JP2908894B2 - How to prepare milk protein - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for releasing denatured protein from casein micelles having heat-denatured whey protein bound to the surface thereof by heat treatment, and for returning the denatured milk protein to its unheated state. The reconstituted protein obtained by the method of the present invention is useful as a raw material for producing dairy products, especially cheese and yogurt.

[0002]

2. Description of the Related Art Milk, including milk, is an important food for nutrition. Especially, milk has a high protein content and is used in various forms. Milk is subjected to milking, homogenization, and sterilization processing steps to be drunk and further processed by spray drying and the like. In this sterilization step, sterilization by heating is usually performed. Heat sterilization depends on sterilization conditions.
Pasteurization to hold for 30 minutes at 70-65 ° C, 70-72 ° C
High-temperature sterilization (HTST method) for 15 seconds at 140 ° C., 140
Ultra-high-temperature sterilization (UHT direct method) in which the temperature is maintained at 2 ° C. for 2 to 3 seconds and ultra-high temperature sterilization (UHT indirect method) in which the temperature is maintained at 120 ° C. to 140 ° C. for 2 to 20 seconds. At present, as a sterilization method, the UHT method is widely used in milk processing in Japan because of high sterilization efficiency and little heat denaturation of milk protein, and other sterilization methods are hardly adopted. Limited to those who need special purpose milk.

It is a well-known fact that milk proteins are denatured by heating. Pasteurization involves a browning reaction due to the so-called aminocarbonyl reaction, and the heat denaturation of the protein is remarkable. On the other hand, the HTST method and the UHT method are generally used for treating milk because they have little protein denaturation and a high bactericidal effect. However, the HTST method, U
Denaturation of whey protein is inevitable even by the HT method.
Milk proteins are roughly classified into casein proteins and whey proteins. Among them, casein is relatively resistant to heat denaturation and 145
It has been confirmed that denaturation does not occur even after heating at 30 ° C. for 30 minutes.
On the other hand, whey protein is susceptible to thermal denaturation and completely solidifies when heated at 75 ° C. for 15 minutes (Rowland, J. Dairy Res.,
vol. 9, 42p, 1938). As described above, the temperature of heat denaturation differs depending on the protein present in milk, but normal sterilized milk contains heat denatured protein in some form.

The protein most susceptible to heat denaturation is β-lactoglobulin, and it has been confirmed that β-lactoglobulin is first denatured by heating to form a complex with casein (EJ Long, et al. , J. Dai
ry Sci., vol. 46, 1329p, 1963). In this way, a model in which the heat-denatured protein covers the surface of the casein micelles is the protein form of the heated milk, and a model has been proposed in which lactalbumin is denatured and bound to this surface when heating is further advanced. (J. Mottar, et al., J. Dairy Sci., V
ol. 72, 2247p, 1989). According to the Mottar model,
First, β-lactoglobulin binds to the casein micelle surface, and then heat-denatured α-lactoglobulin binds to this surface, resulting in a smooth surface, reduced hydrophobicity, and reduced casein network formation. This model is shown in FIG. Thus, the surface of casein (the surface of casein micelles) is covered with the heat-denatured protein, so that the physical properties of the protein are changed. Mott who proposed the above model
According to ar et al., milk protein in such a state becomes less coagulable when yogurt is manufactured using it,
States that it will be a soft card. Similarly, milk subjected to heat treatment has weak rennet coagulation during cheese production,
It has been pointed out that the coagulation time by the rennet is delayed according to the heating time, and that the curd is softened (Kinjiro Yukawa, Milk Protein, 195p, Dairy Technology Promotion Association, Showa 46). It is considered that such a change in coagulability is caused by the fact that the micelle surface of casein is covered by the denatured protein and the casein network-forming ability is reduced. Conventionally, it has been difficult to separate such whey proteins such as β-lactoglobulin and α-lactalbumin bound to the casein micelle surface from casein. In particular, since β-lactoglobulin is one of the proteins causing milk allergy in milk, it has been desired to separate β-lactoglobulin from milk after heat treatment.

[0005]

Heat sterilization of milk, including milk, is inevitable for placing products on current distribution mechanisms. However, milk and the like that have been subjected to such a heat treatment have been considered by those skilled in the art as generally unsuitable for the production of yogurt or cheese. In addition, it has been considered that it is extremely difficult to reduce heat-treated and dried products such as skim milk powder and use them for yogurt and cheese, or it is only possible to reduce the quality of the products. However, the casein micelle surface is exposed by releasing heat-denatured β-lactoglobulin or α-lactalbumin bound to the micelle surface, as shown in the above-mentioned model of Mottar et al.
The rennet responsiveness and yogurt card shape retention will be restored. Further, in this manner, the released β-lactoglobulin and α-lactalbumin can be removed by a general separation method, for example, a method such as ultrafiltration, adsorption chromatography, etc., to obtain milk with less allergy. Becomes possible. Furthermore, from skim milk powder or whole fat milk powder produced by spray drying milk with large seasonal fluctuations,
It becomes possible to produce cheese and yogurt. It is an object of the present invention to provide a method for releasing whey proteins such as α-lactalbumin and β-lactoglobulin bound to casein micelles in heat-treated milk so far.

[0006]

According to the present invention, there is provided Mott.
The whey proteins, such as β-lactoglobulin and α-lactalbumin, present in a bound state on the casein micelle surface as shown by the model of ar et al. can be released from casein micelles by high-pressure treatment. Until now, there has been no report that the denatured protein in such a state could be released.

[0007] The present inventors have studied the effects of high pressure, especially ultra-high pressure, on foods. As a result, when cheese curd is formed, it is subjected to a high pressure treatment, so that calcium chloride which has conventionally been required to be added at the time of curd formation. Was found to be unnecessary, and a patent application was filed as Japanese Patent Application No. 2-177266 as a method for preparing a cheese curd. The present invention has been obtained as a result of further developing the present invention. In the present invention, β-lactoglobulin and α-lactalbumin are bonded to the surface of casein micelles by heat treatment, and rennet reactivity and yogurt card shape retention are reduced in casein aqueous dispersion or milk, for example, high-temperature sterilization treatment And high-temperature spray-dried skim milk,
By subjecting milk with a high heat history to high pressure, for example, 100 MPa or more, particularly preferably 400 MPa or more, the micelle structure of casein is broken, and casein sub-micelles associate in a chain, tuft, or branch. The present inventors have found a phenomenon in which whey proteins such as β-lactoglobulin and α-lactalbumin bound to the micelle surface of casein are released when exhibiting such a structure, and completed the present invention.

In order to apply high pressure, in the case of powdered milk, the solid content is dissolved in water to a concentration of 1 to 30%, preferably 8 to 15%, and the above high pressure is applied at 30 ° C. or lower. High-temperature sterilized milk or the like is subjected to high pressure as it is after sterilization or after concentration or dilution or component adjustment as necessary. In aqueous solution, milk proteins exist as a dispersion of macromolecules of proteins called casein micelles. In order to apply a high pressure, it is easy to use a commercially available ultra-high pressure apparatus. When the treatment temperature is high, the micelles form sub-micellar aggregates and then quickly re-form the original micelles.
The temperature may exceed 0 ° C. Under ultra-high pressure such as 400 MPa, casein micelles break their spherical micellar structure. When observed under an electron microscope, casein micelle structural units called casein sub-micelles are chain-like, tuft-like, or branch-like. It can be confirmed that the structure leads to FIG. 2 shows a state of the micelle having such a structural change. The small spheres in the figure are sub-micelles, which are observed to be in a chain, tuft or branch shape. In addition, skim milk with less fat can be confirmed by translucent emulsion. In such a state, β-lactoglobulin bound to the casein micelle surface,
Whey proteins such as α-lactalbumin are released from casein micelles. The release of the β-lactoglobulin and α-lactalbumin covering the surface from the casein micelles in this way exposes the casein protein, thereby restoring the rennet reactivity and the yogurt curd retention. The milk after such treatment is subjected to treatment such as ultrafiltration and adsorption chromatography, so that the allergen β
Lactoglobulin-free milk can also be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 In this example, an example in which β-lactoglobulin and α-lactalbumin bound by heating are released by high-pressure treatment will be described. The milk was centrifuged into skim milk. When the solid content of this skim milk was analyzed, it was 9%. This skim milk is divided into three equal parts, one of which is
For 10 minutes, cool to 10 ° C., then 400MP
a for 10 minutes. On the other hand, for comparison, one of the three portions was treated as untreated milk, and the other was kept at 100 ° C. for 10 minutes and cooled. Each of these was collected and centrifuged at 100,000 G for 4 hours to separate into a supernatant and a precipitate. The centrifugation conditions at 100,000 G for 4 hours are as follows:
It has been confirmed that casein micelles precipitate. 0.5 ml of each supernatant was collected and treated with sodium dodecyl sulfate (SDS), and 20 microliters thereof were taken, subjected to polyacrylamide gel electrophoresis, and subjected to α-lactalbumin, β-lactoglobulin, casein, immunoglobulin. Was determined as an area ratio using a densitometer. As shown in FIG. 3, the peaks corresponding to α-lactalbumin and β-lactoglobulin are clearly reduced in the heated milk as compared with the untreated milk, and the soluble protein is reduced by heat denaturation. Was. On the other hand, according to the present invention, peaks corresponding to α-lactalbumin and β-lactoglobulin were dissolved and released to the same amount as in untreated milk. It was also observed that casein was partially released. The amount of β-lactoglobulin dissolved from the total protein calculated from each peak is
The ratios were 0.45%, 0.15%, and 0.44%, and it was clear that β-lactoglobulin bound to casein micelles was released by heating.

[0010]

Embodiment 2 In this embodiment, an example in which the rennet coagulability of heat-denatured milk is restored by high-pressure treatment will be described. U
Milk sterilized by HT treatment, skim milk powder produced by spray drying after sterilization by UHT treatment, solid content 8%, 14%
%, 20%, and 100, 20 respectively.
A high pressure of 0, 300, 400 MPa was applied for 10 minutes. 87 μg / ml of rennet was added to the aqueous solution of the milk and skim milk powder thus treated, and the mixture was kept at 30 ° C., and the rennet coagulation was measured using the clotting time as an index. The clotting time was measured using a kinematic viscosity meter (Leo catch, manufactured by Snow Brand Milk Products). As shown in FIG. 4, the clotting time has been shortened and the rennet coagulability has been restored in accordance with the applied pressure, which indicates that α-lactalbumin, β-lactoglobulin, etc. bound to the casein micelle surface. Was confirmed to be released.

[0011]

Example 3 In this example, a decrease in rennet coagulability by heating and a recovery of rennet coagulability according to the present invention are shown. Raw milk having a solid content of non-fat milk of 8% was obtained.
The temperature was maintained at 0 ° C, 60 ° C, 75 ° C, and 90 ° C, respectively. Then, the milk was cooled to 30 ° C. and then divided into two equal parts. On the other hand 4
After treating at 00 MPa for 5 minutes, rennet was similarly added, and rennet coagulation was observed. The rennet coagulability was measured by measuring the clotting time in the same manner as in Example 2. As shown in FIG. 5, the clotting time was rapidly increased from 60 ° C., which is the heat denaturation temperature of the protein, and the rennet coagulation property was reduced. On the other hand, according to the method of the present invention, even when the heat treatment was performed, the clotting time hardly changed and the rennet coagulability did not decrease under these heating conditions. Thus, α-lactalbumin and β-lactoglobulin by heating are 60
It was confirmed that it binds to casein micelles at ℃ and decreases rennet coagulability. In addition, it was confirmed that the rennet solidification property was recovered by performing the pressure treatment at 400 MPa.

[0012]

Embodiment 4 In this embodiment, an example in which yogurt is produced using pasteurized milk is described. The reduced skim milk having a solid content of 10% is further sterilized at 90 ° C. for 10 minutes, cooled and then cooled to 400 MPa.
a) for 5 minutes, and then a lactic acid bacterium culture starter was added at 3% to the total amount, followed by fermentation at 40 ° C. as usual.
After about 4 hours, take out, cool, fermentation state of yogurt,
The state of the yogurt curd was observed. As a result, the obtained yogurt showed the same acidity, pH and curd formation as yogurt prepared from raw milk.

[0013]

According to the practice of the present invention, lactalbumin and lactoglobulin bound to casein micelles are released from the aqueous dispersion of casein micelles and lactalbumin and lactoglobulin bound to casein micelles by heat treatment or the like to produce raw milk. Similar casein micelles can be regenerated. In addition, the milk obtained by this method recovers the reduced rennet coagulability and the yogurt curd shape retention property by heating, and skim milk powder subjected to heat treatment such as spray drying under the same conditions as in the case of using raw milk. Cheese and yogurt can be produced from milk powder. Further, the released β-lactoglobulin can be easily removed, and milk free from allergic diseases can be obtained.

[0014]

[Brief description of the drawings]

FIG. 1 shows the structure of heat-denatured milk protein proposed by Mottar.

FIG. 2 shows an electron micrograph of the structure of micelle particles modified by high-pressure treatment.

FIG. 3 shows an example in which α-lactalbumin and β-lactoglobulin bound by a high-pressure treatment after heat treatment are released by a change in molecular weight.

[Description of Signs] Untreated milk Heated and heated milk Milk according to the present invention

FIG. 4 shows an example in which the rennet coagulation property reduced by the heat treatment is recovered in relation to the pressure treatment pressure and the clotting time at 30 ° C.

[Explanation of symbols]

 -□-Solid content of skim milk 8%-△-Solid content of skim milk 14%-●-Solid content of skim milk 20%-○-UHT milk

FIG. 5 shows an example in which protein denaturation is caused by heat treatment and rennet coagulability is reduced in accordance with the relationship between heating temperature and clotting time.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) A23J 1/00-7/00

Claims (5)

(57) [Claims] 1. A method for preparing a milk protein, which comprises subjecting an aqueous dispersion or milk of casein micelles having whey protein bound to the surface thereof to high pressure treatment to release whey proteins bound to casein micelles. 2. The method according to claim 1, wherein the aqueous dispersion or milk of the casein micelle having whey protein bound to the surface is obtained by heat-treating the casein micelle dispersion or milk. 3. The method according to claim 1, wherein the heat treatment is high-temperature sterilization (HTST), ultra-high-temperature sterilization (UHT), or a heating method for imparting heat denaturation equivalent to these to the milk protein. 4. The method according to claim 1, wherein the high-pressure treatment is an ultra-high pressure of 100 MPa or more. 5. An aqueous dispersion or milk of casein micelles,
A processed milk obtained by dissolving casein powder or milk powder obtained by hot-air drying by a spray drying method.
The method described in any of