Corchorus leaves pectin, a method for preparing the same and use thereof

Abstract

The application discloses a corchorus leaves pectin and a preparation method and application thereof. The corchorus leaves are subjected to enzyme-killing and enzyme-inactivating treatment by boiling water blanching, and then are subjected to low-temperature microwave drying and low-temperature ultrafine grinding to obtain corchorus leaves fine powder. The corchorus leaves fine powder is subjected to decolorization and degreasing by using ethanol, and alcohol-soluble small molecules are removed, so that corchorus leaves alcohol-insoluble substances are prepared. The corchorus leaves alcohol-insoluble substances are extracted by using water as a solvent, and high-temperature resistant amylase is used to remove starch synchronously. The filter residue obtained after filtration is subjected to step-by-step extraction by using ammonium oxalate, dilute hydrochloric acid and dilute alkali solution as solvents, and the extract is subjected to dialysis, ultrasonic treatment and freeze-drying, so that the corchorus leaves pectin with the enhanced effect is finally prepared. The corchorus leaves pectin prepared by the application has increased galacturonic acid content, and the emulsifying capacity, antioxidant capacity and anti-inflammatory activity are enhanced, and the corchorus leaves pectin can be applied to food and functional food.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food and functional food, in particular to a Corchorus leaves pectin, a preparation method thereof and an application thereof. BACKGROUND

[0002] Corchorus is a traditional fiber crop in China, and its stem is an important raw material for producing high-quality fiber. The main cultivated species of Corchorus in China are long fruit Corchorus and round fruit Corchorus. The bast of the stem of Corchorus contains a large amount of pectin components, which need to be removed during the processing of Corchorus fiber to improve the quality of Corchorus fiber. In addition to the stem, the Corchorus leaves also contain pectin components. If the pectin in the Corchorus leaves can be extracted and developed for food and functional food, it will produce significant economic value and health benefits.

[0003] Domestic researchers have carried out the extraction of Corchorus leaf pectin polysaccharides. CN105498708A discloses a preparation method of Corchorus polysaccharide adsorbent, and the Corchorus leaf pectin polysaccharides extracted by supercritical technology can be used for removing hexavalent chromium in water. CN105478085B and CN105536712B disclose an adsorption material mainly composed of Corchorus polysaccharides and a preparation method thereof, and the Corchorus polysaccharides are obtained by extracting the Corchorus leaves and young shoots treated by gas explosion with an acid solution. After the Corchorus polysaccharides are combined with iron, they have good adsorption effect and can be used for removing heavy metals. CN105498708B, CN105536713A and CN105478085A disclose supercritical extraction of Corchorus polysaccharides and its application, and the Corchorus polysaccharides extracted by supercritical enzymatic extraction can be used for solid adsorbents. CN105536713B discloses an adsorption material mainly composed of Corchorus polysaccharides and a preparation method thereof, and the Corchorus polysaccharides are obtained by treating the Corchorus leaves with cellulase, hemicellulase, pectinase and carboxypeptidase B, and the Corchorus polysaccharides extracted by a high-pressure reaction kettle can be used as adsorption materials. However, the Corchorus polysaccharides extracted by these methods are mainly used as adsorption materials for heavy metals, and they are not for food processing, and the structural characteristics and biological activities of the Corchorus leaf pectin polysaccharides themselves are not concerned.

[0004] In the prior art, the jute leaf is usually extracted by water or alcohol to obtain jute leaf extract with antioxidant effect, and there is no report on jute leaf pectin. For example, Feng Xiangyuan et al. (Natural Product Research and Development, 2020, 32: 1278-1284) found that hot water extracted jute leaf polysaccharide has antioxidant activity, but the galacturonic acid content is very low (less than 4%), and the emulsifying ability and anti-inflammatory activity are unknown, and the effect of pretreatment such as blanching and drying on the structure and activity of the extracted polysaccharide is not studied. The pectin in plants has great differences in solubility in different solvents according to the different chemical structures. The pectin in jute leaf also has different solubility characteristics. By stepwise extraction with different solvents, pectin components with different characteristics are expected to be obtained. The galacturonic acid content has a great influence on the physicochemical properties and biological activity of pectin, such as emulsifying ability, antioxidant ability, etc.

[0005] Therefore, it is necessary to provide a preparation method of jute leaf pectin. SUMMARY

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

[0007] The present application provides a preparation method of jute leaf pectin with enhanced effect, comprising the following steps:

[0008] S1, the jute leaf is blanched and enzyme-killed with boiling water, dried, crushed, and sieved through a 300-500 mesh sieve to obtain jute leaf fine powder;

[0009] S2, adding ethanol to the jute leaf fine powder, filtering after decolorization and degreasing, and drying the filter residue to obtain jute leaf alcohol insoluble matter;

[0010] S3, adding water and high-temperature resistant amylase to the jute leaf alcohol insoluble matter, extracting at 70-85℃ for 90-180 minutes, filtering, and reserving the filter residue;

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

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

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

[0014] S7, the extract is treated by ultrasonic, and freeze-dried to obtain jute leaf pectin.

[0015] Preferably, in step S1, the time for the fixation and enzyme inactivation is 70-100 s; the growth period of the jute leaf is 120±5 days; preferably, the pulverization is in a low-temperature ultrafine pulverizer.

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

[0017] Preferably, in step S2, the amount of the ethanol added is 5-10 ml / g of the jute leaf fine powder; preferably, the ethanol is a 95wt% ethanol solution. It should be noted that the unit'ml / g' in the present application refers to the volume-mass ratio of the extraction reagent to the solid to-be-extracted substance, for example, the volume of the ethanol added is 5-10 times the mass of the jute leaf fine powder, and the same applies hereinafter.

[0018] Preferably, the decolorization and degreasing specifically comprises: treatment at 50℃ for 2-6 h, repeated for 3-6 times.

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

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

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

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

[0024] Preferably, in step S7, the power of the ultrasonic wave is 400-800 W, the time is 30-60 min, and the temperature is 35-45℃.

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

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

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

[0028] 1. The present application first adopts short-time blanching with boiling water to treat jute leaves, so as to inactivate pectinase in jute leaves, and prevent the structural properties of pectin in jute leaves from changing and the content of pectin from decreasing due to enzymatic degradation in the drying process.

[0029] 2. The present application uses the method of microwave low-temperature drying to dry jute leaves, and uses a low-temperature ultrafine grinder to perform a grinding treatment, so as to maximize the retention of the structure and properties of pectin without changing. At the same time, the jute fine powder prepared by ultrafine grinding has small particles, which is more conducive to the full dissolution of pectin.

[0030] 3. The present application first uses an ethanol solution to remove grease and color, and then uses a high-temperature resistant amylase to perform a synchronous treatment in the water extraction step, which can effectively remove starch in jute leaves, improve the yield and purity of subsequent pectin extraction, and save extraction time and improve extraction efficiency.

[0031] 4. The present application uses water, ammonium oxalate, hydrochloric acid and sodium hydroxide to perform step-by-step extraction, and finally uses ultrasonic technology to treat the alkali extract, so as to prepare alkali-soluble jute leaf pectin with increased galacturonic acid content and enhanced emulsifying ability, antioxidant capacity and anti-inflammatory activity. The pectin can be applied to food and functional food, which is helpful to realize the high-value utilization of jute leaves. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The removal rate of DPPH free radicals of jute leaf pectin prepared in examples 1-3 and control groups 1-4 of the present application.

[0033] Figure 2 The removal rate of ABTS free radicals of jute leaf pectin prepared in examples 1-3 and control groups 1-4 of the present application.

[0034] Figure 3 The inhibition rate of inflammatory factor IL-6 of jute leaf pectin prepared in examples 1-3 and control groups 1-4 of the present application.

[0035] Figure 4 The inhibition rate of inflammatory factor IL-1β of jute leaf pectin prepared in examples 1-3 and control groups 1-4 of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with specific examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0037] Example 1

[0038] A preparation method of jute leaf pectin with enhanced effect, comprising the following steps:

[0039] (1) Collecting jute leaves grown for about 120 days, performing fixation and enzyme inactivation treatment by using boiling water blanching for 80 seconds, performing low-temperature microwave drying at 45 DEG C for 30 hours, and then performing pulverization in a low-temperature ultrafine pulverizer at 30 DEG C, and then passing through a 400-mesh screen to obtain jute leaf fine powder;

[0040] (2) Placing the jute leaf fine powder in a flask, adding 95% ethanol solution according to a volume-mass ratio of 8ml / g, performing decolorization and degreasing treatment at 50 DEG C for 4 hours, performing a total of 5 times, filtering, and then drying the filter residue in an oven at 40 DEG C to obtain jute leaf alcohol-insoluble matter;

[0041] (3) Adding distilled water and 0.6% high-temperature resistant amylase to the jute leaf alcohol-insoluble matter according to a volume-mass ratio of 15ml / g, and then performing extraction at 75 DEG C for 140 minutes, filtering, and then reserving the filter residue;

[0042] (4) Adding 35mmol / L ammonium oxalate solution to the filter residue obtained in step (3) according to a volume-mass ratio of 16ml / g, and then performing extraction at 22 DEG C for 150 minutes, filtering, and then reserving the filter residue;

[0043] (5) Adding 20mmol / L hydrochloric acid solution to the filter residue obtained in step (4) according to a volume-mass ratio of 14ml / g, and then performing extraction at 75 DEG C for 150 minutes, filtering, and then reserving the filter residue;

[0044] (6) Adding 50mmol / L sodium hydroxide solution to the filter residue obtained in step (5) according to a volume-mass ratio of 16ml / g, and then performing extraction in an ice water bath for 140 minutes, filtering, and then concentrating the filtrate by rotary evaporation at 45 DEG C, and then pouring the concentrated filtrate into a dialysis membrane (molecular weight cut-off 6-8kDa) to dialyze in distilled water for 48 hours, and then reserving the extraction liquid after dialysis.

[0045] (7) Treating the extraction liquid after dialysis in step (6) by using an ultrasonic processor at an ultrasonic power of 600W for 45 minutes, and then controlling the treatment temperature to be 40 DEG C. After freeze-drying treatment, the extraction liquid is obtained, which is jute leaf pectin with enhanced effect.

[0046] Example 2

[0047] A preparation method of jute leaf pectin with enhanced effect, comprising the following steps:

[0048] (1) Collecting jute leaves grown for about 120 days, performing fixation and enzyme inactivation treatment by using boiling water blanching for 70 seconds, performing low-temperature microwave drying at 42 DEG C for 40 hours, and then performing pulverization in a low-temperature ultrafine pulverizer at 25 DEG C, and then passing through a 300-mesh screen to obtain jute leaf fine powder;

[0049] (2) The fine jute leaf powder is placed in a flask, 95% ethanol solution is added according to a volume-mass ratio of 5 ml / g, and the decoloring and degreasing treatment is performed at 50°C for 2 hours, a total of 6 times, and the filter residue is dried in an oven at 40°C to obtain jute leaf alcohol insoluble;

[0050] (3) Distilled water and 0.2% high-temperature resistant amylase are added to the jute leaf alcohol insoluble according to a volume-mass ratio of 10 ml / g, and the extraction is performed at 70°C for 180 minutes, and the filter residue is reserved;

[0051] (4) 50 mmol / L ammonium oxalate solution is added to the filter residue obtained in step (3) according to a volume-mass ratio of 10 ml / g, and the extraction is performed at 20°C for 180 minutes, and the filter residue is reserved;

[0052] (5) 30 mmol / L hydrochloric acid solution is added to the filter residue obtained in step (4) according to a volume-mass ratio of 10 ml / g, and the extraction is performed at 70°C for 180 minutes, and the filter residue is reserved;

[0053] (6) 60 mmol / L sodium hydroxide solution is added to the filter residue obtained in step (5) according to a volume-mass ratio of 10 ml / g, and the extraction is performed in an ice water bath for 180 minutes, and the filtrate is concentrated by rotary evaporation at 45°C, and then poured into a dialysis membrane (molecular weight cut-off 6-8 kDa) and dialyzed in distilled water for 48 hours, and the dialyzed extract is reserved.

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

[0055] Example 3

[0056] A preparation method of a jute leaf pectin with an enhancing effect, comprising the following steps:

[0057] (1) The jute leaves grown for about 120 days are blanched by boiling water for 100 seconds, and then dried by microwave at 48°C for 25 hours, and then crushed in a low-temperature ultrafine grinder at 35°C, and then passed through a 500-mesh sieve to obtain fine jute leaf powder;

[0058] (2) The fine jute leaf powder is placed in a flask, 95% ethanol solution is added according to a volume-mass ratio of 10 ml / g, and the decoloring and degreasing treatment is performed at 50°C for 6 hours, a total of 3 times, and the filter residue is dried in an oven at 40°C to obtain jute leaf alcohol insoluble;

[0059] (3) To the jute leaf alcohol insoluble matter, add distilled water and 1% thermostable amylase at a volume-mass ratio of 10 ml / g, and extract at 85°C for 90 minutes, filter, and reserve the filter residue;

[0060] (4) Add 20 mmol / L ammonium oxalate solution to the filter residue obtained in step (3) at a volume-mass ratio of 20 ml / g, and extract at 25°C for 90 minutes, filter, and reserve the filter residue;

[0061] (5) Add 10 mmol / L hydrochloric acid solution to the filter residue obtained in step (4) at a volume-mass ratio of 20 ml / g, and extract at 85°C for 90 minutes, filter, and reserve the filter residue;

[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, and extract in an ice water bath for 90 minutes, filter, and after the filtrate is concentrated by rotary evaporation at 45°C, pour it into a dialysis membrane (molecular weight cut-off 6-8 kDa), dialyze in distilled water for 48 hours, and reserve the extract after dialysis.

[0063] (7) Use an ultrasonic processor to treat the extract after dialysis in step (6) at an ultrasonic power of 800 W for 30 minutes, and control the treatment temperature at 45°C. After freeze-drying treatment of the extract, a jute leaf pectin with enhanced effect is obtained.

[0064] Control group 1

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

[0066] Control group 2

[0067] On the basis of Example 1, change "crush in a low-temperature super micro-crusher at 30°C, and pass through a 400-mesh sieve" in step (1) to "crush by using a conventional crusher, and pass through a 60-mesh sieve", and the other steps are consistent with Example 1. The jute leaf pectin prepared is control group 2.

[0068] Control group 3

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

[0070] Control group 4

[0071] On the basis of example 1, steps (2) and (3) are combined as follows: the fine powder of jute leaf is placed in a flask, 20 times distilled water and 1% high-temperature-resistant amylase are added according to the volume weight ratio, and extraction is carried out at 85°C for 90 minutes, filtration, and the filter residue is reserved for use. Other steps are consistent with example 1, and the prepared jute leaf pectin is control group 4.

[0072] Experimental example 1

[0073] The galacturonic acid content of the jute leaf pectin of the application is determined by the sulfuric acid-carbazole method (Wang Wenping, Guo Shiyuan, Li Lin, et al. Determination of uronic acid content in the polysaccharide of wild papaya [J]. Food science and technology, 2007, (10): 84-86).

[0074] The determination results of the galacturonic acid content 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 1 56.27±1.87 Control 2 51.26±1.33 Control 3 60.08±1.44 Control 4 57.39±1.72

[0077] From the above experimental results, it can be seen that the galacturonic acid content of the jute leaf pectin prepared in examples 1 to 3 has no significant difference. Compared with control group 1, the galacturonic acid content of the jute leaf pectin prepared after blanching treatment in example 1 is significantly improved; compared with control group 2, the galacturonic acid content of the jute leaf pectin prepared after low-temperature ultrafine grinding in example 1 is significantly improved; compared with control group 3, the galacturonic acid of example 1 after ultrasonic treatment has a small increase; compared with control group 4, the galacturonic acid content of example 1 after ethanol decolorization and degreasing is significantly improved.

[0078] Experimental example 2

[0079] Referring to the literature "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 emulsifying properties of the jute leaf pectin of the application are evaluated by determining the emulsifying capacity and emulsion stability.

[0080] The determination results of the emulsifying capacity and emulsion stability of examples 1 to 3 and control groups 1 to 4 are shown in table 2.

[0081] Table 2

[0082] Group Emulsification 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 1 65.74±2.73 78.06±3.17 Control 2 61.35±2.24 74.23±3.36 Control 3 67.08±3.04 82.86±3.75 Control 4 66.42±2.88 84.51±3.04

[0083] From the above experimental results, it can be seen that the differences in emulsification ability and emulsion stability of jute leaf pectin prepared in Examples 1 to 3 are not significant. Compared with Control Group 1, the emulsification ability and emulsion stability of jute leaf pectin prepared after blanching treatment in Example 1 are significantly improved; compared with Control Group 2, the emulsification ability and emulsion stability of jute leaf pectin prepared after low-temperature ultrafine grinding in Example 1 are significantly improved; compared with Control Group 3, the emulsification ability and emulsion stability after ultrasonic treatment in Example 1 are significantly improved; compared with Control Group 4, the emulsification ability and emulsion stability after ethanol decolorization and degreasing in Example 1 are significantly improved.

[0084] Experimental Example 3

[0085] Referring to the literature “Zhang Z, Wei R, Han Y, et al. Optimization of reflux extraction of polysaccharides and flavonoids from tartary buckwheat and in vitro antioxidant activity of the prepared wine [J]. Journal of Hainan Normal University (Natural Science Edition), 2024, 37(02): 195-202+211”, the antioxidant ability of jute leaf pectin of the present application is evaluated by determining the scavenging ability of DPPH and ABTS free radicals. The antioxidant ability determination results of Examples 1 to 3, Control Groups 1 to 4 are shown in Figure 1 and Figure 2 .

[0086] From Figure 1 and Figure 2 , it can be seen that the DPPH and ABTS free radical scavenging ability of jute leaf pectin prepared in Examples 1, 2, and 3 is relatively close, and at the same concentration, the scavenging ability is significantly higher than that of Control Groups 1, 2, 3, and 4.

[0087] Compared with Control Group 1, the antioxidant ability of jute leaf pectin prepared after blanching treatment in Example 1 is significantly improved; compared with Control Group 2, the antioxidant ability of jute leaf pectin prepared after low-temperature ultrafine grinding in Example 1 is significantly improved; compared with Control Group 3, the antioxidant ability after ultrasonic treatment in Example 1 is significantly improved; compared with Control Group 4, the antioxidant ability after ethanol decolorization and degreasing in Example 1 is significantly improved.

[0088] Example 4

[0089] Referring to the literature “Dong Q, Liang H, Hu C, et al. Effects of spleen polypeptide on TNF-α, IL-1β, IL-6 and IL-17 of LPS-induced RAW264.7 macrophages [J]. Hainan Medicine, 2018, 29(01): 1-3.”, the anti-inflammatory activity of jute leaf pectin of the present application is evaluated by determining the secretion of inflammatory factors IL-6 and IL-1β of macrophages induced by lipopolysaccharide (LPS), and the results are shown in Figure 3 and Figure 4shown.

[0090] By 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 inflammatory factors IL-6 and IL-1β induced by LPS, and the inhibition effect of the three is close, which is significantly higher than that of control groups 1, 2, 3 and 4 under the same concentration.

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

[0092] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can replace or change the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A process for the preparation of jute leaf pectin, characterized in that, The method comprises the following steps: S1, the jute leaf is killed and enzyme-inactivated by using boiling water, dried, crushed, and passed through a 300-500 mesh sieve to obtain jute leaf fine powder; the crushing is performed in a low-temperature super-micro pulverizer; S2, ethanol is added to the jute leaf fine powder, and after decolorization and degreasing, filtration is performed, and the filter residue is dried to obtain jute leaf alcohol-insoluble matter; S3, water and high-temperature-resistant amylase are added to the jute leaf alcohol-insoluble matter, and extraction is performed at 70-85℃ for 90-180 minutes, filtration is performed, and the filter residue is reserved; S4, ammonium oxalate solution is added to the filter residue obtained in step S3, and extraction is performed at 20-25℃ for 90-180 minutes, filtration is performed, and the filter residue is reserved; S5, hydrochloric acid solution is added to the filter residue obtained in step S4, and extraction is performed at 70-85℃ for 90-180 minutes, filtration is performed, and the filter residue is reserved; S6, sodium hydroxide solution is added to the filter residue obtained in step S5, and extraction is performed in an ice water bath for 90-180 minutes, filtration is performed, and the filtrate is concentrated by rotary evaporation and then dialyzed to obtain an extract; S7, the extract is treated by ultrasonic treatment and freeze-dried to obtain jute leaf pectin.

2. The production method according to claim 1, characterized by, In step S1, the time for killing and enzyme-inactivation is 70-100 s; and the growth period of the jute leaf is 120±5 days.

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 the jute leaf fine powder.

4. The production method according to claim 1, characterized by, In step S2, the decolorization and degreasing specifically comprises: treatment at 50℃ for 2-6 h, repeated 3-6 times.

5. 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 high-temperature-resistant amylase used is 0.2%-1% of the mass of the jute leaf alcohol-insoluble matter.

6. The method of claim 1, wherein, 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.

7. 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.

8. The method of claim 1, wherein, 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.

9. The production method according to claim 1, characterized by, In step S6, the dialysis specifically comprises: dialysis of the filtrate in water through a dialysis membrane for 40-60 h.

10. The method of claim 9, wherein, The molecular weight of the dialysis membrane is 6-8 kDa.

11. The method of claim 1, wherein, In step S7, the power of the ultrasonic treatment is 400-800 W, the time is 30-60 minutes, and the temperature is 35-45℃.

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