Gradient preparation device and process of litchi pomace polyphenol and dietary fiber

Abstract

The invention discloses an echelon preparation device and process of litchi pomace polyphenol and dietary fiber, and belongs to the technical field of agricultural waste resource utilization. The device comprises an extraction tank, a column chromatography module, a screw lifter, an ultrasonic probe and a liquid outlet, the process specifically comprises the following steps: (1) adding litchi pomace and choline chloride-glycerol into an extraction tank, extracting free phenol under the assistance of an ultrasonic probe, synchronously adsorbing and separating the free phenol by using a column chromatography module, and recovering the choline chloride-glycerol; and (2) adding choline chloride-malonic acid into the extraction tank, extracting bound phenols and soluble dietary fibers in the residues, carrying out alcohol precipitation treatment on a supernatant solution to respectively obtain bound phenols and soluble dietary fibers, and taking residual residues as insoluble dietary fibers. By designing an extraction and purification integrated device and designing a deep eutectic solvent (DES) choline chloride-glycerol and choline chloride-malonic acid in a targeted manner, efficient and echelon preparation of polyphenols and dietary fibers in litchi pomace is realized.

Description

Technical Field

[0001] This invention relates to the field of agricultural waste resource utilization technology, and more specifically to a tiered preparation device and process for litchi pomace polyphenols and dietary fiber. Background Technology

[0002] Lychee, an important category of tropical fruits, generates a large amount of pomace during processing. Lychee pomace is rich in functional components such as polyphenols (free and bound phenols) and dietary fiber (soluble and insoluble). Polyphenols possess various physiological activities, including antioxidant, anti-inflammatory, and cardiovascular disease prevention properties, while dietary fiber plays a vital role in promoting gut health and lowering cholesterol. However, currently, most lychee pomace is discarded, resulting in a significant waste of resources. Therefore, achieving efficient separation, activity preservation, and tiered utilization of multiple components in pomace is a core challenge in the field of agricultural waste resource utilization.

[0003] Traditional methods for extracting polyphenols and dietary fiber have many drawbacks. For example, in polyphenol extraction, commonly used organic solvent extraction methods, such as ethanol extraction, not only require large amounts of organic solvents and have limited extraction rates, but also leave organic solvent residues, posing a significant environmental hazard. Furthermore, traditional methods struggle to selectively separate free and bound phenols. In dietary fiber extraction, chemical methods easily damage the structure of dietary fiber, affecting its functional properties, and the extraction process is complex and costly. In addition, traditional extraction equipment (such as stirred tanks and fixed-bed chromatography columns) has limited functionality and cannot achieve integrated extraction-purification-solvent recovery operations. For instance, fixed-bed chromatography columns require offline resin loading and cannot dynamically adjust the column height to accommodate different feed-liquid ratios.

[0004] Therefore, how to develop an efficient, environmentally friendly device and process that can achieve the stepwise preparation of multiple components from litchi pomace is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a stepwise preparation device and process for litchi pomace polyphenols and dietary fiber, so as to solve the problems of low extraction efficiency, large loss of activity and complex process of litchi pomace components in the prior art, and realize the high-value comprehensive utilization of litchi pomace.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A stepwise preparation device for polyphenols and dietary fiber from litchi pomace includes an extraction tank, a column chromatography module, a screw lifter, an ultrasonic probe, and a drain outlet.

[0008] The column chromatography module is located inside the extraction tank and consists of two parallel perforated sieve plates and intermediate packing material.

[0009] The screw lifter is connected to the upper sieve plate of the column chromatography module and penetrates the top cover of the extraction tank, and is used to control the lifting of the column chromatography module;

[0010] The ultrasonic probe is arranged on the inner wall of the bottom of the extraction tank, and is used to assist extraction;

[0011] The liquid discharge port is arranged on the bottom of the extraction tank, and is used to discharge the extraction liquid and the residue.

[0012] Further, the intermediate filler of the column chromatography module is LX-17 type macroporous adsorption resin, which is used for specific adsorption of free phenol.

[0013] Further, the screw lifter is connected to the upper sieve plate of the column chromatography module through a screw rod transmission mechanism, and is used to realize the lifting adjustment of the column chromatography module in the extraction tank, so as to adapt to different fruit residue filling amounts.

[0014] Further, the power of the ultrasonic probe is 200-600 W, which is used to strengthen the mass transfer efficiency of deep eutectic solvent (DES) and litchi pomace.

[0015] A gradient preparation process for litchi pomace polyphenols and dietary fiber, using the above device, specifically comprising the following steps:

[0016] (1) adding litchi pomace and choline chloride-glycerol into the extraction tank, assisting extraction of free phenol through the ultrasonic probe, synchronously using the column chromatography module to adsorb and separate free phenol, and recovering choline chloride-glycerol for preparing choline chloride-malonate;

[0017] (2) adding choline chloride-malonate into the extraction tank to extract bound phenol and soluble dietary fiber from the residue, and the supernatant solution is treated by alcohol precipitation to obtain bound phenol and soluble dietary fiber, respectively, and the remaining residue is insoluble dietary fiber.

[0018] Further, in the step (1), the mass ratio of litchi pomace to choline chloride-glycerol is 1:(20-30); and the molar ratio of choline chloride to glycerol in choline chloride-glycerol is 1:(2-4).

[0019] Further, in the step (1), the extraction temperature is 40-60℃, the ultrasonic power is 400-600 W, and the time is 20-40 min; the adsorption time is 40-60 min, and the pH is 3-5.

[0020] Further, in step (1) above, after adsorption, choline chloride-glycerol is released through the drain port and 60% (v / v) ethanol is added for elution under ultrasonic elution at 200-400W for 3-5 hours to obtain free phenol eluent; the recovered choline chloride-glycerol is then distilled under reduced pressure at 80-90℃ and 0.08-0.09MPa for 1-2 hours, and then choline chloride is recovered by crystallization with 3-5 times the volume of anhydrous ethanol. The recovered choline chloride is used to prepare choline chloride-malonic acid.

[0021] Furthermore, in step (2) above, the mass ratio of the residue to choline chloride-malonic acid is 1:(20-30); the molar ratio of choline chloride to malonic acid in choline chloride-malonic acid is 1:(1-2).

[0022] Furthermore, in step (2) above, the extraction temperature is 60-80℃, the ultrasonic power is 400-600W, and the time is 2-3h; the alcohol precipitation treatment is as follows: anhydrous ethanol is added to the supernatant solution to make its final concentration 70%-80% (v / v), and it is allowed to stand for 12-24h. The phenol supernatant solution and soluble dietary fiber precipitate are obtained by centrifugation.

[0023] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. Based on the different main monomers of free polyphenols (mainly proanthocyanidins B1, catechins, gallic acid, etc.) and bound polyphenols (mainly quercetin-3-O-rutin-(1→2)-O-rhamnoside, proanthocyanidins B2, hesperidin, epicatechin, etc.) in litchi pomace, targeted DES was designed to achieve the directional extraction of free phenols and the simultaneous preparation of bound phenols and soluble dietary fiber.

[0025] 2. Ultrasonic-assisted chromatography synergistically enhances mass transfer rate and significantly improves extraction efficiency;

[0026] 3. Step-by-step preparation and full utilization of resources: Through the rational design of process steps, the step-by-step preparation of free phenols, bound phenols, soluble dietary fiber and insoluble dietary fiber in litchi pomace was realized, which maximized the utilization of various components in the pomace, improved resource utilization rate and reduced waste generation.

[0027] 4. This invention discloses a stepwise preparation technology for polyphenols (free phenols and bound phenols) and dietary fiber (soluble and insoluble) from litchi pomace based on DES targeted design and an integrated extraction and purification device. Through the synergistic process of DES targeted design, ultrasonic-assisted extraction and column chromatography separation, it realizes the efficient graded extraction and resource recycling of high value-added components in agricultural waste, and is applicable to the comprehensive utilization of agricultural product processing by-products.

[0028] 5. This invention achieves its purpose through targeted DES design and an integrated extraction and purification device:

[0029] 1) Targeted DES tiered extraction

[0030] Free phenols were specifically extracted using choline chloride-glycerol (hydrogen bond donor / acceptor molar ratio 1:2-1:4), utilizing the hydrogen bonding between the -OH group of glycerol and the phenolic hydroxyl group (bond energy 20-30 kJ / mol) to achieve efficient dissolution. Subsequently, choline chloride-malonic acid (molar ratio 1:1.0-1:2) was introduced, and the acidic environment of malonic acid (pH 2-3) broke the ester bonds between dietary fiber and bound phenols, simultaneously extracting both bound phenols and soluble dietary fiber.

[0031] 2) Ultrasonic extraction-chromatography synergistic enhancement of mass transfer

[0032] Ultrasonic enhancement of DES cavitation and disruption of fruit pomace cell walls, while column chromatography resin adsorbs dissolved free phenols, thus reducing the concentration of free phenols in the solution. The concentration difference drives the dissolution of more free phenols, forming a synergistic effect of "ultrasonic dissolution promotion + chromatographic pull" to improve mass transfer efficiency.

[0033] 3) Solvent recycling and component separation: Choline chloride-glycerol extracted from free phenol is recovered by vacuum distillation to prepare choline chloride-malonic acid, forming a closed-loop solvent recycling; free phenol, bound phenol, soluble dietary fiber and insoluble dietary fiber are separated in stages by column chromatography and alcohol precipitation, realizing the full utilization of fruit pomace components.

[0034] 6. The synergistic innovation of targeted solvent design, ultrasonic enhanced mass transfer, and dynamic chromatography separation in this invention breaks through the technical bottlenecks of low extraction efficiency, large activity loss, and serious solvent waste in traditional methods. It achieves high extraction rate of free phenols, high retention rate of polyphenol antioxidant activity, low solvent recycling and consumption, and small equipment footprint for simultaneous extraction and separation. It provides a green, efficient, and economical solution for the high-value utilization of agricultural waste.

[0035] 7. This invention achieves efficient and stepwise preparation of polyphenols and dietary fiber from litchi pomace by designing an integrated extraction and purification device and targeting the deep eutectic solvent (DES) choline chloride-glycerol and choline chloride-malonic acid. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of the stepwise preparation device for litchi pomace polyphenols and dietary fiber of the present invention. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0039] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0043] This invention discloses a stepwise preparation device for lychee pomace polyphenols and dietary fiber, such as... Figure 1 As shown, it includes an extraction tank, a column chromatography module, a screw lifter, an ultrasonic probe, and a drain port;

[0044] The column chromatography module is located inside the extraction tank and consists of two parallel perforated sieve plates and intermediate packing material.

[0045] The screw lifter is connected to the upper sieve plate of the column chromatography module and passes through the top cover of the extraction tank, and is used to control the lifting and lowering of the column chromatography module;

[0046] An ultrasonic probe is installed on the bottom inner wall of the extraction vessel to assist in extraction;

[0047] The drain outlet is located at the bottom of the extraction tank to drain the extract and residue;

[0048] The intermediate packing material of the column chromatography module is LX-17 macroporous adsorption resin, which is used for the specific adsorption of free phenols.

[0049] The screw lifter is connected to the upper screen plate of the column chromatography module through a screw drive mechanism, which is used to realize the lifting and adjustment of the column chromatography module in the extraction tank to adapt to different pomace loading amounts;

[0050] The ultrasonic probe has a power of 200-600W and is used to enhance the mass transfer efficiency between the deep eutectic solvent (DES) and litchi pomace.

[0051] Example 1

[0052] The step-by-step preparation process of lychee pomace polyphenols and dietary fiber specifically includes the following steps:

[0053] (1) Place the litchi fruit residue in an extraction tank, add targeted choline chloride-glycerol (molar ratio 1:3) at a material-liquid ratio of 1:25, and extract free phenols at 50℃ and 500W ultrasonic assistance for 30 minutes.

[0054] (2) During the extraction of free phenol, the column chromatography module was placed in the extract solution to adsorb free phenol for 50 min at pH 3. Choline chloride-glycerol was released through the drain port and 60% ethanol was added to cover the column chromatography module. The module was ultrasonically desorbed at 300W for 4 h to obtain free phenol eluent.

[0055] (3) The released choline chloride-glycerol was distilled under reduced pressure at 85°C and 0.09 MPa for 1.5 h, and then choline chloride was recovered by crystallization with 4 times the volume of ethanol for the preparation of choline chloride-malonic acid.

[0056] (4) Add choline chloride-malonic acid (molar ratio 1:1.5) to the extraction tank at a material-liquid ratio of 1:25. Extract the bound phenols and soluble dietary fiber from the residue at 70℃ and 500W ultrasonic assistance for 2.5h. Add anhydrous ethanol to the supernatant to make the final concentration 75% (v / v), let stand for 18h, and obtain the bound phenols (supernatant) and soluble dietary fiber (precipitate) by centrifugation. The remaining residue is insoluble dietary fiber.

[0057] Example 2

[0058] The step-by-step preparation process of lychee pomace polyphenols and dietary fiber specifically includes the following steps:

[0059] (1) Place the litchi fruit residue in an extraction tank, add targeted choline chloride-glycerol (molar ratio 1:2) at a material-liquid ratio of 1:20, and extract free phenols at 40℃ and 400W ultrasonic assistance for 40 min.

[0060] (2) During the extraction of free phenol, the column chromatography module was placed in the extract solution to adsorb free phenol for 40 min at pH 3. Choline chloride-glycerol was released through the drain port and 60% ethanol was added to cover the column chromatography module. The module was ultrasonically desorbed at 200W for 5 h to obtain free phenol eluent.

[0061] (3) The released choline chloride-glycerol was distilled under reduced pressure at 80°C and 0.08 MPa for 2 hours, and then choline chloride was recovered by crystallization with 3 times the volume of ethanol for the preparation of choline chloride-malonic acid.

[0062] (4) Add choline chloride-malonic acid (molar ratio 1:1) to the extraction tank at a material-liquid ratio of 1:30. Extract the bound phenols and soluble dietary fiber from the residue at 60℃ and 600W ultrasonic assistance for 2 hours. Add anhydrous ethanol to the supernatant to make the final concentration 70% (v / v). Let it stand for 12 hours. Separate the bound phenols (supernatant) and soluble dietary fiber (precipitate) by centrifugation. The remaining residue is insoluble dietary fiber.

[0063] Example 3

[0064] The step-by-step preparation process of lychee pomace polyphenols and dietary fiber specifically includes the following steps:

[0065] (1) Place the litchi pomace in an extraction tank and add targeted choline chloride-glycerol (molar ratio 1:4) at a material-liquid ratio of 1:30. Extract free phenols at 60℃ and 600W ultrasonic assistance for 20 minutes.

[0066] (2) During the extraction of free phenol, the column chromatography module was placed in the extract solution to adsorb free phenol for 60 min at pH 5. Choline chloride-glycerol was released through the drain port and 60% ethanol was added to cover the column chromatography module. The module was ultrasonically desorbed at 400W for 3 h to obtain free phenol eluent.

[0067] (3) The released choline chloride-glycerol was distilled under reduced pressure at 90℃ and 0.09MPa for 1h, and then choline chloride was recovered by crystallization with 5 times the volume of ethanol for the preparation of choline chloride-malonic acid.

[0068] (4) Add choline chloride-malonic acid (molar ratio 1:2) to the extraction tank at a material-liquid ratio of 1:20. Extract the bound phenols and soluble dietary fiber from the residue at 80℃ and 400W ultrasonic assistance for 3 hours. Add anhydrous ethanol to the supernatant to make the final concentration 80% (v / v). Let it stand for 24 hours. Separate the bound phenols (supernatant) and soluble dietary fiber (precipitate) by centrifugation. The remaining residue is insoluble dietary fiber.

[0069] Comparative Example 1

[0070] The only difference from Example 1 is that "simultaneously during the free phenol extraction process" is replaced with "after the free phenol extraction is completed," specifically including the following steps:

[0071] (1) Place the litchi fruit residue in an extraction tank, add targeted choline chloride-glycerol (molar ratio 1:3) at a material-liquid ratio of 1:25, and extract free phenols at 50℃ and 500W ultrasonic assistance for 30 minutes.

[0072] (2) After the free phenol extraction is completed, the column chromatography module is placed in the extract to adsorb the free phenol for 50 min at pH 3. The choline chloride-glycerol is released through the drain port and 60% ethanol is added to cover the column chromatography module. The module is then ultrasonically desorbed at 300W to obtain the free phenol eluent.

[0073] (3) The released choline chloride-glycerol was distilled under reduced pressure at 85°C and 0.09 MPa for 1.5 h, and then crystallized with 4 times the volume of ethanol to recover choline chloride for the preparation of choline chloride-malonic acid.

[0074] (4) Add the prepared choline chloride-malonic acid (molar ratio 1:1.5) to the extraction tank at a material-liquid ratio of 1:25. Extract the bound phenols and soluble dietary fiber from the residue at 70℃ and 500W ultrasonic assistance for 2.5h. Add anhydrous ethanol to the supernatant to make the final concentration 75% (v / v), let stand for 18h, and obtain the bound phenols (supernatant) and soluble dietary fiber (precipitate) by centrifugation.

[0075] Comparative Example 2

[0076] The only difference from Example 1 is that "choline chloride-glycerol" is replaced with "choline chloride-urea", specifically including the following steps:

[0077] (1) Place the litchi fruit residue in an extraction tank, add choline chloride-urea (molar ratio 1:3) at a material-liquid ratio of 1:25, and extract free phenols at 50℃ and 500W ultrasonic assistance for 30 minutes.

[0078] (2) During the extraction of free phenol, the column chromatography module was placed in the extract to adsorb free phenol for 50 min at pH 3. 60% ethanol was added to cover the column chromatography module and the module was ultrasonically desorbed at 300W for 4 h to obtain the free phenol eluent.

[0079] (3) Add choline chloride-malonic acid (molar ratio 1:1.5) to the extraction tank at a material-liquid ratio of 1:25. Extract the bound phenols and soluble dietary fiber from the residue at 70℃ and 500W ultrasonic assistance for 2.5h. Add anhydrous ethanol to the supernatant to make the final concentration 75% (v / v), let stand for 18h, and obtain the bound phenols (supernatant) and soluble dietary fiber (precipitate) by centrifugation. The remaining residue is insoluble dietary fiber.

[0080] Comparative Example 3

[0081] The only difference from Example 1 is that "choline chloride-malonic acid" is replaced with "choline chloride-ethylene glycol", specifically including the following steps:

[0082] (1) Place the litchi fruit residue in an extraction tank, add targeted choline chloride-glycerol (molar ratio 1:3) at a material-liquid ratio of 1:25, and extract free phenols at 50℃ and 500W ultrasonic assistance for 30 minutes.

[0083] (2) During the extraction of free phenol, the column chromatography module was placed in the extract solution to adsorb free phenol for 50 min at pH 3. Choline chloride-glycerol was released through the drain port and 60% ethanol was added to cover the column chromatography module. The module was ultrasonically desorbed at 300W for 4 h to obtain free phenol eluent.

[0084] (3) The released choline chloride-glycerol was distilled under reduced pressure at 85°C and 0.09 MPa for 1.5 h, and then crystallized with 4 times the volume of ethanol to recover choline chloride and prepare choline chloride-ethylene glycol.

[0085] (4) Add choline chloride-ethylene glycol (molar ratio 1:1.5) to the extraction tank at a material-liquid ratio of 1:25. Extract the bound phenols and soluble dietary fiber from the residue at 70℃ and 500W ultrasonic assistance for 2.5h. Add anhydrous ethanol to the supernatant to make the final concentration 75% (v / v), let stand for 18h, and obtain the bound phenols (supernatant) and soluble dietary fiber (precipitate) by centrifugation. The remaining residue is insoluble dietary fiber.

[0086] Comparative Example 4

[0087] The only difference from Example 1 is that the traditional "organic solvent + alkaline hydrolysis" extraction method is used, which specifically includes the following steps:

[0088] (1) Place the litchi pomace in an extraction tank, add 70% acidified ethanol (adjust pH to 6.0 with 1 mol / L HCl) at a material-to-liquid ratio of 1:25, and extract for 30 min at 50℃ and 500W ultrasonic assistance. The supernatant obtained by centrifugation is the crude extract of free phenol.

[0089] (2) Add LX-17 macroporous resin to the crude free phenol extract to adsorb the free phenol for 50 min at pH 3. After adsorption, transfer the macroporous resin to 60% ethanol and sonicate at 300W for 4 h to obtain the free phenol eluent.

[0090] (3) Add 4 mol / L NaOH to the extraction tank at a material-to-liquid ratio of 1:2, perform alkaline hydrolysis for 4 hours, add concentrated hydrochloric acid to adjust the pH to 7, add anhydrous ethanol to the supernatant to make the final concentration 75% (v / v), let stand for 18 hours, and obtain bound phenol (supernatant) and soluble dietary fiber (precipitate) by centrifugation. The remaining residue is insoluble dietary fiber.

[0091] Comparative Example 5

[0092] The only difference from Example 1 is that the traditional "enzymatic hydrolysis + alkaline hydrolysis" extraction method is used, which specifically includes the following steps:

[0093] (1) Place the litchi pomace in an extraction tank, add 0.02% (w / v) of high-temperature amylase at a material-to-liquid ratio of 1:25, and hydrolyze at 95℃ for 10 min; then add 0.02% (w / v) of saccharifying enzyme and hydrolyze at 60℃ for 30 min; then add 0.02% (w / v) of yeast and ferment at 28℃ for 48 h, and inactivate at 95℃ for 10 min; after cooling, add 0.02% (w / v) of alkaline protease, adjust the pH to 10, and continue hydrolysis at 60℃ for 2 h; the supernatant obtained by centrifugation is the crude free phenol extract;

[0094] (2) Add LX-17 macroporous resin to the crude free phenol extract to adsorb the free phenol for 50 min at pH 3. After adsorption, transfer the macroporous resin to 60% ethanol and sonicate at 300W for 4 h to obtain the free phenol eluent.

[0095] (3) Add 4 mol / L NaOH to the extraction tank at a material-to-liquid ratio of 1:2, perform alkaline hydrolysis for 4 hours, add concentrated hydrochloric acid to adjust the pH to 7, add anhydrous ethanol to the supernatant to make the final concentration 75% (v / v), let stand for 18 hours, and obtain bound phenol (supernatant) and soluble dietary fiber (precipitate) by centrifugation. The remaining residue is insoluble dietary fiber.

[0096] Performance testing

[0097] 1. The yield, purity, and activity of free polyphenols, bound polyphenols, soluble dietary fiber, and insoluble dietary fiber in litchi pomace of Examples 1-3 and Comparative Examples 1-5 were determined.

[0098] The results are shown in Table 1-3.

[0099] Table 1. Effects of different preparation methods on the yield of various components of litchi pomace in Examples 1-3 and Comparative Examples 1-5.

[0100]

[0101] Table 2. Effects of different preparation methods on the purity of various components of litchi pomace in Examples 1-3 and Comparative Examples 1-5.

[0102]

[0103] As shown in Tables 1 and 2, compared with Comparative Examples 1-2, the yield of free phenol and the purity of bound phenol and insoluble dietary fiber in Examples 1-3 were significantly improved. This indicates that the present invention achieves simultaneous extraction and purification, and that the specific DES can promote the dissolution of free phenol and improve its yield. In contrast, the stepwise extraction (Comparative Example 1) or other non-specific DES (Comparative Example 2) affects the dissolution of free phenol, causing it to remain in the matrix, thereby affecting the purity of the subsequent bound phenol and insoluble dietary fiber.

[0104] Compared to Comparative Example 3, the yield and purity of bound phenols and soluble dietary fiber, as well as the purity of insoluble dietary fiber, were significantly improved in Examples 1-3, while the yield of insoluble dietary fiber was significantly reduced. This indicates that different DESs have a significant impact on the extraction effect of bound phenols and soluble dietary fiber. It is possible that choline chloride-malonic acid can target and catalyze the ester bond cleavage of bound phenols and dietary fiber, and at the same time destroy the aggregate structure of dietary fiber through strong hydrogen bonds, achieving simultaneous "release of bound phenols → dissolution of soluble fiber". This significantly improves the extraction yield compared to conventional DES choline chloride-ethylene glycol extraction, thereby reducing the content of bound phenols and soluble dietary fiber in insoluble dietary fiber and improving the purity of each component.

[0105] Compared to traditional extraction methods using organic solvents and alkaline hydrolysis (Comparative Example 4) and enzymatic hydrolysis and alkaline hydrolysis (Comparative Example 5), the yields and purity of free phenols, bound phenols, and soluble dietary fiber, as well as the purity of insoluble dietary fiber, were significantly improved in Examples 1-3. This indicates that compared to traditional solvent extraction, enzymatic hydrolysis, and alkaline hydrolysis, the DES extraction method of this invention enhances solubility selectivity through targeted hydrogen bonding and reduces phenol loss under mild conditions, achieving highly efficient extraction of free and bound phenols. A possible reason is that free phenol molecules (such as catechins and proanthocyanidins) contain multiple phenolic hydroxyl groups. In choline chloride-glycerol DES, the hydroxyl groups of glycerol can form strong hydrogen bonds with the phenolic hydroxyl groups, selectively dissolving free phenols through the "like dissolves like" principle and avoiding non-specific binding with the fruit pomace matrix (such as cellulose and protein). In contrast, solvent methods (such as ethanol) rely on polar dissolution and have low selectivity for free phenols (easily dissolving impurities such as polysaccharides simultaneously, leading to the encapsulation and loss of phenols). Simultaneously, the bound phenols are linked to dietary fiber via ester / ether bonds. The weakly acidic environment of choline chloride-malonic acid DES catalyzes the ester bond cleavage, while the carboxyl group of malonic acid forms hydrogen bonds with the hydroxyl group of dietary fiber, promoting the release and dissolution of the bound phenols. In contrast, although alkaline hydrolysis can break ester bonds, the strong alkalinity leads to the oxidative degradation of some bound phenols. Moreover, compared to enzymatic extraction, the method of this invention can significantly shorten the total extraction time and improve efficiency.

[0106] Table 3. Effects of different preparation methods on the activity of various components in litchi pomace.

[0107]

[0108]

[0109] As shown in Table 3, compared with Comparative Examples 1, 2, 4, and 5, the antioxidant activity of free phenols in Examples 1-3 was significantly improved, indicating that whether extraction and purification are carried out simultaneously, the choice of DES extraction solvent, and the extraction method all have a significant impact on the activity of free phenols.

[0110] Compared with Comparative Examples 3-5, the antioxidant activity of bound phenols and the water retention and oil holding capacity of soluble dietary fiber in Examples 1-3 were significantly improved, indicating that the choice of DES solvent and extraction method for bound phenols and soluble dietary fiber have a significant impact on their activity.

[0111] Compared with Comparative Examples 1-5, the cholesterol adsorption capacity of insoluble dietary fiber in Examples 1-3 was significantly improved, indicating that whether extraction and purification are carried out simultaneously, the choice of free phenols, bound phenols and DES extraction solvent for soluble dietary fiber, and the extraction method all have a significant impact on the activity of insoluble dietary fiber.

[0112] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stepwise preparation device for litchi pomace polyphenols and dietary fiber, characterized in that, Includes extraction tank, column chromatography module, screw lifter, ultrasonic probe and drain port; The column chromatography module is located inside the extraction vessel and consists of two parallel perforated sieve plates and intermediate packing material. The screw lifter is connected to the upper sieve plate of the column chromatography module and passes through the top cover of the extraction tank, and is used to control the lifting and lowering of the column chromatography module; The ultrasonic probe is installed on the bottom inner wall of the extraction vessel to assist in extraction; The drain outlet is located at the bottom of the extraction tank and is used to discharge the extract and residue.

2. The stepwise preparation device for litchi pomace polyphenols and dietary fiber according to claim 1, characterized in that, The intermediate packing material of the column chromatography module is LX-17 macroporous adsorption resin, which is used for the specific adsorption of free phenols.

3. The stepwise preparation apparatus for litchi pomace polyphenols and dietary fiber according to claim 1, characterized in that, The screw lifter is connected to the upper screen plate of the column chromatography module through a lead screw drive mechanism, which is used to realize the lifting and adjustment of the column chromatography module in the extraction tank to adapt to different pomace loading amounts.

4. The stepwise preparation device for litchi pomace polyphenols and dietary fiber according to claim 1, characterized in that, The ultrasonic probe has a power of 200-600W and is used to enhance the mass transfer efficiency between DES and litchi pomace.

5. A step-by-step preparation process for lychee pomace polyphenols and dietary fiber, characterized in that, The apparatus described in any one of claims 1-4 specifically includes the following steps: (1) Add litchi pomace and choline chloride-glycerol into the extraction tank, extract free phenol with the aid of an ultrasonic probe, and simultaneously use a column chromatography module to adsorb and separate free phenol, and recover choline chloride-glycerol for the preparation of choline chloride-malonic acid; (2) Add choline chloride-malonic acid to the extraction tank to extract the bound phenols and soluble dietary fiber from the residue. The supernatant solution is treated with alcohol precipitation to obtain bound phenols and soluble dietary fiber respectively. The remaining residue is insoluble dietary fiber.

6. The step-by-step preparation process of litchi pomace polyphenols and dietary fiber according to claim 5, characterized in that, In step (1), the mass ratio of litchi pomace to choline chloride-glycerol is 1:(20-30); the molar ratio of choline chloride to glycerol in the choline chloride-glycerol is 1:(2-4).

7. The step-by-step preparation process of litchi pomace polyphenols and dietary fiber according to claim 5, characterized in that, In step (1), the extraction temperature is 40-60℃, the ultrasonic power is 400-600W, and the time is 20-40min; the adsorption time is 40-60min, and the pH is 3-5.

8. The step-by-step preparation process of litchi pomace polyphenols and dietary fiber according to claim 5, characterized in that, In step (1), after adsorption, choline chloride-glycerol is released through the drain port and 60% ethanol is added for desorption. The conditions are ultrasonic elution at 200-400W for 3-5 hours to obtain free phenol eluent. The recovered choline chloride-glycerol is then distilled under reduced pressure at 80-90℃ and 0.08-0.09MPa for 1-2 hours. Then, choline chloride is recovered by crystallization with 3-5 times the volume of anhydrous ethanol. The recovered choline chloride is used to prepare choline chloride-malonic acid.

9. The step-by-step preparation process of litchi pomace polyphenols and dietary fiber according to claim 5, characterized in that, In step (2), the mass ratio of the residue to choline chloride-malonic acid is 1:(20-30); the molar ratio of choline chloride to malonic acid in the choline chloride-malonic acid is 1:(1-2).

10. The step-by-step preparation process of litchi pomace polyphenols and dietary fiber according to claim 5, characterized in that, In step (2), the extraction temperature is 60-80℃, the ultrasonic power is 400-600W, and the time is 2-3h; the alcohol precipitation treatment is as follows: anhydrous ethanol is added to the supernatant solution to make its final concentration 70%-80%, and it is allowed to stand for 12-24h. The phenol supernatant solution and soluble dietary fiber precipitate are obtained by centrifugation.

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