METHOD FOR PRODUCING FUNCTIONAL CRYSTALLINE SWEETENER

Abstract

The present invention relates to a method for preparing a crystalline functional sweetener, and more specifically, relates to a method for preparing a crystalline functional sweetener for raising the crystallization yield and increasing the particle size by controlling the content of impurities or production of impurities comprised in a solution for preparing the crystal.

Claims

1.-8. (canceled)

9. A method for controlling the content of allulose conversion material (Impurity-S) contained in a composition for crystallizing allulose as 2 wt/wt % or lower, based on the solid content.

10. The method of claim 9, wherein the method is performed by controlling one or more selected from the group consisting of pH condition and temperature condition, wherein the pH condition is 4 to 7, and wherein the temperature condition is 40° C. or higher to 70° C. or lower.

11. The method of claim 9, wherein the allulose conversion material contains a compound of molecular formula CxHyOz, wherein x is an integer from 3 to 15, y is an integer from 1 to 15, and z is an integer of 1 to 10.

12. The method of claim 9, wherein the allulose conversion material contains one or more kinds selected from the group consisting of allulose dimer, allulose tetramer, levulinic acid (4-oxopentanoic), furfural, Hydroxymethylfurfural (HMF), γ-Hydroxyvaleric acid (GVB), 2,5-Dimethylfuran, 2,5-furandicarboxylic acid (FDCA), 5-hydroxymethyl-2-furoic acid, 2,5-formylfurancarboxylic acid, 2,5-Furandicarbaldehyde, 2,5-bis-(hydroxymethyl)furan, bis(5-formyl-2-furfuryl) ether, 2-Furoic acid, 3-Furoic acid, 5-Hydroxyfurfural, 2,5-Dihydro-2,5-dimethoxyfuran, (2R)-5-Oxotetrahydro-2-furancarboxylic acid, 2,5-formylfuran carboxylic acid, 5,5′-Methylenedi(2-furoic acid), and bis(5-methyl furfuryl) ether.

13. The method of claim 9, wherein the composition of allulose solution is prepared by treating the reaction solution containing allulose with an SMB chromatography separation process and concentrating the obtained allulose fraction at the temperature condition of 40 to 70° C. or lower.

14. The method of claim 13, wherein the concentration process is performed as divided into at least two stages, wherein a primary concentration for the allulose solution is performed to be 30 to 50Bx to obtain a primary concentrate and the primary concentrate is secondarily concentrated to be 60˜85Bx.

15. The method of claim 13, further comprising treating an activated carbon, before conducting the concentration process.

16. The method of claim 9, wherein the allulose solution composition is provided as a dissolved solution in which an allulose crystal or powder is dissolved in water.

17. The method of claim 9, wherein the allulose solution composition has the conductivity of 1,000 uS/cm or lower.

18. The method of claim 9, wherein the allulose conversion material contains 10 to 600 m/z of the ratio of mass/quantity of electric charge measured by an LC/MS analysis method.

19. The method of claim 9, wherein the allulose conversion material contains material having a maximum peak at elution time of 31 min±2 min time measured by a HPLC analysis method.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0083] FIG. 1 is a graph showing the change of content of allulose, when the allulose syrup of pH 5 and 70 Brix concentration was stored by temperature.

[0084] FIG. 2 is a graph showing the change of content of allulose conversion material, when the allulose syrup of pH 5 and 70 Brix concentration was stored by temperature.

[0085] FIG. 3 is a graph showing the change of content of allulose, when the allulose syrup of different pH and 70 Brix concentration was stored at the temperature of 70° C.

[0086] FIG. 4 is a graph showing the change of content of allulose conversion material, when the allulose syrup of different pH and 70 Brix concentration was stored at the temperature of 70° C.

[0087] FIG. 5 is an optical microscopic photograph of allulose powder obtained in Example 5 measured at magnification ×100.

[0088] FIG. 6 is a scanning electron microscope (SEM) photograph of allulose powder obtained in Example 5 measured at magnification ×50.

[0089] FIG. 7 is an infrared spectroscopy (IR) spectrum of allulose crystal obtained in Example 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0090] The present invention will be described in more detail by the following examples. However, the following examples are desirable examples of the present invention, and the present invention is not limited thereto.

Example 1: Allulose Crystal Preparation

[0091] The allulose syrup was prepared from the fructose substrate with the substantially same biological method as the preparation method disclosed in Korean laid-open patent application no. 2014-0054997. After desalting the allulose syrup by passing through the column at the room temperature filled with the cation exchange resin, anion exchange resin and resin mixed of cation and anion exchange resins at the rate of 2 times (1-2 times) ion exchange resin volume per hour to remove impurities like colored and ion components, etc., the high purity of allulose solution was separately collected by using the chromatography filled with the Ca.sup.2+ type of ion exchange resin.

[0092] The high-purity syrup of allulose containing 97 wt/wt % of allulose with 35 Bx (w/w %) was obtained through the high purity separation process (SMB) and concentrated, thereby preparing the allulose syrup for crystallization containing 97 wt/wt % of allulose with 81 Bx (w/w %) and the conductivity of 12 uS/cm. The conductivity of allulose syrup was the value measured on the basis of the solid content of 30 Bx.

[0093] The concentrated allulose syrup for crystallization was cooled slowly from the temperature of 35° C. of the supersaturated state to the temperature of 10° C., to grow the crystal. At this time, the process of adding the allulose seed, and after producing a small amount of crystal nucleus by slowly stirring at the temperature of 35° C., growing the crystal by decreasing the temperature by 1° C. per hour, and dissolving the microcrystal by increasing the temperature of solution to the range of 30 to 35° C. for redissolving the microcrystal produced in the cooling of the crystal growing process. The crystal growing process and microcrystal dissolving process were repeated at least one or more times to perform the crystallization. The allulose crystal produced herein was recovered by drying after removing the mother liquor by centrifuged dehydration and washing the crystal obtained by the primary crystallization with cooling water.

[0094] The content of allulose and content of allulose conversion material (Impurity-S) of raw material for crystallization, and the purity of allulose crystal were analyzed under the following analysis conditions.

[0095] Analysis column: Biolad Aminex HPX-87C column

[0096] Mobile phase: water

[0097] Flow rate: 0.6 ml/min

[0098] Column temperature: 80° C.

[0099] Detector: RI detector

[0100] As the result of HLPC analysis, the content of allulose conversion material (Impurity S) in aqueous allulose solution for crystallization was 0.4 wt/wt %, and the content of allulose was 97.0 wt/wt %.

[0101] The yield of allulose crystal prepared by the method was 63.6%. The yield was represented as a percentage of the weight of recovered allulose crystal powder to the weight of solid of raw material allulose syrup for crystallization.

Examples 2 and 3: Allulose Crystal Preparation

[0102] By performing the substantially same method as the allulose preparation of Example 1, the high-purity syrup of allulose comprising 96.6 wt/wt % of allulose was obtained at the concentration of 35 Bx (w/w %) in Example 2, the high-purity syrup of allulose comprising 95.8 wt/wt % of allulose was concentrated to obtain 35 Bx (w/w %) of syrup in Example 3, and the high-purity syrup of allulose comprising 95.5 wt/wt % of allulose was concentrated to obtain 35 Bx (w/w %) of syrup in Example 6. By concentrating the allulose solutions, Example 2 prepared the allulose syrup of 81 Bx (w/w %) for crystallization including 96.6 wt/wt % allulose with 81 Bx (w/w %) and the conductivity of 14 uS/cm, Example 3 prepared the allulose syrup of 81 Bx (w/w %) for crystallization including 95.8 wt/wt % allulose with 81 Bx (w/w %) and the conductivity of 14 uS/cm, and in Example 6, the allulose syrup for crystallization including 95.5 wt/wt % allulose with 81 Bx (w/w %) and the conductivity of 12 uS/cm was prepared. The conductivities of the allulose syrup were values measured on a solid content basis of 30 Bx.

[0103] According to the same crystallization method as Example 1, the concentrated allulose syrup was crystallized and the crystals were washed with cooling water, and dried to recover the crystals.

[0104] According to the same method as Example 1, The content of allulose and content of allulose conversion material (Impurity-S) of raw material for crystallization, and the purity of allulose crystal were analyzed and the result was shown in the following Table 1.

[0105] Specifically, the yield of the allulose crystals prepared from the allulose syrup for crystallization in Example 2 (the content of the allulose conversion material of 0.3 wt/wt %, and the content of the allulose of 96.6 wt/wt %) was 61.9%, the yield of the allulose crystals prepared from the allulose syrup for crystallization in Example 3 (the content of the allulose conversion material of 0.5 wt/wt %, and the content of the allulose of 95.8 wt/wt %) was 61.6%, and the yield of the allulose crystals prepared from the allulose syrup for crystallization in Example 6 (the content of the allulose conversion material of 0.25 wt/wt %, and the content of the allulose of 95.5 wt/wt %) was 62.1%.

Example 4: Allulose Crystal Preparation

[0106] The high purity allulose syrup including 97.0 wt/wt % allulose was obtained at the concentration of 35 Bx (w/w %) by the high purity separation process (SMB) by conducting the substantially same method as the allulose preparation of Example 1.

[0107] To minimize the impurities contained in the allulose syrup, it was treated by using the appropriate activated carbon at the temperature of 40° C. for 30 min, and then filtered. The allulose syrup after treating the activated carbon was concentrated to be 81 Bx (w/w %), thereby preparing the allulose syrup for crystallization including 97.3 wt/wt % of allulose with 81 Bx (w/w %) and the conductivity of 10 uS/cm.

[0108] The concentrated allulose syrup was cooled slowly from the temperature of 35° C. at the supersaturated state to the temperature of 10° C., to grow the crystal. Then, the process of adding the allulose seed, and after producing a small amount of crystal nucleus by slowly stirring at the temperature of 35° C., growing the crystal by decreasing the temperature by 1° C. per hour, and dissolving the microcrystal by increasing the temperature of solution to the ranges of 30-35° C. to redissolve the microcrystal produced in the cooling in the crystal growing process was carried out. The crystal growing process and microcrystal dissolving process were repeated at least one or more times to perform the crystallization. The allulose crystal produced herein was recovered by drying after removing the mother liquor by centrifuged dehydration and washing the crystal obtained by the primary crystallization with cooling water.

Example 5: Allulose Crystal Preparation

[0109] The high purity allulose syrup including 97.0 wt/wt % allulose was concentrated to obtain the concentration of 35 Bx (w/w %) by the high purity separation process (SMB) by conducting the substantially same method as the allulose preparation of Example 1.

[0110] The allulose syrup was concentrated and the high purity allulose syrup including 97 wt/wt % allulose based on the solid content of 100 wt/wt % was concentrated at the concentration of 81 Bx (w/w %), thereby preparing the allulose syrup for crystallization having the conductivity of 8 uS/cm. According to the same crystallization method as Example 1, the concentrated allulose syrup was crystallized and the crystals were washed with cooling water, and dried to recover the crystals.

[0111] The obtained primary crystal was dissolved in water, thereby preparing the allulose dissolved solution of 81.2 Bx, and as the result of analyzing the allulose dissolved solution by the HPLC analysis of Example 1, the content of allulose conversion material (Impurity S) was 0.07 wt/wt % and the content of allulose was 99.5 wt/wt %.

[0112] The secondary crystallization process was performed with the prepared allulose dissolved solution as a raw material of secondary crystallization process by substantially same method as the primary crystallization method. The secondary crystal prepared herein was recovered by drying after removing the mother liquor by centrifuged dehydration and washing the crystal obtained by the secondary crystallization with cooling water. The yield of secondary crystal was 62.5%.

TABLE-US-00001 TABLE 1 Content of allulose Content of Impurity-S Crystal- Classi- of crystallization of crystallization lization fication undiluted solution (%) undiluted solution (%) yield (%) Example 1 97.0 0.4 63.6 Example 2 96.6 0.3 61.9 Example 3 95.8 0.5 61.6 Example 4 97.3 0.2 62.0 Example 5 99.5 0.07 62.5 Example 6 95.5 0.25 62.1

[0113] As shown in the Table 1, it was confirmed that the allulose crystallization yields of Examples 1 to 3 were over 60%, on the other hand, Comparative Example 1 could not obtain proper crystal when the content of allulose conversion material (Impurity-S) was more than 2 wt/wt %, although the allulose content of crystallization undiluted solution was high, and the crystallization yield was drastically decreased due to small crystals.

Comparative Example 1: Allulose Crystal Preparation when the Content of the Allulose Conversion Material Exceeds 2 wt/wt %

[0114] In order to determine the yield of the allulose crystals when the content of the allulose conversion material in the crystallization solution was more than 2 wt/wt %, acidic pH condition or heat treatment condition was applied to the crystallization solution for secondary crystallization in Example 5 to trigger the formation of the allulose conversion material.

[0115] Specifically, the starting material for secondary crystallization was prepared by dissolving the allulose crystal obtained by performing the primary crystallization in Example 5 in water, and then be heat-treated at the conditions of pH 3.5 and the temperature of 80° C. for 3 hours. According to the same crystallization method as Example 1, the concentrated allulose syrup was crystallized and the crystals were washed with cooling water, and dried to recover the crystals.

[0116] According to the same method as Example 1, the content of allulose and content of allulose conversion material (Impurity-S) of raw material for crystallization, and the purity of allulose crystal were analyzed and the result was shown in the following Table 2.

Comparative Examples 2 and Example 7 to 8: Allulose Crystal Preparation Method by the Content of Allulose Conversion Material

[0117] The starting material for secondary crystallization was prepared by dissolving the allulose crystal obtained by performing the primary crystallization in Example 5 in water, and then be treated at the conditions of pH 4.5 and the temperature of 70° C. for 6, 13 or 24 hours. The content of allulose and content of allulose conversion material (Impurity-S) of raw material for crystallization were shown in Table 2.

[0118] The method of proceeding crystallization using the prepared crystallization solution was carried out in substantially the same method as in Example 1. Specifically, in Comparative Example 2 and Examples 7 to 8, the allulose crystallization processes were performed using different allulose crystallization solution with different heat treatment time, having different allulose content and the allulose conversion material shown in Table 2.

[0119] According to the same method as Example 1, the content of allulose and content of allulose conversion material (Impurity-S) of raw material for crystallization, and the purity of allulose crystal were analyzed and the result was shown in the following Table 2.

TABLE-US-00002 TABLE 2 Content of allulose Content of Impurity-S Crystal- Classi- of crystallization of crystallization lization fication undiluted solution (%) undiluted solution (%) yield (%) Comparative 97.0 2.1 42.4 Example 1 Example 7 98.5 0.65 58.8 Example 8 96.2 1.50 53.1 Comparative 93.3 3.40 29.1 Example 2

[0120] In case of Comparative Example 2, since the purity of allulose was low and the content of allulose conversion material was high, the growth of crystal particles was not gone well and microcrystals were produced, and thus dehydration and washing of crystals were very difficult. In case of Comparative Example 1, it was confirmed that the growth of crystal particle size was not gone well and microcrystals were produced as the content of allulose conversion material was higher, as same as Comparative Examples 2. In case of Example 7 and Example 8, it was confirmed that the content of the allulose conversion material was lower than 2 wt/wt %, indicating a high crystal yield compared to that of the comparative example.

Experimental Example 1

[0121] LC-MS Analysis of Allulose Conversion Material (Impurity S)

[0122] (1) Analysis of Allulose Conversion Material (Impurity S) of Example 2

[0123] The impurities fraction isolated in the peak at the elution time 31±2 min was directly collected in HPLC analysis of allulose syrup for crystallization used in Example 2, and the solution diluted during the separation fraction was freeze-dried and concentrated at approximately 100 times concentration used for the analysis. The molecular weight of allulose conversion material (Impurity S) measured by LC/MS analysis by conducting the analysis of molecular weight of impurities with the liquid chromatograph/mass analyzer (LC/MS system, model name: LTQ, manufacturer: Thermo Finnigan, USA) was the material having the range of 300 to 400 m/z (ratio of mass/quantity of electric charge).

[0124] (2) Analysis of Allulose Conversion Material (Impurity S) of Comparative Examples 2 and Examples 7 to 8

[0125] According to the substantially same as the LC-MS analysis method, the thermal treated crystallization undiluted solutions used in Comparative Examples 2 and Examples 7 to 8 was used. For the changes of molecular weight of allulose and allulose conversion material according to the thermal treatment, LC-MS analysis was conducted, and the result of analysis of content of allulose and content of allulose conversion material (%) comprised in the crystallization undiluted solutions used in Comparative Examples 2 and Examples 7 to 8 was shown in the following Table 3.

[0126] The following Table 3 is data of LC-MS analysis of allulose syrup by thermal treatment time (Example 7, Example 8, Comparative Examples 2), and the numerical values, which the values of area of peak detected by each molecular weight (m/z) were converted into a percentage, were shown in the table. The molecular weight of 179.1 m/z in Row 1 of Table 3 was allulose. Rows 4, 8 and 10 in the following Table 3 represented that the content of allulose conversion material (Impurity S) was increased after the thermal treatment, and the other Rows represented that the content of allulose conversion material (Impurity S) was decreased after the thermal treatment.

TABLE-US-00003 TABLE 3 Comparative Formula Finder Row m/z Example 5 Example 7 Example 8 Example 2 Result 1 179.1 56.68 38.53 31.65 24.75 C6H12O6 2 225.1 9.27 6.26 5.12 4.26 C7H14O8 3 251.1 0.36 1.05 1.09 1.18 C9H16O8 4 341.1 6.03 16.68 18.99 19.71 C12H22O11 5 359.1 21.31 14.66 11.50 8.42 C12H24O12 6 387.1 1.37 3.44 3.91 4.76 C13H24O13 7 485.1 0.04 0.06 0.17 0.61 C18H30O15 8 503.2 0.44 2.11 5.53 9.89 C25H28O11 9 665.2 0.06 0.16 0.60 2.03 C24H42O21 10 683.2 4.13 16.01 18.50 18.51 C24H44O22 11 711.2 0.02 0.02 0.15 0.56 C25H44O23 12 827.3 0.01 0.02 0.06 0.35 C37H48O21 13 845.3 0.09 0.60 1.37 1.92 C30H54O27 14 1007.3 0.01 0.13 0.90 2.31 C36H64O32

[0127] As shown in the analysis result, it was confirmed that the content of allulose was lowered and the content of impurities was raised in the molecular weight analysis as the thermal treatment time was increased. The molecular weight of 179.1 m/z in Row 1 of the Table 3 was allulose, and it was confirmed that the numerical value of peak area value was decreased after the thermal treatment. On the other hand, it could be confirmed that the component detected in the molecular weight of 341 m/z (Table Row 5) was the component increased as thermal treating the crystallization undiluted solution containing allulose, and the material of Dimer-like structure that allulose was modified by dehydration or condensation reaction. As the result of inferring the structure by LC-MS analysis, it could be predicted that it was the material having the chemical formula of C12H22O11, and the allulose denatured polymer. It was confirmed that the content of allulose denatured polymers (tetramer analogues of allulose) having the molecular weight similar to dimer of allulose denatured polymer of C25H28O11, C24H42O21 or C24H44O22 as the thermal treatment was proceeded additionally. This could be considered that the allulose was easily denatured by external stress, for example, acidic pH and/or thermal treatment in Comparative Examples 1 or 2 and the dehydration and condensation reactions were randomly repeated with allulose or allulose conversion material, thereby being converted into the above materials.

[0128] (3) Analysis of the Allulose Conversion Material of Example 3

[0129] In the HPLC analysis of the allulose syrup for crystallization used in Example 3, the separated impurity fraction was directly obtained at a peak of the elution time of 31+/−2 minutes, and the fraction diluted during the HPLC analysis was lyophilized and concentrated about 100 times, and used for analysis. [0130] Name of analyzer: Ultimate-3000 ISQ EC (Thermo Fisher) [0131] Analytical column: Bio-rad Aminex HPX-87C [0132] Column temperature: 80° C. [0133] Flow rate: 0.3 mL/min [0134] Solvent: distilled water [0135] Injection volume: 5

[0136] As a result of LC/MS analysis of the allulose conversion material, there were peaks near at 55.22 m/z, 60.24 m/z, 74.14 m/z, 79.25 m/z, 82.22 m/z, 83.23 m/z, 109 m/z, 117 m/z, 124.26 m/z, 127.1 m/z, 141.5 m/z, 144 m/z, 163.23 m/z, 203.16 m/z, and 365.16 m/z, and the main peaks were near at 127 m/z, 163 m/z, 198.2 to 203 m/z, and 365 m/z.

[0137] Therefore, the allulose conversion material is a derivative material from allulose which is a molecule composed of C, H, and O having 5 to 12 carbon atoms (C), has a molecular weight charge value of 50 m/z or more to 400 m/z or less, contains HMF and levulinic acid components, and includes a derivative material containing a furan structure. Specifically, in the case of the 163 m/z peak, it is considered that an intermediate substance (Furan aldehyde intermediate) from the process in which hexose such as allulose is decomposes to HMF by dehydration reaction. In the case of a peak of 198.2 to 203 m/z, it is considered to be a [C.sub.6H.sub.12O.sub.6+Na].sup.+ molecule in which a Na.sup.+ ion is bonded to an allulose molecule, and in the case of 365 m/z peak, it is considered to be [C.sub.6H.sub.12O.sub.6+Na].sup.+ molecule in which a Na.sup.+ ion is bonded to an allulose dimer molecule.

[0138] Based on the LC/MS analysis results of the allulose conversion material, the compounds included in the allulose conversion material are shown in Table 4 below.

TABLE-US-00004 TABLE 4 molecular weight name Formula (g/mol) levulinic acid(4-oxopentanoic) C5 H8 O3 116.1 furfural C5 H4 O2 96.08 HMF C6 H6 O3 126.1 γ-Hydroxyvaleric acid GVB C5 H10 O3 118.13 2,5-Dimethylfuran C6 H8 O 96.13 2,5-Furandicarboxylic acid C6 H4 O5 156.09 5-hydroxymethyl-2-furoic acid C6 H6 O4 142.1 2,5-formylfurancarboxylic acid C6 H4 O4 140 2,5-Furandicarbaldehyde C6 H4 O3 124 2,5-bis-(hydroxymethyl)furan C6 H8 O3 128 bis(5-formyl-2-furfuryl) ether C12 H10 O5 234 2,5-Furandicarboxylic acid C6 H4 O5 156 2-Furoic acid C5 H4 O3 112 5-Hydroxyfurfural C5 H4 O3 112 3-Furoic acid C5 H4 O3 112 2,5-Dihydro-2,5-dimethoxyfuran C6 H10 O3(C6H12O3) 130 (132) (2R)-5-Oxotetrahydro-2- C5 H6 O4(C6H8O4) 130 (132) furancarboxylic acid 2,5-formylfurancarboxylic C6 H4 O4 138 acid(140) 5,5′-Methylenedi(2-furoic acid) C11 H8 O6 236 (234) (dimer form) bis(5-methyl furfuryl) ether (—OH C12 H12 O5 236 (234) form)

[0139] (4) LC/MS Analysis of 5-HMF

[0140] LC/MS analysis of 5-HMF was performed to confirm that 5-HMF was included in the allulose conversion material.

[0141] As a 5-HMF analysis sample, a standard substance (SIGMA-ALDRICH, CAS Number 67-47-0) was purchased and used.

[0142] As a result, the molecular weight m/z values of the structures which can be generated from 5-HMF by charge transfer, elimination and dehydration in aqueous solution state were measured, having the peaks at 79.09 m/z, 109 m/z, 124.22 m/z, 127 m/z, 144.15 m/z etc, which are partially identical to the result of LC/MS analysis result of the allulose conversion material, indicating that 5-HMF was contained in the allulose conversion material.

Experimental Example 2: Allulose Stability Analysis

[0143] In order to test the effect by temperature of allulose and allulose conversion material, the allulose syrup including 97 wt/wt % of allulose of Example 1 was divided and placed in the same amount of 30 g each and stored in constant-temperature water baths of different temperatures each other, and sampled by time, thereby analyzing the content changes, and the result was shown in FIG. 1 and FIG. 2.

[0144] FIG. 1 is the graph showing the content changes of allulose, when the 70% Brix concentration of allulose syrup of pH 5 was stored by temperature. FIG. 2 is the graph showing the content changes of allulose conversion material, when the 70% Brix concentration of allulose syrup of pH 5 was stored by temperature. As shown in FIG. 1 and FIG. 2, as the storage temperature was higher, the content of allulose was decreased and the content of allulose conversion material (Impurity-S) was increased.

[0145] In addition, to test the effect according to pH of allulose and allulose conversion material, after controlling the syrup of 97.0% allulose content of Example 1 at respectively different pH by using caustic soda and hydrochloric acid solution, it was stored at the same temperature (70° C.) and sampled by time, thereby analyzing the content changes, and the result was shown in FIG. 3 and FIG. 4.

[0146] FIG. 3 is the graph showing the content changes of allulose, when the 70% Brix concentration of allulose syrup of different pH was stored at the temperature of 70° C. FIG. 4 is the graph showing the content changes of allulose conversion material, when the 70% Brix concentration of allulose syrup of different pH was stored at the temperature of 70° C. As shown in FIG. 3 and FIG. 4, as the pH was lower at the temperature of 70° C., the content of allulose was decreased and the content of allulose conversion material (Impurity-S) was increased.

[0147] Accordingly, since the allulose was unstable as pH was lower and temperature was higher, the content of allulose was changed in the actual production process, particularly concentration step. This problem lowered the purity of high purity of allulose, and therefore, largely affected the crystallization step. It was confirmed that the content of specific allulose conversion material (Impurity) produced additionally as the content of allulose was decreased in this process actually, and this component largely affected the crystallization of allulose. It was confirmed that when the content of component of Impurity-S in the various allulose conversion materials was over 2%, this might act as major barrier factor for the growth of allulose crystal particle, and thereby largely affect the particle size of crystal particle and crystallization yield.

Example 3: Analysis of Allulose Crystal Characteristics

[0148] (1): Analysis of Crystal Particle Size Distribution

[0149] The particle size distribution of allulose crystal obtained in Example 5 was confirmed by using standard sieves by Mesh. The Mesh sizes of standard sieves were 20, 30, 40, 60, 80, 100 mesh, and the size distribution of crystal particle was measured by the hole-sizes of standard sieves.

[0150] The hole-sizes of standard sieves by each mesh were 850, 600, 425, 250, 180, and 150 μm. 100 g of each sample was collected and put in standard sieves by mesh size, and passed through the standard sieves by adding vibration. The percentage values were described in Table 5 by measuring the weight of samples remained in sieves by each mesh size. In the following Table 5, the particle size distribution by each mesh was represented by wt % of particle with numerical values.

TABLE-US-00005 TABLE 5 Mesh size (mesh) 100 mesh pass 100mesh↑ 80mesh ↑ 60 mesh↑ 40 mesh↑ 30 mesh↑ 20 mesh↑ Particle size(μm) =150 150< 180< 250< 425< 600< 850< Example 5 0.9   2.6   5.9   20.2   70.0   0.4  0

[0151] As shown in the Table 5, it was confirmed that the allulose crystal of Example 5 exhibited very narrow distribution converging into 90.2 wt % of the particle distribution, and the allulose crystal of Example 3 exhibited the most distribution in 40⬆, but the particle distribution was widely spread as evenly distributed in 80⬆, 60⬆, 40⬆, and 30⬆. It was confirmed that the hard crystal particle having low ratio of long diameter/short diameter as Example 5 had relatively low content of micronized products and uniform distribution of particle size. In addition, the particle having high ratio of long diameter/short diameter and low homogeneity may be micronized by particle breakage in the drying and transferring processes and the particle size may be heterogeneous, thereby having the wide range of particle size distribution.

[0152] (2) Analysis of Crystal Form and Crystal Particle Size

[0153] The optical microscopic photographs of allulose crystals obtained in Example 5 measured by magnification X100 were shown in FIG. 5. The scanning microscopic photograph (SEM) of allulose crystals obtained in Example 5 measured by magnification X100 were shown in FIG. 6.

[0154] In addition, the long diameters (height) and short diameters (width) for 9 samples of allulose crystals obtained in Example 5 were measured, and the particle diameter ratio (=long diameter/short diameter) was obtained and shown in the following Table 6. Specifically, for 5 crystals, the ratio of length of long diameter (gym) was shown, on the basis of short diameter length (μm) as 1.

TABLE-US-00006 TABLE 6 Crystals Example 5 #1 1.3 #2 1.5 #3 1.2 #4 1.2 #5 2.1 #6 1.7 #7 1.7 #8 1.4 #9 2.4 average 1.6

[0155] As shown in FIG. 6, the allulose crystal of the present invention had a rectangle hexahedron or crystal structure close thereto. The ratio of long diameter length (μm) to the short diameter length (μm) of 1 of crystals in the Table 5 showed that average 1.6 in Example 5. Example 5 formed the crystal form of rhombic system close to quadrate as each crystal side was grown homogeneously. In addition, it was confirmed that the ratio of long diameter/short diameter tended to be reduced, as the crystal side was grown homogenously. This was suggested that since other components except for allulose acted as impurities disrupting the crystal growth of pure allulose, as the allulose purity in raw material for crystallization was low, they affected the crystal shape.

[0156] (3) Differential Scanning Calorimetry (DSC) Analysis

[0157] The DSC analysis of allulose crystals obtained in Example 5 was performed under the specific DSC analysis conditions.

[0158] Equipment name DSC [differential scanning calorimetry]

[0159] Manufacturer: Perkin Elmer

[0160] Method: 30 to 250° C., 10° C./min temperature rising, N2 gas purge

[0161] (standard method: refer to ASTM D 3418)

[0162] The result of DSC analysis of allulose crystal was shown in the following Table 7.

TABLE-US-00007 TABLE 7 Classification Tm(° C.) ΔH(J/g) Example 5 127.89 207.5

[0163] As the result of DSC analysis, the crystal in Example 5 had the highest Tm value, and the highest thermal capacity. It could be predicted that as the thermal capacity was higher in the DSC analysis of crystal, it was not easily dissolved, and as the thermal capacity was higher and the width of endothermic peak was narrower, the crystal was formed homogeneously and firmly. In consideration of thermal capacity and endothermic peak enthalpy values of Example 5, it was confirmed that the crystal of Example 5 was formed relatively more homogeneously and firmly.

[0164] (4) Infrared Absorption (IR) Spectrum Analysis

[0165] To confirm the prepared allulose crystal, the infrared absorption (IR) spectrum analysis was carried out for the crystals of Example 5, under the measuring conditions.

[0166] Analysis equipment: TENSOR II with Platinum ATR, manufacturer; Bruker (German)

[0167] Detector: highly sensitive photovoltaic MCT detector with liquid nitrogen cooling.

[0168] Scan number of times: 64 scans at 20 kHz

[0169] Scan range: 800-4,000 cm.sup.−1 and averaged at 4 cm-1 resolution.

[0170] According to the result of infrared absorption (IR) spectrum analysis for the allulose crystal according to the present invention, the allulose crystal had unique structural characteristic as the allulose molecule included functional groups —OH, and C—O—C, C—C, C—OH, etc. in the allulose molecular structure. It demonstrated that the crystals of Example 5 were identical allulose crystals. The IR analysis spectrum was shown in FIG. 7.

[0171] (5) X-Ray Diffraction (XRD) Analysis

[0172] The X-ray diffraction analysis was performed according to the following specific analysis conditions, for the allulose crystals obtained in Example 5, and the result of X-ray diffraction analysis of allulose crystals obtained in Example 5 was shown in Table 8 by selecting the higher (Relative Intensity %) five peaks and morphology specific peaks.

[0173] Analysis equipment: D/MAX-2200 Ultima/PC

[0174] Manufacturer: Rigaku International Corporation (Japan)

[0175] X-ray sauce system target: sealed tube Cu

[0176] Tube voltage: 45 kV/Tube current: 200 mA

[0177] Scan range: 5 to 80° 2θ

[0178] Step size: 0.019°

[0179] Scan speed: 5°/min

TABLE-US-00008 TABLE 8 Angle 2-Theta degree Relative Intensity % 18.78 100.0 15.24 97.6 28.37 9.5 30.84 18.8 31.87 9.0 47.06 4.1

[0180] As shown in the Table 8, it was confirmed that the allulose crystal obtained in Example 5 had specific peaks in 15.24, 18.78 and 30.84; 15.24, 18.78, 30.84, and 28.37; 15.24, 18.78, 30.84 and 31.87; 15.24, 18.78, 30.84 and 47.06; or 15.24, 18.78, 30.84, 28.37, 31.87 and 47.06; of 2θ values in the powder X-ray spectroscopy.