Jute leaf pectin as well as preparation method and application thereof

Abstract

The invention discloses jute leaf pectin as well as a preparation method and application thereof. The method comprises the following steps: blanching jute leaves with boiling water, carrying out enzyme deactivation treatment, carrying out microwave low-temperature drying, and carrying out low-temperature superfine grinding to obtain the jute leaf fine powder. And decolorizing and degreasing the jute leaf fine powder by using ethanol, and removing alcohol-soluble small molecules to prepare the jute leaf alcohol insoluble substance. The method comprises the following steps: extracting by using water as a solvent, synchronously removing starch by using high-temperature-resistant amylase, carrying out step-by-step extraction on filter residues obtained after filtration by using ammonium oxalate, diluted hydrochloric acid and a diluted alkali solution as solvents, dialyzing an extracting solution, carrying out ultrasonic treatment, and freeze-drying, so as to finally prepare the jute leaf pectin with an enhancing effect. The galacturonic acid content of the jute leaf pectin prepared by the method is increased, the emulsifying capacity, the antioxidant capacity and the anti-inflammatory activity are enhanced, and the jute leaf pectin can be applied to food and functional food.

Description

Technical Field

[0001] The invention relates to the technical field of food and functional food, in particular to jute leaf pectin, a preparation method thereof and application thereof. Background Art

[0002] Jute is a traditional fiber crop in my country, and its stalks are an important raw material for producing high-quality fiber. The main cultivated species of jute in my country are long-fruit jute and round-fruit jute. The phloem of jute stems contains a large amount of pectin, which needs to be removed during the jute fiber processing to improve the quality of jute fiber. In addition to the stems, jute leaves also contain pectin. If the pectin in jute leaves can be extracted and developed and applied to food and functional foods, it will have significant economic value and health benefits.

[0003] Domestic researchers have carried out the extraction of pectin polysaccharides from jute leaves. CN105498708A discloses a method for preparing a jute polysaccharide adsorbent. The jute leaf pectin polysaccharides extracted by supercritical technology can be used to remove hexavalent chromium in water. CN105478085B and CN105536712B disclose adsorption materials with jute polysaccharides as the main component and their preparation methods. Jute polysaccharides are obtained by extracting jute leaves and tender shoots treated with gas explosions with an acidic solution. After the jute polysaccharides mentioned in the extraction form a complex with iron, they have a good adsorption effect and can be used for the removal of heavy metals. CN105498708B, CN105536713A and CN105478085A disclose supercritical extraction of jute polysaccharides and their applications. Jute polysaccharides extracted by supercritical enzymatic hydrolysis can be applied to solid adsorbents. CN105536713B discloses an adsorption material with jute polysaccharide as the main component and a preparation method thereof, wherein jute leaves are treated with cellulase, hemicellulase, pectinase, and carboxypeptidase B, and the jute polysaccharide extracted by a high-pressure reactor can be used as an adsorption material. However, the jute polysaccharides extracted by these methods are mainly used as adsorption materials for heavy metals, etc., and are not used for food processing, and the structural characteristics and biological activities of jute leaf pectin polysaccharides themselves are not paid attention to.

[0004] In the prior art, jute leaves are usually extracted with water or alcohol to obtain jute leaf extracts with antioxidant effects, and there are no reports on jute leaf pectin. For example, Feng Xiangyuan et al. (Natural Product Research and Development, 2020, 32: 1278-1284) found that jute leaf polysaccharides extracted with hot water have antioxidant activity, but their galacturonic acid content is extremely low (less than 4%), and their emulsification ability and anti-inflammatory activity are unknown. The effects of pretreatments such as blanching and drying on the structure and activity of extracted polysaccharides have not been studied. The dissolution of pectin in plants in different solvents varies greatly depending on their chemical structure. Pectin in jute leaves also has different solubility characteristics. Using different solvents for step-by-step extraction, it is expected that pectin components with different characteristics can be obtained. The galacturonic acid content has a great influence on the physicochemical properties and biological activity of pectin, such as emulsification ability and antioxidant ability.

[0005] Therefore, it is necessary to provide a method for preparing jute leaf pectin. Summary of the invention

[0006] The object of the present invention is to provide a jute leaf pectin, a preparation method thereof and an application thereof, wherein the content of galacturonic acid in the obtained jute leaf pectin is significantly increased, and the emulsifying ability, antioxidant ability and anti-inflammatory activity are significantly enhanced.

[0007] The present invention provides a method for preparing jute leaf pectin with enhanced effect, comprising the following steps:

[0008] S1. The jute leaves are sterilized with boiling water to inactivate enzymes, dried and crushed, and sieved through a 300-500 mesh sieve to obtain jute leaf fine powder;

[0009] S2, adding ethanol to the jute leaf powder, decolorizing and defatting, filtering, and drying the filter residue to obtain jute leaf alcohol insoluble matter;

[0010] S3, adding water and thermostable amylase to the jute leaf alcohol insoluble matter, extracting at 70-85° C. for 90-180 minutes, filtering, and setting aside the filter residue;

[0011] S4, adding ammonium oxalate solution to the filter residue obtained in step S3, extracting at 20-25° C. for 90-180 minutes, filtering, and setting the filter residue aside;

[0012] S5, adding hydrochloric acid solution to the filter residue obtained in step S4, extracting at 70-85° C. for 90-180 minutes, filtering, and setting the filter residue aside;

[0013] S6, adding sodium hydroxide solution to the filter residue obtained in step S5, extracting in an ice-water bath for 90 to 180 minutes, filtering, concentrating the filtrate by rotary evaporation and then dialyzing to obtain an extract;

[0014] S7. The extract is treated with ultrasound and freeze-dried to obtain jute leaf pectin.

[0015] Preferably, in step S1, the time for sterilizing the jute leaves and inactivating the enzymes is 70 to 100 seconds; the growth period of the jute leaves is 120±5 days; preferably, the pulverization is performed in a low-temperature ultrafine pulverizer.

[0016] Preferably, in step S1, the drying is specifically: microwave drying at 40-50°C.

[0017] Preferably, in step S2, the amount of ethanol added is 5 to 10 ml / g of the jute leaf powder; preferably, the ethanol is a 95 wt% ethanol solution. It should be noted that the unit "ml / g" in the present invention refers to the volume mass ratio of the extraction reagent to the solid extract, for example, the added volume of ethanol is 5 to 10 times the mass of the jute leaf powder, the same below.

[0018] Preferably, the decolorization and degreasing specifically comprises: treating at 50° C. for 2-6 hours, and repeating 3-6 times.

[0019] Preferably, in step S3, the amount of water added is 10-20 ml / g of the mass of the jute leaf alcohol insoluble matter, and the amount of the thermostable amylase used is 0.2% to 1% of the mass of the jute leaf alcohol insoluble matter.

[0020] Preferably, in step S4, the concentration of the ammonium oxalate solution is 20 to 50 mmol / L, and the amount added is 10 to 20 ml / g of the filter residue.

[0021] Preferably, in step S5, the concentration of the hydrochloric acid solution is 10 to 30 mmol / L, and the amount added is 10 to 20 ml / g of the filter residue.

[0022] Preferably, in step S6, the concentration of the sodium hydroxide solution is 30-60 mmol / L, and the amount added is 10-20 ml / g of the filter residue.

[0023] Preferably, in step S6, the dialysis is specifically: the filtrate is dialyzed in water through a dialysis membrane for 40-60 hours; the molecular weight of the dialysis membrane is 6-8 kDa.

[0024] Preferably, in step S7, the power of the ultrasound is 400-800 W, the time is 30-60 minutes, and the temperature is 35-45°C.

[0025] The present invention also provides jute leaf pectin prepared by the above preparation method.

[0026] The present invention also provides application of the jute leaf pectin in food or functional food.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention firstly uses boiling water for a short time to blanch the jute leaves to inactivate the pectinase in the jute leaves, thereby preventing the pectin in the jute leaves from changing its structural characteristics and reducing its content due to enzymatic degradation during the drying process.

[0029] 2. The present invention uses microwave low-temperature drying to dry jute leaves, and uses a low-temperature ultrafine grinder to grind them, which can retain the structure and characteristics of pectin to the greatest extent. At the same time, the jute powder prepared by ultrafine grinding has small particles, which is more conducive to the full dissolution of pectin.

[0030] 3. The present invention first utilizes ethanol solution for degreasing and decolorization, and then utilizes high-temperature resistant amylase for simultaneous treatment in the water extraction step. On the one hand, the starch in the jute leaves can be effectively removed by enzymolysis, thereby improving the subsequent pectin extraction yield and purity; on the other hand, the simultaneous removal of starch can also save extraction time and improve extraction efficiency.

[0031] 4. The present invention uses water, ammonium oxalate, hydrochloric acid and sodium hydroxide for step-by-step extraction, and finally combines ultrasonic technology to treat the alkaline extract to prepare alkali-soluble jute leaf pectin with increased galacturonic acid content, enhanced emulsification ability, antioxidant ability and anti-inflammatory activity. The pectin can be applied to food and functional food, which helps to achieve high-value utilization of jute leaves. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The removal rates of DPPH free radicals of the jute leaf pectins prepared in Examples 1-3 of the present invention and Control Groups 1-4.

[0033] Figure 2 The removal rate of ABTS free radicals of the jute leaf pectin prepared in Examples 1-3 of the present invention and Control Groups 1-4.

[0034] Figure 3 The inhibition rate of the jute leaf pectin prepared in Examples 1-3 of the present invention and Control Groups 1-4 on the inflammatory factor IL-6.

[0035] Figure 4 The inhibition rate of the jute leaf pectin prepared in Examples 1-3 of the present invention and Control Groups 1-4 on the inflammatory factor IL-1β. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Example 1

[0038] A method for preparing jute leaf pectin with enhanced effect comprises the following steps:

[0039] (1) collecting jute leaves grown to about 120 days old, blanching them in boiling water for 80 seconds to kill the enzymes, drying them at 45° C. in a microwave oven for 30 hours, and then pulverizing them in a low-temperature ultrafine grinder at 30° C. and passing them through a 400-mesh sieve to obtain jute leaf fine powder;

[0040] (2) placing jute leaf powder in a flask, adding 95% ethanol solution at a volume mass ratio of 8 ml / g, decolorizing and defatting at 50° C. for 4 hours, a total of 5 times, filtering, and drying the filter residue in an oven at 40° C. to prepare jute leaf alcohol insoluble matter;

[0041] (3) adding distilled water and 0.6% thermostable amylase to the jute leaf alcohol insoluble matter at a volume-to-mass ratio of 15 ml / g, extracting at 75° C. for 140 minutes, filtering, and keeping the residue for later use;

[0042] (4) adding 35 mmol / L ammonium oxalate solution to the filter residue obtained in step (3) at a volume mass ratio of 16 ml / g, extracting at 22° C. for 150 minutes, filtering, and setting the filter residue aside;

[0043] (5) adding 20 mmol / L hydrochloric acid solution to the filter residue obtained in step (4) at a volume mass ratio of 14 ml / g, extracting at 75° C. for 150 minutes, filtering, and setting aside the filter residue;

[0044] (6) Add 50 mmol / L sodium hydroxide solution to the filter residue obtained in step (5) at a volume mass ratio of 16 ml / g, extract in an ice-water bath for 140 minutes, filter, concentrate the filtrate by rotary evaporation at 45°C, pour it into a dialysis membrane (molecular weight cutoff 6-8 kDa), dialyze in distilled water for 48 hours, and use the dialyzed extract for later use.

[0045] (7) The extract after dialyzation in step (6) is treated with an ultrasonic processor at an ultrasonic power of 600 W for 45 minutes, and the treatment temperature is controlled to be 40° C. The extract after freeze-drying is a jute leaf pectin with enhanced effect.

[0046] Example 2

[0047] A method for preparing jute leaf pectin with enhanced effect comprises the following steps:

[0048] (1) collecting jute leaves grown to about 120 days old, blanching them in boiling water for 70 seconds to kill the enzymes, drying them at 42° C. in a microwave oven for 40 hours, and then pulverizing them in a low-temperature ultrafine grinder at 25° C. and passing them through a 300-mesh sieve to obtain jute leaf fine powder;

[0049] (2) placing jute leaf powder in a flask, adding 95% ethanol solution at a volume-to-mass ratio of 5 ml / g, decolorizing and defatting at 50° C. for 2 hours, a total of 6 times, filtering, and drying the filter residue in an oven at 40° C. to prepare jute leaf alcohol insoluble matter;

[0050] (3) adding distilled water and 0.2% thermostable amylase to the jute leaf alcohol insoluble matter at a volume-to-mass ratio of 10 ml / g, extracting at 70° C. for 180 minutes, filtering, and setting aside the residue;

[0051] (4) adding 50 mmol / L ammonium oxalate solution to the filter residue obtained in step (3) at a volume mass ratio of 10 ml / g, extracting at 20° C. for 180 minutes, filtering, and setting the filter residue aside;

[0052] (5) adding 30 mmol / L hydrochloric acid solution to the filter residue obtained in step (4) at a volume mass ratio of 10 ml / g, extracting at 70° C. for 180 minutes, filtering, and setting the filter residue aside;

[0053] (6) Add 60 mmol / L sodium hydroxide solution to the filter residue obtained in step (5) at a volume mass ratio of 10 ml / g, extract in an ice-water bath for 180 min, filter, concentrate the filtrate by rotary evaporation at 45° C., pour into a dialysis membrane (molecular weight cutoff 6-8 kDa), dialyze in distilled water for 48 h, and set aside the extract after dialysis.

[0054] (7) The extract after dialyzation in step (6) is treated with an ultrasonic processor at an ultrasonic power of 400 W for 60 minutes, and the treatment temperature is controlled to be 35° C. The extract after freeze-drying is a jute leaf pectin with enhanced effect.

[0055] Example 3

[0056] A method for preparing jute leaf pectin with enhanced effect comprises the following steps:

[0057] (1) collecting jute leaves grown to about 120 days old, blanching them in boiling water for 100 seconds to kill the enzymes, drying them at 48° C. in a microwave oven for 25 hours, and then pulverizing them in a low-temperature ultrafine grinder at 35° C. and passing them through a 500-mesh sieve to obtain jute leaf fine powder;

[0058] (2) placing jute leaf powder in a flask, adding an ethanol solution with a concentration of 95% at a volume mass ratio of 10 ml / g, decolorizing and defatting the mixture at 50° C. for 6 hours, for a total of 3 times, filtering, and drying the residue in an oven at 40° C. to prepare jute leaf alcohol insoluble matter;

[0059] (3) adding distilled water and 1% thermostable amylase to the jute leaf alcohol insoluble matter at a volume mass ratio of 10 ml / g, extracting at 85° C. for 90 minutes, filtering, and setting aside the residue;

[0060] (4) adding 20 mmol / L ammonium oxalate solution to the filter residue obtained in step (3) at a volume mass ratio of 20 ml / g, extracting at 25° C. for 90 minutes, filtering, and setting the filter residue aside;

[0061] (5) adding 10 mmol / L hydrochloric acid solution to the filter residue obtained in step (4) at a volume mass ratio of 20 ml / g, extracting at 85° C. for 90 minutes, filtering, and setting the filter residue aside;

[0062] (6) Add 30 mmol / L sodium hydroxide solution to the filter residue obtained in step (5) at a volume mass ratio of 20 ml / g, extract in an ice-water bath for 90 minutes, filter, concentrate the filtrate by rotary evaporation at 45°C, pour it into a dialysis membrane (molecular weight cutoff 6-8 kDa), dialyze in distilled water for 48 hours, and use the dialyzed extract for later use.

[0063] (7) The extract after dialyzation in step (6) is treated with an ultrasonic processor at an ultrasonic power of 800 W for 30 minutes, and the treatment temperature is controlled to be 45° C. The extract after freeze-drying is a jute leaf pectin with enhanced effect.

[0064] Control group 1

[0065] On the basis of Example 1, the boiling water blanching treatment in step (1) was omitted, and the other steps were completely consistent with Example 1. The jute leaf pectin prepared was the control group 1.

[0066] Control group 2

[0067] On the basis of Example 1, the step (1) of "crushing in a low-temperature ultrafine pulverizer at 30°C and passing through a 400-mesh sieve" was changed to "crushing in a conventional pulverizer and passing through a 60-mesh sieve", and the other steps were consistent with Example 1. The jute leaf pectin prepared was the control group 2.

[0068] Control group 3

[0069] On the basis of Example 1, the ultrasonic treatment in step (7) was omitted, and the other steps were consistent with Example 1. The jute leaf pectin prepared was the control group 3.

[0070] Control group 4

[0071] On the basis of Example 1, steps (2) and (3) were combined as follows: jute leaf powder was placed in a flask, 20 times distilled water and 1% thermostable amylase were added in a volume-to-weight ratio, extracted at 85° C. for 90 minutes, filtered, and the residue was reserved. The other steps were consistent with Example 1, and the prepared jute leaf pectin was the control group 4.

[0072] Experimental Example 1

[0073] The galacturonic acid content of the jute leaf pectin of the present invention was determined by the sulfuric acid-carbazole method (Wang Wenping, Guo Siyuan, Li Lin, et al. Determination of uronic acid content in wild papaya polysaccharide [J]. Food Science and Technology, 2007, (10): 84-86).

[0074] The results of the galacturonic acid content determination of Examples 1 to 3 and Control Groups 1 to 4 are shown in Table 1.

[0075] Table 1

[0076] Group Galacturonic acid content (%) Example 1 63.45±2.04 Example 2 62.36±1.97 Example 3 62.72±1.61 Control group 1 56.27±1.87 Control group 2 51.26±1.33 Control group 3 60.08±1.44 Control group 4 57.39±1.72

[0077] It can be seen from the above experimental results that the galacturonic acid content of the jute leaf pectin prepared in Examples 1 to 3 is not significantly different. Compared with the control group 1, the galacturonic acid content of the jute leaf pectin prepared in Example 1 after blanching is significantly improved; compared with the control group 2, the galacturonic acid content of the jute leaf pectin prepared in Example 1 after low-temperature ultrafine grinding is significantly improved; compared with the control group 3, the galacturonic acid content of Example 1 after ultrasonic treatment is slightly improved; compared with the control group 4, the galacturonic acid content of Example 1 after ethanol decolorization and defatting is significantly improved.

[0078] Experimental Example 2

[0079] With reference to the document “Bayar, N. Kriaa, M. & Kammoun, R. (2016). Extraction and characterization of three polysaccharides extracted from Opuntia ficus indica cladodes. International Journal of Biological Macromolecules, 92, 441-450.”, the emulsification properties of the jute leaf pectin of the present invention were evaluated by measuring the emulsification ability and emulsification stability.

[0080] The emulsifying ability and emulsifying stability test results of Examples 1 to 3 and Control Groups 1 to 4 are shown in Table 2.

[0081] Table 2

[0082] Group Emulsifying ability (%) Emulsion stability (%) Example 1 76.85±3.11 95.08±4.07 Example 2 74.12±2.68 94.39±3.88 Example 3 75.26±3.39 94.78±3.91 Control group 1 65.74±2.73 78.06±3.17 Control group 2 61.35±2.24 74.23±3.36 Control group 3 67.08±3.04 82.86±3.75 Control group 4 66.42±2.88 84.51±3.04

[0083] It can be seen from the above experimental results that the emulsification ability and emulsification stability of the jute leaf pectin prepared in Examples 1 to 3 are not significantly different. Compared with the control group 1, the emulsification ability and emulsification stability of the jute leaf pectin prepared in Example 1 after blanching are significantly improved; compared with the control group 2, the emulsification ability and emulsification stability of the jute leaf pectin prepared in Example 1 after low-temperature ultrafine grinding are significantly improved; compared with the control group 3, the emulsification ability and emulsification stability of Example 1 after ultrasonic treatment are significantly improved; compared with the control group 4, the emulsification ability and emulsification stability of Example 1 after ethanol decolorization and defatting are significantly improved.

[0084] Experimental Example 3

[0085] Referring to the literature "Zhang Zhishuo, Wei Ran, Han Ying, et al. Optimization of reflux extraction process of polysaccharides and flavonoids from buckwheat and in vitro antioxidant activity of its prepared wine [J]. Journal of Hainan Normal University (Natural Science Edition), 2024, 37(02): 195-202+211", the antioxidant capacity of the jute leaf pectin of the present invention was evaluated by measuring the scavenging ability of DPPH and ABTS free radicals. The antioxidant capacity determination results of Examples 1 to 3 and Control Groups 1 to 4 are shown in Figure 1 and Figure 2 .

[0086] Depend on Figure 1 and Figure 2 It can be seen that the DPPH and ABTS free radical scavenging abilities of the jute leaf pectins prepared in Examples 1, 2, and 3 are relatively close, and at the same concentration, their scavenging abilities are significantly higher than those of the control groups 1, 2, 3, and 4.

[0087] Compared with the control group 1, the antioxidant capacity of the jute leaf pectin prepared by blanching in Example 1 was significantly improved; compared with the control group 2, the antioxidant capacity of the jute leaf pectin prepared by low-temperature ultrafine grinding in Example 1 was significantly improved; compared with the control group 3, the antioxidant capacity of Example 1 after ultrasonic treatment was significantly improved; compared with the control group 4, the antioxidant capacity of Example 1 after ethanol decolorization and defatting was significantly improved.

[0088] Example 4

[0089] Referring to the literature "Dong Qichao, Liang Hui, Hu Cong, et al. Effect of spleen polypeptide on TNF-α, IL-1β, IL-6 and IL-17 induced by Helicobacter pylori lipopolysaccharide in RAW264.7 macrophages [J]. Hainan Medicine, 2018, 29(01): 1-3.", the anti-inflammatory activity of the jute leaf pectin of the present invention was evaluated by measuring the secretion of inflammatory factors IL-6 and IL-1β of macrophages induced by lipopolysaccharide (LPS). The results are as follows: Figure 3 and Figure 4shown.

[0090] Depend on Figure 3 and Figure 4 It can be seen that the jute leaf pectin prepared in Examples 1, 2, and 3 can inhibit the secretion of LPS-induced inflammatory factors IL-6 and IL-1β, and the inhibitory effects of the three are relatively close, and are significantly higher than those of the control groups 1, 2, 3, and 4 at the same concentration.

[0091] Compared with the control group 1, the anti-inflammatory ability of the jute leaf pectin prepared by blanching in Example 1 was significantly improved; compared with the control group 2, the anti-inflammatory ability of the jute leaf pectin prepared by low-temperature ultrafine grinding in Example 1 was significantly improved; compared with the control group 3, the anti-inflammatory ability of Example 1 after ultrasonic treatment was significantly improved; compared with the control group 4, the anti-inflammatory ability of Example 1 after ethanol decolorization and defatting was significantly improved.

[0092] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing jute leaf pectin, characterized in that: The steps include: S1. The jute leaves are sterilized with boiling water to inactivate enzymes, dried and crushed, and sieved through a 300-500 mesh sieve to obtain jute leaf fine powder; S2, adding ethanol to the jute leaf powder, decolorizing and defatting, filtering, and drying the filter residue to obtain jute leaf alcohol insoluble matter; S3, adding water and thermostable amylase to the jute leaf alcohol insoluble matter, extracting at 70-85° C. for 90-180 minutes, filtering, and setting aside the filter residue; S4, adding ammonium oxalate solution to the filter residue obtained in step S3, extracting at 20-25° C. for 90-180 minutes, filtering, and setting the filter residue aside; S5, adding hydrochloric acid solution to the filter residue obtained in step S4, extracting at 70-85° C. for 90-180 minutes, filtering, and setting the filter residue aside; S6, adding sodium hydroxide solution to the filter residue obtained in step S5, extracting in an ice-water bath for 90 to 180 minutes, filtering, concentrating the filtrate by rotary evaporation and then dialyzing to obtain an extract; S7. The extract is treated with ultrasound and freeze-dried to obtain jute leaf pectin.

2. The preparation method according to claim 1, characterized in that: In step S1, the time for killing the enzymes is 70 to 100 seconds; the growth period of the jute leaves is 120±5 days; preferably, the pulverization is performed in a low-temperature ultrafine pulverizer.

3. The preparation method according to claim 1, characterized in that: In step S2, the amount of ethanol added is 5-10 ml / g of jute leaf powder; preferably, the decolorization and defatting specifically includes: treating at 50° C. for 2-6 hours, and repeating 3-6 times.

4. The preparation method according to claim 1, characterized in that: In step S3, the amount of water added is 10-20 ml / g of the mass of the jute leaf alcohol insoluble matter, and the amount of the thermostable amylase used is 0.2% to 1% of the mass of the jute leaf alcohol insoluble matter.

5. The preparation method according to claim 1, characterized in that: In step S4, the concentration of the ammonium oxalate solution is 20-50 mmol / L, and the amount added is 10-20 ml / g of the filter residue.

6. The preparation method according to claim 1, characterized in that: In step S5, the concentration of the hydrochloric acid solution is 10-30 mmol / L, and the amount added is 10-20 ml / g of the filter residue.

7. The preparation method according to claim 1, characterized in that: In step S6, the concentration of the sodium hydroxide solution is 30-60 mmol / L, and the amount added is 10-20 ml / g of the filter residue.

8. The preparation method according to claim 1, characterized in that: In step S6, the dialysis is specifically: the filtrate is dialyzed in water through a dialysis membrane for 40-60 hours; preferably, the molecular weight of the dialysis membrane is 6-8 kDa; preferably, in step S7, the power of the ultrasound is 400-800 W, the time is 30-60 minutes, and the temperature is 35-45°C.

9. Jute leaf pectin prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the jute leaf pectin according to claim 9 in food or functional food.

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