Hydroxypropyl crosslinked starch as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of fine chemical engineering, and discloses hydroxypropyl crosslinked starch as well as a preparation method and application thereof. The preparation method of the hydroxypropyl crosslinked starch comprises the following steps: mixing starch and water to prepare starch milk; adding sodium phytate and urea; adding sodium sulfate and sodium hydroxide after cooling; adding epoxypropane for reaction; and adding sodium trimetaphosphate to react to prepare the hydroxypropyl crosslinked starch. The hydroxypropyl crosslinked starch prepared by the preparation method disclosed by the invention has excellent shear resistance, acid resistance and oxidation resistance.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a hydroxypropyl cross-linked starch, its preparation method, and its applications. Background Technology

[0002] Hydroxypropyl starch is one of the most widely used modified starches in the food industry. The introduction of hydroxypropyl groups imparts better thickening effects and freeze-thaw stability to the starch. To further improve the shear and acid resistance of hydroxypropyl starch, sodium trimetaphosphate or phosphorus oxychloride is often used as a cross-linking agent in the food industry to synthesize hydroxypropyl distarch phosphate. With the development of the food industry, higher requirements are being placed on modified starches. In addition to better shear and acid resistance, they also need to provide better antioxidant properties for specific foods. Currently, improving the antioxidant properties of starch is mainly achieved through two methods: physical mixing of antioxidants and chemical grafting of antioxidants. Physical mixing often suffers from storage instability, while chemical grafting often requires expensive chemical reagents and extremely complex synthesis processes. Therefore, developing a high-antioxidant starch production process with inexpensive raw materials and a simple synthesis route is of great practical significance. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hydroxypropyl cross-linked starch, its preparation method and application, which has excellent shear resistance and acid resistance, as well as excellent antioxidant properties.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing hydroxypropyl cross-linked starch, comprising the following steps: (1) Mix starch and water to prepare starch milk; (2) Add sodium phytate and urea, and react at 50℃-55℃ for 5h-10h; The amount of sodium phytate added is 0.5%-3% of the mass of starch; the amount of urea added is 1%-5% of the mass of starch; (3) After cooling, add sodium sulfate and sodium hydroxide to adjust the pH to alkaline; add propylene oxide to react; (4) Add sodium trimetaphosphate to react, neutralize the pH value, wash, dehydrate and dry to obtain the hydroxypropyl cross-linked starch.

[0005] The preparation method of this invention uses 0.5%-3% (based on dry starch weight) of sodium phytate as a crosslinking agent and 1%-5% (based on dry starch weight) of urea as a catalyst. The specific ratio of sodium phytate and urea works synergistically to overcome the steric hindrance problem when sodium phytate binds to starch, significantly improving the esterification reaction between sodium phytate and starch, and enhancing the shear resistance, acid resistance, and antioxidant properties of starch. The starch treated with sodium phytate and urea is then processed using a wet hydroxypropyl distarch phosphate synthesis process to obtain hydroxypropyl crosslinked starch with excellent shear resistance, acid resistance, and antioxidant properties.

[0006] In a preferred embodiment of the preparation method of hydroxypropyl crosslinked starch according to the present invention, in step (1), the concentration of the starch milk is 25%-40% and the pH value is 6.5-7.5.

[0007] More preferably, the pH value is adjusted using hydrochloric acid or sodium hydroxide.

[0008] In a preferred embodiment of the preparation method of hydroxypropyl cross-linked starch according to the present invention, in step (3), the temperature is cooled to 25℃-30℃; the addition is carried out by flow addition or drop addition; and the alkaline pH value is 10-14.

[0009] The amount of sodium sulfate added is 5%-25% of the starch mass; the amount of sodium hydroxide added is 1%-4% of the starch mass; and the amount of propylene oxide added is 2%-10% of the starch mass.

[0010] The reaction temperature is 40℃-45℃, and the time is 18h-22h; the amount of sodium trimetaphosphate added is 0.01%-0.1% of the starch mass.

[0011] In a preferred embodiment of the preparation method of hydroxypropyl cross-linked starch according to the present invention, in step (4), the reaction time is 3h-8h; and the neutral pH value is 5.0-5.5.

[0012] In a second aspect, the present invention provides a hydroxypropyl cross-linked starch, which is prepared by the preparation method described in the first aspect.

[0013] Thirdly, the present invention provides a food product comprising the hydroxypropyl cross-linked starch described in the second aspect.

[0014] Fourthly, the hydroxypropyl cross-linked starch described in the second aspect of this invention is used in food, pharmaceuticals, and cosmetics.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method of hydroxypropyl cross-linked starch of the present invention can significantly improve the shear resistance, acid resistance and antioxidant properties of starch compared with the currently common wet method for synthesizing hydroxypropyl distarch phosphate; it uses inexpensive raw materials and simple synthesis process to synthesize modified starch with high antioxidant properties, giving starch more application scenarios.

[0016] (2) The hydroxypropyl crosslinked starch prepared by this invention, when sheared for 5 min under high shear conditions (9000 rpm / min), has a complete particle ratio of 65%-85% in the starch paste; when kept at a strong acidic condition (pH 2.5) for 8 days, the viscosity of the starch paste can still maintain 25%-50% of the initial viscosity; it significantly improves the antioxidant properties of starch, with a DPPH· free radical scavenging rate of 45%-60% and a ·OH scavenging rate of 55%-70% at a starch concentration of 1.4 g / mL. Detailed Implementation

[0017] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0018] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0019] Example 1: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: 4 kg of waxy corn starch (14% moisture content) was weighed and prepared into a 35% starch slurry. The pH was adjusted to 7.0, and the temperature was raised to 54°C. Sodium phytate (0.5% by weight of starch, measured on a dry basis; the following examples and comparative examples are also based on dry weight of starch) and urea (2% by weight of starch, measured on a dry basis of starch, the following examples and comparative examples are also based on dry weight of starch) were added for esterification reaction for 10 hours. The temperature was then lowered to 28°C, and sodium sulfate (10% by weight of starch, measured on a dry basis; the following examples and comparative examples are also based on dry weight of starch) and urea (4% by weight of starch) were added. A mixed solution of sodium hydroxide (measured on a dry basis of starch, and the following examples and comparative examples are also measured on a dry basis of starch) was used to adjust the pH of the starch milk to 12. 6% (measured on a dry basis of starch, and the following examples and comparative examples are also measured on a dry basis of starch) of propylene oxide was added. The mixture was heated to 45°C and kept at that temperature for 22 hours. Then, 0.06% (measured on a dry basis of starch, and the following examples and comparative examples are also measured on a dry basis of starch) of sodium trimetaphosphate was added, followed by a cross-linking reaction for 5 hours. After neutralizing the pH to 5.0, the mixture was washed with water equal to the weight of starch, dehydrated, dried, and packaged to obtain hydroxypropyl cross-linked starch.

[0020] Example 2: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 1% sodium phytate and 2% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0021] Example 3: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 2% sodium phytate and 2% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0022] Example 4: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 3% sodium phytate and 2% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0023] Example 5: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, heat to 54℃, add 2% sodium phytate and 1% urea by weight of starch for esterification reaction for 10 h, then cool to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, heat to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0024] Example 6: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 2% sodium phytate and 3% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0025] Example 7: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, heat to 54℃, add 2% sodium phytate and 5% urea by weight of starch for esterification reaction for 10 h, then cool to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, heat to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0026] Comparative Example 1: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Add a mixed solution of sodium sulfate (10% by mass of starch) and sodium hydroxide (4% by mass of starch) to adjust the pH of the starch milk to 12. Add 6% by mass of starch propylene oxide, heat to 45°C, and keep the reaction at this temperature for 22 hours. Then add 0.06% by mass of starch sodium trimetaphosphate and proceed with the cross-linking reaction for 5 hours. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0027] Comparative Example 2: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch slurry with a mass concentration of 35%. Adjust the pH to 7.0, heat to 54℃ for 10 h, then cool to 28℃. Add a mixed solution of sodium sulfate (10% by weight of starch) and sodium hydroxide (4% by weight of starch) to make the pH of the starch slurry 12. Add 6% by weight of propylene oxide, heat to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% by weight of sodium trimetaphosphate and proceed with the cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0028] Comparative Example 3: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, heat to 54℃, add 2% sodium phytate by weight of starch for esterification reaction for 10 h, then cool to 28℃, add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12, add 6% propylene oxide by weight of starch, heat to 45℃, keep the reaction at this temperature for 22 h, add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h, neutralize the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0029] Comparative Example 4: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, heat to 54℃, add 2% urea by weight of starch and react for 10 h. Then cool to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, heat to 45℃ and keep it at that temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with the cross-linking reaction for 5 h. Neutralize the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry and package to obtain hydroxypropyl cross-linked starch.

[0030] Comparative Example 5: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch slurry with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 0.3% sodium phytate and 2% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch slurry 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0031] Comparative Example 6: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch slurry with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 0.4% sodium phytate and 2% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch slurry 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0032] Comparative Example 7: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 3.5% sodium phytate and 2% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of starch milk 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0033] Comparative Example 8: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 2% sodium phytate and 5.5% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0034] Comparative Example 9: A hydroxypropyl cross-linked starch The production process of this hydroxypropyl cross-linked starch includes the following steps: Weigh 4 kg of waxy corn starch (moisture content 14%) and prepare a starch milk with a mass concentration of 35%. Adjust the pH to 7.0, raise the temperature to 54℃, add 2% sodium phytate and 0.5% urea by weight of starch for esterification reaction for 10 h, then lower the temperature to 28℃ and add a mixed solution of 10% sodium sulfate and 4% sodium hydroxide by weight of starch to make the pH of the starch milk 12. Add 6% propylene oxide by weight of starch, raise the temperature to 45℃, and keep the reaction at this temperature for 22 h. Then add 0.06% sodium trimetaphosphate by weight of starch and proceed with cross-linking reaction for 5 h. After neutralizing the pH to 5.0, wash with water equal to the weight of starch, dehydrate, dry, and package to obtain hydroxypropyl cross-linked starch.

[0035] Experimental example: The shear resistance, acid resistance, and antioxidant properties of the hydroxypropyl cross-linked starches prepared in Examples 1-7 and Comparative Examples 1-9 were tested. The testing methods are as follows: (1) Shear resistance test method: starch paste was prepared by the Brabender viscometer method in GB / T 22427.7-2008. The starch paste was divided into two parts and sheared for 5 min at 7000 rpm / min and 9000 rpm / min respectively. The sheared samples were then photographed with an optical microscope and the proportion of intact starch particles was calculated. Each experiment was performed in parallel 5 times.

[0036] (2) Acid resistance test method: The Brabender viscometer method in GB / T 22427.7-2008 was appropriately adjusted, the starch dispersion solvent was adjusted to pH 2.5 buffer solution, the prepared paste was poured into a sealed container and placed at room temperature, and the viscosity of the paste was measured periodically. Each group of experiments was measured in parallel 5 times.

[0037] (3) DPPH· free radical scavenging rate detection method: Starch paste was prepared using the Brabender viscometer method as described in GB / T 22427.7-2008. Sample solutions of different mass concentrations were obtained by diluting the paste with ultrapure water. 2 mL of sample was mixed with 8 mL of 0.1 mmol / L DPPH solution (dissolved in ethanol), vortexed, and reacted immediately in the dark for 30 min. The absorbance of the solution at 517 nm was measured. The DPPH· scavenging rate was calculated using the following formula: In the formula: A is the absorbance of DPPH·ethanol solution; B is the absorbance of DPPH ethanol solution and the sample to be tested; C is the absorbance of anhydrous ethanol and the sample to be tested.

[0038] (4) OH scavenging rate detection method: Starch paste was prepared using the Brabender viscometer method as specified in GB / T 22427.7-2008. Sample solutions of different mass concentrations were obtained by diluting the paste with ultrapure water. 3 mL of sample was added sequentially to 3 mL of 6 mmol / L FeSO4 and 3 mL of 6 mmol / L H2O2. After mixing thoroughly and reacting for 10 min, 3 mL of 6 mmol / L salicylic acid-ethanol solution was added. The mixture was reacted at 37℃ for 30 min, and the absorbance was measured at 510 nm. The calculation formula is as follows: In the formula: A is the absorbance of deionized water, FeSO4, H2O2, and salicylic acid at 510 nm; B is the absorbance of the sample, FeSO4, H2O2, and salicylic acid at 510 nm; C is the absorbance of the sample, FeSO4, H2O2, and deionized water at 510 nm.

[0039] The test results are shown in Table 1-4.

[0040] Table 1. Results of shear resistance test Table 1 shows the percentage of intact starch particles after shearing at different rotational speeds for the hydroxypropyl cross-linked starch samples prepared in Examples 1-7 and Comparative Examples 1-9 after gelatinization. Comparing Examples 1-7 and Comparative Examples 1-9, the synergistic use of 0.5%-3% sodium phytate and 1%-5% urea significantly improved the percentage of intact particles after shearing. In particular, the hydroxypropyl cross-linked starch samples prepared in the examples showed a significant advantage in starch particle integrity under a shearing condition of 9000 rpm / min, demonstrating superior shear resistance.

[0041] Compared to Example 3, Comparative Examples 1 and 2, without the synergistic treatment of sodium phytate and urea, yielded hydroxypropyl cross-linked starch with only 22.45% and 23.33% intact starch particles, respectively, under a shear condition of 9000 rpm / min. Comparative Example 3, without the addition of urea, yielded hydroxypropyl cross-linked starch with only 40.89% intact starch particles under a shear condition of 9000 rpm / min. Comparative Example 4, without the addition of sodium phytate, yielded hydroxypropyl cross-linked starch with only 28.87% intact starch particles under a shear condition of 9000 rpm / min. Comparative Example 5, with the addition of 0.3% sodium phytate, yielded hydroxypropyl cross-linked starch with only 25% intact starch particles under a shear condition of 9000 rpm / min. 0.19%; Comparative Example 6, with the addition of 0.4% sodium phytate, yielded hydroxypropyl cross-linked starch with only 25.06% intact starch particles under 9000 rpm / min shear conditions; Comparative Example 7, with the addition of 3.5% sodium phytate, yielded hydroxypropyl cross-linked starch with only 48.15% intact starch particles under 9000 rpm / min shear conditions; Comparative Example 8, with the addition of 5.5% urea, yielded hydroxypropyl cross-linked starch with only 49.18% intact starch particles under 9000 rpm / min shear conditions; Comparative Example 9, with the addition of 0.5% urea, yielded hydroxypropyl cross-linked starch with only 42.08% intact starch particles under 9000 rpm / min shear conditions.

[0042] Table 2 Results of acid resistance test Table 2 shows the viscosity changes of the hydroxypropyl cross-linked starch samples prepared in Examples 1-7 and Comparative Examples 1-9 at different storage time points after gelatinization in a pH 2.5 buffer solution. The data in the table show that the viscosity of all groups decreased continuously over time, but the viscosity decrease rate of the Example groups was significantly lower than that of the Comparative Example groups.

[0043] Compared to Example 3, Comparative Examples 1 and 2, without the synergistic treatment of sodium phytate and urea, yielded starch pastes with viscosities of only 82 cp and 70 cp, respectively, after 8 days of storage. Comparative Example 3, without the addition of urea, yielded starch pastes with viscosities of only 550 cp after 8 days of storage. Comparative Example 4, without the addition of sodium phytate, yielded starch pastes with viscosities of only 134 cp after 8 days of storage. Comparative Example 5, with the addition of 0.3% sodium phytate, yielded starch pastes with viscosities of only 21 cp after 8 days of storage. 0 cp; Comparative Example 6, with the addition of 0.4% sodium phytate, yielded a starch paste with a viscosity of only 184 cp after 8 days of storage of hydroxypropyl cross-linked starch; Comparative Example 7, with the addition of 3.5% sodium phytate, yielded a starch paste with a viscosity of only 568 cp after 8 days of storage of hydroxypropyl cross-linked starch; Comparative Example 8, with the addition of 5.5% urea, yielded a starch paste with a viscosity of only 642 cp after 8 days of storage of hydroxypropyl cross-linked starch; Comparative Example 9, with the addition of 0.5% urea, yielded a starch paste with a viscosity of only 348 cp after 8 days of storage of hydroxypropyl cross-linked starch.

[0044] Table 3. Results of DPPH·Free Radical Scavenging Rate Detection DPPH· radical scavenging ability analysis is a key method for evaluating the antioxidant activity of compounds in the field of antioxidant research. DPPH· radicals are stable organic free radicals and are widely used in the rapid screening and evaluation of antioxidant capacity in food, pharmaceuticals, cosmetics, and other fields. Table 3 shows the DPPH· radical scavenging rates of hydroxypropyl cross-linked starch samples and VC samples prepared in Examples 1-7 and Comparative Examples 1-9 at different mass concentrations. At mass concentrations of 0.6 mg / mL-1.4 mg / mL, the hydroxypropyl cross-linked starch prepared in Examples 1-7 can effectively improve the DPPH· radical scavenging rate, especially at high concentrations, where the scavenging rate of the example group is 4-5 times that of the comparative example group, demonstrating superior antioxidant performance.

[0045] Compared to Example 3, Comparative Examples 1 and 2, without the synergistic treatment of sodium phytate and urea, showed DPPH· radical scavenging rates of only 12.11% and 11.52% at 1.4 mg / mL of hydroxypropyl cross-linked starch, respectively; Comparative Example 3, without the addition of urea, showed a DPPH· radical scavenging rate of only 28.11% at 1.4 mg / mL of hydroxypropyl cross-linked starch; Comparative Example 4, without the addition of sodium phytate, showed a DPPH· radical scavenging rate of only 15.67% at 1.4 mg / mL of hydroxypropyl cross-linked starch; and Comparative Example 5, with the addition of 0.3% sodium phytate, showed a DPPH· radical scavenging rate of only 13%. 0.54%; Comparative Example 6, with the addition of 0.4% sodium phytate, achieved a DPPH· free radical scavenging rate of only 13.84% at 1.4 mg / mL of hydroxypropyl cross-linked starch; Comparative Example 7, with the addition of 3.5% sodium phytate, achieved a DPPH· free radical scavenging rate of only 38.25% at 1.4 mg / mL of hydroxypropyl cross-linked starch; Comparative Example 8, with the addition of 5.5% urea, achieved a DPPH· free radical scavenging rate of only 36.56% at 1.4 mg / mL of hydroxypropyl cross-linked starch; Comparative Example 9, with the addition of 0.5% urea, achieved a DPPH· free radical scavenging rate of only 27.24% at 1.4 mg / mL of hydroxypropyl cross-linked starch.

[0046] Table 4. Results of OH scavenging rate test Hydroxyl radicals (·OH) are highly reactive reactive oxygen species that can damage biomolecules such as proteins, lipids, and DNA, potentially leading to cell damage, aging, and various diseases. Therefore, determining the scavenging ability of antioxidants or compounds against hydroxyl radicals is an important indicator for evaluating their antioxidant activity. It is commonly used to detect the antioxidant properties of food, pharmaceuticals, and plant extracts. Table 4 shows the ·OH scavenging rates of hydroxypropyl cross-linked starch samples and VC samples prepared in Examples 1-7 and Comparative Examples 1-9 at different mass concentrations. As can be seen from the table, the ·OH scavenging rates of the hydroxypropyl cross-linked starch samples prepared in Examples 1-7 at concentrations ranging from 0.6 mg / mL to 1.4 mg / mL are higher than those of the comparative examples. At a sample concentration of 1.4 mg / mL, the ·OH scavenging rate of some examples reached over 70%, demonstrating a strong scavenging effect on ·OH and strong antioxidant properties.

[0047] Compared with Example 3, Comparative Examples 1 and 2, without the synergistic treatment of sodium phytate and urea, yielded ·OH scavenging rates of only 15.37% and 16.54% at a concentration of 1.4 mg / mL for hydroxypropyl cross-linked starch, respectively; Comparative Example 3, without the addition of urea, yielded a ·OH scavenging rate of only 23.74% at a concentration of 1.4 mg / mL for hydroxypropyl cross-linked starch; Comparative Example 4, without the addition of sodium phytate, yielded a ·OH scavenging rate of only 15.76% at a concentration of 1.4 mg / mL for hydroxypropyl cross-linked starch; and Comparative Example 5, with the addition of 0.3% sodium phytate, yielded a ·OH scavenging rate of only 13%. 0.08%; Comparative Example 6, with the addition of 0.4% sodium phytate, yielded a ·OH scavenging rate of only 12.91% at a concentration of 1.4 mg / mL for hydroxypropyl cross-linked starch; Comparative Example 7, with the addition of 3.5% sodium phytate, yielded a ·OH scavenging rate of only 39.17% at a concentration of 1.4 mg / mL for hydroxypropyl cross-linked starch; Comparative Example 8, with the addition of 5.5% urea, yielded a ·OH scavenging rate of only 38.54% at a concentration of 1.4 mg / mL for hydroxypropyl cross-linked starch; Comparative Example 9, with the addition of 0.5% urea, yielded a ·OH scavenging rate of only 12.07% at a concentration of 1.4 mg / mL for hydroxypropyl cross-linked starch.

[0048] In summary, the results show that the modified starch properties using a combination of sodium phytate and urea can effectively improve the shear resistance, acid resistance, and antioxidant properties of starch, and these properties are positively correlated with the ratio of sodium phytate to urea within a certain range. Too low an addition amount fails to effectively improve starch properties, while too high an addition amount does not significantly improve starch properties. Considering industrial production costs, an addition ratio of 0.5%-3.0% sodium phytate and 1%-5% urea is optimal.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing hydroxypropyl cross-linked starch, characterized in that, Includes the following steps: (1) Mix starch and water to prepare starch milk; (2) Add sodium phytate and urea, and react at 50℃-55℃ for 5h-10h; The amount of sodium phytate added is 0.5%-3% of the mass of starch; the amount of urea added is 1%-5% of the mass of starch; (3) After cooling, add sodium sulfate and sodium hydroxide to adjust the pH to alkaline; add propylene oxide to react; (4) Add sodium trimetaphosphate to react, neutralize the pH value, wash, dehydrate and dry to obtain the hydroxypropyl cross-linked starch.

2. The method for preparing hydroxypropyl cross-linked starch according to claim 1, characterized in that, In step (1), the concentration of the starch milk is 25%-40% and the pH value is 6.5-7.

5.

3. The method for preparing hydroxypropyl cross-linked starch according to claim 2, characterized in that, The pH value is adjusted using hydrochloric acid or sodium hydroxide.

4. The method for preparing hydroxypropyl cross-linked starch according to claim 1, characterized in that, In step (3), the temperature is cooled to 25℃-30℃; the addition is carried out by flow addition or drop addition; the alkaline pH value is 10-14.

5. The method for preparing hydroxypropyl cross-linked starch according to claim 1, characterized in that, In step (3), the amount of sodium sulfate added is 5%-25% of the starch mass; the amount of sodium hydroxide added is 1%-4% of the starch mass; and the amount of propylene oxide added is 2%-10% of the starch mass.

6. The method for preparing hydroxypropyl cross-linked starch according to claim 1, characterized in that, In step (3), the reaction temperature is 40℃-45℃ and the time is 18h-22h; the amount of sodium trimetaphosphate added is 0.01%-0.1% of the mass of starch.

7. The method for preparing hydroxypropyl cross-linked starch according to claim 1, characterized in that, In step (4), the reaction time is 3h-8h; the neutral pH value is 5.0-5.

5.

8. A hydroxypropyl cross-linked starch, characterized in that, It is prepared by any one of the preparation methods described in claims 1-7.

9. A food product, characterized in that, Includes the hydroxypropyl cross-linked starch as described in claim 8.

10. The use of the hydroxypropyl crosslinked starch according to claim 8 in food, pharmaceuticals and cosmetics.

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