A food-grade cross-linking agent with high permeability and its application

Abstract

The present invention relates to a food-grade cross-linking agent with high permeability and its application. The food-grade cross-linking agent with high permeability is a pre-cross-linked oligosaccharide containing two reducing ends in a single molecule obtained by treating pre-cross-linked starch, and can improve substrate performance by reacting with amino substrates to generate Maillard reaction and acetal or hemiacetal reaction with hydroxyl substrates. The cross-linking agent is food-grade, not only has very high safety, but also has the advantages of simple preparation and strong cross-linking activity; in addition, the cross-linking agent also has high permeability, and can significantly improve the stability of cross-linked substrates, especially bulk substrates, when cross-linked.

Description

Technical Field

[0001] The invention relates to the field of crosslinking agents, and in particular to a food-grade crosslinking agent with high permeability and application thereof. Background Art

[0002] A cross-linking agent is a substance that undergoes a cross-linking reaction with a polymer linear macromolecular chain through a chemical bond or a coordination bond, connecting the polymer linear macromolecular chain into a network structure.

[0003] Cross-linking agents can improve the stability of food proteins in the food industry. High-protein foods can form a more stable three-dimensional network structure after cross-linking, and their hydration capacity, stability, storage resistance, taste, etc. are all improved. Glutamine aminotransferase is currently the only non-toxic food cross-linking agent allowed for use in my country. It can be used to cross-link protein glutamine residues and lysine residues to form isopeptide bonds. However, due to the poor permeability of glutamine aminotransferase, it can only complete cross-linking on the surface of the material and cannot enter the interior of the food. Therefore, for large block food raw materials, such as sea cucumbers, abalone, large pieces of meat, etc., its internal cross-linking ability is insufficient. Glutaraldehyde is a small molecule and is also a food additive allowed for use in my country. It has a very small molecular weight and strong permeability. It can penetrate into the interior of block foods and complete cross-linking. However, the toxicity of glutaraldehyde is very high. Therefore, in my country, it can only be used as a stabilizer for collagen casings. A small amount of addition is allowed, but it cannot be used on a large scale in block foods. Therefore, safe and efficient cross-linking agents that can be used for various foods still need to be developed.

[0004] In addition, cross-linking agents have great applications in the materials industry. With the development of modern industry, environmental problems are becoming more and more serious, and hydrogels have become the development trend of the materials industry. In order to improve the mechanical properties of hydrogels after curing, the common solution in the industry is to add cross-linking agents to hydrogels to enhance the degree of cross-linking of the gel. Cross-linking modification can improve the physical and chemical properties of edible hydrogel materials, such as mechanical properties and moisture barrier properties. Good gelation and biodegradability make it one of the research hotspots of edible packaging materials. The performance indicators of hydrogels have been greatly improved, but their mechanical strength and moisture barrier properties are still far behind those of traditional polymer plastic films. Therefore, further research is needed to develop new functional cross-linking agents to meet the application performance of composite hydrogels. Summary of the invention

[0005] In order to make up for the deficiencies of the prior art, the present invention provides a food-grade cross-linking agent with high permeability and application thereof, which at least solves or alleviates a problem existing in the prior art.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] A food-grade cross-linking agent with high permeability, specifically a pre-cross-linked oligosaccharide containing two reducing ends in a single molecule obtained by treating pre-cross-linked starch, which can improve substrate performance by undergoing a Maillard reaction with an amino substrate and producing an acetal or hemiacetal reaction with a hydroxyl substrate.

[0008] Preferably, the pre-crosslinked starch is one of distarch phosphate, acetylated distarch phosphate, acetylated distarch adipate, and hydroxypropyl distarch phosphate.

[0009] The above cross-linking agent can be prepared by the following steps:

[0010] S1: 10-30 parts by weight of pre-cross-linked starch is dissolved in 100 parts by weight of water to prepare a solution, and the pH is adjusted to 3-10, and then fully gelatinized at 100° C.-200° C. for 1-3 hours;

[0011] S2: adding 0.0001-10 parts by weight of treatment agent A, stirring the solution until it becomes clear and transparent, wherein the treatment agent A is at least one of calcium chloride, sodium chloride, magnesium chloride, calcium lactate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate;

[0012] S3: adding 0.0001-1 parts by weight of enzyme A, stirring and reacting at 60° C.-100° C. for 2-4 hours, during which the pH is maintained between 3-10, wherein the enzyme A is at least one of β-amylase, O-glycosidase, cellulase, pectinase, starch debranching enzyme, and α-amylase;

[0013] S4: adding 0.0001-10 parts by weight of treatment agent B, stirring the solution until it is clear and transparent, and removing the precipitate by centrifugation if any, wherein the treatment agent B is selected from at least one of calcium chloride, sodium carbonate, sodium sulfate, potassium carbonate, and potassium sulfate;

[0014] S5: After inactivating the enzyme, dry.

[0015] Preferably, the following treatment step is further included between steps S3 and S4: 0.0001-1 parts by weight of enzyme B is added to the product of S3, and the reaction is stirred at 40°C-100°C for 2-4 hours, during which the pH is maintained between 3-10, wherein the enzyme B is glucoamylase or isoamylase.

[0016] The present application also provides the application of the above-mentioned food-grade cross-linking agent with high permeability. Specifically, the cross-linking substrate is a natural macromolecule including protein, chitosan, polysaccharide or an artificial macromolecule including lysine; the dry weight ratio of the cross-linking agent to the cross-linking substrate is in the range of 1:10-1:50000.

[0017] Preferably, the cross-linking agent can be used to improve the high thermal stability of water-expanded sea cucumbers; the application method is: soak the water-expanded sea cucumbers in a cross-linking agent aqueous solution, the cross-linking temperature is 60-150°C, the cross-linking time is 0.5-6h; the weight concentration of the cross-linking agent aqueous solution is 1g / L-200g / L.

[0018] Preferably, the cross-linking agent can be used to improve the high thermal stability of fresh shrimps; the application method is: the fresh shrimps are processed into shrimp meats and immersed in a cross-linking agent aqueous solution, the cross-linking temperature is 60-150°C, and the cross-linking time is 0.5-6h; the weight concentration of the cross-linking agent aqueous solution is 1g / L-200g / L.

[0019] Preferably, the crosslinking agent can react with chitosan to form chitosan gel when the shear rate reaches 100s -1 When the temperature is 20000 ℃ and the viscosity is 4000 ℃, the apparent viscosity of chitosan gel is still not less than 1000 Pa.s.

[0020] Preferably, the crosslinking agent can react with polylysine to form an active glue; the application method is: dissolving ε-polylysine in a crosslinking agent aqueous solution, the crosslinking temperature is 60-150°C, and the crosslinking time is 0.5-6h; the weight concentration of the crosslinking agent aqueous solution is 1g / L-200g / L.

[0021] The crosslinking agent of the present application can be applied to, but not limited to, food protein stability, clothing finishing cotton fabric performance, coating film formation, new materials, biological modification, petroleum processing, molecular imprinting technology, etc.

[0022] The present invention adopts the above structure, and has the advantages of:

[0023] 1. From the perspective of the cross-linking agent itself:

[0024] First, the cross-linking agent is obtained by processing food-grade pre-cross-linked starch, belongs to a food-grade cross-linking agent, can be directly applied to food, not only has high safety, but also has good biocompatibility, and is easily accepted by the human body and the environment. Second, the cross-linking agent is a pre-cross-linked oligosaccharide containing 2 reducing ends in a single molecule, and can achieve cross-linking of the substrate by a double Maillard reaction when cross-linking with an amino substrate, and the cross-linking activity is relatively strong. Third, the obtained cross-linking agent has a small molecular weight and strong permeability, and can significantly improve the stability of the cross-linked substrate, especially the bulk substrate. Fourth, the cross-linking agent belongs to a glycosyl cross-linking agent, has strong water solubility, and good applicability. Fifth, the cross-linking agent is relatively simple to prepare, has a low production cost, and is easy to promote and apply.

[0025] 2. From the perspective of cross-linking agent application:

[0026] First, the water-soaked sea cucumber treated with the cross-linking agent of the present application has higher thermal stability and storage stability than the products treated with the prior art. Specifically, after high-temperature sterilization, there will be no instability problems such as tissue disintegration, surface collapse, and blurred shape contours; when it is used as a deep-processing raw material or final product, the storage stability will be much better than that of ordinary water-soaked sea cucumbers, with a firm taste, good chewiness, moderate hardness, and better economic value than uncross-linked food.

[0027] Secondly, the shrimp treated with the cross-linking agent of the present application not only increases the tightness and elasticity of the shrimp muscles, but also improves the taste and chewiness of the shrimp. This is because the cross-linking of the shrimp with the cross-linking agent of the present application can improve the water retention of the shrimp muscles, reduce water loss, and maintain the juiciness and tenderness of the muscles. In addition, the use of the cross-linking agent of the present application can also slow down the protein degradation and oxidation reaction of the shrimp muscles, extend its shelf life, and reduce the risk of deterioration and corruption. Furthermore, it also helps to reduce damage and losses during processing and transportation, and improve processing efficiency and the overall quality of the product.

[0028] Thirdly, the cross-linking agent of the present application can also be used to prepare chicken, pork, beef and other foods that are resistant to high temperature sterilization and storage. Compared with existing related products, they have better high heat stability and high pressure stability, which means that during the heating process, meat can better maintain its shape, texture and nutrients, reducing protein denaturation and water loss. In addition, the use of the cross-linking agent of the present application can also help enhance the antioxidant and antibacterial properties of meat, and can delay protein degradation and bacterial growth during storage, thereby extending the storage period of meat products.

[0029] Fourthly, the chitosan gel prepared in the present application has obvious gel characteristics in its rheological properties. This is because after the cross-linking agent of the present application is added, a cross-linked network with a certain structure and performance is formed in the chitosan, which can significantly improve the mechanical properties, chemical resistance and thermal stability of the material. The effect reaches the mechanical strength level of traditional polymer plastics and has better biodegradability.

[0030] Fifthly, the cross-linking agent of the present invention is used to obtain the cross-linked polylysine gel, which has the advantages of good biocompatibility, biodegradability, adjustable physical and chemical properties, and excellent moisture retention and water absorption. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The schematic diagram of the cross-linking principle of the cross-linking agent of the present invention;

[0032] Figure 2 The state diagram of the sea cucumbers in the blank group and the experimental group after cooking in Application Example 1;

[0033] Figure 3 The state diagram of the sea cucumber after steaming in the control group of Application Example 1;

[0034] Figure 4 This is a diagram showing the state of shrimp after steaming in Application Example 2;

[0035] Figure 5 This is a diagram of the state of chitosan before and after cross-linking in Application Example 3;

[0036] Figure 6 It is the apparent viscosity of the gel obtained after cross-linking chitosan in Application Example 3.

[0037] Figure 7 The biodegradability of the gel obtained after chitosan cross-linking in Application Example 3. DETAILED DESCRIPTION

[0038] In order to clearly illustrate the technical features of the present solution, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0039] (I) Preparation of cross-linking agent

[0040] The cross-linking principle of the cross-linking agent of the present application is to produce Maillard reaction with amino groups or acetal / hemiacetal reaction with hydroxyl groups. The preparation and cross-linking principle are shown in Figure 1 , the preparation example is as follows:

[0041] Preparation Example 1:

[0042] 10 parts by weight of acetylated distarch phosphate are dissolved in 100 parts by weight of water to prepare a solution, and the pH is adjusted to 3-4, and then the solution is fully gelatinized at 100°C for 3 hours; then 0.0001-10 parts by weight of calcium chloride are added, and the solution is stirred until it is clear and transparent; then 0.0001 parts by weight of β-amylase are added, and the solution is stirred and reacted at 60°C for 4 hours, during which the pH is maintained at about 3-4; then 0.0001 parts by weight of sodium carbonate are added, and the solution is stirred until it is clear and transparent, and the generated precipitate is removed by centrifugation; then the enzyme is inactivated and dried to obtain the product.

[0043] Preparation Example 2:

[0044] 15 parts by weight of distarch phosphate are dissolved in 100 parts by weight of water to prepare a solution, and the pH is adjusted to about 7, and then fully gelatinized at 150°C for 1.5 hours; then 5 parts by weight of dipotassium hydrogen phosphate are added, and the solution is stirred until it is clear and transparent; then 4.5 parts by weight of cellulase are added, and the reaction is stirred at 60°C-100°C for 3 hours, during which the pH is maintained at about 7; then 5 parts by weight of isoamylase are added, and the reaction is stirred at 70°C for 3 hours, during which the pH is maintained at about 7. The two-step enzyme treatment can better improve the permeability of the cross-linking agent finally obtained; then 5 parts by weight of sodium sulfate are added, and the solution is stirred until it is clear and transparent. If a precipitate is generated, it is removed by centrifugation; then the enzyme is inactivated and dried to obtain the product.

[0045] Preparation Example 3:

[0046] Take 10 parts by weight of acetylated distarch adipate and dissolve it in 100 parts by weight of water to prepare a solution, and adjust the pH to 5-6, and then fully gelatinize it at 150°C for about 2 hours; then add 0.1 parts by weight of calcium chloride, and stir the solution until it is clear and transparent; then add 0.1 parts by weight of α-amylase, stir and react at 100°C for 2 hours, during which the pH is maintained at about 5-6; after the reaction is completed, add 0.1 parts by weight of glucose amylase, stir and react at 100°C for 2 hours, during which the pH is maintained at about 5-6; then add 0.15 parts by weight of sodium carbonate, stir the solution until it is clear and transparent, and remove the generated precipitate by centrifugation; then inactivate the enzyme and dry it to obtain the product.

[0047] Preparation Example 4:

[0048] Take 30 parts by weight of hydroxypropyl distarch phosphate and dissolve it in 100 parts by weight of water to prepare a solution, and adjust the pH to 10, then fully gelatinize at 200°C for 1 hour; then add 10 parts by weight of calcium lactate, stir the solution until it is clear and transparent; then add 1 part by weight of α-amylase, stir and react at 100°C for 2 hours, during which the pH is maintained at 9-10; after the reaction is completed, add 1 part by weight of glucoamylase, stir and react at 100°C for 2 hours, during which the pH is maintained between 9-10. The two-step enzyme treatment can better improve the permeability of the final cross-linking agent. Then add 10 parts by weight of potassium carbonate, stir the solution until it is clear and transparent, and remove the precipitate by centrifugation; then inactivate the enzyme and dry it to obtain the product.

[0049] Combination Figure 1 The cross-linking principle of the cross-linking agent obtained in the above embodiment is specifically described below: Pre-cross-linked starch is composed of pre-cross-linked molecules ( Figure 1 There are also molecules that are not pre-crosslinked to two or more starch chains ( Figure 1 The pink circle in the middle) and the pre-crosslinked molecules with blocked reducing ends ( Figure 1 The Maillard reaction requires a free reducing end to proceed, but pre-crosslinked starch cannot undergo a typical reaction because the reducing end is blocked by the pre-crosslinked molecule (the reducing end -OH is most susceptible to the pre-crosslinked molecule, so it reacts first during the production of pre-crosslinked starch). After being processed by the preparation method of the present application, the glycosidic bond of the pre-crosslinked starch is broken, allowing the reducing end to be released and then used for crosslinking of the substrate.

[0050] (II) Application Experiment

[0051] Application Example 1:

[0052] The crosslinking agent of the present application is used to prepare crosslinking agent aqueous solutions with mass concentrations of 0%, 0.25%, 0.5%, 1%, and 2% for standby use. Soak the dried sea cucumber for 24 hours, then select multiple groups of water-soaked sea cucumbers, remove the internal organs and sand teeth, and put them into the crosslinking agent aqueous solution of corresponding concentration (dry weight ratio is 1:10), then crosslink at 100°C for 0.5h-1h. After the crosslinking is completed, wash the crosslinking agent with clean water. The state of the obtained sea cucumber is shown in the figure Figure 2 The hardness, elasticity, adhesiveness and chewiness of sea cucumbers were tested. The test results are shown in Table 1.

[0053] Table 1 Effects of cross-linking agents on various parameters of sea cucumbers

[0054]

[0055] pass Figure 2 and Figure 3 It can be seen that from the appearance of the sea cucumbers after steaming, the sea cucumbers treated with the cross-linking agent of the present application are significantly better than those without the addition of the cross-linking agent, and at the same concentration, the sea cucumbers treated with the cross-linking agent of the present application are better than those treated with glutamine transaminase.

[0056] As shown in Table 1, the sea cucumbers in the experimental group of the present application are also better than those in the blank group in terms of hardness, elasticity, adhesion, chewiness and other parameters, and are better than those in the control group at the same concentration. This shows that the cross-linking agent of the present application has better permeability and can significantly improve the high thermal stability and storage resistance of water-expanded sea cucumbers.

[0057] Application Example 2:

[0058] The crosslinking agent of the present application was used to prepare crosslinking agent aqueous solutions with mass concentrations of 0%, 0.25%, 0.5%, 1%, and 2% for standby use. Fresh shrimps were purchased from the market, rinsed with cold water, and the shrimp heads and shells were removed and placed in a crosslinking agent aqueous solution of corresponding concentration (dry weight ratio of 1:10), and then crosslinked at 100°C for 1-2 hours. After the crosslinking was completed, the crosslinking agent was washed off with clean water, and the shrimp appearance results were shown in Figure 4 The results of shrimp hardness, elasticity, adhesion, chewiness and other parameters are shown in Table 2.

[0059] Table 2 Effects of cross-linking agents on various parameters of sea cucumbers

[0060]

[0061] pass Figure 4 It can be seen that the shrimp meat in the blank group became soft, fragile, and lost its elasticity, and also had serious problems such as oxidation and water loss. The shrimp meat in the experimental group showed advantages such as more glossy, uniform color, firm texture, complete appearance and enhanced moisturizing properties.

[0062] As shown in Table 2, the shrimps in the experimental group of the cross-linking agent of the present application are better than those in the blank group in terms of hardness, elasticity, adhesion, chewiness and other parameters, and are better than those in the control group. This shows that the cross-linking agent of the present application has good permeability and can significantly improve the high thermal stability of fresh shrimps; in addition, the treatment with the cross-linking agent of the present application helps to reduce the damage and fragmentation of shrimp meat during processing and storage, making its appearance more complete without obvious damage or cracks. Make the texture more compact, and feel more elastic and firm. This improved texture allows consumers to feel the freshness and quality of the shrimp meat.

[0063] Application Example 3

[0064] 3 parts by weight of chitosan were dissolved in 100 parts by weight of 1% (v / v) acetic acid solution, and then 0.5 parts by weight of a cross-linking agent was added to the solution, stirred evenly, and then reacted in a high-temperature sterilizer at 121° C. for 15 minutes to obtain chitosan hydrogel.

[0065] from Figure 5 It can be seen that the state and color of chitosan changed before and after cross-linking, which indicates that chitosan molecules are indeed cross-linked to form chitosan gel, and the dark brown color also proves that the Maillard reaction has occurred.

[0066] Secondly, the present application also uses the rheological viscoelastic characteristics of these mixtures to carefully examine the formation of gels. Figure 6 It can be seen that at the same frequency, the apparent viscosity value of the gel (pre-crosslinked starch hydrolysate) formed by the crosslinking agent of the present application and chitosan is significantly greater than that of the other mixture control groups. And the increase in apparent viscosity is not the sum of the viscosities of each component, but a significantly enhanced phenomenon. This significant difference emphasizes the key role of the crosslinking agent of the present application in the crosslinking process, which can greatly enhance the mechanical strength of the gel.

[0067] Again, the present application also observes the biodegradability of chitosan hydrogel by conducting water solubility experiments. Figure 7 It can be seen that the gel obtained after chitosan cross-linking can be gradually degraded in water in a short time, showing excellent biocompatibility. It is convenient and widely used in the medical field, such as tissue engineering, drug delivery, wound dressings, surgical suture materials, etc., as well as food, cosmetics and other fields.

[0068] Application Example 4

[0069] In addition, the crosslinking agent of the present application can also react with polylysine to form an active glue; the application method is: dissolving ε-polylysine in a crosslinking agent aqueous solution, the crosslinking temperature is 60-150°C, the crosslinking time is 0.5-6h; the weight concentration of the crosslinking agent aqueous solution is 1g / L-200g / L. The obtained polylysine active glue has the advantages of good biocompatibility, biodegradability, adjustable physical and chemical properties, and excellent moisture retention and water absorption.

[0070] As for the application of polylysine active gel, it can be used as a drug delivery system in the biomedical field, can effectively encapsulate drugs, and control the release of drugs under specific conditions (such as pH changes, temperature changes, etc.). In the food industry, the texture and stability of food can be changed by adjusting these parameters, and it can be used as a food stabilizer. It can also be used well in cosmetics and personal care products, for example, it can be used as a matrix for products such as facial masks and skin creams, providing a long-term moisturizing effect. Finally, the gel can also play a role in the field of environmental engineering, using its efficient adsorption capacity to remove heavy metal ions and organic pollutants in water, thereby purifying water quality.

[0071] The above specific implementations cannot be used as limitations on the scope of protection of the present invention. For those skilled in the art, any replacement, improvement or change made to the implementations of the present invention falls within the scope of protection of the present invention. The parts not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A food-grade cross-linking agent with high permeability, characterized in that: The cross-linking agent is a pre-cross-linked oligosaccharide containing two reducing ends in a single molecule obtained by treating pre-cross-linked starch, which can improve the performance of the substrate by reacting with amino substrates to produce Maillard reaction and acetal or hemiacetal reaction with hydroxyl substrates; The pre-cross-linked starch is one of distarch phosphate, acetylated distarch phosphate, acetylated distarch adipate, and hydroxypropyl distarch phosphate; Wherein, the cross-linking agent is prepared by the following steps: S1: 10-30 parts by weight of pre-cross-linked starch is dissolved in 100 parts by weight of water to prepare a solution, and the pH is adjusted to 3-10, and then fully gelatinized at 100° C.-200° C. for 1-3 hours; S2: adding 0.0001-10 parts by weight of treatment agent A, stirring the solution until it becomes clear and transparent, wherein the treatment agent A is at least one of calcium chloride, sodium chloride, magnesium chloride, calcium lactate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate; S3: adding 0.0001-1 parts by weight of enzyme A, stirring and reacting at 60° C.-100° C. for 2-4 hours, during which the pH is maintained between 3-10, wherein the enzyme A is at least one of β-amylase, O-glycosidase, cellulase, pectinase, starch debranching enzyme, and α-amylase; S4: adding 0.0001-10 parts by weight of treatment agent B, stirring the solution until it is clear and transparent, and removing the precipitate by centrifugation if any, wherein the treatment agent B is selected from at least one of calcium chloride, sodium carbonate, sodium sulfate, potassium carbonate, and potassium sulfate; S5: After inactivating the enzyme, dry.

2. The food-grade cross-linking agent with high permeability according to claim 1, characterized in that: The following treatment step is also included between steps S3 and S4: 0.0001-1 parts by weight of enzyme B is added to the product of S3, and the reaction is stirred at 40° C.-100° C. for 2-4 hours, during which the pH is maintained between 3-10, wherein the enzyme B is selected from glucoamylase or isoamylase.

3. An application of a food-grade cross-linking agent with high permeability as claimed in claim 1 or 2, characterized in that: The cross-linked substrate is a natural macromolecule including protein, chitosan and polysaccharide; the dry weight ratio of the cross-linking agent to the cross-linked substrate is in the range of 1:10-1:50000.

4. The use of a food-grade cross-linking agent with high permeability according to claim 3, characterized in that: The cross-linking agent can be used to improve the high thermal stability of water-expanded sea cucumbers; the application method is: soak the water-expanded sea cucumbers in a cross-linking agent aqueous solution, the cross-linking temperature is 60-150°C, the cross-linking time is 0.5-6h; the weight concentration of the cross-linking agent aqueous solution is 1g / L-200g / L.

5. The use of a food-grade cross-linking agent with high permeability according to claim 3, characterized in that: The cross-linking agent can be used to improve the high thermal stability of fresh shrimps; the application method is: the fresh shrimps are processed into shrimp meat and immersed in the cross-linking agent aqueous solution, the cross-linking temperature is 60-150°C, the cross-linking time is 0.5-6h; the weight concentration of the cross-linking agent aqueous solution is 1g / L-200g / L.

6. The use of a food-grade cross-linking agent with high permeability according to claim 3, characterized in that: The crosslinking agent can react with chitosan to form chitosan gel. When the shear rate reaches 100s -1 When the temperature is 20000 ℃ and the viscosity is 4000 ℃, the apparent viscosity of chitosan gel is still not less than 1000 Pa.s.

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