Crystalline isomaltitol and preparation method therefor

Abstract

The present invention belongs to the technical field of functional sugars. Provided are crystalline isomaltitol and a preparation method therefor. In the present invention, an isomaltulose liquid is subjected to a hydrogenation reaction under the action of a catalyst, so as to obtain a hydrogenation reaction liquid; the hydrogenation reaction liquid is sequentially subjected to decoloration and filtration, ion exchange, and concentration, so as to obtain a pre-crystallization material, wherein the solid content of the pre-crystallization material is 50-55%; a seed crystal is added to the pre-crystallization material, and the resulting mixture is then sequentially subjected to slow evaporation, rapid evaporation and cooling crystallization, so as to obtain isomaltitol; and the isomaltitol is centrifuged and dried, so as to obtain crystalline isomaltitol, wherein in the finally obtained isomaltitol crystals, the purity of GPM is 48-50%, the purity of GPS is 50-52%, and the content of water is less than or equal to 1%. An organic solvent does not need to be used, thereby reducing pollution and residues; moreover, the preparation temperature is low, the energy consumption is low, and new equipment is not needed, thereby lowering the costs.

Description

Crystalline isomaltulose and preparation method thereof

[0001] Cross-reference to Related Applications

[0002] This application claims priority to Chinese Patent Application No. 202411907036.8, filed on December 24, 2024, entitled "Crystalline isomaltulose and preparation method thereof", the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the field of functional sugar technology, in particular to a crystalline isomaltulose and a preparation method thereof. BACKGROUND

[0004] Isomaltulose is a functional sugar alcohol composed of two substances, alpha-D-glucopyranosyl-1, 1-mannitol (GPM) and alpha-D-glucopyranosyl-1, 6-sorbitol (GPS). Its sweetness and heat are about half of sucrose, it is non-hygroscopic, and its melting point range is 145-150℃, it is a non-cariogenic sugar. In addition, isomaltulose does not cause blood glucose to rise, and is the ideal sweetener for diabetics. Isomaltulose is highly safe and is certified as GRAS food by the US FDA. In China, it is limited to use ≤100 grams / day as a new resource food. Isomaltulose is mainly used in candies and chocolates.

[0005] There are few crystalline isomaltulose products in the prior art, mostly in the form of powder and granules. Chinese Patent CN117186161A discloses a preparation process for crystalline isomaltulose, which mainly uses high-purity isomaltulose as raw material to react with hydrogen gas under the action of a catalyst to generate isomaltulose solution, and then uses vacuum evaporation crystallization and cooling crystallization to prepare isomaltulose. The mass content of alpha-D-furanosyl-1, 6-sorbitol in the obtained isomaltulose is ≥98.5%, which is a high-purity isomaltulose crystal. The isomaltulose obtained by the crystallization process is usually a single substance, not a mixture of GPM and GPS; the recrystallization process is complicated and is not conducive to production and application.

[0006] Chinese patent CN117603284A discloses a method for recrystallizing isomaltitol, comprising the following steps: obtaining isomaltitol conversion liquid after hydrogenation reaction, filtering to remove the catalyst to obtain isomaltitol clear liquid, heating the isomaltitol clear liquid to 60-75℃, and concentrating it under reduced pressure distillation at a vacuum degree of -0.01 to -0.05 MPa. Concentration is stopped when the sugar concentration of the solution is measured to be 40-90°Bx using a saccharimeter. The solution is then cooled to 15-25℃, resulting in the precipitation of a small amount of crystals. These crystals are then heated to 60-75℃ to melt them into a liquid. Ethanol or methanol is added dropwise for recrystallization, followed by stirring, cooling, and filtration to obtain wet isomaltitol crystals. The wet isomaltitol crystals are then dried to obtain dry isomaltitol crystals. This process for preparing molten isomaltitol consumes excessive energy.

[0007] Chinese patent CN105037454A discloses a method for preparing isomaltitol, comprising the following steps: (1) concentrating a liquid isomaltitol solution and keeping it at a constant temperature; (2) cooling an organic solvent to a temperature below 10°C; (3) dropping molten isomaltitol into the organic solvent pretreated in step (2), where the isomaltitol droplets condense into granular solids upon contact with the cold air; (4) collecting the isomaltitol solids obtained in step (3), drying them with cold air to obtain the desired isomaltitol crystals. This process uses organic solvents, which can easily cause pollution and residues.

[0008] Therefore, there is an urgent need for a method to prepare crystalline isomaltitol containing GPS and GPM, which is energy-efficient, leaves no organic residue, and is suitable for industrial production. Summary of the Invention

[0009] In view of this, the purpose of this invention is to provide a crystalline isomaltitol and its preparation method. The isomaltitol crystals obtained by this invention have a GPM purity of 48-50%, a GPS purity of 50-52%, and a moisture content of ≤1%. It does not require the use of organic solvents, thus reducing pollution and residues. Moreover, the preparation temperature is low and energy consumption is low, and no new equipment is required, thereby reducing costs.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing crystalline isomaltitol, comprising the following steps:

[0012] S1. Hydrogenate isomaltulose liquid under the action of a catalyst to obtain hydrogenated reaction solution;

[0013] The purities of α-D-glucopyranosyl-1,1-mannitol GPM and α-D-glucopyranosyl-1,6-sorbitol GPS in the hydrogenation reaction solution were 44-46%, respectively.

[0014] S2. The hydrogenation reaction solution is sequentially subjected to decolorization filtration, ion exchange, and concentration to obtain the pre-crystallization material;

[0015] The solid content of the pre-crystallization material is 50-55%;

[0016] S3. Add seed crystals to the pre-crystallization material and then perform slow evaporation, rapid evaporation, and cooling crystallization sequentially to obtain isomaltitol;

[0017] S4. The isomaltitol is centrifuged and dried to obtain crystalline isomaltitol;

[0018] The isomaltitol crystals contain 48-50% α-D-glucopyranosyl-1,1-mannitol and 50-52% α-D-glucopyranosyl-1,6-sorbitol; the moisture content is ≤1%.

[0019] Preferably, the solid content of the isomaltulose liquid in S1 is 50-55%, and the pH is 8.5-9.5.

[0020] Preferably, the amount of catalyst added in S1 is 3 to 3.5% of the liquid solid content of isomaltulose;

[0021] The catalyst is Raney nickel.

[0022] Preferably, in step S1, magnesium strips with a liquid solid content of 0.5-1.0% of isomaltulose are added before the hydrogenation reaction to maintain an alkaline environment during the reaction.

[0023] Preferably, the hydrogenation reaction in S1 is carried out at a temperature of 120–135°C, for a time of 2–3 hours, at a pressure of 10–16 MPa, and at a stirring speed of 500–800 rpm / min.

[0024] Preferably, the amount of seed crystals added in S3 is 8.0 to 10.0‰ of the solid content of the material before crystallization; the seed crystals are isomaltitol paste ground with anhydrous ethanol.

[0025] Preferably, the temperature of slow evaporation in S3 is 55-60°C, the pressure is -0.05 to -0.08 MPa, the concentration of the crystalline material after slow evaporation is 50-55%, and the amount of crystal precipitation is 20-22%.

[0026] Preferably, the temperature of rapid evaporation in S3 is 75-85°C, and the pressure is -0.07 to -0.1 MPa; the concentration of the crystalline material after rapid evaporation is 75-80%.

[0027] Preferably, the final temperature of cooling crystallization in S3 is 25-30°C, and the cooling rate is 0.2-0.5°C / h.

[0028] In this invention, isomaltose crystals are obtained through two evaporation crystallization processes and one cooling crystallization process. The inventors discovered that GPM crystallizes easily. By slowly evaporating and crystallizing, GPM is precipitated. In the solution after GPM precipitation, the GPM content is low and insufficient for further precipitation. Although the GPS content is high at this point, the low concentration is insufficient for GPS precipitation. Then, rapid evaporation is used to quickly increase the solution concentration, and GPS is precipitated by cooling crystallization.

[0029] Preferably, the stirring speed for the slow evaporation, rapid evaporation, and cooling crystallization is 150 rpm / min.

[0030] The present invention also provides a method for preparing crystalline isomaltitol, wherein the purity of α-D-glucopyranoside-1,1-mannitol is 48-50%, the purity of α-D-glucopyranoside-1,6-sorbitol is 50-52%, and the moisture content is ≤1%.

[0031] Beneficial technical effects:

[0032] 1. This invention uses hydrogenated isomaltulose as raw material and obtains isomaltulitol crystals through two evaporation crystallizations and one cooling crystallization. The final isomaltulitol crystals have a GPM purity of 48-50%, a GPS purity of 50-52%, and a moisture content of ≤1%. The isomaltulitol crystals with this composition ratio have stable chemical properties, good heat resistance, good fluidity, and are not prone to clumping.

[0033] 2. In traditional preparation methods, isomaltitol granulation first requires chromatographic purification of the hydrogenated solution, then concentration of the isomaltitol solution to a high concentration, close to a molten state, and granulation requires separate equipment. The drying process for isomaltitol via granulation is cumbersome, resulting in high equipment and concentration costs. This invention, however, achieves isomaltitol purification through crystallization, and the crystallization process can be performed on the same production line as the crystallized product, eliminating the need for additional equipment.

[0034] 3. The crystallization process of isomaltitol in this invention does not use organic solvents, which can avoid environmental pollution and reagent residues. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0041] Unless otherwise specified, all equipment or raw materials used in the following embodiments are commercially available.

[0042] Example 1:

[0043] The following is a method for crystallizing isomaltulitol and preparing it:

[0044] S1. Add Raney nickel catalyst with a solid content of 3.0% to isomaltulose liquid with a solid content of 50% and a pH of 8.56, and then add magnesium strips with a solid content of 0.5% to maintain an alkaline environment during the reaction; carry out hydrogenation reaction for 3 hours at a temperature of 120℃, a stirring speed of 500 rpm / min, and a pressure of 10 MPa to obtain hydrogenation reaction solution.

[0045] The ratio of GPM to GPS in the hydrogen reaction solution was found to be 44.32:44.72.

[0046] S2. The hydrogenation reaction solution is decolorized, filtered, ion-exchanged, and concentrated to obtain isomaltitol crystallization pretreatment material with a solid content of 50%;

[0047] The decolorization conditions are as follows: add activated carbon with a dry matter content of 0.5%, then keep it at 80°C for 30 minutes and then filter it using a plate and frame filter.

[0048] During the ion exchange process: the resin combination consists of cation resin, anion resin, and cation resin in sequence; the temperature of the feed solution entering the column during the ion exchange process is 40°C; the pH value of the feed solution exiting the column is 5.32; and the conductivity of the output column is 45.67 μS / cm.

[0049] The concentration conditions are: concentration temperature of 60℃ and vacuum degree of -0.1MPa.

[0050] S3. Add seed crystals with a solid content of 10.0‰ to the pre-crystallization material, and carry out slow evaporation, rapid evaporation and cooling crystallization to obtain isomaltitol;

[0051] The seed crystals are isomaltitol paste made by grinding anhydrous ethanol.

[0052] The slow evaporation temperature is 60℃, the pressure is -0.05MPa, the rotation speed is 150rpm / min, the concentration of the crystalline material is controlled at 50%, and the GPM crystal precipitation rate is 20%.

[0053] The rapid evaporation temperature is 85℃, the pressure is -0.07MPa, the rotation speed is 150rpm / min, and the concentration of the crystalline material is controlled at 75%.

[0054] The final temperature of the cooling crystallization is 30℃, and the cooling rate is 0.2℃ / h;

[0055] S4. The isomalt is centrifuged and dried to obtain isomalt crystals.

[0056] The centrifugation speed was 1300 rpm / min, and the drying temperature was 50℃;

[0057] The purity of GPM in the isomaltose crystals was 48.35%, the purity of GPS was 51.65%, and the moisture content was 0.87%.

[0058] Example 2:

[0059] The following is a method for crystallizing isomaltulitol and preparing it:

[0060] S1. Add Raney nickel catalyst with a solid content of 3.3% to isomaltulose liquid with a solid content of 50% and a pH of 9.02, and then add magnesium strip with a solid content of 1.0% to maintain an alkaline environment during the reaction; carry out the hydrogenation reaction for 2 hours at a temperature of 125℃, a stirring speed of 500 rpm / min, and a pressure of 13 MPa to obtain the hydrogenation reaction solution.

[0061] The ratio of GPM to GPS in the hydrogen reaction solution was measured to be 44.52:45.08.

[0062] S2. The hydrogenation reaction solution is decolorized, filtered, ion-exchanged, and concentrated to obtain isomaltitol crystallization pretreatment material with a solid content of 52.5%;

[0063] The decolorization conditions are as follows: add activated carbon with a dry matter content of 0.5%, then keep it at 80°C for 30 minutes and then filter it using a plate and frame filter.

[0064] During the ion exchange process: the resin combination consists of cation resin, anion resin, and cation resin in sequence; the temperature of the feed solution entering the column during the ion exchange process is 40℃; the pH value of the feed solution exiting the column is 5.87; and the conductivity of the output column is 45.32 μS / cm.

[0065] The concentration conditions are: concentration temperature of 60℃ and vacuum degree of -0.1MPa.

[0066] S3. Add seed crystals with a solid content of 8.0‰ to the pre-crystallization material, and carry out slow evaporation, rapid evaporation and cooling crystallization to obtain isomaltitol;

[0067] The seed crystals are isomaltitol paste made by grinding anhydrous ethanol.

[0068] The slow evaporation was carried out at a temperature of 57°C, a pressure of -0.07 MPa, a rotation speed of 150 rpm / min, a crystallization material concentration of 52.25%, and a GPM crystal precipitation rate of 23%.

[0069] The rapid evaporation is carried out at a temperature of 80°C, a pressure of -0.08 MPa, and a rotation speed of 150 rpm / min, and the concentration of the crystalline material is controlled at 80%.

[0070] The final temperature of the cooling crystallization is 27°C, and the cooling rate is 0.2°C / h.

[0071] S4. The isomalt is centrifuged and dried to obtain isomalt crystals.

[0072] The centrifugation speed is 1500 rpm / min, and the drying temperature is 70℃;

[0073] The purity of GPM in the isomaltose crystals was 49.24%, the purity of GPS was 50.76%, and the moisture content was 0.79%.

[0074] Example 3:

[0075] The following is a method for crystallizing isomaltulitol and preparing it:

[0076] S1. Add Raney nickel catalyst with a solid content of 3.5% to isomaltulose liquid with a solid content of 53% and a pH of 9.23, and then add magnesium strip with a solid content of 0.8% to maintain an alkaline environment during the reaction; carry out hydrogenation reaction for 2 hours at a temperature of 130℃, a stirring speed of 800 rpm / min, and a pressure of 16 MPa to obtain hydrogenation reaction solution.

[0077] The ratio of GPM to GPS in the hydrogen reaction solution was found to be 45.01:45.43.

[0078] S2. The hydrogenation reaction solution is decolorized, filtered, ion-exchanged, and concentrated to obtain isomaltitol crystallization pretreatment material with a solid content of 55%;

[0079] The decolorization conditions are as follows: add activated carbon with a dry matter content of 0.5%, then keep it at 80°C for 30 minutes and then filter it using a plate and frame filter.

[0080] During the ion exchange process: the resin combination consists of cation resin, anion resin, and cation resin in sequence; the temperature of the feed solution entering the column during the ion exchange process is 40℃; the pH value of the feed solution exiting the column is 5.38; and the conductivity of the output column is 37.92 μS / cm.

[0081] The concentration conditions are: concentration temperature of 60℃ and vacuum degree of -0.1MPa.

[0082] S3. Add seed crystals with a solid content of 5.0‰ to the pre-crystallization material, and carry out slow evaporation, rapid evaporation and cooling crystallization to obtain isomaltitol;

[0083] The seed crystals are isomaltitol paste made by grinding anhydrous ethanol.

[0084] The slow evaporation temperature was 55℃, the pressure was -0.08MPa, the rotation speed was 150rpm / min, the concentration of the crystalline material was controlled at 55%, and the GPM crystal precipitation rate was 22%.

[0085] The rapid evaporation is carried out at a temperature of 80°C, a pressure of -0.07 MPa, and a rotation speed of 150 rpm / min, and the concentration of the crystalline material is controlled at 80%.

[0086] The final temperature of the cooling crystallization is 25℃, and the cooling rate is 0.5℃ / h;

[0087] S4. The isomalt is centrifuged and dried to obtain isomalt crystals.

[0088] The centrifugation speed is 1500 rpm / min, and the drying temperature is 70℃;

[0089] The purity of GPM in the isomaltose crystals was 48.76%, the purity of GPS was 51.24%, and the moisture content was 0.87%.

[0090] Example 4:

[0091] The following is a method for crystallizing isomaltulitol and preparing it:

[0092] S1. Add Raney nickel catalyst with a solid content of 3.3% to isomaltulose liquid with a solid content of 50% and a pH of 9.50, and then add magnesium strips with a solid content of 0.8% to maintain an alkaline environment during the reaction; carry out the hydrogenation reaction for 2.5 h at a temperature of 150℃, a stirring speed of 700 rpm / min, and a pressure of 15 MPa to obtain the hydrogenation reaction solution;

[0093] The ratio of GPM to GPS in the hydrogen reaction solution was found to be 45.36:45.76.

[0094] S2. The hydrogenation reaction solution is decolorized, filtered, ion-exchanged, and concentrated to obtain isomaltitol crystallization pretreatment material with a solid content of 52.5%;

[0095] The decolorization conditions are as follows: add activated carbon with a dry matter content of 0.5%, then keep it at 80°C for 30 minutes and then filter it using a plate and frame filter.

[0096] During the ion exchange process: the resin combination consists of cation resin, anion resin, and cation resin in sequence; the temperature of the feed solution entering the column during the ion exchange process is 40°C; the pH value of the feed solution exiting the column is 5.54; and the conductivity of the output column is 47.32 μS / cm.

[0097] The concentration conditions are: concentration temperature of 60℃ and vacuum degree of -0.1MPa.

[0098] S3. Add seed crystals with a solid content of 10.0‰ to the pre-crystallization material, and carry out slow evaporation, rapid evaporation and cooling crystallization to obtain isomaltitol;

[0099] The seed crystals are isomaltitol paste made by grinding anhydrous ethanol.

[0100] The slow evaporation was carried out at a temperature of 60°C, a pressure of -0.07 MPa, a rotation speed of 150 rpm / min, a crystallization material concentration of 52.5%, and a GPM crystal precipitation rate of 22%.

[0101] The rapid evaporation temperature is 85℃, the pressure is -0.1MPa, the rotation speed is 150rpm / min, and the concentration of the crystalline material is controlled at 75%.

[0102] The final temperature of the cooling crystallization is 30℃, and the cooling rate is 0.4℃ / h;

[0103] S4. The isomalt is centrifuged and dried to obtain isomalt crystals.

[0104] The centrifugation speed was 1500 rpm / min, and the drying temperature was 65℃;

[0105] The purity of GPM in the isomaltose crystals was 49.54%, the purity of GPS was 50.46%, and the moisture content was 0.82%.

[0106] Example 5:

[0107] The following is a method for crystallizing isomaltulitol and preparing it:

[0108] S1. Add Raney nickel catalyst with a solid content of 3.0% to isomaltulose liquid with a solid content of 55% and a pH of 9.16, and then add magnesium strips with a solid content of 0.8% to maintain an alkaline environment during the reaction; carry out hydrogenation reaction for 3 hours at a temperature of 130℃, a stirring speed of 700 rpm / min, and a pressure of 15 MPa to obtain hydrogenation reaction solution.

[0109] The ratio of GPM to GPS in the hydrogen reaction solution was measured to be 44.97:45.74.

[0110] S2. The hydrogenation reaction solution is decolorized, filtered, ion-exchanged, and concentrated to obtain isomaltitol crystallization pretreatment material with a solid content of 55%;

[0111] The decolorization conditions are as follows: add activated carbon with a dry matter content of 0.5%, then keep it at 80°C for 30 minutes and then filter it using a plate and frame filter.

[0112] During the ion exchange process: the resin combination consists of cation resin, anion resin, and cation resin in sequence; the temperature of the feed solution entering the column during the ion exchange process is 40°C; the pH value of the feed solution exiting the column is 4.98; and the conductivity of the output column is 48.53 μS / cm.

[0113] The concentration conditions are: concentration temperature of 60℃ and vacuum degree of -0.1MPa.

[0114] S3. Add seed crystals with a solid content of 8.0‰ to the pre-crystallization material, and carry out slow evaporation, rapid evaporation and cooling crystallization to obtain isomaltitol;

[0115] The seed crystals are isomaltitol paste made by grinding anhydrous ethanol.

[0116] The slow evaporation temperature was 55℃, the pressure was -0.08MPa, the rotation speed was 150rpm / min, the concentration of the crystalline material was controlled at 55%, and the GPM crystal precipitation rate was 21%.

[0117] The rapid evaporation is carried out at a temperature of 80°C, a pressure of -0.1 MPa, and a rotation speed of 150 rpm / min, and the concentration of the crystalline material is controlled at 75%.

[0118] The final temperature of the cooling crystallization is 30℃, and the cooling rate is 0.3℃ / h;

[0119] S4. The isomalt is centrifuged and dried to obtain isomalt crystals.

[0120] The centrifugation speed is 1500 rpm / min, and the drying temperature is 60℃;

[0121] The purity of GPM in the isomaltose crystals was 48.97%, the purity of GPS was 51.03%, and the moisture content was 0.86%.

[0122] Comparative Example 1:

[0123] Compared with Example 2, the concentration conditions in step S2 were 75°C, vacuum degree -0.1MPa, and solid content of the pre-crystallization material was 75.0%; the amount of seed crystals added in step S3 was 10‰, and direct cooling crystallization was carried out, with the cooling frequency being the same as in Example 2, and other conditions remaining unchanged; the GPM purity of the isomaltitol crystals obtained in step S4 was 62.72%, the GPS purity was 37.28%, and the moisture content was 0.82%.

[0124] Comparative Example 2:

[0125] Compared to Example 2, step S3 uses direct evaporation crystallization instead of segmented evaporation crystallization. The temperature is controlled at 57°C and the pressure at -0.1 MPa. During the evaporation crystallization process, a 35% concentration of isomaltitol liquid (after decolorization, filtration, and ion exchange) is added as a supplement. After the supplement, the concentration is controlled at 75%. Then, the temperature is lowered for crystallization, and the cooling frequency is the same as in Example 2, with other conditions remaining unchanged. The isomaltitol crystals obtained in step S4 have a GPM purity of 59.99%, a GPS purity of 40.01%, and a moisture content of 0.89%.

[0126] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing crystalline isomalt, characterized in that, The method comprises the following steps: S1. hydrogenating isomaltulose liquid under the action of a catalyst to obtain a hydrogenation reaction liquid; The purity of α-D-glucopyranosyl-1, 1-mannitol and α-D-glucopyranosyl-1, 6-sorbitol in the hydrogenation reaction liquid is 44-46%, respectively; S2. sequentially filtering, ion exchanging and concentrating the hydrogenation reaction liquid to obtain a crystallization precursor; The solid content of the crystallization precursor is 50-55%; S3. adding seed crystals to the crystallization precursor and then sequentially performing slow evaporation, rapid evaporation and temperature reduction crystallization to obtain isomaltitol; S4. centrifuging and drying the isomaltitol to obtain crystalline isomaltitol; The purity of α-D-glucopyranosyl-1, 1-mannitol in the crystalline isomaltitol is 48-50%, and the purity of α-D-glucopyranosyl-1, 6-sorbitol is 50-52%; the moisture content is ≤1%.

2. The method of claim 1, wherein, The solid content of the isomaltulose liquid in S1 is 50-55%, and the pH is 8.5-9.

5.

3. The method of claim 1, wherein, The catalyst is added in an amount of 3-3.5% of the solid content of the isomaltulose liquid in S1. The catalyst is Raney nickel.

4. The method of claim 1, wherein, In S1, 0.5-1.0% of magnesium strips of the solid content of the isomaltulose liquid is added before hydrogenation to maintain an alkaline environment during the reaction.

5. The method of claim 1, wherein, In S1, the hydrogenation reaction is performed at a temperature of 120-135°C for 2-3h under a pressure of 10-16MPa at a stirring speed of 500-800rpm / min.

6. The method of claim 1, wherein, In S3, the seed crystals are added in an amount of 8.0-10.0‰ of the solid content of the crystallization precursor; the seed crystals are isomaltitol paste after ethanol grinding.

7. The method of claim 1, wherein, In S3, the slow evaporation is performed at a temperature of 55-60°C under a pressure of -0.05 to -0.08MPa; the concentration of the crystallization material after slow evaporation is 50-55%; and the crystal precipitation amount is 20-22%.

8. The method of claim 1, wherein, In S3, the rapid evaporation is performed at a temperature of 75-85°C under a pressure of -0.07 to -0.1MPa; the concentration of the crystallization material after rapid evaporation is 75-80%.

9. The method of claim 1, wherein, In S3, the final temperature of the temperature reduction crystallization is 25-30°C, and the temperature reduction rate is 0.2-0.5°C / h.