Method for purifying allulose-containing solution using ion exchange

Abstract

One embodiment of the present invention provides a method for purifying an allulose-containing solution, comprising passing the allulose-containing solution through an ion exchange resin column packed with a mixed-phase ion exchange resin to obtain an ion-purified allulose-containing solution. In this method, the mixed-phase ion exchange resin is a mixture of a strong acid cation exchange resin and a weak basic anion exchange resin, and the weak basic anion exchange resin constituting the mixed-phase ion exchange resin has a quaternary ammonium exchange capacity fraction of 0 to 10%. The method for purifying an allulose-containing solution according to the present invention can not only reduce the electrical conductivity of the allulose-containing solution to an acceptable level, but also minimize allulose loss by inhibiting the conversion of allulose to fructose or other substances by the functional groups of the ion exchange resin. Therefore, the method for purifying an allulose-containing solution according to the present invention is suitable for mass production of high-quality allulose.

Description

[Technical Field]

[0001] The present invention relates to a method for purifying an allulose-containing solution, and more particularly to a method that can minimize allulose loss when purifying an allulose-containing solution using an ion exchange resin. [Background technology]

[0002] D-allulose, also known as D-psicose, is the epimer of fructose at the C3 position. Compared to sugar, D-allulose has 70% the sweetness (Oshima 2006) but only 0.3% of the energy content, making it a functional monosaccharide suitable for use as a low-calorie sweetener in diet foods (Matsuo et al. 2002). Furthermore, D-allulose suppresses glucose absorption and blood glucose levels, making it suitable for use in foods for diabetics and weight loss. It also inhibits the activity of enzymes involved in hepatic lipid synthesis, thereby suppressing abdominal fat accumulation. Therefore, it can be used in a variety of functional foods, including health foods (Matsuo et al. 2001; Iida et al. 2008; Hayashi et al. 2010; Hossain et al. 2011).

[0003] Due to these characteristics, allulose is a good alternative to sugar. However, because it is a rare sugar, a monosaccharide that is rarely found in nature, an efficient method for producing allulose is required for its application in the food industry. The most efficient method for producing allulose industrially is to convert fructose to allulose using a D-allulose 3-epimerization enzyme. The D-allulose-containing reaction product solution produced by the enzymatic reaction is then filtered, decolorized, concentrated, and purified by ion exchange to produce a low-purity solution with a D-allulose content of approximately 20-30% (w / w) based on solids. Furthermore, this low-purity solution with a D-allulose content of approximately 20-30% (w / w) is further purified by simulated moving bed (SMB) chromatography and ion exchange purification to produce a high-purity solution with a D-allulose content of approximately 95-99% (w / w) based on solids.

[0004] Korean Patent Publication No. 10-1988441, relating to allulose purification technology, discloses a method for purifying allulose, including the steps of: mixing an allulose conversion reactant with powdered activated carbon, performing a solid-liquid separation process on the mixture to remove impurities and activated carbon, and obtaining a filtrate; performing an ion purification process using a column packed with an ion exchange resin after the activated carbon treatment step; and performing a simulated moving bed (SMB) chromatography separation step to obtain an allulose fraction and fructose raffinate. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been derived from the conventional technical background, and an object of the present invention is to provide a method for purifying an allulose-containing solution that can minimize allulose loss while achieving an acceptable level of ion purification efficiency using an ion exchange resin. [Means for solving the problem]

[0006] When a D-allulose-containing reaction solution is purified by ion exchange to produce a low-purity solution with a D-allulose content of about 20-30% (w / w) based on solids, some of the allulose is converted to fructose or other substances by the functional groups of the ion exchange resin, resulting in allulose loss. Furthermore, when ion exchange purification is performed after simulated moving bed (SMB) chromatography to produce a high-purity solution with a D-allulose content of about 95-99% (w / w) based on solids, a mixed ion exchange resin composed of a strong acid cation exchange resin and a strong basic anion exchange resin is typically used, resulting in significant allulose loss. The present inventors recognized the inherent problems that arise during the purification of allulose-containing solutions using ion exchange and, to solve these problems, conducted experiments to purify allulose-containing solutions using various combinations of ion exchange resin columns. As a result, they confirmed that allulose loss is minimized when a specific combination of ion exchange resins is used, thereby completing the present invention.

[0007] To achieve the above object, one embodiment of the present invention provides a method for purifying an allulose-containing solution, comprising the step of passing the allulose-containing solution through an ion exchange resin column packed with a mixed-phase ion exchange resin to obtain an ion-purified allulose-containing solution. In this method for purifying an allulose-containing solution, the mixed-phase ion exchange resin is a mixture of a strong acid cation exchange resin and a weak basic anion exchange resin, and the weak basic anion exchange resin constituting the mixed-phase ion exchange resin has an exchange capacity fraction of 0 to 10% for quaternary ammonium.

[0008] To achieve the above object, another embodiment of the present invention provides a method for purifying an allulose-containing solution, comprising the steps of sequentially passing an allulose-containing solution through a first ion exchange resin column packed with a strongly acidic cation exchange resin, a second ion exchange resin column packed with a weakly basic anion exchange resin, and a third ion exchange resin column packed with a mixed-phase ion exchange resin to obtain an ion-purified allulose-containing solution. In this method for purifying an allulose-containing solution, the mixed-phase ion exchange resin is a mixture of a strongly acidic cation exchange resin and a weakly basic anion exchange resin. In addition, in this method for purifying an allulose-containing solution, the weakly basic anion exchange resin packed in the second ion exchange resin column and the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin have a quaternary ammonium exchange capacity fraction of 0 to 10%. [Effects of the Invention]

[0009] The method for purifying an allulose-containing solution according to the present invention can not only reduce the electrical conductivity of the allulose-containing solution to an acceptable level, but also minimize the loss of allulose by inhibiting the conversion of allulose to fructose or other substances by the functional groups of the ion exchange resin. Therefore, the method for purifying an allulose-containing solution according to the present invention is suitable for mass production of high-quality allulose. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be specifically described below.

[0011] The term "exchange capacity fraction" used in the present invention indicates the percentage of the exchange capacity contributed by a specific exchange group to the total exchange capacity of the ion exchange resin.

[0012] The present invention relates to a method for purifying an allulose-containing solution using an ion exchange resin, which can minimize allulose loss while achieving an acceptable level of ion purification efficiency.

[0013] A method for purifying an allulose-containing solution according to one embodiment of the present invention includes passing the allulose-containing solution through an ion exchange resin column packed with a mixed-phase ion exchange resin, which is a mixture of a strong acid cation exchange resin and a weak basic anion exchange resin, to obtain an ion-purified allulose-containing solution.

[0014] The type of the strong acid cation exchange resin constituting the mixed-phase ion exchange resin is not particularly limited and may be selected from, for example, hydrogen ion type (H type) or sodium type (Na type) strong acid cation exchange resins. When using the Na type strong acid cation exchange resin, it can be converted to the H type using an aqueous acid (e.g., HCl) solution of an appropriate concentration before use. The strong acid cation exchange resin may be of a gel type or a porous type, and is preferably of the porous type. The strong acid cation exchange resin has sulfonic acid groups as exchange groups, and the base resin may be a styrene-divinylbenzene copolymer produced by polymerizing a monovinylidene aromatic monomer (e.g., styrene) and a crosslinker (e.g., divinylbenzene (DVB)).

[0015] The type of weakly basic anion exchange resin constituting the mixed-phase ion exchange resin is not particularly limited as long as the exchange capacity fraction of quaternary ammonium is 0 to 10%. For example, the weakly basic anion exchange resin may be a gel type or a porous type, preferably a porous type. The weakly basic anion exchange resin may have a tertiary amine group or a quaternary ammonium group as an exchange group, and the base material may be a styrene-divinylbenzene copolymer prepared by polymerizing a monovinylidene aromatic monomer (e.g., styrene) with a crosslinker (e.g., divinylbenzene (DVB)). The quaternary ammonium group, which is the exchange group present in the weakly basic anion exchange resin, is selected from a type I quaternary ammonium group such as trimethylammonium or a type II quaternary ammonium group such as dimethylethanolammonium. Considering the purification efficiency and minimization of allulose loss, a type I quaternary ammonium group such as trimethylammonium is preferred. When the exchange capacity fraction of quaternary ammonium is 0%, the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin has tertiary amine groups as exchange groups, and the exchange capacity fraction of the tertiary amine groups is 100%. When the exchange capacity fraction of quaternary ammonium is 5%, the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin has quaternary ammonium groups and tertiary amine groups as exchange groups, and the exchange capacity fraction of the tertiary amine groups is 95%. When the exchange capacity fraction of quaternary ammonium is 10%, the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin has quaternary ammonium groups and tertiary amine groups as exchange groups, and the exchange capacity fraction of the tertiary amine groups is 90%. Considering ion purification efficiency, the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin preferably has an exchange capacity fraction of quaternary ammonium of 5 to 10%.

[0016] In a method for purifying an allulose-containing solution according to one example of the present invention, the volume ratio of the strong acidic cation exchange resin and the weak basic anion exchange resin constituting the mixed phase ion exchange resin is not particularly limited, and when taking into consideration ion purification efficiency and minimization of allulose loss, it is preferably 1:1 to 1:4, and more preferably 1:1.5 to 1:3.

[0017] In a method for purifying an allulose-containing solution according to one embodiment of the present invention, the saccharide solid concentration, pH, electrical conductivity, allulose content, etc. of the allulose-containing solution injected into the ion exchange resin column are not particularly limited. In consideration of ion purification efficiency, the allulose-containing solution preferably has a saccharide solid concentration of 5 to 50 Brix (Brix), a pH of 3.5 to 5.5, an electrical conductivity of 5 to 80 μs / cm, and an allulose content of 90 to 99% (w / w) based on the total solid weight, and more preferably has a saccharide solid concentration of 8 to 30 Brix (Brix), a pH of 4 to 5, an electrical conductivity of 15 to 60 μs / cm, and an allulose content of 95 to 99% (w / w) based on the total solid weight.

[0018] In a method for purifying an allulose-containing solution according to one example of the present invention, the temperature of the ion exchange resin column is preferably 30 to 55°C, more preferably 40 to 50°C, taking into consideration ion purification efficiency and minimizing allulose loss. Furthermore, in a method for purifying an allulose-containing solution according to one example of the present invention, when the allulose-containing solution passes through the ion exchange resin column, the space velocity (SV) is not particularly limited, and is preferably 1 to 5, more preferably 1.5 to 3, taking into consideration ion purification efficiency.

[0019] A method for purifying an allulose-containing solution according to another embodiment of the present invention includes sequentially passing the allulose-containing solution through a first ion exchange resin column filled with a strongly acidic cation exchange resin, a second ion exchange resin column filled with a weakly basic anion exchange resin, and a third ion exchange resin column filled with a mixed-phase ion exchange resin, thereby obtaining an ion-purified allulose-containing solution.

[0020] In another embodiment of the present invention, the strong acid cation exchange resin packed in the first ion exchange resin column is not particularly limited in type and may be selected from hydrogen ion type (H type) or sodium type (Na type) strong acid cation exchange resins. When using the Na type strong acid cation exchange resin, it can be converted to H type using an aqueous acid (e.g., HCl) solution of an appropriate concentration before use. The strong acid cation exchange resin may be a gel type or a porous type, and preferably a gel type. The strong acid cation exchange resin has sulfonic acid groups as exchange groups, and the base resin may be a styrene-divinylbenzene copolymer produced by polymerizing a monovinylidene aromatic monomer (e.g., styrene) and a crosslinker (e.g., divinylbenzene (DVB)).

[0021] In another embodiment of the method for purifying an allulose-containing solution according to the present invention, the type of weakly basic anion exchange resin packed in the second ion exchange resin column is not particularly limited as long as the exchange capacity fraction of quaternary ammonium is 0 to 10%. For example, the weakly basic anion exchange resin may be a gel type or a porous type, preferably a porous type. Furthermore, the weakly basic anion exchange resin has a tertiary amine group or a quaternary ammonium group as an exchange group, and the base resin may be a styrene-divinylbenzene copolymer produced by polymerizing a monovinylidene aromatic monomer (e.g., styrene) and a crosslinker (e.g., divinylbenzene (DVB)). The quaternary ammonium group, which is the exchange group present in the weakly basic anion exchange resin, is selected from a type I quaternary ammonium group such as trimethyl ammonium or a type II quaternary ammonium group such as dimethylethanol ammonium. Considering purification efficiency and minimizing allulose loss, a type I quaternary ammonium group such as trimethyl ammonium is preferred. When the exchange capacity fraction of the quaternary ammonium is 0%, the weakly basic anion exchange resin has tertiary amine groups as exchange groups, and the exchange capacity fraction of the tertiary amine groups is 100%. When the exchange capacity fraction of the quaternary ammonium is 5%, the weakly basic anion exchange resin has quaternary ammonium groups and tertiary amine groups as exchange groups, and the exchange capacity fraction of the tertiary amine groups is 95%. Furthermore, when the exchange capacity fraction of quaternary ammonium is 10%, the weakly basic anion exchange resin has quaternary ammonium groups and tertiary amine groups as exchange groups, and the exchange capacity fraction of tertiary amine groups is 90%. In consideration of ion purification efficiency and minimizing allulose loss, the weakly basic anion exchange resin packed in the second ion exchange resin column preferably has tertiary amine groups as exchange groups and the exchange capacity fraction of quaternary ammonium is 0%.

[0022] In another embodiment of the present invention, the mixed-phase ion exchange resin packed in the third ion exchange resin column is a mixture of a strong acid cation exchange resin and a weak basic anion exchange resin. The weak basic anion exchange resin constituting the mixed-phase ion exchange resin has a quaternary ammonium exchange capacity fraction of 0-10%. Considering ion purification efficiency and minimizing allulose loss, the quaternary ammonium exchange capacity fraction is preferably 5-10%. Furthermore, the mixed volume ratio of the strong acid cation exchange resin and the weak basic anion exchange resin constituting the mixed-phase ion exchange resin is preferably 1:1 to 1:4. In another embodiment of the present invention, the technical features of the mixed-phase ion exchange resin packed in the third ion exchange resin column are the same as those described in the embodiment of the present invention, and therefore a detailed description thereof will be omitted.

[0023] In another embodiment of the method for purifying an allulose-containing solution according to the present invention, the volume ratio of the strongly acidic cation exchange resin packed in the first ion exchange resin column, the weakly basic anion exchange resin packed in the second ion exchange resin column, and the mixed-phase ion exchange resin packed in the third ion exchange resin column is not particularly limited, and when considering the ion purification efficiency, it is preferably 1:(0.5-2):(0.5-2), and more preferably 1:(0.65-1.5):(0.65-1.5).

[0024] In another embodiment of the method for purifying an allulose-containing solution according to the present invention, the saccharide solid concentration, pH, electrical conductivity, allulose content, etc. of the allulose-containing solution injected into the first ion exchange resin column are not particularly limited. In consideration of the efficiency of ion purification, the allulose-containing solution preferably has a saccharide solid concentration of 25 to 65 Brix (Brix), a pH of 3.5 to 5.5, an electrical conductivity of 20 to 400 μs / cm, and an allulose content of 10 to 50% (w / w) based on the total weight of the solids, and more preferably has a saccharide solid concentration of 40 to 60 Brix (Brix), a pH of 4 to 5, an electrical conductivity of 50 to 250 μs / cm, and an allulose content of 15 to 35% (w / w) based on the total weight of the solids.

[0025] In another example of the method for purifying an allulose-containing solution according to the present invention, the temperatures of the first ion exchange resin column, the second ion exchange resin column, and the third ion exchange resin column are preferably 30 to 55°C, and more preferably 35 to 45°C, when taking into consideration the ion purification efficiency and minimizing allulose loss. Furthermore, in another example of the method for purifying an allulose-containing solution according to the present invention, when the allulose-containing solution passes through the first ion exchange resin column, the second ion exchange resin column, and the third ion exchange resin column, the space velocity (SV) is not particularly limited, and is preferably 1 to 5, and more preferably 1.5 to 3, when taking into consideration the efficiency of ion purification.

[0026] The present invention will be described in more detail with reference to the following examples, which are intended only to clearly illustrate the technical features of the present invention and are not intended to limit the scope of the present invention.

[0027] 1. Information on ion exchange resins The following Table 1 summarizes the information on the ion exchange resins used in the examples of the present invention. All of the ion exchange resin products listed in Table 1 below can be purchased commercially.

[0028] [Table 1]

[0029] 2. Ion exchange purification of allulose-containing solution Experimental example 1. A fructose solution was contacted with an immobilized allulose epimerization enzyme to carry out an isomerization reaction. Activated carbon was then added to the reaction solution, and the decolorization reaction was carried out at 50°C. The solution was then filtered and concentrated to prepare a low-purity allulose-containing solution with a sugar solids concentration of approximately 50 Brix, a pH of approximately 4.5, and an electrical conductivity of approximately 108 μs / cm. The allulose content in the low-purity allulose-containing solution was approximately 20.44% (w / w) based on the total solids weight. A mixed-phase ion exchange resin was prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a weakly basic anion exchange resin (product name: DS4) in a volume ratio of 1:2. Next, a total of three ion exchange resin columns were prepared by sequentially connecting a first column packed with a strongly acidic cation exchange resin (product name: DS1), a second column packed with a weakly basic anion exchange resin (product name: DS5), and a third column packed with a mixed-phase ion exchange resin. The volume ratio of the cation exchange resin packed in the first column, the anion exchange resin packed in the second column, and the mixed ion exchange resin packed in the third column was 1:1.5:1. The temperature of the ion exchange resin column was maintained at 45°C, and the low-purity allulose-containing solution was passed through the ion exchange resin column at a space velocity (SV) of 2.6 to obtain an ion-purified allulose-containing solution.

[0030] Experimental example 2. A fructose solution was contacted with the immobilized allulose epimerization enzyme to carry out an isomerization reaction. Activated carbon was then added to the reaction solution, and the decolorization reaction was carried out at 50°C. The solution was then filtered and concentrated to prepare a low-purity allulose-containing solution with a sugar solids concentration of approximately 50 Brix, a pH of approximately 4.5, and an electrical conductivity of approximately 118 μs / cm. The allulose content in the low-purity allulose-containing solution was approximately 20.30% (w / w) based on the total weight of solids. A mixed-phase ion exchange resin was prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a weakly basic anion exchange resin (product name: DS4) in a volume ratio of 1:2. Next, a total of three ion exchange resin columns were prepared by sequentially connecting a first column packed with a strongly acidic cation exchange resin (product name: DS1), a second column packed with a weakly basic anion exchange resin (product name: DS4), and a third column packed with a mixed-phase ion exchange resin. The volume ratio of the cation exchange resin packed in the first column, the anion exchange resin packed in the second column, and the mixed ion exchange resin packed in the third column was 1:1.5:1. The temperature of the ion exchange resin column was maintained at 45°C, and the low-purity allulose-containing solution was passed through the ion exchange resin column at a space velocity (SV) of 2.6 to obtain an ion-purified allulose-containing solution.

[0031] Experimental example 3. A fructose solution was contacted with an immobilized allulose epimerization enzyme to carry out an isomerization reaction. Activated carbon was then added to the reaction solution, and the decolorization reaction was carried out at 50°C. The solution was then filtered and concentrated to prepare a low-purity allulose-containing solution with a sugar solids concentration of approximately 50 Brix, a pH of approximately 4.4, and an electrical conductivity of approximately 101 μs / cm. The allulose content in the low-purity allulose-containing solution was approximately 20.41% (w / w) based on the total weight of solids. A mixed-phase ion exchange resin was prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a weakly basic anion exchange resin (product name: DS4) in a volume ratio of 1:2. Next, a total of three ion exchange resin columns were prepared by sequentially connecting a first column packed with a strongly acidic cation exchange resin (product name: DS1), a second column packed with a medium-basic anion exchange resin (product name: DS3), and a third column packed with a mixed-phase ion exchange resin. The volume ratio of the cation exchange resin packed in the first column, the anion exchange resin packed in the second column, and the mixed ion exchange resin packed in the third column was 1:1.5:1. The temperature of the ion exchange resin column was maintained at 45°C, and the low-purity allulose-containing solution was passed through the ion exchange resin column at a space velocity (SV) of 2.6 to obtain an ion-purified allulose-containing solution.

[0032] Experimental example 4. A fructose solution was contacted with an immobilized allulose epimerization enzyme to carry out an isomerization reaction. Activated carbon was then added to the reaction solution, and the decolorization reaction was carried out at 50°C. The solution was then filtered and concentrated to prepare a low-purity allulose-containing solution with a sugar solid concentration of approximately 50 Brix, a pH of approximately 4.5, and an electrical conductivity of approximately 105 μs / cm. The allulose content in the low-purity allulose-containing solution was approximately 20.39% (w / w) based on the total weight of solids. A mixed-phase ion exchange resin was prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a strongly basic anion exchange resin (product name: DS6) in a volume ratio of 1:2. A total of three ion exchange resin columns were prepared by sequentially connecting a first column packed with a strongly acidic cation exchange resin (product name: DS1), a second column packed with a medium-basic anion exchange resin (product name: DS3), and a third column packed with a mixed-phase ion exchange resin. The volume ratio of the cation exchange resin packed in the first column, the anion exchange resin packed in the second column, and the mixed ion exchange resin packed in the third column was 1:1.5:1. The temperature of the ion exchange resin column was maintained at 45°C, and the low-purity allulose-containing solution was passed through the ion exchange resin column at a space velocity (SV) of 2.6 to obtain an ion-purified allulose-containing solution.

[0033] Experimental Example 5. A fructose solution was contacted with the immobilized allulose epimerization enzyme to carry out an isomerization reaction. Activated carbon was then added to the reaction solution, and the decolorization reaction was carried out at 50°C. After that, the reaction solution was filtered, concentrated, and purified using an ion exchange resin to obtain a low-purity allulose-containing solution. The low-purity allulose-containing solution was then subjected to simulated moving bed (SMB) chromatography separation using a column packed with a cation exchange resin with calcium activated groups attached. A high-purity allulose-containing solution with a sugar solid concentration of approximately 10 Brix, a pH of approximately 4.5, and an electrical conductivity of approximately 36 μs / cm was obtained. The allulose content in the high-purity allulose-containing solution was approximately 97.96% (w / w) based on the total solid weight. A mixed-phase ion exchange resin was prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a weakly basic anion exchange resin (product name: DS4) in a volume ratio of 1:2. Then, an ion exchange resin column packed with a mixed-phase ion exchange resin was prepared. The temperature of the ion exchange resin column was maintained at 45°C, and the highly purified allulose-containing solution was passed through the ion exchange resin column at a space velocity (SV) of 2.6 to obtain an ion-purified allulose-containing solution.

[0034] Experimental Example 6. A fructose solution was contacted with the immobilized allulose epimerization enzyme to induce an isomerization reaction. Activated carbon was then added to the reaction solution, and the decolorization reaction was carried out at 50°C. This was followed by filtration, concentration, and purification with an ion exchange resin to obtain a low-purity allulose-containing solution. The low-purity allulose-containing solution was then subjected to simulated moving bed (SMB) chromatography separation using a column packed with a cation exchange resin with calcium activated groups attached to it, yielding a high-purity allulose-containing solution with a sugar solid concentration of approximately 10 Brix, a pH of approximately 4.5, and an electrical conductivity of approximately 40 μS / cm. The allulose content in the high-purity allulose-containing solution was approximately 98.3% (w / w) based on the total solids weight. A mixed-phase ion exchange resin was prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a moderately basic anion exchange resin (product name: DS3) in a volume ratio of 1:2. Then, an ion exchange resin column packed with a mixed-phase ion exchange resin was prepared. The temperature of the ion exchange resin column was maintained at 45°C, and the highly purified allulose-containing solution was passed through the ion exchange resin column at a space velocity (SV) of 2.6 to obtain an ion-purified allulose-containing solution.

[0035] Experimental Example 7. A fructose solution was contacted with the immobilized allulose epimerization enzyme to induce an isomerization reaction. Activated carbon was then added to the reaction solution, and the decolorization reaction was carried out at 50°C. This was followed by filtration, concentration, and purification with an ion exchange resin to obtain a low-purity allulose-containing solution. The low-purity allulose-containing solution was then subjected to simulated moving bed (SMB) chromatography separation using a column packed with a cation exchange resin with calcium activated groups attached. This resulted in a high-purity allulose-containing solution with a sugar solids concentration of approximately 10 Brix, a pH of approximately 4.5, and an electrical conductivity of approximately 36 μs / cm. The allulose content in the high-purity allulose-containing solution was approximately 97.63% (w / w) based on the total solids weight. A mixed-phase ion exchange resin was prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a strongly basic anion exchange resin (product name: DS6) in a volume ratio of 1:2. Then, an ion exchange resin column packed with a mixed-phase ion exchange resin was prepared. The temperature of the ion exchange resin column was maintained at 45°C, and the highly purified allulose-containing solution was passed through the ion exchange resin column at a space velocity (SV) of 2.6 to obtain an ion-purified allulose-containing solution.

[0036] Table 2 below shows the combinations of ion exchange resins used in Experimental Examples 1 to 7.

[0037] [Table 2]

[0038] Table 3 below summarizes the changes in the physical properties of the allulose-containing solution before it was injected into the ion exchange resin column and after it had passed through the ion exchange resin column and been discharged.

[0039] [Table 3]

[0040] As shown in Tables 2 and 3, the allulose-containing solution discharged after passing through the ion exchange resin column exhibited acceptable pH and conductivity levels regardless of the combination of ion exchange resins. However, when the allulose-containing solution passes through the ion exchange resin column for ion purification, the loss of allulose caused by isomerization reactions, etc., varied significantly depending on the combination of ion exchange resins. Specifically, allulose loss was minimized in Experimental Examples 1, 2, and 5. The ion exchange resin columns used in Experimental Examples 1, 2, and 5 all contained a mixed-phase ion exchange resin prepared by mixing a strong acid cation exchange resin (product name: DS2) and a weak basic anion exchange resin (product name: DS4) in a volume ratio of 1:2. On the other hand, the ion exchange resin column used in Experimental Example 3 also contained a mixed-phase ion exchange resin prepared by mixing a strongly acidic cation exchange resin (product name: DS2) and a weakly basic anion exchange resin (product name: DS4) in a volume ratio of 1:2. However, in Experimental Example 3, allulose loss was somewhat large. This result is due to the difference in the anion exchange resin positioned in the second stage of the ion exchange resin column. In Experimental Examples 1 and 2, the anion exchange resin positioned in the second stage was a weakly basic anion exchange resin (product name: DS5) with an exchange capacity fraction of 0% accounted for by quaternary ammonium and a weakly basic anion exchange resin (product name: DS4) with an exchange capacity fraction of 5-10% accounted for by quaternary ammonium, respectively. In contrast, in Experimental Example 3, the anion exchange resin positioned in the second stage was a medium-basic anion exchange resin (product name: DS3) with an exchange capacity fraction of 25% accounted for by quaternary ammonium. The results showed that the greater the exchange capacity fraction occupied by quaternary ammonium in the anion exchange resin located in the second stage of the ion exchange resin column, the greater the allulose loss rate.From the perspective of mass production, the exchange capacity fraction occupied by quaternary ammonium in the anion exchange resin located in the second stage of the ion exchange resin column is preferably 0 to 10%.

[0041] Although the present invention has been described above through examples, it is to be understood that the present invention is not necessarily limited thereto, and various modifications can be made without departing from the scope and spirit of the present invention. Therefore, the scope of protection of the present invention should be interpreted as including all embodiments falling within the scope of the claims attached hereto.

Claims

1. A method comprising the steps of passing an allulose-containing solution through an ion exchange resin column filled with a mixed-phase ion exchange resin to obtain an ion-purified allulose-containing solution, the mixed-phase ion exchange resin is a mixture of a strong acid cation exchange resin and a weak basic anion exchange resin; A method for purifying an allulose-containing solution, wherein the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin has an exchange capacity fraction of quaternary ammonium of 0 to 10%.

2. The method for purifying an allulose-containing solution according to claim 1, wherein the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin has an exchange capacity fraction of quaternary ammonium of 5 to 10%.

3. The method for purifying an allulose-containing solution according to claim 1, characterized in that the mixed-phase ion exchange resin comprises a strongly acidic cation exchange resin and a weakly basic anion exchange resin in a volume ratio of 1:1 to 1:

4.

4. The allulose-containing solution injected into the ion exchange resin column has a sugar solid concentration of 5 to 50 Brix, a pH of 3.5 to 5.5, an electrical conductivity of 5 to 80 μs / cm, and an allulose content of 90 to 99% (w / w) based on the total weight of the solids.

5. A method for obtaining an ion-purified allulose-containing solution, comprising the steps of: sequentially passing an allulose-containing solution through a first ion exchange resin column filled with a strongly acidic cation exchange resin, a second ion exchange resin column filled with a weakly basic anion exchange resin, and a third ion exchange resin column filled with a mixed-phase ion exchange resin, the mixed-phase ion exchange resin is a mixture of a strong acid cation exchange resin and a weak basic anion exchange resin; A method for purifying an allulose-containing solution, characterized in that the weakly basic anion exchange resin packed in the second ion exchange resin column and the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin have a quaternary ammonium exchange capacity fraction of 0 to 10%.

6. The method for purifying an allulose-containing solution according to claim 5, wherein the weakly basic anion exchange resin packed in the second ion exchange resin column has an exchange capacity fraction of quaternary ammonium of 0%.

7. The method for purifying an allulose-containing solution according to claim 5, wherein the weakly basic anion exchange resin constituting the mixed-phase ion exchange resin has a quaternary ammonium exchange capacity fraction of 5 to 10%.

8. The method for purifying an allulose-containing solution according to claim 5, characterized in that the mixed-phase ion exchange resin comprises a strongly acidic cation exchange resin and a weakly basic anion exchange resin in a volume ratio of 1:1 to 1:

4.

9. The method for purifying an allulose-containing solution according to claim 5, characterized in that the volume ratio of the strongly acidic cation exchange resin packed in the first ion exchange resin column, the weakly basic anion exchange resin packed in the second ion exchange resin column, and the mixed-phase ion exchange resin packed in the third ion exchange resin column is 1: (0.5 to 2): (0.5 to 2).

10. The allulose-containing solution injected into the first ion exchange resin column has a sugar solid concentration of 25 to 65 Brix, a pH of 3.5 to 5.5, an electrical conductivity of 20 to 400 μs / cm, and an allulose content of 10 to 50% (w / w) based on the total weight of the solids.

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