Noni polysaccharide and extraction method thereof

Abstract

The invention belongs to the technical field of polysaccharide extraction, and particularly relates to morinda citrifolia polysaccharide and an extraction method thereof. According to the preparation method, the morinda citrifolia pomace is dried by utilizing far infrared assisted pulse vacuum drying, so that excessive moisture in the morinda citrifolia pomace is effectively removed, and active ingredients in the morinda citrifolia pomace can be retained; the dried morinda citrifolia pomace is refined through an airflow superfine grinding technology, the contact area of an extraction solvent and the pomace is increased, and sufficient release of polysaccharide is promoted; water is used as a solvent for extraction, extraction conditions are strictly limited, uniform polysaccharide can be obtained, and the method has the advantages of being high in extraction rate, small in solvent dosage and short in consumed time. The result of the embodiment shows that the extraction rate of the morinda citrifolia polysaccharide obtained by the extraction method disclosed by the invention reaches 16.65-20.67%, and the morinda citrifolia polysaccharide has relatively high antioxidant activity; after the extraction is finished, the extracting solution is subjected to ultrafiltration, the solution part is collected and then dried, small molecular impurities and pigments in the extracting solution can be removed, and the purity of the morinda citrifolia polysaccharide reaches 90% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of polysaccharide extraction, and particularly relates to noni polysaccharide and an extraction method thereof. Background Art

[0002] Noni fruit (Morinda citrifolia L.) is a perennial plant of the Rubiaceae family. More than 200 chemical components have been identified in Noni fruit, mainly anthraquinones, caproic acid, terpenoids, caprylic acid, scopolamine, polysaccharides, polyphenols and alkaloids, which have antioxidant, antibacterial, anti-inflammatory, hypoglycemic, anti-tumor, hypolipidemic and anti-obesity activities.

[0003] At present, most of the noni fruit is processed into noni juice, fruit powder and fruit puree for sale. In the process of processing into products, a large amount of pomace will be produced. As a waste, noni pomace is not well utilized. In addition to containing a large amount of total flavonoids, flavonoid glycosides, polysaccharides, saponins and pectin and other functional components, noni pomace can be used to extract polysaccharides and other useful components to produce noni polysaccharides, which can turn waste into treasure, increase the economic added value of noni fruit, realize the comprehensive utilization value of noni fruit, and reduce environmental pollution.

[0004] Regarding the extraction of polysaccharides, currently the most widely used methods are ultrasound-assisted extraction, microwave-assisted extraction, enzyme method, high-pressure hot water extraction, etc. However, these methods generally have the disadvantages of being time-consuming, consuming a lot of solvent, and having a low extraction rate. Summary of the invention

[0005] The purpose of the present invention is to provide a noni polysaccharide and an extraction method thereof, so as to efficiently extract the noni polysaccharide from noni pomace, improve the extraction efficiency of the noni polysaccharide, and efficiently obtain the noni polysaccharide with higher purity.

[0006] The present invention provides a method for extracting Noni polysaccharide, comprising the following steps:

[0007] Performing far infrared assisted pulse vacuum drying on the noni pomace to obtain dried noni pomace;

[0008] Performing airflow ultrafine grinding on the dried Noni pomace to obtain the Noni pomace powder;

[0009] Extracting the noni pomace powder with water as solvent and collecting the extract; the extract contains noni polysaccharide;

[0010] The extraction is performed 2 to 5 times, each extraction lasts 15 to 20 minutes, the temperature is 100 to 130° C., and the pressure is 6 to 10 MPa.

[0011] Preferably, the moisture content of the Noni pomace powder is ≤12% and the particle size is 20-50 μm.

[0012] Preferably, the far-infrared assisted pulse vacuum drying has a vacuum holding time of 8 to 12 minutes, a vacuum pressure of 6 to 10 kPa, a normal pressure holding time of 5 to 9 minutes, a temperature of 48 to 56° C., a radiation power of 760 to 800 W, and a radiation distance of 10 to 20 cm.

[0013] Preferably, the classifier frequency of the airflow ultrafine grinding is 55-65Hz / 0.5-0.7A, the induced draft fan frequency is 35-45Hz / 7-7.4A, the grinding pressure is 0.5-0.9MPa, the grinding time is 5-7h, the feed airflow is 0.5-0.9MPa, and the grinding airflow is 0.7-0.9MPa.

[0014] Preferably, the mass volume ratio of the Noni pomace powder and water is 1 g: 5-10 mL.

[0015] Preferably, after obtaining the extract, the method further comprises: ultrafiltration of the extract, collecting the solution portion and drying to obtain the Noni polysaccharide;

[0016] The ultrafiltration time is 40-60 minutes, the pressure is 0.25-0.35 MPa, and the temperature is 50-55°C.

[0017] Preferably, the drying comprises vacuum freeze drying.

[0018] Preferably, the pre-freezing temperature of the vacuum freeze drying is -60°C, the pre-freezing time is 2 hours, and after the pre-freezing, the product is dried at a vacuum degree of ≤20Pa.

[0019] The present invention also provides the Noni polysaccharide obtained by the extraction method described in the above technical scheme; the purity of the Noni polysaccharide is ≥90%, and the molecular weight is ≥92.07 kDa.

[0020] Preferably, the monosaccharides in the noni polysaccharide include rhamnose, arabinose, galactose, glucose and galacturonic acid; the molar ratio of the rhamnose, arabinose, galactose, glucose and galacturonic acid is 6-6.5:10-11:31-32:19-20:31.5-32.0.

[0021] Beneficial effects:

[0022] The invention provides a method for extracting noni polysaccharide. The method comprises the following steps: performing far-infrared-assisted pulse vacuum drying on noni pomace to obtain dried noni pomace; performing airflow ultrafine grinding on the dried noni pomace to obtain noni pomace powder; extracting the noni pomace powder with water as solvent and collecting extract; the extract contains noni polysaccharide; the extraction is performed 2 to 5 times, the time of each extraction is 15 to 20 minutes, the temperature is 100 to 130°C, and the pressure is 6 to 10 MPa. The present invention uses far-infrared assisted pulse vacuum drying to dry the noni pomace, which can effectively remove excess water in the noni pomace while further retaining the active ingredients in the noni pomace, creating favorable conditions for the subsequent extraction of noni polysaccharides; the airflow ultrafine grinding technology is used to refine the dried noni pomace, further increasing the contact area between the solvent and the pomace in the extraction process, and promoting the full release of polysaccharides; water is used as a solvent to extract the noni pomace powder, and the extraction conditions are strictly limited to obtain uniform polysaccharides, which has the advantages of high extraction rate, low solvent usage, and short time consumption, while retaining the natural structure and biological activity of the polysaccharide, and significantly reducing energy consumption and waste emissions. The results of the embodiment show that the extraction rate of noni polysaccharides obtained by the extraction method of the present invention reaches 16.65% to 20.67%.

[0023] Furthermore, after the extraction is completed, the extract is ultrafiltered, and the solution portion is collected and dried. The ultrafiltration conditions are limited, which can remove small molecular impurities and pigments in the extract, ensuring the high purity of Noni polysaccharide, reaching more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0025] Figure 1 This is the molecular weight measurement result of Noni polysaccharide obtained in Example 1. DETAILED DESCRIPTION

[0026] The present invention provides a method for extracting Noni polysaccharide, comprising the following steps:

[0027] Performing far infrared assisted pulse vacuum drying on the noni pomace to obtain dried noni pomace;

[0028] Performing airflow ultrafine grinding on the dried Noni pomace to obtain the Noni pomace powder;

[0029] Extracting the noni pomace powder with water as solvent and collecting the extract; the extract contains noni polysaccharide;

[0030] The extraction is performed 2 to 5 times, each extraction lasts 15 to 20 minutes, the temperature is 100 to 130° C., and the pressure is 6 to 10 MPa.

[0031] The invention performs far-infrared-assisted pulse vacuum drying on the noni pomace to obtain dried noni pomace.

[0032] In the present invention, as an embodiment, the moisture content of the dried Noni pomace is ≤12%; as another embodiment, the moisture content of the dried Noni pomace is 11%. As an embodiment, the vacuum holding time of the far-infrared assisted pulse vacuum drying is 8 to 12 minutes; as another embodiment, the vacuum holding time of the far-infrared assisted pulse vacuum drying is 10 minutes. As an embodiment, the vacuum pressure of the far-infrared assisted pulse vacuum drying is 6 to 10 kPa; as another embodiment, the vacuum pressure of the far-infrared assisted pulse vacuum drying is 8 kPa. As an embodiment, the normal pressure holding time of the far-infrared assisted pulse vacuum drying is 5 to 9 minutes; as another embodiment, the normal pressure holding time of the far-infrared assisted pulse vacuum drying is 7 minutes. As an embodiment, the temperature of the far-infrared assisted pulse vacuum drying is 48 to 56°C; as another embodiment, the temperature of the far-infrared assisted pulse vacuum drying is 52°C. As an embodiment, the radiation power of the far-infrared assisted pulse vacuum drying is 760-800W; as another embodiment, the radiation power of the far-infrared assisted pulse vacuum drying is 780W. As an embodiment, the radiation distance of the far-infrared assisted pulse vacuum drying is 10-20cm; as another embodiment, the radiation distance of the far-infrared assisted pulse vacuum drying is 15cm. The present invention utilizes far-infrared assisted pulse vacuum drying to dry the noni pomace, which can further retain the active ingredients in the noni pomace while effectively removing excess water in the noni pomace, creating favorable conditions for the subsequent extraction of noni polysaccharides.

[0033] The present invention has no strict requirements on the source of the Noni pomace, and it can be obtained by conventional methods in the art, for example, by-products and wastes from Noni juice extraction, fruit wine making, and bioactive product preparation, etc., and washed with clean water.

[0034] After obtaining the dried Morinda citrifolia pomace, the present invention performs airflow ultrafine grinding on the dried Morinda citrifolia pomace to obtain Morinda citrifolia pomace powder.

[0035] In the present invention, as an embodiment, the water content of the Noni pomace powder is ≤12%; as another embodiment, the water content of the Noni pomace powder is 11%. As an embodiment, the particle size of the Noni pomace powder is 20-50 μm; as another embodiment, the particle size of the Noni pomace powder is 20 μm.

[0036] In the present invention, as an embodiment, the classifier frequency of the airflow ultrafine pulverization is 55-65Hz / 0.5-0.7A; as another embodiment, the classifier frequency of the airflow ultrafine pulverization is 60Hz / 0.6A. As an embodiment, the induced draft fan frequency of the airflow ultrafine pulverization is 35-45Hz / 7-7.4A; as another embodiment, the induced draft fan frequency of the airflow ultrafine pulverization is 40Hz / 7.2A. As an embodiment, the pulverization pressure of the airflow ultrafine pulverization is 0.5-0.9MPa; as another embodiment, the pulverization pressure of the airflow ultrafine pulverization is 0.7MPa. As an embodiment, the pulverization time of the airflow ultrafine pulverization is 5-7h; as another embodiment, the pulverization time of the airflow ultrafine pulverization is 6h. As an embodiment, the feed airflow of the airflow ultrafine pulverization is 0.5-0.9MPa; as another embodiment, the feed airflow of the airflow ultrafine pulverization is 0.6MPa. As an embodiment, the airflow of the airflow ultrafine grinding is 0.7-0.9MPa; as another embodiment, the airflow of the airflow ultrafine grinding is 0.8MPa. The present invention uses airflow ultrafine grinding technology to refine the dried Noni pomace, further increases the contact area between the solvent and the pomace in the extraction process, and promotes the full release of polysaccharides.

[0037] After obtaining the noni pomace powder, the present invention uses water as a solvent to extract the noni pomace powder and collects an extract; the extract contains noni polysaccharides.

[0038] In the present invention, as an embodiment, the number of extractions is 2 to 5 times; as another embodiment, the number of extractions is 3 to 4 times; as another embodiment, the number of extractions is 3 times. As an embodiment, the time for each extraction is 15 to 20 minutes; as another embodiment, the time for each extraction is 20 minutes. As an embodiment, the temperature for each extraction is 100 to 130°C; as another embodiment, the temperature for each extraction is 110°C. As an embodiment, the pressure for each extraction is 6 to 10MPa; as another embodiment, the pressure for each extraction is 8MPa. As an embodiment, the mass volume ratio of the Noni pomace powder and water is 1g:5 to 10mL; as another embodiment, the mass volume ratio of the Noni pomace powder and water is 1g:8mL. The present invention uses water as solvent and extracts under high temperature and high pressure conditions. It uses the characteristics of protein denaturation under high temperature to naturally exclude protein from the extract, without the need for additional protein removal steps; strictly controls parameters such as temperature, pressure and time to ensure that while efficiently extracting polysaccharides, its natural structure and biological activity are retained to the greatest extent; the high degree of automation, low solvent usage and short time consumption greatly accelerate the dissolution process of polysaccharides, significantly improving the polysaccharide yield, which is higher than the traditional method. The results of the embodiment show that the extraction rate of Noni polysaccharides obtained by the extraction method of the present invention reaches 16.65% to 20.67%.

[0039] After obtaining the extract, the present invention preferably performs ultrafiltration on the extract, collects the solution portion and then dries it to obtain Noni polysaccharide.

[0040] In the present invention, as an embodiment, the ultrafiltration time is 40 to 60 minutes; as another embodiment, the ultrafiltration time is 50 minutes. As an embodiment, the ultrafiltration pressure is 0.25 to 0.35 MPa; as another embodiment, the ultrafiltration pressure is 0.3 MPa. As an embodiment, the ultrafiltration temperature is 50 to 55°C; as another embodiment, the ultrafiltration temperature is 52°C. The present invention ultrafilters the extract to remove small molecule impurities and pigments in the extract, ensuring the high purity of Noni polysaccharides, reaching more than 90%.

[0041] In the present invention, as an embodiment, the drying includes vacuum freeze drying. As an embodiment, the pre-freezing temperature of the vacuum freeze drying is -60°C, the pre-freezing time is 2 hours, and the pre-freezing is followed by drying at a vacuum degree of ≤20Pa. As an embodiment, the pre-freezing temperature of the vacuum freeze drying is -60°C, the pre-freezing time is 2 hours, and the vacuum degree is then 0 to 20Pa.

[0042] The present invention also provides the noni polysaccharide obtained by the extraction method described in the above technical scheme; the purity of the noni polysaccharide is ≥90%, and the molecular weight is ≥92.07kDa; the monosaccharides in the noni polysaccharide include rhamnose, arabinose, galactose, glucose and galacturonic acid; the molar ratio of the rhamnose, arabinose, galactose, glucose and galacturonic acid is 6-6.5:10-11:31-32:19-20:31.5-32.0. As an embodiment, the monosaccharides in the noni polysaccharide include rhamnose, arabinose, galactose, glucose and galacturonic acid; the molar ratio of the rhamnose, arabinose, galactose, glucose and galacturonic acid is 6.1-6.2:10.5-10.7:31.5-31.7:19.6-19.7:32.0. The extraction method provided by the present invention makes full use of the noni pomace that will become waste, extracts noni polysaccharide from the noni pomace, uses less solvent, takes less time, and significantly reduces energy consumption and waste discharge. The extraction rate of noni polysaccharide reaches 16.65% to 20.67%, the purity reaches more than 90%, and has strong antioxidant activity.

[0043] In order to further illustrate the present invention, a kind of Noni polysaccharide and its extraction method provided by the present invention are described in detail below in combination with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] A method for extracting polysaccharides from noni pomace based on rapid solvent extraction technology, comprising the following steps:

[0046] (1) Fresh, disease- and insect-free Noni fruits are selected as raw materials, washed and drained, and the processed Noni fruits are juiced to obtain Noni juice and Noni pomace.

[0047] (2) Drying the noni pomace using far infrared assisted pulse vacuum drying technology; wherein:

[0048] The vacuum holding time of pulse vacuum drying is 10 minutes, the vacuum pressure is 8 kPa, the normal pressure holding time is 7 minutes, the temperature of pulse vacuum drying is 52°C, the radiation power is 780 W, the radiation distance is 15 cm, and the moisture content of noni pomace after drying is 11%.

[0049] (3) The dried noni pomace is pulverized by airflow ultrafine pulverization technology; wherein the ultrafine classifier frequency is set to 60 Hz / 0.6A, the induced draft fan frequency is set to 40 Hz / 7.2A, the pulverization pressure is set to 0.7 MPa, the pulverization time is 6 h, the feed airflow is 0.6 MPa, and the pulverization airflow is 0.8 MPa.

[0050] (4) The crushed noni pomace was extracted for 20 min using rapid solvent extraction technology with deionized water as solvent; the extraction temperature was 110 °C, the extraction pressure was 8 MPa, each extraction time was 15 min, and the number of cycles was 3; the mass volume ratio of noni pomace powder and water was 1 g:8 mL.

[0051] (5) The extracted extract is subjected to ultrafiltration technology to remove small molecular impurities, decolorize and concentrate to obtain a noni polysaccharide solution; wherein the ultrafiltration time is 60 min, the vacuum pressure is 0.25 MPa, and the ultrafiltration temperature is 50° C.; the mass concentration of noni polysaccharide in the noni polysaccharide solution is 3 g / L.

[0052] (6) The noni polysaccharide solution after ultrafiltration is dried using vacuum freeze drying technology; wherein the pre-freezing temperature of the vacuum freeze drying is -60°C, the pre-freezing time is 2 hours, and then the noni polysaccharide is dried at a vacuum degree of 5 Pa to obtain noni polysaccharide.

[0053] Example 2

[0054] A method for extracting polysaccharides from noni pomace based on rapid solvent extraction technology is similar to Example 1, with the only difference being that during the extraction in step (4), the crushed noni pomace is extracted for 20 minutes using rapid solvent extraction technology and deionized water as solvent; the extraction temperature is 100° C., the extraction pressure is 10 MPa, each extraction time is 20 minutes, and the number of cycles is 3 times; the mass volume ratio of noni pomace powder to water is 1 g:6 mL.

[0055] Comparative Example 1

[0056] A method for extracting polysaccharides from noni pomace based on rapid solvent extraction technology is similar to Example 1, with the only difference being that during the extraction in step (4), the crushed noni pomace is extracted for 30 minutes using rapid solvent extraction technology and deionized water as solvent; the extraction temperature is 110° C., the extraction pressure is 8 MPa, each extraction time is 15 minutes, and the number of cycles is 3 times; the mass volume ratio of noni pomace powder to water is 1 g:8 mL.

[0057] Comparative Example 2

[0058] A method for extracting polysaccharides from noni pomace based on rapid solvent extraction technology is similar to Example 1, the only difference being that during the extraction in step (4), the number of cycles is 7 times; and the mass volume ratio of noni pomace powder to water is 1 g:8 mL.

[0059] Comparative Example 3

[0060] A method for extracting polysaccharides from noni pomace based on rapid solvent extraction technology is similar to Example 1, with the only difference being that during the extraction in step (4), the rapid solvent extraction technology is used, deionized water is used as solvent, and the crushed noni pomace is extracted for 30 minutes; the extraction temperature is 150° C., the extraction pressure is 8 MPa, each extraction time is 15 minutes, and the number of cycles is 3 times; the mass volume ratio of noni pomace powder to water is 1 g:8 mL.

[0061] Comparative Example 4

[0062] A method for extracting polysaccharides from noni pomace based on rapid solvent extraction technology is similar to Example 1, except that during the drying step (2), hot air drying is performed in a 55° C. oven for 6 hours, and during the pulverization step (3), a vertical pulverizer is used for pulverization.

[0063] Test Example 1

[0064] The yields of the noni polysaccharides in Examples 1 to 2 and Comparative Examples 1 to 4 were compared, and the purity of the noni polysaccharides obtained was determined by UV-visible spectroscopy. The noni polysaccharides extracted from Comparative Examples 1 to 2 and Comparative Examples 1 to 4 were characterized by gel chromatography. The results are shown in Tables 1 and Figure 1 shown.

[0065] Table 1 Results of yield, purity and molecular weight of Noni polysaccharide under different extraction methods

[0066] Samples to be tested Extraction rate (%) purity(%) Molecular weight (kDa) Example 1 <![CDATA[20.67 a ]]> <![CDATA[92.29 a ]]> <![CDATA[93.19 a <!-- 5 -->]]> Example 2 <![CDATA[16.65 b ]]> <![CDATA[91.36 a ]]> <![CDATA[92.07 b ]]> Comparative Example 1 <![CDATA[10.77 c ]]> <![CDATA[80.85 b ]]> <![CDATA[92.15 b ]]> Comparative Example 2 <![CDATA[12.58 d ]]> <![CDATA[83.60 b ]]> <![CDATA[92.00 b ]]> Comparative Example 3 <![CDATA[9.20 e ]]> <![CDATA[68.99 c ]]> <![CDATA[93.05 a ]]> Comparative Example 4 <![CDATA[8.99 e ]]> <![CDATA[61.11 d ]]> <![CDATA[92.08 b ]]>

[0067] Note: Different lowercase letters in the table indicate statistically significant differences, p<0.05.

[0068] According to Table 1 and Figure 1It can be seen that when the rapid solvent extraction exceeds 20 minutes, the extraction rate decreases (Comparative Example 1); multiple cyclic extractions will also cause the degradation of Noni polysaccharides to a certain extent, reducing the extraction rate (Comparative Example 2); the extraction temperature is 150°C, and the extraction rate decreases (Comparative Example 3); the purity of Noni polysaccharides obtained in Examples 1 to 2 is significantly higher than that in Comparative Examples 1 to 4; the molecular weight of Noni polysaccharides in Example 1 is 93.19 kDa, and it is mainly composed of five monosaccharides: rhamnose, arabinose, galactose, glucose, and galacturonic acid, and the molar ratio is 6.2:10.7:31.5:19.6:32.0; the molecular weight of Noni polysaccharides in Example 2 is 92.07 kDa, and it is mainly composed of five monosaccharides: rhamnose, arabinose, galactose, glucose, and galacturonic acid, and the molar ratio is 6.1:10.5:31.7:19.7:32.0; the molecular weight of Noni polysaccharides in Comparative Example 1 is 92.15 kDa , mainly composed of five monosaccharides: rhamnose, arabinose, galactose, glucose, and galacturonic acid, with a molar ratio of 5.3:10.5:31.9:18.9:33.4; the molecular weight of the noni polysaccharide in comparative example 2 is 92.00 kDa, mainly composed of five monosaccharides: rhamnose, arabinose, galactose, glucose, and galacturonic acid, with a molar ratio of 6.3:10.6:31.1:19.7:32.3; the molecular weight of the noni polysaccharide in comparative example 3 is 92.00 kDa, mainly composed of five monosaccharides: rhamnose, arabinose, galactose, glucose, and galacturonic acid, with a molar ratio of 6.3:10.6:31.1:19.7:32.3 The molecular weight of the polysaccharide is 93.05 kDa, and it is mainly composed of five monosaccharides: rhamnose, arabinose, galactose, glucose, and galacturonic acid, and the molar ratio is 5.1:10.9:36.2:18.5:29.3; the molecular weight of the noni polysaccharide of comparative example 4 is 92.08 kDa, and it is mainly composed of four monosaccharides: arabinose, galactose, glucose, and galacturonic acid, and the molar ratio is 12.8:39.4:17.5:30.3. The noni polysaccharides of the embodiments and comparative examples are homogeneous polysaccharides.

[0069] According to the above content, it can be seen that the extraction method provided by the present invention uses less solvent and is time-saving, and can obtain uniform polysaccharides from noni pomace with a yield higher than 15% and a purity higher than 90%. At the same time, the natural structure and biological activity of the polysaccharide are retained, and the DPPH clearance rate reaches 55%, which has strong antioxidant activity.

[0070] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for extracting Noni polysaccharide, characterized in that: The steps include: performing far infrared assisted pulse vacuum drying on the noni pomace to obtain dried noni pomace; performing airflow ultrafine grinding on the dried Noni pomace to obtain the Noni pomace powder; Extracting the noni pomace powder with water as a solvent and collecting an extract; the extract contains noni polysaccharides; The extraction is performed 2 to 5 times, the extraction time for each time is 15 to 20 minutes, the temperature is 100 to 130° C., and the pressure is 6 to 10 MPa.

2. The extraction method according to claim 1, wherein the moisture content of the Noni pomace powder is ≤12% and the particle size is 20 to 50 μm.

3. The extraction method according to claim 1, wherein The far-infrared assisted pulse vacuum drying has a vacuum holding time of 8 to 12 minutes, a vacuum pressure of 6 to 10 kPa, a normal pressure holding time of 5 to 9 minutes, a temperature of 48 to 56° C., a radiation power of 760 to 800 W, and a radiation distance of 10 to 20 cm.

4. The extraction method according to claim 1, wherein The classifier frequency of the air flow ultrafine grinding is 55-65Hz / 0.5-0.7A, the induced draft fan frequency is 35-45Hz / 7-7.4A, the grinding pressure is 0.5-0.9MPa, the grinding time is 5-7h, the feed air flow is 0.5-0.9MPa, and the grinding air flow is 0.7-0.9MPa.

5. The extraction method according to claim 1, wherein The mass volume ratio of the Noni pomace powder and water is 1g:5-10mL.

6. The extraction method according to claims 1 to 5, characterized in that After obtaining the extract, the method further comprises: ultrafiltration of the extract, collecting the solution portion and drying to obtain the Noni polysaccharide; The ultrafiltration time is 40 to 60 minutes, the pressure is 0.25 to 0.35 MPa, and the temperature is 50 to 55°C.

7. The extraction method according to claim 6, characterized in that The drying includes vacuum freeze drying.

8. The extraction method according to claim 7, characterized in that The pre-freezing temperature of the vacuum freeze drying is -60°C, the pre-freezing time is 2 hours, and the vacuum degree is ≤20Pa after the pre-freezing is completed.

9. The noni polysaccharide obtained by the extraction method according to any one of claims 1 to 8; the purity of the noni polysaccharide is ≥90%, and the molecular weight is ≥92.07 kDa.

10. The Noni polysaccharide according to claim 9, characterized in that The monosaccharides in the noni polysaccharide include rhamnose, arabinose, galactose, glucose and galacturonic acid; the molar ratio of the rhamnose, arabinose, galactose, glucose and galacturonic acid is 6-6.5:10-11:31-32:19-20:31.5-32.0.

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