A dry separation method of starch, protein and fiber in legumes

Abstract

The application provides a dry separation method of starch, protein and fiber in legumes, and belongs to the technical field of food processing. The dry separation method of starch, protein and fiber in legumes provided by the application effectively prevents powder agglomeration, improves the screening efficiency and separation purity of legume protein, starch and fiber through physical field synergistic strengthening of the screening process, and keeps the natural structure and functional properties of legume protein and starch without water and chemical reagents in the whole process. The method is suitable for high-purity starch preparation of legumes, development of functional protein powder and high-value utilization of fiber resources, and has a good market prospect.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a dry separation method for starch, protein and fiber in legumes. Background Technology

[0002] With the rapid development of the food industry, the demand for legume starch and protein in the food industry is increasing. In the traditional processing of legume (such as peas, mung beans, broad beans, etc.) starch and protein, the separation of starch and fiber is mostly achieved through wet grinding and sedimentation, hydrocyclone separation, and dry air classification. Although wet processes can obtain starch with high purity, they consume a lot of water (5-10 tons of water per ton of product), have high energy consumption, and are prone to loss of soluble nutrients (such as B vitamins and minerals). Dry air classification processes have strict requirements on the particle size distribution of materials (such as feed particle size requirement D). 90 The protein size is 10-65 μm, and the protein composition requires D. 90 The particle size is 20-22 μm, requiring significant equipment investment and making it difficult to achieve fine separation of fiber and starch (fiber removal rate is typically below 70%). Furthermore, in existing dry sieving processes, fine powders are prone to agglomeration due to electrostatic adsorption or liquid bridging forces, leading to screen blockage and reduced separation efficiency.

[0003] Therefore, developing a separation technology that is efficient, enables precise separation of fiber and starch, and can overcome powder agglomeration has significant application value. Summary of the Invention

[0004] The purpose of this invention is to provide a dry separation method for starch, protein and fiber in legumes. The dry separation method provided by this invention strengthens the sieving process through physical field synergy, effectively prevents powder agglomeration, and improves the sieving efficiency and separation purity of legume protein, starch and fiber.

[0005] To achieve the objectives of this invention, the following technical solutions are provided: A dry separation method for starch, protein and fiber in legumes includes the following steps: The soybean powder is initially sieved to obtain the undersize material; The undersize material is graded to obtain a protein component and a starch-cellulose mixture; the protein component has a protein content of ≥65 wt%. The starch-fiber mixture is combined with an elastic binder, and then finely sieved to obtain undersized starch and oversized fiber; the purity of the undersized starch is ≥95 wt%. The fine screening is a vibrating screen and / or an ultrasonic screen; the amplitude of the vibrating screen is 1~5mm; the fine screening is carried out under negative pressure conditions.

[0006] Preferably, the mesh size of the screen used for the primary and secondary screenings is 300-400 mesh.

[0007] Preferably, the frequency of the ultrasonic sieving is 20~50Hz.

[0008] Preferably, when the fine screening is a vibrating screen and an ultrasonic screen, the vibrating screen and the ultrasonic screen are applied simultaneously or alternately.

[0009] Preferably, when the alternating application is performed, the duration of each vibration screening and ultrasonic screening is 15-60 seconds, and the interval is 3-10 seconds.

[0010] Preferably, the primary screen is a vibrating screen with an amplitude of 0.8~1.5mm.

[0011] Preferably, the grading is air classification; the grading wheel rotation speed of the air classification is 6000~10000 r / min; the working frequency is 20~50 Hz; the gas-solid concentration is 0.2~0.4 kg material / kg air; and the grading temperature is 25~45℃.

[0012] Preferably, the median particle size D of the soybean powder is... 50 The value is 10~30μm.

[0013] Preferably, the moisture content of the soybean powder is 10-12%.

[0014] Preferably, the elastic catcher is spherical with a diameter of 3-5 mm.

[0015] This invention provides a dry separation method for starch, protein, and fiber in legumes, comprising the following steps: primary sieving of legume powder to obtain undersize material; grading of the undersize material to obtain protein component and starch-fiber mixed component; the protein component having a protein content ≥65wt%; mixing the starch-fiber mixed component with an elastic catch block, followed by fine sieving to obtain undersize starch and oversize fiber; the purity of the undersize starch ≥95wt%; the fine sieving being a vibrating sieve and / or ultrasonic sieve; the amplitude of the vibrating sieve being 1~5mm; the fine sieving being performed under negative pressure conditions. In this invention, the undersize material after primary sieving is graded to separate the protein component; the remaining material is subjected to multi-mode vibration-coupled fine sieving, combined with the synergistic effect of the elastic catch block, to achieve precise separation of starch particles and fiber components, with the oversize material being fiber and the undersize material being starch. This invention enhances the sieving process through a synergistic effect of physical fields, effectively preventing powder agglomeration and improving the sieving efficiency and separation purity of legume protein, starch, and fiber. Furthermore, the entire process is water-free and chemical-free, preserving the natural structure and functional properties of legume protein and starch. This method is applicable to the preparation of high-purity legume starch, the development of functional protein powders, and the high-value utilization of fiber resources, and has promising market prospects. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of the dry separation method for starch, protein and fiber in legumes according to the present invention. Detailed Implementation

[0018] This invention provides a dry separation method for starch, protein, and fiber in legumes, comprising the following steps: The soybean powder is initially sieved to obtain the undersize material; The undersize material is graded to obtain a protein component and a starch-cellulose mixture; the protein component has a protein content of ≥65 wt%. The starch-fiber mixture is combined with an elastic binder, and then finely sieved to obtain undersized starch and oversized fiber; the purity of the undersized starch is ≥95 wt%. The fine screening is a vibrating screen and / or an ultrasonic screen; the amplitude of the vibrating screen is 1~5mm; the fine screening is carried out under negative pressure conditions.

[0019] Unless otherwise specified, all raw materials used in this invention are commercially available products well known to those skilled in the art.

[0020] In this invention, the bean powder is derived from one or more of peas, mung beans, broad beans, and chickpeas; the median particle size D of the bean powder is... 50 The thickness is 10~30μm; in specific embodiments it can be 15 or 30μm; D90≤50μm, preferably 20~50μm; the moisture content of the bean powder is 10~12%, in specific embodiments it can be 10.5 or 11%.

[0021] This invention involves pulverizing soybean raw materials before use to obtain soybean powder; the pulverization is ultrafine pulverization, and this invention does not have special limitations on the pulverization method and conditions, but the material is crushed to a median particle size D. 50 A size of 10~30μm is sufficient.

[0022] In this invention, the mesh size of the primary sieve is 300-400 mesh, and in a specific embodiment it can be 350 mesh. The primary sieve of this invention is for "whole powder" containing a large amount of spherical protein and starch granules. These spherical granules act as a "lubricating phase" to encase the sheet-like fibers. Under conventional single mechanical vibration, the fibers pass through the sieve holes with random orientation probability, which belongs to probability sieve. The fine sieve is for the "purified component" (with a significantly reduced protein content) after the protein has been removed by air separation. The fibers in the material are relatively enriched and have lost their lubricating effect. At this time, the negative pressure under the sieve (0.06MPa) presses the flat sheet-like fibers tightly against the sieve surface to form a bridging structure. At the same time, ultrasonic vibration, frequency vibration and elastic silica gel catcher work together to bounce the fibers up and force them to remain on the sieve. The spherical starch passes through the sieve holes smoothly under the traction of the negative pressure, which belongs to shape-density coupled sieve. The primary sieve and fine sieve of this invention are fundamentally different in terms of sieve basis, physical field effect and process objectives.

[0023] After obtaining the undersize material, this invention classifies the undersize material to obtain protein components and starch-cellulose mixed components. The classification described in this invention is air classification; the classification is carried out at 25~45℃; the air classifier used for the classification is preferably ALPA, sourced from Shandong ALPA Powder Technology. This invention provides a dedicated classifier that can separate components based on specific gravity and particle size. Its characteristic is that precise control can be achieved by adjusting various parameters such as operating frequency, feed rate, conveying air volume, airflow velocity, and secondary air inlet angle. This invention feeds undersized materials into an air classifier for classification. The air classifier is equipped with a classifying wheel, a secondary air inlet, and forms a classification system with an induced draft fan, a cyclone separator, and a dust collector. After being dispersed in the rising airflow, the material enters the classification zone. Under the centrifugal force field generated by the high-speed rotation of the classifying wheel, fine particles (rich in protein) pass through the gaps between the classifying wheel blades and enter the cyclone separator for collection, while coarse particles fall along the cavity wall and are discharged from the bottom after being washed by secondary air. By adjusting the classifying wheel speed (6000~10000 r / min), classification operating frequency (20~50 Hz), conveying air volume, gas-solid concentration (0.2~0.4 kg material / kg air), feeding speed, and secondary air inlet angle and air volume, fine protein particles are made to pass through the gaps between the classifying wheel blades and enter the cyclone separator for collection, resulting in a protein component with a protein purity ≥65%. The remaining material is the component to be purified.

[0024] The separation principle of this invention's air-separation grading is based on the particle size and specific gravity differences of the undersize materials. In legumes, starch particles (approximately 40 μm) and protein particles (3-10 μm) exhibit significant size differences. The air classifier utilizes the differences in centrifugal force, gravity, and inertial force experienced by particles of different sizes in the airflow, resulting in different motion trajectories and thus achieving separation. The entire process is a purely physical separation, without any chemical reactions or reagents. Low-temperature operation ensures the natural quality of the legume protein. This protein component can be used as a plant-based protein ingredient in meal replacement powders, sports nutrition foods, plant-based meat, and special medical foods, meeting the rapidly growing demand in the current plant protein market.

[0025] In this invention, the undersize material is graded to obtain a protein component; the protein component has a protein content of ≥65wt%, preferably 65~75wt%. The remaining components in the protein component of this invention are mainly micronized small starch particles (approximately 20%~28wt%) with particle sizes overlapping with protein particles, as well as a small amount of ultrafine fiber debris, ash, and lipids. These residual starches are natural components that cannot be completely removed by air classification, but they do not affect the application value of protein powder as a functional ingredient. Furthermore, because a large amount of free protein is removed after air classification, the protein content in the material entering the fine screening step is significantly reduced, weakening the 'adhesive bridging' effect of protein on fiber and starch. This allows the subsequent fine screening, using a 300~400 mesh screen under negative pressure and ultrasonic synergy, to effectively retain the flaky fibers on the screen surface. If air classification is not performed before fine screening to remove protein, even with the same coupling field, the fiber removal rate will decrease significantly.

[0026] After obtaining the starch-fiber mixture, this invention mixes the starch-fiber mixture with an elastic binder and then finely sieves it to obtain undersize starch and oversize fiber. The fine sieving in this invention is vibrating sieving and / or ultrasonic sieving; the mesh size of the sieve used is 300-400 mesh, and in a specific embodiment, it can be 350 mesh; the amplitude of the mechanical vibrating sieving is 1-5 mm; the fine sieving is carried out under negative pressure conditions; the frequency of the ultrasonic sieving is 20-50 Hz, and in a specific embodiment, it can be 30 or 40 Hz; when the fine sieving is a combination of vibrating sieving and ultrasonic sieving, the vibrating sieving and ultrasonic sieving are applied simultaneously or alternately; the negative pressure condition can specifically be 0.06±0.01 MPa. This invention couples mechanical vibration and ultrasonic conditions for dry starch sieving, utilizing the synergistic effect of ultrasonic cavitation and frequency modulation to effectively break up soft agglomerates between fine powder particles, significantly improving sieving efficiency. Furthermore, the negative pressure under the sieve creates a directional airflow, which accelerates the passage of qualified powder through the sieve and reduces the residence time of the powder on the sieve surface, avoiding secondary agglomeration during the sieving process, with a fiber removal rate of over 85%.

[0027] Furthermore, the amplitude of the vibrating screen in this invention is 1~5mm. If the amplitude is less than 1mm, the material cannot be effectively loosened and layered on the screen surface, the fine powder agglomerates are difficult to break up, and the conveying force is insufficient, resulting in a decrease in the processing capacity per unit time. If the amplitude is greater than 5mm (such as conventional vibrating screens), the particles are excessively thrown up, which will not only counteract the directional traction effect of the negative pressure (0.06MPa) under the screen on the starch particles, but also cause damage to the natural structure of the protein or destruction of the starch crystallization zone due to excessive mechanical impact force, while also increasing the risk of screen fatigue and breakage.

[0028] In this invention, the elastic catch block is spherical, made of silicone, with a thickness of 3-5 mm and a Shore hardness of 30-50 HA. The silicone catch block of this invention rolls freely on the screen surface with vibration, continuously breaking up local agglomerates, keeping the screen surface clean, extending the screen's service life, and increasing continuous operating time by 2-3 times.

[0029] In this invention, the purity of the sieved starch is ≥95%, preferably 95~98%; the fiber content in the sieved starch is ≤3%, preferably 0.5~2%. The starch separated by this invention can be widely used in the fields of vermicelli, rice noodles, modified starch, biodegradable membrane materials, pharmaceutical excipients, and baked goods, replacing traditional wet-process starch and significantly reducing water consumption and wastewater treatment costs.

[0030] To further illustrate the present invention, the dry separation method for starch, protein and fiber in legumes provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0031] Example 1 according to Figure 1 The flowchart shown illustrates the dry separation of starch, protein, and fiber in peas. The specific steps are as follows: S1. Grinding: Peas (dried to a moisture content of 10±2%, peeled), ultra-finely ground to a median particle size D. 50 =20μm.

[0032] S2. Primary screening: The ultrafine pulverized material obtained in step S1 is fed into a vibrating screening device (amplitude 0.8~1.5mm) and primary screened using a 350-mesh screen to obtain the undersize material.

[0033] S3. Air classification: The material undersized in step S2 is fed into the air classifier for classification to obtain protein components (purity ≥65%) and residual starch-fiber mixed components. S4. Coupled Field Fine Screening: The starch-fiber mixture from step S3 is fed into a vibrating sieve with a screen mesh size of 350 mesh and spherical elastic silicone blocks (5 mm thick) dispersed in the screen. A negative pressure of 0.06 ± 0.01 MPa is introduced below the screen, and ultrasound is continuously applied during the screening process (referred to as mode A). The vibration parameters are set to a mechanical amplitude of 1~3 mm and an ultrasonic frequency modulation of 20~50 Hz. The material on the screen is fiber, and the material under the screen is starch.

[0034] Example 2 S1. Grinding: Peas (dried to a moisture content of 10±2%, peeled), ultra-finely ground to a median particle size D. 50 =20μm.

[0035] S2. Primary screening: The ultrafine pulverized material obtained in step S1 is fed into a vibrating screening device (amplitude 0.8~1.5mm) and primary screened using a 350-mesh screen to obtain the undersize material.

[0036] S3. Air classification: The material undersized in step S2 is fed into the air classifier for classification to obtain protein components (purity ≥65%) and residual starch-fiber mixed components. S4. Coupled Field Fine Screening: The starch-fiber mixture from step S3 is fed into a vibrating screen with a 350-mesh screen and spherical elastic silicone blocks dispersed in the screen. A negative pressure of 0.06±0.01MPa is introduced below the screen. During the screening process, ultrasound is applied alternately (referred to as Mode A): the ultrasonic vibration is turned on for 30 seconds and then turned off. After a 5-second interval, the frequency vibration is turned on for 30 seconds and then turned off. After a 5-second interval, the ultrasonic vibration is turned on again. During the ultrasonic vibration, the frequency vibration is "paused". This cycle is repeated until the screening is completed. The vibration parameters are set to a mechanical amplitude of 1~3mm and an ultrasonic frequency modulation of 20~50Hz. The material on the screen is fiber, and the material under the screen is starch.

[0037] Comparative Example 1 S1. Grinding: Peas (dried to a moisture content of 10±2%, peeled), ultra-finely ground to a median particle size D. 50 =20μm.

[0038] S2. Initial screening: The ultrafine pulverized material obtained in step S1 is fed into a vibrating screening device and screened using a 350-mesh screen to obtain the undersize material.

[0039] S3. Air classification: The material undersized in step S2 is fed into the air classifier for classification to obtain protein components (purity ≥65%) and residual starch-fiber mixed components. S4. Coupled Field Fine Screening: The starch-fiber mixture from step S3 is fed into a vibrating screen with a screen mesh size of 350 mesh and spherical elastic silicone blocks dispersed in the screen. A negative pressure of 0.06±0.01MPa is introduced below the screen to attract the particles. During the screening process, only mechanical vibration occurs (referred to as mode B), with a mechanical amplitude of 1~3mm. The material on the screen is fiber, and the material under the screen is starch.

[0040] Table 1. Screening results of Example 1 and Comparative Example 1

[0041] The results in Table 1 show that the synergistic effect of multi-mode vibration significantly improves the fiber removal rate, and the proposed solution is the most effective.

[0042] Comparative Example 2 S1. Grinding: Peas (dried to a moisture content of 10±2%, peeled), ultra-finely ground to a median particle size D. 50 =20μm.

[0043] S2. Initial screening: The ultrafine pulverized material obtained in step S1 is fed into a vibrating screening device and screened using a 350-mesh screen to obtain the undersize material.

[0044] S3. Air classification: The material undersized in step S2 is fed into the air classifier for classification to obtain protein components (purity ≥65%) and residual starch-fiber mixed components. S4. Coupled Field Fine Screening: The starch-fiber mixture from step S3 is fed into a vibrating screening device with a screen mesh size of 350 mesh. A negative pressure of 0.06±0.01MPa is introduced below the screen to attract the particles, and ultrasound is continuously applied during the screening process. The vibration parameters are set to mechanical amplitude of 1~3mm and ultrasonic frequency modulation of 20~50Hz. The material on the screen is fiber, and the material under the screen is starch.

[0045] Comparative Example 2, a control group without silica gel slubs, showed significant powder accumulation and localized clogging on the sieve surface after 15 minutes of operation, resulting in decreased sieving efficiency. In Example 1, the silica gel slub group showed no significant clogging on the sieve surface after 60 minutes of continuous operation, with the material remaining loose and the fiber content of the undersize material consistently below 5%. This indicates that the silica gel slubs effectively prevent powder agglomeration and sieve clogging, improving process stability.

[0046] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A dry separation method for starch, protein, and fiber in legumes, characterized in that, Includes the following steps: The soybean powder is initially sieved to obtain the undersize material; The undersize material is graded to obtain a protein component and a starch-cellulose mixture; the protein component has a protein content of ≥65 wt%. The starch-fiber mixture is combined with an elastic binder, and then finely sieved to obtain undersized starch and oversized fiber; the purity of the undersized starch is ≥95 wt%. The fine screening is a vibrating screen and / or an ultrasonic screen; the amplitude of the vibrating screen is 1~5mm; the fine screening is carried out under negative pressure conditions.

2. The dry separation method according to claim 1, characterized in that, The mesh size of the screens used for the primary and secondary screenings is 300-400 mesh.

3. The dry separation method according to claim 1, characterized in that, The frequency of the ultrasonic sieving is 20~50Hz.

4. The dry separation method according to claim 1, characterized in that, When the fine screening is a vibrating screen and an ultrasonic screen, the vibrating screen and the ultrasonic screen are applied simultaneously or alternately.

5. The dry separation method according to claim 4, characterized in that, When the alternating application is performed, the duration of each vibration screening and ultrasonic screening is 15-60 seconds, and the interval is 3-10 seconds.

6. The dry separation method according to claim 1, characterized in that, The primary screening is a vibrating screen with an amplitude of 0.8~1.5mm.

7. The dry separation method according to claim 1, characterized in that, The classification is air separation classification; The air classifier has a classifying wheel rotation speed of 6000~10000 r / min; a working frequency of 20~50 Hz; a gas-solid concentration of 0.2~0.4 kg material / kg air; and a classification temperature of 25~45℃.

8. The dry separation method according to claim 1, characterized in that, The median particle size D of the soybean powder 50 The value is 10~30μm.

9. The dry separation method according to claim 1, characterized in that, The moisture content of the soybean powder is 10-12%.

10. The dry separation method according to claim 1, characterized in that, The elastic catcher is spherical with a diameter of 3-5 mm.

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