The invention can be used in various industries, among which the most significant ones are the food, paper, chemical and pharmaceutical industries. In the milk industry, casein is used for the production of cheeses. However, presently the main scope of use of casein is caseinates produced by adding alkaline substances to casein. Depending on these addition substances, sodium, potassium or calcium caseinates may be produced. Caseinates are widely used in the milk industry for the production of cheese analogs, chocolate milk, margarine and many other products.

Casein can be produced by two different methods, namely by acid precipitation and rennet precipitation. The acidic method for the production of casein is a traditional method based on reaching the acid precipitation point of casein. Furthermore, different acids determine a different structure of precipitated casein. For example, casein precipitated by lactic acid is more granular and loose; whereas hydrochloric acid precipitation leads to a more viscous and sticky structure of casein. Rennet casein is produced by enzymatic coagulation of milk and by following optimal conditions of coagulation and clot formation. The formed clot is reduced, heated to the temperature of 58-60° C. by mixing, washed with water and dried. It is worth mentioning that the method of rennet precipitation of casein, contrary to acid precipitation, is an irreversible process. Rennet precipitated casein contains much calcium and phosphates; whereas the quantity of these salts in acid casein is limited. However, both types of casein are remarkable for their resistance to high temperatures and are of high nutritive value.

Technological methods for the production of casein are elaborated in the book of J. Dük{hacek over (s)}tas and D. Ka{hacek over (c)}erauskas, Picno perdirbimo technologija” (Milk processing technology), Vilnius, 1994.

The aforementioned methods for the production of casein are also described in patents of the Russian Federation Nos. 1600671, 1692505, 2199233, 2201099.

Membrane filtration processes (microfiltration, ultrafiltration, nanofiltration and reversible osmosis)—separation (isolation) processes passing under pressure by using porous polymeric or inorganic materials—are widely used in the milk industry. For the last 30 years, these processes have been widely applied in different industries for the purification or concentration of fluid media. Whole milk, skimmed milk, pre-soured milk and whey have been processed with the help of membrane technologies. In contrast to conventional filtration used during isolation of suspended particles of the size of more than 10 μm, membrane filtration processes allow separating particles of the size of less than 10 micron. Membrane filtration allows concentrating isolated particles in a lower volume with regard to the initial volume of liquid. In such a way whey protein concentrates not containing any fats or bacteria can be produced. Information on membrane technologies can be found at www.geafiltration.com.

Casein produced by use of the known methods has the following drawbacks:

1. Caseins are insoluble in water which complicates their direct utilization in different industries. Utilization of caseins requires converting caseins into caseinates or other acceptable forms.

2. Since the method of rennet casein precipitation is an irreversible process, the produced insoluble casein, unlike acid casein, cannot be converted into a soluble colloidal form. This property highly restricts the possibilities of its use.

3. Industrial rennet casein cannot be reprocessed.

4. Casein produced by the acidic method is an acid product; besides, the whey obtained during the production process is also acidic. Before being used, for example, in food industry, such acid products must be neutralized to the value acceptable for use.

The purpose of the invention is production of water-soluble casein without using acid, alkali or any other chemical substances.

The purpose can be achieved by using membrane micro- and ultra-filtration systems which help to separate milk proteins into whey and casein proteins. Casein protein is further treated in the membrane ultrafiltration concentrator without using any binding substances for protein separation.

A membrane method for the production of casein is proposed, where in the beginning of the production whole cow's milk is separated in a separator, wherein the fats and skimmed milk are separated. The method is characterized in that after separation the skimmed milk from an intermediate tank is pasteurized in a plate pasteurizer and stored for 15-75 seconds at the temperature of 50-80° C., the milk is then cooled to 4-10° C. and directed to an intermediate balance tank. From this tank, the milk is supplied to the membrane-type microfiltering and fractionating filter where the milk protein is divided into casein and whey proteins. The separated casein protein—the microfiltration retentate is supplied into the membrane-type ultrafiltration-defiltration filter, wherein the—casein concentrate with the solids content of 14-36%, is obtained as ultrafiltration retentate. The produced concentrated product is transferred to a drier where it is dried to 4-6% moisture, and the produced water-soluble casein powder is first supplied to the cooling cyclone and then—to the packing shop.

The equipment for the production of casein includes a membrane-type microfiltering and fractionating filter, membrane-type ultrafiltration-defiltration filter for casein protein concentration, membrane-type ultrafiltration filter for whey protein concentration.

The membrane-type protein microfiltration-concentration filter is comprised of membranes separating particles of 0.05-10 μm with their surface area of 50-310 m², filtration speed 50-120 l/cm²/h, working temperature 5-28° C.

The membrane-type ultrafiltration-defiltration filter consists of membranes separating particles of 0.001-0.2 μm with their surface area of 50-310 m², filtration speed 50-120 l/cm²/h, working temperature 5-28° C.

The proposed invention is described by the following diagrams;

FIG. 1—General diagram for the production of water-soluble casein from cow's milk.

Whole cow's milk delivered to the production shop is supplied from milk tanker 1 through the receiving pipeline to intermediate tank 2, wherefrom the milk is supplied to heater 3 where it is heated to the temperature of 5-58° C. The heated milk is supplied to milk fat separator 4 for separation of skimmed milk and fats. The skimmed milk produced during the separation is supplied to intermediate tank 5, then—to the plate pasteurizer, where it is stored for 15-75 seconds at the temperature of 50-87° C. Further, in plate pasteurizer 7, the skimmed milk is cooled to 5-28° C. and through intermediate tank 8 is directed to protein membrane-type microfiltering and fractionating filter 9. The microfiltration retentate (casein protein) is supplied through intermediate tank 15 to membrane-type ultrafiltration-defiltration filter 16, wherefrom the produced ultrafiltration retentate—casein protein concentrate with the solids content of 14-36%, is supplied to drier 17, where it is dried to 4-6% moisture. The powder produced in such a way has a native protein structure and is water-soluble.

Characteristics of water-soluble casein:

Casein protein

74-85%

Fats

0.8-2%

Lactose + mineral substances

18-7%

Moisture

4-6%

When casein is produced by the method mentioned above, additional products are derived, namely: whey protein concentrate, cream (FIG. 1). Microfiltration permeate (whey proteins) is supplied through intermediate tank 10 to plate refrigerator 11, wherein it is cooled to 5-28° C. The cooled permeate is supplied to membrane-type ultrafiltration filter 12, wherefrom the ultrafiltration retentate containing 83% of whey proteins and 16-36% of solids is drained. The ultrafiltration retentate is dried in drier 13 to 4-6% moisture, which allows obtaining the whey protein concentrate with the following content:

Whey proteins

85%

Fats

2%

Lactose + mineral substances

7-9%

Moisture

4-6%

Cream with 60% fat is supplied from separator 4 to normalizer 18, whereto the required quantity of microfiltration permeates is supplied through intermediate tank 10. In normalizer 18, the cream is normalized, for example, to the fat content of 40% and is then supplied to cream pasteurizer 19, where it is pasteurized at temperature of 95-105° C. The produced cream is directed for further use.

The advantage of soluble casein produced by the membrane method is that no additional conversion into caseinates is required, whereas it must be carried out when casein is produced by the traditional method. Since casein is the main milk protein used in the cheese production, casein produced by the membrane method can be directly used for cheese production. This allows cutting production costs 3 times.

Also, a big advantage of water-soluble casein is the fact that neither acids or alkali or any other binding substances are used in the production process, which gives an opportunity to receive an environmentally clean product.