Casein and preparation method thereof
By centrifuging and washing yak milk at 6-10℃, and using two calcium-ethanol precipitation methods, the problems of low purity and low degreasing rate in the existing casein production process are solved, and high purity and low fat are achieved The content of casein is suitable for industrial production.
Patent Information
- Application Number
- CN202411675860.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2025-02-14
AI Technical Summary
In the existing casein production process, casein has low purity and low degreasing rate, resulting in high ash content, dark color and poor stability of casein, making it difficult to meet the needs of industrial production.
Centrifuge yak milk at 6-10°C and wash it with water, and then purify casein by two calcium-ethanol precipitation methods to improve the purity of casein and reduce the fat content.
It achieves high purity and low fat content of casein, is suitable for industrial production, and improves the functional characteristics and stability of casein.
Smart Images
Figure BDA0005147019970000051 
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of dairy product preparation, and in particular relates to casein and a preparation method thereof. Background Art
[0002] Yak milk is rich in protein, amino acids, minerals and vitamins, and is easy to digest and absorb and rich in nutrition. Yak milk has a high casein content and rich casein components. At present, there are three main processes for producing casein, namely acid casein, enzyme casein and membrane separation casein. The casein produced by these three methods has certain shortcomings, which are mainly reflected in the following aspects: one is that the purity of casein (on a dry basis) is not high, and the other is that the degreasing rate is low. The obtained casein has high ash content, deep color and poor stability. Its functional properties (such as foaming and emulsifying properties) are affected, and it is difficult to meet the needs of industrial production, thereby limiting the application scope of casein. Summary of the invention
[0003] In view of this, the object of the present invention is to provide a casein and a preparation method thereof. The casein prepared by the method of the present invention has high purity and low fat content.
[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0005] The present invention provides a method for preparing casein, comprising the following steps:
[0006] (1) centrifuging yak milk at 6-10° C. to collect a first precipitate;
[0007] (2) washing the first precipitate with water at 6 to 10° C. and collecting precipitate 1;
[0008] (3) mixing the precipitate 1 with water to obtain a mixed solution, heating the mixed solution, adding calcium chloride to the mixed solution for the first time, stirring, adding an ethanol solution for alcohol precipitation, and collecting the precipitate 2 and the supernatant;
[0009] (4) heating the supernatant, adding calcium chloride for the second time, stirring, adding ethanol solution for alcohol precipitation, collecting precipitate 3, combining precipitate 2 and precipitate 3, and obtaining casein;
[0010] The mass ratio of the precipitate 1 to the first added calcium chloride is 45-55:10;
[0011] The mass ratio of the precipitate 1 to the second added calcium chloride is 45-55:5.
[0012] Preferably, in step (1), the centrifugation is carried out at 4500-5500 r / min for 15-25 min.
[0013] Preferably, in step (2), the washing is performed 1 to 3 times; during each washing, the mass volume ratio of the first precipitate to water is 1:9 to 11.
[0014] Preferably, in step (2), the precipitate 1 is collected by centrifugation at 4500-5500 r / min for 10-20 min.
[0015] Preferably, in step (3), the mass volume ratio of the precipitate 1 to water is 1:15-25.
[0016] Preferably, in step (3), the temperature of the heated mixed solution is 35-40° C.; and the volume ratio of the water to the ethanol solution is 1:0.5-1.5.
[0017] Preferably, in step (4), the temperature at which the supernatant is heated is 35-40° C.; and the volume ratio of the supernatant to the ethanol solution is 1:0.5-1.5.
[0018] Preferably, in step (3) or (4), the temperature of the alcohol precipitation is 3 to 6° C., and the time of the alcohol precipitation is 4 to 6 hours.
[0019] Preferably, in step (3) or (4), the volume percentage of the ethanol solution is 85% to 95%.
[0020] The present invention also provides casein prepared by the above preparation method.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] The present invention provides casein and a preparation method thereof. The present invention can reduce the fat content in casein by centrifuging yak milk at 6 to 10°C and washing with water at 6 to 10°C, and can further improve the purity of casein and reduce the fat content by purifying casein by two calcium-ethanol precipitation methods. The preparation method of the present invention is simple to operate, low in cost, and suitable for industrial production. DETAILED DESCRIPTION
[0023] The present invention provides a method for preparing casein, comprising the following steps:
[0024] (1) centrifuging yak milk at 6-10° C. to collect a first precipitate;
[0025] (2) washing the first precipitate with water at 6 to 10° C. and collecting precipitate 1;
[0026] (3) mixing the precipitate 1 with water to obtain a mixed solution, heating the mixed solution, adding calcium chloride to the mixed solution for the first time, stirring, adding an ethanol solution for alcohol precipitation, and collecting the precipitate 2 and the supernatant;
[0027] (4) heating the supernatant, adding calcium chloride for the second time, stirring, adding ethanol solution for alcohol precipitation, collecting precipitate 3, combining precipitate 2 and precipitate 3, and obtaining casein;
[0028] The mass ratio of the precipitate 1 to the first added calcium chloride is 45-55:10;
[0029] The mass ratio of the precipitate 1 to the second added calcium chloride is 45-55:5.
[0030] In step (1), the centrifugation is carried out at 4500-5500 r / min for 15-25 min. The present invention can ensure better precipitation of casein in yak milk by centrifuging yak milk at 6-10°C, thereby ensuring the casein content and better separating fat.
[0031] In step (2), the present invention washes the first precipitate with water at 6 to 10° C., which can further improve the purity of casein extracted from yak milk. The number of washings is 1 to 3 times, more preferably 2 times; during each washing, the mass volume ratio of the first precipitate to water is 1:9 to 11, more preferably 1:9, 1:10 or 1:11. The present invention further reduces the fat in the precipitate 1 by washing the first precipitate with water at 6 to 10° C. The method of collecting the precipitate 1 is centrifugation at 4500 to 5500 r / min for 10 to 20 min, such as centrifugation at 5000 r / min for 15 min.
[0032] In step (3), the mass volume ratio of the precipitate 1 to water is preferably 1:15-25, more preferably 1:18-23, and more preferably 1:20. The stirring time is 15-25 min, such as 20 min. The temperature of the heated mixed solution is 35-40°C, more preferably 36-39°C, and more preferably 38°C; the volume ratio of water to ethanol solution is preferably 1:0.5-1.5, such as 1:0.5, 1:1 or 1:1.5. In step (4), the temperature of the supernatant heating is 35-40°C, more preferably 36-39°C, and more preferably 38°C; the volume ratio of the supernatant to the ethanol solution is 1:0.5-1.5, such as 1:0.5, 1:1 or 1:1.5. In step (3) or (4), the temperature of the alcohol precipitation is 3 to 6°C, preferably 4 to 5°C, and the time of the alcohol precipitation is preferably 4 to 6 hours, more preferably 4.5 to 5.5 hours, and more preferably 5 hours. In step (3) or (4), the volume percentage of the ethanol solution is preferably 85% to 95%. For example, 90%. The present invention has found through experiments that when purifying casein, adding different amounts of calcium chloride twice and then performing ethanol precipitation can efficiently extract casein from yak milk and improve the purity of casein.
[0033] The present invention also provides casein prepared by the above preparation method.
[0034] The casein prepared by the invention has high purity and low fat content.
[0035] In the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.
[0036] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.
[0037] Example 1
[0038] A method for preparing casein, comprising the following steps:
[0039] (1) Centrifuge yak milk at 8°C at 5000 r / min for 20 min to collect the first precipitate;
[0040] (2) washing 20 g of the first precipitate with 200 mL of 8° C. water, centrifuging at 5000 r / min for 20 min, collecting the second precipitate, adding 150 mL of 8° C. water to 15 g of the second precipitate, centrifuging at 5000 r / min for 20 min, and collecting the third precipitate;
[0041] (3) Mix 50 g of the third precipitate with 1000 mL of water, heat to 38° C., add 10 g of CaCl2, stir for 30 min, add 1000 mL of 90% ethanol solution, precipitate at 5° C. for 5 h, centrifuge at 4000 r / min for 15 min, collect the fourth precipitate and supernatant, heat the supernatant to 38° C., add 5 g of CaCl2 to the heated supernatant, stir for 15 min, add an equal volume of 90% ethanol solution to the supernatant, precipitate at 5° C. for 5 h, centrifuge at 4000 r / min for 15 min, collect the fifth precipitate, combine the fourth precipitate and the fifth precipitate, and freeze-dry to obtain casein.
[0042] Example 2
[0043] A method for preparing casein, comprising the following steps:
[0044] (1) Centrifuge yak milk at 6°C at 5000 r / min for 15 min to collect the first precipitate;
[0045] (2) washing 20 g of the first precipitate with 180 mL of 6° C. water, centrifuging at 5000 r / min for 15 min, collecting the second precipitate, adding 135 mL of 6° C. water to 15 g of the second precipitate, centrifuging at 5000 r / min for 15 min, and collecting the third precipitate;
[0046] (3) 45 g of the third precipitate was mixed with 900 mL of water, heated to 35° C., 10 g of CaCl2 was added, and the mixture was stirred for 30 min. Then, 900 mL of 90% ethanol solution was added, and the mixture was precipitated at 5° C. for 5 h. The mixture was centrifuged at 4000 r / min for 15 min. The fourth precipitate and the supernatant were collected. The supernatant was heated to 35° C., 5 g of CaCl2 was added to the heated supernatant, and the mixture was stirred for 15 min. An equal volume of 90% ethanol solution was added to the supernatant, the mixture was precipitated at 5° C. for 5 h. The mixture was centrifuged at 4000 r / min for 15 min. The fifth precipitate was collected. The fourth precipitate and the fifth precipitate were combined, and freeze-dried to obtain casein.
[0047] Example 3
[0048] A method for preparing casein, comprising the following steps:
[0049] (1) Centrifuge yak milk at 10°C at 5000 r / min for 15 min to collect the first precipitate;
[0050] (2) washing 20 g of the first precipitate with 220 mL of 10° C. water, centrifuging at 5000 r / min for 15 min, collecting the second precipitate, adding 165 mL of 10° C. water to 15 g of the second precipitate, centrifuging at 5000 r / min for 15 min, and collecting the third precipitate;
[0051] (3) Mix 55 g of the third precipitate with 1100 mL of water, heat to 40° C., add 12 g of CaCl2, stir for 30 min, add 1100 mL of 90% ethanol solution, precipitate at 5° C. for 5 h, centrifuge at 4000 r / min for 15 min, collect the fourth precipitate and the supernatant, heat the supernatant to 40° C., add 6 g of CaCl2 to the heated supernatant, stir for 15 min, add an equal volume of 90% ethanol solution to the supernatant, precipitate at 5° C. for 5 h, centrifuge at 4000 r / min for 15 min, collect the fifth precipitate, combine the fourth precipitate and the fifth precipitate, and freeze-dry to obtain casein.
[0052] Comparative Example 1
[0053] The difference between this comparative example and Example 1 is that this comparative example does not include step (2) of Example 1.
[0054] A method for preparing casein, comprising the following steps:
[0055] (1) Centrifuge yak milk at 8°C at 5000 r / min for 20 min to collect the first precipitate;
[0056] (2) 50 g of the first precipitate was mixed with 1000 mL of water, heated to 38° C., 10 g of CaCl2 was added, and the mixture was stirred for 30 min. Then, 1000 mL of 90% ethanol solution was added, and the mixture was precipitated at 5° C. for 5 h. The mixture was centrifuged at 4000 r / min for 15 min. The second precipitate and the supernatant were collected. The supernatant was heated to 38° C., 5 g of CaCl2 was added, and the mixture was stirred for 15 min. Then, an equal volume of 90% ethanol solution was added to the supernatant. The mixture was precipitated at 5° C. for 5 h. The mixture was centrifuged at 4000 r / min for 15 min. The third precipitate was collected. The second precipitate and the third precipitate were combined, and freeze-dried to obtain casein.
[0057] Comparative Example 2
[0058] The difference between this comparative example and Example 1 is that this comparative example only performs the calcium-ethanol precipitation method once;
[0059] A method for preparing casein, comprising the following steps:
[0060] (1) Centrifuge yak milk at 8°C at 5000 r / min for 20 min to collect the first precipitate;
[0061] (2) washing 20 g of the first precipitate with 200 mL of 8° C. water, centrifuging at 5000 r / min for 20 min, collecting the second precipitate, adding 150 mL of 8° C. water to 15 g of the second precipitate, centrifuging at 5000 r / min for 20 min, and collecting the third precipitate;
[0062] (3) 50 g of the third precipitate was mixed with 1000 mL of water, heated to 38° C., 15 g of CaCl2 was added, and stirred for 30 min. Then, 1000 mL of 90% ethanol solution was added, and the mixture was precipitated at 5° C. for 5 h. The mixture was centrifuged at 4000 r / min for 15 min, and the fourth precipitate was collected and freeze-dried to obtain casein.
[0063] Test Example 1
[0064] (1) The purity of casein prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was measured respectively:
[0065] Draw a standard curve: weigh 0.1 g of pure casein, dissolve it in 0.1 mol / mL NaOH solution and make up to 100 mL to prepare a 1 mg / mL casein standard solution.
[0066] Prepare 2, 0.4, 0.6, 0.8, and 1.0 mg / mL casein solutions with the standard solution, calibrate with 0.1 mol / mL NaOH solution, and measure the absorbance of each group at 280 nm. Draw a standard curve with casein concentration as the horizontal axis and absorbance at 280 nm as the vertical axis.
[0067] Purity determination: 0.1 g of casein prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was weighed and dissolved in 0.1 mol / mL NaOH solution and the volume was fixed to 100 mL. The absorbance of the solution at 280 nm was measured, and the casein content in the sample was calculated according to the standard curve. The determination was performed three times, and the results are shown in Table 1.
[0068] Table 1 Different casein purity test results
[0069]
[0070] The results in Table 1 show that the purity of the casein prepared by the present invention is as high as 98.4% or more, which is higher than the purity of the casein prepared in Comparative Examples 1 to 2. Therefore, the casein prepared by the method of the present invention has high purity.
[0071] (2) Determination of fat content of casein prepared in Examples 1 to 3 and Comparative Examples 1 to 2
[0072] Determination of fat:
[0073] (1) Weigh 1 g of casein prepared in Examples 1 to 3 and Comparative Examples 1 to 2 and 1 g of pure casein, add appropriate amounts of a mixture of water and HCl in a volume ratio of 4:5, heat in a water bath at 70 to 80° C., and stir every 10 minutes until the casein is completely dissolved;
[0074] (2) Take out the test tube, add 5 mL of ethanol, mix, cool and pour into the test tube, wash the test tube with 12.5 mL of ether, stopper it, shake and release the air, let it stand for 15 minutes, wash the stopper and the fat attached to the bottle with ether-petroleum ether, let it stand for 15 minutes, aspirate the clarified supernatant into a conical flask with constant weight, add 2.5 mL of ether to the stoppered test tube, shake and let it stand, and then put the supernatant into the conical flask.
[0075] (3) Evaporate the conical flask to dryness on a water bath, dry in an oven at 100°C for 2 h, cool in a desiccator for 30 min, weigh, and calculate the fat content.
[0076] Calculation result: Fat (%) = fat content (g) ÷ casein content (g) × 100.
[0077] Table 2 Determination of fat content of casein obtained by different preparation methods
[0078]
[0079] From the results in Table 2, it can be seen that the fat content of casein prepared by the preparation method of the present invention is less than 2%. Compared with Comparative Examples 1 to 2, the fat content of casein prepared by the preparation method of the present invention is low.
[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing casein, characterized in that: The following steps are involved: (1) centrifuging yak milk at 6-10° C. to collect a first precipitate; (2) washing the first precipitate with water at 6 to 10° C. and collecting precipitate 1; (3) mixing the precipitate 1 with water to obtain a mixed solution, heating the mixed solution, adding calcium chloride to the mixed solution for the first time, stirring, adding an ethanol solution for alcohol precipitation, and collecting the precipitate 2 and the supernatant; (4) heating the supernatant, adding calcium chloride for the second time, stirring, adding ethanol solution for alcohol precipitation, collecting precipitate 3, combining precipitate 2 and precipitate 3, and obtaining casein; The mass ratio of the precipitate 1 to the first added calcium chloride is 45-55:10; The mass ratio of the precipitate 1 to the second added calcium chloride is 45-55:
5.
2. The preparation method according to claim 1, characterized in that: In step (1), the centrifugation method is 4500-5500 r / min for 15-25 min.
3. The preparation method according to claim 1, characterized in that: In step (2), the washing is performed 1 to 3 times; during each washing, the mass volume ratio of the first precipitate to water is 1:9 to 11.
4. The preparation method according to claim 1, characterized in that: In step (2), the precipitate 1 is collected by centrifugation at 4500-5500 r / min for 10-20 min.
5. The preparation method according to claim 1, characterized in that: In step (3), the mass volume ratio of the precipitate 1 to water is 1:15-25.
6. The preparation method according to claim 1, characterized in that: In step (3), the temperature of the heated mixed solution is 35-40° C.; and the volume ratio of the water to the ethanol solution is 1:0.5-1.
5.
7. The preparation method according to claim 1, characterized in that: In step (4), the temperature at which the supernatant is heated is 35-40° C.; and the volume ratio of the supernatant to the ethanol solution is 1:0.5-1.
5.
8. The preparation method according to claim 1, characterized in that: In step (3) or (4), the temperature of the alcohol precipitation is 3 to 6° C., and the time of the alcohol precipitation is 4 to 6 hours.
9. The preparation method according to claim 1, characterized in that: In step (3) or (4), the volume percentage of the ethanol solution is 85% to 95%.
10. Casein prepared according to the preparation method according to any one of claims 1 to 9.