Preparation method and application of vital gluten polypeptide copolymer

Abstract

The invention provides a preparation method and application of a vital gluten polypeptide copolymer, vital gluten polypeptide is prepared by enzymolysis of vital gluten, modified exopolysaccharide nano-micelles are prepared by grafting hydrophobic groups to exopolysaccharide produced by fermentation of Weissella cibaria, then the modified exopolysaccharide nano-micelles and the modified exopolysaccharide nano-micelles are grafted through amido bonds to form a copolymer, yeast cells are carried, and the modified exopolysaccharide nano-micelles are obtained. The copolymer can strengthen a gluten network, inhibit ice crystal recrystallization and protect yeast cells and activity thereof, and has a good low-temperature protection effect on fermentation characteristics of frozen dough.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and particularly relates to a preparation method and application of a gluten polypeptide copolymer. Background Art

[0002] Although corn flour alone can be used to make dough, this dough is made by adding water to corn flour. The particles are bonded together by the adhesion of water and the force applied when kneading the dough. The dough is fragile and cannot maintain good properties under the action of external forces. By modifying corn flour and adding it to corn flour, a significant bonding effect can be produced, thereby improving the ductility and viscoelasticity of the dough. However, since corn flour and modified flour cannot form gluten protein like wheat flour when making dough, the gas produced by yeast fermentation cannot be retained, the dough is difficult to ferment, and the quality of fermented flour products such as steamed buns is poor. The decline in yeast activity during frozen storage is one of the key factors leading to the deterioration of fermented dough quality. During the freezing process, the growth and recrystallization of ice crystals will destroy the yeast cell structure, thereby reducing the number and activity of live yeast in the dough. Therefore, controlling the growth and recrystallization of ice crystals during freezing to slow down the impact of the freezing process on yeast cell activity is the key to improving dough quality. Obtaining safe, compact, specific and highly active antifreeze peptides through enzymatic protein hydrolysis has become an emerging research hotspot. Therefore, the problem to be solved by the present invention is to prepare a frozen corn dough which can strengthen the gluten network structure, improve the dough fermentation ability and protect the yeast cells and their activity. Summary of the invention

[0003] Technical problem to be solved: In view of the above technical problems, the purpose of the present invention is to provide a method for preparing a gluten polypeptide copolymer and its application, wherein gluten polypeptide is prepared by enzymatic hydrolysis of gluten powder, and the extracellular polysaccharide produced by fermentation of Weissella sinensis is modified by grafting hydrophobic groups to prepare modified extracellular polysaccharide nanomicelles, and then the two are grafted through amide bonds to form a copolymer and carried with yeast cells. The copolymer can strengthen the gluten network, inhibit ice crystal recrystallization, protect yeast cells and their activity, and has a good low-temperature protection effect on the fermentation characteristics of frozen dough.

[0004] Technical solution: A gluten polypeptide copolymer, wherein the gluten polypeptide copolymer is a modified extracellular polysaccharide nano-micelle-gluten polypeptide copolymer loaded with yeast cells. Furthermore, the preparation method of the gluten polypeptide copolymer is specifically as follows: (1) dissolving gluten powder in 50° C. deionized water to prepare a gluten solution with a mass fraction of 5-10%, stirring at a constant temperature for 5-10 minutes, and adjusting the pH to 8.5; (2) adding a complex enzyme to the gluten protein solution for enzymolysis, heating in a 100° C. water bath for 10 min to inactivate the enzyme, adjusting the pH to 7.0 after cooling, centrifuging at 4° C. and 8000-10000 r / min for 5-10 min, taking the supernatant, dialyzing, and freeze-drying to obtain gluten polypeptide; (3) Dissolve 5-8 parts of modified extracellular polysaccharide nano-micelles and 3-4 parts of gluten polypeptide in 20-30 parts of water, add 0.5-1 part of activated yeast, and stir evenly to obtain gluten polypeptide copolymer. Furthermore, in step (2), the compound enzyme is a compound of papain and alkaline protease, and the mass ratio is 1:(1-2). Furthermore, in step (2), the addition amount of the compound enzyme is 3-4%, and the enzymolysis time is 3-5h. Furthermore, the preparation method of the modified extracellular polysaccharide nano-micelles in step (3) is: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a rate of 5-8%, ferment at 30°C for 48-60h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, stir at 60°C for 0.5-1h to obtain a deoxycholic acid solution with a concentration of 1-1.5 mg / mL; S4. Mix the deoxycholic acid solution with the extracellular polysaccharide solution, stir at 400-500 rpm for 15-20 hours, dialyze, and freeze-dry to obtain modified extracellular polysaccharide nano-micelles. Furthermore, in step S4, the volume ratio of the deoxycholic acid solution to the extracellular polysaccharide solution is 1:(1-2). Furthermore, the gluten polypeptide copolymer prepared by the preparation method is used in frozen corn dough. Further, the frozen corn dough preparation method is as follows: Step 1: Mix 30-70 parts of corn flour, 30-70 parts of modified corn flour, and 2 parts of sugar to obtain a powder; Step 2: Put the powder in a dough bowl, add 30-40 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Furthermore, the modified corn flour in step 1 is any one of microwave corn flour, baked corn flour, steamed corn flour and extruded corn flour. Furthermore, the microwave corn flour is microwaved at 400W for 4-6 minutes; the baked corn flour is baked at 150°C for 15-25 minutes; the steamed corn flour is steamed in boiling water for 10-30 minutes; and the extruded corn flour is extruded and puffed at a screw speed of 80r / min and 150-180°C. Beneficial effects: 1. The present invention prepares gluten polypeptides by composite enzymolysis of gluten powder with papain and alkaline protease, which can slow down the damage of ice crystals to yeast cells during freezing, keep the yeast cells relatively complete and smooth in surface morphology, improve the survival rate of yeast cells during frozen storage, and have a good low-temperature protection effect on the fermentation characteristics of frozen dough; 2. In the present invention, exopolysaccharides are produced by fermentation of Weissella vesiculosa, and the hydrophobic groups in deoxycholic acid are grafted for modification to prepare modified exopolysaccharide nano-micelles. The produced exopolysaccharides, as high molecular weight glucans, have a three-dimensional network structure, can strengthen the gluten network structure, and improve the dough's gas holding capacity; 3. The modified extracellular polysaccharide nano-micelles prepared in the present invention are connected to the gluten polypeptide via an amide bond. Since the network structure of the modified extracellular polysaccharide nano-micelles enables a certain amount of holes to be formed, the gluten polypeptide can be embedded inside the modified extracellular polysaccharide nano-micelles. Such embedding can improve the stability and bioavailability of the gluten polypeptide. 4. The gluten polypeptide in the copolymer prepared by the present invention interacts with the phospholipid bilayer of the yeast cell membrane through hydrogen bonds, thereby carrying and immobilizing the yeast cells, and embedding the yeast cells inside the copolymer, reducing the free yeast cells in the system, and reducing the probability and degree of damage to the yeast cells by ice crystals during the freezing process; 5. In the present invention, modified corn flour is prepared by microwave, baking, steaming or extrusion puffing. During the modification process of corn flour, starch granules are destroyed, starch molecules are dissolved, and water molecules are combined with free hydroxyl groups of starch molecules through hydrogen bonds, so that the water absorption capacity and binding force of the modified corn flours are enhanced, the degree of freedom of water in the dough is reduced, and the combination with other components is tighter, thereby improving the network structure, softness, fermentation volume, etc. inside the dough, reducing the hardness of the dough, and improving the overall quality of the dough. DETAILED DESCRIPTION The present invention will be further described below in conjunction with embodiments, which are explanations of the present invention and are not limited to the following embodiments: Example 1 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a 5% inoculum, ferment at 30°C for 50 h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, and stir at 60°C for 1 h to prepare a deoxycholic acid solution with a concentration of 1 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in 50°C deionized water to prepare a 5% gluten solution, stir at constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 3% compound enzyme (papain: alkaline protease = 1:1) to the gluten solution for enzymatic hydrolysis for 3 hours, heat in a 100°C water bath for 10 minutes to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000r / min for 10 minutes, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 5 parts of modified extracellular polysaccharide nano-micelles and 4 parts of gluten polypeptide in 25 parts of water, add 0.5 parts of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Example 2 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. The seed solution was inoculated into MRS medium at a 6% inoculum, fermented at 30°C for 50 h, and the supernatant was obtained by centrifugation, which was the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, stir at 60°C for 1h to prepare a deoxycholic acid solution with a concentration of 1.2 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in 50°C deionized water to prepare a 5% gluten solution, stir at constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 3% compound enzyme (papain: alkaline protease = 1:1) to the gluten solution for enzymatic hydrolysis for 3 hours, heat in a 100°C water bath for 10 minutes to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000r / min for 10 minutes, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 5 parts of modified extracellular polysaccharide nano-micelles and 4 parts of gluten polypeptide in 25 parts of water, add 0.5 parts of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Example 3 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at an inoculum rate of 8%, ferment at 30°C for 60h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, stir at 60°C for 1h to prepare a deoxycholic acid solution with a concentration of 1.5 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:2, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in 50°C deionized water to prepare a 5% gluten solution, stir at constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 3% compound enzyme (papain: alkaline protease = 1:1) to the gluten solution for enzymatic hydrolysis for 3 hours, heat in a 100°C water bath for 10 minutes to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000r / min for 10 minutes, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 5 parts of modified extracellular polysaccharide nano-micelles and 4 parts of gluten polypeptide in 25 parts of water, add 0.5 parts of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Example 4 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a 5% inoculum, ferment at 30°C for 50 h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, and stir at 60°C for 1 h to prepare a deoxycholic acid solution with a concentration of 1 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in 50°C deionized water to prepare a 5% gluten solution, stir at constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 3% compound enzyme (papain: alkaline protease = 1:1) to the gluten solution for enzymatic hydrolysis for 3 hours, heat in a 100°C water bath for 10 minutes to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000r / min for 10 minutes, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 5 parts of modified extracellular polysaccharide nano-micelles and 4 parts of gluten polypeptide in 25 parts of water, add 0.5 parts of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Example 5 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a 5% inoculum, ferment at 30°C for 50 h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, and stir at 60°C for 1 h to prepare a deoxycholic acid solution with a concentration of 1 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in deionized water at 50°C to prepare a gluten solution with a mass fraction of 8%, stir at a constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 3% complex enzyme (papain: alkaline protease = 1:1) to the gluten protein solution for enzymatic hydrolysis for 4 hours, heat in a 100°C water bath for 10 minutes to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000r / min for 10 minutes, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 5 parts of modified extracellular polysaccharide nano-micelles and 4 parts of gluten polypeptide in 25 parts of water, add 0.5 parts of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Example 6 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a 5% inoculum, ferment at 30°C for 50 h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, and stir at 60°C for 1 h to prepare a deoxycholic acid solution with a concentration of 1 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in deionized water at 50°C to prepare a gluten solution with a mass fraction of 10%, stir at a constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 4% compound enzyme (papain: alkaline protease = 1:2) to the gluten protein solution for enzymatic hydrolysis for 5 h, heat in a 100°C water bath for 10 min to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000 r / min for 10 min, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 5 parts of modified extracellular polysaccharide nanomicelles and 3 parts of gluten polypeptide in 25 parts of water, add 0.5 parts of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Example 7 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a 5% inoculum, ferment at 30°C for 50 h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, and stir at 60°C for 1 h to prepare a deoxycholic acid solution with a concentration of 1 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in deionized water at 50°C to prepare a gluten solution with a mass fraction of 10%, stir at a constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 4% compound enzyme (papain: alkaline protease = 1:2) to the gluten protein solution for enzymatic hydrolysis for 5 h, heat in a 100°C water bath for 10 min to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000 r / min for 10 min, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 6 parts of modified extracellular polysaccharide nanomicelles and 3 parts of gluten polypeptide in 20 parts of water, add 0.5 parts of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Example 8 The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a 5% inoculum, ferment at 30°C for 50 h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, and stir at 60°C for 1 h to prepare a deoxycholic acid solution with a concentration of 1 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve gluten powder in deionized water at 50°C to prepare a gluten solution with a mass fraction of 10%, stir at a constant temperature for 10 minutes, and adjust the pH to 8.5; S6. Add 4% compound enzyme (papain: alkaline protease = 1:2) to the gluten protein solution for enzymatic hydrolysis for 5 h, heat in a 100°C water bath for 10 min to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000 r / min for 10 min, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S7. Dissolve 8 parts of modified extracellular polysaccharide nano-micelles and 4 parts of gluten polypeptide in 30 parts of water, add 1 part of activated yeast, stir evenly, and obtain gluten polypeptide copolymer. Comparative Example 1 The difference between this comparative example and Example 8 is that no modified extracellular polysaccharide nano-micelles are added, specifically as follows: The preparation method of gluten polypeptide copolymer is as follows: S1. Dissolve gluten powder in 50°C deionized water to prepare a 10% gluten solution, stir at constant temperature for 10 minutes, and adjust the pH to 8.5; S2. Add 4% complex enzyme (papain: alkaline protease = 1:2) to the gluten protein solution for enzymatic hydrolysis for 5 hours, heat in a 100°C water bath for 10 minutes to inactivate the enzyme, adjust the pH to 7.0 after cooling, centrifuge at 4°C and 8000r / min for 10 minutes, take the supernatant, dialyze, and freeze-dry to obtain gluten polypeptide; S3. Dissolve 4 parts of gluten polypeptide in 30 parts of water, add 1 part of activated yeast, and stir evenly to obtain gluten polypeptide copolymer. Comparative Example 2 The difference between this comparative example and Example 8 is that no cereal polypeptide is added, specifically as follows: The preparation method of gluten polypeptide copolymer is as follows: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a 5% inoculum, ferment at 30°C for 50 h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, and stir at 60°C for 1 h to prepare a deoxycholic acid solution with a concentration of 1 mg / mL; S4. The deoxycholic acid solution was mixed with the extracellular polysaccharide solution at a volume ratio of 1:1, stirred at 400 rpm for 20 h, dialyzed, and freeze-dried to obtain modified extracellular polysaccharide nanomicelles; S5. Dissolve 8 parts of modified extracellular polysaccharide nano-micelles in 30 parts of water, add 1 part of activated yeast, and stir evenly to obtain gluten polypeptide copolymer. Yeast cell embedding rate: Table 1 Encapsulation rate of yeast cells in copolymers prepared in Examples 1-8 and Comparative Examples 1-2 Embedding rate (%) Embedding rate (%) Example 1 88.91 Example 6 88.05 Example 2 84.17 Example 7 86.26 Example 3 85.48 Example 8 89.13 Example 4 83.73 Comparative Example 1 — Example 5 87.62 Comparative Example 2 35.21 As shown in Table 1, the embedding rate of yeast cells in the gluten polypeptide copolymers prepared in Examples 1-8 is 83.73-89.13%, while in Comparative Example 1, no modified extracellular polysaccharide nano-micelles are added, and a network structure cannot be formed, so yeast cells cannot be embedded; in Comparative Example 2, no gluten polypeptide is added, and yeast cells cannot be embedded in the nano-micelles by being carried and fixed on the gluten polypeptide through hydrogen bonds, so the embedding rate is significantly reduced to only 35.21%. Therefore, it can be seen that the modified extracellular polysaccharide nano-micelles in the copolymer can form a network structure, and the gluten polypeptide interacts with the phospholipid bilayer of the yeast cell membrane through hydrogen bonds, thereby carrying and immobilizing the yeast cells, and embedding the yeast cells in the copolymer, reducing the free yeast cells in the system and protecting the activity of the yeast cells. The gluten polypeptide copolymer prepared in Example 8 was selected for subsequent preparation of frozen corn dough. Example 9 The preparation method of frozen corn dough is as follows: Step 1: Mix 30 parts of corn flour, 70 parts of microwave corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: Put the powder in a dough bowl, add 30 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Example 10 The preparation method of frozen corn dough is as follows: Step 1: Mix 30 parts of corn flour, 70 parts of microwave corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: Put the powder in a dough bowl, add 30 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Embodiment 11 The preparation method of frozen corn dough is as follows: Step 1: Mix 40 parts of corn flour, 60 parts of roasted corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: Put the powder in a dough bowl, add 30 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Example 12 The preparation method of frozen corn dough is as follows: Step 1: Mix 40 parts of corn flour, 60 parts of steamed corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: Put the powder in a dough bowl, add 35 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Embodiment 13 The preparation method of frozen corn dough is as follows: Step 1: Mix 50 parts of corn flour, 50 parts of steamed corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: Put the powder in a dough bowl, add 40 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Embodiment 14 The preparation method of frozen corn dough is as follows: Step 1: Mix 70 parts of corn flour, 30 parts of extruded corn flour, 2 parts of sugar, and 1 part of baking powder to make a powder; Step 2: Put the powder in a dough bowl, add 40 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Comparative Example 3 The difference between this comparative example and Example 12 is that no modified corn flour is added, specifically as follows: The preparation method of frozen corn dough is as follows: Step 1: Mix 100 parts corn flour, 2 parts sugar and 1 part baking powder to make powder; Step 2: Put the powder in a dough bowl, add 35 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Comparative Example 4 The difference between this comparative example and Example 12 is that the gluten polypeptide copolymer prepared in Comparative Example 1 is as follows: The preparation method of frozen corn dough is as follows: Step 1: Mix 40 parts of corn flour, 60 parts of steamed corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: placing the powder in a dough bowl, adding 35 parts of the gluten polypeptide copolymer prepared in Comparative Example 1 and 60 parts of water, and kneading alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Comparative Example 5 The difference between this comparative example and Example 12 is that the gluten polypeptide copolymer prepared in Comparative Example 2 is as follows: The preparation method of frozen corn dough is as follows: Step 1: Mix 40 parts of corn flour, 60 parts of steamed corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: placing the powder in a dough bowl, adding 35 parts of the gluten polypeptide copolymer prepared in Comparative Example 2 and 60 parts of water, and kneading alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough. Comparative Example 6 The difference between this comparative example and Example 12 is that no gluten polypeptide copolymer is added, and yeast is directly added, as follows: The preparation method of frozen corn dough is as follows: Step 1: Mix 40 parts of corn flour, 60 parts of steamed corn flour, 2 parts of sugar and 1 part of baking powder to make powder; Step 2: Put the powder in a dough cylinder, add 35 parts of activated yeast and 60 parts of water, and knead alternately to make corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40°C refrigerator to obtain frozen corn dough. Performance Test: (1) Moisture distribution The moisture distribution of the samples was measured using a low-field nuclear magnetic resonance imaging analyzer, as shown in Table 2 below: Table 2 Moisture distribution of frozen corn dough prepared in Examples 9-14 and Comparative Examples 3-6 Bound water (%) Free water (%) Example 9 9.45±0.01 0.66±0.01 Example 10 9.66±0.17 0.68±0.03 Embodiment 11 8.96±0.10 0.74±0.02 Example 12 9.91±0.07 0.62±0.01 Embodiment 13 8.88±0.12 0.78±0.01 Embodiment 14 9.12±0.11 0.63±0.02 Comparative Example 3 7.12±0.07 1.15±0.06 Comparative Example 4 9.17±0.10 0.81±0.03 Comparative Example 5 9.09±0.01 0.86±0.03 Comparative Example 6 8.97±0.01 0.73±0.01 As shown in Table 2, the bound water content of the frozen corn dough prepared in Example 12 is the highest at 9.91%, and the free water content is the lowest at 0.62%. The bound water content of the frozen corn dough prepared in Comparative Example 3 without adding modified corn flour is the lowest at 7.12%, and the free water content is the highest at 1.15%. Comparative Examples 4-6 all add modified corn flour to prepare frozen corn dough, and the contents of bound water and free water are not significantly different from those in the examples. Therefore, it can be seen that during the modification process of corn flour, starch granules are destroyed, starch molecules are dissolved, and water molecules are combined with free hydroxyl groups of starch molecules through hydrogen bonds, so that the water absorption capacity and binding force of the modified corn flour are enhanced, the bound water content in the dough is increased, the free water content is reduced, and the combination with other components is closer, thereby improving the dough network structure and overall quality. (2) Yeast cell survival rate The frozen corn doughs prepared in the above Examples 9-14 and Comparative Examples 3-6 were all frozen for 1 week and tested. Determination of yeast count in fresh corn dough (calculated per gram of dough): First, cut 5 g of fresh corn dough from two different parts, the surface and the inner core of the dough, and place it in 45 mL of sterile saline and shake it for 3 minutes to extract yeast; Determination of yeast count in frozen corn dough (calculated per gram of dough): Thaw the frozen corn dough in a 4°C refrigerator until the dough softens, then cut 5 g from two different parts, the surface and the inner core, and place it in 45 mL of sterile saline and shake for about 3 minutes to extract the yeast. Use a 1 mL pipette to take the supernatant of the fresh corn dough and frozen corn dough after shaking, and then add 10 5 After multiple dilution and mixing, obtain the dilution solution. Take 1 mL of the dilution solution and add it to the Bengal red agar medium for coating. After coating, turn the culture dish upside down and place it in a 37°C incubator. After 48 hours of incubation, take it out and count the colonies on the plate. Count two plates for each of the surface dough and the inner dough. Repeat the experiment 3 times and take the average value of the results. The formula for calculating the survival rate of yeast cells after freezing is: P=A / A0×100% Wherein, P is the survival rate of yeast cells after freezing, %; A is the colony count of yeast cells in frozen dough, lgCFU / g; A0 is the colony count of yeast cells in fresh dough, lgCFU / g. Table 3 Yeast cell survival rate of frozen corn dough prepared in Examples 9-14 and Comparative Examples 3-6 Survival rate of yeast cells on bread surface (%) Survival rate of yeast bread in bread core (%) Example 9 96.9 95.1 Example 10 97.1 95.3 Embodiment 11 96.5 94.9 Example 12 97.3 95.6 Embodiment 13 95.8 94.7 Embodiment 14 96.4 94.2 Comparative Example 3 95.2 93.5 Comparative Example 4 89.4 88.2 Comparative Example 5 81.5 79.4 Comparative Example 6 70.3 68.6 As can be seen from Table 3, the frozen corn dough prepared in Example 12 has the highest yeast survival rate, and the difference is not significant in Comparative Example 3, in which no modified corn flour is added; Comparative Example 4 uses the gluten polypeptide copolymer prepared in Comparative Example 1 to prepare the frozen corn dough, and the gluten polypeptide in the copolymer can carry yeast cells, reduce the free yeast cells in the system, and appropriately reduce the damage of ice crystals to yeast cells during the freezing process, but lacks the embedding effect of the modified nano-micelles, so the survival rate of yeast cells also decreases; Comparative Example 5 uses the gluten polypeptide copolymer prepared in Comparative Example 2 to prepare the frozen corn dough, and the network structure of the modified extracellular polysaccharide nano-micelles can only wrap a small amount of yeast cells, and most of the yeast cells cannot be embedded and protected, so the survival rate decreases; Comparative Example 6 does not add the gluten polypeptide copolymer, but directly adds yeast cells, lacks the network structure of the nano-micelles and the carrying of the yeast cells by the gluten polypeptides, so that the yeast cells cannot be embedded in the nano-micelles, so the survival rate decreases significantly. (3) Texture characteristics The texture characteristics of the dough were measured using a TA-XTplus physical property analyzer to obtain indicators such as hardness, elasticity, viscoelasticity, and adhesiveness. Test parameters: Select the P50 probe, the pre-test speed is 2 mm / s, the test speed is 1 mm / s, the post-test speed is 1 mm / s, the compression ratio is 70%, the trigger force is 5 g, and the compression time interval is 5 s. Table 4 Texture properties of frozen corn dough prepared in Examples 9-14 and Comparative Examples 3-6 As can be seen from Table 4, the addition of modified corn flour and gluten polypeptide copolymer reduces the hardness of the dough, increases the elasticity and cohesion, and reduces the adhesiveness; the frozen corn dough prepared in Comparative Example 3 without adding modified corn flour and Comparative Example 6 without adding gluten polypeptide copolymer has higher hardness, lower elasticity and cohesion, and higher adhesiveness; the frozen corn dough prepared in Comparative Example 4 using the gluten polypeptide copolymer prepared in Comparative Example 1 cannot form a tight network structure, so the texture characteristics are also lower than those of the embodiment; Comparative Example 5 uses the gluten polypeptide copolymer prepared in Comparative Example 2 to prepare the frozen corn dough, and the modified extracellular polysaccharide nano-micelles in the copolymer can improve the network structure of the dough, so the overall texture characteristics of the dough are relatively good. (4) Specific volume and height-to-diameter ratio The frozen corn dough prepared in Example 12 and Comparative Examples 3-6 was thawed and kneaded to exhaust the gas generated by the dough until there were no pores inside the dough, and the dough was kneaded into a steamed bun shape; it was placed in a steamer, and the timing was started after the water boiled, and the steaming was started for 20 minutes. The heat was turned off, and the steamed buns were taken out after cooling for 10 minutes and cooled to room temperature to obtain corn steamed buns. The specific volume of corn steamed bread is the ratio of the volume to the mass of the steamed bread. With reference to the national standard GB / T 21118-2007 "Wheat Flour Steamed Bread", the volume was measured by rapeseed displacement method, and the mass of the steamed bread was measured by a balance. The test was repeated 3 times, and the average value was taken to calculate the specific volume. The height and bottom diameter of the corn buns were measured with a vernier caliper. Each indicator was measured three times at different positions and the average value was taken to calculate the height-to-diameter ratio of the corn buns, which is the ratio of the height to the diameter of the buns. Table 5 Specific volume of corn steamed bread obtained by fermentation of frozen corn dough prepared in Example 12 and Comparative Examples 3-6 Example 12 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Specific volume (mL / g) 1.78 1.71 1.62 1.54 1.23 Aspect Ratio 0.73 0.68 0.57 0.60 0.31 Specific volume is an important factor in measuring the quality of corn steamed buns, which can reflect the expansion and air holding capacity of steamed buns. The larger the specific volume, the better the expansion of the steamed buns. The height-to-diameter ratio mainly indicates whether the shape of the steamed buns is firm. As can be seen from Table 5, the addition of modified corn flour and gluten polypeptide copolymer in Example 12 of the present invention enhances the network structure of corn dough, protects yeast cells, increases the gas holding capacity of steamed bread, increases the volume of steamed bread, and has the highest specific volume and height-to-diameter ratio; while the specific volume and height-to-diameter ratio of the corn steamed bread prepared by fermentation without adding modified corn flour in Comparative Example 3 are not significantly affected; the corn steamed bread prepared by fermentation with the gluten polypeptide copolymer prepared in Comparative Example 1 in Comparative Example 4 can fix yeast cells, weaken the damage of frozen ice crystals to yeast cells, slightly affect the fermentation volume, and slightly decrease the specific volume and height-to-diameter ratio; the corn steamed bread prepared by fermentation with the gluten polypeptide copolymer prepared in Comparative Example 2 in Comparative Example 5 can only embed a small amount of yeast cells, the fermentation volume of steamed bread becomes smaller, and the specific volume and height-to-diameter ratio are also decreased; finally, the corn steamed bread prepared by fermentation without adding the gluten polypeptide copolymer in Comparative Example 6, directly adding yeast cells causes the dough to be damaged to a greater extent during the freezing process, and the dough structure is also loose, so the specific volume and height-to-diameter ratio of the steamed bread are significantly decreased. (5) Sensory evaluation The sensory evaluation standard for corn steamed bread was designed with reference to the evaluation standard for wheat flour steamed bread, and slightly modified, as shown in Table 6. The sensory evaluation was mainly composed of 10 food professionals, and the corn steamed bread obtained by fermenting frozen corn dough prepared in Example 12 and Comparative Examples 3-6 was scored in terms of exterior (specific volume, aspect ratio, color, appearance shape) and interior (smell, elasticity, viscosity, structure). Table 6 Sensory scoring standards for corn steamed bread Table 7 Sensory scores of corn steamed bread obtained by fermentation of frozen corn dough prepared in Example 12 and Comparative Examples 3-6 As can be seen from Table 7, the addition of modified corn flour and gluten polypeptide copolymer in the present invention can improve the fermentation characteristics and texture characteristics of frozen dough, and the internal and external properties of the corn steamed bread prepared by fermentation are good, and the sensory score is the highest; the internal and external structures of the frozen dough prepared without adding modified corn flour or gluten polypeptide copolymer will be affected to varying degrees, and thus the sensory score of the prepared corn steamed bread will also decrease accordingly. The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A gluten polypeptide copolymer, characterized in that: The gluten polypeptide copolymer is a modified extracellular polysaccharide nano-micelle-gluten polypeptide copolymer loaded with yeast cells.

2. A gluten polypeptide copolymer according to claim 1, characterized in that: The preparation method of the gluten polypeptide copolymer is specifically as follows: (1) dissolving gluten powder in 50° C. deionized water to prepare a gluten solution with a mass fraction of 5-10%, stirring at a constant temperature for 5-10 minutes, and adjusting the pH to 8.5; (2) adding a complex enzyme to the gluten protein solution for enzymolysis, heating in a 100° C. water bath for 10 min to inactivate the enzyme, adjusting the pH to 7.0 after cooling, centrifuging at 4° C. and 8000-10000 r / min for 5-10 min, taking the supernatant, dialyzing, and freeze-drying to obtain gluten polypeptide; (3) Dissolve 5-8 parts of modified extracellular polysaccharide nano-micelles and 3-4 parts of gluten polypeptide in 20-30 parts of water, add 0.5-1 part of activated yeast, and stir evenly to obtain gluten polypeptide copolymer.

3. The method for preparing a gluten polypeptide copolymer according to claim 2, characterized in that: The composite enzyme in step (2) is a composite of papain and alkaline protease, with a mass ratio of 1:(1-2).

4. The method for preparing a gluten polypeptide copolymer according to claim 2, characterized in that: In the step (2), the amount of the complex enzyme added is 3-4%, and the enzymolysis time is 3-5 hours.

5. The method for preparing a gluten polypeptide copolymer according to claim 2, characterized in that: The preparation method of the modified extracellular polysaccharide nano-micelles in step (3) is: S1. Take the activated Weissella sinus and inoculate it into MRS medium, and culture it in liquid for 24 hours to obtain seed solution; S2. Inoculate the seed liquid into MRS medium at a rate of 5-8%, ferment at 30°C for 48-60h, and centrifuge to obtain the supernatant, which is the extracellular polysaccharide solution; S3. Weigh deoxycholic acid, add ethanol and ultrasonically dissolve it, stir at 60°C for 0.5-1h to obtain a deoxycholic acid solution with a concentration of 1-1.5 mg / mL; S4. Mix the deoxycholic acid solution with the extracellular polysaccharide solution, stir at 400-500 rpm for 15-20 hours, dialyze, and freeze-dry to obtain modified extracellular polysaccharide nano-micelles.

6. The method for preparing a gluten polypeptide copolymer according to claim 5, characterized in that: In step S4, the volume ratio of the deoxycholic acid solution to the extracellular polysaccharide solution is 1:(1-2).

7. Use of the gluten polypeptide copolymer prepared by the preparation method according to any one of claims 1 to 6 in frozen corn dough.

8. The use of the gluten polypeptide copolymer according to claim 7 in frozen corn dough, characterized in that: The frozen corn dough preparation method is as follows: Step 1: Mix 30-70 parts of corn flour, 30-70 parts of modified corn flour, and 2 parts of sugar to obtain a powder; Step 2: Put the powder in a dough bowl, add 30-40 parts of gluten polypeptide copolymer and 60 parts of water, and knead alternately to prepare corn dough; Step 3: Wrap the corn dough with plastic wrap, seal it, and quickly freeze it in a -40℃ refrigerator to obtain frozen corn dough.

9. The use of the gluten polypeptide copolymer according to claim 8 in frozen corn dough, characterized in that: The modified corn flour in step 1 is any one of microwave corn flour, baked corn flour, steamed corn flour and extruded corn flour.

10. The use of the gluten polypeptide copolymer according to claim 9 in frozen corn dough, characterized in that: The microwave corn flour is microwaved at 400W for 4-6 minutes; the baked corn flour is baked at 150°C for 15-25 minutes; the steamed corn flour is steamed in boiling water for 10-30 minutes; and the extruded corn flour is extruded and puffed at a screw speed of 80r / min and 150-180°C.

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