AU651148B2

AU651148B2 - A process for the manufacture of a milk fraction with a high-alfa-lactalbumin content and a product comprising the same

Info

Publication number: AU651148B2
Application number: AU88236/91A
Authority: AU
Inventors: Masanobu Koutake; Ichirou Matsuno; Suzuka Nishizaki; Masaharu Shimatani; Yukio Uchida
Original assignee: Snow Brand Milk Products Co Ltd
Current assignee: Snow Brand Milk Products Co Ltd
Priority date: 1990-11-30
Filing date: 1991-11-27
Publication date: 1994-07-14
Anticipated expiration: 2011-11-27
Also published as: FR2669810A1; NL194998C; AU8823691A; NL9102003A; NZ240725A; FR2669810B1

Description

Our Ref: 413468 P/00/011 Regulation 3:2 1 14

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STADARD PATEN4T 0@ as6 Applicant(s); 0 66 06 6 snow Brand Milk Products Co., Ltd.

1-1, Naebocho 6-chome Higashi-ku sAPoRo-sHI Hokkaido

JAPAN

DAVIES COLLISON CAVE Patent Trade mark Attorneys Level 10, 10 Barrack street SYDNEY NSW 2000 Address for service: invention Title: A process for the manufacture of a milk fraction with a high-alfa-lactalbunin content and a product comprising the same The followinig atatement is a full description of this invention, including the best method of performing it known to me:- 5020 TITLE OF THE INVENTION A PROCESS FOR THE MANUFACTURE OF A MILK FRACTION WITH A HIGH ALFA-LACTALBUMIN CONTENT AND A PRODUCT COMPRISING THE SAME BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to a process for the manufacture of a fraction with a high content of alactalbumin from milk and to a product comprising such a fraction.

Description of the Background Art: Milk serum protein is generally more nutritious and more efficiently utilized by living bodies than casein and soybean protein. Because of this, it is used as a S" substitute for mother milk and a protein source for nutritious feed compositions for human being and animals.

When it is served as a mother milk substitute, in particular, the -use of milk serum protein with a reduced 3lactoglobulin (hereinafter abbreviated as P-Lg) content and enriched a-lactalbumin (hereinafter abbreviated as a-La) content is recommended, since P-Lg, which is a major component of milk serum protein, is not contained in mother milk and acts as an allergen for infant allergy.

Because of this reason, a method of man-facturing milk serum protein as a substitute of mother milk from whey by reducing its B-Lg content and increasing the a-La content has been proposed, to ensure effective utilization of whey protein which is a by-product of cheese production.

As a means of separating and recovering fractions with a high a-La content from whey, a number of trials have been undertaken to effectively utilize the differences in physical and chemical properties of various milk serum proteins. The methods proposed heretofore, however, involved problems such as requirement of complicated processes, a high energy consumption, a low recovery rate, irreversible changes in the protein properties. None of the proposed methods have been viable as an industrial scale manufacturing process. More recently, processes using ultrafiltration (hereinafter abbreviated as UF) have been proposed by Peter Harris (EP53027 and AU77719/81), J. L. Maubois (EP22696), and R. C.

Bottomley (EP311283 and AU22909/88); all processes employing whey as a starting raw material. Studies in actual applications of these processes, however, revealed the difficulties in the exact separation of a-La and P-Lg because of very close molecular weights of a-La and P-Lg; 14,000 Da (a-La) and 36,000 Da dimer and because of fluctuations in the pore sizes of commercially available UF membranes. All processes heretofore proposed employ whey as a starting raw material; there has been no process for the separation and recovery of fractions with a high a-La content from milk.

On the other hand, the UF technology is currently used S *Wo 2 in the milk industry for the manufacture of whey protein concentrate (WPC) and total milk protein (TMP), and for the concentration of cheese milk; its commercial application is substantially limited to the separation of lactose and ash from proteins. With respect to microfiltration (hereinafter abbreviated as MF), on the other hand, their application in the total filtration system is limited to the sludge treatment and removal of precipitates, since in the total filtration system the treatment capacity tends to decrease due to filter clogging, which interferes the characteristics inherently possessed by the membrane. The recent development of the cross-flow system eliminating the cgO° drawbacks in the total filtration system has opened the 04 0 epossibilities of the application of MF techniques to the o e milk industry; studies have been undertaken concerning the removal of bacteria from milk, the concentration of lactic acid bacteria, removal of fat from whey, and the like.

However, no studies have been undertaken with respect to the separation and recovery of milk serum proteins, especially 04 4 those with a high c-La content, from milk by the use of MF r o i technology.

Furthermore, along with the progress in the membrane manufacturing technologies a wide variety of membranes are 00 0 S"produced; those with capability of separating fractions with low to high molecular weights are commercially available. Such a progress expanded the possibility of the application of UF membranes to the separation of milk components which have not been separated by the use of conventional membranes.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel process for efficiently separating and recovering a fraction with a high a-La content from milk.

Another object of the present invention is to provide a novel industrial process for separating and recovering a fraction with a high a-La content from milk.

A further object of the present invention is to provide the fraction with a high a-La content by the above processes and a nutritious composition comprising such a fraction.

S

S. The above first object is achieved according to the present invention by a process which comprises submitting milk, which has been heat treated or while heat treating, to a cross-flow MF treatment or a UF treatment, thus separating and recovering a fraction with a high a-lactalbumin content as a filtrate.

The second object is achieved according to the present invention by a process which comprises submitting the retentate produced by said cross-flow MF or said UF treatment to a Dia-filtration (hereinafter abbreviated as DF) treatment, and combining the filtrate thus obtained with said filtrate obtained by said cross-flow MF or UF treatment.

The third object is achieved according to the present invention by the provision of a powdery milk with a high a- La content by drying said milk fraction with a high a-La content into powder, and the provision of a nutritious composition comprising said fraction together with food or feedstock.

Other and further objects, features and advantages of the present invention will appear more fully from the following description.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS i The present invention has been completed based on the finding that heated milk produces complexes between kappacasein and P-Lg, and a cross-flow MF treatment or a UF treatment of the heated milk enables the complexes with a T larger molecular weight to stay in the retentate side of the membrane, allowing only a-La with a smaller molecular weight to move into the filtrate side. Thus, a whey protein fraction with a high a-La content can be manufactured in an industrial scale according to the present invention. The a.

a-La fraction thus manufactured can be used as a mother milk substitute and as a nutritious composition for human being and animals.

Specifically, the present invention relates to a process for the manufacture of a milk fraction with a high a-La content by the separation and recovery of such a fraction from heat-treated milk by the treatment with a cross-flow MF membrane or a UF membrane with a larger fractional molecular weight.

The heat-treatment of milk may be performed according to the process of the present invention while the milk is treated by a membrane. As previously mentioned, milk contains a-La and P-Lg, and their molecular weights, for example, in cow's milk, are 14,000 Da (a-La) and 36,000 Da (P-Lg, as a dimer). Normally, two compounds with the molecular weight difference with this range can be separated by a membrane with difficulty. 3-Lg is a protein sensitive to heat and forms associations between the molecules or i produces a complex with kappa-casein in casein micelle [Dairy Sci. Abst., 25, 45 (1963); J. Dairy Sci., 48, 1161 (1965)]. The present inventors have been successful in separating a-La from P-L:g by the combined application of 0 s' this characteristic of milk and the membrane separation o tichnology which have achieved a remarkable progress in recent years; by increasing the quasi molecular weight of P-Lg to enlarge the difference in the molecular weights 0 of a-La and J-Lg, and by treating the milk with a cross-flow MF membrane or a UF membrane with a larger fractional molecular weight. As a result, a-La could be manufactured with a good efficiency.

:Any milks can be used in the present invention, ;including milks of cow, goat, sheep, buffalo, etc, irrespective to the content of fats.

Heat-treated milks in the present invention include those experienced a heat history in advance, e.g., pasteurized milks, reduced milks (milks made by dissolving heat-concentrated powder milk into water), preheated fresh milks (including fresh skim milks); and also include those involving a high temperature for the membrane treatment. The heat-treatment is preferably carried out at a temperature above 70 0 C, at which 3-Lg associates or polymerize, or forms a complex with kappa-casein, and preferably below 130 0

C.

Cross-flow MF membrane treatment is a technology which has achieved a remarkable progress in recent years.

Different from the conventional total filtration system, the cross-flow treatment takes a system of passing the feed along the membrane perpendicularly crossing the direction to which the filtrate flows. The system possesses capabilities of maintaining a high treatment capacity and a good fractionation performance of the membrane. MF membranes, on the other hand are directed to separation of particles; thus the pore sizes of the membranes are accurately determined.

Normally, the pore size is between 0.01 Am and sever pm, and the membranes are made of ceramics or polymers. In the present invention, the use of membranes with a pore size of S 0.05-1,0 pm is preferable. Both a-La and P-Lg are difficult to pass through a membrane with a pore size smaller than 0.5 Am, so that their fractionation is impossible. If the 9 pore size is greater than 1.0pm, P-Lg with an increased quasi molecular weight may pass through the membrane together with A portion of casein micelles also pass through the membrane. Thus, a-La cannot be fractionated by such a membrane. In the operation of the 7 D> 41U',t1441Ii 'ATNII A 999.99 cross-flow MF membrane apparatus, the pressure difference across the membrane of below 0.5 MPa and the flow rate along the membrane greater than 0.5 m/sec are preferable for the efficient separation of a-La from P-Lg.

As previously mentioned, UF membranes are currently used in the milk industry for the manufacture of whey protein concentrate (WPC) and total milk protein (TMP), and for the concentration of cheese milk; their application is substantially limited to the separation of lactose and ash t from proteins. Only UF membranes with a fractional S.molecular weight of 8,000-20,000 Da are used in the industry.

According to the present invention, a,-La in milk is selectively passed through a UF membrane by using a membrane with a fractional molecular weight of more than 50000 Pa, preferably 50,000-1,500,000 Da, and more preferably 50,000-1,000,000 Da. The pressure difference across membrane of below 0.5 MPa and the flow rate along the

*C*

membrane greater than 0.5 m/sec are preferable operation conditions for the efficient separation of a-La from A-Lg using such UF membranes.

The process of the present invention is illustrated referring to the following process scheme.

S *8

C"%

Reduced skim milk/ Skim milk/Whole milk Reduced whole milk Heat treatment High-temperature MF/UF or Normal-temperature MF/UF treatment Retentate Filtrate DF Treatment (Dilute treatment) a 6 t Retentate Filtrate

S

UF Treatment e Filtrate Retentate Drying 6 4 Powder Nutrient foods including infant powder milk When milks not treated with heat, such as skim milk or whole milk, are used as a raw material, the milk is heat treated at a temperature higher than 70 0 C, cooled, and treated with a cross-flow MF membrane or a UF membrane at a normal temperature. When the raw milk is not treated with heat in advance, it is subjected to the cross-flow MF treatment or UF treatment at a high temperature to effect the formation of complexes of 3-Lg and kappa-casein while the milk is treated with membrane. When reduced skim milk or reduced whole milk which has been treated with heat is used as a raw material, it is treated with a MF membrane at normal temperature. a-La can pass through the membranes by such treatments providing a-La fractions with a high a-La content. The filtrate thus obtained usually contains a-La of about 0.1% as well as lactose and ash.

Major components of the retentate obtained by the membrane treatment are J-i:g and casein, with a residual amount of a-La. According to a preferred embodiment of the 4* process of the present invention, a liquid not containing a-La may be added to the retentate, and the dilute is treated with a DF membrane to permeate the residual a-La.

The filtrate is combined with the filtrate obtained by the MF treatment.

The filtrate thus obtained contains lactose and ash a beside a-La. According to the present invention, such a filtrate may be treated with a UF membrane through which a- V 4 La cannot permeate, thus fractionating ,-La as a retentate.

The UF membrane used for this purpose should have a fractional molecular weight of smaller than 14,000 Da, since a--a itself has a fractional molecular weight of 14,000 Da.

The UF membrane retentate thus obtained is dried by means of spray drying, freeze-dry, or the like to produce a powder. The powder is added to infant powder milk for use as a mother milk substitute or used as a component of nutrient composition for men or animals.

According to the present invention, inilk fractions with a high a-La content can be separated and recovered from milk in a high yield by the use of the cross-flow MF membrane treatment or the UF treatment in which a membrane with a high fractional molecular weight is used.

The dry powder of the milk fraction thus obtained or the products prepared by the addition of such milk fraction, infant powder milk, are highly nutritious and ensures S" highly efficient protein utilization Other features of the invention will become apparent in e*e the course of the following description of the exemplary embodiments which dre given for illustration of the invention and are not intended to be limiting thereof.

ila*:

EXAMPLES

OS In the Examples below, "concentration factor" is eas.* defined as the ratio of the volume of the fresh feed to the volume of the retentate remaining upon completion of a membrane treatment.

Example 1 Powdery skim milk manufactured by Snow Brand Milk Products Co., Ltd. was used as a raw material. The powdery skim milk was treated with heat at 75 0 C at least for minutes, when skim milk was condensed and dried.

The powdery skim milk was reduced by deionized water to obtain reduced skim milk having the following analytical values Total solids Proteins (Nx6.38) 3.1 a-La/-Lg 0.34 Fats 0.05 Sugars 3.68 Ash 0.67 pH 20 kg of the reduced skim milk was subjected to a cross-flow MF treatment using a ceramic (a-alumina) 0 membrane, Monolith Type-948F (trademark, manufactured by NGK Insulators with a membrane area of 0.35 m 2 and a pore size of 0.1 tm, under operating conditions of 12 0 C, the average pressure difference of 0.1 MPa, and the flow rate of 1.6 m/sec. As a result of the treatment at a concentration

S

factor of 2 each 10 kg of the retentate and 10 kg of the S filtrate were obtained. The ratio of a-La/3-Lg in the filtrate was found to be 2.43 as compared with 0.34 in the skim milk.

The 10 kg of the retentate was then submitted to a DF membrane treatment while adding deionized water to maintain the amount of the retentate 10 kg. The DF treatment was terminated when the amount of the filtrate, which is equivalent to the amount of deionized water added, reached kg. 22.8% of a-La and 2.9% of 3-Lg in the retentate were found to have transferred into 10 kg of the filtrate by the DF treatment. The ratio of a-La/J-Lg in the filtrate was found to be 2.51, demonstrating a high a-La ratio of the filtrate.

The above treatments; the concentration of the retentate by the cross-flow MF treatment (concentration factor: 2) and by the DF treatment (concentration factor: have transferred 32.8% of a-La and 4.6% of P-Lg to the filtrate, showing that the transfer rate of a-La is large as compared with a very small transfer rate of P-Lg.

Example 2 Fresh skim milk having the following analytical values was used.

Total solids 8.81 Proteins (Nx6.38) 3.31 a-La/-Lg 0.33 Fats 0.12 Sugars 4.64 Ash 0.74 pH 6.6 100 of the fresh skim milk was heated in a tank at 85 0

C

for 10 minutes and treated by a cross-flow MF using a ceramic membrane, Ceraflow (trademark, manufactured by Millipore with a membrane area of 0.42 m 2 and a pore size of 0.2 tm, under operating conditions of 50 0 C, the average pressure difference of 0.1 MPa, and the flow rate of m/sec. The concentration was performed in the same manner as in Example 1, followed by the DF treatment also in the same manner as in Example 1.

The rate of transfer of a-La and P-Lg into the filtrate by the MF treatment, in which the retentate was concentrated by a factor of 5, was 37.2 for a-La and 5.2% for J-Lg, and the ratio of a-La/J-Lg in the filtrate was 2.56 as compared with 0.33 of the raw skim milk.

The transfer rate of a-La and J-Lg into the filtrate by the DF treatment was 34.2% for a-La and 4.4% for J-Lg, and the ratio of a-La/j-Lg in the filtrate was 2.80, indicating production of a fraction with a high a-La content.

The above treatments; at the concentration factor 2 of S c the retentate by the cross-flow MF treatment and at the concentration factor of 1 by the DF treatment, have transferred 58.6% of a-La and 9.8% of 3-Lg to the filtrate, showing that the transfer of a larger amount of a-La as compared with 3-Lg in the same way as in Example 1.

Example 3 Concentration and purification of proteins were performed by using 150 kg of the a-La enriched filtrate obtained in Examples 1 and 2. The composition of the 0. .filtrate which wa, treated was as follows.

Total solids 4.18 Proteins (Nx6.38) 0.39 (Pure proteins 0.12) Fats 0 Sugars 3.47 Ash 0.32 pH The above filtrate was concentrated (concentration factor: 50) by the UF apparatus Lab-20 (trademark, a product of Dow Chemical Co.) to which UF membrane GR81 PP (trademark, manufactured by Dow Chemical Co.) with a S* fractional molecular weigh of 6,000 Da and the area of 0.36 m 2 was installed, to obtain 3 kg of a retentate. The composition of retentate was as follows.

a Total solids 20.90 e* Proteins (Nx6.38) 8.94 (Pure proteins 6.00) Fats 0 Sugars 10.38 Ash 1.58 a 0 pH 6.2 The concr-..rations of a-La and A-Lg in this retentate determined by the SDS-PAGE analysis were 3.38% and 1.24%, respectively, with the ratio of a-La/A-Lg being 2.7, the oo same value as the filtrate before the treatment.

In order to further increase the protein concentration, the retentate was subjected to a DF treatment (concentration factor: 1) by adding 9 kg (equivalent to 3 times of the amount of the retentate) of deionized water. The retentate thus obtained (3 kg) had the following composition Total solids 8.89 Proteins (Nx6.38) 6.89 (Pure proteins 6.00) Fats 0 Sugars 1.3 Ash 0.80 pH 6.8 i As is clear from the above composition, the amount of proteins in the total solids was 77.5%.

The concentrations of a-La and 3-Lg in this retentate determined by the SDS-PAGE analysis were 3.36% and 1.20%, S* respectively, with the ratio of a-La/I-Lg remaining the same as the retentate before treatment.

Example 4 The retentate of Example 3 (total solids: 20.90%, proteins: 8.94%, fats: sugars: 10.38%, ash: 1.58%) was desalted by a conventional method, and into 100.6 kg of the desalted retentate (total solids: 18.12%, proteins: 8.05%, fats: sugars: 9.90%, ash: 0.17%) were dissolved 6.4 kg of casein, 32.6 kg of lactose, and 2 kg of vitamins and minerals. The mixture was blended with 27.6 kg of a plant oil to homogenize. The solution thus obtained was sterilized, concentrated, and dried by conventional methods to produce 100 kg of a mother milk substitute.

Example 19.3 kg of powdery skim milk, 32.1 kg of lactose, and 0.8 kg of vitamins and minerals were dissolved into 116.7 kg of desalted retentate of Example 4. The mixture was blended with 27.7 kg of a plant oil to homogenize. The solution thus obtained was sterilized, concentrated, and dried by conventional methods to produce 100 kg of a mother milk substitute.

Example 6 28.5 kg of dextrin and 1.6 kg of vitamins and minerals were dissolved into 288 kg of the desalted retentate of Example 4. The mixture was blended with 16.4 kg of a plant Soil to homogenize. The solution thus obtained was sterilized, concentrated, and dried by conventional methods to produce 100 kg of a powdery nutritious food.

00 Example 7 kg of the same reduced skim milk as used in Example 1 was subjected to the UF treatment in the Lab-20 module (a product of Dow Chemical Co.) to which UF membrane GR40 PP (polysulfone fractional molecular weight: 1,000,000 Da; trademark, manufactured by Dow Chemical Co.) with an area of 0.36 m 2 was installed. Under operating conditions of 12 0

C,

the average pressure difference of 0.3 MPa, and the flow rate of 1.6 m/sec, the skim milk was concentrated up to a concentration factor of 2 to obtain 10 kg of a retentate and kg of a filtrate. 6.5% of a-La and 0.9% of j-Lg originally contained in the skim milk have transferred into the filtrate. Also, as a result of the treatment, the ratio of a-La/J-Lg which was originally 0.34 has increased to 2.32, showing a high concentration of a-La in the filtrate.

The 10 kg of the retentate was then submitted to a DF membrane treatment while adding deionized water to maintain the amount of the retentate 10 kg. The DF treatment was terminated when the amount of the filtrate, which is equivalent to the amount of deionized water added, reached kg. 11.4% of a-La and 1.5% of P-Lg in the retentate were found to have transferred into 10 kg of the filtrate by the DF treatment. The ratio of a-La/P-Lg in the filtrate was found to be 2.30, demonstrating a high a-La ratio of the So filtrate.

"The above treatments; the concentration of the eS retentate by the cross-flow MF treatment (concentration

S.

factor: 2) and the concentration of by the DF treatment (concentration factor: have transferred 16.4% of a-La and 2.3% of j-Lg to the filtrate, demonstrating that the transfer of a larger amount of a-La as compared with P-Lg.

Example 8 100 kg of the fresh skim milk used in Example 2 was Sheated in a tank at 85 0 C for 10 minutes and subjected to the UF treatment in the Lab-20 module (a product of Dow Chemical Co.) to which UF membrane GR-10PP (polysulfone fractional molecular weight: 5,000,000 Da; trademark, manufactured by Dow Chemical Co.) with an area of 0.36 m 2 was installed.

The concentration was carried out up to the concentration factor of 5 under operating conditions of 50°C, the average pressure difference of 0.2 MPa, and the flow rate of 1.6 m/sec. The concentration and the DF treatment were carried out in the same manner as in Example 7. As a result of the concentration at the concentration factor of 5 by the UF treatment, the transfer rate of a-La and P-Lg into the filtrate were 24.8% and respectively, and the ratio of a-La/-Lg, which was originally 0.33, has increased to 2.32, showing a high concentration of a-La in the filtrate.

SI The transfer rate of a-La and P-Lg into the filtrate achieved by the DF treatment were 22.8% and 2.9%, respectively, and the ratio of a-La/3-Lg 2.60, indicating *a the production of a filtrate with a high a-La concentration.

In conclusion, the above treatments; the UF *0 0 treatment at the concentration factor of 5 and the DF treatment at the concentration factor of 1, have transferred about 39.1% of a-La and 6.5% of P-Lg to the filtrate, demonstrating that the transfer of a larger amount of a-La as compared with 3-Lg as they were in Example 7.

*I a Example 9 Concentration and purification of proteins were performed by using 150 kg of the a-La enriched filtrate obtained in Examples 7 and 8. The composition of the filtrate which was treated was as follows.

Total solids 4.08 Proteins (Nx6.38) 0.29 (Pure proteins 0.07) Fats 0 Sugars 3.47 Ash 0.32 pH The above filtrate was concentrated (concentration factor: 50) by the UF apparatus Lab-20 (trademark, a product of Dow Chemical Co.) to which UF membrane GR81 PP (trademark, manufactured by Dow Chemical Co.) with a fractional molecular weigh of 6,000 Da and the area of 0.36 m 2 was installed, to obtain 3 kg of a retentate. The composition of retentate was as follows.

Total solids 17.18 Proteins (Nx6.38) 5.22 (Pure proteins 3.50) Fats 0 Sugars 10.38 Ash 1.58 pH 6.2 The concentrations of a-La and 3-Lg in this retentate

S

determined by the SDS-PAGE analysis were 2.03% and 0.74%, respectively, with the ratio of a-La/0-Lg remaining the same S. as the filtrate before the treatment.

In order to further increase the protein concentration, the retentate was subjected to a DF treatment (concentration factor: 1) by adding 9 kg (equivalent to 3 times of the amount of the retentate) of deionized water. The retentate thus obtained (3 kg) had the following composition Total solids 6.02 Proteins (Nx6.38) 4.02 (Pure proteins 3.50) Fats 0 Sugars 1.3 Ash 0.80 pH 6.8 As is clear from the above composition, the amount of proteins in the total solids was 66.8%.

The concentrations of a-La and j-Lg in this retentate determined by the SDS-PAGE analysis were 2.02% and 0.72%, O B respectively, with the ratio of a-La/J-Lg remaining the same as the retentate before treatment.

Example The retentate of Example 9 (total solids: 17.18%, proteins: 5.22%, fats: sugars: 10.38%, ash: 1.58%) was desalted by a conventional method, and into 172.3 kg of the desalted retentate (total solids: 14.70%, proteins: 4.70%, fats: sugars: 9.90%, ash: 0.10%) were dissolved 6.4 kg of casein, 25.1 kg of lectose, and 2 kg of vitamins and minerals. The mixture was blended with 27.6 kg of a plant 0. oil to homogenize. The solution thus obtained was sterilized, concentrated, and dried by conventional methods to produce 100 kg of a mother milk substitute.

Example 11 19.3 kg of powdery skim milk, 23.9 kg of lactose, and 0.8 kg of vitamins and minerals were dissolved into 199.9 kg of desalted retentate of Example 10. The mixture was blended with 27.7 kg of a plant oil to homogenize. The solution thus obtained was sterilized, concentrated, and dried by conventional methods to produce 100 kg of a mother milk substitute.

Example 12 Ii) 8.2 kg of dextrin and 1.6 kg of vitamins and minerals were dissolved into 493 kg of the desalted retentate of Example 10. The mixture was blended with 16.4 kg of a plant oil to homogenize. The solution thus obtained was sterilized, concentrated, and dried by conventional methods ee *to produce 100 kg of a powdery nutritious food.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

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Claims

1. A process for the manufacture of a milk product comprising a milk fraction having a substantial a- lactalbumin (a-La) content and a reduced 3-lactoglobulin (9-Lg) content, said process comprising selecting as starting material: i) milk which previously has been heat treated, and/or ii) milk which previously has not been heat treated, or sufficiently heat treated, and heat treating said milk so as to increase the quasi-molecular weight of p-Lg present, and then subjecting or the result of (ii) to: a) cross-flow microfiltration treatment, or b) ultrafiltration treatment using a membrane with a fractional molecular weight of more than 50,000 Da, to produce a filtrate containing a-La and a substantially reduced g-Lg content, and a retentate containing a substantial P-Lg content, and recovering ;I said filtrate as said milk product. S

2. The process according to claim 1, wherein said starting material is at least one of: pasteurised milk, reduced milk, heat-concentrated milk, and preheated fresh milk,

3. The process acording to claim 1 or claim 2, wherein the heat treatment of materials and (ii) is at a ID2 I123691 AU413468 PAT 23 e ;a temperature of 70 0 C to 130 0 C.

4. The process according to any one of claims 1 to 3, wherein a starting material is selected, and the treatment in steps or take place at a temperature of 69 0 C or lower.

The process according to any one of claims 1 to 3, wherein a starting material (ii) is selected, and the treatment in steps or take place using a heat- resistant membrane at a temperature of at least 70 0 C.

6. The process according to any one of claims 1 to wherein cross-flow microfiltration treatment is carried out using a ceramic membrane or a polymer membrane, with a pore size of about 0.05 1.0 micron, at a pressure difference across the membrane of below MPa, and at a flow rate along the membrane of greater than 0.5 m/second.

7. The process according to any one of claims 1 to wherein ultrafiltration treatment is carried out using a ceramic membrane or a polymer membrane, with a fractional molecular weight of from 50,000 to 1,500,000, at a pressure difference across the membrane of below MPa, and at a flow rate along the membrane of greater than 0.5 m/second. S

8. The process according to claim 7, wherein the fractional molecular weight is about from 50,000 to 1,000,000.

9. The process according to any one of claims 1 to 8, which has an additional step of submitting the retentate from treatment or to Dia-filtration treatment, and S" separating and then combining the filtrate of the Dia- filtration step with the filtrate obtained from 882d1691 Atl413468 P*AT 24 treatment or as the milk product.

The process according to any one of claims 1 to 9, which has an additional step of submitting the filtrate obtained at the end of the process to an ultrafiltration treatment using a membrane having a fractional molecular weight of about 14,000 Da or smaller, separating and removing in the filtrate any lactose or ash present, and using the retentate containing a-La as the milk product.

11. A process for the manufacture of a milk product substantially as herein described with reference to any one of the Examples thereof.

12. A milk product with a substantial a-La and a reduced f- Lg content whenever prepared according to the process defined in any one of claims 1 to 11.

13. A powdered milk product with a substantial a-La content and a reduced -Lg content comprising a milk product prepared according to the process defined in any one of claims 1 to 11, which has been dried by spray drying or freeze-drying.

14. A mother's milk substitute, or a nutritious food composition for human beings or animals, characterised by containing a milk product manufactured by the process defined in any one of claims 1 to 11, or the powdered milk product according to claim 13. DATED this 14th day of September 1993. SNOW BRAND MILK PRODUCTS Co., LTD By their Patent Attorneys DAVIES COLLISON CAVE *D2 $8236191 AU411468 PAT 2 o to ABSTRACT OF THE DISCLOSURE A process for the manufacture of a milk fraction with a high a-lactalbumin content which comprises submitting milk, which has been heat treated or while heat treating, to a cross-flow microfiltration treatment or a ultrafiltration treatment using a membrane with a fractional molecular weight of more than 5,000, thus transferring a-lactalbumin to the filtrate side for separation and recovery of a- 1: *lactalbumin, and a mother milk substitute or a nutritious composition comprising such a milk fraction. The process is S* capable of reducing the amount of -lactoglobulin and increasing a-lactalbumin yielding a milk fraction with a high a-lactalbumin content and a high nutritive value. The product can be used as a raw material of a mother milk substitute and nutritious composition.