Preparation method of hydroxypropyl distarch phosphate starch

Abstract

The invention discloses a preparation method of hydroxypropyl distarch phosphate starch, and belongs to the technical field of starch. Amylose and amylopectin are compounded and modified to prepare starch with more excellent viscosity, shear force and freeze-thaw stability, and the cross-linking uniformity and the cross-linking efficiency can be improved on the whole by combining a pulsed electric field and an ultrasonic-assisted effect and combining silicon dioxide microsphere loaded zinc oxide as a catalyst; the problem of local excessive crosslinking or non-uniform reaction possibly caused by synchronous reaction is avoided; and the whole process is simple, environmentally friendly and high in operability, the cost and the environmental burden can be effectively reduced through mild process conditions, and the method has good industrial application prospects and market competitive advantages.

Description

Technical Field

[0001] This invention relates to the field of starch technology, and more specifically, to a method for preparing hydroxypropyl distarch phosphate starch. Background Technology

[0002] Hydroxypropyl distarch phosphate starch is a modified starch with both hydroxypropyl and phosphate functional groups, also known as hydroxypropyl distarch phosphate. Due to its excellent transparency, acid resistance, good film-forming properties, and viscosity stability, it is widely used in food, pharmaceutical, textile, papermaking, and oil extraction industries.

[0003] Traditional processes for preparing hydroxypropyl distarch phosphate typically involve two main pathways. One pathway employs a two-step method, first hydroxypropylating the starch and then cross-linking it with phosphorylation. This method is cumbersome, has a long production cycle, and high energy consumption. The other pathway is a conventional one-step method, where starch, propylene oxide (the hydroxypropylating agent), and sodium trimetaphosphate or phosphorus oxychloride (the cross-linking agent) are placed in the same reaction system for simultaneous etherification and cross-linking reactions. However, this method suffers from the following problems: Firstly, it is difficult to achieve optimal cross-linking efficiency simultaneously under the same reaction conditions, resulting in uneven hydroxypropyl substitution or cross-linking degrees and unstable product performance. Secondly, propylene oxide is prone to hydrolysis under alkaline conditions, generating useless propylene glycol, which not only reduces reagent utilization and reaction efficiency but also increases processing difficulty and cost. Thirdly, to promote the penetration and reaction of propylene oxide, existing processes often use high alkali concentrations and reaction temperatures, which can easily lead to excessive swelling or even gelatinization of starch granules, damaging the granule structure. The prolonged reaction time also exacerbates starch hydrolysis and degradation, affecting the stability of the final product.

[0004] Therefore, there is an urgent need for a method for preparing hydroxypropyl distarch phosphate that can overcome the aforementioned defects. An ideal method should be able to efficiently and synergistically promote hydroxypropylation and phosphate crosslinking reactions under mild reaction conditions, minimize side reactions, improve crosslinking efficiency and uniformity, simplify the process, and obtain modified starch products with stable and excellent overall properties. Summary of the Invention

[0005] In view of this, and in order to solve one of the above-mentioned technical problems, the present invention provides a method for preparing hydroxypropyl distarch phosphate starch, the specific technical solution of which is as follows: A method for preparing hydroxypropyl distarch phosphate starch, the method comprising the following steps: S1. Sodium sulfate, sodium hydroxide and deionized water are added to a mixing vessel, then composite starch is added. Under the first stirring condition, the mixture is stirred and then treated with a pulsed electric field to obtain pretreated starch milk. S2. Add propylene oxide to the pretreated starch milk described in step S1 and stir under the second stirring condition; then add crosslinking agent and catalyst and stir under the third stirring condition, with ultrasonic assistance. After the crosslinking reaction is completed, cool, adjust pH, dilute, filter, and take the filtrate. S3. The filtrate is concentrated, washed and dried to obtain hydroxypropyl distarch phosphate starch.

[0006] Further, in step S1, the composite starch is obtained by mixing amylose and amylopectin in a mass ratio of (75~95):(5~25).

[0007] Further, in step S1, the first stirring conditions are: a rotation speed of 500 r / min to 1000 r / min, a temperature of 30℃ to 45℃, and a stirring time of 1 h to 3 h.

[0008] Further, in step S1, the conditions of the pulsed electric field are: 3~5kV / cm, frequency of 50 Hz~80Hz, and pulse width of 5~10μs.

[0009] Further, in step S2, the second stirring conditions are: rotation speed of 50 r / min to 200 r / min, temperature of 45℃ to 50℃, and stirring time of 3h to 5h; The third stirring conditions are: rotation speed of 50 r / min to 200 r / min, temperature of 40℃ to 45℃, and stirring time of 10 min to 30 min.

[0010] Furthermore, the conditions for the ultrasound-assisted effect are: power of 50W~150W, frequency of 20kHz~25kHz, and time of 20min~60min.

[0011] Furthermore, in step S2, the conditions for the crosslinking reaction are: temperature of 50℃~55℃ and time of 5h~8h.

[0012] Further, in step S2, the crosslinking agent is at least one of sodium trimetaphosphate and phosphorus oxychloride.

[0013] Furthermore, in step S2, the catalyst is zinc oxide supported on silica microspheres, and the loading rate is 10 wt%~30 wt%.

[0014] Further, by weight, the proportions of sodium sulfate, sodium hydroxide, composite starch, propylene oxide, crosslinking agent, and catalyst are (13~15):(0.5~2):(80~100):(9~12):(0.01~0.03):(0.03~0.05).

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention modifies starch by compounding amylose and amylopectin, which helps to optimize the preparation of starch with better viscosity and shear strength. The linear molecules of amylose are more prone to intermolecular cross-linking, forming a structural framework, while amylopectin forms a continuous, entangled, three-dimensional flexible network. This allows for the formation of a uniform three-dimensional network structure even with a lower amount of cross-linking agent, thus improving the overall cross-linking degree of the starch. Furthermore, amylose dominates in terms of strength, film-forming properties, and shear resistance, while amylopectin focuses on active viscosity and freeze-thaw stability. This invention, by compounding amylose and amylopectin, solves the problem that traditional single-starch products often struggle to simultaneously achieve both shear resistance and freeze-thaw stability.

[0016] 2. This invention, by introducing pulsed electric field treatment, can efficiently and uniformly destroy the crystalline structure of starch, improve reactivity, and thus help improve the subsequent interaction with propylene oxide and crosslinking agents. In synergy with subsequent ultrasonic treatment, it utilizes the cavitation effect and microjets to increase the steric hindrance of starch chains, promote mass transfer of reactants and uniform dispersion of catalysts, thereby significantly accelerating the crosslinking reaction rate, improving crosslinking uniformity and efficiency, shortening the reaction time, and avoiding the problems of local over-crosslinking or uneven reaction that may be caused by simultaneous reactions.

[0017] 3. The addition of zinc oxide supported on silica microspheres as a catalyst in this invention helps promote the formation of phosphate ester cross-links. The catalytic sites are relatively uniformly distributed, which helps to form a uniform and moderate cross-linking network throughout and between starch granules. This effectively reduces the direct contact and adhesion of starch granules, maintains the dispersion state of starch granules, and thus helps to improve the gelatinization stability and shear resistance of starch.

[0018] 4. The process of this invention is simple, environmentally friendly, and highly operable. It reduces costs and environmental burden, and has good prospects for industrial application and market competitiveness. Detailed Implementation

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] A method for preparing hydroxypropyl distarch phosphate starch according to one embodiment of the present invention includes the following steps: S1. Sodium sulfate, sodium hydroxide and deionized water are added to a mixing vessel, then composite starch is added. Under the first stirring condition, the mixture is stirred and then treated with a pulsed electric field to obtain pretreated starch milk. S2. Add propylene oxide to the pretreated starch milk described in step S1 and stir under the second stirring condition; then add crosslinking agent and catalyst and stir under the third stirring condition, with ultrasonic assistance. After the crosslinking reaction is completed, cool, adjust pH, dilute, filter, and take the filtrate. S3. The filtrate is concentrated, washed and dried to obtain hydroxypropyl distarch phosphate starch.

[0021] In one embodiment, in step S1, the composite starch is obtained by mixing amylose and amylopectin in a mass ratio of (75~95):(5~25).

[0022] In one embodiment, in step S1, the first stirring conditions are: a rotation speed of 500 r / min to 1000 r / min, a temperature of 30°C to 45°C, and a stirring time of 1 h to 3 h.

[0023] In one embodiment, in step S1, the conditions of the pulsed electric field are: 3~5kV / cm, frequency of 50Hz~80Hz, and pulse width of 5~10μs.

[0024] In one embodiment, in step S1, the mass percentage concentration of the pretreated starch milk is 30-45%.

[0025] In one embodiment, in step S2, the second stirring conditions are: a rotation speed of 50 r / min to 200 r / min, a temperature of 45°C to 50°C, and a stirring time of 3 h to 5 h. The third stirring conditions are: rotation speed of 50 r / min to 200 r / min, temperature of 40℃ to 45℃, and stirring time of 10 min to 30 min.

[0026] In one embodiment, the conditions for the ultrasound-assisted effect are: power of 50W~150W, frequency of 20kHz~25kHz, and duration of 20min~60min. This invention utilizes a pulsed electric field followed by ultrasound assistance. The pulsed electric field causes amorphization within the starch granules, exposing more active hydroxyl sites and increasing the number of reaction sites. During the cross-linking reaction stage, ultrasound assistance promotes diffusion and mass transfer within the starch granules, while simultaneously ensuring highly uniform dispersion of the catalyst. This guarantees a uniform reaction at the microscale, significantly improving the efficiency and uniformity of cross-linking.

[0027] In one embodiment, in step S2, the conditions for the crosslinking reaction are: a temperature of 50°C to 55°C and a time of 5h to 8h.

[0028] In one embodiment, in step S2, the crosslinking agent is at least one of sodium trimetaphosphate and phosphorus oxychloride.

[0029] In one embodiment, in step S2, the catalyst is zinc oxide supported on silica microspheres, and the loading rate is 10 wt% to 30 wt%.

[0030] In one embodiment, the catalyst has an average particle size of 10 μm to 20 μm.

[0031] In one embodiment, the ratio of sodium sulfate, sodium hydroxide, composite starch, propylene oxide, crosslinking agent, and catalyst by weight is (13~15):(0.5~2):(80~100):(9~12):(0.01~0.03):(0.03~0.05).

[0032] In one embodiment, in step S2, the pH is adjusted to 5.5-7.0.

[0033] In one embodiment, in step S3, the drying temperature is 100°C to 120°C.

[0034] The above scheme, through optimization of components and processes, can develop an efficient, green, and controllable method for preparing hydroxypropyl distarch phosphate starch. The resulting hydroxypropyl distarch phosphate starch has superior overall performance, giving it greater application value.

[0035] The implementation scheme of the present invention will be described in detail below with reference to specific embodiments. The raw materials, reagents, etc. used in the embodiments that are not described in detail are all commercially available. Example 1:

[0036] A method for preparing hydroxypropyl distarch phosphate starch includes the following steps: S1. By weight, 14 parts of sodium sulfate, 0.5 parts of sodium hydroxide, and deionized water were added to a mixing vessel, followed by 100 parts of composite starch (obtained by mixing amylose and amylopectin in a mass ratio of 75:25). The mixture was stirred at a speed of 500 r / min, a temperature of 40°C, and a stirring time of 3 h. Then, it was treated with a pulsed electric field with the following conditions: 4 kV / cm, a frequency of 50 Hz, and a pulse width of 8 μs, to obtain a pretreated starch milk with a mass percentage concentration of 40%. S2. Add 9 parts of propylene oxide to the pretreated starch milk described in step S1, and stir at 50 r / min and 45°C for 5 h; then add 0.02 parts of sodium trimetaphosphate and 0.03 parts of silica microsphere-supported zinc oxide (particle size 20 μm, loading rate 20 wt%), and stir at 50 r / min and 45°C for 20 min, with ultrasonic assistance provided. The ultrasonic assistance conditions are: power 50 W, frequency 20 kHz, time 30 min, and crosslinking reaction at 50°C for 6 h. Cool, adjust pH to 7.0, add deionized water for dilution, filter, and collect the filtrate. S3. After concentrating and washing the filtrate, dry it at 100°C to obtain hydroxypropyl distarch phosphate starch. Example 2:

[0037] A method for preparing hydroxypropyl distarch phosphate starch includes the following steps: S1. By weight, 13 parts sodium sulfate, 0.5 parts sodium hydroxide, and deionized water were added to a mixing vessel, followed by 100 parts of composite starch (obtained by mixing amylose and amylopectin in a mass ratio of 75:25). The mixture was stirred at a speed of 500 r / min and a temperature of 45°C for 3 hours. Then, it was treated with a pulsed electric field with the following conditions: 5 kV / cm, frequency of 50 Hz, and pulse width of 10 μs, to obtain a pretreated starch milk with a mass percentage concentration of 40%. S2. Add 10 parts of propylene oxide to the pretreated starch milk described in step S1, and stir at 50 r / min and 50°C for 5 h; then add 0.03 parts of sodium trimetaphosphate and 0.03 parts of silica microspheres loaded with zinc oxide (particle size 20 μm, loading rate 20 wt%), and stir at 50 r / min and 45°C for 15 min, with ultrasonic assistance provided. The ultrasonic assistance conditions are: power 50 W, frequency 22 kHz, time 30 min, and crosslinking reaction at 55°C for 7 h. Cool, adjust pH to 7.0, add deionized water for dilution, filter, and collect the filtrate. S3. After concentrating and washing the filtrate, dry it at 100°C to obtain hydroxypropyl distarch phosphate starch. Example 3:

[0038] A method for preparing hydroxypropyl distarch phosphate starch includes the following steps: S1. By weight, 15 parts of sodium sulfate, 0.8 parts of sodium hydroxide, and deionized water were added to a mixing vessel, followed by 100 parts of composite starch (obtained by mixing amylose and amylopectin in a mass ratio of 75:25). The mixture was stirred at a speed of 500 r / min and a temperature of 45°C for 3 hours. Then, it was treated with a pulsed electric field with the following conditions: 5 kV / cm, frequency of 55 Hz, and pulse width of 10 μs, to obtain a pretreated starch milk with a mass percentage concentration of 40%. S2. Add 11 parts of propylene oxide to the pretreated starch milk described in step S1, and stir at 50 r / min and 48°C for 5 h; then add 0.02 parts of sodium trimetaphosphate and 0.04 parts of silica microspheres loaded with zinc oxide (particle size 20 μm, loading rate 20 wt%), and stir at 50 r / min and 45°C for 20 min, with ultrasonic assistance provided. The ultrasonic assistance conditions are: power 50 W, frequency 22 kHz, time 35 min, and crosslinking reaction at 55°C for 8 h. Cool, adjust pH to 7.0, add deionized water for dilution, filter, and collect the filtrate. S3. After concentrating and washing the filtrate, dry it at 100°C to obtain hydroxypropyl distarch phosphate starch.

[0039] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that Comparative Example 1 uses only a single type of amylose, while the rest is the same as Example 3.

[0040] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that Comparative Example 2 uses only a single type of amylopectin, while the rest is the same as Example 3.

[0041] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that Comparative Example 3 did not undergo pulsed electric field treatment in step S1, while the rest was the same as Example 3.

[0042] Comparative Example 4: Compared with Example 3, Comparative Example 4 differs in that ultrasound assistance was not provided in step S2 of Comparative Example 4, while the rest is the same as Example 3.

[0043] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that in step S2 of Comparative Example 5, the catalyst is silica microspheres (without zinc oxide loading), while the rest is the same as in Example 3.

[0044] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that in step S2 of Comparative Example 6, zinc oxide (catalyst) supported on silica microspheres was not added, while the rest was the same as in Example 3.

[0045] I. The hydroxypropyl distarch phosphate starch samples prepared in Examples 1-3 and Comparative Examples 1-6 were respectively added to deionized water to prepare a mixture with a mass fraction of 3%. The mixture was heated to 95°C, stirred for 10 min, cooled to room temperature, and 100 mL of the mixture was poured into a graduated cylinder. After mixing, the mixture was allowed to stand for 24 h, and the volume occupied by the sedimentation portion was recorded. The degree of crosslinking was linearly negatively correlated with the sedimentation volume; the smaller the sedimentation volume, the greater the degree of crosslinking. The results are shown in Table 1 below.

[0046] Table 1: Crosslinking Degree Results Group Sedimentation volume / mL Example 1 23.5 Example 2 24.7 Example 3 21.9 Comparative Example 1 35.7 Comparative Example 2 42.8 Comparative Example 3 33.7 Comparative Example 4 29.7 Comparative Example 5 36.2 Comparative Example 6 43.1 Analysis of the data in Table 1 shows that the combination of amylose and amylopectin in this invention synergistically constructs a uniform cross-linked network that combines rigidity and flexibility. Through the synergistic effect of pulsed electric field and ultrasound assistance, and with the promotion of a catalyst, the deposition volume is small, which helps to improve the degree of cross-linking, and the uniformity and effect of cross-linking are excellent. Compared with Example 3, Comparative Example 1 uses only amylose. Although amylose is easy to cross-link between molecules, it lacks the three-dimensional flexible network formed by amylopectin as support and connection, resulting in poor overall network continuity and weak interparticle bonding, leading to a large sedimentation volume. This indicates that a single component is difficult to construct an ideal three-dimensional network. Comparative Example 2 uses only amylopectin. Amylopectin is highly branched, with large steric hindrance, making intermolecular cross-linking difficult. Although it can form a viscous network, it lacks the cross-linking hubs provided by amylose, resulting in insufficient chemical cross-linking, a loose starch structure, and the weakest anti-settling ability. Comparative Example 3 lacks pulsed electric field pretreatment, resulting in insufficient exposure of the reaction sites inside the starch particles, uneven penetration of reactants, especially cross-linking agents, leading to insufficient internal cross-linking and lower overall cross-linking uniformity and degree. The decrease in crosslinking rate indicates that a certain pulsed electric field can disrupt the crystalline region of starch granules, increasing the amorphous region and reactive sites. In Comparative Example 4, the lack of ultrasonic assistance led to a slower crosslinking reaction rate and decreased uniformity, resulting in a heterogeneous structure with excessive local crosslinking and insufficient overall crosslinking. This indicates that the cavitation effect of ultrasound can strongly promote the mixing, catalyst dispersion, and mass transfer of the reaction system. In Comparative Example 5, the catalyst was silica microspheres without zinc oxide loading, resulting in a significant decrease in crosslinking reaction efficiency and insufficient crosslinking degree. This indicates that single silica microspheres can provide physical dispersion, but their catalytic effect is not as good as that of Example 3. In Comparative Example 6, no catalyst was added, and the reaction relied on spontaneous crosslinking under alkaline conditions, resulting in a slow reaction rate and low degree of crosslinking. This indicates that the addition of a certain amount of silica microspheres loaded with zinc oxide as a catalyst in this invention can significantly improve the degree of crosslinking.

[0047] II. The hydroxypropyl distarch phosphate starch samples prepared in Examples 1-3 and the hydroxypropyl distarch phosphate starch samples prepared in Comparative Examples 1-6 were added to deionized water to prepare a mixture with a mass fraction of 3%. The mixture was heated to 95°C, stirred and gelatinized for 20 min, cooled to room temperature, and subjected to high-speed shearing for 0.5 h at a rotation speed of 3000 r / min. The viscosity was measured using a viscometer. The mixture was then subjected to high-speed shearing for another 0.5 h, and the viscosity was measured again. The higher the viscosity retention rate, the better the shear resistance. The results are shown in Table 2 below.

[0048] Table 2: Shear Performance Results Group Viscosity at 0.5 h shear rate / mPa·s Viscosity after 1 hour of shearing / mPa·s Viscosity retention rate / % Example 1 580.2 534.2 92.1 Example 2 578.9 526.9 91.0 Example 3 591.7 548.6 92.7 Comparative Example 1 520.3 401.3 77.1 Comparative Example 2 672.5 469.7 69.8 Comparative Example 3 548.6 469.3 85.5 Comparative Example 4 536.2 448.9 83.7 Comparative Example 5 527.5 401.3 76.1 Comparative Example 6 519.3 379.7 73.1 Analysis of the data in Table 2 shows that the hydroxypropyl distarch phosphate starch prepared in this invention has excellent shear resistance. After long-term high-speed shearing, the viscosity loss is minimal, indicating that its cross-linked network structure is strong and resilient, effectively resisting mechanical damage and exhibiting overall stability. Compared to Example 3, Comparative Example 1 used only amylose. The cross-linked network formed by amylose was too rigid and lacked toughness. Under high-speed shearing, the brittle cross-linking points were easily broken, and the linear molecular chains were easily straightened and slipped, leading to network structure collapse and a decrease in shear viscosity. Comparative Example 2 used only amylopectin. Although the initial viscosity was high, the retention rate was the lowest, indicating that the combination of amylose and amylopectin promoted shear resistance. The cross-linking uniformity of Comparative Example 3 was not as good as that of Example 3, resulting in a decrease in overall stability. Comparative Example 4 did not use ultrasonic assistance, resulting in a lower cross-linking uniformity than Example 3, leading to a decrease in stability. The catalyst in Comparative Example 5 was not loaded with zinc oxide, resulting in insufficient cross-linking degree, weak network strength, and easy breakage of chemical bonds under shear, leading to lower stability than Example 3. Comparative Example 6 did not add a catalyst, resulting in lower cross-linking catalytic stability than Example 3.

[0049] 3. The hydroxypropyl distarch phosphate starch samples prepared in Examples 1-3 and the hydroxypropyl distarch phosphate starch samples prepared in Comparative Examples 1-6 were added to deionized water and stirred in a 90°C water bath for 30 min to gelatinize. The gelatinized starch was poured into two weighed 50 mL stoppered centrifuge tubes (W0) while hot, cooled to room temperature, and then placed in a 4°C refrigerator for aging for 24 h to form a starch gel. The gel was then removed and weighed again (W1) to accurately record the total mass of each sample. Freeze-thaw cycle: Centrifuge tubes were frozen in a -18℃ freezer for 18 hours, then removed and thawed in a 25℃ constant temperature water bath for 6 hours, completing one freeze-thaw cycle. This process was repeated for a total of 5 cycles. The sample was then placed in a high-speed centrifuge and centrifuged at 4000 rpm for 30 minutes. The supernatant that precipitated from the centrifuge tube was poured off, and any remaining moisture at the tube opening was blotted dry with absorbent paper. Weighing calculation: The total weight (W2) of the centrifuge tube and the remaining mixture was weighed. The freeze-thaw water separation rate was calculated using the following formula: Freeze-thaw water separation rate (%) = [(W1-W2) / (W1-W0)] × 100%. The results are shown in Table 3 below.

[0050] Table 3: Freeze-thaw stability results Group Freeze-thaw water separation rate / % Example 1 14.2 Example 2 15.7 Example 3 13.8 Comparative Example 1 26.7 Comparative Example 2 22.6 Comparative Example 3 19.7 Comparative Example 4 21.3 Comparative Example 5 25.4 Comparative Example 6 29.9 As can be seen from the data analysis in Table 3, the hydroxypropyl distarch phosphate starch prepared by this invention, after optimization of composition and process, forms an excellent three-dimensional cross-linked network, which effectively resists stress concentration and structural damage caused by freeze-thaw cycles and has better stability.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for the preparation of hydroxypropyl distarch phosphate starch, characterized in that, The preparation method comprises the following steps: S1. Sodium sulfate, sodium hydroxide and deionized water are added into a mixing kettle, and then composite starch is added, and after stirring treatment under first stirring conditions, pulse electric field treatment is performed to obtain a pretreated starch milk; S2. Propylene oxide is added to the pretreated starch milk in step S1, and stirring treatment is performed under second stirring conditions; then a crosslinking agent and a catalyst are added, stirring treatment is performed under third stirring conditions, and ultrasonic auxiliary action is set, after the crosslinking reaction is completed, cooling, pH adjustment, dilution and filtration treatment are performed, and the filtrate is taken; S3. After the filtrate is concentrated, washed and dried, hydroxypropyl distarch phosphate starch is obtained.

2. The production method according to claim 1, characterized by, In step S1, the composite starch is obtained by mixing straight-chain starch and branched-chain starch at a mass ratio of (75-95):(5-25).

3. The production method according to claim 1, characterized by, In step S1, the first stirring conditions are that the rotating speed is 500 r / min-1000 r / min, the temperature is 30°C-45°C, and the stirring treatment time is 1 h-3 h.

4. The method of claim 1, wherein, In step S1, the pulse electric field conditions are 3-5 kV / cm, the frequency is 50 Hz-80 Hz, and the pulse width is 5-10 μs.

5. The preparation method according to claim 1, characterized in that, In step S2, the second stirring conditions are that the rotating speed is 50 r / min-200 r / min, the temperature is 45°C-50°C, and the stirring treatment time is 3 h-5 h. The third stirring conditions are that the rotating speed is 50 r / min-200 r / min, the temperature is 40°C-45°C, and the stirring treatment time is 10 min-30 min.

6. The method of claim 1, wherein, The ultrasonic auxiliary action conditions are that the power is 50 W-150 W, the frequency is 20 kHz-25 kHz, and the time is 20 min-60 min.

7. The preparation method according to claim 1, characterized in that, In step S2, the crosslinking reaction conditions are that the temperature is 50°C-55°C, and the time is 5 h-8 h.

8. The method of claim 1, wherein, In step S2, the crosslinking agent is at least one of sodium trimetaphosphate and phosphorus oxychloride.

9. The method of claim 1, wherein, In step S2, the catalyst is zinc oxide supported on silica microspheres, and the loading rate is 10 wt%-30 wt%.

10. The method of claim 1, wherein, The proportions of sodium sulfate, sodium hydroxide, composite starch, propylene oxide, crosslinking agent and catalyst are (13-15):(0.5-2):(80-100):(9-12):(0.01-0.03):(0.03-0.05) by weight.