Extraction method of cottonseed protein

Abstract

The invention discloses an extraction method of cottonseed protein. The extraction method of the cottonseed protein comprises the following steps: S1, performing extraction treatment on cottonseed meal to obtain extract liquor; s2, filtering the extract obtained in the step S1 to obtain trapped fluid, and adjusting the pH value of the obtained trapped fluid until cottonseed protein is separated out; wherein the extraction treatment comprises a step of extracting with an alkaline aqueous solution; the filtering treatment comprises a step of filtering by using a hydrophilic membrane, and the molecular weight cut-off of the hydrophilic membrane is not less than 3KD. The extraction method can remove gossypol under mild conditions to obtain high-purity cottonseed protein, is simple to operate, has good environmental protection performance, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to a method for extracting cottonseed protein. Background Art

[0002] my country is a major cotton producer in the world, and its cotton production ranks first in the world. Cottonseed is a by-product of cotton processing. Cottonseed contains a large amount of oil and protein. It is not only an important oil resource, but also an important plant protein resource. The protein content of cottonseed meal obtained after cottonseed is shelled and oil extracted can reach 40%~50%. The main component of cottonseed protein is globulin, accounting for about 90%, followed by gluten. Cottonseed protein is similar to bean protein in quality, and its nutritional value is much higher than that of cereal protein. Its nutritional evaluation indicators such as protein efficacy ratio (2.0), digestibility (61%), biological value (62%) and protein net utilization rate (41%~47%) are all high, which are similar to soybean protein. In addition, the mineral content in cottonseed meal is consistent with soybean meal, which is much higher than grains. It is a very good natural plant protein feed. After experiments and applications in some dairy farms, it has been proved that the use of cottonseed protein can significantly increase the milk production of dairy cows, improve the quality of dairy products, and save feeding costs.

[0003] However, cottonseed contains gossypol, and gossypol and its derivatives are toxic to humans and animals. The main reason is that gossypol combines with certain enzymes and proteins, destroying the activity of enzymes and the digestibility of proteins, hindering normal metabolism. The gossypol content in cottonseed varies depending on the cotton variety and planting area, ranging from 0.7% to 4.8%. In the process of purification and removal of gossypol in patent CN115819495A, organic solvents are repeatedly extracted, but a large amount of organic waste liquid is also generated, which is not environmentally friendly.

[0004] Therefore, a simple, environmentally friendly cottonseed protein extraction method that can effectively remove cottonpol is urgently needed. Summary of the invention

[0005] In order to overcome the above defects of the existing cottonseed protein purification method, the present invention proposes a cottonseed protein extraction method. The extraction method can remove cottonphenol from cottonseed meal under mild conditions to obtain high-purity cottonseed protein, is simple to operate, has good environmental performance, and is suitable for large-scale industrial production.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for extracting cottonseed protein, which comprises the following steps:

[0008] S1, cottonseed meal is subjected to extraction treatment to obtain an extract;

[0009] S2, the extract obtained in step S1 is filtered to obtain a retentate, and the pH of the retentate is adjusted until cottonseed protein is precipitated;

[0010] in,

[0011] The extraction treatment comprises the step of extracting with an alkaline aqueous solution;

[0012] The filtration treatment includes the step of filtering with a hydrophilic membrane, and the molecular weight cutoff of the hydrophilic membrane is not less than 3KD.

[0013] In the present invention, the cottonseed meal is not limited in any way and can be obtained from conventional commercial sources, and generally refers to a product obtained by using cottonseed as a raw material and removing oil by pre-pressing or direct leaching. Those skilled in the art will know its specific meaning.

[0014] In some embodiments, in step S1, the alkaline aqueous solution is a sodium hydroxide aqueous solution and / or a potassium hydroxide aqueous solution, preferably a potassium hydroxide aqueous solution.

[0015] In some embodiments, in step S1, the pH of the alkaline aqueous solution is 10-13, preferably 12.

[0016] In some embodiments, in step S1, the mass ratio of the cottonseed meal to the alkaline aqueous solution is 1:10-1:20, preferably 1:13-1:17, and further preferably 1:15.

[0017] In some embodiments, in step S1, the extraction temperature is 40-70°C, preferably 45-60°C, for example 50°C.

[0018] In some embodiments, in step S1, the extraction time is 2-10 hours, preferably 3-8 hours, such as 5 hours or 7 hours.

[0019] In some embodiments, in step S1, the extraction is performed under stirring conditions.

[0020] In some embodiments, in step S1, the extraction step further includes a filtration step.

[0021] In some preferred embodiments, in step S1, the extraction treatment includes the step of performing multiple extractions with an alkaline aqueous solution, at least twice, and filtering after each extraction; preferably, when multiple extractions are performed with an alkaline aqueous solution, the type and amount of the alkaline aqueous solution are the same.

[0022] In some embodiments, in step S2, the hydrophilic membrane is a hydrophilic organic membrane, preferably a regenerated cellulose membrane or a polyethersulfone membrane. The hydrophilic membrane is resistant to strong alkali, and during the filtration process using the hydrophilic membrane, the structure of cottonseed protein can be retained to the greatest extent, that is, the protein activity of cottonseed protein is not affected.

[0023] The regenerated cellulose film refers to a film made of conventional regenerated cellulose. Regenerated cellulose means cellulose obtained by chemical or physical treatment using natural cellulose or its derivatives as raw materials.

[0024] In some embodiments, the regenerated cellulose membrane is a commercially available regenerated cellulose membrane.

[0025] In some preferred embodiments, the preparation of the regenerated cellulose film comprises the following steps:

[0026] The wood pulp is dissolved and regenerated by using ionic liquid to prepare a membrane; the ionic liquid preferably includes imidazole ionic liquid and / or choline ionic liquid; the ionic liquid is, for example, 1-(2-hydroxyethyl)-3-methylimidazolium chloride.

[0027] In some specific embodiments, the preparation of the regenerated cellulose film comprises the following steps:

[0028] The ionic liquid and microcrystalline cellulose are mixed, heated until the microcrystalline cellulose is dissolved, and then PEG5000 is added, stirred, and a film is scraped on a plate, and allowed to stand to form a film in water.

[0029] In some embodiments, in step S2, the molecular weight cutoff of the hydrophilic membrane is 3-10KD, preferably 10KD, 5KD or 3KD, and further preferably 3KD.

[0030] In some embodiments, in step S2, the membrane flux of the hydrophilic membrane is 100-120 gpd / d, for example, 110 gpd / d.

[0031] In some embodiments, in step S2, the working pressure of the hydrophilic membrane is 0.3-0.5 MPa, for example, 0.4 MPa.

[0032] In some embodiments, in step S2, the membrane area of ​​the hydrophilic membrane is 3-5 ft 2 , for example 4.0ft 2 .

[0033] In some specific embodiments, in step S2, the hydrophilic membrane is a regenerated cellulose membrane, and the regenerated cellulose membrane meets the following parameters: molecular weight cut-off of 3-10KD, membrane flux of 110gpd / d, working pressure of 0.4MPa, membrane area of ​​4.0ft 2 .

[0034] In some embodiments, in step S2, the temperature in the step of filtering with a hydrophilic membrane is 25-50°C, preferably 30-40°C.

[0035] In some embodiments, in step S2, in the step of filtering with a hydrophilic membrane, the pressure is 0.20-0.50 MPa, preferably 0.30-0.40 MPa.

[0036] In some embodiments, in step S2, the step of filtering with a hydrophilic membrane further includes the following step: adding the alkaline aqueous solution to keep the volume of the obtained retentate consistent with that before filtration.

[0037] In some preferred embodiments, in step S2, the filtration with a hydrophilic membrane is performed twice; more preferably, in the two filtration steps with a hydrophilic membrane, the type, temperature and pressure of the hydrophilic membrane are the same.

[0038] In some embodiments, in step S2, the filtration treatment includes the steps of first filtering with a ceramic filter membrane and then filtering with the hydrophilic membrane. Preferably, before the step of filtering with a ceramic membrane, conventional filtration, such as centrifugal filtration or suction filtration, is also included.

[0039] Among them, the pore size of the ceramic filter membrane is preferably 0.1-0.4um, more preferably 0.1-0.2um, and further preferably 0.1um.

[0040] Wherein, in the step of filtering with a ceramic membrane, the temperature is preferably 25-50°C, more preferably 30-40°C.

[0041] Wherein, in the step of filtering with a ceramic membrane, the pressure is preferably 0.20-0.60 MPa, more preferably 0.30-0.40 MPa, and further preferably 0.30 MPa.

[0042] In some embodiments, in step S2, the pH is 4.0-7.0, preferably 4-5, for example 5.

[0043] In some embodiments, in step S2, the step of adjusting the pH is performed by adding an acid, and the acid may be a conventional acid in the art, such as an aqueous hydrochloric acid solution.

[0044] In some embodiments, in step S2, the step of adjusting the pH further includes a step of concentration, and the step of concentration is preferably performed by reverse osmosis.

[0045] Wherein, the reverse osmosis is performed through a membrane, and the membrane is preferably a polyamide membrane.

[0046] Wherein, the membrane flux of the membrane is preferably 1-5 L / (m²·h), for example 2.5 L / (m²·h).

[0047] Wherein, the working pressure of the membrane is preferably 0.4-0.6 MPa, such as 0.5 MPa.

[0048] Wherein, the membrane area of ​​the membrane is preferably 3-5ft 2 , for example 4.0ft 2 .

[0049] In some specific embodiments, in the concentration step, the membrane is a polyamide membrane, the flux of the polyamide membrane is 2.5 L / (m²·h), the working pressure is 0.5 MPa, and the membrane area is 4.0 ft 2 .

[0050] In some embodiments, in step S2, the step of adjusting the pH further includes filtering the filter cake, washing, and drying.

[0051] In some embodiments, in step S2, the step of adjusting the pH further includes the steps of centrifuging to obtain the supernatant, adding water to stir, standing, centrifuging to remove the supernatant, and drying.

[0052] Wherein, when adding water and stirring, the amount of water added is preferably equal.

[0053] The time for adding water and stirring is, for example, 1 hour.

[0054] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0055] The reagents and raw materials used in the present invention are commercially available.

[0056] The positive and progressive effects of the present invention are:

[0057] The present invention constructs a novel cottonseed protein extraction method based on specific alkali extraction and membrane filtration. The extraction method can effectively remove cottonpol (the minimum cottonpol content can be as low as below 0.005%) and obtain high-purity cottonseed protein (protein purity is as high as over 90%). The method is simple to operate, has mild conditions, is green and environmentally friendly, does not generate organic waste liquid, and is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0058] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0059] Unless otherwise specified, the cottonseed meal used in the following examples and comparative examples is commercially available.

[0060] Unless otherwise specified, the ultrafiltration operations in the following examples and comparative examples were all performed using ultrafiltration membranes, all of which were regenerated cellulose membranes with a molecular weight cutoff of 3-10 KD, a membrane flux of 110 gpd / d, a working pressure of 0.4 MPa, and a membrane area of ​​4.0 ft 2 The preparation method of the regenerated cellulose mainly comprises the following steps:

[0061] Weigh 100 mL of ionic liquid (such as 1-(2-hydroxyethyl)-3-methylimidazolium chloride) and 8 g of microcrystalline cellulose, pour the ionic liquid and microcrystalline cellulose into the same heating bottle, stir magnetically to mix thoroughly; set the temperature of the heating container to 100°C, and start heating when the temperature shows the rated temperature. Heat at the set temperature until the microcrystalline cellulose is completely dissolved, then add 0.16 g of PEG5000, stir for 10 minutes, pour the liquid on the plate, scrape the film, dry it in the air for 10 minutes, and then put the membrane plate into distilled water to form a film.

[0062] Unless otherwise specified, the reverse osmosis operations in the following examples and comparative examples are all performed through membranes. The membranes used are all polyamide membranes with a membrane flux of 2.5 L / (m²·h), a working pressure of 0.5 MPa, and a membrane area of ​​4.0 ft 2 .

[0063] Example 1

[0064] 1kg of commercially available cottonseed meal, 10kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 3 hours, filtering, the filter cake is extracted again with potassium hydroxide aqueous solution, and the filtrate is collected, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 30℃, pressure 0.3Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40% (weight percentage, the same as below), stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, filter, wash the filter cake with a small amount of clean water, dry, and collect the light yellow cottonseed protein.

[0065] Example 2

[0066] 1kg of commercially available cottonseed meal, 10kg of potassium hydroxide aqueous solution (pH=10), stirring temperature 40℃, stirring time 3 hours, filter, filter cake again with potassium hydroxide aqueous solution to repeat the above operation once, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 30℃, pressure 0.3Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, filter, wash the filter cake with a small amount of clean water, dry, and collect the light yellow cottonseed protein.

[0067] Example 3

[0068] 1kg of commercially available cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 3 hours, filter, and extract the filter cake again with potassium hydroxide aqueous solution, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, filter, wash the filter cake with a small amount of clean water, dry, and collect the light yellow cottonseed protein.

[0069] Example 4

[0070] 1kg of commercial cottonseed meal, 20kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 3 hours, filter, and extract the filter cake again with potassium hydroxide aqueous solution, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0071] Example 5

[0072] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 50℃, stirring time 3 hours, filter, and extract the filter cake again with potassium hydroxide aqueous solution, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0073] Example 6

[0074] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 60℃, stirring time 3 hours, filter, and repeat the above operation with potassium hydroxide aqueous solution to extract the filter cake once again, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, and collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0075] Example 7

[0076] 1kg of commercially available cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=10), stirring temperature 60℃, stirring time 3 hours, filter, and extract the filter cake again with potassium hydroxide aqueous solution, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0077] Example 8

[0078] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 5 hours, filter, filter cake again with potassium hydroxide aqueous solution to repeat the above operation once, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0079] Example 9

[0080] 1kg of commercially available cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 7 hours, filter, and extract the filter cake again with potassium hydroxide aqueous solution, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, and collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0081] Example 10

[0082] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 5 hours, filter, and repeat the above operation with potassium hydroxide aqueous solution to extract the filter cake once again, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 30℃, pressure 0.3Mpa, and collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 3KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0083] Embodiment 11

[0084] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 5 hours, filter, and extract the filter cake again with potassium hydroxide aqueous solution, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.3Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 3KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0085] Example 12

[0086] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 5 hours, filter, filter cake again with potassium hydroxide aqueous solution to repeat the above operation once, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.2um, filtration temperature 40℃, pressure 0.3Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0087] Embodiment 13

[0088] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 5 hours, filter, filter cake again with potassium hydroxide aqueous solution to repeat the above operation once, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.4um, filtration temperature 40℃, pressure 0.3Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, pour out the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper layer of water, dry, and collect the light yellow cottonseed protein.

[0089] Embodiment 14

[0090] 1kg of commercial cottonseed meal, 20kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 5 hours, filter, filter cake again with potassium hydroxide aqueous solution to repeat the above operation and extract once, collect the filtrate, which is the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 40℃, pressure 0.4Mpa, collect the permeate. Perform ultrafiltration, regenerated cellulose membrane 5KD, filtration temperature 40℃, pressure 0.3Mpa, add 3 times the volume of potassium hydroxide alkali solution, filter until the volume of the retentate is the same as before ultrafiltration, and collect the retentate. Perform the same ultrafiltration operation again, collect the retentate, perform the same ultrafiltration operation again, collect the retentate, perform reverse osmosis operation, concentrate to a protein content of 40%, stop concentrating, add dilute hydrochloric acid aqueous solution to adjust pH=5, a large amount of solid precipitates, centrifuge, take the supernatant, add an equal amount of water and stir for 1 hour, let stand, centrifuge, remove the upper water, repeat the operation once to dry, and collect the light yellow cottonseed protein.

[0091] Comparative Example 1

[0092] 1kg of commercial cottonseed meal, 15kg of potassium hydroxide aqueous solution (pH=12), stirring temperature 40℃, stirring time 5 hours, filtering, the filter cake is extracted again with potassium hydroxide aqueous solution, and the filtrate is collected as the extract. Collect the filtrate, ceramic membrane 0.1um, filtration temperature 30℃, pressure 0.3Mpa. Perform ultrafiltration, regenerated cellulose membrane 1KD, filtration temperature 40℃, pressure 0.3Mpa, collect the retentate, the membrane package is easily blocked, and the filtration speed is slow.

[0093] Effect Example

[0094] Taking the crude protein content in cottonseed meal as 39%, the content of the finally separated cottonseed protein was detected, and the recovery rate was further calculated; and the content of free cottonpol in the cottonseed protein obtained in each embodiment and comparative example was determined with reference to GB / T13086-2020.

[0095] The results are shown in Table 1.

[0096] Table 1

[0097]

[0098] The above results show that the extraction method of the present invention can obtain cottonseed protein with a gossypol content as low as 0.005% and a protein purity of up to 90%; and in the reverse osmosis process, the pure water produced at the permeate end can be directly used for the preparation of alkali solution. The entire production process is green and environmentally friendly and can be applied to large-scale production.

Claims

1. A method for extracting cottonseed protein, It is characterized in that The method for extracting cottonseed protein comprises the following steps: S1, cottonseed meal is subjected to extraction treatment to obtain an extract; S2, the extract obtained in step S1 is filtered to obtain a retentate, and the pH of the retentate is adjusted until cottonseed protein is precipitated; in, The extraction treatment comprises the step of extracting with an alkaline aqueous solution; The filtration treatment includes the step of filtering with a hydrophilic membrane, and the molecular weight cutoff of the hydrophilic membrane is not less than 3KD.

2. The method for extracting cottonseed protein according to claim 1, It is characterized in that In step S1, the alkaline aqueous solution is a sodium hydroxide aqueous solution and / or a potassium hydroxide aqueous solution, preferably a potassium hydroxide aqueous solution; and / or, in step S1, the pH of the alkaline aqueous solution is 10-13, preferably 12; And / or, in step S1, the mass ratio of the cottonseed meal to the alkaline aqueous solution is 1:10-1:20, preferably 1:13-1:17, and more preferably 1:

15.

3. The method for extracting cottonseed protein according to claim 1, It is characterized in that In step S1, the extraction temperature is 40-70°C, preferably 45-60°C, for example 50°C; And / or, in step S1, the extraction time is 2-10 hours, preferably 3-8 hours, for example 5 hours or 7 hours; And / or, in step S1, the extraction step further includes a filtering step; And / or, in step S1, the extraction is carried out under stirring conditions; Preferably, in step S1, the extraction treatment includes the step of performing multiple extractions with an alkaline aqueous solution, at least twice, and filtering after each extraction; preferably, when performing multiple extractions with an alkaline aqueous solution, the type and amount of the alkaline aqueous solution are the same.

4. The method for extracting cottonseed protein according to claim 1, It is characterized in that In step S2, the molecular weight cutoff of the hydrophilic membrane is 3KD-10KD, such as 10KD, 5KD or 3KD, and more preferably 3KD; And / or, in step S2, the hydrophilic membrane is a hydrophilic organic membrane, more preferably a regenerated cellulose membrane or a polyethersulfone membrane; and / or, in step S2, the membrane flux of the hydrophilic membrane is 100-120 gpd / d, for example, 110 gpd / d; and / or, in step S2, the working pressure of the hydrophilic membrane is 0.3-0.5 MPa, for example 0.4 MPa; And / or, in step S2, the membrane area of ​​the hydrophilic membrane is 3-5 ft 2 , for example 4.0ft 2 .

5. The method for extracting cottonseed protein according to claim 1, It is characterized in that In step S2, the temperature of the filtration step with a hydrophilic membrane is 25-50°C, preferably 30-40°C; And / or, in step S2, in the step of filtering with a hydrophilic membrane, the pressure is 0.20-0.50 MPa, preferably 0.30-0.40 MPa; And / or, in step S2, the step of filtering with a hydrophilic membrane further comprises the following steps: adding the alkaline aqueous solution to keep the volume of the obtained retentate consistent with that before filtration; Preferably, in step S2, the filtration with the hydrophilic membrane is performed twice; more preferably, the type, temperature and pressure of the hydrophilic membrane are the same in the two filtrations.

6. The method for extracting cottonseed protein according to claim 1, It is characterized in that In step S2, the filtration treatment includes the steps of first filtering with a ceramic filter membrane and then filtering with the hydrophilic membrane; Wherein, the pore size of the ceramic filter membrane is preferably 0.1-0.4um, more preferably 0.1-0.2um, and further preferably 0.1um; Wherein, in the step of filtering with a ceramic membrane, the temperature is preferably 25-50°C, more preferably 30-40°C; Wherein, in the step of filtering with a ceramic membrane, the pressure is preferably 0.20-0.60 MPa, more preferably 0.30-0.40 MPa, and further preferably 0.30 MPa; Preferably, before the step of filtering with a ceramic membrane, centrifugal filtration or suction filtration is also included.

7. The method for extracting cottonseed protein according to claim 1, It is characterized in that In step S2, the pH is 4.0-7.0, preferably 4-5, for example 5; And / or, in step S2, the step of adjusting the pH is performed by adding an acid, and the acid is, for example, an aqueous solution of hydrochloric acid.

8. The method for extracting cottonseed protein according to claim 1, It is characterized in that In step S2, the step of adjusting the pH further includes a concentration step, and the concentration step is preferably performed by reverse osmosis; Wherein, the reverse osmosis is preferably performed through a membrane.

9. The method for extracting cottonseed protein according to claim 8, It is characterized in that The membrane is a polyamide membrane; And / or, the membrane flux of the membrane is preferably 1-5 L / (m²·h), for example 2.5 L / (m²·h); and / or, the working pressure of the membrane is preferably 0.4-0.6 MPa, such as 0.5 MPa; And / or, the membrane area of ​​the membrane is preferably 3-5 ft 2 , for example 4.0ft 2 .

10. The method for extracting cottonseed protein according to any one of claims 1 to 9, It is characterized in that In step S2, after the step of adjusting the pH, the steps of filtering the filter cake, washing and drying are also included; Alternatively, in step S2, the step of adjusting the pH further includes the steps of centrifuging to obtain the supernatant, adding water to stir, standing, centrifuging to remove the supernatant, and drying.

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