Method for preparing fish albumen glue polypeptide through probiotic fermentation, fish albumen glue polypeptide and application of fish albumen glue polypeptide

Abstract

The invention discloses a method for preparing fish albumen glue polypeptide through probiotic fermentation, the fish albumen glue polypeptide and application, and relates to the technical field of food processing.The method comprises the steps that fish by-products are smashed, added into an edible alkali solution to be soaked and drained, and pretreated fish by-products are obtained; adding alkaline protease into the pretreated fish byproducts for enzymolysis; adding a glucose solution into the enzymolysis product, heating and deactivating enzyme; sterilizing the enzyme-deactivated mixture to obtain a sterilized mixture; inoculating a mixed strain containing lactobacillus sake JXNU1-3 and bacillus subtilis into the sterilized mixture, and fermenting; and after fermentation is finished, separating and purifying to obtain the fish albumen glue polypeptide. The preparation method has the beneficial effects that the problems of difficulty in treating fish byproducts, low benefit and the like are solved, the reutilization of resources is realized, and the fish albumen glue polypeptide with good gel property and oxidation resistance is prepared and can be used for preparing antioxidant foods, medicines, cosmetics and medical materials.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for preparing fish protein gelatin polypeptide by probiotic fermentation, the fish protein gelatin polypeptide and applications thereof. Background Art

[0002] my country is a major fishing country. In 2022, the output of aquatic products in my country was 68.6591 million tons, an increase of 2.62% over 2022; among them, the output of freshwater fish was 34.0638 million tons, a year-on-year increase of 3.13%. However, as the output continues to increase, the fish by-products produced by freshwater fish processing have also greatly increased. Due to problems such as difficult treatment and low returns, a large amount of fish by-products are discarded, landfilled, incinerated, etc., resulting in serious environmental pollution and waste of resources. Therefore, the comprehensive utilization of fish by-products has become an urgent problem to be solved.

[0003] The prior art discloses a method for continuously producing fish scale collagen peptide chelated calcium salt and fish scale collagen peptide, comprising the following steps: pre-treating fish scales, enzymatically extracting fish scale collagen peptide and calcium solution, purifying fish scale collagen peptide and calcium solution, preparing fish scale collagen peptide chelated calcium salt solution by peptide calcium chelation technology, separating fish scale collagen peptide chelated calcium salt solution to obtain precipitate and supernatant, dissolving the precipitate in water and drying to obtain fish scale collagen peptide chelated calcium salt powder finished product, concentrating the supernatant to remove ethanol and then separating and purifying to obtain fish scale collagen peptide solution, and drying the fish scale collagen peptide solution to obtain fish scale collagen peptide powder finished product. The fish scale collagen peptide chelated calcium salt product produced by the method has high bioavailability and high safety, and is peptide-calcium dual supplement, and the produced fish scale collagen peptide product has low average relative molecular weight and high purity. However, the disadvantage of this method is that the preparation process is complicated and the yield is low. Summary of the invention

[0004] Based on this, the purpose of the present invention is to propose a method for preparing fish protein gelatin polypeptides by probiotic fermentation, so as to solve the problems of difficult treatment of fish by-products and low efficiency, and to prepare fish protein gelatin polypeptides to achieve the reuse of resources.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing fish protein gelatin polypeptide by probiotic fermentation, comprising the following steps: The fish by-products are crushed, added into an edible alkali solution for soaking, and drained to obtain pretreated fish by-products; adding alkaline protease to the pretreated fish by-product for enzymolysis to obtain an enzymolysis product; adding glucose solution to the enzymatic hydrolysis product, heating it to inactivate the enzyme, and obtaining an enzyme-inactivated mixture; sterilizing the enzyme-killing mixture to obtain a sterilized mixture; Inoculating a mixed strain of Lactobacillus sakei JXNU1-3 and Bacillus subtilis into the sterilized mixture for fermentation; After the fermentation is completed, the fish protein gelatin polypeptide is separated and purified to obtain.

[0006] Optionally, the fish by-products include fish scales, fish skin and fish fins.

[0007] Optionally, the fish by-product is mixed with edible alkali in a ratio of 1 g:4-6 mL, the concentration of the edible alkali is 0.2-0.4 mol / L, and the soaking time is 0.5-1.5 h.

[0008] Optionally, the amount of alkaline protease added is 4-6% of the weight of the fish by-product, and the enzyme activity of the alkaline protease is 150000-250000 U / g.

[0009] Optionally, the temperature of the enzymolysis is 50-60° C., the pH of the enzymolysis is 8.5-9.5, and the time of the enzymolysis is 2-4 h. Optionally, the mass fraction of the glucose solution is 8-12%, the amount of the glucose solution added is 5-15% of the weight of the fish by-product, the temperature of the heating treatment is 90-100° C., and the time of the heating treatment is 8-12 min.

[0010] Optionally, the weight ratio of the Lactobacillus sakei JXNU1-3 to the Bacillus subtilis is 1-3:1-3, and the inoculation amount of the mixed bacteria is 2-12% of the weight of the fish by-product.

[0011] Optionally, the fermentation temperature is 25-40° C., and the fermentation time is 40-54 hours.

[0012] In a second aspect, the present invention provides a fish protein gelatin polypeptide prepared by the above method.

[0013] The fish protein gelatin polypeptide prepared by the invention not only has good gel properties, but also has good ABTS and DPPH free radical scavenging ability.

[0014] In a third aspect, the present invention provides a method as described above or use of the fish protein gelatin polypeptide as described above in the preparation of antioxidant foods, drugs, cosmetics and medical materials.

[0015] Compared with the prior art method for preparing fish protein gelatin polypeptide, the fish protein gelatin polypeptide prepared by the present invention has good gel properties and antioxidant properties, and can therefore be used to prepare antioxidant foods, drugs, cosmetics and medical materials.

[0016] The present invention has at least one of the following beneficial effects: 1. The present invention proposes a method for preparing fish protein gelatin polypeptide by probiotic fermentation. The method solves the problems of difficult treatment of fish by-products and low efficiency by soaking fish scales, fish skin and fish fins with edible alkali, enzymolysis and fermentation, and prepares a fish protein gelatin polypeptide to achieve the reuse of resources. The preparation method of the present invention is simple and suitable for industrial production.

[0017] 2. The fish protein gelatin polypeptide prepared by the present invention has good gel properties and antioxidant properties and can be used to prepare antioxidant foods, drugs, cosmetics and medical materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The scavenging ability of the fish protein gelatin polypeptide prepared by the probiotic fermentation method in Examples 1 to 5 of the present invention on ABTS free radicals; Figure 2 The scavenging ability of the fish protein gelatin polypeptide prepared by the probiotic fermentation method in Examples 1 to 5 of the present invention on DPPH free radicals. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] One embodiment of the present invention provides a method for preparing fish protein gelatin polypeptide by probiotic fermentation, comprising the following steps: The fish by-products are crushed, added into an edible alkali solution for soaking, and drained to obtain pretreated fish by-products; adding alkaline protease to the pretreated fish by-product for enzymolysis to obtain an enzymolysis product; adding glucose solution to the enzymatic hydrolysis product, heating it to inactivate the enzyme, and obtaining an enzyme-inactivated mixture; sterilizing the enzyme-killing mixture to obtain a sterilized mixture; Inoculating a mixed strain of Lactobacillus sakei JXNU1-3 and Bacillus subtilis into the sterilized mixture for fermentation; After the fermentation is completed, the fish protein gelatin polypeptide is separated and purified to obtain.

[0021] Among them, the classification name of the sake Lactobacillus JXNU1-3 is Lactobacillus sakei JXNU1-3, which has been deposited in the China Center for Type Culture Collection on October 7, 2023, with a deposit number of CCTCC NO: M 20231834. The detailed information of the sake Lactobacillus JXNU1-3 is recorded in the Chinese patent document with publication number CN117511783A, which is introduced herein and will not be repeated.

[0022] The Bacillus subtilis is a common strain and can be obtained through commercial channels, for example, it can be purchased from the China Industrial Microbiological Culture Collection Administration Center.

[0023] The method can be used to prepare a fish protein gelatin polypeptide with antioxidant properties, and the preparation method is simple.

[0024] In some embodiments, the steps include: Step 1: Crush the fish by-products, add 0.3 mol / L edible alkali at a ratio of 1:5 (w / v), soak for 1 h, and drain.

[0025] Step 2: Add enzyme to the mixture obtained in step 1 for enzymolysis. The enzymolysis conditions are: enzymolysis temperature 55°C, pH 9, alkaline protease 200000 U / g addition amount 5%, material-liquid ratio 1:10, enzymolysis time 3 h. After enzymolysis, add 10% mass fraction of glucose solution to the enzymolysis product. Then place the mixture in a 95°C water bath for 10 minutes to inactivate the enzyme.

[0026] Step 3: sterilize the mixture obtained in step 2 by high pressure, inoculate it after cooling, and ferment it in a shake flask for 48 hours.

[0027] Step 4: After the fermentation of the mixture in step 3 is completed, filtering and separation treatment is performed, and the obtained liquid is concentrated and freeze-dried to obtain fish protein gelatin polypeptide.

[0028] The present invention is further described in detail below with specific examples, but the present invention is not limited to the following specific examples.

[0029] Example 1 A method for preparing fish protein gelatin polypeptide by probiotic fermentation, comprising the following steps: The fish protein gelatin polypeptide is prepared by mixing and fermenting fish by-products with Lactobacillus sake JXNU1-3 and Bacillus subtilis in a weight ratio of 1:3, and the detailed steps are as follows: Step 1: Crush the fish by-products (fish scales, fish skin, and fish fins), add 0.3 mol / L edible alkali at a ratio of 1:5 (w / v), soak for 1 h, and drain.

[0030] Step 2: Add water and enzyme to the mixture obtained in step 1 for enzymolysis. The enzymolysis conditions are: enzymolysis temperature 55 °C, pH 9, alkaline protease 200000 U / g addition amount of 5%, fish by-product and water liquid ratio of 1:10, enzymolysis time 3h. After enzymolysis, add 10% mass fraction of glucose solution to the enzymolysis product, and the amount of glucose solution added is 10% of the weight of the fish by-product. Then place the mixture in a 95 °C water bath for 10 min to inactivate the enzyme.

[0031] Step 3: sterilize the mixture obtained in step 2 by high pressure, and after cooling, inoculate Lactobacillus sakei JXNU1-3 and Bacillus subtilis in a weight ratio of 1:3, and the inoculation amount of the mixed bacteria is 10% of the weight of the fish by-product, and ferment in a shake flask at 35° C. for 48 hours.

[0032] Step 4: After the fermentation of the mixture in step 3 is completed, filtering and separation treatment is performed, and the obtained liquid is concentrated and freeze-dried to obtain fish protein gelatin polypeptide.

[0033] Example 2 A method for preparing fish protein gelatin polypeptide by probiotic fermentation, comprising the following steps: The fish protein gelatin polypeptide is prepared by mixing and fermenting fish by-products with Lactobacillus sake JXNU1-3 and Bacillus subtilis in a weight ratio of 1:2, and the detailed steps are as follows: Step 1: Crush the fish by-products (fish scales, fish skin, and fish fins), add 0.3 mol / L edible alkali at a ratio of 1:5 (w / v), soak for 1 h, and drain.

[0034] Step 2: Add water and enzyme to the mixture obtained in step 1 for enzymolysis. The enzymolysis conditions are: enzymolysis temperature 55 ℃, pH 9, alkaline protease 200000 U / g addition amount 5%, fish by-product and water liquid ratio 1:10, enzymolysis time 3h. After enzymolysis, add 10% mass fraction of glucose solution to the enzymolysis product, and the addition amount of glucose solution is 10%. Then place the mixture in a 95℃ water bath for 10 min to inactivate the enzyme.

[0035] Step 3: sterilize the mixture obtained in step 2 by high pressure, and after cooling, inoculate Lactobacillus sakei JXNU1-3 and Bacillus subtilis in a weight ratio of 1:2, the inoculation amount of the mixed bacteria is 10% of the weight of the fish by-product, and ferment in a shake flask at 35° C. for 48 hours.

[0036] Step 4: After the fermentation of the mixture in step 3 is completed, filtering and separation treatment is performed, and the obtained liquid is concentrated and freeze-dried to obtain fish protein gelatin polypeptide.

[0037] Example 3 A method for preparing fish protein gelatin polypeptide by probiotic fermentation, comprising the following steps: The fish protein gelatin polypeptide is prepared by mixing and fermenting fish by-products with Lactobacillus sake JXNU1-3 and Bacillus subtilis in a weight ratio of 1:1, and the detailed steps are as follows: Step 1: Crush the fish by-products (fish scales, fish skin, and fish fins), add 0.3 mol / L edible alkali at a ratio of 1:5 (w / v), soak for 1 h, and drain.

[0038] Step 2: Add water and enzyme to the mixture obtained in step 1 for enzymolysis. The enzymolysis conditions are: enzymolysis temperature 55 ℃, pH 9, alkaline protease 200000 U / g addition amount 5%, fish by-product and water liquid ratio 1:10, enzymolysis time 3h. After enzymolysis, add 10% mass fraction of glucose solution to the enzymolysis product, and the addition amount of glucose solution is 10%. Then place the mixture in a 95℃ water bath for 10 min to inactivate the enzyme.

[0039] Step 3: sterilize the mixture obtained in step 2 by high pressure, and after cooling, inoculate Lactobacillus sakei JXNU1-3 and Bacillus subtilis in a weight ratio of 1:1, and the inoculation amount of the mixed bacteria is 10% of the weight of the fish by-product, and ferment in a shake flask at 35° C. for 48 hours.

[0040] Step 4: After the fermentation of the mixture in step 3 is completed, filtering and separation treatment is performed, and the obtained liquid is concentrated and freeze-dried to obtain fish protein gelatin polypeptide.

[0041] Example 4 A method for preparing fish protein gelatin polypeptide by probiotic fermentation, comprising the following steps: The fish protein gelatin polypeptide is prepared by mixing and fermenting fish by-products with Lactobacillus sake JXNU1-3 and Bacillus subtilis in a weight ratio of 2:1, and the detailed steps are as follows: Step 1: Crush the fish by-products (fish scales, fish skin, and fish fins), add 0.3 mol / L edible alkali at a ratio of 1:5 (w / v), soak for 1 h, and drain.

[0042] Step 2: Add water and enzyme to the mixture obtained in step 1 for enzymolysis. The enzymolysis conditions are: enzymolysis temperature 55 ℃, pH 9, alkaline protease 200000 U / g addition amount 5%, fish by-product and water liquid ratio 1:10, enzymolysis time 3h. After enzymolysis, add 10% mass fraction of glucose solution to the enzymolysis product, and the addition amount of glucose solution is 10%. Then place the mixture in a 95℃ water bath for 10 min to inactivate the enzyme.

[0043] Step 3: sterilize the mixture obtained in step 2 by high pressure, and after cooling, inoculate Lactobacillus sakei JXNU1-3 and Bacillus subtilis in a weight ratio of 2:1, and the inoculation amount of the mixed bacteria is 10% of the weight of the fish by-product, and ferment in a shake flask at 35°C for 48 hours.

[0044] Step 4: After the fermentation of the mixture in step 3 is completed, filtering and separation treatment is performed, and the obtained liquid is concentrated and freeze-dried to obtain fish protein gelatin polypeptide.

[0045] Example 5 A method for preparing fish protein gelatin polypeptide by probiotic fermentation, comprising the following steps: The fish protein gelatin polypeptide is prepared by mixing and fermenting fish by-products with Lactobacillus sake JXNU1-3 and Bacillus subtilis in a weight ratio of 3:1, and the detailed steps are as follows: Step 1: Crush the fish by-products (fish scales, fish skin, and fish fins), add 0.3 mol / L edible alkali at a ratio of 1:5 (w / v), soak for 1 h, and drain.

[0046] Step 2: Add water and enzyme to the mixture obtained in step 1 for enzymolysis. The enzymolysis conditions are: enzymolysis temperature 55 ℃, pH 9, alkaline protease 200000 U / g addition amount 5%, fish by-product and water liquid ratio 1:10, enzymolysis time 3h. After enzymolysis, add 10% mass fraction of glucose solution to the enzymolysis product, and the addition amount of glucose solution is 10%. Then place the mixture in a 95℃ water bath for 10 min to inactivate the enzyme.

[0047] Step 3: sterilize the mixture obtained in step 2 by high pressure, and after cooling, inoculate Lactobacillus sakei JXNU1-3 and Bacillus subtilis in a weight ratio of 3:1, and the inoculation amount of the mixed bacteria is 10% of the weight of the fish by-product, and ferment in a shake flask at 35°C for 48 hours.

[0048] Step 4: After the fermentation of the mixture in step 3 is completed, filtering and separation treatment is performed, and the obtained liquid is concentrated and freeze-dried to obtain fish protein gelatin polypeptide.

[0049] Comparative Example 1 The difference from Example 1 is that in step 1, "fish meat" is used as the raw material, and the other steps are the same as Example 1.

[0050] Results test and analysis: 1. The gel properties of the fish protein gel polypeptides prepared in Examples 1 to 5 were tested respectively, and the testing method was as follows: (1) Viscosity: The prepared fish protein gel polypeptide was placed in a measuring tube and sealed, and the speed of the induced wave passing through the gel was measured using Doppler technology. The transmitted sound frequency was 10.4 MHz, and the viscosity of the fluid was changed by changing the temperature of the experimental liquid. The flow rate is proportional to the sound intensity and inversely proportional to the viscosity of the liquid.

[0051] (2) Rheology: measured using a rheometer.

[0052] (3) Structural stability: It is measured by the compression mode of the texture analyzer (TPA). The principle is to compress the prepared fish protein gelatin polypeptide twice by simulating the chewing movement of the human mouth to obtain the texture characteristic parameters. (4) Adsorption capacity: gas phase adsorption test and liquid phase adsorption test are used.

[0053] (5) Variable temperature characteristics: Thermogravimetric analysis and thermal conductivity testing are used.

[0054] The test results are shown in Table 1.

[0055] Table 1 Gel properties Note: ① The full score is 10, 10 means the best and 1 means the worst.

[0056] ②This table only shows the relativity between Examples 1 to 5 and Comparative Example 1, not absoluteness.

[0057] ③ The scores of the last four embodiments are consistent because the differences between them are not obvious and the measured values ​​are close.

[0058] 2. The effects of Examples 1 to 5 on the scavenging ability of ABTS and DPPH free radicals were detected by the following method: (1) Effect on ABTS free radical scavenging ability: The ABTS free radical scavenging ability of the samples was determined according to the method of Zhang Lu et al. (Zhang Lu, Liu Pengfei, Tu Zongcai, et al. Comparative analysis of antioxidant and enzyme inhibitory activities of extracts from different parts of Torreya grandis [J]. Food Science). 50 μL of peptide hydrolysates of different concentrations (0.0625-1 mg / mL) prepared under the conditions of enzymatic hydrolysis and fermentation before and after optimization were taken, and the positive control group was 0-0.1 mg / mL glutathione. 150 μL of ABTS cationic solution was added and mixed. The mixture was reacted at room temperature in the dark for 6 min. The absorbance at 734 nm was determined as A1. The sample solution was replaced by 50 μL of distilled water as the reaction system, and the absorbance was determined as A0. The ABTS cationic solution was replaced by 150 μL of distilled water as the reaction system, and the absorbance was determined as A2. The ABTS cationic free radical scavenging ability was calculated according to formula (1), and the results were expressed as percentage scavenging rate.

[0059] Clearance rate / % = A0 -(A1-A2) / A0×100% (2) (2) Effect on DPPH free radical scavenging ability: 50 μL of sample solution diluted to an appropriate concentration was mixed with 150 μL of 0.15 mM DPPH free radical solution (prepared in methanol) on a 96-well ELISA plate. After reacting at room temperature in the dark for 30 min, the absorbance As was measured at 517 nm. The reaction system in which the sample solvent was substituted for the sample was the control group A1, and the reaction system without DPPH and sample was the blank A0. The concentration of positive control glutathione was 0-1 mg / mL. The sample concentration required to achieve a 50% DPPH free radical scavenging rate was expressed as the IC50 value (i.e., the concentration required to scaveng 50% of DPPH free radicals or inhibit 50% of enzyme activity). The calculation formula for DPPH scavenging rate is: Free radical scavenging rate / % = ( (A1-A0)-(As-A0) ) / (A1-A0)×100% The peptides produced by moderate protein hydrolysis have certain antioxidant capacity, which can be evaluated by the ABTS index and DPPH free radical scavenging ability. Figure 1 It can be seen that as the inoculation ratio of sake lactobacillus JXNU1-3 and Bacillus subtilis increases, the ABTS free radical scavenging ability is enhanced. And when the ratio is greater than 1:1, its ABTS free radical scavenging ability remains roughly unchanged. As shown in Table 2, the IC50 values ​​of glutathione for ABTS free radicals in Example 3, Example 1 samples and the control group are (0.88±0.01) mg / mL, (0.22±0.00) mg / mL, and (0.10±0.00) mg / mL, respectively. The IC50 values ​​of Example 3 and Example 1 samples for ABTS free radicals are 9 and 2 times that of the control group, respectively, indicating that when the inoculation ratio of sake lactobacillus JXNU1-3 and Bacillus subtilis is 1:1, the fish protein glue polypeptide solution prepared under the process conditions of enzymatic combined fermentation has a significantly higher scavenging ability for ABTS free radicals than the fish protein glue polypeptide solution prepared when the ratio is 1:3.

[0060] Table 2 IC of two examples and control group to ABTS free radical 50 Depend on Figure 2 It can be seen that as the inoculation ratio of sake lactobacillus JXNU1-3 and Bacillus subtilis increases, the DPPH free radical scavenging ability is enhanced. When the ratio is greater than 1:1, its DPPH free radical scavenging ability remains roughly unchanged. As shown in Table 3, the IC values ​​of glutathione for DPPH free radicals in the samples of Example 3, Example 1 and the control group are 50The values ​​were (1.40±0.05) mg / mL, (0.65±0.14) mg / mL, and (0.34±0.03) mg / mL, respectively. The IC50 values ​​of the samples in Example 1 and Example 3 for DPPH free radicals were 4 and 2 times that of the control group, respectively, indicating that when the inoculation ratio of Lactobacillus sakei JXNU1-3 and Bacillus subtilis was 1:1, the fish protein gelatin polypeptide solution prepared under the process conditions of enzymatic hydrolysis and fermentation had a significantly higher scavenging ability for DPPH free radicals than the fish protein gelatin polypeptide solution prepared under the ratio of 1:3.

[0061] Table 3: IC values ​​of Example 1, Example 3 and the control group for DPPH free radical 50 In summary, the fish protein gelatin polypeptide prepared by the present invention not only has good gel properties, but also has good ABTS and DPPH free radical scavenging ability. Compared with other methods for preparing fish protein gelatin polypeptides, the fish protein gelatin polypeptide prepared by the present invention has good gel properties and antioxidant properties. In addition, while preparing the fish protein gelatin polypeptide, the present invention improves the utilization rate of fish by-products and achieves "turning waste into treasure" to a certain extent.

[0062] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing fish protein gelatin polypeptide by probiotic fermentation, characterized in that: The following steps are involved: The fish by-products are crushed, added into an edible alkali solution for soaking, and drained to obtain pretreated fish by-products; adding alkaline protease to the pretreated fish by-product for enzymolysis to obtain an enzymolysis product; adding glucose solution to the enzymatic hydrolysis product, heating it to inactivate the enzyme, and obtaining an enzyme-inactivated mixture; sterilizing the enzyme-killing mixture to obtain a sterilized mixture; Inoculating a mixed strain of Lactobacillus sakei JXNU1-3 and Bacillus subtilis into the sterilized mixture for fermentation; After the fermentation is completed, the fish protein gelatin polypeptide is separated and purified to obtain.

2. The method according to claim 1, characterized in that The fish by-products include fish scales, fish skin and fish fins.

3. The method according to claim 1, characterized in that The fish by-products and edible alkali are mixed in a ratio of 1 g:4-6 mL, the concentration of the edible alkali is 0.2-0.4 mol / L, and the soaking time is 0.5-1.5 h.

4. The method according to claim 1, characterized in that: The amount of alkaline protease added is 4-6% of the weight of the fish by-product, and the enzyme activity of the alkaline protease is 150000-250000 U / g.

5. The method according to claim 1, characterized in that The temperature of the enzymolysis is 50-60° C., the pH of the enzymolysis is 8.5-9.5, and the time of the enzymolysis is 2-4 h.

6. The method according to claim 1, characterized in that The mass fraction of the glucose solution is 8-12%, the amount of the glucose solution added is 5-15% of the weight of the fish by-product, the temperature of the heating treatment is 90-100° C., and the time of the heating treatment is 8-12 min.

7. The method according to claim 1, characterized in that The weight ratio of the sake lactobacillus JXNU1-3 to the bacillus subtilis is 1-3:1-3, and the inoculation amount of the mixed bacteria is 2-12% of the weight of the fish by-product.

8. The method according to claim 1, characterized in that The fermentation temperature is 25-40° C., and the fermentation time is 40-54 hours.

9. A fish protein gel polypeptide, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the method according to any one of claims 1 to 8 or the fish protein gelatin polypeptide according to claim 9 in the preparation of antioxidant foods, drugs, cosmetics and medical materials.

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