CN118290231A - Method for preventing sugar solution from yellowing in sorbitol production process - Google Patents

Abstract

The invention relates to a method for preventing sugar liquor from yellowing in a sorbitol production process, which comprises the following steps: the hydrogenated liquid is decolorized, ion-exchanged, membrane-filtered, nanofiltration, refined, concentrated and evaporated for crystallization, so that the colored substances generated by the reaction of the protein in the sorbitol hydrogenated liquid and the reducing sugar can be timely removed, the sudden yellowing phenomenon of the sorbitol liquid in the production process is avoided, and the yellowing degree of sorbitol crystal products is reduced; under the condition of one month of accelerated experiment, the yellowness of the sorbitol liquid is reduced from 7.4 to 5.7, and the reduction of the width is more than 20 percent.

Description

Method for preventing sugar solution from yellowing in sorbitol production process

Technical Field

The invention belongs to the technical field of sugar alcohol production, and particularly relates to a method for preventing sugar liquor from yellowing in a sorbitol production process.

Background

In the production process of sorbitol crystals and sorbitol liquid, because the quality of starch serving as a raw material for producing sorbitol is unstable, other components such as protein, lipid, reducing sugar and the like exist, and although the content of the components is low, the components react in the processes of heating, concentrating and boiling sugar liquid, so that the sugar liquid is yellow to influence the quality of a product, and the product is often required to be reworked and decolored for use, thereby greatly increasing the production cost. In the prior art, refining and purifying means of sugar alcohol include decolorization, ion exchange, chromatographic separation, crystallization and the like.

For example, a new process for producing high-purity sorbitol by using a chromatographic separation technology is proposed in the patent of publication number CN108503506A, and the chromatographic separation technology can improve the sorbitol content in sorbitol liquid to 99-99.8%, so that the purification effect is better but the cost is higher. In the patent of publication No. CN107840782A, the sorbitol liquid is separated and purified by adopting a membrane separation technology, the purity of the sorbitol filtered liquid obtained by separation is as high as 95-97%, but when the quality of starch is poor or the earlier process is fluctuated, the yellowing problem of the sorbitol liquid during sugar boiling and crystallization still cannot be avoided. As another example, patent publication No. CN211253771U describes a device for preventing liquid sorbitol from yellowing, which can effectively prevent the liquid sorbitol from yellowing during storage, but the device is used before the liquid sorbitol finished product storage tank, and cannot solve the yellowing phenomenon of sorbitol hydrogenated liquid in the previous stage of liquid sorbitol production. As another patent of publication No. CN217780750U, a system for preventing sorbitol hydrogenated liquid from yellowing is described, by adjusting and controlling the discharging temperature of sorbitol hydrogenated liquid, and blending a certain proportion of citric acid into the hydrogenated liquid, the pH value of the hydrogenated liquid is reduced, which can ensure that the hydrogenated liquid should cope with special production conditions, and needs long-term storage without yellowing, but adding citric acid ions additionally increases the difficulty and burden of subsequent refining procedures.

Therefore, the intrinsic cause of the yellowing of the sorbitol solution is clear, a process scheme with simple procedures and low cost is provided, the problem of the yellowing of the sugar solution in the sorbitol production process is effectively solved, and the problem of improving the product quality of the sorbitol is a problem which needs to be solved by a person skilled in the art.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for preventing sugar liquor from yellowing in the sorbitol production process and improving the product quality of sorbitol crystals.

The invention is realized in such a way that a method for preventing sugar liquor from yellowing in the sorbitol production process is provided, which comprises the following steps:

step one, decoloring hydrogenated liquid: liquefying and saccharifying starch milk to obtain glucose solution, and carrying out active carbon decolorization on sorbitol hydrogenated solution obtained after catalytic hydrogenation treatment of the glucose solution to obtain sorbitol decolorized solution; wherein the sorbitol solution obtained after hydrogenation has a sorbitol content of more than or equal to 93%, the added mass of activated carbon is 0.5-1.0% of the volume of the sorbitol solution, the decoloring treatment temperature is 40-50 ℃, the decoloring treatment time is 1-2 h, and the transmittance of the obtained sorbitol decoloring solution is more than or equal to 98%;

Step two, ion exchange: respectively carrying out ion exchange treatment on the sorbitol decolorized solution by a cation exchange column, an anion exchange column and a mixed bed ion exchange column to obtain sorbitol ion exchange solution; wherein the cation resin is strong acid resin, the anion resin is weak base resin, the discharge conductance of the anion exchange column after ion exchange treatment is less than or equal to 30 mu s/cm, and the pH value is 3.5-8.5; the mixed bed resin is respectively strong acid resin and strong alkali resin, the discharge conductance of the mixed bed ion exchange column after ion exchange treatment is less than or equal to 30 mu s/cm, and the pH value is 5.0-7.5;

Step three, membrane filtration: performing precise membrane filtration treatment on the sorbitol ion exchange liquid to obtain sorbitol filtrate; wherein the pore size of the membrane is 0.45 μm;

Step four, nanofiltration: introducing sorbitol filtrate into a nanofiltration membrane device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in the nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; wherein the refraction of the sorbitol filtrate is 20-50 Brix, the nanofiltration membrane type is PA or PES nanofiltration membrane of 400-1000 Da, the nanofiltration treatment temperature is 40 ℃, and the sorbitol content in the sorbitol nanofiltration solution is more than or equal to 97%;

step five, refining: further refining the sorbitol nanofiltration solution by an adsorption resin column to obtain sorbitol refined solution; wherein the adsorption resin is macroporous adsorption resin with high specific surface area;

Step six, concentrating: evaporating and concentrating the sorbitol refined solution to obtain sorbitol concentrated solution; wherein the refractive index of the sorbitol concentrated solution is 75-85 Brix;

Step seven, evaporating and crystallizing: carrying out vacuum sugar boiling, evaporating and crystallizing treatment on the sorbitol concentrated solution, centrifuging and drying to obtain a sorbitol crystal finished product; wherein the crystallization temperature is 70-75 ℃, and the drying temperature is 40-60 ℃.

Compared with the prior art, the method for preventing the sugar solution from yellowing in the sorbitol production process can timely remove the colored substances generated by the reaction of the protein in the sorbitol hydrogenated solution and the reducing sugar, avoid the sudden yellowing phenomenon of the sorbitol solution in the production process, and reduce the yellowing degree of sorbitol crystal products; under the condition of one month of accelerated experiment, the yellowness of the sorbitol liquid is reduced from 7.4 to 5.7, and the reduction of the width is more than 20 percent.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

The preferred embodiment of the method for preventing sugar liquor from yellowing in the sorbitol production process comprises the following steps:

Step one, decoloring hydrogenated liquid: liquefying and saccharifying starch milk to obtain glucose solution, and carrying out active carbon decolorization on sorbitol hydrogenated solution obtained after catalytic hydrogenation treatment of the glucose solution to obtain sorbitol decolorized solution; wherein the sorbitol solution obtained after hydrogenation has a sorbitol content of not less than 93%, the added mass of activated carbon is 0.5-1.0% of the volume of the sorbitol solution, the decoloring treatment temperature is 40-50 ℃, the decoloring treatment time is 1-2 h, and the transmittance of the obtained sorbitol decoloring solution is not less than 98%.

Step two, ion exchange: respectively carrying out ion exchange treatment on the sorbitol decolorized solution by a cation exchange column, an anion exchange column and a mixed bed ion exchange column to obtain sorbitol ion exchange solution; wherein the cation resin is strong acid resin, the anion resin is weak base resin, the discharge conductance of the anion exchange column after ion exchange treatment is less than or equal to 30 mu s/cm, and the pH value is 3.5-8.5; the mixed bed resin is respectively strong acid and alkali type resin, the discharge conductance of the mixed bed ion exchange column after ion exchange treatment is less than or equal to 30 mu s/cm, and the pH value is 5.0-7.5.

Step three, membrane filtration: performing precise membrane filtration treatment on the sorbitol ion exchange liquid to obtain sorbitol filtrate; wherein the pore size of the membrane is 0.45 μm.

Step four, nanofiltration: introducing sorbitol filtrate into a nanofiltration membrane device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in the nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; wherein the refractive index of the sorbitol filtrate is 20-50 Brix, the nanofiltration membrane type is PA or PES nanofiltration membrane with 400-1000 Da, the nanofiltration treatment temperature is 40 ℃, and the sorbitol content in the sorbitol nanofiltration solution is more than or equal to 97%.

Step five, refining: further refining the sorbitol nanofiltration solution by an adsorption resin column to obtain sorbitol refined solution; wherein the adsorption resin is macroporous adsorption resin with high specific surface area.

Step six, concentrating: evaporating and concentrating the sorbitol refined solution to obtain sorbitol concentrated solution; wherein the refractive index of the sorbitol concentrated solution is 75-85 Brix.

Step seven, evaporating and crystallizing: carrying out vacuum sugar boiling, evaporating and crystallizing treatment on the sorbitol concentrated solution, centrifuging and drying to obtain a sorbitol crystal finished product; wherein the crystallization temperature is 70-75 ℃, and the drying temperature is 40-60 ℃.

The method for preventing yellowing of sugar solution during sorbitol production according to the present invention is further described below by way of specific examples.

Examples

A first embodiment of the method of the present invention for preventing yellowing of a sugar solution during sorbitol production comprises the steps of:

step 11, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has a sorbitol content of 94%, the addition amount of active carbon is 100g, the decoloring temperature is 50 ℃, the decoloring time is 2h, and the light transmittance of the sorbitol decolored liquid reaches 99%.

Step 12, sequentially carrying out ion exchange treatment on the sorbitol decolorization solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange solution was 20. Mu.s/cm, and the pH was 5.0.

And 13, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the membrane pore size of 0.45 mu m to obtain sorbitol filtrate.

Step 14, introducing sorbitol filtrate with the refraction of 50Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content was 97%.

And step 15, further refining the sorbitol nanofiltration liquid through a macroporous adsorption resin column to obtain sorbitol refined liquid.

And step 16, evaporating and concentrating the sorbitol refined solution until the refraction is 80Brix to obtain sorbitol concentrated solution.

And step 17, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing treatment at 75 ℃, centrifuging massecuite, and drying at 60 ℃ to obtain a sorbitol crystal finished product.

And (3) adopting an acceleration experiment method to track yellowing phenomena of the concentrated sorbitol boiled sugar solution and the sorbitol crystal finished product, and adopting a color difference meter to measure the yellowness of the sample after one month, wherein the yellowness of the sample is measured to be 5.80.

Examples

A second embodiment of the method of the present invention for preventing yellowing of a sugar solution during sorbitol production comprises the steps of:

Step 21, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has 94 percent of sorbitol content, 150g of active carbon addition, 45 ℃ of decoloring temperature and 2 hours of decoloring time, and the light transmittance of the sorbitol decolored liquid reaches 98 percent.

Step 22, sequentially passing the sorbitol decolorized solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column for ion exchange treatment to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange solution was 10. Mu.s/cm, and the pH was 5.5.

And step 23, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the membrane pore size of 0.45 mu m to obtain sorbitol filtrate.

Step 24, introducing sorbitol filtrate with the refraction of 35Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content was 98%.

And step 25, further refining the sorbitol nanofiltration solution by a macroporous adsorption resin column to obtain sorbitol refined solution.

And 26, evaporating and concentrating the sorbitol refined solution until the refraction is 85Brix to obtain sorbitol concentrated solution.

And step 27, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing treatment at 75 ℃, centrifuging massecuite, and drying at 45 ℃ to obtain a sorbitol crystal finished product.

And (3) adopting an acceleration experiment method to track yellowing phenomena of the concentrated sorbitol boiled sugar solution and the sorbitol crystal finished product, and adopting a color difference meter to measure the yellowness of the sample after one month, wherein the yellowness of the sample is measured to be 5.75.

Examples

A third embodiment of the method for preventing yellowing of sugar liquor during sorbitol production of the present invention comprises the steps of:

Step 31, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has a sorbitol content of 95%, the addition amount of active carbon is 200g, the decoloring temperature is 45 ℃, the decoloring time is 1h, and the light transmittance of the sorbitol decolored liquid reaches 99%.

Step 32, sequentially passing the sorbitol decolorized solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column for ion exchange treatment to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange solution was 12. Mu.s/cm, and the pH was 7.5.

And 33, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the membrane pore size of 0.45 mu m to obtain sorbitol filtrate.

Step 34, introducing sorbitol filtrate with the refraction of 20Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content was 98%.

And 35, further refining the sorbitol nanofiltration solution by a macroporous adsorption resin column to obtain sorbitol refined solution.

And 36, evaporating and concentrating the sorbitol refined solution until the refraction is 75Brix to obtain sorbitol concentrated solution.

And 37, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing at 70 ℃, centrifuging massecuite, and drying at 40 ℃ to obtain a sorbitol crystal finished product.

And (3) adopting an acceleration experiment method to track yellowing phenomena of the concentrated sorbitol boiled sugar solution and the sorbitol crystal finished product, and adopting a color difference meter to measure the yellowness of the sample after one month, wherein the yellowness of the sample is measured to be 5.72.

In order to make the technical effects of the present invention more clear, the following will be further described with reference to comparative examples.

Comparative example 1

Comparative example 1 is also a sorbitol crystalline product prepared using sorbitol hydrogenated liquid, comprising the steps of:

Step A1, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has a sorbitol content of 94%, the addition amount of active carbon is 100g, the decoloring temperature is 50 ℃, the decoloring time is 2h, and the light transmittance of the sorbitol decolored liquid reaches 99%.

Step A2, enabling the sorbitol decolorized solution to sequentially pass through a cation exchange column, an anion exchange column and a mixed bed ion exchange column for ion exchange treatment to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange solution was 18. Mu.s/cm, and the pH was 5.6.

And A3, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the membrane pore size of 0.45 mu m to obtain sorbitol filtrate.

Step A4, introducing sorbitol filtrate with refraction of 40Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content was 98%.

And step A5, evaporating and concentrating the sorbitol nanofiltration liquid until the refraction is 81Brix to obtain sorbitol concentrate.

And A6, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing treatment at 75 ℃, centrifuging massecuite, and drying at 50 ℃ to obtain a sorbitol crystal finished product.

And (3) adopting an acceleration experiment method to track yellowing phenomena of the concentrated sorbitol boiled sugar solution and the sorbitol crystal finished product, and adopting a color difference meter to measure the yellowness of the sample after one month, wherein the yellowness of the sample is 7.39.

Comparative example 2

Comparative example 2 is also a sorbitol crystalline product prepared using sorbitol hydrogenated liquid, comprising the steps of:

Step B1, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has 94 percent of sorbitol content, 150g of active carbon addition, 50 ℃ of decoloring temperature, 2h of decoloring time and 99 percent of light transmittance of the sorbitol decolored liquid.

Step B2, sequentially passing the sorbitol decolorized solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column for ion exchange treatment to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange solution was 20. Mu.s/cm, and the pH was 6.1.

And B3, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the membrane pore size of 0.45 mu m to obtain sorbitol filtrate.

Step B4, introducing sorbitol filtrate with the refraction of 38Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content was 97%.

And B5, evaporating and concentrating the sorbitol nanofiltration liquid until the refraction is 82Brix to obtain sorbitol concentrate.

And B6, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing treatment at 75 ℃, centrifuging massecuite, and drying at 50 ℃ to obtain a sorbitol crystal finished product.

And (3) adopting an acceleration experiment method to track yellowing phenomena of the concentrated sorbitol boiled sugar solution and the sorbitol crystal finished product, and adopting a color difference meter to measure the yellowness of the sample after one month, wherein the yellowness of the sample is 7.30.

Comparative example 3

Comparative example 3 is also a sorbitol crystalline product prepared using sorbitol hydrogenated liquid, comprising the steps of:

Step C1, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has a sorbitol content of 94%, the addition amount of active carbon is 200g, the decoloring temperature is 50 ℃, the decoloring time is 2h, and the light transmittance of the sorbitol decolored liquid reaches 99%.

Step C2, sequentially passing the sorbitol decolorized solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column for ion exchange treatment to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange solution was 15. Mu.s/cm, and the pH was 6.5.

And C3, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the membrane pore size of 0.45 mu m to obtain sorbitol filtrate.

Step C4, introducing sorbitol filtrate with the refraction of 43Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content was 97%.

And C5, evaporating and concentrating the sorbitol nanofiltration liquid until the refraction is 80Brix to obtain sorbitol concentrate.

And C6, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing treatment at 75 ℃, centrifuging massecuite, and drying at 50 ℃ to obtain a sorbitol crystal finished product.

And (3) adopting an acceleration experiment method to track yellowing phenomena of the concentrated sorbitol boiled sugar solution and the sorbitol crystal finished product, and adopting a color difference meter to measure the yellowness of the sample after one month, wherein the yellowness of the sample is 7.55.

The results of tracking yellowing of sorbitol solutions prepared in examples 1 to 3 and comparative examples 1 to 3 are summarized to obtain the following Table 1.

Table 1 summary of yellowing tracking results for examples 1-3 and comparative examples 1-3

Category(s)	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2	Comparative example 3
							Yellowness degree	5.80	5.75	5.72	7.39	7.30	7.55

From the yellowness results of the table, the yellowness of sorbitol solution is obviously reduced after the technical scheme is adopted.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims (4)

1. A method for preventing sugar liquor from yellowing in a sorbitol production process, which is characterized by comprising the following steps:

step one, decoloring hydrogenated liquid: liquefying and saccharifying starch milk to obtain glucose solution, and carrying out active carbon decolorization on sorbitol hydrogenated solution obtained after catalytic hydrogenation treatment of the glucose solution to obtain sorbitol decolorized solution; wherein the sorbitol solution obtained after hydrogenation has a sorbitol content of more than or equal to 93%, the added mass of activated carbon is 0.5-1.0% of the volume of the sorbitol solution, the decoloring treatment temperature is 40-50 ℃, the decoloring treatment time is 1-2 h, and the transmittance of the obtained sorbitol decoloring solution is more than or equal to 98%;

Step two, ion exchange: respectively carrying out ion exchange treatment on the sorbitol decolorized solution by a cation exchange column, an anion exchange column and a mixed bed ion exchange column to obtain sorbitol ion exchange solution; wherein the cation resin is strong acid resin, the anion resin is weak base resin, the discharge conductance of the anion exchange column after ion exchange treatment is less than or equal to 30 mu s/cm, and the pH value is 3.5-8.5; the mixed bed resin is respectively strong acid resin and strong alkali resin, the discharge conductance of the mixed bed ion exchange column after ion exchange treatment is less than or equal to 30 mu s/cm, and the pH value is 5.0-7.5;

Step three, membrane filtration: performing precise membrane filtration treatment on the sorbitol ion exchange liquid to obtain sorbitol filtrate; wherein the pore size of the membrane is 0.45 μm;

Step four, nanofiltration: introducing sorbitol filtrate into a nanofiltration membrane device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in the nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; wherein the refraction of the sorbitol filtrate is 20-50 Brix, the nanofiltration membrane type is PA or PES nanofiltration membrane of 400-1000 Da, the nanofiltration treatment temperature is 40 ℃, and the sorbitol content in the sorbitol nanofiltration solution is more than or equal to 97%;

step five, refining: further refining the sorbitol nanofiltration solution by an adsorption resin column to obtain sorbitol refined solution; wherein the adsorption resin is macroporous adsorption resin with high specific surface area;

Step six, concentrating: evaporating and concentrating the sorbitol refined solution to obtain sorbitol concentrated solution; wherein the refractive index of the sorbitol concentrated solution is 75-85 Brix;

Step seven, evaporating and crystallizing: carrying out vacuum sugar boiling, evaporating and crystallizing treatment on the sorbitol concentrated solution, centrifuging and drying to obtain a sorbitol crystal finished product; wherein the crystallization temperature is 70-75 ℃, and the drying temperature is 40-60 ℃.

2. A method for preventing yellowing of a sugar solution during sorbitol production according to claim 1, comprising the steps of:

Step 11, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has 94 percent of sorbitol, 100g of active carbon is added, the decoloring temperature is 50 ℃, the decoloring time is 2 hours, and the light transmittance of the sorbitol decolored liquid reaches 99 percent;

step 12, sequentially carrying out ion exchange treatment on the sorbitol decolorization solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange liquid is 20 mu s/cm, and the pH value is 5.0;

Step 13, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the pore size of 0.45 mu m to obtain sorbitol filtrate;

Step 14, introducing sorbitol filtrate with the refraction of 50Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content was 97%;

step 15, further refining the sorbitol nanofiltration solution through a macroporous adsorption resin column to obtain sorbitol refined solution;

step 16, evaporating and concentrating the sorbitol refined solution until the refraction is 80Brix to obtain sorbitol concentrated solution;

and step 17, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing treatment at 75 ℃, centrifuging massecuite, and drying at 60 ℃ to obtain a sorbitol crystal finished product.

3. A method for preventing yellowing of a sugar solution during sorbitol production according to claim 1, comprising the steps of:

step 21, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has 94 percent of sorbitol, 150g of active carbon is added, the decoloring temperature is 45 ℃, the decoloring time is 2 hours, and the light transmittance of the sorbitol decolored liquid reaches 98 percent;

step 22, sequentially passing the sorbitol decolorized solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column for ion exchange treatment to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange liquid is 10 mu s/cm, and the pH is 5.5;

step 23, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the pore size of 0.45 mu m to obtain sorbitol filtrate;

Step 24, introducing sorbitol filtrate with the refraction of 35Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content is 98%;

Step 25, further refining the sorbitol nanofiltration solution by a macroporous adsorption resin column to obtain sorbitol refined solution;

step 26, evaporating and concentrating the sorbitol refined solution until the refraction is 85Brix to obtain sorbitol concentrated solution;

And step 27, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing treatment at 75 ℃, centrifuging massecuite, and drying at 45 ℃ to obtain a sorbitol crystal finished product.

4. A method for preventing yellowing of a sugar solution during sorbitol production according to claim 1, comprising the steps of:

step 31, performing activated carbon decolorization treatment on 20L of sorbitol hydrogenated liquid to obtain sorbitol decolorized liquid; wherein, the sorbitol hydrogenated liquid has a sorbitol content of 95%, the addition amount of active carbon is 200g, the decoloring temperature is 45 ℃, the decoloring time is 1h, and the sorbitol decoloring liquid has a light transmittance of 99%;

step 32, sequentially passing the sorbitol decolorized solution through a cation exchange column, an anion exchange column and a mixed bed ion exchange column for ion exchange treatment to obtain sorbitol ion exchange solution; at this time, the conductance of sorbitol ion exchange liquid is 12 mu s/cm, and the pH value is 7.5;

Step 33, performing precise membrane filtration treatment on the sorbitol ion exchange liquid by adopting a membrane with the membrane pore size of 0.45 mu m to obtain sorbitol filtrate;

Step 34, introducing sorbitol filtrate with the refraction of 20Brix into a nanofiltration device for nanofiltration treatment to obtain a thin solution A and a thick solution B, diluting the thick solution B with purified water, performing circulating concentration in a nanofiltration membrane device to obtain a thin solution C, and mixing the thin solution A and the thin solution C to obtain sorbitol nanofiltration solution; in the sorbitol nanofiltration solution, the sorbitol content is 98%;

step 35, further refining the sorbitol nanofiltration solution by a macroporous adsorption resin column to obtain sorbitol refined solution;

Step 36, evaporating and concentrating the sorbitol refined solution until the refraction is 75Brix to obtain sorbitol concentrated solution;

And 37, introducing the sorbitol concentrated solution into a crystallization device, performing vacuum sugar boiling, evaporating and crystallizing at 70 ℃, centrifuging massecuite, and drying at 40 ℃ to obtain a sorbitol crystal finished product.