Extraction method of low-ash hemp pectin

Abstract

The invention provides an extraction method of low-ash hemp pectin, and particularly relates to an extraction method of hibiscus cannabinus, sisal hemp or ramie pectin, which comprises the following steps: sequentially carrying out pretreatment, deliming treatment, pectin acid extraction, pigment adsorption, alcohol precipitation and filtration, and washing and drying on hibiscus cannabinus, sisal hemp or ramie raw materials to obtain a low-ash pectin product; according to the method disclosed by the invention, high-quality low-ash pectin can be obtained, and the yield is high; moreover, the raw material source of the pectin is expanded, and a new thought is provided for comprehensive utilization of the hibiscus cannabinus, the sisal hemp and the ramie.

Description

Technical Field

[0001] The present invention relates to the field of pectin extraction, and more specifically, to a method for extracting low-ash ramie pectin. Background Art

[0002] Pectin is a polysaccharide, and its composition has two types: homopolysaccharide and heteropolysaccharide. They are mostly present in the plant cell wall and the inner layer of cells, and are abundantly present in the peels of citrus fruits, lemons, grapefruits, etc. It is white to yellowish powder, with a relative molecular mass of about 20 - 400 kDa and is odorless. Generally speaking, the pectin in plant cells can be divided into three types: protopectin, pectin, and pectic acid. Among them, pectin is mainly formed by the linkage of more than 75% methyl-esterified polygalacturonic acid chains, and this pectin is soluble in water; pectic acid is a linear polymer formed by the dehydration condensation of D-galacturonic acid and then linked by α-1,4 glycosidic bonds. Protopectin is mainly composed of a homogalacturonic acid region and a rhamnogalacturonan backbone with neutral sugar side chains. Protopectin exists in an insoluble form in water, and after restricted enzymatic hydrolysis, it can form pectin and pectic acid. The chemical structure of pectin is composed of a glycan formed by the linkage of rhamnose and multiple galacturonic acids as the main chain, and then the side chains of different lengths are respectively composed of xylose, D-galactose, L-arabinose, etc. It is more stable in acidic solutions than in alkaline solutions, and is usually divided into high-ester pectin and low-ester pectin according to its degree of esterification. High-ester pectin forms an irreversible gel in the range of soluble sugar content ≥ 60% and pH 2.6 - 3.4. Low-ester pectin has a part of its methyl esters converted into primary amides, which is not affected by sugar and acid, but needs to combine with divalent ions such as calcium and magnesium to form a gel. Currently, the main methods for extracting pectin include water extraction method, acid method, alkali method, chelation method, etc. Among them, the water extraction method can only extract some pectin that is easily soluble in water, and a large amount of pectin that is insoluble in water will be wasted.

[0003] The application fields of pectin are particularly extensive. In the food industry, it is usually used as a gelling agent, emulsifier, stabilizer, and thickener. Currently, the raw materials of pectin mainly come from fruits (such as citrus fruits, apples, etc.), vegetables (such as carrots, pumpkins, etc.), and other plant parts (such as flaxseed husks, etc.).

[0004] Ramie crops are one of the important sources of natural fibers. In addition to containing a large amount of cellulose fibers, the bast raw materials of ramie crops also contain pectin, hemicellulose, lignin and other gum components. Currently, extensive research has been carried out on the degumming of ramie crop bast raw materials at home and abroad, and remarkable progress has been made.

[0005] However, the traditional way of processing hemp crops mainly obtains textile fiber raw materials, and the pectin they contain is usually degraded during the degumming process and discharged with sewage. This not only causes waste of pectin resources but also may pollute the environment, becoming a major challenge faced by hemp processing enterprises. To solve this problem, the research focus at home and abroad has gradually shifted to the extraction of bast pectin from hemp crops.

[0006] At present, certain progress has been made in the extraction technology of hemp crop pectin, but the pectin obtained still has problems such as high impurity and ash content, and further refining treatment is required to meet the requirements of practical applications. Summary of the Invention

[0007] Based on the above technical problems existing in the prior art, the present invention provides a method for extracting low-ash hemp pectin. Through this method, the obtained pectin has low ash impurities and a high galacturonic acid content, and can be directly used as a food additive or pharmaceutical excipient pectin in the food and pharmaceutical fields.

[0008] To achieve the above object, the technical solution of the present invention is as follows:

[0009] A method for extracting low-ash kenaf / sisal / ramie pectin, comprising the following steps:

[0010] S1. Raw material pretreatment: Wash and inactivate enzymes of the kenaf / sisal / ramie raw materials;

[0011] S2. Ash removal treatment: Add the pretreated raw materials into an ethylenediaminetetraacetic acid solution and / or an ethylenediaminetetraacetic acid disodium solution, and then perform ultrasonic treatment; after ultrasonic treatment, let it stand, separate the solid and liquid, collect the solid and wash it with deionized water to obtain the ash-removed raw materials;

[0012] S3. Acid extraction of pectin: Add the ash-removed raw materials obtained in step S2 into a nitric acid solution, heat up for extraction; after the extraction is completed, separate the solid and liquid, and collect the first filtrate;

[0013] S4. Add a cation exchange resin to the first filtrate for reaction, after the reaction is completed, separate the solid and liquid, and collect the second filtrate;

[0014] S5. Add an ethanol solution with a mass concentration ≥95% to the second filtrate for reaction, after the reaction is completed, separate the solid and liquid, and collect the precipitate;

[0015] S6. Wash and dry the precipitate obtained in step S5 to obtain a low-ash pectin product.

[0016] In some embodiments, in step S2, the concentration of the ethylenediaminetetraacetic acid solution or the ethylenediaminetetraacetic acid disodium solution is 0.5 - 1.5 wt%.

[0017] In some embodiments, in step S2, the solid-liquid ratio of the raw material to the solution is 1 g: 5 - 20 mL; that is, the solid-liquid ratio of the raw material to the ethylenediaminetetraacetic acid solution is 1 g: 5 - 20 mL; or, the solid-liquid ratio of the raw material to the disodium ethylenediaminetetraacetate solution is 1 g: 5 - 20 mL; or, the solid-liquid ratio of the raw material to the mixed solution of ethylenediaminetetraacetic acid solution and disodium ethylenediaminetetraacetate solution is 1 g: 5 - 20 mL.

[0018] In some embodiments, in step S3, the final concentration of the nitric acid solution is 4 - 6 g / L; the material-liquid ratio of the deashed raw material to the nitric acid solution is 1 g: 4 - 6 mL.

[0019] In some embodiments, in step S3, after mixing the deashed raw material and the nitric acid solution, the temperature is raised to 80 - 90 °C, and it is kept warm for 0.5 - 2 h, and ultrasonic treatment is performed once every 20 - 40 min, the ultrasonic power is 200 - 400 w, for 20 - 45 s.

[0020] In some embodiments, in step S2, the deashing treatment method is specifically:

[0021] The pretreated raw material is added to an ethylenediaminetetraacetic acid solution and / or a disodium ethylenediaminetetraacetate solution with a concentration of 0.5 - 1.5 wt% according to a material-liquid ratio of 1 g: 5 - 20 mL, and then ultrasonic treatment is performed at 10 - 50 °C for 20 - 40 min, the ultrasonic power is 30 - 50 kHz; after the ultrasonic treatment is completed, it is left to stand; the total deashing treatment time is controlled within 2 - 4 h.

[0022] In some embodiments, in step S1, the pretreatment method is: after washing the kenaf / sisal / ramie raw material with water, it is placed in a container, and then subjected to a boiling water bath treatment for 2 - 10 min to inactivate pectinase.

[0023] In some embodiments, in step S4, the cation exchange resin is a strongly acidic cation exchange resin; the solid-liquid ratio of the cation exchange resin to the first filtrate is 1 g: 10 - 15 mL.

[0024] In some embodiments, in step S5, the concentration of the ethanol solution is 95 - 99%; the volume of the ethanol solution is 1.5 - 3 times the volume of the second filtrate.

[0025] In some embodiments, in step S6, the precipitate is washed with absolute ethanol, then placed in a vacuum drying oven, dried to constant weight at 40 - 60 °C, and pulverized to obtain a low-ash pectin product.

[0026] In the above technical solution, "kenaf / sisal / ramie" refers to at least one of kenaf, sisal, and ramie.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The present invention uses kenaf / sisal / ramie raw materials, and through pretreatment - deashing treatment - acid extraction of pectin - adsorption of pigments - alcohol precipitation and filtration - washing and drying in sequence, a low - ash pectin product is obtained; by a specific method for pretreating, extracting and post - treating kenaf or sisal or ramie raw materials, the pectin yield is relatively high, and it has low ash content and high galacturonic acid content, and can be directly used as pectin for food additives or pharmaceutical excipients.

[0029] The method of the present invention uses kenaf / sisal / ramie as raw materials for pectin extraction, which expands the source of pectin raw materials and provides new ideas for the comprehensive utilization of kenaf, sisal and ramie. Detailed implementation manners

[0030] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementations disclosed below.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0032] Example 1

[0033] A method for extracting low - ash kenaf pectin includes the following steps:

[0034] S1. Raw material pretreatment: After washing and removing dust from the kenaf bast raw material with tap water, place it in a container, add water and mix, then perform a boiling water bath treatment for 5 min to inactivate pectinase;

[0035] S2. Deashing treatment: Add the pretreated raw material to an ethylenediaminetetraacetic acid solution with a concentration of 1 wt% according to a solid - liquid ratio of 1 g:10 mL, then perform ultrasonic treatment at 50 °C for 30 min with an ultrasonic power of 40 kHz; after the ultrasonic treatment is completed, let it stand for 2 h, perform solid - liquid separation, and wash the collected solid with deionized water to obtain the deashed raw material;

[0036] S3. Acid extraction of pectin: Add the deashed raw material obtained in step S2 to a nitric acid solution and mix, control the final concentration of the nitric acid solution to be 6 g / L, heat up to 85 °C for extraction, keep warm for 2 h, perform ultrasonic treatment once every 20 min with an ultrasonic power of 40 w for 30 s; after the extraction is completed, perform solid - liquid separation and collect the first filtrate;

[0037] S4. Add strongly acidic cation exchange resin to the first filtrate for adsorption reaction. After the reaction is completed, perform solid-liquid separation and collect the second filtrate. The solid-liquid ratio of the first filtrate to the cation exchange resin is 1 g: 10 mL.

[0038] S5. Add an ethanol solution with a mass concentration of 95% and a volume twice that of the second filtrate, mix well, let it stand for precipitation, perform solid-liquid separation, and collect the precipitate.

[0039] S6. Wash the precipitate obtained in step S5 with absolute ethanol, then place it in a vacuum drying oven and dry it to a constant weight at a temperature of 40 °C to obtain the low-ash pectin product.

[0040] Example 2

[0041] A method for extracting low-ash sisal pectin, comprising the following steps:

[0042] S1. Raw material pretreatment: After cleaning and removing impurities from the sisal residue raw material with tap water, place it in a container, add water and mix, then perform boiling water bath treatment for 5 min to inactivate pectinase.

[0043] S2. Ash removal treatment: Add the pretreated raw material to an ethylenediaminetetraacetic acid solution with a concentration of 1 wt% according to a solid-liquid ratio of 1 g: 10 mL, then perform ultrasonic treatment at 50 °C for 30 min, and the ultrasonic power is 40 kHz. After the ultrasonic treatment is completed, let it stand for 2 h, perform solid-liquid separation, and wash the collected solid with deionized water to obtain the ash-removed raw material.

[0044] S3. Acid extraction of pectin: Add the ash-removed raw material obtained in step S2 to a nitric acid solution and mix. Control the final concentration of the nitric acid solution to be 6 g / L, heat up to 85 °C for extraction, keep warm for 2 h, perform ultrasonic treatment once every 20 min, and the ultrasonic power is 40 w for 30 s. After the extraction is completed, perform solid-liquid separation and collect the first filtrate.

[0045] S4. Add strongly acidic cation exchange resin to the first filtrate for adsorption reaction. After the reaction is completed, perform solid-liquid separation and collect the second filtrate. The solid-liquid ratio of the first filtrate to the cation exchange resin is 1 g: 10 mL.

[0046] S5. Add an ethanol solution with a mass concentration of 95% and a volume twice that of the second filtrate, mix well, let it stand for precipitation, perform solid-liquid separation, and collect the precipitate.

[0047] S6. Wash the precipitate obtained in step S5 with absolute ethanol, then place it in a vacuum drying oven and dry it to a constant weight at a temperature of 40 °C to obtain the low-ash pectin product.

[0048] Example 3

[0049] A method for extracting low-ash ramie pectin, comprising the following steps:

[0050] S1. Raw material pretreatment: After washing and removing impurities from ramie bast raw materials with tap water, place them in a container, add water and mix, then perform a boiling water bath treatment for 5 min to inactivate pectinase;

[0051] S2. Demineralization treatment: Add the pretreated raw materials to an ethylenediaminetetraacetic acid solution with a concentration of 1 wt% at a solid-liquid ratio of 1 g:10 mL, then perform ultrasonic treatment at 50 °C for 30 min with an ultrasonic power of 40 kHz; after the ultrasonic treatment is completed, let it stand for 2 h, perform solid-liquid separation, collect the solid and wash it with deionized water to obtain the demineralized raw materials;

[0052] S3. Acid extraction of pectin: Add the demineralized raw materials obtained in step S2 to a nitric acid solution and mix, control the final concentration of the nitric acid solution to be 6 g / L, heat up to 85 °C for extraction, keep warm for 2 h, perform ultrasonic treatment once every 20 min with an ultrasonic power of 40 w for 30 s; after the extraction is completed, perform solid-liquid separation and collect the first filtrate;

[0053] S4. Add a strongly acidic cation exchange resin to the first filtrate for an adsorption reaction. After the reaction is completed, perform solid-liquid separation and collect the second filtrate; the solid-liquid ratio of the first filtrate to the cation exchange resin is 1 g:10 ml;

[0054] S5. Add an ethanol solution with a mass concentration of 95% at 2 times the volume to the second filtrate, mix well, let it stand for precipitation, perform solid-liquid separation, and collect the precipitate;

[0055] S6. Wash the precipitate obtained in step S5 with absolute ethanol, then place it in a vacuum drying oven and dry it to a constant weight at a temperature of 40 °C to obtain a low-ash pectin finished product.

[0056] Comparative Example 1

[0057] A method for extracting low-ash kenaf pectin, comprising the following steps:

[0058] S1. Raw material pretreatment: After washing and removing dust from kenaf bast raw materials with tap water, place them in a container, add water and mix, then perform a boiling water bath treatment for 5 min to inactivate pectinase;

[0059] S2. Demineralization treatment: Add the pretreated raw materials to an ethylenediaminetetraacetic acid solution with a concentration of 1 wt% at a solid-liquid ratio of 1 g:10 mL, then perform ultrasonic treatment at 50 °C for 30 min with an ultrasonic power of 40 kHz; after the ultrasonic treatment is completed, let it stand for 2 h, perform solid-liquid separation, collect the solid and wash it with deionized water to obtain the demineralized raw materials;

[0060] S3. Acid extraction of pectin: Add the deashed raw material obtained in step S2 into a nitric acid solution and mix. Control the final concentration of the nitric acid solution to be 6 g / L, heat up to 85 °C for extraction, keep warm for 2 h, ultrasonicate once every 20 min, with an ultrasonic power of 40 w for 30 s. After the extraction is completed, perform solid-liquid separation and collect the first filtrate.

[0061] S4. Add an ethanol solution with a mass concentration of 95% and a volume 2 times that of the first filtrate, mix well, let it stand for precipitation, perform solid-liquid separation, and collect the precipitate.

[0062] S5. Wash the precipitate obtained in step S4 with absolute ethanol, then place it in a vacuum drying oven and dry it to a constant weight at a temperature of 40 °C to obtain a low-ash pectin product.

[0063] Comparative Example 2

[0064] A method for extracting low-ash kenaf pectin includes the following steps:

[0065] S1. Raw material pretreatment: After washing and dust-removing the kenaf bast raw material with tap water, place it in a container, add water and mix, and then perform a boiling water bath treatment for 5 min to inactivate pectinase.

[0066] S2. Acid extraction of pectin: Add the pretreated raw material to a 6 g / L nitric acid solution according to a bath ratio of 1 g:10 mL, mix, and then add ethylenediaminetetraacetic acid (EDTA) to make its final concentration 1 wt%, heat up to 85 °C for extraction, keep warm for 2 h, ultrasonicate once every 20 min, with an ultrasonic power of 40 w for 30 s. After the extraction is completed, perform solid-liquid separation and collect the first filtrate.

[0067] S3. Add a strongly acidic cation exchange resin to the first filtrate for an adsorption reaction. After the reaction is completed, perform solid-liquid separation and collect the second filtrate; the solid-liquid ratio of the first filtrate to the cation exchange resin is 1 g:10 ml.

[0068] S4. Add an ethanol solution with a mass concentration of 95% and a volume 2 times that of the second filtrate, mix well, let it stand for precipitation, perform solid-liquid separation, and collect the precipitate.

[0069] S5. Wash the precipitate obtained in step S4 with absolute ethanol, then place it in a vacuum drying oven and dry it to a constant weight at a temperature of 40 °C to obtain a low-ash pectin product.

[0070] Comparative Example 3

[0071] A method for extracting low-ash kenaf pectin includes the following steps:

[0072] S1. Raw material pretreatment: After washing and dust-removing the kenaf bast raw material with tap water, place it in a container, add water and mix, and then perform a boiling water bath treatment for 5 min to inactivate pectinase.

[0073] S2. Depickling treatment: Add the pretreated raw materials to deionized water at a solid-liquid ratio of 1 g: 10 mL, then perform ultrasonic treatment at 50 °C for 30 min with an ultrasonic power of 40 kHz; after the ultrasonic treatment is completed, let it stand for 2 h, separate the solid and liquid, collect the solid and wash it with deionized water to obtain the depickled raw materials;

[0074] S3. Acid extraction of pectin: Add the depickled raw materials obtained in step S2 to a nitric acid solution and mix them, control the final concentration of the nitric acid solution to be 6 g / L, heat up to 85 °C for extraction, keep warm for 2 h, perform ultrasonic treatment once every 20 min with an ultrasonic power of 40 W for 30 s; after the extraction is completed, separate the solid and liquid, and collect the first filtrate;

[0075] S4. Add a strongly acidic cation exchange resin to the first filtrate for an adsorption reaction. After the reaction is completed, separate the solid and liquid, and collect the second filtrate; the solid-liquid ratio of the first filtrate to the cation exchange resin is 1 g: 10 mL;

[0076] S5. Add an ethanol solution with a mass concentration of 95% and a volume 2 times that of the second filtrate, mix well, let it stand for precipitation, separate the solid and liquid, and collect the precipitate;

[0077] S6. Wash the precipitate obtained in step S5 with absolute ethanol, then place it in a vacuum drying oven and dry it to a constant weight at a temperature of 40 °C to obtain a low-ash pectin product.

[0078] Comparative Example 4

[0079] A method for extracting low-ash kenaf pectin, comprising the following steps:

[0080] S1. Raw material pretreatment: After washing and removing dust from the kenaf phloem raw materials with tap water, place them in a container, add water and mix, and then perform a boiling water bath treatment for 5 min to inactivate pectinase;

[0081] S2. Depickling treatment: Add the pretreated raw materials to an ethylenediaminetetraacetic acid solution with a concentration of 1 wt% at a solid-liquid ratio of 1 g: 10 mL, then perform ultrasonic treatment at 50 °C for 30 min with an ultrasonic power of 40 kHz; after the ultrasonic treatment is completed, let it stand for 2 h, separate the solid and liquid, collect the solid and wash it with deionized water to obtain the depickled raw materials;

[0082] S3. Acid extraction of pectin: Add the depickled raw materials obtained in step S2 to a sulfuric acid solution and mix them, control the final concentration of the sulfuric acid solution to be 6 g / L, heat up to 85 °C for extraction, keep warm for 2 h, perform ultrasonic treatment once every 20 min with an ultrasonic power of 40 W for 30 s; after the extraction is completed, separate the solid and liquid, and collect the first filtrate;

[0083] S4. Add strongly acidic cation exchange resin to the first filtrate for an adsorption reaction. After the reaction is completed, perform solid-liquid separation and collect the second filtrate. The solid-liquid ratio of the first filtrate to the cation exchange resin is 1 g: 10 mL.

[0084] S5. Add an ethanol solution with a mass concentration of 95% and a volume twice that of the second filtrate, mix well, let it stand for precipitation, perform solid-liquid separation, and collect the precipitate.

[0085] S6. Wash the precipitate obtained in step S5 with absolute ethanol, then place it in a vacuum drying oven and dry it to a constant weight at a temperature of 40 °C to obtain a low-ash pectin product.

[0086] After testing, the quality and yield of the pectin obtained by the methods of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1 below:

[0087] Table 1 Quality and Yield of Pectin in Examples 1-3 and Comparative Examples 1-4

[0088] Pectin yield (%) Galacturonic acid content (%) Ash content (%) Example 1 2.080 84.9 4.43 Example 2 2.164 82.5 3.61 Example 3 1.890 78.7 4.34 Comparative Example 1 1.760 58.6 16.06 Comparative Example 2 1.420 66.0 8.36 Comparative Example 3 1.048 65.9 9.39 Comparative Example 4 2.637 52.4 15.49

[0089] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as falling within the scope described in this specification.

[0090] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A method for extracting low-ash kenaf / sisal / ramie pectin, characterized in that, It includes the following steps: S1. Raw material pretreatment: Wash and inactivate enzymes of kenaf / sisal / ramie raw materials; S2. Depulping treatment: Add the pretreated raw materials into ethylene diamine tetraacetic acid solution and / or disodium ethylene diamine tetraacetate solution, and then perform ultrasonic treatment; after ultrasonic treatment, let it stand, separate solid and liquid, wash the collected solid with deionized water to obtain the deashed raw materials; S3. Acid extraction of pectin: Add the deashed raw materials obtained in step S2 into nitric acid solution, heat up for extraction; after the extraction is completed, separate solid and liquid, and collect the first filtrate; S4. Add cation exchange resin to the first filtrate for reaction, after the reaction is completed, separate solid and liquid, and collect the second filtrate; S5. Add ethanol solution with a mass concentration ≥ 95% to the second filtrate for reaction, after the reaction is completed, separate solid and liquid, and collect the precipitate; S6. Wash and dry the precipitate obtained in step S5 to obtain the low-ash pectin finished product.

2. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that, In step S2, the concentration of the ethylene diamine tetraacetic acid solution or disodium ethylene diamine tetraacetate solution is 0.5 - 1.5 wt%.

3. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that, In step S2, the solid-liquid ratio of the raw materials and the solution is 1 g: 5 - 20 mL.

4. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that In step S3, the final concentration of the nitric acid solution is 4 - 6 g / L; the material-liquid ratio of the deashed raw materials and the nitric acid solution is 1 g: 4 - 6 mL.

5. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that, In step S3, after mixing the deashed raw materials and the nitric acid solution, heat up to 80 - 90 °C, keep warm for 0.5 - 2 h, perform ultrasonic treatment once every 20 - 40 min, the ultrasonic power is 200 - 400 w, and the time is 20 - 45 s.

6. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that, In step S2, the specific method of the deashing treatment is: Add the pretreated raw materials into ethylene diamine tetraacetic acid solution and / or disodium ethylene diamine tetraacetate solution with a concentration of 0.5 - 1.5 wt% according to the solid-liquid ratio of 1 g: 5 - 20 mL, and then perform ultrasonic treatment at 10 - 50 °C for 20 - 40 min, the ultrasonic power is 30 - 50 kHz; after the ultrasonic treatment is completed, let it stand; the total deashing treatment time is controlled within 2 - 4 h.

7. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that, In step S1, the pretreatment method is: Wash the kenaf / sisal / ramie raw materials with water, place them in a container, and then perform boiling water bath treatment for 2 - 10 min to inactivate pectinase.

8. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that, In step S4, the cation exchange resin is a strong acidic cation exchange resin; the solid-liquid ratio of the cation exchange resin and the first filtrate is 1 g: 10 - 15 ml.

9. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, wherein In step S5, the concentration of the ethanol solution is 95 - 99%; the volume of the ethanol solution is 1.5 - 3 times the volume of the second filtrate.

10. The extraction method of low-ash kenaf / sisal / ramie pectin according to claim 1, characterized in that, In step S6, wash the precipitate with absolute ethanol, then place it in a vacuum drying oven, dry it to constant weight at 40 - 60 °C, and pulverize it to obtain the low-ash pectin finished product.