A method for preparing coffee fruit peel extract

Abstract

This application relates to a method for preparing coffee fruit peel extract, belonging to the field of natural product extraction and processing technology. The method includes the following steps: (1) Extraction: coffee fruit peel powder is mixed with citrate-phosphate buffer solution with a pH of 4.5-5.0 at a mass-to-volume ratio of 1:(8-12) (g:mL), and then 1%-5% of polyethylene glycol is added to the mixture, wherein the molecular weight of the polyethylene glycol is 400-4000. After mixing, the mixture is allowed to stand at 20-30℃ for 1-6 hours, and then centrifuged. The supernatant is collected to obtain the centrifuged liquid; (2) Purification; d. Elution: first, elute with 30-37% ethanol aqueous solution at a flow rate of 1-2 BV / h, and discard this eluent; then elute with 40-45% ethanol aqueous solution at a flow rate of 1-2 BV / h, and collect this eluent; (3) Drying. This method can effectively improve the extraction rate of chlorogenic acid and increase the content of chlorogenic acid in the extract. The entire extraction process is efficient, controllable, stable and easy to scale up.

Description

Technical Field

[0001] This application relates to the field of natural product extraction and processing technology, and in particular to a method for preparing coffee fruit peel extract. Background Technology

[0002] Coffee fruit peel, the largest byproduct in the initial processing of coffee, faces a dual contradiction in its traditional disposal: on the one hand, fresh fruit processing companies face pressure to manage biomass waste, as open-air dumping easily breeds mold and pollutes water sources, and even when composted and fermented for use as fertilizer, its utilization value is extremely low; on the other hand, modern nutritional research reveals its value as a "super pomace," containing a certain amount of chlorogenic acid and some rare components unique to coffee. This resource misallocation has prompted the academic community to re-examine pathways for the high-value utilization of coffee fruit peel.

[0003] Chlorogenic acid, widely found in plants, is a phenolic acid with unsaturated double bonds formed from caffeic acid and quinic acid. A study published on December 31, 2024, in *Cellular Senescence* by researchers from the China Academy of Chinese Medical Sciences and China Agricultural University showed that chlorogenic acid can significantly inhibit UV-induced skin cell aging, reduce inflammation levels, significantly improve wrinkles in mice, alleviate skin pathological features, and inhibit aging characteristics. Due to its excellent antioxidant capacity, chlorogenic acid is widely used in food, pharmaceuticals, health products, and skincare. Based on the antioxidant and anti-inflammatory effects of chlorogenic acid, researching its extraction process is of great academic value and practical significance.

[0004] There are many methods for extracting chlorogenic acid from plant-derived natural products, including some traditional and emerging methods, such as water extraction, reflux extraction, ultrasonic extraction, microwave-assisted extraction, enzymatic methods, enzymatic hydrolysis-ultrasonic combination methods, and supercritical fluid extraction.

[0005] The seven common methods for extracting chlorogenic acid mentioned above each have their advantages and disadvantages. Water extraction and reflux extraction, as the most traditional methods, have lower extraction rates and lower purity than other methods. Combining ultrasonic and microwave methods with enzymatic methods can improve extraction rates and purity to some extent. Supercritical fluid extraction (SFE) is a method that uses the temperature and pressure of the extractant fluid to sequentially extract sample components with different solubilities to achieve extraction and separation. This method results in less chlorogenic acid loss, higher quality, and higher extraction efficiency, but its expensive equipment makes it difficult to scale up for mass production.

[0006] In the resource utilization of coffee fruit peel, the pursuit of those skilled in the art has always been to find ways to efficiently, controllably, and stably increase the content and extraction rate of chlorogenic acid in the extract so that it can be easily produced on a large scale. Summary of the Invention

[0007] To address or partially address the problems existing in related technologies, this application provides a method for preparing coffee fruit peel extract. This method can effectively improve the extraction rate of chlorogenic acid and increase the content of chlorogenic acid in the extract. The entire extraction process is efficient, controllable, stable, and easy to scale up for production.

[0008] A method for preparing coffee fruit peel extract according to this application includes the following steps:

[0009] (1) Extraction:

[0010] Coffee fruit peel powder was mixed with citrate-phosphate buffer solution with a pH of 4.5-5.0 at a mass-to-volume ratio of 1:(8-12) (g:mL). Then, 1%-5% of polyethylene glycol with a molecular weight of 400-4000 was added to the mixture. After mixing, the mixture was allowed to stand at 20-30°C for 1-6 hours, then centrifuged and the supernatant was collected to obtain the centrifuged liquid.

[0011] (2) Purification:

[0012] a. Resin pretreatment and equilibration: Use macroporous resin of type XDA-8 or type AB-8, soak in ethanol, wash with water, and then equilibrate with acidic water of pH 3-4;

[0013] b. Sample loading: Load the centrifuged liquid obtained in step (1) onto the equilibrated resin column;

[0014] c. Washing: After loading the sample, wash the resin column and discard the washing solution;

[0015] d. Washing:

[0016] First, elute with a 30-37% ethanol aqueous solution at a flow rate of 1-2 BV / h, and discard this eluent.

[0017] Elute with 40-45% ethanol aqueous solution at a flow rate of 1-2 BV / h and collect the eluent.

[0018] (3) Drying: The eluent collected in step (2) is concentrated into an extract under vacuum and then freeze-dried to obtain a coffee fruit peel extract rich in chlorogenic acid.

[0019] Further, the specific operation of sample loading in the purification step (2) is as follows: after centrifugation, the liquid is loaded onto the equilibrated resin column at a flow rate of 1-2 BV / h, and the loading volume is controlled at 4-8 BV.

[0020] Further, the specific operation of washing the resin column in step (2) of purification is as follows: the resin column is washed with 2-3 BV of acidic water at pH 3-4 at a flow rate of 2-4 BV / h.

[0021] Furthermore, the vacuum concentration in step (3) is carried out at 45°C.

[0022] Furthermore, the elution in step (2) of purification specifically includes:

[0023] First, elute with a 35% ethanol aqueous solution at a flow rate of 1-2 BV / h, and discard this eluent.

[0024] Elute with 45% ethanol aqueous solution at a flow rate of 1-2 BV / h and collect the eluent.

[0025] The beneficial effects of this application are:

[0026] 1. This application creatively introduces polyethylene glycol (molecular weight 400-4000) as an extraction aid in the extraction stage, marking its first application in the field of coffee pericarp extraction. Polyethylene glycol has the following functions:

[0027] Solubilizing and penetration-enhancing effects: Polyethylene glycol molecules can change the polarity of the extraction solvent and reduce surface tension, effectively penetrating into the cell tissue of coffee fruit peel, promoting the dissolution and release of polar target components such as chlorogenic acid, and directly improving the extraction rate of chlorogenic acid.

[0028] In-situ stabilization and protection: Polyethylene glycol can form a protective environment in the extraction system, effectively inhibiting the oxidation, hydrolysis and degradation of phenolic substances such as chlorogenic acid during the extraction process, thereby maximizing the preservation of the integrity of the active ingredients.

[0029] Furthermore, when the molecular weight of polyethylene glycol (PEG) is between 400 and 1500, it falls within the liquid / semi-solid range and exhibits excellent penetration and solubilization capabilities. Due to its small molecular weight, low viscosity, and good flowability, it can quickly penetrate into the coffee fruit peel cells; it is also miscible with water in any proportion, effectively altering solvent polarity and promoting the dissolution of chlorogenic acid. When the molecular weight of PEG is between 1500 and 4000, it falls within the low-melting-point solid range and possesses good stabilizing and protective properties. Its longer molecular chains allow it to more effectively form a protective layer around chlorogenic acid molecules through steric hindrance, inhibiting oxidation and hydrolysis. Simultaneously, it still maintains good water solubility (solubility increases with temperature, but at room temperature, the solubility of PEG 4000 is still >50%). Compared to liquid PEG, its penetration rate may be slightly slower, but PEGs in this molecular weight range can still completely dissolve and function effectively.

[0030] Furthermore, for polyethylene glycol 200: although its permeability is excellent, its molecular chain is too short, and its "protective layer" effect may be too weak, resulting in a less effective stabilizing effect compared to polyethylene glycols with higher molecular weights. For polyethylene glycol 6000 and above: the water dissolution rate slows significantly, and the solution viscosity increases substantially. High viscosity is detrimental to mass transfer, negatively impacting extraction efficiency and increasing the difficulty of subsequent separation and purification. Therefore, the polyethylene glycol used in this application has a molecular weight range of 400-4000.

[0031] Using the method in this application, the average chlorogenic acid content in the coffee fruit peel extract was 13.5%, and the average chlorogenic acid extraction rate was 85.1%.

[0032] 2. This application uses a citrate-phosphate buffer solution with a specific pH range (4.5-5.0) as the extraction solvent. This system has the following advantages:

[0033] Precise pH control and stability: The buffer system composed of citric acid and phosphate can maintain a highly stable pH value under the interference of external factors, providing an optimal and constant weakly acidic environment for the extraction process.

[0034] Highly effective inhibition of pectin dissolution: This pH environment can effectively inhibit the dissolution of a large amount of pectin in coffee fruit peel, reducing the burden on subsequent purification processes from the source, lowering the amount of impurities, and laying a solid foundation for subsequent efficient purification.

[0035] 3. In the purification stage of this application, highly selective enrichment of chlorogenic acid was achieved through the selection of adsorption resins and the optimization of the elution process:

[0036] Precise resin matching: The medium polarity macroporous adsorption resin XDA-8 or the weak polarity macroporous adsorption resin AB-8 are selected. Their surface polarity and pore structure are highly matched with chlorogenic acid molecules, ensuring high adsorption capacity and high selectivity.

[0037] Precise separation by gradient elution: Two-step gradient elution using ethanol-water solutions of specific concentration ranges (30-37% and 40-45%) can precisely separate weakly adsorbed impurities from strongly adsorbed target product chlorogenic acid. This step can effectively remove water-soluble impurities such as sugars and proteins, as well as some lipid-soluble impurities, resulting in a higher purity of chlorogenic acid in the final eluent. Attached Figure Description

[0038] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0039] Figure 1This is a liquid chromatogram of the coffee fruit peel extract (chlorogenic acid content 13.5%) in Example 1.

[0040] Figure 2 This is a liquid chromatogram of the coffee fruit peel extract (chlorogenic acid content 13.2%) in Example 2.

[0041] Figure 3 This is a liquid chromatogram of the coffee fruit peel extract (chlorogenic acid content 13.3%) in Example 3.

[0042] Figure 4 This is a liquid chromatogram of the coffee fruit peel extract (chlorogenic acid content 13.9%) in Example 4.

[0043] Figure 5 This is a liquid chromatogram of coffee fruit peel extract (chlorogenic acid content 6.5%) in Comparative Example 1.

[0044] Figure 6 This is the liquid chromatogram of coffee fruit peel extract (chlorogenic acid content 4.3%) in Comparative Example 2.

[0045] Figure 7 This is the liquid chromatogram of coffee fruit peel extract (chlorogenic acid content 3.8%) in Comparative Example 3. Detailed Implementation

[0046] The embodiments of this application will now be described in more detail with reference to the examples. While embodiments of this application are shown in the examples, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0047] Example 1

[0048] A method for preparing coffee fruit peel extract in this embodiment includes the following steps:

[0049] (1) Extraction:

[0050] Weigh 100g of coffee fruit peel powder and mix it with 1000mL of citrate-phosphate buffer solution (pH 4.5, mass-to-volume ratio 1:10). Add 3% (by mass) of polyethylene glycol (molecular weight 1500) to the mixture, mix well, and let it stand at 20°C for 6 hours. Then centrifuge and collect the supernatant to obtain the centrifuged liquid.

[0051] (2) Purification:

[0052] a. Resin pretreatment and equilibration: Take a certain volume of medium-polarity macroporous adsorption resin XDA-8, soak it in ethanol for 24 hours, and then wash it with deionized water until there is no alcohol odor. Then equilibrate the resin column with hydrochloric acid aqueous solution at pH 3.0 at a flow rate of 2 BV / h until the pH of the effluent stabilizes at 3.0.

[0053] b. Sample loading: Load the centrifuged liquid into the equilibrated resin column at a flow rate of 2 BV / h, with the loading volume controlled at 4 BV.

[0054] c. Washing: After sample loading, wash the resin column with 3 BV of pH 3.0 acidic water at a flow rate of 4 BV / h, and discard the washing solution.

[0055] d. Elution: First, elute 3 BV with 30% ethanol aqueous solution at a flow rate of 2 BV / h, and discard this eluent.

[0056] Elute 4 BV of the eluent with 40% ethanol aqueous solution at a flow rate of 2 BV / h and collect the eluent.

[0057] (3) Drying:

[0058] The collected eluent was concentrated under vacuum at 45°C to a paste-like consistency, and then freeze-dried to obtain a coffee fruit peel extract rich in chlorogenic acid.

[0059] According to the high performance liquid chromatography method of NY / T3514-2019, the chlorogenic acid content in the coffee fruit peel extract rich in chlorogenic acid obtained in this example was 13.5%, and the chlorogenic acid extraction rate was calculated to be 85.3%.

[0060] Example 2

[0061] A method for preparing coffee fruit peel extract in this embodiment includes the following steps:

[0062] (1) Extraction:

[0063] Weigh 100g of coffee fruit peel powder and mix it with 800mL of citrate-phosphate buffer (pH 5.0, mass-to-volume ratio 1:8). Add 1% (by mass) of polyethylene glycol (molecular weight 2000) to the mixture, mix well, and let it stand at 30°C for 1 hour. Then centrifuge and collect the supernatant to obtain the centrifuged liquid.

[0064] (2) Purification:

[0065] a. Resin pretreatment and equilibration: Take a certain volume of medium-polarity macroporous adsorption resin XDA-8, soak it in ethanol for 24 hours, and then wash it with deionized water until there is no alcohol odor. Then equilibrate the resin column with hydrochloric acid aqueous solution at pH 4.0 at a flow rate of 2 BV / h until the pH of the effluent stabilizes at 4.0.

[0066] b. Sample loading: Load the centrifuged liquid into the equilibrated resin column at a flow rate of 1 BV / h, with the loading volume controlled at 8 BV.

[0067] c. Washing: After sample loading, wash the resin column with 2 BV of pH 4.0 acidic water at a flow rate of 2 BV / h, and discard the washing solution.

[0068] d. Washing:

[0069] First, elute 3 BV with 37% ethanol aqueous solution at a flow rate of 1 BV / h, and discard this eluent.

[0070] Elute 4 BV of the eluent with 45% ethanol aqueous solution at a flow rate of 1 BV / h and collect the eluent.

[0071] (3) Drying:

[0072] The collected eluent was concentrated under vacuum at 45°C to a paste-like consistency, and then freeze-dried to obtain a coffee fruit peel extract rich in chlorogenic acid.

[0073] According to the high performance liquid chromatography method of NY / T3514-2019, the chlorogenic acid content in the coffee fruit peel extract rich in chlorogenic acid obtained in this example was 13.2%, and the chlorogenic acid extraction rate was calculated to be 83.3%.

[0074] Example 3

[0075] A method for preparing coffee fruit peel extract in this embodiment includes the following steps:

[0076] (1) Extraction:

[0077] Weigh 100g of coffee fruit peel powder and mix it with 1200mL of citrate-phosphate buffer (pH 4.8, mass-to-volume ratio 1:12). Add 2% (by mass) of polyethylene glycol (molecular weight 400) to the mixture, mix well, and let it stand at 25°C for 3 hours. Then centrifuge and collect the supernatant to obtain the centrifuged liquid.

[0078] (2) Purification:

[0079] a. Resin pretreatment and equilibration: Take a certain volume of medium-polarity macroporous adsorption resin XDA-8, soak it in ethanol for 24 hours, and then wash it with deionized water until there is no alcohol odor. Then equilibrate the resin column with hydrochloric acid aqueous solution at pH 3.5 at a flow rate of 2 BV / h until the pH of the effluent stabilizes at 3.5.

[0080] b. Sample loading: Load the centrifuged liquid into the equilibrated resin column at a flow rate of 1.5 BV / h, with the loading volume controlled at 6 BV.

[0081] c. Washing: After sample loading, wash the resin column with 2.5 BV of pH 3.5 acidic water at a flow rate of 3 BV / h, and discard the washing solution.

[0082] d. Washing:

[0083] First, elute 3 BV with 35% ethanol aqueous solution at a flow rate of 1.5 BV / h, and discard this eluent.

[0084] Elute 4 BV of the eluent with 45% ethanol aqueous solution at a flow rate of 1.5 BV / h and collect the eluent.

[0085] (3) Drying:

[0086] The collected eluent was concentrated under vacuum at 45°C to a paste-like consistency, and then freeze-dried to obtain a coffee fruit peel extract rich in chlorogenic acid.

[0087] According to the high performance liquid chromatography method of NY / T3514-2019, the chlorogenic acid content in the coffee fruit peel extract rich in chlorogenic acid obtained in this example was 13.3%, and the chlorogenic acid extraction rate was calculated to be 84.1%.

[0088] Example 4

[0089] A method for preparing coffee fruit peel extract in this embodiment includes the following steps:

[0090] (1) Extraction:

[0091] Weigh 100g of coffee fruit peel powder and mix it with 1000mL of citrate-phosphate buffer (pH 4.6, mass-to-volume ratio 1:10). Add 5% (by mass) of polyethylene glycol (molecular weight 950) to the mixture, mix well, and let it stand at 22°C for 4 hours. Then centrifuge and collect the supernatant to obtain the centrifuged liquid.

[0092] (2) Purification:

[0093] a. Resin pretreatment and equilibration: Take a certain volume of weakly polar macroporous adsorption resin AB-8, soak it in ethanol for 24 hours, and then wash it with deionized water until there is no alcohol odor. Then equilibrate the resin column with hydrochloric acid aqueous solution at pH 3.2 at a flow rate of 2 BV / h until the pH of the effluent stabilizes at 3.2.

[0094] b. Sample loading: Load the centrifuged liquid into the equilibrated resin column at a flow rate of 1 BV / h, with the loading volume controlled at 5 BV.

[0095] c. Washing: After loading the sample, wash the resin column with 2 BV of pH 3.2 acidic water at a flow rate of 2.5 BV / h, and discard the washing solution.

[0096] d. Washing:

[0097] First, elute 3 BV with 33% ethanol aqueous solution at a flow rate of 1 BV / h, and discard this eluent.

[0098] Elute 4 BV of the eluent with 42% ethanol aqueous solution at a flow rate of 1 BV / h and collect the eluent.

[0099] (3) Drying:

[0100] The collected eluent was concentrated under vacuum at 45°C to a paste-like consistency, and then freeze-dried to obtain a coffee fruit peel extract rich in chlorogenic acid.

[0101] According to the high performance liquid chromatography method of NY / T3514-2019, the chlorogenic acid content in the coffee fruit peel extract rich in chlorogenic acid obtained in this example was 13.9%, and the chlorogenic acid extraction rate was calculated to be 87.7%.

[0102] Comparative Example 1 (Critical extraction environment missing: citrate-phosphate buffer)

[0103] Experimental plan:

[0104] Extraction: Weigh 100g of coffee fruit peel powder and mix it with 1000mL of pure water (instead of citrate-phosphate buffer with pH 4.8) at a mass-to-volume ratio of 1:10. Add 5% (by mass) of polyethylene glycol (molecular weight 400) to the mixture, mix well, and let it stand at 25°C for 3 hours. Then centrifuge and collect the supernatant.

[0105] The subsequent purification and drying steps were exactly the same as in Example 1, yielding the extract.

[0106] The chlorogenic acid content in the extract was 6.5%, and the chlorogenic acid extraction rate was 43.2%.

[0107] Comparative Example 2 (Missing key extractant: polyethylene glycol)

[0108] Experimental plan:

[0109] Extraction: Weigh 100g of coffee fruit peel powder and mix it with 1000mL of citrate-phosphate buffer (pH 4.8) at a mass-to-volume ratio of 1:10. Do not add any polyethylene glycol. Let the mixture stand at 25°C for 3 hours, then centrifuge and collect the supernatant.

[0110] The subsequent purification and drying steps were exactly the same as in Example 2, yielding the extract.

[0111] The chlorogenic acid content in the extract was 4.3%, and the chlorogenic acid extraction rate was 27.8%.

[0112] Comparative Example 3 (using mismatched purification resin)

[0113] Experimental plan:

[0114] Extraction: The extraction steps were exactly the same as in Example 3: using a citrate-phosphate buffer solution with pH 4.8, 5% polyethylene glycol (molecular weight 950) was added, mixed well, and allowed to stand at 25°C for 3 hours. The supernatant was then centrifuged and collected.

[0115] Purification: The resin was replaced with a nonpolar or weakly polar macroporous adsorption resin D101 (D101 is a nonpolar resin, and its adsorption affinity and selectivity for moderately polar chlorogenic acid differ from those of the polar resin XDA-8). The flow rates and volumes for the resin pretreatment, equilibration, loading, and washing steps were kept consistent with those in Example 3.

[0116] Elution: Use the same elution procedure: first elute with 35% aqueous ethanol solution, then elute with 45% aqueous ethanol solution and collect.

[0117] Drying: The procedure is the same as in Example 3; the extract is obtained.

[0118] The chlorogenic acid content in the extract was 3.8%, and the chlorogenic acid extraction rate was 24.3%.

[0119] Results analysis:

[0120] The experiments and results of Comparative Example 1 show that in a pure water environment, a large amount of viscous impurities such as pectin dissolve, resulting in a viscous extract and a cloudy supernatant. During subsequent resin purification, pectin easily clogs the resin channels, leading to slow loading and elution flow rates. The chlorogenic acid content and extraction rate are significantly lower than in Example 1.

[0121] The experiments and results of Comparative Example 2 show that the lack of polyethylene glycol leads to decreased solvent permeability to cell structures and reduced solubility of chlorogenic acid, resulting in lower extraction efficiency and increased oxidative degradation of chlorogenic acid during extraction. The final result is a reduction in the total amount of chlorogenic acid transferred from the raw material to the final product, meaning the extraction rate is significantly lower than in Example 3, demonstrating that polyethylene glycol is crucial for improving the recovery of the target component.

[0122] The experiments and results of Comparative Example 3 show that D101 is a non-polar resin, and its adsorption affinity and selectivity for moderately polar chlorogenic acid are different from those of the polar resin XDA-8.

[0123] Possible scenario 1: The adsorption force is too weak, causing chlorogenic acid to penetrate and be lost during the sample loading and washing stages, resulting in low chlorogenic acid content in the collection section.

[0124] Possible scenario 2: The adsorption force is too strong or the selectivity is poor, resulting in severe co-adsorption of impurities. Furthermore, 45% ethanol cannot effectively elute chlorogenic acid, requiring a higher concentration of ethanol, which causes elution tailing and non-concentrated collection.

[0125] In either case, the extraction rate and content of chlorogenic acid were significantly lower than in Example 3 using XDA-8 resin.

[0126] The above examples and comparative examples fully demonstrate that the optimal chlorogenic acid extraction rate and high chlorogenic acid content product can only be obtained under the synergistic effect of the three elements defined in this invention: "specific extraction environment (buffer solution) + specific extraction aid (polyethylene glycol) + specific purification medium (polar resin XDA-8 / AB-8)". None of these elements can be omitted.

[0127] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing coffee fruit peel extract, characterized in that, Includes the following steps: (1) Extraction: Coffee fruit peel powder was mixed with citrate-phosphate buffer solution with a pH of 4.5-5.0 at a mass-to-volume ratio of 1:(8-12) (g:mL). Then, 1%-5% of polyethylene glycol with a molecular weight of 400-4000 was added to the mixture. After mixing, the mixture was allowed to stand at 20-30°C for 1-6 hours, then centrifuged and the supernatant was collected to obtain the centrifuged liquid. (2) Purification: a. Resin pretreatment and equilibration: Use macroporous resin of type XDA-8 or type AB-8, soak in ethanol, wash with water, and then equilibrate with acidic water at pH 3-4; b. Sample loading: Load the centrifuged liquid obtained in step (1) onto the equilibrated resin column; c. Washing: After loading the sample, wash the resin column and discard the washing solution; d. Washing: First, elute with a 30-37% ethanol aqueous solution at a flow rate of 1-2 BV / h, and discard this eluent. Elute with a 40-45% ethanol aqueous solution at a flow rate of 1-2 BV / h and collect the eluent. (3) Drying: The eluent collected in step (2) is concentrated into an extract under vacuum and then freeze-dried to obtain a coffee fruit peel extract rich in chlorogenic acid.

2. The method for preparing coffee fruit peel extract according to claim 1, characterized in that, The specific operation of sample loading in step (2) purification is as follows: after centrifugation, the liquid is loaded onto the equilibrated resin column at a flow rate of 1-2 BV / h, and the loading volume is controlled at 4-8 BV.

3. The method for preparing coffee fruit peel extract according to claim 1, characterized in that, The specific operation of washing the resin column in step (2) of purification is as follows: wash the resin column with 2-3 BV of acidic water with pH 3-4 at a flow rate of 2-4 BV / h.

4. The method for preparing coffee fruit peel extract according to claim 1, characterized in that, The vacuum concentration in step (3) is carried out at 45°C.

5. The method for preparing coffee fruit peel extract according to claim 1, characterized in that, The elution process in step (2) of purification specifically includes: First, elute with a 35% ethanol aqueous solution at a flow rate of 1-2 BV / h, and discard this eluent. Elute with 45% ethanol aqueous solution at a flow rate of 1-2 BV / h and collect the eluent.

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