A method for preparing yak milk casein

Abstract

The present invention relates to a method for preparing yak casein, and to the technical field of protein peptide preparation, wherein the method comprises the following steps: subjecting the crushed yak Qula raw material to freeze-thaw cycle treatment, and then subjecting it to corona discharge treatment to obtain pretreated yak Qula; adding the pretreated yak Qula to water for dissolution, and then adjusting the pH of the system to alkaline to obtain a first feed liquid; subjecting the first feed liquid to enzymolysis, and then decolorizing and filtering to obtain a second feed liquid; subjecting the second feed liquid to acid precipitation, water washing and drying to obtain the yak casein. On the basis of the prior art, the present invention uses a freeze-thaw cycle-corona discharge combined treatment process without the addition of additional chemical reagents, which not only effectively inhibits the browning phenomenon in the preparation process of yak casein, but also can further reduce its allergenicity, providing a new means for preparing yak casein.

Description

Technical Field

[0001] The invention relates to the technical field of protein peptide preparation, and in particular to a method for preparing yak milk casein. Background Art

[0002] In the field of protein peptide preparation technology, yak milk casein, as a protein product with high nutritional value and unique functional properties, has received extensive attention and research in recent years. As a mammal unique to the plateau, yaks have unique development and utilization value because their dairy products are rich in various nutrients and bioactive substances. However, there are some technical difficulties and challenges in the preparation of yak milk casein.

[0003] Traditional methods for preparing yak milk casein often involve complex chemical treatment steps, such as the use of reagents such as sodium bisulfite to inhibit browning. These chemical treatments not only increase the cost of preparation, but may also introduce harmful chemical residues, affecting the safety and purity of the product. At the same time, during the preparation process, since the protein is prone to oxidation and enzymatic browning reactions, the color of the product becomes darker, affecting the appearance quality and market acceptance. In addition, as an exogenous protein, yak milk casein may be allergenic to some people, limiting its scope of application.

[0004] In view of this, exploring more efficient and environmentally friendly methods for preparing yak milk casein has become a research hotspot for preparing yak milk casein in recent years. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing yak milk casein.

[0006] The present invention provides a method for preparing yak milk casein, the method comprising the following steps:

[0007] The crushed yak qula raw material is subjected to freeze-thaw cycle treatment, and then subjected to corona discharge treatment to obtain pre-treated yak qula;

[0008] The pretreated yak koji is added into water to dissolve, and then the pH of the system is adjusted to alkaline to obtain a first liquid;

[0009] The first feed liquid is subjected to enzymatic hydrolysis, followed by decolorization and filtration to obtain a second feed liquid;

[0010] The second liquid is subjected to acid precipitation, water washing and drying to obtain the yak casein.

[0011] Furthermore, the working condition parameters of the freeze-thaw cycle treatment include: freezing temperature of -40 to -20°C, freezing time of 40 to 60 minutes, thawing temperature of 30 to 40°C, thawing time of 60 to 90 minutes, and the number of freeze-thaw cycle treatments is 5 to 8 times.

[0012] Furthermore, the working condition parameters of the corona discharge treatment include: the electric field intensity of the corona discharge treatment is 3 to 8 kV / m 2 The corona discharge treatment time is 10 to 20 seconds.

[0013] Furthermore, the electric field strength is 6 kV / m 2 , the corona discharge treatment time is 15 seconds.

[0014] Furthermore, the step of adding the pretreated yak koji to water for dissolution, and then adjusting the pH of the system to alkaline to obtain the first feed solution comprises the following process:

[0015] The pretreated yak qula and water are stirred at a weight ratio of 1:1, and then 0.5-1% by weight of calcium hydroxide is added to adjust the pH to 8-9 and centrifuge to collect the filtrate to obtain the first feed liquid.

[0016] Furthermore, the working condition parameters of the enzymatic hydrolysis include: an enzymatic hydrolysis pH of 4.2 to 4.5, an enzymatic hydrolysis temperature of 33 to 37°C, an enzymatic hydrolysis time of 8 to 15 minutes, and enzymatic hydrolysis using a composite enzyme consisting of lipase, lactase and trypsin in a weight ratio of (1 to 2): (3 to 5): (4 to 6). The amount of the composite enzyme added is 0.03 to 0.07 g per 1 kg of the yak qula raw material.

[0017] Furthermore, the decolorization method includes using activated carbon for decolorization, and the added weight of the activated carbon is 0.5-1% of the weight of the yak qula raw material.

[0018] Furthermore, the second liquid is subjected to acid precipitation, water washing and drying to obtain the yak casein protein, which comprises the following process:

[0019] At 28-32° C. and pH 4.5-5.0, the second liquid is acidified with lactic acid at a dilution ratio of 1:(5-7) to obtain a crude yak casein product;

[0020] The crude yak casein product is washed with water and vacuum dried to obtain the yak casein.

[0021] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0022] The embodiment of the present invention provides a method for preparing yak milk casein. On the basis of the prior art, the present invention uses a freeze-thaw cycle-corona discharge combined treatment process without the addition of additional chemical reagents, which not only effectively inhibits the browning phenomenon in the preparation process of yak milk casein, but also can further reduce its allergenicity, thereby providing a new means for preparing yak milk casein. Specifically:

[0023] Freeze-thaw cycle is a physical treatment method. By freezing the yak qula raw material to a low temperature state, and then quickly thawing it to room temperature or higher temperature, it is repeated many times, which is conducive to opening the original tight structure of the yak qula raw material, and helps to promote the transformation of the obtained yak casein into a linear protein structure, providing a more accessible material state for subsequent corona discharge treatment and enzymatic hydrolysis. At the same time, corona discharge can produce high-energy free radicals, ozone and other active substances, which can change the physical and chemical properties of the yak qula raw material and participate in the regulation of browning reaction, reduce the formation of undesirable pigments, improve the color and quality of the product, further promote the change of protein structure and its spatial conformation, reduce its allergenicity, and also facilitate subsequent enzymatic hydrolysis and inhibition of browning reaction.

[0024] In summary, based on the prior art, the present invention not only effectively improves the extraction efficiency of yak milk casein through a freeze-thaw cycle-corona discharge combined treatment process, but also inhibits the browning phenomenon and reduces the allergenicity, providing a novel, environmentally friendly and efficient method for the preparation of yak milk casein. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 A schematic flow chart of a method for preparing yak milk casein provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0030] In a first aspect, the present invention provides a method for preparing yak milk casein, such as Figure 1 As shown, the method comprises the following steps:

[0031] The crushed yak qula raw material is subjected to freeze-thaw cycle treatment, and then subjected to corona discharge treatment to obtain pre-treated yak qula;

[0032] The pretreated yak koji is added into water to dissolve, and then the pH of the system is adjusted to alkaline to obtain a first liquid;

[0033] The first feed liquid is subjected to enzymatic hydrolysis, followed by decolorization and filtration to obtain a second feed liquid;

[0034] The second liquid is subjected to acid precipitation, water washing and drying to obtain the yak casein.

[0035] The embodiment of the present invention provides a method for preparing yak milk casein. On the basis of the prior art, the present invention uses a freeze-thaw cycle-corona discharge combined treatment process without the addition of additional chemical reagents, which not only effectively inhibits the browning phenomenon in the preparation process of yak milk casein, but also can further reduce its allergenicity, thereby providing a new means for preparing yak milk casein. Specifically:

[0036] Freeze-thaw cycle is a physical treatment method. By freezing the yak qula raw material to a low temperature state, and then quickly thawing it to room temperature or higher temperature, it is repeated many times, which is conducive to opening the original tight structure of the yak qula raw material, and helps to promote the transformation of the obtained yak casein into a linear protein structure, providing a more accessible material state for subsequent corona discharge treatment and enzymatic hydrolysis. At the same time, corona discharge can produce high-energy free radicals, ozone and other active substances, which can change the physical and chemical properties of the yak qula raw material and participate in the regulation of browning reaction, reduce the formation of undesirable pigments, improve the color and quality of the product, further promote the change of protein structure and its spatial conformation, reduce its allergenicity, and also facilitate subsequent enzymatic hydrolysis and inhibition of browning reaction.

[0037] In summary, based on the prior art, the present invention not only effectively improves the extraction efficiency of yak milk casein through a freeze-thaw cycle-corona discharge combined treatment process, but also inhibits the browning phenomenon and reduces the allergenicity, providing a novel, environmentally friendly and efficient method for the preparation of yak milk casein.

[0038] In some specific embodiments, the working condition parameters of the freeze-thaw cycle treatment include: freezing temperature of -40 to -20°C, freezing time of 40 to 60 minutes, thawing temperature of 30 to 40°C, thawing time of 60 to 90 minutes, and the number of freeze-thaw cycle treatments is 5 to 8 times.

[0039] In some specific embodiments, the working condition parameters of the corona discharge treatment include: the electric field intensity of the corona discharge treatment is 3-8 kV / m 2 The corona discharge treatment time is 10 to 20 seconds.

[0040] In some specific embodiments, the electric field strength is 6 kV / m 2 , the corona discharge treatment time is 15 seconds.

[0041] In some specific embodiments, the step of adding the pretreated yak koji to water for dissolution, and then adjusting the pH of the system to alkaline to obtain the first feed solution comprises the following process:

[0042] The pretreated yak qula and water are stirred at a weight ratio of 1:1, and then 0.5-1% by weight of calcium hydroxide is added to adjust the pH to 8-9 and centrifuge to collect the filtrate to obtain the first feed liquid.

[0043] In some specific embodiments, the working condition parameters of the enzymatic hydrolysis include: the enzymatic hydrolysis pH is 4.2-4.5, the enzymatic hydrolysis temperature is 33-37°C, the enzymatic hydrolysis time is 8-15 minutes, and the enzymatic hydrolysis is carried out using a composite enzyme composed of lipase, lactase and trypsin in a weight ratio of (1-2):(3-5):(4-6). The amount of the composite enzyme added is 0.03-0.07g per 1kg of the yak qula raw material.

[0044] In some specific embodiments, the decolorization method includes using activated carbon for decolorization, and the weight of the activated carbon added is 0.5-1% of the weight of the yak qula raw material.

[0045] In some specific embodiments, the step of subjecting the second liquid to acid precipitation, water washing and drying to obtain the yak casein comprises the following process:

[0046] At 28-32° C. and pH 4.5-5.0, the second liquid is acidified with lactic acid at a dilution ratio of 1:(5-7) to obtain a crude yak casein product;

[0047] The crude yak casein product is washed with water and vacuum dried to obtain the yak casein.

[0048] It should be noted that in the method for preparing yak casein provided in the embodiment of the present invention, the raw materials involved, unless otherwise specified or limited, can all be commercially available products; at the same time, the process steps and parameters involved can be carried out according to the existing method for preparing yak casein or using existing equipment in a conventional operating manner, and the present invention document will not repeat them.

[0049] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually measured according to current standards. If there is no corresponding current standard, then the conditions recommended by the manufacturer are followed.

[0050] Example 1

[0051] This example provides a method for preparing yak casein, the method comprising the following steps:

[0052] Step (1): subjecting the crushed yak qula raw material to freeze-thaw cycle treatment, and then subjecting it to corona discharge treatment to obtain pre-treated yak qula; wherein the working condition parameters of the freeze-thaw cycle treatment include: a freezing temperature of -30°C, a freezing time of 50 minutes, a thawing temperature of 35°C, a thawing time of 75 minutes, and the number of freeze-thaw cycle treatments is 6 times; the working condition parameters of the corona discharge treatment include: an electric field strength of 6 kV / m 2 , the corona discharge treatment time is 15 seconds;

[0053] Step (2): stirring the pretreated yak koji obtained in step (1) and water in a weight ratio of 1:1, then adding 0.8% by weight of calcium hydroxide to adjust the pH to 8.5 and centrifugally filtering, collecting the filtrate, and obtaining the first feed liquid;

[0054] Step (3): the first liquid obtained in step (2) is adjusted to a pH of 4.4 and a temperature of 35° C., and then enzymatically hydrolyzed for 10 minutes using a composite enzyme consisting of lipase, lactase and trypsin in a weight ratio of 1.5:4:6, with the composite enzyme added in an amount of 0.05 g per 1 kg of the yak qula raw material; after the enzymatic hydrolysis, activated carbon is used for decolorization, and the weight of the activated carbon added is 0.6% of the weight of the yak qula raw material, and filtered to obtain a second liquid;

[0055] Step (4): At 30° C. and pH 4.6, the second liquid obtained in step (3) is subjected to acid precipitation, water washing and vacuum drying using lactic acid at a dilution ratio of 1:6 to obtain the yak casein.

[0056] The protein content of the yak milk casein obtained in this example is 96.1%, and the yield is 92.1%; and the product has a good appearance, is milky white, and has no peculiar smell.

[0057] Example 2

[0058] This example provides a method for preparing yak casein, the method comprising the following steps:

[0059] Step (1): subjecting the crushed yak qula raw material to freeze-thaw cycle treatment, and then subjecting it to corona discharge treatment to obtain pre-treated yak qula; wherein the working condition parameters of the freeze-thaw cycle treatment include: a freezing temperature of -20°C, a freezing time of 60 minutes, a thawing temperature of 30°C, a thawing time of 90 minutes, and the number of freeze-thaw cycle treatments is 8 times; the working condition parameters of the corona discharge treatment include: an electric field strength of 8 kV / m 2 , the corona discharge treatment time is 10 seconds;

[0060] Step (2): stirring the pretreated yak koji obtained in step (1) and water in a weight ratio of 1:1, then adding 0.8% by weight of calcium hydroxide to adjust the pH to 8.5 and centrifugally filtering, collecting the filtrate, and obtaining the first feed liquid;

[0061] Step (3): the first liquid obtained in step (2) is adjusted to a pH of 4.4 and a temperature of 35° C., and then enzymatically hydrolyzed for 10 minutes using a composite enzyme consisting of lipase, lactase and trypsin in a weight ratio of 1.5:4:6, with the composite enzyme added in an amount of 0.05 g per 1 kg of the yak qula raw material; after the enzymatic hydrolysis, activated carbon is used for decolorization, and the weight of the activated carbon added is 0.6% of the weight of the yak qula raw material, and filtered to obtain a second liquid;

[0062] Step (4): At 30° C. and pH 4.6, the second liquid obtained in step (3) is subjected to acid precipitation, water washing and vacuum drying using lactic acid at a dilution ratio of 1:6 to obtain the yak casein.

[0063] The protein content of the yak milk casein obtained in this example is 95.7%, and the yield is 86.4%; and the product has a good appearance, is milky white, and has no peculiar smell.

[0064] Example 3

[0065] This example provides a method for preparing yak casein, the method comprising the following steps:

[0066] Step (1): subjecting the crushed yak qula raw material to freeze-thaw cycle treatment, and then subjecting it to corona discharge treatment to obtain pre-treated yak qula; wherein the working condition parameters of the freeze-thaw cycle treatment include: a freezing temperature of -40°C, a freezing time of 40 minutes, a thawing temperature of 40°C, a thawing time of 60 minutes, and the number of freeze-thaw cycle treatments is 5 times; the working condition parameters of the corona discharge treatment include: an electric field strength of 3 kV / m 2 , the corona discharge treatment time is 20 seconds;

[0067] Step (2): stirring the pretreated yak koji obtained in step (1) and water in a weight ratio of 1:1, then adding 0.8% by weight of calcium hydroxide to adjust the pH to 8.5 and centrifugally filtering, collecting the filtrate, and obtaining the first feed liquid;

[0068] Step (3): the first liquid obtained in step (2) is adjusted to a pH of 4.4 and a temperature of 35° C., and then enzymatically hydrolyzed for 10 minutes using a composite enzyme consisting of lipase, lactase and trypsin in a weight ratio of 1.5:4:6, with the composite enzyme added in an amount of 0.05 g per 1 kg of the yak qula raw material; after the enzymatic hydrolysis, activated carbon is used for decolorization, and the weight of the activated carbon added is 0.6% of the weight of the yak qula raw material, and filtered to obtain a second liquid;

[0069] Step (4): At 30° C. and pH 4.6, the second liquid obtained in step (3) is subjected to acid precipitation, water washing and vacuum drying using lactic acid at a dilution ratio of 1:6 to obtain the yak casein.

[0070] The protein content of the yak milk casein obtained in this example is 94.9%, and the yield is 88.7%; and the product has a good appearance, is milky white, and has no peculiar smell.

[0071] Comparative Example 1

[0072] This example provides a method for preparing yak milk casein, which differs from Example 1 only in that: in step (1), corona discharge treatment is first performed, and then freeze-thaw cycle treatment is performed; the remaining steps and parameters are the same.

[0073] The above method for preparing yak milk casein comprises the following steps:

[0074] Step (1): subjecting the crushed yak qula raw material to corona discharge treatment, and then subjecting it to freeze-thaw cycle treatment to obtain pre-treated yak qula; wherein the working condition parameters of the freeze-thaw cycle treatment include: a freezing temperature of -30°C, a freezing time of 50 minutes, a thawing temperature of 35°C, a thawing time of 75 minutes, and the number of freeze-thaw cycle treatments is 6 times; the working condition parameters of the corona discharge treatment include: an electric field strength of 6 kV / m 2 , the corona discharge treatment time is 15 seconds;

[0075] Step (2): stirring the pretreated yak koji obtained in step (1) and water in a weight ratio of 1:1, then adding 0.8% by weight of calcium hydroxide to adjust the pH to 8.5 and centrifugally filtering, collecting the filtrate, and obtaining the first feed liquid;

[0076] Step (3): the first liquid obtained in step (2) is adjusted to a pH of 4.4 and a temperature of 35° C., and then enzymatically hydrolyzed for 10 minutes using a composite enzyme consisting of lipase, lactase and trypsin in a weight ratio of 1.5:4:6, with the composite enzyme added in an amount of 0.05 g per 1 kg of the yak qula raw material; after the enzymatic hydrolysis, activated carbon is used for decolorization, and the weight of the activated carbon added is 0.6% of the weight of the yak qula raw material, and filtered to obtain a second liquid;

[0077] Step (4): At 30° C. and pH 4.6, the second liquid obtained in step (3) is subjected to acid precipitation, water washing and vacuum drying using lactic acid at a dilution ratio of 1:6 to obtain the yak casein.

[0078] The protein content of the yak milk casein obtained in this example is 93.8%, and the yield is 83.2%; and the product appearance is poor, slightly dark brown, and has no peculiar smell.

[0079] Test Case

[0080] This example aims to compare the allergenicity of yak milk casein obtained by the method of Example 1, Comparative Example 1 and Example 1 in the prior art CN 102726592 A through LAD2 (human mast cell) cell sensitization experiment.

[0081] 1. Experimental materials: LAD2 (human mast cell) cell line, XGI-1640 culture medium, serum of patients with milk allergy (1:50 dilution for standby use), PBS (phosphate buffered saline), HEPES buffer, yak milk casein samples obtained by the method of Example 1, Comparative Example 1 and Example 1 in the prior art CN102726592A, 7. β-hexosaminidase release rate determination kit.

[0082] 2. Experimental methods:

[0083] 2.1 Cell culture and activation:

[0084] Thawed LAD2 cells were transferred into XGI-1640 medium.

[0085] The cells were activated and cultured in a constant temperature incubator at 37°C and 5% CO2 until the cells were in good condition.

[0086] 2.2 Preparation of cell suspension:

[0087] The concentration of the activated cell suspension was adjusted to 1×10 6 Pieces / mL.

[0088] The cell suspension was seeded onto a 96-well plate, with 100 μL added to each well.

[0089] 2.3. Serum incubation:

[0090] Add 20 μL of milk allergy patient serum (1:50 dilution) to each well.

[0091] Incubate at 37°C, 5% CO2 for 24 hours.

[0092] 2.4. Cell washing:

[0093] The 96-well plate was centrifuged at 500×g for 5 minutes, and the supernatant was removed.

[0094] The cells were washed three times with PBS and the supernatant was removed by centrifugation after each wash.

[0095] 2.5. Sample processing and incubation:

[0096] Add 100 μL of HEPES buffer to each well to resuspend the cells.

[0097] 20 μL of yak milk casein samples obtained by the method of Example 1, Comparative Example 1 and Example 1 in the prior art CN 102726592 A were added respectively.

[0098] Incubate at 37°C for 2 hours.

[0099] 2.6. Determination of β-hexosaminidase release rate:

[0100] The 96-well plate was centrifuged at 500 × g for 5 minutes and the supernatant was collected.

[0101] According to the instructions of the β-hexosaminidase release rate assay kit, the β-hexosaminidase release rate in the supernatant was measured. The β-hexosaminidase release rate (%) of each group of samples was recorded, as shown in Table 1; by comparing the β-hexosaminidase release rates of each group of samples, the sensitization was evaluated. The higher the β-hexosaminidase release rate, the stronger the sensitization.

[0102] Table 1

[0103] Test samples β-hexosaminidase release rate (%) Example 1 20.9 Comparative Example 1 34.7 Basic control group 41.3

[0104] As can be seen from Table 1, the β-hexosaminidase release rate of the yak milk casein provided by the embodiment of the present invention is lower, indicating that it has lower allergenicity.

[0105] In summary, the embodiments of the present invention provide a method for preparing yak casein. On the basis of the prior art, the present invention adopts a freeze-thaw cycle-corona discharge combined treatment process without the addition of additional chemical reagents, which not only effectively inhibits the browning phenomenon in the preparation process of yak casein, but also can further reduce its allergenicity, thereby providing a new means for preparing yak casein.

[0106] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0107] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing yak milk casein, characterized in that: The method comprises the following steps: The crushed yak qula raw material is subjected to freeze-thaw cycle treatment, and then subjected to corona discharge treatment to obtain pre-treated yak qula; The pretreated yak koji is added into water to dissolve, and then the pH of the system is adjusted to alkaline to obtain a first liquid; The first feed liquid is subjected to enzymatic hydrolysis, followed by decolorization and filtration to obtain a second feed liquid; The second liquid is subjected to acid precipitation, water washing and drying to obtain the yak casein.

2. The method for preparing yak milk casein according to claim 1, characterized in that: The working condition parameters of the freeze-thaw cycle treatment include: a freezing temperature of -40 to -20°C, a freezing time of 40 to 60 minutes, a thawing temperature of 30 to 40°C, a thawing time of 60 to 90 minutes, and the number of freeze-thaw cycle treatments is 5 to 8 times.

3. The method for preparing yak milk casein according to claim 1, characterized in that: The working condition parameters of the corona discharge treatment include: the electric field intensity of the corona discharge treatment is 3-8 kV / m 2 The corona discharge treatment time is 10 to 20 seconds.

4. The method for preparing yak milk casein according to claim 3, characterized in that: The electric field strength is 6 kV / m 2 , the corona discharge treatment time is 15 seconds.

5. The method for preparing yak milk casein according to claim 1, characterized in that: The step of adding the pretreated yak koji to water for dissolution, and then adjusting the pH of the system to alkaline to obtain the first feed solution comprises the following process: The pretreated yak qula and water are stirred at a weight ratio of 1:1, and then 0.5-1% by weight of calcium hydroxide is added to adjust the pH to 8-9 and centrifuge to collect the filtrate to obtain the first feed liquid.

6. The method for preparing yak milk casein according to claim 1, characterized in that: The working condition parameters of the enzymatic hydrolysis include: an enzymatic hydrolysis pH of 4.2 to 4.5, an enzymatic hydrolysis temperature of 33 to 37° C., an enzymatic hydrolysis time of 8 to 15 minutes, and enzymatic hydrolysis using a composite enzyme consisting of lipase, lactase and trypsin in a weight ratio of (1 to 2):(3 to 5):(4 to 6). The amount of the composite enzyme added is 0.03 to 0.07 g per 1 kg of the yak qula raw material.

7. The method for preparing yak milk casein according to claim 1, characterized in that: The decolorization method includes using activated carbon for decolorization, and the added weight of the activated carbon is 0.5-1% of the weight of the yak qula raw material.

8. The method for preparing yak milk casein according to claim 1, characterized in that: The step of subjecting the second liquid to acid precipitation, water washing and drying to obtain the yak casein protein comprises the following process: At 28-32° C. and pH 4.5-5.0, the second liquid is acidified with lactic acid at a dilution ratio of 1:(5-7) to obtain a crude yak casein product; The crude yak casein product is washed with water and vacuum dried to obtain the yak casein.

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