Cassava modified starch and production method thereof

Abstract

The cassava modified starch is prepared from the following raw materials in parts by weight: cassava starch, an esterifying agent, a coupling agent, a cross-linking agent and a surfactant. The invention also discloses a production method, which comprises the following steps: S1, pretreatment: dissolving cassava starch in water, stirring to form a suspension, performing ultrasonic treatment on the suspension, and drying; s2, cross-linking treatment: stirring and dissolving the pretreated cassava starch in water, stirring to form suspension slurry, adjusting the pH value, adding a cross-linking agent, and heating for reaction; s3, esterification treatment: after the cross-linking treatment reaction is completed, adjusting the pH value of the mixture, adding an esterifying agent and a surfactant while stirring, and heating for reaction; s4, coupling treatment: after esterification treatment is completed, adjusting the pH value of the mixture, adding a coupling agent, and heating for reaction; and S5, obtaining a finished product: neutralizing, washing, drying and crushing the mixture subjected to coupling treatment to obtain the cassava modified starch. The water absorption rate of the cassava starch can be remarkably reduced, and the performance of the cassava starch is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of modified starch, and in particular relates to modified cassava starch and a production method thereof. Background Art

[0002] Cassava starch is a powder made by dehydrating and drying cassava rhizomes after starch extraction. It is widely used in various fields. In the food industry, cassava starch is used as a thickener, stabilizer, adhesive, emulsifier, etc. to improve the taste, texture and stability of food. For example, adding cassava starch to sauces, dressings, pastries, cakes, ice cream and other foods can increase their viscosity and taste. In meat products and instant noodles, cassava starch can be used as an adhesive to help products stick together. In the pulp, fiber and textile, paint and coating industries, cassava starch can be used as an adhesive, slurry and stabilizer. For example, in the papermaking process, cassava modified starch can make fiber particles more compact and improve the quality and thickness of paper. In the fiber and textile industry, cassava starch can be used to make high-performance fibers and composite materials. In the paint and coating industry, it can improve the mechanical properties and stability of the coating.

[0003] Cassava starch has good physical and chemical properties and a wide range of applications, but the molecular structure of cassava starch contains a large number of hydroxyl (-OH) groups. These hydroxyl groups are extremely hydrophilic and can form hydrogen bonds with water molecules, allowing cassava starch to absorb a large amount of water. In addition, cassava starch is composed of long-chain polysaccharides, and there are many gaps between these polysaccharide molecules to accommodate water molecules. Therefore, cassava starch has strong hygroscopic properties, resulting in insufficient applicability in certain scenarios or fields, especially in the application of paper products. The high hygroscopicity of cassava starch will cause the strength and quality of the paper to decrease, making the paper prone to moisture and deformation; in the application of textile products, the high hygroscopicity of cassava starch may cause the performance of textiles to be unstable in humid environments.

[0004] Modified cassava starch is a type of cassava starch that has been chemically or physically treated. The "modification" of modified cassava starch refers to changing its original properties by chemical or physical methods, thereby giving the starch new properties and making it more practical in different application scenarios. The modification process can include acid treatment, alkali treatment, enzyme treatment or heat treatment. These processes can improve the starch's properties such as viscosity, stability, solubility and gelling ability.

[0005] However, the modified cassava starch in the prior art is not effective enough in improving the hygroscopicity of cassava starch and is not obvious in reducing the hygroscopicity of cassava starch, so the applicability of the modified cassava starch is still insufficient. Summary of the invention

[0006] The object of the present invention is to provide a cassava modified starch and a production method thereof, so as to solve the technical problems raised in the above background technology.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A modified cassava starch is prepared from the following raw materials in parts by weight: 100-180 parts of cassava starch, 3-8 parts of an esterifying agent, 5-12 parts of a coupling agent, 0.1-1 parts of a cross-linking agent, and 0.1-0.3 parts of a surfactant.

[0009] Furthermore, the esterification agent is acetic anhydride.

[0010] Furthermore, the coupling agent is methyltrimethoxysilane or ethoxysilane.

[0011] Furthermore, the cross-linking agent is one of sodium tripolyphosphate, disodium hydrogen phosphate and trisodium phosphate.

[0012] Furthermore, the surfactant is Tween-80.

[0013] A method for producing modified cassava starch comprises the following steps:

[0014] S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment and drying;

[0015] S2 cross-linking treatment: dissolving the pre-treated cassava starch in water by stirring to form a suspension slurry, adjusting the pH, adding a cross-linking agent, and heating for reaction;

[0016] S3 esterification treatment: After the cross-linking treatment reaction is completed, the pH of the mixture is adjusted, the esterification agent and the surfactant are added with stirring, and the mixture is heated for reaction;

[0017] S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted, a coupling agent is added, and the mixture is heated for reaction;

[0018] S5 finished product: neutralize the mixture after coupling treatment, wash, dry and crush to obtain cassava modified starch.

[0019] Furthermore, in S1, the power of the ultrasonic wave is 200-300W, and the treatment time is 30-60min.

[0020] Furthermore, in step S2, the pH is adjusted to 9-10; the temperature of the heating reaction is 25-35° C., and the time is 1-2 h.

[0021] Furthermore, in step S3, the pH is adjusted to 8-9; the temperature of the heating reaction is 20-40° C., and the time is 1-2 h.

[0022] Furthermore, in step S4, the pH is adjusted to 5-6; the heating reaction temperature is 50-60° C. and the time is 2-3 hours.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention uses a cross-linking agent, an esterifying agent and a coupling agent to perform a denaturation treatment on cassava starch, thereby improving the hygroscopicity of cassava starch. Through the effects of the cross-linking agent, the esterifying agent and the coupling agent, the water absorption rate of cassava starch can be significantly reduced, the performance of cassava starch is improved, and the application field of cassava starch is expanded.

[0025] 2. The present invention first cross-links cassava starch with a cross-linking agent, so that the starch molecules form a stable three-dimensional network structure, increase the stability and strength of the starch molecular structure, and can also keep the starch unchanged in the subsequent esterification and coupling process, while improving the efficiency of the esterification and coupling reaction. And the cross-linking reaction can expose more reaction sites, making it easier for the esterifier and the coupling agent to react, improving the modification effect, in addition, when the phosphoric acid cross-linking agent is cross-linked with the starch molecule, the chemical bond formed can stabilize the ester group generated by the subsequent esterification reaction, preventing the ester group from being dissociated during the reaction, thereby ensuring the esterification effect. The acetic anhydride esterifier converts the hydroxyl group (-OH) in the cassava starch into an ester group (-OC=O) through an esterification reaction, which can significantly reduce the number of hydrophilic groups in the starch molecule, thereby reducing the ability of the starch to absorb water. The silane group is introduced into the cassava starch molecule through a silanization reaction, and the silane group of the coupling agent is hydrophobic, forming a hydrophobic layer on the surface of the starch molecule, so that the surface of the starch molecule is difficult to combine with water molecules, thereby further reducing the hygroscopicity. The use of esterifying agent and coupling agent together reduces the hydrophilic groups of starch molecules and generates a hydrophobic layer, which gives the starch molecules multiple hydrophobic properties. The three interact with each other and can synergistically enhance the effect, thereby significantly reducing the hygroscopicity of cassava starch.

[0026] 3. Before the modification, the present invention first performs ultrasonic pretreatment on cassava starch, so that the cassava starch particles are subjected to mechanical vibration and cavitation, thereby destroying the surface structure of the particles, increasing its reactivity, making it easier for the reactants in the subsequent modification to enter the starch particles, and promoting the reaction. After the ultrasonic treatment, the cassava starch particles can be evenly dispersed in the suspension, avoiding particle agglomeration, ensuring that the starch particles are fully in contact with the reactants, and improving the uniformity and efficiency of the reaction. After the ultrasonic treatment, the starch particles can be exposed to more hydroxyl groups, providing more reaction sites, which is conducive to the denaturation treatment reaction. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, preferred embodiments are given below to further describe the present invention in detail. However, it should be noted that many details listed in the specification are only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the present invention, and these aspects of the present invention can be implemented even without these specific details.

[0028] A modified cassava starch is prepared from the following raw materials in parts by weight: 100-180 parts of cassava starch, 3-8 parts of acetic anhydride esterification agent, 5-12 parts of coupling agent, 0.1-1 part of cross-linking agent and 0.1-0.3 part of Tween-80 surfactant.

[0029] The coupling agent is methyltrimethoxysilane or ethoxysilane.

[0030] The cross-linking agent is one of sodium tripolyphosphate, disodium hydrogen phosphate and trisodium phosphate.

[0031] A method for producing modified cassava starch comprises the following steps:

[0032] S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment at an ultrasonic power of 200-300W for 30-60min, followed by drying after treatment;

[0033] S2 cross-linking treatment: dissolving the pre-treated cassava starch in water to form a suspension slurry, adjusting the pH to 9-10, adding a cross-linking agent, and heating the reaction at 25-35°C for 1-2h;

[0034] S3 esterification treatment: After the cross-linking treatment reaction is completed, adjust the pH of the mixture to 8-9, add the esterification agent and Tween-80 surfactant with stirring, and heat the reaction at a temperature of 20-40°C for 1-2h;

[0035] S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted to 5-6, a coupling agent is added, and the mixture is heated at 50-60°C for 2-3h;

[0036] S5 finished product: neutralize the mixture after coupling treatment, wash, dry and crush to obtain cassava modified starch.

[0037] The principle of the present invention is:

[0038] (I) Function and mechanism of raw materials

[0039] 1. Cassava starch: main ingredient.

[0040] 2. Cross-linking agent (sodium tripolyphosphate, disodium hydrogen phosphate, trisodium phosphate): Initiate cross-linking reaction to form chemical bonds between cassava starch molecules. This cross-linking structure makes the starch molecules closer together, forming a three-dimensional network structure, which limits the penetration and absorption of water molecules and improves the structural stability and mechanical strength of starch. In addition, the cross-linking reaction can expose more reaction sites and a more stable reaction environment, making it easier to react in subsequent steps.

[0041] 2. Acetic anhydride esterification agent: There are a large number of hydroxyl (-OH) groups in starch molecules, which easily form hydrogen bonds and combine with water molecules, making cassava starch highly hygroscopic. The esterification agent converts the hydroxyl (-OH) in cassava starch into ester groups (-OC=O) through esterification reaction. Ester groups are not easy to interact with water molecules. Therefore, after esterification, the number of hydrophilic groups in starch molecules can be reduced, thereby reducing the ability of starch to absorb water.

[0042] 3. Coupling agent (methyltrimethoxysilane or ethoxysilane): Silane groups are introduced into cassava starch molecules through silanization reaction. The silane groups of the coupling agent are hydrophobic, forming a hydrophobic layer on the surface of the starch molecules, making it difficult for the starch molecule surface to combine with water molecules, thereby further reducing hygroscopicity. In addition, silane coupling agents can also improve the interface and compatibility of starch molecules, so that when they are used in various materials, they can better combine with other substrates.

[0043] 4. Surfactant: Surfactant can increase the solubility of esterification reactants, make the reactants more evenly distributed in the solution, and improve the reaction efficiency; and surfactant can reduce the interfacial tension between the reactants, promote the esterification reaction, and make the reaction more rapid and thorough. In addition, through the action of surfactant, the surface contact area of ​​the reactants is increased, further promoting the esterification reaction.

[0044] 2. Raw material dosage

[0045] Reasonable raw material dosage has an important impact on the final product. For example, the dosage of cross-linking agent ensures the formation of sufficient cross-linking bonds, so that the starch can form a stable structure, and can prevent excessive use from causing the product to be hard and brittle. The dosage of esterification agent and coupling agent ensures the adequacy of the reaction and prevents waste and by-product generation caused by excessive use. The dosage of surfactant has sufficient dispersion and stabilization effect, and prevents foam and separation problems that may be caused by excessive use.

[0046] 3. Process Optimization

[0047] 1. Process sequence: A reasonable process sequence also has an important impact on the preparation of the product. This application adopts the process sequence of pretreatment-crosslinking-esterification-coupling. By first performing ultrasonic pretreatment on cassava starch, the performance of the original starch molecules is improved; pretreatment and then esterification and coupling can ensure that a firm three-dimensional network structure is formed between starch molecules. This can provide a stable foundation and improve the mechanical strength and thermal stability of the entire system. If esterification and coupling are performed first, the subsequent crosslinking reaction may be limited by the previously modified molecular structure and the efficiency is low. And the occurrence of the crosslinking reaction requires the participation of the hydroxyl group (-OH) on the starch molecule. By crosslinking first, it can be ensured that these reaction sites are used to form a three-dimensional network structure. If esterification is performed first, the hydroxyl group will be consumed by the esterification reaction, which may affect the progress of the crosslinking reaction.

[0048] 2. Process conditions:

[0049] Process conditions affect the quality of the final product. The performance of the final product can be guaranteed by selectively controlling and optimizing the process parameters of each step.

[0050] The following is a more specific example.

[0051] Example 1

[0052] A modified cassava starch is prepared from the following raw materials in parts by weight: 150 parts of cassava starch, 0.5 parts of sodium tripolyphosphate crosslinking agent, 8 parts of acetic anhydride esterifying agent, 10 parts of methyltrimethoxysilane coupling agent and 0.1 parts of Tween-80 surfactant.

[0053] A method for producing modified cassava starch comprises the following steps:

[0054] S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment at an ultrasonic power of 200 W for 40 min, followed by drying after treatment;

[0055] S2 cross-linking treatment: the pre-treated cassava starch was dissolved in water by stirring to form a suspension slurry, the pH was adjusted to 9, a cross-linking agent was added, and the mixture was heated at 25°C for 2 hours;

[0056] S3 esterification treatment: After the cross-linking treatment reaction is completed, the pH of the mixture is adjusted to 8, and the esterification agent and Tween-80 surfactant are added with stirring, and the reaction is heated at 25°C for 1.5 hours;

[0057] S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted to 5, a coupling agent is added, and the mixture is heated at 60°C for 3 hours;

[0058] S5 finished product: neutralize the mixture after coupling treatment, wash, dry and crush to obtain cassava modified starch.

[0059] Example 2

[0060] A modified cassava starch is prepared from the following raw materials in parts by weight: 120 parts of cassava starch, 0.1 parts of disodium hydrogen phosphate cross-linking agent, 4 parts of acetic anhydride esterifying agent, 8 parts of ethoxysilane coupling agent, and 0.2 parts of Tween-80 surfactant.

[0061] A method for producing modified cassava starch comprises the following steps:

[0062] S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment at an ultrasonic power of 300 W for 30 min, followed by drying after treatment;

[0063] S2 cross-linking treatment: the pre-treated cassava starch was dissolved in water by stirring to form a suspension slurry, the pH was adjusted to 10, a cross-linking agent was added, and the reaction was heated at 27°C for 1.2h;

[0064] S3 esterification treatment: After the cross-linking treatment reaction is completed, the pH of the mixture is adjusted to 8, and the esterification agent and Tween-80 surfactant are added with stirring, and the mixture is heated at 40°C for 2 hours;

[0065] S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted to 6, a coupling agent is added, and the mixture is heated at 55°C for 2.5 hours;

[0066] S5 finished product: neutralize the mixture after coupling treatment, wash, dry and crush to obtain cassava modified starch.

[0067] Example 3

[0068] A modified cassava starch is prepared from the following raw materials in parts by weight: 100 parts of cassava starch, 1 part of trisodium phosphate cross-linking agent, 6 parts of acetic anhydride esterifying agent, 5 parts of methyltrimethoxysilane coupling agent and 0.1 part of Tween-80 surfactant.

[0069] A method for producing modified cassava starch comprises the following steps:

[0070] S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment at an ultrasonic power of 300 W for 60 min, followed by drying after treatment;

[0071] S2 cross-linking treatment: the pre-treated cassava starch was dissolved in water by stirring to form a suspension slurry, the pH was adjusted to 10, a cross-linking agent was added, and the reaction was heated at 30°C for 1.5h;

[0072] S3 esterification treatment: After the cross-linking treatment reaction is completed, the pH of the mixture is adjusted to 9, and the esterification agent and Tween-80 surfactant are added with stirring, and the mixture is heated at 30°C for 1 hour;

[0073] S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted to 6, a coupling agent is added, and the mixture is heated at 60°C for 2 hours;

[0074] S5 finished product: neutralize the mixture after coupling treatment, wash, dry and crush to obtain cassava modified starch.

[0075] Example 4

[0076] A modified cassava starch is prepared from the following raw materials in parts by weight: 180 parts of cassava starch, 0.8 parts of disodium hydrogen phosphate cross-linking agent, 3 parts of acetic anhydride esterifying agent, 10 parts of methyltrimethoxysilane coupling agent, and 0.3 parts of Tween-80 surfactant.

[0077] A method for producing modified cassava starch comprises the following steps:

[0078] S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment at an ultrasonic power of 200 W for 50 min, followed by drying after treatment;

[0079] S2 cross-linking treatment: the pre-treated cassava starch was dissolved in water by stirring to form a suspension slurry, the pH was adjusted to 9, a cross-linking agent was added, and the mixture was heated at 35°C for 1 h;

[0080] S3 esterification treatment: After the cross-linking treatment reaction is completed, the pH of the mixture is adjusted to 9, and the esterification agent and Tween-80 surfactant are added with stirring, and the reaction is heated at 35°C for 1.8 hours;

[0081] S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted to 5, a coupling agent is added, and the mixture is heated at 50°C for 2 hours;

[0082] S5 finished product: neutralize the mixture after coupling treatment, wash, dry and crush to obtain cassava modified starch.

[0083] Example 5

[0084] A modified cassava starch is prepared from the following raw materials in parts by weight: 160 parts of cassava starch, 0.2 parts of a sodium tripolyphosphate crosslinking agent, 5 parts of an acetic anhydride esterifying agent, 12 parts of a methyltrimethoxysilane coupling agent, and 0.2 parts of a Tween-80 surfactant.

[0085] A method for producing modified cassava starch comprises the following steps:

[0086] S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment at an ultrasonic power of 200 W for 40 min, followed by drying after treatment;

[0087] S2 cross-linking treatment: the pre-treated cassava starch was dissolved in water by stirring to form a suspension slurry, the pH was adjusted to 9, a cross-linking agent was added, and the reaction was heated at 32°C for 1.8h;

[0088] S3 esterification treatment: After the cross-linking treatment reaction is completed, the pH of the mixture is adjusted to 9, and the esterification agent and Tween-80 surfactant are added with stirring, and the mixture is heated at 20°C for 1.2 hours;

[0089] S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted to 6, a coupling agent is added, and the mixture is heated at 60°C for 3 hours;

[0090] S5 finished product: neutralize the mixture after coupling treatment, wash, dry and crush to obtain cassava modified starch.

[0091] Comparative Example 1

[0092] The method is substantially the same as Example 1, except that the cassava starch is not subjected to modification treatment.

[0093] Comparative Example 2

[0094] The method is basically the same as Example 1, except that the modified cassava starch is modified only by using a cross-linking agent.

[0095] Comparative Example 3

[0096] The method is basically the same as Example 1, except that, in the modified cassava starch, only an esterifying agent is used for modification.

[0097] Comparative Example 4

[0098] The method is basically the same as Example 1, except that, in the modified cassava starch, only a coupling agent is used for modification.

[0099] Comparative Example 5

[0100] The method is basically the same as Example 1, except that the cassava modified starch is not pretreated in the production method.

[0101] 1. Experiment on hygroscopic properties of cassava modified starch

[0102] Weigh the same mass of modified cassava starch from Examples 1-5 and Comparative Examples 1-5, weigh three portions of each, put them into deionized water at 25°C, and soak them at room temperature for 72 hours respectively. After soaking, remove the water from the surface of the modified cassava starch and dry it, weigh it, calculate the average water absorption rate of each example and comparative example, and record the results as shown in Table 1.

[0103] Water absorption rate = (m2-m1) / m1×100%.

[0104] Wherein, m1 is the initial mass of cassava modified starch; m2 is the weight after soaking.

[0105] Table 1 Water absorption of cassava modified starch

[0106]

[0107]

[0108] From Table 1 we can see that:

[0109] (1) The modified cassava starch prepared in Examples 1-5 of the present application has a 72h water absorption rate of 10.2%, 12.1%, 14.7%, 11.8% and 12.4%, respectively. The 72h water absorption rate of Example 1 reaches 10.2%, indicating that the present application can significantly reduce the water absorption of cassava starch by modifying the cassava starch with a cross-linking agent, an esterifying agent and a coupling agent.

[0110] (2) In Comparative Examples 1-4, the cassava starch that was not denatured and not completely treated with the crosslinking agent, esterifying agent and coupling agent of the present application had a 72h water absorption rate of 33.6%, 27.4%, 24.7% and 29.7%, respectively, which were all inferior to Examples 1-5 of the present application. It can be seen that the crosslinking agent, esterifying agent and coupling agent used in the present application to denature cassava starch can interact with each other, synergistically enhance the effect, and jointly reduce the water absorption of cassava starch.

[0111] This is because: the cassava starch is first cross-linked with a cross-linking agent to form a stable three-dimensional network structure of starch molecules, increase the stability and strength of the starch molecular structure, and enable the starch to maintain its shape unchanged during the subsequent esterification and coupling process, while improving the efficiency of the esterification and coupling reactions. In addition, the cross-linking reaction can expose more reaction sites, making it easier for the esterifier and coupling agent to react and improving the modification effect. In addition, when the phosphoric acid cross-linking agent cross-links with the starch molecules, the chemical bonds formed can stabilize the ester groups generated by the subsequent esterification reaction and prevent the ester groups from being dissociated during the reaction, thereby ensuring the esterification effect. The acetic anhydride esterifier converts the hydroxyl group (-OH) in the cassava starch into an ester group (-OC=O) through an esterification reaction, which can significantly reduce the number of hydrophilic groups in the starch molecules, thereby reducing the ability of the starch to absorb water. The silane group is introduced into the cassava starch molecule through a silanization reaction. The silane group of the coupling agent is hydrophobic and forms a hydrophobic layer on the surface of the starch molecule, making it difficult for the starch molecule surface to bind to water molecules, thereby further reducing the hygroscopicity. The use of esterifying agent and coupling agent together reduces the hydrophilic groups of starch molecules and generates hydrophobic layers, which gives the starch molecules multiple hydrophobic properties, thereby significantly reducing the hygroscopicity of cassava starch.

[0112] (3) Comparative Example 5, which did not adopt the ultrasonic pretreatment of the present application, had a 72h water absorption rate of 20.3%, which was also lower than that of Examples 1-5 of the present application. This shows that the present application can significantly reduce the hygroscopic properties of cassava starch by first subjecting cassava starch to ultrasonic pretreatment.

[0113] This is due to:

[0114] Ultrasonic waves can cause mechanical vibration and cavitation of cassava starch particles, thereby destroying the surface structure of the particles, increasing their reactivity, and making it easier for the reactants in the subsequent modification to enter the starch particles and promote the reaction. After ultrasonic treatment, the cassava starch particles can be evenly dispersed in the suspension, avoiding particle agglomeration, ensuring that the starch particles are in full contact with the reactants, and improving the uniformity and efficiency of the reaction. After ultrasonic treatment, the starch particles can expose more hydroxyl groups, providing more reaction sites, which is conducive to the denaturation reaction.

[0115] 2. Contact angle experiment of cassava modified starch

[0116] 1 g of each of the modified cassava starches prepared in Example 1 and Comparative Examples 1-5 was taken as a sample, pressed into a film on a tablet press, and then placed on a glass slide. The water drop contact angle was measured using a contact angle meter. Each sample was tested 5 times, and the average value was taken. The results are recorded as shown in Table 2.

[0117] Table 2 Contact angle of cassava modified starch

[0118] project Contact angle / ° Example 1 91.4 Comparative Example 1 33.7 Comparative Example 2 47.4 Comparative Example 3 53.8 Comparative Example 4 45.1

[0119] As can be seen from Table 2, the contact angle of the modified cassava starch in Example 1 is 91.4°, indicating that in the modified cassava starch in Example 1, the attachment and penetration of water molecules on the surface of the modified cassava starch are greatly hindered; while the contact angles of the modified cassava starch in Comparative Examples 1-4 are 33.7°, 47.4°, 53.8°, and 45.1°, respectively, which are all smaller than Example 1 of the present application, indicating that compared with Example 1 of the present application, water molecules are more likely to attach and penetrate the modified cassava starch in Comparative Examples 1-4. Therefore, the modified cassava starch prepared by the crosslinking agent, esterifying agent, and coupling agent in the present application can increase the contact angle between starch molecules and water, increase the hindrance of water molecule attachment and penetration, and thus significantly reduce the hygroscopic properties of the modified cassava starch.

[0120] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A cassava modified starch, characterized in that: The invention is prepared from the following raw materials in parts by weight: 100-180 parts of cassava starch, 3-8 parts of an esterifying agent, 5-12 parts of a coupling agent, 0.1-1 parts of a cross-linking agent and 0.1-0.3 parts of a surfactant.

2. A cassava modified starch according to claim 1, characterized in that: The esterifying agent is acetic anhydride.

3. A cassava modified starch according to claim 1, characterized in that: The coupling agent is methyltrimethoxysilane or ethoxysilane.

4. A cassava modified starch according to claim 1, characterized in that: The cross-linking agent is one of sodium tripolyphosphate, disodium hydrogen phosphate and trisodium phosphate.

5. A cassava modified starch according to claim 1, characterized in that: The surfactant is Tween-80.

6. A method for producing modified cassava starch according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1 pretreatment: dissolving cassava starch in water, stirring to form a suspension, and then subjecting the suspension to ultrasonic treatment and drying; S2 cross-linking treatment: dissolving the pre-treated cassava starch in water by stirring to form a suspension slurry, adjusting the pH, adding a cross-linking agent, and heating for reaction; S3 esterification treatment: After the cross-linking treatment reaction is completed, the pH of the mixture is adjusted, the esterification agent and the surfactant are added with stirring, and the mixture is heated for reaction; S4 coupling treatment: after the esterification treatment is completed, the pH of the mixture is adjusted, a coupling agent is added, and the mixture is heated for reaction; S5 Finished product: The mixture after coupling treatment is neutralized, washed, dried and crushed to obtain cassava modified starch.

7. The method for producing modified cassava starch according to claim 6, characterized in that: In S1, the power of the ultrasonic wave is 200-300W, and the treatment time is 30-60min.

8. The method for producing modified cassava starch according to claim 6, characterized in that: In step S2, the pH is adjusted to 9-10; the heating reaction temperature is 25-35° C. and the time is 1-2 hours.

9. The method for producing modified cassava starch according to claim 6, characterized in that: In step S3, the pH is adjusted to 8-9; the heating reaction temperature is 20-40° C. and the time is 1-2 h.

10. The method for producing modified cassava starch according to claim 6, characterized in that: In step S4, the pH is adjusted to 5-6; the heating reaction temperature is 50-60° C. and the time is 2-3 hours.

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