Method for extracting broccoli pectin

Abstract

The invention relates to a broccoli pectin extraction method, which comprises: (1) raw material pretreatment: washing broccoli stems, slicing, carrying out hot air drying, and grinding into powder; (2) preparing a deep-eutectic solvent: selecting choline chloride as a reagent 1; and mixing the reagent 1 and the reagent 2 according to different molar ratios, incubating at the temperature of 80-100 DEG C, and magnetically stirring at the speed of 600-800 rpm until a clear and transparent liquid is formed. After the liquid is cooled to room temperature, the liquid is still not solidified, and the eutectic solvent is formed. (3) extraction treatment: mixing with a deep eutectic solvent (choline chloride and urea) according to a solid-liquid ratio of 1: (20-60), and continuously stirring at 60-80 DEG C at a rotating speed of 600-800 rpm for 1-3 hours to obtain an extracting solution; (4) centrifugal filtration: filtering the liquid with 300-mesh gauze, and then centrifuging for 15 minutes at the speed of 3500 rpm to obtain a supernatant; and (5) purifying and drying: adding absolute ethyl alcohol with the volume 3 times that of the supernate into the supernate, precipitating for 12 hours at room temperature, then centrifuging to obtain a pectin crude extract which is centrifuged for 15 minutes at 3500 rpm, and purifying and freeze-drying to obtain the broccoli stem pectin.

Description

Technical Field

[0001] The invention belongs to the field of plant pectin extraction, and particularly relates to a broccoli pectin extraction method. Background Art

[0002] Broccoli, also known as Brassica oleracea var.italica, is an annual plant of the genus Brassica in the family Cruciferae. It has attracted much attention from researchers because of its rich nutrition and rich in various active ingredients. In recent years, with the increasing demand for broccoli in the international market, the production of broccoli in China has increased day by day, and currently accounts for about 40.2% of the world's total broccoli production, ranking first in the world. The edible part of broccoli is the flower head, which accounts for 25% to 40% of its total weight. After broccoli is produced, the stem part is not reasonably utilized, but directly thrown away, which not only wastes high-quality resources, but also causes environmental pollution. The traditional strong acid extraction method of pectin uses strong acid, which leads to a large waste of water resources and causes serious pollution to the environment. Therefore, studying the reuse of these wastes has both great economic benefits and can reduce environmental pollution.

[0003] Pectin is a macromolecular polymer derived from plants and plays a key role in the growth and maturation of cells. It is mainly distributed in the primary cell wall and intercellular layer (middle layer) of plants, accounting for about 40% of the dry matter of the cell wall of fruits and vegetables. In the food industry, pectin is often used as a gelling agent, especially in the production of jams and jellies, to meet consumer needs by adjusting the taste and consistency.

[0004] At present, pectin extraction technologies include microwave-assisted extraction, ultrasound-assisted extraction, pressurized-assisted extraction, high-pressure homogenization extraction, enzymatic extraction, and low-eutectic solvent extraction. However, the traditional strong acid extraction method is no longer applicable because it uses strong acids, resulting in a large amount of water waste and serious pollution to the environment. Therefore, it is urgent to develop a simple, efficient and environmentally friendly method for extracting pectin from broccoli stems to achieve the comprehensive utilization of broccoli by-products and promote its further industrialization. This not only contributes to the efficient use of resources, but also opens up new paths for the application of pectin in food, medicine and other industrial fields. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for extracting broccoli pectin, which can effectively improve the extraction efficiency of broccoli stem pectin while reducing the use of strong acid, which is safe and environmentally friendly.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented through the following technical solutions:

[0007] A method for extracting broccoli pectin, comprising the following steps:

[0008] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air, and then grind them into powder;

[0009] (2) Preparation of low eutectic solvent: Choline chloride was selected as reagent 1. Reagent 1 and reagent 2 were mixed in different molar ratios, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear and transparent liquid was formed; after cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent;

[0010] (3) Extraction treatment: After mixing with a low eutectic solvent (choline chloride and urea) at a solid-liquid ratio of 1:(20-60), stirring continuously at 600-80°C and a rotation speed of 600-800 rpm for 1-3 hours to obtain an extract;

[0011] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3500 rpm for 15 min to obtain the supernatant;

[0012] (5) Purification and drying: Add 3 times the volume of anhydrous ethanol to the supernatant and precipitate at room temperature for 12 hours; then centrifuge at 3500 rpm for 15 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0013] Furthermore, the fresh pomace in step (1) is apple peel or citrus peel pomace.

[0014] Furthermore, in the step (1), the mass ratio of fresh pomace to deionized water is 1:3, the frequency of ultrasonic homogenization is 40 kHz, the homogenization time is 10 min, and the enzyme inactivation time is 1-5 s.

[0015] Furthermore, in the step (2), the mass ratio of the enzyme-killed homogenized slurry to the plant chelating peptide is 100:0.01-0.03, and the speed of the heat-insulating stirring is 40-60 r / min.

[0016] Furthermore, during the cooking process in step (3), the slurry needs to be continuously stirred at a speed of 20-40 r / min.

[0017] Furthermore, in step (4), the temperature of the high-temperature hot steam is 110-120° C., and the time for introducing the hot steam is 30-40 minutes.

[0018] Furthermore, in the step (5), the mass ratio of the melted slurry to the cellulase, hemicellulase, glycosidase and amylase is 100: 0.06-0.08: 0.1-0.14: 0.02-0.06: 0.1-0.2.

[0019] Furthermore, in step (6), the centrifugal speed is 4000-5000 r / min, and the centrifugal time is 10-15 min.

[0020] Furthermore, the concentrated solution obtained in step (7) is 1 / 5-1 / 8 of the original volume.

[0021] Furthermore, the temperature of the low-temperature freeze-drying in step (8) is minus 5°C to minus 10°C, and the ground pectin is passed through an 80-mesh sieve.

[0022] The present invention provides a method for extracting broccoli stem pectin, which has the following advantages compared with the prior art:

[0023] The present invention adopts a low eutectic solvent extraction method to extract pectin from broccoli stems. The method has the advantages of being green and efficient, having high extraction efficiency, low extraction cost, simple extraction process, and being stable and reliable. The method of the present invention can promote the industrialization development of broccoli stem pectin. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the pectin obtained in Example 1.

[0025] Figure 2 Fourier infrared analysis results of pectin obtained by different extraction methods.

[0026] Figure 3 Scanning electron microscopy images (left) and atomic force microscopy analysis (right) of pectin obtained by different extraction methods.

[0027] Figure 4 The results of small angle X-ray scattering analysis of pectin obtained by different extraction methods. (A) Small angle X-ray scattering curves of different pectins; (B) Kratky curves of different pectins; (C) Guinier gyration radius of different pectins; (D) Guinier radius of the cross section of the scattering curves of different pectins.

[0028] Figure 5 The results show the alleviating effect of pectin obtained by different extraction methods on lipid deposition in HepG2 cells induced by FFA.

[0029] Figure 6 This is the effect of pectin obtained by different extraction methods on lipid metabolism-related indicators of FFA-induced HepG2 cells.

[0030] Figure 7 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] like Figure 1-7 As shown, a method for extracting broccoli pectin comprises the following steps:

[0033] The broccoli stems were cleaned, sliced, hot-air dried, and then ground; mixed with a low eutectic solvent at a solid-liquid ratio of 1:30, and stirred continuously at 600 rpm for 1 hour at 80°C to obtain an extract. The extract was filtered through a 300-mesh gauze, and then centrifuged at 3500 rpm for 15 minutes to obtain a supernatant. Three times the volume of anhydrous ethanol was added to the supernatant, precipitated at room temperature for 12 hours, and then centrifuged at 3500 rpm for 15 minutes to obtain a crude pectin extract. Broccoli stem pectin was obtained by purification and freeze-drying. By screening the yields of 14 broccoli stem pectin extraction methods, DES2, 5, and 12 could not form DES for the extraction of broccoli pectin. The monosaccharide and molecular weight composition of the other 11 groups of DES were studied by ion chromatography and high-performance liquid chromatography ( Figure 1 and Table 1). The results showed that DES-8 (HBA choline chloride: HBD urea, 1:3) had the highest yield (4.68%), which was significantly higher than traditional extraction (acid extraction 1.28-4.13%; alkali extraction 1.44-3.37%; enzyme extraction 2.34%). In addition, different extraction methods had significant differences in monosaccharide and molecular weight composition (Table 1). There were 10 types with galacturonic acid content (%) higher than 60%, among which the galacturonic acid content of pectin extracted by pH-1 accounted for the highest proportion (about 85.81%). The above results show that although the extraction methods are different, pH has a significant effect on the monosaccharide and molecular weight composition of extracted pectin.

[0034] Table 1 shows the conditions, yield, molecular weight and monosaccharide composition distribution of pectin extracted by different extraction methods.

[0035]

[0036] According to the extraction yield, monosaccharide and molecular weight composition of pectin obtained by different extraction methods, 8 kinds of pectin were selected for further structural characterization, namely DES-6 (D6), DES-7 (D7), DES-8 (D8), DES-9 (D9), DES-11 (D11), DES-13 (D13), pH-1 (P1), and pH-11 (P11). Figure 2As shown in Figure 2, there are significant differences in the structure of pectins obtained by different extraction methods. For example, the 1639 to 1740 cm -1 The absorption peaks near 1010 to 1150 cm-1 may be due to the absorption of esterification and free carboxyl groups, which may indicate the difference in the degree of methyl esterification of pectin. -1 The peaks near the 200 nm and 200 nm indicate that there are significant differences in the monosaccharide composition, such as the possible presence of pyranose. The results of scanning electron microscopy and atomic force microscopy are shown in Figure 2. Figure 3 As shown in the figure, there are significant differences in the conformation of pectin obtained by different extraction methods. The pectin obtained by D6 and P11 obviously has a majority of branched structures, while the pectin extracted by D8 and P1 has more straight-chain structures. In summary, the pectin extracted by D6 and P11 is more similar in monosaccharide composition, HG and RG-1 ratio and structural characterization, and has significant differences in composition with the pectin extracted by D8 and P1.

[0037] SAXS scattering curves of pectin obtained by different extraction methods are shown in Figure 2. Figure 4 As shown. With the increase of q value, the scattering intensity of broccoli pectin shows a downward trend, and the basic shape of the scattering diagram remains unchanged. Small-angle X-ray scattering technology is an important method for studying the submicroscopic internal structure of materials. The scattering intensity of the P11 scattering curve is significantly higher than that of other pectins, which may be due to the fact that P11 has more RG-I region content and a more complex cross-linked network structure, and its spatial conformation may be different from other pectins.

[0038] The obtained scattering curve is used to construct the Kratky curve ( Figure 4 B), further evaluate the effect of different extraction methods on the conformation of broccoli pectin. Kratky curves can reflect the spatial structure of pectin and highlight the scattering characteristics in the high q value range. Kratky curves can reflect the spatial structure of pectin and are mainly used to distinguish between curves and Gaussian chains, rod structures and three-dimensional structures. The Kratky curves of all pectins showed a monotonous increase in the name, indicating that the pectins obtained by DES and traditional acid-base extraction have a disordered extended conformation.

[0039] By Guinier analysis at low q values ​​[lnI(q) vs q 2 ] The radius of gyration Rg can be obtained, which corresponds to the degree of structural extension of the macromolecule. Rg represents the average distance between the polymer and the center of mass, that is, the single-chain molecules in the pectin aggregate are analogous to a circle. The radius of this circle is called the radius of gyration Rg, which can be obtained from the slope of the linear region. Figure 4The Rg values ​​of D6, D8, D11, P1 and P1 obtained by C are 23.3nm, 21.61nm, 21.16nm, 21.74nm and 24.66nm respectively. Among them, the Rg values ​​of DES-extracted pectins D8, D11 and P1 are smaller, which further indicates that the pectin chains are more compact. In order to gain a deeper understanding of the fine size of the pectin chains, we used cross-sectional Guinier analysis [ln(qI(q)) vs q 2 ] to determine the Rc of the extracted pectin chain. The cross section of a single-chain molecule in a pectin aggregate is analogous to a circle, and the radius of this circle is called the cross-sectional radius Rc. For elongated macromolecules, Rc can provide information about the degree of bending along the length of the molecule. Figure 4 It can be seen from D that the Rc values ​​of D6, D8, D11, P1 and P1 are 15.51nm, 17.87nm, 17nm, 17.12nm and 14.86nm respectively. The values ​​of D8, D11 and P1 are larger than those of other pectins, indicating that the structures of D8, D11 and P1 pectins are more compact. Comprehensive SAXS data analysis shows that the conformations of D8, D11 and P1 pectins are more compact, with smaller Rg and larger Rc.

[0040] Through screening of pectin monosaccharide and molecular weight composition, we selected pectin extracted by 5 methods, including 3 DES extractions, 1 alkali extraction, and 1 acid extraction, to study the improvement of lipid deposition in liver cells in vitro. CCK-8 experiments confirmed that pectin extracted by different extraction methods was non-toxic to HepG2 cells at a concentration of 500 μg / mL and 1 mM FFA ( Figure 5 A). Based on the preliminary experimental results, the pectin obtained under different extraction conditions at a concentration of 250 μg / mL was finally selected to alleviate FFA-induced lipid deposition in liver cells. Figure 5 Compared with the FFA control group, the pectins obtained by the four extraction methods of D6, D8, D11, and P1 can significantly inhibit lipid deposition in HepG2 cells. Oil Red O staining further confirmed that the pectins obtained by the above four extraction methods significantly reduced lipids in HepG2 (stained red or orange by Oil Red O). Figure 6It can be seen that the results of the HepG2 experiment showed that D6 and D8 pectins can significantly inhibit the accumulation of triglycerides, high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C), and inhibit the activity of glutamicoxalacetic transaminase (AST) and alanine aminotransferase (ALT). D11 and P1 can inhibit the lipid deposition of HepG2 cells induced by free fatty acids by inhibiting the accumulation of total cholesterol, HDL-C and LDL-C and reducing the activity of ALT.

[0041] Embodiment 1:

[0042] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder;

[0043] (2) Preparation of low eutectic solvent: Choline chloride and urea were mixed in a molar ratio of 1:3, and then 30% by mass of water was added to mix, incubated at 80°C, and magnetically stirred at a speed of 600-800 rpm until a clear and transparent liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0044] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 600 rpm for 1 h to obtain an extract;

[0045] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0046] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0047] Embodiment 2:

[0048] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through an 80-mesh sieve;

[0049] (2) Preparation of low eutectic solvent: Choline chloride and urea were mixed in a molar ratio of 1:3, and then 20% by mass of water was added to the mixture, incubated at 80-100°C, and magnetically stirred at a speed of 600-800 rpm until a clear and transparent liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0050] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent in a mass ratio of 1:20, and stirred at 800 rpm for 1 h to obtain an extract;

[0051] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0052] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0053] Embodiment 3:

[0054] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0055] (2) Preparation of low eutectic solvent: Choline chloride and urea were mixed in a molar ratio of 1:3, and then 30% by mass of water was added to the mixture, incubated at 80-100°C, and magnetically stirred at a speed of 600-800 rpm until a clear and transparent liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0056] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:40, and stirred at 800 rpm for 1 h to obtain an extract;

[0057] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0058] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0059] Comparative Example 1:

[0060] Pectin extraction process, the extraction steps include:

[0061] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0062] (2) Preparation of aqueous solutions of different pH values: Add different volumes of concentrated hydrochloric acid or sodium hydroxide to 6 different volumes of water, respectively, until the pH values ​​of the 6 different volumes of water are 1, 2, 3, 9, 10, and 11, respectively.

[0063] (3) Extraction treatment: The sample powder was mixed with aqueous solutions of different pH values ​​at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0064] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0065] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0066] Comparative Example 2:

[0067] Pectin extraction process, the extraction steps include:

[0068] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0069] (2) Preparation of a low eutectic solvent: Choline chloride and lactic acid were mixed in a molar ratio of 1:2, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0070] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0071] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0072] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0073] Comparative Example 3:

[0074] Pectin extraction process, the extraction steps include:

[0075] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0076] (2) Preparation of low eutectic solvent: Choline chloride and glycerol were mixed in a molar ratio of 1:2, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0077] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0078] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0079] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0080] Comparative Example 4:

[0081] Pectin extraction process, the extraction steps include:

[0082] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0083] (2) Preparation of low eutectic solvent: Choline chloride and propylene glycol were mixed in a molar ratio of 1:2, and then 20% by mass of water was added to the mixture, incubated at 80-100°C, and magnetically stirred at a speed of 600-800 rpm until a clear and transparent liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0084] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0085] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0086] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0087] Comparative Example 5:

[0088] Pectin extraction process, the extraction steps include:

[0089] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0090] (2) Preparation of low eutectic solvent: Potassium carbonate and propylene glycol were mixed in a molar ratio of 1:2, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0091] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0092] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0093] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0094] Comparative Example 6:

[0095] Pectin extraction process, the extraction steps include:

[0096] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0097] (2) Preparation of a low eutectic solvent: Choline chloride and urea were mixed at a molar ratio of 1:2, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0098] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0099] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0100] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0101] Comparative Example 7:

[0102] Pectin extraction process, the extraction steps include:

[0103] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0104] (2) Preparation of low eutectic solvent: Lactic acid, glucose and water were mixed in a molar ratio of 6:1:6, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0105] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0106] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0107] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0108] Comparative Example 8:

[0109] Pectin extraction process, the extraction steps include:

[0110] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0111] (2) Preparation of low eutectic solvent: betaine and citric acid were mixed in a molar ratio of 1:2, and then 30% of water was added to the mixture, incubated at 80-100°C, and magnetically stirred at a speed of 600-800 rpm until a clear and transparent liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0112] (3) Extraction treatment: After the sample powder is mixed with the low eutectic solvent at a mass ratio of 1:30, a 30% water system is added and mixed, and the mixture is stirred at a speed of 800 rpm for 1 h to obtain an extract;

[0113] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0114] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0115] Comparative Example 9:

[0116] Pectin extraction process, the extraction steps include:

[0117] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0118] (2) Preparation of low eutectic solvent: Choline chloride and citric acid monohydrate were mixed in a molar ratio of 1:1, and then 30% by mass of water was added to mix, incubated at 80-100°C, and magnetically stirred at a speed of 600-800 rpm until a clear and transparent liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0119] (3) Extraction treatment: After the sample powder is mixed with the low eutectic solvent at a mass ratio of 1:30, a 30% water system is added and mixed, and the mixture is stirred at a speed of 800 rpm for 1 h to obtain an extract;

[0120] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0121] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0122] Comparative Example 10:

[0123] Pectin extraction process, the extraction steps include:

[0124] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0125] (2) Preparation of low eutectic solvent: citric acid, glucose and water were mixed in a molar ratio of 1:3:3, and then 30% of water was added to the mixture by mass, incubated at 80-100°C, and magnetically stirred at a speed of 600-800 rpm until a clear and transparent liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0126] (3) Extraction treatment: The sample powder was mixed with the deep eutectic solvent at a mass ratio of 1:30, and stirred at 800 rpm for 1 h to obtain an extract;

[0127] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0128] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge at 3500-4500 rpm for 15-30 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

[0129] Comparative Example 11:

[0130] Pectin extraction process, the extraction steps include:

[0131] (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air at 40-60°C, and then grind them into powder and pass them through a 60-mesh sieve;

[0132] (2) Preparation of low eutectic solvent: Choline chloride, glucose and water were mixed in a molar ratio of 5:2:5, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear liquid was formed. After cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent.

[0133] (3) Extraction treatment: After the sample powder is mixed with the low eutectic solvent at a mass ratio of 1:30, a 30% water system is added and mixed, and the mixture is stirred at a speed of 800 rpm for 1 h to obtain an extract;

[0134] (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3000-4000 rpm for 15-30 min to obtain the supernatant;

[0135] (5) Purification and drying: Add 3-4 times the volume of anhydrous ethanol to the supernatant, precipitate at room temperature for 12 hours, and then centrifuge to obtain

[0136] Detection:

[0137] The yields of pectin extracted from the above Examples 1-3 and Comparative Examples 1-11 were detected respectively, and the results are shown in Table 2:

[0138]

[0139] It can be seen from Table 2 that compared with traditional strong acids, strong bases and other low eutectic solvents, the low eutectic solvent in the present application can effectively improve the yield of pectin.

[0140] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined in the claims.

Claims

1. A method for extracting broccoli pectin, characterized in that: The broccoli pectin extraction method comprises the following steps: (1) Raw material pretreatment: clean the broccoli stems, slice them, dry them with hot air, and then grind them into powder; (2) Preparation of low eutectic solvent: Choline chloride was selected as reagent 1. Reagent 1 and reagent 2 were mixed in different molar ratios, incubated at 80-100°C, and magnetically stirred at 600-800 rpm until a clear and transparent liquid was formed; after cooling to room temperature, the liquid still did not solidify, indicating the formation of a low eutectic solvent; (3) Extraction treatment: After mixing with a low eutectic solvent (choline chloride and urea) at a solid-liquid ratio of 1:(20-60), stirring continuously at 600-80°C and a rotation speed of 600-800 rpm for 1-3 hours to obtain an extract; (4) Centrifugal filtration: The liquid was filtered through 300-mesh gauze, and then centrifuged at 3500 rpm for 15 min to obtain the supernatant; (5) Purification and drying: Add 3 times the volume of anhydrous ethanol to the supernatant and precipitate at room temperature for 12 hours; then centrifuge at 3500 rpm for 15 minutes to obtain a crude pectin extract, purify, and freeze-dry to obtain broccoli stem pectin.

2. The method for extracting broccoli pectin according to claim 1, characterized in that: In the step (1), the fresh pomace is apple peel or citrus peel pomace.

3. The method for extracting broccoli pectin according to claim 1, characterized in that: In the step (1), the mass ratio of fresh pomace to deionized water is 1:3, the frequency of ultrasonic homogenization is 40 kHz, the homogenization time is 10 min, and the enzyme inactivation time is 1-5 s.

4. The method for extracting broccoli pectin according to claim 1, characterized in that: In the step (2), the mass ratio of the enzyme-killed homogenized slurry to the plant chelating peptide is 100:0.01-0.03, and the speed of the heat-insulating stirring is 40-60 r / min.

5. The method for extracting broccoli pectin according to claim 1, characterized in that: During the cooking process in step (3), the slurry needs to be continuously stirred at a speed of 20-40 r / min.

6. The method for extracting broccoli pectin according to claim 1, characterized in that: In step (4), the temperature of the high-temperature hot steam is 110-120° C., and the time for passing the hot steam is 30-40 minutes.

7. The method for extracting broccoli pectin according to claim 1, characterized in that: In the step (5), the mass ratio of the melted slurry to the cellulase, hemicellulase, glycosidase and amylase is 100: 0.06-0.08: 0.1-0.14: 0.02-0.06: 0.1-0.

2.

8. The method for extracting broccoli pectin according to claim 1, characterized in that: The centrifugal speed in step (6) is 4000-5000 r / min, and the centrifugal time is 10-15 min.

9. The method for extracting broccoli pectin according to claim 1, characterized in that: The concentrated solution obtained in step (7) is 1 / 5-1 / 8 of the original volume.

10. The method for extracting broccoli pectin according to claim 1, characterized in that: The temperature of the low-temperature freeze-drying in the step (8) is -5°C to -10°C, and the ground pectin is passed through an 80-mesh sieve.

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