Method for large-scale selective preparation of different crystal form starch-fatty acid complex resistant starches and its application

Abstract

This invention belongs to the field of food processing and health product technology, specifically relating to a method for the controllable and selective preparation of starch-fatty acid complexes of different crystalline forms and its applications. The method includes: debranching high-amylose starch, compounding the debranched starch with fatty acids, and selectively preparing pure type I and pure type II complexes simply by controlling the compounding temperature and time (10–16 h), with the resulting complexes exhibiting high purity. Compared to natural starch, the two different crystalline forms of the prepared complexes have higher enzyme resistance, lower digestion rates and degrees of digestion, and better potential hypoglycemic and intestinal probiotic effects, which is beneficial for developing low glycemic index foods or health products, improving intestinal microecology, and enhancing human nutrition and health. This invention features high process selectivity, high product purity, a simple route, low cost, and is suitable for large-scale commercial production and continuous dynamic production.

Description

Invention Field

[0001] This invention belongs to the field of food processing and health product technology, and relates to starch-lipid complexes, crystal forms, and different digestibility regulation methods. Specifically, this invention relates to a method for the large-scale selective preparation of resistant starch with different crystal forms of starch-fatty acid complexes, a method for different digestibility regulation methods, and their applications in food and health products. Background Technology

[0002] Starch and lipids are essential nutrients in food, playing a crucial role in its texture, flavor, and nutritional quality. Starch is composed of linear amylose and branched amylopectin. Amylose forms starch-lipid complexes with lipids through non-covalent interactions such as hydrophobic interactions and hydrogen bonds in suitable media. Amylopectin, due to its highly branched structure, is less likely to form complexes with lipids. The formation and crystal structure of starch-lipid complexes are influenced by various factors, including the preparation method, the source and properties of starch and lipids, and the complexation conditions. To promote complex formation, pullulanase or isoamylase are commonly used to debranch starch, yielding more linear dextran chains and thus enhancing its lipid-complexing ability. The formation of starch-lipid complexes can hinder starch gelatinization, delay starch retrogradation, and reduce starch digestibility.

[0003] Currently, processes for preparing pure type I or type II starch-fatty acid complexes (e.g., extrusion) suffer from high energy costs, low product purity, and limited availability of starch raw materials (only applicable to natural starch). Therefore, precisely controlling processing temperature and time to prepare high-purity and enzyme-resistant type I or type II starch-fatty acid complex resistant starch using a greener, lower-cost process remains a significant technological bottleneck, severely restricting the application of starch-lipid complexes as a type of resistant starch in food and health products.

[0004] Based on this, in this patent application, the applicant uses starch debranching technology to process natural starch and then combines it with fatty acids of different chain lengths. By controlling different processing conditions (temperature and time), starch-fatty acid complexes with different crystal forms (type I or type II) are prepared, all of which have good enzyme resistance. Therefore, they have good potential effects such as lowering blood sugar and promoting intestinal health. This is of great significance for developing low glycemic index foods or health products, thereby improving intestinal microecology and human nutrition and health.

[0005] Debranched starch, in this invention, refers to debranched high amylose starch, which is obtained by debranching high amylose corn starch to obtain more linear dextran chains that can complex with fatty acids.

[0006] Type I complex resistant starch: namely, crystalline I starch-fatty acid complex and crystalline I starch-fatty acid complex resistant starch, with a melting temperature of approximately 85–105℃.

[0007] Type II complex resistant starch: namely, crystalline type II starch-fatty acid complex, crystalline type II starch-fatty acid complex resistant starch, with a melting temperature of approximately 106-125℃.

[0008] Hydrothermal method: In this invention patent, it refers to a method of heating debranched starch and fatty acids in a closed reaction vessel using water as a solvent, according to certain processing conditions, such as temperature, time, magnetic stirring speed, etc.

[0009] Italicized g: The unit used in the centrifugation step, referring to the unit of measurement of centrifugal force at a specific acceleration. Summary of the Invention

[0010] The main technical problem solved by this invention is to provide a controllable preparation method for forming a pure type I or pure type II complex with debranched high amylose corn starch and fatty acids by precisely controlling the reaction temperature and reaction time, and the formed complex can reduce starch digestibility.

[0011] This invention proposes a method for the large-scale selective preparation of starch-fatty acid complexes with different crystal forms and its applications.

[0012] To controllably and selectively prepare type I or type II complexes, the method of the present invention includes:

[0013] (1) This invention uses pullulanase to debranch high amylose corn starch to prepare debranched high amylose corn starch as an important raw material for preparing the final product; (2) This invention mixes debranched starch with fatty acids and uses a hydrothermal method to prepare resistant starches of different crystal forms of starch-fatty acid complexes; (3) This invention obtains pure type I and / or pure type II complexes for different fatty acids by precisely controlling the reaction temperature and reaction time.

[0014] Specifically, the present invention provides a method for large-scale selective preparation of starch-fatty acid complexes with different crystal forms, comprising the following steps:

[0015] (1) High amylose is debranched using a bio-enzyme (starch debranching enzyme) with starch debranching function to obtain debranched high amylose; (2) Debranched high amylose is mixed with fatty acids in a solvent to obtain a debranched starch-fatty acid suspension; (3) The debranched starch-fatty acid suspension is heated at a reaction temperature of 65-95℃ for 5-20h to obtain a debranched starch-fatty acid complex.

[0016] Further: In step (1), the starch debranching enzyme was selected from pullulanase; the high amylose was selected from high amylose corn starch. In step (2), the fatty acids were selected from fatty acids with different carbon chain lengths: C8~C999. 18 Preferred ingredients: lauric acid, myristic acid, palmitic acid, stearic acid; the solvent in step (2) is water.

[0017] Furthermore, the method for large-scale selective preparation of starch-fatty acid complexes of different crystal forms described in this invention is characterized by: (1) preparing a starch suspension of high amylose corn starch, heating and gelatinizing it, adding pullulanase in a water bath, and performing a debranching reaction; inactivating the enzyme by heating, and freeze-drying to obtain debranched high amylose corn starch; (2) taking debranched high amylose corn starch and fatty acids, adding them to water, and mixing to obtain a debranched starch-fatty acid suspension; (3) heating and gelatinizing the debranched starch-fatty acid suspension, stirring and heating it in a water bath at 65-95°C for 5-20 hours; centrifuging, collecting the precipitate, and freeze-drying to obtain a debranched starch-fatty acid complex resistant starch sample.

[0018] Furthermore, the method for large-scale selective preparation of starch-fatty acid complexes of different crystal forms described in this invention is characterized by: (1) preparing a starch suspension by adjusting high amylose corn starch with a sodium acetate buffer solution of pH=5.0, heating it at 120-150℃ until the starch gelatinizes, adding pullulanase in a water bath at 50-80℃, and debranching it for 6-48 hours; inactivating the enzyme by heating for 10-60 minutes, and freeze-drying for 12 hours to obtain debranched high amylose corn starch; (2) taking 1g of debranched high amylose corn starch and 50mg of fatty acids in 100mL of water and stirring evenly to obtain a debranched starch-fatty acid suspension; (3) heating the debranched starch-fatty acid suspension at 130-140℃ to gelatinize it, stirring and heating it in a water bath at 65-95℃ for 8-20 hours; centrifuging at 6500g for 20 minutes, collecting the precipitate, washing it once with 75% ethanol solution, centrifuging it at 8000g for 15 minutes, freeze-drying it, and sieving it to obtain a debranched starch-fatty acid complex resistant starch sample.

[0019] Furthermore, the method for large-scale selective preparation of starch-fatty acid complexes of different crystal forms described in this invention is characterized by: (1) preparing a 10% (g / mL) starch suspension by using a 0.2M sodium acetate buffer solution with pH=5.0 to prepare high amylose corn starch; mixing well, heating the starch suspension at 130°C for 1 h until the starch is completely gelatinized, then transferring it to a 60°C water bath, adding pullulanase to the system at an enzyme concentration of 80 NPUN / g, stirring at 600 rpm, and continuing the debranching reaction for 18 h; heating to 100°C to inactivate the enzyme for 30 min, and freeze-drying the obtained debranched starch paste for 12 h to obtain debranched high amylose corn starch; 2) Weigh 1g of debranched high amylose corn starch and 50mg of fatty acid into 100mL of pure water, stir, and obtain a debranched starch-fatty acid suspension; (3) Heat the debranched starch-fatty acid suspension in a 135℃ autoclave for 30min until the starch is completely gelatinized, heat in a 70℃ water bath for 10h, and stir; after the reaction, centrifuge the sample at 6500g for 20min to separate the precipitate and supernatant; wash the precipitate with 75% ethanol solution, centrifuge at 8000g for 15min to separate the precipitate and supernatant, collect the precipitate, freeze dry for 12h, grind, and pass through an 80-mesh sieve to obtain a debranched starch-fatty acid complex resistant starch sample.

[0020] The method for large-scale selective preparation of starch-fatty acid complexes with different crystal forms according to the present invention is characterized in that: in step (3), heating is accompanied by continuous stirring at a stirring rate of 600 rpm.

[0021] The starch-fatty acid complex prepared by the method of the present invention has a melting temperature of 90-125℃.

[0022] Preparation of type I starch-fatty acid complex

[0023] This invention also provides a method for the large-scale selective preparation of type I starch-lipid-anti-acid complexes, characterized in that:

[0024] After starch gelatinization in step (3), the reaction temperature in the water bath is 65-75℃, and the reaction time is 8-12 hours. Preferably, after starch gelatinization in step (3), the reaction is carried out in a water bath at 70℃ for 10 hours.

[0025] The pure type I complex described in this invention has a melting temperature of 95.0–105.0 °C; the half-maximum width at half maximum (FWHM) of the diffraction peaks in X-ray diffraction are 0.49–0.84 (7.5°), 1.27–1.61 (13.0°), and 1.47–1.66 (19.9°); the digestibility is 56.8–67.7%, and the digestion rate is 0.0135–0.0155.

[0026] Preparation of type II starch-fatty acid complex

[0027] This invention also provides a method for the large-scale selective preparation of type II starch-fatty acid complexes, characterized in that:

[0028] After starch gelatinization in step (3), the reaction temperature is heated in a water bath at 85–95°C for 14–18 hours. Preferably, after starch gelatinization in step (3), the reaction is heated in a water bath at 90°C for 16 hours.

[0029] The pure type II complex described in this invention has a melting temperature of 109.0–121.0 °C; a half-maximum width at half maximum (FWHM) of 0.30–0.37 (7.5°) in X-ray diffraction; a half-maximum width (FWHM) of 0.49–0.66 (13.0°); and a half-maximum width (FWHM) of 0.56–0.67 (19.9°); a digestibility of 51.6–55.5% and a digestion rate of 0.0122–0.0134.

[0030] The type II complex of the present invention exhibits a smaller full width at half maximum (FWHM) in X-ray diffraction compared to the corresponding type I complex.

[0031] The starch-fatty acid complex prepared by the above method can be used as a slow-digesting and low-digestibility food and health food.

[0032] The high amylose corn starch described in this invention has an amylose content of more than 50%, thereby promoting the formation of more starch-fatty acid complexes.

[0033] In this invention, carbon chains with different lengths (C) are selected. s ~C 18 Fatty acids, such as lauric acid, myristic acid, palmitic acid, and stearic acid, form a stable V-shaped crystal structure.

[0034] In step (1) of this invention, the buffer concentration is 0.2M and the pH is 5.0.

[0035] In step (1) of this invention, based on 10g of high amylose corn starch, the buffer solution is used in a volume of 100mL. This is to promote starch dispersion and dissolution.

[0036] In step (1) of this invention, the starch gelatinization temperature is 130°C, and the heating time is 1 hour. This further promotes the dissolution and dispersion of high amylose corn starch.

[0037] The ratio of pullulanase to starch added in step (1) of this invention is 80:1 (NPUN / g).

[0038] In step (1) of this invention, the starch debranching reaction temperature is 50–60°C, and the reaction time is 18–24 h. This promotes the full interaction between high amylose corn starch and pullulanase.

[0039] In step (1) of this invention, the enzyme inactivation temperature is 100℃ and the enzyme inactivation time is 30min.

[0040] In step (2) of this invention, based on 1g of debranched starch, the amount of pure water used is 100mL. This is to promote starch dispersion and dissolution.

[0041] In step (2) of this invention, the mass ratio of debranched starch to fatty acids is 20:1.

[0042] In step (3) of this invention, the heating temperature is 135°C and the heating time is 30 minutes. This further promotes the dissolution and dispersion of debranched starch.

[0043] In step (3) of this invention, the reaction temperature is 70–90°C, and the reaction time is 10–16 h. This promotes the formation of more starch-fatty acid complexes.

[0044] Furthermore, in step (3) of the present invention, the preferred reaction temperature for the type I complex is 70°C and the reaction time is 10h; the preferred reaction temperature for the type II complex is 90°C and the reaction time is 16h.

[0045] In step (3) of the present invention, the centrifugal force is 6500-8000g and the centrifugation time is 15-20min.

[0046] Steps (1) and (3) of the present invention are accompanied by continuous stirring at a stirring rate of 600 rpm.

[0047] In another aspect, the present invention provides a starch-based product with a slow digestibility and low digestibility. The product described in this invention contains the aforementioned starch-fatty acid complex.

[0048] The products described in this invention include food or health products.

[0049] In another aspect of the present invention, the present invention proposes a method for large-scale selective and controllable preparation of type I and type II starch-fatty acid complexes, or the application of type I and type II starch-fatty acid complexes prepared by the above controllable method in reducing the rate and extent of starch digestion.

[0050] In another aspect of the invention, the invention proposes the application of the above-mentioned type I and type II starch-fatty acid complex resistant starch in the preparation of products that can reduce the rate and extent of starch digestion.

[0051] The present invention also claims protection for the use of starch-fatty acid complex resistant starch in the prevention and improvement of metabolic diseases and imbalances related to starch digestibility (such as type 2 diabetes, obesity, cardiovascular and cerebrovascular diseases, etc.).

[0052] The process method described in this patent application has the following advantages compared with traditional methods:

[0053] This invention prepares debranched high amylose corn starch as an important intermediate raw material for the preparation of the final product;

[0054] This invention enables the preparation of type I or type II starch-fatty acid complex resistant starch simply by controlling the reaction temperature and reaction time, and the product has high purity.

[0055] Compared to traditional sample preparation methods such as extrusion, the process described in this patent application can prepare type I or type II complexes simply by controlling the reaction temperature and reaction time, resulting in complexes with high purity. Specifically, the melting temperature of the type I complex is 95.0–105.0℃, and the melting temperature of the type II complex is 109.0–121.0℃. The type II complex exhibits good enzyme resistance due to its high thermal stability and favorable crystal structure, thus showing great potential in controlling postprandial blood glucose. The type I complex is more beneficial for improving the color and texture of starch-based foods, enhancing their sensory characteristics. Therefore, by controlling the addition ratio of type I and type II complexes, products with excellent sensory quality and nutritional properties can be produced.

[0056] The two different crystalline complexes prepared by this invention exhibit higher enzyme resistance compared to natural starch, and the pure type II complex shows a lower digestibility rate and degree of digestion than the pure type I complex. The controllable preparation method provided by this invention, which produces starch-lipid complexes of different crystalline forms, possesses low starch digestibility, thus exhibiting better potential for lowering blood sugar and promoting gut health. This is of great significance for developing low glycemic index foods or health products, thereby improving gut microbiota and human nutrition and health.

[0057] Even more surprisingly, in the process of optimizing process parameters, even compared with the applicant's comparative scheme (such as constant temperature heating in a water bath at 80°C, reaction for 10 hours, etc.), the present invention adjusts key parameters to achieve selective preparation of type I complex resistant starch and type II complex resistant starch with different crystal forms, which has never been achieved in previous research results.

[0058] The process route of this invention is simple and easy to control, with low cost, high yield, and easy technology transfer. It is also convenient for large-scale commercial production of type I and type II complex resistant starch. Through parameter adjustment, continuous production of type I and type II starch, as well as dynamic production adjustment, can even be achieved. Attached Figure Description

[0059] Figure 1 (A / B / C / D) are DSC spectra of resistant starch with different crystalline forms of starch-fatty acid complexes, respectively.

[0060] Figure 2 (A / B / C / D) are X-ray diffraction patterns of resistant starch with different crystalline forms of starch-fatty acid complexes:

[0061] Figure 3 (A / B / C / D) are in vitro simulated digestion curves of resistant starch with different crystalline starch-fatty acid complexes. Detailed Implementation

[0062] To facilitate understanding of the present invention, a more complete description will be provided below with reference to the accompanying drawings. Those skilled in the art will understand that the following description only provides preferred embodiments of the invention and should not be construed as limiting the scope of the invention. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature or as per the product manual.

[0063] The experimental materials involved in the following embodiments:

[0064] High-amylose corn starch, lauric acid, myristic acid, palmitic acid, stearic acid, and pullulanase. All other chemical reagents used were of analytical grade.

[0065] Example 1: Preparation of Debranched High Amylose Corn Starch

[0066] High-amylose corn starch was prepared into a 10% (g / mL) starch suspension using a 0.2M sodium acetate buffer solution with a pH of 5.0. The suspension was mixed thoroughly and heated at 130℃ for 1 hour until complete gelatinization. The mixture was then transferred to a 60℃ precision-controlled magnetically stirred water bath. Pullulanase was added to the system at a concentration of 80 NPUN / g to debranch the starch. The debranching reaction was continued for 18 hours at a stirring speed of 600 rpm. After the reaction, the system was heated to 100℃ and maintained for 30 minutes to inactivate the enzyme. The resulting debranched starch paste was freeze-dried for 12 hours to obtain debranched high-amylose corn starch.

[0067] Example 2: Lauric acid, 70°C water bath, reaction time 10 hours.

[0068] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of lauric acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0069] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 70℃ precision temperature-controlled magnetically stirred water bath and reacted for 10 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-lauric acid complex resistant starch sample.

[0070] Example 3: Lauric acid, 90°C water bath, reaction time 16 hours.

[0071] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of lauric acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0072] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 90℃ precision-controlled magnetically stirred water bath and reacted for 16 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated again. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-lauric acid complex resistant starch sample.

[0073] Example 4: Myristic acid, 70°C water bath, reaction time 10 hours.

[0074] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of myristic acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0075] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 70℃ precision-controlled magnetically stirred water bath and reacted for 10 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-myristic acid complex resistant starch sample.

[0076] Example 5: Myristic acid, 90°C water bath, reaction time 16 hours.

[0077] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of myristic acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0078] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 90℃ precision-controlled magnetically stirred water bath and reacted for 16 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-myristic acid complex resistant starch sample.

[0079] Example 6: Palmitic acid, 70°C water bath, reaction time 10 hours.

[0080] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of palmitic acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0081] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 70℃ precision temperature-controlled magnetically stirred water bath and reacted for 10 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-palmitic acid complex resistant starch sample.

[0082] Example 7: Palmitic acid, 90°C water bath, reaction time 16 hours.

[0083] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of palmitic acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0084] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 90℃ precision-controlled magnetically stirred water bath and reacted for 16 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-palmitic acid complex resistant starch sample.

[0085] Example 8: Stearic acid, 70°C water bath, reaction time 10 hours.

[0086] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of stearic acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0087] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 70℃ precision temperature-controlled magnetically stirred water bath and reacted for 10 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-stearic acid complex resistant starch sample.

[0088] Example 9: Stearic acid, 90°C water bath, reaction time 16 hours.

[0089] Take 1g of debranched high amylose corn starch from Example 1 and 50mg of stearic acid, add them to 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0090] The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. It was then transferred to a 90℃ precision-controlled magnetically stirred water bath and reacted for 16 h at a stirring speed of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and supernatant. The precipitate was washed once with 75% ethanol solution, centrifuged at 8000 g for 15 min, and the precipitate and supernatant were separated. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-stearic acid complex resistant starch sample.

[0091] To further illustrate the technical content and effects of the present invention, the applicant further designed the following experimental comparative examples 1 to 8 and conducted comparative analysis.

[0092] Comparative Example 1

[0093] Accurately weigh 20g of high amylose corn starch into 100mL of pure water and stir well. Heat at 135℃ for 30min, freeze dry, and grind to obtain gelled high amylose corn starch.

[0094] Comparative Example 2

[0095] (1) A 10% (g / mL) starch suspension was prepared by mixing high amylose corn starch with a 0.2M sodium acetate buffer solution at pH 5.0. The starch suspension was heated at 130℃ for 1 h until the starch was completely gelatinized. Then, it was transferred to a 60℃ precision temperature-controlled magnetically stirred water bath. Pullulanase was added to the system at a concentration of 80 NPUN / g to debranch the starch. The debranching reaction was carried out for 18 h with a stirring speed of 600 rpm. After the reaction was completed, the system was heated to 100℃ and maintained for 30 min to inactivate the enzyme. The resulting debranched starch paste was freeze-dried for 12 h to obtain debranched high amylose corn starch.

[0096] (2) Accurately weigh 1g of debranched high amylose corn starch and 50mg of lauric acid into 100mL of pure water and stir evenly to obtain a debranched starch-fatty acid suspension.

[0097] (3) The debranched starch-fatty acid suspension was heated in a 135℃ autoclave for 30 min until the starch was completely gelatinized. Then, it was transferred to an 80℃ precision temperature-controlled magnetically stirred water bath for 10 h with a stirring rate of 600 rpm. After the reaction, the sample was centrifuged at 6500 g for 20 min to separate the precipitate and the supernatant. The precipitate was washed once with 75% ethanol solution and then centrifuged at 8000 g for 15 min to separate the precipitate and the supernatant. The precipitate was collected, freeze-dried for 12 h, ground, and passed through an 80-mesh sieve to obtain the debranched starch-lauric acid complex resistant starch sample.

[0098] Comparative Example 3

[0099] The reaction temperature of debranched starch with lauric acid was 90℃, and other processing and preparation methods were the same as those in Comparative Example 2.

[0100] Comparative Example 4

[0101] The added fatty acid was myristic acid, and the other processing and preparation methods were the same as those in Comparative Example 2.

[0102] Comparative Example 5

[0103] The reaction temperature of debranched starch with myristic acid was 90℃, and other processing and preparation methods were the same as those in Comparative Example 4.

[0104] Comparative Example 6

[0105] The added fatty acid was palmitic acid, and the other processing and preparation methods were the same as those in Comparative Example 2.

[0106] Comparative Example 7

[0107] The reaction temperature of debranched starch with palmitic acid was 90℃, and other processing and preparation methods were the same as those in Comparative Example 6.

[0108] Comparative Example 8

[0109] The added fatty acid was stearic acid, and the other processing and preparation methods were the same as those in Comparative Example 2.

[0110] Comparative Example 9

[0111] The reaction temperature of debranched starch with stearic acid was 90℃, and other processing and preparation methods were the same as those in Comparative Example 8.

[0112] Relevant test results for all examples and comparative examples prepared by the method of this invention:

[0113] Example 10: Comparison of Differential Scanning Calorimetry Results

[0114] The melting enthalpy of the resistant starch in the starch-fatty acid complex was measured using a differential scanning calorimeter (200F3, Netzsch, Germany) equipped with a thermal analysis data station. Approximately 3 mg of sample (dry basis) was accurately weighed into a 40 μL aluminum sample dish. Distilled water at a 1:3 starch:water ratio (w / v) was added to the crucible, which was then sealed and allowed to stand at room temperature for 12 h. The crucible was then heated from 20 °C to 130 °C at a rate of 10 °C / min. An empty crucible was used as a blank control. The melting enthalpy of the complex was obtained using data logging software.

[0115] The thermodynamic properties of the composite samples obtained in the examples and comparative examples were characterized. The results are as follows: Figure 1 As shown in Tables 1 and 2.

[0116] Table 1. Thermodynamic transformation parameters of type I complex in the complex samples.

[0117]

[0118]

[0119] ND: No data detected

[0120] Table 2. Thermodynamic transformation parameters of type II complexes in the complex samples.

[0121]

[0122]

[0123] ND: No data detected

[0124] The applicant found that when compounded at 70°C for 10 hours, debranched starch formed pure type I complexes with all four fatty acids (Examples 2, 4, 6, 8). When compounded at 90°C for 16 hours, debranched starch formed pure type II complexes with all four fatty acids (Examples 3, 5, 7, 9). Furthermore, no melting peak was detected in gelled starch (Comparative Example 1). When compounded at 80°C for 10 hours, lauric acid formed a pure type II complex with debranched starch (Comparative Example 2); myristic acid and palmitic acid formed complexes with debranched starch containing both type I and type II compounds (Comparative Examples 4, 6); and stearic acid formed a pure type I complex with debranched starch (Comparative Example 8). When compounded at 90°C for 10 hours, lauric acid, myristic acid, and palmitic acid formed pure type II complexes with debranched starch (Comparative Examples 3, 5, 7); while stearic acid formed a complex with both type I and type II compounds (Comparative Example 9). In summary, only when compounded at 70℃ for 10 hours can debranched starch and all four fatty acids form pure type I complexes; only when compounded at 90℃ for 16 hours can debranched starch and all four fatty acids form pure type II complexes.

[0125] Example 11 X-ray diffraction analysis comparison

[0126] XRD diffraction patterns of resistant starch-fatty acid complex were obtained using X-ray diffraction (XRD) to analyze its long-range crystal order. Before analysis, the sample was equilibrated in a desiccator containing saturated sodium chloride solution for one week. Scanning analysis was performed at a scan rate of 2° / min and a step size of 0.02° within the range of 5–35°. The crystallinity of the complex and the full width at half maximum (FWHM) values ​​of the diffraction peaks at 7.5°, 13.0°, and 19.9° were calculated using the instrument's built-in analysis software, DIFFRAC.EVA. The principle of crystallinity calculation is as follows:

[0127] XC = Wc / (Wc + Wa)

[0128] Wc and Wa represent the areas of the scattering packets of the crystalline peak and the amorphous peak, respectively.

[0129] The results are as follows Figure 2 As shown in Table 3.

[0130] Table 3. Long-range ordered structural parameters of the composite samples

[0131]

[0132]

[0133] ND: No data detected

[0134] The applicant found that, except for Comparative Example 1, all samples exhibited three distinct diffraction peaks at 7.5°, 13.0°, and 19.9°, indicating a V-type crystal structure. Specifically, the relative crystallinities of the pure type II complexes (Examples 3, 5, 7, and 9) formed after compounding at 90°C for 16 hours were 29.7%, 50.3%, 46.8%, and 45.0%, respectively; while the relative crystallinities of the pure type I complexes (Examples 2, 4, 6, and 8) formed after compounding at 70°C for 10 hours were 26.9%, 38.1%, 36.8%, and 40.6%, respectively, indicating that the pure type II complexes corresponding to the same fatty acid have a higher long-range crystal order than the pure type I complexes. Furthermore, the pure type II complexes (Examples 3, 5, 7, and 9) had lower half-widths (WHMs) than the pure type I complexes (Examples 2, 4, 6, and 8), indicating that the type II complexes have a more perfect crystal structure. No XRD diffraction peaks were detected in the gelled starch (Comparative Example 1). Except for lauric acid, the crystallinity and XRD peak half-width values ​​of the complexes formed by compounding the same fatty acids with debranched starch at 80℃ and 90℃ for 10 h (Comparative Examples 4-9) were between those of their corresponding pure type I complexes (Examples 4, 6, 8) and pure type II complexes (Examples 5, 7, 9). The crystallinity of the complexes formed by compounding lauric acid with debranched starch at 80℃ and 90℃ for 10 h (Comparative Examples 2, 3) was higher than that of their corresponding pure type I complexes (Example 2) and pure type II complexes (Example 3), while the XRD peak half-width values ​​were lower than those of their corresponding pure type I complexes (Example 2) and pure type II complexes (Example 3). This may be because the stability of debranched starch-lauric acid is poor, and the long compounding time leads to the destruction of its structure.

[0135] Example 12: Comparison of digestion rate and final digestibility of the complex

[0136] The complex sample was co-conjugated with porcine pancreatic α-amylase in sodium acetate buffer at a constant temperature (37°C, 200 rpm). The digested suspension (100 μL) was collected over a time range (0–300 min) and added to 900 μL of Na₂CO₃ (0.3 M) solution to terminate the amylase hydrolysis reaction. The mixture was then centrifuged at 13,000 g for 10 min. Reducing sugars in the supernatant were determined using the PAHBAH method.

[0137] The digestion curve was fitted using the logarithm of slope (LOS) plot method, and the first-order kinetic parameters were calculated.

[0138]

[0139] Where ln(dC / dt) represents the slope of the LOS plot, k(min -1) represents the starch digestion rate coefficient, and this formula shows the linear relationship between LOS and digestion time (t).

[0140] The digestion process of Comparative Examples 1-8, Examples 2-9, and Comparative Examples 1-8 was determined using an in vitro simulated small intestinal digestion model. The digestion rate and final digestibility of the complexes were determined based on first-order kinetic simulation. Results are as follows: Figure 3 As shown in Table 4,

[0141] Table 4. Digestibility and digestibility of pure type I and type II debranched starch-fatty acid complexes

[0142]

[0143]

[0144] The applicant found that gelled starch (Comparative Example 1, ~60%) was rapidly digested primarily within the first 45 minutes, with a digestibility of 74.8% after 300 minutes. In contrast, Examples 2–9 (Type I or Type II complexes) exhibited lower starch digestibility (51.6–67.7%) throughout the digestion process. Furthermore, Examples 2–9 (Type I or Type II complexes) had a slow digestion rate (k value = 0.012–0.016 min). -1 This is significantly lower than the digestion rate of Comparative Example 1 (gelatinized starch) (k value = 0.020 min). -1Furthermore, Examples 3, 5, 7, and 9 (pure type II complexes) exhibited lower starch digestibility and digestion rate than Examples 2, 4, 6, and 8 (pure type I complexes). The digestibility (53.99%) and digestion rate (0.0127) of Comparative Example 2 were between those of Example 2 (56.82%, 0.0135) and Example 3 (53.57%, 0.0124). However, the digestibility (51.54%) and digestion rate (0.0120) of Comparative Example 3 were both lower than those of Example 2 (56.82%, 0.0135) and Example 3 (53.57%, 0.0124), which may be related to the structure of the complex. The digestibility (55.39–57.86%) and digestion rate (0.0139–0.0146) of Comparative Examples 4 and 5 were between those of Example 4 (59.32%, 0.0147) and Example 5 (51.58%, 0.0123). The digestibility (65.73–67.00%) and digestion rate (0.0147–0.0149) of Comparative Examples 6 and 7 were between those of Example 6 (67.11%, 0.0153) and Example 7 (53.53%, 0.0126). The digestibility (66.73–66.84%) and digestion rate (0.0148–0.0150) of Comparative Examples 8 and 9 were between those of Example 8 (67.72%, 0.0155) and Example 9 (55.47%, 0.0132). In conclusion, the digestibility of the complex is determined by its structure.

[0145] Therefore, it can be seen that pure type I and type II starch-fatty acid complexes can significantly reduce starch digestibility compared to gelled starch, and pure type II complexes have a lower digestion rate and degree compared to pure type I complexes.

[0146] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

[0147] All modifications made without creative effort, based on the concept of this invention, fall within the protection scope of this invention.

Claims

1. A method for preparing type I starch-fatty acid complex, comprising the following steps: (1) Prepare a starch suspension from high amylose corn starch, 120~150 o C. Heat until starch gelatinizes, place in a water bath, add pullulanase, and perform a debranching reaction; inactivate the enzyme by heating, freeze dry, and obtain debranched high amylose corn starch. (2) Take debranched high-amylose corn starch and fatty acids, add them to water, mix well, and obtain a debranched starch-fatty acid suspension; wherein the fatty acids are selected from lauric acid, myristic acid, palmitic acid and stearic acid; (3) Set the debranched starch-fatty acid suspension at 130~140°C. o Heat and gelatinize in a high-pressure sterilizer at 65-75°C. o The mixture was heated in a water bath with stirring for 8-12 hours; after centrifugation, the precipitate was collected and freeze-dried to obtain type I starch-fatty acid complex.

2. The method for preparing type I starch-fatty acid complex according to claim 1, characterized in that: (1) Prepare a starch suspension by mixing high amylose corn starch with a sodium acetate buffer solution at pH 5.0, and then add 120~150 ml of the solution. o Heat C until the starch gelatinizes, 50-80°C. o In a C water bath, pullulanase was added, and the debranching reaction was carried out for 6–48 h; the enzyme was inactivated by heating for 10–60 min, and the mixture was freeze-dried for 12 h to obtain debranched high amylose corn starch. (2) Take 1 g of debranched high amylose corn starch and 50 mg of fatty acids in 100 mL of water and stir evenly to obtain a debranched starch-fatty acid suspension; wherein the fatty acids are selected from lauric acid, myristic acid, palmitic acid and stearic acid; (3) Stir the debranched starch-fatty acid suspension at 130~140°C. o Heat to gelatinize at 65-75°C. o The mixture was heated in a water bath with stirring for 8-12 hours. After centrifugation at 6500 g for 20 minutes, the precipitate was collected, washed once with 75% ethanol solution, centrifuged at 8000 g for 20 minutes, freeze-dried, and sieved to obtain the de-type I starch-fatty acid complex.

3. The method for preparing type I starch-fatty acid complex according to claim 2, characterized in that: After starch gelatinization in step (3), 70 o The reaction was carried out under constant temperature heating in a water bath for 10 hours.

4. The method for preparing type I starch-fatty acid complex according to any one of claims 1-3, characterized in that: The stirring speed is 600 rpm.

5. A type I starch-fatty acid complex prepared by the method according to any one of claims 1-3, characterized in that: Melting temperature is 95–105 °C o C.

6. A type I starch-fatty acid complex prepared by the method according to any one of claims 1-3, wherein the characteristic peaks in X-ray diffraction include: 7.5°：0.49～0.84；13.0°：1.27～1.61； 19.9°：1.47～1.66。 7. A type I starch-fatty acid complex prepared by the method according to any one of claims 1-3, characterized in that: The digestibility is 56.8%–67.7%.

8. A type I starch-fatty acid complex prepared by the method according to any one of claims 1-3, its use as a food with slow digestion rate and low digestibility, and its use in the preparation of medicines for preventing and improving metabolic diseases related to starch digestibility.

9. A type I starch-fatty acid complex prepared by the method according to any one of claims 1-3, and its use as a health food with slow digestion rate and low digestibility.

10. A method for preparing a type II starch-fatty acid complex, comprising the following steps: (1) Prepare a starch suspension from high amylose corn starch, 120~150 o C. Heat until starch gelatinizes, place in a water bath, add pullulanase, and perform a debranching reaction; inactivate the enzyme by heating, freeze dry, and obtain debranched high amylose corn starch. (2) Take debranched high amylose corn starch and fatty acids, add them to water, mix well, and obtain a debranched starch-fatty acid suspension; wherein the fatty acids are selected from lauric acid, myristic acid, palmitic acid and stearic acid; (3) Set the debranched starch-fatty acid suspension at 130~140°C. o Heat and gelatinize in a high-pressure sterilizer at 85-95°C. o The mixture was heated in a water bath with stirring for 14-18 hours; after centrifugation, the precipitate was collected and freeze-dried to obtain type II starch-fatty acid complex.

11. The method for preparing type II starch-fatty acid complex according to claim 10, characterized in that: (1) Prepare a starch suspension by mixing high amylose corn starch with a sodium acetate buffer solution at pH 5.0, and then add 120~150 ml of the solution. o Heat C until the starch gelatinizes, 50-80°C. o In a C water bath, pullulanase was added, and the debranching reaction was carried out for 6–48 h; the enzyme was inactivated by heating for 10–60 min, and the mixture was freeze-dried for 12 h to obtain debranched high amylose corn starch. (2) Take 1 g of debranched high amylose corn starch and 50 mg of fatty acids in 100 mL of water and stir evenly to obtain a debranched starch-fatty acid suspension; wherein the fatty acids are selected from lauric acid, myristic acid, palmitic acid and stearic acid; (3) Stir the debranched starch-fatty acid suspension at 130~140°C. o Heat to gelatinize, 85~95°C o The reaction was carried out by stirring and heating in a water bath for 14-18 hours; centrifuged at 6500 g for 20 min, the precipitate was collected, washed once with 75% ethanol solution, centrifuged at 8000 g for 20 min, freeze-dried, and sieved to obtain type II starch-fatty acid complex.

12. A method for preparing type II starch-fatty acid complex according to claim 11, characterized in that: After starch gelatinization in step (3), 90 o The reaction was carried out under constant temperature heating in a water bath for 16 hours.

13. The method for preparing type II starch-fatty acid complex according to any one of claims 10-12, characterized in that: The stirring speed is 600 rpm.

14. A type II starch-fatty acid complex prepared by the method according to any one of claims 10-12, characterized in that: Melting temperature is 109–121°C o C.

15. A type II starch-fatty acid complex prepared by the method according to any one of claims 10-12, wherein the characteristic peaks in X-ray diffraction include: 7.5°：0.30～0.37；13.0°：0.49～0.66； 19.9°：0.56～0.67。 16. A type II starch-fatty acid complex prepared by the method according to any one of claims 10-12, characterized in that: The digestibility is 51.6%–55.5%.

17. A type II starch-fatty acid complex prepared by the method according to any one of claims 10-12, its use as a food with slow digestion rate and low digestibility, and its use in the preparation of pharmaceuticals for the prevention and improvement of metabolic diseases related to starch digestibility.

18. A type II starch-fatty acid complex prepared by the method according to any one of claims 10-12, and its use as a health food with slow digestion rate and low digestibility.

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