Method for extracting cellulose, pectin and polyphenols from pome fruit by-products

Abstract

The present application belongs to the technical field of fruit by-product processing, and particularly relates to a method for extracting cellulose, pectin and polyphenol from pear by-product. The present application utilizes the thermo-mechanical-chemical effect of steam explosion to treat the pear by-product through steam explosion, so that most of hemicellulose and lignin can be removed, and the cellulose, pectin and polyphenol can be efficiently and rapidly extracted, thereby shortening the production cycle of the cellulose, pectin and polyphenol and improving the efficiency. Furthermore, the present application uses a combination of choline chloride and ethanol as a low eutectic solvent, and compared with other types of hydrogen bond acceptors and hydrogen bond donors, the polyphenol extraction effect is the most significant. The present application provides a method for laying a foundation for further development and utilization of pear residue cellulose, pectin and polyphenol, and improves the comprehensive utilization rate of pear processing by-products.

Description

Technical Field

[0001] This invention belongs to the field of fruit by-product processing technology, specifically relating to a method for extracting cellulose, pectin and polyphenols from pear fruit by-products. Background Technology

[0002] Pear pomace refers to the waste products generated after processing fresh pears into juice, dry, and canned goods. It mainly includes pear peel, pulp, core, and stem, accounting for approximately 40%–50% of the original fresh fruit weight. Because pear pomace contains some stone cells, its palatability after initial processing is poor, and its recycling rate is low. It is usually treated as waste. Furthermore, fresh pomace is highly susceptible to spoilage and mold if not treated immediately, affecting its utilization and causing significant problems for production enterprises and the environment. However, pear pomace contains abundant polysaccharides, phenolic substances, flavonoids, cellulose, and hemicellulose, making it a good source of high-quality bioactive components.

[0003] Cellulose is a green and sustainable material that can be used in the manufacture of many high-value products, including regenerated cellulose, cellulose ethers, esters, and nanocrystalline cellulose. Cellulose and hemicellulose separation technology has always been a hot topic in the research community. Currently, common extraction methods for cellulose are physical and chemical methods. The former mainly involves high-pressure cooking and microwave treatment, which involves pretreatment with sodium hydroxide solution after pulverizing the material, followed by cooking or microwave treatment under high temperature and pressure. However, this method produces a lot of cellulose impurities and results in a low extraction rate. Moreover, high-pressure cooking often uses large-scale cooking equipment, which consumes a lot of electricity, involves excessive pressure, and is dangerous to operate; the chemicals used in chemical methods can easily cause secondary pollution to the environment. These methods generate a lot of pollution and easily damage cellulose.

[0004] Pectin is a plant-based acidic polysaccharide with a backbone of poly-α-1,4-D-galacturonic acid polysaccharide. Its excellent gelling and emulsifying stability have made it an important natural additive in the food, pharmaceutical, daily chemical, and textile industries. Currently, pectin extraction methods mainly include acid extraction, enzymatic extraction, and salt extraction. The most commonly used method is acid extraction, which typically involves hydrolyzing protopectin into water-soluble pectin in an acidic solution with a specific pH under heating conditions, forming a pectin aqueous solution. Enzymatic extraction utilizes enzymes such as cellulase and hemicellulase to remove cellulose and hemicellulose from the cell walls, degrading macromolecules in the pectin or converting insoluble pectin into water-soluble pectin, thus extracting it. However, enzymatic extraction of pectin has a long reaction time, usually exceeding 10 hours. Salt extraction typically uses ammonium oxalate to convert insoluble calcium pectate into soluble ammonium salts, increasing the solubility of insoluble pectin. Existing methods generally suffer from low pectin yield and incomplete extraction.

[0005] Polyphenols, a large class of secondary metabolites, are found in almost all kinds of plants and have potential health-promoting effects. Currently, polyphenol extraction typically utilizes ethanol for maceration, concentration and purification, ethyl acetate extraction, and acetone for crude product purification. This method is cumbersome; while it increases polyphenol purity, the yield is low. Furthermore, due to the use of organic solvents such as ethyl acetate and acetone, reagent residues are inevitably present in the extract, limiting its application. Summary of the Invention

[0006] The purpose of this invention is to provide a method for extracting cellulose, pectin, and polyphenols from pear fruit by-products, thereby improving the extraction rate of cellulose, pectin, and polyphenols from pear fruit by-products. The obtained cellulose has a uniform particle size distribution, a large aspect ratio, and high crystallinity. Pectin has the effect of regulating anti-inflammatory activity, and polyphenols have antioxidant activity. This method improves the utilization rate of pear fruit processing by-products, is simple, and is environmentally friendly.

[0007] To achieve the above objectives, the present invention provides a method for extracting one or more of cellulose, pectin, and polyphenols from pear fruit by-products, comprising the following steps:

[0008] The pear fruit by-products were subjected to steam explosion treatment and pulverization treatment in sequence to obtain pear residue powder; the steam explosion pressure of the steam explosion treatment was 0.3 to 2.0 MPa;

[0009] The pear pomace powder is extracted; the extraction includes one or more of cellulose extraction, pectin extraction and polyphenol extraction.

[0010] The steps of cellulose extraction include: first extraction of the pear pomace powder using an alkaline solution, collecting the filter residue after vacuum filtration; bleaching the filter residue using hydrogen peroxide, collecting the filter residue after vacuum filtration, and drying it to obtain crude pear cellulose; the pH value of the alkaline solution is 8-12.

[0011] The pectin extraction steps include: performing a second extraction on the pear pomace powder using an acid solution and collecting the extract; subjecting the extract to alcohol precipitation and collecting the precipitate to obtain pear pectin.

[0012] The polyphenol extraction steps include: mixing the pear pomace powder and a eutectic solvent solution, ultrasonically extracting, and collecting the extract; the extract contains pear fruit polyphenols; the eutectic solvent solution includes a hydrogen bond acceptor and a hydrogen bond donor; the hydrogen bond acceptor includes choline chloride; the hydrogen bond donor includes ethanol; and the molar ratio of choline chloride to ethanol is 1:(1-3).

[0013] Preferably, the steam explosion treatment time is 1 to 5 minutes; the medium for the steam explosion treatment is saturated steam; and the temperature of the saturated steam is 160 to 230°C.

[0014] Preferably, the temperature of the first extraction is 75-90℃, and the time is 2-4 hours;

[0015] During cellulose extraction, the mass-to-volume ratio of pear pomace powder to alkaline solution is 0.5–2 g: 10–50 mL; the alkaline solution includes sodium hydroxide solution with a mass concentration of 7.5–15 wt%.

[0016] Preferably, the bleaching treatment is performed three times, with each bleaching treatment conducted at a temperature of 75–90°C for 45–70 minutes.

[0017] The hydrogen peroxide has a mass concentration of 1–2.5 wt%.

[0018] Preferably, after obtaining the crude cellulose from the pear fruit, the method further includes: mixing the crude cellulose from the pear fruit with a purification solution, reacting at 90-120°C for 20-60 minutes, collecting the filter residue after vacuum filtration, and drying to obtain purified pear fruit cellulose.

[0019] The purification solution comprises 70-80 wt.% acetic acid solution and 65-70 wt.% nitric acid solution; the volume ratio of the acetic acid solution to the nitric acid solution is (1-10):(1-30).

[0020] Preferably, the second extraction temperature is 75-85℃ and the time is 1.5-3h.

[0021] Preferably, during pectin extraction, the mass-to-volume ratio of pear pomace powder to acid solution is 0.5–2 g: 10–50 mL; the acid solution includes hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 0.05–0.15 mol / L.

[0022] Preferably, the alcohol precipitation time is 10-15 hours; the alcohol precipitation uses anhydrous ethanol, and the volume ratio of the extract to anhydrous ethanol is 1:(1-5).

[0023] Preferably, during the polyphenol extraction, the mass-to-volume ratio of the pear pomace powder to the eutectic solvent solution is 1 g: (15-35) mL; and the water content of the mixture of the pear fruit by-product powder and the eutectic solvent solution is 20-60%.

[0024] Preferably, the ultrasonic extraction time is 20-60 minutes and the power is 300-700W.

[0025] Beneficial effects:

[0026] This invention provides a method for extracting one or more of cellulose, pectin, and polyphenols from pear fruit by-products. The method involves sequentially subjecting the pear fruit by-products to steam explosion and pulverization to obtain pear pomace powder. The steam explosion pressure is 0.3–2.0 MPa. The pear pomace powder is then subjected to cellulose extraction, pectin extraction, or polyphenol extraction. The cellulose extraction step includes: performing a first extraction on the pear pomace powder using an alkaline solution, followed by vacuum filtration and collection of the filter residue; bleaching the filter residue using a sodium hypochlorite solution, followed by vacuum filtration and collection of the filter residue. The pear pomace powder is dried to obtain crude cellulose. The pectin extraction step includes: a second extraction of the pear pomace powder using hydrochloric acid solution, and collection of the extract; alcohol precipitation of the extract, collection of the precipitate, and obtaining pear pectin; mixing the pear pomace powder with a eutectic solvent solution, ultrasonic extraction, and collection of the extract; the extract contains pear polyphenols; the eutectic solvent solution includes hydrogen bond acceptors and hydrogen bond donors; the hydrogen bond acceptor includes choline chloride; the hydrogen bond donor includes ethanol; the molar ratio of choline chloride to ethanol is 1:(1-3). This invention uses steam explosion treatment, making full use of the thermomechanical and chemical effects of steam explosion, which can effectively remove most of the hemicellulose and lignin in the pear pomace powder. Combined with subsequent extraction steps, it can efficiently and rapidly prepare cellulose, pectin, and polyphenols, shortening the production cycle of cellulose, pectin, and polyphenols, improving efficiency, and laying the foundation for the further development and utilization of pear pomace cellulose, pectin, and polyphenols. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0028] Figure 1 Particle size distribution of cellulose under different steam explosion pressures;

[0029] Figure 2 Scanning electron micrographs of cellulose under different steam explosion pressures; different lowercase letters indicate significant data relationships (P<0.05);

[0030] Figure 3 Scanning electron microscope images of cellulose under different steam explosion pressures;

[0031] Figure 4 Infrared spectra of cellulose under different steam explosion pressures;

[0032] Figure 5 The graphs show the results of thermal stability testing of cellulose under different steam explosion pressures; where A is the TGA graph and B is the DTG graph.

[0033] Figure 6The water-holding and oil-holding properties of cellulose under different steam explosion pressures are shown; different lowercase or uppercase letters indicate significant data relationships (P<0.05).

[0034] Figure 7 Plots show the glucose adsorption (A) and cholesterol adsorption (B) of cellulose under different steam explosion pressures; different lowercase letters indicate significant data relationships (P<0.05).

[0035] Figure 8 Digestion characteristics of cellulose under different steam explosion pressures;

[0036] Figure 9 The values ​​represent the pectin extraction rate under different steam explosion pressures; different lowercase letters indicate significant data relationships (P<0.05).

[0037] Figure 10 The values ​​represent the flavonoid and polyphenol content of pectin under different steam explosion pressures; different lowercase letters indicate significant data relationships (P<0.05).

[0038] Figure 11 These are SEM images of pectin under different steam explosion pressures;

[0039] Figure 12 These are the FT-IR spectra of pectin under different steam explosion pressures;

[0040] Figure 13 This is a graph showing the molecular weight efflux curves of pectin under different steam explosion pressures.

[0041] Figure 14 This is the effect of different concentrations of pectin on the cell proliferation rate of RAW264.7 cells in Comparative Example 2.

[0042] Figure 15 The effect of pectin on TNF-α production in RAW264.7 cells under different steam explosion pressures;

[0043] Figure 16 The effect of pectin on IL-1β production in RAW264.7 cells under different steam explosion pressures;

[0044] Figure 17 The graph shows the extraction results of polyphenols under different eutectic solvents (compositions);

[0045] Figure 18 The graph shows the extraction results of polyphenols under different eutectic solvents (molar ratio of choline chloride and ethanol);

[0046] Figure 19 The graph shows the extraction results of polyphenols at different moisture contents.

[0047] Figure 20The graph shows the extraction results of polyphenols at different solid-liquid ratios.

[0048] Figure 21 The graph shows the extraction results of polyphenols under different solid-liquid ratios and ultrasonic times.

[0049] Figure 22 This is a graph showing the in vitro antioxidant capacity of the polyphenol solution obtained in Example 14;

[0050] in, Figures 14-22 Different lowercase letters in the text indicate significant data relationships (P<0.05). Detailed Implementation

[0051] This invention provides a method for extracting one or more of cellulose, pectin, and polyphenols from pear fruit by-products, comprising the following steps:

[0052] The pear fruit by-products were subjected to steam explosion treatment and pulverization treatment in sequence to obtain pear residue powder; the steam explosion pressure of the steam explosion treatment was 0.3 to 2.0 MPa;

[0053] The pear pomace powder is extracted; the extraction includes one or more of cellulose extraction, pectin extraction and polyphenol extraction.

[0054] The steps of cellulose extraction include: first extraction of the pear pomace powder using an alkaline solution, collecting the filter residue after vacuum filtration; bleaching the filter residue using hydrogen peroxide, collecting the filter residue after vacuum filtration, and drying it to obtain crude pear cellulose; the pH value of the alkaline solution is 8-12.

[0055] The pectin extraction steps include: performing a second extraction on the pear pomace powder using an acid solution and collecting the extract; subjecting the extract to alcohol precipitation and collecting the precipitate to obtain pear pectin.

[0056] The polyphenol extraction steps include: mixing the pear pomace powder and a eutectic solvent solution, ultrasonically extracting, and collecting the extract; the extract contains pear fruit polyphenols; the eutectic solvent solution includes a hydrogen bond acceptor and a hydrogen bond donor; the hydrogen bond acceptor includes choline chloride; the hydrogen bond donor includes ethanol; and the molar ratio of choline chloride to ethanol is 1:(1-3).

[0057] This invention involves steam explosion treatment of pear fruit byproducts to obtain pear pomace. The steam explosion pressure in this invention is 0.3–2.0 MPa; in one embodiment, the steam explosion pressure is 0.3–1.5 MPa; in another embodiment, the steam explosion pressure is 0.3–0.9 MPa. In one embodiment, the steam explosion treatment time is 1–5 minutes; in another embodiment, the steam explosion treatment time is 2–3 minutes. In one embodiment, the medium for steam explosion treatment is saturated steam; in one embodiment, the temperature of the saturated steam is 160°C–230°C; in another embodiment, the temperature of the saturated steam is 180°C–200°C; in yet another embodiment, the temperature of the saturated steam is 200°C. In one embodiment, this invention utilizes a high-pressure tank for the steam explosion treatment. This invention employs a steam explosion treatment method, which fully utilizes the thermomechanical and chemical effects of steam explosion to effectively remove most of the hemicellulose and lignin from pear pomace powder, laying the foundation for the efficient and rapid extraction of cellulose, pectin, and polyphenols from pear pomace.

[0058] In one embodiment, the pear fruit by-products are pulverized before being subjected to steam explosion treatment. In one embodiment, the pulverization time is 2-5 minutes; in another embodiment, the pulverization time is 2 minutes. In one embodiment, a high-speed blender is used for the pulverization process.

[0059] After obtaining the pear pomace, the present invention pulverizes the pear pomace to obtain pear pomace powder. In one embodiment, the pulverization time is 2-5 minutes; in another embodiment, the pulverization time is 2 minutes. In one embodiment, the pulverization process uses a high-speed blender. In another embodiment, the present invention dries the pear pomace to a constant weight before performing the pulverization process. The present invention does not have strict requirements on the drying method; conventional methods in the art can be used.

[0060] After obtaining the pear pomace powder, the present invention performs a first extraction on the pear pomace powder using an alkaline solution, followed by vacuum filtration and collection of the filter residue. In one embodiment, the temperature of the first extraction is 75–90°C; in another embodiment, the temperature of the first extraction is 85°C. In one embodiment, the extraction time is 2–4 hours; in another embodiment, the extraction time is 4 hours. In one embodiment, the pH value of the alkaline solution is 10. In one embodiment, the mass-to-volume ratio of the pear pomace powder to the alkaline solution is 0.5–2 g: 10–50 mL. In one embodiment, the first extraction is performed by stirring. In another embodiment, the mass-to-volume ratio of the pear pomace powder to the alkaline solution is 1 g: 20 mL. In one embodiment, the alkaline solution includes a sodium hydroxide solution with a mass concentration of 7.5–15 wt%; in another embodiment, the mass concentration of the sodium hydroxide solution is 10 wt%. The present invention does not have strict requirements on the vacuum filtration method; conventional methods in the art can be used.

[0061] After obtaining the filter residue, the present invention bleachs the filter residue with hydrogen peroxide, collects the residue after vacuum filtration, and dries it to obtain pear crude cellulose. As one embodiment, after obtaining the filter residue, the present invention washes it to neutrality. As one embodiment, distilled water is used for washing.

[0062] In one embodiment, the bleaching treatment of the present invention is performed three times, with each bleaching treatment conducted at a temperature of 75–90°C; in another embodiment, the bleaching treatment is conducted at a temperature of 85°C; in one embodiment, the bleaching treatment lasts for 45–70 minutes; in another embodiment, the bleaching treatment lasts for 60 minutes. In one embodiment, the hydrogen peroxide has a mass concentration of 1–2.5 wt%; in another embodiment, the hydrogen peroxide has a mass concentration of 2 wt%. In one embodiment, the drying includes freeze-drying. The present invention does not impose strict requirements on the specific drying steps, and conventional operations in the art can be used.

[0063] In one embodiment, after obtaining the crude pear cellulose, the present invention mixes the crude pear cellulose with a purification solution, reacts at 90-120°C for 20-60 min, collects the filter residue after vacuum filtration, and dries it to obtain purified pear cellulose. In one embodiment, the purification solution comprises 70-80 wt.% acetic acid solution and 65-70 wt.% nitric acid solution; in another embodiment, the purification solution comprises 80 wt.% acetic acid solution and 70 wt.% nitric acid solution. In one embodiment, the volume ratio of acetic acid solution to nitric acid solution in the purification solution is (1-10):(1-30); in another embodiment, the volume ratio of acetic acid solution to nitric acid solution in the purification solution is (2-8):(10-25); in yet another embodiment, the volume ratio of acetic acid solution to nitric acid solution in the purification solution is (5-6):(15-20). In specific embodiments, the present invention can arbitrarily select values ​​within the range of (1-10):(1-30), such as 1:10, 1:20, 1:25, 1:30, 10:1, 10:2, 10:3, 10:7, 10:10, 10:15, 10:18, 10:20, 10:25, or 10:30, etc. As one embodiment, after obtaining the filter residue, the present invention washes the filter residue to neutrality before proceeding with the drying step. As one embodiment, the washing uses distilled water and 95% v / v ethanol. The present invention does not have strict requirements on the vacuum filtration method; conventional methods in the art can be used. As one embodiment, the drying includes freeze drying. The present invention does not have strict requirements on the specific steps of the drying; conventional operations in the art can be used.

[0064] This invention employs a steam explosion treatment method, fully utilizing the thermomechanical and chemical effects of steam explosion to effectively remove most of the hemicellulose and lignin from pear pomace powder. After obtaining the pear pomace powder, it undergoes alkali treatment and sodium chlorite bleaching, as well as subsequent purification steps. This allows for the efficient and rapid preparation of cellulose, shortening the cellulose production cycle, improving efficiency, and laying the foundation for the further development and utilization of pear pomace cellulose.

[0065] After obtaining the pear pomace powder, the present invention performs a second extraction on the pear pomace powder using an acid solution, and collects the extract. In one embodiment, the temperature of the second extraction is 75–85°C; in another embodiment, the temperature of the second extraction is 80°C; in one embodiment, the extraction time is 1.5–3 hours; in another embodiment, the extraction time is 2 hours. In one embodiment, the mass-to-volume ratio of the pear pomace powder to the acid solution is 0.5–2 g: 10–50 mL. In one embodiment, the second extraction is performed by stirring. In another embodiment, the mass-to-volume ratio of the pear pomace powder to the acid solution is 1 g: 20 mL. In one embodiment, the acid solution includes a hydrochloric acid solution with a concentration of 0.05–0.15 mol / L; in another embodiment, the concentration of the hydrochloric acid solution is 0.1 mol / L. In one embodiment, the extraction is collected by cooling filtration. The present invention does not have strict requirements on the cooling filtration method; conventional methods in the art can be used.

[0066] After obtaining the extract, the present invention performs alcohol precipitation on the extract, collects the precipitate, and obtains pear pectin. In one embodiment, the alcohol precipitation time is 10–15 hours; in another embodiment, the alcohol precipitation time is 12 hours. In one embodiment, anhydrous ethanol is used for the alcohol precipitation, and the volume ratio of the extract to anhydrous ethanol is 1:(1–5); in another embodiment, the volume ratio of the extract to anhydrous ethanol is 1:3.

[0067] This invention employs a steam explosion treatment method, which fully utilizes the thermomechanical and chemical effects of steam explosion to effectively remove most of the hemicellulose and lignin from pear pomace powder. After obtaining the pear pomace powder, acid solution extraction and alcohol precipitation are performed to efficiently and quickly prepare pectin, shortening the pectin production cycle and improving efficiency, thus laying the foundation for the further development and utilization of pear pomace pectin.

[0068] After obtaining the pear pomace powder, the present invention mixes the pear pomace powder with a eutectic solvent solution, extracts it using ultrasound, and collects the extract. The extract contains pear polyphenols. The eutectic solvent solution includes hydrogen bond acceptors and hydrogen bond donors. The hydrogen bond acceptor includes choline chloride. The hydrogen bond donor includes ethanol. The molar ratio of choline chloride to ethanol is 1:(1-3). In another embodiment, the molar ratio of choline chloride to ethanol is 1:2. In one embodiment, the mass-to-volume ratio of the pear pomace powder to the eutectic solvent solution is 1 g:(15-35) mL. In another embodiment, the mass-to-volume ratio of the pear pomace powder to the eutectic solvent solution is 1 g:(20-30) mL. In one embodiment, the water content of the mixture of the pear fruit by-product powder and the eutectic solvent solution is 20-60%; in another embodiment, the water content of the mixture of the pear fruit by-product powder and the eutectic solvent solution is 30-50%; in yet another embodiment, the water content of the mixture of the pear fruit by-product powder and the eutectic solvent solution is 40%. In one embodiment, the ultrasonic extraction time is 20-60 min; in another embodiment, the ultrasonic extraction time is 20 or 40 min. In one embodiment, the ultrasonic extraction power is 300-700 W; in yet another embodiment, the ultrasonic extraction power is 360 W.

[0069] This invention uses a combination of choline chloride and ethanol as a eutectic solvent, which has the characteristics of low melting point and low toxicity, and can protect the environment. Compared with other types of hydrogen bond acceptors and hydrogen bond donors, it has the most significant effect on polyphenol extraction. Through a simple process, the extraction efficiency of polyphenols from pear fruit by-products can be maximized.

[0070] To further illustrate the present invention, the method for extracting cellulose, pectin and polyphenols from pear fruit by-products provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] A method for extracting cellulose from pear fruit by-products comprises the following steps:

[0073] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0074] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.3MPa, and the pressure holding time was 3min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0075] (3) Crude extraction of cellulose: 50g of pear pomace powder was placed in 1000mL of 10wt% sodium hydroxide solution and stirred in a water bath at 85℃ for 4h. After stirring, the mixture was filtered under reduced pressure and washed until neutral. The filter residue was bleached three times with 1000mL of 2wt% sodium hypochlorite solution and then filtered under reduced pressure. The filter residue after reduced pressure filtration was thoroughly washed with distilled water until neutral and then freeze-dried to obtain crude cellulose.

[0076] (4) Purification of cellulose: 10g of crude cellulose was placed in 300mL of a mixed solution of 80wt% acetic acid and 70wt% nitric acid (volume ratio of 80wt% acetic acid to 70wt% nitric acid was 10:1) and reacted at 100℃ for 30min. After the reaction was completed, the mixture was filtered under reduced pressure. The filter residue was thoroughly washed with distilled water until neutral and then freeze-dried to obtain pure cellulose.

[0077] Example 2

[0078] A method for extracting cellulose from pear fruit by-products similar to that in Example 1, the only difference being that the steam explosion pressure is 0.6 MPa during step (2) steam explosion.

[0079] Example 3

[0080] A method for extracting cellulose from pear fruit by-products similar to that in Example 1, the only difference being that the steam explosion pressure is 0.9 MPa during steam explosion in step (2).

[0081] Comparative Example 1

[0082] A method for extracting cellulose from pear fruit by-products similar to that in Example 1, the only difference being that the steam explosion pressure in step (2) is atmospheric pressure 0.1 MPa.

[0083] Test Example 1: Determination of Cellulose Extraction Rate

[0084] Based on the cellulose content of the pear pomace, the extraction rates of crude cellulose and pure cellulose in Examples 1-3 and Comparative Example 1 were statistically analyzed, and the results are shown in Table 1.

[0085] Table 1 Extraction rates of crude and pure cellulose under different treatment methods

[0086] Handling method Steam explosion pressure / MPa Crude cellulose extraction rate Pure cellulose extraction rate Comparative Example 1 0.1 <![CDATA[22.28±0.04 c ]]> <![CDATA[12.07±0.39 c ]]> Example 1 0.3 <![CDATA[28.38±0.68 b ]]> <![CDATA[17.26±1.33 b ]]> Example 2 0.6 <![CDATA[32.18±1.02 a ]]> <![CDATA[18.90±0.52 b ]]> Example 3 0.9 <![CDATA[34.07±0.43 a ]]> <![CDATA[24.03±1.15 a ]]>

[0087] Note: Different lowercase letters in the same column of the table represent significant data relationships (P<0.05), and the same applies below.

[0088] As shown in Table 1, compared with the untreated pear pomace (Comparative Example 1), the cellulose extraction rate of the pear pomace significantly increased after steam explosion treatment. Furthermore, the extraction rates of both crude and pure cellulose increased with increasing steam explosion pressure. During steam explosion, acidic hydrolysis, mechanical-like fracture, hydrogen bond disruption, and structural rearrangement occur, all of which contribute to the increased cellulose extraction rate of the pear pomace.

[0089] Test Example 2: Determination of Cellulose Structure Characterization

[0090] The pure cellulose obtained in Examples 1-3 and Comparative Example 1 was used as the test samples, and the following tests were performed.

[0091] (1) The particle size of the samples was determined using a Malvern particle size analyzer. The results showed that, compared with Comparative Example 1, steam explosion treatment in Examples 1-3 reduced the particle size of cellulose. The particle size first decreased and then increased with increasing steam explosion pressure. Figure 1 During steam explosion, acid-like hydrolysis occurs, causing low-molecular-weight substances to dissolve and reducing the degree of fiber polymerization; mechanical-like fracture occurs, causing macromolecular bonds to break and amorphous regions to be destroyed; structural rearrangement occurs, increasing the mobility of cellulose chains and facilitating the transformation of cellulose into an ordered structure.

[0092] (2) The Zeta potential of the sample was characterized using a Zeta potential meter. The results showed that the Zeta potential results were inversely related to the particle size distribution results. Compared with Comparative Example 1, steam explosion treatment in Examples 1-3 increased the Zeta potential of cellulose, and the Zeta potential was negatively correlated with particle size. Figure 2 Furthermore, the cellulose obtained in Comparative Example 1 and Examples 1-3 all carried a negative charge, indicating that uronic acid groups were generated during the acid purification of cellulose, thus resulting in a negative charge.

[0093] (3) The morphology of the samples was characterized using a scanning electron microscope. The results showed that the cellulose particles in Comparative Example 1 without steam explosion treatment were larger and smoother; the particles in Examples 1-3 after steam explosion treatment were smaller and more porous. Figure 3 This is because lignin and hemicellulose have been partially removed, the dense fiber structure has been damaged to some extent, and the cellulose has been degraded due to steam explosion.

[0094] (4) The molecular structure of the test samples was characterized using infrared spectroscopy. The results showed that different test samples exhibited different molecular structures at 3600 cm⁻¹. -1 and 2800cm -1There are two relatively strong absorption peaks, which are characteristic peaks of the stretching vibrations of -OH and -CH, respectively. These two groups are present in all three components. 1732cm -1 The absorption peak corresponds to the characteristic peaks of the acetyl and sugar carbonyl ester groups of hemicellulose, or the characteristic peaks of the carboxylic acid ester groups of ferulic acid and p-coumaric acid in lignin. The slight decrease in the intensity of this peak indicates partial hydrolysis of hemicellulose or lignin. Figure 4 Since the experimental temperature of 200℃ is within the temperature range where hemicellulose is most prone to hydrolysis, it indicates that hemicellulose underwent hydrolysis during the steam explosion pretreatment, leading to a decrease in the intensity of the absorption peak at that point.

[0095] (5) Weight loss between 20 and 130°C is attributed to absorbed moisture on the material surface, including semi-adsorbed water and intermolecular hydrogen bonds; weight loss between 240 and 400°C is attributed to the loss of hemicellulose and cellulose. Thermogravimetric analysis (TGA) was used to characterize the thermal stability of the samples. The results showed that, compared to the untreated cellulose in Example 1, the TGA loss continuously increased. Figure 5 (A). The characteristic peak temperatures of thermal decomposition of cellulose obtained under different steam explosion pressures (0.1 MPa, 0.3 MPa, 0.6 MPa, and 0.9 MPa) were 282.25℃, 302.28℃, 296.73℃, and 322.75℃, respectively. This indicates that the cellulose extracted after steam explosion in Examples 1-3 has high thermal stability. Figure 5 (B)

[0096] Test Example 3: Determination of the functional properties of cellulose

[0097] The pure cellulose obtained in Examples 1-3 and Comparative Example 1 was used as the test samples, and the following tests were performed.

[0098] (1) The water-holding and oil-holding properties of the samples were determined by weighing. The results showed that steam explosion treatment in Examples 1-3 significantly enhanced the water-holding and oil-holding properties of cellulose. Both water-holding and oil-holding properties increased first and then decreased with increasing steam explosion pressure. Figure 6 It is related to particle size; the smaller the particle size, the larger the contact area and the stronger the ability to adsorb water and oil.

[0099] (2) The glucose adsorption capacity of the test sample was determined by the DNS colorimetric method and the cholesterol adsorption capacity was determined by the o-phthalaldehyde method. The results showed that the glucose adsorption capacity and cholesterol adsorption capacity first increased and then decreased with the increase of steam explosion pressure. Steam explosion treatment can improve the adsorption characteristics of cellulose. Figure 7 Steam explosion treatment can reduce particle size, increasing the contact area between glucose and cholesterol and cellulose, thereby improving adsorption properties.

[0100] (3) The digestive characteristics of the test samples were simulated using an in vitro gastrointestinal tract, with 0–4 h representing simulated gastric digestion and 4–8 h representing simulated intestinal digestion. The results showed that cellulose was mainly digested in the stomach. The digestibility increased with increasing steam explosion pressure, indicating that steam explosion improved the digestibility of cellulose. Figure 8 This is related to particle size.

[0101] Example 4

[0102] A method for extracting pectin from pear fruit by-products comprises the following steps:

[0103] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0104] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.3MPa, and the pressure holding time was 3min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0105] (3) Extraction of pectin: The pear pomace powder obtained in step (2) was placed in 0.1 mol / L HCl solution, stirred at 80°C for 2 h, cooled and filtered, and the filtrate was collected; the filtrate was then precipitated with 3 times the volume of anhydrous ethanol for 12 h, the precipitate was collected by filtration, and dried at 50°C to constant weight to obtain pectin.

[0106] Example 5

[0107] A method for extracting pectin from pear fruit by-products similar to Example 4, the only difference being that the steam explosion pressure is 0.6 MPa during steam explosion in step (2).

[0108] Example 6

[0109] A method for extracting pectin from pear fruit by-products similar to Example 4, the only difference being that the steam explosion pressure is 0.9 MPa during steam explosion in step (2).

[0110] Example 7

[0111] A method for extracting pectin from pear fruit by-products similar to that in Example 4, the only difference being that the steam explosion pressure is 1.2 MPa during steam explosion in step (2).

[0112] Example 8

[0113] A method for extracting pectin from pear fruit by-products similar to Example 4, the only difference being that the steam explosion pressure is 1.5 MPa during step (2) steam explosion.

[0114] Comparative Example 2

[0115] A method for extracting pectin from pear fruit by-products similar to Example 4, the only difference being that the steam explosion pressure during step (2) is atmospheric pressure 0.1 MPa.

[0116] Test Example 4

[0117] The pectin obtained in Examples 4-8 and Comparative Example 2 was used as the test samples and the following tests were performed.

[0118] (1) The pectin extraction rates of Examples 4-8 and Comparative Example 2 were statistically analyzed. The results showed that, compared with Comparative Example 2 (0.1 MPa), the extraction rate first increased and then decreased with increasing steam explosion pressure. The maximum value appeared at 0.3 MPa, with an extraction rate of 8.76%, and the minimum value appeared at 1.5 MPa, with an extraction rate of 3.51%. Figure 9 This is likely because under high temperature and pressure steam, the degree of cellulose polymerization decreases, hemicellulose partially degrades, lignin softens, and the strength of lateral cell bonds weakens. When pressure is suddenly reduced, the rapid expansion of steam in the pores of the apple pomace creates a "bursting" effect that strips away lignin and tears the pear pomace cell tissue into fine fibers, allowing the extraction solvent to fully penetrate and facilitating pectin precipitation. However, high pressure can easily lead to carbonization, thus reducing the yield. Therefore, the optimal steam burst pressure is 0.3 MPa.

[0119] (2) The total phenol content of the samples was determined by the Folin-Ciocalteu method, and the total flavonoid content was determined by the nitrite-aluminum nitrate-sodium hydroxide colorimetric method. The results showed that the total flavonoid and total phenol contents increased continuously with the increase of steam explosion pressure, reaching a maximum at 1.5 MPa, which were 42.203 mg / mL and 1.316 mg / g, respectively. Compared with Comparative Example 2 (0.1 MPa), the total flavonoid content was 0.937 mg / mL and the total phenol content was 0.234 mg / g, which increased by 45.04 times and 5.62 times, respectively. Figure 10 This is presumably because the higher the saturated vapor pressure, the greater the mechanical action, the more severely the intact structure of bioactive substances is damaged, the lower the mass transfer resistance, and the more favorable it is for the extraction of bioactive substances.

[0120] (3) The samples were scanned using a Zeiss Sigma 300 scanning electron microscope. The results showed that the pectin surface of Comparative Example 2 without steam explosion treatment exhibited a loose and porous state compared to the entangled state of the pectin after treatment with 1.2 MPa and 1.5 MPa. However, as the steam explosion pressure increased, the pectin surface at 0.3 MPa and 0.6 MPa exhibited a more dense and porous state. Figure 11This may be due to structural damage caused by increased gas explosion pressure. Further increases in gas explosion pressure lead to a smoother surface, increased wrinkles, and a sheet-like appearance, with varying degrees of pectin fragmentation and irregularity. This may be due to differences in the chemical composition, linear structure, and branched structure of the pectin.

[0121] (4) Infrared spectroscopy of the test samples was performed using the potassium bromide pellet method. The results showed that all different test samples were within the range of 3364 cm⁻¹. -1 The broad peaks are a result of intramolecular or intermolecular OH stretching vibrations; all are around 1735 cm⁻¹. -1 The absorption peaks appear nearby, which are due to the stretching vibrations of the ester bond formed by the carboxyl group of GalA (-COOR, C=O); all are at 1629 cm⁻¹. -1 A strong absorption peak appears nearby, which is due to the asymmetric stretching vibration of the carboxylate (-COO-); all are around 1014 cm⁻¹. -1 The absorption peaks appearing nearby are caused by CO stretching vibrations. The pectins obtained in Examples 4-8 and Comparative Example 2 have the same type of structural regions, particularly in the "fingerprint region" (1300-800 cm⁻¹). -1 The differences within this range indicate that pectin varies slightly in structure and monosaccharide composition. Figure 12 ).

[0122] (5) The molecular weight of the sample was determined by GPC gel permeation chromatography, and the results are shown in Table 2 and... Figure 13 .

[0123] Table 2. Weight-average molecular weight, number-average molecular weight, and polydispersity index of different pectin samples.

[0124] Pectin sample Steam explosion pressure / MPa <![CDATA[Weight-average molecular weight (M w )]]> <![CDATA[Number average molecular weight (M n )]]> <![CDATA[Polydispersity index (M w / M n )]]> Comparative Example 2 0.1 509132 359374 1.47 Example 4 0.3 679979 477961 1.42 Example 5 0.6 352856 306712 1.15 Example 6 0.9 483850 292675 1.65 Example 7 1.2 446816 343677 1.3

[0125] According to Table 2 and Figure 13 It can be seen that the molecular weight distribution of different pectin samples is uneven, exhibiting a broad distribution. It mainly consists of three peaks. The molecular weight of the pectin of this invention is mainly concentrated in the range of 352-679 kDa, accounting for 36.81% (1.2 MPa) to 91.46% (0.9 MPa) of the total molecules, respectively. It also contains some small molecule peaks in the range of 1.3-167 kDa, accounting for 1.51% (0.9 MPa) to 37.97% (1.2 MPa) of the total molecules, respectively. These are presumably small molecule proteins, soluble pigments, and inorganic salts remaining from the polysaccharide extraction process. Compared to Comparative Example 2, the molecular weight distribution of the pectin obtained in Examples 4-8 is more concentrated.

[0126] (6) Liquid chromatography was performed using a Shimadzu LC-2030C 3D PLUS system to determine the monosaccharide composition and pectin structure of the sample. The results are shown in Tables 3 and 4.

[0127] Table 3 Monosaccharide composition (molar percentage, %) of different pectin samples

[0128]

[0129] Table 4. Structural information of different pectin samples

[0130]

[0131] As shown in Tables 3 and 4, the different pectin samples are all typical RG-I type pectin, containing mainly monosaccharides such as glucose, fructose, arabinose, rhamnose, galacturonic acid, mannose, galactose, and xylose. The highest GalA molar percentage was 28.98% at 0.6 MPa, and the lowest was 10.83% at 1.2 MPa. The highest Ara molar percentage was 30.10% (0.9 MPa), and the lowest was 6.94% (1.2 MPa), while the Rha molar percentage ranged from 4.58% (1.2 MPa) to 9.86% (0.6 MPa). Pectin is generally considered to be mainly composed of HG and RG-I regions. The HG region is mainly composed of galacturonic acid, while the main chain of the RG-I region is composed of rhamnose and galactose. Therefore, the Rha / GalA ratio can be used to reflect the amount of RG-I region structure in pectin; the closer the ratio is to 1, the greater the proportion of RG-I region structure in the pectin. The (Ara+Gal) / Rha ratio reflects the branching degree of the RG-I region. The proportion of HG region in pectin ranges from 2.52% (1.5 MPa) to 19.12% (0.6 MPa), while the proportion of RG-I region ranges from 26.94% (1.2 MPa) to 67.34% (0.6 MPa), exhibiting typical characteristics of RG-I type pectin. The branching degree results show that pear pectin from various treatments has a good degree of branching. Compared with Comparative Example 2, the pectin obtained in Examples 4-8 has a reduced straight chain and an increased branching chain.

[0132] (7) In vitro cell experiments were conducted (Zhu Junhao. Structural characterization and immunomodulatory effects of extracellular polysaccharides from Ganoderma lucidum [D]. Chengdu University, 2021.). Blank culture medium was used as a blank control (BC), and lipopolysaccharide was used as a positive control (LPS). The effects of different concentrations of pectin (2, 4, 6, 8, 10 mg / mL) of Comparative Example 2 on the viability of RAW264.7 cells were determined. The results showed that the pectin obtained in Comparative Example 2 could increase the proliferation rate of RAW264.7 cells without toxic side effects. Figure 14After determining the optimal pectin concentration to be 8 mg / mL, the effects of the pectin obtained in Comparative Example 2 and Examples 4-7 on the anti-inflammatory activity of RAW264.7 cells were measured. The results showed that the secretion of TNF-α in RAW264.7 cells treated with pectin was significantly reduced compared to the LPS model group, and the decrease in TNF-α secretion was more significant in Examples 4-7 than in Comparative Example 2. Therefore, the pectin obtained in this invention possesses certain anti-inflammatory activity. Figure 15 Compared with the blank control (BC), IL-1β secretion increased significantly after LPS induction. However, IL-1β secretion decreased significantly in all pectin-treated groups compared to the LPS model group. The lowest IL-1β secretion was observed in the 0.9 MPa pectin-treated group (16.44 pg / mL), indicating a better anti-inflammatory effect. Figure 16 ).

[0133] Example 9

[0134] A method for extracting polyphenols from pear fruit by-products comprises the following steps:

[0135] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0136] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.6MPa, and the pressure holding time was 2min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0137] (3) Extraction of polyphenols: Accurately weigh 0.2g of pear pomace powder obtained in step (2), add the corresponding volume of eutectic solvent to the pear pomace powder according to the solid-liquid ratio of 1g:20mL, control the water content to 30%, perform ultrasonic extraction at room temperature for 40min at 360W, centrifuge at 7500r / min for 10min, take the supernatant to obtain polyphenol solution, and store it for later use.

[0138] The eutectic solvent is any one of the following: Chcl-CA solution, Chcl-MA solution, Chcl-Fru solution, Chcl-Xyl solution, Chcl-EA solution, and Chl-EtOH solution;

[0139] The Chcl-CA solution is composed of citric acid and choline chloride, wherein the molar ratio of citric acid to choline chloride is 2:1.

[0140] The Chcl-MA solution is composed of malic acid and choline chloride, wherein the molar ratio of malic acid to choline chloride is 2:1.

[0141] The Chcl-Fru solution consists of galactose and choline chloride, with a molar ratio of galactose to choline chloride of 2:1.

[0142] The Chcl-Xyl solution is composed of xylose and choline chloride, wherein the molar ratio of xylose to choline chloride is 2:1;

[0143] The Chcl-EA solution is composed of choline chloride and ethyl acetate, wherein the molar ratio of choline chloride to ethyl acetate is 1:2.

[0144] The Chcl-EtOH solution is composed of choline chloride and ethanol, wherein the molar ratio of choline chloride to ethanol is 1:2.

[0145] Test Example 5

[0146] The concentration of polyphenols in the polyphenol solutions extracted with different eutectic solvents in Example 9 was determined using the Folin-Ciocalteu colorimetric method. The results showed that the combination of ethanol and choline chloride had the highest extraction rate, reaching 5.53%, which was significantly higher than that of other eutectic solvents. Figure 17 ).

[0147] Example 10

[0148] A method for extracting polyphenols from pear fruit by-products comprises the following steps:

[0149] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0150] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.6MPa, and the pressure holding time was 2min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0151] (3) Extraction of polyphenols: Accurately weigh 0.2g of pear pomace powder obtained in step (2), add the corresponding volume of eutectic solvent composed of choline chloride and ethanol (molar ratio of choline chloride and ethanol (3:1, 2:1, 1:1, 1:2 or 1:3) to the pear pomace powder according to the solid-liquid ratio of 1g:20mL, control the water content to 30%, perform ultrasonic extraction at 360W for 40min at room temperature, centrifuge at 7500r / min for 10min, take the supernatant to obtain polyphenol solution, and store it for later use.

[0152] Test Example 6

[0153] The concentration of polyphenols in the polyphenol solutions extracted with different eutectic solvents in Example 10 was determined using the Folin-Ciocalteu colorimetric method. The results showed that the polyphenol extraction rate increased with the increase of the molar percentage of ethanol in the system, reaching a maximum of 5.32% at a ratio of 1:2, which was significantly higher than that of other treatments. Figure 18 ).

[0154] Example 11

[0155] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0156] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.6MPa, and the pressure holding time was 2min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0157] (3) Extraction of polyphenols: Accurately weigh 0.2g of pear pomace powder obtained in step (2), add a eutectic solvent composed of choline chloride and ethanol (molar ratio of choline chloride and ethanol 1:2) to the pear pomace powder according to a solid-liquid ratio of 1g:20mL, control the water content to 10%, 20%, 30%, 40%, 50% or 60%, perform ultrasonic extraction at 360W for 40min at room temperature, centrifuge at 7500r / min for 10min, take the supernatant to obtain polyphenol solution, and store it for later use.

[0158] Test Example 7

[0159] The concentration of polyphenols in different polyphenol solutions in Example 11 was determined using the Folin-Ciocalteu colorimetric method. The results showed that the polyphenol extraction rate first increased and then decreased with increasing water content, reaching its maximum at 50% water content (0.16%), which was significantly higher than other treatments. Figure 19 ).

[0160] Example 12

[0161] A method for extracting polyphenols from pear fruit by-products comprises the following steps:

[0162] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0163] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.6MPa, and the pressure holding time was 2min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0164] (3) Extraction of polyphenols: Accurately weigh 0.2g of pear pomace powder obtained in step (2), and add a eutectic solvent composed of choline chloride and ethanol (molar ratio of choline chloride and ethanol 1:2) to the pear pomace powder according to different solid-liquid ratios (1:10, 1:15, 1:20, 1:25, 1:30, 1:35, unit g:mL), control the water content to 50%, perform ultrasonic extraction at 360W for 40min at room temperature, centrifuge at 7500r / min for 10min, take the supernatant to obtain polyphenol solution, and store it for later use.

[0165] Test Example 8

[0166] The concentration of polyphenols in different polyphenol solutions in Example 12 was determined using the Folin-Ciocalteu colorimetric method. The results showed that the polyphenol extraction rate first increased and then decreased with decreasing solid-liquid ratio, ranging from 0.91% (1:10) to 2.76% (1:30). The extraction rate was highest at a solid-liquid ratio of 1:30, reaching 2.76%, which was significantly higher than other treatments. Figure 20 ).

[0167] Example 13

[0168] A method for extracting polyphenols from pear fruit by-products comprises the following steps:

[0169] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0170] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.6MPa, and the pressure holding time was 2min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0171] (3) Extraction of polyphenols: Accurately weigh 0.2g of pear pomace powder obtained in step (2), add a eutectic solvent composed of choline chloride and ethanol (molar ratio of choline chloride and ethanol 1:2) to the pear pomace powder according to a solid-liquid ratio of 1g:30mL, control the water content to 50%, perform ultrasonic extraction at room temperature for a certain time (20, 30, 40, 50, 60min), centrifuge at 7500r / min for 10min, take the supernatant to obtain polyphenol solution, and store it for later use.

[0172] Test Example 9

[0173] The concentration of polyphenols in different polyphenol solutions in Example 13 was determined using the Folin-Ciocalteu colorimetric method. The results showed that the ultrasonic extraction time affected the polyphenol extraction rate, with the highest extraction rate (8.61%) observed at an extraction time of 40 min, significantly higher than other times. Figure 21 ).

[0174] Example 14

[0175] A method for extracting polyphenols from pear fruit by-products comprises the following steps:

[0176] (1) Pretreatment: Pear fruit by-products were crushed for 2 minutes using a wall-breaking machine to obtain pear residue;

[0177] (2) Steam explosion: The pear residue was placed in the high-pressure tank of the steam explosion test bench. Saturated steam was used as the medium. The temperature of the saturated steam was 180℃~230℃, the steam explosion pressure was 0.6MPa, and the pressure holding time was 2min. The high temperature and high pressure valve was quickly opened to release the material into the storage tank. The pear residue in the storage tank was collected and dried to constant weight. Then, the dried pear residue was crushed for 2min using a wall-breaking machine to obtain pear residue powder for later use.

[0178] (3) Extraction of polyphenols: Accurately weigh 0.2g of pear pomace powder obtained in step (2), add a eutectic solvent composed of choline chloride and ethanol (molar ratio of choline chloride and ethanol 1:2) to the pear pomace powder according to a solid-liquid ratio of 1g:30mL, control the water content to 50%, perform ultrasonic extraction at 360W for 40min at room temperature, centrifuge at 7500r / min for 10min, take the supernatant to obtain polyphenol solution, and determine the polyphenol concentration to be 4.14±0.08mg / mL by the Folin-Ciocalteu colorimetric method.

[0179] Test Case 10

[0180] The DPPH radical scavenging capacity, ABTS radical scavenging capacity, and total antioxidant capacity of the polyphenol solution obtained in Example 14 were tested using Solarbio DPPH radical scavenging kit, ABTS radical scavenging capacity kit, and total antioxidant capacity kit, respectively. The results are as follows: Figure 22 As shown.

[0181] according to Figure 22 It can be seen that the scavenging rate of ABTS free radicals increases with increasing polyphenol concentration, indicating that the ability of polyphenols to scavenge ABTS free radicals is concentration-dependent. The DPPH free radical scavenging rate and total antioxidant capacity show a trend of first increasing and then decreasing. The polyphenol concentration of 35 mg / mL shows the best scavenging effect on DPPH free radicals, with a scavenging rate of 45.16%. The decrease may be due to the degradation or conversion of free phenols into other components in the system. The highest ABTS free radical scavenging rate can reach 38.82%, and the total antioxidant capacity of polyphenols indicates that the highest iron ion reducing capacity of polyphenols can reach 33.32 μmol / g.

[0182] As can be seen from the above, the method provided by this invention is simple and can efficiently and quickly extract cellulose, pectin and polyphenols from pear fruit by-products, shortening the production cycle of pear fruit cellulose, pectin and polyphenols, with high extraction efficiency, laying the foundation for the further development and utilization of pear pomace cellulose, pectin and polyphenols.

[0183] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for extracting cellulose from pear fruit by-products, characterized in that, Includes the following steps: The pear fruit by-products were subjected to steam explosion treatment and pulverization treatment in sequence to obtain pear residue powder; the steam explosion pressure of the steam explosion treatment was 0.3~0.9 MPa; The cellulose extraction steps include: first extraction of the pear pomace powder using an alkaline solution, collecting the filter residue after vacuum filtration; bleaching the filter residue using sodium hypochlorite, collecting the filter residue after vacuum filtration, and drying it to obtain pear crude cellulose. The alkaline solution includes a sodium hydroxide solution with a mass concentration of 7.5-15 wt%. The steam explosion treatment time is 1~5 min; the medium for the steam explosion treatment is saturated steam; the temperature of the saturated steam is 160~230℃; After obtaining the crude cellulose from the pear fruit, the process further includes: mixing the crude cellulose from the pear fruit with the purification solution, reacting at 90~120℃ for 20~60 min, collecting the filter residue after vacuum filtration, and drying to obtain purified pear fruit cellulose. The purification solution comprises 70-80 wt.% acetic acid solution and 65-70 wt.% nitric acid solution; the volume ratio of the acetic acid solution to the nitric acid solution is (1-10):(1-30).

2. The method according to claim 1, characterized in that, The first extraction was performed at a temperature of 75-90℃ for 2-4 hours. The mass-to-volume ratio of the pear residue powder to the alkaline solution is 0.5~2g:10~50mL.

3. The method according to claim 1, characterized in that, The bleaching process is performed three times, with each bleaching process conducted at a temperature of 75-90°C for 45-70 minutes.

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