Preparation method of isomaltulose crystal

Abstract

The invention relates to a preparation method of an isomaltulose crystal. The preparation method of the isomaltulose crystal comprises the following steps: (1) stirring and mixing a sucrose solution and sucrose isomerase; (2) adding an isomaltulose seed crystal, feeding cane sugar, and keeping stirring in the whole process; and (3) performing centrifugal separation to obtain isomaltulose crystals. According to the method, sucrose isomerism is carried out by adopting sucrose isomerase to obtain isomaltulose, isomaltulose crystal seeds are added in the conversion process, meanwhile, the sucrose is fed, the conversion and crystallization processes are carried out at the same time, isomaltulose gradually generated through conversion grows on the crystal seeds at the same time, and the obtained crystals are regular in crystal form, high in purity and uniform in particle size.

Description

Technical Field

[0001] The invention relates to the field of sugar preparation, and in particular to a method for preparing isomaltulose crystals. Background Art

[0002] Isomaltulose, namely 6-O-α-D-pyranosyl-D-fructose, also known as palatinose, exists in small amounts in natural honey, with a content of up to 1%. As an isomer of sucrose, isomaltulose has similar physical properties and taste to sucrose, and has anti-caries and prebiotic effects. It can also improve brain function, improve human memory, inhibit fat accumulation and prevent obesity. It does not cause blood sugar and insulin to rise. It is an ideal substitute sweetener for sucrose. It is also an internationally recognized safe substitute for sucrose. Therefore, it is widely used in candy, chocolate, baked goods, dairy products and special population foods, and has a good application prospect in the food industry. With the improvement of social economy and the development of health awareness, people are paying more and more attention to high-quality healthy life, and low-calorie and zero-sugar food and beverages are gradually becoming important consumer products. In addition, health problems such as obesity, high blood sugar, and dental caries have also increased consumers' consumption tendency for low-sugar foods. Isomaltulose has received widespread attention as a functional sweetener to replace sucrose.

[0003] At present, the preparation methods of isomaltulose mainly include chemical conversion method and biological conversion method. Due to the problems of high energy consumption and strong pollution in the chemical conversion method, and the immature technology, the preparation of isomaltulose becomes very difficult. Therefore, biological conversion methods including enzyme conversion method and microbial conversion method have been widely used at home and abroad. The biological conversion method is based on the sucrose isomerization method to convert isomaltulose, that is, the α-1,2-glycosidic bond between glucose and fructose in the sucrose molecule isomerized into α-1,6-glycosidic bond to form isomaltulose and α-1,1-glycosidic bond to form trehalulose. For example, CN105907818A discloses a process for producing isomaltulose, which uses Serratia as a strain to culture bacterial cells, adds a certain amount of physiological saline to the obtained bacterial cells to prepare a suspension, adds a certain concentration of sucrose solution to the suspension, and places the mixture in a desktop constant temperature shaker at a speed of 200 r / min and a temperature of 30°C for reaction. Isomaltulose is obtained after a period of reaction. This method uses a microorganism that can synthesize sucrose isomerase as a catalyst for production, involves microbial cultivation, and has problems such as high operating requirements, long cycle, and complex post-processing process.

[0004] In summary, how to provide a method for preparing isomaltulose crystals efficiently by directly utilizing sucrose isomerase has become one of the problems to be solved urgently in the art. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing isomaltulose crystals. The present invention adopts sucrose isomerase to isomerize sucrose to obtain isomaltulose, and isomaltulose seed crystals are added during the conversion process, and sucrose is added at the same time. The conversion and crystallization processes are carried out simultaneously, and the isomaltulose gradually generated by the conversion grows on the seed crystals at the same time.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing isomaltulose crystals, the method for preparing isomaltulose crystals comprising the following steps:

[0008] (1) stirring and mixing a sucrose solution and sucrose isomerase;

[0009] (2) adding isomaltulose seed crystals and sucrose in a continuous stream, while maintaining stirring throughout the process;

[0010] (3) After centrifugation, isomaltulose crystals are obtained.

[0011] The present invention adopts sucrose isomerase to isomerize sucrose to obtain isomaltulose, adds isomaltulose seed during the conversion process, and simultaneously streams sucrose, and the conversion and crystallization process are carried out simultaneously, and the isomaltulose gradually generated by the conversion grows on the seed at the same time, and the obtained crystal has a regular crystal form, high purity, and uniform particle size. The conversion and crystallization process are carried out simultaneously, and the conversion balance is promoted to tilt toward isomaltulose, and the product conversion rate is higher. As the conversion process proceeds, sucrose is streamed to achieve higher production efficiency and yield, and the purity of the crystal can be guaranteed while saving energy to a great extent. After separating the crystals, the mother liquor can be put into sucrose to carry out the next round of conversion process, so as to realize the recycling of the enzyme and a higher product yield.

[0012] Preferably, the mass fraction of sucrose in the sucrose solution in step (1) is 30% to 75% (for example, it can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%, etc.).

[0013] Preferably, the solvent of the sucrose solution in step (1) comprises water.

[0014] Preferably, the ratio of sucrose to sucrose isomerase in the sucrose solution in step (1) is 1g: (200-700)U.

[0015] The specific value of the above (200~700)U can be 200U, 250U, 300U, 350U, 400U, 450U, 500U, 550U, 600U, 650U or 700U, etc.

[0016] Preferably, the stirring and mixing time in step (1) is 10 to 48 hours (for example, it can be 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours or 48 hours, etc.).

[0017] Preferably, the stirring and mixing temperature in step (1) is 18-60°C (for example, it can be 18°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, etc.).

[0018] Preferably, the stirring speed of the stirring and mixing in step (1) is 10 to 300 rpm (for example, it can be 10 rpm, 20 rpm, 50 rpm, 70 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm or 300 rpm, etc.).

[0019] Preferably, the isomaltulose seed crystals in step (2) are 80-200 mesh (for example, 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 140 mesh, 150 mesh, 160 mesh, 170 mesh, 180 mesh, 190 mesh or 200 mesh, etc.).

[0020] Preferably, the mass ratio of the isomaltulose seed crystals in step (2) to the sucrose solution in step (1) is 1:(200-10000).

[0021] The specific values ​​of the above (200-10000) can be 200, 500, 700, 1000, 1500, 2000, 5000, 7000 or 10000, etc.

[0022] Preferably, the time of the addition in step (2) is 0 to 96 h (for example, 0 h, 10 h, 20 h, 30 h, 40 h, 50 h, 60 h, 70 h, 80 h, 90 h or 96 h, etc.), preferably 15 to 55 h (for example, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h or 55 h, etc.).

[0023] Preferably, the rate of addition in step (2) is 0.1% to 20% (for example, 0.1%, 0.5%, 1%, 2%, 5%, 7%, 10%, 15% or 20%, etc.) of the mass of the sucrose solution added in step (1) per hour, preferably 0.5% to 2% (for example, 0.5%, 0.7%, 0.9%, 1%, 1.1%, 1.3%, 1.5%, 1.7% or 2%, etc.).

[0024] Preferably, the stirring temperature in step (2) is 18-60°C (for example, it may be 18°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, etc.).

[0025] Preferably, the stirring speed of the stirring in step (2) is 10 to 300 rpm (for example, it can be 10 rpm, 20 rpm, 50 rpm, 70 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm or 300 rpm, etc.).

[0026] Preferably, after the sucrose is added in step (2), stirring is continued until the sucrose conversion rate is ≥ 98% (for example, it may be 98%, 98.2%, 98.5%, 99%, 99.5% or 100%, etc.), and then step (2) is terminated.

[0027] In the present invention, the sucrose conversion rate ≥ 98% means that 98% or more of the sucrose is converted into isomaltulose or impurities, and the sucrose includes the initial reactant sucrose solution and the sucrose solid added in step (2) to improve the product conversion rate.

[0028] Preferably, the temperature of the continued stirring is 18-60°C (for example, it can be 18°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, etc.), and the rotation speed is 10-300rpm (for example, it can be 10rpm, 20rpm, 50rpm, 70rpm, 100rpm, 150rpm, 200rpm, 250rpm or 300rpm, etc.).

[0029] Preferably, the slurry obtained after step (2) contains isomaltulose, trehalulose, glucose, fructose and sucrose, wherein the mass percentage of sucrose is ≤2% (for example, it may be 2%, 1.5%, 1% or 0.5%, etc.).

[0030] The crystal slurry obtained by the invention contains isomaltulose crystals and a mother liquor containing enzymes and other impurities. The mother liquor has a high osmotic pressure and can avoid the risk of bacterial contamination during the conversion process.

[0031] Preferably, the centrifugal rotation speed in step (3) is 500-1500 rpm (for example, it can be 500 rpm, 700 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1300 rpm or 1500 rpm, etc.).

[0032] Preferably, the centrifugation time in step (3) is 10 to 20 min (for example, it may be 10 min, 12 min, 14 min, 15 min, 16 min, 18 min or 20 min, etc.).

[0033] Preferably, after obtaining isomaltulose crystals after centrifugal separation in step (3), the method further comprises any one of the following steps:

[0034] (I) drying the isomaltulose crystals at 65-75° C. (e.g., 65° C., 67° C., 69° C., 70° C., 71° C., 73° C., or 75° C.) for 1.5-2.5 h (e.g., 1.5 h, 1.7 h, 1.9 h, 2 h, 2.1 h, 2.3 h, or 2.5 h);

[0035] (II) adding water to dissolve the isomaltulose crystals at 80-90° C. (e.g., 80° C., 81° C., 82° C., 83° C., 84° C., 85° C., 86° C., 87° C., 88° C., 89° C., or 90° C., etc.) until the mass fraction of isomaltulose in the solution is 60%-80% (e.g., 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, or 80%, etc.), stirring at a speed of 10-20 rpm (e.g., 10 rpm, 12 rpm, 14 rpm, 15 rpm, 16 rpm, 18 rpm, or 20 rpm), and heating at a speed of 4-6° C. / h (e.g., The mixture is cooled to 15-25°C (for example, 15°C, 17°C, 19°C, 20°C, 21°C, 23°C or 25°C) at a cooling rate of 4°C / h, 4.2°C / h, 4.4°C / h, 4.6°C / h, 4.8°C / h, 5°C / h, 5.2°C / h, 5.4°C / h, 5.6°C / h, 5.8°C / h or 6°C / h, etc.), centrifuged to obtain crystals, and dried at 65-75°C (for example, 65°C, 67°C, 69°C, 70°C, 71°C, 73°C or 75°C, etc.) for 1.5-2.5h (for example, 1.5h, 1.7h, 1.9h, 2h, 2.1h, 2.3h or 2.5h, etc.).

[0036] Preferably, the mother liquor obtained after the centrifugal separation in step (3) is recycled to the next round of conversion.

[0037] Preferably, the method for preparing isomaltulose crystals comprises the following steps:

[0038] (1) A sucrose aqueous solution containing 30% to 75% by mass of sucrose is stirred and mixed with sucrose isomerase, wherein the ratio of sucrose to sucrose isomerase in the sucrose aqueous solution is 1 g: (200 to 700) U, the stirring time is 10 to 48 h, the temperature is 18 to 60° C., and the stirring speed is 10 to 300 rpm;

[0039] (2) adding 80-200 mesh isomaltulose seed crystals, the mass ratio of the isomaltulose seed crystals to the sucrose solution in step (1) being 1:(200-10000), adding sucrose in a continuous manner, the addition rate being 0.1%-20% of the mass of the sucrose solution in step (1) per hour, the continuous addition being 0-96 hours, the whole process being maintained at 18-60° C. and stirring at 10-300 rpm, and the stirring being continued until the sucrose conversion rate is ≥98%, and the stirring being terminated, the temperature for continued stirring being 18-60° C. and the rotation speed being 10-300 rpm;

[0040] (3) Centrifuging at 500-1500 rpm for 10-20 min to separate isomaltulose crystals and mother liquor, recycling the mother liquor to the next round of conversion, and taking the isomaltulose crystals to perform any one of the following steps:

[0041] (I) drying the isomaltulose crystals at 65-75° C. for 1.5-2.5 hours;

[0042] (II) adding water to dissolve the isomaltulose crystals at 80-90° C. until the mass fraction of isomaltulose in the solution is 60%-80%, stirring at a speed of 10-20 rpm, cooling to 15-25° C. at a cooling rate of 4-6° C. / h, centrifuging to obtain crystals, and drying at 65-75° C. for 1.5-2.5 h.

[0043] Other specific point values ​​within the above numerical ranges can be selected and will not be described in detail here.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention adopts sucrose isomerase to isomerize sucrose to obtain isomaltulose, adds isomaltulose seed during the conversion process, and simultaneously streams sucrose, and the conversion and crystallization process are carried out simultaneously, and the isomaltulose gradually generated by the conversion grows on the seed at the same time, and the obtained crystal has a regular crystal form, high purity, and uniform particle size. The conversion and crystallization process are carried out simultaneously, and the conversion balance is promoted to tilt toward isomaltulose, and the product conversion rate is higher. As the conversion process proceeds, sucrose is streamed to achieve higher production efficiency and yield, and the purity of the crystal can be guaranteed while saving energy to a great extent. After separating the crystals, the mother liquor can be put into sucrose to carry out the next round of conversion process, so as to realize the recycling of the enzyme and a higher product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is an enlarged view of the crystal structure of isomaltulose prepared in Example 1. DETAILED DESCRIPTION

[0047] To further illustrate the technical means and effects of the present invention, the present invention is further described below in conjunction with the embodiments and drawings. It should be understood that the specific implementation methods described herein are only used to explain the present invention, rather than to limit the present invention.

[0048] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0049] Example 1

[0050] This embodiment provides a method for preparing isomaltulose crystals, comprising the following steps:

[0051] (1) A sucrose aqueous solution containing 65% by mass of sucrose is stirred and mixed with sucrose isomerase, wherein the ratio of sucrose to sucrose isomerase in the sucrose aqueous solution is 1 g:450 U.

[0052] (2) Stir the mixture at 40°C and 50 rpm for 20 h.

[0053] (3) Add 150 mesh isomaltulose seed crystals, and the mass ratio of the added seed crystals to the initial sucrose aqueous solution is 1:2000.

[0054] (4) Sucrose was added at a rate of 1% of the initial mass of the sucrose solution per hour for 42 hours, and stirring was maintained at 40°C and 50 rpm throughout the process.

[0055] (5) Continue stirring at 40°C and 50 rpm until the conversion rate reaches 98.5%.

[0056] (6) The obtained slurry was centrifuged at 1000 rpm for 15 min to separate the isomaltulose crystals and the mother liquor. The mother liquor was reused in the next round of conversion. The crystals were dissolved in water at 85°C to obtain a solution with a mass fraction of 78% isomaltulose. The solution was stirred at 15 rpm and gradually cooled from 85°C to 20°C at a cooling rate of 5°C / h. The obtained slurry was centrifuged to obtain crystals, which were dried at 70°C for 2 h. The purity of the obtained isomaltulose crystals was 99.8%. The enlarged structure of the isomaltulose crystal is shown in the figure below. Figure 1 shown.

[0057] Example 2

[0058] This embodiment provides a method for preparing isomaltulose crystals, comprising the following steps:

[0059] (1) A sucrose aqueous solution containing 30% by mass of sucrose is stirred and mixed with sucrose isomerase, wherein the ratio of sucrose to sucrose isomerase in the sucrose aqueous solution is 1 g:700 U.

[0060] (2) Stir the mixture at 18°C ​​and 300 rpm for 10 h.

[0061] (3) adding 80-mesh isomaltulose seed crystals, wherein the mass ratio of the added seed crystals to the initial sucrose aqueous solution is 1:10,000.

[0062] (4) Sucrose was added at a rate of 2% of the initial mass of the sucrose solution per hour for 15 h, and stirring was maintained at 18° C. and 300 rpm throughout the process.

[0063] (5) Continue stirring at 18°C ​​and 300 rpm until the conversion rate reaches 99.5%.

[0064] (6) The obtained slurry was centrifuged at 500 rpm for 20 min to separate isomaltulose crystals and mother liquor. The mother liquor was reused in the next round of conversion. The obtained crystals were dried at 70° C. for 2 h. The purity of the crystals was 99.2%.

[0065] Example 3

[0066] This embodiment provides a method for preparing isomaltulose crystals, comprising the following steps:

[0067] (1) A sucrose aqueous solution containing 75% by mass of sucrose is stirred and mixed with sucrose isomerase, wherein the ratio of sucrose to sucrose isomerase in the sucrose aqueous solution is 1 g:200 U.

[0068] (2) Place at 60°C and stir at 10 rpm for 48 h.

[0069] (3) Add 200-mesh isomaltulose seed crystals, and the mass ratio of the added seed crystals to the initial sucrose aqueous solution is 1:200.

[0070] (4) Sucrose was added at a rate of 0.5% of the initial mass of the sucrose solution per hour for 55 h, and stirring was maintained at 60° C. and 10 rpm throughout the process.

[0071] (5) Continue stirring at 60°C and 10 rpm until the conversion rate reaches 98%.

[0072] (6) The obtained slurry was centrifuged at 1500 rpm for 10 min to separate isomaltulose crystals and mother liquor. The mother liquor was recycled to the next round of conversion. The crystals were dissolved in water at 90°C to obtain a solution with a mass fraction of 76% isomaltulose. The solution was stirred at 15 rpm and gradually cooled from 90°C to 15°C at a cooling rate of 6°C / h. The obtained slurry was centrifuged to obtain crystals, which were dried at 65°C for 2.5 h. The purity of the obtained isomaltulose crystals was 99.0%.

[0073] Example 4

[0074] This embodiment provides a method for preparing isomaltulose crystals, which is different from Embodiment 1 only in that in step (1), the ratio of sucrose to sucrose isomerase in the sucrose aqueous solution is 1 g:150 U.

[0075] Example 5

[0076] This embodiment provides a method for preparing isomaltulose crystals, which is different from Embodiment 1 only in that in step (1), the ratio of sucrose to sucrose isomerase in the sucrose aqueous solution is 1 g:750 U.

[0077] Example 6

[0078] This embodiment provides a method for preparing isomaltulose crystals, which is different from Embodiment 1 only in that the stirring reaction time in step (2) is 8 hours.

[0079] Example 7

[0080] This embodiment provides a method for preparing isomaltulose crystals, which is different from Embodiment 1 only in that the stirring reaction time in step (2) is 50 hours.

[0081] Example 8

[0082] This embodiment provides a method for preparing isomaltulose crystals, which is different from Embodiment 1 only in that the mass ratio of the isomaltulose seed crystals added in step (3) to the mass ratio of the initial sucrose aqueous solution is 1:150.

[0083] Example 9

[0084] This embodiment provides a method for preparing isomaltulose crystals, which is different from Embodiment 1 only in that the mass ratio of the isomaltulose seed crystals added in step (3) to the mass ratio of the initial sucrose aqueous solution is 1:10500.

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing isomaltulose crystals, which differs from Example 1 only in that step (4) is not performed.

[0087] Test Example 1

[0088] This test example uses steps (1)-(5) in the preparation method of isomaltulose crystals provided in Examples 1-9 and Comparative Example 1 to obtain a crystal slurry containing isomaltulose crystals and mother liquor, and the mass percentage of each component in the crystal slurry is detected by the liquid chromatography detection method in GB1886.182-2016. The detection method includes the following steps: 1. The crystal slurry is mixed evenly, and after being dissolved and diluted with an appropriate amount of water, it is used as a sample solution to be detected; 2. Under the conditions specified in the chromatography, the sample solution is sampled and tested, and the components in the crystal slurry are qualitatively analyzed according to the peak time of the standard solution. The results are shown in Table 1. Among them, Example 4, Example 6 and Comparative Example 1 still cannot reach a conversion rate of 98.5% by extending the time of step (5). Table 1 records the proportion of each component when the sucrose conversion rate of Example 4, Example 6 and Comparative Example 1 is the maximum.

[0089] Table 1

[0090]

[0091]

[0092] From Table 1, we can conclude that:

[0093] (1) By comparing Example 1 with Example 4 and Example 5, it can be seen that when the proportion of sucrose isomerase added is small, the conversion rate of more than 98% cannot be achieved; when the proportion of isomaltulose is low and the proportion of enzyme added is large, the content of isomaltulose is not significantly increased.

[0094] (2) By comparing Example 1 with Example 6 and Example 7, it can be seen that the enzymatic reaction time is too short to reach a conversion rate of more than 98%, and the proportion of isomaltulose in the slurry is low; after reaching saturation, extending the enzymatic reaction time does not significantly improve the conversion rate of sucrose to isomaltulose.

[0095] (3) Comparing Example 1 with Example 8 and Example 9, it can be seen that the amount of isomaltulose crystals added has no significant effect on the yield of isomaltulose.

[0096] (4) Comparing Example 1 with Comparative Example 1, it can be seen that during the sucrose conversion process, the flow addition of sucrose can promote the conversion balance to tilt toward isomaltulose, thereby improving the product conversion rate.

[0097] Test Example 2

[0098] This test example used steps (1)-(5) of the method for preparing isomaltulose crystals provided in Examples 1-3 and 8-9 to obtain a slurry containing isomaltulose crystals and mother liquor. The slurry was centrifuged at 1000 rpm for 15 min to separate the isomaltulose crystals. The particle size and mass ratio of the obtained crystals were measured. The results are shown in Table 2.

[0099] Table 2

[0100]

[0101]

[0102] Comparing Example 1 with Example 8 and Example 9 in Table 2, it can be seen that adding too much isomaltulose seed crystals will result in a smaller crystal particle size, increase the difficulty of centrifugal separation, and reduce the crystal recovery rate; adding too little isomaltulose seed crystals will result in a larger crystal particle size, reduce the target crystal content, and reduce the yield of finished isomaltulose.

[0103] In summary, the present invention provides a method for preparing isomaltulose crystals, wherein sucrose isomerase is used to isomerize sucrose to obtain isomaltulose, isomaltulose seed crystals are added during the conversion process, and sucrose is added at the same time, the conversion and crystallization processes are carried out simultaneously, and the isomaltulose gradually generated by the conversion grows on the seed crystals at the same time, and the obtained crystals have regular crystal shape, high purity and uniform particle size.

[0104] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing isomaltulose crystals, characterized in that: The preparation method of isomaltulose crystals comprises the following steps: (1) stirring and mixing a sucrose solution and sucrose isomerase; (2) adding isomaltulose seed crystals and sucrose in a continuous stream, while maintaining stirring throughout the process; (3) After centrifugation, isomaltulose crystals are obtained.

2. The method for preparing isomaltulose crystals according to claim 1, characterized in that: The mass fraction of sucrose in the sucrose solution in step (1) is 30% to 75%; Preferably, the solvent of the sucrose solution in step (1) comprises water; Preferably, the ratio of sucrose to sucrose isomerase in the sucrose solution in step (1) is 1g: (200-700)U.

3. The method for preparing isomaltulose crystals according to claim 1 or 2, characterized in that: The stirring and mixing time in step (1) is 10 to 48 hours; Preferably, the stirring and mixing temperature in step (1) is 18 to 60° C. Preferably, the stirring speed of the stirring and mixing in step (1) is 10 to 300 rpm.

4. The method for preparing isomaltulose crystals according to any one of claims 1 to 3, characterized in that: The isomaltulose seed crystals in step (2) are 80-200 mesh; Preferably, the mass ratio of the isomaltulose seed crystals in step (2) to the sucrose solution in step (1) is 1:(200-10000).

5. The method for preparing isomaltulose crystals according to any one of claims 1 to 4, characterized in that: The time of the addition in step (2) is 0 to 96 hours, preferably 15 to 55 hours; Preferably, the rate of the flow addition in step (2) is 0.1% to 20% of the mass of the sucrose solution in step (1) per hour, preferably 0.5% to 2%.

6. The method for preparing isomaltulose crystals according to any one of claims 1 to 5, characterized in that: The stirring temperature in step (2) is 18 to 60° C. Preferably, the stirring speed of the stirring in step (2) is 10 to 300 rpm; Preferably, after the sucrose is added in step (2), stirring is continued until the sucrose conversion rate is ≥ 98% and then step (2) is terminated; Preferably, the temperature of the continued stirring is 18-60° C., and the rotation speed is 10-300 rpm.

7. The method for preparing isomaltulose crystals according to any one of claims 1 to 6, characterized in that: The crystal slurry obtained after step (2) contains isomaltulose, trehalulose, glucose, fructose and sucrose, wherein the mass percentage of sucrose is ≤2%.

8. The method for preparing isomaltulose crystals according to any one of claims 1 to 7, characterized in that: The centrifugal speed in step (3) is 500-1500 rpm; Preferably, the centrifugation time in step (3) is 10 to 20 minutes.

9. The method for preparing isomaltulose crystals according to any one of claims 1 to 8, characterized in that: After obtaining isomaltulose crystals after centrifugal separation in step (3), the method further comprises any one of the following steps: (I) drying the isomaltulose crystals at 65-75° C. for 1.5-2.5 hours; (II) adding water to dissolve the isomaltulose crystals at 80-90° C. until the mass fraction of isomaltulose in the solution is 60%-80%, stirring at a speed of 10-20 rpm, cooling to 15-25° C. at a cooling rate of 4-6° C. / h, centrifuging to obtain crystals, and drying at 65-75° C. for 1.5-2.5 h; Preferably, the mother liquor obtained after the centrifugal separation in step (3) is recycled to the next round of conversion.

10. The method for preparing isomaltulose crystals according to any one of claims 1 to 9, characterized in that: The preparation method of isomaltulose crystals comprises the following steps: (1) A sucrose aqueous solution containing 30% to 75% by mass of sucrose is stirred and mixed with sucrose isomerase, wherein the ratio of sucrose to sucrose isomerase in the sucrose aqueous solution is 1 g: (200 to 700) U, the stirring time is 10 to 48 h, the temperature is 18 to 60° C., and the stirring speed is 10 to 300 rpm; (2) adding 80-200 mesh isomaltulose seed crystals, the mass ratio of the isomaltulose seed crystals to the sucrose solution in step (1) being 1:(200-10000), adding sucrose in a continuous manner, the addition rate being 0.1%-20% of the mass of the sucrose solution in step (1) per hour, the continuous addition being 0-96 hours, the whole process being maintained at 18-60° C. and stirring at 10-300 rpm, and the stirring being continued until the sucrose conversion rate is ≥98%, and the stirring being terminated, the temperature for continued stirring being 18-60° C. and the rotation speed being 10-300 rpm; (3) Centrifuging at 500-1500 rpm for 10-20 min to separate isomaltulose crystals and mother liquor, recycling the mother liquor to the next round of conversion, and taking the isomaltulose crystals to perform any one of the following steps: (I) drying the isomaltulose crystals at 65-75° C. for 1.5-2.5 hours; (II) adding water to dissolve the isomaltulose crystals at 80-90° C. until the mass fraction of isomaltulose in the solution is 60%-80%, stirring at a speed of 10-20 rpm, cooling to 15-25° C. at a cooling rate of 4-6° C. / h, centrifuging to obtain crystals, and drying at 65-75° C. for 1.5-2.5 h.

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