A method for preparing crystalline fructose derived from sucrose

Abstract

The present invention provides a method for preparing crystalline fructose derived from sucrose, and belongs to the technical field of functional sugars. The preparation method of the present invention comprises the following steps: enzymolysis of a sucrose solution to obtain an enzymolysis solution; subjecting the enzymolysis solution to a first refining and a first chromatographic separation in sequence to obtain a first fructose solution and a first glucose solution; subjecting the first fructose solution to a second refining, crystallization, and centrifugation in sequence to obtain a mother liquor and wet fructose; at the same time, subjecting the first glucose solution to a third refining and isomerization in sequence to obtain a fructose / glucose mixed solution; subjecting the fructose / glucose mixed solution to a fourth refining and a second chromatographic separation to obtain a second fructose solution and a second glucose solution; and drying the wet fructose to obtain crystalline fructose. The present invention uses sucrose as a raw material to prepare crystalline fructose, reduces the use of acid and alkali, closely controls the material fluidity and the corresponding temperature zone, is conducive to the formation of a monodisperse crystal form and an increase in the number of crystals, and improves the crystallization yield.

Description

Technical Field

[0001] The invention relates to the technical field of functional sugars, and in particular to a method for preparing crystalline fructose derived from sucrose. Background Art

[0002] Crystalline fructose (also called D-fructose or fructose) is a white crystalline solid with high crystallinity and sweet taste. It has high solubility and can be quickly dissolved in water. Its melting point is lower than that of sucrose, at 103-105℃. Its sweetness is 1.2-1.8 times that of sucrose. It is the sweetest natural sugar in nature and a non-cariogenic sugar. It has the highest stability at pH 3.3. Its caloric value is 4.1Kcal / g. It is a low GI food, which is beneficial for controlling blood sugar, quickly eliminating fatigue and enhancing physical endurance. It is a monosaccharide that does not require intestinal digestion and can be directly absorbed, which can reduce the burden on gastrointestinal function. Fructose is also easily replaced by protein in the body, reducing the loss of postoperative protein, which is beneficial for recovery after surgery and has a fast decomposition rate of alcohol, making it suitable for hangover. It is an ideal sucrose substitute and can be widely used in the food field.

[0003] According to the current state of the art, the raw materials for industrial production of crystalline fructose are mainly starch and sucrose, and the raw material requirement for crystalline fructose in Kosher certification must be sucrose. Chinese patent CN104673942A discloses a method for producing crystalline fructose from sucrose, which includes five main steps: sucrose hydrolysis, decolorization and separation, chromatographic separation, evaporation concentration, and crystallization and drying, to process sucrose into crystalline fructose with a fructose content of more than 99%.

[0004] In view of the defects of the current existing production process, there are problems such as high energy consumption, high pollution, high cost, low production efficiency and allergenic factors in the production process, which affect the application range of the product. Therefore, it is necessary to improve the existing technology. The present invention uses sucrose as raw material to avoid the risk of allergenicity, and changes the crystallization process to improve the crystal adhesion problem, improve production efficiency, and make the mesh distribution more specific. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing crystalline fructose derived from sucrose. The present invention mainly solves the problems of complex production process, high energy consumption, high pollution, high cost, low production efficiency and allergic factors in the current prior art, which affect the application scope of the product, by optimizing the configuration of process parameters such as enzymatic hydrolysis, decolorization, cross-linking, chromatographic separation, evaporation concentration and crystallization in the production process.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing crystalline fructose derived from sucrose, comprising the following steps:

[0008] S1. enzymatically hydrolyzing the sucrose solution to obtain an enzymatic hydrolyzate;

[0009] The solid content of the sucrose solution is 35-40%;

[0010] The enzymatic hydrolysate has a fructose content of 48-49%, a glucose content of 48-49%, and a content of other miscellaneous sugars of 2-4%;

[0011] S2. subjecting the enzymatic hydrolysate to a first purification and a first chromatographic separation to obtain a first fructose solution and a first glucose solution;

[0012] The purity of the first fructose solution is greater than 98%, and the purity of the first glucose solution is greater than 90%;

[0013] S3. The first fructose solution is sequentially subjected to a second refining, crystallization, and centrifugation to obtain a mother liquor and wet fructose;

[0014] At the same time, the first glucose solution is successively subjected to third refining and isomerization to obtain a fructose / glucose mixed solution;

[0015] The fructose / glucose mixed solution is subjected to a fourth refining and a second chromatographic separation to obtain a second fructose solution and a second glucose solution;

[0016] The second fructose solution is greater than 98%, and the second glucose solution is greater than 85%;

[0017] S4. drying the wet fructose to obtain crystalline fructose;

[0018] adding the mother solution obtained in S3 to the fructose / glucose mixed solution;

[0019] adding the second fructose solution obtained in S3 to the first fructose solution;

[0020] The second glucose solution obtained in S3 is added to the first glucose solution.

[0021] Preferably, the enzymatic hydrolysis method in S1 is: adding 0.5-0.8% sucrase by dry weight of sucrose solution, and performing enzymatic hydrolysis for 20-24 hours at 35-40° C. and pH 6.0-6.5.

[0022] Preferably, the first chromatographic separation parameters in S2 are: feed-water ratio of 1:1-1:1.2, temperature of 55-60°C, and processing volume of 0.04-0.045 T.DS / m 3 •h.

[0023] Preferably, the isomerization conditions in S3 are as follows: the solid content of the feed is 48-52%, the pH is 5.0-7.0, the temperature is 55-60° C., and the processing capacity is 2-2.5 BV / h.

[0024] Preferably, the specific steps of crystallization in S3 are:

[0025] Add 0.05% of the dry weight of the material as seed crystals, and stir for 3 hours at a stirring speed of 150-160rpm / min; after the stirring is completed, start feeding crystallization, and the feeding conditions are: 3-8 hours, the feeding rate is 0.2t / h, the feeding sugar concentration is 67% fructose, and the sugar concentration is controlled to be 84% during the period; 8-15 hours, the feeding rate is 0.6t / h, the feeding sugar concentration is 69% fructose, and the sugar concentration is controlled to be 84.5%; 15-24 hours, the feeding rate is 1t / h, the feeding sugar concentration is 67% fructose, and the sugar concentration is controlled to be 85%; the temperature is controlled at 44°C during the feeding process;

[0026] After the crystallization of the feed is completed, boil the sugar; the boiling temperature is 45°C, and the sugar concentration is increased to 86%;

[0027] After the sugar boiling is finished, cool down and crystallize: keep it at the sugar boiling temperature for 2 hours, then cool it down to 28°C at a frequency of 0.5°C / h.

[0028] Preferably, the S3 centrifuge has a rotation speed of 4000-5000 rpm / min, a centrifugation time of 25-35 min, a washing water mass of 0.05%-1% of the system, and a crystalline fructose purity of ≥99.5%.

[0029] Preferably, the S3 drying conditions are: temperature 50-60° C., moisture content ≤0.5%.

[0030] Preferably, the second chromatographic separation parameters in S4 are: feed-water ratio of 1:1-1:1.2, temperature of 55-60°C, and processing volume of 0.04-0.045 T.DS / m 3 •h.

[0031] Preferably, the purity of the crystalline fructose in S4 is greater than 99.5%, the moisture content is less than 0.05%, the yield is 58-60%, and the product mesh size is concentrated in the range of 60-80 meshes.

[0032] Preferably, the specific methods of the first refining, the second refining, the third refining and the fourth refining are independently: the material is subjected to decolorization, ion exchange and concentration in sequence.

[0033] Preferably, the decolorization conditions of the first refining, the second refining, the third refining and the fourth refining are: 0.6-0.8% activated carbon dry basis, temperature 80±2°C, stirring for 30 minutes; the index after decolorization is transmittance ≥96%, no impurities, colorless or light yellow;

[0034] The ion exchange conditions are: the combination of ion exchange resin column is cation resin~anion resin~cation resin~anion resin, the column inlet temperature is 35~55℃, the column outlet pH is 5.0~7.0, and the conductivity is less than 50us / cm;

[0035] The conditions for concentration in the first refining are: using a multi-stage falling film evaporator, the material temperature is 45-50°C, and the solid content is 55-60%;

[0036] The conditions for concentration in the second refining are: using a multi-stage falling film evaporator, the material temperature is ≥50°C, and the solid content is 83-85%;

[0037] The concentration conditions in the third refining are: using a multi-stage falling film evaporator, the material temperature is 45-50°C, and the solid content is 48-52%;

[0038] The concentration conditions in the fourth refining are: using a multi-stage falling film evaporator, the material temperature is 45-50° C., and the solid content is 55-60%.

[0039] Beneficial technical effects:

[0040] (1) The present invention uses sucrose as a raw material, thereby avoiding allergens introduced by starch raw materials.

[0041] (2) The present invention uses sucrose as a raw material to prepare crystalline fructose, and adopts an enzymatic sucrose hydrolysis process to obtain the fructose source, thereby reducing the use of acid and alkali, not involving a liquefaction process, and reducing steam and energy consumption.

[0042] (3) The present invention improves the utilization rate of raw materials and reduces production costs by recycling the raffinate.

[0043] (4) The present invention utilizes chromatographic separation technology twice to circulate the glucose solution and the fructose solution, thereby making the purification process smooth and stable, ensuring that crystalline fructose with a purity higher than 99.5% can be continuously produced, thereby improving production efficiency.

[0044] (5) The continuous feeding control parameter technology adopted by the present invention closely controls the material fluidity and the corresponding temperature zone, which is conducive to the formation of monodisperse crystals and the increase in the number of crystals, thereby greatly improving the crystallization yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Flow chart of the method for preparing crystalline fructose derived from sucrose.

[0046] Figure 2 This is a picture of fructose crystals before centrifugation in Example 1.

[0047] Figure 3 This is a picture of fructose crystals before centrifugation in Example 2.

[0048] Figure 4 This is a picture of fructose crystals in Comparative Example 1 before centrifugation.

[0049] Figure 5 This is a picture of fructose crystals in Comparative Example 2 before centrifugation. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further illustrated by the following examples.

[0051] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0052] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0053] In addition, it should be understood that although this specification is described according to the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. These other implementation modes are also covered within the protection scope of the present invention.

[0054] It should also be understood that the specific embodiments described above are only used to explain the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention / invention.

[0055] Unless otherwise specified, the equipment or raw materials used in the following examples can be commercially available.

[0056] Example 1

[0057] This embodiment provides a method for preparing crystalline fructose derived from sucrose, and the specific steps are as follows:

[0058] (1) Enzymatic hydrolysis of sucrose

[0059] The solid content of sucrose solution was adjusted to 40%, pH: 6.3, 0.6% enzyme was added, and the temperature was 38°C for 24 hours. Samples were taken and tested by HPLC to find that the fructose content was 49% and the glucose content was 48.5%. The enzyme was inactivated by high temperature at 85°C for 30 minutes to obtain an enzymatic hydrolyzate of fructose and glucose with a fructose content of 49%.

[0060] (2) First purification of enzymatic hydrolysate

[0061] The enzymatic hydrolysate was stored in a reaction tank, activated carbon with a dry weight of 0.8% was added to the tank, and the plate-frame decolorization was carried out at 80°C for 30 minutes. The transmittance of the filtrate was 96%. Two pairs of D001 and 301P continuous ion exchange resin columns were used for ion exchange desalination using the positive inlet and negative outlet method. The temperature was controlled to be 40°C at the column inlet temperature, 5.5 at the column outlet pH, 2BV / h at the flow rate, and 27.3us / cm at the outlet conductivity. During concentration, the sugar solution was sent to a six-effect vacuum evaporator. When the vacuum degree was -0.1MPa, the heating steam valve was opened, and the outlet temperature was controlled to be 45°C. When the solid content of the sugar solution reached 58%, the evaporation process was completed, and a mixed solution with a fructose content of 49% was obtained in this process.

[0062] (3) First chromatographic separation

[0063] The mixed solution is chromatographed to obtain a first fructose solution and a first glucose solution. The specific parameters are solid content of 58%, material-water ratio of 1:1, temperature of 56°C, and processing capacity of 0.04 T.DS / m 3 •h, after separation and purification, the fructose purity in the first fructose solution is 98%; the fructose content in the first glucose solution is 5%, and the glucose content is 90%.

[0064] (4) Second refining, crystallization and centrifugation of the first fructose solution

[0065] Second refining: add 0.8% of dry weight of activated carbon to the first fructose solution, keep it at 80℃ for 30min for plate-frame decolorization, and the transmittance of the filtrate is 96.5%; use two pairs of D001 and 301P continuous ion exchange resin columns for ion exchange desalination, control the temperature to be 40℃ at the column inlet temperature, 5.5 at the column outlet pH, flow rate to be 2BV / h, and the discharge conductivity to be 18us / cm. When concentrating, send the sugar solution to a six-effect vacuum evaporator, control the discharge temperature to be 45℃, and when the solid content of the sugar solution reaches 84%, the evaporation process is completed, at which time the transmittance is 97% and the fructose purity is 98.2%.

[0066] Crystallization: The above fructose concentrate is transported to the crystallization tank through a pipeline. The crystallization process is divided into continuous feeding evaporation crystallization and cooling crystallization. The initial feed volume is 18T, the solid content is 84%, when the material temperature reaches 41℃, the amount of seed crystals added is 0.05% of the material dry basis, the stirring speed is 150-160rpm / min and remains unchanged, and stabilizes for 3h after adding the seed crystals. Feeding starts after 3h, 3-8h, the feeding rate is 0.2t / h, the feeding sugar concentration is 67% fructose, and the sugar concentration is controlled to 84% during the period; 8-15h, the feeding rate is 0.6t / h, the feeding sugar concentration is 69% fructose, and the sugar concentration is controlled to 84.5%; 15-24h, the feeding rate is 1t / h, the feeding sugar concentration is 67% fructose, and the sugar concentration is controlled to 85%. The temperature is controlled at 44℃ during the feeding process.

[0067] During the sugar boiling stage, the temperature is controlled at 45°C, increasing the sugar concentration by 86%.

[0068] The cooling crystallization conditions are: after keeping warm for 2 hours, the temperature is lowered to 28°C at a frequency of 0.5°C / h, and this cycle takes 34 hours.

[0069] After cooling, the crystal was examined under a microscope. The results were as follows: Figure 2 As shown, the crystals are almost free of adhesion and the crystal size distribution is relatively uniform.

[0070] The entire crystallization cycle took 60 h to complete.

[0071] Centrifugation: The obtained material is separated by a centrifuge at a speed of 5000 rpm / min for 30 minutes. During this period, the crystals are washed with 0.5% water to obtain mother liquor and wet fructose.

[0072] After centrifugation, the mother liquor is mixed with the isomerized sugar solution and enters the chromatogram together for secondary chromatographic separation and purification.

[0073] (5) The first glucose solution is sequentially subjected to the third purification, isomerization, and fourth purification

[0074] Third refining: add 0.8% of dry weight of activated carbon, keep at 80℃ for 30min for plate-frame decolorization, the transmittance of the filtrate is 96.5%; use two pairs of D001 and 301P continuous ion exchange resin columns for ion exchange desalination, control the temperature to 40℃ for column inlet temperature, 5.5 for column outlet pH, flow rate to 2BV / h, and discharge conductivity to 27us / cm. When concentrating, send the sugar solution to a six-effect vacuum evaporator, control the discharge temperature to 45℃, and complete the evaporation process when the solid content of the sugar solution reaches 50%.

[0075] Isomerization: When the feed liquid enters the isomerization column, the solid content is 50%, pH: 5.5, temperature 58°C, flow rate is 2BV / h, and a fructose / glucose mixed solution is obtained;

[0076] Fourth refining: add 0.8% of dry weight of activated carbon, keep warm at 80℃ for 30min for plate-frame decolorization, the transmittance of the filtrate is 97%; use two pairs of D001 and 301P continuous ion exchange resin columns for ion exchange desalination, control the temperature to 45℃ for column inlet temperature, 5.8 for column outlet pH, flow rate to 2BV / h, and discharge conductivity to 25us / cm. When concentrating, send the sugar solution to a six-effect vacuum evaporator, control the discharge temperature to 45℃, and complete the evaporation process when the solid content of the sugar solution reaches 58%.

[0077] (6) Secondary chromatographic separation

[0078] The fructose / glucose mixed solution was subjected to secondary chromatographic separation. The specific parameters were solid content of 58%, material-water ratio of 1:1, temperature of 56°C, and processing capacity of 0.04 T.DS / m 3 •h. After separation and purification, the fructose purity in the fructose solution is 98%; the fructose content in the glucose solution is 4.8% and the glucose content is 90%.

[0079] (7) Drying wet fructose to obtain crystalline fructose

[0080] The wet fructose crystal particles are dried to finally produce high-purity crystalline fructose with a fructose content of 99.5% and a yield of 58.06%. The product mesh size is concentrated in the range of 60-80 meshes.

[0081] During the preparation process, the mother liquor and the diglucose solution are recycled; the mother liquor is added to the fructose / glucose mixed solution and continued to be used as a raw material for preparation; the second glucose solution is added to the first glucose solution as a raw material for preparation.

[0082] adding the obtained second fructose solution to the first fructose solution to jointly prepare crystalline fructose;

[0083] The cost can be reduced by recycling the residual material and combining the fructose solution for treatment.

[0084] Embodiment 2

[0085] Crystallized fructose was prepared according to the method of Example 1, except that the sugar concentration and flow rate of the added material during the crystallization process in step (4) were different. The initial feed volume was 18T, the solid content was 85%, the amount of seed crystals added was 0.05% on a dry basis, the stirring speed was maintained at 155rpm / min, and the feed was started after the seed crystals were added and stabilized for 2h. From 2-8h, the feed sugar concentration was 66% and the feed rate was 0.2t / h; from 8-15h, the feed sugar concentration was 67% and the feed rate was 0.5t / h; from 15-24h, the feed sugar concentration was 69% and the feed rate was 0.8t / h. The temperature was controlled at 42°C during the feeding period.

[0086] Referring to the microscopic examination step in Example 1, the crystals were examined under a microscopic examination before centrifugation. The results of the microscopic examination are as follows: Figure 3 As shown, the crystals are almost non-sticky and the crystal sizes are relatively uniform.

[0087] The final product is high-purity crystalline fructose with a fructose content of 99.6% and a yield of 59.98%. The product mesh size is concentrated in the range of 60-80 meshes.

[0088] The mesh distribution of Example 1 and Example 2 was measured, and the results are shown in Table 1, indicating that the mesh distribution of the controlled product of the present invention is mainly concentrated in 60-80 meshes, which can be formulated for people in need.

[0089] Table 1

[0090] Serial number Below 40 mesh 40-60 mesh 60-80 mesh 80-100 mesh More than 100 mesh Yield Embodiment 1 0.07% 0.51% 85.56% 12.34% 1.52% 58.06% Embodiment 2 0.04% 0.38% 88.79% 10.24% 0.55% 59.98%

[0091] Comparative Example 1

[0092] Crystallized fructose was prepared according to the method of Example 2, except that the sugar concentration and flow rate of the added material in the crystallization process of step (4) were different. The initial feed volume was 18T, the solid content was 85%, the amount of seed crystals added was 0.05% on a dry basis, the stirring speed was maintained at 150rpm / min, and the feed was started after the seed crystals were added and stabilized for 2h. During the 2-24h feeding period, the sugar concentration of the fructose solution fed was 68%, and the flow rate was always 0.6t / h. The feeding temperature was controlled at 42°C.

[0093] Referring to the microscopic examination step in Example 1, the crystals were examined under a microscopic examination before centrifugation. The results of the microscopic examination are as follows: Figure 4 As shown, the crystals are adhered to each other, and the crystal size distribution is uneven, with small crystals appearing.

[0094] The final product is high-purity crystalline fructose with a fructose content of 99.3% and a yield of 45.56%. The product mesh size is concentrated in the range of 40-60 meshes.

[0095] Comparative Example 2

[0096] Crystallized fructose was prepared according to the method of Example 1, except that the feeding process was started after 3 hours in the crystallization process of step (4): 3-8 hours, the feeding sugar concentration was 70%, and the feeding rate was 0.9 t / h; 8-15 hours, the feeding sugar concentration was 67%, and the feeding rate was 0.6 t / h; 15-24 hours, the feeding sugar concentration was 65%, and the feeding rate was 0.4 t / h. During this period, the temperature was controlled at 43°C and the stirring speed was 160 rpm / min.

[0097] Referring to the microscopic examination step in Example 1, the crystals were examined under a microscopic examination before centrifugation. The results of the microscopic examination are as follows: Figure 5 As shown, the crystals are severely adhered.

[0098] Finally, high-purity crystalline fructose with a fructose content of 99.1% and a yield of 40% is produced. The mesh size of the obtained crystalline fructose product is concentrated in the range of 40-60 meshes.

[0099] The crystallization parameters of Comparative Examples 1 and 2 are shown in Table 2.

[0100] Table 2

[0101] Serial number Below 40 mesh 40-60 mesh 60-80 mesh 80-100 mesh More than 100 mesh Yield Comparative Example 1 3.46% 79.53% 10.86% 4.34% 1.81% 45.56% Comparative Example 2 4.56% 81.94% 8.52% 3.24% 1.74% 40%

[0102] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing crystalline fructose derived from sucrose, characterized in that: The following steps are involved: S1. enzymatically hydrolyzing the sucrose solution to obtain an enzymatic hydrolyzate; The solid content of the sucrose solution is 35-40%; The enzymatic hydrolysate has a fructose content of 48-49%, a glucose content of 48-49%, and a content of other miscellaneous sugars of 2-4%; S2. subjecting the enzymatic hydrolysate to a first purification and a first chromatographic separation to obtain a first fructose solution and a first glucose solution; The purity of the first fructose solution is greater than 98%, and the purity of the first glucose solution is greater than 90%; S3. The first fructose solution is sequentially subjected to a second refining, crystallization, and centrifugation to obtain a mother liquor and wet fructose; At the same time, the first glucose solution is successively subjected to third refining and isomerization to obtain a fructose / glucose mixed solution; The fructose / glucose mixed solution is subjected to a fourth refining and a second chromatographic separation to obtain a second fructose solution and a second glucose solution; The purity of the second fructose solution is greater than 98%, and the purity of the second glucose solution is greater than 85%; S4. drying the wet fructose to obtain crystalline fructose; adding the mother solution obtained in S3 to the fructose / glucose mixed solution; adding the second fructose solution obtained in S3 to the first fructose solution; adding the second glucose solution obtained in S3 to the first glucose solution; The specific steps of crystallization in S3 are: Add 0.05% of the dry weight of the material as seed crystals, and stir for 3 hours at a stirring speed of 150-160rpm / min; after the stirring is completed, start feeding crystallization, and the feeding conditions are: 3-8 hours, the feeding rate is 0.2t / h, the feeding sugar concentration is 67% fructose, and the sugar concentration is controlled to be 84% during the period; 8-15 hours, the feeding rate is 0.6t / h, the feeding sugar concentration is 69% fructose, and the sugar concentration is controlled to be 84.5%; 15-24 hours, the feeding rate is 1t / h, the feeding sugar concentration is 67% fructose, and the sugar concentration is controlled to be 85%; the temperature is controlled at 44°C during the feeding process; After the crystallization of the feed is completed, boil the sugar; the boiling temperature is 45°C, and the sugar concentration is increased to 86%; After the sugar is boiled, cool down and crystallize: keep the sugar boiling temperature for 2 hours, then cool down to 28°C at a frequency of 0.5°C / h; The purity of the crystalline fructose in the S4 is greater than 99.5%, the moisture content is less than 0.05%, the yield is 58-60%, and the product mesh size is concentrated in the range of 60-80 meshes.

2. The preparation method according to claim 1, characterized in that: The enzymatic hydrolysis method in S1 is: adding 0.5-0.8% sucrase by dry basis weight of sucrose solution, and performing enzymatic hydrolysis for 20-24 hours at 35-40° C. and pH 6.0-6.

5.

3. The preparation method according to claim 1, characterized in that: The isomerization conditions in S3 are as follows: the solid content of the feed is 48-52%, the pH is 5.0-7.0, the temperature is 55-60° C., and the processing capacity is 2-2.5 BV / h.

4. The preparation method according to claim 1, characterized in that: The S3 centrifuge has a rotation speed of 4000-5000 rpm / min, a centrifugation time of 25-35 min, a washing water mass of 0.05%-1% of the system, and a crystallized fructose purity of ≥99.5%.

5. The preparation method according to claim 1, characterized in that: The S3 drying conditions are: temperature 50-60° C., moisture content ≤0.5%.

6. The preparation method according to claim 1, characterized in that: The specific methods of the first refining, the second refining, the third refining and the fourth refining are independent of each other: the material is subjected to decolorization, ion exchange and concentration in sequence.

7. The preparation method according to claim 6, characterized in that: The decolorization conditions of the first refining, the second refining, the third refining and the fourth refining are: 0.6-0.8% of the activated carbon dry basis, the temperature is 80±2°C, and the temperature is kept and stirred for 30 minutes; the index after decolorization is the transmittance ≥96%, no impurities, colorless or light yellow; The ion exchange conditions are: the combination of ion exchange resin column is cation resin~anion resin~cation resin~anion resin, the column inlet temperature is 35~55℃, the column outlet pH is 5.0~7.0, and the conductivity is less than 50us / cm; The conditions for concentration in the first refining are: using a multi-stage falling film evaporator, the material temperature is 45-50°C, and the solid content is 55-60%; The conditions for concentration in the second refining are: using a multi-stage falling film evaporator, the material temperature is ≥50°C, and the solid content is 83-85%; The concentration conditions in the third refining are: using a multi-stage falling film evaporator, the material temperature is 45-50°C, and the solid content is 48-52%; The concentration conditions in the fourth refining are: using a multi-stage falling film evaporator, the material temperature is 45-50° C., and the solid content is 55-60%.

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