Modified kudzuvine root starch as well as preparation method and application thereof

Abstract

The invention discloses modified kudzuvine root starch and a preparation method and application thereof, and relates to the technical field of starch modification, the preparation method of the modified kudzuvine root starch comprises the following steps: mixing kudzuvine root starch with a solvent, and carrying out heat treatment in a reflux state; the solvent comprises an alcohol reagent. A solvent containing an alcohol reagent is used for performing reflux heat treatment on the modified kudzuvine root starch, so that expansion and disintegration of starch particles are inhibited, the original form and crystal form of the starch particles are kept, and the viscosity and retrogradation value of the kudzuvine root starch are improved; compared with solvent extraction treatment containing an alcohol reagent, the cold water solubility, the expansibility and the water-holding capacity of the pueraria starch are improved, and the endothermic enthalpy H and the relative crystallinity of the pueraria starch are reduced. Therefore, the solvent containing the alcohol reagent effectively improves the hydration characteristic and the gelatinization characteristic of the kudzuvine root starch, and the application range of the kudzuvine root starch is expanded. High hydrostatic pressure treatment can be carried out on the radix puerariae starch after heat treatment, the performance change of the radix puerariae starch is promoted synergistically, and the application range is expanded.

Description

Technical Field

[0001] This invention relates to the field of starch modification technology, and in particular to a modified kudzu starch, its preparation method, and its application. Background Technology

[0002] Kudzu starch (KS) is one of the main components of kudzu root, accounting for approximately 30-80% of its dry weight. Besides its medicinal uses, kudzu root typically uses a water washing and sedimentation method to separate KS for various food production applications. Due to its rich content of functional components such as puerarin, KS is commonly found in solid beverages for hangover relief and liver protection, and can also be used as an ingredient in the production of noodles, vermicelli, biscuits, yogurt, bread, and other food products.

[0003] However, natural KS has inherent drawbacks such as low solubility, poor stability, and poor reconstitution properties. In order to meet the production needs of different foods and broaden its application range, it is usually improved. Summary of the Invention

[0004] The main objective of this invention is to propose a modified kudzu starch, its preparation method, and its application, aiming to solve the problems of low solubility and limited application range of natural kudzu starch in the prior art.

[0005] To achieve the above objectives, this invention proposes a method for preparing modified kudzu starch, comprising the following steps:

[0006] Kudzu starch is mixed with a solvent and heat-treated under reflux to obtain modified kudzu starch; the solvent includes an alcohol reagent.

[0007] In one embodiment, the alcohol reagent includes ethanol or methanol.

[0008] In one embodiment, 3-5 mL of solvent is mixed with 1 g of kudzu starch; and / or,

[0009] The heat treatment temperature is 80–85°C; and / or,

[0010] The heat treatment time is 25 to 35 minutes.

[0011] In one embodiment, the solvent includes alcohol and water.

[0012] In one embodiment, the volume ratio of the alcohol to water is (1-10):1.

[0013] In one implementation, the following steps are included:

[0014] Kudzu starch was mixed with a solvent and heat-treated under reflux to obtain heat-treated kudzu starch.

[0015] The heat-treated kudzu starch was subjected to high hydrostatic pressure treatment to obtain modified kudzu starch.

[0016] In one embodiment, the high hydrostatic pressure treatment is performed at a pressure of 500–700 MPa; and / or,

[0017] The high hydrostatic pressure treatment time is 50–70 minutes.

[0018] In one embodiment, the solvent comprises an alcohol and water, wherein the volume ratio of the alcohol to water is (1-10):1.

[0019] The present invention also provides a modified kudzu starch, which is prepared by the modified kudzu starch preparation method described above.

[0020] The present invention also provides a modified kudzu starch prepared by the aforementioned method, or the application of the aforementioned modified kudzu starch in the preparation of food additives or food.

[0021] In the technical solution of this invention, modified kudzu starch is subjected to reflux heat treatment using a solvent containing an alcohol reagent. This not only inhibits the swelling and disintegration of starch granules, maintains the original morphology and crystal form of the starch granules, and improves the viscosity and retrogradation value of kudzu starch, but also enhances its cold water solubility, swelling power, and water-holding capacity, while reducing its endothermic enthalpy ΔH and relative crystallinity. Therefore, the solvent containing the alcohol reagent effectively improves the hydration and gelatinization properties of kudzu starch, expanding its application range. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 Image A shows the SEM image of the kudzu starch prepared in Comparative Example 3 at 1000×. Figure 1 (B) is a SEM image of the kudzu starch prepared in Comparative Example 3 at 2000×. Figure 1 (C) is the particle size distribution diagram of the kudzu starch prepared in Comparative Example 3;

[0024] Figure 2 Image A shows the SEM image of the kudzu starch prepared in Comparative Example 1 at 1000×. Figure 2 (B) is a SEM image of the kudzu starch prepared in Comparative Example 1 at 2000×. Figure 2 (C) is the particle size distribution diagram of the kudzu starch prepared in Comparative Example 1;

[0025] Figure 3 Image A is a SEM image of the kudzu starch prepared in Example 1 at 1000×. Figure 3 Image (B) is a SEM image of the kudzu starch prepared in Example 1 at 2000×. Figure 3 (C) is the particle size distribution diagram of the kudzu starch prepared in Example 1;

[0026] Figure 4 Image (A) is a SEM image of the kudzu starch prepared in Example 2 at 1000×. Figure 4 Image (B) is a SEM image of the kudzu starch prepared in Example 2 at 2000×. Figure 4 (C) is the particle size distribution diagram of the kudzu starch prepared in Example 2;

[0027] Figure 5 Image (A) is a SEM image of kudzu starch prepared in Comparative Example 2 at 1000×. Figure 5 Image (B) is a SEM image of the kudzu starch prepared in Comparative Example 2 at 2000×. Figure 5 (C) is the particle size distribution diagram of the kudzu starch prepared in Comparative Example 2;

[0028] Figure 6 Image A is a SEM image of kudzu starch prepared in Example 3 at 1000×. Figure 6 Image (B) is a SEM image of the kudzu starch prepared in Example 3 at 2000×. Figure 6 (C) is the particle size distribution diagram of the kudzu starch prepared in Example 3;

[0029] Figure 7 Image A is a SEM image of the kudzu starch prepared in Example 4 at 1000×. Figure 7 Image (B) is a SEM image of the kudzu starch prepared in Example 4 at 2000×. Figure 7 (C) is the particle size distribution diagram of the kudzu starch prepared in Example 4;

[0030] Figure 8 The figures show the hydration characteristics of the modified kudzu starch prepared in Examples 1-4 and Comparative Examples 1-3 of this invention.

[0031] Figure 9 The RVA gelatinization curves of the modified kudzu starch prepared in Examples 1-4 and Comparative Examples 1-3 of this invention are shown.

[0032] Figure 10The DSC curves of the modified kudzu starch prepared in Examples 1-4 and Comparative Examples 1-3 of this invention are shown.

[0033] Figure 11 The XRD patterns of the modified kudzu starch prepared in Examples 1-4 and Comparative Examples 1-3 of this invention are shown below.

[0034] Figure 12 The modified kudzu starch prepared in Examples 1-4 and Comparative Examples 1-3 of this invention was subjected to a temperature of 4000 cm⁻¹. -1 -400cm -1 Mid-infrared full spectrum of the range;

[0035] Figure 13 China Figure 6 The enlarged image shows the modified kudzu starch prepared in Examples 1-4 and Comparative Examples 1-3 at 1800 cm⁻¹. -1 -800cm -1 Mid-infrared spectrum of the range.

[0036] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Kudzu starch (KS) is one of the main components of kudzu root, accounting for approximately 30-80% of its dry weight. Besides its medicinal uses, kudzu root typically uses a water washing and sedimentation method to separate KS for various food production applications. Due to its rich content of functional components such as puerarin, KS is commonly found in solid beverages for hangover relief and liver protection, and can also be used as an ingredient in the production of noodles, vermicelli, biscuits, yogurt, bread, and other food products.

[0039] However, natural KS has inherent drawbacks such as low solubility, poor stability, and poor reconstitution properties. In order to meet the production needs of different foods and broaden its application range, it is usually improved.

[0040] In view of this, the present invention proposes a method for preparing modified kudzu starch, comprising the following steps: mixing kudzu starch with a solvent and heat-treating it under reflux to obtain modified kudzu starch; wherein the solvent includes an alcohol reagent.

[0041] In the technical solution of this invention, modified kudzu starch is subjected to reflux heat treatment using a solvent containing an alcohol reagent. This not only inhibits the swelling and disintegration of starch granules, maintains the original morphology and crystal form of the starch granules, and improves the viscosity and retrogradation value of kudzu starch, but also enhances its cold water solubility, swelling power, and water-holding capacity, while reducing its endothermic enthalpy ΔH and relative crystallinity. Therefore, the solvent containing the alcohol reagent effectively improves the hydration and gelatinization properties of kudzu starch, expanding its application range.

[0042] It should be noted that when the alcohol reagent is ethanol, the solvent in this invention can be anhydrous ethanol or an aqueous solution of ethanol, both of which are within the scope of protection of this invention. When the solvent is anhydrous ethanol, it has no significant effect on or change on the particle size of kudzu starch; when the solvent is an aqueous solution of ethanol, it has a significant effect on the particle size of kudzu starch. This is because water in the alcohol-water system promotes the expansion and disintegration of starch granules, while ethanol inhibits the expansion of starch granules. Under the combined effect of the two, the starch crystal structure can be destroyed while the morphology of starch granules can be maintained. In addition, during the reaction, ethanol can form a V-shaped complex with starch molecules. When the ethanol is removed, a V-shaped metastable cavity structure is left, thereby greatly improving the cold water solubility of starch granules.

[0043] In some embodiments, the alcohol reagent includes ethanol or methanol. That is, the alcohol reagent only needs to have the ability to inhibit the swelling of starch granules.

[0044] In some embodiments, 3-5 mL of solvent is mixed with 1 g of kudzu starch; and / or, the heat treatment temperature is 80-85°C; and / or, the heat treatment time is 25-35 min. It is understood that simultaneously controlling the heat treatment temperature and time, as well as the ratio of solvent to kudzu starch, within the above ranges can ensure that the kudzu starch is sufficiently modified, giving it high cold water solubility and viscosity. Preferably, the heat treatment temperature is 82°C, and the heat treatment time is 30 min.

[0045] In some embodiments, the solvent comprises alcohol and water. Preferably, in some embodiments, the volume ratio of alcohol to water is (1-10):1. It is understood that the volume ratio of alcohol to water can be 1:1, 1.5:1, 2:1, or even 10:1, all within the scope of protection of this invention. That is, the larger the volume proportion of alcohol in the alcohol solution, the smaller the particle size change after reflux heat treatment, the lower the solubility in cold water, the lower the viscosity and retrogradation value of the gelatinized liquid, and the greater the relative crystallinity. In other words, by adjusting the ratio of alcohol to water, modified starch particles with different particle sizes, solubilities, viscosities, retrogradation values, and relative crystallinities can be obtained, and suitable application scenarios can be selected according to the characteristics of modified kudzu starch. It should be noted that the modified kudzu starch obtained with an ethanol concentration of 50% has better performance than that obtained with 100% ethanol. According to the experimental process, increasing the ethanol concentration can increase the processing temperature, and then the modification effect is better; if the ethanol concentration is low, then the processing temperature cannot be too high.

[0046] In some embodiments, the method includes the following steps: mixing kudzu starch with a solvent and heat-treating it under reflux to obtain heat-treated kudzu starch; subjecting the heat-treated kudzu starch to high hydrostatic pressure treatment to obtain modified kudzu starch.

[0047] High hydrostatic pressure (HHP) treatment typically involves placing packaged food into a pressure vessel filled with water or other liquid media, applying pressure by pumping in more liquid and increasing the pressure inside the vessel to a specified level. The entire process does not significantly affect the structure of the food because the pressure acts uniformly on all parts of the object. In the technical solution of this invention, when the solvent is an alcohol reagent, the heat-treated kudzu starch is directly subjected to HHP treatment; if the solvent is alcohol and water, the water in the heat-treated kudzu starch must be removed beforehand using anhydrous alcohol reagents or other means before HHP treatment. That is, during HHP treatment, the kudzu starch contains no water, only alcohol. Compared to non-pressure treatment, under pressure conditions, the particle size of kudzu starch granules is increased while maintaining the morphology of the starch granules essentially unchanged. This increases the cold water solubility, water-holding capacity, and swelling capacity of the kudzu starch granules, and increases the chance of starch chain breakage and rearrangement (increased sedimentation), but reduces the viscosity, retrogradation value, relative crystallinity, and endothermic enthalpy ΔH of the kudzu starch granules. It should be noted that if the heat-treated kudzu starch is to be bagged, it needs to be vacuum-sealed before being subjected to high hydrostatic pressure treatment. If it is not subjected to ultra-high pressure treatment under vacuum conditions, the bag will burst.

[0048] It should be noted that HHP treatment and reflux hot alcohol treatment have a synergistic effect, which is reflected in three aspects: (1) synergistically promoting the decrease of endothermic enthalpy ΔH; (2) synergistically promoting the increase of particle size; (3) synergistically promoting the increase of cold water solubility, swelling force and water holding capacity.

[0049] In some embodiments, the high hydrostatic pressure treatment is performed at a pressure of 500–700 MPa; and / or for a duration of 50–70 minutes. Simultaneously controlling the pressure and time of the high hydrostatic pressure treatment within the above ranges ensures increased particle size, cold water solubility, water-holding capacity, and swelling power of kudzu starch. Preferably, the high hydrostatic pressure treatment is performed at a pressure of 600 MPa for 1 hour.

[0050] In some embodiments, the solvent comprises alcohol and water, wherein the volume ratio of alcohol to water is (1-10):1. Most preferably, compared to unmodified kudzu starch, the alcohol is ethanol and the volume ratio of ethanol to water is 1:1. The modified kudzu starch obtained by reflux heat treatment and HHP treatment exhibits a 28.42% increase in particle size, a 646.78% increase in cold water solubility, a 39.24% increase in swelling power, and a 232.78% increase in water holding capacity, respectively. The final viscosity is increased by 26.92%, the endothermic enthalpy ΔH decreases by 13.09%, and the relative crystallinity decreases by 11.04%. The proportion of short-range ordered structures in the molecule also decreases.

[0051] This invention also provides a modified kudzu starch, which is prepared by the modified kudzu starch preparation method described above. Therefore, it possesses all the beneficial effects of the aforementioned modified kudzu starch preparation method, which will not be elaborated further here.

[0052] This invention also provides a method for preparing modified kudzu starch, as described above, and its application in the preparation of food additives or food products. Therefore, it possesses all the beneficial effects of the aforementioned method for preparing modified kudzu starch or the aforementioned modified kudzu starch, which will not be elaborated upon here.

[0053] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0054] Example 1

[0055] A modified kudzu starch is prepared by the following steps:

[0056] A 50% (v / v) aqueous ethanol solution was prepared and placed in a round-bottom flask. A mechanical stirrer and reflux condenser were installed. The ethanol solution was preheated to 82°C. KS (purchased from Hubei Gebaisui Ge Industry Co., Ltd., food grade) was slowly added at a feed-to-liquid ratio of 1:4 (w / v). The mixture was stirred and refluxed for 30 minutes to obtain the hot-treated ethanol solution. While still hot, the hot-treated solution was poured into anhydrous ethanol and thoroughly stirred to dehydrate, yielding the dehydrated solution. The dehydrated liquid was centrifuged at 4000 r / min for 20 min, the precipitate was removed, and the product was vacuum packaged and placed in an ultra-high pressure device (HPP.L2-700 / 1 ultra-high pressure treatment equipment, purchased from Tianjin Huatai Senmiao Biotechnology Co., Ltd.) and held at 600 MPa for 1 h. The precipitate after ultra-high pressure treatment was washed with anhydrous ethanol and then filtered. The filter cake was placed in a 50℃ oven and dried to constant weight to obtain a dry filter cake. The dry filter cake was crushed in a mortar and pestle and passed through a 100-mesh sieve to obtain modified kudzu starch, denoted as A50-H-KS.

[0057] The differences between Examples 2-4, Comparative Examples 1-2, and Example 1 are shown in Table 1.

[0058] Table 1. Differences between Examples 2-4, Comparative Examples 1-2, and Example 1

[0059]

[0060] Comparative Example 3

[0061] A type of kudzu starch is prepared by the following steps:

[0062] Add 50% ethanol to kudzu starch at a material-to-liquid ratio of 1:4 and soak for 30 minutes. Centrifuge, take the precipitate, wash and dehydrate it with 100% ethanol, and dry the dehydrated precipitate at 50℃ to obtain kudzu starch, denoted as KS.

[0063] Performance testing

[0064] The morphology, particle size, hydration characteristics, gelatinization characteristics, thermal characteristics, crystal characteristics, and infrared spectra of kudzu starch from Examples 1-4 and Comparative Examples 1-4 were measured, and the results are as follows:

[0065] 1. Morphology and Particle Size: The samples were adhered to conductive adhesive, sputtered with gold, and then tested using a scanning electron microscope (SEM). The particle morphology of the samples was observed at 1000× and 2000×. The particle size of the acquired SEM images was measured using ImageJ software. The results are as follows: Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown.

[0066] Depend on Figure 1 (C) to Figure 7 Analysis of the particle size distribution diagram of (C) shows that the D of A50-KS and A50-H-KS are different. 50 The micrometers were 5.87 μm and 6.19 μm, respectively, representing increases of 21.78% and 28.42% compared to KS (4.82 μm); the Di of A100-KS and A100-H-KS were... 50 The particle sizes were 4.85 μm and 6.06 μm, respectively, representing increases of 0.62% and 25.73% compared to KS. A0-KS and A0-H-KS particles, on the other hand, were completely gelatinized and disintegrated, showing no obvious particle morphology, which is clearly visible in the SEM images. Particle size data indicate that ethanol helps inhibit the swelling of KS particles, while HHP treatment increases the swelling of KS particles. Maintaining particle morphology is crucial for maintaining the viscosity of starch paste. In a pure water environment, starch particles absorb water and gradually swell until they disintegrate at a certain temperature. However, in an alcohol-water solvent system, ethanol competes with water for the opportunity to bind with starch molecules, reducing the penetration and swelling effect of water molecules on starch, thereby inhibiting the swelling of starch particles.

[0067] Depend on Figure 1 (A) and (B) to Figure 7 Scanning electron microscopy images (A) and (B) show that KS particles are irregular in shape, with relatively smooth surfaces and obvious agglomeration. A0-KS and A0-H-KS, which did not use ethanol as a solvent, both exhibit typical lumps formed after starch granules gelatinize. Figure 2 as well as Figure 5 (at point a), the appearance is irregular and the surface is porous; the morphology and surface of A100-KS particles using 100% ethanol solvent are not significantly different from KS, and the particles also appear as aggregates; while the A50-KS particles using 50% ethanol solvent, as well as the A50-H-KS and A100-H-KS particles treated with HHP, are in a monodisperse state, and the particle morphology is not significantly different from KS, but some particles have rough surfaces with micropores ( Figure 3 , Figure 6 as well as Figure 7 (See point b). This indicates that during the preparation of modified starch using the hot alcohol method, as the ethanol content in the solvent decreases and the moisture content increases, wrinkles and pores begin to appear on the surface of the starch granules. Further reduction of the ethanol content will lead to the bursting and disintegration of the starch granules.

[0068] Overall, A50-KS, A50-H-KS, A100-KS, and A100-H-KS all maintained their granule morphology in the presence of ethanol solvent, but the changes in the internal structure of starch granules under different conditions require further verification. A0-KS and A0-H-KS without ethanol solvent failed to maintain their granule morphology, leading to gelatinization and disintegration of the starch granules at 82°C. Furthermore, HHP treatment further exacerbated the swelling of starch granules. This is mainly because the solvent, driven by ultra-high hydrostatic pressure, disrupted the hydrogen bonds between starch molecular chains, inserting into the double helix structure and causing starch molecules to unwind, thus resulting in granule swelling.

[0069] 2. Hydration characteristics analysis:

[0070] (1) Moisture content determination: The moisture content of the sample was determined using a rapid moisture analyzer, with the test endpoint set at 0.002% / min; moisture determination facilitates subsequent sampling and testing.

[0071] (2) Cold-water solubility (CS, %) determination: Weigh 2.0 g of sample (dry basis, m0, g), place it in a 100 mL beaker, add 50 mL of pure water, stir magnetically at room temperature for 1 h, then transfer to a centrifuge tube, centrifuge at 4000 r / min for 20 min, take out the supernatant and pour it into a dried and constant-weight petri dish (m1, g), dry at 95 ℃ until constant weight (m2, g), and calculate the cold-water solubility according to the following formula:

[0072]

[0073] (3) Swelling capacity (SC, mL / g) determination: Weigh 2.0 g (dry basis, m1) of sample into a 20 mL graduated cylinder, shake the cylinder up and down until the sample volume no longer changes, and record the powder volume V1 on the graduated cylinder scale. Then add 15 mL of pure water to the graduated cylinder and shake thoroughly until homogeneous. Let it stand at room temperature for 24 h, and record the volume V2 after the powder settles. Calculate SC using the following formula:

[0074]

[0075] (4) Water-holding capacity (WHC, g / g): Weigh approximately 0.5 g of sample (dry weight, m1) and place it in a 15 mL centrifuge tube. Record the sum of the mass of the sample and the centrifuge tube as m2. Add 10 mL of pure water. Shake continuously at room temperature for 30 min, then let stand for 24 h. After that, centrifuge at 5000 r / min for 20 min, discard the supernatant, and retain the precipitate. Record the total mass of the centrifuge tube and the precipitate as m3. Calculate the WHC of the sample using the following formula:

[0076]

[0077] (5) Condensation determination (C, %): Weigh 0.1g of sample (dry basis), place it in a 15mL glass graduated tube, add 10mL of pure water, shake thoroughly, gelatinize in a boiling water bath for 30min, cool to room temperature and record the volume of gelatinized liquid V1. After standing at room temperature for 48h, the starch settles and a clear boundary line appears in the graduated tube. Record the volume of supernatant V2. Calculate the condensation using the following formula:

[0078]

[0079] (6) Transmittance (T, %) of gelatinized solution: Weigh 1g of starch (dry basis) and 100mL of pure water into a 100mL reagent bottle with a cap. Heat and shake in a boiling water bath for 1 hour to gelatinize. After cooling to room temperature, place the gelatinized solution in a cuvette of a colorimeter. The measurement mode is transmission mode, with a wavelength range of 400–800nm. The colorimeter is calibrated with pure water, and the transmittance (T) of the sample is read. Results are as follows: Figure 8 As shown.

[0080] Depend on Figure 8 It can be seen that the solubility, swelling power, and water holding capacity of cold water all follow the same pattern: A0-H-KS>A0-KS>A50-H-KS>A50-KS>A100-H-KS>A100-KS>KS; the sedimentation property is A0-KS≈A50-KS≈A0-H-KS≈A50-H-KS>A100-H-KS≈KS>A100-KS; and the transmittance is KS≈A100-KS≈A100-H-KS>A50-KS>A50-H-KS>A0-KS>A0-H-KS. Cold water solubility, swelling power, and water-holding capacity all reflect the strength of starch's ability to bind with water. A0-H-KS and A0-KS are both water-soluble and were completely gelatinized during processing. Therefore, upon redissolving in water, water can rapidly associate with the hydroxyl groups in the starch molecules to complete hydration. However, A50-H-KS, A50-KS, A100-H-KS, and A100-KS all contain ethanol as a solvent. Although the particles swell during sample preparation, they still maintain their shape. Therefore, upon redissolving in water, the water association rate is relatively slow.

[0081] During the cooling process of starch gelatinized liquid, molecular rearrangement occurs through hydrogen bonding, leading to the gradual precipitation of water, a phenomenon known as sedimentation. Higher sedimentation indicates a greater number of straight-chain molecules in the gelatinized liquid. Simultaneously, this rearrangement during cooling also reduces its permeability. The higher sedimentation and lower permeability of A0-KS, A50-KS, A0-H-KS, and A50-H-KS may be related to the gelatinization of starch granules and the branching and chain breakage of starch during the HHP process. A large number of short straight-chain molecules are more prone to rearrangement during cooling. In summary, treatment with an alcohol-water solvent combined with HHP at 82°C effectively improves the cold water solubility, swelling power, and water-holding capacity of KS, but it accelerates the sedimentation of the gelatinized liquid and reduces permeability. Compared with KS, A50-H-KS showed improvements in cold water solubility, swelling power, and water holding capacity of 2.71%, 1.29 mL / g, and 1.55 g / g, respectively, representing increases of 646.78%, 39.24%, and 232.78%.

[0082] (3) Gelatinization property test

[0083] Test Method: Weigh 2.5g of sample (dry basis) into the aluminum cylinder of the Rapid Viscosity Analyzer (RVA), add 25g of pure water, mix thoroughly with the agitator, and quickly load the sample onto the instrument for testing. The test procedure is as follows: Rotate the agitator at 960 r / min for 10s, then reduce the speed to 160 r / min. Equilibrate the slurry at 50℃ for 1 min, then heat it to 95℃ at a rate of 12℃ / min, hold at 95℃ for 2.5 min, then cool it to 50℃ at the same rate, and finally hold at 50℃ for 2 min to complete the test and obtain the gelatinization curve. The gelatinization curve results are as follows: Figure 9 As shown, the gelatinization characteristic parameters are shown in Table 2.

[0084] Table 2. Gelatinization characteristic parameters of kudzu starch in Examples 1-4 and Comparative Examples 1-3.

[0085]

[0086] Depend on Figure 9It can be seen that the viscosities of A0-KS and A0-H-KS are much lower than those of other treatment groups, and A0-H-KS is lower than A0-KS; while the viscosity curves of A50-KS, A50-H-KS, A100-KS, and A100-H-KS are higher than those of KS. Table 2 shows that the final viscosity of each group of samples is A50-KS≈A50-H-KS>A100-KS>A100-H-KS>KS>A0-KS>A0-H-KS, and the regression value also shows the same trend. Compared with KS, the final viscosity of A50-KS and A50-H-KS is 29.13% and 26.92% higher, respectively, while the regression value is 14.22% and 10.94% higher, respectively. The above data show that hot alcohol solution treatment can increase the viscosity of KS, but HHP treatment will decrease the viscosity of KS.

[0087] A0-KS and A0-H-KS undergo gelatinization during processing, disrupting the ordered structure of starch granules. Some linear molecules leak out of the granules, resulting in a looser molecular structure, reduced swelling capacity, and weakened intermolecular forces, thus lowering starch viscosity. During hot alcohol treatment (A50-KS, A50-H-KS, A100-KS, and A100-H-KS), linear starch forms a V-shaped complex with ethanol, maintaining the starch granule shape. After drying, the ethanol evaporates, leaving a V-shaped single-helix cavity. When the modified starch is re-dissolved in water, water molecules rapidly enter the cavity, causing the amorphous amylopectin to quickly absorb water and swell, leading to increased viscosity. The viscosity decrease caused by HHP treatment is due to the high pressure disrupting the non-covalent bonds such as hydrogen bonds between starch molecules, making the starch molecule structure even looser.

[0088] (4) Thermal property testing

[0089] Test method: Weigh 5 mg of sample into a crucible for differential scanning calorimetry (DSC), add 10 μL of pure water, cap the crucible, and equilibrate in a 4℃ refrigerator for 24 h before testing. Use an empty crucible as a reference. The heating rate is 10℃ / min, the scanning range is 30–120℃, and nitrogen is purged at 50 mL / min. Obtain the DSC curve. The results of the DSC curve are shown below. Figure 10 As shown, the parameters of the endothermic peak are shown in Table 3.

[0090] Table 3. Thermodynamic parameters of kudzu starch in Examples 1-4 and Comparative Examples 1-3

[0091] sample <![CDATA[T0]]> <![CDATA[T p ]]> <![CDATA[T c ]]> △T △H KS 72.47±0.20b 82.63±0.22c 87.00±0.36d 14.53±0.28c 5.96±0.10a A0-KS 83.30±0.38a 87.08±0.48a 91.56±1.50a 8.26±1.12d 0.62±0.20c A50-KS 72.45±0.55b 81.41±0.05d 86.17±0.17d 13.72±0.47c 5.59±0.27ab A100-KS 59.14±0.02d 81.22±0.08d 88.71±0.15bc 29.57±0.13a 5.80±0.04a A0-H-KS 81.97±0.10a 85.69±0.09b 89.79±0.71b 7.82±0.80d 0.59±0.12c A50-H-KS 72.28±0.10b 81.49±0.16d 86.18±0.13d 13.89±0.19c 5.18±0.09b A100-H-KS 65.21±2.59c 81.61±0.56d 88.29±0.85c 23.08±1.76b 5.43±0.76ab

[0092] Depend on Figure 10It can be seen that the endothermic peaks of A0-KS and A0-H-KS are relatively small and shift towards the high-temperature region; the endothermic peaks of A50-KS and A50-H-KS are in the range of 70-90℃, and the peak shape is similar to that of KS; while the endothermic peaks of A100-KS and A100-H-KS are relatively wider than those of KS, distributed in the range of 60-90℃. Table 3 shows that A0-KS and A0-H-KS have the highest T0, Tp, and Tc, but the smallest ΔT and ΔH; the T0, Tp, Tc, and ΔT of A50-KS and A50-H-KS are not significantly different from those of KS, but ΔH is significantly reduced; while the Tp and Tc of A100-KS and A100-H-KS are not significantly different from those of KS, but T0 and ΔH are significantly reduced, and ΔT is significantly increased.

[0093] The changes in the endothermic enthalpy of A0-KS and A0-H-KS are mainly due to the fact that these two groups of samples had already gelatinized in the ethanol-free solvent. The relatively non-dense crystalline regions in the starch granules were completely destroyed and presented a disordered state, while the few remaining perfect crystals were very dense. Higher temperatures were required to destroy them during regelatinization, thus shifting the endothermic peak to the high-temperature region. In addition, the small proportion of perfect crystals in the starch granules also resulted in a smaller ΔH during regelatinization. The decrease in ΔH caused by A50-KS and A50-H-KS is related to the destruction of the starch crystal structure by the alcohol-water solution, but this destruction did not lead to the disintegration of the granules. The ΔH of A50-KS and A50-H-KS decreased by 6.21% and 13.09% respectively compared to KS, indicating that hot alcohol solution treatment can destroy the starch crystal structure, and HHP exacerbates this process.

[0094] (5) Crystal characteristic testing

[0095] Test method: A scan step of 0.02° was used to collect diffraction data with diffraction angles 2θ ranging from 5 to 60°, obtaining X-ray diffraction patterns (XRD). Diffraction data within the 5–30° range were used to establish a baseline using Origin 2021, and the crystalline region below the curve (A0) was calculated. c ) and non-crystalline regions (A a Area, relative crystallinity (R c , %) is calculated using the following formula:

[0096]

[0097] result Figure 11 As shown.

[0098] Depend on Figure 11It can be seen that KS has sharp absorption peaks at 15.14°, 17.12°, 17.92°, and 23.02°, which is typical of the A-type crystal structure. A0-KS and A0-H-KS show a shrinkage at 15.14°, while the absorption peaks at 17.12°, 17.92°, and 23.02° disappear. In addition, two new absorption peaks appear at 13.18° and 19.86°, indicating that the crystal structure of these two groups of samples changed from A-type to V-type after gelatinization. The absorption peak positions and morphologies of the four groups of samples, A50-KS, A50-H-KS, A100-KS, and A100-H-KS, did not show significant changes in the XRD patterns.

[0099] Further calculations of Rc revealed that A0-KS and A0-H-KS decreased by 20.26% and 20.47% relative to KS, respectively, representing reductions of 84.42% and 85.29%. A50-KS and A50-H-KS decreased by 2.12% and 2.65%, respectively, representing reductions of 8.83% and 11.04%. A100-KS and A100-H-KS decreased by 0.32% and 0.87%, respectively, representing reductions of 1.33% and 3.63%. During the hot alcohol treatment, the gradual transformation of starch crystal forms from A, B, and C types to V type is the fundamental reason for the changes in its cold water solubility and gelatinization properties. A higher proportion of V type results in higher cold water solubility, but a sharp decrease in viscosity. In this application, although the crystal form of A50-KS, A50-H-KS, A100-KS and A100-H-KS did not change to V-type, the Rc decreased. This may be related to conditions such as ethanol concentration and reaction temperature. However, the decrease in Rc confirms the decrease in ΔH in the DSC test, further indicating that the destruction of the starch granule crystal structure during the hot alcohol treatment led to a series of changes in physicochemical properties.

[0100] (6) FTIR spectroscopy test

[0101] Test method: Mix 2 mg of sample with 200 mg of KBr in a mortar and grind evenly, then compress into tablets using a tablet press. The test mode is Absorption; the scanning band is 4000–400 cm⁻¹. -1 ; Resolution 4cm -1 The sample was scanned 32 times. The results are as follows: Figure 12 and Figure 13 As shown.

[0102] Depend on Figure 12 It can be known that 3424cm -1 The nearby absorption peak is due to the OH stretching vibration, at 2934 cm⁻¹. -1 The nearby area is experiencing CH stretching vibration, 1609 cm. -1 The vicinity is due to the shear vibration of two OH groups in a water molecule, 950–1250 cm⁻¹. -1Several consecutive strong absorption peaks are the stretching vibrations of CO and CC, and this region is sensitive to the short-range ordered structure in starch molecules. Figure 13 It is clearly visible that A0-KS and A0-H-KS are at 1020cm. -1 The nearby absorption peak disappears, while the 1609 cm⁻¹ peak... -1 The absorption peak intensity increases near 1020 cm⁻¹; while that of A50-KS and A50-H-KS is higher at 1020 cm⁻¹. -1 Although the nearby absorption peaks did not disappear, their absorption intensity was lower compared to KS. (1020 cm⁻¹) -1 The absorption peaks near the starch molecule are generally considered to be proportional to the proportion of short-range ordered structures in the starch molecule; the greater the peak intensity, the more short-range ordered structures there are. A0-KS, A0-H-KS, A50-KS, and A50-H-KS have absorption peaks around 1020 cm⁻¹. -1 The disappearance and weakening of the peaks indicate that the short-range ordered structure was disrupted during sample preparation.

[0103] It should be noted that all the above test data were calculated using Origin 2021 to determine the mean, standard deviation, and significance of each test value. The significance was calculated using the Fisher-LSD method, with P < 0.05.

[0104] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing modified kudzu starch, characterized in that, Includes the following steps: Kudzu starch is mixed with a solvent and heat-treated under reflux to obtain modified kudzu starch; the solvent includes an alcohol reagent.

2. The method for preparing modified kudzu starch as described in claim 1, characterized in that, The alcohol reagent includes ethanol or methanol.

3. The method for preparing modified kudzu starch as described in claim 1, characterized in that, Mix 3–5 mL of solvent with 1 g of kudzu starch; and / or, The heat treatment temperature is 80–85°C; and / or, The heat treatment time is 25 to 35 minutes.

4. The method for preparing modified kudzu starch as described in claim 1, characterized in that, The solvents include alcohol and water.

5. The method for preparing modified kudzu starch as described in claim 4, characterized in that, The volume ratio of the alcohol to water is (1-10):

1.

6. The method for preparing modified kudzu starch as described in claim 1, characterized in that, Includes the following steps: Kudzu starch was mixed with a solvent and heat-treated under reflux to obtain heat-treated kudzu starch. The heat-treated kudzu starch was subjected to high hydrostatic pressure treatment to obtain modified kudzu starch.

7. The method for preparing modified kudzu starch as described in claim 6, characterized in that, The high hydrostatic pressure treatment is performed at a pressure of 500–700 MPa; and / or, The high hydrostatic pressure treatment time is 50–70 minutes.

8. The method for preparing modified kudzu starch as described in claim 6, characterized in that, The solvent comprises alcohol and water, wherein the volume ratio of alcohol to water is (1-10):

1.

9. A modified kudzu starch, characterized in that, The modified kudzu starch is prepared by the method described in any one of claims 1 to 8.

10. The modified kudzu starch prepared by the method of any one of claims 1 to 8, or the modified kudzu starch as described in claim 9, is used in the preparation of food additives or food.

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