Method for improving comprehensive performance of fish protein glue composite membrane and fish protein glue composite membrane

Abstract

The invention discloses a method for improving the comprehensive performance of a fish protein glue composite film and the fish protein glue composite film, and relates to the technical field of food film package preparation. The preparation method comprises the following steps: S1, mixing a fish protein glue solution, a gellan gum solution and a microbial glutamine transaminase solution to obtain a first mixed solution; s2, adding glycerol into the first mixed solution, and stirring to obtain a second mixed solution; s3, the second mixed solution is placed in a mold, crosslinking and drying are conducted at the preset temperature and the preset humidity at the same time, demolding is conducted, and the fish protein glue composite film is obtained. When the fish protein glue prepared by the method provided by the invention is applied to the manufacturing process of the film, the safety performance of the film can be effectively improved, the advantage of degradability is beneficial to environmental protection, and in addition, the film produced by adopting the fish skin protein glue has the advantages of degradability, edibility, good comprehensive performance and the like.

Description

Technical Field

[0001] This invention relates to the field of food film packaging technology, specifically to a method for improving the overall performance of fish protein glue composite film and the fish protein glue composite film. Background Technology

[0002] With increasing public and researcher concern about food packaging safety and environmental protection, traditional plastic films are gradually being replaced by biodegradable alternatives, among which edible protein-based films have emerged as a promising solution. Fish protein gelatin is an attractive alternative, possessing physicochemical properties comparable to those of mammals while maintaining cost-effectiveness. However, the practical implementation of fish protein gelatin remains challenged by its inherently low imino acid content (proline and hydroxyproline), which directly compromises the mechanical strength and thermal stability of the derived films—critical parameters for food packaging applications.

[0003] Currently, the modification strategies for fish protein gels include enzymatic, chemical, and physical methods. However, the overall performance of fish protein gels modified by existing technologies is generally poor, especially in terms of mechanical and barrier properties, making them prone to damage or oxygen permeation during use. Therefore, it is necessary to improve the overall performance of fish protein gel composite membranes to expand their application range. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a method for improving the overall performance of fish protein glue composite membranes and a fish protein glue composite membrane itself. To address the aforementioned technical challenges, this invention achieves better overall performance of fish protein glue composite membranes through composite modification and in-situ crosslinking. By constructing a multi-dimensional index system encompassing mechanical properties, barrier properties (water vapor, ultraviolet light, and oxygen), structural characterization (Fourier transform infrared spectroscopy and X-ray diffraction), scanning electron microscopy, and thermal performance analysis (differential scanning calorimetry and thermogravimetric analysis), a method for scalable preparation of improved fish protein glue composite membranes is proposed.

[0005] Microbial transglutaminase, as a highly efficient enzyme cross-linking agent, can catalyze the reaction between the ε-amino group of lysine residues and the γ-carboxamide group of glutamine residues in proteins, forming GL covalent bonds between intramolecular and intermolecular cross-links. Gellan gum is a polysaccharide fermented by microorganisms, mainly composed of glucose, glucuronic acid, and rhamnose in a 2:1:1 ratio. It is a linear polysaccharide composed of four monosaccharides as repeating structural units. The inventors discovered that using microbial transglutaminase and gellan gum can effectively improve the performance of fish protein gel composite membranes.

[0006] Typically, the reaction temperature for crosslinking fish protein gel with microbial transglutaminase is around 50°C, followed by enzyme inactivation with boiling water. However, at this temperature (90-100°C), protein structure may change, for example, from a more stable triple helix to an unstable single helix, which has certain limitations. Therefore, in this invention, a strategy combining gellan gum-microbial transglutaminase composite modification and in-situ crosslinking is adopted to improve the overall performance of fish protein gel films. Unlike traditional continuous methods, this innovative approach synchronizes crosslinking with film dehydration: as the substrate undergoes controlled drying, the enzyme activity of microbial transglutaminase gradually decreases with the reduction of moisture, eliminating the need for a separate inactivation step. The in-situ strategy has three significant advantages: First, by eliminating the separate water bath crosslinking step, it can shorten the time. Second, it avoids the risk of protein denaturation caused by traditional high-temperature enzyme inactivation treatment, effectively maintaining the integrity of the native conformation. More importantly, in-situ crosslinking may lead to more complete crosslinking, promoting the formation of a denser three-dimensional crosslinked network. This provides a new approach for developing efficient and environmentally friendly fish protein gel composite film modification processes.

[0007] The technical solution of the present invention is as follows:

[0008] The first aspect of the present invention provides a method for improving the overall performance of fish protein adhesive composite films, comprising the following steps:

[0009] S1. Mix the fish protein gel solution, gellan gum solution, and microbial transglutaminase solution to obtain the first mixed solution;

[0010] S2. Add glycerol to the first mixed solution and stir to obtain a second mixed solution;

[0011] S3. Place the second mixed solution in a mold, crosslink and dry it at a preset temperature and humidity, then demold to obtain the fish protein glue composite film.

[0012] In a preferred embodiment of the present invention, in step S1, the fish protein gel solution, gellan gum solution, and microbial transglutaminase solution are added in a volume ratio of 1:1:1.

[0013] In a preferred embodiment of the present invention, in step S1, the mass concentration of the fish protein gel solution is 21%.

[0014] In a preferred embodiment of the present invention, in step S1, the mass concentration of the gellan gum solution is 0.3%.

[0015] In a preferred embodiment of the present invention, in step S1, the mass concentration of the microbial transglutaminase solution is 0.3%.

[0016] In a preferred embodiment of the present invention, in step S2, the amount of glycerol added is 30% of the mass of the fish protein gel.

[0017] In a preferred embodiment of the present invention, in step S3, the preset temperature is 50°C, the preset humidity is 50%, and the time for cross-linking and drying is 10 hours.

[0018] A second aspect of the present invention provides a fish protein glue composite film, which is prepared by the above method, wherein the fish protein glue composite film is an amorphous polymer.

[0019] The product prepared by this invention exhibits excellent overall properties. Specifically, the tensile strength of the gellan gum-microbial transglutaminase in-situ crosslinked fish protein gel film is increased by 92.35% compared to the original fish protein gel film, and its transmittance at 280 nm is only 18.55%, demonstrating optimal mechanical properties and UV resistance. Correspondingly, the water vapor permeability decreases from 50.88% to 28.38%, and the peroxide value decreases from 4.81 meq / kg to 3.17 meq / kg, exhibiting optimal water vapor and oxygen barrier properties.

[0020] In a preferred embodiment of the present invention, the fish protein gel composite film has a transmittance of 18.55% at 280 nm.

[0021] In a preferred embodiment of the present invention, the peroxide value of the fish protein gel composite film is 3.17 meq / kg.

[0022] This invention has at least one of the following beneficial effects:

[0023] 1. A strategy combining gellan gum-microbial transglutaminase composite modification and in-situ crosslinking was adopted to improve the overall performance of the film. On the one hand, gellan gum and microbial transglutaminase have a synergistic effect, which helps the raw materials to fully crosslink, thus making the protein gel film exhibit larger and denser aggregates. Furthermore, the intermolecular interaction between the covalent crosslinking molecules of gellan gum and microbial transglutaminase helps to enhance the stability of the structure. On the other hand, unlike traditional continuous methods, this invention innovatively performs crosslinking and film dehydration simultaneously, i.e., in-situ crosslinking. As the substrate undergoes controlled drying, the enzyme activity of microbial transglutaminase gradually weakens with the reduction of moisture, eliminating the need for a separate inactivation step. In-situ crosslinking not only shortens the time but also avoids the risk of protein denaturation caused by traditional high-temperature enzyme inactivation treatment, effectively maintaining the integrity of the natural conformation of the fish protein gel. More importantly, in-situ crosslinking may lead to more complete crosslinking, promoting the formation of a denser three-dimensional crosslinked network.

[0024] 2. This invention solves the problems of low mechanical strength, poor barrier properties, and poor thermal performance of fish protein glue composite films by optimizing the cross-linking method of microbial transglutaminase. Specifically, the in-situ cross-linking strategy of gellan gum-microbial transglutaminase significantly improves the overall performance of the fish protein glue film. The tensile strength of the gellan gum-microbial transglutaminase in-situ cross-linked fish protein glue film is increased by 92.35% compared to the original fish protein glue film, and the transmittance at 280 nm is only 18.55%, exhibiting optimal mechanical properties and UV resistance. Correspondingly, the water vapor permeability decreases from 50.88% to 28.38%, and the peroxide value decreases from 4.81 meq / kg to 3.17 meq / kg, demonstrating optimal water vapor and oxygen barrier performance. Attached Figure Description

[0025] Figure 1 The tensile strength of the microbial glutamine transaminase and gellan gum modified fish protein glue composite film in the example of this invention.

[0026] Figure 2 The water vapor permeability of the microbial glutamine transaminase and gellan gum modified fish protein gel composite membrane in the example of this invention.

[0027] Figure 3 The light transmittance of the microbial glutamine transaminase and gellan gum modified fish protein glue composite film in the example of the present invention.

[0028] Figure 4 This refers to the oxygen barrier properties of the microbial glutamine transaminase and gellan gum-modified fish protein gel composite membrane in this invention example.

[0029] Figure 5 The Fourier transform infrared spectrum of the microbial glutamine transaminase and gellan gum-modified fish protein gel composite membrane in this invention example is shown.

[0030] Figure 6 X-ray diffraction of the microbial glutamine transaminase and gellan gum-modified fish protein gel composite membrane in the example of this invention.

[0031] Figure 7 Differential calorimetry scanning is used to measure the microbial transglutaminase and gellan gum-modified fish protein gel composite membrane in this invention example.

[0032] Figure 8 Thermogravimetric analysis of the microbial glutamine transaminase and gellan gum-modified fish protein gel composite membrane in this invention example.

[0033] Figure 9 This is a scanning electron microscope image of the microbial glutamine transaminase and gellan gum-modified fish protein gel composite membrane in an example of the present invention. Detailed Implementation

[0034] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0035] Example 1

[0036] 1. Materials and Methods

[0037] 1.1 Experimental Materials

[0038] Fish protein gel (from a company in Jiangsu); gellan gum (from a company in Jiangxi); microbial transglutaminase (from a company in Jiangsu); deionized water was used in the experiment.

[0039] 1.2 Experimental Methods

[0040] Solutions of fish protein gelatin, microbial transglutaminase, and gellan gum were prepared at mass concentrations of 21%, 0.3%, and 0.3%, respectively. For combined modification with microbial transglutaminase and gellan gum, the three solutions were uniformly mixed in a 1:1:1 volume ratio. If modification was performed solely with microbial transglutaminase or gellan gum, the corresponding amount of water was added following the same steps. Additionally, 30% glycerol (based on the mass of fish protein gelatin) was added as a plasticizer, and the mixture was stirred until homogeneous. Subsequently, the solution containing microbial transglutaminase was divided into two groups. One group was crosslinked in a 50°C water bath for 60 minutes, followed by enzyme inactivation by heating at 90°C for 10 minutes. The other group was directly placed in an incubator and dried during crosslinking. Finally, the prepared film-forming solution was poured into 90mm × 90mm plastic petri dishes and dried in an incubator at 50°C and 50% RH for 10 hours to obtain the composite membrane sample. After drying, all composite membrane samples were placed in a drying container with a relative humidity of 50% for 48 hours to equilibrate, and then the membrane was peeled off to test the performance of the composite membrane.

[0041] Specifically, the experimental design is divided into 6 groups, and the specific experimental procedures for the 6 groups are as follows:

[0042] FG group (i.e., pure fish protein gel film group): Add 21% fish protein gel solution to twice the volume of water, then add 30% glycerol (calculated by the mass of fish protein gel), incubate in a water bath at 50°C for 60 minutes, and then heat at 90°C for 10 minutes.

[0043] FG-MTG group (i.e., microbial transglutaminase single modification + traditional cross-linked fish protein gel film group): 21% fish protein gel solution, 0.3% microbial transglutaminase and an equal volume of water were mixed, and then 30% glycerol (calculated according to the mass of fish protein gel) was added. The mixture was mixed evenly and cross-linked in a 50°C water bath for 60 minutes. Then the enzyme was inactivated by heating at 90°C for 10 minutes.

[0044] FG-MTG-IS group (i.e., microbial transglutaminase single modification + in-situ cross-linked fish protein gel film group): 21% fish protein gel solution, 0.3% microbial transglutaminase and an equal volume of water were mixed, and then 30% glycerol (calculated according to the mass of fish protein gel) was added. The mixture was mixed evenly and dried in an incubator at 50℃ and 50% RH for 10 hours.

[0045] FG-GG group (i.e., gellan gum single-modified fish protein gel film group): Mix 21% fish protein gel solution, 0.3% gellan gum solution and an equal volume of water, then add 30% glycerol (calculated according to the mass of fish protein gel), mix well, and dry in an incubator at 50℃ and 50%RH for 10 hours.

[0046] FG-GG-MTG group (i.e., composite modification + traditional cross-linked fish protein gel film group): 21% fish protein gel solution, 0.3% microbial transglutaminase and 0.3% gellan gum solution are mixed, and then 30% glycerol (calculated according to the mass of fish protein gel) is added. The mixture is mixed evenly and cross-linked in a 50°C water bath for 60 minutes. Then, the enzyme is inactivated by heating at 90°C for 10 minutes.

[0047] FG-GG-MTG-IS group (i.e., composite modification + in-situ cross-linked fish protein gel film group): Mix 21% fish protein gel solution, 0.3% microbial transglutaminase and 0.3% gellan gum solution, then add 30% glycerol (calculated according to the mass of fish protein gel), mix evenly, and dry in an incubator at 50℃ and 50% RH for 10 hours.

[0048] 1.3 Tensile Strength

[0049] The film was cut into strips of 20 mm × 50 mm, and the tensile strength of the composite film samples was tested using a texture analyzer. The initial distance was set to 30 mm, the tensile rate to 1 mm / s, and the trigger force to 5 g.

[0050] 1.4 Water vapor permeability

[0051] Anhydrous calcium chloride was divided into small beakers of equal size, then dried in an oven at 105°C to constant weight, and the mouths of the beakers were covered with a thin film. The small beakers were placed in a sealed glass container with a small amount of water at the bottom, and the ambient temperature was kept constant at 25°C. The weight of the beakers was recorded every 12 hours.

[0052] 1.5% light transmittance

[0053] The film was cut into strips of 1 cm × 5 cm in length and scanned in the wavelength range of 200-800 nm using a UV-Vis spectrophotometer to determine the transmittance of the film in the UV and visible wavelength range.

[0054] 1.6 Determination of oxygen barrier properties

[0055] Place peanut oil in a small beaker and seal the mouth of the beaker with a thin film. Place the small beaker in a 50℃, 70% RH incubator to accelerate oxidation. Peanut oil peroxidation was evaluated using the iodine titration method according to the People's Republic of China National Standard GB / T5009.227-2016 (General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, 2016). Dissolve 2g of peanut oil in 30mL of a 2:3 (v / v) mixture of acetic acid and chloroform, then add 1mL of saturated potassium iodide and shake in the dark for 3 minutes. Then, add 100mL of distilled water and 1mL of starch indicator to the mixture. Titrate the solution with 0.002mol / L sodium thiosulfate until the blue color disappears and record the amount of sodium thiosulfate consumed.

[0056] 1.7 Fourier Infrared Spectroscopy

[0057] The interactions between components in the thin film were analyzed using total reflectance infrared spectroscopy. The thin film sample, dried in a silica gel desiccator for 48 hours, was placed in the sample chamber. The infrared wavenumber range was set to 4000–400 cm⁻¹. -1 The resolution is set to 4cm. -1 The Fourier transform infrared spectrum of the composite membrane was analyzed after scanning equilibrium.

[0058] 1.8X-ray diffraction

[0059] Different thin film patterns were obtained using X-ray diffraction. Cu Kα radiation was used. Each sample was scanned at 40 kV and 30 mA at a scan rate of 0.05° / s at a diffraction angle of 2θ from 3° to 60°.

[0060] 1.9 Scanning electron microscope

[0061] The film morphology was characterized using scanning electron microscopy. Before observation, a layer of gold was coated onto the sample in a vacuum and fixed to the stage with double-sided tape. Each sample was transferred to a cold stage and observed at an accelerating voltage of 10 kV and a magnification of 5000.

[0062] 1.10 Differential Calorimetry Scan

[0063] Thermal properties were characterized using a differential calorimeter. Before measurement, each 3-4 mg sample was conditioned in a drying container for 7 days. Heating was performed at a rate of 10 °C / min over a temperature range of 20 °C to 220 °C. Nitrogen gas was introduced at a flow rate of 20 cm⁻¹. 3 A flow rate of / min is used to blow air into the sample chamber.

[0064] 1.11 Thermogravimetric Analysis

[0065] Thermogravimetric analysis (TGA) was performed on the films from the same batch. Approximately 5-10 mg of film sample was accurately weighed and placed in an alumina crucible. Under a nitrogen atmosphere, a heating program from 30°C to 600°C was used at a rate of 10°C / min. -1 The rate was analyzed.

[0066] 2 Results and Analysis

[0067] 2.1 Tensile Strength Analysis

[0068] Mechanical properties are one of the key factors determining the quality and specific application of thin films. Figure 1 It was found that the tensile strength of the composite-modified fish protein gel films (FG-GG-MTG group, FG-GG-MTG-IS group) was significantly higher than that of the single-modified films (FG-MTG group, FG-MTG-IS group, and FG-GG group) and the pure fish protein gel film (FG group), indicating that composite modification can significantly improve the tensile strength of the film. Furthermore, based on the composite modification, the in-situ crosslinked film (FG-GG-MTG-IS group) showed significantly higher tensile strength than the conventionally crosslinked film (FG-GG-MTG group), reaching a maximum value that was 92.35% higher than the pure fish protein gel film (FG group). This may be due to the combined effect of the formation of denser covalent and hydrogen bonds between microbial transglutaminase, gellan gum, and fish protein gel.

[0069] 2.2 Water vapor permeability analysis

[0070] Generally, the film needs to have low water vapor permeability to slow down food spoilage.

[0071] like Figure 2 As shown, the water vapor permeability of the in-situ crosslinked fish protein glue composite membrane (FG-GG-MTG-IS group) was significantly lower than that of the conventional crosslinking method (FG-GG-MTG group). This is because in-situ crosslinking may produce a denser network structure, thereby preventing water vapor diffusion. Furthermore, among the fish protein glue composite membranes modified with gellan gum, the in-situ crosslinked membrane exhibited the best water vapor permeability, significantly higher than that of the conventional crosslinking method, and 27.08% lower than that of the pure fish protein glue composite membrane. These results indicate that in-situ crosslinking based on composite modification can effectively improve the water resistance of fish protein glue composite membranes.

[0072] 2.3 Analysis of UV Resistance

[0073] Food packaging should have a certain degree of resistance to ultraviolet radiation to slow down food spoilage and maintain its nutritional value. For example... Figure 3As shown, all films exhibited strong UV blocking capabilities in the 200-280 nm wavelength range, with transmittance values ​​below 50%. The pure fish protein gel film had a transmittance of 43.27% at 280 nm, while the transmittance levels of the microbial transglutaminase modified films (traditional crosslinking and in-situ crosslinking) were significantly reduced, at 22.21% and 20.13%, respectively. Notably, based on gellan gum modification, the transmittance of the microbial transglutaminase conventional crosslinking and in-situ crosslinking were 19.13% and 18.65%, respectively, with the gellan gum-microbial transglutaminase in-situ crosslinking exhibiting the best UV shielding performance. This may be attributed to the covalent bonds generated by crosslinking leading to a tighter structure, or it may be due to the exposure of more aromatic amino acids, such as phenylalanine and tyrosine, after crosslinking, which have strong absorption capabilities in the 200-300 nm range.

[0074] 2.4 Peroxide value analysis

[0075] Peroxide value is a key indicator reflecting the oxygen barrier effectiveness of packaging materials. For example... Figure 4 As shown, the pure fish protein gelatin composite membrane exhibited the highest peroxide value, reaching 4.81 meq / kg, indicating poor oxygen barrier performance. The films modified with microbial transglutaminase (TCT) (both conventional and in-situ crosslinking) showed significantly improved oxygen resistance, with peroxide values ​​decreasing to 4.47 meq / kg and 4.28 meq / kg, respectively. Further optimization was achieved through compound modification, reducing the peroxide value of gellan gum-microbial transglutaminase conventional and in-situ crosslinking membranes to 3.51 meq / kg and 3.17 meq / kg, respectively. We can reasonably hypothesize that the free volume within the fish protein gelatin composite membrane is significantly reduced under the combined modification of microbial transglutaminase and gellan gum, thereby blocking oxygen permeation, and that in-situ crosslinking exhibits the best oxygen barrier performance.

[0076] 2.5 Fourier transform infrared spectrum

[0077] observe Figure 5 As can be seen, all spectra exhibit similar patterns, confirming that the interaction between fish protein gel and gellan gum or microbial transglutaminase does not disrupt the functional groups of the basic fish protein gel. In all fish protein gel films, the amide A band appears at approximately 3299 cm⁻¹. -1 This is attributed to the stretching vibrations of the OH and NH groups. The spectra of all samples show a range of 1700–1600 cm⁻¹. -1 (Amide I) and 1590-1500cm -1 The main absorption bands in the amide region of (amide II). Within these absorption bands, 1600-1700 cm⁻¹... -1 The amide I band between 1700-1600 cm⁻¹ is the most useful peak for infrared analysis of protein secondary structure.-1 In the amide I band, the peak of pure fish protein gel is 1644.3 cm⁻¹. -1 The in-situ cross-linking of gellan gum and microbial transglutaminase reached 1638.1 cm. -1 The results confirmed that the addition of microbial transglutaminase and gellan gum induced covalent and non-covalent crosslinking of the fish protein gel film.

[0078] 2.6X-ray diffraction

[0079] observe Figure 6 It was observed that all the films exhibited broad diffraction peaks only around 2θ = 22°, confirming that they are amorphous polymers. Although the peak positions remained unchanged across different treatments, significant variations in peak intensity were observed. The peak intensity of the fish protein gel film modified with microbial transglutaminase increased significantly (both conventional and in-situ crosslinking). Furthermore, the peak intensity was highest in the gellan gum-microbial transglutaminase in-situ crosslinking. This can be attributed to the non-covalent and covalent crosslinking of gellan gum and microbial transglutaminase leading to polymerization of the fish protein gel, forming larger polymers. This helps reduce the porosity of the protein network structure and increase its crystallinity.

[0080] 2.7 Scanning Electron Microscope

[0081] The morphology of a thin film fundamentally determines its corresponding physical and chemical properties. Observation Figure 7 It was found that, compared with pure fish protein gel film, the images of fish protein gel film modified with microbial transglutaminase showed larger and denser particles. In addition, the gellan gum-microbial transglutaminase modified fish protein gel film exhibited larger and denser aggregates, with the most dense in-situ crosslinking, which can be attributed to the synergistic effect of gellan gum and microbial transglutaminase.

[0082] 2.8 Differential Calorimetry Scan

[0083] The thermal properties of films are crucial for their application in the food and pharmaceutical industries, as packaging materials are frequently subjected to heating processes during product manufacturing and consumption. Figure 8 The thermodynamic curves of the thin film are shown, and the highest thermal transition temperature (T0) is analyzed. m ).like Figure 8 As shown, the T-type of pure fish protein gel film m Compared to (79.755℃), the T of fish protein membrane modified with microbial transglutaminase... m The temperature increased significantly, reaching 81.173℃ with the traditional method and 86.039℃ with in-situ crosslinking. The fish protein gel film T with in-situ crosslinking of gellan gum and microbial transglutaminase was... mIt reached a maximum temperature of 127.857℃. This can be attributed to the synergistic effect of microbial transglutaminase and gellan gum, where covalent cross-linking and intermolecular interactions contribute to enhancing structural stability, thereby leading to T m The increase.

[0084] 2.9 Thermogravimetric Analysis

[0085] Thermogravimetric analysis (TGA) can assess the thermal degradation behavior of samples and effectively evaluate the thermal stability of thin films. The curves are shown below. Figure 9 As shown, the process consists of three main thermal decomposition regions: 30-150℃, 150-400℃, and 400-600℃. In the second stage, it is associated with the loss of low molecular weight protein components in the film and the evaporation and degradation of glycerol used as a plasticizer. In this stage, the mass loss of the pure fish protein gelatin film is approximately 71.57%. The mass loss of the fish protein gelatin film modified with microbial transglutaminase is approximately 69.19% and 68.97% (traditional crosslinking and in-situ crosslinking), respectively. Furthermore, in the composite modification, the loss rates of traditional crosslinking and in-situ crosslinking further decrease, reaching 68.23% and 67.22%, respectively. This can be attributed to the covalent and hydrogen bond interactions between microbial transglutaminase and gellan gum with fish protein gelatin molecules.

[0086] This invention addresses the problems of low mechanical strength, poor barrier properties, and poor thermal performance of fish protein glue composite films by optimizing the cross-linking method of microbial transglutaminase. Specifically, the in-situ cross-linking strategy of gellan gum-microbial transglutaminase significantly improves the overall performance of the fish protein glue film. The tensile strength of the gellan gum-microbial transglutaminase in-situ cross-linked fish protein glue film is increased by 92.35% compared to the original fish protein glue film, and the transmittance at 280 nm is only 18.55%, exhibiting optimal mechanical properties and UV resistance. Correspondingly, the water vapor permeability decreases from 50.88% to 28.38%, and the peroxide value decreases from 4.81 meq / kg to 3.17 meq / kg, demonstrating optimal water vapor and oxygen barrier properties. Furthermore, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy were used to confirm the covalent and non-covalent cross-linking effects of the gellan gum-microbial transglutaminase in-situ cross-linking on the fish protein glue film. Finally, differential scanning calorimetry and thermogravimetric analysis confirmed that the fish protein gel film cross-linked with gellan gum-microbial transglutaminase in situ had the best thermal properties.

[0087] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the overall performance of fish protein adhesive composite films, characterized in that, Includes the following steps: S1. Mix the fish protein gel solution, gellan gum solution, and microbial transglutaminase solution to obtain the first mixed solution; S2. Add glycerol to the first mixed solution and stir to obtain a second mixed solution; S3. Place the second mixed solution in a mold, crosslink and dry it at a preset temperature and humidity, then demold to obtain the fish protein glue composite film.

2. The method according to claim 1, characterized in that, In step S1, the fish protein gel solution, gellan gum solution, and microbial transglutaminase solution are added in a volume ratio of 1:1:

1.

3. The method according to claim 1, characterized in that, In step S1, the mass concentration of the fish protein gel solution is 21%.

4. The method according to claim 1, characterized in that, In step S1, the mass concentration of the gellan gum solution is 0.3%.

5. The method according to claim 1, characterized in that, In step S1, the mass concentration of the microbial transglutaminase solution is 0.3%.

6. The method according to claim 1, characterized in that, In step S2, the amount of glycerol added is 30% of the mass of the fish protein gel.

7. The method according to claim 1, characterized in that, In step S3, the preset temperature is 50℃, the preset humidity is 50%, and the time for cross-linking and drying is 10 hours.

8. A fish protein gel composite film, characterized in that, The fish protein gel composite film is prepared by the method according to any one of claims 1 to 7, wherein the fish protein gel composite film is an amorphous polymer.

9. The fish protein gel composite film according to claim 8, characterized in that, The fish protein gel composite film has a transmittance of 18.55% at 280 nm.

10. The fish protein gel composite film according to claim 8, characterized in that, The peroxide value of the fish protein gel composite film is 3.17 meq / kg.

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