A method for improving the stability of whey protein and its application in special medical foods

Abstract

The present invention relates to the technical field of special medical formula food, and specifically to a method for improving the stability of whey protein and its application in special medical food, comprising the following steps: A, uniformly dispersing whey protein in water, adding sulfur-containing amino acids, obtaining whey protein suspension 1, and placing it in an ice bath for standby use; B, preparing an appropriate amount of hot water, adding the hot water to the whey protein suspension 1 under high-speed shearing conditions, and maintaining high-speed shearing to obtain whey protein suspension 2; C, homogenizing the whey protein suspension 2 to obtain a stable whey protein product. The present invention improves the heat resistance, ionic strength resistance, and stability of whey protein at high temperatures with other proteins by processing whey protein and adding sulfur-containing amino acids.

Description

Technical Field

[0001] The invention relates to the technical field of special medical formula foods, and in particular to a method for improving the stability of whey protein and an application thereof in special medical formula foods. Background Art

[0002] Formulated foods for special medical purposes are specially processed and prepared to meet the nutritional needs of people with limited food intake, digestive and absorption disorders, metabolic disorders or other specific disease states. Formulated foods for special medical purposes are mainly divided into two dosage forms: powders and emulsions, of which powders are divided into two preparation methods: wet method and dry method. Since my country issued the "GB29922-2013 General Rules for Formulated Foods for Special Medical Purposes" in 2016, there has been only one registered product of ordinary complete nutritional formula emulsion among special medical foods, and its protein is a single protein source with good stability. This is because the formula of the complete nutritional emulsion is complex and the process conditions are harsh, resulting in extremely poor protein stability during the preparation process, and the product undergoes flocculation, precipitation, and aggregation after sterilization. Among the protein-containing products of special medical foods, the stability of whey protein is one of the worst proteins, but the bioavailability and amino acid score of whey protein are the highest among proteins. When whey protein is present in FSMPs, obvious agglomeration will occur during the sterilization stage, especially when the product contains whey protein and other proteins, the phenomenon will be more obvious, resulting in extremely poor product sensory quality and poor compliance in using the product. Therefore, improving the stability of whey protein in FSMP emulsion products, especially the stability compared with other types of proteins under high temperature sterilization conditions, will greatly improve the nutritional adequacy, bioavailability and compliance of the product. Summary of the invention

[0003] The present invention aims to improve the heat resistance, ionic strength resistance, and stability with other proteins at high temperatures of whey protein by treating whey protein and adding sulfur-containing amino acids.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A method for improving the stability of whey protein comprises the following steps:

[0006] A. Evenly dispersing whey protein in water, adding sulfur-containing amino acids to obtain a whey protein suspension 1, and placing it in an ice bath for standby use;

[0007] B. preparing an appropriate amount of hot water, and quickly adding the hot water to the whey protein suspension 1 under high-speed shearing conditions, and maintaining high-speed shearing to obtain a whey protein suspension 2;

[0008] C. Homogenize the whey protein suspension 2 to obtain a stable whey protein product.

[0009] The invention can greatly improve the thermal stability of whey protein by instantaneously heating whey protein and coordinating the homogenization method. What is more unexpected is that adding a proper amount of sulfur-containing amino acids during the whey treatment process can not only improve the thermal stability of the whey protein itself, but also greatly improve the compatibility of the whey protein with other proteins. Even in the presence of an emulsion with a high particle concentration, the product compounded with the whey protein and other proteins still has extremely high heat resistance and stability.

[0010] After research, it was found that since whey protein is a long-chain macromolecular substance, there are a large number of sulfur-containing amino acids, and these sulfur-containing amino acids are folded in the protein structure under normal circumstances. However, during the processing, the folded structure of a heated whey protein will open, causing these sulfur-containing amino acids to be exposed, and mutually combined to form a disulfide bond, causing the whey protein long chain to be combined, and flocculation has occurred. If it is a composite emulsion, when the folded structure of whey protein is opened under the heated state, the folded structure of other proteins will also be opened, and the whey protein long chain will further be combined with the long chain of other proteins to form a disulfide bond, causing more serious flocculation. The present invention opens the folded structure of whey protein in advance by instant heating, and the sulphur bond is exposed in advance. At this time, there are more active small molecule sulfur-containing amino acids in the solution, and these amino acids are more likely to be combined with the sulfur-containing amino acids contained in whey protein, so that whey protein forms a disulfide bond with the sulfur-containing amino acids, and the activity of the sulfur-containing amino acids on the closed whey protein long chain is suppressed, thereby suppressing the generation of protein flocculation.

[0011] In step B, high-speed shearing is performed to achieve a violent tumbling state of the liquid surface and to maintain it continuously, and the specific shearing speed can be adjusted according to different shearing head sizes. Afterwards, hot water is quickly added thereto to slightly denature the whey protein, and the folded structure is opened to expose the sulfide bond, and is combined with the small molecule sulfur-containing amino acids in the solution to form a disulfide bond, thereby forming a stable protein, and the activity of the sulfur-containing amino acids on the long chain of the whey protein is blocked, and further combination to produce flocculation cannot occur in subsequent processing. The speed of adding hot water should be fast, not too slow, and too slow is easy to quickly cool down after being added to the system and cannot effectively cause the whey protein to denature, and the sulfide bond is difficult to expose and thus difficult to form a disulfide bond with the sulfur-containing amino acids.

[0012] The ice bath method includes, but is not limited to, a refrigeration unit heat exchange method using a solution such as frozen water or ethylene glycol, and a method of placing the solution in ice water and letting it stand.

[0013] Preferably, in step A, the sulfur-containing amino acid includes one or more of cysteine ​​and methionine.

[0014] According to the structural formula, the sulfur-containing bonds of cysteine ​​and methionine are located at one end of the structural formula, which is easy to be freed to generate sulfur-containing free radicals, and thus easily combine with the exposed sulfur bonds of whey protein to form disulfide bonds. In comparison, adding cysteine ​​is more effective than methionine because cysteine ​​is a -SH bond, which is easier to be freed to generate free radicals than -SCH3 of methionine.

[0015] Preferably, in step A, the pH value is further adjusted to adjust the whey protein suspension 1 to a weak alkaline state.

[0016] Preferably, in step A, the pH of the whey protein suspension 1 is adjusted to be greater than 7 and less than 9.

[0017] The pH adjuster includes, but is not limited to, sodium hydroxide, potassium hydroxide, calcium oxide, magnesium oxide and other commonly used acid-base adjusters. The pH value is strictly maintained at pH 7 to pH 9, excluding pH 7 and pH 9.

[0018] Homogenization methods include, but are not limited to, high pressure homogenization, membrane homogenization, microfluidization homogenization, and the like.

[0019] Preferably, in the whey protein suspension 1, the mass ratio of the whey protein to water is 1-40:100, and the mass content of the sulfur-containing amino acid is 0.001%-0.01%; in step B, the mass ratio of the whey protein to the hot water is 1-40:100.

[0020] In step A, some water is first added for dispersion, and then hot water is added in step B to improve the thermal stability of whey protein. After the hot water is added, the total mass content of whey protein is controlled to be between 1% and 20%, and the temperature of the whey protein suspension 2 is ensured to be between 50 and 70°C.

[0021] Preferably, in step B, the temperature of the whey protein suspension 1 is 25-50°C, the temperature of the hot water is ≥95°C, and the temperature of the whey protein suspension 2 is 50-70°C.

[0022] The water heating method includes but is not limited to heating by electricity, fire, high pressure, etc. The water temperature is ≥95°C. There is no upper limit on the temperature and it can be superheated water. The premise of adding an appropriate amount of hot water is to ensure that the temperature of the whey protein suspension 2 is 50-70°C.

[0023] Preferably, in step B, after the hot water is added, high-speed shearing is maintained for 5 to 20 minutes; in step C, the homogenization is high-pressure homogenization with a homogenization pressure of 300 to 700 bar, which is performed 2 to 6 times.

[0024] An application of the method for improving the stability of whey protein in special medical foods.

[0025] The present invention is mainly used in solid beverages, special medical purpose formula foods and enteral nutrition preparations containing protein products, including but not limited to ordinary complete nutritional milk for special medical purpose formula foods, special medical purpose formula food powder (wet method), special medical purpose formula food non-complete nutritional components (protein components, amino acid components, etc.), special medical purpose formula food specific complete nutritional milk and special medical purpose formula food powder and enteral nutrition preparations (diseases include but are not limited to tumors, kidney disease, diabetes, respiratory system diseases, liver diseases, muscle wasting syndrome, trauma, infection, surgery and other stress states, inflammatory bowel disease, food protein allergy, refractory epilepsy, gastrointestinal absorption disorders, pancreatitis, abnormal fatty acid metabolism, obesity, fat reduction surgery, etc.).

[0026] Preferably, the whey protein stabilizing product is applied to a special medical food emulsion; when other proteins besides whey protein exist in the special medical food emulsion, in the dispersion and dissolution step, after the dispersion and dissolution of other materials are completed, the other proteins are dispersed first, and the pH of the system is adjusted to weak alkalinity, and then the whey protein stabilizing product is added while performing high-speed shearing, and then homogenization, filling, and sterilization processes are performed to obtain the special medical food emulsion.

[0027] Preferably, the other proteins include one or more of caseinate, casein, concentrated milk protein, soy protein, and pea protein; the pH of the regulating system is adjusted to a pH greater than 7 and less than 9; the temperature of the whey protein stabilized product is maintained at 40-50° C. Other proteins include but are not limited to one or more of caseinate, casein, concentrated milk protein, soy protein, and pea protein.

[0028] The optimal temperature for the stable whey protein product is between 40 and 50°C, but is not limited to other temperatures.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention improves the heat resistance, ionic strength resistance, stability with other proteins at high temperatures and the like of whey protein by treating whey protein and adding sulfur-containing amino acids. The heat resistance of whey protein and whey protein and other proteins has always been a technical problem of functional food and health food products. Even though whey protein is very popular in clinical nutrition, its poor thermal stability is the main reason why related liquid products are not applied in clinical practice. The innovation of the present invention is that the thermal stability of whey protein can be greatly improved by instantaneous heating of whey protein and a method of matching homogenization. What is more unexpected is that adding an appropriate amount of sulfur-containing amino acids during the whey treatment process can not only improve the thermal stability of whey protein itself, but also greatly improve the compatibility of whey protein with other proteins. Even in the presence of an emulsion with a high particle concentration, the product compounded with whey protein and other proteins still has extremely high heat resistance and stability. In addition, since pH value is a very critical factor in achieving the stability of whey protein and whey protein compounded with other proteins in liquid products, too high or too low pH value will affect its stability. Therefore, this technology is mainly used in neutral or weakly alkaline products such as solid beverages, beverages, special medical foods and enteral nutrition. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0032] Figure 2 This is a product status diagram of Example 1;

[0033] Figure 3 is the particle size distribution diagram of Example 1;

[0034] Figure 4 This is the product status diagram of Comparative Example 1;

[0035] Figure 5 This is the product status diagram of Comparative Example 2;

[0036] Figure 6 This is a diagram of the product of Comparative Example 3 in a vertical placement state;

[0037] Figure 7 This is a diagram of the horizontal placement state of the product of Comparative Example 3;

[0038] Figure 8 It is the product status diagram of comparative example 4;

[0039] Fig. 9 This is the product status diagram of Comparative Example 5;

[0040] Fig.10 This is a product status diagram of Example 2;

[0041] Fig.11 is the particle size distribution diagram of Example 2;

[0042] Fig.12 This is a product status diagram of Example 3;

[0043] Fig.13 is the particle size distribution diagram of Example 3;

[0044] Fig.14 This is the product status diagram of Comparative Example 6;

[0045] Fig.15 This is the product status diagram of Comparative Example 7;

[0046] Fig.16 It is the particle size distribution diagram of Comparative Example 7;

[0047] Fig.17 This is a product status diagram of Comparative Example 8;

[0048] Fig.18 This is the particle size distribution diagram of Comparative Example 8. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific embodiments.

[0050] Example 1

[0051] like Figure 1 As shown, weigh 80g whey protein, use a high-speed disperser to evenly disperse the whey protein in 500mL purified water, and add 1g of cysteine ​​until it is evenly dispersed and there is no visible lumps. Use 1M NaOH to adjust the whey protein to pH 8. Place the iron bucket containing the dispersed whey protein in ice water, and use an induction cooker to heat 500mL purified water until it boils. Turn on the high-speed shearing machine, the shearing speed is 6000rpm, and the whey protein suspension is sheared at a high speed. At the same time, pour in the prepared boiling water. After pouring in boiling water, the temperature of the whey protein solution is 60℃; keep the shearing speed of the shearing machine for 5 minutes, and then high-temperature treated whey protein is homogenized at high pressure, with a homogenization pressure of 600bar and 2 homogenization times. After homogenization is completed, the whey protein is filled and sterilized at 121℃ for 15 minutes.

[0052] Comparative Example 1

[0053] Weigh 80g of whey protein and evenly disperse it in 500mL of purified water using a high-speed disperser until no lumps are visible. Use 1M NaOH to adjust the pH of the whey protein to 8. After the whey protein suspension is directly filled, it is sterilized at 121°C for 15 minutes.

[0054] Comparative Example 2

[0055] Weigh 80g of whey protein and evenly disperse it in 500mL of purified water using a high-speed disperser. Add 1g of cysteine ​​until it is evenly dispersed without visible lumps. Use 1M NaOH to adjust the pH of the whey protein to 8. After the whey protein suspension is directly filled, it is sterilized at 121°C for 15 minutes.

[0056] Comparative Example 3

[0057] Weigh 80g of whey protein, use a high-speed disperser to evenly disperse the whey protein in 500mL of purified water, and add 1.25g of cysteine ​​until it is evenly dispersed and there are no visible lumps. Use 1M NaOH to adjust the whey protein to pH 8. Place the iron bucket containing the dispersed whey protein in ice water, and use an induction cooker to heat 500mL of purified water until it boils. Turn on the high-speed shearing machine, the shearing speed is 6000rpm, and the whey protein suspension is sheared at a high speed. At the same time, pour in the prepared boiling water. After pouring in boiling water, the temperature of the whey protein solution is 60℃; keep the shearing speed of the shearing machine for 5 minutes, and then high-pressure homogenize the high-temperature treated whey protein, the homogenization pressure is 600bar, and the number of homogenizations is 2 times. After the homogenization is completed, the whey protein is filled and sterilized at 121℃ for 15 minutes.

[0058] Comparative Example 4

[0059] Weigh 80g of whey protein, use a high-speed disperser to evenly disperse the whey protein in 500mL of purified water, and add 1g of cysteine ​​until it is evenly dispersed and there are no visible lumps. Use 1M NaOH to adjust the whey protein to pH 7. Place the iron bucket containing the dispersed whey protein in ice water, and use an induction cooker to heat 500mL of purified water until it boils. Turn on the high-speed shearing machine, shear the whey protein suspension at a shear speed of 6000rpm, and pour in the prepared boiling water at the same time. After pouring in boiling water, the temperature of the whey protein solution is 58°C; keep the shearing speed of the shearing machine for 5 minutes, and then high-pressure homogenize the high-temperature treated whey protein, with a homogenization pressure of 600bar and 2 homogenization times. After the homogenization is completed, the whey protein is filled and sterilized at 121°C for 15 minutes.

[0060] Comparative Example 5

[0061] Weigh 80g of whey protein, use a high-speed disperser to evenly disperse the whey protein in 500mL of purified water, and add 1g of cysteine ​​until it is evenly dispersed and there are no visible lumps. Use 1M NaOH to adjust the whey protein to pH 9. Place the iron bucket containing the dispersed whey protein in ice water, and use an induction cooker to heat 500mL of purified water until it boils. Turn on the high-speed shearing machine, and the shear speed is 6000rpm to shear the whey protein suspension at high speed. At the same time, pour in the prepared boiling water. After pouring in boiling water, the temperature of the whey protein solution is 58℃; keep the shearing speed of the shearing machine for 5 minutes, and then high-pressure homogenize the high-temperature treated whey protein, with a homogenization pressure of 600bar and 2 homogenization times. After the homogenization is completed, the whey protein is filled and sterilized at 121℃ for 15 minutes.

[0062] Example 2

[0063] Weigh 50g of whey protein, use a high-speed disperser to evenly disperse the whey protein in 500mL of purified water, and add 0.8g of methionine until it is evenly dispersed and there are no visible lumps. Use 1M NaOH to adjust the whey protein to pH 8. Place the iron bucket containing the dispersed whey protein in ice water, and use an induction cooker to heat 500mL of purified water until it boils. Turn on the high-speed shearing machine, and the shear speed is 6000rpm to shear the whey protein suspension at high speed. At the same time, pour in the prepared boiling water. After pouring in boiling water, the temperature of the whey protein solution is 58℃; keep the shearing speed of the shearing machine for 5 minutes, and then high-pressure homogenize the high-temperature treated whey protein, with a homogenization pressure of 600bar and 2 homogenization times. After the homogenization is completed, the whey protein is filled and sterilized at 121℃ for 15 minutes.

[0064] Example 3

[0065] 23g whey protein was measured and evenly dispersed in 500mL purified water using a high-speed disperser. At the same time, 0.05g of cysteine ​​was added until it was evenly dispersed and no lumps were visible. 1M NaOH was used to adjust the whey protein to pH 7.5. The iron bucket containing the dispersed whey protein was placed in ice water, and 500mL purified water was heated by an induction cooker until it boiled. The high-speed shearing machine was turned on, and the shearing speed was 6000rpm to shear the whey protein suspension at a high speed. At the same time, the prepared boiling water was poured in. After pouring the boiling water, the temperature of the whey protein solution was 56°C; after shearing for 5 minutes at the shearing speed of the shearing machine, the high-temperature treated whey protein was subjected to high-pressure homogenization, the homogenization pressure was 600bar, and the homogenization times were 2 times. After the homogenization was completed, the whey protein suspension was cooled to 45°C for standby use.

[0066] Weigh 310g of calcium caseinate, 600g of maltodextrin, 60g of resistant dextrin, 250g of blended oil, 4.5g of vitamins, 45g of minerals, 1g of thickener, and 1800mL of water. Use a high-speed disperser to disperse calcium caseinate, maltodextrin, resistant dextrin, blended oil, vitamins, minerals, thickeners and other materials into 1800mL of water until they are evenly dispersed. Replace the disperser with a high-speed shearing machine, use a speed of 7000rpm to shear the above suspension at high speed, and pour the above-prepared whey protein into it, shear for about 5 minutes until the emulsion is uniform. Use a slit-type high-pressure homogenizer with a homogenization pressure of 400bar, homogenize twice, fill the homogenized emulsion and sterilize it at high temperature, and the sterilization temperature is 121℃ for 15 minutes.

[0067] Comparative Example 6

[0068] The emulsion was prepared according to Example 3, except that, in the first step, during the treatment of the whey protein, only homogenization and heating were performed, and cysteine ​​and methionine were not added.

[0069] Comparative Example 7

[0070] Weigh 50g of whey protein, use a high-speed disperser to evenly disperse the whey protein in 500mL of purified water, and add 0.8g of cystine until it is evenly dispersed and no lumps are visible. Use 1M NaOH to adjust the whey protein to pH 8. Place the iron bucket containing the dispersed whey protein in ice water, and use an induction cooker to heat 500mL of purified water until it boils. Turn on the high-speed shearing machine, shear the whey protein suspension at a shear speed of 6000rpm, and pour in the prepared boiling water at the same time. After pouring in boiling water, the temperature of the whey protein solution is 58°C; keep the shearing speed of the shearing machine for 5 minutes, and then high-pressure homogenize the high-temperature treated whey protein, with a homogenization pressure of 600bar and 2 homogenization times. After the homogenization is completed, the whey protein is filled and sterilized at 121°C for 15 minutes.

[0071] Comparative Example 8

[0072] Weigh 50g of whey protein, use a high-speed disperser to evenly disperse the whey protein in 500mL of purified water, and add 0.8g of taurine until it is evenly dispersed and there are no visible lumps. Use 1M NaOH to adjust the whey protein to pH 8. Place the iron bucket containing the dispersed whey protein in ice water, and use an induction cooker to heat 500mL of purified water until it boils. Turn on the high-speed shearing machine, shear the whey protein suspension at a shear speed of 6000rpm, and pour in the prepared boiling water at the same time. After pouring in boiling water, the temperature of the whey protein solution is 58°C; keep the shearing speed of the shearing machine for 5 minutes, and then high-pressure homogenize the high-temperature treated whey protein, with a homogenization pressure of 600bar and 2 homogenization times. After homogenization is completed, the whey protein is filled and sterilized at 121°C for 15 minutes.

[0073] Effect Example 1

[0074] Observation and statistics were performed on Examples 1 to 3 of the present invention and Comparative Examples 1 to 8, and the results are shown in Table 1.

[0075] Table 1

[0076]

[0077] As can be seen from Table 1, only Examples 1 to 3 using the method of the present invention can obtain products with uniformity problems, while Comparative Examples 1 to 8 using the method of the present invention all have different problems. It can be seen that the present invention achieves unexpected effects of improving the heat resistance, ionic strength resistance, and stability with other proteins at high temperatures of whey protein by treating whey protein and adding sulfur-containing amino acids.

[0078] Effect Example 2

[0079] Example 1 was observed, and the results were as follows Figure 2 As shown in the figure, the sterilized whey protein suspension is a uniform milky white suspension without foreign matter, flocculation or agglomeration. Figure 3 As shown, the particle size distribution is normally distributed with a single particle size peak and an average particle size of 307 nm, which proves that the present invention greatly improves the heat resistance of whey protein.

[0080] Comparative Example 1 was observed, and the results were as follows Figure 4 As shown, after sterilization, the whey protein suspension produced large flocs and precipitated to the bottom.

[0081] Comparative Example 2 was observed, and the results were as follows Figure 5 As shown, the whey protein suspension produced a large amount of colloid after sterilization.

[0082] Comparative Example 3 was placed vertically for observation, and the results were as follows: Figure 6As shown in FIG. 1 , when the amount of cysteine ​​added exceeds the requirement of the patent to 0.125%, the whey protein suspension forms a jelly-like substance. Figure 7 As shown, when the colorimetric tube is placed flat, a jelly-like substance is formed in the center of the whey protein suspension, and water is separated from the jelly-like substance.

[0083] Comparative Example 4 was observed, and the results were as follows Figure 8 As shown, when the pH of the processed whey protein is at a neutral pH of 7, a large amount of floccules are hung on the wall of the filling bottle after the whey protein is sterilized. It is impossible to prepare a heat-resistant and stable whey protein suspension at this pH value.

[0084] Comparative Example 5 was observed, and the results were as follows Fig. 9 As shown, when the whey protein is treated at pH 9, the whey protein suspension is stratified after sterilization, and the whey protein suspension changes from white to brown. At this pH value, a heat-resistant and stable whey protein suspension cannot be prepared.

[0085] Example 2 was observed, and the results were as follows Fig.10 As shown, the suspension is uniform and milky white, which is consistent with the cysteine ​​result of Example 1. The particle size distribution test of Example 2 is performed, and the results are as follows Fig.11 As shown, whey protein has a uniform particle size distribution under high temperature sterilization conditions, and the particle size is only 324 nm, which proves that the present invention greatly improves the heat resistance of whey protein.

[0086] Example 3 was observed, and the results were as follows Fig.12 As shown, the emulsion is uniform, and no foreign matter, flocculants, etc. are found. The particle size distribution test of Example 3 is performed, and the results are as follows Fig.13 As shown, due to the complex ingredients, the emulsion prepared in the experimental group showed two peaks, and the overall particle size was 870 nm, proving that the emulsion was very stable.

[0087] Comparative Example 6 was observed, and the results were as follows Fig.14 As shown, large aggregates and floccules can be seen in the emulsion, and obvious thermal instability occurs.

[0088] Comparative Example 7 was observed, and the results were as follows Fig.15 As shown, the suspension is uniform and milky white. The particle size distribution test of Comparative Example 7 is performed, and the results are as follows Fig.16 As shown in the figure, whey protein has a multi-peak particle size distribution under high-temperature sterilization conditions, and the particle size is relatively large, reaching 1.37um, which proves that cystine cannot improve the heat resistance of whey protein very well. This may be related to the fact that the sulfur-containing bond of cysteine ​​is located in the central part of the chemical structure and is not easy to produce sulfur-containing free radicals.

[0089] Comparative Example 8 was observed, and the results were as follows Fig.17 As shown, the suspension is uniform and milky white. The particle size distribution test of Comparative Example 8 is performed, and the results are as follows Fig.18 As shown in the figure, whey protein shows multi-peak and multi-particle size distribution under high temperature sterilization conditions, and the particle size is relatively large, which is 704nm. This proves that taurine cannot improve the heat resistance of whey protein very well. This may be related to the fact that the sulfur-containing bond of taurine is located in the central part of the chemical structure and is not easy to produce sulfur-containing free radicals.

[0090] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for improving the stability of whey protein, characterized in that: The steps include: A. 80 g of whey protein was uniformly dispersed in 500 mL of water, 1 g of cysteine ​​was added to obtain a whey protein suspension 1, the whey protein suspension 1 was adjusted to pH 8, and placed in an ice bath for standby use; B. Prepare 500 mL of hot water, and under high-speed shear conditions, quickly add the hot water to the whey protein suspension 1, and keep high-speed shearing to obtain a whey protein suspension 2; the temperature of the whey protein suspension 1 is 25-50° C., the temperature of the hot water is ≥95° C., and the temperature of the whey protein suspension 2 is 50-70° C.; C. Homogenize the whey protein suspension 2 to obtain a stable whey protein product.

2. A method for improving the stability of whey protein, characterized in that: The steps include: A. 50 g of whey protein was uniformly dispersed in 500 mL of water, and 0.8 g of methionine was added to obtain a whey protein suspension 1. The whey protein suspension 1 was adjusted to pH 8 and placed in an ice bath for standby use; B. Prepare 500 mL of hot water, and under high-speed shear conditions, quickly add the hot water to the whey protein suspension 1, and keep high-speed shearing to obtain a whey protein suspension 2; the temperature of the whey protein suspension 1 is 25-50° C., the temperature of the hot water is ≥95° C., and the temperature of the whey protein suspension 2 is 50-70° C.; C. Homogenize the whey protein suspension 2 to obtain a stable whey protein product.

3. A method for improving the stability of whey protein, characterized in that: The steps include: A. Disperse 23 g of whey protein in 500 mL of water, add 0.05 g of cysteine ​​to obtain a whey protein suspension 1, adjust the pH of the whey protein suspension 1 to 7.5, and place it in an ice bath for standby use; B. Prepare 500 mL of hot water, and under high-speed shear conditions, quickly add the hot water to the whey protein suspension 1, and keep high-speed shearing to obtain a whey protein suspension 2; the temperature of the whey protein suspension 1 is 25-50° C., the temperature of the hot water is ≥95° C., and the temperature of the whey protein suspension 2 is 50-70° C.; C. Homogenize the whey protein suspension 2 to obtain a stable whey protein product.

4. The method for improving the stability of whey protein according to any one of claims 1 to 3, characterized in that: In step B, after the hot water is added, high-speed shearing is maintained for 5 to 20 minutes; in step C, the homogenization is high-pressure homogenization with a homogenization pressure of 300 to 700 bar, which is performed 2 to 6 times.

5. Use of the method for improving the stability of whey protein according to any one of claims 1 to 3 in the preparation of special medical foods.

6. The use according to claim 5, characterized in that: The whey protein stabilized product is applied to the preparation of a special medical food emulsion; the special medical food emulsion contains other proteins besides whey protein.

7. The use according to claim 6, characterized in that: The other proteins include one or more of casein, concentrated milk protein, soy protein, and pea protein; the temperature of the whey protein stabilized product is maintained at 40-50° C. during use.

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