An easily dispersible water-retaining agent, its preparation method and application

Abstract

This invention belongs to the field of hydrogel material preparation technology, specifically relating to the preparation and application of an easily dispersible water-retaining agent. The water-retaining agent can be prepared through a simple operation. It is composed of gelatin and vanillin. Due to the grafting effect of vanillin and gelatin, this invention significantly prolongs the solidification time of the gelatin solution, giving the water-retaining agent good fluidity for a longer period, allowing it to be mixed into the application system via injection. Furthermore, through the cross-linking action of transglutaminase, it catalyzes the covalent cross-linking of gelatin chains, making it different from other gelatin gels; it does not melt upon heating after cooling and solidification, exhibiting thermal stability. This water-retaining agent, with its easily dispersible and thermally irreversible properties, has advantages in the mechanical mixing of application systems, which is beneficial for improving the structure of applied products and is expected to be widely used in food pre-processing, biomedical materials, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a method for preparing and applying an easily dispersible water-retaining agent. Background Technology

[0002] Hydrogels are hydrophilic three-dimensional cross-linked polymeric networks that contain large amounts of water or biological fluids without losing their structure, exhibiting a strong ability to absorb and retain water. Gelatin is currently the most commonly used protein material for forming food hydrogels. It is a mixture of different polypeptide chains formed by the partial hydrolysis of collagen. Collagen can be converted into gelatin by cleaving the hydrogen bonds and covalent bonds in collagen, thereby transforming the stable triple-helix form of collagen into a coiled, soluble gelatin. Water-retaining agents enhance water retention in food systems and participate in the system's framework, acting as heat transfer media during processing and end-use.

[0003] The dispersion state of ingredients in a food formulation is crucial for the uniformity of overall texture and mouthfeel. Gelatin solutions solidify at room temperature, and solidified gelatin is not conducive to its dispersion in food systems. While heating can melt it, it can cause other food components to mature prematurely. Therefore, direct heating is not advisable during ingredient homogenization. When gelatin forms a gel network, hydroxyproline and proline stabilize the ordered network conformation. However, the melting point of gelatin gel is only around 25–31°C. As the temperature rises, the gel state transforms into a molten colloidal state, causing gelatin to be lost from the food components.

[0004] Gelatin is composed of 18 amino acids, of which approximately 57% are glycine, proline, and hydroxyproline. Its main characteristic is the repeated "glycine-XY sequence," where "X" is usually proline and "Y" is primarily hydroxyproline. The gel network formed by gelatin relies mainly on the stable and ordered conformation of hydroxyproline and proline. However, low levels of hydroxyproline and proline in gelatin can lead to lower gel strength, gelation temperature, and melting temperature. Therefore, modification of gelatin is essential to improve its functional properties. Gelatin modification methods include enzymatic methods, chemical methods, and mechanical treatment.

[0005] Pre-cooked dishes generally refer to semi-finished or finished products made from various agricultural, livestock, poultry, and aquatic products as raw materials, combined with food additives, and processed through pre-selection, preparation, and other techniques. Pre-cooked minced meat products are typically made from muscle and fat tissue with added salt, spices, and other ingredients, through a series of processing steps including chopping, cooling, heating, and packaging. A common challenge with pre-cooked minced meat products is their coarse texture and loose structure, primarily due to moisture loss. In actual production, food moisture retention agents are usually added. These agents are quality improvers, often referring to phosphates used in meat and aquatic product processing to enhance moisture stability and water retention. However, phosphate-based moisture retention agents may pose health risks. Excessive phosphate intake can lead to abnormal calcium and phosphorus metabolism, causing problems such as decreased blood calcium levels; furthermore, the introduction of salt-based moisture retention agents is detrimental to reducing or controlling salt content in food. In comparison, edible gelatin, as a gelling agent, does not introduce the side effect of high salt content and can increase the protein content of food. In meat processing, the application of edible gelatin can improve the physical properties of meat products, increase their binding and water-holding capacity, and give them a better texture. However, gelatin encounters new problems in culinary applications. Firstly, gelatin solutions gradually solidify when left to stand at room temperature. Secondly, gelatin gels have poor thermal stability; when the temperature rises, the triple helix structure and chemical-physical three-dimensional network in the gelatin gel decompose, and the gelled state transitions to a fluid state. Therefore, the design of pre-prepared dishes containing gelatin needs to consider how to address these gelatin-related issues. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an easily dispersible water-retaining agent, which improves the fluidity of gelatin at room temperature by grafting vanillin and gelatin.

[0008] Accordingly, the present invention also provides a method for preparing an easily dispersible water-retaining agent and its application. The preparation method is simple and low in cost, and is suitable for industrial production.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] In a first aspect, the present invention provides an easily dispersible water-retaining agent, which is mainly made of the following raw materials: gelatin and vanillin.

[0012] Optionally, the water-retaining agent is formed by grafting vanillin functional groups onto gelatin molecules.

[0013] In this invention, vanillin, chemically named 4-hydroxy-3-methoxybenzaldehyde, has the structural formula shown below.Figure 1 .

[0014] Vanillin can modify fish skin gelatin, extending its setting time at room temperature and improving its fluidity. Furthermore, the introduction of specific groups from vanillin can further enhance the antibacterial and antioxidant properties of gelatin.

[0015] Vanillin and gelatin can interact non-covalently. The hydroxyl groups attached to the benzene ring of vanillin interact with the carboxyl groups of gelatin through hydrogen bonds, thereby improving the functional properties of gelatin. Vanillin may interact with the carboxyl groups of gelatin through hydrogen bonds, and its structural characteristics of hydrophobic interaction with the hydrophobic side chains of gelatin may also lead to self-assembly grafting with gelatin, delaying the cross-linking of molecular chains and improving the fluidity of gelatin solutions.

[0016] This invention further modifies gelatin through enzymatic and chemical methods. The gelatin can interact via non-covalent bonds (hydrophobic, ionic, and hydrogen bonds) or covalent bonds.

[0017] The present invention further describes the grafting of vanillin functional groups onto gelatin molecular chains under ultrasonic, stirring, and water bath heating conditions.

[0018] Experiments have shown that the water-retaining agent obtained by this invention gradually solidifies after standing at room temperature for 30 minutes, while the gelatin solution solidifies after standing at room temperature for 15 minutes.

[0019] Optionally, the raw materials may further include: tea polyphenols and / or transglutaminase.

[0020] Tea polyphenols, derived from tea leaves, are mixtures containing various organic polyhydroxy compounds, including catechins, anthocyanins, flavonols, and phenolic acids. In the non-covalent interaction between gelatin and polyphenols, polyphenols are excellent hydrogen donors, capable of forming hydrogen bonds with the carbonyl groups of proteins. The gelatin of this invention, under the combined action of tea polyphenols and vanillin, alters its chemical properties, resulting in a significantly longer setting time at room temperature; this extension is more pronounced than that achieved solely through the action of tea polyphenols or vanillin. Tea polyphenols and vanillin may act on gelatin through different mechanisms, thereby resulting in significantly stronger fluidity at room temperature for the same molar amount of gelatin, demonstrating a synergistic effect. Simultaneously, tea polyphenols and vanillin in this invention also synergistically enhance antibacterial and antioxidant effects.

[0021] Optionally, vanillin is 0.15 to 0.30% of the gelatin mass;

[0022] Optionally, the tea polyphenols are 0.8–0.15% of the gelatin mass;

[0023] This invention further utilizes transglutaminase (MTGase) to achieve acyl transfer, cross-linking, and deamidation of gelatin molecular chains, promoting covalent cross-linking of gelatin chains and thus improving the thermal stability of gelatin.

[0024] This invention further enhances the excellent thermally irreversible properties of gelatin gel by excessive modification of transglutaminase.

[0025] The amount of transglutaminase added is 25-30% of the gelatin mass.

[0026] Gelatin is a mixture of different polypeptide chains formed by the partial hydrolysis of collagen. It has a high molecular weight and a fibrous appearance. Gelatin contains over 82% protein, with the remainder being water and inorganic salts. It is composed of 18 amino acids, of which approximately 57% are glycine, proline, and hydroxyproline, and the remaining approximately 43% are glutamic acid, alanine, arginine, and aspartic acid, among others.

[0027] Glutamine transaminase is a monomeric protein with an active center, consisting of 331 amino groups and a molecular weight of approximately 38,000. It can catalyze intramolecular and intermolecular covalent cross-linking of proteins and peptides, thereby improving the structure and function of proteins. In this invention, its role is to promote the formation of chemically cross-linked ε-(γ-glutamine)-lysine isopeptide bonds between the γ-carboxamide group of glutamine residues and the ε-amino group of lysine residues in gelatin gel.

[0028] Gelatin molecules contain numerous active functional groups, thus this invention improves the flowability of gelatin at room temperature through a combination of physical and chemical modifications. This invention introduces transglutaminase to modify the gelatin gel, enhancing its thermal stability. Under the catalysis of transglutaminase, the γ-carboxamide group of glutamine residues and the ε-amino group of lysine residues in gelatin form chemically cross-linked ε-(γ-glutamine)-lysine isopeptide bonds. Upon cooling, the hydrogen bonds and hydrogen-bonded hydration within the gelatin molecule, forming a triple-helix-like structure, and the ε-(γ-glutamine)-lysine isopeptide bonds create a stronger chemical-physical three-dimensional network. Furthermore, during food processing or heating of semi-cooked pre-prepared dishes, the gel matrix with this chemical three-dimensional network hinders the disintegration of the triple-helix structure, at which point the gelatin gel exhibits thermal irreversibility.

[0029] The water-retaining agent of this invention has excellent performance and feasibility, bringing more convenience and opportunities to the food processing industry.

[0030] The water-retaining agent obtained by over-modifying gelatin gel with glutamine transferase in this invention gradually solidifies after standing at room temperature for 30 minutes. After solidification, an irreversible thermal phenomenon may occur.

[0031] Optionally, the gelatin is one or more of the following: collagen-based materials such as bone glue, fish glue, bovine glue, and plant glue; the fish glue is preferably fish skin gelatin, and the bovine glue is preferably bovine hide gelatin.

[0032] Secondly, the present invention also provides a method for preparing the above-mentioned easily dispersible water-retaining agent, which includes the following steps:

[0033] The gelatin is one or more of the following: bone glue, fish glue, plant glue, etc.; the fish glue is preferably fish skin gelatin.

[0034] or

[0035] The water-retaining agent is a composite mixture prepared by adding vanillin solution and tea polyphenol solution to the gelatin solution.

[0036] Optionally, the gelatin content in the gelatin solution is 10-14 wt%; more preferably, it is 12 wt%.

[0037] Optionally, the method for preparing the fish skin gelatin solution includes the following steps: adding gelatin to deionized water and heating and stirring at 68-72°C to dissolve it.

[0038] Optionally, the vanillin content in the vanillin solution is 6–10 g / L; more preferably, it is 8 g / L.

[0039] Optionally, the preparation method of the gelatin-vanillin mixed solution includes: adding vanillin solution to the fish skin gelatin solution and heating to 65-75°C for 15-25 minutes.

[0040] Optionally, the preparation method of the composite mixture includes the following steps: adding vanillin solution and tea polyphenol solution to gelatin solution, and maintaining in a water bath at 65-75°C for 15-25 minutes to obtain the composite mixture.

[0041] Optionally, the preparation method further includes the following steps: adding transglutaminase to the gelatin-vanillin mixture or composite mixture to complete the cross-linking reaction and obtain the water-retaining agent;

[0042] or

[0043] The water-retaining agent also includes transglutaminase stored independently of the composite mixture or the gelatin-vanillin mixture.

[0044] When using, add it separately to the material to be preserved. For example, if the material to be preserved is minced fish, minced pork, minced chicken, etc., inject the compound mixture or the gelatin-vanillin mixture with transglutaminase first, and then inject transglutaminase.

[0045] The above actually provides two methods for adding transglutaminase: whether the transglutaminase is added to the gelatin-vanillin mixture or composite mixture to complete cross-linking before injection, or injected separately, a gel can be successfully formed.

[0046] More specifically, after adding glutamin transferase to the gelatin-vanillin mixed solution and stirring evenly, the cross-linking reaction is completed by maintaining it in a water bath at 38-42°C for 40 min to 1 h 20 min.

[0047] Thirdly, the present invention also provides the application of the above-mentioned easily dispersible water-retaining agent in a gel.

[0048] Optionally, the gel is a meat paste gel, and the water-retaining agent is injected into meat paste or a complex containing meat paste;

[0049] Preferably, the water-retaining agent and the minced meat are in the following weight ratio: 100 parts by weight of minced meat and 6 parts by weight of water-retaining agent.

[0050] More specifically, taking grass carp surimi as the material to be retained as an example. Mixing the water-retaining agent with the grass carp surimi: Inject a 70°C gelatin-vanillin mixed solution into the surimi. Immediately inject a transglutaminase solution into the surimi, and mix thoroughly using a mortar and pestle or homogenizer. Slowly draw the surimi complex using a syringe with a cut end, pour it into cylindrical slurries, and then seal the cut end of the syringe with plastic wrap.

[0051] Optionally, a two-stage heating method is used: the surimi complex in the syringe is placed in a 40°C water bath and heated for 30 minutes, then immediately placed in a 90°C water bath and heated for 20 minutes, and finally placed in ice water to cool for 10 minutes.

[0052] (III) Beneficial Effects

[0053] The water-retaining agent provided by this invention is composed of gelatin and vanillin. Due to the grafting effect of vanillin and gelatin, this invention significantly prolongs the time required for gelatin solution to solidify, so that the water-retaining agent has good fluidity for a longer period of time and can be mixed and dispersed into the application system by injection. Furthermore, through the cross-linking effect of Tg enzyme, the covalent cross-linking of gelatin chains is catalyzed, making it different from other gelatin gels. After cooling and solidification, it will not melt upon heating and has thermal stability, thus increasing its solidification time. Attached Figure Description

[0054] Figure 1 The structural formula of vanillin;

[0055] Figure 2 This is a flowchart of the water-retaining agent preparation method in Example 4;

[0056] Figure 3The graph shows the flowability results of a single-factor experiment on gelatin concentration.

[0057] Figure 4 The graph shows the flowability results of the single-factor experiment on vanillin concentration.

[0058] Figure 5 The graph shows the flowability results of a single-factor experiment with heating temperature.

[0059] Figure 6 The graph shows the flowability results of a single-factor experiment with heating time.

[0060] Figure 7 This is a flowchart of the preparation method of meat paste gel in Example 8;

[0061] Figure 8 The graph shows the test results of the gel strength of the water-retaining agent obtained in Example 4;

[0062] Figure 9 The graph shows the experimental results of the thermal reversibility of the water-retaining agent obtained in Example 4;

[0063] Figure 10 The graph shows the water-holding capacity test results of the minced meat gel in Example 8 under different water-retaining agent concentrations;

[0064] Figure 11 The graph shows the test results of the gel strength of the minced meat gel in Example 8 under different water-retaining agent concentrations;

[0065] Figure 12 The storage modulus of the gel obtained in Example 8 and its control group were measured.

[0066] Figure 13 The loss modulus of the gel obtained in Example 8 and its control group was measured.

[0067] Figure 14 The loss coefficients were measured for the gel obtained in Example 8 and its control group.

[0068] Figure 15 The apparent viscosity of the gel obtained in Example 8 and its control group was measured.

[0069] Figure 16 The cooking loss rate was measured for the gel obtained in Example 8 and its control group.

[0070] Figure 17 The textural parameters of the gel obtained in Example 8 and its control group were measured.

[0071] Figure 18 The restoring strength values ​​were measured for the gel obtained in Example 8 and its control group.

[0072] Figure 19 The heat flow rate was measured for the gel obtained in Example 8 and its control group.

[0073] Figure 20 The freezeable water content was measured for the gel obtained in Example 8 and its control group.

[0074] Figure 21 The response value of the electronic tongue sensor was measured for the meat paste gel product containing the water-retaining agent.

[0075] Figure 22 Measure the response value of the electronic tongue sensor for the blank group;

[0076] Figure 23 Radar chart for flavor prediction of the minced meat product obtained in Example 8;

[0077] Figure 24 Radar chart predicting the taste of the blank group. Detailed Implementation

[0078] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below through specific embodiments, but is not limited thereto.

[0079] Example 1

[0080] This embodiment provides an easily dispersible water-retaining agent, which is a solution composed of gelatin and vanillin grafted together. The weight parts of gelatin and vanillin are 100 parts gelatin and 0.20 parts vanillin, respectively.

[0081] In some other specific embodiments, other components are also added to the water-retaining agent, including:

[0082] Sorbitol, calcium propionate, and sodium diacetate were added to enhance the preservation and antibacterial effects.

[0083] Adding sodium bicarbonate can buffer the pH of the system.

[0084] Xanthan gum was added at 0.5 wt% and guar gum at 1.00 wt% to strengthen the gel network.

[0085] Example 2

[0086] This embodiment provides an easily dispersible water-retaining agent, which is a solution composed of gelatin and vanillin grafted together, and forms a thermally irreversible gel after being modified by Tg enzyme.

[0087] The weight ratio of gelatin and vanillin is: 100 parts by weight of gelatin, 0.20 parts by weight of vanillin, and 25 parts by weight of transglutaminase.

[0088] Example 3

[0089] This embodiment provides a method for preparing an easily dispersible water-retaining agent, the steps of which are as follows:

[0090] Preparation of S1 fish skin gelatin solution: Add fish skin gelatin to deionized water, heat and stir at 68°C for 35 minutes to dissolve, and obtain a gelatin solution with a fish skin gelatin content of 14wt%.

[0091] Preparation of S2 vanillin solution: Add vanillin to deionized water and shake with a shaker to dissolve it, so as to obtain a vanillin solution with a concentration of 10 g / L.

[0092] S3, with vanillin at 0.15% of the gelatin mass, added vanillin solution to fish skin gelatin solution and heated to 75℃ for 15 minutes to obtain gelatin-vanillin mixture, thus preparing a water-retaining agent.

[0093] Example 4

[0094] like Figure 2 As shown in the figure, this embodiment provides a method for preparing an easily dispersible water-retaining agent, the steps of which are as follows:

[0095] Preparation of S1 fish skin gelatin solution: Add fish skin gelatin to deionized water, heat and stir at 70°C for 30 minutes to dissolve, and use sonication to remove excess air bubbles to obtain a gelatin solution with a fish skin gelatin content of 12wt%.

[0096] Preparation of S2 vanillin solution: Add vanillin to deionized water and shake with a shaker to dissolve it, to obtain a vanillin solution with a concentration of 8 g / L.

[0097] S3. Vanillin was added to fish skin gelatin solution at 0.20% of the gelatin mass. The mixture was stirred with a magnetic stirrer and ultrasonically treated to remove air bubbles. The mixture was then placed in a 70°C water bath for 20 minutes to obtain a gelatin-vanillin mixture, which was used to prepare a water-retaining agent.

[0098] The experimental results showed that the water-retaining agent had significant antifreeze activity compared with the blank control group: the bacterial survival rate of the water-retaining agent group reached 80±0.1%, while the bacterial survival rate of the blank control group was only 20±0.1%, and the water-retaining agent increased the freezing survival rate of bacteria by 30%.

[0099] Example 5

[0100] This embodiment provides a method for preparing an easily dispersible water-retaining agent, the steps of which are as follows:

[0101] Preparation of S1 fish skin gelatin solution: Add fish skin gelatin to deionized water, heat and stir at 70°C for 30 minutes to dissolve, and use sonication to remove excess air bubbles to obtain a gelatin solution with a fish skin gelatin content of 12wt%.

[0102] Preparation of S2 vanillin solution: Add vanillin to deionized water and shake with a shaker to dissolve it, to obtain a vanillin solution with a concentration of 8 g / L.

[0103] Preparation of S3 tea polyphenol solution: Add tea polyphenols to deionized water and dissolve by shaking with a shaker to obtain a tea polyphenol solution with a concentration of 0.5 g / L;

[0104] S4, with vanillin at 0.20% of the gelatin mass and tea polyphenols at 1.00% of the gelatin mass, added vanillin solution and vanillin solution to fish skin gelatin solution, mixed with a magnetic stirrer, and ultrasonically treated to remove air bubbles. The mixture was then placed in a 70℃ water bath for 20 minutes to obtain a gelatin-vanillin-tea polyphenol complex, thus preparing a composite phenolic water-retaining agent.

[0105] Example 6

[0106] This embodiment provides a method for preparing an easily dispersible water-retaining agent, the steps of which are as follows:

[0107] Preparation of S1 gelatin solution: Add fish skin gelatin to deionized water, heat and stir at 70°C for 30 minutes to dissolve, and use sonication to remove excess air bubbles. The resulting gelatin solution contains 12 wt% fish skin gelatin.

[0108] Preparation of S2 vanillin solution: Add vanillin to deionized water and shake with a shaker to dissolve it, to obtain a vanillin solution with a concentration of 8 g / L.

[0109] S3. Vanillin was added to the fish skin gelatin solution at 0.20% of the gelatin mass. The mixture was stirred with a magnetic stirrer and ultrasonically treated to remove air bubbles. The mixture was then heated in a 70°C water bath for 15 minutes to obtain a gelatin-vanillin mixture.

[0110] S4 Glutamine transaminase crosslinking reaction: Glutamine transaminase is added to a gelatin-vanillin mixed solution, wherein the amount of glutamine transaminase added is 37% of the mass of gelatin. After stirring evenly, the solution is kept in a 40°C water bath for 1 hour to obtain an easily dispersible water-retaining agent.

[0111] Example 7

[0112] This embodiment provides a method for preparing an easily dispersible water-retaining agent, the steps of which are as follows:

[0113] Preparation of S1 gelatin solution: Add bovine gelatin to deionized water, heat and stir at 60°C for 20 minutes to dissolve, and sonicate to remove excess air bubbles. The content of bovine gelatin is 20wt% gelatin solution.

[0114] Preparation of S2 vanillin solution: Add vanillin to deionized water and shake with a shaker to dissolve it, to obtain a vanillin solution with a concentration of 8 g / L.

[0115] S3. Vanillin is 0.25% of the gelatin mass. The vanillin solution is added to the fish skin gelatin solution, mixed with a magnetic stirrer, and ultrasonically treated to remove air bubbles. The mixture is then heated in a 70°C water bath for 15 minutes to obtain a gelatin-vanillin mixture.

[0116] S4 Glutamine transaminase crosslinking reaction: Glutamine transaminase is added to a gelatin-vanillin mixed solution, wherein the amount of glutamine transaminase added is 33% of the mass of bovine gelatin. After stirring evenly, the solution is kept in a 40°C water bath for 1 hour to obtain an easily dispersible water-retaining agent.

[0117] Example 8

[0118] This embodiment provides a method for preparing fish paste gel using an easily dispersible water-retaining agent, the steps of which are as follows:

[0119] Preparation of S1 grass carp surimi:

[0120] S11 Stun fresh grass carp, remove the white fish meat and rinse it clean; use a meat grinder to grind the fish meat into fish paste;

[0121] S12 Repeat the following cleaning steps twice:

[0122] Add the fish paste to deionized water at 4°C at a ratio of 1:3 (w / v); stir at a constant speed for 5 minutes with an electric stirrer, and centrifuge at 6000 rpm for 5 minutes at 4°C to obtain the cleaned fish paste.

[0123] The mixing steps for S2 water-retaining agent and grass carp surimi are as follows:

[0124] Add 6% of the grass carp surimi by weight of the water-retaining agent obtained in Example 4 at 70°C and inject it into the grass carp surimi. Immediately afterwards, add 33% of the gelatin mass of the transglutaminase solution and inject the Tg enzyme into the surimi. Mix well using a mortar and pestle or homogenizer. Slowly draw the surimi complex with a syringe with a cut side and pour it into a cylindrical surimi. Seal the cut side of the syringe with plastic wrap.

[0125] Preparation of S3 grass carp surimi gel: The surimi complex was heated in a 40℃ water bath for 30 min, then in a 90℃ water bath for 20 min, and finally cooled in ice water for 10 min to obtain grass carp surimi gel.

[0126] The preparation method of the fish paste gel in this embodiment is shown in the following flowchart. Figure 7 As shown.

[0127] To verify the flowability and thermal stability of the water-retaining agent obtained in this invention, the following experiments were conducted:

[0128] Experiment 1: Inverted Liquidity Analysis

[0129] Inject the sample into a centrifuge tube, let it stand at room temperature for a period of time, and then invert the tubes simultaneously to observe the differences in flowability. The flowability is divided into three categories: solidified state, semi-solidified state, and fluidized state.

[0130] The basic preparation method for the experimental samples is as follows:

[0131] Preparation of S1 fish skin gelatin solution: Add fish skin gelatin to deionized water, heat and stir at 70°C for 30 minutes to dissolve, and sonicate to remove excess air bubbles to obtain gelatin solution.

[0132] Preparation of S2 vanillin solution: Add vanillin to deionized water and shake with a shaker to dissolve it, to obtain a vanillin solution with a concentration of 8 g / L.

[0133] S3. Vanillin solution was added to fish skin gelatin solution, mixed with a magnetic stirrer, and ultrasonically treated to remove air bubbles. The mixture was then heated in a 70°C water bath for 1 hour to obtain a gelatin-vanillin mixture.

[0134] 1. Single-factor experiment on gelatin concentration:

[0135] In this experiment, based on the basic preparation method of the experimental sample, in step S3, vanillin solution was added to fish skin gelatin solution at 0.25% of gelatin mass (vanillin / gelatin, m / m);

[0136] In step S1, the gelatin concentration of the gelatin solution was set to 6%, 7%, 8%, 9%, 10%, 12%, and 14% for different levels of single-factor experiments, and corresponding gelatin-vanillin mixture experimental samples were prepared, which were recorded as the experimental group. The sample prepared in step S3 without vanillin solution was used as the control sample, and the samples prepared at the same single-factor levels as above were recorded as the control group. The flowability was measured after standing at room temperature (25℃) for 20 minutes, and the results were as follows. Figure 3 The result.

[0137] from Figure 3 As shown, at a gelatin concentration of 10%, the control group was semi-solid, while the experimental group was fluid. At a gelatin concentration of 12%, the experimental group was semi-solid, while the control group solidified at the top. When the gelatin concentration increased to 14%, the experimental group with added vanillin also exhibited gelation at the top. Therefore, 12% is the maximum gelatin concentration that allows the system to maintain fluidity after standing and cooling.

[0138] 2. Single-factor experiment on vanillin concentration

[0139] In this experiment, based on the basic preparation method of the experimental samples, the gelatin concentration of the gelatin solution in step S1 was 12%. In step S3, vanillin solution was added to the fish skin gelatin solution at vanillin concentrations of 0.10%, 0.15%, 0.20%, 0.25%, and 0.30% of the gelatin mass (vanillin / gelatin, m / m) to design a single-factor experiment. The gelatin-vanillin mixture samples prepared under different factor levels were tested and, after standing at room temperature (25℃) for 20 minutes, were placed in a fluid state to obtain the following results: Figure 4 The result.

[0140] from Figure 4 The results showed that samples with vanillin concentrations of 0.10% and 0.15% adhered to the centrifuge tube walls after inversion, exhibiting a semi-solid state. The sample with a vanillin concentration of 0.20% was free-flowing, with all the solution flowing to the bottom of the centrifuge tube after inversion, and the sample with a vanillin concentration of 0.20% flowed to the bottom of the centrifuge tube very quickly after inversion. Therefore, it can be concluded that a minimum vanillin concentration of 0.20% significantly improves the flowability of the gelatin-vanillin mixture.

[0141] 3. Single-factor experiment on heating temperature

[0142] In this experiment, based on the basic preparation method of the experimental samples, the gelatin concentration of the gelatin solution in step S1 was 12%; in step S3, vanillin solution was added to the fish skin gelatin solution at 0.25% of the gelatin mass (vanillin / gelatin, m / m); in step S3, gelatin-vanillin mixtures were obtained by heating in water baths at 60℃, 65℃, 70℃, 75℃ and 80℃ for 1 hour respectively, and a single-factor multi-level experiment was designed accordingly; the gelatin-vanillin mixture experimental samples prepared under different factor levels were recorded as experimental groups, and the sample prepared in step S3 without the addition of vanillin solution was used as the control sample. The sample prepared under the same single-factor level design was recorded as the control group; the fluidity was measured after standing at room temperature (25℃) for 20 minutes, and the results were as follows. Figure 5 The result.

[0143] from Figure 5 It can be seen that: the experimental samples obtained by the experimental group under heating conditions of 70 and 75℃ were observed to be in a flowing liquid state after cooling (25℃) and being inverted; the experimental samples obtained under heating conditions of 60, 65 and 80℃ were observed to be in a semi-solid state after cooling and being inverted; at the same time, under all heating temperature conditions, the samples obtained by the control group formed a gel at the top after cooling and being inverted.

[0144] Therefore, we can conclude that 70℃ is the minimum reaction temperature at which the gelatin solution retains its fluidity after vanillin grafting.

[0145] 4. Single-factor experiment on heating time

[0146] In this experiment, based on the basic preparation method of the experimental samples, the gelatin concentration of the gelatin solution in step S1 was 12%; in step S3, vanillin solution was added to the fish skin gelatin solution at 0.25% of the gelatin mass (vanillin / gelatin, m / m); in step S3, gelatin-vanillin mixtures were obtained by heating in a 70℃ water bath for 20, 40, 60, 80, and 100 min respectively, and a single-factor multi-level experiment was designed accordingly; the gelatin-vanillin mixture experimental samples prepared under different factor levels were recorded as experimental groups, and the sample prepared in step S3 without adding vanillin solution was used as the control sample. The sample prepared under the same single-factor level design was recorded as the control group; the fluidity was measured after standing at room temperature (25℃) for 20 min, and the results were as follows. Figure 6 The result.

[0147] from Figure 6 The results showed that, in the samples obtained after heating for 20 and 40 minutes, the control group exhibited gelation, while the experimental group maintained fluidity. This indicates that a minimum heating time of 20 minutes is sufficient to achieve fluidity in the obtained samples, significantly improving fluidity and enabling easy dispersion at room temperature. Choosing 20 minutes reduces energy consumption and lowers preparation costs.

[0148] Experiment 2: Gel Strength Measurement

[0149] The water-retaining agent sample obtained in Example 4 was cooled and allowed to solidify completely. Its gel strength was then measured, with the sample prepared in step S3 without vanillin solution used as a blank sample. Specifically, 10 mL of the sample was poured into a 25 mL beaker and left at room temperature for 16–18 hours. The measurement parameters were as follows: gel strength was measured using a TA-XTplus texture analyzer with a P / 5S probe, a measurement speed of 2.00 mm / s, a compression ratio of 50%, and a pressure of 20.0 g. Gel strength was expressed as the product of breaking strength (g) and indentation depth (mm). The experimental results are as follows: Figure 8 As shown, there was no significant difference in gel strength between the experimental group and the blank group (P<0.05), indicating that vanillin can increase the fluidity of gelatin solution before solidification without weakening its gel strength after cooling and solidification.

[0150] Experiment 3: Rheological Property Analysis of Water-Retaining Agents

[0151] The water-retaining agent sample obtained in Example 4 was subjected to temperature scanning while still hot. The specific experimental procedure used a 50mm plate as a probe, with a temperature range of 5-50℃ and 50-5℃, a heating / cooling rate of 2℃ / min, strain of 1%, and frequency of 1Hz. The storage modulus (G') and loss modulus (G) were recorded as functions of temperature.

[0152] like Figure 9 As shown, the water-retaining agent exhibits intersection points between G' and G during both the heating and cooling stages. These intersection points are considered the melting temperature and gelation temperature of the gelatin gel, respectively. This indicates that the gel of the gelatin-vanillin system is thermally reversible. Under the experimental conditions, the temperature corresponding to the intersection of the storage modulus and loss modulus of the gelatin gel during the cooling stage is 21.82℃, and the melting temperature of the gel during the heating stage is 25.67℃. This further demonstrates that the gelatin-vanillin system exhibits good flowability at room temperature (25℃).

[0153] Experiment 4: Application of water-retaining agents in surimi gel

[0154] To determine the optimal weight ratio of water-retaining agent to surimi gel, the water-holding capacity and gel strength of grass carp surimi gels prepared with different water-retaining agent addition ratios were measured.

[0155] The grass carp surimi gel was prepared using the method described in Example 8. In step S2, the water-retaining agent obtained in Example 4 was taken at 70°C at 0%, 2%, 4%, 6%, 8%, 10%, 12%, and 14% of the grass carp surimi mass, respectively. Grass carp surimi gels with different water-retaining agent addition ratios were then prepared.

[0156] The specific experimental method for determining water-holding capacity is as follows: Take 1g of fish paste gel sample, accurately weigh it, wrap it in filter paper, centrifuge at 5000g for 10 minutes, then remove the sample and accurately weigh it again. The water-holding capacity of the gel is the ratio of the sample mass before centrifugation to the mass after centrifugation. Each treatment is measured in triplicate. The results are as follows: Figure 10 As shown; from Figure 10 It can be seen that the water-retaining agent can stabilize the water retention capacity of the product when applied to the surimi at a weight ratio of 2-16%. In particular, when the weight ratio of the water-retaining agent to the surimi is 6%, the water-holding capacity of the surimi gel is not significantly different from that of the blank group (0%), while the water-holding capacity is significantly improved at 14% and 16%.

[0157] The specific experimental method for determining gel strength is as follows: The surimi gel is ejected from a syringe and cut into cylinders 1 cm in length (20 mm in diameter). The gel strength is then measured using a TA-XT plus texture analyzer with the following parameters: P / 5S probe, measuring speed 2.00 mm / s, compression ratio 50%, and pressure 20.0 g. The gel strength is expressed as the product of breaking strength (g) and indentation depth (mm). The test results are as follows: Figure 11 As shown, Figure 11 It can be seen that when the weight fraction of water-retaining agent relative to fish paste is 2%, 4%, and 6%, the fish paste gel products exhibit good gel strength.

[0158] Taking into account both gel strength and water retention capacity, when the water-retaining agent is added at a ratio of 6% by weight, the surimi gel exhibits both high gel strength and water retention capacity.

[0159] Experiment 5, Characteristic Analysis of the Fish Paste Gel Obtained in Example 8

[0160] In this experiment, the water-retaining agent group refers to the surimi gel prepared by adding a water-retaining agent, that is, surimi gel prepared by adding 0.1% (equivalent to 33% of the weight of gelatin) of transglutaminase by weight of surimi and a certain amount of water-retaining agent to surimi in a two-stage heating process followed by cooling; the control group refers to the surimi gel prepared without adding a water-retaining agent, but with the addition of deionized water equivalent to the weight of the water-retaining agent in the water-retaining agent group, that is, surimi gel prepared by adding 0.1% of transglutaminase by weight of surimi and a certain amount of deionized water to surimi in a two-stage heating process followed by cooling.

[0161] 1. Temperature scanning analysis

[0162] Temperature scanning experiments can elucidate the effect of water-retaining agents on the gel-forming ability of surimi gels. Storage modulus is commonly used as an indicator of gel formation to study the dynamic rheological properties of surimi gels. The specific experimental method is as follows: 2-3 g of surimi gel is weighed and placed on the stage of a rheometer. The distance between the plate and the stage is adjusted to 1000 μm. After the surimi gel has made sufficient contact with the plate, excess surimi is removed. The measurement conditions are: strain 1%, frequency 0.1 Hz, temperature scanning range 20℃–90℃, heating rate 2℃ / min. The changes in elastic modulus, loss modulus, and loss coefficient of the surimi gel during the heating process are observed.

[0163] The rheological temperature scanning results of the blank group (gel obtained without water-retaining agent in Example 8), the water-retaining agent group (gel obtained in Example 8), and the control group (gel obtained by replacing the water-retaining agent in Example 8 with the same mass of deionized water) are shown in [the table below]. Figure 12-14 .

[0164] from Figure 12-14The results show that the storage modulus and loss modulus (i.e., loss coefficient) of the three groups of surimi products exhibit similar trends with temperature: both the loss modulus and storage modulus first increase to their maximum values ​​and then decrease. The loss modulus of the blank and control groups increased at 50-70℃ and decreased significantly at 70-90℃, while the loss modulus of the water-retaining agent group increased at 50-80℃ and decreased at 80-90℃. During heating, the collision of myosin structures generates more viscous sol, causing an increase in loss modulus in the initial heating stage. As the temperature continues to rise, the continuous interaction and cross-linking between protein molecules intensify, leading to a continuous increase in gel elasticity and a gradual decrease in loss modulus. When the temperature rises further, the loss modulus of the surimi reaches its minimum and no longer fluctuates significantly, indicating that the surimi has undergone maximum gelation. During the initial heating stage, the storage modulus of the blank group, control group, and water-retaining agent group did not increase significantly. However, when the temperature rose above 50℃, the storage modulus increased significantly. The control group reached its peak storage modulus at around 70℃, the blank group at around 75℃, and the water-retaining agent group. After 50℃, the increase in storage modulus was relatively slow, but the upward trend continued until 85℃, at which point the storage modulus reached its peak, and the peak storage modulus of the water-retaining agent group was higher than that of the blank group and control group. The loss coefficients of the three groups increased from 30-40℃, decreased somewhat from 40-50℃, and increased further after 50℃. The loss coefficients of the blank group and control group reached their maximum values ​​at around 65℃, while the loss coefficient of the water-retaining agent group reached its maximum value at around 75℃, which was higher than that of the blank group and control group. This indicates that the water-retaining agent can improve the stability of the surimi gel at high temperatures and may play a role in filling the cross-linked network matrix.

[0165] 2. Apparent viscosity

[0166] Apparent viscosity experiments were conducted to compare the flowability of the surimi system. The experimental method involved a shear rate of 0.1 s⁻¹ at 25°C. -1 Gradually increase to 100s -1 Record the change in apparent viscosity with shear rate. The rheological apparent viscosity test results of the surimi gel products from the blank group (gel obtained without water-retaining agent in Example 8), the water-retaining agent group (gel obtained in Example 8), and the control group (gel obtained by replacing the water-retaining agent in Example 8 with the same mass of deionized water) are shown in [the table below]. Figure 15 The results showed that as the shear rate increased, the apparent viscosity decreased, exhibiting shear-thinning behavior. This is because as the shear rate increases, the bonds between protein molecular chains are disrupted, and molecules tend to align in the same direction, weakening the frictional force between the fluid and the shear surface, leading to a decrease in viscosity. The three sets of apparent viscosity curves almost overlapped, indicating that the addition of 6% water or water-retaining agent has little effect on the interactions between the substances in the surimi system.

[0167] 3. Losses during cooking

[0168] The experimental method involved accurately weighing 3.0 g of gel samples from different treatment groups, placing them in self-sealing bags, sealing them, heating them in a 90°C water bath for 30 min, cooling them to room temperature, wiping the surface moisture with filter paper, and then weighing them. Data were processed according to the following formula, with each treatment group measured three times in parallel, and the result was the average of the three measurements.

[0169] The cooking loss test results of blank surimi gel products, surimi gel products injected with 6% water-retaining agent, and negative control surimi gel products are as follows: Figure 16 It can be seen that compared with the surimi gel in the control group, the surimi gel in the water-retaining agent group has less loss during cooking. This indicates that the water-retaining agent can effectively bind water into the gel network during the heat processing of food, giving the surimi better water retention.

[0170] 4. Full texture

[0171] Experimental method for full texture analysis: The surimi gel prepared by the two-stage heating method in Example 8 was ejected from the syringe and cut into cylinders with a length of 1 cm (diameter of 20 mm). The texture analysis of the surimi gel was then performed using a texture analyzer equipped with a P / 36R cylindrical probe (probe diameter of 36 mm). The full texture test results of the surimi gel products in the blank group (gel obtained without water-retaining agent in Example 8), the water-retaining agent group (gel obtained in Example 8), and the control group (gel obtained by replacing the water-retaining agent in Example 8 with the same mass of deionized water) are shown in [the table below]. Figure 17 Key data (resilience) results can be found in [link to relevant documentation]. Figure 18 The results showed that, compared with the addition of 6% water by weight of surimi, the surimi gel product injected with 6% water-retaining agent exhibited better textural parameters and more stable properties.

[0172] 5. Thermal effect test

[0173] Like many meat products, surimi gel requires refrigeration. However, refrigeration can cause water to freeze into ice, damaging the food structure. This experiment investigated the effect of water-retaining agents on reducing freezing damage, characterized by the content of freezeable water. Approximately 15 mg of the surimi gel sample obtained in Example 8 was accurately weighed and sealed in an alumina crucible. Nitrogen was used as a protective gas. The sealed crucible was placed in a differential scanning calorimeter, and the measurement parameters were: temperature -40 to 40 °C, heating rate 10 °C / min. -1 N2 flow rate 40-50 mL / min -1The freezeable water content (including free water and non-flowing water) of the surimi gel was determined by measuring the enthalpy change of the surimi gel near 0°C. The non-freezing water content was the difference between the total water content and the freezeable water content. The total water content was measured using a rapid moisture analyzer. The formula for calculating the freezeable water content is as follows.

[0174]

[0175] The thermal effect measurement results of the surimi gel products corresponding to the blank group (gel obtained without water-retaining agent in Example 8), the water-retaining agent group (gel obtained in Example 8), and the control group (gel obtained by replacing the water-retaining agent in Example 8 with the same mass of deionized water) are shown in the figure. Figures 19-20 .Depend on Figure 19 As shown, at around 0℃, the control group's surimi gel product had a significantly larger water endothermic peak area, while the blank group and the water-retaining agent group's surimi gel products had similar water endothermic peak areas. Further analysis of the freezeable water content of the three samples (…) Figure 20 The study found that the fish paste gel products in the water-retaining agent group had the lowest freezeable water content. This indicates that the water-retaining agent of the present invention can effectively bind water, resulting in less water freezing into ice crystals during the freezing process. Therefore, applying the water-retaining agent to food is beneficial for maintaining the quality of food systems during long-distance, long-term cold chain transportation and storage, and reducing the damage to cells and proteins caused by ice crystal formation and recrystallization.

[0176] 6. Electronic tongue analysis

[0177] Weigh 15.00 g of fish surimi and its products, add 100 mL of distilled water, homogenize with a mixer for 30 s, then centrifuge (4℃, 10000 r / min, 10 min). Collect the supernatant, filter with qualitative filter paper, and collect the filtrate. Measure the response value using an ASTREE type taste analyzer (electronic tongue) sensor. Figure 21-24 As shown, the main flavors of the surimi gel products of the blank group (gel obtained without water-retaining agent in Example 8) and the water-retaining agent group (gel obtained in Example 8) are bitter, sour, and umami, respectively. The sensor data signals are similar, which indicates that although the water-retaining agent contains vanillin, an addition of only 0.2% will not produce significant flavor changes.

[0178] In summary, the water-retaining agent based on gelatin grafted with vanillin and cross-linked with Tg enzyme provided by this invention, through quantitative addition of vanillin to a gelatin solution and treatment with ultrasound, stirring, and water bath heating, allows the active functional groups of gelatin and vanillin to fully combine, resulting in a gelatin composite solution with good flowability at room temperature. Furthermore, by over-modifying the gelatin gel with Tg enzyme, the formation of chemically cross-linked ε-(γ-glutamine)-lysine isopeptide bonds between the γ-carboxamide group of glutamine residues and the ε-amino group of lysine residues is promoted, further forming a stronger chemical-physical three-dimensional network, making the gelatin gel exhibit thermal irreversibility.

[0179] The innovation of this water-retaining agent lies in its low-cost and highly safe raw materials, the pioneering use of vanillin to increase solution fluidity, and its simple, rapid, and energy-efficient production process. Simultaneously, the introduction of transglutaminase imparts thermal stability to the gel, achieving multiple benefits including both flowability / injectability and irreversible thermal stability. This water-retaining agent can be applied in food, biomedicine, and other fields. Taking the preservation of the quality of pre-prepared dishes as an example, specifically in the preparation of traditional surimi gel, it can improve the water-holding capacity of the gel while reducing raw material costs. Furthermore, the addition of vanillin may provide a preservative effect. The application process of this water-retaining agent in food is simple and convenient, facilitating its widespread adoption in the pre-preparation of traditional cuisines and contributing to the preservation, inheritance, and innovative development of traditional foods.

[0180] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-retaining agent which is easily dispersible, characterized in that, It is mainly made from the following raw materials: gelatin, vanillin, and tea polyphenols; The vanillin and the tea polyphenols form a non-covalent interaction with the gelatin; The vanillin is 0.15 to 0.30% of the gelatin mass; The tea polyphenols comprise 0.8–0.15% of the gelatin mass; The water-retaining agent is cross-linked with transglutaminase to form a gel. The amount of transglutaminase added is 25-37% of the gelatin mass.

2. The easily dispersible water retaining agent according to claim 1, wherein The gelatin is one or a combination of two or more of the following: bone glue, fish glue, and bovine glue.

3. The water-retaining agent according to claim 2, wherein The fish glue is selected from fish skin gelatin, and the cow glue is selected from cowhide gelatin.

4. A method of producing the easily dispersible water retaining agent as claimed in claim 1, characterized by, The steps are as follows: Vanillin solution and tea polyphenol solution are added to gelatin solution to prepare a composite mixture; then transglutaminase is added to the composite mixture to complete the cross-linking reaction and obtain the water-retaining agent.

5. The method for preparing the easily dispersible water-retaining agent as described in claim 4, characterized in that, The composite mixture is prepared by adding vanillin solution and tea polyphenol solution to gelatin solution and maintaining the mixture in a water bath at 65-75°C for 15-25 minutes to obtain the composite mixture.

6. The use of an easily dispersible water-retaining agent as described in any one of claims 1-3 in gels and foods.

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