A resistant dextrin and its preparation method

Abstract

The present invention belongs to the technical field of deep processing of starch, and particularly relates to a resistant dextrin and a preparation method thereof. The present invention adjusts the pH value of the starch milk to 4.6 - 5.1, which not only denatures the starch to facilitate subsequent dextrinization, but also removes protein impurities in the starch, reducing the subsequent refining burden. The present invention controls the temperature of the first dextrinization to be 120 - 130 °C, avoiding the problem of dark color of the crude resistant dextrin caused by high temperature. At the same time, the pressure of the first dextrinization is controlled to be -0.05 - -0.07 MPa, so that after the first dextrinization, the proportion of resistant dextrin with a degree of polymerization <6 is about 80 wt%. Then, the second dextrinization is carried out to ensure that there are sufficient small molecule sugars in the system during the second dextrinization, facilitating the generation of a highly uniform resistant dextrin under mild conditions, and the content of resistant dextrin with a degree of polymerization of 7 - 13 in the dietary fiber of the crude resistant dextrin is 81 wt%.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep processing of starch, and particularly relates to a resistant dextrin and a preparation method thereof. Background Art

[0002] Resistant dextrin is a water-soluble dietary fiber with a low molecular weight. It is not utilized by bacteria until it reaches the colon after being ingested by the human body, and it produces short-chain fatty acids beneficial to the human body. It has a positive effect on reducing blood sugar, blood lipids, etc. It has a uniform appearance and a mild taste, and has broad application potential in the food industry.

[0003] The prior art discloses a resistant dextrin with an average degree of polymerization of 6-12 and a preparation method thereof. An acid solution is added to starch and reacted at 80-120°C and normal pressure for 2-4 h; then the acid is added and the temperature is further raised to 150-200°C for gelatinization reaction for 15-30 min; then deionized water is added and acid hydrolysis is carried out at 80-100°C for 1-2 h. Due to the high gelatinization reaction temperature in the above preparation method, the color of the crude resistant dextrin is deep. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a resistant dextrin and a preparation method thereof. The crude resistant dextrin obtained by the preparation method of the present invention has a light chromaticity, does not require complex refining treatment subsequently, has low energy consumption, and still obtains a resistant dextrin with a uniform degree of polymerization.

[0005] The present invention provides a preparation method of a resistant dextrin, comprising the following steps:

[0006] Adjust the pH value of the starch milk to 4.6-5.1, and obtain modified starch milk through filtration;

[0007] Perform first dextrinization on the modified starch milk to obtain a first dextrinization system. The pH of the first dextrinization is 3.0-3.5, the temperature is 120-130°C, the pressure is -0.05--0.07 MPa, and the time is 40-50 min;

[0008] Perform second dextrinization on the first dextrinization system to obtain a crude resistant dextrin. The pH of the second dextrinization is 2.0-2.5, the temperature is 110-120°C, the pressure is -0.08--0.09 MPa, and the time is 30-40 min; during the second dextrinization process, the DE value of the system is monitored in real time. When the DE value is 5-6, a fructose chromatographic raffinate is added to make the DE value 10-12;

[0009] Refine the crude resistant dextrin to obtain the resistant dextrin.

[0010] Preferably, the Baume degree of the starch milk is 20-25 Bé, and the pH is 6.0-7.0.

[0011] Preferably, the reagent for adjusting the pH value of the starch milk to 4.6-5.1 is an organic acid or an inorganic acid. The organic acid includes one or more of citric acid, malic acid, tartaric acid, and lactic acid, and the inorganic acid includes phosphoric acid.

[0012] Preferably, the glucose content in the raffinate of fructose chromatography is 8-12 wt%.

[0013] Preferably, the refining includes decolorization, desalting, and chromatographic purification in sequence to obtain the resistant dextrin.

[0014] Preferably, the decolorization is carried out with activated carbon. The mass of the activated carbon used for the activated carbon decolorization is 1-2% of the dry basis mass of the crude resistant dextrin. The temperature of the decolorization is 55-60 °C, the time is 15-20 min, and the number of decolorization times is 1 time. After the decolorization, filtration is also included to obtain the decolorized liquid.

[0015] Preferably, the desalting is carried out with ion exchange resin. The ion exchange resin used for the ion exchange resin desalting includes strong acid cation exchange resin D001 and weak base anion exchange resin D301P. The temperature of the decolorized liquid is 35-40 °C, the flow rate of the decolorized liquid is 1-3 BV / h, and the number of desalting times is 1 time. After the desalting, it also includes: concentrating the obtained desalted liquid to obtain a concentrated desalted liquid for subsequent chromatographic purification.

[0016] Preferably, the chromatographic purification is carried out with potassium-type chromatographic resin. The parameters of the potassium-type chromatographic resin purification include: temperature is 60-70 °C, liquid-to-solid ratio is 1:1.3-1.5, feed rate is 1.2-1.5 m 3 / h, operating pressure is 0.2-0.3 MPa, and the number of chromatographic purification times is 1 time.

[0017] Preferably, after the chromatographic purification, it also includes: concentrating the obtained chromatographically purified liquid to a solid content of 55-65 wt%, and drying to obtain the resistant dextrin.

[0018] The present invention also provides a resistant dextrin obtained by the preparation method of the above technical solution. The dietary fiber content in the resistant dextrin is ≥90 wt%, the content of the resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber is 90-95 wt%, the light transmittance is ≥99%, and the chromaticity is <100 RBU.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for preparing resistant dextrin, comprising the following steps: adjusting the pH value of starch milk to 4.6 - 5.1, and filtering to obtain modified starch milk; subjecting the modified starch milk to primary dextrinization to obtain a primary dextrinization system, wherein the pH of the primary dextrinization is 3.0 - 3.5, the temperature is 120 - 130°C, the pressure is -0.05 - -0.07 MPa, and the time is 40 - 50 min; subjecting the primary dextrinization system to secondary dextrinization to obtain crude resistant dextrin, wherein the pH of the secondary dextrinization is 2.0 - 2.5, the temperature is 110 - 120°C, the pressure is -0.08 - -0.09 MPa, and the time is 30 - 40 min; monitoring the DE value of the system in real time during the secondary dextrinization process, and when the DE value is 5 - 6, adding the raffinate of fructose chromatography to make the DE value 10 - 12; refining the crude resistant dextrin to obtain the resistant dextrin.

[0021] The present invention first adjusts the pH value of starch milk to 4.6 - 5.1, which can not only denature starch, facilitating subsequent dextrinization, but also remove excess protein impurities in starch, reducing the subsequent refining burden and thus improving the product yield. The present invention controls the temperature of the primary dextrinization to 120 - 130°C, avoiding the problem of dark color of the crude resistant dextrin caused by high temperature. At the same time, by controlling the pH of the primary dextrinization to 3.0 - 3.5, the temperature to 120 - 130°C, and the pressure to -0.05 - -0.07 MPa, the DE value of the primary dextrinization process and the obtained primary dextrinization system is in the range of 8 - 10, providing sufficient small molecule monomers for the secondary dextrinization, ensuring that after the secondary dextrinization, a resistant dextrin with a uniform degree of polymerization is obtained. At the same time, the above parameter settings of the primary dextrinization result in the proportion of resistant dextrin with a degree of polymerization <6 in the obtained primary dextrinization system being about 80 wt%, combined with sufficient small molecule monomers, which is beneficial to obtaining a resistant dextrin with a uniform degree of polymerization. Then, the secondary dextrinization is carried out at a pH of 2.0 - 2.5, a temperature of 110 - 120°C, and a pressure of -0.08 - -0.09 MPa for 30 - 40 min. During the secondary dextrinization process, the DE value of the system is monitored in real time. When the DE value is 5 - 6, the raffinate of fructose chromatography is added to make the DE value 10 - 12. The addition of the raffinate of fructose chromatography ensures that there are sufficient small molecule monomers in the system during the secondary dextrinization process, facilitating the formation of a highly uniform resistant dextrin under mild conditions, such that the crude resistant dextrin has a dietary fiber content of 81 wt%, a chromaticity of 404 - 426 RBU, and a light transmittance of 85 - 86%. The content of resistant dextrin with a degree of polymerization of 7 - 13 in the dietary fiber is 80 - 81 wt%. In addition, by controlling the DE value of the system during the secondary dextrinization process with the raffinate of fructose chromatography, the added value of the raffinate of fructose chromatography is increased.

[0022] Further, the number of times of decolorization, desalting, and chromatographic purification is 1, which simplifies the refining process and reduces energy consumption; however, it still ensures that the final resistant dextrin has excellent uniform degree of polymerization, light transmittance, chromaticity, and low 5-hydroxymethylfurfural content. The data of the examples show that: the dietary fiber content in the resistant dextrin is ≥90 wt%, the content of resistant dextrin with a degree of polymerization of 7 to 13 in the dietary fiber is 93 to 95 wt%, the light transmittance is ≥99%, and the chromaticity is <100 RBU. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the preparation method of the resistant dextrin provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Figure 1 It is a flow chart of the preparation method of the resistant dextrin provided by the present invention. The preparation method of the present invention will be described in detail below in combination with Figure 1 Describe in detail the preparation method of the present invention.

[0025] The present invention provides a preparation method of resistant dextrin, comprising the following steps:

[0026] Adjust the pH value of the starch milk to 4.6 - 5.1, and obtain modified starch milk after filtration;

[0027] Perform the first dextrinization on the modified starch milk to obtain a first dextrinization system. The pH of the first dextrinization is 3.0 - 3.5, the temperature is 120 - 130 °C, the pressure is -0.05 - -0.07 MPa, and the time is 40 - 50 min;

[0028] Perform the second dextrinization on the first dextrinization system to obtain crude resistant dextrin. The pH of the second dextrinization is 2.0 - 2.5, the temperature is 110 - 120 °C, the pressure is -0.08 - -0.09 MPa, and the time is 30 - 40 min; During the second dextrinization process, monitor the DE value of the system in real time. When the DE value is 5 - 6, add the fructose chromatographic raffinate to make the DE value 10 - 12;

[0029] Refine the crude resistant dextrin to obtain the resistant dextrin.

[0030] Unless otherwise specified, the raw materials used in the present invention are preferably commercially available products.

[0031] The present invention adjusts the pH value of the starch milk to 4.6 - 5.1, and obtains modified starch milk after filtration.

[0032] In the present invention, the Baume degree of the starch milk is preferably 20 - 25 Bé, and the pH is preferably 6.0 - 7.0.

[0033] In the present invention, the method for preparing the starch milk preferably includes the following steps: mixing starch and water to obtain the starch milk.

[0034] In the present invention, the reagent for adjusting the pH value of the starch milk to 4.6 - 5.1 is preferably an organic acid or an inorganic acid, and more preferably an organic acid. In the present invention, the organic acid preferably includes one or more of citric acid, malic acid, tartaric acid, and lactic acid. In the present invention, the inorganic acid preferably includes phosphoric acid.

[0035] The present invention does not make specific limitations on the filtration, and the operations well-known to those skilled in the art can be adopted.

[0036] In the present invention, adjusting the pH value of the starch milk to 4.6 - 5.1 can not only denature the starch, which is beneficial to subsequent dextrinization; at the same time, it reaches the isoelectric point of the protein in the starch milk, and the protein can be removed after filtration, reducing the difficulty of subsequent product refining and the cost of refining. The present invention does not require an additional protein removal step, and the process is simple.

[0037] After obtaining the modified starch milk, the present invention subjects the modified starch milk to the first dextrinization to obtain a first dextrinization system. The pH of the first dextrinization is 3.0 - 3.5, the temperature is 120 - 130 °C, the pressure is -0.05 - -0.07 MPa, preferably -0.06 MPa, and the time is 40 - 50 min.

[0038] In the present invention, the pH of the first dextrinization is 3.0 - 3.5, specifically preferably 3.0, 3.1, 3.2, 3.3, 3.4, or 3.5; the temperature is 120 - 130 °C, specifically preferably 120 °C, 125 °C, or 130 °C; the pressure is -0.05 - -0.07 MPa, preferably -0.06 MPa; the time is 40 - 50 min, specifically preferably 40 min, 45 min, or 50 min. In the present invention, the pH of the first dextrinization is preferably adjusted by an organic acid or an inorganic acid, and the types of the organic acid or the inorganic acid are preferably the same as those in the above technical solution, which will not be elaborated here.

[0039] After the first dextrinization, the present invention preferably directly obtains the first dextrinization system without any post-treatment.

[0040] The present invention controls the pH of the first dextrinization to 3.0 - 3.5, the temperature to 120 - 130 °C, and the pressure to -0.05 - -0.07 MPa, so that the process of the first dextrinization and the DE value of the obtained first dextrinization system are in the range of 8 - 10, providing sufficient small molecule monomers for the second dextrinization, and further ensuring the polymerization degree to be unified; at the same time, the proportion of resistant dextrins with a polymerization degree < 6 in the first dextrinization system is about 80 wt%.

[0041] After obtaining the first dextrinization system, the present invention performs second dextrinization on the first dextrinization system to obtain a crude resistant dextrin. The pH of the second dextrinization is 2.0 - 2.5, the temperature is 110 - 120°C, the pressure is -0.08 - -0.09 MPa, and the time is 30 - 40 min. During the second dextrinization process, the DE value of the system is monitored in real time. When the DE value is 5 - 6, a fructose chromatographic raffinate is added to make the DE value 10 - 12.

[0042] In the present invention, the pH of the second dextrinization is 2.0 - 2.5, specifically preferably 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5; the temperature is 110 - 120°C, specifically preferably 110°C, 115°C or 120°C; the pressure is -0.08 - -0.09 MPa, specifically preferably -0.08 MPa or -0.09 MPa; the time is 30 - 40 min, specifically preferably 30 min, 35 min or 40 min. In the present invention, the pH of the second dextrinization is preferably adjusted by an organic acid or an inorganic acid, and the types of the organic acid or the inorganic acid are preferably the same as those in the above technical solution, which will not be elaborated here.

[0043] In the present invention, during the second dextrinization process, the DE value of the system is monitored in real time. When the DE value is 5 - 6, a fructose chromatographic raffinate is added to make the DE value 10 - 12. In the present invention, the fructose chromatographic raffinate refers to the remaining liquid after chromatographically extracting fructose; the fructose chromatographic raffinate contains glucose and fructose. In the present invention, the glucose content in the fructose chromatographic raffinate is preferably 8 - 12 wt%.

[0044] After the second dextrinization, the present invention preferably directly obtains the crude resistant dextrin without any post-treatment.

[0045] In the present invention, during the second dextrinization process, the DE value of the system is monitored in real time. When the DE value is 5 - 6, a fructose chromatographic raffinate is added to make the DE value 10 - 12. The addition of the fructose chromatographic raffinate ensures that there are sufficient small molecule sugars in the system during the second dextrinization, facilitating the formation of a highly homogeneous resistant dextrin under mild conditions. The crude resistant dextrin contains 81 wt% dietary fiber, the chromaticity is 404 - 426 RBU, and the light transmittance is 85 - 86%. The content of resistant dextrin with a degree of polymerization of 7 - 13 in the dietary fiber is 80 - 81 wt%.

[0046] After obtaining the crude resistant dextrin, the present invention refines the crude resistant dextrin to obtain the resistant dextrin.

[0047] In the present invention, the refining preferably includes performing decolorization, desalting and chromatographic purification in sequence to obtain the resistant dextrin.

[0048] In the present invention, the decolorization is preferably carried out with activated carbon, and the mass of the activated carbon used for the activated carbon decolorization is preferably 1-2% of the dry basis mass of the crude resistant dextrin, specifically preferably 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8% or 2%. In the present invention, the temperature of the decolorization is preferably 55-60 °C, the time is preferably 15-20 min, and the number of times of the decolorization is preferably 1 time. After the decolorization, the present invention preferably further includes filtration to obtain a decolorized liquid; the decolorized liquid is desalted.

[0049] In the present invention, the desalting is preferably carried out with ion exchange resin, and the ion exchange resin used for the ion exchange resin desalting preferably includes strong acid cation exchange resin D001 and weak base anion exchange resin D301P. In the present invention, the temperature of the decolorized liquid is preferably 35-40 °C, the flow rate of the decolorized liquid is preferably 1-3 BV / h, specifically preferably 1 BV / h, 2 BV / h or 3 BV / h; the number of times of the desalting is preferably 1 time. After the desalting, the present invention preferably further includes concentrating the obtained desalted liquid to obtain a concentrated desalted liquid for subsequent chromatographic purification. In the present invention, the solid content in the concentrated desalted liquid is preferably 50-60 wt%; the pH value of the concentrated desalted liquid is preferably 6.

[0050] In the present invention, the chromatographic purification is preferably carried out with potassium-type chromatographic resin, and the parameters of the potassium-type chromatographic resin purification include: the temperature is preferably 60-70 °C, specifically preferably 60 °C, 65 °C or 70 °C; the ratio of liquid to resin is preferably 1:1.3-1.5, specifically preferably 1:1.3, 1:1.4 or 1:1.5; the feeding amount is preferably 1.2-1.5 m 3 / h, specifically preferably 1.2 m 3 / h, 1.3 m 3 / h, 1.4 m 3 / h or 1.5 m 3 / h; the operating pressure is preferably 0.2-0.3 MPa, specifically preferably 0.2 MPa, 0.25 MPa or 0.3 MPa; the number of times of the chromatographic purification is preferably 1 time.

[0051] After the chromatographic purification, the present invention preferably further includes: concentrating the obtained chromatographically purified liquid to a solid content of 55-65 wt%, and drying to obtain the resistant dextrin. In the present invention, the concentration method is preferably triple-effect concentration. The present invention does not make special requirements on the drying method, and the methods commonly used by those skilled in the art can be adopted.

[0052] The present invention also provides resistant dextrin obtained by the preparation method described in the above technical solution. In the resistant dextrin, the dietary fiber content is ≥ 90 wt%, the content of resistant dextrin with a degree of polymerization of 7 - 13 in the dietary fiber is 93 - 95 wt%, the light transmittance is ≥ 99%, and the chromaticity is < 100 RBU.

[0053] In the present invention, the dietary fiber content in the resistant dextrin is ≥ 90 wt%, preferably 91 - 93 wt%; the content of resistant dextrin with a degree of polymerization of 7 - 13 in the dietary fiber is 93 - 95%. In the present invention, the light transmittance of the resistant dextrin is ≥ 99%, preferably 99.3 - 99.5%; the chromaticity is < 100 RBU, preferably 95 - 98%; the pH value is preferably 4 - 6.

[0054] In the present invention, the degree of polymerization of the resistant dextrin is concentrated in the range of 7 - 13, which is easy to absorb and utilize and also has certain embedding characteristics.

[0055] The resistant dextrin product prepared by the present invention has good transparency.

[0056] To further illustrate the present invention, the resistant dextrin and its preparation method provided by the present invention will be described in detail below with reference to examples, but they should not be construed as limiting the protection scope of the present invention.

[0057] In the examples or comparative examples of the present invention, the detection method for protein: In accordance with GB / T 22427.10 - 2008 "Determination of nitrogen content in starches and their derivatives", the nitrogen content is converted into protein with a coefficient of 6.25.

[0058] The detection method for dietary fiber: In accordance with the second method, enzymatic gravimetry - liquid chromatography method, in GB / T 22224 - 2008 "Determination of dietary fiber in foods - Enzymatic gravimetry and enzymatic gravimetry - liquid chromatography method".

[0059] The detection method for light transmittance: In accordance with the light transmittance detection method in Section 6.7 of GB / T 20881 - 2017 "Isomaltooligosaccharides".

[0060] Example 1

[0061] The preparation method of resistant dextrin includes the following steps:

[0062] (1) Mix starch and water to obtain a starch milk, wherein the pH value is 6.0 and the Baume degree is 20 Bé.

[0063] (2) Adjust the pH value of the starch milk to 4.6 with citric acid, and after filtration, obtain a protein - removed modified starch milk, wherein the protein removal rate is 98.5%.

[0064] (3) Adjust the pH value of the modified starch milk to 3.0 with citric acid, and carry out the first dextrinization at 120 °C and -0.06 MPa for 50 min. During the process of the first dextrinization system, the DE value of the system is in the range of 8 - 10, and the first dextrinization system is obtained; in the first dextrinization system, the DE value is 9.5, and the proportion of resistant dextrin with a polymerization degree < 6 is 80 wt%.

[0065] (4) Continue to adjust the pH value of the first dextrinization system to 2.0 with citric acid, and carry out the second dextrinization at 110 °C and -0.09 MPa for 40 min. During the second dextrinization, the DE value of the system is monitored in real time. When the second dextrinization proceeds to 10 min, the DE value of the system is 5.3. Add the fructose chromatographic raffinate (glucose content is 12 wt%) to make the DE value 11.6, and continue the second dextrinization until the end to obtain the crude resistant dextrin; the dietary fiber content in the crude resistant dextrin is 81 wt%, the 5-hydroxymethylfurfural content is 0.08 wt%, the light transmittance is 85%, and the chromaticity is 426 RBU; the content of resistant dextrin with a polymerization degree of 7 - 13 in the dietary fiber is 81 wt%.

[0066] (5) According to the mass of the activated carbon being 1% of the dry basis mass of the crude resistant dextrin, add activated carbon to the crude resistant dextrin, heat to 55 °C and keep warm for 20 min for decolorization; after decolorization, filter to obtain the decolorized feed liquid; the decolorized feed liquid is desalted using strong acid cation exchange resin D001 and weak base anion exchange resin D301P to obtain the desalted feed liquid; among them, the temperature of the decolorized feed liquid is 35 °C, the flow rate of the decolorized feed liquid is 1 BV / h, and the pH value of the desalted feed liquid is 5.5.

[0067] (6) Concentrate the desalted feed liquid to a concentrated desalted liquid with a solid content of 55 wt%; among them, the pH value of the concentrated desalted liquid is 6.0, and use potassium type chromatographic resin to chromatographically purify the concentrated desalted liquid. The operating conditions include: the temperature is 60 °C, the feed liquid ratio is 1:1.3, the feed rate is 1.2 m 3 / h, the operating pressure is 0.2 MPa, and the chromatographically purified feed liquid is obtained. The product yield of the chromatographic separation process is 93%, and the calculation method is the ratio of the mass of the resistant dextrin obtained by chromatographic purification to the mass of the resistant dextrin before separation × 100%.

[0068] (7) Subject the chromatographically purified feed liquid to triple-effect concentration, concentrate to a solid mass content of 65 wt%, and dry to obtain the finished product of resistant dextrin.

[0069] After testing, the dietary fiber content in the finished product of resistant dextrin is 93 wt%, the 5-hydroxymethylfurfural content is 0.05 wt%, the light transmittance is 99.5%, and the chromaticity is 98 RBU; the content of resistant dextrin with a polymerization degree of 7 - 13 in the dietary fiber is 95 wt%.

[0070] Example 2

[0071] A method for preparing resistant dextrin, comprising the following steps:

[0072] (1) Mix starch and water to obtain a starch milk with a pH value of 7.0 and a Baume degree of 25 Bé.

[0073] (2) Adjust the pH value of the starch milk to 5.1 with citric acid, and after filtration, obtain a denatured starch milk with protein removed, wherein the protein removal rate is 98%.

[0074] (3) Adjust the pH value of the denatured starch milk to 3.5 with citric acid, and carry out the first dextrinization at 130 °C and -0.06 MPa for 40 min. During the process of the first dextrinization system, the DE value of the system is in the range of 8-10, and a first dextrinization system is obtained; in the first dextrinization system, the DE value is 8.7, and the proportion of resistant dextrin with a polymerization degree <6 is 80 wt%.

[0075] (4) Continue to adjust the pH value of the first dextrinization system to 2.5 with citric acid, and carry out the second dextrinization at 120 °C and -0.09 MPa for 30 min. During the second dextrinization, the DE value of the system is monitored in real time. When the second dextrinization proceeds to 10 min and the DE value of the system is 5.5, add the fructose chromatographic raffinate (glucose content is 8 wt%) to make the DE value 10.8, and continue the second dextrinization until the end to obtain a crude resistant dextrin; the dietary fiber content in the crude resistant dextrin is 81 wt%, the 5-hydroxymethylfurfural content is 0.07 wt%, the light transmittance is 86%, and the chromaticity is 404 RBU; the content of resistant dextrin with a polymerization degree in the range of 7-13 in the dietary fiber is 80 wt%.

[0076] (5) Add activated carbon to the crude resistant dextrin according to the mass of the activated carbon being 2% of the dry basis mass of the crude resistant dextrin, and heat to 60 °C for 15 min for decolorization; after decolorization, filter to obtain a decolorized feed liquid; the decolorized feed liquid is desalted with strong acid cation exchange resin D001 and weak base anion exchange resin D301P to obtain a desalted feed liquid; wherein, the temperature of the decolorized feed liquid is 40 °C, the flow rate of the decolorized feed liquid is 3 BV / h, and the pH value of the desalted feed liquid is 5.5.

[0077] (6) Concentrate the desalted feed liquid to a concentrated desalted liquid with a solid content of 60 wt%; wherein the pH value of the concentrated desalted liquid is 7.0, and use potassium-type chromatographic resin to carry out chromatographic purification on the concentrated desalted liquid. The operating conditions include: temperature is 70 °C, the ratio of feed liquid to resin is 1:1.5, the feed rate is 1.5 m 3 / h, the operating pressure is 0.3 MPa, to obtain a chromatographically purified feed liquid, and the product yield of the chromatographic separation process is 94%,

[0078] (7) The chromatographically purified feed solution was concentrated by triple-effect evaporation until the solid content reached 65%, and then dried to obtain resistant dextrin.

[0079] After testing, the content of dietary fiber in the resistant dextrin was 91 wt%, the content of 5-hydroxymethylfurfural was 0.04 wt%, the light transmittance was 99.3%, and the chromaticity was 95 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 93 wt%.

[0080] Comparative Example 1

[0081] The difference between Comparative Example 1 and Example 1 was only in step (4): during the second dextrinization process, the fructose chromatographic raffinate was not added.

[0082] After testing, the content of dietary fiber in the crude resistant dextrin was 81 wt%, the content of 5-hydroxymethylfurfural was 0.09 wt%, the light transmittance was 86%, and the chromaticity was 406 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 55 wt%.

[0083] After refining and purification, the content of dietary fiber in the obtained finished product of resistant dextrin was 90 wt%, the content of 5-hydroxymethylfurfural was 0.07 wt%, the light transmittance was 99.1%, and the chromaticity was 93 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 68 wt%.

[0084] Comparative Example 2

[0085] The difference from Example 1 was that in step (2), the pH of the starch milk was adjusted to 5.5.

[0086] After testing, the content of dietary fiber in the crude resistant dextrin was 81 wt%, the content of 5-hydroxymethylfurfural was 0.10 wt%, the light transmittance was 75%, and the chromaticity was 704 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 74 wt%.

[0087] After refining and purification, the content of dietary fiber in the obtained finished product of resistant dextrin was 89 wt%, the content of 5-hydroxymethylfurfural was 0.08 wt%, the light transmittance was 87.9%, and the chromaticity was 203 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 86 wt%.

[0088] Comparative Example 3

[0089] The difference between Comparative Example 3 and Example 1 was only in step (4): the condition of the second dextrinization was: reacting at normal pressure for 40 min at 150 °C.

[0090] After detection, the content of dietary fiber in the crude resistant dextrin is 65 wt%, the content of 5-hydroxymethylfurfural is 0.12 wt%, the light transmittance is 76%, and the chromaticity is 802 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber is 60 wt%.

[0091] After detection, in the prepared resistant dextrin, the content of dietary fiber is 85 wt%, the content of 5-hydroxymethylfurfural is 0.09 wt%, the light transmittance is 86.5%, and the chromaticity is 308 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 is 79 wt%.

[0092] Comparative Example 4

[0093] The difference between Comparative Example 4 and Example 1 lies only in step (4): the conditions for the second dextrinization are: reacting at normal pressure at 130 °C for 50 min.

[0094] After detection, the content of dietary fiber in the crude resistant dextrin is 62 wt%, the content of 5-hydroxymethylfurfural is 0.11 wt%, the light transmittance is 78%, and the chromaticity is 507 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber is 58 wt%.

[0095] After detection, the content of dietary fiber in the prepared resistant dextrin is 80 wt%, the content of 5-hydroxymethylfurfural is 0.08 wt%, the light transmittance is 88.5%, and the chromaticity is 154 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber is 74%.

[0096] Comparative Example 5

[0097] The difference between Comparative Example 5 and Example 1 lies only in that step (3) is omitted.

[0098] After detection, the content of dietary fiber in the crude resistant dextrin is 80 wt%, the content of 5-hydroxymethylfurfural is 0.07 wt%, the light transmittance is 82%, and the chromaticity is 413 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber is 65 wt%.

[0099] After detection, the content of dietary fiber in the prepared resistant dextrin is 90 wt%, the content of 5-hydroxymethylfurfural is 0.06 wt%, the light transmittance is 98.6%, and the chromaticity is 106 RBU; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber is 78 wt%.

[0100] Comparative Example 6

[0101] The difference between Comparative Example 6 and Example is that: in step (3), the conditions for the first dextrinization are: reacting at normal pressure at 90 °C for 30 min, and the others are the same as in Example 1.

[0102] After detection, in the crude resistant dextrin, the dietary fiber content is 81 wt%, the 5-hydroxymethylfurfural content is 0.08 wt%, the light transmittance is 86%, and the chromaticity is 392 RBU; the content of resistant dextrin with a degree of polymerization of 7 - 13 in the dietary fiber is 69 wt%.

[0103] After detection, in the prepared resistant dextrin, the mass content of dietary fiber is 91 wt%, the 5-hydroxymethylfurfural content is 0.05 wt%, the light transmittance is 98.5%, and the chromaticity is 104 RBU; the content of resistant dextrin with a degree of polymerization of 7 - 13 in the dietary fiber is 82 wt%.

[0104] Table 1 Performance parameters of the crude resistant dextrin and the finished product resistant dextrin obtained in the examples and comparative examples

[0105]

[0106] As can be seen from Table 1: By comparing the results of Example 1 and Comparative Example 1, it can be seen that at low temperatures, the conditions for the second dextrinization are milder, and the amount of hydrolyzed small-molecule sugars decreases. Without adding fructose chromatographic raffinate, the proportion of resistant dextrin with a degree of polymerization of 7-13 in the product is small and heterogeneous. By comparing Example 1 and Comparative Example 2, it can be seen that the pH value of the starch milk was adjusted to 5.5 for the first time, which did not reach the isoelectric point of most proteins in the starch milk, resulting in many side reactions and a deep color of the product in the subsequent dextrinization reaction. In the second dextrinization, the impurities generated by side reactions led to uncontrollable polymerization, and the degree of polymerization of the product was poor and heterogeneous. By comparing Example 1 and Comparative Example 3, it can be seen that after increasing the temperature of the second dextrinization, the content of 5-hydroxymethylfurfural increased sharply, the color became darker, and the light transmittance was poor. This is because at a continuous high temperature, it is conducive to the rapid synthesis of 5-hydroxymethylfurfural. In addition, when the temperature continues to rise, 5-hydroxymethylfurfural will further decompose, producing some gas and liquid products; resulting in a high content of 5-hydroxymethylfurfural in the product, a deep color, and a burnt bitter taste, and the product quality is poor. By comparing Example 1 and Comparative Example 4, it can be seen that after reducing the temperature of the second dextrinization and not evacuating, under normal pressure, the optimum temperature for polymerization was not reached, so the degree of polymerization of the product was poor. By comparing Example 1 and Comparative Example 5, it can be seen that: due to the reduction of the first dextrinization, the content of 5-hydroxymethylfurfural decreased, but due to the short time of the second dextrinization and the lack of the first dextrinization, the degree of polymerization of the product was poor and heterogeneous. By comparing Example 1 and Comparative Example 6, it can be seen that the first dextrinization was carried out under the conditions of 90°C and normal pressure. Although the content of 5-hydroxymethylfurfural decreased significantly and the color was light after reducing the temperature, due to the low temperature and no pressure in the first dextrinization, only hydrolysis could be achieved, and then the second dextrinization reaction was carried out. Therefore, the degree of polymerization of the crude resistant dextrin produced was poor. Both Comparative Example 5 and Comparative Example 6 only carried out one dextrinization reaction, but Comparative Example 6 was equivalent to having one more hydrolysis reaction, accumulating small-molecule sugars. Therefore, the dietary fiber content and the content of the degree of polymerization in the range of 7-13 in Comparative Example 6 were slightly higher than those in Comparative Example 5.

[0107] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments according to the embodiments of the present invention without creative labor, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A method for preparing resistant dextrin, characterized in that: The following steps are involved: The pH value of the starch milk is adjusted to 4.6-5.1, and modified starch milk is obtained by filtering. The modified starch milk is subjected to a first dextrinization to obtain a first dextrinization system, wherein the pH of the first dextrinization is 3.0-3.5, the temperature is 120-130° C., the pressure is -0.05-0.07 MPa, and the time is 40-50 min; The first dextrinization system is subjected to a second dextrinization to obtain a crude resistant dextrin product, wherein the pH of the second dextrinization is 2.0-2.5, the temperature is 110-120° C., the pressure is -0.08-0.09 MPa, and the time is 30-40 min; during the second dextrinization, the DE value of the system is monitored in real time, and when the DE value is 5-6, fructose chromatography residual solution is added to make the DE value 10-12; The crude resistant dextrin is refined to obtain the resistant dextrin.

2. The preparation method according to claim 1, characterized in that: The starch milk has a Baume degree of 20-25 Bé and a pH value of 6.0-7.

0.

3. The preparation method according to claim 1 or 2, characterized in that: The reagent for adjusting the pH value of starch milk to 4.6-5.1 is an organic acid or an inorganic acid, wherein the organic acid includes one or more of citric acid, malic acid, tartaric acid and lactic acid, and the inorganic acid includes phosphoric acid.

4. The preparation method according to claim 1, characterized in that: The glucose content in the fructose chromatography raffinate is 8-12 wt %.

5. The preparation method according to claim 1, characterized in that: The refining comprises sequentially performing decolorization, desalting and chromatography purification to obtain the resistant dextrin.

6. The preparation method according to claim 5, characterized in that: The decolorization is performed by activated carbon decolorization, the mass of the activated carbon used in the activated carbon decolorization is 1-2% of the dry mass of the crude resistant dextrin, the decolorization temperature is 55-60°C, the time is 15-20min, and the decolorization frequency is 1 time; After the decolorization, the method further comprises filtering to obtain a decolorized liquid.

7. The preparation method according to claim 6, characterized in that: The desalination is ion exchange resin desalination, the ion exchange resin used in the ion exchange resin desalination includes strong acid cation exchange resin D001 and weak base anion exchange resin D301P, the temperature of the decolorizing liquid is 35-40°C, the flow rate of the decolorizing liquid is 1-3BV / h, and the number of desalination is 1 time; After the desalting, the method further comprises: concentrating the obtained desalted liquid, and performing subsequent chromatographic purification on the obtained concentrated desalted liquid.

8. The preparation method according to claim 5, characterized in that: The chromatographic purification is potassium-type chromatographic resin purification, and the parameters of the potassium-type chromatographic resin purification include: temperature of 60-70°C, material-liquid ratio of 1:1.3-1.5, feed volume of 1.2-1.5m 3 / h, the operating pressure is 0.2-0.3 MPa, and the number of chromatographic purification is 1 time.

9. The preparation method according to claim 5 or 8, characterized in that: After the chromatographic purification, the method further comprises: concentrating the chromatographically purified material to a solid content of 55-65wt%, and drying to obtain the resistant dextrin.

10. The resistant dextrin obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The dietary fiber content of the resistant dextrin is ≥90wt%, the content of the resistant dextrin with a polymerization degree of 7-13 in the dietary fiber is 93-95wt%, the light transmittance is ≥99%, and the chromaticity is <100RBU.

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