Method for improving stability of whey protein and application of whey protein in special medical food

Abstract

The invention relates to a method for improving the stability of whey protein and application of the whey protein in food for special medicine, and the method comprises the following steps: A, uniformly dispersing the whey protein in water, shearing at normal temperature to obtain a whey protein suspension 1, and adjusting the pH value to alkalescence for later use; b, dissolving phospholipid in hot water, heating the whey protein suspension 1 to a specific temperature, and adding the phospholipid aqueous solution into the whey protein suspension 1 under a high-speed shearing condition to obtain a whey protein suspension 2; c, the whey protein suspension 2 is subjected to heat preservation and continuous shearing, and a whey protein suspension 3 is obtained after a period of time; and D, homogenizing the whey protein suspension 3 to obtain the whey protein stable product. According to the invention, the whey protein is pretreated to expose the internal hydrophobic structure, and the phospholipid is combined with the hydrophobic part of the whey protein to stabilize the structure of the whey protein, so that the problem that the whey protein is easy to aggregate, flocculate and precipitate at high temperature is solved, and the application of the whey protein in special medical food is improved.

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. Liquid preparations are more convenient to use and more effective than powders, and are the development trend of enteral nutrition in the future. However, due to the poor stability and high technical difficulty of liquid preparations, they have high requirements for product formula design and production processes. Since my country issued the "GB29922-2013 General Rules for Formulated Foods for Special Medical Purposes" in 2016, there have been only 4 registered ordinary complete nutrition formula emulsion dosage forms among special medical foods, and the protein source of existing emulsion products is single. This is because the formula of the complete nutrition emulsion is complex and the process conditions are harsh. Protein is prone to flocculation, precipitation, aggregation and other phenomena during the preparation process. This dosage form has high requirements for protein stability. Whey protein can be absorbed and digested by the body quickly, has rich branched-chain amino acids and leucine content, can effectively promote muscle synthesis, inhibit muscle degradation, etc., and the bioavailability and amino acid score of whey protein are the highest among proteins. Compared with other proteins, whey protein is more sensitive to heat and has poorer stability. No successful whey protein emulsion products using moist heat sterilization technology have been found in China. Therefore, improving the stability of whey protein in special medical food emulsion products will greatly improve the nutritional adequacy, bioavailability and compliance of the products. Carrying out research on whey protein raw material processing technology and stabilization technology, solving the problem of protein flocculation and precipitation are the key technologies that need to be solved in this project. Summary of the invention

[0003] The purpose of the present invention is to solve the problem that whey protein is easy to aggregate, flocculate and precipitate at high temperature by processing whey protein and adding phospholipids, so as to improve the application of whey protein in special medical foods.

[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. Dissolve phospholipids in hot water to obtain a phospholipid aqueous solution for later use;

[0007] B. Evenly dispersing whey protein in water, and shearing to obtain whey protein suspension 1;

[0008] C. Heating and shearing the whey protein suspension 1, and then adding the phospholipid aqueous solution to the whey protein suspension 1 to obtain a whey protein suspension 2;

[0009] D. keeping the whey protein suspension 2 warm and continuously shearing to obtain a whey protein suspension 3;

[0010] E. Homogenize the whey protein suspension 3 to obtain a stable whey protein product.

[0011] The present invention precisely controls the denaturation conditions of whey protein to expose the internal hydrophobic groups without irreversible chemical bond breaking and cross-linking reactions, and uses safe and mild amphiphilic lecithin to combine with the hydrophobic groups exposed by whey protein. The method of homogenization can greatly improve the thermal stability of whey protein, solve the problem of easy flocculation and precipitation of whey protein in the thermal processing system, and improve the application of whey protein in special medical emulsion products. At the same time, the use of physical processing and the addition of mild-flavored lecithin ensures that the flavor of the processed whey protein does not change significantly, making it more easily accepted by the audience.

[0012] After research, it was found that the main components of whey protein are α-lactoglobulin and β-lactalbumin. As a globular protein, as the temperature rises, the non-covalent bonds are destroyed, the structure begins to unfold, the internal structure of the protein is opened, and the hydrophobic groups, sulfhydryl groups and disulfide bonds inside the spherical structure are exposed. The initial unfolding is reversible; when it is above the denaturation temperature for a long time, its secondary and tertiary structures are irreversibly destroyed, promoting the formation of hydrophobic interactions and aggregation between molecules, and the whey protein undergoes coagulation, sedimentation and denaturation. The present invention controls the whey protein in the thermal denaturation process, exposes the hydrophobic groups inside the protein in advance, and uses small molecular phospholipids to bind the exposed hydrophobic groups inside the protein, which can reduce the exposed hydrophobic groups between protein molecules after heating, thereby reducing the interaction between the sulfhydryl groups and disulfide bonds between molecules and the aggregation generated by the hydrophobic interaction, generating non-natural dimers, trimers and tetramers to form aggregates with higher molecular weights, inhibiting the agglomeration of the protein, so that the protein has better solubility in the solution.

[0013] Preferably, in step B and step D, the shearing speed includes 4500-6500 rpm; in step C, the shearing speed includes 2500-3200 rpm; in step A, the hot water temperature includes 65-75°C; in step B, the temperature of the whey protein suspension 1 includes 20-30°C; in step C, the temperature of the whey protein suspension 2; in step D, the temperature of the whey protein suspension 3 includes 65-75°C.

[0014] After the dissolution in step B is completed, the temperature should be kept as low as possible, preferably at 20 to 30 degrees, and then quickly heated up when used.

[0015] Preferably, in step A, the mass content of the phospholipid is 0.1% to 1%, and the mass ratio of the phospholipid to the hot water is 1 to 40:100; in step B, in the whey protein suspension 1, the mass ratio of the whey protein to water is 1 to 10:40; in step C, the specific operation of heating and shearing includes: immediately placing the whey protein suspension 1 in a 60-70°C water bath for heating and shearing to obtain the whey protein suspension 2; in step D, the specific operation of heat preservation and continuous shearing includes: keeping the whey protein suspension 2 in a 65-75°C water bath, continuously shearing for 5 to 10 minutes, and obtaining the whey protein suspension 3.

[0016] In step C, the reaction temperature is precisely controlled and the suspension is kept under continuous shearing. The temperature is controlled within a temperature range where the protein folding structure just opens to expose the hydrophobic groups, but the disulfide bonds are not broken and the free thiol groups fail to obtain reactive activity.

[0017] In step D, the temperature of the whey protein suspension 2 is strictly controlled within the temperature range of 65 to 75° C., and after reaching the temperature, the shear rate is appropriately increased and the shear time is strictly controlled within 5 to 10 min. The shear speed is selected according to the depth of the container and the surface area of ​​the liquid. In principle, the liquid surface can be kept rolling but not splashing.

[0018] Preferably, in step A, the method of dissolving the phospholipid in the hot water includes dissolution by magnetic stirring; in step B, it also includes adjusting the pH to adjust the whey protein suspension 1 to a weak alkaline state; in step E, the homogenization includes one or more of high-pressure homogenization, membrane homogenization, and microfluidization homogenization.

[0019] Preferably, in step A, the phospholipids include but are not limited to one or more of soybean lecithin, egg yolk lecithin, and sunflower seed lecithin; in step B, the pH is adjusted to be greater than 7 and less than 9; in step E, the homogenization is high-pressure homogenization with a pressure of 300 to 700 bar, and is performed 2 to 6 times.

[0020] Lecithin is a special natural small molecule surfactant with a relative molecular weight of about 0.760kDp. It is usually derived from the cell membrane of plants, animals or microbial tissues and is widely used as a food emulsifier. Among all natural emulsifiers, lecithin is relatively stable and can better maintain the stability of droplets under weakly alkaline pH conditions. Lecithin also has antioxidant properties and can inhibit the oxidation of sulfhydryl groups when combined with proteins, thereby reducing the phenomenon of emulsion coagulation due to heat.

[0021] pH regulators include but are not limited to sodium hydroxide, potassium hydroxide, calcium oxide, magnesium oxide and other commonly used acid-base regulators, and the pH value is strictly maintained at pH 7 to pH 9, excluding pH 7 and pH 9. pH adjustment is performed after shearing to adjust the system to a weak alkaline state so that the whey protein can better expose the internal hydrophobic groups at the critical temperature of denaturation.

[0022] A stable whey protein product obtained by the method for improving the stability of whey protein.

[0023] The present invention exposes the internal hydrophobic structure by pretreating whey protein, and combines the amphiphilic phospholipids with the hydrophobic part of the whey protein to stabilize the structure of the whey protein, thereby solving the problem that the whey protein is easy to aggregate, flocculate and precipitate at high temperature, and improving the application of whey protein in special medical foods.

[0024] An application of the whey protein stabilized product as described above is used for preparing special medical foods.

[0025] Preferably, the whey protein stabilized product is dissolved and homogenized with other ingredients and then sterilized to form a uniform and stable special medical emulsion product containing whey protein that meets regulatory requirements.

[0026] Preferably, when other proteins exist in the special medical emulsion product, after the other materials are dispersed and dissolved, the other proteins are first added for dispersion, and the pH is adjusted to make the system weakly alkaline, and then the whey protein stabilization product is added while high-speed shearing is performed, followed by homogenization and sterilization to obtain the special medical emulsion product.

[0027] Preferably, the other proteins include one or more of caseinate, casein, concentrated milk protein, soy protein, and pea protein; the pH adjustment includes adjusting the pH of the system to greater than 7 and less than 9; the high-speed shear rate includes 2500-3500rpm; the temperature of the whey protein stabilized product is maintained at 40-50°C during use.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention improves the heat resistance, ionic strength resistance, stability with other proteins at high temperatures, etc. of whey protein by pretreating whey protein and adding phospholipids. Whey protein contains a full range of essential amino acids with rich content, which are high-quality amino acids. Compared with casein, whey protein can be absorbed and digested faster by the body. It has rich content of branched-chain amino acids and leucine. Branched-chain amino acids can effectively promote muscle synthesis and inhibit muscle degradation, and leucine has been proven to play an important role in maintaining and repairing muscles. Therefore, whey protein has always been a focus of clinical attention. However, technically, whey protein is easy to condense and precipitate at high temperatures, which has become a key technical problem that limits the application of whey protein in products such as functional foods, health foods and special medical foods. The innovative point of the present invention is that the denaturation temperature of whey protein is strictly controlled, and the method of coordinating homogenization can greatly improve the thermal stability of whey protein. What is more unexpected is that adding an appropriate amount of phospholipids during the whey treatment process can not only improve the thermal stability of whey protein itself, but also well improve the compatibility of whey protein with other proteins. Even in the presence of an emulsion with high particle concentration, the product of whey protein compounded with other proteins still has extremely high heat resistance and stability. In addition, the phospholipids have a mild flavor, and adding them into whey protein will not bring the influence of bad flavor, which is more conducive to the application of whey protein in products. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Product status diagram for implementation example 1;

[0031] Figure 2 The particle size distribution diagram of Example 1;

[0032] Figure 3 This is the characteristic transmittance spectrum of the emulsion stability of Example 1. The color of the curve represents the order of test time, red is the earlier test time, and green is the later test time;

[0033] Figure 4 This is the product status diagram of Comparative Example 1;

[0034] Figure 5 It is the particle size distribution diagram of Comparative Example 1;

[0035] Figure 6 This is the characteristic transmittance spectrum of the emulsion stability of Comparative Example 1. The color of the curve represents the order of test time, with red indicating an earlier test time and green indicating a later test time;

[0036] Figure 7 This is the product status diagram for implementation example 2;

[0037] Figure 8 This is the particle size distribution diagram of Example 2;

[0038] Fig. 9This is the product status diagram of Comparative Example 2. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Example 1

[0041] Weigh 270g purified water and place it in a 70℃ water bath for insulation. After the water temperature reaches 70℃, add the weighed 4g soybean lecithin and turn on the magnetic stirring to dissolve; weigh 100g whey protein, use a high-speed disperser to evenly disperse the whey protein in 1000mL purified water, shear speed 6000rpm, shear time 15 minutes, until the whey protein is completely dissolved. Use 1M NaOH to adjust the whey protein to pH 8.5, place the whey protein in a 70℃ water bath for slow shearing, the shear speed is 2500rpm, until the temperature rises to 70℃, the heating time does not exceed 5min, after the temperature reaches 70℃, add the prepared soybean lecithin aqueous solution to the whey protein aqueous solution, and turn on the high-speed shear machine for high-speed shearing in advance, the shear speed is 6000rpm, keep the high-speed shearing for 10min, and then perform high-pressure homogenization on the processed whey protein, the homogenization pressure is 400bar, and the homogenization times are 2 times. After homogenization is completed, the whey protein is filled and sterilized at 121°C for 15 minutes.

[0042] Comparative Example 1

[0043] Weigh 270g of purified water and place it in a 70℃ water bath to keep warm. After the water temperature reaches 70℃, add the weighed 4g of soybean lecithin and turn on the magnetic stirring to dissolve. After dissolution, cool the soybean lecithin aqueous solution to 20℃; weigh 100g of whey protein, and use a high-speed disperser to evenly disperse the whey protein in 1000mL, 20℃ purified water, with a shear speed of 6000rpm and a shear time of 15 minutes until the whey protein is completely dissolved. Use 1M NaOH to adjust the whey protein to pH 8.5, and homogenize the whey protein aqueous solution and the soybean lecithin aqueous solution at room temperature, respectively. The homogenization pressure is 400bar and the homogenization times are 2 times. After homogenization, add the soybean lecithin aqueous solution to the whey protein aqueous solution, turn on the high-speed shearing machine for high-speed shearing, maintain high-speed shearing for 10min, and then fill the mixed solution and sterilize it at 121℃ for 15 minutes.

[0044] Example 2

[0045] Weigh 270g purified water and place it in a 70℃ water bath for insulation. After the water temperature reaches 70℃, add the weighed 4g soybean lecithin and turn on the magnetic stirring to dissolve; weigh 100g whey protein, use a high-speed disperser to evenly disperse the whey protein in 1000mL purified water, shear speed 6000rpm, shear time 15 minutes, until the whey protein is completely dissolved. Use 1M NaOH to adjust the whey protein to pH 8.5, place the whey protein in a 70℃ water bath for slow shearing, the shear speed is 2500rpm, until the temperature rises to 70℃, the heating time does not exceed 5min, after the temperature reaches 70℃, add the prepared soybean lecithin aqueous solution to the whey protein aqueous solution, and turn on the high-speed shear machine for high-speed shearing in advance, the shear speed is 6000rpm, keep the high-speed shearing for 10min, and then perform high-pressure homogenization on the processed whey protein, the homogenization pressure is 400bar, and the homogenization times are 2 times. After homogenization is completed, the whey protein suspension is cooled to 45°C and set aside.

[0046] Weigh 336g of calcium caseinate, 207g of maltodextrin, 90g of resistant dextrin, 350g of blended oil, 6g of vitamins, 60g of minerals, 1.5g of thickener, and 3000mL of water. Use a high-speed shearing machine to disperse calcium caseinate, maltodextrin, resistant dextrin, blended oil, thickener and other materials in water at a speed of 3000rpm until they are evenly dispersed, then pour the above-prepared whey protein suspension into it, add vitamins and minerals after shearing for about 5 minutes, and continue shearing 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.

[0047] Comparative Example 2

[0048] Weigh 270g blended oil and place it in a 70℃ water bath for insulation. After the oil temperature reaches 70℃, add the weighed 4g soybean lecithin, turn on magnetic stirring to dissolve, and cool the oil phase to room temperature after dissolution; weigh 100g whey protein, use a high-speed disperser to evenly disperse the whey protein in 1000mL purified water, shear speed 6000rpm, shear time 15 minutes, until the whey protein is completely dissolved, use 1M NaOH to adjust the whey protein to pH 8.5, and keep the whey protein aqueous solution temperature at 4℃. The prepared soybean lecithin oil solution is added to the whey protein aqueous solution, and the high-speed shearing machine is turned on in advance for high-speed shearing. After keeping high-speed shearing for 10min, the processed whey protein is subjected to high-pressure homogenization, homogenization pressure 400bar, and homogenization times 2 times. After homogenization is completed, the whey protein suspension is cooled to 45℃ for standby use.

[0049] Weigh 336g of calcium caseinate, 207g of maltodextrin, 90g of resistant dextrin, 80g of blended oil, 6g of vitamins, 60g of minerals, 1.5g of thickener, and 3000mL of water. Use a high-speed shearing machine to disperse calcium caseinate, maltodextrin, resistant dextrin, blended oil, thickener and other materials in water at a speed of 3000rpm until they are evenly dispersed, then pour the above-prepared whey protein suspension into it, add vitamins and minerals after shearing for about 5 minutes, and continue shearing 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.

[0050] The sensory results of Examples 1-2 and Comparative Examples 1-2 of the present invention are shown in Table 1:

[0051] Table 1

[0052]

[0053]

[0054] As can be seen from Table 1, the products of Example 1 and Example 2 pre-treated by the method of the present invention are relatively stable after sterilization, have uniform emulsion characteristics, can stabilize the whey protein product and improve the stability of the whey protein after mixing with other ingredients at high temperature.

[0055] Example 1 was observed, and the results were as follows Figure 1 As shown in Figure 2, after sterilization, the whey protein presents a stable uniform emulsion with an average particle size of 0.176 μm and a single-peak distribution of particle size. Figure 2 As shown, the stability characteristic transmittance spectrum is as follows Figure 3 As shown, the stability characteristic transmittance spectrum of Comparative Example 1 ( Figure 6 ), it can be seen from the comparison that the spectrum lines of Example 1 are densely distributed and the curve changes smoothly, indicating that as the centrifugation time continues to increase, the emulsion of Example 1 is more stable.

[0056] Comparative Example 1 was observed, and the results were as follows Figure 4 As shown in the figure, when the whey protein is not heated and the whey protein and phospholipids are not homogenized together, part of the mixed solution after sterilization appears white and floating. Figure 5 As shown, it presents a bimodal distribution, and the average particle size is 0.276 μm, which is larger than the particle size of Example 1. This shows that after being treated by the method of the present invention, under the premise of the same formula, the finished product of Example 1 is more stable than the finished product of Comparative Example 1.

[0057] Example 2 was observed, and the results were as follows Figure 7As shown, the emulsion is uniform, and no flocculation or obvious precipitation is observed. The particle size distribution test of Example 2 is performed, and the results are as follows Figure 8 As shown, the average particle size of the emulsion is 0.406 μm, and the particle size presents a unimodal distribution, indicating that the emulsion system is uniform and stable.

[0058] Comparative Example 2 was observed, and the results were as follows Fig. 9 As shown, the emulsion state after sterilization is porridge-like. The sample formula of Comparative Example 2 is the same as that of Example 2. The phospholipids in Comparative Example 2 are dissolved in the oil phase liquid and mixed with whey protein (i.e., the traditional emulsion preparation process), which greatly reduces the chance of phospholipids combining with the hydrophobic groups in whey protein, indicating that phospholipids are not the main factor in improving the stability of whey protein. It is necessary to combine the invention method of this patent, pre-treat the whey protein to expose the internal hydrophobic structure, and combine the amphiphilic phospholipids with the hydrophobic parts of the whey protein to achieve the purpose of the patent of this invention and improve the application of whey protein in special medical foods.

[0059] The above disclosure is only the preferred embodiment of the present invention, which 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. Dissolve phospholipids in hot water to obtain a phospholipid aqueous solution for later use; B. Evenly dispersing whey protein in water, and shearing to obtain whey protein suspension 1; C. Heating and shearing the whey protein suspension 1, and then adding the phospholipid aqueous solution to the whey protein suspension 1 to obtain a whey protein suspension 2; D. keeping the whey protein suspension 2 warm and continuously shearing to obtain a whey protein suspension 3; E. Homogenize the whey protein suspension 3 to obtain a stable whey protein product.

2. The method for improving the stability of whey protein according to claim 1, characterized in that: In step B and step D, the shearing rotation speed includes 4500-6500 rpm; in step C, the shearing rotation speed includes 2500-3200 rpm; in step A, the hot water temperature includes 65-75° C.; in step B, the temperature of the whey protein suspension 1 includes 20-30° C.; in step C, the temperature of the whey protein suspension 2; in step D, the temperature of the whey protein suspension 3 includes 65-75° C.

3. The method for improving the stability of whey protein according to claim 1, characterized in that: In step A, the mass content of the phospholipid is 0.1% to 1%, and the mass ratio of the phospholipid to the hot water is 1 to 40:100; in step B, in the whey protein suspension 1, the mass ratio of the whey protein to water is 1 to 10:40; In step C, the specific operation of heating and shearing includes: immediately placing the whey protein suspension 1 in a 65-75° C. water bath to heat and shear, so as to obtain the whey protein suspension 2; and the specific operation of heat preservation and continuous shearing in step D includes: keeping the whey protein suspension 2 in a 65-75° C. water bath, continuously shearing for 5-10 minutes, so as to obtain the whey protein suspension 3.

4. The method for improving the stability of whey protein according to claim 1, characterized in that: In step A, the method of dissolving the phospholipid in the hot water includes dissolution by magnetic stirring; in step B, it also includes adjusting the pH to adjust the whey protein suspension 1 to a weak alkaline state; in step E, the homogenization includes one or more of high-pressure homogenization, membrane homogenization, and microfluidization homogenization.

5. The method for improving the stability of whey protein according to claim 4, characterized in that: In step A, the phospholipids include one or more of soybean lecithin, egg yolk lecithin, and sunflower seed lecithin; in step B, the pH is adjusted to be greater than 7 and less than 9; in step E, the homogenization is high-pressure homogenization with a pressure of 300 to 700 bar, and is performed 2 to 6 times.

6. A stable whey protein product obtained by the method for improving the stability of whey protein as claimed in claim 1.

7. An application of the whey protein stabilized product as claimed in claim 6, characterized in that: Used to prepare special medical foods.

8. The use according to claim 7, characterized in that The whey protein stabilized product is dissolved and homogenized with other ingredients and then sterilized to form a uniform and stable special medical emulsion product containing whey protein that meets regulatory requirements.

9. The use according to claim 8, characterized in that When other proteins exist in the special medical emulsion product, after the other materials are dispersed and dissolved, the other proteins are first added for dispersion, and the pH is adjusted to make the system weakly alkaline. Then, the whey protein stabilization product is added while high-speed shearing is performed, and then homogenization and sterilization are performed to obtain the special medical emulsion product.

10. The use according to claim 9, characterized in that The other proteins include one or more of caseinate, casein, concentrated milk protein, soy protein, and pea protein; the pH adjustment includes adjusting the system pH to greater than 7 and less than 9; the high-speed shear rate includes 2500-3500rpm; the whey protein stabilized product is maintained at a temperature of 40-50°C during use.

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