Enzymolysis process

Abstract

The invention relates to the technical field of enzymolysis, in particular to an enzymolysis process which comprises the following steps: cutting dry fish skin into pieces, and adding water to obtain rehydrated fish skin; performing multi-stage enzymolysis and enzyme inactivation treatment on the rehydrated fish skin to obtain enzymatic hydrolysate; adding absolute ethyl alcohol, a demulsifier and sodium chloride into the enzymatic hydrolysate, stirring for dissolving, and standing for layering to obtain an ethanol phase and a polypeptide water phase; adding a composite adsorbent into the polypeptide water phase, stirring and adsorbing, then transferring into a plate-and-frame filter press, and collecting filtrate; the filtrate is pumped into an ultrafiltration membrane unit, permeate is collected, then the permeate enters a nanofiltration membrane unit to be desalted and concentrated, a concentrated solution is obtained, the concentrated solution is transferred into a spray dryer, and the collagen peptide is obtained. A chelating agent and citric acid are added in the rehydration stage, on one hand, metal ions causing fishy smell amplification in the fish skin are chelated, and peculiar smell substances generated by catalyzing fat oxidation and protein degradation are avoided; on the other hand, the acidity of the system is adjusted, mucus and impurities on the surface of the fish skin can be partially dissolved, and peculiar smell sources are further reduced.

Description

Technical Field

[0001] This invention relates to the field of enzymatic hydrolysis technology, and in particular to an enzymatic hydrolysis process. Background Technology

[0002] Enzymatic hydrolysis, also known as enzymatic hydrolysis or enzyme-catalyzed degradation, refers to the process of using enzymes as biological catalysts to specifically break down large molecular substrates (such as proteins, starch, and cellulose) into smaller molecular products (such as peptides, amino acids, and glucose) under mild conditions (such as room temperature, normal pressure, and a specific pH value).

[0003] Collagen peptides are small-molecule peptides extracted from animal connective tissue, possessing excellent bioactivity and absorption properties. They can be directly utilized by skin cells, stimulating fibroblast proliferation and accelerating collagen regeneration. Therefore, they play an important role in beauty and anti-aging, joint health, and bone protection.

[0004] Freshwater fish skin is a mainstream raw material for extracting collagen peptides due to its wide availability, low cost, and high collagen content. However, freshwater fish skin contains a relatively high amount of sulfur-containing amino acids, precursors to fishy odors, and fat components. If not processed thoroughly, it can easily produce volatile fishy-smelling substances. To mask this odor, large amounts of sweeteners, flavorings, and other seasonings are often added during production. This not only dilutes the actual effective content of collagen peptides in the product but also affects the taste and quality of the product, thus restricting its overall quality. Summary of the Invention

[0005] In view of the shortcomings of traditional freshwater fish skin enzymatic hydrolysis for collagen peptide preparation mentioned in the background art, such as severe off-odor and the need to add a lot of seasonings, the present invention provides an enzymatic hydrolysis process that, through synergistic enzymatic hydrolysis and optimized operation process, inhibits the generation of off-odor substances from the source and can achieve deodorization of products without the need to add a lot of seasonings.

[0006] To achieve the above objectives, the present invention provides an enzymatic hydrolysis process comprising the following preparation steps: S1. Take 100 parts of dried fish skin by weight, cut it into pieces and put it into water with a weight of 3 times that of the dried fish skin. Add 0.3 to 0.8 parts of chelating agent and 0.1 to 0.5 parts of citric acid, stir to dissolve, soak at a constant temperature of 35°C for 2.5 hours, take it out and wash off the surface impurities, drain the water and get rehydrated fish skin. S2. Transfer the rehydrated fish skin into the reaction vessel, add 100 parts of water, add sodium hydroxide solution to adjust the pH of the system to 8.2, heat to 40℃, add 0.8-2.5 parts of lipase, stir and disperse, keep warm and react for 45 minutes, after enzyme inactivation treatment, let stand for 20 minutes, skim off the upper layer of floating oil to obtain degreased slurry; S3. Transfer the defatted slurry into a colloid mill to fully break it down and refine it to obtain collagen slurry. S4. Transfer the collagen slurry into an enzymatic hydrolysis tank, add 0.8-1.5 parts of calcium chloride, add citric acid solution to adjust the pH to 6.5, heat to 50℃, add 0.5-1.5 parts of endopeptidase, stir and disperse, and perform primary enzymatic hydrolysis for 1.5 hours. S5. After the first-stage enzymatic hydrolysis is completed, add sodium hydroxide solution to adjust the pH of the system to 8.2, raise the temperature to 55℃, add 1.5 to 2 parts of alkaline protease, stir and disperse, and perform second-stage enzymatic hydrolysis for 2 hours. S6. After the second-stage enzymatic hydrolysis, citric acid solution was added to adjust the pH to 7.5, the temperature was lowered to 48℃, 0.7-1.5 parts of exonuclease were added, the mixture was stirred and dispersed, and the third-stage enzymatic hydrolysis was carried out for 1 hour. After enzyme inactivation treatment, the enzymatic hydrolysate was obtained. S7. Add 20% to 30% of the enzymatic hydrolysate mass of anhydrous ethanol to the enzymatic hydrolysate, stir for 25 min, first add 0.1% to 0.5% of the total mass of the system of demulsifier, stir for 5 min, then add 8% to 15% of the total mass of the system of sodium chloride, stir to dissolve for 20 min, let stand to separate the layers, and obtain the ethanol phase and the polypeptide aqueous phase. S8. Add 3.5 to 8 parts of composite adsorbent to the aqueous phase of the polypeptide, stir and adsorb for 30 minutes, then transfer to a plate and frame filter press and collect the filtrate. S9. The filtrate is pumped into the ultrafiltration membrane unit, and the permeate is collected. Then the permeate enters the nanofiltration membrane unit for desalting and concentration to obtain a concentrate. The concentrate is then transferred to a spray dryer to obtain collagen peptides.

[0007] Preferably, the composite adsorbent is composed of activated carbon, diatomaceous earth, and β-cyclodextrin in a mass ratio of 2:3:1.

[0008] Preferably, the demulsifier is sodium stearoyl lactylate.

[0009] Preferably, the chelating agent is disodium ethylenediaminetetraacetate.

[0010] Preferably, the ultrafiltration membrane unit operates at an operating pressure of 0.5 MPa, and the nanofiltration membrane unit operates at an operating pressure of 1.2 MPa.

[0011] Preferably, the lipase is Aspergillus oryzae lipase with an activity of 20,000 U / g.

[0012] Preferably, the endopeptide is papain with an activity of 60,000 U / g.

[0013] Preferably, the alkaline protease is alkaline protease 2709 with an activity of 100,000 U / g.

[0014] Preferably, the exonuclease is composed of aminopeptidase with an activity of 50,000 U / g and carboxypeptidase with an activity of 20,000 U / g in a mass ratio of 1:2.

[0015] After adopting the above technical solution, the beneficial effects of the present invention are: Adding chelating agents and citric acid during the rehydration stage serves two purposes: firstly, it chelates metal ions in the fish skin that amplify the fishy smell, preventing them from catalyzing fat oxidation and protein degradation to produce off-odor substances; secondly, it adjusts the acidity of the system, which can partially dissolve the mucus and impurities on the surface of the fish skin, further reducing the source of off-odors. Detailed Implementation

[0016] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0017] Example 1 This embodiment provides an enzymatic hydrolysis process, and the specific preparation steps and technical details are as follows.

[0018] Step 1: Raw material pretreatment and rehydration to remove fishy smell Weigh 100 parts (by weight, the same below) of dried tilapia skin free from mold and putrefaction, cut it into uniform pieces of 1cm × 1cm, and put it into a pre-prepared soaking solution, which is made of 0.3 parts disodium EDTA, 0.1 parts citric acid, and 300 parts water. Soak the dried fish skin at a constant temperature of 35℃ for 2.5 hours, then rinse it three times with water, each time for no less than 1 minute, to remove surface impurities. Drain the water to obtain rehydrated fish skin.

[0019] Disodium EDTA, acting as a chelating agent, can chelate metal ions in fish skin that amplify the fishy odor, preventing them from catalyzing fat oxidation and protein degradation to produce off-odor substances. This reduces the formation of aldehydes and ketones, thus minimizing the odor at its source. Citric acid, used to increase the system's acidity, can partially dissolve mucus and impurities on the fish skin surface, further reducing the source of odor. Citric acid also softens the collagen fiber structure of the fish skin, aiding rehydration and reducing the difficulty of subsequent degreasing.

[0020] If the dried fish skin is to be stored for a long period of time (e.g., more than 8 months), it needs to be soaked a second time after the first soaking. Put the rehydrated fish skin that has completed the first soaking into 200 parts of water, and add 0.8 parts of compound antioxidant deodorizing agent (made of vitamin C, tea polyphenols and rosemary extract in a mass ratio of 3:2:1). Seal and soak at 25°C for 1.5 hours, stirring once every 20 minutes (30 seconds each time, 30 r / min). After taking it out, rinse it with water 3 times, each time for no less than 1 minute, to wash away surface impurities and drain the water to obtain the rehydrated fish skin after the second soaking.

[0021] Fish skin stored for an extended period may have developed peroxides due to fat oxidation. Vitamin C can convert these peroxides into odorless alcohols through a reduction reaction, preventing further decomposition into strong-smelling molecules such as aldehydes and ketones. The phenolic hydroxyl groups of tea polyphenols can form hydrogen bonds or hydrophobic interactions with the aldehydes, ketones, and amines already present in the fish skin, anchoring the odor molecules to the tea polyphenol molecules, which are then thoroughly removed through rinsing. The phenolic components in rosemary extract can react with the core odor-causing substances in fish skin (mainly aldehydes and ketones produced by fat oxidation), and its own mild flavor does not introduce new odors.

[0022] Step 2: Targeted degreasing treatment After soaking once or twice, the rehydrated fish skin is transferred to a reaction vessel. 100 parts of water are added, and a 5% sodium hydroxide solution is added dropwise to adjust the pH to 8.2. The temperature is raised to 40°C and maintained. 0.8 parts of Aspergillus oryzae lipase with an activity of 20,000 U / g are added, and the mixture is stirred at 150 rpm for 45 minutes for enzymatic hydrolysis.

[0023] After enzymatic hydrolysis, the system is heated to 85°C and kept at that temperature for 15 minutes to inactivate the enzyme. After cooling to 40°C, it is allowed to stand for 20 minutes. The upper layer of floating oil is skimmed off to obtain the degreased slurry.

[0024] Step 3: Grinding and refining The defatted slurry is transferred to a colloid mill to fully break it down and refine it, thus obtaining collagen slurry.

[0025] Step 4: Primary enzymatic hydrolysis Transfer the collagen slurry into an enzymatic hydrolysis tank, add 0.8 parts of calcium chloride, add 10% citric acid solution to adjust the pH to 6.5, heat to 50℃, add 0.5 parts of papain (endopeptide) with an activity of 60,000 U / g, stir and disperse at 200 r / min, and enzymatically hydrolyze for 1.5 h.

[0026] Calcium chloride acts as an activator to enhance the activity of papain and stabilize the enzyme's spatial structure.

[0027] Step 5: Secondary enzymatic hydrolysis After the first-stage enzymatic hydrolysis was completed, a 5% sodium hydroxide solution was added dropwise to adjust the pH of the system to 8.2. The temperature was raised to 55°C, and 1.5 parts of alkaline protease 2709 with an activity of 100,000 U / g were added. The mixture was stirred and dispersed at 250 r / min and enzymatically hydrolyzed for 2 h.

[0028] Step Six: Tertiary Enzymatic Digestion After the secondary enzymatic hydrolysis, a 10% citric acid solution was added to adjust the pH to 7.5, the temperature was lowered to 48℃, 0.7 parts of exonuclease were added, and the mixture was stirred and dispersed at 180 rpm for 1 hour. The exonuclease was composed of aminopeptidase with an activity of 50,000 U / g and carboxypeptidase with an activity of 20,000 U / g in a mass ratio of 1:2.

[0029] After the three-stage enzymatic hydrolysis is completed, the system is heated to 90℃ and kept at that temperature for 15 minutes to inactivate the enzyme. After cooling to 60℃, 0.2% of the system mass of diatomaceous earth filter aid is added. After stirring and adsorption for 10 minutes, the filtrate is collected using a plate and frame filter press (pressure 0.3MPa) to obtain the enzymatic hydrolysate.

[0030] Step 7: Efficient Impurity Removal and Layering Add 20% anhydrous ethanol (by weight of the enzymatic hydrolysate) to the hydrolysate and stir at 200 rpm for 25 min. First, add 0.1% sodium stearoyl lactylate (by weight of the total system mass) and stir for 5 min. Then, add 8% sodium chloride (by weight of the total system mass) and stir to dissolve for 20 min. After stirring, transfer to a centrifuge and centrifuge at 4000 rpm for 15 min. Let stand for 15 min to separate the phases, obtaining the ethanol phase and the aqueous phase of the peptide.

[0031] The fishy and off-odors in the enzymatic hydrolysate mainly come from amines (such as trimethylamine and histamine) produced by lipid oxidation products and amino acid decarboxylation. Ethanol has both hydrophobic and hydrophilic groups. Its hydrophobic groups combine with hydrophobic odor substances, stripping off the odor substances adsorbed on the surface of the polypeptides, thus separating the odor substances from the aqueous phase.

[0032] The enzymatic hydrolysate contains peptides, residual fats, fatty acids, and other substances, which easily form a stable oil-in-water emulsion. Odor-containing oil droplets are encapsulated by the hydrophilic ends of peptide molecules and dispersed in the aqueous phase. Sodium stearoyl lactylate, an anionic surfactant, can disrupt the charge balance and stability of the interfacial membrane, promoting oil droplet aggregation and sedimentation, thus preventing emulsion stabilization and subsequent separation failure during salting out.

[0033] Ethanol and water form a stable mixture through hydrogen bonds. The addition of sodium chloride introduces interactions between ions and molecules, disrupting the miscibility equilibrium between ethanol and water through the salting-out effect.

[0034] Step 8: Adsorption and Purification Activated carbon, diatomaceous earth, and β-cyclodextrin were dry-mixed at a mass ratio of 2:3:1 to prepare a composite adsorbent. 3.5 parts of the composite adsorbent were added to the separated polypeptide aqueous phase, and the mixture was stirred at 150 r / min for 30 min for adsorption. The mixture was then transferred to a plate and frame filter press (pressure 0.4 MPa) to collect the filtrate.

[0035] β-Cyclodextrin has a hydrophobic cavity structure, which can specifically encapsulate hydrophobic odor substances (such as trimethylamine) through inclusion complexation, further removing fishy smells, without affecting the activity of the peptides.

[0036] The filtrate is pumped into an ultrafiltration membrane unit at an operating pressure of 0.5 MPa to remove incompletely removed large molecular weight proteins, colloidal particles, and other impurities, allowing only small molecular weight collagen peptides (≤3 kDa) to pass through. The permeate is then pumped into a nanofiltration membrane unit for desalting and concentration at an operating pressure of 1.2 MPa to obtain a concentrate. The concentrate is then transferred to a spray dryer to obtain collagen peptides.

[0037] Example 2 The enzymatic hydrolysis process provided in this embodiment includes the following preparation steps: S1. Take 100 parts of dried fish skin, cut it into pieces and put it into water with a weight of 3 times its weight. Add 0.5 parts of chelating agent and 0.3 parts of citric acid, stir until dissolved, soak at a constant temperature of 35℃ for 2.5 hours, take it out and wash off the surface impurities, drain the water, and you will get rehydrated fish skin. S2. Transfer the rehydrated fish skin into the reaction vessel, add 100 parts of water, add sodium hydroxide solution to adjust the pH of the system to 8.2, heat to 40℃, add 1.2 parts of lipase, stir and disperse, keep warm and react for 45 minutes, after enzyme inactivation treatment, let stand for 20 minutes, skim off the upper layer of floating oil to obtain degreased slurry; S3. Transfer the defatted slurry into a colloid mill to fully break it down and refine it to obtain collagen slurry. S4. Transfer the collagen slurry into an enzymatic hydrolysis tank, add 1.2 parts calcium chloride, add citric acid solution to adjust the pH to 6.5, heat to 50℃, add 0.8 parts endopeptide, stir and disperse, and perform primary enzymatic hydrolysis for 1.5 hours; S5. After the first-stage enzymatic hydrolysis is completed, sodium hydroxide solution is added dropwise to adjust the pH of the system to 8.2, the temperature is raised to 55℃, 1.8 parts of alkaline protease are added, the mixture is stirred and dispersed, and the second-stage enzymatic hydrolysis is carried out for 2 hours. S6. After the second-stage enzymatic hydrolysis, citric acid solution was added to adjust the pH to 7.5, the temperature was lowered to 48℃, 1.2 parts of exonuclease were added, the mixture was stirred and dispersed, and the third-stage enzymatic hydrolysis was carried out for 1 hour. After enzyme inactivation treatment, the enzymatic hydrolysate was obtained. S7. Add 25% anhydrous ethanol (by weight of the enzyme hydrolysate) to the enzyme hydrolysate and stir for 25 min. First, add 0.35% demulsifier (by weight of the total system) and stir for 5 min. Then, add 12% sodium chloride (by weight of the total system) and stir to dissolve for 20 min. Allow to stand and separate into layers to obtain the ethanol phase and the polypeptide aqueous phase. S8. Add 5.5 parts of composite adsorbent to the aqueous phase of the polypeptide, stir and adsorb for 30 min, then transfer to a plate and frame filter press and collect the filtrate. S9. The filtrate is pumped into the ultrafiltration membrane unit, and the permeate is collected. Then the permeate enters the nanofiltration membrane unit for desalting and concentration to obtain a concentrate. The concentrate is then transferred to a spray dryer to obtain collagen peptides.

[0038] The other steps and conditions of the preparation process are the same as in Example 1.

[0039] Example 3 The enzymatic hydrolysis process provided in this embodiment includes the following preparation steps: S1. Take 100 parts of dried fish skin, cut it into pieces and put it into water with a weight of 3 times its weight. Add 0.8 parts of chelating agent and 0.5 parts of citric acid, stir until dissolved, soak at a constant temperature of 35℃ for 2.5 hours, take it out and wash off the surface impurities, drain the water, and you will get rehydrated fish skin. S2. Transfer the rehydrated fish skin into the reaction vessel, add 100 parts of water, add sodium hydroxide solution to adjust the pH of the system to 8.2, heat to 40℃, add 2.5 parts of lipase, stir and disperse, keep warm for 45 minutes, after enzyme inactivation treatment, let stand for 20 minutes, skim off the upper layer of floating oil to obtain degreased slurry; S3. Transfer the defatted slurry into a colloid mill to fully break it down and refine it to obtain collagen slurry. S4. Transfer the collagen slurry into an enzymatic hydrolysis tank, add 1.5 parts calcium chloride, add citric acid solution to adjust the pH to 6.5, heat to 50℃, add 1.5 parts endopeptide, stir and disperse, and perform primary enzymatic hydrolysis for 1.5 hours. S5. After the first-stage enzymatic hydrolysis is completed, sodium hydroxide solution is added dropwise to adjust the pH of the system to 8.2, the temperature is raised to 55℃, 2 parts of alkaline protease are added, and the mixture is stirred and dispersed. Second-stage enzymatic hydrolysis is carried out for 2 hours. S6. After the second-stage enzymatic hydrolysis, citric acid solution was added to adjust the pH to 7.5, the temperature was lowered to 48℃, 1.5 parts of exonuclease were added, the mixture was stirred and dispersed, and the third-stage enzymatic hydrolysis was carried out for 1 hour. After enzyme inactivation treatment, the enzymatic hydrolysate was obtained. S7. Add 30% anhydrous ethanol by mass of the enzymatic hydrolysate to the enzymatic hydrolysate, stir for 25 min, first add 0.5% demulsifier by mass of the total system, stir for 5 min, then add 15% sodium chloride by mass of the total system, stir to dissolve for 20 min, let stand to separate the layers, and obtain the ethanol phase and the polypeptide aqueous phase. S8. Add 8 parts of composite adsorbent to the aqueous phase of the polypeptide, stir and adsorb for 30 min, then transfer to a plate and frame filter press and collect the filtrate. S9. The filtrate is pumped into the ultrafiltration membrane unit, and the permeate is collected. Then the permeate enters the nanofiltration membrane unit for desalting and concentration to obtain a concentrate. The concentrate is then transferred to a spray dryer to obtain collagen peptides.

[0040] The other steps and conditions of the preparation process are the same as in Example 1.

[0041] Comparative Example 1 Unlike Example 1, the enzymatic hydrolysate was not subjected to efficient impurity removal, layering, and adsorption purification. The enzymatic hydrolysate was directly pumped into the ultrafiltration membrane unit, the permeate was collected, and then the permeate entered the nanofiltration membrane unit for desalting and concentration to obtain a concentrate. The concentrate was then transferred to a spray dryer to obtain collagen peptides.

[0042] The other steps and conditions of the preparation process are the same as in Example 1.

[0043] Comparative Example 2 Unlike Example 1, the enzymatic hydrolysate was not subjected to efficient impurity removal and stratification. Instead, it was purified by adsorption and pumped into an ultrafiltration membrane unit. The permeate was collected and then entered a nanofiltration membrane unit for desalting and concentration to obtain a concentrate. The concentrate was then transferred to a spray dryer to obtain collagen peptides.

[0044] The other steps and conditions of the preparation process are the same as in Example 1.

[0045] Comparative Example 3 Unlike Example 1, the enzymatic hydrolysate is not purified by adsorption. The polypeptide aqueous phase after efficient impurity removal and separation is pumped into the ultrafiltration membrane unit, the permeate is collected, and then the permeate enters the nanofiltration membrane unit for desalting and concentration to obtain a concentrate. The concentrate is then transferred to a spray dryer to obtain collagen peptides.

[0046] The other steps and conditions of the preparation process are the same as in Example 1.

[0047] The collagen peptides obtained in the examples and comparative examples were evaluated, and the specific evaluation results are shown in Table 1.

[0048] Table 1 Comparison of Evaluation Indicators

[0049] Examples 1-3, due to the use of a combination of ethanol stripping and composite adsorbent, had no obvious odor. In contrast, Comparative Example 1 (lacking two purification steps) had a strong fishy smell, and Comparative Example 2 (lacking a stratification step) and Comparative Example 3 (lacking adsorption purification) had significantly stronger fishy smells than the examples. This proves that the deodorization system of the present invention can remove odor substances from multiple dimensions and solves the technical pain point of incomplete deodorization in existing processes.

[0050] The embodiments described above are not exhaustive and do not limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. An enzymatic hydrolysis process, characterized in that, The preparation steps include the following: S1. Take 100 parts of dried fish skin by weight, cut it into pieces and put it into water with a weight of 3 times that of the dried fish skin. Add 0.3 to 0.8 parts of chelating agent and 0.1 to 0.5 parts of citric acid, stir to dissolve, soak at a constant temperature of 35°C for 2.5 hours, take it out and wash off the surface impurities, drain the water and get rehydrated fish skin. S2. Transfer the rehydrated fish skin into the reaction vessel, add 100 parts of water, add sodium hydroxide solution to adjust the pH of the system to 8.2, heat to 40℃, add 0.8-2.5 parts of lipase, stir and disperse, keep warm and react for 45 minutes, after enzyme inactivation treatment, let stand for 20 minutes, skim off the upper layer of floating oil to obtain degreased slurry; S3. Transfer the defatted slurry into a colloid mill to fully break it down and refine it to obtain collagen slurry. S4. Transfer the collagen slurry into an enzymatic hydrolysis tank, add 0.8-1.5 parts of calcium chloride, add citric acid solution to adjust the pH to 6.5, heat to 50℃, add 0.5-1.5 parts of endopeptidase, stir and disperse, and perform primary enzymatic hydrolysis for 1.5 hours. S5. After the first-stage enzymatic hydrolysis is completed, add sodium hydroxide solution to adjust the pH of the system to 8.2, raise the temperature to 55℃, add 1.5 to 2 parts of alkaline protease, stir and disperse, and perform second-stage enzymatic hydrolysis for 2 hours. S6. After the second-stage enzymatic hydrolysis, citric acid solution was added to adjust the pH to 7.5, the temperature was lowered to 48℃, 0.7-1.5 parts of exonuclease were added, the mixture was stirred and dispersed, and the third-stage enzymatic hydrolysis was carried out for 1 hour. After enzyme inactivation treatment, the enzymatic hydrolysate was obtained. S7. Add 20% to 30% of the enzymatic hydrolysate mass of anhydrous ethanol to the enzymatic hydrolysate, stir for 25 min, first add 0.1% to 0.5% of the total mass of the system of demulsifier, stir for 5 min, then add 8% to 15% of the total mass of the system of sodium chloride, stir to dissolve for 20 min, let stand to separate the layers, and obtain the ethanol phase and the polypeptide aqueous phase. S8. Add 3.5 to 8 parts of composite adsorbent to the aqueous phase of the polypeptide, stir and adsorb for 30 minutes, then transfer to a plate and frame filter press and collect the filtrate. S9. The filtrate is pumped into the ultrafiltration membrane unit, and the permeate is collected. Then the permeate enters the nanofiltration membrane unit for desalting and concentration to obtain a concentrate. The concentrate is then transferred to a spray dryer to obtain collagen peptides.

2. The enzymatic hydrolysis process according to claim 1, characterized in that: The composite adsorbent is composed of activated carbon, diatomaceous earth, and β-cyclodextrin in a mass ratio of 2:3:

1.

3. The enzymatic hydrolysis process according to claim 2, characterized in that: The demulsifier is sodium stearoyl lactylate.

4. The enzymatic hydrolysis process according to claim 3, characterized in that: The chelating agent is disodium ethylenediaminetetraacetate.

5. The enzymatic hydrolysis process according to claim 4, characterized in that: The ultrafiltration membrane unit operates at a pressure of 0.5 MPa, and the nanofiltration membrane unit operates at a pressure of 1.2 MPa.

6. The enzymatic hydrolysis process according to claim 1, characterized in that: The lipase is Aspergillus oryzae lipase with an activity of 20,000 U / g.

7. The enzymatic hydrolysis process according to claim 1, characterized in that: The endopeptide is papain with an activity of 60,000 U / g.

8. The enzymatic hydrolysis process according to claim 1, characterized in that: The alkaline protease is alkaline protease 2709 with an activity of 100,000 U / g.

9. The enzymatic hydrolysis process according to claim 1, characterized in that: The exonuclease is composed of aminopeptidase with an activity of 50,000 U / g and carboxypeptidase with an activity of 20,000 U / g in a mass ratio of 1:2.

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