High-purity low-density resistant dextrin and preparation method thereof

Abstract

The invention belongs to the technical field of functional food, and particularly relates to high-purity low-density resistant dextrin and a preparation method thereof.The preparation method comprises the steps that corn starch and water are mixed, the pH value is adjusted, a high-temperature reaction is conducted to obtain a dextrinized product, and enzymatic hydrolysate is obtained after enzymolysis; sequentially adding two modified compounds, namely a trimethoxy benzoyl resistant dextrin derivative and resistant dextrin-1-(2-oxopyrrolidine) carbamate, into the enzymatic hydrolysate according to a specific proportion, and carrying out a reaction; and performing concentration, ethanol precipitation, decoloration, purification and drying on the mixture obtained by the reaction. According to the method, specific functional groups are introduced into a resistant dextrin molecular chain through covalent modification, the anti-digestion characteristic, the prebiotic activity and the drug loading capacity of the product are remarkably improved, and the obtained product is high in purity, low in density and suitable for the fields of food and drugs.

Description

Technical Field

[0001] This invention belongs to the field of functional food technology, specifically relating to a high-purity, low-density resistant dextrin and its preparation method. Background Technology

[0002] Resistant dextrin, a water-soluble dietary fiber, plays an increasingly important role in functional foods and pharmaceutical excipients. It is produced by acid-heat processing, partial hydrolysis, and repolymerization of starch. The glycosidic bond structure in its molecule resists the breakdown by digestive enzymes in the small intestine, allowing it to enter the large intestine intact and be selectively fermented and utilized by the gut microbiota. This characteristic endows it with a variety of recognized physiological benefits, including but not limited to regulating postprandial blood glucose response, improving lipid metabolism, promoting the proliferation of beneficial gut bacteria, and enhancing mineral absorption. Therefore, resistant dextrin is widely used in low glycemic index foods, prebiotic products, weight management formulas, and health foods that require improved bowel function, becoming a key functional ingredient connecting daily diet and health management.

[0003] Despite the numerous advantages of resistant dextrin, existing products and technologies still face several significant limitations, restricting the full realization of its efficacy and the expansion of its application scope. Firstly, from a purity perspective, resistant dextrin produced by conventional processes often contains a certain proportion of digestible sugars. The presence of these impurities weakens its core value in maintaining stable blood sugar levels and as pure dietary fiber. The preparation of high-purity products typically relies on complex chromatographic separation techniques, resulting in high production costs and hindering large-scale industrial production. Secondly, the functionality of traditional resistant dextrin is relatively limited, primarily relying on its inherent physical resistance to digestion. Effective methods are lacking for specifically enhancing its biological activities, such as improving its ability to promote the growth of specific probiotics, imparting antioxidant or anti-inflammatory adjuvant functions, and improving the loading and controlled-release performance of active ingredients when used as a drug carrier. Finally, common chemical modification methods often employ conventional reagents such as citric acid, acetic anhydride, or octenyl succinic anhydride. While these modifications can alter the physicochemical properties of dextrin to some extent, the introduced functional groups lack novelty and may not simultaneously meet the stringent safety and functionality requirements of both the food and pharmaceutical industries.

[0004] To overcome the aforementioned technological bottlenecks, the industry urgently needs to develop an innovative strategy aimed at simultaneously improving the purity and diversifying the functions of resistant dextrin products without relying on expensive purification processes. This invention is an innovative exploration undertaken against this backdrop. Its core idea lies in designing and synthesizing two novel, safe, and applicable functional compounds suitable for the food and pharmaceutical fields, and using them as key modifiers. Through an efficient covalent modification process, these compounds are precisely introduced into the molecular backbone of resistant dextrin. This strategy not only aims to further enhance the product's anti-digestion properties through the introduced steric hindrance and hydrophobic interactions, but also strives to endow the final product with potential targeted prebiotic activity, mucosal affinity, and enhanced drug binding capacity through the grafted specific functional groups. The complete preparation scheme provided by this invention, from the synthesis of two dedicated modifiers to their integration and application in the formation of resistant dextrin, forms a systematic solution, ultimately aiming to obtain a novel resistant dextrin product with high purity, low density, and complex functions, thereby meeting the growing demand for high-performance excipients in modern functional foods and high-end drug delivery systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-purity, low-density resistant dextrin and its preparation method.

[0006] In a first aspect, the present invention provides a method for preparing high-purity, low-density resistant dextrin, comprising the steps of: S1. By weight, mix 80-120 parts of corn starch with 400-600 parts of deionized water and stir to obtain starch slurry; adjust the pH of starch slurry to 2.4-2.6, place it in a high-pressure reactor, and react at 135-145℃ to obtain a reaction mixture; cool the reaction mixture to 60-70℃, add 1-2 parts of medium-temperature α-amylase, and hydrolyze at 60-70℃, then heat to 115-125℃ to inactivate the enzyme to obtain an enzymatic hydrolysate; transfer the enzymatic hydrolysate to a reactor, and at 84-86℃, add 3-8 parts of 3,4,5-trimethoxybenzoyl resistant dextrin derivative and 2-6 parts of resistant dextrin-1-(2-oxopyrrolidine)carbamate, and react under stirring to obtain a mixture; S2. Concentrate the mixture; add ethanol to precipitate, let stand, centrifuge to collect the precipitate, disperse the precipitate in water, decolorize with activated carbon at 68-72℃, filter to obtain filtrate; purify the filtrate to obtain purified solution, and dry the purified solution.

[0007] In this invention, the key to the overall formation mechanism of high-purity, low-density resistant dextrin lies in the synergistic effect of the two customized derivatives mentioned above during the pyrolysis and recombination process of dextrin. Initially, corn starch undergoes complex reactions such as hydrolysis, transglycosylation, and repolymerization under acidic high-temperature conditions, generating a primary mixture of resistant dextrin containing linear and branched fragments. Subsequently, precise enzymatic hydrolysis by mesophilic α-amylase is used to molecularly tailor this mixture, a step that regulates the molecular weight distribution and exposes more active sites. The two derivatives added later are not simply physically mixed; rather, under heating and stirring, their pre-existing large substituent groups (trimethoxybenzoyl and pyrrolidone carbamate) undergo profound physicochemical interactions with the primary dextrin molecular chains. These large side groups act as molecular "spacer pillars," effectively hindering the close proximity and orderly arrangement of dextrin molecular chains through steric hindrance, thus inhibiting the formation of high-density crystalline regions or compact aggregates. Simultaneously, these side elements themselves may also crosslink or entangle with the dextrin backbone or other derivative molecules through intermolecular van der Waals forces, hydrophobic interactions, or weak hydrogen bonds, thereby constructing a looser, more porous internal network structure. This structure is preserved and purified during subsequent alcohol precipitation and purification processes. Components with overly compact structures or those failing to effectively integrate into this loose network are selectively removed. The final product not only has high purity but also achieves a "low-density" characteristic due to its greater porosity and lower stacking density. Therefore, the mechanism of the entire preparation method is a sophisticated process that starts with molecular design, obtains functionalized derivatives through chemical modification, and then uses their physicochemical effects to regulate the higher-order structure of the final product.

[0008] As a preferred technical solution of the present invention, in step S1, the enzymatic hydrolysis time is 30-40 min at 60-70℃.

[0009] As a preferred embodiment of the present invention, in step S2, the decolorization time with activated carbon at 68-72°C is 30-40 minutes.

[0010] As a preferred embodiment of the present invention, the method for preparing the 3,4,5-trimethoxybenzoyl resistant dextrin derivative includes: A1. By weight, under dry nitrogen protection, 40-60 parts of 3,4,5-trimethoxybenzoic acid and 180-220 parts of anhydrous dichloromethane are added to a three-necked flask and cooled to 0-5°C. While stirring, 24-26 parts of thionyl chloride are added dropwise. After the addition is complete, the temperature is raised to 38-42°C and refluxed. After the reaction is complete, the mixture is distilled under reduced pressure at 38-42°C to obtain 3,4,5-trimethoxybenzoyl chloride. A2. Dissolve 8-12 parts of 3,4,5-trimethoxybenzoyl chloride in 100-150 parts of anhydrous dichloromethane to obtain an organic phase solution of acyl chloride; dissolve 4-6 parts of resistant dextrin in 200-300 parts of an aqueous solution containing 2-5 parts of sodium hydroxide, cool to 0-5℃, and add 0.5-2 parts of tetrabutylammonium bromide to obtain an aqueous phase solution of resistant dextrin; under stirring, add the organic phase solution of acyl chloride dropwise to the aqueous phase solution of resistant dextrin and react at 0-10℃; after the reaction is complete, allow to stand and separate the liquids, adjust the pH of the aqueous phase to neutral, add ethanol to precipitate; filter to obtain a solid product, wash the solid product successively with deionized water and ethanol, and dry under vacuum at 48-52℃.

[0011] In this invention, the preparation mechanism of the trimethoxybenzoyl resistant dextrin derivative is essentially a classic acyl chloride and subsequent esterification reaction. Starting with trimethoxybenzoic acid, the hydroxyl group in the carboxyl group is replaced by a chlorine atom under the action of thionyl chloride, forming a highly reactive acyl chloride intermediate. This process involves a nucleophilic attack of the carboxylic acid oxygen atom on the sulfur atom, followed by the elimination of sulfur dioxide and hydrogen chloride to generate the acyl chloride. Subsequently, this acyl chloride reacts with resistant dextrin. The hydroxyl groups abundant in the resistant dextrin molecular backbone can partially form more nucleophilic oxygen anions in an alkaline aqueous environment. In a two-phase reaction system and with the promotion of the phase-transfer catalyst tetrabutylammonium bromide, the dextrin oxygen anions in the aqueous phase cross the phase interface and encounter the acyl chloride molecules dissolved in the organic phase dichloromethane. The dextrin oxygen anions act as nucleophiles, attacking the partially positively charged carbonyl carbon atom in the acyl chloride molecule, resulting in a nucleophilic substitution reaction. The chloride ion departs as a leaving group, forming a new ester bond that covalently grafts the entire trimethoxybenzoyl group onto the sugar chain of the resistant dextrin. The introduction of this derivative aims to provide subsequent products with steric hindrance and specific properties due to the aromatic ring structure.

[0012] As a preferred embodiment of the present invention, in step A1, the reflux reaction time at 38-42°C is 3-5 hours.

[0013] As a preferred embodiment of the present invention, in step A2, the reaction time at 0-10°C is 2-4 hours.

[0014] As a preferred embodiment of the present invention, the method for preparing the resistant dextrin-1-(2-oxopyrrolidine)carbamate includes: B1. By weight, add 18-22 parts of 2-pyrrolidone to 140-160 parts of anhydrous toluene. While stirring and cooling in an ice-water bath, pass dry hydrogen chloride gas through to obtain a 2-pyrrolidone hydrochloride suspension. While stirring at 0-5°C, add 16-20 parts of a solution of trichloroethylene gas dissolved in 48-52 parts of anhydrous toluene dropwise to the 2-pyrrolidone hydrochloride suspension. After the addition is complete, raise the temperature to 60-80°C to react, and cool to room temperature to obtain an organic phase solution containing an isocyanate intermediate. B2. Disperse 6-10 parts of resistant dextrin in a mixed solvent consisting of 100-150 parts of anhydrous dimethyl sulfoxide and 100-150 parts of anhydrous N,N-dimethylformamide containing 0.5-2 parts of triethylamine, and stir at 50-60°C to obtain a dispersion; add an organic phase solution containing an isocyanate intermediate dropwise to the dispersion at 0-10°C with continuous stirring; after the addition is complete, continue the reaction at 25-40°C to obtain a reaction mixture; pour the reaction mixture into diethyl ether to precipitate; collect the precipitate by centrifugation, wash the precipitate with anhydrous diethyl ether to obtain a crude product; redissolve the crude product in deionized water, place it in a dialysis bag for dialyzing, obtain a dialysate, and freeze-dry the dialysate.

[0015] In this invention, the core of the preparation mechanism of the resistant dextrin-1-(2-oxopyrrolidine)carbamate lies in the construction of stable carbamate chemical bonds through a two-step reaction to achieve functional modification. The first step is the preparation of a key isocyanate intermediate, using di-pyrrolidone as the starting material. It first combines with dry hydrogen chloride gas in anhydrous toluene to form the corresponding hydrochloride, which activates the reaction site of the nitrogen atom on the pyrrolidone ring. Subsequently, under low temperature conditions, the hydrochloride reacts with triphosgene. Triphosgene, as a highly efficient and relatively safe acyl chloride and dehydration reagent, promotes elimination and carbonylation on the nitrogen atom, ultimately generating a highly reactive isocyanate intermediate in situ. Its structural feature is that the pyrrolidone ring is connected to a highly electron-deficient isocyanate group through a nitrogen atom. The second step involves the construction of the carbamate bond and product formation. Resistant dextrin is dispersed in a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide, with a triethylamine catalyst added. This alkaline environment facilitates the slight deprotonation of the hydroxyl groups on the resistant dextrin molecular chain, enhancing its nucleophilicity. Under continuous stirring and cooling, an organic phase solution containing the aforementioned isocyanate intermediate is added dropwise to the resistant dextrin dispersion system. The highly electrophilic carbon atoms in the isocyanate groups are immediately subjected to nucleophilic attack by the resistant dextrin hydroxyl anions, resulting in an addition reaction. This reaction process... In this process, the double bond of the isocyanate group opens, the oxygen atom of the hydroxyl group combines with the carbon atom of the isocyanate to form a new carbon-oxygen single bond, while the nitrogen atom forms an amino group. Ultimately, a strong carbamate bridging structure is constructed between the oxygen atom of the resistant dextrin and the nitrogen atom of the pyrrolidone ring. This covalent connection permanently introduces the di-oxopyrrolidine ring into the resistant dextrin polysaccharide backbone in the form of a side chain, thereby endowing it with new functional properties. The entire reaction pathway is highly specific, and the generated carbamate bonds are chemically stable, ensuring the structural clarity and performance reliability of the modified product.

[0016] As a preferred embodiment of the present invention, in step B1, the reaction time is 2-4 hours after heating to 60-80°C.

[0017] As a preferred embodiment of the present invention, in step B2, the stirring time at 50-60°C is 2-4 hours.

[0018] In a second aspect, the present invention provides a high-purity low-density resistant dextrin prepared according to the method for preparing the high-purity low-density resistant dextrin described above.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The most direct and prominent effect of this method is that it can efficiently and stably prepare resistant dextrin with high purity and low physical density. By combining the precisely controlled acid-thermal reaction and enzymatic hydrolysis process in the steps, the precise depolymerization and recombination of starch molecular chains are achieved, laying the foundation for obtaining a well-structured dextrin framework. Subsequently, by using a combination of purification methods such as ethanol precipitation, activated carbon decolorization and ion exchange purification, residual digestible sugars, ionic impurities and pigments in the reaction system can be effectively removed, thereby stabilizing the purity of the final product to an extremely high level. At the same time, the unique modification reaction and subsequent spray drying process make the final product exhibit a porous and loose microstructure, significantly reducing its bulk density. This high purity ensures the stability and reliability of the product's physiological functions, while the low density greatly improves the product's flowability, dispersibility and reconstitution properties, giving it significant application advantages in the subsequent processing, mixing and formulation of food and pharmaceuticals.

[0020] (2) The core inventive effect of this invention lies in the successful conferral of complex and enhanced functional properties to resistant dextrin beyond those of traditional products through the covalent integration of two modified compounds. The introduced trimethoxybenzoyl derivative, with its aromatic ring structure and methoxy group, generates significant steric hindrance and hydrophobic interactions, which can more effectively hinder the contact and binding of amylase and glycosidic bonds in the digestive tract, thereby significantly enhancing the product's anti-enzymatic digestion performance at the molecular level. At the same time, the introduced resistant dextrin-1-(2-oxopyrrolidine)carbamate, with its inherent five-membered lactam ring, has good hydrophilicity and hydrogen bonding ability. This can improve the hydration and solubility stability of the modified dextrin, and also enhance its affinity for biomolecules such as proteins and peptides. This dual modification strategy not only allows the product to retain its basic function as dietary fiber, but also endows it with potential controlled release carrier characteristics and enhanced mucosal affinity, broadening its application potential in high-value-added fields such as prebiotic preparations and oral drug delivery systems.

[0021] (3) From the overall perspective of the preparation process, this invention achieves a unity of methodological innovation and industrial feasibility, with comprehensive technical effects. Addressing the technical bottleneck of polysaccharides' difficulty in homogeneous reactions in conventional organic solvents, this invention creatively employs an interfacial reaction mechanism facilitated by a phase transfer catalyst in a two-phase system of aqueous and organic phases to synthesize two key modified compounds. This method is mild, highly efficient, and effectively solves the key problem of insufficient contact between the modifying reagent and the polysaccharide matrix. For resistant dextrin-1-(2-oxopyrrolidine)carbamate, it innovatively constructs carbamate bonds through the direct addition reaction of the isocyanate intermediate with the resistant dextrin hydroxyl group. This pathway exhibits high reaction specificity, effectively avoiding side reactions and ensuring the precise and stable grafting of functional groups onto the polymer chain. The entire preparation process, from the conversion and functionalization of raw starch to the purification and drying of the product, is seamlessly integrated. The reagents and raw materials used are readily available and comply with food and pharmaceutical regulations, avoiding complex and expensive purification equipment. Therefore, what this invention provides is not only a high-performance product, but also a complete, reliable, and scalable production technology solution that can stably produce resistant dextrin with superior physicochemical properties and unique functionality, meeting the market's urgent demand for next-generation functional food ingredients and pharmaceutical excipients. Detailed Implementation

[0022] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention. Example

[0023] This embodiment provides a method for preparing high-purity, low-density resistant dextrin, the steps of which include: Preparation of 3,4,5-trimethoxybenzoyl resistant dextrin derivative (compound I): A1. Preparation of Acyl Chloride. Under dry nitrogen protection, 50.0 g of 3,4,5-trimethoxybenzoic acid and 200.0 g of anhydrous dichloromethane were added to a 500 mL dry three-necked flask. A magnetic stirrer, thermometer, and constant-pressure dropping funnel were assembled. The reaction flask was placed in an ice-salt bath and cooled to 0 °C. Under vigorous stirring (600 rpm), 25.0 g of thionyl chloride was slowly added dropwise through the constant-pressure dropping funnel, controlling the dropping rate to maintain the internal temperature of the reaction system below 5 °C. The dropping process took approximately 1 hour. After the addition was complete, the ice bath was removed, and the reaction system was heated to 40 °C and refluxed at this temperature for 4 hours. After the reaction was completed, the reaction apparatus was changed to a vacuum distillation apparatus. Excess thionyl chloride and solvent dichloromethane were distilled off under conditions of a 40 °C water bath and -0.095 MPa to obtain a pale yellow oily liquid, 3,4,5-trimethoxybenzoyl chloride, which was sealed and stored in a desiccator for later use.

[0024] A2. Esterification Reaction. Accurately weigh 10.0 g of the 3,4,5-trimethoxybenzoyl chloride prepared in the previous step and dissolve it in 125.0 g of anhydrous dichloromethane to obtain a clear organic phase solution. In another 1000 mL three-necked flask, accurately weigh 5.0 g of resistant dextrin (DE value ≤10, moisture content <5%) and add 250.0 g of pre-prepared 2.0 wt% sodium hydroxide aqueous solution. Stir at 400 rpm for 30 min at 25 °C until completely dissolved to obtain a transparent, viscous aqueous phase solution. Transfer this aqueous phase solution to an ice-water bath and cool to 0 °C, then add 1.0 g of tetrabutylammonium bromide. Under vigorous mechanical stirring (800 rpm), slowly add the above organic phase solution of acyl chloride to the cooled resistant dextrin aqueous phase solution through a constant pressure dropping funnel. During the addition process, control the temperature of the reaction solution to not exceed 5 °C, and the addition time is approximately 40 min. After the addition was complete, the reaction was continued at 5°C for 3 hours, with vigorous stirring throughout to form a stable emulsion. After the reaction was complete, the reaction mixture was transferred to a 1L separatory funnel and allowed to stand for 30 minutes to allow complete phase separation. The lower aqueous phase was carefully separated and collected. The pH of the aqueous phase was slowly adjusted to 7.0 with 0.1mol / L dilute hydrochloric acid under stirring. Then, three times the volume (approximately 750mL) of 95% ethanol was slowly added to the neutral aqueous phase under stirring, immediately resulting in a large amount of white flocculent precipitate. The mixture was allowed to stand at 4°C for 12 hours to allow complete precipitation. The precipitate was collected by centrifugation (4500rpm, 10min), and the resulting solid was washed twice each with 200mL of deionized water and 100mL of 70% ethanol. Finally, the solid was placed in a vacuum drying oven and dried at 50°C and -0.08MPa for 24 hours to obtain a white powder product, designated as compound I.

[0025] Preparation of resistant dextrin-1-(2-oxopyrrolidine)carbamate (compound II): B1. Under dry nitrogen protection, 20.0 g of 2-pyrrolidone was added to 150.0 g of anhydrous toluene in a 500 mL dry three-necked flask. A stirrer, thermometer, gas inlet tube, and tail gas absorption device (connected to the alkali solution bottle) were assembled. While stirring (500 rpm) and cooling in an ice-salt bath, dry hydrogen chloride gas was introduced through the gas inlet tube at a rate of 2-3 bubbles per second until saturation was reached, approximately 30 min. The system became a white, viscous suspension, yielding a 2-pyrrolidone hydrochloride suspension. Maintaining 3°C and vigorous stirring, a solution of 18.0 g of trichloroethylene dissolved in 50.0 g of anhydrous toluene was slowly added dropwise through a constant-pressure dropping funnel at approximately 1 mL / min to prevent foam overflow. The addition process took 50 min. After the addition was complete, the ice bath was removed, and the mixture was heated in an oil bath, slowly increasing the temperature to 70°C at a rate of approximately 5°C / min. The reaction was carried out at this temperature for 3 h. In the later stages of the reaction, the suspended solid gradually dissolved, and the solution became a pale yellow, clear liquid. After the reaction was completed, the system was cooled to room temperature by an ice-water bath to obtain an organic phase solution containing the 1-isocyanate-2-pyrrolidone intermediate. The solution was sealed and kept for later use, avoiding contact with moisture.

[0026] B2. Accurately weigh 8.0 g of resistant dextrin (DE value ≤ 10, moisture content < 5%) and place it in a 500 mL dry three-necked flask. Disperse the flask in a mixed solvent consisting of 125.0 g of anhydrous dimethyl sulfoxide and 125.0 g of anhydrous N,N-dimethylformamide, containing 1.0 g of triethylamine. Equip the three-necked flask with a mechanical stirrer and a condenser. Stir at 400 rpm for 3 hours in a 55°C oil bath until the resistant dextrin fully swells, resulting in a homogeneous, transparent, and high-viscosity dispersion. Transfer this dispersion to an ice-water bath and cool to 5°C. Under continuous vigorous mechanical stirring (800 rpm), slowly add the entire organic phase solution containing the isocyanate intermediate obtained in step B1 to the dispersion using a constant-pressure dropping funnel. Control the reaction temperature during the addition process to not exceed 10°C by adjusting the dropping rate and the ice bath volume. The addition time is approximately 1 hour. After the addition was complete, the ice bath was removed, and the reaction solution was allowed to naturally warm to 30°C. The reaction was then carried out at this temperature in the dark for 18 hours, with the reaction flask wrapped in aluminum foil. After the reaction was complete, the reaction mixture was slowly poured into 1000 mL of vigorously stirred anhydrous diethyl ether, producing a white fibrous precipitate. The precipitate was collected by centrifugation (5000 rpm, 10 min) and washed three times with 100 mL of anhydrous diethyl ether each time. The crude product was dispersed with a glass rod and redissolved in 100 mL of deionized water. Any insoluble matter was removed by centrifugation. The clear solution was placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed against flowing deionized water for 48 hours, changing the water every hour. Finally, the solution in the dialysis bag was freeze-dried to -50°C, and then dried at -50°C and 0.1 mBar for 48 hours to obtain compound II.

[0027] Preparation of high-purity, low-density resistant dextrin: S1. Weigh 100.0g of corn starch and 500.0g of deionized water into a 2L beaker and mix. Stir continuously at 500rpm for 30min to obtain a homogeneous starch slurry. Use 0.1mol / L hydrochloric acid solution, adding it slowly dropwise with stirring to precisely adjust the pH of the starch slurry to 2.5. Transfer the pH-adjusted starch slurry to a 1L high-pressure reactor, seal it, and program the temperature to 140℃ at a rate of 2℃ / min. Perform an acid-thermal reaction at 140℃±1℃ for 90min, maintaining an internal stirring speed of 200rpm during the reaction. After the reaction, rapidly cool the reaction mixture to 95℃ using circulating cooling water in the reactor jacket. Add 1.5g of mesophilic α-amylase to the cooled reaction mixture and perform enzymatic hydrolysis at 95℃±0.5℃ with the pH naturally decreasing (maintained within the 5.5-6.5 range) for precisely 35min. After enzymatic hydrolysis, the temperature was increased to 120°C at a rate of 3°C / min and maintained at this temperature for 10 min to ensure complete enzyme inactivation, yielding an enzymatic hydrolysate with a DE value of approximately 8. The obtained hydrolysate was transferred to a 2L jacketed, heated, and mechanically stirred three-necked flask, and the temperature was increased and maintained at 85°C ± 1°C. 4.5 g of compound I and 3.0 g of compound II were then precisely added sequentially, while maintaining a stirring speed of 300 rpm. The reaction was carried out at this temperature for 5 h.

[0028] S2. After the reaction is complete, the reaction mixture is concentrated to approximately 1 / 3 of its original volume by rotary evaporation in a 65°C water bath at -0.085 MPa. Three times the volume of 95% ethanol is slowly added to the concentrate while stirring, and the mixture is allowed to stand overnight. The precipitate is collected by centrifugation (5000 rpm, 15 min). The precipitate is redispersed in 200.0 g of deionized water to form a homogeneous dispersion. 6.0 g of powdered activated carbon is added to the dispersion, and the mixture is stirred and decolorized in a 70°C water bath for 35 min. While still hot, the mixture is vacuum filtered using a Buchner funnel and double-layered medium-speed qualitative filter paper to obtain a clear filtrate. The filtrate is then passed sequentially through a series of glass columns containing 200 mL of strong acid cation exchange resin and 200 mL of strong base anion exchange resin at a flow rate of 5 mL / min for desalting and purification. The effluent is collected and dried in a small spray dryer with an inlet air temperature of 180°C, an outlet air temperature of 90°C, and a material pump flow rate of 10 mL / min. The white powder collected from the bottom of the drying tower and the cyclone separator is the final product, denoted as sample E1. Example

[0029] The difference between this embodiment and Embodiment 1 is that, Preparation of Compound I: 40.0 g of 3,4,5-trimethoxybenzoic acid and 180.0 g of anhydrous dichloromethane were mixed in a three-necked flask and cooled to 3 °C in an ice-water bath. 24.0 g of thionyl chloride was added dropwise with stirring at 600 rpm, maintaining the temperature below 8 °C for 1 h. After the addition was complete, the mixture was refluxed at 38 °C for 5 h. After the reaction was complete, the acyl chloride was obtained by vacuum distillation at 38 °C and -0.095 MPa. 8.0 g of this acyl chloride was dissolved in 100.0 g of anhydrous dichloromethane. Separately, 4.0 g of resistant dextrin (DE value ≤ 10) was dissolved in 220.0 g of 1.8 wt% sodium hydroxide aqueous solution. After complete dissolution, the solution was cooled to 2 °C, and 0.5 g of tetrabutylammonium bromide was added. The acyl chloride solution was added dropwise to the aqueous phase with vigorous stirring at 800 rpm, maintaining the temperature below 3 °C for 30 min. After the addition was complete, the reaction was continued at 3°C ​​for 4 hours. After the reaction was complete, the mixture was separated. The pH of the aqueous phase was adjusted to 7.0 with dilute hydrochloric acid, and three volumes of 95% ethanol were added to precipitate the precipitate. The precipitate was allowed to stand for 12 hours. The precipitate was collected by centrifugation, washed with water and then with alcohol, and dried under vacuum at 50°C for 24 hours to obtain compound I.

[0030] Preparation of Compound II: 22.0 g of 2-pyrrolidone was added to 160.0 g of anhydrous toluene, and dry hydrogen chloride gas was passed through to obtain a hydrochloride suspension. A solution of 20.0 g of triphosgene in 52.0 g of toluene was added dropwise at 5 °C. After the addition was complete, the temperature was raised to 80 °C and reacted for 2 h. The mixture was then cooled to obtain an isocyanate intermediate solution. Separately, 10.0 g of resistant dextrin was dispersed in a mixed solvent containing 2.0 g of triethylamine in 150.0 g of anhydrous dimethyl sulfoxide and 150.0 g of anhydrous N,N-dimethylformamide. The mixture was stirred at 60 °C for 2 h to obtain a dispersion. The intermediate solution was added dropwise to the dispersion at 10 °C with stirring. After the addition was complete, the mixture was reacted at 40 °C for 12 h. After the reaction, the precipitate was added to diethyl ether, centrifuged and washed, and the crude product was dialyzed and freeze-dried to obtain Compound II.

[0031] Weigh 80.0 g of corn starch and mix with 400.0 g of deionized water, stirring at 500 rpm for 30 min to obtain a starch slurry. Adjust the pH to 2.4 with 0.1 mol / L hydrochloric acid. Place the starch slurry in a high-pressure reactor, heat to 135 °C at 2 °C / min, and react at 135 °C ± 1 °C for 100 min, stirring at 200 rpm during the reaction. After the reaction, cool to 94 °C. Add 1.0 g of medium-temperature α-amylase and hydrolyze at 94 °C ± 0.5 °C for 30 min. Then heat to 115 °C and hold for 10 min to inactivate the enzyme, obtaining the enzymatic hydrolysate. Heat the enzymatic hydrolysate to 84 °C, and add 3.0 g of compound I and 2.0 g of compound II sequentially, stirring for 4 h. Subsequent concentration, alcohol precipitation, decolorization, ion exchange purification, and spray drying steps are the same as in Example 1, yielding product sample E2. Example

[0032] The difference between this embodiment and Example 1 is that, in the preparation of compound I: 60.0 g of 3,4,5-trimethoxybenzoic acid and 220.0 g of anhydrous dichloromethane were mixed in a three-necked flask and cooled to 5°C in an ice-water bath. 26.0 g of thionyl chloride was added dropwise while stirring at 600 rpm, maintaining the temperature below 10°C for 1.2 h. After the addition was complete, the temperature was raised to 42°C and refluxed for 3 h. After the reaction was complete, the acyl chloride was obtained by vacuum distillation at 42°C and -0.095 MPa. 12.0 g of this acyl chloride was dissolved in 150.0 g of anhydrous dichloromethane. Separately, 6.0 g of resistant dextrin (DE value ≤ 10) was dissolved in 280.0 g of 2.5 wt% sodium hydroxide aqueous solution. After complete dissolution, the solution was cooled to 5°C, and 2.0 g of tetrabutylammonium bromide was added. Under vigorous stirring at 800 rpm, the acyl chloride solution was added dropwise to the aqueous phase, maintaining the temperature below 10°C during the addition process, and the addition time was 50 min. After the addition was complete, the reaction was continued at 10°C for 2 h. After the reaction was completed, the liquid was separated, and the pH of the aqueous phase was adjusted to 7.0 with dilute hydrochloric acid. Three volumes of 95% ethanol were added to precipitate the precipitate, which was then allowed to stand for 12 h. The precipitate was collected by centrifugation, washed with water and then with alcohol, and dried under vacuum at 50°C for 24 h to obtain compound I.

[0033] Preparation of Compound II: 18.0 g of 2-pyrrolidone was added to 140.0 g of anhydrous toluene, and dry hydrogen chloride gas was passed through to obtain a hydrochloride suspension. A solution of 16.0 g of triphosgene in 50.0 g of toluene was added dropwise at 0 °C. After the addition was complete, the temperature was raised to 60 °C and reacted for 4 h. The mixture was then cooled to obtain an isocyanate intermediate solution. Separately, 6.0 g of resistant dextrin was dispersed in a mixed solvent containing 0.5 g of triethylamine in 100.0 g of anhydrous dimethyl sulfoxide and 100.0 g of anhydrous N,N-dimethylformamide. The mixture was stirred at 50 °C for 4 h to obtain a dispersion. The intermediate solution was added dropwise to the dispersion at 5 °C with stirring. After the addition was complete, the mixture was reacted at 25 °C for 24 h. After the reaction, the precipitate was added to diethyl ether, centrifuged and washed, and the crude product was dialyzed and freeze-dried to obtain Compound II.

[0034] 120.0 g of corn starch was weighed and mixed with 600.0 g of deionized water, and stirred at 500 rpm for 30 min to obtain a starch slurry. The pH was adjusted to 2.6 with 0.1 mol / L hydrochloric acid. The starch slurry was placed in a high-pressure reactor and heated to 145 °C at a rate of 2 °C / min, and reacted at 145 °C ± 1 °C for 80 min, with stirring at 200 rpm during the reaction. After the reaction, the mixture was cooled to 96 °C. 2.0 g of medium-temperature α-amylase was added, and enzymatic hydrolysis was carried out at 96 °C ± 0.5 °C for 40 min. The temperature was then raised to 125 °C and held for 10 min to inactivate the enzyme, yielding an enzymatic hydrolysate. The hydrolysate was heated to 86 °C, and 8.0 g of compound I and 6.0 g of compound II were added sequentially, and the mixture was stirred for 6 h. Subsequent concentration, alcohol precipitation, decolorization, ion exchange purification, and spray drying were performed as in Example 1 to obtain product sample E3.

[0035] Comparative Example 1 The difference between this comparative example and Example 1 is that, except for the absence of any compound I and compound II in the enzymatic hydrolysate modification step, the amounts of raw materials, preparation steps, and conditions are exactly the same as in Example 1. Specifically, the enzymatic hydrolysate is directly subjected to subsequent concentration, alcohol precipitation, decolorization, purification, and drying operations at 85°C to obtain the unmodified resistant dextrin product, denoted as Sample C1.

[0036] Comparative Example 2 The difference between this comparative example and Example 1 is that, except for the addition of only 4.5g of compound I in the enzymatic hydrolysate modification step and the omission of compound II, the amounts of raw materials, preparation steps, and conditions are exactly the same as in Example 1. A resistant dextrin product modified with only one compound was obtained, denoted as sample C2.

[0037] Comparative Example 3 The difference between this comparative example and Example 1 is that, except for the use of 4.5 g of citric acid to replace compound I and 3.0 g of propylene oxide to replace compound II in the enzymatic hydrolysate modification step, the amounts of raw materials, preparation steps, and conditions are exactly the same as in Example 1. The modification reaction was carried out at 85°C and pH 8.5 (adjusted with sodium carbonate) for 5 hours. The resistant dextrin product treated with the conventional modifier was obtained and designated as sample C3.

[0038] Comparative Example 4 The difference between this comparative example and Example 1 is that only 3g of compound II was added, and compound I was not added. The amounts of other raw materials, preparation steps, and conditions were exactly the same as in Example 1. A resistant dextrin product modified with only one compound was obtained, denoted as sample C4.

[0039] The performance of the high-purity, low-density resistant dextrins obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to national and industry standards. All performance tests were conducted in a constant temperature and humidity laboratory environment of 25°C and 50% relative humidity. The test samples were samples E1, E2, and E3 prepared in Examples 1-3 and samples C1, C2, C3, and C4 prepared in Comparative Examples 1-4. All samples were dried to constant weight in a vacuum drying oven at 50°C before testing.

[0040] The resistant dextrin content was determined using an enzymatic gravimetric method combined with high-performance liquid chromatography (HPLC) for verification. The specific steps were as follows: 100.00 mg of the sample was accurately weighed and placed in a 50 mL stoppered centrifuge tube. 10.00 mL of simulated small intestinal digestion fluid, preheated to 37°C, was added. This digestion fluid was prepared with phosphate buffer (pH 5.2) and contained pancreatic amylase and amyloglucosidase, with enzyme activities of 300 U / mL and 20 U / mL, respectively. The centrifuge tube was placed in a 37°C water bath and incubated at 150 rpm for 16 h. After incubation, 40.00 mL of pre-cooled anhydrous ethanol was immediately added to each tube to terminate the reaction and precipitate the undigested polysaccharides. The tubes were then allowed to stand at 4°C for 1 h. Subsequently, the tubes were centrifuged at 4000 rpm for 20 min and carefully discarded. Discard the supernatant, wash the precipitate three times with 10 mL of 85% ethanol solution each time, and centrifuge. Transfer the washed precipitate to a pre-weighed weighing dish and dry it in an oven at 105℃ until constant weight. Weigh and calculate the mass of the resistant component; the percentage of the obtained weight to the initial sample mass is the resistant dextrin content. To verify the results, filter the supernatant before ethanol precipitation through a 0.45 μm filter membrane and analyze the content of digestible sugars such as glucose and maltose using a high-performance liquid chromatography (HPLC) system equipped with a differential refractive index detector. The chromatographic column is an amino-bonded phase column, the column temperature is 40℃, the mobile phase is a 75:25 volume ratio mixture of acetonitrile and water, and the flow rate is 1.0 mL / min. The sum of the resistant dextrin content and the digestible sugar content should be between 98% and 102% to ensure analytical reliability.

[0041] The bulk density was determined using the fixed-volume pouring method: a dry and clean 10mL graduated cylinder was placed on an electronic balance and zeroed. The sample to be tested was slowly poured into the graduated cylinder through a funnel until it reached the 10.0mL mark. The graduated cylinder should not be vibrated or struck during the pouring process. The total mass of the graduated cylinder and the sample was weighed, and the weight of the graduated cylinder itself was subtracted to obtain the sample mass. The bulk density was obtained by dividing the sample mass by the 10mL volume. The result was expressed in g / mL. Each sample was measured in parallel 5 times and the average value was taken.

[0042] The method for determining water solubility is as follows: Accurately weigh 1.000g of sample into a 100mL beaker, add 25.0mL of deionized water at 25℃, and place it on a magnetic stirrer and stir at 300rpm for 30min to ensure complete dispersion of the sample; then transfer the entire suspension to a 50mL centrifuge tube and centrifuge at 4000rpm for 15min; carefully pipette 10mL of the supernatant into a pre-weighed aluminum pan and dry it in an oven at 105℃ until constant weight; the mass of the dried residue divided by the mass of the sample corresponding to the supernatant taken and then multiplied by 100% is the water solubility percentage of the sample.

[0043] The method for determining water-holding capacity is as follows: Accurately weigh 0.500g of sample into a 15mL pre-weighed centrifuge tube, add 10.00mL of deionized water, mix with a vortex mixer for 10s, and let stand at room temperature (25℃) for 1h, gently shaking once every 15min during this period; after standing, centrifuge at 3000rpm for 20min, carefully pour out the supernatant, and invert the centrifuge tube on filter paper for 10min to drain free water; weigh the total mass of the centrifuge tube with gel-like precipitate again. The water-holding capacity is expressed as the number of grams of water held per gram of dry sample, and the calculation formula is (final gel mass - dry sample mass) / dry sample mass.

[0044] Thermal stability analysis was performed using a differential scanning calorimeter: 3.00 mg of sample was accurately weighed and placed in a covered aluminum sample crucible and sealed tightly, with an empty crucible used as a reference; under nitrogen protection, the flow rate was 50 mL / min, and the temperature was scanned from 30 °C to 300 °C at a heating rate of 10 °C / min, and the heat flow curve as a function of temperature was recorded; the endothermic or exothermic peaks on the curve were analyzed, and the initial decomposition temperature, peak temperature, and enthalpy were recorded.

[0045] The prebiotic potential was evaluated using an in vitro batch fecal fermentation model: In an anaerobic workstation, 0.200 g of sample was added as the sole carbon source to a fermentation flask containing 10 mL of sterilized composite culture medium, with the pH adjusted to 6.8. 10% (v / v) of fresh fecal homogenate filtrate from healthy adults was inoculated as the microbial source. The fermentation flask was placed in a 37°C constant-temperature shaker and cultured at 100 rpm in the dark for 24 h. After the culture was completed, 1 mL of the fermentation broth was immediately mixed with 0.2 mL of 50% sulfuric acid to terminate the reaction and acidify it. Subsequently, the total concentration of short-chain fatty acids such as acetic acid, propionic acid, and butyric acid was determined using a gas chromatograph equipped with a flame ionization detector. The results were expressed as μmol / mL of fermentation broth.

[0046] In vitro drug loading capacity assessment used vitamin B12 as a model drug: a vitamin B12 phosphate buffer solution with a concentration of 100 mg / L and a pH of 7.4 was prepared; 10 mL of this solution was taken into a 20 mL glass bottle, 50 mg of the sample to be tested was added, and the solution was placed in a constant temperature shaker at 37℃ and shaken at 200 rpm in the dark for 24 h to reach adsorption equilibrium; then the mixture was centrifuged at 12000 rpm for 10 min, the supernatant was taken and appropriately diluted, and the absorbance was measured at a wavelength of 361 nm using a UV-Vis spectrophotometer. The concentration of vitamin B12 remaining in the supernatant was calculated according to the pre-plotted standard curve; the loading capacity was expressed as the number of milligrams of vitamin B12 adsorbed per gram of sample.

[0047] The performance test data above are shown in Table 1.

[0048] Table 1 Performance Test Results

[0049] The test results in Table 1 above clearly show that the high-purity, low-density resistant dextrin prepared in Examples 1-3, compared with Comparative Examples 1-4, comprehensively and synergistically solves the core problems of insufficient purity, single function, and limited effectiveness of traditional modification methods in the prior art for resistant dextrin products.

[0050] First, regarding the improvement of product purity and basic physical properties, the resistant dextrin content of the products in the examples was significantly higher than that in the comparative examples, with Example 1 reaching 97.5% and the comparative example only reaching 91.2%. This directly confirms that the present invention effectively reduces digestible sugars and other impurities through the covalent binding of specific modified compounds with dextrin chains and subsequent purification processes, achieving the goal of high purification. At the same time, the bulk density of the products in the examples was between 0.25-0.28 g / mL, far lower than that of the comparative example of 0.38 g / mL, proving that the modification process and technology created a looser particle structure, successfully achieving low density and greatly improving the processing applicability of the product.

[0051] Secondly, in terms of overcoming the limitation of single function and endowing multiple functions, the examples demonstrated excellent comprehensive performance: their in vitro short-chain fatty acid yield was as high as 40.8-42.6 μmol / mL, which was significantly better than the 35.2 μmol / mL of Comparative Example 1. This indicates that the specific functional groups introduced in this invention (such as the pyrrolidone structure derived from Compound II) can be more effectively utilized by the intestinal flora, significantly enhancing the prebiotic potential of the product. More notably, the loading capacity of the example for the model drug vitamin B12 reached 55.7 to 58.3 mg / g, which is nearly double that of 32.5 mg / g in Comparative Example 1. This strongly demonstrates that the synergistic effect of the aromatic hydrophobic domain introduced by Compound I and the hydrogen bonding site introduced by Compound II greatly enhances the binding capacity of the product as a drug carrier, thus successfully endowing it with a highly efficient loading function that traditional resistant dextrin does not possess.

[0052] Finally, in verifying the advancement and necessity of the modification strategy, Comparative Example 2, modified only with Compound I, achieved a drug loading of only 46.8 mg / g, lower than Comparative Example 1, indicating that single modification cannot achieve the best synergistic effect. Comparative Example 3, using traditional modifiers such as citric acid and propylene oxide, showed significantly lower performance in all key indicators, including purity, prebiotic activity, and drug loading, compared to the examples. This directly demonstrates that the two novel modified compounds and their preparation methods designed in this invention have significant advantages over traditional technologies in solving the problems of functionalization depth and efficiency. In summary, this invention, through innovative compound design and preparation processes, not only simultaneously improves the purity and physical properties of resistant dextrin, but more importantly, through precise molecular modification, endows it with enhanced prebiotic activity and superior drug loading function, thus solving the functional limitations and technical bottlenecks of existing products in one stop.

Claims

1. A method for preparing high-purity, low-density resistant dextrin, characterized in that the steps include... include: S1. By weight, mix 80-120 parts of corn starch with 400-600 parts of deionized water and stir to obtain starch slurry; adjust the pH of starch slurry to 2.4-2.6, place it in a high-pressure reactor, and react at 135-145℃ to obtain a reaction mixture; cool the reaction mixture to 60-70℃, add 1-2 parts of medium-temperature α-amylase, and hydrolyze at 60-70℃, then heat to 115-125℃ to inactivate the enzyme to obtain an enzymatic hydrolysate; transfer the enzymatic hydrolysate to a reactor, and at 84-86℃, add 3-8 parts of 3,4,5-trimethoxybenzoyl resistant dextrin derivative and 2-6 parts of resistant dextrin-1-(2-oxopyrrolidine)carbamate, and react under stirring to obtain a mixture; S2. Concentrate the mixture; add ethanol to precipitate, let stand, centrifuge to collect the precipitate, disperse the precipitate in water, decolorize with activated carbon at 68-72℃, filter, and obtain the filtrate. The filtrate was purified to obtain a purified solution, which was then dried.

2. The method for preparing high-purity, low-density resistant dextrin according to claim 1, characterized in that, In step S1, the enzymatic hydrolysis time is 30-40 minutes at 60-70℃.

3. The method for preparing high-purity, low-density resistant dextrin according to claim 1, characterized in that, In step S2, the decolorization time with activated carbon at 68-72℃ is 30-40 minutes.

4. The method for preparing high-purity, low-density resistant dextrin according to claim 1, characterized in that, The preparation method of the 3,4,5-trimethoxybenzoyl resistant dextrin derivative includes: A1. By weight, under dry nitrogen protection, 40-60 parts of 3,4,5-trimethoxybenzoic acid and 180-220 parts of anhydrous dichloromethane are added to a three-necked flask and cooled to 0-5°C. While stirring, 24-26 parts of thionyl chloride are added dropwise. After the addition is complete, the temperature is raised to 38-42°C and refluxed. After the reaction is complete, the mixture is distilled under reduced pressure at 38-42°C to obtain 3,4,5-trimethoxybenzoyl chloride. A2. Dissolve 8-12 parts of 3,4,5-trimethoxybenzoyl chloride in 100-150 parts of anhydrous dichloromethane to obtain an organic phase solution of acyl chloride; dissolve 4-6 parts of resistant dextrin in 200-300 parts of an aqueous solution containing 2-5 parts of sodium hydroxide, cool to 0-5℃, and add 0.5-2 parts of tetrabutylammonium bromide to obtain an aqueous phase solution of resistant dextrin; under stirring, add the organic phase solution of acyl chloride dropwise to the aqueous phase solution of resistant dextrin and react at 0-10℃; after the reaction is complete, allow to stand and separate the liquids, adjust the pH of the aqueous phase to neutral, add ethanol to precipitate; filter to obtain a solid product, wash the solid product successively with deionized water and ethanol, and dry under vacuum at 48-52℃.

5. The method for preparing high-purity, low-density resistant dextrin according to claim 4, characterized in that, In step A1, the reflux reaction time at 38-42℃ is 3-5 hours.

6. The method for preparing high-purity, low-density resistant dextrin according to claim 4, characterized in that, In step A2, the reaction time at 0-10℃ is 2-4 hours.

7. The method for preparing high-purity, low-density resistant dextrin according to claim 1, characterized in that, The method for preparing the resistant dextrin-1-(2-oxopyrrolidine)carbamate includes: B1. By weight, add 18-22 parts of 2-pyrrolidone to 140-160 parts of anhydrous toluene. While stirring and cooling in an ice-water bath, pass dry hydrogen chloride gas through to obtain a 2-pyrrolidone hydrochloride suspension. While stirring at 0-5°C, add 16-20 parts of a solution of trichloroethylene gas dissolved in 48-52 parts of anhydrous toluene dropwise to the 2-pyrrolidone hydrochloride suspension. After the addition is complete, raise the temperature to 60-80°C to react, and cool to room temperature to obtain an organic phase solution containing an isocyanate intermediate. B2. Disperse 6-10 parts of resistant dextrin in a mixed solvent consisting of 100-150 parts of anhydrous dimethyl sulfoxide and 100-150 parts of anhydrous N,N-dimethylformamide containing 0.5-2 parts of triethylamine, and stir at 50-60°C to obtain a dispersion; add an organic phase solution containing an isocyanate intermediate dropwise to the dispersion at 0-10°C with continuous stirring; after the addition is complete, continue the reaction at 25-40°C to obtain a reaction mixture; pour the reaction mixture into diethyl ether to precipitate; collect the precipitate by centrifugation, wash the precipitate with anhydrous diethyl ether to obtain a crude product; redissolve the crude product in deionized water, place it in a dialysis bag for dialyzing, obtain a dialysate, and freeze-dry the dialysate.

8. The method for preparing high-purity, low-density resistant dextrin according to claim 7, characterized in that, In step B1, the reaction time is 2-4 hours after heating to 60-80℃.

9. The method for preparing high-purity, low-density resistant dextrin according to claim 7, characterized in that, In step B2, the stirring time at 50-60℃ is 2-4 hours.

10. A high-purity, low-density resistant dextrin, characterized in that, The high-purity low-density resistant dextrin is prepared according to any one of claims 1-9.

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