Extraction process and application of cottonseed peptides and cottonseed fiber

Abstract

The present invention relates to an extraction process and application of cottonseed peptides and cottonseed fibers. Through a series of supporting processes such as leaching with sulfurous acid aqueous solution, impact needle milling, screening with gravity and pressure curve screens, and countercurrent washing on cottonseed meal and / or cottonseed protein powder, the separation of cottonseed hulls, cottonseed fibers, and cottonseed proteins is achieved, promoting the transformation of cottonseed proteins from the bound state with cottonseed hulls and cottonseed fibers into water-soluble cottonseed proteins. After dehydration and drying, cottonseed fibers are obtained. Further, the cottonseed proteins are hydrolyzed and complex enzymatically hydrolyzed to obtain an enzymatically hydrolyzed peptide solution, which is then concentrated and spray-dried to obtain cottonseed peptides (enzymatically hydrolyzed cottonseed proteins). The extraction rate of cottonseed proteins is significantly increased, reaching 42.6 - 50.2%. The content of oligopeptides with a molecular weight below 1000 Daltons in the enzymatically hydrolyzed cottonseed proteins exceeds 82%, the content of free gossypol is below 400 mg / kg, and the removal rate is as high as over 85%. The prepared cottonseed peptides are completely water-soluble, clear and transparent, and have no bitter taste, and can be safely used in fields such as feed, food, biomaterials, cosmetics, and drugs.

Description

Technical Field

[0001] The invention belongs to the technical field of biological peptide preparation, and particularly relates to an extraction process and application of cottonseed peptide and cottonseed fiber. Background Art

[0002] Existing technical solutions are divided into two technical routes: from cottonseed meal or cottonseed protein powder to purified cottonseed concentrated protein and then to cottonseed peptides (referred to as the two-step cottonseed peptide technical route); and from cottonseed meal or cottonseed protein powder directly to cottonseed peptides (referred to as the one-step cottonseed peptide technical route). In the existing technical solutions, the biosynthesis of cottonseed protein in cottonseed meal or cottonseed protein powder is symbiotic and mutually entrained with fat, cottonseed fiber, ash, water, etc. in the cell wall of cottonseed kernels, and is wrapped in cotton husks and cottonseed fibers. There is a problem of unifying the stirring intensity and separation coefficient to completely separate the cottonseed protein entrained in cotton husks and cottonseed fibers. There is no specific technical solution for completely separating the cottonseed protein entrained in cotton husks and cottonseed fibers, and it needs to be solved urgently; in the two-step cottonseed peptide technical route, soaking cottonseed meal or In the laboratory, the separation of residue and liquid from cottonseed protein powder mostly adopts the high-speed centrifugation separation method with a speed of about 4000r / min, and there is no industrial residue-liquid separation scheme; in the one-step cottonseed peptide technical route, the separation of residue and liquid from cottonseed meal or cottonseed protein powder enzymatic hydrolysate mostly adopts the high-speed centrifugation separation method with a speed of about 4000r / min, and there is no industrial residue-liquid separation scheme; both the two-step cottonseed peptide technical route and the one-step cottonseed peptide technical route need to solve the problem of recovering cottonseed protein or cottonseed peptide in the separation residue to improve the overall yield. Patent application CN102206290A discloses a method for extracting cottonseed oligosaccharides and cottonseed protein oligopeptides from cottonseed meal. The method uses a microfiltration membrane for impurity removal and concentration, and then spray-drying, alkali dissolution, enzymatic hydrolysis, decolorization, centrifugation, and then uses a microfiltration membrane and a nanofiltration membrane for impurity removal and concentration to obtain cottonseed protein oligopeptides. The prepared oligopeptides (200~1000Dal) have a content of more than 90%, but the protein peptide extraction rate of this method is lower than 46%, and the extraction rate is not high. The microfiltration membrane and nanofiltration membrane have large losses, and the membrane needs to be replaced regularly. The process is complicated, uneconomical, and the production cost is high. It is difficult to achieve industrial production using microfiltration membranes and nanofiltration membranes, and the production speed is slow. In summary, the current technology is mostly aimed at the research on the component extraction process of cottonseed protein, and there are still deficiencies in specific industrial production. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides an extraction process for cottonseed peptides and cottonseed fiber. The content of oligopeptides with a molecular weight lower than 1000 daltons in the prepared cottonseed peptides exceeds 82%. The cottonseed peptides are completely water-soluble, clear and transparent, without bitterness, and have a low content of free gossypol, and can be safely used in animal feed, food packaging materials, bioplastics, food functional additives, biological media and enzyme synthesis, biodegradable materials, and cosmetics. The following is the specific content of the present invention:

[0004] In the first aspect, the present invention provides an extraction process for cottonseed peptides and cottonseed fiber, comprising the following steps:

[0005] S1. Extraction with sulfurous acid aqueous solution

[0006] The cottonseed meal and / or cottonseed protein powder are soaked in a sulfurous acid aqueous solution with a concentration of 0.05 - 2.5% for extraction. The solid-liquid ratio is 1 g: 3 - 20 mL, the extraction time is 2 - 12 hours, and the extraction temperature is 40 - 65°C to obtain a cottonseed meal soaking solution;

[0007] S2. Separation of cottonseed hulls, cottonseed fiber, and cottonseed protein

[0008] The cottonseed meal soaking solution obtained in step S1 is pumped to a No. 1 impact pin mill by a centrifugal pump. Through high-speed collision (rotation speed of 3000 - 5000 r / min, time about 60 - 90 min), the cottonseed protein mixed in the cottonseed hulls and cottonseed fiber is further released and transferred into the aqueous solution to obtain a coarsely ground cottonseed meal soaking solution; then the coarsely ground cottonseed meal soaking solution is sent to a coarsely ground pit and pumped to a No. 1 two-stage series gravity curve screen by a centrifugal pump. The gravity curve screen has slit widths of 30 - 50 mm (larger than the size of wet large cotton hulls) and 30 - 10 mm (larger than the size of wet medium and small cotton hulls) in sequence. The oversize is wet cotton hulls (the wet cotton hulls are mixed with water at a mass ratio of 1: 3 - 6 and sent to a cottonseed hull temporary storage tank with a stirrer. The cottonseed protein remaining in the wet cotton hulls is transferred into the aqueous solution by water to reduce the cottonseed protein content in the wet cotton hulls and improve the cottonseed protein recovery rate), and the undersize is a cottonseed protein solution containing cottonseed fiber;

[0009] Furthermore, the cottonseed protein solution containing cottonseed fiber is sent to a No. 2 impact pin mill. Through high-speed collision (rotation speed of 3000 - 5000 r / min, time about 100 - 120 min), the cottonseed protein mixed in the cottonseed fiber is further released and transferred into the aqueous solution to obtain a finely ground cottonseed fiber protein solution; then the finely ground cottonseed fiber protein solution is sent to a finely ground pit and pumped to a No. 1 pressure curve screen. The slit width of the No. 1 pressure curve screen is 100 - 150 μm (smaller than the size of wet cottonseed fiber). After screening, the oversize is wet cottonseed fiber, and the undersize is cottonseed protein solution I;

[0010] The cottonseed meal soaking solution obtained in step S1 is successively processed by a 1# impact needle mill and a 1# two-stage series gravity curve screen to obtain wet cotton hulls and cottonseed protein solution containing cottonseed fibers. The screen slot gaps of the 1# two-stage series gravity curve screen are 30 - 50 mm and 30 - 10 mm in sequence. Then, the cottonseed protein solution containing cottonseed fibers is successively processed by a 2# impact needle mill and a 1# pressure curve screen with a screen slot gap of 100 - 150 μm, and wet cottonseed fibers and cottonseed protein solution I are obtained by screening. Then, the wet cottonseed fibers are sent to a 2# pressure curve screen group for countercurrent washing. The 2# pressure curve screen group includes pressure curve screens from the 1st stage to the 6th stage (each stage of the pressure curve screen includes a 120° pressure curve screen, a cottonseed fiber trough for oversize material, a centrifugal pump for cottonseed fibers, a cottonseed protein washing solution trough for undersize material, and a centrifugal pump for cottonseed protein washing solution). The screen slot gaps of the 1st stage and the 6th stage pressure curve screens are 30 - 50 μm, and the screen slot gaps of the 2nd stage to the 5th stage pressure curve screens are 60 - 150 μm;

[0011] The wet cottonseed fibers are added to the 1st stage pressure curve screen by the 1st stage centrifugal pump for cottonseed fibers. After washing and screening by the 1st stage pressure curve screen, the oversize material is the 1st stage cottonseed fibers and enters the 2nd cottonseed fiber trough for temporary storage, and the undersize material is the 1st stage cottonseed protein washing solution and enters the 1st stage cottonseed protein washing solution trough for temporary storage;

[0012] It is successively subjected to classification washing and screening by the 1st stage to the 6th stage pressure curve screens. After washing and screening by each stage of the pressure curve screen, the oversize material is cottonseed fibers, and the undersize material is cottonseed protein washing solution. The oversize material enters the next stage of the pressure curve screen for washing and screening to obtain cottonseed protein detached from the cottonseed fibers. The finally washed and screened cottonseed fibers are pumped out of the pressure curve screen group from the 6th stage cottonseed fiber temporary storage tank (the 1st stage cottonseed fibers with the highest cottonseed protein concentration gradually enter the 6th stage cottonseed fiber temporary storage tank from the 1st stage. Therefore, the cottonseed protein concentration in the 6th stage cottonseed fibers is the lowest), and then dehydrated and dried to obtain dry cottonseed fibers;

[0013] The 2nd to 5th stage pressure curve screens mainly play a washing role. In the washing process of each stage of the pressure curve screen, the cottonseed protein washing liquid obtained by screening the next stage of the pressure curve screen is used to wash the oversize material obtained by screening the previous stage of the pressure curve screen. The initial washing liquid is clear water, which is added from the 6th stage pressure curve screen (added from the cottonseed protein washing liquid tank of the 6th stage undersize material into the cottonseed fiber tank of the 5th stage oversize material, and pumped into the screen surface of the 6th stage pressure curve screen by the centrifugal pump of the 5th stage cottonseed fiber tank for screening). After washing and screening the oversize material of the 5th stage pressure curve screen, the undersize material obtained is the 6th stage cottonseed protein washing liquid, which enters the 5th stage cottonseed protein washing liquid tank for temporary storage, and the oversize material is the 6th stage cottonseed fiber, which enters the 6th stage cottonseed fiber tank for temporary storage. The cottonseed protein washing liquid is transported from the 6th stage pressure curve screen to the 1st stage pressure curve screen in sequence, and at the same time, it washes and screens the oversize material of the previous stage pressure curve screen. The finally obtained cottonseed protein washing liquid is pumped out from the 1st stage cottonseed protein washing liquid tank (gradually flowing back from the 6th stage cottonseed protein washing liquid tank to the 1st stage cottonseed protein washing liquid tank according to the countercurrent principle. Therefore, the cottonseed protein concentration in the 1st stage cottonseed protein washing liquid is the highest), and then concentrated to obtain cottonseed protein liquid II;

[0014] S3. Hydrolysis of cottonseed protein

[0015] After collecting and mixing cottonseed protein liquid I and cottonseed protein liquid II obtained in step S2, they are separated by a disc high-speed centrifuge or a horizontal screw sedimentation centrifuge. The liquid phase is the purified cottonseed protein liquid, and the solid phase is cottonseed fiber residue. The purified cottonseed protein liquid is concentrated to a concentration of 15 - 25 wt%, and then undergoes high-temperature hydrolysis (hydrolysis temperature is 70 - 121 °C, hydrolysis pH is 4.5 - 9.0, hydrolysis time is 8 s - 45 min), and then the temperature is lowered. Then, flocculation is carried out near the isoelectric point under acidic conditions (the flocculation is to adjust the pH to 3.0 - 6.5 for flocculation precipitation, flocculation temperature is 5 - 75 °C, flocculation time is 5 - 60 min) to obtain cottonseed protein. The cottonseed protein is washed, filtered, and vacuum dehydrated to obtain cottonseed protein cake and dehydrated protein liquid;

[0016] S4. Enzymatic hydrolysis of cottonseed protein

[0017] The cottonseed protein cake obtained in step S3 is redissolved in water to prepare a mixed material liquid with a concentration of 1 - 50 wt%, heated to 60 - 121 °C and maintained for 10 - 45 min, then cooled to 30 - 65 °C, the pH is adjusted to 3 - 10.5, and alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase, and flavor protease are added in sequence for enzymatic hydrolysis. The addition amount of the enzyme is 0.1 - 15 wt%. The compounding ratio of the alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase, and flavor protease is 10 - 15:3 - 5:3 - 5:2 - 4:1 - 2:0.5 - 3. The enzymatic hydrolysis time is 0.5 - 12 h, and the enzymatic hydrolysis temperature is 35 - 65 °C. After heating and inactivating, the enzymatically hydrolyzed peptide liquid is obtained;

[0018] S5. Concentration and drying

[0019] Concentrate the enzymatically hydrolyzed peptide solution obtained in step S4 to a concentration of 10 - 50 wt%, then filter to remove impurities and solid particles. Spray-dry the liquid and conduct heat exchange with hot air at 170 - 210 °C. The inlet air temperature for spray drying is 120 - 190 °C, and the outlet air temperature is 50 - 90 °C. Collect the cottonseed peptide dry powder obtained.

[0020] Furthermore, the structure of the 1# two-stage series gravity curve screen in the present invention mainly includes a housing, a raw material receiver, a screen-under material receiver, and a frame for fixing the screen surface, etc. The gravity curve screen has a special cutting and screening function, with a large production capacity and is not easily blocked. The working principle of the gravity curve screen is as follows: The liquid-solid mixed material is distributed over the entire screen surface. When the material moves along the arc-shaped gravity curve screen surface (the screen surface curvature includes but is not limited to 50° - 60°), centrifugal force and inertial force are generated. The centrifugal force of fine particles is greater than the inertial force. Under the action of the centrifugal force, the liquid and fine particle materials leak through the screen holes, while under the action of the inertial force, the residues on the screen slide down along the screen surface.

[0021] Furthermore, the 1# pressure curve screen and the 2# pressure curve screen group in the present invention are a kind of high-efficiency screen that relies on pressure for wet material screening. The structure of the pressure curve screen mainly includes a housing, a feeder, a screen mesh, a screen-under material receiver, a screen-under material receiving funnel, and a frame for fixing the screen surface, etc. The screen surface is the key component of the pressure curve screen, and the screen surface curvature includes but is not limited to 120° - 300°. During operation, the wet material is sprayed from the nozzle orifice (the nozzle diameter is 1 / 2 - 3 / 4 inch, and the nozzle flow rate is 9.1 - 20.5 m 3 / h) under a pressure of 0.18 - 0.42 Mpa, generating a high feeding jet speed from the pressure to produce a tangential force. The materials on the screen are discharged from the slag outlet, and the liquid materials under the screen enter the screen-under material receiving funnel (slurry outlet).

[0022] Furthermore, the yield of cottonseed peptide obtained by the extraction process of cottonseed peptide and cottonseed fiber of the present invention is 42 - 50.2%, and the yield of dry cottonseed fiber is 48 - 58%.

[0023] In the second aspect, the present invention also provides a kind of cottonseed peptide. The extraction rate of the cottonseed peptide exceeds 40%, the content of oligopeptides with a molecular weight lower than 1000 daltons exceeds 82%, the content of free gossypol is lower than 400 mg / kg, the moisture content is lower than 5.5%, the crude protein content is higher than 65%, the crude ash content is lower than 11.5%, and the content of acid-soluble protein (accounting for the crude protein content) exceeds 62%.

[0024] In a third aspect, the present invention further provides a dry cottonseed fiber, wherein the dry cottonseed fiber is obtained by dehydrating and drying wet cottonseed fiber obtained by the cottonseed peptide and cottonseed fiber extraction process of the present invention.

[0025] In a fourth aspect, the present invention also provides the use of cottonseed peptides in animal feed, food packaging materials, bioplastics, functional foods, biological culture media and enzyme synthesis, biodegradable materials, cosmetics and medicines.

[0026] The invention adopts a sulfurous acid aqueous solution to extract cottonseed meal and cottonseed protein powder, and aims to wet the cottonseed meal with water to swell cottonseed hulls, cottonseed fibers and cottonseed proteins, and the sulfurous acid aqueous solution extracts cottonseed proteins mixed in cottonseed hulls and cottonseed fibers into the aqueous solution, so that the cottonseed proteins in the cottonseed meal and cottonseed protein powder are transformed from the state of being combined with cottonseed hulls and cottonseed fibers into water-soluble cottonseed proteins, thereby realizing the water-soluble extraction of cottonseed proteins.

[0027] The present invention separates cottonseed hulls, cottonseed fibers, and cottonseed proteins from cottonseed meal and cottonseed protein powder, and separates cottonseed hulls from cottonseed protein liquid containing cottonseed fibers by a 1# impact pin mill and a 1# two-stage series gravity curved screen; separates wet cottonseed fibers from cottonseed protein liquid by a 2# impact pin mill and a 1# pressure curved screen; and further reduces cottonseed proteins in cottonseed fibers by a 2# pressure curved screen group combined with a countercurrent washing process, and separates cottonseed fibers from cottonseed proteins. The separation process can achieve maximum separation of cottonseed hulls, cottonseed fibers, and cottonseed proteins, and obtains higher purity and yield of cottonseed fibers and cottonseed proteins, and has higher application value.

[0028] The cottonseed peptide is prepared by enzymatic hydrolysis using a composite enzyme consisting of alkaline protease, neutral protease, acidic protease, cottonpol decomposing enzyme, keratinase and flavor protein protease, and the synergistic effect of multiple enzymes is utilized to maximize the different advantages of the enzyme cleavage sites of various enzymes. The compounding of different types of proteases often has a synergistic effect, which is not only beneficial to shortening the enzymatic hydrolysis time and improving the hydrolysis degree, but also can obtain an enzymatic hydrolyzate with better molecular weight composition and distribution.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention extracts cottonseed peptides from cottonseed meal and cottonseed protein powder raw materials using an aqueous sulfurous acid solution, which can transform the cottonseed protein in the cottonseed meal and cottonseed protein powder raw materials from the bound state with cottonseed hulls and cottonseed fibers into water-soluble cottonseed protein, thus achieving the maximum degree of water-soluble extraction of cottonseed protein. The present invention adopts processes such as a 1# impact needle mill, a 1# two-stage series gravity curve screen, a 2# impact needle mill, a 1# pressure curve screen, and a 2# pressure curve screen group combined with countercurrent washing to maximize the separation of cottonseed fibers and cottonseed protein, and improve the purity and yield of cottonseed fibers and cottonseed protein. The present invention uses a composite enzyme to enzymatically hydrolyze cottonseed meal and cottonseed protein powder raw materials to prepare cottonseed peptides. The composite enzyme used has thorough enzymatic hydrolysis, which improves the acid-soluble protein content of the cottonseed peptide product. Among them, the content of acid-soluble protein (oligopeptide) exceeds 60%, and the content of acid-soluble protein (oligopeptide) with a molecular weight lower than 1000 daltons is higher than 82%. The obtained cottonseed peptide is completely water-soluble, clear and transparent, without bitterness, has a fresh sweet taste, the content of free gossypol is lower than 400 mg / kg, and the removal rate is as high as 85%. It is safe and has no toxic side effects, and can be widely used in fields such as animal feed, food packaging materials, biodegradable plastics, food functional additives, biological culture media and enzyme synthesis, biodegradable materials, and cosmetics. Detailed implementation manners

[0031] In the experimental methods of the following examples of the present invention that do not specify specific conditions, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. All kinds of common chemical reagents used in the examples are commercially available products.

[0032] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] To make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific implementation manners. It should be understood that these descriptions are exemplary and not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0034] The alkaline protease, neutral protease, acid protease, keratinase and flavor protease used in the examples of the present invention are all purchased from Shandong Longkete Enzyme Preparation Co., Ltd.; the 1# impact needle mill, 2# impact needle mill, 1# two-stage series gravity curve screen, 1# pressure curve screen and 2# pressure curve screen group used in the examples of the present invention are all purchased from Yixing Yidian Machinery Equipment Co., Ltd.;

[0035] The free gossypol degrading enzyme is a protein solution obtained by culturing a self-selected strain. The self-selected strain is isolated by diluting rotten cottonseed meal and obtained through comparison of the fluorescence area of the free gossypol degrading zone. After being cultured in a slant, a shaking flask, and a first-stage seed tank, it enters the fermentation tank for culturing for about 36 h. When the wet weight of the centrifuged bacterial cells is within 5 - 15%, the protein solution is obtained. Further, the bacterial cells are broken by ultrasonic wave or high-pressure homogenizer to obtain the protein solution, and the free gossypol degrading enzyme is obtained after rotary evaporation drying or concentrated spray drying.

[0036] Example 1 Preparation of cottonseed peptides and cottonseed fibers

[0037] The preparation steps of cottonseed peptides and cottonseed fibers in this example are as follows:

[0038] S1. Extraction with sulfurous acid aqueous solution

[0039] The cottonseed meal and / or cottonseed protein powder are soaked in a 0.25% sulfurous acid aqueous solution for extraction. The material-liquid ratio is 1 g:10 mL, the extraction time is 10 h, the extraction temperature is 60 °C, and the cottonseed meal soaking solution is obtained.

[0040] S2. Separation of cottonseed hulls, cottonseed fibers, and cottonseed proteins

[0041] The cottonseed meal soaking solution obtained in step S1 is pumped to a No. 1 impact needle mill for treatment (rotation speed is 3000 r / min, time is 90 min) to obtain a coarsely ground cottonseed meal soaking solution. Then the coarsely ground cottonseed meal soaking solution is sent to a coarsely ground pit and pumped to a No. 1 two-stage series gravity curve screen by a centrifugal pump. It passes through a No. 1 series gravity curve screen with a slit gap of 50 mm (larger than the size of wet large cottonseed hulls) and 30 mm (larger than the size of wet medium and small cottonseed hulls) in sequence (the screen surface arc is 60°). The oversize is wet cottonseed hulls, and the undersize is a cottonseed protein solution containing cottonseed fibers. The wet cottonseed hulls are mixed with water at a mass ratio of 1:5 and sent to a cottonseed hull temporary storage tank with a stirrer. The cottonseed protein remaining in the wet cottonseed hulls is transferred to the aqueous solution with water and merged with the cottonseed protein solution containing cottonseed fibers in the undersize;

[0042] Furthermore, the merged cottonseed protein solution containing cottonseed fibers is sent to a No. 2 impact needle mill for treatment (rotation speed is 3000 r / min, time is 100 min) to obtain a finely ground cottonseed fiber protein solution. Then the finely ground cottonseed fiber protein solution is sent to a finely ground pit and pumped to a No. 1 pressure curve screen by a centrifugal pump. The slit gap of the No. 1 pressure curve screen is 100 μm (smaller than the size of wet cottonseed fibers), the screen surface arc is 120°, the feeding pressure is 0.28 - 0.42 Mpa, the nozzle diameter is 1 / 2 inch, and the nozzle flow rate is 9.1 - 11 m 3 / h. The oversize is wet cottonseed fibers, and the undersize is cottonseed protein solution I;

[0043] Further, the wet cottonseed fiber is fed into a wet cottonseed fiber temporary storage tank and pumped into the 2# pressure curved sieve group by a centrifugal pump for countercurrent washing of the cottonseed fiber. The 2# pressure curved sieve group includes pressure curved sieves from level 1 to level 6 (each level of pressure curved sieve includes a pressure curved sieve with a screen surface arc of 120°, a cottonseed fiber tank for oversize material, a centrifugal pump for cottonseed fiber in the tank, a tank for cottonseed protein washing liquid for undersize material, and a centrifugal pump for cottonseed protein washing liquid). The screen slot gap of the first-level pressure curved sieve is 30 μm, the screen slot gaps of the second-level to fifth-level pressure curved sieves are 60 μm, the screen slot gap of the sixth-level pressure curved sieve is 50 μm, the feed pressure is 0.28 - 0.42 Mpa, the nozzle diameter is 1 / 2 inch, and the nozzle flow rate is 9.1 - 11 m 3 / h;

[0044] The wet cottonseed fiber is added to the first-level pressure curved sieve by the first-level centrifugal pump for cottonseed fiber. After being washed and screened by the first-level pressure curved sieve, the oversize material is the first-level cottonseed fiber and enters the second cottonseed fiber tank for temporary storage, and the undersize material is the first-level cottonseed protein washing liquid and enters the first-level cottonseed protein washing liquid tank for temporary storage. It is sequentially washed and screened through the first-level to sixth-level pressure curved sieves. After being washed and screened by each level of pressure curved sieve, the oversize material is cottonseed fiber, and the undersize material is cottonseed protein washing liquid. The oversize material enters the next-level pressure curved sieve for washing and screening to obtain the cottonseed protein separated from the cottonseed fiber. The finally washed and screened cottonseed fiber is pumped out of the pressure curved sieve group from the sixth-level cottonseed fiber temporary storage tank (the first-level cottonseed fiber with the highest cottonseed protein concentration gradually enters the sixth-level cottonseed fiber temporary storage tank from the first level. Therefore, the cottonseed protein concentration in the sixth-level cottonseed fiber is the lowest), and then dehydrated and dried to obtain dry cottonseed fiber;

[0045] The second-level to fifth-level pressure curved sieves mainly play a role in washing. The washing process of each level of pressure curved sieve is to wash the oversize material obtained by screening the previous-level pressure curved sieve with the cottonseed protein washing liquid obtained by screening the next-level pressure curved sieve. The initial washing liquid is clear water, which is added from the sixth-level pressure curved sieve (added from the sixth-level tank for cottonseed protein washing liquid for undersize material to the fifth-level cottonseed fiber tank for oversize material, and pumped onto the screen surface of the sixth-level pressure curved sieve by the fifth-level centrifugal pump for cottonseed fiber in the tank for screening). After washing and screening the oversize material of the fifth-level pressure curved sieve, the undersize material is the sixth-level cottonseed protein washing liquid and enters the fifth-level cottonseed protein washing liquid tank for temporary storage, and the oversize material is the sixth-level cottonseed fiber and enters the sixth-level cottonseed fiber tank for temporary storage. The cottonseed protein washing liquid is sequentially transported from the sixth-level pressure curved sieve to the first-level pressure curved sieve, and at the same time, the oversize material of the previous-level pressure curved sieve is washed and screened. The finally obtained cottonseed protein washing liquid is pumped out of the first-level cottonseed protein washing liquid tank (flowing countercurrently from the sixth-level cottonseed protein washing liquid tank to the first-level cottonseed protein washing liquid tank according to the countercurrent principle. Therefore, the cottonseed protein concentration in the first-level cottonseed protein washing liquid is the highest), and then concentrated to obtain cottonseed protein liquid II;

[0046] S3. Hydrolysis of cottonseed protein

[0047] Collect the cottonseed protein solution I and cottonseed protein solution II obtained in step S2, mix them, separate them by a disc high-speed centrifuge (or a horizontal screw sedimentation centrifuge). The liquid phase is the purified cottonseed protein solution, and the solid phase is cottonseed fiber residue. Concentrate the purified cottonseed protein solution to a concentration of 15 wt%, then conduct high-temperature hydrolysis (hydrolysis temperature is 90°C, hydrolysis pH is 5.6, hydrolysis time is 25 min) in sequence, cool down, and then adjust the pH to 4.0 - 6.5 for flocculation (flocculation temperature is 45°C, flocculation time is 45 min) to obtain cottonseed protein. Conduct vacuum dehydration on the cottonseed protein, wash it with water, and then continue vacuum dehydration to obtain cottonseed protein cake and dehydrated protein solution;

[0048] S4. Enzymatic hydrolysis of cottonseed protein

[0049] Dissolve the cottonseed protein cake obtained in step S3 in water to make a mixed material liquid with a concentration of 5 wt%, heat it to 90°C and keep it for 45 min, then cool it down to 45°C, adjust the pH to 8.5, and sequentially add alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase and flavor protease for enzymatic hydrolysis. The total enzyme addition amount in the mixed material liquid is 0.9 wt%. The compounding ratio of the alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase and flavor protease is 15:5:5:4:2:3, the enzymatic hydrolysis time is 8 h, the enzymatic hydrolysis temperature is 40°C, and heat inactivation is carried out to obtain enzymatic hydrolysate peptide solution;

[0050] S5. Concentration and drying

[0051] Concentrate the enzymatic hydrolysate peptide solution obtained in step S4 to a concentration of 40 wt%, then filter to remove impurities to remove solid particles, conduct spray drying on the liquid and conduct heat exchange with 170°C hot air. The inlet air temperature of the spray drying is 190°C, the exhaust air temperature is 80°C, and cottonseed peptide dry powder is collected.

[0052] Example 2 Preparation of cottonseed peptide and cottonseed fiber

[0053] The preparation steps of cottonseed peptide and cottonseed fiber in this example are specifically as follows:

[0054] S1. Extraction with sulfurous acid aqueous solution

[0055] Soak cottonseed meal and / or cottonseed protein powder in a sulfurous acid aqueous solution with a concentration of 0.5% for extraction. The material-liquid ratio is 1 g:8 mL, the extraction time is 8 h, the extraction temperature is 55°C, and cottonseed meal soaking solution is obtained;

[0056] S2. Separation of cottonseed hull, cottonseed fiber and cottonseed protein

[0057] Pump the cottonseed meal soaking solution obtained in step S1 to a No. 1 impact pin mill for treatment (rotation speed: 3000 r / min, time: 90 min) to obtain a coarsely ground cottonseed meal soaking solution. Then, send the coarsely ground cottonseed meal soaking solution to a coarsely ground pit, and pump it to a No. 1 two-stage series gravity curve screen with sieve gaps of 50 mm (larger than the size of wet large cotton hulls) and 30 mm (larger than the size of wet medium and small cotton hulls) in sequence. The sieve surface arcs of the No. 1 series gravity curve screen are both 60°. The material on the sieve is wet cotton hulls, and the material under the sieve is cottonseed protein solution containing cottonseed fibers. Mix the wet cotton hulls and water at a mass ratio of 1:5 and send them to a cottonseed hull temporary storage tank equipped with a stirrer. Transfer the cottonseed protein remaining in the wet cotton hulls to the aqueous solution with water and combine it with the cottonseed protein solution containing cottonseed fibers under the sieve;

[0058] Further, send the combined cottonseed protein solution containing cottonseed fibers to a No. 2 impact pin mill for treatment (rotation speed: 3000 r / min, time: 100 min) to obtain a finely ground cottonseed fiber protein solution. Then, send the finely ground cottonseed fiber protein solution to a fine grinding pit, and pump it to a No. 1 pressure curve screen. The sieve gap of the No. 1 pressure curve screen is 100 μm (smaller than the size of wet cottonseed fibers), the sieve surface arc is 120°, the feeding pressure is 0.28 - 0.42 Mpa, the nozzle diameter is 1 / 2 inch, and the nozzle flow rate is 9.1 - 11 m 3 / h. After screening, the material on the sieve is wet cottonseed fibers, and the material under the sieve is cottonseed protein solution I;

[0059] Further, send the wet cottonseed fibers to a wet cottonseed fiber temporary storage tank, and pump them into a No. 2 pressure curve screen group for countercurrent washing of cottonseed fibers. The No. 2 pressure curve screen group includes pressure curve screens from level 1 to level 6 (each level of pressure curve screen includes a pressure curve screen with a sieve surface arc of 120°, a cottonseed fiber tank for the material on the sieve, a centrifugal pump for the cottonseed fiber tank, a cottonseed protein washing solution tank for the material under the sieve, and a centrifugal pump for the cottonseed protein washing solution). The sieve gap of the first-level pressure curve screen is 30 μm, the sieve gaps of the second-level to fifth-level pressure curve screens are 60 μm, the sieve gap of the sixth-level pressure curve screen is 50 μm, the feeding pressure is 0.28 - 0.42 Mpa, the nozzle diameter is 1 / 2 inch, and the nozzle flow rate is 9.1 - 11 m 3 / h;

[0060] The wet cottonseed fiber is added from the first-stage pressure curved sieve by the first-stage cottonseed fiber centrifugal pump. After being washed and screened by the first-stage pressure curved sieve, the oversize material is the first-stage cottonseed fiber, which enters the second cottonseed fiber tank for temporary storage. The undersize material is the first-stage cottonseed protein washing liquid, which enters the first-stage cottonseed protein washing liquid tank for temporary storage. It is successively subjected to classification washing and screening through the first-stage to the sixth-stage pressure curved sieves. After each stage of pressure curved sieve for washing and screening, the oversize material is cottonseed fiber, and the undersize material is cottonseed protein washing liquid. The oversize material enters the next-stage pressure curved sieve for washing and screening to obtain the cottonseed protein detached from the cottonseed fiber. The finally washed and screened cottonseed fiber is pumped out of the pressure curved sieve group from the sixth-stage cottonseed fiber temporary storage tank (including the first-stage cottonseed fiber with the highest cottonseed protein concentration gradually entering from the first stage to the sixth-stage cottonseed fiber temporary storage tank. Therefore, the cottonseed protein concentration in the sixth-stage cottonseed fiber is the lowest), and then dehydrated and dried to obtain dry cottonseed fiber;

[0061] The second to fifth-stage pressure curved sieves mainly play a washing role. The washing process of each stage of pressure curved sieve is to wash the oversize material obtained by screening the previous-stage pressure curved sieve with the cottonseed protein washing liquid obtained by screening the next-stage pressure curved sieve. The initial washing liquid is clear water, which is added from the sixth-stage pressure curved sieve (added from the sixth-stage undersize cottonseed protein washing liquid tank to the fifth-stage oversize cottonseed fiber tank, and pumped into the sixth-stage pressure curved sieve screen for screening by the fifth-stage cottonseed fiber tank centrifugal pump), and the oversize material of the fifth-stage pressure curved sieve is washed and screened. The undersize material obtained is the sixth-stage cottonseed protein washing liquid, which enters the fifth-stage cottonseed protein washing liquid tank for temporary storage. The oversize material is the sixth-stage cottonseed fiber, which enters the sixth-stage cottonseed fiber tank for temporary storage. The cottonseed protein washing liquid is successively transported from the sixth-stage pressure curved sieve to the first-stage pressure curved sieve, and at the same time, the oversize material of the previous-stage pressure curved sieve is washed and screened. The finally obtained cottonseed protein washing liquid is pumped out from the first-stage cottonseed protein washing liquid tank (flowing back from the sixth-stage cottonseed protein washing liquid tank to the first-stage cottonseed protein washing liquid tank gradually according to the countercurrent principle. Therefore, the cottonseed protein concentration in the first-stage cottonseed protein washing liquid is the highest), and then concentrated to obtain cottonseed protein liquid II;

[0062] S3. Hydrolysis of cottonseed protein

[0063] Collect and mix the cottonseed protein liquid I and cottonseed protein liquid II obtained in step S2, and separate them by a disc high-speed centrifuge (or a horizontal screw sedimentation centrifuge). The liquid phase is the pure cottonseed protein liquid, and the solid phase is cottonseed fiber residue. Concentrate the pure cottonseed protein liquid to a concentration of 18 wt%, and then successively carry out high-temperature hydrolysis (hydrolysis temperature is 121 °C, hydrolysis pH is 7.8, hydrolysis time is 20 s), cool down, and then adjust the pH to 4.0 - 6.5 for flocculation (flocculation temperature is 25 °C, flocculation time is 25 min) to obtain cottonseed protein. Vacuum dehydrate the cottonseed protein, wash it with water, and then continue vacuum dehydration to obtain cottonseed protein cake;

[0064] S4. Proteolysis of cottonseed protein

[0065] Dissolve the cottonseed protein cake obtained in step S3 in water to make a mixed solution with a concentration of 10 wt%, heat it to 90 °C and keep it for 45 min, then cool it down to 45 °C, adjust the pH to 8.5, and sequentially add alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase and flavor protease for proteolysis. The total enzyme addition amount in the mixed solution is 1.5 wt%. The compounding ratio of the alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase and flavor protease is 12:4:4:3:1.3:1.0. The proteolysis time is 10 h, the proteolysis temperature is 45 °C, and heat inactivation is carried out to obtain the enzymolysis peptide solution;

[0066] S5. Concentration and drying

[0067] Concentrate the enzymolysis peptide solution obtained in step S4 to a concentration of 45 wt%, then filter to remove impurities and remove solid particles. Spray dry the liquid and carry out heat exchange with hot air at 175 °C. The inlet air temperature of the spray drying is 190 °C, and the outlet air temperature is 85 °C. Collect the cottonseed peptide dry powder.

[0068] Example 3 Preparation of cottonseed peptide and cottonseed fiber

[0069] The preparation steps of cottonseed peptide and cottonseed fiber in this example are specifically as follows:

[0070] S1. Extraction with sulfurous acid aqueous solution

[0071] Soak the cottonseed meal and / or cottonseed protein powder in a sulfurous acid aqueous solution with a concentration of 1.2% for extraction. The material-liquid ratio is 1 g:16 mL, the extraction time is 6 h, and the extraction temperature is 50 °C to obtain the cottonseed meal soaking solution;

[0072] S2. Separation of cottonseed hull, cottonseed fiber and cottonseed protein

[0073] Pump the cottonseed meal soaking solution obtained in step S1 to a No. 1 impact needle mill for treatment (rotation speed is 3000 r / min, time is 90 min) to obtain a coarsely ground cottonseed meal soaking solution. Then send the coarsely ground cottonseed meal soaking solution to a coarsely ground pit, and pump it to a No. 1 two-stage series gravity curve screen with sieve gaps of 50 mm (larger than the size of wet large cotton hulls) and 30 mm (larger than the size of wet medium and small cotton hulls) in sequence. The 1# series gravity curve screen (the screen surface arc is 60°). The material on the screen is wet cotton hulls, and the material under the screen is cottonseed protein liquid containing cottonseed fiber. Mix the wet cotton hulls with water at a mass ratio of 1:5 and send them to a cottonseed hull temporary storage tank with a stirrer. Transfer the cottonseed protein remaining in the wet cotton hulls to the aqueous solution with water and merge it with the cottonseed protein liquid containing cottonseed fiber under the screen;

[0074] Further, the combined cottonseed protein solution containing cottonseed fibers is sent to a 2# impact needle mill for treatment (rotation speed is 3000 r / min, time is 100 min) to obtain a finely ground cottonseed fiber protein solution. Then, the finely ground cottonseed fiber protein solution is sent to a fine grinding pit and pumped to a 1# pressure curved screen by a centrifugal pump. The screen slot gap of the 1# pressure curved screen is 100 μm (less than the size of wet cottonseed fibers), the screen surface radian is 120°, the feeding pressure is 0.28 - 0.42 Mpa, the nozzle diameter is 1 / 2 inch, and the nozzle flow rate is 9.1 - 11 m 3 / h. The oversize is wet cottonseed fibers, and the undersize is cottonseed protein solution I obtained by screening;

[0075] Further, the wet cottonseed fibers are sent to a wet cottonseed fiber temporary storage tank and pumped into a 2# pressure curved screen group for countercurrent washing of cottonseed fibers. The 2# pressure curved screen group includes pressure curved screens from level 1 to level 6 (each level of pressure curved screen includes a pressure curved screen with a screen surface radian of 120°, an oversize cottonseed fiber tank, a cottonseed fiber tank centrifugal pump, an undersize cottonseed protein washing solution tank, and a cottonseed protein washing solution centrifugal pump). The screen slot gap of the first-level pressure curved screen is 30 μm, the screen slot gaps of the second-level to fifth-level pressure curved screens are 60 μm, and the screen slot gap of the sixth-level pressure curved screen is 50 μm. The feeding pressure is 0.28 - 0.42 Mpa, the nozzle diameter is 1 / 2 inch, and the nozzle flow rate is 9.1 - 11 m 3 / h;

[0076] The wet cottonseed fibers are added to the first-level pressure curved screen by the first-level cottonseed fiber centrifugal pump. After washing and screening by the first-level pressure curved screen, the oversize is the first-level cottonseed fibers that enter the second cottonseed fiber tank for temporary storage, and the undersize is the first-level cottonseed protein washing solution that enters the first-level cottonseed protein washing solution tank for temporary storage. They are sequentially washed and screened through the first-level to sixth-level pressure curved screens. After washing and screening by each level of pressure curved screen, the oversize is cottonseed fibers, and the undersize is cottonseed protein washing solution. The oversize enters the next-level pressure curved screen for washing and screening to obtain the cottonseed protein detached from the cottonseed fibers. The finally washed and screened cottonseed fibers are pumped out of the pressure curved screen group from the sixth-level cottonseed fiber temporary storage tank (the first-level cottonseed fibers with the highest cottonseed protein concentration gradually enter the sixth-level cottonseed fiber temporary storage tank from the first level, so the cottonseed protein concentration in the sixth-level cottonseed fibers is the lowest), and then dehydrated and dried to obtain dry cottonseed fibers;

[0077] The 2nd to 5th stage pressure curved screens mainly play a washing role. In the washing process of each stage of pressure curved screen, the cottonseed protein washing liquid obtained by screening in the next stage of pressure curved screen is used to wash the oversize materials obtained by screening in the previous stage of pressure curved screen. The initial washing liquid is clear water, which is added from the 6th stage pressure curved screen (added from the cottonseed protein washing liquid tank of the 6th stage undersize materials to the cottonseed fiber tank of the 5th stage oversize materials, and pumped into the screen surface of the 6th stage pressure curved screen by the centrifugal pump of the 5th stage cottonseed fiber tank for screening). After washing and screening the oversize materials of the 5th stage pressure curved screen, the undersize materials are the 6th stage cottonseed protein washing liquid and enter the 5th stage cottonseed protein washing liquid tank for temporary storage, and the oversize materials are the 6th stage cottonseed fibers and enter the 6th stage cottonseed fiber tank for temporary storage. The cottonseed protein washing liquid is transported from the 6th stage pressure curved screen to the 1st stage pressure curved screen in sequence, and at the same time, it washes and screens the oversize materials of the previous stage pressure curved screen. The finally obtained cottonseed protein washing liquid is pumped out from the 1st stage cottonseed protein washing liquid tank (gradually flowing back from the 6th stage cottonseed protein washing liquid tank to the 1st stage cottonseed protein washing liquid tank according to the countercurrent principle. Therefore, the cottonseed protein concentration in the 1st stage cottonseed protein washing liquid is the highest), and then concentrated to obtain cottonseed protein liquid II;

[0078] S3. Hydrolysis of cottonseed protein

[0079] Collect the cottonseed protein liquid I and cottonseed protein liquid II obtained in step S2 and mix them. Separate them by a disc high-speed centrifuge (or a horizontal screw sedimentation centrifuge). The liquid phase is the purified cottonseed protein liquid, and the solid phase is cottonseed fiber residue. Concentrate the purified cottonseed protein liquid to a concentration of 23wt%. Then, conduct high-temperature hydrolysis (hydrolysis temperature is 75°C, hydrolysis pH is 4.6, hydrolysis time is 40min) and cool down, and then adjust the pH to 4.0 - 6.5 for flocculation (flocculation temperature is 10°C, flocculation time is 10min) to obtain cottonseed protein. Vacuum dehydrate the cottonseed protein, wash it with water, and then continue vacuum dehydration to obtain cottonseed protein cake;

[0080] S4. Enzymatic hydrolysis of cottonseed protein

[0081] Dissolve the cottonseed protein cake obtained in step S3 in water to make a mixture liquid with a concentration of 45wt%. Heat it to 90°C and keep it for 45min, then cool it down to 45°C, adjust the pH to 8.5, and add alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase and flavor protease for enzymatic hydrolysis in sequence. The total enzyme addition amount in the mixture liquid is 4wt%. The compounding ratio of the alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase, flavor protease is 10:3:3:2:1:0.5. The enzymatic hydrolysis time is 12h, and the enzymatic hydrolysis temperature is 55°C. Heat inactivate to obtain enzymolysis peptide liquid;

[0082] S5. Concentration and drying

[0083] The enzymatically hydrolyzed peptide solution obtained in step S4 was concentrated to a concentration of 49 wt%, and then filtered to remove impurities and solid particles. The liquid was spray-dried and heat-exchanged with hot air at 180 °C. The inlet temperature of the spray-drying was 190 °C, and the outlet temperature was 90 °C. Cottonseed peptide dry powder was collected.

[0084] Experimental Example 1: Physicochemical properties of cottonseed peptide and cottonseed fiber, and test and results of cottonseed fiber

[0085] In this experimental example, the physicochemical properties of the cottonseed peptide and the cottonseed fiber prepared in Examples 1 to 3 were tested. The test methods are as follows:

[0086] Table 1: Determination methods for physicochemical properties of cottonseed peptide and extraction rate of cottonseed fiber

[0087]

[0088] The results obtained according to the test methods in Table 1 above are shown in Table 2:

[0089] Table 2: Determination results for physicochemical properties of cottonseed peptide and extraction rate of cottonseed fiber

[0090]

[0091] It can be seen from the results in Table 2 that the present invention mainly adopts the preparation process of extracting cottonseed protein with sulfurous acid, separating cottonseed hulls by gravity curve sieve, separating cottonseed fiber and cottonseed protein by pressure curve sieve, hydrolyzing and enzymatically hydrolyzing cottonseed protein with compound enzymes, and spray-drying the enzymatically hydrolyzed solution of cottonseed protein after concentration, obtaining cottonseed peptide with a proportion of oligopeptides less than 1000 Dalton exceeding 82%, a free gossypol content lower than 400 mg / kg and a removal rate as high as 85%, and an extraction rate as high as 50.2%. The extraction rate of cottonseed fiber can reach 48.1 - 55.4%. The prepared cottonseed peptide can be golden yellow, without bitterness, with a fresh sweet taste, and can be widely used in fields such as animal feed, functional food, biological culture medium and enzyme synthesis, biodegradable materials, cosmetics and pharmaceuticals, etc., being safe and having no toxic side effects.

[0092] Comparative Example 1

[0093] The difference between the extraction process of this comparative example and that of Example 3 lies in that different compound enzymes were used in the enzymatic hydrolysis process in preparation step S4, and the total enzyme addition amount was the same. The compound enzyme formula was: the compounding ratio of alkaline protease, neutral protease, free gossypol degrading enzyme, and keratinase was 11:3.5:3.5:2.5; the remaining steps were the same as those in Example 3.

[0094] Comparative Example 2

[0095] The difference between this comparative example and the extraction process of Example 3 lies in that different complex enzymes are used in the enzymatic hydrolysis process in Preparation Step S4, and the total enzyme addition amount is the same. The complex enzyme formula is: the compounding ratio of alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase, and flavor protease is 5:5:10:3:2:0.5, and the remaining steps are the same as those in Example 3.

[0096] Comparative Example 3

[0097] The difference between this comparative example and the extraction process of Example 3 lies in that the sieve slot gaps of the 1# two-stage series gravity curve sieve in Step S2 are 40 mm (greater than the size of wet large cottonseed hulls) and 20 mm (greater than the size of wet medium and small cottonseed hulls) respectively, the sieve slot gap of the 1# pressure curve sieve is 80 μm (less than the size of wet cottonseed fiber), the sieve surface of the first stage of the 2# pressure curve sieve group is 30 μm, the sieve slot gaps of the 2nd to 5th stages of the 2# pressure curve sieve are 50 μm, and the sieve slot gap of the 6th stage of the 2# pressure curve sieve is 35 μm, and the remaining steps are the same as those in Example 3.

[0098] Comparative Example 4

[0099] The difference between this comparative example and the extraction process of Example 3 lies in that in the countercurrent washing process of Step S2, only the screening process of the first-stage pressure curve sieve is carried out, and the screening steps of the 2nd to 6th stage pressure curve sieves are omitted, and the remaining steps are the same as those in Example 3.

[0100] Comparative Example 5

[0101] The difference between this comparative example and the extraction process of Example 3 lies in that instead of using sulfurous acid aqueous solution for leaching, sodium sulfite aqueous solution is used for leaching, and the remaining steps are the same as those in Example 3.

[0102] Test Example 2: Physical and Chemical Property Tests and Results of Cottonseed Peptide and Cottonseed Fiber

[0103] In this test example, the physical and chemical properties of the cottonseed peptide prepared in Comparative Examples 1 - 5 and the extraction rate of cottonseed fiber are tested. The test method is the same as that in Test Example 1, and the test results are shown in Table 3;

[0104] Table 3: Determination Results of Physical and Chemical Properties of Cottonseed Peptide and Extraction Rate of Cottonseed Fiber

[0105]

[0106] As can be seen from the results in Table 3, by adjusting process parameters such as the leaching solution, the composition and ratio of the composite enzyme, and the gravity and pressure curved sieves, etc., it has a great impact on the crude protein content, acid-soluble protein content, free gossypol content, extraction rate, molecular weight distribution, appearance, taste, etc. of the cottonseed enzymolysis protein (cottonseed peptide) product. Among them, in Comparative Example 1 and Comparative Example 2, enzymolysis was carried out using a composite enzyme composition or ratio different from that of Example 3, and the proportion of acid-soluble protein in the obtained cottonseed peptide decreased by about 2 - 5%. In Comparative Example 1, the proportion of oligopeptides with a molecular weight less than 1000 Da decreased by 9.5%. In Comparative Example 2, the oligopeptide content was low. It can be seen that the composition and content of the composite enzyme in the preparation process of the present invention are crucial for oligopeptides. In Comparative Example 3 and Comparative Example 4, the curved sieve process parameters and the countercurrent washing procedure in the preparation process were adjusted, and it was found that the sieve gap of the gravity and pressure curved sieves caused a decrease in the extraction rate of cottonseed peptide and a certain degree of decrease in the protein content. In Comparative Example 5, sodium sulfite was used for leaching, and the cottonseed peptide and acid-soluble protein contents decreased significantly, and some pigments could not be removed.

[0107] For the sake of brevity in description, the above-described embodiments only express several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. Without contradiction, those skilled in the art can combine and combine different embodiments and the features of different embodiments described in this specification. Without departing from the concept of the present invention, several improvements made all fall within the protection scope of the present invention.

Claims

1. An extraction process of cottonseed peptides and cottonseed fibers, characterized in that, It includes the following steps: S1. Leaching with sulfurous acid aqueous solution Soak cottonseed meal in sulfurous acid aqueous solution to obtain cottonseed meal soaking solution by leaching; S2. Separation of cottonseed fiber and cottonseed protein The cottonseed meal soaking solution obtained in step S1 is successively treated by a 1# impact needle mill and a 1# two-stage series gravity curve screen to obtain wet cotton hulls and cottonseed protein solution containing cottonseed fiber. The screen slot gaps of the 1# two-stage series gravity curve screen are 30 - 50 mm and 30 - 10 mm in sequence; then the cottonseed protein solution containing cottonseed fiber is successively treated by a 2# impact needle mill and a 1# pressure curve screen with a screen slot gap of 100 - 150 μm to screen and obtain wet cottonseed fiber and cottonseed protein solution I; then the wet cottonseed fiber is sent to a 2# pressure curve screen group for countercurrent washing. The 2# pressure curve screen group includes pressure curve screens from the 1st stage to the 6th stage. The screen slot gaps of the 1st stage and the 6th stage pressure curve screens are 30 - 50 μm, and the screen slot gaps of the 2nd stage to the 5th stage pressure curve screens are 60 - 150 μm; The wet cottonseed fiber is added into the 1st stage pressure curve screen and successively undergoes washing and screening through the 1st stage to the 6th stage pressure curve screens. After washing and screening through each stage of the pressure curve screen, the oversize is cottonseed fiber, and the undersize is cottonseed protein washing solution. The finally washed and screened cottonseed fiber is output from the 6th stage pressure curve screen, and then undergoes dehydration and drying to obtain dry cottonseed fiber; The washing process of each stage of the pressure curve screen is to wash the oversize obtained by screening in the previous stage of the pressure curve screen with the cottonseed protein washing solution obtained by screening in the next stage of the pressure curve screen. The initial washing solution is clear water, which is added from the 6th stage pressure curve screen to wash the oversize of the 5th stage pressure curve screen to obtain the 6th stage cottonseed protein washing solution. It successively passes through the 6th stage to the 1st stage pressure curve screens and washes the oversize of the previous stage pressure curve screen. The finally obtained cottonseed protein washing solution is output from the 1st stage pressure curve screen, and then concentrated to obtain cottonseed protein solution II; S3. Post-treatment of cottonseed protein Mix the cottonseed protein solution I and cottonseed protein solution II obtained in step S2 and successively undergo hydrolysis, flocculation, washing, and dehydration to obtain cottonseed protein cake. After the cottonseed protein cake is redissolved in water, it is enzymatically hydrolyzed by a composite enzyme to obtain enzymolysis peptide solution. The enzymolysis peptide solution is subjected to heat exchange with hot air by spray drying to collect cottonseed peptide; The composite enzyme in step S3 is a mixture of alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase, and flavor protease. The mass ratio of alkaline protease, neutral protease, acidic protease, free gossypol degrading enzyme, keratinase, and flavor protease is 10 - 15:3 - 5:3 - 5:2 - 4:1 - 2:0.5 - 3; The addition amount of the composite enzyme in step S3 is 0.1 - 5 wt%.

2. The extraction process of cottonseed peptides and cottonseed fibers according to claim 1, wherein The mass concentration of the sulfurous acid aqueous solution in step S1 is 0.05 - 2.5%, and the material-liquid ratio is 1 g:3 - 20 mL.

3. The extraction process of cottonseed peptides and cottonseed fibers according to claim 1, characterized in that, In the step S2, the rotational speeds of the 1# impact needle mill and the 2# impact needle mill are 3000 - 5000 r / min; the screen surface radian of the 1# two-stage series gravity curve screen is 50° - 60°; the screen surface radian in the 1# pressure curve screen and the 2# pressure curve screen group is 120° - 300°, the feeding pressure is 0.18 - 0.42 Mpa, the nozzle diameter is 1 / 2 - 3 / 4 inch, and the nozzle flow rate is 9.1 - 20.5 m 3 / h.

4. The extraction process of cottonseed peptides and cottonseed fibers according to claim 1, characterized in that In the step S3, the hydrolysis temperature is 70~121°C, the hydrolysis time is 8 s~45 min, and the hydrolysis pH is 4.5~9.

0. For flocculation, the pH is adjusted to 3.0~6.5 for flocculation precipitation, the flocculation temperature is 5~75°C, and the flocculation time is 5~60 min.

5. The extraction process of cottonseed peptides and cottonseed fibers according to claim 1, characterized in that, In the step S3, the inlet air temperature for spray drying is 120~190°C, the exhaust air temperature is 50~90°C, and the hot air temperature is 170~210°C.

6. The cottonseed peptide prepared by the extraction process of cottonseed peptide and cottonseed fiber according to any one of claims 1 to 5, characterized in that, The crude protein content of the cottonseed peptide exceeds 65%, the acid-soluble protein content in the crude protein exceeds 62%, the content of oligopeptides with a molecular weight below 1000 Dalton in the cottonseed peptide exceeds 82%, and the free gossypol content is below 400 mg / kg.

Images