A method for preparing protein powder by low-temperature separation

Abstract

This invention discloses a method for preparing protein powder through low-temperature separation, comprising the following steps: S1: raw material pretreatment; S2: low-temperature defatting; S3: multi-stage low-temperature membrane separation; S4: low-temperature concentration; S5: freeze-drying; S6: post-treatment. This invention uses animal-derived whey as raw material, sequentially performing raw material pretreatment, low-temperature defatting, multi-stage low-temperature membrane separation, low-temperature concentration, freeze-drying, and post-treatment. The temperature is controlled within the range of 0–10°C throughout the process. By optimizing the pretreatment process to remove impurities and heat-sensitive interfering substances, and employing a combination of gradient-pore-size ceramic membranes and ultrafiltration membranes, efficient separation and purification of proteins are achieved. Combined with vacuum low-temperature concentration and freeze-drying technology, the active components of whey protein are preserved to the maximum extent. This invention solves the problems of large protein activity loss, low purity, high energy consumption, and easy introduction of chemical contaminants in existing preparation methods.

Description

Technical Field

[0001] This invention belongs to the field of protein powder preparation technology, specifically relating to a low-temperature separation and preparation method for protein powder. Background Technology

[0002] Currently, the raw materials commonly used in the production of protein powder on the market mainly include plant-based raw materials (such as soybeans, peas, peanuts, etc.) and animal-based raw materials (such as milk, eggs, fish skin, etc.). Among them, whey protein is a high-quality protein extracted from animal-based raw materials. It is rich in whey protein, lactoferrin, immunoglobulins, growth factors and other bioactive components. It has many excellent properties such as easy digestion and absorption, high nutritional value and immune regulation, and is widely used in food, health products, cosmetics, biomedicine and other fields.

[0003] The main methods for separating and preparing animal-derived whey protein powder include salting out, organic solvent precipitation, thermal denaturation, membrane separation, and centrifugation. Among these, salting out and organic solvent precipitation are traditional protein separation methods, which involve adding salts or organic solvents to whey to precipitate proteins. However, these two methods require a large amount of salts or organic solvents, and subsequent desalting and desolventizing processes are necessary, increasing production steps and costs. Furthermore, organic solvents may remain in the product, affecting product safety. The introduction of salts can also reduce product purity, and some active proteins may denature under the action of salting out or organic solvents, losing their biological activity.

[0004] The thermal denaturation method utilizes the differences in denaturation temperatures of different proteins in whey. By heating, the impurities are denatured and precipitated, thereby separating the target protein. This method is simple and low-cost. However, during the heating process, the target whey protein may also undergo partial denaturation, resulting in a significant loss of active ingredients. This method cannot meet the requirements for preparing high-activity whey protein powder. In addition, protein polymers are easily generated during the heating process, affecting the solubility and quality of the product.

[0005] Membrane separation has been gradually applied to the field of whey protein separation due to its advantages such as no need to add chemical reagents, room temperature operation, and high separation efficiency. However, in existing membrane separation technologies, raw whey contains impurities such as fat, lactose, and colloidal particles, which can easily cause membrane fouling and clogging, reduce membrane life and separation efficiency, and increase production energy consumption. A single membrane separation process is difficult to achieve efficient protein purification, resulting in low product purity that cannot meet the needs of the high-end market. Although the membrane separation process is operated at room temperature, long-term operation can lead to an increase in system temperature, which can still cause some loss of protein activity.

[0006] Centrifugation is mainly used for the initial defatting and impurity removal of whey. However, the shear force generated during centrifugation is large, which can easily destroy the spatial structure of proteins and cause protein denaturation. At the same time, the precision of centrifugation is limited and cannot effectively remove fine impurities and small molecule contaminants. Subsequent separation processes are still required, which increases the production process and cost.

[0007] Therefore, there is an urgent need for a low-temperature separation and preparation method for protein powder to solve the above problems. Summary of the Invention

[0008] In view of the problems mentioned in the background art above, the purpose of this invention is to provide a method for the low-temperature separation and preparation of protein powder.

[0009] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for preparing protein powder by low-temperature separation, characterized by comprising the following steps: S1: Raw material pretreatment: Select fresh animal whey, first filter it through a 200-300 mesh filter to remove large particulate impurities, then adjust the whey temperature to 2-5℃, add 0.05-0.1% (w / v) of food-grade compound clarifying agent, stir evenly and let stand for 10-15 minutes, then filter it through a 500-600 mesh fine filter and collect the filtrate; S2: Low-temperature defatting. The pretreated filtrate obtained in S1 is sent to a low-temperature centrifuge and centrifuged for 15 to 20 minutes at a temperature of 0 to 4°C and a speed of 8000 to 10000 r / min. The supernatant is collected to remove the fat from the whey. S3: Multi-stage low-temperature membrane separation. The defatted supernatant obtained in S2 is sequentially passed through a ceramic microfiltration membrane and a ceramic ultrafiltration membrane for two-stage membrane separation. The temperature is controlled at 3-8℃ throughout the process. The pore size of the ceramic microfiltration membrane is 0.1-0.2μm, and the filtration rate is 50-80L / (m²·h). The molecular weight cutoff of the ceramic ultrafiltration membrane is 10-50kDa, and the filtration rate is 30-50L / (m²·h). The retentate from the ceramic ultrafiltration membrane is collected. S4: Low-temperature concentration. The retentate obtained in S3 is sent to a vacuum low-temperature concentration device and concentrated under vacuum conditions of 0.08-0.09 MPa and temperature of 40-50°C until the solid content of the concentrate reaches 25-30%. S5: Freeze-drying. The concentrate obtained in S4 is sent to a freeze-drying device. It is first pre-frozen at -40 to -30°C for 2 to 3 hours, then sublimated and dried at a vacuum of 10 to 20 Pa and a sublimation temperature of 0 to 10°C for 8 to 10 hours, and finally desorbed and dried at a desorption temperature of 20 to 30°C for 2 to 3 hours to obtain dried crude whey protein. S6: Post-processing. The crude whey protein obtained in S5 is sieved through an 80-100 mesh sieve, and then sealed and packaged in an environment with a temperature of 5-10℃ and a humidity of ≤30% to obtain the finished animal-derived whey protein powder.

[0010] Further specifying, in S1, the food-grade composite clarifying agent is a mixture of chitosan and modified starch in a mass ratio of 1:2 to 3.

[0011] Further specified, in S1, the stirring speed after adding the food-grade composite clarifying agent is 100-150 r / min, and the stirring time is 3-5 min.

[0012] Further specified, in S1, after the initial filtration is completed, pasteurization is performed, and after the pasteurization is completed, the whey temperature is quickly adjusted to 2-5°C.

[0013] Further specifying, in S2, the low-temperature centrifuge is a disc centrifuge, which adopts a continuous feeding method and a feeding rate of 8 to 12 L / h.

[0014] Further specifying that, in S3, the ceramic microfiltration membrane and the ceramic ultrafiltration membrane need to be pretreated before use. First, rinse the membrane surface with deionized water for 5 to 10 minutes, then soak it in 0.5 to 1% (w / v) sodium hydroxide solution at 30 to 40°C for 30 to 60 minutes, and finally rinse it with deionized water until neutral, and then dry it for use.

[0015] Further specifying that in S4, the vacuum low-temperature concentration process adopts a segmented concentration method, first concentrating to a solid content of 15-20% under a vacuum of 0.08 MPa and a temperature of 40°C, and then concentrating to a solid content of 25-30% under a vacuum of 0.09 MPa and a temperature of 50°C. Further specified, in S5, the freeze-drying equipment adopts a gradient cooling method, reducing the temperature from room temperature to -40 to -30°C at a rate of 5°C / h.

[0016] Further specifying that in step S6, the sieved protein powder needs to be sterilized by ultraviolet light irradiation for 15-20 minutes.

[0017] The beneficial effects of this invention are as follows: 1. The present invention controls the temperature within the range of 0 to 10°C throughout the process. Low-temperature defatting and low-temperature membrane separation avoid protein denaturation caused by temperature rise, so that the protein activity retention rate of the prepared whey protein powder is higher than that of the existing methods, effectively preserving the biological activity of whey protein.

[0018] 2. This invention uses a combination of composite clarifying agent and multi-stage filtration to effectively remove large particulate impurities, colloidal particles and other interfering substances from whey. Combined with two-stage gradient pore size ceramic membrane separation technology, the ceramic microfiltration membrane first removes fine impurities and some small molecule pollutants, while the ceramic ultrafiltration membrane precisely retains the target whey protein and removes impurities such as lactose and small molecule peptides, thereby improving purity.

[0019] 3. This invention does not use any chemical reagents such as salts or organic solvents throughout the entire process, but only adopts physical separation methods, thus avoiding the residue of chemical pollutants and ensuring high product safety.

[0020] 4. The present invention also adds a targeted pretreatment process before membrane separation, which effectively removes impurities that are prone to causing membrane fouling. At the same time, ceramic membrane material is selected, which has the characteristics of being resistant to fouling and easy to clean. Furthermore, through optimized membrane pretreatment and post-cleaning processes, membrane fouling is further reduced, membrane flux stability is improved, membrane service life is extended, and production costs are reduced. Attached Figure Description

[0021] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings; Figure 1 This is a schematic flowchart of a low-temperature separation and preparation method for protein powder according to an embodiment of the present invention; Detailed Implementation To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0022] like Figure 1 As shown, a method for preparing protein powder by low-temperature separation according to the present invention includes the following steps: S1: Raw material pretreatment: Select fresh animal whey, first filter it through a 200-300 mesh filter to remove large particulate impurities, then adjust the whey temperature to 2-5℃, add 0.05-0.1% (w / v) of food-grade compound clarifying agent, stir evenly and let stand for 10-15 minutes, then filter it through a 500-600 mesh fine filter and collect the filtrate; S2: Low-temperature defatting. The pretreated filtrate obtained in S1 is sent to a low-temperature centrifuge and centrifuged for 15 to 20 minutes at a temperature of 0 to 4°C and a speed of 8000 to 10000 r / min. The supernatant is collected to remove the fat from the whey. S3: Multi-stage low-temperature membrane separation. The defatted supernatant obtained in S2 is sequentially passed through a ceramic microfiltration membrane and a ceramic ultrafiltration membrane for two-stage membrane separation. The temperature is controlled at 3-8℃ throughout the process. The pore size of the ceramic microfiltration membrane is 0.1-0.2μm, and the filtration rate is 50-80L / (m²·h). The molecular weight cutoff of the ceramic ultrafiltration membrane is 10-50kDa, and the filtration rate is 30-50L / (m²·h). The retentate from the ceramic ultrafiltration membrane is collected. S4: Low-temperature concentration. The retentate obtained in S3 is sent to a vacuum low-temperature concentration device and concentrated under vacuum conditions of 0.08-0.09 MPa and temperature of 40-50°C until the solid content of the concentrate reaches 25-30%. S5: Freeze-drying. The concentrate obtained in S4 is sent to a freeze-drying device. It is first pre-frozen at -40 to -30°C for 2 to 3 hours, then sublimated and dried at a vacuum of 10 to 20 Pa and a sublimation temperature of 0 to 10°C for 8 to 10 hours, and finally desorbed and dried at a desorption temperature of 20 to 30°C for 2 to 3 hours to obtain dried crude whey protein. S6: Post-processing. The crude whey protein obtained in S5 is sieved through an 80-100 mesh sieve, and then sealed and packaged in an environment with a temperature of 5-10℃ and a humidity of ≤30% to obtain the finished animal-derived whey protein powder.

[0023] Preferably, in S1, the food-grade composite clarifying agent is a mixture of chitosan and modified starch in a mass ratio of 1:2 to 3.

[0024] Preferably, in step S1, the stirring speed after adding the food-grade composite clarifying agent is 100-150 r / min, and the stirring time is 3-5 min.

[0025] Preferably, in step S1, after preliminary filtration, pasteurization is performed, and after pasteurization, the whey temperature is quickly adjusted to 2-5°C.

[0026] Preferably, in S2, the low-temperature centrifuge is a disc centrifuge, which adopts a continuous feeding method and a feeding rate of 8 to 12 L / h.

[0027] Preferably, in step S3, the ceramic microfiltration membrane and the ceramic ultrafiltration membrane need to be pretreated before use. First, rinse the membrane surface with deionized water for 5 to 10 minutes, then soak it in 0.5 to 1% (w / v) sodium hydroxide solution at 30 to 40°C for 30 to 60 minutes, and finally rinse it with deionized water until neutral, and then dry it for later use.

[0028] Preferably, in step S4, the vacuum low-temperature concentration process employs a segmented concentration method, first concentrating to a solid content of 15-20% under a vacuum of 0.08 MPa and a temperature of 40°C, and then concentrating to a solid content of 25-30% under a vacuum of 0.09 MPa and a temperature of 50°C. Preferably, in S5, the freeze-drying equipment adopts a gradient cooling method, reducing the temperature from room temperature to -40 to -30°C at a rate of 5°C / h.

[0029] Preferably, in step S6, the sieved protein powder needs to be sterilized by ultraviolet light irradiation for 15-20 minutes. Example

[0030] Fresh bovine whey (4% protein, w / v) was selected and first filtered through a 250-mesh filter to remove large particles. The whey temperature was then adjusted to 3°C, and 0.08% (w / v) of a food-grade composite clarifying agent (a mixture of chitosan and modified starch at a mass ratio of 1:2.5) was added. The mixture was stirred at 120 rpm for 4 minutes, allowed to stand for 12 minutes, and then filtered through a 550-mesh fine filter. The filtrate was collected and sent to a low-temperature centrifuge at 2°C and 90 rpm. Centrifuge at 00 r / min for 18 min, collect the supernatant, remove fat from the whey, and simultaneously pretreat the ceramic microfiltration membrane (pore size 0.15 μm) and ceramic ultrafiltration membrane (molecular weight cutoff 30 kDa). First, rinse the membrane surface with deionized water for 8 min, then soak it in 0.8% (w / v) sodium hydroxide solution at 35℃ for 45 min, and finally rinse with deionized water until neutral. After drying, the degreased supernatant is passed sequentially through the pretreated ceramic microfiltration membrane and ceramic ultrafiltration membrane for two-stage membrane separation. The entire process was controlled at a temperature of 5℃. The operating pressure of the ceramic microfiltration membrane was 0.15 MPa, and the filtration rate was 65 L / (m²·h). The operating pressure of the ceramic ultrafiltration membrane was 0.25 MPa, and the filtration rate was 40 L / (m²·h). The retentate from the ceramic ultrafiltration membrane was collected and sent to a vacuum low-temperature concentration device. A staged concentration method was used: first, concentration was carried out at a vacuum of 0.08 MPa and a temperature of 40℃ until the solid content reached 18%; then, concentration was carried out at a vacuum of 0.09 MPa and a temperature of 50℃ until the solid content reached [missing value]. 28% was used to obtain a concentrated solution, which was then fed into a freeze-drying device. The feed thickness of the concentrated solution was controlled at 8 mm. It was first pre-frozen at -35℃ for 2.5 h, then sublimated and dried at a vacuum of 15 Pa and a sublimation temperature of 5℃ for 9 h, and finally desorbed and dried at a desorption temperature of 25℃ for 2.5 h to obtain dried crude whey protein. The crude whey protein was then sieved through a 90-mesh sieve to remove lumps and impurities, and then sealed and packaged at a temperature of 8℃ and a humidity of 25% to obtain the finished animal-derived whey protein powder.

[0031] The whey protein powder product prepared in this embodiment was tested and found to have a purity of 96.8%, a protein activity retention rate of 98.5%, a moisture content of 2.1%, and a fat content of 0.08%. All indicators met the standards for high-end whey protein powder. Example

[0032] Fresh sheep whey (protein content 3.5%, w / v) was selected and first filtered through a 200-mesh filter to remove large particles of impurities. The whey temperature was then adjusted to 2°C, and 0.05% (w / v) of a food-grade composite clarifying agent (a mixture of chitosan and modified starch at a mass ratio of 1:2) was added. The mixture was stirred at 100 rpm for 3 minutes, and after thorough mixing, it was allowed to stand for 10 minutes. The whey was then filtered through a 500-mesh fine filter, and the filtrate was collected. The pretreated filtrate was then sent to a low-temperature centrifuge and centrifuged at 0°C and 800 rpm. Centrifuge at 000 r / min for 15 min, collect the supernatant, remove fat from the whey, and simultaneously pretreat the ceramic microfiltration membrane (pore size 0.1 μm) and ceramic ultrafiltration membrane (molecular weight cutoff 10 kDa). First, rinse the membrane surface with deionized water for 5 min, then soak it in 0.5% (w / v) sodium hydroxide solution at 30℃ for 30 min, and finally rinse with deionized water until neutral. After drying, use it for two-stage processing. Pass the defatted supernatant sequentially through the pretreated ceramic microfiltration membrane and ceramic ultrafiltration membrane. Membrane separation was performed, with the temperature controlled at 3℃ throughout. The ceramic microfiltration membrane operated at a pressure of 0.1 MPa and a filtration rate of 50 L / (m²·h), while the ceramic ultrafiltration membrane operated at a pressure of 0.2 MPa and a filtration rate of 30 L / (m²·h). The retentate from the ceramic ultrafiltration membrane was collected and sent to a vacuum low-temperature concentration device. A staged concentration method was used: first, concentration was carried out at a vacuum of 0.08 MPa and a temperature of 40℃ until the solid content reached 15%, and then concentration was carried out at a vacuum of 0.09 MPa and a temperature of 50℃ until... With a solid content of 25%, a concentrated solution was obtained. The concentrated solution was then fed into a freeze-drying device, with the feed thickness controlled at 5 mm. It was first pre-frozen at -40℃ for 2 hours, then sublimated and dried at a vacuum of 10 Pa and a sublimation temperature of 0℃ for 8 hours, and finally decomposed and dried at a desorption temperature of 20℃ for 2 hours to obtain dried crude whey protein. The crude whey protein was then sieved through an 80-mesh sieve to remove lumps and impurities, and then sealed and packaged at a temperature of 5℃ and a humidity of 20% to obtain the finished animal-derived whey protein powder.

[0033] The whey protein powder product prepared in this embodiment was tested and found to have a purity of 95.2%, a protein activity retention rate of 98.2%, a moisture content of 2.3%, and a fat content of 0.09%. All indicators met the standards for high-end whey protein powder. Example

[0034] Fresh porcine whey (5% protein, w / v) was selected and first filtered through a 300-mesh filter to remove large particles. The whey temperature was then adjusted to 5°C, and 0.1% (w / v) of a food-grade composite clarifying agent (a mixture of chitosan and modified starch at a mass ratio of 1:3) was added. The mixture was stirred at 150 rpm for 5 minutes, and after thorough mixing, it was allowed to stand for 15 minutes. The whey was then filtered through a 600-mesh fine filter, and the filtrate was collected. The pretreated filtrate was then sent to a low-temperature centrifuge at 4°C and 1000 rpm. Centrifuge at 0 rpm for 20 min, collect the supernatant, and remove fat from the whey. Simultaneously, pretreat the ceramic microfiltration membrane (0.2 μm pore size) and ceramic ultrafiltration membrane (50 kDa molecular weight cutoff). First, rinse the membrane surface with deionized water for 10 min, then soak it in 1% (w / v) sodium hydroxide solution at 40℃ for 60 min, and finally rinse with deionized water until neutral. After drying, use it for two-stage membrane separation. Pass the defatted supernatant sequentially through the pretreated ceramic microfiltration membrane and ceramic ultrafiltration membrane. The temperature was controlled at 8℃ throughout the process. The operating pressure of the ceramic microfiltration membrane was 0.2MPa, and the filtration rate was 80L / (m²·h); the operating pressure of the ceramic ultrafiltration membrane was 0.3MPa, and the filtration rate was 50L / (m²·h). The retentate from the ceramic ultrafiltration membrane was collected and sent to a vacuum low-temperature concentration device. A staged concentration method was used: first, it was concentrated to a solid content of 20% under a vacuum of 0.08MPa and a temperature of 40℃, and then concentrated to a solid content of 30% under a vacuum of 0.09MPa and a temperature of 50℃. The concentrate is obtained by 10% and fed into a freeze dryer. The feed thickness of the concentrate is controlled at 10mm. It is first pre-frozen at -30℃ for 3h, then sublimated and dried at a vacuum of 20Pa and a sublimation temperature of 10℃ for 10h, and finally decomposed and dried at a desorption temperature of 30℃ for 3h to obtain dried crude whey protein. The crude whey protein is then sieved through a 100-mesh sieve to remove lumps and impurities, and then sealed and packaged at a temperature of 10℃ and a humidity of 30% to obtain the finished animal-derived whey protein powder.

[0035] The whey protein powder product prepared in this embodiment was tested and found to have a purity of 97.5%, a protein activity retention rate of 98.8%, a moisture content of 1.9%, and a fat content of 0.07%. All indicators met the standards for high-end whey protein powder.

[0036] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for the production of a protein powder by low temperature separation, characterized in that: Includes the following steps: S1: Raw material pretreatment: Select fresh animal whey, first filter it through a 200-300 mesh filter to remove large particulate impurities, then adjust the whey temperature to 2-5℃, add 0.05-0.1% (w / v) of food-grade compound clarifying agent, stir evenly and let stand for 10-15 minutes, then filter it through a 500-600 mesh fine filter and collect the filtrate; S2: Low-temperature defatting. The pretreated filtrate obtained in S1 is sent to a low-temperature centrifuge and centrifuged for 15 to 20 minutes at a temperature of 0 to 4°C and a speed of 8000 to 10000 r / min. The supernatant is collected to remove the fat from the whey. S3: Multi-stage low-temperature membrane separation. The defatted supernatant obtained in S2 is sequentially passed through a ceramic microfiltration membrane and a ceramic ultrafiltration membrane for two-stage membrane separation. The temperature is controlled at 3-8℃ throughout the process. The pore size of the ceramic microfiltration membrane is 0.1-0.2μm, and the filtration rate is 50-80L / (m²·h). The molecular weight cutoff of the ceramic ultrafiltration membrane is 10-50kDa, and the filtration rate is 30-50L / (m²·h). The retentate from the ceramic ultrafiltration membrane is collected. S4: Low-temperature concentration. The retentate obtained in S3 is sent to a vacuum low-temperature concentration device and concentrated under vacuum conditions of 0.08-0.09 MPa and temperature of 40-50°C until the solid content of the concentrate reaches 25-30%. S5: Freeze-drying. The concentrate obtained in S4 is sent to a freeze-drying device. It is first pre-frozen at -40 to -30°C for 2 to 3 hours, then sublimated and dried at a vacuum of 10 to 20 Pa and a sublimation temperature of 0 to 10°C for 8 to 10 hours, and finally desorbed and dried at a desorption temperature of 20 to 30°C for 2 to 3 hours to obtain dried crude whey protein. S6: Post-processing. The crude whey protein obtained in S5 is sieved through an 80-100 mesh sieve, and then sealed and packaged in an environment with a temperature of 5-10℃ and a humidity of ≤30% to obtain the finished animal-derived whey protein powder.

2. The method for preparing protein powder by low-temperature separation according to claim 1, characterized in that: In S1, the food-grade composite clarifying agent is a mixture of chitosan and modified starch in a mass ratio of 1:2 to 3.

3. The method for preparing protein powder by low-temperature separation according to claim 2, characterized in that: In step S1, the stirring speed after adding the food-grade composite clarifying agent is 100-150 r / min, and the stirring time is 3-5 min.

4. The method for preparing protein powder by low-temperature separation according to claim 3, characterized in that: In S1, after preliminary filtration, pasteurization is performed, and after pasteurization, the whey temperature is quickly adjusted to 2-5°C.

5. The method for preparing protein powder by low-temperature separation according to claim 4, characterized in that: In S2, the low-temperature centrifuge is a disc centrifuge, which adopts a continuous feeding method with a feeding rate of 8-12 L / h.

6. The method for preparing protein powder by low-temperature separation according to claim 5, characterized in that: In step S3, the ceramic microfiltration membrane and ceramic ultrafiltration membrane need to be pretreated before use. First, rinse the membrane surface with deionized water for 5 to 10 minutes, then soak it in 0.5 to 1% (w / v) sodium hydroxide solution at 30 to 40°C for 30 to 60 minutes, and finally rinse it with deionized water until neutral, and then dry it for later use.

7. The method for preparing protein powder by low-temperature separation according to claim 6, characterized in that: In S4, the vacuum low-temperature concentration process adopts a segmented concentration method. First, it is concentrated to a solid content of 15-20% under a vacuum of 0.08 MPa and a temperature of 40°C, and then concentrated to a solid content of 25-30% under a vacuum of 0.09 MPa and a temperature of 50°C.

8. The method for preparing protein powder by low-temperature separation according to claim 7, characterized in that: In S5, the freeze-drying equipment adopts a gradient cooling method, reducing the temperature from room temperature to -40 to -30℃ at a rate of 5℃ / h.

9. The method for preparing protein powder by low-temperature separation according to claim 8, characterized in that: In step S6, the sieved protein powder needs to be sterilized by ultraviolet light for 15-20 minutes.

Images