High-purity resistant dextrin and preparation method thereof

Abstract

The invention relates to high-purity resistant dextrin and a preparation method thereof, and belongs to the technical field of starch processing.According to the technical scheme, a resistant dextrin semi-finished product with the high dietary fiber content is obtained through the synergistic effect of steam explosion assisted acidolysis, high-temperature treatment, ultrahigh-pressure treatment and enzymolysis treatment; and obtaining the high-purity resistant dextrin through a series of refining processes. Through the synergistic effect of steam explosion and ultrahigh pressure treatment, the solubility of pyrodextrin is remarkably improved, and meanwhile, the molecular weight of starch is reduced through steam explosion assisted acidolysis and high-temperature treatment; therefore, the resistant dextrin with high dietary fiber content can be obtained by using a small amount of alpha-amylase and trans-glycosidase and performing enzymolysis for a short time. The use amount of alpha-amylase and transglycosidase is small, so that the pollution of zymoprotein to a filter membrane or resin is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of starch processing, and specifically relates to high-purity resistant dextrin and a preparation method thereof. Background Art

[0002] As a water-soluble dietary fiber, resistant dextrin has physical properties such as high solubility, strong heat resistance and strong excipient performance, making it the preferred dietary fiber. With the expansion of the application field of deep-processed resistant dextrin products, the task of researching and developing resistant dextrin with excellent quality and high content has become of great significance.

[0003] At present, the common preparation method of resistant dextrin is to first generate pyrodextrin by acid-heat method, then perform 2 to 3 long-term enzymolysis, and finally refine to obtain resistant dextrin. This process has the disadvantages of time-consuming, energy-consuming and low efficiency. In addition, after enzymolysis, residual enzyme protein in the product will increase the pollution of ultrafiltration membrane, nanofiltration membrane or ion exchange resin used in the subsequent refining process, seriously affecting the service life of the filter membrane or resin, and increasing the difficulty of subsequent refining and purification. Therefore, it is necessary to provide a method for preparing high-purity resistant dextrin that can solve the above problems. Summary of the invention

[0004] The object of the present invention is to provide a high-purity resistant dextrin and a preparation method thereof, wherein a resistant dextrin semi-finished product with a high dietary fiber content is obtained through the synergistic effect of steam explosion-assisted acid hydrolysis, high temperature treatment, ultra-high pressure treatment and enzymatic hydrolysis, and then a series of refining processes are used to obtain high-purity resistant dextrin.

[0005] The technical problem to be solved by the present invention is that the commonly used preparation method of resistant dextrin is to first generate pyrodextrin by an acid-heat method, then perform 2 to 3 long-term enzymatic hydrolysis, and finally obtain resistant dextrin by refining. This process has the disadvantages of being time-consuming, energy-consuming and inefficient. In addition, after enzymatic hydrolysis, residual enzyme protein in the product will aggravate the pollution of ultrafiltration membranes, nanofiltration membranes or ion exchange resins used in the subsequent refining process, seriously affecting the service life of the filter membrane or resin, and increasing the difficulty of subsequent refining and purification.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing high-purity resistant dextrin comprises the following steps:

[0008] A1. Mix starch and acid evenly and add them into the steam explosion cylinder. Close the cover and introduce high-temperature saturated steam to make the pressure in the cylinder reach the set pressure and maintain it for a certain time. Open the pneumatic valve to release the pressure instantly to obtain the material.

[0009] During the above operation, steam explosion is performed while acid hydrolysis is in progress, which can accelerate the acid hydrolysis reaction and produce more small-molecule starch.

[0010] Furthermore, in step A1, the starch is at least one of corn starch, wheat starch, tapioca starch, potato starch, and rice starch.

[0011] Furthermore, in step A1, the moisture content of starch is 12-20%.

[0012] Furthermore, in step A1, the acid is citric acid or phosphoric acid.

[0013] Furthermore, in step A1, the amount of acid added is 1-4% of the mass of starch.

[0014] Furthermore, in step A1, the pressure is set to 0.7-1.8 MPa and the holding time is 20-60 s.

[0015] A2, drying the material, and then subjecting it to high temperature treatment to obtain pyrodextrin;

[0016] Furthermore, in step A2, the temperature of the high temperature treatment is 155-165° C., and the time is 50-90 min.

[0017] A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin;

[0018] During the above operation, the pyrodextrin is subjected to ultrahigh pressure treatment, which further depolymerizes the pyrodextrin and increases its solubility, making it easier for α-amylase to hydrolyze the pyrodextrin and improving the efficiency of hydrolysis. The present invention performs steam explosion while acid hydrolyzing, so that a pore structure is generated inside the starch and the solubility is improved. Therefore, steam explosion and ultrahigh pressure treatment have a synergistic effect, which can jointly improve the solubility of pyrodextrin and facilitate the enzyme preparation to play a role.

[0019] Furthermore, in step A3, the ultrahigh pressure treatment conditions are: pressure of 260-350 MPa, and treatment time of 5-9 min.

[0020] A4, adding deionized water to the ultrahigh pressure treated pyrodextrin to prepare an emulsion, first adding α-amylase to the emulsion for a primary enzymolysis reaction, then adding transaminase for a secondary enzymolysis reaction, and after the reaction, killing the enzyme to obtain a resistant dextrin semi-finished product;

[0021] During the above operation, due to the synergistic effect of steam explosion and ultra-high pressure treatment, the solubility of pyrodextrin is significantly improved, and the molecular weight of the obtained pyrodextrin is reduced after steam explosion-assisted acid hydrolysis and high temperature treatment, so that resistant dextrin with high dietary fiber content can be obtained with less α-amylase and transaminase in a shorter enzymatic hydrolysis time. The small amount of α-amylase and transaminase used reduces the contamination of enzyme proteins on the filter membrane or resin.

[0022] Furthermore, in step A4, the amount of α-amylase added is 0.13-0.2% of the mass of the emulsion.

[0023] Furthermore, in step A4, the amount of transglycosidase added is 0.1-0.16% of the mass of the emulsion.

[0024] Further, in step A4, the temperature of the enzymatic hydrolysis reaction is 60-65°C and the time is 10-20 min;

[0025] During an enzymatic hydrolysis process, the enzymatic hydrolysis time and the amount of α-amylase used are crucial to the final yield of resistant dextrin. When the enzymatic hydrolysis time is too long or the amount of α-amylase used is too much, a large amount of glucose or maltose will be produced, thereby reducing the yield of resistant dextrin.

[0026] Furthermore, in step A4, the temperature of the secondary enzymatic hydrolysis reaction is 52-60° C. and the time is 7-12 h.

[0027] Furthermore, in step A4, the volume ratio of the ultrahigh pressure treated pyrodextrin to deionized water is 1:(2.5-3.5).

[0028] A5. Refining the resistant dextrin semi-finished product and finally drying it to obtain high-purity resistant dextrin.

[0029] Furthermore, in step A5, the specific refining steps are: the resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane, then nanofiltered through a nanofiltration membrane, and then decolorized using multiple parallel coal-based granular carbon columns, and then decolorized using a macroporous resin and desalted using an ion exchange resin.

[0030] In the above refining process, ultrafiltration is first performed through an ultrafiltration membrane to remove large molecular impurities such as enzyme proteins, and then the filtrate is subjected to nanofiltration to remove small molecular glucose and maltose. Then, multiple parallel coal-based granular carbon columns and macroporous resins are used for decolorization and ion exchange resin desalination to obtain high-purity resistant dextrin.

[0031] Furthermore, the molecular weight cut-off of the ultrafiltration membrane is 4000-5000Da.

[0032] Furthermore, the molecular weight cut-off of the nanofiltration membrane is 200-400Da.

[0033] Furthermore, when coal-based granular carbon columns are used for decolorization, the material flow rate is 600-1000 mL / h, the decolorization temperature is 60-70°C, and the carbon columns are 5-6 parallel carbon columns.

[0034] Furthermore, when macroporous resin is used for decolorization, the decolorization temperature is 30-50° C. and the flow rate is 1-4 BV / h.

[0035] Furthermore, when ion exchange resin is used for desalination, the decolorization temperature is 30-50° C. and the flow rate is 1-4 BV / h.

[0036] The present invention also provides high-purity resistant dextrin prepared by the method.

[0037] Beneficial effects of the present invention:

[0038] (1) In the technical scheme of the present invention, the present invention obtains a resistant dextrin semi-finished product with a high dietary fiber content through the synergistic effect of steam explosion-assisted acid hydrolysis, high temperature treatment, ultra-high pressure treatment and enzymatic hydrolysis, and then obtains high-purity resistant dextrin through a series of refining processes.

[0039] (2) In the technical solution of the present invention, pyrodextrin is subjected to ultrahigh pressure treatment, which further depolymerizes pyrodextrin and increases its solubility, making it easier for α-amylase to hydrolyze pyrodextrin and improving the efficiency of hydrolysis. The present invention performs steam explosion while acid hydrolysis, so that a pore structure is generated inside the starch and its solubility is improved. Therefore, steam explosion and ultrahigh pressure treatment have a synergistic effect, which can jointly improve the solubility of pyrodextrin and facilitate the enzyme preparation to play a role.

[0040] (3) In the technical solution of the present invention, due to the synergistic effect of steam explosion and ultra-high pressure treatment, the solubility of pyrodextrin is significantly improved. At the same time, steam explosion-assisted acid hydrolysis and high temperature treatment reduce the molecular weight of the obtained pyrodextrin, so that α-amylase and transaminase can obtain resistant dextrin with high dietary fiber content at a lower dosage and shorter enzymatic hydrolysis time. The small dosage of α-amylase and transaminase reduces the contamination of enzyme proteins on the filter membrane or resin. DETAILED DESCRIPTION

[0041] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In the following examples: the enzymatic activity of α-amylase is 5000 U / g; the enzymatic activity of transaminase is 10000 U / g.

[0043] Example 1

[0044] A method for preparing high-purity resistant dextrin comprises the following steps:

[0045] A1. Mix corn starch (water content is 12%) and citric acid (the amount of citric acid added is 1% of the mass of starch) and add them into the steam explosion cylinder. Close the cover and introduce high-temperature saturated steam to make the pressure in the cylinder reach the set pressure of 0.7MPa and maintain it for 20s. After the pressure is reached, open the pneumatic valve to release the pressure instantly to obtain the material.

[0046] A2, drying the material, and then high temperature treating at 155°C for 50 min to obtain pyrodextrin;

[0047] A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin, wherein the ultra-high pressure treatment conditions are: pressure of 260 MPa, and treatment time of 5 min;

[0048] A4, deionized water was added to the ultra-high pressure treated pyrodextrin to prepare an emulsion (the volume ratio of the high pressure treated pyrodextrin to deionized water was 1:2.5), α-amylase was first added to the emulsion (the amount of α-amylase added was 0.13% of the mass of the emulsion), and a primary enzymatic reaction was carried out at 60° C. for 10 min, and then transaminase was added (the amount of transaminase added was 0.1% of the mass of the emulsion), and a secondary enzymatic reaction was carried out at 52° C. for 7 h. After the reaction, the enzyme was inactivated to obtain a resistant dextrin semi-finished product;

[0049] A5. The resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 4000Da, and then nanofiltered through a nanofiltration membrane with a molecular weight cutoff of 200Da, and then decolorized using 5 parallel coal-based granular carbon columns (the material flow rate is 600mL / h, and the decolorization temperature is 60°C), followed by macroporous resin decolorization (using AB-8 macroporous resin, the decolorization temperature is 30°C, and the flow rate is 1BV / h), ion exchange resin desalination (using D280 resin, the decolorization temperature is 30°C, and the flow rate is 1BV / h), and finally spray drying to obtain high-purity resistant dextrin.

[0050] Example 2

[0051] A method for preparing high-purity resistant dextrin comprises the following steps:

[0052] A1. Mix corn starch (water content is 15%) and citric acid (the amount of citric acid added is 2% of the mass of starch) and add them into the steam explosion cylinder. Close the cover and pass high-temperature saturated steam to make the pressure in the cylinder reach the set pressure of 1MPa and maintain it for 30s. After the pressure is reached, open the pneumatic valve to release the pressure instantly to obtain the material.

[0053] A2, drying the material, and then high temperature treating at 160°C for 60 min to obtain pyrodextrin;

[0054] A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin, wherein the ultra-high pressure treatment conditions are: pressure of 300 MPa, and treatment time of 7 min;

[0055] A4, deionized water was added to the ultra-high pressure treated pyrodextrin to prepare an emulsion (the volume ratio of the high pressure treated pyrodextrin and deionized water was 1:3), α-amylase was first added to the emulsion (the amount of α-amylase added was 0.16% of the mass of the emulsion), and a primary enzymatic reaction was carried out at 60° C. for 14 min, and then transaminase was added (the amount of transaminase added was 0.12% of the mass of the emulsion), and a secondary enzymatic reaction was carried out at 55° C. for 9 h. After the reaction, the enzyme was inactivated to obtain a resistant dextrin semi-finished product;

[0056] A5. The resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 4000Da, and then nanofiltered through a nanofiltration membrane with a molecular weight cutoff of 200Da, and then decolorized using 5 parallel coal-based granular carbon columns (the material flow rate is 700mL / h, and the decolorization temperature is 60°C), followed by macroporous resin decolorization (using AB-8 macroporous resin, the decolorization temperature is 40°C, and the flow rate is 2BV / h), ion exchange resin desalination (using D280 resin, the decolorization temperature is 30°C, and the flow rate is 2BV / h), and finally spray drying to obtain high-purity resistant dextrin.

[0057] Example 3

[0058] A method for preparing high-purity resistant dextrin comprises the following steps:

[0059] A1. Mix corn starch (water content is 16%) and citric acid (the amount of citric acid added is 2.6% of the mass of starch) and add them into the steam explosion cylinder. Close the cover and introduce high-temperature saturated steam to make the pressure in the cylinder reach the set pressure of 1.4MPa and maintain it for 40s. After the pressure is reached, open the pneumatic valve to release the pressure instantly to obtain the material.

[0060] A2, drying the material, and then high temperature treating at 160°C for 75 minutes to obtain pyrodextrin;

[0061] A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin, wherein the ultra-high pressure treatment conditions are: pressure of 310 MPa, and treatment time of 7 min;

[0062] A4, deionized water was added to the ultra-high pressure treated pyrodextrin to prepare an emulsion (the volume ratio of the high pressure treated pyrodextrin to deionized water was 1:3), α-amylase was first added to the emulsion (the amount of α-amylase added was 0.17% of the mass of the emulsion), and a primary enzymatic reaction was carried out at 60° C. for 17 min, and then transaminase was added (the amount of transaminase added was 0.14% of the mass of the emulsion), and a secondary enzymatic reaction was carried out at 60° C. for 10 h. After the reaction, the enzyme was inactivated to obtain a resistant dextrin semi-finished product;

[0063] A5. The resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 4000Da, and then nanofiltered through a nanofiltration membrane with a molecular weight cutoff of 300Da, and then decolorized using 6 parallel coal-based granular carbon columns (the material flow rate is 800mL / h, and the decolorization temperature is 65°C), followed by macroporous resin decolorization (using AB-8 macroporous resin, the decolorization temperature is 40°C, and the flow rate is 2.5BV / h), ion exchange resin desalination (using D280 resin, the decolorization temperature is 40°C, and the flow rate is 2.5BV / h), and finally spray drying to obtain high-purity resistant dextrin.

[0064] Example 4

[0065] A method for preparing high-purity resistant dextrin comprises the following steps:

[0066] A1. Mix corn starch (water content is 18%) and citric acid (the amount of citric acid added is 3% of the mass of starch) and add them into the steam explosion cylinder. Close the cover and introduce high-temperature saturated steam to make the pressure in the cylinder reach the set pressure of 1.5MPa and maintain it for 50s. After the pressure is reached, open the pneumatic valve to release the pressure instantly to obtain the material.

[0067] A2, drying the material, and then high temperature treating at 65°C for 70 minutes to obtain pyrodextrin;

[0068] A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin, wherein the ultra-high pressure treatment conditions are: pressure of 340 MPa, and treatment time of 6 min;

[0069] A4, deionized water was added to the ultra-high pressure treated pyrodextrin to prepare an emulsion (the volume ratio of the high pressure treated pyrodextrin to deionized water was 1:3.2), α-amylase was first added to the emulsion (the amount of α-amylase added was 0.18% of the mass of the emulsion), and a primary enzymatic reaction was carried out at -65°C for 13 minutes, and then transaminase was added (the amount of transaminase added was 0.16% of the mass of the emulsion), and a secondary enzymatic reaction was carried out at 60°C for 8 hours. After the reaction, the enzyme was inactivated to obtain a resistant dextrin semi-finished product;

[0070] A5. The resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 5000Da, and then nanofiltered through a nanofiltration membrane with a molecular weight cutoff of 200Da, and then decolorized using 6 parallel coal-based granular carbon columns (the material flow rate is 900mL / h, and the decolorization temperature is 70°C), followed by macroporous resin decolorization (using AB-8 macroporous resin, the decolorization temperature is 50°C, and the flow rate is 3BV / h), ion exchange resin desalination (using D280 resin, the decolorization temperature is 50°C, and the flow rate is 3BV / h), and finally spray drying to obtain high-purity resistant dextrin.

[0071] Example 5

[0072] A method for preparing high-purity resistant dextrin comprises the following steps:

[0073] A1. Mix corn starch (water content is 20%) and phosphoric acid (the amount of phosphoric acid added is 4% of the mass of starch) and add them into the steam explosion cylinder. Close the cover and introduce high-temperature saturated steam to make the pressure in the cylinder reach the set pressure of 1.8MPa and maintain it for 60s. After the pressure is reached, open the pneumatic valve to release the pressure instantly to obtain the material.

[0074] A2, drying the material, and then high temperature treating at 165°C for 90 minutes to obtain pyrodextrin;

[0075] A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin, wherein the ultra-high pressure treatment conditions are: pressure of 350 MPa, and treatment time of 9 min;

[0076] A4, deionized water was added to the ultra-high pressure treated pyrodextrin to prepare an emulsion (the volume ratio of the high pressure treated pyrodextrin to deionized water was 1:3.5), α-amylase was first added to the emulsion (the amount of α-amylase added was 0.13% of the mass of the emulsion), and a primary enzymatic reaction was carried out at 65° C. for 20 min, and then transaminase was added (the amount of transaminase added was 0.16% of the mass of the emulsion), and a secondary enzymatic reaction was carried out at 60° C. for 12 h. After the reaction, the enzyme was inactivated to obtain a resistant dextrin semi-finished product;

[0077] A5. The resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 5000Da, and then nanofiltered through a nanofiltration membrane with a molecular weight cutoff of 400Da, and then decolorized using 6 parallel coal-based granular carbon columns (the material flow rate is 1000mL / h, and the decolorization temperature is 70°C), followed by macroporous resin decolorization (using AB-8 macroporous resin, the decolorization temperature is 50°C, and the flow rate is 4BV / h), ion exchange resin desalination (using D280 resin, the decolorization temperature is 50°C, and the flow rate is 4BV / h), and finally spray drying to obtain high-purity resistant dextrin.

[0078] Comparative Example 1

[0079] A method for preparing high-purity resistant dextrin comprises the following steps:

[0080] A1. Mix corn starch (water content 15%) and 2% citric acid aqueous solution (the amount of citric acid added is 2% of the mass of starch) evenly, soak for 2 hours and then filter to obtain a material;

[0081] A2, drying the material, and then high temperature treating at 160°C for 60 min to obtain pyrodextrin;

[0082] A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin, wherein the ultra-high pressure treatment conditions are: pressure of 300 MPa, and treatment time of 7 min;

[0083] A4, deionized water was added to the ultra-high pressure treated pyrodextrin to prepare an emulsion (the volume ratio of the high pressure treated pyrodextrin and deionized water was 1:3), α-amylase was first added to the emulsion (the amount of α-amylase added was 0.16% of the mass of the emulsion), and a primary enzymatic reaction was carried out at 60° C. for 14 min, and then transaminase was added (the amount of transaminase added was 0.12% of the mass of the emulsion), and a secondary enzymatic reaction was carried out at 55° C. for 9 h. After the reaction, the enzyme was inactivated to obtain a resistant dextrin semi-finished product;

[0084] A5. The resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane with a molecular weight cutoff of 4000Da, and then nanofiltered through a nanofiltration membrane with a molecular weight cutoff of 200Da, and then decolorized using 5 parallel coal-based granular carbon columns (the material flow rate is 700mL / h, and the decolorization temperature is 60°C), followed by macroporous resin decolorization (using AB-8 macroporous resin, the decolorization temperature is 40°C, and the flow rate is 2BV / h), ion exchange resin desalination (using D280 resin, the decolorization temperature is 30°C, and the flow rate is 2BV / h), and finally spray drying to obtain high-purity resistant dextrin.

[0085] Compared with Example 2, Comparative Example 1 did not perform steam explosion during the acidolysis process.

[0086] Comparative Example 2

[0087] Compared with Example 2, step A3 treatment is not performed in Comparative Example 2, that is, ultrahigh pressure treatment is not performed, and other steps and raw materials are the same as those in Example 2.

[0088] Comparative Example 3

[0089] Compared with Example 2, in Comparative Example 3, the enzymatic hydrolysis reaction was performed for 30 minutes, and the other steps and raw materials were the same as those in Example 2.

[0090] Comparative Example 4

[0091] Compared with Example 2, the amount of α-amylase added in Comparative Example 4 is 0.3% of the mass of the emulsion, and the other steps and raw materials are the same as those in Example 2.

[0092] Performance Testing

[0093] The resistant dextrin semi-finished products and high-purity resistant dextrin finished products prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to performance tests:

[0094] (1) Resistant dextrin content: measured according to GB / T 22224-2008;

[0095] (2) Transmittance: Prepare the resistant dextrin semi-finished product or high-purity resistant dextrin finished product with freshly boiled and cooled neutral distilled water into a test solution with a dry matter content of 30%. Pour the test solution into a 1 cm cuvette and measure the transmittance of the test solution using a spectrophotometer at a wavelength of 440 nm with distilled water as a reference.

[0096] (3) Solubility of pyrodextrin: Weigh 1 g of each of the ultrahigh pressure treated pyrodextrins obtained in Examples 1 to 5 and Comparative Examples 1, 3, and 4, and the high temperature treated pyrodextrin obtained in Comparative Example 2, and dissolve them in 10 mL of distilled water. Then centrifuge at 6800 g for 5 min, separate the supernatant, dry the supernatant in a drying oven at 40° C. for 24 h, then heat at 130° C. for 1.5 h, weigh (A), and calculate the solubility; solubility=[A / (B×(1-C))]×100%, where B is the mass of pyrodextrin; and C is the water content of pyrodextrin.

[0097] Table 1

[0098]

[0099]

[0100] It can be seen from the data in Table 1 that the resistant dextrin semi-finished product prepared by the present invention has a high dietary fiber content, and after being treated by a refining process, the purity of the resistant dextrin finished product is improved. It can be seen from the data of Comparative Example 2 and Comparative Example 1 that since steam explosion was not performed during the acid hydrolysis process, only conventional acid hydrolysis was performed, resulting in a significant decrease in the dietary fiber content of the resistant dextrin semi-finished product, and also resulting in a decrease in the solubility of pyrodextrin. It can be seen from the data of Comparative Example 2 and Comparative Example 2 that since no ultra-high pressure treatment was performed, the solubility of pyrodextrin decreased, resulting in a significant decrease in the dietary fiber content of the resistant dextrin semi-finished product. It can be seen from the data of Comparative Example 2 and Comparative Examples 3 and 4 that if the amount of α-amylase added is too high or the enzymolysis time is longer, the dietary fiber content of the resistant dextrin semi-finished product will decrease.

[0101] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0102] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing high-purity resistant dextrin, characterized in that: The following steps are involved: A1. Mix starch and acid evenly and add them into the steam explosion cylinder. Close the cover and introduce high-temperature saturated steam to make the pressure in the cylinder reach the set pressure and maintain it for a certain time. Open the pneumatic valve to release the pressure instantly to obtain the material. A2, drying the material, and then subjecting it to high temperature treatment to obtain pyrodextrin; A3, subjecting the pyrodextrin to ultra-high pressure treatment to obtain ultra-high pressure treated pyrodextrin; A4, adding deionized water to the ultrahigh pressure treated pyrodextrin to prepare an emulsion, first adding α-amylase to the emulsion for a primary enzymolysis reaction, then adding transaminase for a secondary enzymolysis reaction, and after the reaction, killing the enzyme to obtain a resistant dextrin semi-finished product; A5. Refining the resistant dextrin semi-finished product and finally drying it to obtain high-purity resistant dextrin.

2. The method for preparing a high-purity resistant dextrin according to claim 1, characterized in that: In the step A1, the moisture content of the starch is 12-20%.

3. The method for preparing a high-purity resistant dextrin according to claim 1, characterized in that: In the step A1, the pressure is set to 0.7-1.8 MPa and the holding time is 20-60 s.

4. The method for preparing a high-purity resistant dextrin according to claim 1, characterized in that: In the step A2, the high temperature treatment is performed at a temperature of 155-165° C. and a time of 50-90 min.

5. The method for preparing a high-purity resistant dextrin according to claim 1, characterized in that: In step A3, the ultrahigh pressure treatment conditions are: pressure of 260-350 MPa, and treatment time of 5-9 min.

6. The method for preparing high-purity resistant dextrin according to claim 1, characterized in that: In the step A4, the amount of α-amylase added is 0.13-0.2% of the mass of the emulsion, the temperature of one enzymatic hydrolysis reaction is 60-65° C., and the time is 10-20 min.

7. The method for preparing high-purity resistant dextrin according to claim 1, characterized in that: In the step A4, the amount of transaminase added is 0.1-0.16% of the mass of the emulsion, the temperature of the secondary enzymatic hydrolysis reaction is 52-60° C., and the time is 7-12 hours.

8. The method for preparing high-purity resistant dextrin according to claim 1, characterized in that: In step A5, the specific refining steps are: the resistant dextrin semi-finished product is first ultrafiltered through an ultrafiltration membrane, then nanofiltered through a nanofiltration membrane, and then decolorized using multiple parallel coal-based granular carbon columns, and then decolorized using a macroporous resin and desalted using an ion exchange resin.

9. The method for preparing high-purity resistant dextrin according to claim 8, characterized in that: The molecular weight cutoff of the ultrafiltration membrane is 4000-5000Da, the molecular weight cutoff of the nanofiltration membrane is 200-400Da, and when the coal-based particle carbon column is used for decolorization, the material flow rate is 600-1000mL / h, the decolorization temperature is 60-70°C, and the carbon column is 5-6 parallel carbon columns.

10. A high-purity resistant dextrin prepared by the preparation method according to any one of claims 1 to 9.

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