WO1991014377A1

WO1991014377A1 - Processing of mixtures containing lipids and proteins and products so produced

Info

Publication number: WO1991014377A1
Application number: PCT/AU1991/000104
Authority: WO
Inventors: Corran Norman Stuart Mclachlan; Gary Norris Kerkin; Peter Vines
Original assignee: Portwall Pty Limited
Priority date: 1990-03-21
Filing date: 1991-03-21
Publication date: 1991-10-03
Also published as: CS159391A2; AU2040495A; WO1991014373A1; AU7468191A; CS76491A2; AU7547691A

Abstract

There is described a process for recovery of at least part of the proteins and/or non-lipid-solids from an aqueous liquid containing lipids and proteins comprising bringing a supercritical fluid at a suitable temperature and pressure and of a type such that at least part of the lipid is soluble therein, into contact with the liquid under conditions such that at least a part of the lipid component in the liquid is taken up by the fluid then recovering at least part of the protein and/or non-lipid solid from the residue. The process for example is useful in producing caseins, other proteins and lactose from the residue of milk after extracting the lipids with supercritical carbon dioxide.

Description

PROCESSING OF MIXTURES CONTAINING LIPIDS AND PROTEINS AND

PRODUCTS SO PRODUCED

FIELD OF THE INVENTION

This invention relates to the removal of lipids from mixtures o lipids, proteins, water and other solids, the processing of proteins and other solids, and the products so obtained. In particular the invention relates to the production of fat-free caseins, whey proteins, and lactose.

BACKGROUND

Milks consist of lipids, proteins, carbohydrates, salts and wat the actual compositions depending on the mammals which produce them, their food, seasonal and annual weather variations, and geography. In general bovine milks contain 3-5% lipids by weig which consist of about 98% triglycerides with small amounts of free fatty acids, mono- and diglycerides, phospholipids, sterol and hydrocarbons, 3-4% proteins consisting of caseins and whey proteins, and 2-5% lactose. The total solids range from about 8-12% of the whole milk.

The proteins of milk are an important source of nutritional foo additives and ingredients used as binders, emulsion and foam stabilisers in processed foods. Industrial uses of milk protei includes paper coatings, glues, plastics and artificial fibres.

The caseins of bovine milk are described as consisting of alpha caseins (42-63% of total proteins), beta-caseins (26-37%) and kappa-caseins (6-13%) [Whitney, R.M. ; "Proteins of Milk", in Fundamentals of Dairy Chemistry, ed Noble P. Wong, 3rd ed. , Va Nostrand Reinhold Company, New York, 1988, p82]. The whey proteins are described as consisting of beta-lactoglobulins (6- of total proteins), alpha-lactalbumins (1.7-5.7%), bovine seru albumin (0.6-1.3%) and immunoglobulins (1.4-6.0%) [ibid].

Conventionally produced proteins from bovine milk typically contain 1-5% lipids and this is considered to detract from the functionality of the products, particularly with respect to di and food ingredient uses. Thus caseins, or their derivatives su as sodium or calcium caseinates containing relatively high level of lipids are unsuitable for use in fat-free diets, and the stability of a foam supported by whey proteins is significantly reduced in the presence of lipids. Beverages containing whey proteins display some turbidity when lipids are present and an unsightly "neck-ring" develops in bottles.

This invention provides for the production of protein products from mammalian milks which are substantially lipid-free and whic do not suffer the disadvantages outlined above.

PRIOR ART

Caseins are usually precipitated from bovine skim milk by acidification or rennet coagulation. [Bassette, R. , Acosta, J.S "Composition of Milk Products", ibid, p72]. When acid is added the complex of calcium caseinate and calcium phosphate which constitute the caseins portion of milk proteins, is dissociated with the maximum precipitation occurring at the isoelectric poin of pH 4.6. Further treatment of the remaining liquor (whey) aft the separation of precipitated caseins by ultrafiltration, rever osmosis, gel filtration, electrodialysis, or ion exchange enable fractionation of the whey proteins and lactose.

Conventional methods of manufacturing casein are reviewed by Southward [ "Modern Dairy Technology Volume 1 : Advances in Milk Processing" , ed. R.K. Robinson, Elsevier Applied Science Publication, London, 317-368].

Whitney ["Proteins of Milk" in Fundamentals of Dairy Chemistry, Noble P. Wong, 3rd ed.. Van Nostrand Reinhold Company, New York, 1988, p 128] describes conventional fractionation of caseins whe "whole" casein is first precipitated from skim milk, the classic method being acidification to the pH of minimum solubility. Temperatures from 2-35°C have been used with minimum solubility occurring at a pH of 4.3 at 35^βC. Fractionation may be achieved by methods using differential solubility in which the whole case is differentially dissolved in solvents such as 50% alcohol by varying the pH, temperature and ionic strength with agents such ammonium acetate. Alternatively the whole casein may be dispers in strong urea and the casein fractions separated by dilution, p adjustment and finally the addition of ammonium sulphate.

Other methods developed to fractionate caseins include partitioning into two-phase water-ethanol-phenol or water-ethano collidine systems, electrophoresis, and chromatography employing anion-exchange, cation-exchange, adsorption onto hydroxyapatite and gel filtration.

Whitney reports similar methods for the fractionation of whey proteins after first separating the proteins, or protein concentrates, from the other whey components. Methods used for initial separation include reducing the pH to 3.2 and then complexing with carboxyl-methyl-cellulose. The complex is remov by centrifuging. In another method cations are removed by eluti the whey through an ion exchange column, the pH is adjusted to 3 and the proteins are then complexed with sodium hexametaphosphat The complex is removed by centrifugat on and the sodium hexametaphosphate removed by ion exchange or gel filtration. Wh protein concentrates are prepared by complexing with ferripolyphosphate, gel filtration, ultrafiltration, reverse osmosis or electrodialysis.

Differential solubility, electrophoresis, and chromatography are used to fractionate the whey proteins following initial precipitation. The former method involves sequential adjustment of pH by addition of acid or ammonium hydroxide, and/or bufferin solutions, followed by the addition of ammonium sulphate. The resulting precipitates are separated and they and the supernatan liquors are further treated until the desired fractions are recovered.

Liquid-liquid separation methods may also be applicable to milk proteins [Abbott, N.L., Hatton, T.A. : "Liquid-liquid extraction for protein separations", Chem. Eng. Progress, 84 (August, 1988) 31-41]. The coagulation of casein is affected by temperature and pH.

Studies of viscosity and coagulation rate indicated the onset o precipitation of caseins at a -pH of about 6 at 55^βC, pH 5.5 at

35 "C , and pH 5 at 25^βC. The maximum coagulation rate more than doubled when the temperature was increased from 35^βC to 55^βC. pH at which maximum coagulation rate occurred reduced from abou

4.8 at 35^βC to about 4.7 at 55°C. The yield of casein coagula generally increased with pH in the range 4.0 to 4.8 and increas with temperature in the range 35 to 55^βC. [Kim, B.Y., Kinsella

J.E.; "Effect of temperature and pH on the coagulation of casei

Milchwissenschaft, 44 (10, 1989), 622-625].

Carbon dioxide has been used to precipitate caseins from skim m at pressures to 55 bar. [Jordan, P.J., Lay, K. , Ngan, N. Rodle G.F.; "Casein precipitation using high pressure carbon dioxide" N. Z. J. Dairy Sci . and Tech . , 22(1987), 246-256]. Typical skim milk contains 3.3 to 3.7% protein, and 0.3-0.6% fat, (6-9% tota solids) . The pressure required to achieve maximum precipitatio decreased markedly as the temperature was increased at temperatures between 40^βC and 70^βC. Recovery higher than 99 percent was achieved at higher pressure whilst at the same time granular precipitations were obtained allowing easy drainage.

Precipitation of caseins have been observed during cholesterol removal trials from milk-fats with supercritical carbon dioxide [Bradley, R.L.; "Removal of cholesterol from milk fat using supercritical carbon dioxide", J. Dairy Science, 72 (1989), 283 2840]. The pH in the extraction vessel was reported, as being about 3.

SUMMARY OF THE INVENTION

This invention provides a process in which a mixture containing lipids and proteins and water is brought into contact with a fl in a supercritical state in an extractor at a temperature and pressure such that the major portion of the lipids are extracte from the mixture leaving the proteins and other components substantially free of lipids. The lipids removed from the mixt are subsequently recovered from the fluid. The processing of t residue is the subject of this invention. The process is preferably continuous but may be operated in a suitable batchwise manner.

The mixture may be a mammalian_^milk or milk product such as ski milk resulting from separation of cream from milk, or cream or concentrate of milk or other dairy fluid of bovine origin, or a extract or product of vegetables which contain lipids and proteins, or a product containing lipids and protein from fish other animal source. This invention will be further described with reference to mixtures formed from bovine milk but is not limited to such mixtures.

The fluid is preferably carbon dioxide but N^O, SF_β, CF₃C1, CF-Cl-_/ CH-CF-, C,Fg, CHF,, ethane, propane, butane, ethylene o acetone, which are considered unobjectionable from a health poi of view can also be used. Mixtures of these fluids can also be used. This invention will be further described with reference the use of carbon dioxide alone.

When skim milk, cream or milk concentrate is treated with carbo dioxide at a high pressure, the amount of the lipid fraction th is extracted into the carbon dioxide fluid varies with the temperature of the extraction. When the carbon dioxide is in a supercritical state, substantially all of the lipid materials w be extracted into the supercritical fluid.

The temperature at which the mixture is contacted with the flui preferably will be between 32^βC and 80^βC, the pressure preferab will be between 75 bar and 350 bar. More preferably the temperature will be between 32°C and 50°C, so as to limit the thermal effects on heat-sensitive materials, and the pressure w be between 150 bar and 280 bar.

To achieve optimum separation of the lipids from the liquor the carbon dioxide preferably must intimately contact the surface o thin film of the mixture in a continuous co-current or counter- current manner. The mixture may be converted into the form of thin film in any known manner such as passing the mixture over surface in the form of a thin film covering the surface, by passing the mixture through a cascade or packed bed, containing rings or other distribution systems known to the art, or a devic which corresponds to a thin film surface evaporator or the like, or by spray nozzle or other droplet generating device.

Alternatively the extraction may take place in a liquid-fluid extraction involving plate mixer-settler units. The separation process is not limited but is to follow process steps well recognised in the art of chemical engineers.

In the extractor, with an acidic fluid like carbon dioxide, caseins are precipitated at the same time as the lipid materials in total or in part, are extracted into the high pressure fluid phase.

The differential density between the supercritical fluid and wat can also be maximised within the above constraints to facilitate separation of the caseins precipitated.

The caseins so formed are generally granular and are carried fro the extractor together with the dissolved whey protein, sugars a mineral salts and water. The whole caseins may be separated fro the solution by filtration or hydrocyclone, or other method know to the arts of chemical engineering or food processing such as ultrafiltration, reverse osmosis, gel filtration or ion exchange The separated solids may be dewatered preferably by further treatment with supercritical carbon dioxide at a temperature and pressure such that water is reasonably soluble in the supercritical fluid. However filtration and drying, or evaporation and spray drying, or other method known^" to the art o food processing may be used. Alternatively the recovered casein may be fractionated by stepwise adjustment of the pH optionally with the addition of pH controlling agents such as acids and alkalis and the addition of suitable agents such as ammonium acetate and ethanol to assist in the precipitation of the fractions. This treatment may be effected in the presence of subcritical or supercritical carbon dioxide whereby the pH is controlled by temperature, pressure or additives, or the fractionation may be by any methods known to the art. The fractions may be separated and dewatered as described above for whole caseins. The supernatant liquor remaining after removal of the caseins ma then be further treated by carbon dioxide at temperatures and pressures and/or with the addition of pH reducing or other agent such that the whey proteins present are precipitated. The whole whey proteins are separated from the solution as described above for caseins and the recovered solids may be further treated by stepwise control of temperature, pressure, pH or additions of suitable agents such as ammonium hydroxide and ammonium sulphate to effect fractionation of the whey proteins. Alternatively the whey proteins may be fractionated by methods known to the art.

These materials may be subsequently recovered, dewatered and dri as described above for caseins.

The whole caseins and whole whey proteins formed by this process have different functional properties than those formed by other processes, primarily through their low fat content, and are products of this invention. The fractions of the caseins, including alpha- beta- and kappa-caseins, and the fractions of t whey proteins, including beta-lactoglobulins, alpha-lactalbumins bovine serum albumin and immunoglobulins, formed from this proce also have different functional properties from those formed from other processes, due mainly to their low fat content, and are products of this invention.

The liquor remaining after recovery of the whole caseins and who whey proteins may be further treated by evaporation and drying o other method known to the art to recover lactose which is substantially free of fat. This product differs frbm lactose prepared by other processes by virtue of its low fat or fat-free composition, and is a product of this invention.

The lipid-laden supercritical fluid leaving the extractor may be treated to remove sterols and to recover the lipids from the flu as described in our N.Z. Patent Application No. 221503 (1987) PC Application No. GB 88/00739. The appropriate embodiments of tha application are incorporated in this invention by reference. Th cholesterol may be recovered as detailed in that application. Following recovery of the lipids from the fluid, the fluid is recycled.

All materials leaving the extraction system optionally are passe through a degassing device consisting of a vacuum chamber, or a nitrogen sparging system into a vacuum or modest pressure, or so other method of degassing known to the art, to remove residual carbon dioxide. Optionally the carbon dioxide may be recovered and recompressed for recycle to the extractor.

An advantage of this invention is the bacteriocidal nature of hi pressure carbon dioxide. This attribute, cited in our applicati No. 221503, reduces the numbers of bacteria in the products to insignificant levels allowing the products to be used in, for example, invalid and infant foods where such bacteria would be otherwise unacceptable.

The attached figure illustrates the process diagrammatically. A step 1 the lipid protein mixture is introduced to the supercritical fluid stream in the extractor vessel. At step 2 t undissolved material is removed from the extractor and whole casein separated from the solution. At step 3 the caseins are fractionated to produce casein fractions as desired. The resulting solids are dewatered. The supernatant solution from step 2 is treated at step 4 to precipitate whey proteins which a separated from the liquid at step 5. At step 6 the whey protein are fractionated as desired and the resulting solids dewatered.

At step 7 the lipid-laden supercritical fluid is presented to an adsorbent to remove any sterols present, and at step 8 the lipid are recovered from the fluid. At step 9 the carbon dioxide is recompressed and recycled to the extractor.

While in this specification reference has been made to preferred embodiments, the invention, is not to be construed as being limit thereto. Moreover where reference is made to a specific feature or process step and equivalents are known to exist to such featu or step, such equivalent features or steps are incorporated here as if specifically set forth. Example 1

Milk concentrate in liquid form containing 61.3% moisture, 11.9 fat, 10.5% protein and 16.3% other solids-not-fat was introduce into supercritical carbon dioxide at a rate of 4 kg/h. The car dioxide flow rate was 100 kg/h. The two fluids were contacted a temperature of 35^βC, and a pressure of 250 bar. After contac the fat-rich carbon dioxide stream was passed to a separator wh dissolved fat and water were removed. The carbon dioxide was recirculated.

The dissolved material recovered from the separator was found t contain 33.9% fat, 65.2% moisture and 0.2% solids-not-fat. Two separate phases were found in the ratio of 34.3% of a fat-rich 65.7% aqueous. The fat-rich phase contained less than 1% moist and the aqueous phase contained less than 1% total solids.

The residue not dissolved in the carbon dioxide was recovered a found to contain a precipitate which was identified as caseins. The composition was 59.2% moisture 0.2% fat, 15.8% proteins, an 24.8% other solids. The precipitated caseins were removed and further treatment of the remaining liquor yielded a precipitate which was identified as whey proteins.

All percentages are expressed on a weight basis.

Example 2

A residue stream containing 72% moisture, 0.2% fat, 12.8% prote and 15.0% other solids-not-fat, decanted from the extraction vessel following contact between supercritical carbon dioxide a a concentrated milk stream was allowed to settle in a separatin vessel. Supernatant whey was decanted leaving casein precipita containing 7.1% moisture, 89.7% protein, 0.8% fat and 2.3% othe solids-not-fat.

The whey stream containing 81.4% moisture, 0.1% fat, 1.7% prote and 16.8% other solids-not-fat, was further contacted with supercritical carbon dioxide at a rate of 160 g/h. The carbon dioxide flow rate was 14 kg/h. The two fluids were contacted a temperature of 43^βC and a pressure of 250 bar. After contact t carbon dioxide was passed to the first extraction vessel. The residue not dissolved in t ,h1e0 carbon dioxide was recovered an found to contain 77.5% moisture, negligible fat, 2.1% protein in the form of whey proteins precipitate, and 20.4% other solids-no fat.

The whey proteins precipitate was removed from the solution and dried.

All percentages are expressed on a weight basis.

Referring to the diagram, the flows and compositions were:

183.1 23.1 160.0 132.0 28.

Claims

WE CLAIM: U

1. A process for recovery of at least part of the proteins and or non-lipid-solids from an aqueous liquid containing lipid and proteins comprising bringing a supercritical fluid at a suitable temperature and pressure and of a type such that a least part of the lipid is soluble therein, into contact wi the liquid under conditions such that at least a part of th lipid component in the liquid is taken up by the fluid then recovering at least part of the protein and/or non-lipid solid from the residue.

2. A process according to claim 1 in which substantially all the lipid is taken up by the fluid so that the residue is substantially free of lipid.

3. A process according to claim 1 or 2 wherein the fluid contacts the mixture in an extractor.

4. A process according to claim 3 where the contact is in a continuous co-current or counter-current manner.

5. A process according to any one of claims 1 to 4 in which t lipid and protein mixture is a mammalian milk or milk product.

6. A process according to any one of claims 1 to 4 in which t lipid and protein mixture is milk, skim milk, cream, concentrated milk or other dairy fluid of bovine origin.

7. A process according to any one of claims 1 to 4 in which t lipid and protein mixture is comprised of vegetable lipids and proteins.

8. A process according to any one of claims 1 to 4 in which t lipid and protein mixture is comprised of fish lipids and proteins.

9. A process according to any one of claims 1 to 4 in which th lipid and protein mixture is comprised of other animal lipi and proteins.

10. A process according to claims 1 to 9 in which the fluid in supercritical state is selected from carbon dioxide, N,0, SF_β, CF-C1, CF₂C1₂ CH₂CF₂, C3F₀, CHF.,, ethane, propane, butane, ethylene or acetone and mixtures thereof.

11. A process according to claim 10 in which the fluid is carbo dioxide.

12. A process according to claim 11 in which temperature of the carbon dioxide is between 32^βC and 80°C and the pressure is between 75 bar and 350 bar.

13. A process according to claim 12 in which temperature of the carbon dioxide is between 32^βC and 50^βC and the pressure is between 150 bar and 280 bar.

14. A process according to claim 12 or 13 in which contact between the carbon dioxide and the lipid and protein mixtur results in the precipitation of caseins or other proteins.

15. A process according to claim 14 in which the suspended caseins or proteins are separated from the aqueous phase.

16. A process according to claim 15 in which the separation is filtration, hydrocyclone, ultrafiltration, reverse osmosis, gel filtration, or ion exchange.

17. A process according to claim 15 or 16 in which the caseins proteins so separated are dewatered.

18. A process according to claim 17 in which dewatering is by contact with supercritical carbon dioxide.

19. A process according to claim 17 or 18 in which dewatering by filtration and drying or evaporation and spray drying, other suitable method.

20. The fat-free whole caseins or proteins obtained by any one claims 15 to 19.

21. A process according to claims 14 or 15 in which the casein so separated are fractionated into alpha-, beta- and kappa caseins.

22. A process according to claim 21 in which fractionation is stepwise adjustment of pH in subcritical or supercritical carbon dioxide, such adjustment being effected by control temperature and pressure.

23. A process according to claim 22 in which pH controlling agents such as acids or alkalis are added.

24. A process according to claim 22 or claim 23 in which agent such as ethanol and ammonium acetate are added so as to successively fractionate the alpha-, beta- and kappa-casei fractions of whole caseins.

25. A process according to claims 14 or 15 in which the furthe separation of the caseins is effected by ion exchange, gel filtration, chromatographic adsorption or electrophoresis, any other suitable method preferably in a supercritical carbon dioxide environment.

26. A process according to any one of claims 21 or 25 in which the casein fractions so separated are dewatered.

27. A process according to claim 26 in which dewatering is by contact with supercritrical carbon dioxide.

28. A process according to claim 26 in which dewatering is by filtration and drying, or evaporation and spray drying, or other suitable method.

29. The fat-free alpha-casein obtained by claims 21 to 28.

30. The fat-free beta-casein obtained by claims 21 to 28.

31. The fat-free kappa-casein obtained by claims 21 to 28.

32. A process according to claim 15 or 16 wherein the filtrate solid-reduced phase so formed is contacted with supercriti carbon dioxide, such that whey proteins, if present, are precipitated.

33. A process as claimed in claim 32 wherein a suitable dilute acid or other pH reducing agent is added.

34. A process according to claim 15 to 16 wherein the filtrate solid-reduced phase so formed is heated or treated by acid otherwise treated such that whey proteins if present are precipitated.

35. A process according to claims 32 to 34 in which the whey proteins precipitated are separated from the aqueous phase which they are suspended.

36. A process according to claim 35 in which the separation is filtration, hydrocyclone, ultrafiltration, reverse osmosis, gel filtration, or ion exchange.

37. A process according to claim 35 or 36 in which^" the whole w proteins so produced are dewatered.

38. A process according to claim 32 to 37 in which dewatering by contact with supercritical carbon dioxide.

39. A processing according to claim 37 in which dewatering is filtration and drying, or evaporation and spray drying, or other suitable method.

40. The fat-free whole whey proteins obtained by the method of any one of claims 35 to 39.

41. A process according to any one of claims 32 to 36 in which the whey proteins so separated are subjected to stepwise adjustments of pH in subcritical or supercritical carbon dioxide, such adjustment being effected by control of temperature and pressure, so as to successively fractionate the alpha-lactalbumin, beta-lactoglobulin, immuno-globulin, and bovine serum albumin fractions of whole whey proteins.

42. A process according to claim 41 wherein pH controlling agen such as acids or alkalis are added.

43. A process according to claim 41 or 42 wherein agents such as ammonium sulphate are added.

44. A process according to any one of claims 32 to 36 in which the whey proteins are further fractionated by ion exchange, gel filtration, chromatographic adsorption or electrophoresis, or any other suitable method.

45. A process according to claim 44 conducted in a supercritica carbon dioxide environment.

46 A process according to any one of claims 41 to 45 in which the whey protein fractions so separated are dewatered.

47. A process according to claim 46 wherein dewatering is by contact with supercritical carbon dioxide.

48. A process according to claim 46 or 47 in which dewatering i by filtration and drying, or evaporation and spray drying, other suitable method.

49. The fat-free alpha-lactalbumins obtained by any one of clai 41 to 48.

50. The fat-free beta-lactoglobulins obtained by any one of claims 41 to 48.

51. The fat-free immunoglobulins obtained by any one of claims to 48.

52. The fat-free bovine seruiR albumins obtained by any one of claims 41 to 48.

53. A process according to claim 35 or 36 in which the liquor remaining after separation of the whey proteins precipitat is evaporated or otherwise dewatered to form a dried lacto product.

54. A process according to claim 53 conducted in a supercritic carbon dioxide environment.

55. The fat-free lactose obtained by claim 53 or 54.

56. A process according to any one of claims 1 to 19, 21 to 28 32 to 39, 41 to 48, 53 and 54 in which the lipid-laden supercritical fluid is passed through a suitable adsorbent such that cholesterol is preferentially adsorbed.

57. A process according to claim 56 in which the adsorbent is regenerated by passing a solvent through the adsorbent suc that the cholesterol is eluted from it and optionally is subsequently recovered, such solvent preferably being a supercritical fluid optionally with the addition of a cosolvent.

58. A process according to claims 56 or 57 in which the substantially lipid-laden fluid is subjected to changes in temperature and pressure such that the lipids become essentially insoluble in the fluid and are recovered from fluid.

59. A process according to claim 58 in which the carbon dioxid is recycled to the extractor after recompression and appropriate heating and/or cooling.

60. A process according to any one of claims 1 to 19, 21 to 28,

32 to 39, 41 to 48, 53 and 54 in which any or all of the solids recovered from the.processes are degassed by passing the solids through a vacuum chamber, or a nitrogen sparging system into a vacuum or modest pressure, or other appropria method of removing the residual fluid.

61. A process according to claim 60 in which the fluid so remov is recovered and recompressed for recycling to the extracto

62. A process according to any one of claims 1 to 19, 21 to 28, 32 to 39, 41 to 48, 53 and 54 in which water is added to th extractor or to the subcritical or supercritical fluid or otherwise.