A low temperature extraction method of coffee liquor

Abstract

The present application belongs to the technical field of coffee making, and particularly relates to a low-temperature extraction method of coffee liquid. The low-temperature extraction method of coffee liquid comprises the following steps: (1) peeling coffee fresh fruits to retain endocarp, endosperm and embryo, and obtaining peeled coffee beans; (2) adding water to the peeled coffee beans, sterilizing, then adding fermentation inoculum to obtain fermentation material, and carrying out anaerobic fermentation to obtain fermentation liquid; (3) after the fermentation is completed, sterilizing, drying, crushing to obtain coffee powder, mixing the coffee powder with water, then carrying out pressure treatment, filtering to obtain coffee extraction liquid and coffee residue; (4) drying the coffee residue, adding the residue into an extraction kettle to carry out supercritical carbon dioxide extraction, obtaining extraction, filtering to obtain extraction product; (5) mixing the coffee extraction liquid and the extraction product to obtain coffee liquid. The coffee liquid of the present application has suitable content of gallic acid, high antioxidant property, excellent taste and aroma.

Description

A low-temperature extraction method for coffee liquid Technical Field

[0001] This invention belongs to the field of coffee making technology, specifically relating to a low-temperature extraction method for coffee liquid. Background Technology

[0002] Yunnan, as one of China's major coffee-growing regions, boasts a suitable geographical environment and climate ideal for the cultivation of Arabica coffee beans. Arabica beans from Yunnan are beloved by coffee enthusiasts for their unique flavor characteristics, securing a place in the specialty coffee market and providing consumers with more diverse choices.

[0003] As consumers increasingly demand higher quality and better taste in coffee, traditional high-temperature extraction methods are no longer sufficient to meet market needs. Low-temperature extraction methods primarily address these issues by lowering the extraction temperature. Low-temperature extraction allows for a gentler extraction of purer, smoother, and more complex flavor components from coffee grounds over a longer period, avoiding the negative effects of high-temperature extraction. Furthermore, the lower temperature better preserves the volatile aroma components in the coffee, resulting in a final coffee with superior aroma and flavor.

[0004] Gallic acid is a polyphenolic compound that naturally exists in coffee and is considered an important indicator of coffee quality. Gallic acid itself has a certain bitterness and astringency; a suitable amount can add depth to coffee, making its flavor richer and more layered. At the same time, gallic acid has antioxidant effects, helping to protect the body from free radical damage. Gallic acid can react with other components, affecting the aroma and flavor of the final product.

[0005] However, the gallic acid content in coffee liquid prepared by low-temperature extraction in existing technologies is not ideal, which affects both the antioxidant properties of the coffee liquid and the depth of its flavor. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature extraction method for coffee liquid.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for low-temperature extraction of coffee liquid, comprising the following steps:

[0009] (1) Remove the outer pericarp, mesocarp, pectin layer and endocarp of fresh coffee cherries, and retain the endocarp, endosperm and embryo to obtain peeled coffee beans;

[0010] (2) Add water to peeled coffee beans, sterilize, then add fermentation agent to obtain fermentation material, carry out anaerobic fermentation, and obtain fermentation liquid;

[0011] (3) After fermentation, sterilize, dry and crush the fermented peeled coffee beans to obtain coffee powder, mix the coffee powder and water, pressurize and filter to obtain coffee extract and coffee grounds.

[0012] (4) Dry the coffee grounds, add them to the extraction vessel for supercritical carbon dioxide extraction, obtain the extract, filter, and obtain the extraction product;

[0013] (5) Mix the coffee extract and the extract product to obtain coffee liquid.

[0014] Preferably, the anaerobic fermentation conditions in step (2) are a fermentation temperature of 25-30℃ and a fermentation time of 30-35h.

[0015] Preferably, the fermentation agent in step (2) includes Lactobacillus plantarum and Lactobacillus reuteri.

[0016] Preferably, the amount of *Lactobacillus reuteri* used in the fermentation material in step (2) is 2 × 10⁻⁶. 7 -6×10 7 CFU / mL, the amount of *Lactobacillus plantarum* used in the fermentation material is 1×10⁻⁶. 7 -3×10 7 CFU / mL.

[0017] Preferably, the number of Lactobacillus reuteri in the fermentation material in step (2) is 1.5-2 times the number of Lactobacillus plantarum.

[0018] This invention improves the gallic acid content in coffee liquid, enhances its antioxidant properties, and improves its flavor by fermenting peeled coffee beans with specific microorganisms.

[0019] Preferably, the pressurization conditions in step (3) are: pressurization pressure of 120-130 MPa, pressurization time of 20-30 min; and temperature control of 2-5℃ during pressurization.

[0020] Preferably, the conditions for supercritical carbon dioxide extraction in step (4) are: extraction pressure of 35-40 MPa, extraction temperature of 35-40℃, extraction time of 2-3 h, and CO2 fluid flow rate of 12-17 kg / h.

[0021] This invention improves the aroma content of coffee liquid by treating fermented and pressurized coffee grounds with supercritical carbon dioxide. At the same time, the specific supercritical carbon dioxide extraction conditions can ensure that the gallic acid content is appropriate, resulting in a better depth of flavor in the coffee liquid.

[0022] Preferably, a 0.1-0.5 μm filter membrane is used in step (3).

[0023] Preferably, a 0.1-0.5 μm filter membrane is used in step (4).

[0024] Preferably, in step (3), the material is dried to a moisture content of 8-10 wt% and crushed to a mesh size of less than 100 mesh.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0026] 1. This invention improves the gallic acid content in coffee liquid, enhances its antioxidant properties, and improves its flavor by fermenting peeled coffee beans with specific strains of bacteria.

[0027] 2. This invention improves the content of aroma components in coffee liquid by treating fermented and pressurized coffee grounds with supercritical carbon dioxide. At the same time, the specific supercritical carbon dioxide extraction conditions can ensure that the gallic acid content is appropriate, resulting in a better depth of flavor in the coffee liquid. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] All raw materials used in the following embodiments of the present invention are commercially available products:

[0030] Lactobacillus plantarum, product code TS279067, Ningbo Taisto Biotechnology Co., Ltd.

[0031] Lactobacillus reuteri, product code TS339580, Ningbo Taisto Biotechnology Co., Ltd.

[0032] Lactobacillus delbrueckii, product code TS301396, Ningbo Taisto Biotechnology Co., Ltd.

[0033] Example 1

[0034] This embodiment provides a low-temperature extraction method for coffee liquid, including the following steps:

[0035] (1) Coffee cherries consist of the pericarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The pericarp, mesocarp, pectin layer, and endocarp of fresh coffee cherries are removed using a peeling machine, while the endocarp, endosperm, and embryo are retained to obtain peeled coffee beans.

[0036] (2) Add water at 4 times the weight of the peeled coffee beans to the peeled coffee beans, sterilize, then add fermentation inoculum to obtain fermentation material, and carry out anaerobic fermentation to obtain fermentation liquid. The fermentation temperature is 27℃; the fermentation time is 32h; the fermentation inoculum includes Lactobacillus plantarum and Lactobacillus reuteri, and the amount of Lactobacillus reuteri in the fermentation material is 4×10 7 CFU / mL, the amount of *Lactobacillus plantarum* used in the fermentation material is 2 × 10⁻⁶. 7 CFU / mL. The number of viable Lactobacillus reuteri in the fermentation feed is twice that of viable Lactobacillus plantarum.

[0037] (3) After fermentation, sterilize and dry until the moisture content reaches 9wt%, crush to less than 100 mesh to obtain coffee powder. Mix coffee powder and water at a weight ratio of 1:1.4 and then pressurize. The pressurization pressure is 125MPa and the pressurization time is 25min. The temperature is controlled at 4℃ during the pressurization process. After depressurization, filter with a 0.45μm filter membrane to obtain coffee extract and coffee grounds.

[0038] (4) Dry the coffee grounds to a moisture content of 3wt%, add them to the extraction vessel for supercritical carbon dioxide extraction, the extraction pressure is 38MPa, the extraction temperature is 37℃, the extraction time is 2.5h, the CO2 fluid flow rate is 15kg / h, the extract is obtained, and the extract is filtered using a 0.45μm filter membrane to obtain the extraction product.

[0039] (5) Mix the coffee extract and the extract product to obtain coffee liquid.

[0040] Example 2

[0041] This embodiment provides a low-temperature extraction method for coffee liquid, including the following steps:

[0042] (1) Coffee cherries consist of the pericarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The pericarp, mesocarp, pectin layer, and endocarp of fresh coffee cherries are removed using a peeling machine, while the endocarp, endosperm, and embryo are retained to obtain peeled coffee beans.

[0043] (2) Add water at 4 times the weight of the peeled coffee beans to the peeled coffee beans, sterilize, then add a fermentation agent to obtain a fermentation mixture. Perform anaerobic fermentation to obtain a fermentation broth. The fermentation temperature is 25℃; the fermentation time is 35 hours. The fermentation agent includes *Lactobacillus plantarum* and *Lactobacillus reuteri*, and the amount of *Lactobacillus reuteri* in the fermentation mixture is 3.5 × 10⁻⁶. 7 The concentration of *Lactobacillus plantarum* in the fermentation substrate was 2.5 × 10⁻⁶ CFU / mL. 7 CFU / mL. The number of viable Lactobacillus reuteri in the fermentation feed is twice that of viable Lactobacillus plantarum.

[0044] (3) After fermentation, sterilize and dry until the moisture content reaches 8wt%, crush to less than 100 mesh to obtain coffee powder. Mix coffee powder and water at a weight ratio of 1:1.3 and then pressurize. The pressurization pressure is 130MPa and the pressurization time is 20min. The temperature is controlled at 5℃ during the pressurization process. After depressurization, filter with a 0.45μm filter membrane to obtain coffee extract and coffee grounds.

[0045] (4) Dry the coffee grounds to a moisture content of 4wt%, add them to the extraction vessel for supercritical carbon dioxide extraction, the extraction pressure is 40MPa, the extraction temperature is 35℃, the extraction time is 3h, the CO2 fluid flow rate is 12kg / h, the extract is obtained, and the extract is filtered using a 0.45μm filter membrane to obtain the extraction product.

[0046] (5) Mix the coffee extract and the extract product to obtain coffee liquid.

[0047] Example 3

[0048] This embodiment provides a low-temperature extraction method for coffee liquid, including the following steps:

[0049] (1) Coffee cherries consist of the pericarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The pericarp, mesocarp, pectin layer, and endocarp of fresh coffee cherries are removed using a peeling machine, while the endocarp, endosperm, and embryo are retained to obtain peeled coffee beans.

[0050] (2) Add 4 times the weight of water to peeled coffee beans, sterilize, then add fermentation inoculum to obtain fermentation material, and carry out anaerobic fermentation to obtain fermentation liquid. The fermentation temperature is 30℃; the fermentation time is 30h; the fermentation inoculum includes Lactobacillus plantarum and Lactobacillus reuteri, and the amount of Lactobacillus reuteri in the fermentation material is 4.5×10 7 The concentration of *Lactobacillus plantarum* in the fermentation substrate was 1.5 × 10⁻⁶ CFU / mL. 7 CFU / mL. The number of viable Lactobacillus reuteri in the fermentation feed is twice that of viable Lactobacillus plantarum.

[0051] (3) After fermentation, sterilize and dry until the moisture content reaches 10wt%, crush to less than 100 mesh to obtain coffee powder. Mix coffee powder and water at a weight ratio of 1:1.5 and then pressurize. The pressurization pressure is 120MPa and the pressurization time is 30min. The temperature is controlled at 4℃ during the pressurization process. After depressurization, filter with a 0.45μm filter membrane to obtain coffee extract and coffee grounds.

[0052] (4) Dry the coffee grounds to a moisture content of less than 5%, add them to the extraction vessel for supercritical carbon dioxide extraction, the extraction pressure is 35 MPa, the extraction temperature is 40℃, the extraction time is 2 h, the flow rate of CO2 fluid is 17 kg / h, the extract is obtained, and the extract is filtered using a 0.45 μm filter membrane to obtain the extraction product.

[0053] (5) Mix the coffee extract and the extract product to obtain coffee liquid.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that the fermentation agent is *Lactobacillus reuteri*, and the amount of *Lactobacillus reuteri* in the fermentation material is 6 × 10⁻⁶. 7 CFU / mL.

[0056] Comparative Example 2

[0057] The difference between this comparative example and Example 1 is that the fermentation agent is *Lactobacillus plantarum*, and the amount of *Lactobacillus plantarum* used in the fermentation material is 6 × 10⁻⁶. 7 CFU / mL.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that the fermentation agent includes *Lactobacillus plantarum* and *Lactobacillus reuteri*, and the amount of *Lactobacillus reuteri* in the fermentation material is 2 × 10⁻⁶. 7 CFU / mL, the amount of *Lactobacillus plantarum* used in the fermentation material is 4 × 10⁻⁶ CFU / mL. 7 CFU / mL.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that the fermentation agent includes *Lactobacillus delbrueckii* and *Lactobacillus reuteri*, and the amount of *Lactobacillus reuteri* in the fermentation material is 4 × 10⁻⁶. 7 CFU / mL, the amount of *Lactobacillus delbrueckii* used in the fermentation feed is 2 × 10⁻⁶. 7 CFU / mL.

[0062] Comparative Example 5

[0063] The difference between this comparative example and Example 1 is that supercritical carbon dioxide extraction was not performed.

[0064] Specifically, it is a low-temperature extraction method for coffee liquid, comprising the following steps:

[0065] (1) Coffee cherries consist of the pericarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The pericarp, mesocarp, pectin layer, and endocarp of fresh coffee cherries are removed using a peeling machine, while the endocarp, endosperm, and embryo are retained to obtain peeled coffee beans.

[0066] (2) Add 4 times the weight of water to the peeled coffee beans, sterilize, then add a fermentation agent to obtain a fermentation mixture. Perform anaerobic fermentation to obtain a fermentation broth. The fermentation temperature is 27℃; the fermentation time is 32 hours. The fermentation agent includes *Lactobacillus plantarum* and *Lactobacillus reuteri*, and the amount of *Lactobacillus reuteri* in the fermentation mixture is 4 × 10⁻⁶. 7 CFU / mL, the amount of *Lactobacillus plantarum* used in the fermentation material is 2 × 10⁻⁶. 7 CFU / mL.

[0067] (3) After fermentation, sterilize and dry until the moisture content reaches 9wt%, crush to less than 100 mesh to obtain coffee powder. Mix coffee powder and water at a weight ratio of 1:1.4 and then pressurize. The pressurization pressure is 125MPa and the pressurization time is 25min. The temperature is controlled at 4℃ during the pressurization process. After depressurization, filter with a 0.45μm filter membrane to obtain coffee liquid.

[0068] Comparative Example 6

[0069] The difference between this comparative example and Example 1 is that the supercritical carbon dioxide extraction conditions are: extraction pressure of 30 MPa, extraction temperature of 30 °C, extraction time of 4 h, and CO2 fluid flow rate of 10 kg / h.

[0070] Performance testing

[0071] Coffee liquor was prepared from fresh Arabica coffee cherries from Yunnan using the low-temperature extraction methods of Examples 1-3 and Comparative Examples 1-6, and then tested.

[0072] 1. Take 100 mL of coffee solution, add 3 mL of Folin-Ciocalteu and 5 mL of methanol solution, and dilute to 50 mL with distilled water. Shake well and heat to 50℃ for 60 min. After cooling to room temperature, determine gallic acid in the coffee solution using a standard detection method: high performance liquid chromatography (HPLC). Mobile phase: methanol / water. Set up 3 parallel groups and calculate the average value. The results are shown in Table 1.

[0073] Table 1. Gallic acid content in coffee liquid

[0074] Gallic acid content (g / L): Example 1 4.35; Example 2 4.21; Example 3 4.28; Comparative Example 1 3.73; Comparative Example 2 5.12; Comparative Example 3 3.97; Comparative Example 4 5.04; Comparative Example 5 3.45; Comparative Example 6 4.97 surface

[0075] 2. The content of flavor-enhancing substances in coffee liquid was determined by referring to the specific detection method in publication number CN112806459B.

[0076] Aldehydes include 3-methylbutanal, 2-butenal, acetaldehyde, and 2-pentenal.

[0077] Esters include ethyl acetate, methyl 3-methylbutyrate, ethyl 3-methylbutyrate, ethyl valerate, and butyrolactone.

[0078] Phenolic substances include 4-vinylguaiacol and phenol.

[0079] Pyrazines include 2-methylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, and 2,3-diethyl-5-methylpyrazine.

[0080] Pyrroles include 2-methylpyrrole, N-furfurylpyrrole, 2-formyl-1-methylpyrrole, and 2-acetyl-1-methylpyrrole.

[0081] The results are shown in Table 2.

[0082] Table 2. Test results of aroma components in coffee liquid (wt%)

[0083]

[0084] 3. Thirty professional coffee tasters in the industry conducted sensory evaluations of the coffee liquids from Examples 1-3 and Comparative Examples 1-6, testing the taste and mouthfeel. Satisfaction levels increased from 1 to 10, with 10 being the most satisfactory score. Scores were rounded to one decimal place, and the average was calculated. The results are shown in Table 3.

[0085] The main items related to taste and texture include:

[0086] Taste: includes the following elements: acidity; sweetness; bitterness; flavor.

[0087] Taste: Includes the following elements: body; texture; smoothness; finish.

[0088] Table 3 Sensory rating results

[0089] Taste and Texture Examples 19.8 Example 29.5 Example 39.6 Comparative Example 18.2 Comparative Example 25.3 Comparative Example 38.8 Comparative Example 46.1 Comparative Example 56.8 Comparative Example 67.6 surface

[0090] As shown in Tables 1-3, the coffee liquid prepared in Examples 1-3 has a suitable gallic acid content, good taste, high aroma component content, and improved coffee liquid quality.

[0091] Comparative Examples 1-4 demonstrate that only by using specific strains and dosages of bacteria during fermentation can the gallic acid content be optimized, thereby improving both antioxidant properties and the flavor of the coffee. Comparative Example 2 used *Lactobacillus plantarum*, and Comparative Example 4 used *Lactobacillus delbrueckii* and *Lactobacillus reuteri*, resulting in excessive gallic acid content and negatively impacting the flavor of the coffee (as shown in Table 3).

[0092] In Comparative Example 5, without supercritical carbon dioxide extraction, the gallic acid content was too low, resulting in a decline in the coffee's flavor, a decrease in the content of aroma components in the coffee liquid, and a decline in the coffee's quality.

[0093] In Comparative Example 6, the change in supercritical carbon dioxide extraction conditions led to a decrease in the content of aroma components in the coffee liquid, and also resulted in an excessively high content of gallic acid, which reduced the taste of the coffee liquid.

[0094] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-temperature extraction method for coffee liquid, characterized in that, Includes the following steps: (1) Peel the fresh coffee cherries, retaining the pectin, endosperm, and embryo, to obtain peeled coffee beans; (2) Add water to the peeled coffee beans, sterilize, and then add fermentation agents to obtain fermentation material, and carry out anaerobic fermentation to obtain fermentation liquid; (3) After fermentation, sterilize, dry, and crush to obtain coffee powder, mix the coffee powder and water, pressurize, filter, and obtain coffee extract and coffee grounds; (4) Dry the coffee grounds, add them to the extraction vessel for supercritical carbon dioxide extraction to obtain extract, filter the extract to obtain extraction product; (5) Mix the coffee extract and extraction product to obtain coffee liquid; The fermentation agents mentioned in step (2) include Lactobacillus plantarum (product number TS279067) and Lactobacillus reuteri (product number TS339580); The amount of Lactobacillus reuteri in the fermentation material mentioned in step (2) is 2×10 7 -6×10 7 CFU / mL, the amount of *Lactobacillus plantarum* used in the fermentation material is 1×10⁻⁶. 7 -3×10 7 CFU / mL; The number of Lactobacillus reuteri in the fermentation material in step (2) is 1.5-2.0 times the number of Lactobacillus plantarum.

2. The low-temperature extraction method for coffee liquid according to claim 1, characterized in that, In step (2), the anaerobic fermentation temperature is 25-30℃ and the time is 30-35h.

3. The low-temperature extraction method for coffee liquid according to claim 1, characterized in that, In step (3), the pressurization pressure is 120-130 MPa, the time is 20-30 min, and the temperature is controlled at 2-5℃.

4. The low-temperature extraction method for coffee liquid according to claim 1, characterized in that, In step (4), the pressure of supercritical carbon dioxide extraction is 35-40 MPa, the temperature is 35-40℃, the time is 2-3 h, and the flow rate of CO2 fluid is 12-17 kg / h.

5. The low-temperature extraction method for coffee liquid according to claim 1, characterized in that, In step (3), a 0.1-0.5 μm filter membrane is used for filtration.

6. The low-temperature extraction method for coffee liquid according to claim 1, characterized in that, In step (4), a 0.1-0.5 μm filter membrane is used for filtration.

7. The low-temperature extraction method for coffee liquid according to claim 1, characterized in that, Step (3) Dry until the moisture content reaches 8-10 wt%, and crush to less than 100 mesh.

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