Resistance dextrin and preparation method thereof

Abstract

The invention belongs to the technical field of starch deep processing, and particularly relates to resistant dextrin and a preparation method thereof. According to the invention, the pH value of the starch milk is adjusted to 4.6-5.1, so that starch is denatured and subsequent dextrinization is facilitated; protein impurities in the starch can be removed, and the subsequent refining burden is relieved. The temperature of the first dextrinization is controlled to be 120-130 DEG C, so that the problem that the color of the crude resistant dextrin product is dark due to high temperature is avoided; meanwhile, the pressure of the first dextrinization is controlled to be-0.05 to-0.07 MPa, so that after the first dextrinization, the proportion of the resistant dextrin with the polymerization degree smaller than 6 is about 80 wt%; the method comprises the following steps of: performing secondary dextrinization to ensure that sufficient small molecular sugar exists in a system during the secondary dextrinization, so that resistant dextrin with high uniformity can be conveniently generated under a mild condition, and the content of the resistant dextrin with the polymerization degree of 7-13 in dietary fibers in a resistant dextrin crude product is 81wt%.

Description

Technical Field

[0001] This invention belongs to the field of starch deep processing technology, specifically relating to a resistant dextrin and its preparation method. Background Technology

[0002] Resistant dextrin is a low-molecular-weight, water-soluble dietary fiber. After being ingested by the human body, it is only utilized by bacteria in the colon to produce short-chain fatty acids that are beneficial to the human body. It has positive effects on lowering blood sugar and blood lipids. It has a uniform appearance and mild taste, and has broad application potential in the food industry.

[0003] Existing technologies disclose resistant dextrin with an average degree of polymerization of 6-12 and its preparation method. The method involves adding an acid solution to starch and reacting at 80-120°C under normal pressure for 2-4 hours; then adding more acid and continuing the temperature rise to 150-200°C for gelatinization for 15-30 minutes; finally, adding deionized water and performing acidic hydrolysis at 80-100°C for 1-2 hours. Due to the high gelatinization temperature, the crude resistant dextrin produced by this method has a dark color. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a resistant dextrin and a method for preparing the same. The crude resistant dextrin obtained by the method of this invention has a light color, does not require complex refining processes, consumes less energy, and still yields resistant dextrin with uniform polymer density.

[0005] This invention provides a method for preparing resistant dextrin, comprising the following steps: The pH of the starch milk was adjusted to 4.6-5.1, and after filtration, modified starch milk was obtained. The modified starch milk is subjected to a first dextrinization to obtain a first dextrinization system. The pH of the first dextrinization is 3.0~3.5, the temperature is 120~130℃, the pressure is -0.05~-0.07MPa, and the time is 40~50min. The first dextrinization system was subjected to a second dextrinization to obtain resistant crude dextrin. The pH of the second dextrinization was 2.0~2.5, the temperature was 110~120℃, the pressure was -0.08~-0.09MPa, and the time was 30~40min. During the second dextrinization process, the DE value of the system was monitored in real time. When the DE value was 5~6, fructose chromatographic residue was added to make the DE value 10~12. The crude resistant dextrin is purified to obtain the resistant dextrin.

[0006] Preferably, the starch milk has a Baume degree of 20-25 Bé and a pH of 6.0-7.0.

[0007] Preferably, the reagent used to adjust the pH of the 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.

[0008] Preferably, the glucose content in the fructose chromatographic residue is 8-12 wt%.

[0009] Preferably, the purification process includes sequentially performing decolorization, desalting, and chromatographic purification to obtain the resistant dextrin.

[0010] Preferably, the decolorization is performed using activated carbon, and the mass of activated carbon used for decolorization is 1-2% of the dry basis mass of the crude resistant dextrin. The decolorization temperature is 55-60℃, the time is 15-20 min, and the decolorization is performed once. After decolorization, the mixture is filtered to obtain a decolorized liquid.

[0011] Preferably, the desalination is performed using ion exchange resin, and the ion exchange resin used for the desalination includes strong acid cation exchange resin D001 and weak base anion exchange resin D301P. The temperature of the decolorizing solution is 35~40℃, the flow rate of the decolorizing solution is 1~3 BV / h, and the desalination is performed once. After desalination, the method further includes concentrating the obtained desalted solution and performing subsequent chromatographic purification on the obtained concentrated desalted solution.

[0012] Preferably, the chromatographic purification is performed using potassium-form chromatographic resin, and the parameters for potassium-form chromatographic resin purification include: temperature of 60-70°C, material-to-liquid ratio of 1:1.3-1.5, and feed rate of 1.2-1.5 mg / L. 3 The operating pressure is 0.2~0.3MPa, and the chromatographic purification is performed once per hour.

[0013] Preferably, after chromatographic purification, the method further includes: concentrating the obtained chromatographic purified material to a solid content of 55-65 wt%, and drying it to obtain the resistant dextrin.

[0014] The present invention also provides resistant dextrin prepared by the preparation method described above, wherein the resistant dextrin contains ≥90wt% dietary fiber, the dietary fiber contains 90-95wt% resistant dextrin with a degree of polymerization of 7-13, the light transmittance is ≥99%, and the color is <100RBU.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing resistant dextrin, comprising the following steps: adjusting the pH of starch milk to 4.6-5.1, filtering to obtain modified starch milk; subjecting the modified starch milk 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℃, the pressure is -0.05--0.07MPa, and the time is 40-50min; subjecting the first dextrinization system to a second dextrinization to obtain crude resistant dextrin, wherein the pH of the second dextrinization is 2.0-2.5, the temperature is 110-120℃, the pressure is -0.08--0.09MPa, and the time is 30-40min; during the second dextrinization process, monitoring the DE value of the system in real time, and when the DE value is 5-6, adding fructose chromatographic residue to make the DE value 10-12; and purifying the crude resistant dextrin to obtain the resistant dextrin.

[0016] This invention first adjusts the pH of the starch milk to 4.6-5.1, which not only denatures the starch, facilitating subsequent dextrinization, but also removes excess protein impurities from the starch, reducing the burden of subsequent refining and thus improving product yield. The invention controls the temperature of the first dextrinization at 120-130℃, avoiding the problem of dark color in the crude resistant dextrin product caused by high temperatures. Simultaneously, it controls the pH of the first dextrinization at 3.0-3.5, the temperature at 120-130℃, and the pressure at -0.05--0.07 MPa, ensuring that the DE value of the first dextrinization process and the resulting first dextrinization system is within the range of 8-10. This provides sufficient small molecule monomers for the second dextrinization, ensuring that a resistant dextrin with a uniform degree of polymerization is obtained after the second dextrinization. Furthermore, the parameter settings for the first dextrinization result in approximately 80 wt% resistant dextrin with a degree of polymerization <6 in the obtained first dextrinization system. Combined with sufficient small molecule monomers, this facilitates the obtaining of resistant dextrin with a uniform degree of polymerization. Dextrin was first processed; then, a second dextrinization was carried out at pH 2.0–2.5, temperature 110–120℃, and pressure -0.08–-0.09 MPa for 30–40 min. During the second dextrinization, the DE value of the system was monitored in real time. When the DE value was 5–6, fructose chromatographic residue was added to bring the DE value to 10–12. The addition of fructose chromatographic residue ensured that the system contained sufficient small-molecule monomers during the second dextrinization process, facilitating the generation of highly homogeneous resistant dextrin under mild conditions. This resulted in a crude resistant dextrin product with a dietary fiber content of 81 wt%, a color intensity of 404–426 RBU, and a transmittance of 85–86%. The content of resistant dextrin with a degree of polymerization of 7–13 in the dietary fiber was 80–81 wt%. Furthermore, controlling the DE value of the system during the second dextrinization process using fructose chromatographic residue increased the added value of the fructose chromatographic residue.

[0017] Furthermore, the decolorization, desalting, and chromatographic purification are performed only once, simplifying the purification process and reducing energy consumption; however, it still ensures that the final resistant dextrin has excellent uniform degree of polymerization, transmittance, color, and low 5-hydroxymethylfurfural content. Data from the examples show that the resistant dextrin contains ≥90wt% dietary fiber, and the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber is 93-95wt%, with transmittance ≥99% and color <100 RBU. Attached Figure Description

[0018] Figure 1 The flowchart illustrates the preparation method of resistant dextrin provided by this invention. Detailed Implementation

[0019] Figure 1 The following is a flowchart of the preparation method of resistant dextrin provided by the present invention, in conjunction with... Figure 1 The preparation method of the present invention will be described in detail.

[0020] This invention provides a method for preparing resistant dextrin, comprising the following steps: The pH of the starch milk was adjusted to 4.6-5.1, and after filtration, modified starch milk was obtained. The modified starch milk is subjected to a first dextrinization to obtain a first dextrinization system. The pH of the first dextrinization is 3.0~3.5, the temperature is 120~130℃, the pressure is -0.05~-0.07MPa, and the time is 40~50min. The first dextrinization system was subjected to a second dextrinization to obtain resistant crude dextrin. The pH of the second dextrinization was 2.0~2.5, the temperature was 110~120℃, the pressure was -0.08~-0.09MPa, and the time was 30~40min. During the second dextrinization process, the DE value of the system was monitored in real time. When the DE value was 5~6, fructose chromatographic residue was added to make the DE value 10~12. The crude resistant dextrin is purified to obtain the resistant dextrin.

[0021] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0022] The present invention adjusts the pH value of starch milk to 4.6~5.1, and after filtration, obtains modified starch milk.

[0023] In this invention, the starch milk preferably has a Baume degree of 20-25 Bé and a pH of 6.0-7.0.

[0024] In this invention, the method for preparing the starch milk preferably includes the following steps: mixing starch and water to obtain the starch milk.

[0025] In this invention, the reagent used to adjust the pH of the starch milk to 4.6-5.1 is preferably an organic acid or an inorganic acid, more preferably an organic acid. In this invention, the organic acid preferably includes one or more of citric acid, malic acid, tartaric acid, and lactic acid. In this invention, the inorganic acid preferably includes phosphoric acid.

[0026] The present invention does not specifically limit the filtering method; any operation known to those skilled in the art can be used.

[0027] In this invention, adjusting the pH of the starch milk to 4.6-5.1 not only denatures the starch, which is beneficial for subsequent dextrinization, but also reaches the isoelectric point of the proteins in the starch milk. This allows for protein removal after filtration, reducing the difficulty and cost of subsequent product refining. This invention eliminates the need for an additional protein removal step, making the process simple.

[0028] After obtaining the modified starch milk, the present invention performs a 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℃, the pressure is -0.05~-0.07MPa, preferably -0.06MPa, and the time is 40~50min.

[0029] In this invention, the pH of the first dextrinization is 3.0~3.5, preferably 3.0, 3.1, 3.2, 3.3, 3.4 or 3.5; the temperature is 120~130℃, preferably 120℃, 125℃ or 130℃; the pressure is -0.05~-0.07MPa, preferably -0.06MPa; and the time is 40~50min, preferably 40min, 45min or 50min. In this invention, the pH of the first dextrinization is preferably adjusted by an organic acid or inorganic acid, and the types of organic or inorganic acids are preferably consistent with the above technical solutions, and will not be repeated here.

[0030] After the first dextrinization, the present invention preferably obtains the first dextrinized system directly without any post-processing.

[0031] The present invention controls the pH of the first dextrinization to be 3.0~3.5, the temperature to be 120~130℃, and the pressure to be -0.05~-0.07MPa, so that the DE value of the first dextrinization process and the resulting first dextrinization system is in the range of 8~10, providing sufficient small molecule monomers for the second dextrinization, thereby ensuring the degree of polymerization is uniform; at the same time, the proportion of resistant dextrin with a degree of polymerization <6 in the first dextrinization system is about 80wt%.

[0032] After obtaining the first dextrinization system, the present invention performs a second dextrinization on the first dextrinization system to obtain resistant crude dextrin. The pH of the second dextrinization is 2.0~2.5, the temperature is 110~120℃, the pressure is -0.08~-0.09MPa, and the time is 30~40min. During the second dextrinization process, the DE value of the system is monitored in real time. When the DE value is 5~6, fructose chromatographic residue is added to make the DE value 10~12.

[0033] In this invention, the pH of the second dextrinization is 2.0~2.5, preferably 2.0, 2.1, 2.2, 2.3, 2.4 or 2.5; the temperature is 110~120℃, preferably 110℃, 115℃ or 120℃; the pressure is -0.08~-0.09MPa, preferably -0.08MPa or -0.09MPa; and the time is 30~40min, preferably 30min, 35min or 40min. In this invention, the pH of the second dextrinization is preferably adjusted by an organic acid or inorganic acid, and the types of organic or inorganic acids are preferably consistent with the above technical solutions, and will not be repeated here.

[0034] In this invention, the DE value of the system is monitored in real time during the second dextrinization process. When the DE value is 5-6, fructose chromatographic residue is added to bring the DE value to 10-12. In this invention, the fructose chromatographic residue refers to the liquid remaining after fructose extraction by chromatography; the fructose chromatographic residue contains glucose and fructose. In this invention, the glucose content in the fructose chromatographic residue is preferably 8-12 wt%.

[0035] After the second dextrinization, the present invention preferably obtains the crude resistant dextrin directly without any post-processing.

[0036] In this invention, the DE value of the system is monitored in real time during the second dextrinization process. When the DE value is 5-6, fructose chromatographic residue is added to make the DE value 10-12. The addition of fructose chromatographic residue ensures that there are sufficient small molecule sugars in the system during the second dextrinization, which facilitates the generation of highly homogeneous resistant dextrin under mild conditions. The crude resistant dextrin contains 81 wt% dietary fiber, has a color of 404-426 RBU, and a transmittance of 85-86%. The dietary fiber contains 80-81 wt% resistant dextrin with a degree of polymerization of 7-13.

[0037] After obtaining the crude resistant dextrin, the present invention refines the crude resistant dextrin to obtain the resistant dextrin.

[0038] In this invention, the refining process preferably includes sequentially performing decolorization, desalting, and chromatographic purification to obtain the resistant dextrin.

[0039] In this invention, the decolorization is preferably performed using activated carbon. The activated carbon used for decolorization is preferably 1-2% of the dry basis weight of the crude resistant dextrin, specifically preferably 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, or 2%. In this invention, the decolorization temperature is preferably 55-60°C, the decolorization time is preferably 15-20 minutes, and the decolorization is preferably performed once. After decolorization, this invention preferably further includes filtration to obtain a decolorized solution; the decolorized solution is then desalted.

[0040] In this invention, the desalination is preferably performed using ion exchange resin, and the ion exchange resin used for desalination preferably includes strong acid cation exchange resin D001 and weak base anion exchange resin D301P. In this invention, the temperature of the decolorizing solution is preferably 35-40°C, and the flow rate of the decolorizing solution is preferably 1-3 BV / h, specifically preferably 1 BV / h, 2 BV / h, or 3 BV / h; the number of desalination cycles is preferably one. After desalination, this invention preferably further includes concentrating the obtained desalted solution, and then subjecting the concentrated desalted solution to subsequent chromatographic purification. In this invention, the solid content in the concentrated desalted solution is preferably 50-60 wt%; the pH value of the concentrated desalted solution is preferably 6.

[0041] In this invention, the chromatographic purification is preferably carried out using potassium-type chromatographic resin. The parameters for this potassium-type chromatographic resin purification include: a temperature preferably of 60-70°C, specifically 60°C, 65°C, or 70°C; a material-to-liquid ratio preferably of 1:1.3-1.5, specifically 1:1.3, 1:1.4, or 1:1.5; and a feed rate preferably of 1.2-1.5 mg / L. 3 / h, specifically preferably 1.2m 3 / h, 1.3m 3 / h, 1.4m 3 / h or 1.5m 3 / h; the operating pressure is preferably 0.2~0.3MPa, specifically preferably 0.2MPa, 0.25MPa or 0.3MPa; the number of chromatographic purifications is preferably 1.

[0042] Following chromatographic purification, the present invention preferably further includes: concentrating the obtained purified chromatographic material to a solid content of 55-65 wt%, followed by drying to obtain the resistant dextrin. In this invention, the concentration method is preferably triple-effect concentration. The present invention does not impose special requirements on the drying method; methods commonly used by those skilled in the art can be employed.

[0043] The present invention also provides resistant dextrin obtained by the preparation method described above, wherein the resistant dextrin has a dietary fiber content ≥90wt%, the dietary fiber contains 93-95wt% resistant dextrin with a degree of polymerization of 7-13, a light transmittance ≥99%, and a colorimetry <100RBU.

[0044] In this invention, the resistant dextrin contains ≥90 wt% dietary fiber, 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 this invention, the resistant dextrin has a light transmittance ≥99%, preferably 99.3-99.5%; a color intensity <100 RBU, preferably 95-98%; and a pH value preferably 4-6.

[0045] In this invention, the degree of polymerization of the resistant dextrin is concentrated in the range of 7 to 13, which makes it easy to absorb and utilize, and also has certain encapsulation characteristics.

[0046] The resistant dextrin product obtained by this invention has good transparency.

[0047] To further illustrate the present invention, the resistant dextrin and its preparation method provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0048] In the embodiments or comparative examples of this invention, the protein detection method is as follows: according to GB / T 22427.10-2008 "Determination of Nitrogen Content in Starch and its Derivatives", the nitrogen content is converted to protein content coefficient of 6.25.

[0049] The detection method for dietary fiber is as follows: according to the second method of enzyme gravimetric method-liquid chromatography in GB / T 22224-2008 "Determination of dietary fiber in food by enzyme gravimetric method and enzyme gravimetric method-liquid chromatography".

[0050] Transmittance testing method: according to the transmittance testing method in Section 6.7 of GB / T 20881-2017 "Isomaltooligosaccharide".

[0051] Example 1 The preparation method of resistant dextrin includes the following steps: (1) Mix starch and water to obtain starch milk, wherein the pH value is 6.0 and the Baume degree is 20 Bé.

[0052] (2) The pH of the starch milk was adjusted to 4.6 by citric acid, and after filtration, the modified starch milk with protein removed was obtained, wherein the protein removal rate was 98.5%.

[0053] (3) The pH of the modified starch milk was adjusted to 3.0 by citric acid. The first dextrinization was carried out at 120℃ and -0.06MPa for 50 min. During the first dextrinization process, the DE value of the system was in the range of 8~10, and the first dextrinization system was obtained. In the first dextrinization system, the DE value was 9.5 and the proportion of resistant dextrin with a degree of polymerization <6 was 80wt%.

[0054] (4) Continue to adjust the pH of the first dextrinization system to 2.0 using citric acid, and carry out the second dextrinization at 110℃ and -0.09MPa for 40 min. During the second dextrinization, monitor the DE value of the system in real time. When the second dextrinization is carried out for 10 min, the DE value of the system is 5.3. Add fructose chromatographic residue (glucose content is 12wt%) to make the DE value 11.6. Continue the second dextrinization until the end to obtain crude resistant dextrin. The crude resistant dextrin contains 81wt% dietary fiber, 0.08wt% 5-hydroxymethylfurfural, 85% transmittance, and 426RBU color. The dietary fiber contains 81wt% resistant dextrin with a degree of polymerization of 7~13.

[0055] (5) The activated carbon was added to the crude resistant dextrin at a mass of 1% of the dry basis mass of the crude resistant dextrin, and heated to 55°C and kept warm for 20 min for decolorization. After decolorization, the mixture was filtered to obtain a decolorized solution. The decolorized solution was desalted using strong acid cation exchange resin D001 and weak base anion exchange resin D301P to obtain a desalted solution. The temperature of the decolorized solution was 35°C, the flow rate of the decolorized solution was 1 BV / h, and the pH value of the desalted solution was 5.5.

[0056] (6) Concentrate the desalting solution to a concentrated desalting solution with a solid content of 55 wt%; wherein the pH value of the concentrated desalting solution is 6.0, and perform chromatographic purification of the concentrated desalting solution using potassium-type chromatographic resin. The operating conditions include: temperature of 60℃, feed-to-liquid ratio of 1:1.3, and feed rate of 1.2 m³ / min. 3 The operating pressure was 0.2 MPa, and the chromatographically purified feed solution was obtained. The product yield of the chromatographic separation process was 93%, which was calculated as the ratio of the mass of the resistant dextrin obtained by chromatographic purification to the mass of the resistant dextrin before separation × 100%.

[0057] (7) The chromatographically purified solution was concentrated using a triple-effect concentration method until the solid content was 65 wt%, and then dried to obtain the resistant dextrin product.

[0058] The test results showed that the resistant dextrin product contained 93 wt% dietary fiber, 0.05 wt% 5-hydroxymethylfurfural, 99.5% light transmittance, and 98 RBU color; the dietary fiber contained 95 wt% resistant dextrin with a degree of polymerization of 7-13.

[0059] Example 2 The preparation method of resistant dextrin includes the following steps: (1) Mix starch and water to obtain starch milk with a pH of 7.0 and a Baume degree of 25 Bé.

[0060] (2) The pH of the starch milk was adjusted to 5.1 by citric acid, and after filtration, the modified starch milk with protein removed was obtained, wherein the protein removal rate was 98%.

[0061] (3) The pH of the starch milk was adjusted to 3.5 by citric acid. The first dextrinization was carried out at 130℃ and -0.06MPa for 40 min. During the first dextrinization process, the DE value of the system was in the range of 8~10, and the first dextrinization system was obtained. In the first dextrinization system, the DE value was 8.7 and the proportion of resistant dextrin with a degree of polymerization <6 was 80wt%.

[0062] (4) Continue to adjust the pH of the first dextrinization system to 2.5 using citric acid, and carry out the second dextrinization at 120℃ and -0.09MPa for 30 min. During the second dextrinization, monitor the DE value of the system in real time. When the DE value of the system is 5.5 after 10 min of the second dextrinization, add fructose chromatographic residue (glucose content is 8wt%) to make the DE value 10.8. Continue the second dextrinization until the end to obtain crude resistant dextrin. The crude resistant dextrin contains 81wt% dietary fiber, 0.07wt% 5-hydroxymethylfurfural, 86% transmittance, and 404RBU color. The dietary fiber contains 80wt% resistant dextrin with a degree of polymerization of 7~13.

[0063] (5) The activated carbon was added to the crude resistant dextrin at a mass of 2% of the dry basis mass of the crude resistant dextrin, and heated to 60°C and kept warm for 15 min for decolorization. After decolorization, the mixture was filtered to obtain a decolorized solution. The decolorized solution was desalted using strong acid cation exchange resin D001 and weak base anion exchange resin D301P to obtain a desalted solution. The temperature of the decolorized solution was 40°C, the flow rate of the decolorized solution was 3 BV / h, and the pH value of the desalted solution was 5.5.

[0064] (6) Concentrate the desalting solution to a concentrated desalting solution with a solid content of 60 wt%; wherein the pH value of the concentrated desalting solution is 7.0, and the concentrated desalting solution is purified by chromatography using potassium-type chromatographic resin. The operating conditions include: temperature of 70℃, feed-to-liquid ratio of 1:1.5, and feed rate of 1.5 m³ / min. 3 The chromatographic purification solution was obtained at a rate of 94% per hour and an operating pressure of 0.3 MPa. (7) The chromatographically purified solution was concentrated using a triple-effect concentration method until the solid content was 65%, and then dried to obtain resistant dextrin.

[0065] The test results showed that the resistant dextrin contained 91 wt% dietary fiber, 0.04 wt% 5-hydroxymethylfurfural, 99.3% light transmittance, and 95 RBU color; the resistant dextrin with a degree of polymerization of 7-13 contained 93 wt% dietary fiber.

[0066] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that in step (4): during the second dextrinization process, no fructose chromatographic extract was added.

[0067] The test results showed that the crude resistant dextrin contained 81 wt% dietary fiber, 0.09 wt% 5-hydroxymethylfurfural, 86% light transmittance, and 406 RBU color; the dietary fiber contained 55 wt% resistant dextrin with a degree of polymerization of 7-13.

[0068] The refined and purified resistant dextrin contained 90 wt% dietary fiber, 0.07 wt% 5-hydroxymethylfurfural, 99.1% light transmittance, and 93 RBU color; the dietary fiber contained 68 wt% resistant dextrin with a degree of polymerization of 7-13.

[0069] Comparative Example 2 The difference from Example 1 is that step (2) adjusts the pH of the starch milk to 5.5.

[0070] The test results showed that the crude resistant dextrin contained 81 wt% dietary fiber, 0.10 wt% 5-hydroxymethylfurfural, 75% light transmittance, and 704 RBU color; the dietary fiber contained 74 wt% resistant dextrin with a degree of polymerization of 7-13.

[0071] The refined and purified resistant dextrin contained 89 wt% dietary fiber, 0.08 wt% 5-hydroxymethylfurfural, 87.9% light transmittance, and 203 RBU color; the dietary fiber contained 86 wt% resistant dextrin with a degree of polymerization of 7-13.

[0072] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is in step (4): the conditions for the second dextrinization are: reaction at 150°C and atmospheric pressure for 40 min.

[0073] The test results showed that the crude resistant dextrin contained 65 wt% dietary fiber, 0.12 wt% 5-hydroxymethylfurfural, 76% light transmittance, and 802 RBU color; the dietary fiber contained 60 wt% resistant dextrin with a degree of polymerization of 7-13.

[0074] The obtained resistant dextrin contained 85 wt% dietary fiber, 0.09 wt% 5-hydroxymethylfurfural, 86.5% light transmittance, and 308 RBU color; the content of resistant dextrin with a degree of polymerization of 7-13 was 79 wt%.

[0075] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is in step (4): the conditions for the second dextrinization are: reaction at 130°C and atmospheric pressure for 50 min.

[0076] The test results showed that the crude resistant dextrin contained 62 wt% dietary fiber, 0.11 wt% 5-hydroxymethylfurfural, 78% light transmittance, and 507 RBU color; the dietary fiber contained 58 wt% resistant dextrin with a degree of polymerization of 7-13.

[0077] The obtained resistant dextrin contained 80 wt% dietary fiber, 0.08 wt% 5-hydroxymethylfurfural, 88.5% light transmittance, and 154 RBU color; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 74%.

[0078] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that step (3) is omitted.

[0079] The test results showed that the crude resistant dextrin contained 80 wt% dietary fiber, 0.07 wt% 5-hydroxymethylfurfural, 82% light transmittance, and 413 RBU color; the dietary fiber contained 65 wt% resistant dextrin with a degree of polymerization of 7-13.

[0080] The obtained resistant dextrin contained 90 wt% dietary fiber, 0.06 wt% 5-hydroxymethylfurfural, 98.6% light transmittance, and 106 RBU color; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 78 wt%.

[0081] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that in step (3), the conditions for the first dextrinization are: reaction at 90°C and atmospheric pressure for 30 min, and the rest is the same as in Example 1.

[0082] The test results showed that the crude resistant dextrin contained 81 wt% dietary fiber, 0.08 wt% 5-hydroxymethylfurfural, 86% light transmittance, and 392 RBU color; the dietary fiber contained 69 wt% resistant dextrin with a degree of polymerization of 7-13.

[0083] The obtained resistant dextrin contained 91 wt% dietary fiber, 0.05 wt% 5-hydroxymethylfurfural, 98.5% light transmittance, and 104 RBU color; the content of resistant dextrin with a degree of polymerization of 7-13 in the dietary fiber was 82 wt%.

[0084] Table 1. Performance parameters of crude and finished resistant dextrin obtained from the examples and comparative examples.

[0085] Table 1 shows that, comparing the results of Example 1 and Comparative Example 1, the conditions for the second dextrinization are milder at low temperatures, resulting in fewer small-molecule sugars being hydrolyzed. Without the addition of fructose chromatographic extract, the proportion of resistant dextrin with a degree of polymerization of 7-13 is small and uneven. Comparing Example 1 and Comparative Example 2, the initial adjustment of the starch milk pH to 5.5 did not reach the isoelectric point of most proteins in the starch milk, leading to more side reactions and a darker product color in the subsequent dextrinization reaction. In the second dextrinization, impurities generated by the side reactions made the polymerization process uncontrollable, resulting in a poor and uneven degree of polymerization in the product. Comparative Examples 1 and 3 show that increasing the second dextrinization temperature leads to a sharp increase in 5-hydroxymethylfurfural content, increased color, and poor light transmittance. This is because sustained high temperatures promote rapid synthesis of 5-hydroxymethylfurfural. Furthermore, as the temperature continues to rise, 5-hydroxymethylfurfural decomposes further, producing gaseous and liquid products, resulting in a high 5-hydroxymethylfurfural content, dark color, a burnt taste, and poor product quality. Comparative Examples 1 and 4 show that lowering the second dextrinization temperature without vacuuming, and operating at ambient pressure, prevents the reaching of the optimal polymerization temperature, resulting in a poor degree of polymerization. Comparative Examples 1 and 5 show that reducing the first dextrinization lowers the 5-hydroxymethylfurfural content, but the short second dextrinization time and lack of first dextrinization result in a poor and uneven degree of polymerization in the product. Comparing Example 1 and Comparative Example 6, it can be seen that the first dextrinization was carried out at 90°C and atmospheric pressure. Although the 5-hydroxymethylfurfural content and color were significantly reduced after lowering the temperature, the first dextrinization was carried out at a low temperature without pressure, only reaching the degree of hydrolysis before proceeding to the second dextrinization reaction. Therefore, the resulting crude resistant dextrin had a poor degree of polymerization. Comparative Examples 5 and 6 both underwent only one dextrinization reaction, but Comparative Example 6 had an additional hydrolysis step, accumulating small molecule sugars. Therefore, the dietary fiber content and degree of polymerization (7-13) of Comparative Example 6 were slightly higher than those of Comparative Example 5.

[0086] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within 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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