NZ237639A - Process for separating proteins and/or non-lipid solids of milk from milk lipids using supercritical fluids - Google Patents

Description

Patents Form No. 5 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Divisional out of Cognated After Provisional No. 233031 dated 21 March 1990 No. 234494 dated 13 July 1990 No. 236064 dated 13 November 1990 PROCESSING OF MIXTURES CONTAINING LIPIDS AND PROTEINS AND PRODUCTS SO PRODUCED WE, PORTWALL PTY LIMITED, a company incorporated under the laws of N.S.W., Australia of 1st Floor, 77 Main Street, Blacktown, NSW 2148, Australia hereby declare the invention, for which We pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: FIELD OF THE INVENTION This invention relates to the removal of lipids from mixtures of 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 water, 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 weight which consist of about 98% triglycerides with small amounts of free fatty acids, mono- and diglycerides, phospholipids, sterols 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 food additives and ingredients used as binders, emulsion and foam stabilisers in processed foods. Industrial uses of milk proteins 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., Van Nostrand Reinhold Company, New York, 1988, p82]. The whey proteins are described as consisting of beta-lactoglobulins (6-13% of total proteins), alpha-lactalbumins (1.7-5.7%), bovine serum 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 diets 23 7 6 3 9/W*-' and food ingredient uses. Thus caseins, or their derivatives such as sodium or calcium caseinates containing relatively high levels 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 mcimmalian milks which are substantially lipid-free and which 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 point of pH 4.6. Further treatment of the remaining liquor (whey) after the separation of precipitated caseins by ultrafiltration, reverse osmosis, gel filtration, electrodialysis, or ion exchange enables 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, ed Noble P. Wong, 3rd ed., Van Nostrand Reinhold Company, New York, 1988, p 128] describes conventional fractionation of caseins where "whole" casein is first precipitated from skim milk, the classical 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°C. Fractionation may be achieved by methods using differential solubility in which the whole casein is differentially dissolved in solvents such as 50% alcohol by varying the pH, temperature and ionic strength with agents such as ammonium acetate. Alternatively the whole casein may be dispersed in strong urea and the casein fractions separated by dilution, pH adjustment and finally the addition of ammonium sulphate.

Other methods developed to fractionate caseins include partitioning into two-phase water-ethanol-phenol or water-ethanol-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 removed by centrifuging. In another method cations are removed by eluting the whey through an ion exchange column, the pH is adjusted to 3.0 and the proteins are then complexed with sodium hexametaphosphate. The complex is removed by centrifugation and the sodium hexametaphosphate removed by ion exchange or gel filtration. Whey 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 buffering solutions, followed by the addition of ammonium sulphate. The resulting precipitates are separated and they and the supernatant 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.s "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 of precipitation of caseins at a pH of about 6 at 55°C, pH 5.5 at 35°C, and pH 5 at 25°C. The maximum coagulation rate more than doubled when the temperature was increased from 35°C to 55°C. The pH at which maximum coagulation rate occurred reduced from about 4.8 at 35°C 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 increased with temperature in the range 35 to 55°C. [Kim, B.Y., Kinsella, J.E.; "Effect of temperature and pH on the coagulation of casein", Milchwissenschaft, 44 (10, 1989), 622-625].

Carbon dioxide has been used to precipitate caseins from skim milk at pressures to 55 bar. [Jordan, P.J., Lay, K., Ngan, N. Rodley, 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% total solids). The pressure required to achieve maximum precipitation decreased markedly as the temperature was increased at temperatures between 40°C and 70°C. 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), 2834-2840]. 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 fluid in a supercritical state in an extractor at a temperature and pressure such that the major portion of the lipids are extracted from the mixture leaving the proteins and other components substantially free of lipids. The lipids removed from the mixture are subsequently recovered from the fluid. The processing of the residue is the subject of this invention. 6 The process is preferably continuous but may be operated in a suitable batchwise maimer.

The mixture may be a mammalian milk or milk product such as skim milk resulting from separation of cream from milk, or cream or a concentrate of milk or other dairy fluid of bovine origin. 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 ^0, SFg, CF^Cl, CF2CI2, CH2CF2' C'3F8' CHF3/ ethane' propane, butane, ethylene or acetone, which are considered unobjectionable from a health point of view can also be used. Mixtures of these fluids can also be used. This invention will be further described with reference to the use of carbon dioxide alone.

When skim milk, cream or milk concentrate is treated with carbon dioxide at a high pressure, the amount of the lipid fraction that 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 will be extracted into the supercritical fluid.

The temperature at which the mixture is contacted with the fluid preferably will be between 32°C and 80°C, the pressure preferably 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 will 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 of a thin film of the mixture in a continuous co-current or counter-current manner. The mixture may be converted into the form of a thin film in any known manner such as passing the mixture over a surface in the form of a thin film covering th<=_surface, by passing the mixture through a cascade or packed J 23 7 6 39MW rings or other distribution systems known to the art, or a device 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 water 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 from the extractor together with the dissolved whey protein, sugars and mineral salts and water. The whole caseins may be separated from the solution by filtration or hydrocyclone, or other method known 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 a 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 of food processing may be used. Alternatively the recovered caseins 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. 23 7 6 3§/V0/V The supernatant liquor remaining after removal of the caseins may then be further treated by carbon dioxide at temperatures and pressures and/or with the addition of pH reducing or other agents 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 dried 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 the whey proteins, including beta-lactoglobulins, alpha-lactalbumins, bovine serum albumin and immunoglobulins, formed from this process 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 whole whey proteins may be further treated by evaporation and drying or other method known to the art to recover lactose which is substantially free of fat. This product differs from 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 fluid as described in our N.Z. Patent Application No. 221503 (1987) PCT Application No. GB 88/00739. The appropriate embodiments of that ~ application are incorporated in this invention by reference. The cholesterol may be recovered as detailed in that application. 2 3 7 6 3 9/WH Following recovery of the lipids from the fluid/ the fluid is recycled.

All materials leaving the extraction system optionally are passed through a degassing device consisting of a vacuum chamber, or a nitrogen sparging system into a vacuum or modest pressure, or some 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 high pressure carbon dioxide. This attribute, cited in our application 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. At step 1 the lipid protein mixture is introduced to the supercritical fluid stream in the extractor vessel. At step 2 the 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 are separated from the liquid at step 5. At step 6 the whey proteins 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 lipids 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 limited thereto. Moreover where reference is made to a specific feature or process step and equivalents are known to exist to such feature or step, such equivalent features or steps are incorporated herein as if specifically set forth. 2 3 7 6 3 9/M/4I 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 introduced into supercritical carbon dioxide at a rate of 4 kg/h. The carbon dioxide flow rate was 100 kg/h. The two fluids were contacted at a temperature of 35°C, and a pressure of 250 bar. After contact the fat-rich carbon dioxide stream was passed to a separator where dissolved fat and water were removed. The carbon dioxide was recirculated.

The dissolved material recovered from the separator was found to 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 and 65.7% aqueous. The fat-rich phase contained less than 1% moisture and the aqueous phase contained less than 1% total solids.

The residue not dissolved in the carbon dioxide was recovered and found to contain a precipitate which was identified as caseins. The composition was 59.2% moisture 0.2% fat, 15.8% proteins, and 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% protein and 15.0% other solids-not-fat, decanted from the extraction vessel following contact between supercritical carbon dioxide and a concentrated milk stream was allowed to settle in a separating vessel. Supernatant whey was decanted leaving casein precipitate containing 7.1% moisture, 89.7% protein, 0.8% fat and 2.3% other solids-not-fat.

The whey stream containing 81.4% moisture, 0.1% fat, 1.7% protein 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 at a temperature of 43°C and a pressure of 250 bar. After contact the carbon dioxide was passed to the first extraction vessel. 2 3 7 § 3 9/lto/y - n - The residue not dissolved in the carbon dioxide was recovered and found to contain 77.5% moisture, negligible fat, 2.1% protein in the form of whey proteins precipitate, and 20.4% other solids-not-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: fat protein other water A % g/h 0.2 0.4 12.8 23.4 15.0 27.5 72.0 131.8 183.1 B % g/h 0.8 0.2 89.7 20.7 2.3 0.6 7.1 1.6 23.1 C % g/h 0.1 0.2 1.7 2.7 16.8 26.9 81.4 130.2 160.0 D % g/h neg 2.1 2.7 .4 26.9 77.5 102.3 132.0 E % g/h 0.6 0.2 neg neg 99.4 27.8 28.0 12

Claims (37)

WHAT WE CLAIM IS: L/'

1. A process for recovery of at least part of the proteins and/ or non-lipid-solids from a mammalian milk or milk product 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.

2. A process according to claim 1 in which substantially all of 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 the lipid and protein mixture is milk, skim milk, cream, concentrated milk or other dairy fluid of bovine origin. 4. 13 2 3 4l

6. A process according to claim 5 in which the lipid and protein mixture is comprised of other animal lipids and proteins.

7. A process according to any one of claims 1 to 6 in which the fluid in a supercritical state is selected from carbon dioxide, No0, SF^, CF_C1, CF„C10, CH„CF„, CnFo; CHF_, ethane, Z b J Z Z Z Z 3 o o propane, butane, ethylene or acetone and mixtures thereof.

8. A process according to claim 7 in which the fluid is carbon dioxide.

9. A process according to claim 8 in which temperature of the carbon dioxide is between 32°C and 80°C and the pressure is between 75 bar and 350 bar.

10. A process according to claim 9 in which temperature of the carbon dioxide is between 32°C and 50°C and the pressure is between 150 bar and 280 bar.

11. A process according to claim 9 or 10 in which contact between the carbon dioxide and the lipid and protein mixture results in the precipitation of caseins or other proteins.

12. A process according to claim 11 in which the suspended caseins or proteins are separated from the aqueous phase.

13. A process according to claim 12 in which the separation is by filtration, hydrocyclone, ultrafiltration, reverse osmosis, gel filtration, or ion exchange.

14. A process according to claim 12 or 13 in which the caseins or proteins so separated are dewatered.

15. A process according to claim 14 in which dewatering is by contact with supercritical carbon dioxide. -14 - 23/63 9/^o/M

16. A process according to claim 14 or 15 in which dewatering is by filtration and drying or evaporation and spray drying, or other suitable method.

17. The fat-free whole caseins or proteins obtained by any one of claims 12 to 16.

18. A process according to claims 11 or 12 in which the caseins so separated are fractionated into alpha-, beta- and kappa-caseins .

19. A process according to claim 18 in which fractionation is by stepwise adjustment of pH in subcritical or supercritical carbon dioxide, such adjustment being effected by control of temperature and pressure.

20. A process according to claim 19 in which pH controlling agents such as acids or alkalis are added.

21. A process according to claim 19 or claim 20 in which agents such as ethanol and ammonium acetate are added so as to successively fractionate the alpha-, beta- and kappa-casein fractions of whole caseins.

22. A process according to claims 11 or 12 in which the further separation of the caseins is effected by ion exchange, gel filtration, chromatographic adsorption or electrophoresis, or any other suitable method.

23. A process according to claim 22 in which the further separation is carried out in a supercritical carbon dioxide environment.

24. A process according to any one of claims 18, 22 or 23 in which the casein fractions so separated are dewatered.

A process according to claim 24 in which dewatering is by contact with supercritrical carbon dioxide. 15

26. A process according to claim 24 in which dewatering is by filtration and drying, or evaporation and spray drying, or other suitable method.

27. The fat-free alpha-casein obtained by any one of claims 18 to 26 .

28. The fat-free beta-casein obtained by any one of claims 18 to 26 .

29. The fat-free kappa-casein obtained by any one of claims 18 to 26 .

30. A process according to claim 12 or 13 wherein the filtrate or solid-reduced phase so formed is contacted with supercritical carbon dioxide, such that whey proteins, if present, are precipitated.

31. A process as claimed in claim 30 wherein a suitable dilute acid or other pH reducing agent is added.

32. A process according to claim 12 or 16 wherein the filtrate or solid-reduced phase so formed is heated or treated by acid or otherwise treated such that whey proteins if present are precipitated.

33. A process according to any one of claims 3 0 to 32 in which the whey proteins precipitated are separated from the aqueous phase in which they are suspended.

34. A process according to claim 33 in which the separation is by filtration, hydrocyclone, ultrafiltration, reverse osmosis, gel filtration, or ion exchange.

35. A process according to claim 33 or 34 in which the whole whey proteins so produced are dewatered. . ....

36 37 38 39 40 41 42 43 44 45 -16 - 237 65 9/uc)j<^\ A process according to any one of claims 3 0 to 35 in which dewatering is by contact with supercritical carbon dioxide. A processing according to claim 3 5 in which dewatering is by filtration and drying, or evaporation and spray drying, or other suitable method. The fat-free whole whey proteins obtained by the method of any one of claims 33 to

37. A process according to any one of claims 3 0 to 34 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. A process according to claim 3 9 wherein pH controlling agents such as acids or alkalis are added. A process according to claim 3 9 or 40 wherein agents such as ammonium sulphate are added. A process according to any one of claims 3 0 to 34 in which the whey proteins are further fractionated by ion exchange, gel filtration, chromatographic adsorption or electrophoresis, or any other suitable method. A process according to claim 42 conducted in a supercritical carbon dioxide environment. A process according to any one of claims 39 to 43 in which the whey protein fractions so separated are dewatered. A process according to claim 44 wherein dewatering i a contact with supercritical carbon dioxide. /* 'o\;46;47;48;49;50;51;52;53;54;55;CS7;- !7 - — - " ^;A process according to claim 44 or 45 in which dewatering is by filtration and drying, or evaporation and spray drying, or other suitable method.;The fat-free alpha-lactalbumins obtained by any one of claims 39 to 46.;The fat-free beta-lactoglobulins obtained by any one of claims 39 to 46.;The fat-free immunoglobulins obtained by any one of claims 3 9 to 46.;The fat-free bovine serum albumins obtained by any one of claims 39 to 46.;\;A process according to claim 33 or 34 in which the liquor remaining after separation of the whey proteins precipitate is evaporated or otherwise dewatered to form a dried lactose product.;A process according to claim 51 conducted in a supercritical carbon dioxide environment.;The fat-free lactose obtained by claim 51 or 52.;A process according to any one of claims 1 to 16, 18 to 26, 30 to 37, 39 to 46, 51 and 52 in which the lipid-laden supercritical fluid is passed through a suitable adsorbent such that cholesterol is preferentially adsorbed.;A process according to claim 54 in which the adsorbent is regenerated by passing a solvent through the adsorbent such that the cholesterol is eluted from it and optionally is subsequently recovered, such solvent preferably being a supercritical fluid optionally with the addition cosolvent.;18;/;63 9 (*o(M

56. A process according to claims 54 or 55 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 the fluid.

57. A process according to claim 56 in which the carbon dioxide is recycled to the extractor after recompression and appropriate heating and/or cooling.

58. A process according to any one of claims 1 to 16, 18 to 26, 30 to 37, 39 to 46, 51 and 52 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 appropriate method of removing the residual fluid.

59. A process according to claim 58 in which the fluid so removed is recovered and recompressed for recycling to the extractor.

60. A process according to any one of claims 1 to 16, 18 to 26, 30 to 37, 39 to 46, 51 and 52 in which water is added to the extractor or to the subcritical or supercritical fluid or otherwise. PORTWALL PTY LIMITED By their Attorneys BALDWIN. SON & CAREY dt/specs/tenon