A process for the processing of whey proteins

Abstract

The application belongs to the technical field of protein processing, and particularly relates to a processing technology of whey protein, which comprises the following steps: subjecting cow milk to homogenization treatment; adding a foaming substance into the homogenized liquid, wherein the foaming substance is bicarbonate and citric acid, and the addition amount of the foaming substance is 3-7% of the mass of fresh cow milk; collecting the supernatant of the cow milk under the condition of high-speed centrifugation at room temperature; and separating and removing casein in the supernatant of the cow milk to obtain whey protein liquid of the cow milk. In the application, the addition of the foaming substance can change the structure of casein colloidal particles, so that casein is separated in large quantities, the purity of the whey protein is improved, a complicated purification step is not needed, the purification cost of the whey protein is reduced, and resources are saved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of protein processing, and particularly relates to a processing technology of whey protein, and more particularly to a technology for extracting and processing whey protein from cow milk. BACKGROUND

[0002] Whey protein is a protein extracted from cow milk, which has high nutritional value and is easy to digest and absorb. Whey protein contains various essential amino acids and branched-chain amino acids, and also contains a variety of bioactive protein components such as beta-lactoglobulin, alpha-lactalbumin, lactoferrin, immunoglobulin, bovine serum albumin and bioactive peptides. It is the best source of protein for the human body. Whey protein has many benefits for the human body. It can help control weight, increase muscle mass, promote the growth of teeth and bones, and enhance immunity. At the same time, it also has significant effects on anti-fatigue, anti-aging, promoting the development of infants' brains, and maintaining cardiovascular health. Adding whey protein to the diet can protect the health of people of all ages.

[0003] The processing and purification methods of whey protein include ethanol fractionation precipitation method, membrane filtration method, etc. Among them, the ethanol fractionation precipitation method uses ethanol to cause protein precipitation, which requires selecting a suitable ethanol concentration. The ethanol concentration is related to the molecular weight and biochemical characteristics of the impurities to be removed. However, ethanol can easily cause protein denaturation, and the precipitated protein cannot be redissolved, resulting in low yield of whey protein. The membrane filtration method uses a semi-permeable membrane as a barrier to separate and filter proteins of different molecular weights according to the concentration difference on both sides of the semi-permeable membrane. This method does not cause protein denaturation, but the membrane filtration speed is slow, and long-time separation and filtration operation can easily cause pollution and deterioration, also resulting in low yield of whey protein.

[0004] In order to improve the extraction rate of whey protein, many scholars have also conducted other researches. For example, CN106387088B reduces the content of casein protein and improves the yield of yak whey protein; "Long L, Wei Z, Xiaodong Y, et al. Process optimization for foam separation of yak whey protein by responsesurface methodology [J]. Separation Science and Technology, 2018, 53(14):2327-2337" effectively recovers whey protein from yak whey wastewater, and establishes a foam separation method suitable for nomadic herdsmen. The recovery rate of whey protein can reach 88.3%, and the enrichment rate can reach 9.25.

[0005] Although the main proteins of cow milk and goat milk are casein and whey protein, the mass ratio of casein to whey protein in goat milk is about 65:35, and the mass ratio of casein to whey protein in cow milk is about 80:20, that is, cow milk also contains a lot of casein, which greatly interferes with the extraction of whey protein. However, the prior art only makes targeted improvements on the separation of casein and whey protein in goat milk, and rarely separates casein and whey protein in cow milk. Therefore, it is necessary to provide a method for effectively separating casein and whey protein in cow milk. SUMMARY

[0006] In order to effectively separate casein and whey protein in cow milk and obtain high-purity and high-yield cow milk whey protein, the present application provides a processing process of whey protein, which uses cow milk as raw material, and obtains high-purity whey protein through separation, extraction and processing.

[0007] It should be noted that there are great differences between the components of cow milk and goat milk. For example, most of the sugars in cow milk are lactose, and there are also a small amount of glucose, galactose, etc. In goat milk, lactose and galactose are the main components, and the lactose particles in goat milk are relatively small, so goat milk is usually more easily digested and absorbed by the human body than cow milk. For example, the content of folic acid in cow milk is higher than that in goat milk, while the content of vitamin A, D, etc. in goat milk is higher than that in cow milk. With the difference between the components of cow milk and goat milk, the difference in chemical properties of compounds, the impurity components that need to be removed for the target product of extracting whey protein are different, and the interference is also different. Therefore, when extracting and purifying whey protein, the existing technology often uses different processing methods for goat milk and cow milk, such as "CN106387088B" and "Long L, Wei Z, Xiaodong Y, et al. Process optimization for foam separation of yak whey protein by response surface methodology [J]. Separation Science and Technology, 2018, 53(14):2327-2337" use completely different processing methods.

[0008] Therefore, the purpose of the present application is to provide a processing process of whey protein, which is aimed at the separation and processing of whey protein in cow milk, and includes the following steps:

[0009] (1) homogenizing fresh cow milk;

[0010] The homogenization treatment refers to placing fresh milk in a 37-40℃ constant-temperature water bath shaker for incubation for 20-30 min, and the rotation speed of the shaker is 60-80 rpm. Fresh milk refers to milk that is separated from a cow within 24 h, and the structure of nutritional components has not changed, and the content of whey protein is also at a relatively high level.

[0011] Milk fat is the fat part in milk. Due to the different polarity of milk fat and protein in milk, in fresh milk, the milk fat is mainly dispersed in the form of micro-fat balls of different sizes, and the casein in fresh milk is mixed with other proteins, and the mixing degree of protein and fat is not high. At this time, if fresh milk is directly centrifuged, the milk fat cannot be combined with casein, and the operation of high-speed centrifugation can only separate fat from protein and other substances, and the casein precipitate is less.

[0012] After the fresh milk is subjected to the homogenization treatment, the milk fat is fully mixed with protein, sugar and other substances, and the mixing degree of protein and fat is high. Although the just-homogenized milk has a high mixing degree, due to the different charges and polarities of protein, fat, sugar and other substances in the milk, the homogenized milk has a tendency to become heterogeneous again, and the motion potential of protein, fat and sugar molecules is large. At this time, in combination with high-speed centrifugation, the fat layer and the supernatant of milk and protein are fully separated, and a large amount of casein can be precipitated.

[0013] (2) After the homogenization is completed, the sample and the container containing the sample are transferred to the experimental bench, and the foaming substance is immediately added to the homogenized liquid. It is noted that the foaming substance is added within 5 min after the homogenization is completed, and the effect is best.

[0014] At pH 4.6, casein is precipitated but whey protein is not precipitated, which is the basis for separating casein and whey protein. Whey protein has good solubility and a relatively small molecular weight, while casein has a large molecular weight and a complex quaternary structure, and exists in the form of casein colloidal particles, and the casein structure also contains a phosphate group. According to the research of the present application, the addition of the foaming substance before high-speed centrifugation after the homogenization of milk can change the structure of casein colloidal particles, so that the casein is precipitated during the subsequent high-speed centrifugation.

[0015] In the present application, the foaming substance is bicarbonate and citric acid, and the addition amount of the foaming substance is 3-7% of the mass of fresh milk. The water content in fresh milk is about 85-90%, and after the bicarbonate and citric acid are added to fresh milk, a large amount of carbon dioxide is generated to form foam. Preferably, the bicarbonate is sodium bicarbonate, also known as baking soda. Food-grade sodium bicarbonate has high safety, so food-grade sodium bicarbonate is selected as the raw material in the present application. Citric acid, also known as citric acid, is also a safe additive of food grade. Sodium citrate, the reaction product of citric acid and sodium bicarbonate, is also a substance with high safety, and the reaction equation is as follows:

[0016] 3NaHCO3+C6H8O7(+H2O)=Na3C6H5O7+3CO2↑+3H2O, see Figure 1 .

[0017] (3) centrifuging at room temperature 18-25℃, centrifugal speed≥17000g, centrifugal time≥0.5h; after centrifuging, discarding the upper fat and the lower precipitate, collecting the supernatant of the milk;

[0018] (4) removing casein in the supernatant of the milk by isoelectric precipitation to obtain whey protein solution.

[0019] Preferably, in the foaming agent, the molar ratio of sodium bicarbonate to citric acid is 3:1, and both of them can be completely reacted.

[0020] Preferably, in the processing technology of whey protein, the adding amount of the foaming agent is 4-5% of the mass of fresh milk. The foam generated by the adding amount can remove more casein.

[0021] Preferably, in the processing technology of whey protein, the pH of the supernatant of the milk is adjusted to 4.6-4.7, and then the supernatant is left to stand until no more precipitate is precipitated, and then the precipitate containing a large amount of casein is removed by centrifugation, and the supernatant containing whey protein is collected, so that the whey protein solution of milk is obtained. It should be noted that the pH is adjusted by using conventional reagents such as hydrochloric acid or sodium hydroxide.

[0022] Preferably, in the processing technology of whey protein, in step (4), the centrifugation is carried out at 4℃ for 20-30min at 5000g.

[0023] Preferably, in the processing technology of whey protein, the supernatant of the milk is added with the foaming agent again, and then the casein in the supernatant of the milk is removed.

[0024] Preferably, in the processing technology of whey protein, the mass of the foaming agent added in the supernatant of the milk for the second time is 1-2% of the mass of the supernatant of the milk. Since a large amount of fat and some casein have been removed from the supernatant of the milk, foaming becomes easy, so in the purpose of saving materials and cost, too much foaming agent does not need to be added this time.

[0025] Preferably, in the processing technology of whey protein, the whey protein solution is freeze-dried to obtain freeze-dried powder, which is convenient for transportation.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] After the fresh milk is homogenized, the milk fat is fully mixed with the protein, sugar and other substances, at this time, the fat layer is separated from the supernatant of the milk and the protein, and a large amount of casein can be precipitated. According to the research of the present application, the addition of the foaming substance can change the structure of the casein colloidal particles, separate a large amount of casein, and improve the purity of the whey protein. Without complex purification steps, the cost of whey protein purification is reduced, and resources are saved.

[0028] According to the research results of the present application, the foaming substance is added before homogenization and high-speed centrifugation, and in the range of 4-5% of the addition amount, the casein and whey protein show a better separation degree.

[0029] According to the research results of the present application, the foaming substance is added for the second time before the isoelectric point separation, which can deeply remove the casein and improve the yield and purity of the whey protein. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The reaction equation of the foaming principle of the present application.

[0031] Figure 2 The SDS-PAGE results of each sample. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solutions of the present application and implement them, the present application will be further described below in combination with specific embodiments and drawings. In the description of the present application, if not specially stated, the reagents used are commercially available, and the methods used are conventional techniques in the art.

[0033] After the fresh milk is homogenized, the milk fat is fully mixed with the protein, sugar and other substances, and the just-homogenized milk has a high mixing degree, but due to the different charges and polarities of the protein, fat and sugar in the milk, the homogenized milk has a tendency to become heterogeneous again. At this time, the fat layer is separated from the supernatant of the milk and the protein, and a large amount of casein can be precipitated. According to the research of the present application, the foaming substance is added before homogenization and high-speed centrifugation, which can change the structure of the casein colloidal particles and precipitate the casein during subsequent high-speed centrifugation.

[0034] Based on this, the present application provides a processing technology of whey protein, which comprises the following steps:

[0035] (1) Homogenizing the milk.

[0036] (2) Add a foaming substance to the homogenized liquid, the foaming substance being bicarbonate and citric acid, the foaming substance being added in an amount of 3-7% of the mass of the fresh milk; after the bicarbonate and citric acid are added to the fresh milk, a large amount of carbon dioxide is generated when water is encountered, forming foam. The casein colloid particle structure is changed, so that the casein is precipitated when subsequent high-speed centrifugation is performed. Note that in the following examples and control groups, after homogenization is completed, the sample is transferred together with the container containing the sample to the benchtop, and the foaming substance is immediately added, within 3 minutes after homogenization is completed.

[0037] (3) High-speed centrifugation is performed at room temperature, and the supernatant of the milk is collected.

[0038] (4) The casein in the supernatant of the milk is separated and removed by isoelectric point precipitation, to obtain whey protein liquid of the milk. At pH 4.6, the casein is precipitated while the whey protein is not precipitated, and this characteristic is the basis for separating the casein and the whey protein.

[0039] Some specific examples of the present application are described below.

[0040] I. Reagents

[0041] (1) Fresh milk: purchased on the market.

[0042] (2) Sodium bicarbonate: food grade.

[0043] (3) Citric acid: food grade.

[0044] (4) SDS-PAGE loading buffer: purchased from Thermo.

[0045] (5) Whey protein detection kit, Shanghai Tongwei.

[0046] (6) Casein detection kit, Shanghai Zhiyan.

[0047] II. Methods

[0048] (1) SDS-PAGE

[0049] 5 μL of the whey protein liquid sample of the milk is mixed with the loading buffer and boiled for 5 min, and then cooled for standby use.

[0050] Prepare 15% separation gel and 5% concentration gel, and then add the treated sample to the electrophoresis tank, and perform electrophoresis at 100 V for 30 min, and then perform electrophoresis at 140 V for 100 min. After the electrophoresis is completed, perform Coomassie brilliant blue G-250 staining on the gel for 30 min, and then decolorize until the background is transparent.

[0051] Among them, the SDS-PAGE conditions of the samples of each example and control group are the same, such as the same loading amount during electrophoresis, and other electrophoresis operation methods are also the same.

[0052] (2) Calculation of whey protein yield

[0053] Whey protein yield % = 100 x (mass of whey protein in whey protein solution of step (4) / mass of whey protein in fresh milk)

[0054] (3) Calculation of casein removal rate

[0055] Casein removal rate A % = 100 x [(mass of casein in fresh milk - mass of casein in supernatant of step (3) / mass of casein in fresh milk]

[0056] Casein removal rate B % = 100 x [(mass of casein in fresh milk - mass of casein in whey protein solution of step (4) / mass of casein in fresh milk]

[0057] (4) Data processing

[0058] The casein removal rate and the yield of whey protein are measured in triplicate, and the average value is taken.

[0059] Example 1

[0060] A processing method of whey protein, comprising the following steps:

[0061] (1) Homogenizing fresh milk;

[0062] The homogenization refers to incubating fresh milk in a 37°C constant temperature water bath shaker for 20 min, and the rotation speed of the shaker is 60 rpm.

[0063] Fresh milk refers to milk that is separated from a cow within 24 hours.

[0064] (2) Adding foaming material to the homogenized liquid and standing for 10 min;

[0065] The foaming material is sodium bicarbonate and citric acid, and the addition amount of the foaming material is 3% of the mass of fresh milk, and the molar ratio of sodium bicarbonate to citric acid is 3:1.

[0066] The reaction product of citric acid and sodium bicarbonate, sodium citrate, is also a high-safety material, and the reaction equation is as follows:

[0067] 3NaHCO3+C6H8O7(+H2O)=Na3C6H5O7+3CO2↑+3H2O

[0068] (3) Centrifuging at 18°C, the centrifugation speed is 17000g, and the centrifugation time is 30 min; after centrifugation, the upper fat and the lower precipitate are discarded, and the supernatant of milk is collected.

[0069] (4) Isolate and remove casein in the supernatant of bovine milk by isoelectric precipitation to obtain whey protein solution of bovine milk, specifically:

[0070] Adjust the pH of the supernatant of bovine milk to 4.6, stand for 30 min, no precipitate is precipitated, then remove the precipitate by centrifugation at 5000g for 20 min at 4°C, the precipitate contains a large amount of casein, collect the supernatant, the supernatant contains whey protein, thus obtaining whey protein solution of bovine milk.

[0071] III. Effect of different amounts of foaming substances (the first amount of addition) on extraction

[0072] The amount of foaming substance added is used as a single factor change, and the effects of different amounts of foaming substance on extraction are explored by Examples 2-5, including the following steps:

[0073] (1) Homogenize fresh bovine milk;

[0074] The homogenization treatment refers to incubating fresh bovine milk in a 37°C constant temperature water bath shaker for 20 min, and the rotation speed of the shaker is 60 rpm.

[0075] Fresh bovine milk refers to bovine milk that has been separated from the body of a cow for 24 hours or less.

[0076] (2) Add foaming substances to the homogenized liquid and stand for 10 min;

[0077] The foaming substance is sodium bicarbonate and citric acid, and the amount of foaming substance added is 4%, 5%, 6%, or 7% of the mass of fresh bovine milk, and the molar ratio of sodium bicarbonate to citric acid is 3:1.

[0078] It should be noted that the amounts of foaming substance added are 4%, 5%, 6%, or 7% respectively corresponding to Examples 2-5.

[0079] The reaction product of citric acid and sodium bicarbonate, sodium citrate, is also a highly safe substance, and the reaction equation is as follows:

[0080] 3NaHCO3+C6H8O7(+H2O)=Na3C6H5O7+3CO2↑+3H2O

[0081] (3) Centrifuge at 18°C, centrifuge at 17000g for 30 min; after centrifugation, discard the upper fat and lower precipitate, and collect the supernatant of bovine milk.

[0082] (4) Isolate and remove casein in the supernatant of bovine milk by isoelectric precipitation to obtain whey protein solution of bovine milk, specifically:

[0083] Adjust the pH of the milk supernatant to 4.6, let it stand for 30 minutes until no more precipitate forms, then centrifuge at 5000g for 20 minutes at 4°C to remove the precipitate. The precipitate contains a large amount of casein. Collect the supernatant, which contains whey protein, thus obtaining milk whey protein solution.

[0084] The whey protein yield and casein removal rate were tested in Examples 1-5. Since the foaming agent is the main innovative point of this invention, this invention is the first to conceive of using a foaming agent in the whey protein extraction process. Therefore, Examples 1-5 were set up to explore the effect of different amounts of foaming agent added on the extraction results, obtaining a relatively large range for the amount of foaming agent added. Adjustments made by those skilled in the art based on this range are all within the scope of this invention. The test results are shown in Table 1. As can be seen from Table 1, when the amount of foaming agent added varies within the range of 3-7%, the whey protein yield shows a trend of first increasing and then decreasing. The whey protein yield is best at 4-5%, therefore 4-5% is determined to be the optimal amount of foaming agent added. Simultaneously, when the amount of foaming agent added varies within the range of 3-7%, the casein removal rates A and B also show a trend of first increasing and then decreasing, corresponding to the trend of whey protein yield, i.e., the higher the casein removal rate, the higher the whey protein yield. Taking into account the results of whey protein yield, casein removal rate A, and casein removal rate B, the optimal range for the amount of foaming agent added is 4-5% of the fresh milk mass.

[0085] Figure 2 The electrophoresis results of whey protein solutions prepared in Examples 2-3 and Control Group 1 show that the casein bands in the whey obtained in Examples 2-3 are significantly weaker, indicating that the casein removal rate is very high.

[0086] Table 1. Results of whey protein yield and casein removal rate tests.

[0087] Test group Whey protein yield (%) Casein removal rate A (%) Casein removal rate B (%) Example 1 (3%) 70.2 8.3 74.4 Example 2 (4%) 76.3 13.8 80.6 Example 3 (5%) 77.4 14.7 81.1 Example 4 (6%) 71.6 9.2 73.2 Example 5 (7%) 70.1 8.4 71.0 Fresh cow milk control 100 0 0

[0088] IV. Effect of the Number of Times Foaming Substances Added on Extraction

[0089] Using the number of times foaming material is added as a single factor, the effects of different numbers of times foaming material is added on the extraction were investigated through Example 6 and Control Group 1.

[0090] Example 6

[0091] A whey protein processing method includes the following steps:

[0092] (1) Homogenize the fresh milk;

[0093] The homogenization treatment refers to placing fresh milk in a 37℃ constant temperature water bath shaker for incubation for 20 min, and the rotation speed of the shaker is 60 rpm.

[0094] Fresh milk refers to milk that is separated from the body of a cow within 24 hours.

[0095] (2) Adding a foaming substance to the homogenized liquid and standing for 10 min;

[0096] The foaming substance is sodium bicarbonate and citric acid, and the addition amount of the foaming substance is 4% of the mass of fresh milk, and the molar ratio of sodium bicarbonate to citric acid is 3:1.

[0097] The reaction product of citric acid and sodium bicarbonate, sodium citrate, is also a substance with high safety, and the reaction equation is as follows:

[0098] 3NaHCO3+C6H8O7(+H2O)=Na3C6H5O7+3CO2↑+3H2O

[0099] (3) Centrifugation at 18℃, centrifugation speed 17000g, centrifugation time 30 min; after centrifugation, discard the upper fat and lower precipitate, and collect the supernatant of the milk.

[0100] Adding a foaming substance to the supernatant of the milk and standing for 10 min;

[0101] The foaming substance is sodium bicarbonate and citric acid, and the addition amount of the foaming substance is 1% of the mass of fresh milk, and the molar ratio of sodium bicarbonate to citric acid is 3:1.

[0102] (4) Separating and removing casein in the supernatant of the milk by isoelectric point precipitation method to obtain whey protein liquid of the milk, specifically:

[0103] Adjusting the pH of the supernatant of the milk to 4.6, standing for 30 min, no precipitate is precipitated, then centrifuging at 5000g at 4℃ for 20 min to remove the precipitate, the precipitate contains a large amount of casein, and the supernatant contains whey protein, thus obtaining the whey protein liquid of the milk.

[0104] Control group 1

[0105] A processing process of whey protein, comprising the following steps:

[0106] (1) Homogenizing fresh milk;

[0107] The homogenization treatment refers to placing fresh milk in a 37℃ constant temperature water bath shaker for incubation for 20 min, and the rotation speed of the shaker is 60 rpm.

[0108] Fresh milk refers to milk that is separated from the body of a cow within 24 hours.

[0109] (2) centrifugation at 18℃, centrifugal speed 17000g, centrifugal time 30min; after centrifugation, discard the upper fat and the lower precipitate, collect the supernatant of the bovine milk.

[0110] (3) remove casein in the supernatant of the bovine milk by isoelectric precipitation to obtain whey protein solution of the bovine milk, specifically as follows:

[0111] adjust the pH of the supernatant of the bovine milk to 4.6, stand for 30min, no precipitate is precipitated, then remove the precipitate by centrifugation at 5000g for 20min at 4℃, the precipitate contains a large amount of casein, collect the supernatant, the supernatant contains whey protein, thus the whey protein solution of the bovine milk is obtained.

[0112] Test the yield of whey protein and the removal rate of casein of Example 2, Control Group 1 and Example 6. In biochemical reactions, the change of reaction parameters is the key to the results, so parameter optimization experiments are often the premise of paper research. In the extraction process of whey protein in the present application, the addition amount and the addition times of the foaming substance are the keys to the yield of whey protein, therefore, the present application explores the influence of the addition times of the foaming substance on the yield of whey protein through Examples 1-5, and the influence of different addition times of the foaming substance on the yield of whey protein through Example 2 and Example 6, the results are shown in Table 2. Example 2 is a one-time foaming treatment, Example 6 is a two-time foaming treatment, in addition, we use the process without foaming treatment as Control Group 1, the results in Table 2 show that after two-time foaming treatment, the yield of whey protein can reach 83.3%, the removal rate B of casein can reach 90.5, and the purity of the obtained whey protein is the highest. Therefore, the two-time foaming treatment process is preferably adopted.

[0113] Table 2 Test results of the yield of whey protein and the removal rate of casein

[0114]

[0115] V. Influence of different addition amounts of foaming substance (the second addition amount) on extraction

[0116] Take the second addition amount of the foaming substance as a single factor change, and explore the influence of different addition amounts of the foaming substance on extraction through Examples 7-8 and Control Group 2, including the following steps:

[0117] (1) homogenize fresh bovine milk;

[0118] The homogenization treatment refers to incubating fresh bovine milk in a 37℃ constant temperature water bath shaker for 20min, and the rotation speed of the shaker is 60rpm.

[0119] Fresh bovine milk refers to bovine milk that is separated from the body of a cow within 24 hours.

[0120] (2) adding foaming substance in the homogenate, standing for 10 min;

[0121] The foaming substance is sodium bicarbonate and citric acid, the adding amount of the first foaming substance is 4% of the fresh milk, and the molar ratio of sodium bicarbonate to citric acid is 3:1.

[0122] The reaction product of citric acid and sodium bicarbonate, sodium citrate, is also a high-safety substance, and the reaction equation is as follows:

[0123] 3NaHCO3+C6H8O7(+H2O)=Na3C6H5O7+3CO2↑+3H2O

[0124] (3) centrifuging at 18℃, the centrifugal speed is 17000g, and the centrifugal time is 30 min; after centrifuging, the upper fat and the lower precipitate are discarded, and the supernatant of the milk is collected.

[0125] Adding foaming substance in the supernatant of the milk, standing for 10 min;

[0126] The foaming substance is sodium bicarbonate and citric acid, the adding amount of the second foaming substance is 1.5%, 2%, or 3% of the fresh milk, and the molar ratio of sodium bicarbonate to citric acid is 3:1.

[0127] (4) removing casein in the supernatant of the milk by isoelectric precipitation to obtain whey protein solution of the milk, specifically:

[0128] Adjusting the pH of the supernatant of the milk to 4.6, standing for 30 min, no precipitate is precipitated, then removing the precipitate by centrifuging at 5000g for 20 min at 4℃, the precipitate contains a large amount of casein, and the supernatant contains whey protein, thus obtaining the whey protein solution of the milk.

[0129] Test Example 6-8, whey protein yield and casein removal rate of Control Group 2. The study of this part is to continue the study of the above "fourth", and to follow the "twice adding foaming material process", and to explore the influence of the second foaming material addition amount on the whey protein yield and casein removal rate. The results are shown in Table 3. Among them, Example 6 represents the amount of the second addition of foaming material is 1%, Example 7 represents the amount of the second addition of foaming material is 1.5%, Example 8 represents the amount of the second addition of foaming material is 2%, and Control Group 2 represents the amount of the second addition of foaming material is 3%. The amount of the second addition of foaming material of Control Group 2 is higher than that of Examples 6-8, and the results show that the whey protein yield and casein removal rate A and casein removal rate B of Control Group 2 are not as good as those of Examples 6-8, which shows that the more the amount of the second addition of foaming material, the better, and the amount of the second addition of foaming material is not as much as the first time. The reason is that the first addition of foaming material is more because the first impurity is more, and the second addition of foaming material is added after high-speed centrifugation. After high-speed centrifugation, a lot of impurities such as fat and part of casein are removed. If too much foaming material is added the second time, there is no physical combination of fat and other impurities with gas, and too much gas penetrates into the surface of whey protein molecules, which changes the physical structure of whey protein too much, which is not conducive to the obtaining of whey protein.

[0130] Table 3 Test results of whey protein yield and casein removal rate

[0131]

[0132] It should be noted that when the present application involves a numerical range, it should be understood that each numerical range has two endpoints and any number between the two endpoints can be selected. Since the same steps and examples are used, the preferred embodiments of the present application are described in order to prevent repetition. Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they understand the basic inventive concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0133] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A processing method for whey protein, characterized in that, Includes the following steps: Fresh milk is homogenized. A foaming agent is added to the homogenizing liquid. The foaming agent is bicarbonate and citric acid. The amount of foaming agent added is 3-7% of the mass of fresh milk. The bicarbonate is sodium bicarbonate. The milk supernatant was collected by high-speed centrifugation at room temperature. Casein was separated and removed from the supernatant of cow's milk to obtain whey protein solution of cow's milk; The molar ratio of sodium bicarbonate to citric acid is 3:

1.

2. The processing method for whey protein according to claim 1, characterized in that, The amount of foaming agent added is 4-5% of the weight of fresh milk.

3. The processing method for whey protein according to claim 1, characterized in that, The room temperature is 18-25℃.

4. The processing method for whey protein according to claim 3, characterized in that, The foaming substance is added to the milk supernatant for another treatment, and then the casein in the milk supernatant is separated and removed.

5. The processing method for whey protein according to claim 4, characterized in that, The mass of the foaming agent added a second time to the milk supernatant accounts for 1-2% of the mass of the milk supernatant.

6. The processing method for whey protein according to claim 1, characterized in that, Casein was removed from the supernatant of cow's milk by isoelectric point precipitation to obtain a whey protein solution from cow's milk.

7. The processing method for whey protein according to claim 6, characterized in that, The whey protein solution was freeze-dried to obtain freeze-dried powder.

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