Slow-digestion high-satiety self-assembled whey protein and preparation method thereof

Abstract

The preparation method comprises the following steps: by taking whey protein isolate as a raw material, carrying out pulsed electric field treatment, adding glutamine transaminase (TG enzyme) for cross-linking, obtaining whey protein powder which is low in water content and easy to store and transport through a microwave freeze-drying technology, redissolving the whey protein powder, self-assembling the whey protein powder into colloid, and carrying out freeze-drying to obtain the slow-digestion high-satiety self-assembled whey protein. And the protein supplement has the advantages of slow digestion and high satiety, and is helpful for weight management of eaters.

Description

Technical Field

[0001] The invention relates to a slow-digestion high-satiety self-assembling whey protein and a preparation method thereof, and belongs to the field of food processing. Background Art

[0002] Whey protein isolate (WPI) is a high-purity whey protein obtained through ultrafiltration and other purification processes based on concentrated whey protein, with a purity of more than 90%. It has a high content of high-quality protein and is easy to digest and absorb, and is favored by certain groups of people with specific needs, such as: fitness enthusiasts who do heavy resistance training, athletes who do high-intensity training, and patients who need high-quality protein for physical recovery.

[0003] In addition, more and more people are paying attention to the help of high-protein diet in weight management, especially for obese people. When they eat a high-protein diet, it can increase the secretion of satiety hormones such as PYY and GLP-1, while reducing the level of hunger hormones, thereby reducing appetite and increasing satiety; increase the basal metabolic rate (BMR) and resting metabolic rate (RMR), helping the body burn more calories after eating and during sleep; protect muscle content and prevent a decrease in metabolic rate; and the thermal effect of protein is high, so more energy is required to digest and metabolize protein.

[0004] WPI contains a large number of active peptide fragments. After gastrointestinal digestion, the active peptides contained will be released, which will stimulate the release of satiety hormones. WPI also contains up to 25% of three branched-chain amino acids (BCAA), namely: leucine, isoleucine and valine. They can stimulate muscle growth and reduce body fat percentage. In particular, leucine can inhibit SESN2, thereby activating the mTORC1 signaling pathway and promoting muscle protein synthesis.

[0005] However, due to its good water solubility, WPI has a very fast gastric emptying time in the body, usually within 30 minutes. The volume of the stomach is reduced in a short period of time, which will affect the feeling of fullness. In addition, the main β-lactoglobulin and α-lactalbumin in WPI are allergenic to some people and can cause gastrointestinal discomfort such as diarrhea. Therefore, there is an urgent need for a slowly digestible protein that can be slowly digested in the body after a one-time dose, prolong its residence time in the gastrointestinal tract, slowly release active peptides and amino acids, maintain a long-lasting feeling of fullness in the body, reduce appetite, and achieve weight management control.

[0006] Some slow digesting proteins currently available on the market are mainly composed of casein, or casein is compounded with WPI. Casein encounters calcium phosphate in the stomach, forming calcium bridges and polymerizing into micellar casein, which brings about a slow digestion effect. Alternatively, they are made into protein gels, where protein and water combine to form a relatively stable three-dimensional structure, which reduces the emptying rate of protein in the stomach and reduces the contact area with pepsin, achieving slow digestion.

[0007] However, existing slow-digesting proteins have the following problems:

[0008] (1) In compounded slow-digesting proteins, the protein that plays a slow-digesting role is mainly casein, but its BCAA content is much lower than that of WPI, and its stimulation for muscle growth is weaker, and it cannot achieve the same effect as WPI;

[0009] (2) β-lactoglobulin and α-lactalbumin contained in commonly used WPI have certain allergenicity;

[0010] (3) Although protein gel can achieve slow digestion, it is very easy to deteriorate due to its high water content, which makes its storage requirements more stringent, increasing storage costs; at the same time, due to the large volume of gel, it will also lead to increased transportation costs.

[0011] In view of the above-mentioned disadvantages that WPI is digested quickly, the human body may not be able to absorb it quickly and efficiently, and cannot maintain the amino acid level in the body under the condition of not eating for a long time, CN99812255.6 discloses slowly digestible protein and its use, but the patent still has the following problems:

[0012] (1) This product mainly enters the human body through the intestines and cannot be taken orally. It has a high intake threshold and cannot be used as a daily protein supplement. Its audience is relatively narrow;

[0013] (2) The protein content is low. The product contains only 5% protein. To meet the protein requirement, a large amount of intake is required, which puts a burden on the gastrointestinal tract.

[0014] (3) By adding alginate to combine with protein, slow digestion of protein is achieved, which has a certain effect on protein absorption in the body.

[0015] In view of the drawback of the allergenic components in WPI mentioned above, CN113016930A discloses a method for preparing low-allergenic whey protein by extreme conditions-assisted glycosylation modification combined with an enzyme method and the prepared low-allergenic whey protein, but the following problems still exist:

[0016] (1) By glycosylation of WPI with glucose, the reaction cannot be completely completed and some glucose will still exist, causing the human body to over-intake sugar while taking in protein;

[0017] (2) Enzymatic hydrolysis can reduce the allergenicity of β-lactoglobulin, but the product after enzymatic hydrolysis contains a large amount of peptides and increases bitterness;

[0018] (3) The ultrasonic treatment uses an ultrasonic crusher, but the sample size is small and difficult to realize industrialization.

[0019] In view of the above-mentioned disadvantages of difficult storage and high transportation cost of protein gel, CN201922257731.5 discloses a collagen drying device, but the following problems still exist:

[0020] (1) It is still essentially spray drying, but the protein gel has high viscosity and a stable gel structure, which makes feeding difficult and easily clogs the nozzle;

[0021] (2) If the gel is pretreated by high-speed dispersion and then spray-dried, although powder is formed, the protein gel structure is severely damaged and the gel cannot be formed after re-dissolution. Summary of the invention

[0022] The purpose of the present invention is to provide a slow digestion, high satiety self-assembling whey protein and a preparation method thereof, specifically to develop a slow digestion, high BCAA content and spontaneous gelling whey isolate (Slow digesting WPI, SDW) after dissolution. First, WPI is pretreated with a pulsed electric field (PEF) to promote the unfolding of its three-dimensional structure and increase the binding sites of TG enzyme; then TG enzyme is added to cross-link it, increase the degree of polymerization, form a three-dimensional network tight and stable gel, and finally microwave-assisted drying is used to obtain SDW protein powder.

[0023] The technical solution adopted by the present invention to solve the problem is:

[0024] The first object of the present invention is to provide a slowly digestible and highly satiety self-assembling whey protein, wherein the slowly digestible and highly satiety self-assembling whey protein spontaneously forms a gel after being dissolved in water, and the gel elastic modulus of the slowly digestible and highly satiety self-assembling whey protein is ≥200Pa.

[0025] The slow-digestion high-satiety self-assembling whey protein has a digestibility of less than 50% at 60 minutes.

[0026] The digestibility of the slowly digestible and highly satiety-satiating self-assembling whey protein is below 85% in 120 minutes.

[0027] Optionally, in one embodiment of the present invention, the water content of the slowly digestible and highly satiety self-assembling whey protein is ≤6%, the BCAA content of the slowly digestible and highly satiety self-assembling whey protein is ≥25, and the slowly digestible and highly satiety self-assembling whey protein does not contain β-lactoglobulin and α-lactalbumin.

[0028] Further optionally, in one embodiment of the present invention, the water content of the slowly digestible high satiety self-assembling whey protein is 5%-6%. Specifically, in one embodiment, the water content of the slowly digestible high satiety self-assembling whey protein is 5.45%. It should be noted that the above water contents are all calculated by mass.

[0029] Optionally, in one embodiment of the present invention, the BCAA content of the slowly digestible high satiety self-assembling whey protein is 25%-28%. Specifically, in one embodiment, the BCAA content of the slowly digestible high satiety self-assembling whey protein is 26.5%. It should be noted that the above BCAA contents are all calculated by weight.

[0030] Optionally, in one embodiment of the present invention, the slowly digestible and highly satiety self-assembling whey protein spontaneously forms a gel after being dissolved in water.

[0031] Optionally, in one embodiment of the present invention, the gel elastic modulus of the slowly digestible and highly satiety self-assembling whey protein is 200-240Pa.

[0032] The second object of the present invention is to provide a method for preparing a slowly digestible and highly satiety self-assembling whey protein, comprising the following steps:

[0033] Step (1): treating a whey protein isolate (WPI) solution with a pulsed electric field (PEF) to open its three-dimensional structure, expose the internally hidden hydrophobic groups, increase the binding sites for subsequent enzyme cross-linking, and moderately modify β-lactoglobulin and α-lactalbumin;

[0034] Step (2): adding glutamine aminotransferase (TG enzyme) to the protein solution treated by the pulse electric field to cross-link and form a protein gel;

[0035] Step (3): subjecting the protein gel to microwave freeze drying (MFD).

[0036] The preparation method of the present invention mainly comprises the following points:

[0037] (1) First, a pulsed electric field is used to change the tertiary structure of WPI, increase the cross-linking sites of TG enzyme, and improve the cross-linking efficiency; at the same time, the β-fold and β-turn content in the secondary structure of the protein decreases, while the random coil structure increases, causing the allergenic factors such as β-lactoglobulin to be slightly denatured, thereby reducing the allergenicity of WPI.

[0038] (2) Add TG enzyme to cross-link the WPI solution after pulse electric field treatment. TG enzyme catalyzes the binding reaction between the ε-amino group on the lysine residue and the γ-hydroxyamide group on the glutamine residue in the protein molecule, forming ε-(γ-glutamyl) lysine peptide bonds within and between protein molecules. Therefore, WPI will polymerize into large molecular proteins and form a stable protein gel through non-covalent bonding.

[0039] (3) Microwave-assisted freeze drying (MFD) turns the gel into powder, which is easy to store and transport. The more heat that microwaves can provide makes drying faster and more uniform, with lower energy consumption and less nutritional loss, and reduces the loss of volatile substances, so that the shape and smell of the material are closer to the original material. This advantage makes MFD more suitable for food drying. Another advantage is that MFD dehydration is more thorough, and the material is not easily oxidized, so it can be stored for a longer time. Moreover, during MFD, microwaves can inactivate TG enzymes, eliminating the operation process of heating to inactivate enzymes, improving processing efficiency and reducing production costs. Finally, easily soluble and slowly digestible WPI powder is obtained.

[0040] Optionally, in one embodiment of the present invention, the concentration of the initial whey protein solution is 15%-25% (w / v).

[0041] Optionally, in one embodiment of the present invention, in the preparation method of step (1), the pulse electric field treatment intensity is 14-20 kV / cm, and the treatment time is 5-20 min.

[0042] Optionally, in one embodiment of the present invention, in the preparation method of step (2), 10-40 U / g protein of TG enzyme is added during cross-linking. TG enzyme is purchased from Novozymes.

[0043] Optionally, in one embodiment of the present invention, in the preparation method of step (2), the temperature of the cross-linking reaction of the protein solution is 50-60°C, and the cross-linking time is 30-40 min.

[0044] Optionally, in one embodiment of the present invention, in the preparation method of step (3), the microwave power of microwave freeze drying MFD is 500-700w, and the vacuum degree is 120-200pa.

[0045] Optionally, in one embodiment of the present invention, in the preparation method of step (3), the drying temperature of the protein gel is lower than -40°C, and the drying time is 5-8h.

[0046] The third object of the present invention is to provide a use of a slowly digestible and highly satiety-sensitive self-assembling whey protein SDW in food or medicine.

[0047] Optionally, in one embodiment of the present invention, the slowly digestible high satiety self-assembling whey protein SDW is used as a food supplement in food, including meal replacement foods for improving satiety and / or controlling body weight.

[0048] Optionally, in one embodiment of the present invention, the slowly digestible and highly satiety self-assembling whey protein is used to delay the gastric emptying rate.

[0049] Further optionally, in one embodiment of the present invention, the slowly digestible and highly satiety self-assembling whey protein is used to delay the gastric emptying rate to no less than 120 min.

[0050] The slowly digestible and highly satiety-enhancing self-assembling whey protein SDW prepared by the present invention is added to food or medicine, especially food, as a food supplement. When it is dissolved in water, it can spontaneously form a gel, delay the gastric emptying rate within 120 minutes, increase satiety, and reduce body weight.

[0051] The advantages and positive effects of the present invention are:

[0052] (1) The present invention adopts pulsed electric field treatment to modify whey protein, which can not only improve the cross-linking efficiency of TG enzyme thereon, but also greatly reduce the allergenicity of WPI.

[0053] (2) The pulsed electric field modified WPI in the previous step can improve the cross-linking efficiency of TG enzyme, cross-link large molecular weight proteins, and form a gel.

[0054] (3) Microwave freeze-drying can not only dry the gel efficiently to obtain protein powder that is easy to transport and store, but also inactivate the enzyme through microwaves, thereby increasing processing efficiency.

[0055] (4) After WPI powder is redissolved, it will self-assemble into a protein gel and remain stable under acidic conditions and 25-40°C, achieving slow digestion.

[0056] (5) The present invention can increase satiety, suppress appetite, and effectively reduce people's desire for food when controlling their diet to lose weight, which is beneficial for weight management of people with heavy weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1Graph showing the effect of temperature on the storage modulus and loss modulus of SDW according to the present invention.

[0058] Figure 2 It is the in vitro digestion diagram of WPI, SDW and casein of the present invention.

[0059] Figure 3 It is a graph of the intestinal propulsion rate of mice after gavage with deionized water (DW), WPI and SDW samples of the present invention, respectively.

[0060] Figure 4 The graphs are of the changes over time of (a) cholecystokinin (CCK) and (b) glucagon-like peptide-1 (GLP-1) in the gastrointestinal tract of mice after oral administration of DW, WPI and SDW samples of the present invention.

[0061] Figure 5 Graphs showing (a) food intake and (b) body weight of mice subjected to long-term DW, WPI and SDW dietary supplementation according to the present invention. DETAILED DESCRIPTION

[0062] The present invention is intended to provide a method for preparing a slowly digestible and highly satiety self-assembling whey protein, comprising the following steps:

[0063] Step (1): treating a whey protein isolate (WPI) solution with a pulsed electric field (PEF) to open its three-dimensional structure, expose the internally hidden hydrophobic groups, increase the binding sites for subsequent enzyme cross-linking, and moderately modify β-lactoglobulin and α-lactalbumin;

[0064] Step (2): adding glutamine aminotransferase (TG enzyme) to the protein solution treated by the pulse electric field to cross-link and form a protein gel;

[0065] Step (3): subjecting the protein gel to microwave freeze drying (MFD).

[0066] Specifically, in some examples, the concentration of the initial whey protein solution is 15%-25% (w / v).

[0067] Specifically, in some examples, in the preparation method of step (1), the pulse electric field treatment intensity is 14-20 kV / cm. Specifically in some examples, the pulse electric field treatment intensity can be selected to be 14, 16 and 20 kV / cm, respectively, and the treatment time of the protein solution at each intensity of the electric field is independently 5-20 minutes.

[0068] Specifically, in some examples, in the preparation method of step (2), 10-40 U / g protein of TG enzyme is added during cross-linking. TG enzyme is purchased from Novozymes.

[0069] Specifically, in some examples, in the preparation method of step (2), the temperature of the protein solution cross-linking reaction is 50-60°C, and the cross-linking time is 30-40 minutes.

[0070] Specifically, in some examples, in the preparation method of step (3), the microwave power of microwave freeze drying MFD is 500-700w, and the vacuum degree is 120-200pa.

[0071] Specifically, in some examples, in the preparation method of step (3), the drying temperature of the protein gel is lower than -40°C, and the drying time is 5-8 hours.

[0072] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0073] Example 1

[0074] (1) Stir and dissolve 10 L of 20% (w / v) WPI solution and remove the precipitate by ultrafiltration to ensure complete dissolution.

[0075] (2) Treat it with a pulse electric field of 14Kv / cm for 15 minutes.

[0076] (3) The treated protein solution was heated to 50°C, 40 U / g protein of TGase was added, and cross-linking was continued for 40 min to obtain a stable protein gel.

[0077] (4) The gel was dried using MFD. When the temperature was lower than -40°C, drying was started with a microwave power of 600 W, a vacuum degree of 200 Pa, and a drying time of 6 h. Protein powder with a water content as low as 5.45 wt% was obtained, wherein the BCAA content was 26.5 wt%.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is that there is no pulse treatment in step (2), which is intended to explore the effect of pulse treatment on WPI. Specifically, the following steps are included:

[0080] (1) Stir and dissolve 10 L of 20% (w / v) WPI solution and remove the precipitate by ultrafiltration to ensure complete dissolution.

[0081] (2) The protein solution was heated to 50°C, 40 U / g protein of TG enzyme was added, and cross-linking was continued for 180 min to obtain a protein solution, but a stable protein gel could not be formed.

[0082] This is because there are fewer cross-linking sites for TG enzyme reaction in WPI, so the cross-linking efficiency is low, and even after long-term cross-linking treatment, a stable gel cannot be formed.

[0083] Comparative Example 2

[0084] The difference between this comparative example and Example 1 is that the drying method in step (3) is different, and the purpose is to explore the effect of microwave freeze drying on WPI. Specifically, the following steps are included:

[0085] (1) Stir and dissolve 10 L of 20% (w / v) WPI solution and remove the precipitate by ultrafiltration to ensure complete dissolution.

[0086] (2) Treat it with a pulse electric field of 20 Kv / cm for 10 min.

[0087] (3) The treated protein solution was heated to 50°C, 40 U / g protein of TGase was added, and cross-linking was continued for 40 min to obtain a stable protein gel.

[0088] (4) The gel was dried using a low-temperature hot air drying method: the drying temperature was 50° C., and the drying time was 20 h, thereby obtaining a protein powder with a water content as low as 4.3%.

[0089] The solubility of the protein sample after hot air drying was poor, which might be due to the excessive polymerization and denaturation of the protein during the drying process, which made it impossible to redissolve and form a gel.

[0090] Test Case

[0091] Physical and chemical properties: The rheological properties of the protein gel were tested using the Discovery Hybrid Rheometer-3 rheometer. The gastric environment was simulated, the pH was adjusted to 3, and the test temperature was 25-40°C. The changes in the elastic modulus and loss modulus of the gel were tested ( Figure 1 ).from Figure 1 It can be seen that SDW can maintain a stable gel state in the simulated gastric environment (37°C, pH 3), that is, G' is greater than G", and the gel elastic modulus G' reaches more than 200Pa, with a maximum value of 234Pa.

[0092] Static in vitro digestion experiment: The digestion rate of WPI, casein and SDW was evaluated using the INFOGEST static in vitro simulated digestion model. The digestion time was 4 hours, and samples were taken every 30 minutes. 20% trichloroacetic acid was used for precipitation. The precipitate was regarded as undigested protein, and the protein content in the precipitate was measured by the Kjeldahl method. The digestibility was calculated using the following formula:

[0093]

[0094] from Figure 2It can be seen that in the 4-hour in vitro digestion experiment, WPI had the fastest digestion rate, reaching 89.15%, but SDW could achieve a digestion rate similar to that of casein, which were 38.14% and 37.82%, respectively.

[0095] Short-term in vivo digestion experiment: C57BL / 6J mice were used as experimental subjects for in vivo digestion test. After fasting for 12 hours, mice were gavaged with equal volumes of deionized water, 10% (w / v) WPI and 10% (w / v) SDW samples containing rhodamine B. The mice were anesthetized with carbon dioxide gas within 0-120 minutes and their gastrointestinal tract was collected for fluorescence imaging ( Figure 3 ). Figure 3 In a, 30 minutes after gavage, fluorescence can be detected in most parts of the intestines of the DW and WPI groups, and the propulsion rate in the DW group is close to 100%, significantly higher than 75.59% of WPI. However, most of the fluorescence intensity in the SDW group is concentrated in the stomach, and the propulsion rate is only 33.72%, indicating that at 30 minutes of digestion, the SDW sample is still mainly in the gastric digestion stage and has not been emptied into the small intestine in large quantities. Figure 3 As can be seen from the graphs bc, after 60 and 120 minutes of digestion, the fluorescent area in the intestine of the DW group gradually decreased, which may be due to the fact that the water transport rate in the intestine was too fast, causing many fluorescent indicators to be excreted from the body with urine. After 60 minutes of digestion in the WPI group, more than half of the intestinal tissue showed fluorescence (72.62%). As the digestion time further increased to 120 minutes, the entire intestine was fluorescently distributed, and its intestinal propulsion rate also reached nearly 100%, which was not significantly different from the DW group, indicating that it had been almost completely digested after intestinal peristalsis. However, the propulsion rate of the SDW group at 60 minutes only increased to 42.57%, which was significantly lower than the other two groups at the same time. At 120 minutes, the propulsion rate was 82.69%, which still did not reach 100%, indicating that during the 120-minute in vivo digestion period, its intestinal digestion was still lower than that of WPI.

[0096] Collect serum and test related hormone levels ( Figure 4). After gavage of the two protein samples, WPI and SDW, the CCK concentration in the serum showed an upward trend, and the SDW group was slightly higher than the WPI group. Both reached a peak at 60 minutes, which were 56.10ng / L and 61.28ng / L, respectively. At 120 minutes, the CCK in the WPI group dropped to 32.35ng / L, while the CCK content in the SDW group was 66.63ng / L, still maintaining a relatively high level. The GLP-1 content in the serum of mice in the WPI and SDW groups continued to increase at 30 minutes and 60 minutes, and reached a peak level at 60 minutes, which were 6.35pmol / L and 7.50pmol / L, respectively. Although the indicators of both groups decreased at 120 minutes, the SDW group only dropped to 6.85pmol / L, while the WPI group dropped sharply to 3.02pmol / L.

[0097] Long-term feeding experiment: Obese C57BL / 6J mice (weight > 40g) were used as experimental subjects for long-term feeding test. The mice were divided into 3 groups. While drinking water and taking food (high-fat diet) freely, they were gavaged with equal volume of deionized water, 10% (w / v) WPI and 10% (w / v) SDW samples every day for 8 weeks. The average food intake was recorded and calculated every day, and the weight change was recorded every week.

[0098] result Figure 5 As shown in the figure, the food intake of mice in the DW group and the WPI group was 4.12g / day and 4.07g / day, respectively, while the food intake of mice in the SDW group was significantly reduced to only 3.36g / day. The average body weight of mice in the DW group and the WPI group increased steadily with the feeding time, increasing to 45.2g and 44.3g, respectively. In contrast, the average body weight of mice in the SDW group continued to decrease to 36.7g, indicating that dietary supplementation with SDW has the effect of suppressing appetite and is beneficial to weight management.

[0099] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, which all belong to the protection scope of the present invention.

Claims

1. A slow-digesting, high-satiety self-assembling whey protein, characterized in that: The slow-digesting and high-satiety self-assembling whey protein spontaneously forms a gel after being dissolved in water, and the elastic modulus of the gel is ≥200 Pa. The slow-digestion high-satiety self-assembling whey protein has a digestibility of less than 50% at 60 minutes. The digestibility of the slowly digestible and highly satiety-satiating self-assembling whey protein is below 85% in 120 minutes.

2. The slowly digestible and highly satiety self-assembling whey protein according to claim 1, characterized in that: The water content of the slowly digestible and highly satiety self-assembling whey protein is ≤6%, the BCAA content of the slowly digestible and highly satiety self-assembling whey protein is ≥25%, and the slowly digestible and highly satiety self-assembling whey protein does not contain β-lactoglobulin and α-lactalbumin; Preferably, the water content of the slowly digestible and highly satiety-sensitive self-assembling whey protein is 5%-6%, and / or Preferably, the BCAA content of the slow-digesting and high-satiety self-assembling whey protein is 25%-28%, and / or Preferably, the gel elastic modulus of the slowly digestible and highly satiety self-assembling whey protein is 200-240 Pa.

3. A method for preparing a slow-digesting, high-satiety self-assembling whey protein, characterized in that: The following steps are involved: Step (1): treating an initial whey protein isolate solution using a pulsed electric field; Step (2): adding glutamine aminotransferase for cross-linking to form a protein gel; Step (3): subjecting the protein gel to microwave freeze drying.

4. The method according to claim 3, characterized in that The concentration of the initial whey protein solution is 15%-25% w / v.

5. The method according to claim 3, characterized in that: In the preparation method of step (1), the pulse electric field treatment intensity is 14-20 kV / cm, and the protein solution treatment time is 5-20 min.

6. The method according to claim 3, characterized in that In the preparation method of step (2), the TG enzyme added during cross-linking is 10-40 U / g protein.

7. The method according to claim 3, characterized in that In the preparation method of step (2), the temperature of the cross-linking reaction is 50-60° C., and the cross-linking time is 30-40 min.

8. The method according to claim 3, characterized in that In the preparation method of step (3), the microwave power of microwave freeze-drying is 500-700W, and the vacuum degree is 120-200Pa.

9. The method according to claim 3, characterized in that: In the preparation method of step (3), the drying temperature of the protein gel is lower than -40°C and the drying time is 5-8 hours.

10. Use of the slowly digestible and highly satiety self-assembling whey protein according to claims 1-9 in food or medicine, Preferably, the slowly digestible high satiety self-assembling whey protein is used to delay gastric emptying rate, and / or Preferably, the slowly digestible and highly satiety self-assembling whey protein is used to delay the gastric emptying rate by no less than 120 min.

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