Fish protein glue composite gel capable of slowly releasing VD3 and calcium citrate and preparation method of fish protein glue composite gel

Abstract

The invention discloses a fish protein glue composite gel capable of slowly releasing VD3 and calcium citrate and a preparation method of the fish protein glue composite gel, and relates to the technical field of food processing. The fish protein glue composite gel is prepared from the following raw materials in parts by weight: 9.0 to 10.0 parts of fish protein glue, 2.0 to 3.0 parts of maltodextrin, 0.7 to 0.9 part of calcium citrate, 0.003 to 0.005 part of VD3 and 85.9 to 88.2 parts of deionized water. The traditional Chinese medicine composition further comprises 0.01 to 0.3 part of MTGase. On the basis of the fish protein glue, maltodextrin and MTGase are added as modifiers, so that the obtained composite gel has the characteristic of slowly releasing VD3 and calcium citrate in simulated gastrointestinal tracts, has better bioavailability and bioactivity than oral free VD3 and calcium citrate, has better gel performance and slow release performance than non-crosslinked fish protein glue gel, and can be applied to the field of gastrointestinal tracts, such as gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts, gastrointestinal tracts and gastrointestinal tracts. The material can be used as a packaging material for packaging and gastrointestinal tract delivery of active substances.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and in particular to a fish protein gel composite gel for sustained-release of vitamin D3 and calcium citrate and a preparation method thereof. Background Art

[0002] The average daily calcium intake in my country is approximately 400 mg, only half the recommended intake in the Dietary Reference Intakes for Chinese Residents. Calcium is a crucial micronutrient widely recognized to influence bone health and human metabolism. Calcium enters the bloodstream through food or supplements, maintaining a dynamic balance of calcium in the blood and bones. However, inadequate calcium intake is a common problem worldwide. Studies have shown that among adults who rely solely on food for minerals and vitamins, approximately 38% have insufficient calcium intake, and approximately 93% have insufficient vitamin D3 intake. Vitamin D3 is essential for calcium absorption and plays a key role in calcium absorption, bone homeostasis, calcium-phosphorus balance, bone repair, and osteoporosis treatment. When calcium is consumed without the supplemental vitamin D3, it is not absorbed by cells and is excreted from the body as calcium salts. Therefore, supplemental calcium and vitamin D3 intake outside of the diet is necessary. Calcium supplements are available in a variety of forms, with products containing a complex of calcium citrate and calcium carbonate being the most commonly used. Compared to calcium carbonate, calcium citrate has high bioavailability and solubility over a wide pH range, with fasting and mealtime absorption rates of 27.2% and 21.6%, respectively. Therefore, calcium citrate is considered an effective dietary calcium supplement. However, its absorption is significantly reduced in the gastrointestinal tract due to factors such as oxalate, phytate, high sugar content, and a high sulfur-to-calcium ratio. Vitamin D3 can be taken with calcium salts to enhance calcium absorption by mediating both active and paracellular calcium absorption modes. However, vitamin D3 itself is extremely acid-instable, making it easily destroyed in the gastrointestinal tract. Using an appropriate encapsulation system to encapsulate sustained-release calcium citrate and vitamin D3 may be an effective solution to this dilemma.

[0003] Encapsulation in an appropriate encapsulation system maintains the functionality of the encapsulated substance and protects it during storage and digestion. The application of encapsulation technology maximizes the bioactivity of the encapsulated substance and reduces the potential for side effects caused by excessive encapsulation by quantifying the encapsulated substance content. Although encapsulation in food environments has been practiced for decades, many shortcomings and gaps remain. For example, encapsulation systems in the food industry generally require the encapsulation material to be edible and highly compatible with the encapsulated substance. Among various encapsulation materials, maltodextrin is a highly competitive option due to its high encapsulation performance, low cost, high heat resistance, high physical resistance, good flavor, and high water solubility. However, the use of maltodextrin alone results in the immediate release of the encapsulated active ingredient upon contact with the hydrophilic matrix. Therefore, it needs to be combined with other biomaterials for better encapsulation. Protein glues are an excellent carrier for bioactive substances due to their excellent biocompatibility, degradability, sustained release properties, high thermal resistance, and cross-linking ability. However, mammalian protein glues pose risks of diseases such as mad cow disease and foot-and-mouth disease, as well as dietary taboos such as those in Islam. Fish protein glue, also extracted from fish byproducts, effectively avoids these shortcomings. It boasts advantages such as high safety, good market compatibility, and abundant raw materials, and is considered a highly promising biomaterial. However, fish protein glue has a lower amino acid content than mammalian protein glue, resulting in insufficient gelling properties, which greatly limits its application as an encapsulation material. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a fish protein gel composite gel for sustained release of VD3 and calcium citrate and a preparation method thereof.

[0005] Currently, extensive research is underway to improve the gelling properties of fish protein gels, with physical, chemical, and enzymatic modification being common approaches. Enzymatic modification offers significant advantages, such as high efficiency, specificity, and mild reaction conditions, and holds great potential for application. Due to its safety and efficacy, microbial transglutaminase (MTGase) has been successfully used to modify fish protein gels. MTGase catalyzes the acyl transfer reaction between the γ-carboxamide and the ε-amine of glutamine residues, forming intramolecular and intermolecular crosslinks within fish protein gels. MTGase enhances the gelling properties of fish protein gels and, to a certain extent, delays their in vitro gastrointestinal digestion. However, studies on its use as an encapsulation material for the delivery of active substances and its effect on the intestinal absorption of encapsulated active substances have been limited.

[0006] In order to overcome the shortcomings of the above-mentioned background technology and solve the technical problem that oral free VD3 and calcium citrate are released in large quantities in the gastrointestinal tract, resulting in VD3 inactivation or calcium ion precipitation, thereby leading to decreased calcium absorption, the present invention provides a fish protein gel composite gel that slowly releases VD3 and calcium citrate and a preparation method thereof. The fish protein gel-based composite gel of the present invention is based on fish protein gel, and maltodextrin and MTGase are added as modifiers. The resulting composite gel has the characteristics of slowly releasing VD3 and calcium citrate in a simulated gastrointestinal tract, has better bioavailability and bioactivity than oral free VD3 and calcium citrate, and has better gel properties and sustained release properties than uncross-linked fish protein gel. It can be used as an encapsulation material for encapsulating and delivering active substances to the gastrointestinal tract, providing a new perspective for the research and development of new VD3 and calcium citrate supplements.

[0007] The technical solutions of the present invention are as follows: The first aspect of the present invention provides a fish protein gel composite gel for sustained-release of VD3 and calcium citrate, wherein the fish protein gel composite gel comprises the following raw materials in parts by weight: 9.0-10.0 parts of fish protein gel, 2.0-3.0 parts of maltodextrin, 0.7-0.9 parts of calcium citrate, 0.003-0.005 parts of VD3, and 85.9-88.2 parts of deionized water.

[0008] Preferably, the amount of each raw material added is as follows: 9.0-10.0 parts of fish protein glue, 2.0-3.0 parts of maltodextrin, 0.8 part of calcium citrate, 0.004 parts of VD3, and 85.9-88.2 parts of deionized water.

[0009] Preferably, the fish protein glue composite gel further comprises the following raw materials in parts by weight: 0.15-0.3 parts of MTGase.

[0010] Preferably, the amount of MTGase added is 0.2-0.3 parts by weight.

[0011] More preferably, the amount of MTGase added is 0.25 parts by weight.

[0012] A second aspect of the present invention provides a method for preparing the fish protein glue composite gel, the method comprising the following steps: S1, add deionized water to the mixed fish protein glue and calcium citrate, heat and stir to completely dissolve them to obtain a first solution; S2. Add deionized water to the evenly mixed maltodextrin and VD3, heat and stir until the maltodextrin and VD3 are completely dissolved to obtain a second solution; S3, mixing the first solution and the second solution uniformly to obtain a third solution; S4. Let the third solution stand to obtain a fish protein gel composite gel.

[0013] Preferably, when the raw material further comprises MTGase, the preparation method comprises the following steps: S1, add deionized water to the mixed fish protein glue and calcium citrate, heat and stir to completely dissolve them to obtain a first solution; S2. Add deionized water to the evenly mixed maltodextrin and VD3, heat and stir until the maltodextrin and VD3 are completely dissolved to obtain a second solution; S3, mixing the first solution and the second solution uniformly to obtain a third solution; S4. Add MTGase to the third solution to react. After the reaction is completed, inactivate the enzyme and allow the mixture to stand to obtain a fish protein gel composite gel.

[0014] Preferably, in steps S1 and S2, the heating temperature is 35-45°C.

[0015] Preferably, in step S3, a disperser is used to mix uniformly at 10,000 to 14,000 rpm / min for 1 to 3 minutes.

[0016] Preferably, in step S4, when the raw materials further include MTGase, the reaction time is 1.5-2.5 h, the enzyme is inactivated at 100° C. for 4-6 min, and the mixture is quickly taken out and allowed to stand at 4° C.

[0017] The present invention has at least one of the following beneficial effects: (1) The fish protein gelatin-based composite gel of the present invention improves the various defects of pure fish protein gelatin encapsulation materials. The improved composite gel is rich in nutritional value, contains fish protein gelatin, contains multiple amino acids, has good biocompatibility, and can be completely digested by the human body.

[0018] (2) The components of the fish protein gelatin-based composite gel provided by the present invention are well compatible, and have strong gel properties, encapsulation efficiency, storage stability, and the ability to resist digestion and slowly release VD3 and calcium ions, so that the various properties required for it as an encapsulation material are fully improved and comprehensively enhanced.

[0019] (3) Compared with traditional encapsulation and delivery materials, the fish protein gel-based composite gel provided by the present invention has the advantages of edibility, biodegradability, and environmental friendliness. It is suitable for the encapsulation of active substances, and the preparation method is green, safe, simple, and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FTIR spectra of fish protein gel, maltodextrin, VD3 and the fish protein gel composite gel sample containing VD3 prepared in Example 3.

[0021] Figure 2 The storage stability of the samples at room temperature is listed from left to right as follows: Comparative Example 1, Comparative Example 2, Comparative Example 3, Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6.

[0022] Figure 3 The digestion release rate of the composite gel VD3 obtained in each embodiment and comparative example is shown.

[0023] Figure 4 The digestion release rate of the composite gel calcium citrate obtained in each embodiment and comparative example is shown. DETAILED DESCRIPTION

[0024] 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 with reference to 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 intended to limit the present invention.

[0025] Example 1 A fish protein gel composite gel for sustained-release of vitamin D3 and calcium citrate comprises the following components in parts by weight: 9.0 parts of fish protein gel, 2.0 parts of maltodextrin, 0.8 parts of calcium citrate, 0.004 parts of vitamin D3, and 88.2 parts of deionized water.

[0026] The preparation method of the above-mentioned fish protein glue composite gel comprises the following steps: 1) Accurately weigh each material according to the formula requirements; 2) Mix fish protein gelatin and calcium citrate evenly, add deionized water, and heat with stirring at 40°C for 1 h to completely dissolve, thereby obtaining a first solution; 3) Mix maltodextrin and vitamin D3 evenly, add deionized water, and heat at 40°C with stirring for 1 hour to completely dissolve the maltodextrin and vitamin D3 to obtain a second solution. 4) After the first and second solutions are evenly mixed, use a disperser to mix at 12,000 rpm / min for 2 minutes to obtain a third solution; 5) allowing the third solution to stand to obtain a composite gel sample; Example 2 The preparation steps of the fish protein gel composite gel of sustained-release VD3 and calcium citrate in Example 2 are the same as those in Example 1, except that the raw materials in Example 2 include, by weight, 10.0 parts of fish protein gel, 3.0 parts of maltodextrin, 0.8 parts of calcium citrate, 0.004 parts of VD3, and 86.2 parts of deionized water.

[0027] Example 3 The preparation steps of the fish protein gel composite gel of sustained-release VD3 and calcium citrate in Example 3 are the same as those in Example 1, except that the raw materials in Example 3 include, by weight, 10.0 parts of fish protein gel, 3.0 parts of maltodextrin, 0.15 parts of MTGase, 0.8 parts of calcium citrate, 0.004 parts of VD3, and 86.05 parts of deionized water.

[0028] The preparation method of the above-mentioned fish protein glue composite gel comprises the following steps: 1) Accurately weigh each material according to the formula requirements; 2) Mix fish protein gelatin and calcium citrate evenly, add deionized water, and heat with stirring at 40°C for 1 h to completely dissolve, thereby obtaining a first solution; 3) Mix maltodextrin and vitamin D3 evenly, add deionized water, and heat at 40°C with stirring for 1 hour to completely dissolve the maltodextrin and vitamin D3 to obtain a second solution. 4) After the first and second solutions are evenly mixed, use a disperser to mix at 12,000 rpm / min for 2 minutes to obtain a third solution; 5) Add MTGase to the third solution, react for 2 h, inactivate the enzyme at 100°C for 5 min, quickly remove the solution and allow to stand at 4°C to obtain a composite gel sample; Example 4 The preparation steps of the fish protein gel composite gel of sustained-release VD3 and calcium citrate in Example 4 are the same as those in Example 3, except that the raw materials in Example 4 include, by weight, 10.0 parts of fish protein gel, 3.0 parts of maltodextrin, 0.20 parts of MTGase, 0.8 parts of calcium citrate, 0.004 parts of VD3, and 86.0 parts of deionized water.

[0029] Example 5 The preparation steps of the fish protein gel composite gel of sustained-release VD3 and calcium citrate in Example 5 are the same as those in Example 3, except that the raw materials in Example 5 include, by weight, 10.0 parts of fish protein gel, 3.0 parts of maltodextrin, 0.25 parts of MTGase, 0.8 parts of calcium citrate, 0.004 parts of VD3, and 85.95 parts of deionized water.

[0030] Example 6 The preparation steps of the fish protein gel composite gel of sustained-release VD3 and calcium citrate in Example 6 are the same as those in Example 3, except that the raw materials in Example 6 include, by weight, 10.0 parts of fish protein gel, 3.0 parts of maltodextrin, 0.30 parts of MTGase, 0.8 parts of calcium citrate, 0.004 parts of VD3, and 85.9 parts of deionized water.

[0031] Comparative Example 1 Comparative Example 1 was prepared by mixing 0.8 parts of calcium citrate, 0.004 parts of VD3, and 99.2 parts of deionized water, calculated by weight.

[0032] Comparative Example 2 Comparative Example 2 The preparation steps of the fish protein gel composite gel of sustained-release VD3 and calcium citrate are the same as those of Example 1, except that the raw materials of Comparative Example 2 include, by weight, 3.0 parts of maltodextrin, 0.8 parts of calcium citrate, 0.004 parts of VD3, and 95.9 parts of deionized water.

[0033] Comparative Example 3 Comparative Example 3 The fish protein gel composite gel of sustained-release VD3 and calcium citrate is prepared in the same steps as in Example 1, except that the raw materials in Comparative Example 3 include, by weight, 10.0 parts of fish protein gel, 0.8 parts of calcium citrate, 0.004 parts of VD3, and 88.9 parts of deionized water.

[0034] The performance of the fish protein gel composite gel obtained in the above examples and comparative examples was tested according to the following method: 1. Determination of sample cross-linking degree The o-phthalaldehyde (OPA) spectrometric method was used to determine the degree of cross-linking in fish protein composite gels, and the parameters of the detection system were optimized. Specifically, the OPA reagent was prepared by dissolving 1.9069 g of borax in 50 ml of deionized water, 1 g of sodium dodecyl sulfate (SDS) in 5 ml of deionized water, 0.08 g of o-phthalaldehyde in 1 ml of methanol, and 0.088 g of 1,4-dimercaptothreitol (DTT). These four substances were mixed in order and the resulting solution was brought to a volume of 100 ml. For the assay, 200 μL of the sample to be tested was thoroughly mixed with 4 mL of the OPA reagent. After reacting for 2 minutes at room temperature, the absorbance was immediately measured at 340 nm using a UV-visible spectrophotometer. A concentration-absorbance standard curve (R²>0.999) was established based on L-lysine standards. The free amino group content in the sample was quantitatively analyzed by colorimetry to characterize the cross-linking degree of the fish protein glue molecules. The cross-linking degree was calculated as follows: 2. Encapsulation efficiency of VD3 and calcium citrate VD3 encapsulation efficiency (EE) determination method The VD3 encapsulation efficiency is accurately evaluated by ultraviolet spectrophotometry. At room temperature, 10 ml of the fish protein gel composite gel sample obtained in the embodiment and comparative example was dispersed in 15 mL of chromatographic grade n-hexane, vortexed at 3,000 rpm for 2 minutes, and then centrifuged at 10,000 rpm for 10 minutes to efficiently separate the unencapsulated VD3. The supernatant was taken and the absorbance value was measured at 264 nm using a UV-visible spectrophotometer. A concentration-absorbance calibration curve was established based on the VD3 standard (R²>0.999). The formula for calculating the VD3 encapsulation efficiency is as follows: Freshly prepared fish protein gel composite gel samples from the examples and comparative examples were centrifuged at 10,000 rpm for 10 minutes. After centrifugation, the supernatant was carefully aspirated. The calcium ion concentration in the supernatant was then measured using inductively coupled plasma (ICP) spectroscopy. The calcium citrate (CC) encapsulation efficiency was calculated using the following formula: 3. Determination of gelation and melting temperature of fish protein gel composite 18 mL samples of the fish protein gel composite gels obtained in the Examples and Comparative Examples were transferred to PP50 cylinders. The temperature sweep protocol consisted of three consecutive stages: a cooling stage from 40°C to 5°C (at a controlled cooling rate of 0.5°C / min), a constant temperature stage at 5°C (for 5 minutes), and a heating stage from 5°C to 40°C (at a controlled heating rate of 0.5°C / min). The dynamic strain amplitude was logarithmically modulated, decreasing from 5% to 0.1% during cooling and increasing from 0.1% to 5.0% during heating. The measurements were performed at a fixed oscillatory frequency of 1 Hz.

[0035] 4. Fourier transform infrared spectroscopy (FTIR) The samples were characterized by FTIR. 1 mg of freeze-dried sample (fish protein gel, maltodextrin, VD3, and the fish protein gel containing VD3 prepared in Example 3) was thoroughly ground and mixed with 100 mg of dry chromatographic grade potassium bromide in an agate mortar and pressed into transparent test slices. Detection was performed using an infrared spectrophotometer with a scanning range of 4000 cm -1 Up to 400cm -1 , the resolution is set to 4 cm -1 , accumulating 64 scans to obtain high signal-to-noise ratio spectral data.

[0036] 5. Storage stability Store freshly prepared samples at room temperature. Collect samples on the 1st, 3rd, 7th, 15th, and 21st day, and observe the status of the samples accordingly.

[0037] 6. In vitro simulated digestion study Fish protein gel composite gels containing different MTGase concentrations (w / w) were prepared at pH 1.5. Pepsin was added at a 1:50 (w / w) ratio of enzyme (MTGase) to fish protein gel to initiate enzymatic digestion. After incubation in a 37°C water bath for 2 h, the pepsin reaction was terminated by neutralizing the pH to 7.0 with 0.20 M NaOH to obtain gastric-digested (GD) samples.

[0038] Trypsin was then added to the GD samples at a mass ratio of 1:25 (MTGase:fish protein gel) to initiate enzymatic digestion. After incubation in a 37°C water bath for 2 hours, gastrointestinal digestion (GID) samples were obtained. Undigested (UD) samples were generated as a control group by adding inactivated pepsin to the samples under GID conditions. All samples were stored at 4°C until analysis.

[0039] The free amino group content in the digested samples was quantified by o-phthalaldehyde (OPA) spectrophotometry. The gastrointestinal digestibility was calculated using the following formula: Gastric digestibility is expressed as the percentage change in free amino acid content before and after gastric digestion. Intestinal digestibility is expressed as the percentage change in free amino acid content before and after intestinal digestion. Gastric digestibility and intestinal digestibility are calculated as follows: 7. Release rate of VD3 and calcium citrate After gastric digestion, the calcium ion release rate of the sample was determined by ICP using the same method as for the calcium citrate entrapment determination. Samples were taken every 30 minutes to determine the amount of vitamin D3. The vitamin D3 release rate was measured by UV spectrophotometry using the same method as for the vitamin D3 entrapment determination.

[0040] The results are shown in Table 1 and Figures 1 to 4 shown.

[0041] Table 1 Test results of composite gel properties obtained in various examples and comparative examples As shown in Table 1, the composite gels prepared in the Examples exhibited higher VD3 and calcium citrate encapsulation efficiencies, as well as higher gel and melt temperatures, compared to Comparative Examples 1-3. Cross-linked Examples 3-6 exhibited lower gastrointestinal digestion compared to Examples 1-2 and Comparative Examples 1-3, demonstrating resistance to digestion. Highly cross-linked Examples 4-6 formed a thermally irreversible state, maintaining a gel state. Comparative Example 1-2, lacking the presence of fish protein gel, remained in a solution state, making it impossible to measure gel and melt temperatures.

[0042] Depend on Figure 1 It can be seen that the VD3 in the enzyme-crosslinked fish protein gelatin composite gel of the present invention is at 3000–2800 cm -1 The C–H stretching vibration band disappears at 1350–650 cm -1 The spectral peak simplification phenomenon appears in the fingerprint region, indicating that VD3 is well encapsulated.

[0043] Figure 2 From left to right are listed as follows: Comparative Example 1, Comparative Example 2, Comparative Example 3, Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Figure 2 It can be seen that the stability of the examples is stronger than that of the comparative example, among which Examples 4-5 with a high degree of cross-linking can always remain in a gel state without precipitation of VD3 and calcium citrate.

[0044] Depend on Figure 3 、 4 As can be seen, the free Comparative Examples 1-2 almost completely released VD3 and calcium citrate at the beginning of gastrointestinal digestion, while VD3 activity decreased to a certain extent, with Comparative Example 1 being completely inactivated at the end of gastric digestion. However, as the degree of cross-linking increased, the ability to sustainably release VD3 and calcium citrate against digestion significantly improved, and compared to Comparative Example 1, it also maintained a certain level of VD3 activity protection.

[0045] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A fish protein gel composite gel of sustained-release vitamin D3 and calcium citrate, characterized in that: The fish protein glue composite gel comprises the following raw materials in parts by weight: 9.0-10.0 parts of fish protein glue, 2.0-3.0 parts of maltodextrin, 0.7-0.9 parts of calcium citrate, 0.003-0.005 parts of vitamin D3, and 85.9-88.2 parts of deionized water.

2. The fish protein glue composite gel according to claim 1, characterized in that The amount of each raw material added is as follows: 9.0-10.0 parts of fish protein glue, 2.0-3.0 parts of maltodextrin, 0.8 part of calcium citrate, 0.004 parts of VD3, and 85.9-88.2 parts of deionized water.

3. The fish protein glue composite gel according to claim 1 or 2, characterized in that The fish protein glue composite gel is also calculated by weight The invention comprises the following raw materials: 0.15-0.3 parts of MTGase.

4. The fish protein glue composite gel according to claim 3, characterized in that The amount of MTGase added is 0.2-0.3 parts by weight.

5. The fish protein glue composite gel according to claim 3, characterized in that The amount of MTGase added is 0.25 parts by weight.

6. The method for preparing the fish protein glue composite gel according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: S1, add deionized water to the mixed fish protein glue and calcium citrate, heat and stir to completely dissolve them to obtain a first solution; S2. Add deionized water to the evenly mixed maltodextrin and VD3, heat and stir until the maltodextrin and VD3 are completely dissolved to obtain a second solution; S3, mixing the first solution and the second solution uniformly to obtain a third solution; S4. Let the third solution stand to obtain a fish protein gel composite gel.

7. The preparation method according to claim 6, characterized in that When the raw materials further include MTGase, step S4 specifically includes: S4. Add MTGase to the third solution to react. After the reaction is completed, inactivate the enzyme and allow the mixture to stand to obtain a fish protein gel composite gel.

8. The preparation method according to claim 6 or 7, characterized in that In steps S1 and S2, the heating temperature is 35-45°C.

9. The preparation method according to claim 6 or 7, characterized in that: In step S3, a disperser is used to mix uniformly at 10,000 to 14,000 rpm / min for 1 to 3 minutes.

10. The preparation method according to claim 7, characterized in that In step S4, when the raw materials also include MTGase, the reaction time is 1.5-2.5 h, the enzyme is inactivated at 100° C. for 4-6 min, and the mixture is quickly taken out and allowed to stand at 4° C.

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