阅读说明：本技术 一种乙酰化二淀粉磷酸酯变性淀粉及其制备方法和应用 (Acetylated distarch phosphate modified starch and preparation method and application thereof ) 是由 李克文 栾庆民 孔刘娟 张莉 熊小兰 李新华 刘开昌 吴吉才 柴雄 于 2021-11-01 设计创作，主要内容包括：本发明公开了一种乙酰化二淀粉磷酸酯变性淀粉及其制备方法和应用,向水分含量≤1%的淀粉中喷洒盐酸,搅拌反应后静置至粉体膨胀,于50-120℃烘40-90min,得预处理淀粉,加入无水硫酸钠和碳酸钠,喷洒三氯氧磷,搅拌均匀后再次加入碳酸钠,静置至粉体膨胀后于40-50℃保温30～50min,得磷酸酯交联淀粉,加水配成淀粉乳,调节pH9-10,升温至33-35℃后加入催化剂,滴加醋酸酐,保持体系pH 8.4-8.6,滴加完成后反应30-40min,得乙酰化二淀粉磷酸酯粗品,精制。本发明通过对淀粉进行预处理,并进行交联、酯化,提高交联度和取代度,明显提高了改性淀粉的理化性质,同时使变性淀粉具有特殊的凝胶凝结性质,固液相均稳定不易发生沉降,液相不出现分层等,可应用于饮品及口服液等液体食品中。(The invention discloses acetylated distarch phosphate modified starch and a preparation method and application thereof, hydrochloric acid is sprayed into starch with the moisture content less than or equal to 1 percent, the mixture is stirred and reacted, then the mixture is kept stand until the powder is expanded, the mixture is dried for 40-90min at 50-120 ℃ to obtain pretreated starch, anhydrous sodium sulfate and sodium carbonate are added, phosphorus oxychloride is sprayed, the sodium carbonate is added again after the mixture is stirred uniformly, the mixture is kept stand until the powder is expanded, the temperature is kept at 40-50 ℃ for 30-50 min to obtain phosphate crosslinked starch, the mixture is added with water to prepare starch milk, the pH is adjusted to 9-10, the catalyst is added after the temperature is raised to 33-35 ℃, acetic anhydride is dripped, the pH of the system is kept at 8.4-8.6, the reaction is carried out for 30-40min after the dripping is finished, and acetylated distarch phosphate crude product is obtained and refined. The invention improves the crosslinking degree and the substitution degree by pretreating, crosslinking and esterifying the starch, obviously improves the physical and chemical properties of the modified starch, simultaneously ensures that the modified starch has special gel coagulation property, has stable solid-liquid phase and difficult sedimentation, has no layering of the liquid phase and the like, and can be applied to liquid foods such as drinks, oral liquid and the like.)

1. The acetylated distarch phosphate modified starch is characterized by being prepared by the following method:

(1) pretreatment: spraying hydrochloric acid with a mass of 0.5-2% of the dry mass of the starch into the starch, continuously stirring for reaction for 20-30 min, standing until the powder expands, and then drying at 50-120 ℃ for 40-90min to obtain pretreated starch;

(2) and (3) crosslinking: adding anhydrous sodium sulfate and sodium carbonate into the pretreated starch, uniformly stirring, spraying phosphorus oxychloride with the content of 0.05-0.1% of the dry starch basis, uniformly stirring, adding sodium carbonate again, uniformly stirring, standing until the powder expands, and keeping the temperature at 40-50 ℃ for 30-50 min to obtain phosphate ester crosslinked starch;

(3) esterification: preparing phosphate crosslinked starch and water into starch milk, adjusting the pH value to 9-10, stirring and heating to 33-35 ℃, adding a catalyst, then dropwise adding acetic anhydride accounting for 3-7% of the dry weight of the starch, and keeping the pH value of a reaction system to 8.4-8.6; after the dropwise addition is finished, controlling the pH value to be 8.4-8.6, and continuously reacting for 30-40min to obtain an acetylated distarch phosphate crude product;

(4) and (5) refining.

2. The acetylated distarch phosphate modified starch of claim 1, wherein the starch in step (1) is corn starch dried to a moisture content of 1% or less; the concentration of the hydrochloric acid is 1 percent.

3. The acetylated distarch phosphate modified starch of claim 1, wherein the spraying of step (1) and step (2) is carried out while stirring the starch throughout; the dripping time of the acetic anhydride in the step (3) is 60-70 min.

4. The acetylated distarch phosphate modified starch according to claim 1, wherein the anhydrous sodium sulfate and sodium carbonate are added in step (2) in amounts of 0.5-1% and 1-2% by weight of the starch on a dry basis, respectively, and the sodium carbonate is added again in amounts of 0.5-1% by weight of the starch on a dry basis.

5. The acetylated distarch phosphate modified starch according to claim 1, wherein the catalyst in step (3) is pyridine added in an amount of 0.01% by weight of the starch on a dry basis.

6. The acetylated distarch phosphate modified starch of claim 1, wherein the weight ratio of phosphate crosslinked starch to water in step (3) is 1: 2-3.

7. The acetylated distarch phosphate modified starch of claim 1, wherein the refining process in step (3) is: adjusting the pH value of the starch milk of the acetylated distarch phosphate crude product to 4.2-4.5, stopping the esterification reaction, and obtaining the acetylated distarch phosphate finished product after filtering, washing, drying at low temperature and crushing.

8. A method for preparing the acetylated distarch phosphate modified starch according to any one of claims 1 to 7, comprising the following steps:

(1) pretreatment: spraying hydrochloric acid with a mass of 0.5-2% of the dry mass of the starch into the starch, continuously stirring for reaction for 20-30 min, standing until the powder expands, and then drying at 50-120 ℃ for 40-90min to obtain pretreated starch;

(2) and (3) crosslinking: adding anhydrous sodium sulfate and sodium carbonate into the pretreated starch, uniformly stirring, spraying phosphorus oxychloride with the content of 0.05-0.1% of the dry starch basis, uniformly stirring, adding sodium carbonate again, uniformly stirring, standing until the powder expands, and keeping the temperature at 40-50 ℃ for 30-50 min to obtain phosphate ester crosslinked starch;

(3) esterification: preparing phosphate crosslinked starch and water into starch milk, adjusting the pH value to 9-10, stirring and heating to 33-35 ℃, adding a catalyst, then dropwise adding acetic anhydride accounting for 3-7% of the dry weight of the starch, and keeping the pH value of a reaction system to 8.4-8.6; after the dropwise addition is finished, controlling the pH value to be 8.4-8.6, and continuously reacting for 30-40min to obtain an acetylated distarch phosphate crude product;

(4) and (5) refining.

9. Use of an acetylated distarch phosphate modified starch according to any one of claims 1 to 7 in a liquid food product.

10. The use of acetylated distarch phosphate modified starch according to claim 9 in a liquid food product, said liquid food product being a beverage or an oral liquid.

Technical Field

The invention belongs to the technical field of modified starch preparation, and particularly relates to acetylated distarch phosphate modified starch and a preparation method and application thereof.

Background

Starch molecules are polymers of glucose units, including amylose and amylopectin, consisting of alpha-D-1, 4-and alpha-D-1, 6-glucosidic bonds, respectively, and the C2, C3 and C6 bonds of each unit have free hydroxyl groups as reactive units, which are reactive with a number of compounds, e.g.when some compounds contain two or more groups reactive with hydroxyl groups, it is possible to form crosslinks with hydroxyl groups on the same or different molecules, and under alkaline conditions the reactive units on the starch molecules are activated and the reactive units can be replaced by esterification agents and joined together by hydrogen bonds, thus improving the properties of the starch. The acetylated distarch phosphate modified starch is esterified and crosslinked composite modified starch obtained by acetylating and reacting original starch with phosphate, and has the characteristics of good film forming property, good fluidity, high thermal stability, strong acid resistance and the like.

Chinese patent CN 109400723A discloses a preparation process of acetylated distarch phosphate, which adopts ultrasonic treatment of starch milk to improve the specific surface area of starch and generate micropores on the surface of starch, and improve the crosslinking and esterification efficiency of starch, thereby improving the properties of freeze-thaw stability, crosslinking degree and the like of modified starch. Chinese patent CN 107163152A discloses a preparation method of acetylated starch phosphate for oyster sauce, which effectively avoids the phenomenon of water layering of oyster sauce during storage by improving the water retention of acetylated distarch phosphate to oyster sauce. Chinese patent CN 111732670A discloses an acetylated distarch phosphate for yoghourt, which can significantly enhance the apparent viscosity, water holding capacity and storage stability of yoghourt when applied to the yoghourt.

Due to different preparation process conditions, the obtained modified starch has different properties, and has certain advantages and disadvantages when being applied to different foods, such as meatballs or yoghourt products, and the effect is different. In addition, in the prior art, the preparation method of the modified starch mostly adopts wet crosslinking, and the starch is hydrolyzed in aqueous solution to influence the binding property of crosslinking and further influence the application performance in food.

Disclosure of Invention

Aiming at the problem of low esterification and crosslinking degree in the preparation process of acetylated distarch phosphate modified starch in the prior art, the invention provides acetylated distarch phosphate modified starch and a preparation method and application thereof.

The invention is realized by the following technical scheme:

an acetylated distarch phosphate modified starch is prepared by the following method:

(1) pretreatment: spraying hydrochloric acid with a mass of 0.5-2% of the dry mass of the starch into the starch, continuously stirring for reaction for 20-30 min, standing until the powder expands, and then drying at 50-120 ℃ for 40-90min to obtain pretreated starch;

(2) and (3) crosslinking: adding anhydrous sodium sulfate and sodium carbonate into the pretreated starch, uniformly stirring, spraying phosphorus oxychloride with the content of 0.05-0.1% of the dry starch basis, uniformly stirring, adding sodium carbonate again, uniformly stirring, standing until the powder expands, and keeping the temperature at 40-50 ℃ for 30-50 min to obtain phosphate ester crosslinked starch;

(3) esterification: preparing phosphate crosslinked starch and water into starch milk, adjusting the pH value to 9-10, stirring and heating to 33-35 ℃, adding a catalyst, then dropwise adding acetic anhydride accounting for 3-7% of the dry weight of the starch, and keeping the pH value of a reaction system to 8.4-8.6; after the dropwise addition is finished, controlling the pH value to be 8.4-8.6, and continuously reacting for 30-40min to obtain an acetylated distarch phosphate crude product;

(4) and (5) refining.

Further, the starch in the step (1) is corn starch which is dried until the moisture content is less than or equal to 1 percent; the concentration of the hydrochloric acid is 1 percent.

Further, stirring starch all the time in the spraying process of the step (1) and the step (2); the dripping time of the acetic anhydride in the step (3) is 60-70 min.

Further, the adding amount of the anhydrous sodium sulfate and the sodium carbonate in the step (2) is 0.5-1% and 1-2% of the dry weight of the starch respectively, and the adding amount of the sodium carbonate is 0.5-1% of the dry weight of the starch again.

Further, the catalyst in the step (3) is pyridine, and the adding amount of the pyridine is 0.01 percent of the dry weight of the starch.

Further, the weight ratio of the phosphate ester cross-linked starch to the water in the step (3) is 1: 2-3.

Further, the refining method in the step (3) is as follows: adjusting the pH value of the starch milk of the acetylated distarch phosphate crude product to 4.2-4.5, stopping the esterification reaction, and obtaining the acetylated distarch phosphate finished product after filtering, washing, drying at low temperature and crushing.

In the invention, the preparation method of the acetylated distarch phosphate modified starch comprises the following steps:

(1) pretreatment: spraying hydrochloric acid with a mass of 0.5-2% of the dry mass of the starch into the starch, continuously stirring for reaction for 20-30 min, standing until the powder expands, and then drying at 50-120 ℃ for 40-90min to obtain pretreated starch;

(2) and (3) crosslinking: adding anhydrous sodium sulfate and sodium carbonate into the pretreated starch, uniformly stirring, spraying phosphorus oxychloride with the content of 0.05-0.1% of the dry starch basis, uniformly stirring, adding sodium carbonate again, uniformly stirring, standing until the powder expands, and keeping the temperature at 40-50 ℃ for 30-50 min to obtain phosphate ester crosslinked starch;

(3) esterification: preparing phosphate crosslinked starch and water into starch milk, adjusting the pH value to 9-10, stirring and heating to 33-35 ℃, adding a catalyst, then dropwise adding acetic anhydride accounting for 3-7% of the dry weight of the starch, and keeping the pH value of a reaction system to 8.4-8.6; after the dropwise addition is finished, controlling the pH value to be 8.4-8.6, and continuously reacting for 30-40min to obtain an acetylated distarch phosphate crude product;

(4) and (5) refining.

In the invention, the acetylated distarch phosphate modified starch is applied to liquid food.

In the invention, the acetylated distarch phosphate modified starch is applied to liquid food, and the liquid food is beverage or oral liquid.

The starch molecule is composed of amylose and amylopectin, and during the hydrolysis process of the starch, a proper amount of acid can firstly cause the hydrolysis of alpha-1.6 glycosidic bonds in certain molecules, so that the amylose content in the starch is increased, the hydroxyl activity on the amylose molecule is improved, the starch is easy to activate, and further the starch is easy to crosslink and esterify. By pretreating starch, i.e. drying the starch to below 1% moisture, amylose hydrolysis can be reduced; after the starch is sprayed with acid, high-temperature treatment can cause hydrolysis of alpha-1, 6 glycosidic bonds, so that the content of amylose in the starch is increased, the activity of hydroxyl groups on amylose molecules is improved, the amylose molecules are easy to activate, and further, the crosslinking degree and the substitution degree are improved; the influence of the substitution degree and the crosslinking degree of the esterified and crosslinked starch obviously improves the physicochemical property of the modified starch, simultaneously ensures that the modified starch has special gel coagulation property, ensures that a solid-liquid phase is stable and not easy to settle, does not cause layering of a stable liquid phase and the like, and can be applied to liquid foods such as drinks, oral liquid and the like

Advantageous effects

The acetylated distarch phosphate modified starch prepared by the invention has the advantages that the starch is pretreated, and is crosslinked and esterified, so that the crosslinking degree and the substitution degree are improved, the physicochemical property of the modified starch is obviously improved, meanwhile, the modified starch has special gel coagulation property, the solid-liquid phase is stable and is not easy to settle, the stable liquid phase is not layered, and the like, and the acetylated distarch phosphate modified starch can be applied to liquid foods such as drinks, oral liquids, and the like.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.

The starch in the embodiment of the invention is corn starch with 14% of moisture content.

Example 1

(1) Pretreatment: drying corn starch to water content of 0.8%, then uniformly spraying hydrochloric acid (hydrochloric acid concentration of 1%) with a mass of 0.5% of dry mass of starch into the starch, stirring the starch all the time in the spraying process, continuously stirring for 30 minutes after spraying is finished, standing the starch until the powder expands, and then drying for 90 minutes at 70 ℃ to obtain pretreated starch;

(2) and (3) crosslinking: adding anhydrous sodium sulfate accounting for 0.5 percent of the dry mass of the starch and anhydrous sodium carbonate accounting for 1.5 percent of the dry mass of the starch into the pretreated starch, uniformly stirring, spraying phosphorus oxychloride accounting for 0.1 percent of the dry mass of the starch, stirring the starch all the time in the spraying process, and continuously stirring until the mixture is completely uniform after the spraying is finished; then adding anhydrous sodium carbonate with the dry basis of 0.8 percent again, uniformly stirring, standing the starch until the powder expands, and then rolling and preserving the temperature for 40min at 45 ℃ to obtain phosphate ester crosslinked starch;

(3) esterification: preparing phosphate crosslinked starch and water into starch milk according to the ratio of 1:2, adding alkali to adjust the pH value of the starch milk to 9.5, stirring and heating to 35 ℃, adding 0.01% of pyridine of a starch dry basis as a catalyst into the starch milk, then dropwise adding acetic anhydride with the mass of 5% of the starch dry basis into the starch milk, wherein the dropwise adding time is 60min, the pH value of a reaction system is kept between 8.4 and 8.6 all the time in the process of dropwise adding the acetic anhydride, after the dropwise adding is finished, controlling the pH value to be between 8.4 and 8.6, and continuously reacting for 40min to obtain a crude acetylated distarch phosphate;

(4) refining: regulating the pH value of the crude starch milk to 4.5, terminating the esterification reaction, and obtaining the finished product of the acetylated distarch phosphate after filtering, washing, drying at low temperature and crushing.

Example 2

(1) Pretreatment: drying corn starch to water content of 0.7%, then uniformly spraying hydrochloric acid (hydrochloric acid concentration of 1%) with a mass of 1% of dry basis of starch into the starch, stirring the starch all the time in the spraying process, continuously stirring for 20 minutes after spraying is finished, standing the starch until the powder expands, and then drying for 80 minutes at 80 ℃ to obtain pretreated starch;

(2) and (3) crosslinking: adding anhydrous sodium sulfate and sodium carbonate which are 0.6 percent and 2 percent of the dry mass of the starch into the pretreated starch, and uniformly stirring; spraying phosphorus oxychloride with 0.1% of dry starch basis, stirring the starch all the time in the spraying process, continuously stirring until the starch is completely uniform after the spraying is finished, then adding sodium carbonate with 0.6% of dry starch basis again, stirring uniformly, standing the starch until the powder expands, and then rolling and preserving the temperature for 50min at 40 ℃ to obtain phosphate ester crosslinked starch;

(3) esterification: preparing phosphate crosslinked starch and water into starch milk according to the proportion of 1:3, adding alkali to adjust the pH value of the starch milk to 9, stirring and heating to 35 ℃, adding 0.01% of dry-based pyridine as a catalyst into the starch milk, then dropwise adding acetic anhydride with the mass of 7% of the dry-based mass of the starch into the starch milk, wherein the dropwise adding time is 70min, the pH value of a reaction system is kept between 8.4 and 8.6 all the time in the process of dropwise adding the acid anhydride, after the dropwise adding is finished, controlling the pH value to be between 8.4 and 8.6, and continuously reacting for 40min to obtain a crude acetylated distarch phosphate;

(4) refining: adjusting the pH value of the crude starch milk to 4.2, terminating the esterification reaction, and obtaining the finished product of the acetylated distarch phosphate after filtering, washing, drying at low temperature and crushing.

Example 3

(1) Pretreatment: drying corn starch to water content of 0.9%, then uniformly spraying hydrochloric acid (hydrochloric acid concentration of 1%) with a mass of 2% of dry basis mass of the starch into the starch, stirring the starch all the time in the spraying process, continuously stirring for 25 minutes after spraying is finished, standing the starch until the powder expands, and then drying for 50 minutes at 120 ℃ to obtain pretreated starch;

(2) and (3) crosslinking: adding anhydrous sodium sulfate accounting for 1 percent of the dry mass of the starch and sodium carbonate accounting for 1 percent of the dry mass of the starch into the pretreated starch, and uniformly stirring; spraying phosphorus oxychloride with 0.1% of dry starch basis, stirring the starch all the time in the spraying process, and continuously stirring until the starch is completely uniform after the spraying is finished; then adding sodium carbonate with the starch dry basis of 1 percent again, stirring uniformly, standing the starch until the powder expands, and then rolling and preserving the temperature for 35min with the temperature of 50 ℃ to obtain phosphate ester crosslinked starch;

(3) esterification: preparing phosphate crosslinked starch and water into starch milk according to the ratio of 1:2.5, adding alkali to adjust the pH value of the starch milk to 9.8, stirring and heating to 33 ℃, adding 0.01% of pyridine serving as a catalyst based on dry basis into the starch milk, then dropwise adding acetic anhydride with the mass of 4.5% of the dry basis of the starch into the starch milk, wherein the dropwise adding time is 60min, the pH value of a reaction system is kept to be 8.4-8.6 all the time in the process of dropwise adding the acetic anhydride, after the dropwise adding is finished, controlling the pH value to be 8.4-8.6, and continuously reacting for 35min to obtain an acetylated distarch phosphate crude product;

(4) refining: adjusting the pH value of the crude starch milk to 4.4, terminating the esterification reaction, and obtaining the finished product of the acetylated distarch phosphate after filtering, washing, drying at low temperature and crushing.

Comparative example 1

(1) And (3) crosslinking: drying corn starch to water content of 0.8%, adding anhydrous sodium sulfate 0.5% of dry mass of the starch and anhydrous sodium carbonate 1.5%, stirring uniformly, spraying phosphorus oxychloride 0.1% of dry mass of the starch, stirring the starch all the time in the spraying process, and continuously stirring to be completely uniform after the spraying is finished; then adding anhydrous sodium carbonate with the dry basis of 0.8 percent again, uniformly stirring, standing the starch until the powder expands, and then rolling and preserving the temperature for 40min at 45 ℃ to obtain phosphate ester crosslinked starch;

(2) esterification: preparing phosphate crosslinked starch and water into starch milk according to the ratio of 1:2, adding alkali to adjust the pH value of the starch milk to 9.5, stirring and heating to 35 ℃, adding 0.01% of pyridine of a starch dry basis as a catalyst into the starch milk, then dropwise adding acetic anhydride with the mass of 5% of the starch dry basis into the starch milk, wherein the dropwise adding time is 60min, the pH value of a reaction system is kept between 8.4 and 8.6 all the time in the process of dropwise adding the acetic anhydride, after the dropwise adding is finished, controlling the pH value to be between 8.4 and 8.6, and continuously reacting for 40min to obtain a crude acetylated distarch phosphate;

(3) refining: regulating the pH value of the crude starch milk to 4.5, terminating the esterification reaction, and obtaining the finished product of the acetylated distarch phosphate after filtering, washing, drying at low temperature and crushing.

Comparative example 2

(1) And (3) crosslinking: adding anhydrous sodium sulfate accounting for 0.5 percent of the dry mass of the starch and sodium carbonate accounting for 1.5 percent of the dry mass of the starch into raw corn starch, uniformly stirring, spraying phosphorus oxychloride accounting for 0.1 percent of the dry mass of the starch, stirring the starch all the time in the spraying process, and continuously stirring until the mixture is completely uniform after the spraying is finished; then adding anhydrous sodium carbonate with the dry basis of 0.8 percent again, uniformly stirring, standing the starch until the powder expands, and then rolling and preserving the temperature for 40min at 45 ℃ to obtain phosphate ester crosslinked starch;

(2) esterification: preparing phosphate crosslinked starch and water into starch milk according to the ratio of 1:2, adding alkali to adjust the pH value of the starch milk to 9.5, stirring and heating to 35 ℃, adding 0.01% of dry-basis pyridine as a catalyst into the starch milk, then dropwise adding acetic anhydride with the mass of 5% of the dry basis of the starch into the starch milk, wherein the dropwise adding time is 60min, the pH value of a reaction system is kept between 8.4 and 8.6 all the time in the process of dropwise adding the acetic anhydride, after the dropwise adding is finished, controlling the pH value to be between 8.4 and 8.6, and continuously reacting for 40min to obtain a crude acetylated distarch phosphate;

(3) refining: adjusting the pH value of the crude starch milk to 4.5, terminating the esterification reaction, and obtaining the finished product of the acetylated distarch phosphate after filtering, washing, drying at low temperature and crushing.

Comparative example 3

(1) And (3) crosslinking: preparing starch milk from raw corn starch and water according to the ratio of 1:2, adjusting the pH value to 10 with alkali liquor, adding phosphorus oxychloride, and stirring and reacting at 45 ℃ for 40min to obtain phosphate ester cross-linked starch milk;

(2) esterification: adjusting the pH value of phosphate ester cross-linked starch milk to 9.5, stirring and heating to 35 ℃, then dropwise adding acetic anhydride with the mass of 5% of the dry mass of the starch into the starch milk, wherein the dropwise adding time is 60min, the pH value of a reaction system is kept between 8.4 and 8.6 all the time in the process of dropwise adding the acetic anhydride, after the dropwise adding is finished, controlling the pH value to be between 8.4 and 8.6, and continuously reacting for 40min to obtain an acetylated distarch phosphate ester crude product;

(3) refining: adjusting the pH value of the crude starch milk to 4.5, terminating the esterification reaction, and obtaining the finished product of the acetylated distarch phosphate after filtering, washing, drying at low temperature and crushing.

Comparative example 4

(1) And (3) crosslinking: preparing starch milk from raw corn starch and water according to the ratio of 1:2, adjusting the pH value to 9-11 with alkali liquor, adding phosphorus oxychloride, and reacting at 40-50 deg.C for 40min under stirring to obtain phosphate ester crosslinked starch milk;

(2) esterification: adjusting the pH value of the phosphate ester cross-linked starch milk to 9-10, stirring and heating to 35 ℃, adding 0.01% of pyridine on a dry basis into the starch milk as a catalyst, then dropwise adding acetic anhydride with the mass of 5% of the dry basis of the starch into the starch milk, wherein the dropwise adding time is 60min, and the pH value of a reaction system is kept between 8.4 and 8.6 all the time in the process of dropwise adding the acid anhydride; after the dropwise addition is finished, controlling the pH value to be 8.4-8.6, and continuously reacting for 40min to obtain an acetylated distarch phosphate crude product;

(3) refining: adjusting the pH value of the crude starch milk to 4.5, terminating the esterification reaction, and obtaining the finished product of the acetylated distarch phosphate after filtering, washing, drying at low temperature and crushing.

Test examples

EXAMPLES 1-3, COMPARATIVE EXAMPLES 1-3, Properties of acetylated distarch phosphate prepared

(1) And (3) testing the transmittance:

the acetylated distarch phosphate prepared in examples 1-3 and comparative examples 1-3 was prepared into 6% starch milk, which was heated to 95 ℃ under stirring, heat-preserved for 15min, cooled, adjusted to zero point with distilled water at 620nm, and measured for transmittance, with the results shown in the following table.

(2) And (3) testing the freeze-thaw stability:

the acetylated distarch phosphate prepared in examples 1-3 and comparative examples 1-3 was formulated into 3% starch milk, which was gelatinized in boiling water for 20min to fully gelatinize the starch milk, taken out and naturally cooled to room temperature, then placed in a refrigerator at-18 ℃ for freezing for a day and night, taken out and naturally thawed at room temperature for 6h, observed for a number of times of freeze thawing until the colloidal structure of the starch paste was destroyed and clear water was precipitated or turned into a spongy form, and the number of freeze thawing times was recorded, with the results shown in the following table.

(3) Viscosity:

the acetylated distarch phosphates prepared in examples 1-3 and comparative examples 1-3 were prepared into 6% starch milk, and the gelatinization temperature and peak viscosity of the starch milk were measured by a brabender viscometer, and the results are shown in the following table.

(4) Coagulation property:

acetylated distarch phosphates prepared in examples 1-3 and comparative examples 1-3 were each weighed 3g into a 500ml beaker,adding 280ml of water, placing the mixture into a magnetic stirrer, stirring the mixture for 30min, gelatinizing the mixture in a water bath kettle at the temperature of between 90 and 100 ℃ for 15min until the solution becomes milky transparent, cooling the solution to the temperature of 60 ℃, keeping the temperature constant, dripping the solution to the pH value of 8.5 to 9.0 by using 0.1mol/L NaOH solution, maintaining the pH value for 5min, and recording the volume of the required NaOH. Then taking out the rotor, adding water to total amount of solution of 300g, centrifuging at 4800r/min for 15min, taking distilled water as reference, collecting supernatant, and measuring absorbance A at 650nm₁Refining the rest solution at 4 deg.C for 72 hr, centrifuging at 4800r/min for 15min, collecting supernatant, and measuring absorbance A at 650nm₂. The formula for calculating the coagulation value is as follows:

coagulation value = (10)^-A2-10^-A1）*100%。

(5) Sedimentation volume:

the crosslinking degree of the crosslinked starch is in a linear and negative correlation with the sedimentation product, and the sedimentation product is used for expressing the crosslinking degree.

0.5g of each of the acetylated distarch phosphate prepared in examples 1-3 and comparative examples 1-3 was weighed, prepared into a starch emulsion with a mass fraction of 2% with distilled water, heated in a water bath at 82-85 ℃ for 2min, taken out, left to cool at room temperature, 10ml of the paste was put into two centrifuge tubes, centrifuged at 4000r/min for 2min, the centrifuged supernatant was poured into centrifuge tubes of the same volume, the volume of the supernatant was read, the sedimentation volume was calculated, and 3 parallel determinations were performed on each sample;

sedimentation volume (ml) = 10-supernatant volume.

(6) And (3) measuring the degree of substitution:

5g of each of the acetylated distarch phosphates prepared in examples 1 to 3 and comparative examples 1 to 3 was accurately weighed in a 250ml iodine flask, 50ml of distilled water was added and mixed, 2 drops of 1% phenolphthalein indicator were added dropwise, after mixing, 0.1mol/L NaOH solution was added dropwise until reddish color did not disappear, 25ml of 0.5mol/L sodium hydroxide standard solution was added, and the mixture was placed on a constant temperature water bath speed-regulating oscillator and mechanically oscillated for 30min for saponification. Washing the inner walls of the bottle stopper and the iodine bottle with a small amount of distilled water, dripping the saponified solution with 0.5mol/L hydrochloric acid standard solution until the red color disappears to obtain the final point, and recording the volume of the consumed hydrochloric acid. Taking native starch as a blank control test;

acetyl groupBase content W_ac（%）=

V2: volume of hydrochloric acid consumed for the blank (ml); v1: sample consumption hydrochloric acid volume (ml);

c: the concentration of hydrochloric acid (mol/L); m: sample weight (g)

Degree of substitution DS = esterified starch

The results are shown in Table 1 below

TABLE 1 modified starch Properties test results for acetylated distarch phosphate

。

As can be seen from the results in Table 1, the acetylated distarch phosphate obtained by the preparation method of the present invention, due to the addition of the pretreatment step and the subsequent dry crosslinking step, reduces the average molecular weight and chain length of the resulting modified starch as a whole, so that the obtained product has high transmittance and freeze-thaw stability, high crosslinking degree due to sedimentation value, a relatively moderate viscosity value, and a high sedimentation value, and is suitable for application to liquid beverages.