Method for improving hot paste viscosity stability of oxidized esterified starch

Abstract

The invention discloses a method for improving the hot paste viscosity stability of oxidized esterified starch, and belongs to the technical field of modified starch. The invention discloses a method for improving hot paste viscosity stability of oxidized esterified starch, which comprises the following steps: by taking starch as a raw material, hydrogen peroxide as an oxidizing agent, vinyl acetate as an esterifying agent and sodium trimetaphosphate as a hot paste viscosity stabilizer, adding a sodium trimetaphosphate solution in batches according to the reaction pH value in an esterification process; the viscosity of the oxidized esterified starch paste liquid is maintained; meanwhile, the hot paste viscosity stability of the oxidized esterified starch is improved. The method is easy to operate, low in cost and high in practicability.

Description

Technical Field

[0001] The present invention relates to the technical field of modified starch, and more specifically, to a method for improving the thermal paste viscosity stability of oxidized esterified starch. Background Art

[0002] As is well known, starch is a natural product, which is not only rich in resources and low in price, but also widely used. With the development of technology, the performance of natural starch cannot meet the needs of industrial development. Therefore, physical, chemical, biological and composite modification of starch is carried out to change the performance of natural starch to meet the market demand.

[0003] Oxidized esterified starch is an important starch derivative. Through oxidation and esterification reactions, functional groups such as carboxyl groups and ester groups are introduced into starch molecules, thereby changing the properties of starch, such as paste viscosity, gelatinization temperature, water absorption, etc., and making it widely used in many fields such as food, papermaking, textile, medicine, and so on.

[0004] With the market demand, the application field of oxidized esterified starch expands and downstream customers have higher requirements for product quality. Improving product quality is currently the fundamental for production enterprises to gain a foothold in the market. When downstream customers use it, oxidized esterified starch is used after heating and gelatinization. As the heating time prolongs, the viscosity changes greatly, that is, the thermal paste viscosity stability is poor, the product quality is unstable, and the process is difficult to control.

[0005] Therefore, providing a method for improving the thermal paste viscosity stability of oxidized esterified starch is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for improving the thermal paste viscosity stability of oxidized esterified starch, aiming to solve the problems of unstable paste viscosity and poor thermal paste viscosity stability of oxidized esterified starch. Specifically, the thermal paste viscosity of oxidized esterified starch changes little with the prolongation of time at a certain high temperature.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme: A method for improving the thermal paste viscosity stability of oxidized esterified starch, comprising the following steps: (1) Weigh starch milk, hydrogen peroxide solution, vinyl acetate and sodium trimetaphosphate solution. The dosage of the hydrogen peroxide solution is 0.75 wt% of the starch, the dosage of the vinyl acetate is 4.5 wt% of the starch, and the dosage of the sodium trimetaphosphate is 0.15 wt% of the starch.

[0008] (2) Oxidation reaction: Add 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is between 8.0 - 8.5, add hydrogen peroxide solution at a rate of 2.5 kg / min. After adding, start timing for 3 h for the oxidation reaction. Control the temperature at 50 - 55 °C and the pH value at 8.0 - 8.5. When the pH value decreases during the process, adjust it with 3% sodium hydroxide. After the oxidation reaction, add a reducing agent and react for 10 - 15 min. The dosage of the reducing agent is 0.01 wt% of the starch.

[0009] (3) Esterification reaction: Adjust the pH value of the material to 10.0 - 10.1 with 10% sodium carbonate solution. Add 2 / 3 of the sodium trimetaphosphate solution, and then add vinyl acetate at a rate of 22 kg / min. When the pH value of the material drops to 9.5 - 9.8, add the remaining sodium trimetaphosphate solution simultaneously until the addition of vinyl acetate is completed and start timing, and react for 3 h. Maintain the temperature at 25 - 30 °C during the reaction; after the reaction, adjust the pH value of the material to 4.50 - 5.00 with 10% hydrochloric acid.

[0010] (4) Centrifuge and dry the product to obtain the finished product.

[0011] Further, the preparation method of the starch milk described in step (1) is: Dissolve starch in water to make a starch milk; the concentration of the starch milk is 40 - 45 wt%.

[0012] Further, the starch is corn starch.

[0013] Further, the hydrogen peroxide content in the hydrogen peroxide solution described in step (1) is 27.5 - 29 wt%.

[0014] Further, the vinyl acetate described in step (1) is a liquid with a content of ≥99%.

[0015] Further, the reducing agent described in step (2) is sodium metabisulfite or sodium thiosulfate.

[0016] Further, the preparation method of the sodium trimetaphosphate solution described in step (1): Weigh 0.15 wt% of sodium trimetaphosphate based on the mass of starch, and dissolve it into a 3 - 5% sodium trimetaphosphate solution for use.

[0017] Further, the drying in step (4) is to dry until the moisture content of the finished product is ≤14%.

[0018] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a method for improving the thermal paste viscosity stability of oxidized esterified starch. Sodium trimetaphosphate is used as the thermal paste viscosity stabilizer. During the reaction of starch with the esterifying agent, the pH value in the material decreases with the reaction time. Therefore, sodium trimetaphosphate is added in two stages, enabling the starch to carry out a cross-linking reaction with sodium trimetaphosphate while undergoing an esterification reaction with vinyl acetate. With the change of the pH value of the material during the cross-linking process, the cross-linking process is easy to control, maintaining the viscosity stability and solving the problem of poor thermal paste viscosity stability of oxidized esterified starch, which is convenient for the use of downstream customers. Specific Embodiments

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0020] The hydrogen peroxide solution (hydrogen peroxide ≥ 27.5%) was purchased from Dezhou Shihua Chemical Co., Ltd.; vinyl acetate was purchased from Tianjin Damao Chemical Reagent Factory.

[0021] Example 1 A method for improving the thermal paste viscosity stability of oxidized esterified starch includes the following steps: (1) Preparation of starch milk: Weigh 10 tons of corn starch and dissolve it in water to make a starch milk with a concentration of 40 wt%.

[0022] (2) Oxidation reaction: Weigh the hydrogen peroxide solution, and the dosage of the hydrogen peroxide solution is 0.75 wt% of the starch mass, with a hydrogen peroxide content of 27.5%; add a 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is 8.0, add the hydrogen peroxide solution at a rate of 2.5 kg / min. After adding, time for 3 h for the oxidation reaction, control the temperature at 50 - 55 °C, and the pH value at 8.0 - 8.5. When the pH value decreases during the process, adjust the pH value with 3% sodium hydroxide; after the oxidation reaction, add sodium metabisulfite reductant and react for 10 min, and the dosage of the reductant is 0.01 wt% of the starch.

[0023] (3)Esterification reaction: Weigh 0.15 wt% of sodium trimetaphosphate based on the mass of starch, and prepare a sodium trimetaphosphate solution with a concentration of 3%. Then weigh vinyl acetate, and the amount of vinyl acetate used is 4.5 wt% of the starch. Adjust the pH value of the material to 10.0 with 10% sodium carbonate solution, add 2 / 3 of the sodium trimetaphosphate solution, and then add vinyl acetate at a speed of 22 kg / min. When the pH value of the material drops to 9.5, add the remaining sodium trimetaphosphate solution simultaneously until the addition of vinyl acetate is completed and start timing. React for 3 h, and maintain the temperature at 25 - 30 °C during the reaction. After the reaction, adjust the pH value of the material to 4.50 with 10% hydrochloric acid to end the reaction and obtain the product.

[0024] (4)Centrifuge the product and air-dry it until the moisture content of the finished product is 13.5% to obtain the finished product, and measure the viscosity of the finished product paste and the thermal paste stability.

[0025] Example 2 A method for improving the thermal paste viscosity stability of oxidized esterified starch, comprising the following steps: (1)Preparation of starch milk: Weigh 10 tons of corn starch and dissolve it in water to adjust the slurry into a starch milk with a concentration of 43 wt%.

[0026] (2)Oxidation reaction: Weigh hydrogen peroxide solution, and the amount of hydrogen peroxide solution used is 0.75 wt% of the starch mass, and the concentration of hydrogen peroxide is 28.0%; Add 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is 8.3, add the hydrogen peroxide solution at a speed of 2.5 kg / min. After the addition, start timing for 3 h for the oxidation reaction, control the temperature at 50 - 55 °C, and the pH value at 8.0 - 8.5. When the pH value decreases during the process, adjust the pH value with 3% sodium hydroxide; After the oxidation reaction, add sodium thiosulfate reducing agent and react for 13 min, and the amount of the reducing agent used is 0.01 wt% of the starch.

[0027] (3)Esterification reaction: Weigh 0.15 wt% of sodium trimetaphosphate based on the mass of starch, and prepare a sodium trimetaphosphate solution with a concentration of 4%. Then weigh vinyl acetate, and the amount of vinyl acetate used is 4.5 wt% of the starch. Adjust the pH value of the material to 10.05 with 10% sodium carbonate solution, add 2 / 3 of the sodium trimetaphosphate solution, and then add vinyl acetate at a speed of 22 kg / min. When the pH value of the material drops to 9.7, add the remaining sodium trimetaphosphate solution simultaneously until the addition of vinyl acetate is completed and start timing. React for 3 h, and maintain the temperature at 25 - 30 °C during the reaction. After the reaction, adjust the pH value of the material to 4.80 with 10% hydrochloric acid to end the reaction and obtain the product.

[0028] (4)Centrifuge the product and air-dry it until the moisture content of the finished product is 13.0% to obtain the finished product, and measure the viscosity of the finished product paste and the thermal paste stability.

[0029] Example 3 A method for improving the thermal paste viscosity stability of oxidized esterified starch, comprising the following steps: (1) Preparation of starch milk: Weigh 10 tons of corn starch and dissolve it in water to make a starch milk with a concentration of 45 wt%.

[0030] (2) Oxidation reaction: Weigh hydrogen peroxide solution, the dosage of hydrogen peroxide solution is 0.75 wt% of the starch mass, and the concentration of hydrogen peroxide is 29.0%; add 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is 8.5, add the hydrogen peroxide solution at a rate of 2.5 kg / min. After adding, start timing for 3 h for the oxidation reaction, control the temperature at 50 - 55 °C, and the pH value at 8.0 - 8.5. When the pH value decreases during the process, adjust the pH value with 3% sodium hydroxide; after the oxidation reaction, add sodium metabisulfite reducing agent and react for 15 min, and the dosage of the reducing agent is 0.01 wt% of the starch.

[0031] (3) Esterification reaction: Weigh 0.15 wt% of sodium trimetaphosphate based on the starch mass, and prepare a sodium trimetaphosphate solution with a concentration of 5%; then weigh vinyl acetate, and the dosage of vinyl acetate is 4.5 wt% of the starch. Adjust the pH value of the material to 10.10 with 10% sodium carbonate solution, add 2 / 3 of the sodium trimetaphosphate solution, and then add vinyl acetate at a rate of 22 kg / min. When the pH value of the material drops to 9.8, add the remaining sodium trimetaphosphate simultaneously until the vinyl acetate is added completely and start timing for 3 h. Keep the temperature at 25 - 30 °C during the reaction. After the reaction, adjust the pH value of the material to 5.00 with 10% hydrochloric acid to end the reaction and obtain the product.

[0032] (4) Centrifuge the product and dry it with air flow until the moisture content of the finished product is 13.8% to obtain the finished product, and measure the viscosity and thermal paste stability of the finished product paste.

[0033] Comparative Example 1 (Conventional Process 1) A method for improving the thermal paste viscosity stability of oxidized esterified starch, comprising the following steps: (1) Preparation of starch milk: Weigh 10 tons of corn starch and dissolve it in water to make a starch milk with a concentration of 45 wt%.

[0034] (2) Oxidation reaction: Weigh hydrogen peroxide solution. The dosage of hydrogen peroxide solution is 0.75 wt% of the starch mass, and the concentration of hydrogen peroxide is 29.0%. Add 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is 8.5, add the hydrogen peroxide solution at a rate of 2.5 kg / min. After adding, time for 3 h for the oxidation reaction. Control the temperature at 50 - 55 °C and the pH value at 8.0 - 8.5. When the pH value decreases during the process, adjust it with 3% sodium hydroxide. After the oxidation reaction, add sodium metabisulfite reducing agent and react for 10 min. The dosage of the reducing agent is 0.01 wt% of the starch.

[0035] (3) Esterification reaction: Weigh vinyl acetate. The dosage of vinyl acetate is 4.5 wt% of the starch. Adjust the pH value of the material to 10.10 with 10% sodium carbonate solution. Add vinyl acetate at a rate of 22 kg / min until it is completely added, and then time for 3 h for the reaction. Keep the temperature at 25 - 30 °C during the reaction. After the reaction, adjust the pH value of the material to 5.00 with 10% hydrochloric acid to end the reaction and obtain the product.

[0036] (4) Centrifuge the product and air-dry it until the moisture content of the finished product is 13.8% to obtain the finished product, and measure the viscosity of the finished product paste and the thermal paste stability.

[0037] Comparative Example 2 (Adding sodium trimetaphosphate all at once) A method for improving the thermal paste viscosity stability of oxidized esterified starch, comprising the following steps: (1) Preparation of starch milk: Weigh 10 tons of corn starch and dissolve it in water to make a starch milk with a concentration of 43 wt%.

[0038] (2) Oxidation reaction: Weigh hydrogen peroxide solution. The dosage of hydrogen peroxide solution is 0.75 wt% of the starch mass, and the concentration of hydrogen peroxide is 28.0%. Add 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is 8.3, add the hydrogen peroxide solution at a rate of 2.5 kg / min. After adding, time for 3 h for the oxidation reaction. Control the temperature at 50 - 55 °C and the pH value at 8.0 - 8.5. When the pH value decreases during the process, adjust it with 3% sodium hydroxide. After the oxidation reaction, add sodium metabisulfite reducing agent and react for 15 min. The dosage of the reducing agent is 0.01 wt% of the starch.

[0039] (3)Esterification reaction: Weigh sodium trimetaphosphate at 0.15 wt% of the starch mass, and prepare a sodium trimetaphosphate solution with a concentration of 4%. Then weigh vinyl acetate, and the dosage of vinyl acetate is 4.5 wt% of the starch. Adjust the pH value of the material to 10.05 with 10% sodium carbonate solution, add the sodium trimetaphosphate solution, and then add vinyl acetate at a speed of 22 kg / min until the addition of vinyl acetate is completed and timing starts. React for 3 h, and maintain the temperature at 25 - 30 °C during the reaction. After the reaction, adjust the pH value of the material to 4.80 with 10% hydrochloric acid to end the reaction and obtain the product.

[0040] (4)Centrifuge the product and air-dry it until the moisture content of the finished product is 13.0% to obtain the finished product, and measure the viscosity of the finished product paste and the heat paste stability.

[0041] Comparative Example 3 (Conventional Process 2) A method for improving the heat paste viscosity stability of oxidized esterified starch, comprising the following steps: (1)Preparation of starch milk: Weigh 10 tons of corn starch and dissolve it in water to adjust the slurry into a starch milk with a concentration of 40 wt%.

[0042] (2)Oxidation reaction: Weigh hydrogen peroxide solution, and the dosage of hydrogen peroxide solution is 0.75 wt% of the starch mass, and the concentration of hydrogen peroxide is 27.5%; Add 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is 8.0, add the hydrogen peroxide solution at 2.5 kg / min. After adding, time for 3 h for the oxidation reaction, control the temperature at 50 - 55 °C, and the pH value at 8.0 - 8.5. When the pH value decreases during the process, adjust the pH value with 3% sodium hydroxide; After the oxidation reaction, add sodium metabisulfite reducing agent and react for 10 min, and the dosage of the reducing agent is 0.01 wt% of the starch.

[0043] (3)Esterification reaction: Weigh vinyl acetate, and the dosage of vinyl acetate is 4.5 wt% of the starch. Adjust the pH value of the material to 10.0 with 10% sodium carbonate solution, and add vinyl acetate at a speed of 22 kg / min until the addition of vinyl acetate is completed and timing starts. React for 3 h, and maintain the temperature at 25 - 30 °C during the reaction. After the reaction, adjust the pH value of the material to 4.50 with 10% hydrochloric acid to end the reaction and obtain the product.

[0044] (4)Centrifuge the product and air-dry it until the moisture content of the finished product is 13.5% to obtain the finished product, and measure the viscosity of the finished product paste and the heat paste stability.

[0045] Viscosity detection method for the oxidized esterified starch prepared in Examples 1-3 and Comparative Examples 1-3: Prepare the finished oxidized esterified starch into a starch emulsion with a concentration of 6%, stir evenly, place it in a boiling water bath for heating up. When the temperature of the starch emulsion rises to 95 °C, start timing for 1 h, detect the viscosity with an NDJ-79 viscometer, record the data, continue to keep warm until 3 h, detect the viscosity with an NDJ-79 viscometer, and record the data. The results are shown in Table 1.

[0046] The calculation formula for the hot paste stability is: Hot paste stability (%) = viscosity at 3 h / viscosity at 1 h × 100.

[0047] Table 1 Comparison table of detection data for Examples 1-3 and Comparative Examples 1-3

[0048] The results in Table 1 show that the viscosities of the oxidized esterified starches obtained in Examples 1-3 are relatively stable, and the hot paste stabilities are all better than those of Comparative Examples 1-3.

[0049] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for improving the hot paste viscosity stability of oxidized esterified starch, characterized in that: The following steps are involved: (1) Weigh starch milk, hydrogen peroxide solution, vinyl acetate and sodium trimetaphosphate solution, wherein the amount of hydrogen peroxide solution is 0.75wt% of the starch, the amount of vinyl acetate is 4.5wt% of the starch, and the amount of sodium trimetaphosphate is 0.15wt% of the starch; (2) Oxidation reaction: add 3% sodium hydroxide solution to the starch milk to adjust the pH value. When the pH value is between 8.0 and 8.5, add hydrogen peroxide solution at a rate of 2.5 kg / min. After the addition is completed, the oxidation reaction is carried out for 3 hours. The temperature is controlled at 50-55°C and the pH value is between 8.0 and 8.

5. When the pH value decreases in the middle, 3% sodium hydroxide is used to adjust the pH value. After the oxidation reaction, a reducing agent is added to react for 10-15 minutes. The amount of the reducing agent is 0.01wt% of the starch. (3) Esterification reaction: Use 10% sodium carbonate solution to adjust the pH value of the material to 10.0-10.1, add 2 / 3 of the sodium trimetaphosphate solution, and then add vinyl acetate at a rate of 22 kg / min. When the pH value of the material drops to 9.5-9.8, add the remaining sodium trimetaphosphate solution at the same time, and start timing when the vinyl acetate is added. The reaction time is 3 hours, and the temperature is maintained at 25-30 ° C during the reaction process; after the reaction is completed, use 10% hydrochloric acid to adjust the pH value of the material to 4.50-5.00; (4) Centrifuge the product and dry it to obtain the finished product.

2. A method for improving the hot paste viscosity stability of oxidized esterified starch according to claim 1, characterized in that: The preparation method of the starch milk described in step (1) is: dissolving starch in water to prepare starch milk; the concentration of the starch milk is 40-45wt%.

3. A method for improving the hot paste viscosity stability of oxidized esterified starch according to claim 2, characterized in that: The starch is corn starch.

4. A method for improving the hot paste viscosity stability of oxidized esterified starch according to claim 1, characterized in that: The hydrogen peroxide content in the hydrogen peroxide solution in step (1) is 27.5-29wt%.

5. A method for improving the hot paste viscosity stability of oxidized esterified starch according to claim 1, characterized in that: The vinyl acetate described in step (1) is liquid, and its content is ≥99%.

6. A method for improving the hot paste viscosity stability of oxidized esterified starch according to claim 1, characterized in that: The reducing agent in step (2) is sodium pyrosulfite or sodium thiosulfate.

7. A method for improving the hot paste viscosity stability of oxidized esterified starch according to claim 1, characterized in that: The preparation method of the sodium trimetaphosphate solution in step (1) is as follows: weigh 0.15wt% sodium trimetaphosphate by weight of starch and dissolve it into a 3-5% sodium trimetaphosphate solution for use.

8. A method for improving the hot paste viscosity stability of oxidized esterified starch according to claim 1, characterized in that: The drying in step (4) is performed until the moisture content of the finished product is ≤14%.

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