

6. The process of claim 5, wherein the skimmed milk is adjusted to a dry matter content of about 50% by weight in step (ii).

7. The process of claim 5, wherein a permeate is used as a milk fraction which is obtained by ultrafiltration of milk.

8. The process of claim 5, wherein an amount of milk permeate is added to the skimmed milk concentrate such that a lactose content of about 45 to about 60% by weight is obtained, based on dry matter.

9. The process of claim 5, wherein the standardised skimmed milk concentrate is spray-dried.

10. The process of claim 9, wherein spray-drying is performed at temperatures within the range of about 180 to about 260 C.

11. The process of claim 5, wherein further additives are added to the standardised skimmed milk concentrate before, during or after drying.

12. The process of claim 5, wherein a powder having a protein content of at least 34% by weight is obtained.

13. The process of claim 5, wherein a powder having a lactose content of about 48 to about 59% by weight is obtained.

14. The process of claim 5, wherein a powder having an ash content of a maximum of 7% by weight is obtained.

15. A process for the production of food for toddlers, comprising utilizing the milk protein concentrate of claim 1.

Description

DESCRIPTION OF THE INVENTION

[0011] A first subject matter of the invention relates to a milk protein concentrate, obtainable or obtained by: [0012] (i) skimming the cream from raw milk, obtaining a skimmed milk fraction having a dry matter content of about 5 to about 15% by weight, and particularly about 10% by weight; [0013] (ii) concentrating the skimmed milk fraction of step (i) to a dry matter content of about 45 to about 60% by weight; [0014] (iii) standardising the skimmed milk concentrate of step (ii) by adding a milk fraction; and [0015] (iv) drying the standardised skimmed milk concentrate to a powder having a dry matter content of at least 95% by weight,
with the proviso that a milk permeate is used for standardisation, which was previously subjected to electrodialysis.

[0016] A further subject matter of the invention relates to a process for the production of skimmed milk protein concentrates, comprising or consisting of the following steps: [0017] (i) providing a skimmed milk with a dry matter content of about 5 to about 15% by weight, and particularly about 10% by weight; [0018] (ii) concentrating the skimmed milk of step (a) to a dry matter content of about 45 to about 60% by weight; [0019] (iii) standardising the skimmed milk concentrate of step (ii) using a milk fraction; and [0020] (iv) drying the standardised skimmed milk concentrate of step (iii), obtaining a skimmed milk protein concentrate with a dry matter content of at least 95% by weight,
which is characterised in that a milk permeate is used for standardisation, which was previously subjected to electrodialysis.

[0021] Surprisingly, it was found that, by means of these measures, a protein concentrate was obtained that fully complies with the above described requirements, i.e., having a protein content of at least 34% by weight and a lactose content of about 45 to about 60% by weight and an ash content of a maximum of 7.5, preferably about 6.5 to about 7.2% by weight in the non-fat dry matter.

PROCESS OF PRODUCTION

[0022] The process of the invention may be based on both raw milk and skimmed milk as, in any case, the first process step consists of providing skimmed milk having a dry matter content within the range of about 5 to 15% by weight, and particularly of 9 to 10% by weight. This is typically a standard skimmed milk, obtained after skimming the cream from the raw milk in the separator, and typically having a dry matter content of about 30% by weight.

Concentration

[0023] In a conventional evaporator, a further portion of water is subsequently removed from the skimmed milk such obtained, obtaining a concentrate with a dry matter content within the range of about 45 to about 60% by weight, and typically about 50% by weight.

Standardisation

[0024] As mentioned above, the skimmed milk concentrate such obtained has an ash content that is too high for the subsequent application that specifically concerns milk powders for toddlers, so that a standardisation step is becoming necessary at this point. To this end, a lactose-containing dairy stream, i.e., a milk permeate is added to the concentrate. This is preferably a milk permeate, obtained by ultrafiltration of milk, i.e., raw milk, whole milk or skimmed milk.

[0025] Standardisation, i.e., the addition of the diluate may be performed at different steps of the process, for example, it may be blended with the milk before or after it is heated, i.e., before the separation step. It is also possible to add the diluate before pasteurisation or during any of the concentration steps.

Ultrafiltration

[0026] Ultrafiltration is a filtration process from the field of membrane technology, by means of which macro-molecular substances and small particles may be separated from a medium and concentrated. The degree of separation is decisive for the difference between macrofiltration, ultrafiltration and nanofiltration. If the cut-off limit (or also cut-off) is 100 nm or more, it is referred to microfiltration. If the cut-off limit is in the range between 2-100 nm, this is referred to as ultrafiltration. In the case of nanofiltration, the cut-off limit is below 2 nm. In each of these cases, this concerns purely physical, i.e., mechanical membrane separation methods which apply the principle of mechanical size exclusion: all particles in the fluids which are larger than the membrane pores are retained by the membrane. The driving force in both separation methods is the differential pressure between the inlet and the outlet of the filter area, which is between 0.1 and 10 bar.

[0027] The cut-off limits of nanofiltration membranes are also indicated in form of the NMWC (Nominal Molecular Weight Cut-Off, also referred to as MWCO, Molecular Weight Cut Off, unit: Dalton). It is defined as the minimal molecular mass of more global molecules, 90% of which are 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 on filtration may be made by means of the flux (water value) (transmembrane flux or passage rate). Ideally, it is proportional to the transmembrane pressure and reciprocal to the membrane resistance. These sizes are determined both by the characteristics of the membrane used and by concentration polarisation and possibly occurring fouling. The passage rate relates to 1 m.sup.2 of membrane area. Its unit is l/(m.sup.2h bar).

[0028] Membranes having a pore size within the range of about 1,000 to about 50,000, and preferably about 5,000 to about 25,000 Dalton have proven to be particularly suitable for ultrafiltration. Under these conditions, both lactose and ash as well as mineral substances pass the membrane in the ultrafiltration step and accumulate in the permeate.

[0029] The material of the filtration areaboth in ultrafiltration and in nanofiltrationmay represent stainless steel, polymer materials, ceramics, aluminium oxide or textile fabric. Filter elements appear in different forms: candle filters, flat membranes, spiral coil membranes, bag filters and hollow fibre modules, all of which are, in principle, suitable within the meaning of the present invention. However, spiral coil membranes made of polymer materials or candle filters made of ceramics or aluminium oxide are preferably used, where the first form of embodiment has proved to be particularly preferred for ultrafiltration, and the second one for nanofiltration.

[0030] Ultrafiltration within the meaning of the present invention may be performed hot or cold, i.e., within the temperature range of about 10 to about 60 C. However, it is preferred to operate at temperatures in the lower range from 10 to about 20 C.

Electrodialysis

[0031] The permeate from the ultrafiltration step of the raw milk is rich in lactose, but it does also contain a high amount of ash, i.e., mineral components which, eventually, give the resulting milk powder a bitter taste. It has now been proven that electrodialysis is a simple and inexpensive method to deplete the ash content in the permeate such that only values of a maximum of 7.5% by weight, and particularly 6.5 to 7.2% by weight were achieved in the final product, which no longer leads to any perceivable bitter taste.

[0032] Electrodialysis is an electro-chemically driven membrane process in which ion exchanger membranes are used in combination with an electric potential difference to separate ionic species from uncharged solvents or from contaminations.

[0033] To this end, the space between two electrodes in an electrodialysis separator is separated by a stack of alternating anion and cation exchanger membranes. Each pair of ion exchanger membranes forms a separate cell. In technical systems, these stacks consist of more than two hundred membrane pairs. If a direct electric current is applied to the electrodes, the anions migrate to the anode. The anions may simply pass the positively charged anion exchanger membranes but they are stopped at the respective negatively charged cation exchanger membrane. As the same process (obviously with opposite signs) is performed with the cations, the net effect of electrodialysis is a concentration of salts in the cells with odd numbers (anion exchanger membrane/cation exchanger membrane), while the cells with even numbers (cation exchanger membrane/anion exchanger membrane) suffer a depletion of salt. The solutions with increased salt concentrations are combined to form the concentrate, while the salt-depleted solutions form the diluate.

[0034] It is recommended to finally treat the diluate with a cation exchanger (polisher) and, particularly, to separate any sodium ions that had been introduced by dialysis.

[0035] The dialysed ultrafiltered milk permeate (UF permeate) such obtained is subsequently added to the skimmed milk concentrate in an amount such that the required, and desired lactose content of about 45 to about 60% by weight is obtained, based on the dried finished product.

Drying

[0036] In the final process step, the product is dried. Preferably, spray-drying is applied, whereby the temperature at the inlet typically is about 180 to about 260 C., and about 80 to about 105 C. at the outlet. As a result, the fraction does not need any cooling before entering the tower. Temperatures of 60 to 70 C. are even preferred in this process, as this reduces the risk of denaturation of the proteins. Alternatively, the products may also be dehydrated by freeze drying.

[0037] Further additives such as, for example, lactoferrin, lecithins, vitamins or food emulsifiers and the like may be added to the product before but preferably after drying.

INDUSTRIAL APPLICABILITY

[0038] A further subject matter of the invention relates to the use of both the milk protein concentrates of the invention and the products obtained according to the process of the invention for the production of foods for toddlers.

EXAMPLES

Comparison Example V1A

Production of a UF Permeate

[0039] 500 L of milk was pasteurised and subjected to ultrafiltration at 25 C. using a polymer membrane having a pore size of 10,000 Dalton. Separately, the retentate was further processed, and the permeate was further used for standardisation.

Comparison Example V1B

Production of a Protein Concentrate with a Typical Ash Content

[0040] 1,000 L of skimmed milk with a dry matter content of 9% by weight was placed into an evaporator and was gently concentrated at about 70 C. to a dry matter content of 50% by weight. The permeate of example V1A was added to the concentrate in an amount such that a protein content of 34% by weight and a lactose content of 50% by weight was achieved, based on dry matter. Subsequently, the standardised milk concentrate was placed into a spray tower and was dried at 220 C. The resulting powder showed the following composition:

Dry matter content: 95.6% by weight
Protein content, based on dry matter: 34.1% by weight
Lactose content, based on dry matter: 51.3% by weight
Ash content, based on dry matter: 8.4% by weight

[0041] 75 g of the powder were dissolved in 100 g of water at 20 C. and homogenised. The product showed a bitter taste with an astringent touch.

Example 1A

Production of a Dialysed UF Permeate

[0042] 500 L of milk was pasteurised and subjected to ultrafiltration at 25 C. with a polymer membrane having a pore size 10,000 Dalton. Separately, the retentate was further processed. and the permeate was placed into an electrodialysis stack. In doing so, a lactose-rich and low-ash product was obtained, which was further used for standardisation.

Example 1B

Production of a Protein Concentrate with a Reduced Ash Content

[0043] 1,000 L of skimmed milk with a dry matter content of 9% by weight was placed into an evaporator and was gently concentrated at about 70 C. to a dry matter content of 50% by weight. The diluate of example 1A was added to the concentrate in an amount such that a protein content of 34% by weight and a lactose content of 51% by weight was achieved, based on dry matter. Subsequently, the standardised milk concentrate was placed into a spray tower and was dried at 220 C. The resulting powder showed the following composition:

Dry matter content: 95.1% by weight
Protein content, based on dry matter: 34.3% by weight
Lactose content, based on dry matter: 51.8% by weight
Ash content, based on dry matter: 6.8% by weight

[0044] 75 g of the powder were dissolved in 100 g of water at 20 C. and homogenised. The powder shows a flawless taste without any bitter or astringent touch.