阅读说明：本技术 一种金桂花粗多糖的脱色纯化方法 (Method for decoloring and purifying osmanthus fragrans crude polysaccharide ) 是由 吴晖 陈永 张猛猛 曾凡柯 张艺哲 于 2021-08-11 设计创作，主要内容包括：本发明公开了一种金桂花粗多糖的脱色纯化方法。该方法包括：对烘干后的金桂花粉碎、脱脂、浸提、离心后,将其浸提液低温冷冻后再室温解冻,使冷冻的金桂花多糖浸提液在部分融化时在表层产生色素聚集现象,弃去表面色素聚集层后,浓缩,脱蛋白,醇沉得到金桂花粗多糖析出物,加水复溶,对金桂花多糖复溶液也进行冻融法脱色,弃去表面色素聚集层,经透析后冷冻干燥,得脱色纯化后的金桂花粗多糖。本发明通过冻融法处理金桂花粗多糖浸提液和复溶液,获得金桂花粗多糖浸提液脱色率介于50％-52％,金桂花粗多糖析出物保留率介于76％-78％、金桂花粗多糖中总糖百分比介于80％-82％的脱色纯化方法,脱色效果显著,多糖保留率较高。(The invention discloses a method for decoloring and purifying golden osmanthus crude polysaccharide. The method comprises the following steps: crushing, degreasing, leaching and centrifuging the dried golden osmanthus, freezing the leaching liquor at low temperature, then thawing at room temperature, enabling the surface layer of the frozen golden osmanthus polysaccharide leaching liquor to generate pigment aggregation when part of the frozen golden osmanthus polysaccharide leaching liquor is melted, removing the surface pigment aggregation layer, concentrating, deproteinizing, precipitating with ethanol to obtain a golden osmanthus crude polysaccharide precipitate, adding water for redissolution, performing freeze thawing method on the golden osmanthus polysaccharide complex solution for decoloring, removing the surface pigment aggregation layer, dialyzing, and freeze-drying to obtain the decolored and purified golden osmanthus crude polysaccharide. According to the invention, the golden osmanthus crude polysaccharide leaching liquor and the compound solution are treated by a freeze-thaw method, so that the decoloring rate of the golden osmanthus crude polysaccharide leaching liquor is 50-52%, the retention rate of the golden osmanthus crude polysaccharide educt is 76-78%, and the total sugar percentage in the golden osmanthus crude polysaccharide is 80-82%, so that the decoloring purification method has the advantages of remarkable decoloring effect and high polysaccharide retention rate.)

1. A method for decoloring and purifying crude osmanthus fragrans polysaccharide is characterized by comprising the following steps:

(1) drying, crushing and sieving the osmanthus fragrans flowers to obtain osmanthus fragrans flower fine powder;

(2) removing the lipid and the fat-soluble pigment of the osmanthus fragrans fine powder in the step (1) by a Soxhlet extraction method, and drying in vacuum to obtain the osmanthus fragrans fine powder which is degreased and has the fat-soluble pigment removed;

(3) adding the gold osmanthus fine powder subjected to degreasing and fat-soluble pigment removal in the step (2) into water, and leaching under a stirring state to obtain gold osmanthus polysaccharide leaching liquor;

(4) centrifuging and separating the golden osmanthus polysaccharide leaching liquor obtained in the step (3) to obtain a precipitate, taking a supernatant, carrying out suction filtration on the supernatant, taking a filtrate, carrying out freeze thawing treatment on the filtrate, and removing a surface pigment aggregation layer to obtain a decolorized golden osmanthus polysaccharide leaching liquor;

(5) decompressing and concentrating the decolorized osmanthus fragrans polysaccharide leaching liquor in the step (4) to obtain a concentrated solution, removing protein from the concentrated solution by adopting a Sevage method to obtain a concentrated solution after protein removal, mixing the concentrated solution after protein removal with absolute ethyl alcohol, carrying out alcohol precipitation treatment, centrifuging to obtain precipitate and obtaining a coarse osmanthus fragrans polysaccharide precipitate;

(6) and (3) adding distilled water into the coarse polysaccharide educt of the osmanthus fragrans of the step (5) for re-dissolving to obtain a re-solution, performing freeze thawing treatment on the re-solution, removing a surface pigment aggregation layer, dialyzing, and performing freeze drying to obtain the decolored and purified coarse osmanthus fragrans polysaccharide.

2. The method for decoloring and purifying the crude polysaccharide of Osmanthus fragrans' flowers as claimed in claim 1, wherein the size of the sieve of step (1) is 40-60 meshes.

3. The method for decoloring and purifying the crude polysaccharide of osmanthus fragrans according to claim 1, wherein in the step (2), the reflux times for removing the lipid and the fat-soluble pigment from the fine osmanthus fragrans powder by the Soxhlet extraction method are 6 to 8 times.

4. The method for decoloring and purifying the crude polysaccharide of Osmanthus fragrans flower according to claim 1, wherein the vacuum drying in the step (2) is performed at 45-55 ℃ for 3-5 hours.

5. The method for decoloring and purifying the crude polysaccharide of osmanthus fragrans according to claim 1, wherein the feed-liquid ratio of the fine powder of osmanthus fragrans after degreasing and fat-soluble pigment removal in the step (3) to water is 1:20-1:40 g/mL.

6. The method for decoloring and purifying the crude polysaccharide of Osmanthus fragrans' flower according to claim 1, wherein the temperature of the leaching treatment in the step (3) is 95-99 ℃, and the time of the leaching treatment is 3.5-5 h.

7. The method for decoloring and purifying the crude polysaccharide of Osmanthus fragrans' flowers as claimed in claim 1, wherein the rotation speed of the centrifugation in the step (4) is 6000-10000r/min, the temperature of the centrifugation is 4-6 ℃, and the time of the centrifugation is 10-15 min.

8. The method for decoloring and purifying the crude polysaccharide of Osmanthus fragrans according to claim 1, wherein the freeze-thaw treatment in the step (4) comprises: the filtrate is completely frozen in an environment of-5 to-20 ℃ within 3 to 6 hours, and then is placed in a room temperature environment for 0.5 hour.

9. The method for decoloring and purifying the crude osmanthus fragrans polysaccharide of claim 1, wherein the volume of the concentrated solution in the step (5) is 1/3 to 1/5 of the volume of the decolored osmanthus fragrans polysaccharide leaching solution, and the volume of the absolute ethyl alcohol is 4 times of the volume of the solution after protein removal.

10. The method for decoloring and purifying the crude polysaccharide of osmanthus fragrans according to any one of claims 1 to 9, wherein the redissolving mass-to-volume ratio of the crude polysaccharide educt of osmanthus fragrans in the step (6) to distilled water is 1:30-1:50 g/mL; the freeze-thaw treatment comprises: firstly, the redissolution is placed in an environment with the temperature of-5 to-20 ℃ for cooling within 3 to 6 hours until the redissolution is completely frozen, and then the redissolution is placed in a room temperature environment for 0.5 hour; the number of times of freeze-thaw treatment is 1-3.

Technical Field

The invention belongs to the field of polysaccharide extraction, and particularly relates to a method for decoloring and purifying crude osmanthus fragrans polysaccharide.

Background

Water extraction and alcohol precipitation are the most common extraction methods for plant polysaccharides, but the polysaccharides of plant roots, stems, leaves, flowers, fruits and seeds generally contain abundant pigments with complex components, and a large amount of pigments are dissolved out in the hot water extraction link, so that the obtained plant polysaccharide leaching liquor is often brown, red, green, yellow and the like, and the purification, structural characterization and biological activity exploration of the crude polysaccharides subjected to alcohol precipitation are influenced significantly, so that decoloration treatment is required.

The conventional methods for removing the pigment in the crude polysaccharide comprise an activated carbon method, an oxidation method (hydrogen peroxide, hypochlorous acid and the like), a macroporous resin adsorption method, a reverse micelle method and the like. The polysaccharide loss can be caused when the activated carbon adsorption method is used for decoloring, and the activated carbon is difficult to remove; h₂O₂The excessive use amount can cause the oxidative degradation of the polysaccharide, thereby causing the loss of the polysaccharide; the macroporous resin adsorption method has higher decoloring cost, needs regeneration treatment and is only suitable for a system with less treatment capacity, small viscosity and low pigment content; the decolorization by the reverse micelle method has the defects of harmful reagent, difficult recovery and high cost; the novel methods such as polyamide and cold arc-photocatalysis-adsorption decolorization methods are limited in application due to the reasons of cost, test conditions, instruments and equipment and the like.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a method for decoloring and purifying the crude osmanthus fragrans polysaccharide.

Based on the research report that the golden osmanthus polysaccharide is not decolorized at present, the invention aims to provide a method for decolorizing and purifying golden osmanthus crude polysaccharide. The method has the advantages of simple and easy operation steps, obvious pigment removing effect and high polysaccharide retention rate, belongs to physical method for decoloring, and can keep the structure and the biological activity of the polysaccharide.

The purpose of the invention is realized by at least one of the following technical solutions.

The invention provides a method for decoloring and purifying golden osmanthus crude polysaccharide, which comprises the following steps:

(1) drying, crushing and sieving the osmanthus fragrans flowers to obtain osmanthus fragrans flower fine powder;

(2) removing the lipid and part of the fat-soluble pigment of the osmanthus fragrans fine powder in the step (1) by a Soxhlet extraction method, and drying in vacuum to obtain the osmanthus fragrans fine powder which is degreased and has part of the fat-soluble pigment removed;

(3) adding the gold osmanthus fine powder subjected to degreasing and partial fat-soluble pigment removal in the step (2) into water, and leaching under a magnetic stirring state to obtain gold osmanthus polysaccharide leaching liquor;

(4) centrifuging and separating the golden osmanthus polysaccharide leaching liquor obtained in the step (3) to obtain a precipitate, taking a supernatant, then passing the supernatant through a suction filtration device, taking a filtrate, performing freeze thawing treatment on the filtrate, and removing a surface pigment aggregation layer to obtain a decolorized golden osmanthus polysaccharide leaching liquor;

(5) decompressing and concentrating the decolorized osmanthus fragrans polysaccharide leaching liquor in the step (4) to obtain a concentrated solution, removing protein from the concentrated solution by adopting a Sevage method to obtain a protein-removed concentrated solution, mixing the protein-removed concentrated solution with absolute ethyl alcohol, performing alcohol precipitation, centrifuging to obtain precipitate and obtaining a coarse osmanthus fragrans polysaccharide precipitate;

(6) and (3) adding water to re-dissolve the coarse osmanthus fragrans polysaccharide educt in the step (5) to obtain a re-solution, performing freeze thawing treatment on the re-solution, removing a surface pigment aggregation layer, dialyzing for 45-50h, and freeze-drying (the dialyzate is deionized water) to obtain the decolored and purified coarse osmanthus fragrans polysaccharide.

Further, the size of the sieve holes of the sieve in the step (1) is 40-60 meshes.

Further, in the step (2), the number of times of removing the lipid and the fat-soluble pigment from the osmanthus fragrans fine powder by the Soxhlet extraction method is 6-8.

Further, the temperature of the vacuum drying in the step (2) is 45-55 ℃, and the drying time is 3-5 h.

Further, the feed-liquid ratio of the gold osmanthus fine powder subjected to degreasing and partial fat-soluble pigment removal in the step (3) to water is 1:20-1:40 g/mL.

Further, the temperature of the leaching treatment in the step (3) is 95-99 ℃, and the time of the leaching treatment is 3.5-5 h.

Further, the rotation speed of the centrifugation in the step (4) is 6000-10000r/min, the temperature of the centrifugation is 4-6 ℃, and the time of the centrifugation is 10-15 min;

further, the freeze-thaw treatment of step (4) includes: the filtrate is placed in an environment of-5 ℃ to-20 ℃ for 3-6h to be cooled to be completely frozen, and then placed in a room temperature environment for 0.5h (during the period, the temperature is raised to be partially melted, and the pigment is gathered on the surface layer). The invention finds that the low-temperature freeze thawing method has obvious decoloring effect on the osmanthus fragrans polysaccharide leaching solution and re-dissolving solution.

Further, the volume of the concentrated solution in the step (5) is 1/3-1/5 of the volume of the decolorized golden osmanthus polysaccharide leaching solution.

Preferably, the volume of the absolute ethyl alcohol in the step (5) is 4 times of the volume of the solution after the protein is removed.

Further, the mass-volume ratio of the osmanthus fragrans crude polysaccharide educt to water in the step (6) is 1:30-1:50 g/mL;

further, the freeze-thaw treatment of step (6) includes: firstly, the redissolution is placed in an environment with the temperature of-5 to-20 ℃ for 3 to 6 hours to be completely frozen, and then is placed in a room temperature environment for 0.5 hour to be heated until part of the redissolution is melted and the pigment is gathered on the surface layer; the number of times of freeze-thaw treatment is 1-3.

Compared with the prior art, the invention has the following advantages and beneficial effects:

according to the method for decoloring and purifying the golden osmanthus fragrans polysaccharide, provided by the invention, the golden osmanthus fragrans polysaccharide leaching liquor and the compound solution are treated by a freeze-thaw method, so that a decoloring and purifying technology that the decoloring rate of the golden osmanthus fragrans polysaccharide leaching liquor is 50% -52%, the retention rate of the golden osmanthus fragrans polysaccharide educt is 76% -78%, and the total sugar percentage in the golden osmanthus fragrans polysaccharide is 80% -82% is obtained, is simple, safe, economic and environment-friendly to operate, has a remarkable decoloring effect, has a good retention effect on the golden osmanthus fragrans polysaccharide, and has little influence on the bioactivity of the golden osmanthus fragrans polysaccharide.

Drawings

Fig. 1 is a flow chart of a method for decoloring and purifying crude osmanthus fragrans polysaccharide provided by the embodiment of the present invention;

FIG. 2 is a 400-700nm ultraviolet full-waveband scanning map before the gold osmanthus fragrans polysaccharide leaching solution is decolorized in the embodiment of the invention;

fig. 3 is a standard curve used for determining the percentage of total sugar in the osmanthus fragrans crude polysaccharide in the embodiment of the present invention.

Detailed Description

The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.

The decolorization ratio of the osmanthus fragrans polysaccharide leaching solution in the following examples is calculated by the following method. The method comprises the following steps: firstly, scanning the wavelength position of the maximum absorption peak of the osmanthus fragrans polysaccharide leaching solution before decolorization at the position of 400-700nm (as shown in figure 2), then measuring the light absorption value (namely OD value) of the osmanthus fragrans polysaccharide leaching solution before and after decolorization at the maximum absorption wavelength (the maximum absorption wavelength in the test is 420nm), and substituting the OD value into the following formula (1) to obtain the decolorization rate:

(1)

the mass retention rate of the osmanthus fragrans crude polysaccharide precipitate in the following embodiment is calculated by adopting the following formula (2):

(2)

the total sugar percentage in the crude osmanthus fragrans polysaccharide finally obtained in the following examples can be measured by a phenol-sulfuric acid method. A standard curve was plotted with the glucose concentration as the abscissa and the absorbance (OD value) at 490nm as the ordinate (see FIG. 3). And (3) measuring the OD value of the crude osmanthus fragrans polysaccharide solution at 490nm, substituting the OD value into a standard curve equation, calculating the total sugar mass in the crude osmanthus fragrans polysaccharide, and substituting the total sugar mass into a formula (3) to obtain the total sugar percentage in the corresponding crude osmanthus fragrans polysaccharide.

(3)

Example 1

A method for decolorizing and purifying crude polysaccharide of Osmanthus fragrans (see figure 1) comprises the following steps:

(1) drying and crushing the osmanthus fragrans, and sieving the osmanthus fragrans by a 40-mesh sieve to obtain osmanthus fragrans fine powder;

(2) removing the lipid and part of the fat-soluble pigment of the osmanthus fragrans fine powder in the step (1) by a Soxhlet extraction method, extracting for 6 times by refluxing, and drying in vacuum (the temperature is 45 ℃ and the time is 5 hours) to obtain the osmanthus fragrans fine powder with degreasing and part of the fat-soluble pigment removed;

(3) adding distilled water into the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment in the step (2), wherein the material-liquid ratio of the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment to the water is 1:30g/mL, and leaching under the magnetic stirring state, wherein the leaching temperature is 95 ℃, and the leaching time is 5 hours, so as to obtain a gold osmanthus polysaccharide leaching solution;

(4) and (3) carrying out centrifugal separation and precipitation on the golden osmanthus polysaccharide leaching liquor obtained in the step (3), wherein the centrifugal rotating speed is 6000r/min, the centrifugal temperature is 6 ℃, the centrifugal time is 15min, taking supernate, carrying out suction filtration on the supernate, taking filtrate, and carrying out freeze-thaw treatment on the filtrate, wherein the freeze-thaw treatment comprises the following steps: putting the filtrate in an environment of-5 ℃ for 6 hours, cooling to completely freeze the filtrate, then putting the filtrate in a room temperature environment for 0.5 hour, heating until part of the filtrate is melted and the pigment aggregation phenomenon appears on the surface layer, removing the pigment aggregation layer on the surface to obtain a decolorized gold-osmanthus polysaccharide leaching solution, wherein the decolorization rate is 50%;

(5) concentrating the decolorized golden osmanthus polysaccharide leaching liquor in the step (4) to obtain a concentrated solution, wherein the volume of the concentrated solution is 1/5 of the volume of the decolorized golden osmanthus polysaccharide leaching liquor, removing protein from the concentrated solution by adopting a Sevage method to obtain a protein-removed concentrated solution, mixing the protein-removed concentrated solution with 4 times of absolute ethyl alcohol, wherein the volume of the absolute ethyl alcohol is 4 times of the volume of the protein-removed solution, carrying out alcohol precipitation treatment, centrifuging to obtain a precipitate, and obtaining a crude golden osmanthus polysaccharide precipitate;

(6) adding water to re-dissolve the coarse osmanthus fragrans polysaccharide educt in the step (5), wherein the mass-volume ratio of the coarse osmanthus fragrans polysaccharide educt to the distilled water is 1:30g/mL to obtain a reconstituted solution, and performing freeze-thaw treatment on the reconstituted solution, wherein the freeze-thaw treatment comprises the following steps: firstly, the redissolution is placed in an environment with the temperature of minus 5 ℃ for 4 hours to be cooled completely and the pigment is gathered on the surface layer, and then the redissolution is placed in an environment with the room temperature for 0.5 hour to be heated to be partially melted; and (3) performing freeze thawing treatment for 1 time, removing a surface pigment aggregation layer, dialyzing for 48 hours, and performing vacuum freeze drying to obtain the uniform yellowish crude osmanthus fragrans polysaccharide. The crude osmanthus fragrans polysaccharide which is not decolorized by the freeze-thaw method is dark black, which shows that the freeze-thaw method has obvious decolorization effect on the crude osmanthus fragrans polysaccharide. The mass retention rate of the coarse polysaccharide educt of the osmanthus fragrans flowers is 78%, and the total sugar percentage in the coarse polysaccharide of the osmanthus fragrans flowers before and after decolorization is improved from 52% to 80%.

Example 2

A method for decoloring and purifying crude osmanthus fragrans polysaccharide comprises the following steps:

(1) drying flos Osmanthi Fragrantis, pulverizing, and sieving (mesh size is 50 mesh) to obtain flos Osmanthi Fragrantis fine powder;

(2) removing the lipid and part of the fat-soluble pigment of the osmanthus fragrans fine powder in the step (1) by a Soxhlet extraction method, performing reflux extraction for 7 times, and performing vacuum drying (at the temperature of 50 ℃ for 4 hours) to obtain the osmanthus fragrans fine powder with degreasing and part of the fat-soluble pigment removed;

(3) adding distilled water into the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment in the step (2), wherein the material-liquid ratio of the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment to the water is 1:40g/mL, and carrying out leaching treatment under a magnetic stirring state, wherein the leaching treatment temperature is 97 ℃, and the leaching treatment time is 4 hours, so as to obtain a gold osmanthus polysaccharide leaching liquor;

(4) centrifuging and separating the golden osmanthus polysaccharide leaching liquor obtained in the step (3) for precipitation, wherein the centrifugation rotating speed is 8500r/min, the centrifugation temperature is 5 ℃, and the centrifugation time is 12.5min, taking supernate, carrying out suction filtration on the supernate, taking filtrate, and carrying out freeze-thaw treatment on the filtrate, wherein the freeze-thaw treatment comprises: putting the filtrate in an environment of-10 ℃ for cooling within 4.5h until the filtrate is completely frozen, then putting the filtrate in a room temperature environment for heating within 0.5h until part of the filtrate is melted and the pigment aggregation phenomenon appears on the surface layer, removing the pigment aggregation layer on the surface to obtain a decolorized golden osmanthus polysaccharide leaching solution, and determining that the decolorization rate of the golden osmanthus polysaccharide leaching solution is 52%;

(5) concentrating the decolorized golden osmanthus polysaccharide leaching liquor in the step (4) to obtain a concentrated solution, wherein the volume of the concentrated solution is 1/4 of the volume of the decolorized golden osmanthus polysaccharide leaching liquor, removing protein from the concentrated solution by adopting a Sevage method to obtain a solution after protein removal, mixing the solution after protein removal with absolute ethyl alcohol, wherein the volume of the absolute ethyl alcohol is 4 times of the volume of the solution after protein removal, carrying out alcohol precipitation, centrifuging, and taking precipitate to obtain a crude golden osmanthus polysaccharide precipitate;

(6) adding water to the coarse osmanthus fragrans polysaccharide educt obtained in the step (5) for redissolving, wherein the mass-volume ratio of the coarse osmanthus fragrans polysaccharide educt to the water is 1:40g/mL, so as to obtain a redissolution, and performing freeze-thaw treatment on the redissolution, wherein the freeze-thaw treatment comprises: firstly, the redissolution is placed in an environment with the temperature of minus 10 ℃ for cooling within 4.5h until the redissolution is completely frozen, and then the redissolution is placed in an environment with the room temperature for heating within 0.5h until the redissolution is partially melted and the pigment aggregation phenomenon appears on the surface layer; and (3) performing freeze thawing treatment for 2 times, removing a surface pigment aggregation layer, dialyzing for 48 hours, and performing vacuum freeze drying to obtain the uniform yellowish crude osmanthus fragrans polysaccharide. The crude osmanthus fragrans polysaccharide which is not decolorized by the freeze-thaw method is dark black, which shows that the freeze-thaw method has obvious decolorization effect on the crude osmanthus fragrans polysaccharide. The mass retention rate of the coarse polysaccharide educt of the osmanthus fragrans flowers is 77%, and the total sugar percentage in the coarse polysaccharide of the osmanthus fragrans flowers before and after decolorization is improved from 52% to 81%.

Example 3

A method for decoloring and purifying crude osmanthus fragrans polysaccharide comprises the following steps:

(1) drying flos Osmanthi Fragrantis, pulverizing, and sieving (mesh size is 60 meshes) to obtain flos Osmanthi Fragrantis fine powder;

(2) removing the lipid and part of the fat-soluble pigment of the osmanthus fragrans fine powder in the step (1) by a Soxhlet extraction method, performing reflux extraction for 8 times, and performing vacuum drying (at the temperature of 55 ℃ for 3 hours) to obtain the osmanthus fragrans fine powder with degreasing and part of the fat-soluble pigment removed;

(3) adding the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment in the step (2) into water, wherein the material-to-liquid ratio of the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment to the water is 1:50g/mL, and leaching under a magnetic stirring state, wherein the leaching temperature is 99 ℃, and the leaching time is 3.5 hours, so as to obtain a gold osmanthus polysaccharide leaching solution;

(4) and (3) carrying out centrifugal separation and precipitation on the osmanthus fragrans polysaccharide leaching liquor obtained in the step (3), wherein the centrifugal rotating speed is 10000r/min, the centrifugal temperature is 4 ℃, the centrifugal time is 10min, taking supernate, carrying out suction filtration on the supernate, taking filtrate, and carrying out freeze-thaw treatment on the filtrate, wherein the freeze-thaw treatment comprises the following steps: putting the filtrate in an environment of-20 ℃ for cooling within 3h until the filtrate is completely frozen, then putting the filtrate in a room temperature environment for heating within 0.5h until part of the filtrate is melted and the pigment aggregation phenomenon appears on the surface layer, removing the pigment aggregation layer on the surface to obtain a decolorized osmanthus fragrans polysaccharide leaching solution, wherein the decolorization rate is 52%;

(5) concentrating the decolorized golden osmanthus polysaccharide leaching liquor in the step (4) to obtain a concentrated solution, wherein the volume of the concentrated solution is 1/3 of the volume of the decolorized golden osmanthus polysaccharide leaching liquor, removing protein from the concentrated solution by adopting a Sevage method to obtain a solution with protein removed, mixing the solution with protein removed with absolute ethyl alcohol, wherein the volume of the absolute ethyl alcohol is 4 times of the volume of the solution with protein removed, carrying out alcohol precipitation, centrifuging, and taking precipitate to obtain a crude golden osmanthus polysaccharide precipitate;

(6) adding water to the coarse osmanthus fragrans polysaccharide educt obtained in the step (5) for redissolving, wherein the mass-volume ratio of the coarse osmanthus fragrans polysaccharide educt to the water is 1:50g/mL, so as to obtain a redissolution, and performing freeze-thaw treatment on the redissolution, wherein the freeze-thaw treatment comprises: firstly, the redissolved solution is placed in an environment with the temperature of minus 5 ℃ for 3 hours to be cooled to be completely frozen, and then is placed in a room temperature environment for 0.5 hour to be heated until part of the redissolved solution is melted and the pigment aggregation phenomenon appears on the surface layer; and (3) performing freeze thawing treatment, removing a surface pigment aggregation layer, dialyzing for 48 hours, and performing vacuum freeze drying to obtain the uniform yellowish crude osmanthus fragrans polysaccharide. The crude osmanthus fragrans polysaccharide which is not decolorized by the freeze-thaw method is dark black, which shows that the freeze-thaw method has obvious decolorization effect on the crude osmanthus fragrans polysaccharide. The mass retention rate of the coarse polysaccharide educt of the osmanthus fragrans flowers is 76%, and the total sugar percentage in the coarse polysaccharide of the osmanthus fragrans flowers before and after decolorization is improved from 52% to 82%.

Example 4

A method for decoloring and purifying crude osmanthus fragrans polysaccharide comprises the following steps:

(1) drying and crushing the osmanthus fragrans, and sieving the osmanthus fragrans by a 50-mesh sieve (the sieve pore size is 60 meshes) to obtain osmanthus fragrans fine powder;

(2) removing the lipid and part of the fat-soluble pigment of the osmanthus fragrans fine powder in the step (1) by a Soxhlet extraction method, performing reflux extraction for 6 times, and performing vacuum drying (at the temperature of 55 ℃ for 3 hours) to obtain the osmanthus fragrans fine powder with degreasing and part of the fat-soluble pigment removed;

(3) adding distilled water into the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment in the step (2), wherein the material-liquid ratio of the gold osmanthus fine powder subjected to degreasing and partial removal of the fat-soluble pigment to the water is 1:30g/mL, and performing leaching treatment under a magnetic stirring state, wherein the leaching treatment temperature is 99 ℃, and the leaching treatment time is 4 hours, so as to obtain a gold osmanthus polysaccharide leaching liquor;

(4) centrifuging and separating the golden osmanthus polysaccharide leaching liquor obtained in the step (3) for precipitation, wherein the centrifugation rotating speed is 9000r/min, the centrifugation temperature is 4 ℃, the centrifugation time is 11min, taking supernate, carrying out suction filtration on the supernate, taking filtrate, and carrying out freeze-thaw treatment on the filtrate, wherein the freeze-thaw treatment comprises: putting the filtrate in an environment of-20 ℃ for cooling within 3h until the filtrate is completely frozen, then putting the filtrate in a room temperature environment for heating within 1.5h until part of the filtrate is melted and surface pigment aggregation occurs, removing a surface pigment aggregation layer to obtain a decolorized gold-osmanthus polysaccharide leaching solution, wherein the decolorization rate is 51%;

(5) concentrating the decolorized golden osmanthus polysaccharide leaching liquor in the step (4) to obtain a concentrated solution, wherein the volume of the concentrated solution is 1/3 of the volume of the decolorized golden osmanthus polysaccharide leaching liquor, removing protein from the concentrated solution by adopting a Sevage method to obtain a solution after protein removal, mixing the solution after protein removal with absolute ethyl alcohol, wherein the volume of the absolute ethyl alcohol is 4 times of the volume of the solution after protein removal, carrying out alcohol precipitation, centrifuging, and taking precipitate to obtain a crude golden osmanthus polysaccharide precipitate;

(6) adding water to the coarse osmanthus fragrans polysaccharide educt obtained in the step (5) for redissolving, wherein the mass-volume ratio of the coarse osmanthus fragrans polysaccharide educt to the water is 1:30g/mL, so as to obtain a redissolution, and performing freeze-thaw treatment on the redissolution, wherein the freeze-thaw treatment comprises: the complex solution is placed in an environment with the temperature of minus 20 ℃ for 3 hours to be cooled to be completely frozen, and then placed in an environment with the room temperature for 0.5 hour to be heated until the complex solution is partially melted and the pigment aggregation phenomenon appears on the surface layer; and (3) performing freeze thawing treatment for 2 times, removing a surface pigment aggregation layer, dialyzing for 48 hours, and performing vacuum freeze drying to obtain the uniform yellowish crude osmanthus fragrans polysaccharide. The crude osmanthus fragrans polysaccharide which is not decolorized by the freeze-thaw method is dark black, which shows that the freeze-thaw method has obvious decolorization effect on the crude osmanthus fragrans polysaccharide. The mass retention rate of the coarse polysaccharide educt of the osmanthus fragrans flowers is 77%, and the total sugar percentage in the coarse polysaccharide of the osmanthus fragrans flowers before and after decolorization is improved from 52% to 81%.

The above examples are only preferred embodiments of the present invention, which are intended to be illustrative and not limiting, and those skilled in the art should understand that they can make various changes, substitutions and alterations without departing from the spirit and scope of the invention.