Method for extracting protein, endosperm fiber and starch from low-fat corn flour

Abstract

The invention relates to the technical field of corn deep processing, and particularly discloses a method for extracting protein, endosperm fiber and starch from low-fat corn flour. According to the method, a mild alkalescence environment and biological enzymolysis are combined with a physical separation means, irreversible damage to a protein structure is avoided, the biological activity of the protein can be guaranteed, impurities can be effectively removed, and therefore the high-purity and high-quality isolated protein is obtained, and the blank of the current technology in the aspect of obtaining high-quality isolated protein is filled up. Meanwhile, the corn endosperm fibers and the corn starch are also obtained, so that each effective component in the corn can be fully utilized, and the additional value of the corn flour is greatly improved. The innovative process of'one powder for multiple extraction 'provided by the invention provides a new technical path and development direction for sustainable development of the corn deep processing industry, and has a relatively high application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of deep processing of corn, and particularly to a method for extracting protein, endosperm fiber and starch from low-fat corn flour. Background Art

[0002] With the continuous improvement of people's demand for food nutrition and health and the in-depth exploration of the deep processing industry of agricultural products, corn, as one of the world's three major food crops, the comprehensive utilization value of its processed product, low-fat corn flour, has attracted increasing attention. Low-fat corn flour contains rich components such as protein, endosperm fiber and starch, and these components have broad application prospects in many fields such as food, medicine, and chemical industry. Protein can be used to produce high-nutrition foods, feed additives and bioactive peptides; endosperm fiber, as a high-quality dietary fiber, helps to regulate the human intestinal function and has important value in the development of functional foods; starch is an indispensable basic raw material in industries such as food processing, papermaking, and textile.

[0003] In the field of deep processing of corn, traditional starch production mostly adopts the wet process of sulfurous acid soaking. Sulfurous acid is added in the soaking section of this process, and corn is soaked at 50-60°C for 40-50h. During this process, sulfur dioxide generated by the decomposition of sulfurous acid will cause serious pollution to the environment, and the soaking water consumption is extremely large, which not only wastes water resources, but also generates a strong pungent smell, bringing a heavy burden to the surrounding ecological environment. After sulfurous acid soaking, a large amount of sulfides remain in corn germ, corn husk, corn protein and corn starch, which is difficult to meet the food hygiene and safety standards. To reduce the sulfide content in the product, enterprises need to additionally configure desulfurization equipment, which undoubtedly greatly increases the equipment investment and energy consumption costs.

[0004] In addition, the yield of corn protein powder obtained by the traditional wet process is only 5.5%, and the protein content is about 60%. A large amount of water-soluble protein is dissolved in corn steep liquor and cannot be efficiently utilized. In addition, corn protein isolate with a high market value and a protein content of ≥80% cannot be produced by the traditional wet process, resulting in low economic benefits of starch processing. Therefore, developing a new method that is green and efficient, can simultaneously extract protein, endosperm fiber and starch from low-fat corn flour, and improve product quality and economic benefits has become the key to promoting the sustainable development of the deep processing industry of corn. Summary of the Invention

[0005] In view of the problems in the prior art wet process, such as low yield of corn protein powder, inability to obtain corn protein isolate with a protein content of ≥80%, environmental pollution and high energy consumption, the present invention provides a method for extracting protein, endosperm fiber and starch from low-fat corn flour.

[0006] To solve the above technical problems, the technical solution provided by the present invention is:

[0007] A method for extracting protein, endosperm fiber and starch from low-fat corn flour, comprising the following steps:

[0008] S1. Add low-fat corn flour to water to obtain a low-fat corn flour slurry; adjust the pH of the low-fat corn flour slurry to weakly alkaline, add a complex enzyme, mix evenly, and soak to obtain an enzymolysis material; wherein, the complex enzyme includes alkaline protease and triglyceride hydrolase;

[0009] S2. Crush and homogenize the enzymolysis material, add water, and filter to obtain endosperm fiber and a filtrate;

[0010] S3. Centrifuge the filtrate to obtain a crude liquid-phase protein and a crude solid-phase starch; wash, dehydrate, and dry the crude solid-phase starch to obtain corn starch;

[0011] S4. Centrifuge the crude liquid-phase protein again to obtain a liquid-phase separated protein solution and a solid-phase concentrated protein;

[0012] S5. Adjust the pH of the liquid-phase separated protein solution to the isoelectric point, let it stand for precipitation, separate, wash, and dry to obtain separated protein.

[0013] Compared with the prior art, the method for extracting protein, endosperm fiber and starch from low-fat corn flour provided by the present invention first adjusts the low-fat corn flour slurry to a weakly alkaline environment and adds a complex enzyme composed of alkaline protease and triglyceride hydrolase for soaking treatment. The alkaline environment is conducive to the dissolution and dispersion of proteins. At the same time, alkaline protease can effectively destroy the binding force between proteins and other components, making it easier to release from the complex corn flour system. Triglyceride hydrolase can hydrolyze fat components to avoid the interference of fat on the protein extraction process. The two work synergistically, greatly improving the protein extraction efficiency and thus increasing the yield of corn protein powder. Subsequently, through physical separation means, endosperm fiber and corn starch are gradually separated, laying a good foundation for the subsequent separation and concentration of protein and the separation of protein. Finally, separated protein is obtained by the method of precipitation at the isoelectric point. This method can accurately precipitate proteins from the solution, while other impurities such as small molecule substances and salts remain dissolved under isoelectric point conditions and will not precipitate with proteins, which is conducive to more efficiently removing residual small molecule impurities and salts, greatly improving the purity of separated protein, and ensuring the acquisition of high-purity corn separated protein. At the same time, the separated protein obtained by separation at the isoelectric point can maintain its original functional activity, enabling the obtained corn separated protein to retain its original functional characteristics, which is more conducive to the exertion of its functions and meets the requirements of industries with extremely high protein purity requirements such as food and medicine.

[0014] Specifically, in S1, the particle size of the low-fat corn flour is 50 mesh to 70 mesh.

[0015] Further, in S1, the mass concentration of the low-fat corn flour slurry is 35% to 40%.

[0016] Further, in S1, the weak alkalinity refers to a pH of 7.5 to 8.0.

[0017] Specifically, an aqueous sodium hydroxide solution is used to adjust the pH to 7.5 to 8.0, and the mass concentration of the aqueous sodium hydroxide solution is 3% to 4%.

[0018] Further, in S1, the mass ratio of the alkaline protease to the triacylglycerol hydrolase is 6:4 to 7:3.

[0019] Further, in S1, the addition amount of the complex enzyme is 0.1% to 0.2% of the mass of the low-fat corn flour.

[0020] It should be noted that in the present invention, the alkaline protease and the triacylglycerol hydrolase can be selected from commercially available alkaline proteases and triacylglycerol hydrolases commonly used in industry, and the present invention does not make special limitations. Specifically, in S1, the enzyme activity of the alkaline protease ≥100000 U / mL, and the enzyme activity of the triacylglycerol hydrolase ≥20000 U / mL.

[0021] Further, in S1, the temperature of the soaking is 20°C to 30°C, and the soaking time is 40 min to 60 min.

[0022] The present invention uses the method of soaking at room temperature for enzymatic hydrolysis, which lays a good foundation for subsequent separation of proteins and other substances. At the same time, compared with the traditional wet process (soaking at 50 - 60°C for 40 - 50 h), it significantly reduces the production energy consumption, improves the production efficiency, and at the same time, avoids the destruction of the protein structure and activity.

[0023] Specifically, in S1, stirring is carried out simultaneously during the soaking process, and the stirring speed is 80 r / min to 120 r / min.

[0024] Further, in S2, the enzymatically hydrolyzed material is broken and homogenized to a particle size of 50 μm to 70 μm.

[0025] Specifically, in S2, the enzymatically hydrolyzed material is first added to a colloid mill for primary crushing, and then a tubular homogenizer is used for secondary crushing. The particle size of the primary crushing is 120 μm to 150 μm, and the particle size of the secondary crushing is 50 μm to 70 μm.

[0026] More specifically, in S2, the gap between the grinding discs of the above colloid mill is 0.5 mm to 1 mm, the circulation time of the colloid mill is 2 min to 3 min; the pressure of the tubular homogenizer is 8 MPa to 20 MPa.

[0027] Further, in S2, the addition amount of water is 3 to 4 times the mass of low-fat corn flour.

[0028] Further, in S2, the filtration is performed by screening through a two-stage sieve. Among them, the mesh number of the first-stage sieve is 60 to 70 meshes, and the mesh number of the second-stage sieve is 90 to 100 meshes.

[0029] Preferably, the mesh number of the first-stage sieve is 70 meshes, and the mesh number of the second-stage sieve is 90 meshes.

[0030] Further, in S3, the rotation speed of the centrifugation is 9000 r / min to 11000 r / min, and the centrifugation time is 2 min to 5 min.

[0031] Further, in S3, the washing is performed by swirling water washing, and the dehydration is performed by a scraper centrifuge. The moisture content of the filter cake after dehydration is 35% to 45%.

[0032] Further, in S3 and S4, the centrifugation is both performed by a horizontal screw decanter centrifuge.

[0033] Further, in S4, the rotation speed of the centrifugation is 4000 r / min to 6000 r / min, and the centrifugation time is 2 min to 5 min.

[0034] Further, in S5, the pH of the isoelectric point is 4.5 to 5.0.

[0035] Specifically, in S5, it is adjusted to the isoelectric point with dilute sulfuric acid.

[0036] Specifically, in S5, after standing and precipitating, it is centrifuged using a horizontal screw decanter centrifuge. Clear water is added to wash the solid phase obtained by centrifugation, and it is filtered using a plate and frame filter press and dried to obtain corn protein isolate.

[0037] Exemplarily, in S5, the rotation speed of the horizontal screw decanter centrifuge is 4000 r / min to 6000 r / min, for 2 min to 5 min.

[0038] The protein content of the corn protein isolate obtained by the separation of the present invention is greater than 85%, rich in lutein, and can be used as a food-grade protein powder, filling the gap of corn edible protein powder; the protein content of the concentrated protein powder is greater than 45%, and it can be used as a feed-grade protein; by mixing and drying the separated protein and the concentrated protein, a mixed protein powder with a protein content of 68% to 72% can be obtained, which can be used as a special protein powder for aquatic feed and pet feed, and can also be used as a food-grade protein powder.

[0039] Corn endosperm fiber, different from corn husk fiber, has a fiber content greater than 80%, an absorption rate of 1:5, can be used as dietary fiber, added to pasta and baked goods, can also be used as a weight loss and blood sugar lowering additive, and can also be used as a raw material for pet cat litter.

[0040] Corn starch has physical properties such as a low gelatinization temperature, low viscosity, and short paste process. It can better play functions such as thickening and gelling during the food processing process. At the same time, it is also very suitable for internal addition in papermaking, surface sizing, carton adhesives, and feed additives, replacing high-value cassava starch.

[0041] The present invention uses a mild weak alkaline environment and biological enzymatic hydrolysis, combined with physical separation means, to avoid irreversible damage to the protein structure, which can not only guarantee the biological activity of the protein but also effectively remove impurities, thereby obtaining high-purity and high-quality separated protein, filling the gap in the current process for obtaining high-quality separated protein. At the same time, the present invention also obtains corn endosperm fiber and corn starch, which is conducive to the full utilization of each effective component in corn and greatly improves the added value of corn flour. The innovative process of "extracting multiple products from one powder" provided by the present invention provides a new technical path and development direction for the sustainable development of the corn deep processing industry and has high application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic flow chart of extracting protein, starch, and endosperm fiber from low-fat corn flour in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] To better illustrate the present invention, further examples are given below through embodiments.

[0045] In the following embodiments, the enzyme activity of the alkaline protease used is 100000 U / mL, and the enzyme activity of the triacylglycerol hydrolase is 20000 U / mL.

[0046] Example 1

[0047] This embodiment provides a method for extracting protein, endosperm fiber, and starch from low-fat corn flour, including the following steps:

[0048] S1, Add 1600 kg of low-fat corn flour with a particle size of 60 mesh (moisture 14.00%, crude protein content 7.86%) to 2500 kg of process water at 25°C, stir evenly at a stirring speed of 90 r / min to obtain corn slurry;

[0049] S2. Mix alkaline protease and triacylglycerol lipase in a mass ratio of 7:3 to obtain a composite enzyme. Adjust the pH of the corn steep liquor prepared above to 7.8 with a 3% sodium hydroxide aqueous solution by mass concentration, add 2.4 kg of the composite enzyme, stir and soak at room temperature for 50 min to obtain an enzymolyzed material.

[0050] S3. Add the above enzymolyzed material to a colloid mill for primary crushing, and crush the particle size to 130 - 140 μm. Then add the crushed material to a tubular homogenizer for secondary crushing, and crush the particle size to 55 - 65 μm. Add 6000 kg of process water at room temperature to the crushed material, stir evenly, and filter it through a secondary sieve. The mesh number of the first - stage centrifugal sieve is 70 meshes, and the mesh number of the second - stage centrifugal sieve is 100 meshes. Combine and wash the materials on the sieve, and dry them to obtain 48 kg of endosperm fiber.

[0051] The gap between the grinding discs of the colloid mill is 0.8 mm, and the circulation time of the colloid mill is 3 min; the pressure of the tubular homogenizer is 10 MPa.

[0052] S4. Centrifuge the filtrate obtained in step S3 with a horizontal spiral settling centrifuge at 10000 r / min for 3 min to obtain a crude liquid - phase protein and a crude solid - phase starch. Subject the crude solid - phase starch to hydrocyclone washing, dewatering with a scraper centrifuge, and drying to obtain 1384 kg of corn starch.

[0053] S5. Centrifuge the above - obtained crude liquid - phase protein with a horizontal spiral settling centrifuge at 5000 r / min for 3 min to obtain a protein solution and a solid - phase protein. After drying the solid - phase protein, obtain 70.4 kg of corn protein concentrate.

[0054] S6. Adjust the pH of the protein solution to 5.0 with a 25% sulfuric acid solution by mass concentration, then centrifuge it with a horizontal spiral settling centrifuge at 5000 r / min for 3 min. Add 500 kg of clear water to wash the obtained precipitate, filter it with a plate - and - frame filter press, and dry it to obtain 89.6 kg of corn protein isolate.

[0055] The mass, yield, and protein content of the materials obtained in each step of this example are shown in Table 1.

[0056] Table 1

[0057] Material Name Mass / g Moisture / % Yield (dry basis) / % Crude protein content / % Corn starch 1384.00 14.05 86.45 0.35 Endosperm fiber 48.00 8.22 3.20 12.85 Isolated protein 89.60 14.56 5.56 86.95 Concentrated protein 70.40 10.01 4.60 47.27

[0058] Compare the viscosity properties of the corn starch prepared in this example with the corn starch products prepared by the traditional wet - process technology on the market. The data are shown in Table 2.

[0059] Table 2

[0060]

[0061] Example 2

[0062] This example provides a method for extracting protein, endosperm fiber and starch from low-fat corn flour, which includes the following steps:

[0063] S1. Add 1600 kg of low-fat corn flour with a particle size of 60 mesh into 2970 kg of process water at 25 °C, stir evenly at a stirring speed of 120 r / min to obtain corn slurry;

[0064] S2. Mix alkaline protease and triacylglycerol hydrolase according to a mass ratio of 6:4 to obtain a composite enzyme; adjust the pH of the above-prepared corn slurry to 8.0 with a 4% sodium hydroxide aqueous solution by mass concentration, add 3.2 kg of the composite enzyme, stir and soak at room temperature for 40 min to obtain an enzymolyzed material;

[0065] S3. Add the above enzymolyzed material into a colloid mill for primary crushing, crush the particle size to 120 - 130 μm, then add the crushed material into a tubular homogenizer for secondary crushing, crush the particle size to 60 - 70 μm, add 4800 kg of process water at room temperature to the crushed material, stir evenly, and filter through a secondary sieve. The screen mesh of the primary centrifugal sieve is 70 mesh, and the screen mesh of the secondary centrifugal sieve is 100 mesh. Combine and wash the materials on the sieve, and dry to obtain 45.44 kg of endosperm fiber;

[0066] The grinding disc gap of the colloid mill is 1 mm, and the circulation time of the colloid mill is 2 min; the pressure of the tubular homogenizer is 8 MPa;

[0067] S4. Centrifuge the filtrate obtained in step S3 with a horizontal scroll decanter centrifuge at 9000 r / min for 5 min to obtain a liquid-phase crude protein and a solid-phase crude starch; subject the solid-phase crude starch to hydrocyclone washing, dehydration with a knife centrifuge, and drying to obtain 1386.4 kg of corn starch;

[0068] S5. Centrifuge the above-obtained liquid-phase crude protein with a horizontal scroll decanter centrifuge at 4000 r / min for 5 min to obtain a protein solution and a solid-phase protein. After drying the solid-phase protein, obtain 72.16 kg of corn protein concentrate;

[0069] S6. Adjust the pH of the protein solution to 4.5 with a 20% sulfuric acid solution by mass concentration, then centrifuge with a horizontal scroll decanter centrifuge at 4000 r / min for 5 min, add 520 kg of clear water to wash the obtained precipitate, filter with a plate and frame filter press, and dry to obtain 87.52 kg of corn protein isolate.

[0070] The quality, yield, and protein content of the materials obtained in each step of this example are shown in Table 3.

[0071] Table 3

[0072]

[0073]

[0074] Example 3

[0075] This example provides a method for extracting protein, endosperm fiber, and starch from low-fat corn flour, including the following steps:

[0076] S1. Add 1600 kg of low-fat corn flour with a particle size of 60 mesh to 2700 kg of process water at 25°C, stir evenly at a stirring speed of 80 r / min to obtain corn slurry;

[0077] S2. Mix alkaline protease and triacylglycerol hydrolase in a mass ratio of 7:3 to obtain a composite enzyme; adjust the pH of the above-prepared corn slurry to 7.5 with a 3% sodium hydroxide aqueous solution by mass concentration, add 1.6 kg of the composite enzyme, stir and soak at room temperature for 60 min to obtain an enzymatically hydrolyzed material;

[0078] S3. Add the above enzymatically hydrolyzed material to a colloid mill for primary crushing, crush the particle size to 140 - 150 μm, then add the crushed material to a tubular homogenizer for secondary crushing, crush the particle size to 50 - 60 μm, add 6400 kg of process water at room temperature to the crushed material, stir evenly, and filter through a secondary sieve. The screen mesh of the primary centrifugal sieve is 70 mesh, and the screen mesh of the secondary centrifugal sieve is 100 mesh. Combine and wash the materials on the sieve, and dry to obtain 46.9 kg of endosperm fiber;

[0079] The gap between the grinding discs of the colloid mill is 0.5 mm, and the circulation time of the colloid mill is 3 min; the pressure of the tubular homogenizer is 20 MPa;

[0080] S4. Centrifuge the filtrate obtained in step S3 with a horizontal spiral sedimentation centrifuge at 11000 r / min for 2 min to obtain a liquid-phase crude protein and a solid-phase crude starch; subject the solid-phase crude starch to hydrocyclone washing, dewatering with a scraper centrifuge, and drying to obtain 1385.8 kg of corn starch;

[0081] S5. Centrifuge the above-obtained liquid-phase crude protein with a horizontal spiral sedimentation centrifuge at 6000 r / min for 2 min to obtain a protein solution and a solid-phase protein. After drying the solid-phase protein, obtain 71.8 kg of corn protein concentrate;

[0082] S6. Adjust the pH of the protein solution to 4.7 with a sulfuric acid solution having a mass concentration of 30%, then centrifuge at 6000 r / min for 2 min using a horizontal spiral sedimentation centrifuge. Add 506 kg of clear water to the obtained precipitate for washing, filter using a plate and frame filter press, and dry to obtain 88.41 kg of corn protein isolate.

[0083] The mass, yield, and protein content of the materials obtained in each step of this example are shown in Table 4.

[0084] Table 4

[0085] Material Name Mass / g Moisture / % Yield (dry basis) / % Crude protein content / % Corn starch 1385.80 14.15 86.46 0.39 Endosperm fiber 46.90 11.27 3.02 12.42 Isolated protein 88.41 13.87 5.53 87.38 Concentrated protein 71.80 11.56 4.61 47.15

[0086] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for extracting protein, endosperm fiber and starch from low-fat corn flour, characterized in that: The steps include: S1, adding low-fat corn flour into water to obtain low-fat corn flour slurry; adjusting the pH of the low-fat corn flour slurry to weak alkaline, adding a composite enzyme, mixing evenly, and soaking to obtain an enzymatic material; wherein the composite enzyme includes alkaline protease and triglyceride hydrolase; S2, crushing and homogenizing the enzymatically hydrolyzed material, adding water, and filtering to obtain endosperm fiber and filtrate; S3, centrifuging the filtrate to obtain a crude liquid protein product and a crude solid starch product; washing, dehydrating and drying the crude solid starch product to obtain corn starch; S4, centrifuging the crude liquid protein product again to obtain a liquid phase separated protein solution and a solid phase concentrated protein; S5, adjusting the pH of the liquid phase separated protein solution to the isoelectric point, allowing to stand for precipitation, separating, washing, and drying to obtain separated protein.

2. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S1, the mass concentration of the low-fat corn flour slurry is 35% to 40%; and / or In S1, the weak alkalinity refers to a pH of 7.5 to 8.

0.

3. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S1, the mass ratio of the alkaline protease to the triacylglycerol hydrolase is 6:4 to 7:3; and / or In S1, the added amount of the complex enzyme is 0.1% to 0.2% of the mass of the low-fat corn flour.

4. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S1, the soaking temperature is 20°C to 30°C, and the soaking time is 40min to 60min.

5. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S2, the enzymatic hydrolysis material is crushed and homogenized to a particle size of 50 μm to 70 μm.

6. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S2, the amount of water added is 3 to 4 times the mass of the low-fat corn flour.

7. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S2, the filtering is performed using a two-stage sieve, wherein the mesh number of the first stage sieve is 60-70 meshes, and the mesh number of the second stage sieve is 90-100 meshes.

8. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S3, the centrifugal speed is 9000r / min to 11000r / min, and the centrifugal time is 2min to 5min; and / or In S3 and S4, the centrifugation is performed using a horizontal screw sedimentation centrifuge.

9. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S4, the centrifugal speed is 4000 r / min to 6000 r / min, and the centrifugal time is 2 min to 5 min.

10. The method for extracting protein, endosperm fiber and starch from low-fat corn flour according to claim 1, characterized in that: In S5, the pH of the isoelectric point is 4.5 to 5.0.

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