Low-temperature extraction method of coffee liquid

Abstract

The invention 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 the coffee liquid comprises the following steps: (1) peeling fresh coffee fruits, and retaining inner pectin, endosperm and embryos to obtain peeled coffee beans; (2) adding water into the peeled coffee beans, sterilizing, then adding a fermentation inoculant to obtain a fermentation material, and carrying out anaerobic fermentation to obtain fermentation liquor; (3) after fermentation is finished, sterilizing, drying and crushing to obtain coffee powder, mixing the coffee powder with water, pressurizing and filtering to obtain coffee extract and coffee grounds; (4) drying the coffee grounds, adding the dried coffee grounds into an extraction kettle, carrying out supercritical carbon dioxide extraction to obtain an extract, and filtering to obtain an extraction product; and (5) mixing the coffee extract and the extraction product to obtain the coffee liquid. The coffee liquid disclosed by the invention is appropriate in gallic acid content, high in oxidation resistance and excellent in mouth feel and fragrance.

Description

Technical Field

[0001] The invention belongs to the technical field of coffee making, and particularly relates to a low-temperature extraction method for coffee liquid. Background Art

[0002] As one of China's major coffee-growing regions, Yunnan's favorable geographical environment and climatic conditions are ideal for growing Arabica coffee beans. Yunnan-produced Arabica beans are favored by coffee lovers for their unique flavor profile, carving a niche in the specialty coffee market and offering consumers a more diverse range of choices.

[0003] As consumers' demands for coffee quality and taste continue to rise, traditional high-temperature extraction methods are no longer able to meet market demands. Low-temperature extraction methods primarily mitigate these issues by lowering the extraction temperature. Low-temperature extraction gently extracts purer, smoother, and more complex flavor components from ground coffee over a longer period of time, avoiding the negative effects of high-temperature extraction. Furthermore, lower temperatures better preserve volatile aroma components in the coffee, resulting in a coffee liquid with a superior aroma and taste.

[0004] Gallic acid, a polyphenolic compound naturally found in coffee, has become a key indicator of coffee quality. While inherently bitter and astringent, a moderate amount can add depth to coffee, enriching its flavor and creating a richer, more complex flavor. Gallic acid also possesses antioxidant properties, helping to protect the body from free radical damage. Gallic acid can react with other ingredients, affecting the aroma and flavor of the final product.

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

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

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

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

[0009] (1) removing the exocarp, mesocarp, pectin layer, and endocarp of fresh coffee berries, while retaining the endocarp, endosperm, and embryo to obtain peeled coffee beans;

[0010] (2) adding water to the peeled coffee beans, sterilizing them, and then adding a fermentation agent to obtain a fermentation material, performing anaerobic fermentation to obtain a fermentation liquid;

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

[0012] (4) drying the coffee grounds, adding them into an extraction kettle for supercritical carbon dioxide extraction to obtain an extract, and filtering to obtain an extraction product;

[0013] (5) The coffee extract and the extraction product are mixed to obtain coffee liquid.

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

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

[0016] Preferably, the amount of Lactobacillus reuteri in the fermentation material in step (2) is 2×10 7 -6×10 7 CFU / mL, the amount of plant lactobacillus in the fermentation material is 1×10 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] The present invention ferments peeled coffee beans using a specific strain of bacteria, thereby improving the gallic acid content in the coffee liquid, enhancing the antioxidant property of the coffee liquid, and improving the flavor of the coffee.

[0019] Preferably, the conditions for the pressurization treatment in step (3) are as follows: the pressurization pressure is 120-130 MPa, the pressurization time is 20-30 min; and the temperature during the pressurization treatment is controlled at 2-5°C.

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

[0021] The present invention improves the content of aroma components in the coffee liquid by subjecting the fermented and pressurized coffee grounds to supercritical carbon dioxide treatment. At the same time, the specific supercritical carbon dioxide extraction conditions can ensure an appropriate gallic acid content, and the coffee liquid has a better taste depth.

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

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

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

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

[0026] 1. The present invention uses a specific strain of bacteria to ferment peeled coffee beans, thereby improving the gallic acid content in the coffee liquid, enhancing the antioxidant properties of the coffee liquid, and improving the flavor of the coffee.

[0027] 2. The present invention improves the content of aroma components in the coffee liquid by subjecting the fermented and pressurized coffee grounds to supercritical carbon dioxide treatment. At the same time, the specific supercritical carbon dioxide extraction conditions can ensure an appropriate gallic acid content, and the coffee liquid has a better taste depth. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0029] The raw materials used in the following examples of the present invention are all commercially available commodities:

[0030] Lactobacillus plantarum, product number TS279067, Ningbo Testo Biotechnology Co., Ltd.

[0031] Lactobacillus reuteri, product number TS339580, Ningbo Testo Biotechnology Co., Ltd.

[0032] Lactobacillus delbrueckii, product number TS301396, Ningbo Testo Biotechnology Co., Ltd.

[0033] Example 1

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

[0035] (1) Coffee cherries include the exocarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The exocarp, 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) adding water 4 times the weight of the peeled coffee beans to the peeled coffee beans, sterilizing the beans, and then adding a fermentation agent to obtain a fermentation material, and performing anaerobic fermentation to obtain a fermentation liquid. The fermentation temperature is 27° C. and the fermentation time is 32 hours. The fermentation agent includes Lactobacillus plantarum and Lactobacillus reuteri. The amount of Lactobacillus reuteri in the fermentation material is 4×10 7 CFU / mL, the amount of plant lactobacillus in the fermentation material is 2×10 7 The number of viable Lactobacillus reuteri bacteria in the fermentation material is twice the number of viable Lactobacillus plantarum bacteria.

[0037] (3) After the fermentation is completed, the coffee powder is sterilized, dried to a moisture content of 9 wt%, and crushed to less than 100 mesh to obtain coffee powder. The coffee powder and water are mixed in a weight ratio of 1:1.4, and then pressurized at a pressure of 125 MPa for 25 min. The temperature is controlled at 4°C during the pressurization process. After depressurization, the coffee powder is filtered using a 0.45 μm filter membrane to obtain coffee extract and coffee grounds.

[0038] (4) drying the coffee grounds to a water content of 3 wt % and adding them to an extraction kettle for supercritical carbon dioxide extraction at an extraction pressure of 38 MPa, an extraction temperature of 37° C., an extraction time of 2.5 h, and a CO 2 fluid flow rate of 15 kg / h to obtain an extract, which was filtered using a 0.45 μm filter membrane to obtain an extract product;

[0039] (5) The coffee extract and the extraction product are mixed to obtain coffee liquid.

[0040] Example 2

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

[0042] (1) Coffee cherries include the exocarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The exocarp, 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) adding water 4 times the weight of the peeled coffee beans to the peeled coffee beans, sterilizing the beans, and then adding a fermentation agent to obtain a fermentation material, and performing anaerobic fermentation to obtain a fermentation liquid. The fermentation temperature is 25° C. and the fermentation time is 35 hours. The fermentation agent includes Lactobacillus plantarum and Lactobacillus reuteri, and the amount of Lactobacillus reuteri in the fermentation material is 3.5×10 7 CFU / mL, the amount of plant lactobacillus in the fermentation material is 2.5×10 7 The number of viable Lactobacillus reuteri bacteria in the fermentation material is twice the number of viable Lactobacillus plantarum bacteria.

[0044] (3) After the fermentation is completed, the mixture is sterilized, dried to a moisture content of 8 wt%, and crushed to less than 100 mesh to obtain coffee powder. The coffee powder and water are mixed in a weight ratio of 1:1.3, and then pressurized at a pressure of 130 MPa for 20 min. The temperature is controlled at 5°C during the pressurization process. After depressurization, the mixture is filtered using a 0.45 μm filter membrane to obtain coffee extract and coffee grounds.

[0045] (4) drying the coffee grounds to a water content of 4 wt %, adding them to an extraction kettle for supercritical carbon dioxide extraction at an extraction pressure of 40 MPa, an extraction temperature of 35° C., an extraction time of 3 h, and a CO 2 fluid flow rate of 12 kg / h to obtain an extract, which was filtered using a 0.45 μm filter membrane to obtain an extract product;

[0046] (5) The coffee extract and the extraction product are mixed to obtain coffee liquid.

[0047] Example 3

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

[0049] (1) Coffee cherries include the exocarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The exocarp, 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) adding 4 times the weight of water to the peeled coffee beans, sterilizing the beans, and then adding a fermentation agent to obtain a fermentation material, performing anaerobic fermentation to obtain a fermentation liquid, the fermentation temperature being 30° C. and the fermentation time being 30 h; the fermentation agent comprising Lactobacillus plantarum and Lactobacillus reuteri, the amount of Lactobacillus reuteri in the fermentation material being 4.5×10 7 CFU / mL, the amount of plant lactobacillus in the fermentation material is 1.5×10 7 The number of viable Lactobacillus reuteri bacteria in the fermentation material is twice the number of viable Lactobacillus plantarum bacteria.

[0051] (3) After the fermentation is completed, the coffee powder is sterilized, dried to a moisture content of 10 wt%, and crushed to less than 100 mesh to obtain coffee powder. The coffee powder and water are mixed in a weight ratio of 1:1.5, and then pressurized at a pressure of 120 MPa for 30 min. The temperature is controlled at 4°C during the pressurization process. After depressurization, the coffee powder is filtered using a 0.45 μm filter membrane to obtain coffee extract and coffee grounds.

[0052] (4) drying the coffee grounds to a moisture content of less than 5%, adding the grounds to an extraction kettle for supercritical carbon dioxide extraction at an extraction pressure of 35 MPa, an extraction temperature of 40° C., an extraction time of 2 h, and a CO2 fluid flow rate of 17 kg / h to obtain an extract, which was filtered using a 0.45 μm filter membrane to obtain an extract product;

[0053] (5) The coffee extract and the extraction product are mixed 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 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 in the fermentation material is 6×10 7 CFU / mL.

[0058] Comparative Example 3

[0059] The difference between this comparative example and Example 1 is that the fermentation bacteria include Lactobacillus plantarum and Lactobacillus reuteri, and the amount of Lactobacillus reuteri in the fermentation material is 2×10 7 CFU / mL, the amount of plant lactobacillus in the fermentation material is 4×10 7 CFU / mL.

[0060] Comparative Example 4

[0061] The difference between this comparative example and Example 1 is that the fermentation bacteria include Lactobacillus delbrueckii and Lactobacillus reuteri, and the amount of Lactobacillus reuteri in the fermentation material is 4×10 7 CFU / mL, the amount of Lactobacillus delbrueckii in the fermentation material is 2×10 7 CFU / mL.

[0062] Comparative Example 5

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

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

[0065] (1) Coffee cherries include the exocarp, mesocarp, pectin layer, endocarp, endocarp (silver skin), endosperm, and embryo. The exocarp, 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) adding 4 times the weight of water to the peeled coffee beans, sterilizing the beans, and then adding a fermentation agent to obtain a fermentation material, performing anaerobic fermentation to obtain a fermentation liquid, the fermentation temperature being 27° C. and the fermentation time being 32 h; the fermentation agent comprising Lactobacillus plantarum and Lactobacillus reuteri, the amount of Lactobacillus reuteri in the fermentation material being 4×10 7 CFU / mL, the amount of plant lactobacillus in the fermentation material is 2×10 7 CFU / mL.

[0067] (3) After the fermentation is completed, the mixture is sterilized, dried to a moisture content of 9 wt%, and crushed to less than 100 mesh to obtain coffee powder. The coffee powder and water are mixed at a weight ratio of 1:1.4, and then pressurized at a pressure of 125 MPa for 25 min. The temperature is controlled at 4°C during the pressurization process. After the pressure is released, the mixture is filtered using a 0.45 μm filter membrane to obtain coffee liquid.

[0068] Comparative Example 6

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

[0070] Performance Testing

[0071] Fresh Arabica coffee berries produced in Yunnan were used to prepare coffee liquid using the low-temperature extraction methods of Examples 1-3 and Comparative Examples 1-6, and the coffee liquid was then tested.

[0072] 1. Add 3 mL of forin phenol and 5 mL of methanol to 100 mL of coffee liquid. Dose to 50 mL with distilled water, shake thoroughly, and heat to 50°C for 60 minutes. After cooling to room temperature, determine gallic acid in the coffee liquid using standard high-performance liquid chromatography (HPLC). The mobile phase was methanol / water. Three replicates were performed and the average value was calculated. 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

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

[0076] Aldehyde substances 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 mass percentage (wt%) of aroma components in coffee liquid

[0083]

[0084] 3. Thirty professional coffee tasters in the industry conducted a sensory evaluation of the coffee liquids of Examples 1-3 and Comparative Examples 1-6, testing the taste and mouthfeel. Satisfaction was assessed on a scale of 1 to 10, with 10 being the most satisfactory. The scores were rounded to one decimal place and the average was calculated. The results are shown in Table 3.

[0085] The main items of taste and texture are:

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

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

[0088] Table 3 Sensory evaluation results

[0089] Taste and texture Example 1 9.8 Example 2 9.5 Example 3 9.6 Comparative Example 1 8.2 Comparative Example 2 5.3 Comparative Example 3 8.8 Comparative Example 4 6.1 Comparative Example 5 6.8 Comparative Example 6 7.6

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

[0091] Comparative Examples 1-4 demonstrate that only by using specific strains and dosages for fermentation can the gallic acid content be optimized, enhancing both antioxidant properties and the flavor of the coffee. The use of Lactobacillus plantarum in Comparative Example 2 and Lactobacillus delbrueckii and Lactobacillus reuteri in Comparative Example 4 resulted in excessive gallic acid content, affecting the flavor of the coffee (as shown in Table 3).

[0092] In Comparative Example 5, supercritical carbon dioxide extraction was not performed, and the gallic acid content was too low, the taste of the coffee was reduced, the content of aroma components in the coffee liquid was reduced, and the quality of the coffee was reduced.

[0093] In Comparative Example 6, the supercritical carbon dioxide extraction conditions were changed, and the content of aroma components in the coffee liquid decreased. At the same time, it also resulted in an excessively high gallic acid content, which reduced the taste of the coffee liquid.

[0094] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for low-temperature extraction of coffee liquid, characterized in that: The following steps are involved: (1) peeling fresh coffee berries, retaining the pectin, endosperm and embryo, to obtain peeled coffee beans; (2) adding water to the peeled coffee beans, sterilizing them, and then adding a fermentation agent to obtain a fermentation material, performing anaerobic fermentation to obtain a fermentation liquid; (3) After fermentation, sterilize, dry, and crush to obtain coffee powder, mix the coffee powder with water, pressurize, and filter to obtain coffee extract and coffee grounds; (4) drying the coffee grounds, adding them to an extraction kettle for supercritical carbon dioxide extraction to obtain an extract, and filtering the extract to obtain an extraction product; (5) The coffee extract and the extraction product are mixed to obtain coffee liquid.

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

3. The low-temperature extraction method of coffee liquid according to claim 2, characterized in that: The fermentation bacteria in step (2) include Lactobacillus plantarum and Lactobacillus reuteri.

4. The low-temperature extraction method of coffee liquid according to claim 3, characterized in that: The amount of Lactobacillus reuteri in the fermentation material in step (2) is 2×10 7 -6×10 7 CFU / mL, the amount of plant lactobacillus in the fermentation material is 1×10 7 -3×10 7 CFU / mL.

5. The low-temperature extraction method of coffee liquid according to claim 4, characterized in that: In step (2), the number of Lactobacillus reuteri in the fermentation material is 1.5-2.0 times the number of Lactobacillus plantarum.

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

7. The low-temperature extraction method of 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° C., the time is 2-3 h, and the flow rate of CO2 fluid is 12-17 kg / h.

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

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

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

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