Process for purifying and desalting psicose by electrodialysis method

Abstract

The invention relates to the technical field of purification and concentration, in particular to a process for purifying and desalting psicose by an electrodialysis method. The electrodialysis method purification desalting process comprises the following steps: isomerizing a D-fructose solution to obtain a D-psicose solution; the D-psicose solution is decolored through activated carbon, and a decolored D-psicose solution is obtained; purifying and desalting the decolored D-psicose solution by adopting an electrodialysis method to obtain a purified and desalted D-psicose solution; enabling the purified and desalted D-psicose solution to pass through a chromatographic separation system to obtain a D-fructose mother solution and a D-psicose separation solution; the D-psicose separation solution is concentrated, cooled and crystallized, and the electrodialysis method purification desalting process is completed. The process for purifying and desalting the psicose by the electrodialysis method has the advantages of high efficiency, economy, stability and environment friendliness, and a new purification and desalting scheme is provided for production of the psicose.

Description

Technical Field

[0001] The invention relates to the technical field of purification and concentration, and in particular to an electrodialysis purification and desalination process for psicose. Background Art

[0002] Allulose is the diastereomer corresponding to the carbon number 3 of D-fructose and has a sweet taste. However, unlike sweeteners such as fructose or sucrose, it is hardly metabolized in the body and has virtually no calories. In addition, it has almost no effect on weight gain because it inhibits the formation of body fat. Therefore, allulose can replace sucrose to help increase the sweetness of food without affecting blood sugar in the body, and has a good effect on the treatment and control of diabetes.

[0003] The traditional method for producing D-psicose is mainly to produce D-psicose through surface isomerization of D-fructose, and then obtain D-psicose through decolorization, desalination, concentration, separation and purification of the D-psicose solution. The purity of the final product D-psicose is generally greater than or equal to 98wt% of crystals.

[0004] In the production process of allulose, purification and desalination are key steps to ensure product quality. Generally, an ion exchange system is used for treatment, but this method requires acid washing, alkali washing and pure water washing of the required ion exchange system. This process will produce a large amount of washing wastewater, and there will also be a certain amount of industrial waste - waste ion exchange resin. The treatment of the above-mentioned three industrial wastes not only greatly increases the cost, but also is not conducive to expanding the scale of production. At present, the commonly used purification and desalination methods in the industry also include reverse osmosis. Reverse osmosis is easily affected by the quality of the influent water, and the equipment maintenance cost is high. Therefore, it is necessary to develop a more efficient and economical purification and desalination process. Summary of the invention

[0005] The present invention provides an electrodialysis purification and desalination process for psicose, so as to solve the environmental problems caused by the large amount of industrial wastewater and industrial waste generated by the desalination using an ion exchange system in the existing psicose production process, as well as the cost problems caused by the subsequent treatment of industrial waste. At the same time, the production efficiency is improved, the production cycle is shortened, and the purpose of efficient production is finally achieved.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: an electrodialysis purification and desalination process of psicose, comprising the following steps:

[0007] (1) isomerizing the D-fructose solution to obtain a D-psicose solution;

[0008] (2) decolorizing the D-psicose solution by passing it through activated carbon to obtain a decolorized D-psicose solution;

[0009] (3) purifying and desalting the decolorized D-psicose solution by electrodialysis to obtain a purified and desalted D-psicose solution;

[0010] (4) passing the purified and desalted D-psicose solution through a chromatographic separation system to obtain a D-fructose mother liquor and a D-psicose separation solution;

[0011] (5) The D-psicose separation solution is concentrated and cooled for crystallization, thereby completing the electrodialysis purification and desalination process.

[0012] Preferably, in the above-mentioned electrodialysis purification and desalination process of psicose, the concentration of the D-fructose solution in step (1) is 30 wt%;

[0013] The isomerization method in step (1) is: isomerizing the D-fructose solution by means of psicose isomerase, which specifically comprises the following steps:

[0014] Adding cobalt chloride to the D-fructose solution, then adding sodium hydroxide to adjust the pH to 7.5, and finally adding psicose isomerase to obtain a mixed solution, and then stirring to react;

[0015] The content of cobalt chloride in the mixed solution is 1 mmol / L;

[0016] The content of psicose isomerase in the mixed solution is 1 g / L;

[0017] The reaction time is 2h.

[0018] Preferably, in the above-mentioned electrodialysis purification and desalination process of D-psicose, the mass of the activated carbon in step (2) is 0.01 to 2 wt % of the dry mass of the D-psicose solution.

[0019] Preferably, in the above-mentioned electrodialysis purification and desalination process of D-psicose, the conditions of the electrodialysis method in step (3) are: the equipment is one electrodialysis equipment or two or more electrodialysis equipment are connected in series, and the flow rate of the decolorized D-psicose solution is 6 to 12 m / s. 3 / h, the voltage is 160-250V, the current is 50-150A, and the ion exchange membrane is a homogeneous membrane, a heterogeneous membrane or an alloy membrane.

[0020] Preferably, in the above-mentioned electrodialysis purification and desalting process for psicose, the chromatographic separation system in step (4) is a gel-type polystyrene calcium type chromatographic system.

[0021] Preferably, in the above electrodialysis purification and desalination process of psicose, the concentration in step (5) is vacuum evaporation concentration; the conditions of the vacuum evaporation concentration are: vacuum pressure of -0.06 to -0.1 MPa;

[0022] The cooling crystallization in step (5) is performed by cooling the temperature to 38-42°C at a cooling rate of 0.4-0.6°C / h, and then cooling the temperature to 20-25°C at a cooling rate of 0.8-1.2°C / h.

[0023] Preferably, in the above-mentioned electrodialysis purification and desalination process of psicose, the D-fructose mother liquor in step (4) is returned to step (1).

[0024] Preferably, in the above-mentioned electrodialysis purification and desalination process for psicose, the mother liquor after the cooling crystallization treatment in step (5) is returned to step (5).

[0025] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. From the perspective of energy conservation and environmental protection, the existing allulose production process uses an ion exchange system for desalination operation. On average, 3.6 tons of wastewater and 50 kg of waste are generated for every ton of allulose product produced. However, the electrodialysis process of the present invention generates a total of 0.5 tons of wastewater and 10 kg of waste, which greatly reduces the discharge of industrial wastes and achieves the goal of energy conservation and emission reduction.

[0027] 2. From the perspective of product quality, the purity of the allulose after two purifications by electrodialysis can reach 98.5 wt% or above, and the production quality meets the relevant standards (purity greater than 98 wt%).

[0028] 3. From the perspective of industrial time cost calculation, the existing production cycle of allulose, namely the steps of isomerization, decolorization, desalination, concentration, separation and purification, can be greatly shortened by adopting the process flow of the present invention.

[0029] 4. From the perspective of industrial auxiliary material cost calculation, since electrodialysis is used instead of ion exchange resin process, there is no need to use activation water and pH adjusters (such as hydrochloric acid, sodium hydroxide, etc.) required by the ion exchange resin process, thus greatly reducing production costs.

[0030] In summary, the present invention provides a process for purification and desalination by electrodialysis in the production of psicose, which has the advantages of high efficiency, economy, stability and environmental protection, and provides a new purification and desalination scheme for the production of psicose. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0032] A process for purifying and desalting allulose by electrodialysis, comprising the following steps:

[0033] (1) isomerizing the D-fructose solution to obtain a D-psicose solution;

[0034] (2) decolorizing the D-psicose solution by passing it through activated carbon to obtain a decolorized D-psicose solution;

[0035] (3) purifying and desalting the decolorized D-psicose solution by electrodialysis to obtain a purified and desalted D-psicose solution;

[0036] (4) passing the purified and desalted D-psicose solution through a chromatographic separation system to obtain a D-fructose mother liquor and a D-psicose separation solution;

[0037] (5) The D-psicose separation solution is concentrated and cooled for crystallization, thereby completing the electrodialysis purification and desalination process.

[0038] In the present invention, the concentration of the D-fructose solution in step (1) is preferably 30 wt%.

[0039] In the present invention, the isomerization method in step (1) is: isomerizing the D-fructose solution by means of psicose isomerase, specifically comprising the following steps:

[0040] Adding cobalt chloride to the D-fructose solution, then adding sodium hydroxide solution to adjust the pH to 7.5, and finally adding psicose isomerase to obtain a mixed solution, and then stirring to react;

[0041] The concentration of the sodium hydroxide solution is 0.1 mol / L;

[0042] The content of cobalt chloride in the mixed solution is 1 mmol / L;

[0043] The content of psicose isomerase in the mixed solution is 1 g / L;

[0044] The reaction time is 2h.

[0045] The D-psicose isomerase is a prior art, and the D-psicose isomerase is preferably D-psicose 3-epimerase.

[0046] In the present invention, the mass of the activated carbon in step (2) is 0.01 to 2 wt % of the dry mass of the D-psicose solution.

[0047] In the present invention, the specific process of the electrodialysis method is:

[0048] The decolorized D-psicose solution is introduced into the anode chamber of the electrodialysis device; then a DC electric field is applied between the anode chamber and the cathode chamber of the electrodialysis device; under the action of the electric field, cations in the decolorized D-psicose solution migrate to the cathode chamber, and anions migrate to the anode chamber; through the selective permeability of the ion exchange membrane in the electrodialysis device, the cations and anions are respectively retained in the corresponding chambers; the purified and desalted D-psicose solution in the anode chamber is collected to complete the purification and desalination process. The electrodialysis device of the present invention can use conventional ion exchange membranes, such as cation exchange membranes and anion exchange membranes, as well as a DC power supply and corresponding auxiliary equipment such as pipelines and pumps.

[0049] In the present invention, the conditions of the electrodialysis method in step (3) are: the device is one electrodialysis device or two or more electrodialysis devices are connected in series, and the flow rate of the decolorized D-psicose solution is preferably 6 to 12 m / s. 3 / h, more preferably 7 to 11 m 3 / h, more preferably 8 to 10 m 3 / h; the voltage is preferably 160-250V, more preferably 170-230V, more preferably 180-200V; the current is preferably 50-150A, more preferably 60-120A, more preferably 80-110A; the ion exchange membrane is a homogeneous membrane, a heterogeneous membrane or an alloy membrane.

[0050] In the present invention, the filler in the chromatographic separation system in step (4) is a gel-type polystyrene calcium-type chromatographic system.

[0051] In the present invention, the concentration in step (5) is vacuum evaporation concentration; the conditions of the vacuum evaporation concentration are: the vacuum pressure is preferably -0.06 to -0.1 MPa, more preferably -0.07 to -0.9 MPa, and more preferably -0.8 to -0.85 MPa.

[0052] In the present invention, the cooling crystallization in step (5) is to cool the temperature to 38-42°C at a cooling rate of 0.4-0.6°C / h, more preferably to cool the temperature to 39-41°C at a cooling rate of 0.4-0.58°C / h, and more preferably to cool the temperature to 39.5-40°C at a cooling rate of 0.4-0.6°C / h; and then cool the temperature to 20-25°C at a cooling rate of 0.8-1.2°C / h, more preferably to cool the temperature to 21-24°C at a cooling rate of 0.9-1.1°C / h, and more preferably to cool the temperature to 22-23°C at a cooling rate of 0.95-1.0°C / h.

[0053] In the present invention, the D-fructose mother liquor in step (4) is returned to step (1).

[0054] In the present invention, the mother liquor after the cooling crystallization treatment in step (5) is returned to step (5).

[0055] The present invention also provides psicose prepared by an electrodialysis purification and desalting process of psicose.

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Example 1

[0058] like Figure 1 The electrodialysis purification and desalination process of psicose shown comprises the following steps:

[0059] A D-fructose solution with a concentration of 30wt% isomerized by psicose isomerase to obtain a D-psicose solution, wherein the psicose isomerase is a D-psicose 3-epimerase. The D-fructose solution is isomerized by psicose isomerase, and specifically comprises the following steps: adding cobalt chloride to the D-fructose solution, then adding sodium hydroxide solution to adjust the pH to 7.5, and finally adding psicose isomerase to obtain a mixed solution, and then stirring the solution at 50°C; the concentration of the sodium hydroxide solution is 0.1mol / L; the content of cobalt chloride in the mixed solution is 1mmol / L; the content of psicose isomerase in the mixed solution is 1g / L; the reaction time is 2h; the isomerized psicose solution contains a certain amount of ions;

[0060] Decolorizing the D-psicose solution by passing through powdered activated carbon, wherein the mass of the powdered activated carbon is 2wt% of the dry mass of the D-psicose solution, and filtering out the activated carbon after decolorization to obtain a decolorized D-psicose solution; wherein the decolorization temperature is 60° C.; and the light transmittance of the decolorized D-psicose solution is 99.1%;

[0061] The decolorized D-psicose solution is purified and desalted by electrodialysis to obtain a purified and desalted D-psicose solution; wherein the equipment uses multiple electrodialysis devices in series for treatment, and the flow rate of the decolorized D-psicose solution is 7m 3 / h, voltage of 170V, current of 50A, homogeneous membrane used in the membrane stack, temperature of 60°C; the conductivity of the purified and desalted D-psicose solution after the electrodialysis treatment is ≤20μs / cm. This step can remove most of the ions in the D-psicose solution.

[0062] The purified and desalted D-psicose solution passes through a chromatographic separation system, wherein the filler in the chromatographic separation system is a gel-type polystyrene calcium-type chromatographic system, to obtain a D-fructose mother liquor and a D-psicose separation solution; wherein the chromatographic separation temperature is 60° C., thereby reducing the viscosity of the solution and improving production efficiency; subsequently, the D-fructose mother liquor is mixed with a fructose solution raw material and continues to participate in a production cycle to reduce production costs;

[0063] The D-psicose separation solution is concentrated and cooled for crystallization, wherein the concentration is vacuum evaporation concentration, the vacuum pressure is -0.1MPa, the cooling crystallization is cooling down to 382°C at a cooling rate of 0.6°C / h, and then cooling down to room temperature at a cooling rate of 0.8°C / h, that is, the electrodialysis purification and desalination process is completed; the mother liquor after cooling and crystallization is returned for concentration and cooling crystallization. The purity of D-psicose produced by this process can reach 98.5wt% or more, wherein more than 85wt% of the D-psicose crystals have a particle size of 40 to 400μm, with better purity and higher crystallinity.

[0064] In Example 1, the cost of reverse osmosis concentration is 14 yuan / ton (including electrodialysis membrane replacement costs, electricity costs, cleaning agents, equipment maintenance costs, etc.); based on the calculation of processing 300 tons of sugar solution per day, removing one ton of water can save 56 yuan, and removing 240 tons per day, the cost savings is 13,440 yuan.

[0065] Example 2

[0066] like Figure 1 The electrodialysis purification and desalination process of psicose shown comprises the following steps:

[0067] A solution containing D-fructose at a concentration of 30wt% isomerized by psicose isomerase to obtain a D-psicose solution, wherein the psicose isomerase is a D-psicose 3-epimerase. The D-fructose solution is isomerized by psicose isomerase, and specifically comprises the following steps: adding cobalt chloride to the D-fructose solution, then adding sodium hydroxide solution to adjust the pH to 7.5, and finally adding psicose isomerase to obtain a mixed solution, and then stirring the solution at 60°C; the concentration of the sodium hydroxide solution is 0.1mol / L; the content of cobalt chloride in the mixed solution is 1mmol / L; the content of psicose isomerase in the mixed solution is 1g / L; the reaction time is 2h; the isomerized psicose solution contains a certain amount of ions;

[0068] Decolorizing the D-psicose solution by passing through powdered activated carbon, wherein the mass of the powdered activated carbon is 2wt% of the dry mass of the D-psicose solution, and filtering out the activated carbon after decolorization to obtain a decolorized D-psicose solution; wherein the decolorization temperature is 60° C.; and the light transmittance of the decolorized D-psicose solution is 99.3%;

[0069] The decolorized D-psicose solution is purified and desalted by electrodialysis to obtain a purified and desalted D-psicose solution; wherein the equipment uses multiple electrodialysis devices in series for treatment, and the flow rate of the decolorized D-psicose solution is 10m 3 / h, the voltage is 200V, the current is 90A, the membrane stack uses a homogeneous membrane, and the temperature is 60°C; the conductivity of the D-psicose solution after purification and desalination after the electrodialysis treatment is ≤20μs / cm. This step can remove most of the ions in the D-psicose solution.

[0070] The purified and desalted D-psicose solution passes through a chromatographic separation system, wherein the filler in the chromatographic separation system is a gel-type polystyrene calcium-type chromatographic system, to obtain a D-fructose mother liquor and a D-psicose separation solution; wherein the chromatographic separation temperature is 60° C., thereby reducing the viscosity of the solution and improving production efficiency; subsequently, the D-fructose mother liquor is mixed with a fructose solution raw material and continues to participate in a production cycle to reduce production costs;

[0071] The D-psicose separation solution is concentrated and cooled for crystallization, wherein the concentration is vacuum evaporation concentration, the vacuum pressure is -0.06MPa, the cooling crystallization is cooling down to 382°C at a cooling rate of 0.4°C / h, and then cooling down to room temperature at a cooling rate of 1°C / h, that is, the electrodialysis purification and desalination process is completed; the mother liquor after cooling and crystallization is returned for concentration and cooling crystallization. The purity of D-psicose produced by this process can reach 98.5wt% or more, wherein more than 85wt% of the D-psicose crystals have a particle size of 40 to 400μm, with better purity and higher crystallinity.

[0072] In Example 2, the cost of reverse osmosis concentration is 14 yuan / ton (including electrodialysis membrane replacement costs, electricity costs, cleaning agents, equipment maintenance costs, etc.); based on the calculation of processing 300 tons of sugar solution per day, removing one ton of water can save 56 yuan, and removing 240 tons per day, the cost savings is 13,440 yuan.

[0073] Example 3

[0074] like Figure 1 The electrodialysis purification and desalination process of psicose shown comprises the following steps:

[0075] A solution containing D-fructose at a concentration of 30wt% isomerized by psicose isomerase to obtain a D-psicose solution, wherein the psicose isomerase is a D-psicose 3-epimerase. The D-fructose solution is isomerized by psicose isomerase, and specifically comprises the following steps: adding cobalt chloride to the D-fructose solution, then adding sodium hydroxide solution to adjust the pH to 7.5, and finally adding psicose isomerase to obtain a mixed solution, and then stirring the solution at 60°C; the concentration of the sodium hydroxide solution is 0.1mol / L; the content of cobalt chloride in the mixed solution is 1mmol / L; the content of psicose isomerase in the mixed solution is 1g / L; the reaction time is 2h; the isomerized psicose solution contains a certain amount of ions;

[0076] Decolorizing the D-psicose solution by a powdered activated carbon system, wherein the mass of the powdered activated carbon is 2wt% of the dry mass of the D-psicose solution, and filtering out the activated carbon after decolorization to obtain a decolorized D-psicose solution; wherein the decolorization temperature is 60° C.; and the light transmittance of the decolorized D-psicose solution is 99.3%;

[0077] The decolorized D-psicose solution is purified and desalted by electrodialysis to obtain a purified and desalted D-psicose solution; wherein the equipment uses multiple electrodialysis devices in series for treatment, and the flow rate of the decolorized D-psicose solution is 11m 3 / h, voltage of 230V, current of 140A, homogeneous membrane used in the membrane stack, temperature of 60°C; the conductivity of the purified and desalted D-psicose solution after the electrodialysis treatment is ≤20μs / cm. This step can remove most of the ions in the D-psicose solution.

[0078] The purified and desalted D-psicose solution passes through a chromatographic separation system, wherein the filler in the chromatographic separation system is a gel-type polystyrene calcium-type chromatographic system, to obtain a D-fructose mother liquor and a D-psicose separation solution; wherein the chromatographic separation temperature is 60° C., thereby reducing the viscosity of the solution and improving production efficiency; subsequently, the D-fructose mother liquor is mixed with a fructose solution raw material and continues to participate in a production cycle to reduce production costs;

[0079] The D-psicose separation solution is concentrated and cooled for crystallization, wherein the concentration is vacuum evaporation concentration, the vacuum pressure is -0.08MPa, the cooling crystallization is cooling down to 382°C at a cooling rate of 0.5°C / h, and then cooling down to room temperature at a cooling rate of 1.2°C / h, that is, the electrodialysis purification and desalination process is completed; the mother liquor after cooling and crystallization is returned for concentration and cooling crystallization. The purity of D-psicose produced by this process can reach 98.5wt% or more, wherein more than 85wt% of the D-psicose crystals have a particle size of 40 to 400μm, with better purity and higher crystallinity.

[0080] In Example 3, the cost of reverse osmosis concentration is 14 yuan / ton (including electrodialysis membrane replacement costs, electricity costs, cleaning agents, equipment maintenance costs, etc.); based on the calculation of processing 300 tons of sugar solution per day, removing one ton of water can save 56 yuan, and removing 240 tons per day, the cost savings is 13,440 yuan.

[0081] Comparative Example 1

[0082] A solution containing D-fructose at a concentration of 30wt% isomerized by psicose isomerase to obtain a D-psicose solution, wherein the psicose isomerase is a D-psicose 3-epimerase. The D-fructose solution is isomerized by psicose isomerase, and specifically comprises the following steps: adding cobalt chloride to the D-fructose solution, then adding sodium hydroxide solution to adjust the pH to 7.5, and finally adding psicose isomerase to obtain a mixed solution, and then stirring the solution at 60°C; the concentration of the sodium hydroxide solution is 0.1mol / L; the content of cobalt chloride in the mixed solution is 1mmol / L; the content of psicose isomerase in the mixed solution is 1g / L; the reaction time is 2h; the isomerized psicose solution contains a certain amount of ions;

[0083] Decolorizing the D-psicose solution by passing it through powdered activated carbon, wherein the mass of the powdered activated carbon is 2 wt % of the dry mass of the D-psicose solution, and filtering out the activated carbon after decolorization to obtain a decolorized D-psicose solution; wherein the decolorization temperature is 60° C.; and the light transmittance of the decolorized D-psicose solution is 99.3%;

[0084] The decolorized D-psicose solution is sequentially subjected to a cation resin column and anion resin column, and the conductivity of the D-psicose solution after adsorption and desalination is ≤20μs / cm. This step can remove most of the borate ions in the D-psicose solution. After the cation resin and the anion resin are saturated with adsorption, they need to be activated with 4% hydrochloric acid and 4% sodium hydroxide respectively, and then flushed with a large amount of pure water until the outlet is neutral; in order to ensure the stability of production in industry, four columns are often used in combination, namely, cation resin column-anion resin column-cation resin column-anion resin column; the resin life is limited and needs to be replenished regularly, and all of them need to be replaced once every two years, and the spent ion exchange resin is treated as industrial waste. This step produces a certain amount of industrial wastewater and waste.

[0085] The purified and desalted D-psicose solution passes through a chromatographic separation system, which is a gel-type polystyrene calcium-type chromatographic system, to obtain a D-fructose mother liquor and a D-psicose separation solution; wherein the chromatographic separation temperature is 60° C., thereby reducing the viscosity of the solution and improving production efficiency; subsequently, the D-fructose mother liquor is mixed with the fructose solution raw material to continue to participate in the production cycle, so as to reduce production costs;

[0086] The D-psicose separation solution is concentrated and cooled for crystallization, wherein the concentration is vacuum evaporation concentration, the vacuum pressure is -0.08MPa, the cooling crystallization is cooling down to 382°C at a cooling rate of 0.5°C / h, and then cooling down to room temperature at a cooling rate of 1.2°C / h, that is, the electrodialysis purification and desalination process is completed; the mother liquor after cooling and crystallization is returned for concentration and cooling crystallization. The purity of D-psicose produced by this process can reach 98.5wt% or more, wherein more than 85wt% of the D-psicose crystals have a particle size of 40 to 400μm, with better purity and higher crystallinity.

[0087] In Comparative Example 1, the cost of purification and desalination using an ion exchange system is 70 yuan / ton (including the cost of replacing ion exchange membranes, electricity, activated cleaning agents, equipment maintenance costs, etc.); based on the calculation of processing 300 tons of sugar solution per day, removing one ton of water can save 56 yuan, and removing 240 tons a day saves 13,440 yuan.

[0088] In summary, compared with the prior art solutions, the present invention has the following advantages:

[0089] High efficiency: Electrodialysis can quickly and effectively remove salt from allulose solution and improve the purity of the product.

[0090] Economical: Electrodialysis equipment is simple, easy to operate, and has low maintenance costs. It has more economic advantages than ion exchange and reverse osmosis.

[0091] Stability: The electrodialysis method is less affected by the quality of the influent water and can maintain a stable purification effect.

[0092] Environmental protection: Electrodialysis does not require the addition of chemical reagents, reducing wastewater generation and environmental pollution.

[0093] The key point of the present invention is to use the principle of electrodialysis to achieve purification and desalination of the psicose solution, and to achieve efficient and economical purification effects by optimizing the electric field strength, the selection of ion exchange membranes and the operating conditions. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A process for purifying and desalting psicose by electrodialysis, characterized in that: The following steps are involved: (1) isomerizing the D-fructose solution to obtain a D-psicose solution; (2) decolorizing the D-psicose solution by passing it through activated carbon to obtain a decolorized D-psicose solution; (3) purifying and desalting the decolorized D-psicose solution by electrodialysis to obtain a purified and desalted D-psicose solution; (4) passing the purified and desalted D-psicose solution through a chromatographic separation system to obtain a D-fructose mother liquor and a D-psicose separation solution; (5) The D-psicose separation solution is concentrated and cooled for crystallization, thereby completing the electrodialysis purification and desalination process.

2. The electrodialysis purification and desalination process of psicose according to claim 1, characterized in that: The concentration of the D-fructose solution in step (1) is 30wt%; The isomerization method in step (1) is: isomerizing the D-fructose solution by means of psicose isomerase, which specifically comprises the following steps: Adding cobalt chloride to the D-fructose solution, then adding sodium hydroxide to adjust the pH to 7.5, and finally adding psicose isomerase to obtain a mixed solution, and then stirring to react; The content of cobalt chloride in the mixed solution is 1 mmol / L; The content of psicose isomerase in the mixed solution is 1 g / L; The reaction time is 2h.

3. The electrodialysis purification and desalination process of psicose according to claim 1, characterized in that: The mass of the activated carbon in step (2) is 0.01 to 2 wt % of the dry mass of the D-psicose solution.

4. The electrodialysis purification and desalination process of psicose according to claim 1, characterized in that: The conditions of the electrodialysis method in step (3) are: the equipment is one electrodialysis equipment or two or more electrodialysis equipment are connected in series, and the flow rate of the decolorized D-psicose solution is 6 to 12 m / s. 3 / h, the voltage is 160-250V, the current is 50-150A, and the ion exchange membrane is a homogeneous membrane, a heterogeneous membrane or an alloy membrane.

5. The electrodialysis purification and desalination process of psicose according to claim 1, characterized in that: The chromatographic separation system in step (4) is a gel-type polystyrene calcium type chromatographic system.

6. The electrodialysis purification and desalination process of psicose according to claim 1, characterized in that: The concentration in step (5) is vacuum evaporation concentration; the conditions of the vacuum evaporation concentration are: vacuum pressure of -0.06 to -0.1 MPa; The cooling crystallization in step (5) is performed by cooling the temperature to 38-42°C at a cooling rate of 0.4-0.6°C / h, and then cooling the temperature to 20-25°C at a cooling rate of 0.8-1.2°C / h.

7. The electrodialysis purification and desalination process of psicose according to claim 1, characterized in that: The D-fructose mother liquor in step (4) is returned to step (1).

8. The electrodialysis purification and desalination process of psicose according to claim 1, characterized in that: The mother liquor after the cooling crystallization treatment in step (5) is returned to step (5).

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