A method for extracting chlorogenic acid, a coffee byproduct

Abstract

This invention provides a method for extracting chlorogenic acid, a coffee byproduct. Using fresh coffee peel and coffee grounds as raw materials, chlorogenic acid is extracted using ethanol extraction and ultrasound-assisted extraction. Through single-factor and orthogonal experiments, the average chlorogenic acid content in the extract from fresh coffee peel under the conditions of 50% ethanol concentration, 60 min of ultrasound, 40℃ ultrasound temperature, and a solid-liquid ratio of 1:12 (g / mL) was 0.075 mg / mL. The average chlorogenic acid content in the extract from coffee grounds under the conditions of 50% ethanol concentration, 6 h of extraction time, and a solid-liquid ratio of 1:15 (g / mL) was 0.059 mg / mL. Antioxidant activity assays showed that the chlorogenic acid extracted from both coffee byproducts exhibited good antioxidant activity. This invention not only reduces the waste of coffee byproducts but also realizes their deep processing and high-value utilization, which is conducive to promoting the sustainable development of the coffee industry.

Description

Technical Field

[0001] This invention belongs to the field of agricultural and forestry by-product resource utilization and natural product extraction and separation technology, specifically relating to a method for extracting chlorogenic acid from coffee by-products, fresh coffee peel and coffee grounds. Background Technology

[0002] The word "coffee" (Coffea spp.) originates from Arabic and means "plant beverage." Along with tea and cocoa, it is considered one of the world's three most popular beverages. Coffee beans are the berries of plants belonging to the genus *Coffea* in the family Rubiaceae. The coffee berry has a complex structure, consisting mainly of the pericarp, pulp (pectin), parchment, seed coat (silverskin), and coffee bean. Coffee cultivation in China is primarily concentrated in Yunnan Province, accounting for over 98% of the country's total planting area and production, mainly producing high-quality Arabica coffee (*Coffea arabica*).

[0003] The nutritional value and unique flavor of coffee are mainly attributed to its rich content of various bioactive components, such as caffeine, proteins, sugars, and polyphenolic compounds, especially phenolic acids. The phenolic acids in coffee primarily include caffeic acid, ferulic acid, chlorogenic acid, p-coumaric acid, vanillic acid, p-hydroxybenzoic acid, as well as organic acids such as formic acid, malic acid, and citric acid. Among these, chlorogenic acids (such as caffeoylquinic acid, feruloylquinic acid, and p-cinnamoylquinic acid) constitute the largest proportion. Chlorogenic acid has attracted widespread attention due to its significant physiological activities (such as anti-obesity, anti-diabetic, blood pressure lowering, antibacterial, and strong antioxidant properties), and its applications have expanded to fields such as aquaculture, where it has been proven to improve the growth performance, immune function, and muscle quality of aquatic animals.

[0004] Statistics show that Yunnan's coffee exports alone reached 32,500 tons in 2024, a year-on-year increase of 358%. This industrial expansion has brought increasingly severe environmental challenges—a large amount of byproducts generated during coffee processing (such as coffee peels and grounds) have not been effectively treated and utilized. These wastes are rich in high-value functional components such as pectin, caffeine, protein, sugars, and polyphenols (especially chlorogenic acid). Currently, the technology for processing coffee byproducts is relatively limited, resulting in low resource utilization rates. This not only causes environmental pollution but also hinders their application in high-value fields such as food and medicine. Therefore, promoting the sustainable development of the coffee industry urgently requires strengthening research on the deep processing and high-value utilization of byproducts. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for extracting chlorogenic acid from coffee by-products, which addresses the shortcomings of the prior art. The method uses fresh coffee peel and coffee grounds as raw materials and employs alcohol extraction and ultrasonic-assisted extraction to extract chlorogenic acid, thus providing technical support for the resource utilization of coffee by-products.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for extracting chlorogenic acid, a coffee by-product, wherein the coffee by-product includes fresh coffee peel and coffee grounds, and the extraction method is an alcohol extraction method, specifically: crushing the fresh coffee peel or coffee grounds and adding an ethanol solution for extraction.

[0007] Preferably, ultrasonic-assisted extraction is used when extracting chlorogenic acid from fresh coffee peels; when extracting chlorogenic acid from fresh coffee peels, the mass fraction of the ethanol solution is 50%~70%, the material-to-liquid ratio is 1g:(9~15mL), the ultrasonic frequency is 45kHz, the ultrasonic power is 100W, the ultrasonic temperature is 40~60℃, and the ultrasonic time is 60~80min.

[0008] Preferably, when extracting chlorogenic acid from coffee grounds, the mass fraction of the ethanol solution is 50%~70%, the material-to-liquid ratio is 1g:(5~15mL), and the extraction time is 6~12h.

[0009] Compared with the prior art, the present invention has the following significant technical effects: 1. This invention employs ethanol extraction and ultrasound-assisted extraction to extract chlorogenic acid from fresh coffee peels and coffee grounds. Based on single-factor experiments, orthogonal experiments were used to systematically optimize the extraction process parameters. It was found that the average chlorogenic acid content in the extract from fresh coffee peels under the conditions of 50% ethanol concentration, 60 min of ultrasound time, 40℃ ultrasound temperature (45 kHz ultrasound frequency, 100 W ultrasound power), and a solid-liquid ratio of 1:12 (g / mL) was 0.075 mg / mL. The average chlorogenic acid content in the extract from coffee grounds under the conditions of 50% ethanol concentration, 6 h of extraction time, and a solid-liquid ratio of 1:15 (g / mL) was 0.059 mg / mL. The antioxidant activity of the obtained chlorogenic acid extracts was determined using the DPPH scavenging rate as an indicator. The results showed that chlorogenic acid in both coffee byproducts exhibited good antioxidant activity.

[0010] 2. This invention not only reduces the waste of coffee by-products, but also realizes the deep processing and high-value utilization of coffee by-products, which is conducive to promoting the sustainable development of the coffee industry.

[0011] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0012] Figure 1This is the chlorogenic acid standard curve of the present invention; Figure 2 This describes the effect of ethanol concentration on the extraction of chlorogenic acid from fresh coffee peels in Example 1 of this invention. Figure 3 This refers to the effect of ultrasound time on the extraction of chlorogenic acid from fresh coffee peel in Example 1 of this invention. Figure 4 This refers to the effect of ultrasonic temperature on the extraction of chlorogenic acid from fresh coffee peel in Example 1 of this invention. Figure 5 This describes the effect of the material-to-liquid ratio on the extraction of chlorogenic acid from fresh coffee fruit peels in Example 1 of this invention. Figure 6 This is the effect of ethanol concentration on the extraction of chlorogenic acid from coffee grounds in Example 2 of the present invention; Figure 7 This describes the effect of soaking time on the extraction of chlorogenic acid from coffee grounds in Example 2 of the present invention. Figure 8 This describes the effect of the material-to-liquid ratio on the extraction of chlorogenic acid from coffee grounds in Example 2 of this invention. Detailed Implementation

[0013] The coffee rind used in this invention is the outer skin of the coffee bean, peeled off during the peeling and pulping stage. It is rich in pectin, sugars, polyphenols, and organic acids, and is one of the main solid byproducts of the initial coffee processing stage. The raw material is sourced from a coffee processing plant.

[0014] The coffee grounds used in this invention refer to the solid residue remaining after green coffee beans have been roasted, ground, and brewed (or extracted). They are a core byproduct of both consumer and instant coffee production processes, containing large amounts of cellulose, lignin, chlorogenic acid, caffeine, and protein, and retaining high levels of antioxidant and bioactivity. The raw materials are sourced from coffee shops.

[0015] The chlorogenic acid standard (AR) of this invention was purchased from Maclean's Reagent Company. The method for constructing the chlorogenic acid standard curve is as follows: First, accurately weigh 0.01 g of the chlorogenic acid standard and place it in a beaker, dissolve it in deionized water, and dilute to 50 mL to obtain a chlorogenic acid stock solution with a concentration of 0.2 mg / mL. Then, accurately measure 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 mL of the chlorogenic acid stock solution into 25 mL volumetric flasks, and dilute to volume with anhydrous ethanol to obtain chlorogenic acid standard solutions with mass concentrations of 0.004, 0.008, 0.012, 0.016, 0.02, 0.024, and 0.028 mg / mL, respectively. Measure the absorbance at 329 nm using a UV-Vis spectrophotometer. Plot the standard curve with the chlorogenic acid standard solution concentration as the x-axis and the corresponding absorbance value as the y-axis (see [link to standard curve]). Figure 1Analysis yields the linear regression equation: y = 22.616x + 0.0136, with a correlation coefficient R0. 2 =0.9958, indicating that the absorbance of chlorogenic acid is linearly related to its concentration and the linearity is good. Example 1

[0016] This embodiment describes a method for extracting chlorogenic acid from fresh coffee fruit peels, and the steps are as follows: Accurately weigh the fresh fruit peel powder and place it in an Erlenmeyer flask. Add ethanol solution and perform ultrasonic-assisted extraction using an ultrasonic cleaner. After extraction, cool to room temperature, centrifuge, and collect the supernatant to obtain the crude extract. Accurately transfer 1.00 mL of the supernatant to a 25 mL volumetric flask protected from light, dilute to volume with anhydrous ethanol (AR), shake well, and allow to stand. Measure the absorbance at 329 nm using a UV-Vis spectrophotometer. Substitute the absorbance values ​​into the chlorogenic acid standard curve equation to calculate the total chlorogenic acid concentration c (mg / mL) of the sample solution.

[0017] Single-factor experiments were conducted to investigate the effects of four factors—ethanol concentration, ultrasonic time, ultrasonic temperature, and solid-liquid ratio—on the chlorogenic acid content extracted from fresh coffee fruit peels. The details are as follows: (1) Ethanol concentration: 2.0g of fresh coffee peel powder was placed in a 250mL Erlenmeyer flask, and ethanol solutions with mass fractions of 40%, 50%, 60%, 70%, and 80% were added respectively, while maintaining a material-to-liquid ratio of 1:9 (g / mL). The mixture was ultrasonically treated for 30min at a frequency of 45kHz, a power of 100W, and a temperature of 30℃. The extract was transferred to a 25mL volumetric flask with a 1mL pipette, and after being diluted to volume with anhydrous ethanol, the absorbance at a wavelength of 329nm was measured. The content of chlorogenic acid in the extract (mg / mL) was calculated, and the average value of the three experiments was taken.

[0018] The results are as follows Figure 2 As shown, the concentration of chlorogenic acid first increases and then decreases with increasing ethanol concentration, reaching a maximum of 0.057 mg / mL in the coffee peel extract when the ethanol concentration is 60%. This initial increase followed by a decrease in chlorogenic acid content may be because when the ethanol concentration is too low, the chlorogenic acid in the coffee peel is not completely extracted, while when the ethanol concentration is too high, the extraction of chlorogenic acid is inhibited, while the dissolution of flavonoids, pigments, or other phenolic substances is accelerated, resulting in a lower chlorogenic acid content. Therefore, a preliminary ethanol concentration of 60% was chosen.

[0019] (2) Ultrasonic time: 2.0g of fresh coffee peel powder was placed in a 250mL conical flask, and 60% ethanol solution was added to maintain a material-liquid ratio of 1:9 (g / mL). The mixture was ultrasonically treated for 40min, 50min, 60min, 70min and 80min at a frequency of 45kHz, a power of 100W and a temperature of 30℃, respectively. The extract was transferred in the same way and the chlorogenic acid content (mg / mL) in the extract was determined.

[0020] The results are as follows Figure 3 As shown, the chlorogenic acid concentration first increases and then decreases with increasing ultrasonic time. The relationship between chlorogenic acid concentration and ultrasonic time has a peak value, reaching its maximum of 0.11 mg / mL in the extract when the ultrasonic time is 70 min. This phenomenon may be because chlorogenic acid in the coffee peel is not completely extracted when the ultrasonic time is less than 70 min, while flavonoids, pigments, or other phenolic substances in the coffee peel are also extracted when the ultrasonic time is greater than 70 min, resulting in a lower chlorogenic acid content. Therefore, an ultrasonic time of 70 min was initially selected.

[0021] (3) Ultrasonic temperature: 2.0g of fresh coffee peel powder was placed in a 250mL conical flask, and 60% ethanol solution was added to maintain a material-liquid ratio of 1:9 (g / mL). The mixture was ultrasonically treated for 70min at a frequency of 45kHz and a power of 100W. The ultrasonic temperatures were 30℃, 40℃, 50℃, 60℃ and 70℃. The extract was transferred in the same way and the chlorogenic acid content (mg / mL) in the extract was determined.

[0022] The results are as follows Figure 4 As shown, the chlorogenic acid content in the coffee peel extract increases with increasing ultrasonic temperature, and stabilizes when the temperature exceeds 50℃. This phenomenon may be due to the increased molecular velocity at higher temperatures, leading to the gradual leaching of chlorogenic acid from the coffee peel. Chlorogenic acid is a heat-sensitive substance; temperatures above 50℃ may cause degradation, affecting its content determination. Therefore, to ensure the yield of chlorogenic acid, an ultrasonic temperature of 50℃ was initially selected.

[0023] (4) Material-liquid ratio: 2.0g of fresh coffee peel powder was placed in a 250mL Erlenmeyer flask, and 60% ethanol solution was added. The material-liquid ratio was kept at 1:6, 1:9, 1:12, 1:15, and 1:18 (g / mL). The mixture was ultrasonically treated for 70min at a frequency of 45kHz, a power of 100W, and a temperature of 50℃. The extract was transferred in the same way and the chlorogenic acid content (mg / mL) in the extract was determined.

[0024] The results are as follows Figure 5As shown, it is evident that the concentration of chlorogenic acid in fresh coffee fruit peel reaches a peak with increasing solid-liquid ratio, peaking at 0.082 mg / mL at a solid-liquid ratio of 1:9 (g / mL). While a higher solid-liquid ratio may seem to increase the solubility of chlorogenic acid, excessively high ratios may not significantly enhance mass transfer between ethanol and coffee fruit peel powder. Furthermore, excessive extractant may dilute the concentration of chlorogenic acid in the extract, affecting its content. Therefore, a solid-liquid ratio of 1:9 (g / mL) was initially selected.

[0025] Based on single-factor experiments, four factors—ethanol concentration, ultrasonic time, ultrasonic temperature, and liquid-to-solid ratio—were used to conduct L9(3) experiments. 4 An orthogonal experiment was conducted to investigate the effect of chlorogenic acid extraction from fresh coffee peel. The levels of the experimental factors are shown in Table 1.

[0026] Table 1. L9 (3) Extract of chlorogenic acid from fresh coffee fruit peel 4 Orthogonal factor levels The results of the orthogonal experiment are shown in Table 2: Table 2. Range analysis of orthogonal experiments for extracting chlorogenic acid from fresh coffee fruit peels. The results showed that the optimal process combination was A1B1C1D2, with an ethanol concentration of 50%, ultrasonic treatment for 60 min, ultrasonic temperature of 50℃, and a material-to-liquid ratio of 1:12 (g / mL). The influencing factors were: material-to-liquid ratio > ultrasonic temperature > ultrasonic time > ethanol concentration. Example 2

[0027] This embodiment describes a method for extracting chlorogenic acid from coffee grounds, and the steps are as follows: Coffee grounds were weighed into an Erlenmeyer flask and soaked in ethanol solution for extraction. After a certain period of time, the extract was obtained. 1.0 mL of the extract was placed in a 25 mL volumetric flask and diluted to volume with anhydrous ethanol. The absorbance was measured at a wavelength of 329 nm. The chlorogenic acid content (mg / mL) in the extract was calculated by substituting the values ​​into the chlorogenic acid standard curve equation.

[0028] Single-factor experiments were conducted to investigate the effects of ethanol concentration, extraction time, and solid-liquid ratio on the chlorogenic acid content extracted from coffee grounds, as detailed below: (1) Ethanol concentration: 2.0 g of fruit peel powder was placed in a 250 mL Erlenmeyer flask, and ethanol solutions with mass fractions of 40%, 50%, 60%, 70%, and 80% were added respectively, maintaining a material-to-liquid ratio of 1:15 (g / mL). After soaking and extraction for 3 h, the extract was obtained. The extract was transferred to a 25 mL volumetric flask using a 1 mL pipette, and after being diluted to volume with anhydrous ethanol, the absorbance was measured to calculate the chlorogenic acid content (mg / mL) in the extract. The average value of the three experiments was taken.

[0029] The results are as follows Figure 6 As shown, the extraction efficiency of chlorogenic acid from coffee grounds exhibits a significant dynamic correlation with ethanol concentration. With increasing ethanol concentration, the solubility of chlorogenic acid increases, promoting its gradual dissolution in coffee grounds. The extraction efficiency reaches a peak of 0.0357 mg / mL when the ethanol concentration reaches 60%. When the ethanol concentration exceeds 60%, excessively high concentrations may inhibit the dissolution of chlorogenic acid, accelerate the leaching of other polyphenols, flavonoids, and other substances in the coffee grounds, and may also cause intermolecular interactions of chlorogenic acid, reducing solubility. Therefore, an ethanol concentration of 60% was initially chosen.

[0030] (2) Soaking time: 2.0 g of fruit peel powder was placed in a 250 mL Erlenmeyer flask, and 60% ethanol solution was added to maintain a material-to-liquid ratio of 1:15 (g / mL). The extract was obtained after soaking for 3 h, 6 h, 9 h, 12 h, and 15 h respectively. The chlorogenic acid content (mg / mL) in the extract was determined by the same method.

[0031] The results are as follows Figure 7 As shown, the chlorogenic acid content in coffee grounds initially increases and then decreases with increasing steeping time, reaching a maximum of 0.0296 mg / mL at 12 hours. While chlorogenic acid gradually leaches out with increasing steeping time, other components are also leached out after 12 hours. This may be due to denaturation of chlorogenic acid caused by prolonged steeping, leading to a decrease in chlorogenic acid concentration. Therefore, a preliminary steeping time of 12 hours was chosen.

[0032] (3) Material-liquid ratio: 2.0 g of fruit peel powder was placed in a 250 mL Erlenmeyer flask, and 60% ethanol solution was added to maintain a material-liquid ratio of 1:3, 1:5, 1:10, 1:15, and 1:20 (g / mL). After soaking and extraction for 12 h, the extract was obtained. The chlorogenic acid content (mg / mL) in the extract was determined using the same method.

[0033] The results are as follows Figure 8 As shown, the chlorogenic acid content in coffee grounds initially increases and then decreases with increasing solid-liquid ratio, reaching a maximum of 0.0666 mg / mL at a solid-liquid ratio of 1:5 (g / mL). This phenomenon may be because when the solid-liquid ratio is too low, the extract becomes saturated, preventing sufficient contact between ethanol and coffee, and thus incomplete leaching of chlorogenic acid from the coffee grounds. However, when the solid-liquid ratio is too high, other active substances such as polyphenols and flavonoids in the coffee grounds are also leached out. Excessive extractant may also dilute the concentration of chlorogenic acid in the extract, affecting its content. Increasing the solid-liquid ratio also increases costs and is detrimental to subsequent processing. Therefore, a solid-liquid ratio of 1:5 (g / mL) was initially chosen.

[0034] Based on single-factor experimental data, according to L9(3) 3 An orthogonal experiment was conducted to study the effects of three factors: ethanol concentration, extraction time, and solid-liquid ratio, with three levels for each factor (Table 3).

[0035] Table 3. L9 (3) extracted from coffee grounds using chlorogenic acid 3 Orthogonal experiment factor levels The results of the orthogonal experiment are shown in Table 4: Table 4. Range analysis of orthogonal experiments for extracting chlorogenic acid from coffee grounds. The results showed that the optimal extraction process A1B3C1 was 50% ethanol concentration, 6 h extraction time, and a material-to-liquid ratio of 1:5 (g / mL). Under these conditions, the chlorogenic acid concentration was found to be 0.059 mg / mL in the verification experiment. The influencing factors, from largest to smallest, were: material-to-liquid ratio > ethanol concentration > soaking time. Example 3

[0036] This example describes the determination of the antioxidant activity of chlorogenic acid extracted from coffee byproducts.

[0037] 0.0039 g of 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) was dissolved in methanol and diluted to 100 mL to prepare a 0.1 mmol / L DPPH solution, which was then placed in the dark. Then, 5 mL of chlorogenic acid extracts from Examples 1 and 2 were added to an equal volume of DPPH solution and placed in the dark for 30 min. The absorbance A1 was measured at 517 nm. The absorbance A0 of a mixture of anhydrous ethanol and an equal volume of DPPH solution was measured as a blank. The scavenging rate was calculated.

[0038] , The results are shown in Table 5: Table 5. Determination of antioxidant activity of chlorogenic acid in coffee byproducts This indicates that chlorogenic acid obtained from fresh coffee fruit peel has a greater DPPH scavenging rate, possibly due to the higher chlorogenic acid content in fresh coffee fruit peel.

[0039] In summary, this invention employs alcohol extraction and ultrasonic-assisted extraction to extract chlorogenic acid from fresh coffee peels and coffee grounds. This not only reduces the waste of coffee by-products but also enables the deep processing and high-value utilization of coffee by-products, which is conducive to promoting the sustainable development of the coffee industry.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for extracting chlorogenic acid, a coffee byproduct, characterized in that, The coffee by-products include fresh coffee peels and coffee grounds, and the extraction method is alcohol extraction, specifically: the fresh coffee peels or coffee grounds are crushed and extracted with an ethanol solution.

2. The method according to claim 1, characterized in that, The ethanol solution has a mass fraction of 50% to 70%.

3. The method according to claim 2, characterized in that, Ultrasonic extraction was also used to extract chlorogenic acid from the fresh coffee fruit peel.

4. The method according to claim 3, characterized in that, The material-to-liquid ratio for extracting chlorogenic acid from fresh coffee fruit peel is 1g:(9~15mL), the ultrasonic frequency is 45kHz, the ultrasonic power is 100W, the ultrasonic temperature is 40~60℃, and the ultrasonic time is 60~80min.

5. The method according to claim 2, characterized in that, The ratio of chlorogenic acid extracted from coffee grounds is 1g:(5~15mL), and the extraction time is 6~12h.

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