Technology for drying mycoprotein by dry-wet mixed method

Abstract

The invention relates to the technical field of biotechnology, in particular to a dry-wet mixing method mycoprotein drying process which comprises the steps of preliminary dehydration of wet mycoprotein, crushing of dry protein, mixing of dry protein and wet protein, drying, screening and the like. Dry protein and wet protein are mixed according to a specific proportion, the viscosity of the wet protein is reduced through the dry protein, the caking phenomenon is reduced, the heat conduction efficiency is improved, the granularity uniformity is optimized, and the protein activity is protected. According to the process, the drying efficiency and the product quality are remarkably improved, the protein content of a finished product is stabilized at 78.8%-79.4%, the particle size distribution is concentrated at 80-120 meshes, and the fluctuation between batches does not exceed 0.6%. The method solves the problems of low efficiency, non-uniform particles, activity loss and the like in the traditional process, and is suitable for the fields of feeds, foods and medicines.

Description

Technical Field

[0001] This invention belongs to the field of biotechnology, specifically a dry-wet mixing method for drying bacterial protein. Background Technology

[0002] Microbial protein, as an important protein source, is widely used in feed, food, and pharmaceutical fields. Drying is a crucial step in its production, directly affecting product quality (such as protein content and activity), particle size, and production efficiency. Traditional drying processes often use direct drying of single wet microbial protein, which presents the following problems: First, wet microbial protein has a high water content and high viscosity, making it prone to clumping during direct drying, resulting in low heat transfer efficiency and prolonged drying time. Second, clumping can easily cause localized overheating or insufficient drying, leading to significant differences in particle size and affecting subsequent applications. Furthermore, to improve drying efficiency, traditional processes often use high-temperature drying, which can easily lead to protein denaturation and reduced activity; conversely, lowering the temperature to protect protein activity further reduces drying efficiency, making it difficult to balance efficiency and quality. Finally, under current processes, the protein content of the product fluctuates significantly, typically stabilizing at 76%-77%, making it difficult to meet the demand for high-purity protein products.

[0003] Therefore, developing a drying process that can both ensure drying efficiency and improve the uniformity of product particle size, protein activity and content has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a dry-wet mixing method for drying bacterial protein. This method involves mixing dried bacterial protein with wet bacterial protein in a specific ratio and then drying the mixture, thereby solving the problems of low drying efficiency, uneven particle size, loss of protein activity, and poor stability of protein content in traditional processes.

[0005] In a first aspect, this application provides a dry-wet mixing method for drying bacterial protein, comprising the following steps:

[0006] S10: Perform preliminary dehydration treatment on the wet bacterial protein after fermentation culture, control its water content to 60-70%, and set it aside for later use;

[0007] S20: Select dried bacterial protein as dry protein raw material, with a protein content of not less than 76% and a moisture content of not more than 5%, and crush it to a particle size of 80-120 mesh.

[0008] S30: Add the dry protein prepared in step S20 to the wet protein in step S10 at a mass ratio of 15%, and mix thoroughly using a stirring device to ensure that the dry protein is evenly dispersed in the wet protein to form a mixture.

[0009] S40: The mixture formed in step S30 is fed into a drying device, the inlet air temperature is controlled at 700-750℃, the outlet air temperature is controlled at 120-150℃, the drying time is controlled at 20-30min, until the moisture content of the mixture drops to below 5%, and the standard deviation of the particle size distribution of the finished bacterial protein is below 0.5.

[0010] S50: Cool the dried material to room temperature and then sieve it through a screening device with a screen mesh size of 100-120 to obtain the finished bacterial protein.

[0011] According to this application, by mixing dry protein and wet protein in a specific ratio, the dry protein reduces the viscosity of the wet protein, minimizing clumping, while simultaneously increasing the contact area between the material and hot air, thereby improving heat transfer efficiency and shortening drying time. The dry protein acts as a "seed" during the mixing process, promoting the formation of regular particles from the wet protein during drying, thus improving particle size uniformity. Furthermore, by optimizing the drying temperature and time, localized overheating that could lead to protein denaturation is avoided, thereby protecting protein activity and improving the stability of protein content.

[0012] Preferably, the preliminary dehydration treatment in step S10 uses centrifugation or filtration to control the water content of the wet bacterial protein to 60-70%. The centrifugation speed is 3000-5000 r / min, and the filtration pressure is 0.2-0.5 MPa.

[0013] Preferably, the dry protein pulverization process in step S20 uses a universal pulverizer with a pulverization time of 5-10 minutes and a pulverizer speed of 2000-3000 r / min.

[0014] Preferably, the stirring device in step S30 is a twin-shaft screw mixer, with a stirring time of 5-15 min and a stirring speed of 200-400 r / min.

[0015] Preferably, the drying equipment in step S40 is a fluidized bed dryer or a spray dryer. The airflow velocity of the fluidized bed dryer is 1-2 meters per second, and the nozzle orifice diameter of the spray dryer is 0.5-1.5 mm, and the spray pressure is 0.3-0.6 MPa.

[0016] Preferably, the screening device in step S50 is a vibrating screen with a vibration frequency of 10-20Hz and an amplitude of 1-3mm.

[0017] Secondly, this application provides a bacterial protein product, prepared according to the dry-wet mixing method bacterial protein drying process described in any embodiment of the first aspect. The protein content of this bacterial protein product is stable at 78.8-79.4%, the particle size distribution is concentrated in the range of 80-120 mesh, and the batch-to-batch fluctuation range does not exceed 0.6%.

[0018] According to this application, the addition of dry protein significantly reduces the viscosity of wet protein, decreases clumping, and improves heat transfer efficiency. By optimizing drying temperature and time, the impact of localized overheating on protein activity is avoided, while simultaneously improving the stability of protein content. Experimental data show that the bacterial protein products produced using this process have a 5-8% higher protein activity retention rate, a 10-15% higher drying efficiency, and a more than 12% higher throughput per unit time compared to traditional processes.

[0019] Preferably, the proportion of dry protein added can be adjusted according to the initial moisture content of the wet protein. When the initial moisture content of the wet protein is 60-65%, the proportion of dry protein added is 10-15%; when the initial moisture content of the wet protein is 65-70%, the proportion of dry protein added is 15-20%.

[0020] Preferably, the drying temperature and time can be adjusted according to the initial moisture content of the wet protein and the proportion of dry protein added. When the initial moisture content of the wet protein is 60-65% and the proportion of dry protein added is 10-15%, the drying temperature is 700-720℃ and the drying time is 20-25 minutes; when the initial moisture content of the wet protein is 65-70% and the proportion of dry protein added is 15-20%, the drying temperature is 720-750℃ and the drying time is 25-30 minutes.

[0021] Preferably, the particle size of the dry protein can be adjusted according to the particle characteristics of the wet protein. When the wet protein particles are large, the particle size of the dry protein is 80-100 mesh; when the wet protein particles are small, the particle size of the dry protein is 100-120 mesh.

[0022] Preferably, the moisture content of the mixture can be further reduced by adjusting the drying time and temperature. When the drying time is 20-25 minutes, the moisture content of the mixture can be reduced to 4-5%; when the drying time is 25-30 minutes, the moisture content of the mixture can be reduced to 3-4%.

[0023] Preferably, the particle size distribution of the finished bacterial protein can be further optimized by adjusting the vibration frequency and amplitude of the screening equipment. When the vibration frequency is 10-15Hz and the amplitude is 1-2mm, the particle size distribution of the finished bacterial protein is concentrated in 80-100 mesh; when the vibration frequency is 15-20Hz and the amplitude is 2-3mm, the particle size distribution of the finished bacterial protein is concentrated in 100-120 mesh.

[0024] As a preferred option, the protein activity of the finished bacterial protein can be detected by high performance liquid chromatography, and its water-soluble protein content is increased by 5-8% compared with the traditional process.

[0025] As a preferred option, the protein content of the finished bacterial cell protein can be detected by the Kjeldahl method, and its protein content is stable at 78.8-79.4%, which is about 2% higher than that of the traditional process.

[0026] As a preferred option, the particle size uniformity of the finished bacterial protein can be detected by a laser particle size analyzer, and the standard deviation of its particle size distribution is reduced by 30-40% compared with the traditional process.

[0027] As a preferred option, the batch-to-batch fluctuation range of the finished bacterial protein can be verified through multiple repeated experiments, and the fluctuation range does not exceed 0.6%, which is significantly lower than that of traditional processes.

[0028] According to this application, by mixing dry protein and wet protein in a specific ratio and then drying them, the problems of low drying efficiency, uneven particle size, loss of protein activity, and poor stability of protein content in traditional processes are solved. Experimental data show that the microbial protein products produced using this process have high protein content, good particle size uniformity, and high protein activity, making them suitable for use in feed, food, and pharmaceutical fields.

[0029] Preferably, the dried protein can be sourced from commercially available high-purity bacterial protein products or bacterial protein products prepared through other processes. The protein content of the dried protein should be no less than 76%, and the water content should not exceed 5%.

[0030] Preferably, the source of wet protein can be bacterial cell protein from fermentation culture or bacterial cell protein products prepared by other processes. The initial water content of the wet protein should be 60-70%.

[0031] Preferably, the choice of mixing equipment can be adjusted according to the production scale. For small-scale production, a single-shaft screw mixer can be selected; for large-scale production, a twin-shaft screw mixer or a multi-shaft screw mixer can be selected.

[0032] Preferably, the choice of drying equipment can be adjusted according to production needs. For continuous production, a fluidized bed dryer can be selected; for intermittent production, a spray dryer can be selected.

[0033] Preferably, the selection of screening equipment can be adjusted according to the finished product particle size requirements. For products with higher particle size requirements, a vibrating screen can be selected; for products with lower particle size requirements, a drum screen can be selected.

[0034] According to this application, by optimizing key parameters such as the wet-dry protein mixing ratio, drying temperature, and time, a synergistic improvement in drying efficiency and product quality was achieved. Experimental data shows that the bacterial protein products produced using this process have high industrial application value.

[0035] As a preferred option, the ratio of dry to wet protein can be fine-tuned according to the actual production equipment and raw material characteristics, but the core technical solution remains unchanged.

[0036] As a preferred option, the drying temperature and time can be finely adjusted according to actual production conditions, but the core technical solution remains unchanged.

[0037] As a preferred option, the vibration frequency and amplitude of the screening equipment can be finely adjusted according to actual production needs, but the core technical solution remains unchanged.

[0038] According to this application, the problem of balancing efficiency and quality in traditional drying methods is solved by using the approach of mixing wet and dry proteins and optimizing parameters. This significantly improves the protein content, particle size uniformity, and activity of the bacterial protein product, and has high industrial application value. Attached Figure Description

[0039] Figure 1 is a flowchart of the dry and wet mixing method for drying bacterial protein according to the present invention.

[0040] The attached figures are labeled as follows:

[0041] 1. Fermentation tank; 2. Centrifuge; 3. Filtration device; 4. Universal pulverizer; 5. Twin-shaft screw mixer; 6. Fluidized bed dryer; 7. Spray dryer; 8. Vibrating screen; 9. Drum screen; 10. Finished product collection device. Detailed Implementation

[0042] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0043] In a first aspect, this application provides a dry-wet mixing method for drying bacterial protein, comprising the following steps:

[0044] S10: Perform preliminary dehydration on the wet bacterial protein after fermentation, controlling its moisture content to 60-70%, and set aside for later use. Preliminary dehydration is performed using centrifugation or filtration. The centrifugation speed is 3000-5000 r / min, and the filtration pressure is 0.2-0.5 MPa. In actual operation, the wet bacterial protein in fermenter 1 is transported through pipeline to centrifuge 2 or filtration device 3 for preliminary dehydration. If centrifuge 2 is used, the speed is set to 3500 r / min, and the moisture content of the wet bacterial protein is observed to be approximately 65%. If filtration device 3 is used, the filtration pressure is adjusted to 0.3 MPa, and the moisture content of the wet bacterial protein is confirmed to be approximately 68% by weighing.

[0045] S20: Select dried bacterial protein as the raw material for dry protein processing. Its protein content should be no less than 76%, and its moisture content no more than 5%. Grind it to a particle size of 80-120 mesh. The dry protein can be a commercially available high-purity bacterial protein product or a bacterial protein product prepared through other processes. In actual operation, the dry protein raw material is fed into a universal grinder 4 for grinding. The grinding time is set to 8 minutes, and the grinder speed is 2500 r / min. The particle size of the ground dry protein is checked using a sieve to ensure it meets the 80-120 mesh requirement.

[0046] S30: Add the dry protein prepared in step S20 to the wet protein in step S10 at a mass ratio of 15%, and mix thoroughly using a stirring device to ensure that the dry protein is evenly dispersed in the wet protein, forming a mixture. The stirring device is a twin-screw mixer 5, with a stirring time of 10 minutes and a stirring speed of 300 r / min. In actual operation, the wet bacterial protein and dry protein are added to the twin-screw mixer 5 in the specified proportions, the equipment is started, and the mixing process is observed to ensure that the dry protein is completely dispersed in the wet protein, forming a homogeneous mixture.

[0047] S40: The mixture formed in step S30 is fed into a drying device. The inlet air temperature is controlled at 700-750℃, the outlet air temperature at 120-150℃, and the drying time at 20-30 minutes, until the moisture content of the mixture drops below 5%. The drying device is a fluidized bed dryer 6 or a spray dryer 7. It should be noted that after the dry and wet mixture is mixed, the dry protein coats the wet protein particles, preventing the wet protein from directly contacting the high-temperature inlet air; at the same time, the outlet air temperature is controlled at 120-150℃ to ensure that the internal temperature of the material is below the protein denaturation threshold (approximately 150℃), achieving a balance between efficient drying and activity protection. In actual operation, if a fluidized bed dryer 6 is used, the airflow velocity is set to 1.5 m / s, the inlet air temperature to 720℃, the outlet air temperature to 130℃, and the drying time to 25 min. If a spray dryer 7 is used, the nozzle diameter is set to 1 mm, the spray pressure to 0.5 MPa, the inlet air temperature to 730℃, the outlet air temperature to 140℃, and the drying time to 28 min. The moisture content of the mixture is tested by sampling to ensure it is reduced to below 4%.

[0048] S50: Cool the dried material to room temperature and then sieve it using a screening device with a screen mesh size of 100-120 mesh to obtain the finished bacterial protein. The screening device is either a vibrating screen 8 or a drum screen 9. In actual operation, if a vibrating screen 8 is used, the vibration frequency is set to 15Hz and the amplitude to 2mm; if a drum screen 9 is used, the drum speed is set to 10 revolutions per minute. After screening, the finished bacterial protein is collected in the finished product collection device 10.

[0049] In some embodiments, the proportion of dry protein added can be adjusted according to the initial moisture content of the wet protein. When the initial moisture content of the wet protein is 60-65%, the proportion of dry protein added is 10-15%; when the initial moisture content of the wet protein is 65-70%, the proportion of dry protein added is 15-20%. In practice, the proportion of dry protein added is adjusted according to the moisture content measurement results of the wet protein. For example, if the moisture content of the wet protein is 62%, the proportion of dry protein added is 12%; if the moisture content of the wet protein is 68%, the proportion of dry protein added is 18%.

[0050] In some implementations, the drying temperature and time can be adjusted according to the initial moisture content of the wet protein and the proportion of dry protein added. Increasing the moisture content of the wet protein and the proportion of dry protein increases the heat capacity and moisture evaporation requirements of the mixture; therefore, the drying temperature and time need to be increased simultaneously to ensure the moisture content meets the standard without damaging the protein structure. When the initial moisture content of the wet protein is 60-65% and the proportion of dry protein added is 10-15%, the drying temperature is 700-720℃ and the drying time is 20-25 minutes; when the initial moisture content of the wet protein is 65-70% and the proportion of dry protein added is 15-20%, the drying temperature is 720-750℃ and the drying time is 25-30 minutes. In actual operation, the parameters of the drying equipment are adjusted according to the initial moisture content of the wet protein and the proportion of dry protein added. For example, if the initial moisture content of the wet protein is 63% and the proportion of dry protein added is 13%, then the drying temperature is set to 710℃ and the drying time is 23 minutes; if the initial moisture content of the wet protein is 67% and the proportion of dry protein added is 17%, then the drying temperature is set to 740℃ and the drying time is 27 minutes.

[0051] In some implementations, the particle size of the dried protein can be adjusted according to the particle characteristics of the wet protein. When the wet protein particles are large, the particle size of the dried protein is 80-100 mesh; when the wet protein particles are small, the particle size of the dried protein is 100-120 mesh. In actual operation, the grinding parameters of the dried protein are adjusted according to the particle characteristics of the wet protein. For example, if the wet protein particles are large, the grinding time is set to 7 minutes and the grinder speed is set to 2800 r / min; if the wet protein particles are small, the grinding time is set to 9 minutes and the grinder speed is set to 2200 r / min.

[0052] In some implementations, the moisture content of the mixture can be further reduced by adjusting the drying time and temperature. When the drying time is 20-25 minutes, the moisture content of the mixture can be reduced to 4-5%; when the drying time is 25-30 minutes, the moisture content can be reduced to 3-4%. In actual operation, the parameters of the drying equipment are adjusted according to the moisture content test results of the mixture. For example, if the moisture content of the mixture is 4.5%, the drying time is extended to 26 minutes; if the moisture content of the mixture is 3.8%, the drying time is shortened to 24 minutes.

[0053] In some embodiments, the particle size distribution of the finished bacterial protein can be further optimized by adjusting the vibration frequency and amplitude of the screening equipment. When the vibration frequency is 10-15 Hz and the amplitude is 1-2 mm, the particle size distribution of the finished bacterial protein is concentrated in the range of 80-100 mesh; when the vibration frequency is 15-20 Hz and the amplitude is 2-3 mm, the particle size distribution of the finished bacterial protein is concentrated in the range of 100-120 mesh. In actual operation, the parameters of the screening equipment are adjusted according to the required particle size distribution of the finished bacterial protein. For example, if a particle size distribution of 90 mesh is required, the vibration frequency is set to 12 Hz and the amplitude to 1.5 mm; if a particle size distribution of 110 mesh is required, the vibration frequency is set to 18 Hz and the amplitude to 2.5 mm.

[0054] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0055] Example 1

[0056] S10: The wet bacterial protein in fermenter 1 is transported to centrifuge 2 through a pipeline. The centrifugation speed is set to 3500 r / min. After preliminary dehydration, the water content of the wet bacterial protein is 65%.

[0057] S20: Feed the dry protein raw material into the universal pulverizer 4 for pulverization. Set the pulverization time to 8 minutes and the pulverizer speed to 2500 r / min. The particle size of the pulverized dry protein is 100 mesh.

[0058] S30: Add wet bacterial protein and dry protein to twin-screw mixer 5 at a mass ratio of 15%, set the stirring time to 10 min and the stirring speed to 300 r / min to form a mixture.

[0059] S40: The mixture is fed into the fluidized bed dryer 6, the airflow velocity is set to 1.5 m / s, the inlet air temperature is 720℃, the outlet air temperature is 130℃, the drying time is 25 min, and the moisture content of the mixture is reduced to 4%.

[0060] S50: Cool the dried material to room temperature and sieve it through a vibrating screen 8. Set the vibration frequency to 15Hz and the amplitude to 2mm to obtain the finished bacterial protein.

[0061] Example 2

[0062] S10: The wet bacterial protein in fermenter 1 is transported to filter device 3 through a pipeline. The filter pressure is set to 0.4 MPa. After preliminary dehydration, the water content of the wet bacterial protein is 68%.

[0063] S20: The dry protein raw material is fed into the universal pulverizer 4 for pulverization. The pulverization time is set to 7 minutes, the pulverizer speed is 2800 r / min, and the particle size of the pulverized dry protein is 90 mesh.

[0064] S30: Add wet bacterial protein and dry protein to the twin-screw mixer 5 at a mass ratio of 18%, set the stirring time to 12 min and the stirring speed to 350 r / min to form a mixture.

[0065] S40: The mixture is fed into the spray dryer 7, the nozzle orifice diameter is set to 1.2mm, the spray pressure is 0.4MPa, the inlet air temperature is 730℃, the outlet air temperature is 140℃, the drying time is 28min, and the moisture content of the mixture is reduced to 3.5%.

[0066] S50: Cool the dried material to room temperature and sieve it through a drum screen 9. Set the drum speed to 12 revolutions per minute to obtain the finished bacterial protein.

[0067] Comparative Example 1

[0068] S10: The wet bacterial protein in fermenter 1 is transported to centrifuge 2 through a pipeline. The centrifugation speed is set to 3000 r / min. After preliminary dehydration, the water content of the wet bacterial protein is 70%.

[0069] S20: Feed the dry protein raw material into the universal pulverizer 4 for pulverization. Set the pulverization time to 5 minutes and the pulverizer speed to 2000 r / min. The particle size of the pulverized dry protein is 80 mesh.

[0070] S30: Add wet bacterial protein and dry protein to a single-shaft screw mixer at a mass ratio of 10%, set the stirring time to 5 minutes and the stirring speed to 200 r / min to form a mixture.

[0071] S40: The mixture is fed into the fluidized bed dryer 6, the airflow velocity is set to 1 meter per second, the inlet air temperature is 700℃, the outlet air temperature is 120℃, the drying time is 20 minutes, and the moisture content of the mixture is reduced to 5%.

[0072] S50: Cool the dried material to room temperature and sieve it through a vibrating screen 8. Set the vibration frequency to 10Hz and the amplitude to 1mm to obtain the finished bacterial protein.

[0073] Comparative Example 2

[0074] S10: The wet bacterial protein in fermenter 1 is transported to filter device 3 through a pipeline. The filter pressure is set to 0.5MPa. After preliminary dehydration, the water content of the wet bacterial protein is 60%.

[0075] S20: The dry protein raw material is fed into the universal pulverizer 4 for pulverization. The pulverization time is set to 10 minutes, the pulverizer speed is 3000 r / min, and the particle size of the pulverized dry protein is 120 mesh.

[0076] S30: Add wet bacterial protein and dry protein to the twin-screw mixer 5 at a mass ratio of 20%, set the stirring time to 15 min and the stirring speed to 400 r / min to form a mixture.

[0077] S40: The mixture is fed into the spray dryer 7, the nozzle orifice diameter is set to 1.5mm, the spray pressure is 0.6MPa, the inlet air temperature is 750℃, the outlet air temperature is 150℃, the drying time is 30min, and the moisture content of the mixture is reduced to 5%.

[0078] S50: Cool the dried material to room temperature and sieve it through a drum screen 9. Set the drum speed to 15 revolutions per minute to obtain the finished bacterial protein.

[0079] The protein content of the finished bacterial cells obtained in the above examples and comparative examples was determined using the Kjeldahl method, the standard deviation of particle size distribution was determined using a laser particle size analyzer, and the water-soluble protein content was determined using high-performance liquid chromatography (HPLC). The batch-to-batch fluctuation range was also statistically analyzed. The standard deviation of particle size distribution was determined using a laser particle size analyzer, and the calculation method was the sample standard deviation of particle size distribution; the results are dimensionless. The results are shown in the table below:

[0080]

[0081] As shown in the table above, the finished bacterial protein obtained in this application embodiment has a higher protein content, a smaller standard deviation of particle size distribution, and a higher water-soluble protein content compared to the comparative example, while also exhibiting a smaller batch-to-batch variation. In Comparative Example 1, the high moisture content of the wet bacterial protein and the low proportion of added dry protein resulted in lower protein content and water-soluble protein content in the finished bacterial protein. In Comparative Example 2, although the moisture content of the wet bacterial protein was low and the proportion of added dry protein was high, the excessively long drying temperature and time led to a larger standard deviation of particle size distribution and a larger batch-to-batch variation in the finished bacterial protein.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A dry-wet mixed method for drying bacterial protein, characterized in that, Includes the following steps: S10: Perform preliminary dehydration treatment on the wet bacterial protein after fermentation culture, control its water content to 60-70%, and set it aside for later use; S20: Select dried bacterial protein as dry protein raw material, with a protein content of not less than 76% and a moisture content of not more than 5%, and crush it to a particle size of 80-120 mesh. S30: Add the dry protein prepared in step S20 to the wet protein in step S10 at a mass ratio of 15%, and mix thoroughly using a stirring device to form a mixture. S40: The mixture formed in step S30 is fed into a drying device, the inlet air temperature is controlled at 700-750℃, the outlet air temperature is controlled at 120-150℃, the drying time is controlled at 20-30min, until the moisture content of the mixture drops to below 5%, and the standard deviation of the particle size distribution of the finished bacterial protein is below 0.

5. S50: Cool the dried material to room temperature and then sieve it through a screening device with a screen mesh size of 100-120 to obtain the finished bacterial protein.

2. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, The preliminary dehydration treatment in step S10 is carried out by centrifugation or filtration. The centrifugation speed is 3000-5000 r / min and the filtration pressure is 0.2-0.5 MPa.

3. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, The dry protein pulverization process in step S20 uses a universal pulverizer with a pulverization time of 5-10 minutes and a pulverizer speed of 2000-3000 r / min.

4. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, The mixing equipment in step S30 is a twin-shaft screw mixer, with a mixing time of 5-15 minutes and a mixing speed of 200-400 r / min.

5. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, The drying equipment in step S40 is a fluidized bed dryer or a spray dryer. The airflow velocity of the fluidized bed dryer is 1-2 meters per second, and the nozzle orifice diameter of the spray dryer is 0.5-1.5 mm, and the spray pressure is 0.3-0.6 MPa.

6. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, The screening equipment in step S50 is a vibrating screen with a vibration frequency of 10-20Hz and an amplitude of 1-3mm.

7. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, The proportion of dry protein added in step S30 can be adjusted according to the initial moisture content of the wet protein. When the initial moisture content of the wet protein is 60-65%, the proportion of dry protein added is 10-15%; when the initial moisture content of the wet protein is 65-70%, the proportion of dry protein added is 15-20%.

8. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, The drying temperature and time in step S40 can be adjusted according to the initial moisture content of the wet protein and the proportion of dry protein added. When the initial moisture content of the wet protein is 60-65% and the proportion of dry protein added is 10-15%, the drying temperature is 700-720℃ and the drying time is 20-25min. When the initial moisture content of the wet protein is 65-70% and the proportion of dry protein added is 15-20%, the drying temperature is 720-750℃ and the drying time is 25-30min.

9. The dry-wet mixing method for drying bacterial protein according to claim 1, characterized in that, In step S20, the particle size of the dry protein can be adjusted according to the particle characteristics of the wet protein. When the wet protein particles are large, the particle size of the dry protein is 80-100 mesh; when the wet protein particles are small, the particle size of the dry protein is 100-120 mesh.

10. A bacterial protein product, characterized in that, Its protein content is stable at 78.8-79.4%, the particle size distribution is concentrated in 80-120 mesh, and the batch-to-batch fluctuation range does not exceed 0.6%, and it is prepared by the dry-wet mixing method of bacterial protein drying process as described in any one of claims 1-9.

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