AU618985B2 - Water-soluble milk protein and process for producing same - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SP' "ICATICN (ORIG AL) 618 Int. Class Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: i APPLICANT'S REFERENCE: SNOW-28FYNM-933-ka Name(s) of Applicant(s): Snow Brand Milk Products Co., Ltd Address(es) of Applicant(s): 1-1, Naebocho 6-chome, Higashi-ku, Sapporo-shi, Hokkaido, UNITED STATES OF AMERICA.

Address for Service is: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Complete Specification for the invention entitled: WATER-SOLUBLE MILK PROTEIN AND PROCESS FOR PRODUC:NG SAME Our Ref 123356 POF Code: 1566/59229 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6003q/ 1

SPECIFICATION

Title of the Invention: Water-Soluble Milk Protein and Process for Producing Same Background of the Invention: 1) Filed of the Invention: *e This invention relates to a water-soluble milk protein which is useful as a material for the supply of minerals and as a material for the manufacture of nutritious foods and which is characterized in that it is soluble in water and its aqueous solutions are coagulated again with the aid of divalent or trjvalent metallic ions, a process for producing 0@ the milk protein, and coagulated curd obtained from the milk protein in powder form.

2) Description of the Prior Art: Conventionally known milk protein powders produced by the rennet reaction include rennet casein and powdered cheese.

S• However, these powders have the disadvantage that their use as food materials is limited because of their insolubility in water. Acid casein, which is obtained from cow's milk by isoelectric point precipitation at pH 4.6, can be dissolved in water by raising its pH. However, this casein is combined with the positive ions (for the most part, univalent metallic ions such as Na+ and used for pH adjustment during the aforesaid isoelectric point precipitation. Thus, this casein occurs in the form of sodium casein or potassium casein and has a relatively high content of such metals. In addition, this casein has a strong odor. These disadvantages place restrictions on the range of its use.

Summary of the Invention: It is the primary object of the present invention to provide a process for the production of a water-soluble milk protein which is characterized in that it is soluble in water, it has a very low content of metals such as Na, it has little odor of casein, and its aqeuous solutions are coagulated with the aid of divalent or trivalent metallic ions.

presenf According to the pr.snat invention, a water-soluble milk S* protein is produced by desalting cow's milk or processed milk S" while keeping its pH at 6.0 or above, until the calcium bound to the casein in the milk is removed to a high degree, and then drying the resulting calcium-free milk. Alternatively, a water-soluble milk protein can also be produced by concentrating the calcium-free milk and then drying the

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concentrated milk, or by subjecting the calcium-free milk to the rennet reaction by the addition of a milk-coagulating enzyme and then drying the renneted milk.

Detailed description of the Preferred Embodiments: In the process of the present invention, a starting material, which may be cow's milk or processed milk, is subjected to a desalting treatment while its pH is kept at or higher with an alkali such as NaOH or KOH, until the calcium bound to the casein in the milk is removed to a high degree. As a result of this removal of calcium, the formation of curd by coagulation will not occur even after the ,/(-casein presnet in the casein is converted into para-K-casein by the additon of a starter or a milk-coagulating enzyme.

Accordingly, a water-soluble milk protein powder is obtained by drying the starting milk which has been desalted in the above-described manner. Similarly, if the desalted 6 milk is subjected to the rennet reaction and then dried, there 0* is obtained a water-soluble rennet milk protein powder.

i In the process of the present invention, the aforesaid S desalting treatment is preferably accomplished by :i electrodialysis. Usually, this makes it possible to remove about 90% of the calcium present in the milk. As a result of this desalting treatment, the calcium bound to the casein in the milk is removed to a high degree, so that the formation of coagulated curd does not occur even when the desalted milk is dried or when the desalted milk is subjected to the rennet reaction. Thus, the powder obtained by drying the desalted milk or the renneted milk remains soluble in water.

In drying the desalted milk to convert it into powder, the milk may be concentrated in advance. This concentration can be efficiently carried out by ultrafiltratlon. The drying of the desalted milk may be carried out by freeze-drying or spray drying.

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The milk protein powder obtained in the above-described manner exhibits such good water solubility that it dissolves readily in water even at a high concentration of the order of about Moreover, if divalent or trivalent metallic ions are added to an aqueous solution of the aforesaid milk protein powder, it is coagulated to form a plastic curd having plasticity. For example, if an aqueous solution of a divalent metallic salt such as CaCI 2 or FeSO 4 is added to a 20% aqueous C solution of the rennet milk protein powder, a plastic curd having stretching properties is formed. If an aqueous solution of a trivalent metallic salt such as FeC13 is added, a good plastic curd is also formed, though it does not exhibit s" remakable stretching properties. However, even if an aqueous solution of a univalent metallic salt such as NaC1 or KC1, no curd is formed.

As described above, the present invention makes it possible to produce a milk protein powder which is characterized in that it is soluble in water, its aqueous solutions are coagulated by the addition of divalent or trivalent metallic ions to form a good plastic curd, and it has low Na and K contents as compared with sodium casein and potassium casein.

Accordingly, if divalent or trivalent metallic ions as described above are added, in the form of a mineral useful for nutritional purposes, to an aqueous solution of the milk protein powder obtained in accordance with the present invention, there can be formed a curd consisting of the milk protein to which the mineral is bound.

Thus, the milk protein powder of the present invention can be widely utilized as a material for the manufacture of various health foods and will hence be able to find new s oo applications in which conventional milk protein powders have never been used.

The present invention is further illustrated by the e following examples. In these examples, all percentages are by weight unless otherwide stated.

Example 1 As the- .tar4 g milk, there was used 60 kg of skimmed milk containing 8.83% of toal solids, 0.08% of lipids, 2.99% of Sproteins, 4.44% of lactose and 0.75% of ash (with a calcium content of 124 mg/100 Using an electrodialyzer (Model TS- 24; manufactured by Tokuyama Soda this skimmed milk was S* highly desalted until its calcium content reached 10.9 mg/ 100g. During this desalting treatment, the pH of the skimmed milk was kept at 6.2 by adding small amounts of Na0H.

The skimmed milk which had been highly desalted in the above-described manner was pasteurized at 65 0 C for 30 minutes, cooled to 50 0 C and then concentrated by factor of 4.5 in a batch type ultrafiltration apparatus (Modle LAB-20 having a GR61 polypropylene membrane with an area of 0.36 m 2 manufactured by DDS Thus, there was obtained 13.3 kg of desalted and concentrated milk. 12 kg of this desalted and concentrated milk was cooled to 30 0 C and inoculated with 0.01% of frozen BD-starter culture as a lactic acid bacterium starter. Thereafter, 30 ppm of rennet (manufactured by Christian-Hansen Co.) was added thereto and the rennet e. reaction was effected for 30 minutes.

Ii The milk so treated was divided into two parts. One of them was rapidly frozen with liquid nitrogen and then freezedried, and the other was spray-dried. Thus, there were obtained 1.2 kg each of rennet milk protein powders. In addition, another powder was obtained in the same manner as described above, except that, 30 minutes after the additon of rennet, the milk was heated at 85° C for 10 minutes to inactivate the rennet.

When these powders were dissolved in water, all of them were found to be easily soluble at concentrations of up to The following Examples 2 and 3 illustrate several applications of the milk protein powder of the present invention.

Example 2 To a 20% aqeuous solution of each of the rennet milk protein powders obtained in Example 1 was added each of aqueous solutions of CaCl 2 FeSO 4 NaCl and FeC 3 Although j NaC1 caused no curd formation, CaCl 2 and FeSO 4 formed a plastic curd having stretching properties. FeCl 3 also formed a good curd, though it did not exhibit remarkable stretching properties.

Example 3 Using a syringe, a 20% aqueous solution of each of the rennet milk protein powders obtained in Example 1 was dropped into each of aqueous solutions of CaC12 and FeSO 4 Thus, there were obtained spherules of coagulated curd. Accordingly, it seems possible to produce casein capsules from this powder.

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Claims (8)

1. A process for the production of a water-soluble milk protein which comprises the steps of subjecting cow's milk or processed milk to electrodialysis while keeping its pH at or higher, until the calcium bound to the casein in the milk is removed to a high degree; and drying the resulting calcium- free milk.

A process as claimed in claim 1 wherein the calcium- free milk is concentrated prior to the drying step. a'-

3. A prcoess as claimed in claim 2 wherein the S concentration is carried out by ultrafiltration. 1i

4. A process for the production of a water-soluble milk protein which comprises the stec.s of subjecting cow's milk or processed milk to electrodialysis while keeping its pH at or higher, until the calcium bound to the casein in the milk is removed to a high degree; subjecting the resulting calcium- free milk to the rennet reaction by the additon of a milk- i coagulating enzyme; and drying the renneted milk. j

5. A process as claimed in claim 1 or 4 wherein about by weight of the calcium bound to the casein in the milk is removed.

6. A water-soluble milk protein powder obtained by a process as claimed in claim 1 or 4.

7. Coagulated curd obtained by coagulating a solution of the water-soluble milk protein powder of claim 6 with the aid of divalent or trivalent metallic ions. 2

8. A process according to claim 1 or claim 4 substantially as hereinbefore described with reference to any one of the examples. DATED: 24 October 1991 PHILLIPS ORMONDE FITZPATRICK Attorneys for: SNOW BRAND MILK PRODUCTS CO., LTD. r r 2 i ;i I :I :i 4 ;:q Br rvG -9