IMPROVED METHOD FOR MANUFACTURING ALLULOSE

Abstract

The present disclosure relates to an improved method for producing allulose and, more particularly, to a method for preparing a fructose-containing raw material solution by using raw sugar as a raw substrate used in the production process.

Claims

1. A method for producing allulose, the method comprising the steps of: preparing a fructose-containing raw material by obtaining an invert sugar syrup containing fructose and glucose using a raw material for sugar production containing sugar and an invertase, and putting it into a fructose separation process, and performing an allulose conversion reaction using the fructose-containing raw material.

2. The method of claim 1, wherein the method does not include an isomerization reaction of starch-derived glucose or a step of separating or purifying sugar from raw materials for sugar production.

3. The method of claim 1, wherein the fructose separation step comprises at least one selected from the group consisting of an activated carbon treatment step, an ion purification step, a high-purity separation step using simulated moving bed (SMB) chromatography, and a concentration step for the invert sugar syrup.

4. The method of claim 1, wherein the fructose separation step comprises an ion purification step, a high-purity separation step using simulated moving bed (SMB) chromatography, and a concentration step for the invert sugar syrup.

5. The method of claim 1, wherein the invert sugar syrup comprises fructose, glucose, and disaccharide or higher saccharide.

6. The method of claim 1, wherein the invert sugar syrup has a saccharide solid content of 10 wt % or more.

7. The method of claim 1, wherein the invert sugar syrup undergoes a fructose separation step to prepare a fructose-containing raw material containing 90 wt % or more of fructose based on the total saccharide solid content of the fructose-containing raw material.

8. The method of claim 1, wherein the total content of fructose and glucose is 90 wt % or more, based on the total saccharide solid content of the invert sugar syrup.

9. The method of claim 1, wherein fructose is included in an amount of 40 wt % or more, and glucose is included in an amount of 60 wt % or less, based 100 wt % of the total solid content of fructose and glucose contained in the invert sugar syrup.

10. The method of claim 1, wherein the fructose-containing raw material contains 0.001 to 2.2 mg/L of 5-HMF.

11. The method of claim 1, wherein the fructose-containing raw material has a content of oligosaccharides having DP3 or higher in an amount 2.0 wt % or less based on the solid content.

12. The method of claim 1, wherein the allulose conversion product comprises 0.001 to 5.7 mg/L of 5-HMF.

13. The method of claim 1, wherein the raw material for sugar production is a juice or concentrate of sugar cane or sugar beet, or a crystal obtained by removing molasses from the juice or concentrate.

14. The method of claim 1, wherein the raw material for sugar production is obtained by dissolving a crystal obtained by removing molasses from the juice or concentrate.

15. The method of claim 1, wherein the invert sugar syrup is obtained by adjusting the raw material for invertase treatment using a juice or concentrate of the raw material for sugar production, or a crystal obtained by removing molasses from the juice or concentrate, to a temperature of 55 to 75° C. and a pH of 4.0 to 5.0, and treating 0.01% to 1.0 wt % of invertase, based on the solid content of the the raw material for invertase treatment.

16. The method of claim 1, wherein the allulose conversion product is obtained by subjecting a fructose-containing raw material to a biological allulose conversion process.

17. The method of claim 1, wherein the fructose content of the fructose-containing raw material put into the allulose conversion reaction is 85 wt % or more based on 100 wt % of the total saccharide solid content.

18. The method of claim 1, wherein the allulose conversion reaction uses a biological having an allulose conversion rate of 15% to 70%.

19. The method of claim 1, which further comprises a step of obtaining allulose crystals and a crystallization mother liquor by concentrating an allulose fraction, and crystallizing allulose from the concentrate.

20. An allulose-containing composition comprising 1.0 wt % or less of 5-HMF, based on the solid content.

21. The allulose-containing composition of claim 20, wherein the composition contains 0.001 to 5.7 mg/L of 5-HMF.

22. The allulose-containing composition of claim 20, which is a product prepared by the method comprising the steps of preparing a fructose-containing raw material by obtaining an sugar syrup containing fructose and glucose using a raw material for sugar production containing sugar and an invertase, and putting it into a fructose separation process to prepare a fructose-containing raw material, and performing an allulose conversion reaction using the fructose-containing raw material.

23. The composition of claim 20, which comprises at least 5 wt % of allulose, based on the solid content.

74. The composition of claim 20, wherein the content of oligosaccharides having DP3 or higher is 2.0 wt % or less based on the solid content.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0107] FIG. 1 is an HPLC analysis result of an allulose conversion product prepared using raw sugar-derived fructose according to an embodiment of the present disclosure;

[0108] FIG. 2 is an HPLC analysis result of an allulose conversion product prepared using starch-derived fructose according to Comparative Example 1;

[0109] FIGS. 3 to 9 are HPLC analysis results of samples obtained in a sugar production process using raw sugar, where each sample is a raw sugar solution and a crystallization mother liquid for sugar production; and

[0110] FIG. 10 shows a standard curve for HMF content analysis using HPLC for starch-derived allulose and raw sugar-derived allulose solutions.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0111] The present disclosure will be described in more detail with reference to the following examples, but these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure.

Example 1: Production of Allulose Using Raw Materials for Sugar Production

[0112] 220 kg of raw sugar and 180 kg of distilled water were mixed, and the mixture was adjusted to pH 4.12 with 1N HCl to prepare a reaction solution having a solid content of 55 Brix. The reaction solution was treated with 0.1 wt % of invertase (Sumizyme INV-L, Ockzone Biochem) under temperature conditions, and the treated solution was reacted for 24 hours to obtain a reaction product solution containing 50.0 wt % of glucose and 48.6 wt % of fructose. The raw sugar was prepared from sugar cane, and has a sugar content of 98.5%.

[0113] The reaction product solution was treated with 1.0 wt % of activated carbon at a temperature of 80° C., and decolorized for 30 minutes, and the activated carbon was filtered to perform discoloration treatment. The decolorization-treated reaction product solution was flown through a cation exchange resin (SCRB), an anion exchange resin (AMP24), and a mixed resin (MB) of cation and anion exchange resins at a rate of twice the volume of the ion exchange resin per hour, thereby removing impurities such as colored and ionic components. The product from which the impurities were removed was subjected to a high-purity separation process (SMB) for fructose fractionation using a chromatography filled with a calcium (Ca.sup.2+) type ion exchange resin. Thereby, a fructose fraction having a fructose content of 85 wt % in the solid content was obtained. The fructose fraction was concentrated to obtain a fructose solution having a solid content of 50 wt % and a fructose content of 98.1 wt %.

[0114] Allulose was prepared using the prepared fructose raw material. Specifically, the allulose conversion step and the separation step were performed using the prepared fructose solution having a solid content of 50 wt % and a fructose content of 98.1 wt % at a flow rate of 3.8 m3/hr. The allulose content of the reactant obtained through the allulose conversion step was 20 to 23 wt %, and after ion purification, it was flowed through a separation step at a concentration of 45 to 50 wt %. Raffinate generated during separation using Ca+ type separation (SMB) resin was generated by 3 m3 per hour.

[0115] In the allulose conversion step, a fructose solution was flown through a column in which an allulose enzyme was immobilized to obtain a low-purity allulose having an allulose content of 21.8 wt %. Specifically, the allulose syrup was prepared from a fructose substrate by a biological method according to the production method as described in KR 10-1318422B.

[0116] Then, low-purity allulose was flown through an anion exchange resin and a mixed resin of cation and anion exchange resins to obtain a low-purity allulose that has flown through the ion resin. With respect to the low-purity allulose flown through the resin, a high-purity allulose fraction was separated using chromatography filled with a calcium (Ca.sup.2+) type ion exchange resin to prepare a high-purity allulose with an allulose content of 95 wt % or more. The high-purity allulose was flown through an anion exchange resin and a mixed resin of cation and anion exchange resins to obtain an ion-purified high-purity allulose. The obtained ion-purified high-purity allulose was concentrated to prepare a high-purity allulose concentrate having a solid content of 72 brix and a purity of 98.5 wt %.

Comparative Example 1: Production of Starch-Derived Allulose and Analysis of 5-HMF Content

[0117] In the method for producing allulose syrup in this Comparative Example, the allulose conversion step and the separation step of Example 1 were substantially performed, but as a substrate for the allulose conversion reaction, the starch-derived fructose raw material containing 90 wt % of fructose was reacted with 50 mM PIPES buffer solution under the conditions of pH 7.5 and 60° C. to obtain an allulose concentrate having a solid content 72 brix and an allulose purity of 97.5 wt %.

[0118] The starch-derived fructose was mixed with water so that the amount of corn starch was 30 to 35 wt %, and then subjected to enzyme hydrolysis to obtain a saccharified solution having glucose content of 88 wt % or more. Then, the saccharified solution was subjected to vacuum drum filtration to remove insoluble substances. Thereby, a fructose isomerization product (fructose content 42 wt % syrup) was obtained. The reaction product (fructose content 42 wt % syrup) that has subjected to the fructose isomerization step was flown through the first ion purification step consisting of a strong acid resin, a weak basic resin, and a strongly acidic resin and a weakly basic mixed resin, and the concentrated to 50 wt % of solids via ion purification, and then passed through SMB chromatography step. The fructose fraction was subjected to secondary ion purification and concentration steps to obtain a fructose-containing raw material solution having a solid content of 50 Brix and a fructose content of 90 wt %.

[0119] Using the fructose-containing solution, an allulose conversion product was prepared in substantially the same manner as in the allulose production process of Example 1. The ion purification, separation step using Ca+ type separation (SMB) resin, ion purification, and concentration process were performed to produce allulose. The final obtained allulose solution was prepared as a high-purity allulose concentrate having a solid content of 72 Brix and an allulose purity of up to 99 wt % (95 to 99wt % in the process).

Test Example 1: Analysis of 5-HMF Content of Allulose Derived from Raw Materials for Sugar Production

(1) Preparation of Analysis Samples

[0120] Two samples were prepared, including a high-purity fructose solution (sample 1), which is a raw material substrate for allulose production prepared in Example 1, and a high-purity allulose (sample :2) that has undergone a concentration process, and diluted to 5 Brix by adding purified water to prepare an analysis sample for 5-HMF analysis.

(2) Analysis Using a Spectrophotometer

[0121] As a method for measuring 5-HMF content using a spectrophotometer, the analysis sample was placed in a 1 ml quartz cuvette, measured with a spectrophotometer at absorbance at 280 nm and absorbance at 250 nm, and calculated according to Equation 1 to obtain 5-HMF content in the sample. Measurement result of 5-HMF content using the spectrophotometer and the measurement results of 5-HMF content using HPLC analysis are shown in Table 1 below. In Equation 1, A (280 nm) and A (250 nm) are absorbance values measured at 280 nm or 250 nm, respectively. The measurement results of 5-HMF content using the spectrophotometer are shown in Table 1 below.

[00001]$\begin{array}{cc}\mathrm{HMF}\left(\mathrm{mg}/L\right)=\frac{\left\{\left(A\left(280\mathrm{nm}\right)-A\left(250\mathrm{nm}\right)\right)-0.00149\right\}}{0.0923}& \left[\mathrm{Equation}1\right]\end{array}$

[0122] According to the measurement result of 5-HMF content using the spectrophotometer in Table 1 below, Sample 1 of Example 1, in which fructose, a substrate of the allulose conversion reaction, was prepared from raw sugar, had an HMF content of 0.53 (mg/L). Starch-derived fructose (Comparative sample 1) according to Comparative Example 1 in Table 2 below was analyzed spectrophotometrically. As a result, considering that the content of HMF was 2.29 (mg/L), it was confirmed that the HMF content of the raw sugar-derived fructose substrate of Example 1 was very low.

[0123] Samples 1 and 2 according to Example 1 showed a remarkable difference in HMF content from Comparative samples 1 and 2 according to Comparative Example 1. Therefore, it could be confirmed that according to this Example, the fructose-containing raw material derived from the raw material for sugar production and the allulose syrup prepared using the same only have a difference in 5-HMF content in fructose-containing raw materials, but also has a difference in HMF content in produced and separated allulose syrup, as compared with starch-derived fructose-containing raw materials and allulose syrup produced using them, and that it maintained a remarkably lower state than Comparative Example.

(3) HPLC Analysis

[0124] As an analysis method of 5-HMF content using HPLC analysis, specifically, as the HPLC-UV analysis conditions for the prepared analytical sample, the analysis was performed at 30° C. using a C18 (Shiseido, Capcell pak 4.6 mm Φ×250 mm) column, while flowing 90% (v/v) of water and 10% (v/v) of methanol as the mobile phase at a flow rate of 0.6 ml/min, and it was analyzed using a UV Detector. The sample analysis result using the HPLC analysis shows the area of each peak in the HPLC result graph in Table 1 below, and the relative content of the C18 compound (HMF) contained in each sample can be confirmed by using the peak area of the C18 compound (5-HMF) by HPLC analysis.

TABLE-US-00001 TABLE 1 Spectrophotometric C18 area analysis by HPLC Sample A280 nm A250 nm HMF(mg/L) analysis Sample 1 0.151 0.101 0.53 * Sample 2 0.452 0.226 1.24 83.6

[0125] It was confirmed that the content of 5-HMF in the sample obtained in the allulose production process using raw sugar was lower as compared with a comparative sample obtained in the allulose production process using starch-derived fructose. Therefore, it was confirmed that the product according to Example 1 had a higher allulose purity. Considering the C18 area by HPLC analysis in Table 1, it was confirmed that the difference from the HMF content conducted in Test Example 2 is significantly large. It was confirmed that when measured on samples of the same solid content, the peak of HMF is high, and when compared based on the area, the starch-derived allulose slightly increases in the amount of HMF. Especially when checking the sample 2 and the Comparative sample 2 that have completed the final concentration step, it was confirmed that the area value had a large difference.

[0126] Therefore, in the production of raw sugar-derived allulose, it is possible to produce high-purity allulose with higher purity and fewer by-products than conventional starch-derived allulose.

Test Example 2: Analysis of By-Product Content of Starch-Derived Allulose

(1) Preparation of Analytical Sample's

[0127] For the allulose prepared in Comparative Example 1, two types of samples were obtained for each process in the same manner as the sample of Test Example 1, and diluted to 5 brix by adding purified water to prepare an analytical sample.

[0128] Specifically, in the process for producing allulose, two sample groups were collected including high-purity starch-free high-purity fructose solution (Comparative sample 1) and concentrated high-purity allulose (Comparative sample 2) as the raw material substrate, and diluted to 5 brix for 5-HMF analysis to prepare an analytical sample.

(2) Analysis Using a Spectrophotometer

[0129] The analytical sample was analyzed in substantially the same manner as the measuring method of 5-HMF content using a spectrophotometer according to Test Example 1. The measurement results of 5-HMF content using the spectrophotometer are shown in Table 2 below.

[0130] It was confirmed that there was a significant difference in HMF content between raw sugar-derived fructose-containing raw materials and starch-derived fructose-containing raw materials. When starch-derived allulose is produced, the number of manufacturing steps increases as compared with raw sugar-derived allulose, and the amount of HMF becomes higher than that of raw sugar-derived allulose. In this example, comparing Comparative sample 2 and sample 2, it can be confirmed that there is a difference in the amount of final HMF, and raw sugar-derived allulose is higher even in the purity of the final allulose.

[0131] Therefore, in the production of raw sugar-derived allulose, it was confirmed that high-purity allulose with high purity and few by-products can be produced as compared with allulose made from starch.

(3) HPLC Analysis

[0132] The analytical sample was analyzed in substantially the same manner as the analysis method for 5-HMF content using HPLC analysis according to Test Example 1. As for the sample analysis result using the above HPLC analysis, the area of each peak in the HPLC result graph is shown in Table 2 below.

TABLE-US-00002 TABLE 2 Spectrophotometric C18 area analysis by HPLC Sample A280 nm A250 nm HMF(mg/L) analysis Comparative 2.359 2.146 2.29 * sample 1 Comparative 0.767 0.227 5.83 136.8 sample 2

[0133] HMF can be measured with UV Detector using HPLC. In order to compare the relative difference between HMF of raw sugar-derived allulose and starch-derived allulose, HPLC was measured by setting the same concentration. As a result, when sample 6 and Comparative sample 6 are confirmed, it is possible to confirm the difference in area. Further, it can be confirmed that the amount of HMF is proportional to the area, but the amount of HMF in raw sugar-derived allulose is small.

Test Example 3: Analysis of the By-Products Contents in Allulose Products for each Production Step

[0134] A fructose solution, which is a raw material substrate for allulose production prepared in Example 1, was obtained. As the fructose solution, a fructose solution having a solid content of 50 Brix and a fructose content of 98.1 wt % was used for analysis as sample 6-1. The allulose conversion product obtained by the allulose conversion step using the fructose solution was used as sample 6-2, the purified product in which the allulose conversion product was subjected to ion purification was used as sample 6-3, the allulose fraction obtained by separating the purified product subjected to ion purification using a Ca.sup.2+ type separation (SMB) resin was used as sample 6-4, the purified product obtained by purifying the allulose fraction was used as sample 6-5, and a high-purity allulose concentrate having a purity of 98.5 wt % with a solid content of 72 Brix obtained by concentrating the purified product was used as sample 6-6.

[0135] A starch-derived fructose solution, which is a raw material substrate for allulose production, was obtained according to Comparative Example 1. As the fructose solution, a fructose solution having a solid content of 50 Brix and a fructose content of 90 wt % was used as a Comparative sample 6-1 for analysis. The allulose conversion product obtained by the allulose conversion step using the fructose solution was used as a Comparative sample 6-2, the purified product obtained by ion-purifying the allulose conversion product was used as a Comparative sample 6-3, the allulose fraction obtained by separating the purified product subjected to ion purification using a Ca+ type separation (SMB) resin was used as a Comparative sample 6-4, the purified product obtained by purifying the allulose fraction was used as Comparative sample 6-5, and a high-purity allulose concentrate having a solid content of 72 Brix and a purity of 95 wt % obtained by concentrating the purified product watts used as a Comparative sample 6-6.

[0136] Purified water was added to the prepared samples 6-1 to 6-6 and Comparative samples 6-1 to 6-6 and diluted with 5 Brix to prepare an analytical sample for 5-HMF analysis. The 5-HMF analysis method was performed by HPLC analysis in substantially the same manner as the 5-HMF content analysis method in the sample of Test Example 1, and the analysis results are shown in Table 3 below. In Table 3 below, the amount of change (percentage) is expressed as a percentage of the. relative content of HMF included in each sample based on the HMF content included in the raw material sample 6-1 or Comparative sample 6-1. The standard curve used for the HPLC analysis is shown in FIG. 10.

TABLE-US-00003 TABLE 3 Changed amount(%) based on Sample ppm raw material sample 6-1 4.36 100% sample 6-2 137.97 3085%  sample 6-3 4.25  18% sample 6-4 17.03 311% sample 6-5 7.96 103% sample 6-6 8.37 113% Comparative sample 6-1 16.4 100% Comparative sample 6-2 110.9 576% Comparative sample 6-3 42.1 157% Comparative sample 6-4 82.1 401% Comparative sample 6-5 63.7 288% Comparative sample 6-6 46.0 180%

[0137] In Table 3, the content of 5-HMF in the sample obtained in the allulose production process using raw sugar, and the content of 5-HMF in the sample obtained in the allulose production process using starch was measured for each sample collected by each production process. According to the results of Table 3, it can be understood that the content of HMF does not depend on the raw material, but rather the content of by-products of the final product increases according to the process at the time of producing the product. In one example, reviewing Table 3, it is possible to confirm the difference in the HMF content of the product compared to the HMF content of the raw material high fructose. Therefore, it is possible to reduce the content of by-products at the time of producing raw sugar-derived allulose.

Test Example 4: Analysis of Storage Stability of Allulose Products

[0138] The high-purity allulose produced in Example 1 and Comparative Example 1 was used as a sample. Specifically, the final allulose solutions prepared in Example 1 and Comparative Example 1 were adjusted to a solid content of 70 Brix and pH 4, 5, 6, and 7 to prepare analytical samples. 10 ml each was taken and used for analysis.

[0139] The analytical samples were stored at 70° C. for 24 hours under conditions of pH 4, 5, 6, and 7 and subjected to a severe test. To determine the allulose content and the content of by-products, an HPLC analyzer was used. As the HPLC-UV analysis conditions, the analysis was performed at 30° C. using a C18 (Shiseido, Capcell pak 4.6 mm Φ×250 mm) column, while flowing 90% (v/v) of water and 10% (v/v) of methanol as the mobile phase at a flow rate of 0.6 ml/min, and it was analyzed using a UV Detector. The HPLC analysis results of the sample of Example 1 are shown in Table 1 below, and the HPLC analysis results of the Comparative sample of Comparative Example 1 are shown in Table 2 below.

[0140] As shown in the HPLC analysis result graph of FIG. 1, the allulose sample according to Example 1 showed a small decrease in storage conditions as compared with the starch-derived allulose of Comparative Example 1, and increase in the content of the by-product (5-HMF) is also less than that of the starch-derived allulose of Comparative Example 1.

[0141] As shown in the HPLC analysis result graph of FIG. 2, it was confirmed that on the starch-derived allulose of Comparative Example 1, the decrease in the allulose content and the increase in the by-product (5-HMF) content were significantly higher than those of the raw sugar-derived allulose of Example 1 under the storage condition at 70° C. for 24 hours.

[0142] Therefore, it was confirmed that the storage stability of raw sugar-derived allulose is higher than that of starch-derived allulose.

Test Example 5: Analysis of pH Stability of Allulose Products

[0143] The high-purity allulose prepared in Example 1 and Comparative Example 1 was used as a sample. Specifically, the final allulose solution prepared in Example I and Comparative Example 1 was adjusted to pH 4, 5, 6, and 7 using 1N HCl and 1N NaOH, and then the solid content was adjusted to 70 Brix, and the pH was adjusted to pH 4, 5, 6, and 7, respectively, to prepare an analytical sample. Each 10 ml of the assay sample was taken and used for the assay.

[0144] Then, the analytical sample was stored at 70° C. for 24 hours and subjected to a severe test. Then, the allulose content and the by-product content were analyzed in substantially the same manner as the HPLC analysis method of Test Example 1. The HPLC analysis results for the sample of Example 1 and the sample of Comparative Example 1 are shown in Table 4 below. The allulose content immediately after the preparation of the assay sample was used as a control.

TABLE-US-00004 TABLE 4 Reduced pH Control After 24 amount Sample condition group hours (wt %) Example 1 4 98.1 92.6 5.5 Example 1 5 98.3 95.5 2.8 Example 1 6 98.2 96.0 2.2 Example 1 7 98.2 96.2 2.0 Comparative Example 1 4 96.7 89.9 6.8 Comparative Example 1 5 97.0 92.7 4.3 Comparative Example 1 6 96.9 92.8 4.0 Comparative Example 1 7 96.9 93.3 3.6

[0145] Comparing the results of storage under harsh conditions according to pH conditions for the allulose syrup obtained in Example 1 and Comparative Example 1, it was confirmed that the amount of reduction of raw sugar-derived allulose according to Example 1 is small compared to the starch-derived allulose of Comparative Example 1, and the raw sugar-derived allulose is more preferable in terms of storage stability according to pH conditions.

Test Example 6: Analysis of By-Products for Each Step of Sugar Purification Process

[0146] Sugar is produced by re-purifying the mother liquor during progress of crystallization in the existing sugar production process. The mother liquid was obtained and the by-products for each process were analyzed under the same conditions as those of Test Example 2 by HPLC method. Specifically, the analysis samples were raw sugar, mother liquid 1, mother liquid 2, mother liquid 3, and mother liquid 4.

[0147] Raw sugar was collected and analyzed before entering the existing process, and when this raw sugar was dissolved and crystallized, sugar was released, and the remaining solution is called mother liquor 1. When mother liquor 1 is crystallized again, sugar with a lower quality than the crystallization in the first stage is produced, and the remaining liquid is called mother liquor 2. In this manner, sugar was crystallized two more times, and mother liquid 3 and mother liquid 4 were obtained sequentially. The liquid that remains alter crystallization in the process of crystallizing sugar is called mother liquor. As the crystallization step proceeds, the concentration of impurities in the mother liquor becomes more intense. Therefore, when the existing raw sugar is dissolved and sugar crystallization is promoted, impurities become thick in the mother liquor remaining excluding the sugar obtained as a product.

[0148] As a result of analyzing the sample obtained in the sugar production process, many unknown peaks were detected, and these substances are produced as sugar and are discarded in the same way as wastewater, which may cause future environmental problems. When sugar converts to allulose, a large amount of by-products are generated in the process of producing even sugar, which requires a process that has to deal with many by-products before producing allulose.

[0149] As shown in FIGS. 3 to 9, when sugar converts to allulose, a large amount of by-products are generated in the process of producing even sugar, which requires a process to process many by-products until allulose is produced. When allulose is produced directly from raw sugar as in Examples, since it goes directly to allulose without going through this process, it is advantageous because a separate process of generating by-products is eliminated.