Method for improving extraction rate of pectin and polyphenol in citrus peel

Abstract

The invention relates to a method for improving the extraction rate of pectin and polyphenol in citrus peel. The method comprises the following steps: S1, carrying out infiltration treatment on citrus peel and water, carrying out steam explosion treatment on the infiltrated citrus peel for 1-5 minutes under 0.1-1.0 MPa, and sequentially carrying out first drying treatment, first crushing treatment and first sieving treatment on the obtained steam explosion material to obtain citrus peel powder; s2, mixing the citrus peel powder with water, and performing first extraction treatment to obtain a first solid phase and a first liquid phase; s3, mixing the first liquid phase with absolute ethyl alcohol, carrying out first precipitation treatment, and carrying out second drying treatment on an obtained precipitate material, so as to obtain citrus peel pectin; s4, mixing the first solid phase with an alkali solution, and performing second extraction treatment to obtain a second solid phase and a second liquid phase; and adjusting the pH value of the second liquid phase to 1-6, and carrying out second precipitation treatment to obtain a polyphenol crude extract. The method has the advantages of being green, efficient, low in cost and simple in process, and the extraction rate of pectin and polyphenol is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of pectin extraction and polyphenol extraction, and in particular, to a method for improving the extraction rate of pectin and polyphenol in citrus peel. Background Art

[0002] Citrus is one of the most widely grown fruits in the world, and its byproduct, citrus peel, has a huge output. At present, the treatment methods of citrus peel mainly focus on extracting functional components, directly using it as feed, soil conditioner and biotransformation. However, these treatment methods have some problems, such as the high cost of extracting functional components, which limits its large-scale production in industry; directly using it as feed leads to poor digestion and absorption by animals; and the application effect as a soil conditioner is not obvious.

[0003] Citrus peel residue is rich in functional ingredients such as pectin and polyphenols. Pectin is a natural macromolecular acidic polysaccharide with functional properties such as thickening, stabilization, gelling, and emulsification. It has the effects of lowering blood lipids, lowering cholesterol, anti-irradiation, adsorbing heavy metal ions, and moisturizing the intestines. At the same time, pectin can also regulate intestinal flora, relieve colitis symptoms, and prevent inflammation-induced colon epithelial cell apoptosis. However, pectin is entangled with other components in the plant cell wall such as cellulose, and it is difficult to fully release during the extraction process, which limits the application of pectin in the food and beverage industry. Polyphenol compounds have multiple biological activities such as anti-tumor, anti-cancer, anti-mutagenic, anti-inflammatory, antibacterial, anti-oxidant, anti-viral, and anti-allergic, and can be used in the development of functional foods and drugs. Citrus peel residue after pectin extraction can be used to extract polyphenols.

[0004] The existing pectin extraction technologies include acid extraction, ultrasonic-assisted extraction, microwave-assisted extraction, subcritical water extraction, etc. The traditional acid extraction method uses a large amount of inorganic acid, which is easy to produce acid wastewater, causing secondary environmental pollution; long-term microwave exposure may cause pectin molecular degradation; under subcritical water extraction conditions, the molecular weight, galacturonic acid content, esterification degree and neutral monosaccharide composition of pectin are all affected by the subcritical water temperature. Moreover, these technologies are often aimed at the extraction of a single component, and it is difficult to achieve the simultaneous extraction of multiple components, which limits the comprehensive utilization efficiency of citrus peel residue.

[0005] Steam explosion technology is a kind of ejection steam explosion technology that can achieve steam explosion in milliseconds. However, after steam explosion, the raw materials usually need to be treated with acid, alkali, enzyme, etc., and currently, pectin and polyphenols in citrus peels have not been extracted simultaneously through this technology. Therefore, the development of a green, efficient, low-cost method that can increase the extraction rate of pectin and polyphenols in citrus peels is an urgent problem to be solved in the industry. Summary of the invention

[0006] In order to further improve the extraction rate of pectin and polyphenols in citrus peel, the present disclosure provides a method for improving the extraction rate of pectin and polyphenols in citrus peel.

[0007] In order to achieve the above object, the present disclosure provides a method for improving the extraction rate of pectin and polyphenols in citrus peel in a first aspect, the method comprising the following steps: S1, soaking citrus peel with water, subjecting the soaked citrus peel to steam explosion at 0.1-1.0 MPa for 1-5 min, and sequentially subjecting the obtained steam explosion material to a first drying treatment, a first crushing treatment and a first sieving treatment to obtain citrus peel powder; S2, mixing the citrus peel powder with water and performing a first extraction process to obtain a first solid phase and a first liquid phase; S3, mixing the first liquid phase with anhydrous ethanol to perform a first precipitation treatment, and performing a second drying treatment on the obtained precipitation material to obtain citrus peel pectin; S4, mixing the first solid phase with an alkaline solution and performing a second leaching treatment to obtain a second solid phase and a second liquid phase; adjusting the pH value of the second liquid phase to 1-6 and performing a second precipitation treatment to obtain a crude polyphenol extract; Wherein, in step S2, the first extraction treatment is ultrasonic extraction treatment or microwave extraction treatment.

[0008] Optionally, in step S1, the weight ratio of the citrus peel to water is 1:(0.2-0.5); the time of the infiltration treatment is 2-4 hours; the conditions of the steam explosion treatment include: pressure of 0.1-0.5 MPa, time of 1-3 min; the conditions of the first drying treatment include: temperature of 40-60°C, time of 2-12 hours; the conditions of the first screening treatment include: the mesh size of the sieve is 20-80 meshes.

[0009] Optionally, in step S1, before the infiltration treatment, the method further includes: washing and cutting the citrus peel; Wherein, the citrus peel is selected from one or more of grapefruit peel, orange peel, tangerine peel, mandarin peel and tangerine peel.

[0010] Optionally, in step S2, the weight ratio of the citrus peel powder to water is 1:(5-30).

[0011] Optionally, the conditions of the ultrasonic extraction treatment include: temperature of 20-50°C, power of 50-150W, and time of 10-60min; The microwave extraction treatment conditions include: power of 200-700W and time of 1-10min.

[0012] Optionally, in step S3, the volume ratio of the first liquid phase to anhydrous ethanol is 1:(1-3).

[0013] Optionally, in step S3, the time of the first precipitation treatment is 8-12 hours; the conditions of the second drying treatment include: temperature of 40-60° C., time of 8-24 hours.

[0014] Optionally, in step S4, the mass ratio of the first solid phase to the alkaline solution is 1:(5-30); The pH value of the alkaline solution is 8-14, wherein the alkaline solution is selected from one or more of sodium hydroxide solution, calcium hydroxide solution, potassium hydroxide solution, ammonia water and barium hydroxide solution.

[0015] Optionally, the conditions of the second leaching treatment include: temperature of 20-40°C and time of 3-9h.

[0016] A second aspect of the present disclosure provides citrus peel pectin prepared by the method described in the first aspect.

[0017] Through the above technical scheme, the present disclosure provides a method for improving the extraction rate of pectin and polyphenols in citrus peel. By combining steam explosion treatment with water extraction treatment, and combining ultrasound or microwave as an auxiliary, the method of the present disclosure can extract pectin at a natural pH value, and perform secondary extraction on the pomace to obtain citrus peel polyphenols; the extraction rate of pectin and polyphenols is improved. In addition, the method of the present disclosure has the advantages of being green, efficient, low-cost, and simple in process, and has good application prospects in industry.

[0018] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings: Figure 1 It is a chromatogram of the monosaccharide composition of the pectin of Example 1 of the present disclosure. DETAILED DESCRIPTION

[0020] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0021] In the present disclosure, the first drying process and the second drying process may use an instrument conventionally used by those skilled in the art, for example, a drying machine.

[0022] The first aspect of the present disclosure provides a method for improving the extraction rate of pectin and polyphenols in citrus peel, the method comprising the following steps: S1, soaking citrus peel with water, subjecting the soaked citrus peel to steam explosion at 0.1-1.0 MPa for 1-5 min, and sequentially subjecting the obtained steam explosion material to a first drying treatment, a first crushing treatment and a first sieving treatment to obtain citrus peel powder; S2, mixing the citrus peel powder with water and performing a first extraction process to obtain a first solid phase and a first liquid phase; S3, mixing the first liquid phase with anhydrous ethanol to perform a first precipitation treatment, and performing a second drying treatment on the obtained precipitation material to obtain citrus peel pectin; S4, mixing the first solid phase with an alkaline solution and performing a second leaching treatment to obtain a second solid phase and a second liquid phase; adjusting the pH value of the second liquid phase to 1-6 and performing a second precipitation treatment to obtain a crude polyphenol extract; Wherein, in step S2, the first extraction treatment is ultrasonic extraction treatment or microwave extraction treatment.

[0023] In the present disclosure, by combining steam explosion treatment with water extraction treatment, and combining ultrasound or microwave as an auxiliary, the method disclosed in the present disclosure can extract pectin at a natural pH value, and perform secondary extraction on the pomace to obtain citrus peel polyphenols. The method disclosed in the present disclosure effectively avoids the introduction of substances such as acids, alkalis or enzymes in the pre-treatment or extraction treatment of citrus peel, avoids the process of using substances such as acids, alkalis or enzymes to form difficult-to-treat industrial wastewater, and avoids the use of inorganic acids, high temperature conditions and other environmentally unfriendly problems; the method disclosed in the present disclosure has the advantages of being green, efficient, low-cost, and simple in process, and realizes the simultaneous extraction of pectin and polyphenols, which not only improves the extraction rate of pectin, but also can improve the extraction rate of polyphenols. The method disclosed in the present disclosure maximizes benefits and minimizes environmental damage, and has good application prospects in industry.

[0024] At the same time, the method disclosed in the present invention can enrich the rhamnogalacturonan I (RG-I) region of pectin in citrus peel and extract pectin containing a higher RG-I content.

[0025] In the present disclosure, the steam explosion treatment is to place the soaked citrus peel into a preheated steam explosion device, set the pressure to 0.1-1.0 MPa, the time to 1-5 minutes, then pass steam until the time is up, and finally release the pressure instantly to achieve the explosion effect.

[0026] In one embodiment of the present disclosure, the steam explosion treatment conditions include: a pressure of 0.1-1.0 MPa, preferably 0.1-0.5 MPa; a time of 1-5 min, preferably 1-3 min. When the citrus peel is within the pressure range of the above embodiment, the tissue structure of the citrus peel is destroyed and the cell wall is broken.

[0027] In the present disclosure, the citrus peel is cleaned and cut into pieces before the infiltration treatment, and the size of the pieces is not particularly limited in the present disclosure. The citrus peel includes one or more of grapefruit peel, orange peel, tangerine peel, mandarin peel and tangerine peel.

[0028] In one embodiment of the present disclosure, the weight ratio of the citrus peel to water is 1:(0.2-0.5); the time of the infiltration treatment is 2-4 hours; the infiltration treatment is generally performed at room temperature to promote the penetration of water vapor during the explosion process and improve the effect of steam explosion.

[0029] According to the present disclosure, the steam-exploded material obtained by the steam explosion treatment needs to be dried to remove moisture from the steam-exploded material. In one embodiment of the present disclosure, the conditions of the first drying treatment include: a temperature of 40-60°C and a time of 2-12 hours. After the drying treatment, a first crushing treatment and a first screening treatment are performed to obtain a citrus peel powder with uniform particle size, wherein the first crushing treatment can use a crusher conventionally used by those skilled in the art; the conditions of the first screening treatment include: the mesh number of the sieve is 20-80 meshes.

[0030] According to the present disclosure, in the first leaching process, the weight ratio of citrus peel powder to water can vary in a wide range. In one embodiment of the present disclosure, in step S2, the weight ratio of citrus peel powder to water is 1: (5-30).

[0031] When the water extraction method is used to extract pectin, the present invention can also combine ultrasound or microwave as an auxiliary to fully release the pectin in the citrus peel powder.

[0032] In one embodiment, the conditions of the ultrasonic extraction treatment include: temperature of 20-50° C., power of 50-150 W, and time of 10-60 min. In the above embodiment, citrus peel pectin can be obtained gently and efficiently.

[0033] In another embodiment, the microwave extraction treatment conditions include: power of 200-700 W, time of 1-10 min. In the above embodiment, when the microwave extraction treatment power is in the range of 200-700 W, the microwave extraction treatment sample is controlled to be maintained at about 100° C., which can quickly increase the pectin extraction rate in a short time.

[0034] In the present disclosure, after the first leaching treatment, a first separation treatment is performed to obtain a first solid phase and a first liquid phase, wherein the first separation treatment can adopt a method conventionally adopted by those skilled in the art, such as filtration treatment and centrifugation treatment.

[0035] In the present disclosure, ethanol precipitation treatment is used to obtain precipitation material, wherein the volume ratio of the first liquid phase to anhydrous ethanol is 1: (1-3); the obtained precipitation material is subjected to a second drying treatment to obtain citrus peel pectin, wherein, in step S3, the conditions of the second drying treatment include: a temperature of 40-60°C and a time of 8-24h.

[0036] In the present disclosure, the first solid phase obtained in step S3 can be used to extract polyphenols in citrus peel, wherein the polyphenols in citrus peel may be at least one of hesperidin, naringin, neohesperidin, catechins, anthocyanins, flavonols and phenolic acids. The present disclosure uses alkaline extraction to extract polyphenols. In one embodiment of the present disclosure, in step S4, the mass ratio of the first solid phase to the alkaline solution is 1: (5-30); the pH value of the alkaline solution is 8-14, wherein the alkaline solution is selected from one or more of sodium hydroxide solution, calcium hydroxide solution, potassium hydroxide solution, ammonia water and barium hydroxide solution.

[0037] In one embodiment of the present disclosure, the conditions of the second leaching treatment include: temperature of 20-40° C. and time of 3-9 h.

[0038] In the present disclosure, after the second leaching treatment, a second separation treatment is performed to obtain a second solid phase and a second liquid phase. The second separation treatment can be performed by a method conventionally used by those skilled in the art, such as filtration treatment or centrifugation treatment. A pH adjuster is used to adjust the pH value of the second liquid phase to 1-6, wherein the pH adjuster is selected from at least one of hydrochloric acid, citric acid, phosphoric acid and acetic acid.

[0039] In the present disclosure, in step S4, the second solid phase obtained can be subjected to a third drying treatment to obtain citrus peel high-fiber powder. The treatment conditions of the third drying treatment include: a temperature of 40-60° C. and a time of 8-24 hours.

[0040] A second aspect of the present disclosure provides citrus peel pectin prepared by the method described in the first aspect.

[0041] In this disclosure, Figure 1 As shown, Figure 11 is fucose, 2 is rhamnose, 3 is arabinose, 4 is galactose, 5 is glucose, 6 is xylose, 7 is galacturonic acid, and 8 is glucuronic acid. The pectin monosaccharide composition includes galacturonic acid, fucose, rhamnose, arabinose, galactose, xylose, glucose and glucuronic acid; the esterification degree is 55-70%; among them, the content of rhamnogalacturonan I (RG-I) is 30-40 mol%.

[0042] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0043] In the following examples, unless otherwise specified, the raw materials and reagents used are all commercially available products.

[0044] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0045] Example 1 The grapefruit peel was washed and cut into small pieces, the citrus peel was mixed with water in a volume ratio of 1:0.3 and then soaked for 2 hours, and then the soaked citrus peel was steam exploded at 0.5 MPa for 1 minute, the steam-exploded material was dried at 40° C. for 3 hours, and then crushed and sieved with a 40-mesh sieve to obtain grapefruit peel powder; The pomelo peel powder and water are mixed at a weight ratio of 1:20, and then ultrasonically extracted at 40° C. and 100 W for 1 hour, and then centrifuged at 20° C. and 8000 rpm to obtain a first solid phase and a first liquid phase; After the first liquid phase is cooled to room temperature, the first liquid phase and anhydrous ethanol are mixed in a volume ratio of 1:3 to perform a first precipitation treatment, and the obtained precipitation material is dried at 40° C. for 8 hours to obtain grapefruit peel pectin; The first solid phase was mixed with saturated lime water at a volume ratio of 1:30, and soaked at room temperature for 6 hours, and filtered to obtain a second solid phase and a second filtrate phase, and the second solid phase was dried at 40° C. for 8 hours to obtain grapefruit peel high-fiber powder; The pH value of the second filtrate was adjusted to 5 with hydrochloric acid, kept at 50°C for 1 hour, and placed at room temperature for 4 hours. The crude polyphenol extract was obtained after filtration.

[0046] Example 2 This embodiment adopts the same method as that of embodiment 1, except that the pomelo peel powder and water are mixed at a weight ratio of 1:20, and then subjected to microwave extraction at 600 W for 4 min, and then centrifuged at 20° C. and 8000 rpm to obtain a first solid phase and a first liquid phase; The remaining steps were the same as those in Example 1 to prepare crude extracts of grapefruit peel pectin and polyphenols.

[0047] Comparative Example 1 This example adopts the same method as that of Example 1, except that ultrasonic leaching is not used, and leaching is directly performed at 50° C. for 1 h; The remaining steps were the same as those in Example 1 to prepare crude extracts of grapefruit peel pectin and polyphenols.

[0048] Comparative Example 2 This embodiment adopts the same method as that of embodiment 1, except that, instead of steam explosion treatment, the grapefruit peel is directly cut into pieces and dried at 60° C. for 24 h, powdered and passed through a 40-mesh sieve to obtain a powder which is mixed with water and subjected to ultrasonic extraction treatment; The remaining steps were the same as those in Example 1 to prepare crude extracts of grapefruit peel pectin and polyphenols.

[0049] Comparative Example 3 This embodiment adopts the same method as that of embodiment 2, except that, instead of steam explosion treatment, the grapefruit peel is directly cut into pieces, dried at 60° C. for 24 h, powdered, and passed through a 40-mesh sieve to obtain a powder, mixed with water, and subjected to microwave extraction treatment; The remaining steps were the same as those in Example 2 to prepare crude extracts of grapefruit peel pectin and polyphenols.

[0050] Comparative Example 4 This embodiment adopts the same method as comparative example 1, except that, instead of steam explosion treatment, the grapefruit peel is directly cut into pieces, dried at 60° C. for 24 h, powdered, and passed through a 40-mesh sieve to obtain a powder, which is then mixed with water for extraction treatment; The remaining steps were the same as those in Comparative Example 1 to prepare crude extracts of grapefruit peel pectin and polyphenols.

[0051] Comparative Example 5 This example adopts the same method as Example 1, except that the soaked citrus peel is subjected to steam explosion treatment at 3 MPa for 5 minutes.

[0052] The remaining steps were the same as those in Example 1 to prepare crude extracts of grapefruit peel pectin and polyphenols.

[0053] Test Case The calculation method of pomelo peel pectin extraction rate is:

[0054] Where: 1 is the pectin extraction rate (%), m 1 is the pectin mass (g), m 0 is the mass of grapefruit peel dry powder (g).

[0055] The calculation method for the extraction rate of polyphenol crude extract is:

[0056] Where: 2 is the polyphenol extraction rate (mg / g), m 2 is the mass of polyphenol crude extract (mg), m 0 is the mass of grapefruit peel dry powder (g).

[0057] The following tests were performed on the grapefruit peel pectin extracted from the examples and comparative examples: (1) Monosaccharide composition detection: The monosaccharide composition was determined using an ion chromatography system. A 20 mL solution of trifluoroacetic acid (TFA; 2 mol / L) of pectin sample was hydrolyzed to 20 mg of pectin at 120 °C for 2 h. Subsequently, the pectin hydrolysis solution was blown dry with nitrogen and redissolved in 20 mL of ultrapure water. After dilution 10 times, the sample was injected into the system through a 0.22 μm filter. The eluents A, B, and C were 15 mmol / L sodium hydroxide, a mixture of 15 mmol / L sodium hydroxide and 100 mmol / L NaOAC, and ultrapure water, respectively, with a flow rate of 0.3 mL / min.

[0058] (2) Esterification degree detection: Fourier transform infrared spectra and methyl esterification degree FTIR spectra of pectin samples were obtained using an infrared spectrometer. 5 mg of each sample was mixed with 500 mg of dry potassium bromide (spectral grade), and the ground mixture was pressed into a particle plate for subsequent testing. The wave number range was 4000-400 cm −1 The number of scans was 64. Origin software was used for data analysis.

[0059] (3) Calculation of RG-I content: RG-I (mol%) = 2 × rhamnose content (mol%) + arabinose content (mol%) + galactose content (mol%).

[0060] The results are shown in Table 1.

[0061] Table 1

[0062] As shown in Table 1, the pectin extraction rate and the polyphenol crude extract extraction rate of Examples 1-2 are much higher than those of Comparative Examples 1-5, indicating that the method disclosed in the present invention can further improve the pectin extraction rate and the polyphenol crude extract extraction rate.

[0063] Furthermore, the galacturonic acid content of the pectin prepared by the method of the present disclosure is reduced, and the RG-I content of the pectin is increased, indicating that the pectin prepared in Examples 1-2 of the present disclosure has a different structure from the pectin prepared in Comparative Examples 1-5.

[0064] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0065] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0066] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for improving the extraction rate of pectin and polyphenols in citrus peel, characterized in that: The method comprises the following steps: S1, soaking citrus peel with water, subjecting the soaked citrus peel to steam explosion at 0.1-1.0 MPa for 1-5 min, and sequentially subjecting the obtained steam explosion material to a first drying treatment, a first crushing treatment and a first sieving treatment to obtain citrus peel powder; S2, mixing the citrus peel powder with water and performing a first extraction process to obtain a first solid phase and a first liquid phase; S3, mixing the first liquid phase with anhydrous ethanol to perform a first precipitation treatment, and performing a second drying treatment on the obtained precipitation material to obtain citrus peel pectin; S4, mixing the first solid phase with an alkaline solution and performing a second leaching treatment to obtain a second solid phase and a second liquid phase; adjusting the pH value of the second liquid phase to 1-6 and performing a second precipitation treatment to obtain a crude polyphenol extract; Wherein, in step S2, the first extraction treatment is ultrasonic extraction treatment or microwave extraction treatment.

2. The method according to claim 1, wherein: In step S1, the weight ratio of the citrus peel to water is 1:(0.2-0.5); The time of the infiltration treatment is 2-4h; The steam explosion treatment conditions include: pressure of 0.1-0.5 MPa, time of 1-3 min; The conditions of the first drying treatment include: a temperature of 40-60°C and a time of 2-12 hours; The conditions of the first sieving treatment include: the mesh number of the sieve is 20-80 meshes.

3. The method according to claim 1, wherein: In step S1, before the infiltration treatment, the method further includes: washing and cutting the citrus peel; Wherein, the citrus peel is selected from one or more of grapefruit peel, orange peel, tangerine peel, mandarin peel and tangerine peel.

4. The method according to claim 1, wherein: In step S2, the weight ratio of the citrus peel powder to water is 1:(5-30).

5. The method according to claim 4, wherein: The conditions of the ultrasonic extraction treatment include: temperature of 20-50°C, power of 50-150W, and time of 10-60min; The microwave extraction treatment conditions include: power of 200-700W and time of 1-10min.

6. The method according to claim 1, wherein: In step S3, the volume ratio of the first liquid phase to anhydrous ethanol is 1:(1-3).

7. The method according to claim 1, wherein: In step S3, the first precipitation treatment time is 8-12 hours; The conditions of the second drying treatment include: a temperature of 40-60° C. and a time of 8-24 hours.

8. The method according to claim 1, wherein: In step S4, the mass ratio of the first solid phase to the alkaline solution is 1:(5-30); The pH value of the alkaline solution is 8-14, wherein the alkaline solution is selected from one or more of sodium hydroxide solution, calcium hydroxide solution, potassium hydroxide solution, ammonia water and barium hydroxide solution.

9. The method according to claim 8, wherein: The conditions of the second leaching treatment include: temperature of 20-40°C and time of 3-9h.

10. Citrus peel pectin prepared by the method according to any one of claims 1 to 9.

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