Preparation method of protein peptide capable of improving flavor, function and stability

Abstract

The invention belongs to the technical field of polypeptide processing, and particularly relates to a preparation method of a protein peptide capable of improving flavor and functions. According to the method, chub is adopted as a raw material, food-grade protease is adopted, full-fish protein peptide obtained through moderate enzymolysis and xylooligosaccharide are subjected to a glycosylation reaction under the mild condition, nitrogen is adopted for replacing air, and the flavor and the anti-oxidation function of the full-fish protein peptide can be effectively improved; compared with the original whole-fish protein peptide and the whole-fish protein glycopeptide prepared by adopting air for glycosylation reaction, the whole-fish protein glycopeptide prepared by adopting the method disclosed by the invention has lighter fishy smell and bitter taste, can effectively improve the acceptability of the masses, has a stronger antioxidant function and good storage stability, and can be used for preparing the whole-fish protein glycopeptide. The method can be widely applied to special foods and nutritious foods.

Description

Technical Field

[0001] The invention belongs to the technical field of polypeptide processing, and in particular relates to a method for preparing a protein peptide capable of improving flavor, function and stability. Background Art

[0002] Fish such as silver carp are rich in protein and have a balanced amino acid composition, making them high-quality raw materials for producing protein peptides. Fish protein peptides have the functions of anti-oxidation, regulating blood lipids, and improving atherosclerosis, and are good dietary supplements. However, the presence of fishy and bitter smells seriously affects consumers' acceptance of silver carp protein peptides, limiting the application of fish protein peptides. Existing technologies for improving the unpleasant flavor of protein peptides mainly include (1) physical mixing, that is, simple physical mixing with sweeteners, flavor enhancers or taste improvers to mask the unpleasant flavor of protein peptides. (2) physical adsorption, that is, treating protein peptides with activated carbon, resins or other adsorbents to remove bitterness and fishy smell. (3) microencapsulation, that is, encapsulating protein peptides in tiny capsules to mask the unpleasant flavor. (4) membrane separation technology, that is, using membrane technologies such as ultrafiltration, nanofiltration or reverse osmosis to selectively separate according to molecular size or charge, which can effectively remove small molecule peptides that cause fishy and bitter tastes.

[0003] For the above-mentioned technologies, the following problems may exist: (1) Physical mixing does not really change its flavor characteristics. Unpleasant flavors may gradually appear during product storage or taste experience. (2) Physical adsorption may not only remove bitter and fishy substances, but also remove beneficial components in protein peptides, such as nutrients and bioactive molecules, thereby reducing the nutritional value and physiological efficacy of the product. (3) Microencapsulation equipment, materials and processes are often more expensive. This will increase the production cost of the product and may lead to an increase in the price of the final product. (4) Membrane separation equipment and special membrane materials are usually expensive, which will also increase the production cost of the product. In recent years, oligosaccharides have been widely used in the food and health fields due to their low calories and good prebiotic effects. However, there are still insufficient invention patents and research on the use of oligosaccharides to improve the flavor characteristics of protein peptides and enhance their antioxidant capacity. Summary of the invention

[0004] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a method for preparing protein peptides that can improve flavor, function and stability, which can solve the problems of high cost and poor effect existing in the prior art, and improve the flavor characteristics, antioxidant capacity and storage stability of whole fish protein peptides.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a protein peptide capable of improving flavor, function and stability, the method comprising the following steps:

[0007] S1: Take silver carp as raw material, remove the gills, viscera and black film, wash and grind into fish mince;

[0008] S2: adding deionized water to the minced fish meat in a ratio of 1:2 (w / v) to 1:3 (w / v), stirring the mixture thoroughly, and then placing the mixture in a high pressure steam sterilizer and cooking it at 121° C. for 60 to 120 minutes to obtain a minced fish meat solution;

[0009] S3: heating the fish paste solution obtained in step S2 to 50° C. in a water bath, and then adding food-grade protease, wherein the amount of the food-grade protease added is 0.5% to 1.0%, and the enzymolysis time is 1 to 3 hours;

[0010] S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide;

[0011] S5: Dissolve xylooligosaccharides and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 0.25:1 (w / w) to 1:1 (w / w), then transfer to a sealed screw-capped glass tube with a nitrogen content of not less than 92%, heat at 70°C to 90°C for 1 to 2 hours, and quickly place in an ice water bath to terminate the reaction after heating, and obtain silver carp protein glycopeptide after vacuum freeze-drying.

[0012] Further, in step S5, air is replaced by 95% to 100% nitrogen.

[0013] Further, in step S5, the prime oligosaccharide is xylooligosaccharide.

[0014] Furthermore, the concentration of the silver carp whole fish protein peptide is 5% to 10%.

[0015] Furthermore, the food-grade protease is a composite protease.

[0016] Furthermore, the component ratio of the composite protease includes alkaline protease: papain: flavor protease = 1-2:1-2:1.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The whole fish protein glycopeptide prepared by the method has a lighter fishy smell and bitterness than the original whole fish protein peptide, which can effectively improve the public's acceptance. At the same time, it has a higher antioxidant function and can be widely used in special food and nutritional food;

[0019] (2) In this method, the use of xylooligosaccharides can effectively improve the flavor and antioxidant function of whole fish protein peptides;

[0020] (3) In this method, nitrogen is used to replace air for glycosylation reaction, thereby significantly improving the flavor and antioxidant function of whole fish protein peptides;

[0021] (4) In this method, the whole fish protein glycopeptide developed using whole fish protein peptides and oligosaccharides does not require the addition of acid or alkali to adjust the pH during the entire processing process, which can effectively maintain the good functional properties and safety of the product;

[0022] (5) The preparation process of this method is safe and efficient. Food-grade protease is used, and the whole fish protein peptide obtained by moderate enzymatic hydrolysis reacts with oligoxylose under mild conditions without any additives. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments.

[0024] Embodiment 1:

[0025] In this embodiment, the preparation method comprises the following steps:

[0026] S1: Take silver carp as raw material, remove the gills, viscera and black film, wash with tap water and grind into fish mince;

[0027] S2: add deionized water to the minced fish meat at a ratio of 1:2 (w / v), stir thoroughly, and then place the whole in a high pressure steam sterilizer and cook at 121°C for 120 min to inactivate endogenous enzymes, thereby obtaining a minced fish meat solution;

[0028] S3: The fish paste solution obtained in step S2 is heated to 50° C. in a water bath, and then a composite protease (alkaline protease: papain: flavor protease = 1:1:1) is added in an amount of 0.5% and the enzymolysis time is 3 h;

[0029] S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide;

[0030] S5: Dissolve the xylooligosaccharides and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 1:1 (w / w) (the concentration of the silver carp protein peptide is 10%), then transfer to a sealed screw-cap glass tube containing nitrogen, heat at 90°C for 2h, and quickly place in an ice water bath to terminate the reaction after heating. After vacuum freeze-drying, the silver carp protein glycopeptide is obtained.

[0031] Embodiment 2:

[0032] In this embodiment, the preparation method comprises the following steps:

[0033] S1: Take silver carp as raw material, remove the gills, viscera and black film, wash with tap water and grind into fish mince;

[0034] S2: add deionized water to the minced fish meat at a ratio of 1:2 (w / v), stir thoroughly, and then place the whole in a high pressure steam sterilizer and cook at 121°C for 120 min to inactivate endogenous enzymes, thereby obtaining a minced fish meat solution;

[0035] S3: The fish paste solution obtained in step S2 is heated to 50° C. in a water bath, and then a composite protease (alkaline protease: papain: flavor protease = 1:1:1) is added in an amount of 0.5% and the enzymolysis time is 3 h;

[0036] S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide;

[0037] S5: Dissolve the oligosaccharide and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 1:1 (w / w) (the concentration of the silver carp protein peptide is 10%), then transfer to a sealed screw-cap glass tube containing 100% nitrogen, heat at 90°C for 2h, and quickly place in an ice water bath to terminate the reaction after heating. After vacuum freeze-drying, the silver carp protein glycopeptide is obtained.

[0038] Embodiment three:

[0039] In this embodiment, the preparation method comprises the following steps:

[0040] S1: Take silver carp as raw material, remove the gills, viscera and black film, wash with tap water and grind into fish mince;

[0041] S2: add deionized water to the minced fish meat at a ratio of 1:2 (w / v), stir thoroughly, and then place the whole in a high pressure steam sterilizer and cook at 121°C for 120 min to inactivate endogenous enzymes, thereby obtaining a minced fish meat solution;

[0042] S3: The fish paste solution obtained in step S2 is heated to 50° C. in a water bath, and then a composite protease (alkaline protease: papain: flavor protease = 1:1:1) is added in an amount of 0.5% and the enzymolysis time is 3 h;

[0043] S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide;

[0044] S5: Dissolve oligofructose and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 1:1 (w / w) (the concentration of silver carp protein peptide is 10%), then transfer to a sealed screw-cap glass tube containing 100% nitrogen, heat at 90°C for 2h, and quickly place in an ice water bath to terminate the reaction after heating. After vacuum freeze-drying, silver carp protein glycopeptide is obtained.

[0045] Comparative Example 1:

[0046] In this comparative example, the preparation method comprises the following steps:

[0047] S1: Take silver carp as raw material, remove the gills, viscera and black film, wash with tap water and grind into fish mince;

[0048] S2: add deionized water to the minced fish meat at a ratio of 1:3 (w / v), stir thoroughly, and then place the whole in a high-pressure steam sterilizer and cook at 121°C for 60 minutes to inactivate endogenous enzymes, thereby obtaining a minced fish meat solution;

[0049] S3: The fish paste solution obtained in step S2 is heated to 50° C. in a water bath, and then a composite protease (alkaline protease: papain: flavor protease = 2:1:1) is added in an amount of 0.5% and the enzymolysis time is 3 h;

[0050] S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide;

[0051] S5: Dissolve xylooligosaccharides and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 0.5:1 (w / w) (the concentration of silver carp protein peptide is 7%), then transfer to a sealed screw-cap glass tube containing 95% nitrogen, heat at 70°C for 2h, and quickly place in an ice water bath to terminate the reaction after heating. After vacuum freeze-drying, silver carp protein glycopeptide is obtained.

[0052] Comparative Example 2:

[0053] In this comparative example, the preparation method comprises the following steps:

[0054] S1: Take silver carp as raw material, remove the gills, viscera and black film, wash with tap water and grind into fish mince;

[0055] S2: add deionized water to the minced fish meat at a ratio of 1:3 (w / v), stir thoroughly, and then place the whole in a high-pressure steam sterilizer and cook at 121°C for 90 minutes to inactivate endogenous enzymes, thereby obtaining a minced fish meat solution;

[0056] S3: The fish paste solution obtained in step S2 is heated to 50° C. in a water bath, and then a composite protease (alkaline protease: papain: flavor protease = 2:2:1) is added in an amount of 0.6% and the enzymolysis time is 1 h;

[0057] S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide;

[0058] S5: Dissolve galacto-oligosaccharide and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 1:1 (w / w) (the concentration of silver carp protein peptide is 8%), then transfer to a sealed screw-cap glass tube containing 95% nitrogen, heat at 70°C for 1h, and quickly place in an ice water bath to terminate the reaction after heating. After vacuum freeze-drying, silver carp protein glycopeptide is obtained.

[0059] Comparative Example 3:

[0060] In this comparative example, the preparation method comprises the following steps:

[0061] S1: Take silver carp as raw material, remove the gills, viscera and black film, wash with tap water and grind into fish mince;

[0062] S2: add deionized water to the minced fish meat at a ratio of 1:2 (w / v), stir thoroughly, and then place the whole in a high pressure steam sterilizer and cook at 121°C for 120 min to inactivate endogenous enzymes, thereby obtaining a minced fish meat solution;

[0063] S3: The fish paste solution obtained in step S2 is heated to 50° C. in a water bath, and then a composite protease (alkaline protease: papain: flavor protease = 1:2:1) is added in an amount of 0.75% and the enzymolysis time is 1 h;

[0064] S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide;

[0065] S5: Dissolve oligofructose and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 0.5:1 (w / w) (the concentration of silver carp protein peptide is 8%), then transfer to a sealed screw-cap glass tube containing 95% nitrogen, heat at 70°C for 1h, and quickly place in an ice water bath to terminate the reaction after heating. After vacuum freeze-drying, silver carp protein glycopeptide is obtained.

[0066] Comparative Example 4:

[0067] In this comparative example, the other steps are the same as those in Example 1, except that in step S5, the mixture is transferred to a sealed screw-capped glass tube containing only ordinary air.

[0068] Comparative Example 5:

[0069] In this comparative example, the other steps are the same as those of Example 1, except that in step S5, the silver carp protein peptide obtained in step S4 is fully dissolved in deionized water (the concentration of the silver carp protein peptide is 10%).

[0070] Comparative Example 6:

[0071] In this comparative example, only the xylooligosaccharide in Example 1 was fully dissolved in deionized water (the concentration of xylooligosaccharide was 10%).

[0072] Comparative Example 7:

[0073] In this comparative example, only the galacto-oligosaccharide in Example 2 was fully dissolved in deionized water (the concentration of galacto-oligosaccharide was 10%).

[0074] Comparative Example 8:

[0075] In this comparative example, only the oligofructose in Example 3 was fully dissolved in deionized water (the concentration of oligofructose was 10%).

[0076] Test example 1:

[0077] Sensory evaluation test of whole fish protein glycopeptides based on this method.

[0078] In order to demonstrate the improvement effect of the method on the flavor of whole fish protein peptide, sensory evaluation tests were conducted on Examples 1 to 3 and Comparative Examples 1 to 8.

[0079] The sensory evaluation test was carried out as follows:

[0080] There were 30 members of the sensory evaluation panel (12 men and 18 women), aged between 20 and 30 years old. The experiment used seven sensory qualities for descriptive analysis, including caramel, bitterness, saltiness, sourness, umami, and fishy taste. Before the formal experiment, all panel members were informed of the definitions of these tastes and received training on how to feel these qualities using corresponding reference materials. The sample solutions were incubated at 45°C before testing to minimize the potential impact of temperature on the evaluation process. Each sample was then assigned a three-digit code and randomly distributed to each member participating in the sensory evaluation. After tasting each sample, the participating members scored the intensity of each sensory quality on a scale of 0 to 5 (0 = none / very weak, 5 = very strong). The final sensory evaluation scores are shown in Table 1 below:

[0081] Table 1 Sensory evaluation scores

[0082]

[0083]

[0084] Test Example 2:

[0085] In order to demonstrate the effect of the present method on enhancing the antioxidant capacity of whole fish protein peptides, the antioxidant capacity of Examples 1 to 3 and Comparative Examples 1 to 8 were measured.

[0086] The specific determination method includes the following steps:

[0087] (1) Determination of total reducing power: Take 1 mL of a 0.5 mg / mL sample, add 2.5 mL of 0.2 M phosphate buffer (pH 6.6) and 2.5 mL of 1% (mass fraction) potassium ferricyanide solution, mix well, and then heat in a 50°C water bath for 20 min. Take out and cool quickly, add 2.5 mL of 10% (mass fraction) trichloroacetic acid (TCA) solution, mix well, and then centrifuge at 3000 g for 10 min. Take 2.5 mL of the supernatant, add 2.5 mL of deionized water and 0.5 mL of 1% (mass fraction) ferric chloride solution, mix well, react at room temperature for 10 min, and measure the absorbance at a wavelength of 700 nm. The reducing power can be expressed by the absorbance value at a wavelength of 700 nm.

[0088] (2) Ferrous ion reducing ability: The assay reagent consists of 2,4,6-tripyridyltriazine (10 mM, dissolved in 40 mM hydrochloric acid), ferric chloride (20 mM) and acetate buffer (0.3 M, pH 3.6) in a ratio of 1:1:10. The diluted sample is mixed with the assay reagent and incubated at 37°C in the dark for 30 min. The absorbance of the mixture is then measured at a wavelength of 593 nm using a spectrophotometer. A standard curve is constructed using ferric sulfate heptahydrate (FeSO4·H2O) at a concentration of 0.1-1 mM. The ferrous ion reducing ability is calculated as mM FeSO4 / mg sample.

[0089] (3) DPPH free radical scavenging ability: Take 1.5 mL of 0.5 mg / mL sample, add 1.5 mL of 99.5% ethanol and 0.675 mL of 0.02% DPPH ethanol solution, mix, oscillate, place in a light-proof water bath at room temperature for 30 minutes, and then detect the absorbance of the system at 517 nm. The lower the absorbance, the stronger the system's ability to scavenge DPPH free radicals. The blank control is to replace 1.5 mL of sample solution with 1.5 mL of deionized water. Trolox (water-soluble vitamin E) with a concentration of 50-300 μmol / L is used to construct a standard curve. The activity of the sample is expressed as μmol Trolox equivalent (TE) / mg protein.

[0090] The specific data of the above three antioxidant capacities are shown in Table 2 below:

[0091] Table 2 Antioxidant capacity

[0092]

[0093]

[0094] Test Example 3:

[0095] In order to demonstrate the storage stability of the whole fish protein glycopeptide prepared by the present method, the sensory evaluation scores and antioxidant capacity of Examples 1 to 3 and Comparative Example 5 at different storage time points were measured.

[0096] The storage stability test was carried out as follows:

[0097] The whole fish protein glycopeptide obtained in Example 1, Example 2, Example 3 and Comparative Example 5 and the whole fish protein peptide only after heating were respectively packed in composite film vacuum packaging bags, evacuated and heat-sealed, and all samples were stored at room temperature (25° C.) in the dark for 3 months. The samples with a storage period of 0 month, 1 month, 2 months and 3 months were subjected to sensory evaluation and antioxidant capacity determination, and the determination results are shown in Tables 3 and 4 below:

[0098] Table 3 Sensory evaluation scores at different storage times

[0099]

[0100]

[0101] Table 4 Antioxidant capacity at different storage times

[0102]

[0103]

[0104] As can be seen from Table 1, the oligosaccharides mentioned in this method can reduce the fishy smell and bitterness of the whole fish protein peptide after modification, and enhance the caramel taste of the whole fish protein peptide, which is conducive to the improvement of the acceptance of the whole fish protein peptide. In all the embodiments, the improvement of the fishy smell and bitterness of the silver carp protein peptide in Example 1 is the most significant, indicating that the flavor improvement effect of oligoxylose on the silver carp protein peptide is significantly better than other oligosaccharides. In addition, compared with Example 1, the caramel taste and acceptance of the whole fish protein glycopeptide in Comparative Example 4 have decreased to a certain extent, indicating that replacing air with nitrogen during glycosylation has a significant effect on improving the flavor of the whole fish protein glycopeptide.

[0105] As can be seen from Table 2, the embodiments described in the present method can enhance the total reducing power, iron ion reducing ability and DPPH free radical scavenging ability of silver carp protein peptides to varying degrees compared with the comparative examples. It shows that oligosaccharide modification not only improves the flavor of whole fish protein peptides, but also has a significant enhancing effect on its antioxidant capacity. Among all oligosaccharides, oligoxylose has the most significant enhancement on the antioxidant capacity of silver carp protein peptides. It can be found in the storage stability test of whole fish protein glycopeptides (Tables 3 and 4) that with the extension of storage period, oligoxylose can better maintain the caramel flavor, acceptance and antioxidant capacity of whole fish protein glycopeptides, and replacing air with nitrogen has a significant effect on improving the storage stability of whole fish protein glycopeptides. .

[0106] The above test results prove that the use of oligosaccharides to glycosylate whole fish protein peptides in nitrogen replacement of air can effectively improve their flavor, which is specifically manifested in the reduction of fishy smell and bitterness, more caramel flavor, and improved overall acceptance. At the same time, the antioxidant capacity of whole fish protein glycopeptides modified by glycosylation with nitrogen replacement of air is significantly improved compared with protein peptides modified by glycosylation with air. Replacing air with nitrogen during the glycosylation reaction can effectively improve the storage stability of whole fish protein glycopeptides. . Therefore, it is an effective method to use oligosaccharides to improve the flavor of whole fish protein peptides through glycosylation reaction and combine nitrogen replacement of air to improve its antioxidant function and storage stability.

Claims

1. A method for preparing a protein peptide capable of improving flavor, function and stability, characterized in that: The method comprises the following steps: S1: Take silver carp as raw material, remove the gills, viscera and black film, wash and grind into fish mince; S2: adding deionized water to the minced fish meat in a ratio of 1:2 (w / v) to 1:3 (w / v), stirring the mixture thoroughly, and then placing the mixture in a high pressure steam sterilizer and cooking it at 121° C. for 60 to 120 minutes to obtain a minced fish meat solution; S3: heating the fish paste solution obtained in step S2 to 50° C. in a water bath, and then adding food-grade protease, wherein the amount of the food-grade protease added is 0.5% to 1.0%, and the enzymolysis time is 1 to 3 hours; S4: After the enzymatic hydrolysis is completed, the whole is placed in a water bath at 95°C for 15 minutes to inactivate the enzyme, then cooled to room temperature, and centrifuged at 4000r / min for 20 minutes. The supernatant is vacuum freeze-dried to obtain silver carp whole fish protein peptide; S5: Dissolve the oligosaccharide and the silver carp protein peptide obtained in step S4 in deionized water at a ratio of 0.25:1 (w / w) to 1:1 (w / w), then transfer to a sealed screw-capped glass tube with a nitrogen content of not less than 92%, heat at 70°C to 90°C for 1 to 2 hours, and quickly place in an ice water bath to terminate the reaction after heating, and obtain the silver carp protein glycopeptide after vacuum freeze-drying.

2. The method for preparing a protein peptide capable of improving flavor, function and stability according to claim 1, characterized in that: In step S5, the nitrogen-enriched gas refers to replacing air with 95% to 100% nitrogen.

3. The method for preparing a protein peptide capable of improving flavor, function and stability according to claim 1, characterized in that: In step S5, the oligosaccharide is xylo-oligosaccharide.

4. The method for preparing a protein peptide capable of improving flavor, function and stability according to claim 1, characterized in that: In step S5, the concentration of the silver carp whole fish protein peptide is 5% to 10%.

5. The method for preparing a protein peptide capable of improving flavor, function and stability according to claim 1, characterized in that: In step S3, the food-grade protease is a composite protease.

6. The method for preparing a protein peptide capable of improving flavor, function and stability according to claim 3, characterized in that: The component ratio of the composite protease includes alkaline protease: papain: flavor protease = 1-2:1-2:1.

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