Method for producing polycrystalline resistant starch

Abstract

This method for producing polycrystalline resistant starch uses high amylose cornstarch as a raw material, plasma activated water of pH 4-5 to produce a high concentration starch milk, and combines pullulanase with ultrasonic-assisted complexing technology to maintain the heat-resistant B-type crystals, declustering the non-heat-resistant amorphous regions of starch and efficiently complexing them with fatty acids, and crystallizing by cooling to form B+VI crystals, and furthermore, toughening treatment to obtain A+B+VII crystals with higher heat resistance. The produced polycrystalline resistant starch has a high content of 69.6%, high heat stability and crystallinity, and good mouthfeel, and can be used as a functional food ingredient in foods, and is of practical value for regulating blood sugar and cholesterol levels, managing intestinal health, etc.

Description

[Technical field]

[0001] The present invention relates to a method for producing polycrystalline resistant starch and belongs to the technical field of starch modification. [Background technology]

[0002] Common resistant starches are mainly classified into five types: RS1 (physically embedded starch), RS2 (natural resistant starch granules), RS3 (retrograded starch), RS4 (chemically modified starch), and RS5 (starch-lipid complex). RS1 and RS2 exist naturally, and the crystal type is closely related to the starch origin. Rice starch such as corn has A-type crystals, while raw bananas and potatoes have B-type crystals. RS1 and RS2 usually have poor thermal stability, and these two types of RS are almost lost during the thermal processing process. RS3 is generated during the recrystallization process of starch, and A-type or B-type crystals can be generated by adjusting the recrystallization conditions such as regeneration temperature and moisture content. The difference in heat resistance of the product is large (70℃~150℃) and water retention is low. RS4 is obtained by changing the starch molecular structure through the introduction of chemical functional groups, but its production takes time, the product quality may change, the reaction rate is low, and it pollutes the environment. At the same time, the food industry needs to take special consideration of product safety requirements, and there are significant restrictions on the reagents used. RS5 is a V-type crystal, which is classified into two types, VI-type crystal and VII-type crystal, according to heat resistance. VI-type crystal has a relatively low structural order and a dissociation temperature of about 95℃-105℃. VII-type crystal has a relatively high structural order and a dissociation temperature of about 115℃-130℃. VI-type crystal is generally produced at a relatively low temperature, while VII-type crystal needs to be formed under high temperature and long-term conditions.

[0003] Among them, natural starch particles with a certain degree of resistance to enzymatic degradation are called RS2, such as raw banana starch and potato starch, but they usually have poor thermal stability and are mostly lost during thermal processing. High amylose corn starch has a B-type crystal structure, a high amylose content, a linearly arranged molecular structure, can withstand a certain high temperature, and partially retains the highly ordered heat-resistant B-type crystals after steaming. Even after thermal processing, the resistant starch content reaches 40%, and it is the only RS2-type resistant starch that can be supplied on a large scale at present. However, the amylose content is a major factor that determines the texture and digestive properties of food. Generally, starches with low to medium amylose content have a good texture, but high amylose corn starch has a high amylose content, so it is hard and has a poor texture.

[0004] There are reports that coating with fatty acids can solve problems such as food texture and digestive characteristics.

[0005] For example, CN109549173A discloses a new type of resistant starch that is debranched by pullulanase and then combined with long-chain saturated fatty acids, and the fifth new type of resistant starch (RS5) is obtained, with the RS5 content exceeding 57.5%. However, this method has the following disadvantages: (1) Starch gelatinization and secondary gelatinization are both performed at high temperatures of 120°C or higher for a long time, so that the high amylose corn starch is completely gelatinized and the heat-resistant B-type crystals are completely destroyed, and finally only RS5 with V-type crystals is obtained, which dissociates at around 90°C and has poor heat resistance. (2) Starch gelatinization and secondary gelatinization need to be performed at 120°C or higher for a long time, and the required conditions cannot be met at normal temperature and pressure, so special high-temperature and high-pressure equipment must be used, resulting in high energy consumption and high costs.

[0006] In addition, it has been reported that B+V-type crystalline resistant starch can be obtained based on RS5 (starch-lipid complex) through methods such as regeneration, alkali treatment, high-speed homogenization, and high hydrostatic pressure, but the mentioned alkali treatment requires the use of sodium hydroxide and hydrochloric acid, and the high-speed homogenization and high hydrostatic pressure methods require specific equipment and have problems such as high costs. In addition, CN115353570A discloses a method for producing binary complex resistant starch (RS4+RS5), in which RS4-type resistant starch is produced by esterification modification, and is further produced by blending monoglyceride, and the resistant starch exhibits V-type crystalline form, has a resistant starch content of about 60%, and needs to be further improved in digestibility, and it has been reported that the use of chemical modification reagents causes problems such as restrictions on safety requirements in the food industry and environmental pollution. Summary of the Invention [Problem to be solved by the invention]

[0007] In order to solve at least one of the above technical problems, the present invention provides a method for producing polycrystalline resistant starch, which maintains the heat-resistant B-type crystals of high amylose corn starch, effectively complexes with fatty acids after declustering non-heat-resistant amorphous regions, and controls the crystallization characteristics to form B+VI-type crystals by cooling and crystallizing, and converts the B+VI-type crystals into A+B+VII-type crystals, and the resulting product has a high resistant starch content (as high as 67%-69%), a high crystallinity (40% or more), good heat resistance (resistance starch content is reduced by less than 5% after resistant starch is boiled in water for 10 min), and better texture (fatty acid content is 4.8g / 100g or more). In addition, the method of the present invention is easy to operate, can be realized at room temperature and pressure, and is low cost. [Means for solving the problem]

[0008] The first object of the present invention is to provide a method for producing polycrystalline resistant starch, which comprises producing starch milk using plasma activated water of pH 4-5, then declustering the non-heat-resistant amorphous regions of starch using pullulanase, strengthening the complexation of starch with fatty acids by ultrasonic treatment, crystallizing by cooling, and further converting by toughening treatment to obtain polycrystalline resistant starch (having three types of crystal forms, A, B, and VII, named A+B+VII type crystalline resistant starch).

[0009] In one embodiment, the method specifically comprises: Preparation of plasma activated starch milk: Step (1) of adding high amylose corn starch to plasma activated water having a pH of 4 to 5 to prepare starch milk; Declustering of amorphous regions of starch: Step (2) of gelatinizing the starch milk obtained in step (1), adding pullulanase to decluster it, and subjecting it to enzymatic hydrolysis; Ultrasonic-assisted fatty acid complexation: adding fatty acid to the enzymatically decomposed starch milk in step (2) and subjecting it to ultrasonic treatment to obtain a fatty acid complexation product in step (3); and (4) cooling and crystallizing the fatty acid complexed product obtained in step (3) by cooling, crystallizing, toughening, dehydrating, washing and drying to obtain polycrystalline (A+B+VII type) crystalline resistant starch. In one embodiment, in step (1), the starch milk has a mass of 15% to 18% by mass (w / w, based on the dry weight of starch relative to the total mass of the starch milk).

[0010] In one embodiment, in step (2), the gelatinization is carried out at a temperature of 90 to 100° C. for a time of 25 to 35 minutes.

[0011] In one embodiment, in step (2), the declustering enzymatic degradation is carried out at a temperature of 55 to 65° C. for a time of 12 to 24 hours, and the amount of pullulanase added is 40 to 50 ASPU / g dry starch. The declustering enzymatic degradation is to convert non-heat-resistant amorphous regions into short chains of amylose with pullulanase while retaining heat-resistant B-crystals in high amylose cornstarch.

[0012] In one embodiment, in step (3), the fatty acid is any one of oleic acid, linoleic acid, and linolenic acid.

[0013] In one embodiment, in step (3), the fatty acid is added to the enzymatically decomposed starch milk at 70 to 90° C., and the amount of the fatty acid added is 6% to 10% of the dry mass of the starch. The fatty acid is any one of oleic acid, linoleic acid, and linolenic acid.

[0014] In one embodiment, in step (3), the ultrasonic frequency is 25 to 35 kHz, the ultrasonic output is 300 to 400 W, and the ultrasonic treatment time is 30 to 60 minutes.

[0015] In one embodiment, in step (4), in the cooling crystallization, the product is rapidly cooled to 3 to 5° C. at an average cooling rate of 5 to 10° C. / min, and crystallized at this temperature for 30 to 60 minutes.

[0016] In one embodiment, in the toughening step (4), the toughening is performed at 45 to 55° C. for 96 to 120 hours.

[0017] In one embodiment, in the step (4), the drying comprises drying with hot air at 50 to 60° C. for 6 to 10 hours.

[0018] In one embodiment, in step (3), the fatty acid added is a water-insoluble fatty acid, and needs to be dispersed in anhydrous ethanol in an amount of 0.05 to 0.1 times the volume of the starch milk.

[0019] In one embodiment, in step (4), the dehydration is performed at a centrifugation speed of 4000 to 5000 rpm for a centrifugation time of 8 to 15 minutes.

[0020] A second object of the present invention is to provide a polycrystalline resistant starch produced by the above method.

[0021] A third object of the present invention is to provide a use of the above-mentioned method or polycrystalline resistant starch in the production of functional foods.

[0022] In said use, the functional food may include functional foods capable of improving intestinal health, preventing diabetes, and protecting the intestinal barrier.

[0023] In the present invention, high amylose corn starch refers to corn starch having an amylose content of more than 70%.

[0024] [Effects of the invention] The advantageous effects of the present invention are as follows: (1) While maintaining the heat-stable B-type crystals, the heat-unstable B-type crystals are complexed with fatty acids with the assistance of ultrasound to form an amylose-lipid complex, which converts them into heat-resistant V-type crystals that have a three-dimensional helical structure, excellent heat stability, and are less susceptible to action of amylase, thereby increasing the resistant starch content and improving heat stability. (2) By using plasma activated water with pH 4-5, the weak acidic components in it can act on the amorphous region of starch, reduce the viscosity of high amylose corn starch milk, improve the problem that the solid content of starch milk system by hydrothermal gelatinization is extremely low (5%-7%), increase the utilization rate of starch, and improve the problem that the viscosity of starch milk system is high, which is unfavorable for complexation with fatty acids. Plasma activated water is a weak acidic system, which is favorable for amylose to form a spiral regardless of the degree of unsaturation of fatty acids, and strengthens hydrophobic interactions, thereby promoting the formation of starch-fatty acid complexes. By avoiding the use of plasma activated water with high acidity, it is possible to effectively prevent the strong acidic components from attacking the crystalline region of starch, prevent the destruction of heat-resistant B-type crystals, and prevent the inactivation of pullulanase. (3) The rapid cooling crystallization method can promote the formation of a large amount of crystal nuclei, and the appropriate temperature can be maintained to promote crystal growth, which can facilitate the formation of higher crystallinity and larger crystallite size of V-type crystalline starch, make the crystal structure more perfect, and improve the stability of the complex. (4) The toughening treatment can change the deposition state inside starch particles, melt starch crystals, rearrange the molecules, and improve the crystallinity. High-amylose cornstarch can also obtain A-type crystals by the toughening treatment.

[0025] The present invention has at least the following advantages: The method of the present invention is simple in operation, can be carried out at normal temperature and pressure, and is low in cost. The polycrystalline resistant starch produced by the above method has a resistant starch content of 67% or more (as high as 67% to 69%) measured by the Englyst method, and the crystallinity measured by XRD is significantly increased compared to high amylose corn starch in the case of steaming, allowing for an increase in the resistant starch content and an improvement in crystallinity (crystallinity of 40% or more). When the resistant starch was treated in a boiling water bath for 10 minutes and measured by the Englyst method, the resistant starch content decreased by less than 5%, indicating that the present invention has significantly improved the heat resistance of the resistant starch. In addition, the introduction of unsaturated fatty acids (fatty acid content of 4.8 g / 100 g or more) into the resistant starch enhances the mouthfeel, protects the intestinal barrier, and plays a role in regulating intestinal microorganisms. This polycrystalline resistant starch not only has unique food processing properties such as good rheological properties and stability, improved mouthfeel, and reduced food expansion, but also has excellent physiological functions such as improving intestinal health, preventing diabetes, and protecting the intestinal barrier, making it highly valuable in industry and showing great potential for market development. [Brief description of the drawings]

[0026] [Figure 1] 1 is an XRD pattern of polycrystalline resistant starch of Example 1 of the present invention. [Diagram 2] 1 is an XRD pattern of resistant starch of Comparative Example 5 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The technical solutions of the present invention will be described below with reference to examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Unless specific conditions are described in the examples, they are carried out according to standard conditions or conditions suggested by the manufacturer. Unless the manufacturers of the reagents or equipment used are specified, they are all standard products available on the market.

[0028] 1. Measurement of resistant starch content The resistant starch content was measured with reference to the Englyst method. The starch-fatty acid complex produced and deionized water were mixed uniformly and vortex-shaken. The test tubes were placed in a 37°C shaking water bath, and 10 glass beads and 4mL sodium acetate buffer (0.5mol / L, pH 5.2) were added to each test tube and incubated for 30min. The freshly prepared mixed enzyme solution was added and shaken in a 37°C water bath. 0.1mL of the hydrolyzate was collected at 0, 10, 20, 30, 45, 60, 90, 120, and 180min intervals, and added to 0.9mL of 90% ethanol solution to inactivate the enzyme. The glucose content in the incubation solution was measured using a glucose measurement kit. The resistant starch content was calculated using the following formula from the values ​​of G120 (glucose released after incubation for 120 minutes) and Ws (weight of the sample). TIFF0007660692000001.tif12170

[0029] 2. Production of plasma activated water Distilled water was placed in a cylindrical tube with a diameter of 3 cm and a height of 15 cm. The plasma jet probe was placed 25 cm away from the water surface and excited for 40 to 60 s using an atmospheric pressure plasma jet excitation device to obtain plasma activated water with a pH of 4 to 5.

[0030] 3. High amylose cornstarch The high amylose cornstarch was Xiangyu 1945 purchased from ▲sen▼ (the character for "whole" under the grass radical) Yinxiangyu (Beijing) Biotechnology Co., Ltd.

[0031] 4. Pullulanase Pullulanase was purchased from SIGMA-ALDRICH.

[0032] 5. Measurement of crystallinity The crystal structure of the samples was measured using an X-ray diffractometer, selecting a Cu-Kα light source (40 kV, 30 mA) and scanning from 4° to 30° (2θ) at a scanning rate of 2° / min. The relative crystallinity RC was calculated using the MDI Jade 6.0 software with the following method: TIFF0007660692000002.tif13170Here, A c and A a represent the areas of the crystalline and amorphous regions, respectively, in the X-ray diffraction pattern.

[0033] Example 1 The method for producing polycrystalline resistant starch specifically includes the following steps: 10g of high amylose cornstarch sieved through a 100 mesh sieve was weighed and prepared into a starch milk with a solid content of 15% using plasma activated water with a pH value of 5. The starch milk was then gelatinized at 95°C for 30min, cooled to 60°C, and added with pullulanase of 45 ASPU / g dry starch for 18h declustering. After inactivating the enzyme with boiling water, the temperature was lowered to 80°C. Then, 6% oleic acid based on the starch dry weight was added, and ultrasonic treatment was performed at 80°C for 45min with an ultrasonic frequency of 30kHz and an output of 350W. The ultrasonic product was then rapidly cooled to 4°C at an average cooling rate of 8°C / min, crystallized at this temperature for 45min, and then heated to 50°C for toughening for 108h. It was then centrifuged at 4500rpm for 12min and washed three times with 50% ethanol. Finally, the sample was dried in hot air at 55°C for 8 h, crushed, and sieved through a 100 mesh sieve to obtain polycrystalline resistant starch. When measured by the Englyst method, the resistant starch content reached 69.6%. When the product was subjected to XRD testing (Figure 1), the diffraction peaks at the 2θ angles of 7.4°, 13°, and 19.7° suggested the formation of V-type crystals, and the diffraction peaks at the 2θ angles of 5.4°, 16.8°, and 23° suggested the presence of A-type and B-type crystals. The resistant starch had an A+B+VII crystal form and a crystallinity of 41.7%. When the starch was placed in a boiling water bath for 10 minutes, the resistant starch content was measured by the Englyst method, and the fatty acid content of the product was measured to be 4.91g / 100g.

[0034] Example 2 The method for producing polycrystalline resistant starch specifically includes the following steps: 10g of high amylose cornstarch sieved through a 100 mesh sieve was weighed and prepared into a starch milk with a solid content of 16% using plasma activated water with a pH value of 4.5, then the starch milk was gelatinized at 90°C for 35min, cooled to 55°C, added with pullulanase of 40 ASPU / g dry starch for 24h declustering, inactivated the enzyme with boiling water, cooled to 70°C, then added 8% oleic acid based on the starch dry weight basis, ultrasonicated at 70°C for 60min with an ultrasonic frequency of 25kHz and an output of 400W, and the product was rapidly cooled to 3°C with an average cooling rate of 5°C / min, crystallized at this temperature for 60min, and then heated to 45°C for toughening for 120h. It was cooled to room temperature, then centrifuged at 4000rpm for 15min, and washed three times with 40% ethanol. Finally, the sample was dried in hot air at 50°C for 10 h, crushed, and sieved through a 100-mesh sieve to obtain polycrystalline resistant starch. The resistant starch had the A+B+VII crystal form with a degree of crystallinity of 40.9% and a resistant starch content of 68.3% as measured by the Englyst method. After placing the starch in a boiling water bath for 10 minutes, the resistant starch content had only decreased by 4.2% as measured by the Englyst method. The fatty acid content of the product was determined to be 4.83 g / 100 g.

[0035] Example 3 The method for producing polycrystalline resistant starch specifically includes the following steps: 10g of high amylose cornstarch sieved through a nominal 100 mesh sieve was weighed out and prepared into a starch milk with a solid content of 18% using plasma activated water with a pH value of 4. The starch milk was then gelatinized at 100°C for 25min, cooled to 65°C, and added with pullulanase of 50 ASPU / g dry starch for 12h declustering. After inactivating the enzyme with boiling water, the temperature was lowered to 90°C, and 10% oleic acid was added based on the starch dry weight, and ultrasonic treatment was performed at 90°C for 30min with an ultrasonic frequency of 35kHz and an output of 300W. The product was rapidly cooled to 5°C at an average cooling rate of 10°C / min, crystallized at this temperature for 30min, and then heated to 55°C for toughening for 96h. It was cooled to room temperature, then centrifuged at 5000rpm for 8min, and washed three times with 60% ethanol. Finally, the sample was dried in hot air at 60°C for 6 h, crushed, and sieved through a 100 mesh sieve to obtain polycrystalline resistant starch. The resistant starch was A+B+VII crystalline with a degree of crystallinity of 40.6% and reached a resistant starch content of 67.5% as measured by the Englyst method. After 10 minutes in a boiling water bath, the resistant starch content had only decreased by 4.5% as measured by the Englyst method. The fatty acid content of the product was determined to be 4.81 g / 100 g.

[0036] Comparative Example 1 The effects of plasma-activated water, pullulanase, ultrasonic treatment, and toughening by cooling crystallization on the production of resistant starch were investigated by varying one or more of the conditions while keeping the remaining process steps and parameters the same as in Example 1, and the results are shown in Table 1. [Table 1]

[0037] Comparative Example 2 The only difference from Example 1 was that the plasma activated water with pH 5 was replaced with a sodium acetate solution with pH 5, and the other steps and parameters were the same as those in Example 1. The resistant starch had a crystallinity of 31.2% for the A+B+VII crystal type and a resistant starch content of 53.7% as determined by the Englyst method. After placing the starch in a boiling water bath for 10 minutes, the resistant starch content as determined by the Englyst method decreased by 9.8%. The fatty acid content of the product was determined to be 3.86 g / 100 g. Compared with the resistant starch prepared in Example 1, the resistant starch content, crystallinity, and fatty acid content are all reduced. + It is believed that this is because it affects the formation of hydrogen bonds between starch segments, reducing the degree of ordering of the starch chains.

[0038] Comparative Example 3 The only difference from Example 1 was that the plasma-activated water of pH 5 was mixed with the starch milk of 15% solids, but the plasma-activated water of pH 3 was mixed with the starch milk of 15% solids. The remaining steps and parameters were the same as those of Example 1. The resistant starch had a crystal form of A+B+VII, a degree of crystallinity of 37.7%, and a resistant starch content of 59.6% as measured by the Englyst method. After placing the starch in a boiling water bath for 10 minutes, the resistant starch content as measured by the Englyst method decreased by 7.6%. The fatty acid content of the product was measured to be 4.51 g / 100 g. Compared with the resistant starch prepared in Example 1, the content and crystallinity of the resistant starch were significantly decreased, and the difference in fatty acid content was large. This is because the low pH destroys the crystalline regions of starch, decreasing the crystallinity. In addition, the low pH limits the pullulanase activity.

[0039] Comparative Example 4 The only difference from Example 1 was that the plasma-activated water of pH 5 was mixed with the starch milk with a solid content of 15% instead of the plasma-activated water of pH 6 was mixed with the starch milk with a solid content of 15%. The remaining steps and parameters were the same as those of Example 1. The resistant starch had a crystal form of A+B+VII, a degree of crystallinity of 36.3%, and a resistant starch content of 57.8% as measured by the Englyst method. After placing the starch in a boiling water bath for 10 minutes, the resistant starch content as measured by the Englyst method decreased by 8.4%. The fatty acid content of the product was measured to be 4.48 g / 100 g. Compared with the resistant starch prepared in Example 1, the content and crystallinity of resistant starch are significantly decreased, and the difference in fatty acid content is large. This is because the effect of plasma-activated water with a relatively high pH value on the amorphous region of starch is limited, and the viscosity of high amylose corn starch milk cannot be effectively reduced, which is unfavorable to the complexation of fatty acid.

[0040] Comparative Example 5 The only difference from Example 1 is that "the ultrasonically treated product is rapidly cooled to 4°C at an average cooling rate of 8°C / min, crystallized at that temperature for 45 min, and then heated to 50°C for toughening for 108 h" is changed to "the ultrasonically treated product is naturally cooled to 20°C at room temperature, and then heated to 45°C for toughening for 72 h". The other steps and parameters were the same as those of Example 1. The resistant starch content was determined to be 56.2% by Englyst method. XRD testing of the product (Figure 2) showed the formation of B+VI crystalline form with a crystallinity of 32.7%. After placing the starch in a boiling water bath for 10 minutes, the resistant starch content was determined to be 8.9% by Englyst method. The fatty acid content of the product was determined to be 4.31 g / 100 g. Compared with the resistant starch prepared in Example 1, only B+VI crystalline form was formed. The difference in resistant starch content, crystallinity and fatty acid content was large. This is because the crystal nuclei formed by natural cooling are few, which is disadvantageous for V-type crystalline starch to form higher crystallinity and larger crystallite size. Moreover, the toughening time is insufficient, and the helical order and crystal perfection of starch cannot be effectively improved.

[0041] As described above, the raw material of the present invention is a high amylose corn starch with special utility value. The resistant starch produced by the present invention has a better texture than simple RS2 high amylose corn starch, and has an increased resistant starch content, improved crystallinity, and excellent heat resistance. The present invention complexes fatty acids with starch, has a protective effect against unsaturated fatty acids, and imparts the function and effect of unsaturated fatty acids to resistant starch. This resistant starch not only has unique food processing properties such as good rheological properties and stability, improved mouthfeel, and reduced food expansion, but also has excellent physiological functions such as preventing diabetes, improving intestinal health, and protecting the intestinal barrier, and has high industrial utility value and is expected to have a promising future market development.

[0042] The present invention has been disclosed above by way of preferred embodiments, but these embodiments do not limit the present invention, and a person skilled in the art can make any changes or modifications without departing from the spirit and scope of the present invention, and therefore the scope of the rights of the present invention is defined by the claims.

Claims

1. A method for producing polycrystalline resistant starch, comprising: A method for producing a polycrystalline resistant starch, comprising: producing starch milk using plasma activated water having a pH of 4-5 and high amylose cornstarch; then declustering the starch using pullulanase; strengthening the complexation of the starch with fatty acids by ultrasonic treatment; crystallizing the starch by cooling at an average cooling rate of 5-10°C / min; and converting the B+VI type crystals to A+B+VII type crystals by a toughening treatment that controls the crystallization characteristics to obtain a polycrystalline resistant starch.

2. (1) adding high amylose cornstarch to plasma activated water having a pH of 4-5 to prepare starch milk; Step (2) of gelatinizing the starch milk obtained in step (1), adding pullulanase to decluster it, and subjecting it to an enzymatic hydrolysis treatment; Step (3) of adding fatty acid to the starch milk enzymatically decomposed in step (2) and subjecting it to ultrasonic treatment to obtain a fatty acid complex product; and (4) cooling the fatty acid complexed product obtained in step (3) to crystallize, toughen, dehydrate, wash and dry to obtain polycrystalline resistant starch.

3. The method according to claim 2, wherein in step (1), the solid content of the high amylose corn starch in the starch milk is 15% by mass to 18% by mass.

4. The method according to claim 2, wherein in step (2), the declustering enzymatic degradation is carried out at a temperature of 55-65° C. for a time of 12-24 h, and the amount of pullulanase added is 40-50 ASPU / g dry starch.

5. The method according to claim 2, wherein in step (3), the fatty acid is added to the enzymatically hydrolyzed starch milk at 70 to 90°C, and the amount of the fatty acid added is 6% to 10% of the dry mass of the starch.

6. The method according to claim 5 , wherein the fatty acid is any one of oleic acid, linoleic acid, and linolenic acid.

7. 3. The method according to claim 2, wherein in step (3), the ultrasonic frequency is 25-35 kHz, the ultrasonic output is 300-400 W, and the ultrasonic treatment time is 30-60 min.

8. The method according to claim 2, wherein in step (4), in the cooling crystallization, the product is rapidly cooled to 3-5°C at an average cooling rate of 5-10°C / min, and crystallized at a temperature of 3-5°C for 30-60 min.

9. The method according to claim 2, wherein in step (4), the toughening is performed at 45 to 55° C. for 96 to 120 h.

10. Use of polycrystalline resistant starch in the method according to any one of claims 1 to 9 in the manufacture of functional foods.

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