D-PSICOSE CRYSTAL AND PREPARATION METHOD THEREOF

Abstract

The invention provides a D-psicose crystal and a preparation method thereof. The method comprises: adding a seed crystal to a D-psicose solution and stirring uniformly, subjecting the solution to crystallization by gradient cooling and constant-temperature crystallization alternately at 50-30° C., stopping the crystallization until the temperature of the solution is 30° C., separating the crystal by centrifugation, washing and drying, to obtain a D-psicose crystal. Rather than evaporative crystallization, organic solvent-assisted crystallization and ultrasonication, controllable crystallization by gradient cooling, constant-temperature crystallization, and other technical means are employed. Thus, the invention has low requirements for equipment, simple process, low energy consumption, and low preparation cost, and thus particularly suitable for large-scale industrial production and processing. The purity of the D-psicose crystal obtained is ≥98.5%, 80% by weight or more of the crystal has a grain size in the range of 20-40 meshes, and the yield per crystallization is ≥70%.

Claims

1. A method for preparing a D-psicose crystal, comprising: adding a seed crystal to a D-psicose solution and stirring uniformly, subjecting the resulting solution to crystallization by gradient cooling crystallization and constant-temperature crystallization alternately over a range of temperature from 50 to 30° C., stopping the crystallization until the temperature of the solution is 30° C., separating the crystal by centrifugation, washing with water, and drying, to obtain a D-psicose crystal.

2. The method for preparing a D-psicose according to claim 1, wherein the D-psicose solution has a concentration in percent by weight of ≥83% (w/w), the purity of D-psicose is >95% (w/w), and the solution is maintained at a temperature of 50-60° C.

3. The method for preparing a D-psicose according to claim 1, wherein the seed crystal is D-psicose seed crystal, having a grain size ranging from 80 to 100 meshes, and added in an amount of 0.01-1% on dry weight basis of the D-psicose solution.

4. The method for preparing a D-psicose according to claim 1, wherein the solution is stirred for 20-30 s at a speed of 150-200 rpm after the seed crystal is added.

5. The method for preparing a D-psicose according to claim 1, wherein the gradient cooling crystallization comprises: stirring the D-psicose solution added with the seed crystal at a temperature of 50° C., with gradient cooling at a rate of 0.02-0.2 ° C./h.

6. The method for preparing a D-psicose according to claim 1, wherein the constant-temperature crystallization comprises : stirring the D-psicose solution for 8-15 h respectively at a constant temperature that is any temperature from the range of 47-45° C., the range of 43-42° C., the range of 41-40° C. and the range of 39-38° C.

7. The method for preparing a D-psicose according to claim 1, wherein the separation by centrifugation comprises centrifugation for 20-30 min at 4000-5000 rpm; and the drying comprises drying in a fluidized bed at 40-50° C. until the moisture content is less than 0.05%.

8. The method for preparing a D-psicose according to claim 1, wherein during preparation process, the yield of D-psicose crystal per crystallization is ≥70%.

9. A D-psicose crystal prepared by the method according to claim 1.

10. The D-psicose crystal according to claim 9, wherein the purity of the D-psicose crystal is ≥98.5%, and 80% by weight or more of the crystal has a grain size in the range of 20-40 meshes.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Unless otherwise specified, the techniques used in the example are conventional techniques familiar to those skilled in the art, and the raw materials used are all commercially available products.

[0026] Unless otherwise indicated, Various raw materials, reagents, instruments and equipment used in the present invention are all commercially available or can be prepared by existing methods.

[0027] In the present invention, the crystallization apparatus, stirrer, fluidized bed and drying device are all devices available to technicians in the art, as long as they can meet the specified conditions, and there is no need to change or adjust the devices.

[0028] In the present invention, the yield is calculated by the formula: Yield (%)=(weight of dried D-psicose crystal/weight of D-psicose in D-psicose solution before crystallization)×100%.

[0029] In the present invention, the rate of crystal grain size distribution is calculated by the mass fraction of the crystal, that is, the percentage of the crystal mass within a certain size range relative to the total crystal mass.

Example 1

[0030] A method for preparing D-psicose crystal comprises specifically the following steps:

[0031] D-psicose seed crystal was added to a D-psicose solution, where the D-psicose solution had a concentration of 83 wt %, the purity of D-psicose was 98.0%, the grain size of the D-psicose seed crystal was 80 meshes, and the D-psicose seed crystal was added in an amount of 0.1% on dry weight basis of the D-psicose solution. After the seed crystal was added, the solution was stirred at 150 rpm for 20 s.

[0032] The temperature of the D-psicose solution was lowered from 50° C. to 45.2° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 11 h at 45.2° C.

[0033] After constant-temperature crystallization at 45.2° C., the temperature was lowered to 42° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 42° C.

[0034] After constant-temperature crystallization at 42° C., the temperature was lowered to 40.6° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 40.6° C.

[0035] After constant-temperature crystallization at 40.6° C., the temperature was lowered to 38.4° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 38.4° C.

[0036] After constant-temperature crystallization at 38.4° C., the temperature was lowered to 30° C. at a rate of 0.2° C./h, and then the crystallization was stopped. The stirring speed was controlled at 50 rpm during the whole crystallization process.

[0037] After crystallization, the solution was centrifuged at 4000 rpm for 20 min. The crystal was collected, washed 2-3 times with pure water, and dried in a fluidized bed at 45° C. to a moisture content of less than 0.05%. The crystal was sieved, and the purity of the product was detected by HPLC. A D-psicose product with a purity of 99.8% (w/w) and 82% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization process was 72%. Detailed grain size distribution rates are shown in Table 1.

TABLE-US-00001 TABLE 1 Grain size Distribution rate (%) Less than 20 meshes 3.86 20-40 meshes 82 40-60 meshes 8.21 Greater than 60 meshes 5.93

Example 2

[0038] A method for preparing D-psicose crystal comprises specifically the following steps:

[0039] D-psicose seed crystal was added to a D-psicose solution, where the D-psicose solution had a concentration of 84 wt %, the purity of D-psicose was 98.0%, the grain size of the D-psicose seed crystal was 100 meshes, and the D-psicose seed crystal was added in an amount of 0.3% on dry weight basis of the D-psicose solution. After the seed crystal was added, the solution was stirred at 150 rpm for 20 s.

[0040] The temperature of the D-psicose solution was lowered from 50° C. to 45.9° C. at a rate of 0.1° C./h, followed by constant-temperature crystallization for 12 h at 45.9° C.

[0041] After constant-temperature crystallization at 45.9° C., the temperature was lowered to 42° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 42° C.

[0042] After constant-temperature crystallization at 42° C., the temperature was lowered to 40.6° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 40.6° C.

[0043] After constant-temperature crystallization at 40.6° C., the temperature was lowered to 38.4° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 38.4° C.

[0044] After constant-temperature crystallization at 38.4° C., the temperature was lowered to 30° C. at a rate of 0.2° C./h, and then the crystallization was stopped. The stirring speed was controlled at 50 rpm during the whole crystallization process.

[0045] After crystallization, the solution was centrifuged at 4000 rpm for 20 min. The crystal was collected, washed 2-3 times with pure water, and dried in a fluidized bed at 45° C. to a moisture content of less than 0.05%. The crystal was sieved, and the purity of the product was detected by HPLC. A D-psicose product with a purity of 99.4% (w/w) and 80.5% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 71.2%. Detailed grain size distribution rates are shown in Table 2.

TABLE-US-00002 TABLE 2 Grain size Distribution rate (%) Less than 20 meshes 3.45 20-40 meshes 80.5 40-60 meshes 8.2 Greater than 60 meshes 7.85

Example 3

[0046] A method for preparing D-psicose crystal comprises specifically the following steps:

[0047] D-psicose seed crystal was added to a D-psicose solution, where the D-psicose solution had a concentration of 84 wt %, the purity of D-psicose was 98.0%, the grain size of the D-psicose seed crystal was 80 meshes, and the D-psicose seed crystal was added in an amount of 0.1% on dry weight basis of the D-psicose solution. After the seed crystal was added, the solution was stirred at 150 rpm for 20 s.

[0048] The temperature of the D-psicose solution was lowered from 50° C. to 45.2° C. at a rate of 0.2° C./h followed by constant-temperature crystallization for 11 h at 45.2° C.

[0049] After constant-temperature crystallization at 45.2° C., the temperature was lowered to 42.4° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 10 h at 42.4° C.

[0050] After constant-temperature crystallization at 42.4° C., the temperature was lowered to 40.6° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 40.6° C.

[0051] After constant-temperature crystallization at 40.6° C., the temperature was lowered to 38.4° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 38.4° C.

[0052] After constant-temperature crystallization at 38.4° C., the temperature was lowered to 30° C. at a rate of 0.2° C./h, and then the crystallization was stopped. The stirring speed was controlled at 50 rpm during the whole crystallization process.

[0053] After crystallization, the solution was centrifuged at 4000 rpm for 20 min. The crystal was collected, washed 2-3 times with pure water, and dried in a fluidized bed at 45° C. to a moisture content of less than 0.05%. The crystal was sieved, and the purity of the product was detected by HPLC. A D-psicose product with a purity of 99.6% (w/w) and 81.3% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 70.9%. Detailed grain size distribution rates are shown in Table 3.

TABLE-US-00003 TABLE 3 Grain size Distribution rate (%) Less than 20 meshes 3.82 20-40 meshes 81.3 40-60 meshes 8.03 Greater than 60 meshes 6.85

Example 4

[0054] A method for preparing D-psicose crystal comprises specifically the following steps:

[0055] D-psicose seed crystal was added to a D-psicose solution, where the D-psicose solution had a concentration of 84 wt %, the purity of D-psicose was 98.0%, the grain size of the D-psicose seed crystal was 80 meshes, and the D-psicose seed crystal was added in an amount of 0.1% on dry weight basis of the D-psicose solution. After the seed crystal was added, the solution was stirred at 150 rpm for 20 s.

[0056] The temperature of the D-psicose solution was lowered from 50° C. to 45.2° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 11 h at 45.2° C.

[0057] After constant-temperature crystallization at 45.2° C., the temperature was lowered to 42° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 42° C.

[0058] After constant-temperature crystallization at 42° C., the temperature was lowered to 40.2° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 40.2° C.

[0059] After constant-temperature crystallization at 40.2° C., the temperature was lowered to 38.4° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 38.4° C.

[0060] After constant-temperature crystallization at 38.4° C., the temperature was lowered to 30° C. at a rate of 0.2° C./h, and then the crystallization was stopped. The stirring speed was controlled at 50 rpm during the whole process.

[0061] After crystallization, the solution was centrifuged at 4000 rpm for 20 min. The crystal was collected, washed 2-3 times with pure water, and dried in a fluidized bed at 45° C. to a moisture content of less than 0.05%. The crystal was sieved, and the purity of the product was detected by HPLC. A D-psicose product with a purity of 99.8% (w/w) and 80.6% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 71%. Detailed grain size distribution rates are shown in Table 4.

TABLE-US-00004 TABLE 4 Grain size Distribution rate (%) Less than 20 meshes 3.03 20-40 meshes 80.6 40-60 meshes 8.72 Greater than 60 meshes 7.65

Example 5

[0062] A method for preparing D-psicose crystal comprises specifically the following steps:

[0063] D-psicose seed crystal was added to a D-psicose solution, where the D-psicose solution had a concentration of 84 wt %, the purity of D-psicose was 98.0%, the grain size of the D-psicose seed crystal was 80 meshes, and the D-psicose seed crystal was added in an amount of 0.1% on dry weight basis of the D-psicose solution. After the seed crystal was added, the solution was stirred at 150 rpm for 20 s.

[0064] The temperature of the D-psicose solution was lowered from 50° C. to 45.2° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 11 h at 45.2° C.

[0065] After constant-temperature crystallization at 45.2° C., the temperature was lowered to 42° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 42° C.

[0066] After constant-temperature crystallization at 42° C., the temperature was lowered to 40.6° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 40.6° C.

[0067] After constant-temperature crystallization at 40.6° C., the temperature was lowered to 38.8° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 38.8° C.

[0068] After constant-temperature crystallization at 38.8° C., the temperature was lowered to 30° C. at a rate of 0.2° C./h, and then the crystallization was stopped. The stirring speed was controlled at 50 rpm during the whole process.

[0069] After crystallization, the solution was centrifuged at 4000 rpm for 20 min. The crystal was collected, washed 2-3 times with pure water, and dried in a fluidized bed at 45° C. to a moisture content of less than 0.05%. The crystal was sieved, and the purity of the product was detected by HPLC. A D-psicose product with a purity of 99.5% (w/w) and 80.9% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 71.5%. Detailed grain size distribution rates are shown in Table 5.

TABLE-US-00005 TABLE 5 Grain size Distribution rate (%) Less than 20 meshes 3.43 20-40 meshes 80.9 40-60 meshes 8.02 Greater than 60 meshes 7.65

Example 6

[0070] A method for preparing D-psicose crystal comprises specifically the following steps:

[0071] D-psicose seed crystal was added to a D-psicose solution, where the D-psicose solution had a concentration of 83 wt %, the purity of D-psicose was 98.0%, the grain size of the D-psicose seed crystal was 80 meshes, and the D-psicose seed crystal was added in an amount of 0.08% on dry weight basis of the D-psicose solution. After the seed crystal was added, the solution was stirred at 150 rpm for 20 s.

[0072] The temperature of the D-psicose solution was lowered from 50° C. to 45.2° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 11 h at 45.2° C.

[0073] After constant-temperature crystallization at 45.2° C., the temperature was lowered to 42° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 42° C.

[0074] After constant-temperature crystallization at 42° C., the temperature was lowered to 40.6° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 40.6° C.

[0075] After constant-temperature crystallization at 40.6° C., the temperature was lowered to 38.4° C. at a rate of 0.2° C./h, followed by constant-temperature crystallization for 12 h at 38.4° C.

[0076] After constant-temperature crystallization at 38.4° C., the temperature was lowered to 30° C. at a rate of 0.2° C./h, and then the crystallization was stopped. The stirring speed was controlled at 50 rpm during the whole crystallization process.

[0077] After crystallization, the solution was centrifuged at 4000 rpm for 20 min. The crystal was collected, washed 2-3 times with pure water, and dried in a fluidized bed at 45° C. to a moisture content of less than 0.05%. The crystal was sieved, and the purity of the product was detected by HPLC. A D-psicose product with a purity of 99.6% (w/w) and 81.2% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 71.4%. Detailed grain size distribution rates are shown in Table 6.

TABLE-US-00006 TABLE 6 Grain size Distribution rate (%) Less than 20 meshes 3.36 20-40 meshes 81.2 40-60 meshes 8.01 Greater than 60 meshes 7.43

Comparative Example 1

[0078] a D-psicose crystal was prepared according to the method described in Example 1, except that the constant-temperature crystallization for 11 h at 45.2° C., constant-temperature crystallization for 12 h at 42° C., constant-temperature crystallization for 12 h at 40.6° C. and constant-temperature crystallization for 12 h at 38.4° C. were omitted. That is, the D-psicose solution was cooled from 50° C., at a rate of 0.2° C./hr, and then the crystallization was stopped after the temperature was lowered to 30° C. The other steps were the same as those in Example 1. A D-psicose product with a purity of 99.3% (w/w) and 20.4% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 72%. Detailed grain size distribution rates are shown in Table 7.

TABLE-US-00007 TABLE 7 Grain size Distribution rate (%) Less than 20 meshes 1.21 20-40 meshes 20.4 40-60 meshes 42.65 Greater than 60 meshes 35.74

Comparative Example 2

[0079] a D-psicose crystal was prepared according to the method described in Example 1, except that the grain size of the Dpsicose seed crystal added was 60 meshes. The other steps were the same as those in Example 1. A D-psicose product with a purity of 98.7% (w/w) and 40.2% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 68.9%. Detailed grain size distribution rates are shown in Table 8.

TABLE-US-00008 TABLE 8 Grain size Distribution rate (%) Less than 20 meshes 1.33 20-40 meshes 40.2 40-60 meshes 38.4 Greater than 60 meshes 20.07

Comparative Example 3

[0080] a D-psicose crystal was prepared according to the method described in Example 1, except that the grain size of the Dpsicose seed crystal added was 150 meshes. The other steps were the same as those in Example 1. A D-psicose product with a purity of 98.4% (w/w) and 38.5% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 71.2%. Detailed grain size distribution rates are shown in Table 9.

TABLE-US-00009 TABLE 9 Grain size Distribution rate (%) Less than 20 meshes 1.14 20-40 meshes 38.5 40-60 meshes 39.8 Greater than 60 meshes 20.56

Comparative Example 4

[0081] a D-psicose crystal was prepared according to the method described in Example 1, except that the stirring speed was controlled at 150 rpm during the whole crystallization process. The other steps were the same as those in Example 1. A D-psicose product with a purity of 99.2% (w/w) and 36.7% of the grains having a size ranging from 20-40 meshes was obtained, and the yield of the crystallization was 70.8%. Detailed grain size distribution rates are shown in Table 10.

TABLE-US-00010 TABLE 10 Grain size Distribution rate (%) Less than 20 meshes 1.02 20-40 meshes 36.7 40-60 meshes 37.9 Greater than 60 meshes 24.38

[0082] The foregoing descriptions of specific exemplary embodiments of the present invention are illustrative and exemplary, and these descriptions are not intended to limit the present invention to specific forms disclosed. Obviously, various changes and variations can be made according to the above teachings. The choice and description of exemplary embodiments are intended to explain the specific principles and practical applications of the present invention, so that the technicians in the art can realize and utilize various exemplary embodiments of the present invention as well as various options and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.