A method for preparing coffee concentrate

Abstract

The present invention relates to the technical field of coffee processing, and in particular to a method for preparing a coffee concentrate. The method of the present invention comprises the following steps: grinding coffee beans, adding them into water for ultrasonic extraction, filtering, and obtaining a coffee extract and coffee grounds; adding the coffee grounds into an ethanol solution for extraction, and then reducing pressure and concentrating to remove ethanol to obtain coffee oil; uniformly mixing the coffee oil with the coffee extract, cooling, and standing to obtain a coffee oil layer and a coffee liquid layer; concentrating the coffee liquid layer and mixing it with the coffee oil layer to obtain the coffee concentrate. The method of the present invention is simple, does not require special equipment, has a short preparation time, saves time and cost, and is easy to mass industrialize. The coffee concentrate prepared by the method of the present invention can retain aroma components such as faint floral and fruity aromas, has high body and good flavor.

Description

Technical Field

[0001] The invention relates to the technical field of coffee processing, in particular to a method for preparing coffee concentrate. Background Art

[0002] In terms of describing coffee flavor, the internationally accepted dimensions include acidity, aroma, sweetness, bitterness, mellowness, aftertaste, etc. At present, the main coffee flavors are floral and fruity sour flavors dominated by fruit or flower aromas; spicy and caramel flavors dominated by pine resin, thiol and caramel aromas; caramel chocolate flavors dominated by caramel, nuts, chocolate and almonds. Floral aroma is the most precious flavor of boutique coffee. The coffee flavor restoration currently on the market mainly refers to the restoration of spicy and caramel flavors and caramel chocolate flavors. There are no reported methods for retaining floral and fruity aromas in coffee. In industry, there is no industrialized method to effectively retain floral and fruity aromas in products.

[0003] Industrially, coffee extraction includes hot extraction and cold extraction. In order to improve the extraction rate and extraction speed during hot extraction, heating and pressurization are often used for extraction. However, since the chemical reaction between compounds during the heating process is difficult to control, the taste of coffee produced in different batches is often inconsistent. And since organic acids and other substances are prone to oxidation reactions, the freshness of coffee is reduced. And low-content aroma components such as floral and fruity aromas are difficult to recover and restore, resulting in a low degree of flavor restoration of hot-extracted coffee. Compared with hot-extracted coffee, cold-brewed coffee is extracted at low temperatures, and the retention of floral and fruity aromas and other aroma components is significantly increased, and the oxidation of acidic substances is reduced, making the coffee fresher, and the taste is softer, and it is not easy to produce bitter taste. Coffee liquid prepared by cold extraction, ice drip extraction and other methods at home and abroad is sought after by the market. However, due to the long extraction time and low extraction efficiency of cold extraction, it leads to high production costs. And due to the low-temperature treatment of cold extraction, it is difficult to dissolve substances such as oils in coffee, resulting in a low alcohol content of coffee liquid.

[0004] After coffee is extracted, in order to reduce costs, concentration is usually used. Concentration can be hot or cold. The hot concentration process destroys the heat-sensitive flavor, aroma, and nutrients in the coffee, seriously affecting the quality of the product. There are two main methods of cold concentration: membrane concentration and frozen concentration. Membrane concentration concentrates the coffee liquid at room temperature, but the adsorption of the membrane causes serious loss of flavor, especially the loss of aroma components such as floral and fruity aromas, resulting in a huge difference between the flavor of the coffee concentrate and the flavor of the original liquid, making it difficult to restore the flavor of the coffee liquid. Frozen concentration is concentrated at low temperatures such as around 0°C, so the flavor is better retained, but the production efficiency is low. It usually needs to be concentrated several times, and each concentration takes more than 20 hours. The equipment has low processing capacity and is expensive. Summary of the invention

[0005] Based on the above content, the present invention provides a method for preparing a coffee concentrate. The coffee concentrate prepared by the present invention can retain aroma components such as faint floral and fruity aromas.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a method for preparing a coffee concentrate, comprising the following steps:

[0008] The coffee beans are crushed and added into water for ultrasonic extraction, and then filtered to obtain coffee extract and coffee grounds;

[0009] The coffee grounds are added into an ethanol solution for extraction, and then concentrated under reduced pressure to remove the ethanol to obtain coffee oil;

[0010] The coffee oil and the coffee extract are uniformly mixed, cooled, and allowed to stand to obtain a coffee oil layer and a coffee liquid layer;

[0011] The coffee liquid layer is concentrated and mixed with the coffee oil layer to obtain the coffee concentrated liquid.

[0012] In some embodiments of the present invention, the temperature of the ultrasonic extraction is 0-30°C; the time of the ultrasonic extraction is 10-60 min; and the solid-liquid ratio of the coffee beans to the water is 1:(3-10).

[0013] In some embodiments of the present invention, the ethanol solution is an ethanol aqueous solution with a volume concentration of 80%-95%.

[0014] In some embodiments of the present invention, the temperature of the reduced pressure concentration to remove ethanol is 30-60°C.

[0015] In some embodiments of the present invention, the cooling is specifically cooling to 0-8°C at a cooling rate of 3-5°C / h.

[0016] In some embodiments of the present invention, the standing time is 8-12 hours.

[0017] In some embodiments of the present invention, the coffee liquid layer is filtered through a ceramic membrane and concentrated through a reverse osmosis membrane to a mass concentration of 7% to 30%.

[0018] In some embodiments of the present invention, after the coffee liquid layer is concentrated and mixed with the coffee oil layer, the steps of degassing, nitrogen filling and packaging are also included. Before packaging, the step of adjusting the pH value is also included.

[0019] In some embodiments of the present invention, the packaging further includes a step of sterilizing in a water bath at 60-100° C. for 20-60 min.

[0020] A second technical solution of the present invention is a coffee concentrate prepared according to the above-mentioned preparation method.

[0021] A third technical solution of the present invention is a method for retaining faint floral and fruity aroma components in coffee concentrate, using the above-mentioned method for preparing coffee concentrate.

[0022] The present invention discloses the following technical effects:

[0023] The method of the invention is simple, does not require special equipment, has a short preparation time, saves time cost, and is easy for large-scale industrial production.

[0024] The coffee concentrate prepared by the method of the present invention can retain aroma components such as faint floral and fruity aromas, and has high body and good flavor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 The flavor retention of the coffee concentrates prepared in Example 1 and Comparative Example 1.

[0027] Figure 2 The flavor retention of the coffee concentrates prepared in Example 1 and Comparative Example 2.

[0028] Figure 3 The flavor retention of the coffee concentrates prepared in Example 1 and Comparative Example 3.

[0029] Figure 4 The flavor retention of the cold brew concentrate and coffee concentrate prepared in Comparative Examples 4 and 7.

[0030] Figure 5 The flavor retention of the cold brew concentrate and coffee concentrate prepared in Comparative Examples 4 and 6.

[0031] Figure 6 The flavor retention of the cold brew concentrate and coffee concentrate prepared in Comparative Examples 4 and 5.

[0032] Figure 7 The flavor retention of the cold brew stock solution and coffee concentrate prepared in Comparative Example 4 and Example 1.

[0033] Figure 8 The flavor retention of the cold brew concentrate and coffee concentrate prepared in Comparative Examples 4 and 8. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] The "room temperature" and "normal temperature" mentioned in the present invention, unless otherwise specified, all mean 20-30°C.

[0040] A first aspect of the present invention provides a method for preparing a coffee concentrate, comprising the following steps:

[0041] (1) Coffee beans are crushed to a particle size of 10-80 mesh.

[0042] (2) Add water to the ground coffee at a material-liquid ratio of 1:3-1:10, the water temperature is 0-30°C, ultrasonic extraction is performed for 10-60 minutes, and the coffee extract is separated from the coffee grounds by filtration. In step (2), ultrasonic extraction is performed for 10-60 minutes, and the temperature is controlled at a water temperature of 0-30°C to ensure that the extraction is performed under low temperature conditions to prevent chemical reactions between compounds during the heating process that cause taste changes, and to prevent the loss of volatile components caused by heating. In addition, ultrasound improves the extraction efficiency through cavitation, and the extraction time can be increased from the original soaking time of about 12 hours to less than 60 minutes. The present invention has no special requirements for the power of ultrasound, and the ultrasound power commonly used in the field can be used.

[0043] (3) Add 80%-95% ethanol to the coffee grounds at a material-liquid ratio of 1:3-1:6, extract for 5-60 minutes, and remove the ethanol by vacuum concentration at 30-60° C. to obtain coffee oil. In step (3), the extraction of coffee oil and subsequent mixing with coffee extract increase the mellowness and aftertaste of the cold brew coffee.

[0044] The present invention also attempts to extract coffee oil using other organic solvents such as ethyl acetate, petroleum ether, etc. or supercritical CO2 extraction methods, but other organic solvents such as ethyl acetate and petroleum ether will have residual taste, affecting the flavor of the coffee concentrate. The supercritical CO2 extraction method has high requirements for equipment and large investment.

[0045] (4) At room temperature, add coffee oil to coffee extract and mix evenly, then slowly cool down at a rate of 3-5°C / h to 0-8°C. Do not freeze, and let stand overnight until the oil and coffee extract are fully separated. In step (4), first, mix at room temperature. The temperature is low, which reduces the loss of volatile components by evaporation. Secondly, add coffee oil to coffee extract and mix evenly. Since coffee oil is insoluble in water, it needs to be fully mixed to allow the oil to fully contact with the aroma substances in the coffee extract. Aroma is generally a volatile fat-soluble component that is easily dissolved in coffee oil, thereby preventing the aroma components from volatilizing. Slowly cool down again at a rate of 3-5°C / h. The cooling rate should not be too fast. Too fast a rate will cause the oil to suddenly condense when it is cold, and the aroma substances will not have time to be dissolved by the oil, and will still be free in the solution and lost in subsequent membrane filtration. Slow cooling is conducive to the aroma substances being fully dissolved in the oil and completely separated from the coffee extract. Finally, store it at 0-8°C and let it stand overnight. In this step, the coffee liquid does not freeze, and under low temperature conditions, the separation and stratification of oil and coffee liquid are accelerated, which is conducive to the effective separation of oil and water in the later stage.

[0046] (5) Separate the coffee oil layer, take the coffee liquid layer, filter it through a ceramic membrane, and concentrate it through a reverse osmosis membrane to a mass concentration of 7%-30%, then mix it evenly with the coffee oil layer, degas, fill it with nitrogen, and package it. In step (5), separate the coffee oil layer, take the coffee liquid layer, filter it through a ceramic membrane, and concentrate it through a reverse osmosis membrane to a mass concentration of 7%-30%. In the treatment method of the previous step (i.e., step (4)), the oil-dissolved aroma components are separated so that the membrane filtration and membrane concentration processes only treat the coffee liquid without affecting the aroma components. The concentrated coffee liquid is then mixed evenly with the coffee oil layer, degassed, filled with nitrogen, and packaged. Coffee liquid is difficult to store mainly because of the presence of oxygen in the environment or the microenvironment of the coffee liquid. Degassing is an effective method to remove oxygen from the liquid, which is generally carried out under vacuum conditions. Under vacuum conditions, in addition to oxygen, other volatile components (such as aroma, etc.) are easily volatilized and lost. In the present invention, due to the slow cooling treatment in the previous step, the aroma components and the oil are fully dissolved, so that in the negative pressure degassing process in this step, volatile components such as floral and fruity aromas are not lost, thereby achieving the effect of retaining the aroma.

[0047] In step (5), depending on the type of coffee, you can choose to directly package or adjust the pH value before packaging.

[0048] (6) The packaged coffee liquid is sterilized by water bath sterilization at 60-100℃ for 20-60 min to obtain a coffee concentrate with high floral and fruity aroma. As the water bath sterilization temperature decreases, the water bath sterilization time increases, otherwise it will lead to insufficient sterilization, which will affect the aroma, flavor, acidity, mellowness, etc. of the prepared coffee concentrate; for example, ① at a temperature below 90℃, when the water bath sterilization temperature is 85℃, the water bath sterilization time is not less than 35 min, and 35-60 min is acceptable (the time period can be extended upward for compatibility, but the time period is not compatible when it is reduced downward); ② at 90℃ and above, when the water bath sterilization temperature is 90℃, the water bath sterilization time is 30 min, and 30-45 min is acceptable. If it is further extended to more than 45 (45-60 min), the coffee flavor will change.

[0049] A second aspect of the present invention provides a coffee concentrate prepared according to the above-mentioned preparation method.

[0050] A third aspect of the present invention provides a method for retaining faint floral and fruity aroma components in coffee concentrate, using the above-mentioned method for preparing coffee concentrate.

[0051] The present invention is further described below by way of examples.

[0052] Example 1

[0053] This embodiment provides a method for preparing coffee concentrate, the steps are as follows:

[0054] (1) Coffee beans are crushed to a particle size of 80 mesh.

[0055] (2) The ground coffee was added to water at a solid-liquid ratio of 1:10 (g:mL) at 20°C. Ultrasonic extraction was performed for 40 min, and the coffee extract was separated from the coffee grounds by filtration.

[0056] (3) Add 95% ethanol by volume to coffee grounds at a solid-liquid ratio of 1:5 (g: mL), extract for 30 min, and concentrate under reduced pressure at 40 °C to remove ethanol to obtain coffee oil.

[0057] (4) At room temperature, add coffee oil to coffee extract and mix evenly. Slowly cool down at a rate of 5°C / h to 4°C. Do not allow it to freeze. Let it stand overnight until the oil and coffee extract are fully separated.

[0058] (5) Separate the coffee oil layer, take the coffee liquid layer, filter it through a ceramic membrane, and concentrate it through a reverse osmosis membrane to a concentration of 9%, then mix it evenly with the coffee oil layer, degas, fill it with nitrogen, and package it.

[0059] (6) The packaged coffee liquid is sterilized by heat sterilization in a 90°C water bath for 30 min to obtain a coffee concentrate with highly retained floral and fruity aroma.

[0060] Comparative Example 1

[0061] The only difference from Example 1 is that in step (3), ethanol with a volume concentration of 70% is used; the remaining steps and parameters are the same as those in Example 1.

[0062] Comparative Example 2

[0063] The only difference from Example 1 is that in step (6), the water bath sterilization temperature is 121° C. and the time is 30 min; the remaining steps and parameters are the same as in Example 1.

[0064] Comparative Example 3

[0065] The only difference from Example 1 is that in step (6), the water bath sterilization temperature is 80° C. and the time is 20 min; the remaining steps and parameters are the same as in Example 1.

[0066] Comparative Example 4

[0067] After the coffee beans are crushed (80 mesh), water is added at a powder-water ratio of 1:12 (g: mL), placed in a refrigerator at 4°C and soaked for 12 hours. The filtrate is the coffee cold brew stock solution.

[0068] Comparative Example 5 (Membrane Concentrate)

[0069] The only difference from Example 1 is that step (4) is omitted. In step (5), the coffee extract is directly filtered through a ceramic membrane and concentrated through a reverse osmosis membrane to a concentration of 9%, and then mixed evenly with coffee oil, degassed, nitrogen-filled, and packaged. The remaining steps and parameters are the same as those in Example 1.

[0070] Comparative Example 6

[0071] The only difference from Example 1 is that the cooling method in step (4) is a natural cooling step at room temperature; the remaining steps and parameters are the same as those in Example 1.

[0072] Comparative Example 7

[0073] The only difference from Example 1 is that the cooling method in step (4) is rapid cooling at -40°C (-40~-80°C has equivalent technical effects); the remaining steps and parameters are the same as in Example 1.

[0074] Comparative Example 8

[0075] The only difference from Example 1 is that step (3) is omitted. In step (4), the coffee extract is slowly cooled at room temperature at a cooling rate of 3-5°C / h to 4°C without freezing, and is left to stand overnight until the oil and coffee extract are fully separated (i.e., in step (4), the coffee extract is directly cooled and the addition of coffee oil is omitted). The remaining steps and parameters are the same as those in Example 1.

[0076] Sensory evaluation was performed on the cold-brew stock solutions and coffee concentrates prepared in Example 1 and Comparative Examples 1-8 (the flavor of the cold-brew stock solution in Comparative Example 4 was evaluated directly after preparation, and the flavor evaluation of the other examples or comparative examples was the flavor evaluation of the prepared coffee concentrate samples after storage for 1 month):

[0077] The sensory evaluation panel consists of 10 people (5 men and 5 women), all of whom are specialty coffee quality graders (Q-Graders) who can accurately identify the quality of coffee. The sensory evaluation is carried out in accordance with the sensory evaluation standards established by the Specialty Coffee Association of America (SCA), and the aroma, flavor, acidity, body, uniformity, clean cup, balance, sweetness and other indicators are selected to evaluate and determine the flavor attributes of the samples. All samples are provided at room temperature of 20°C and evaluated in random order.

[0078] Each treatment was tested five times independently and samples were taken for evaluation by tasters. Tasters rated the intensity of the attribute using a 0-10 scale, with 0.25 points as an increment (0 = none; 10 = extremely strong). The results are as follows.

[0079] 1. Aroma description

[0080] Example 1: white floral aroma, citrus, berries, and honey; flavor: ripe citrus, berries, red berries; juice feeling; aftertaste: medium-long, obvious sweetness, bright sourness, relatively balanced overall sourness and bitterness, smooth.

[0081] Comparative Example 1 (70% ethanol extraction): strong bitterness, obvious smoke, short aftertaste, and less positive flavor.

[0082] Comparative Example 2 (sterilization at 121°C for 30 min): sharp and irritating sour taste, and reduced body.

[0083] Comparative Example 3 (inadequate sterilization): inferior acid appeared (obvious sour smell, such as rotten and sour fruit).

[0084] Comparative Example 4 (cold brew stock): Main notes are white floral, citrus, slightly berry, and honey; Flavor: ripe citrus, sweet orange, slightly berry, red berry; Juicy feeling; Aftertaste: medium long, obvious sweetness, bright sourness, relatively balanced overall sourness and bitterness, soft and smooth.

[0085] Comparative Example 5 (membrane concentrate): slightly citrus flavor; weak juice feeling; aftertaste: medium-long, obvious sweetness, acidity changes, overall acidity and bitterness are relatively balanced, smooth.

[0086] 2. Flavor

[0087] The flavor retention of the coffee concentrate prepared in Example 1 and Comparative Example 1 is as follows: Figure 1 As shown (in the figure, the concentrated liquid of the present invention represents Example 1, and the coffee liquid obtained by 70% ethanol extraction treatment represents Comparative Example 1).

[0088] The flavor retention of the coffee concentrate prepared in Example 1 and Comparative Example 2 is as follows: Figure 2 As shown (in the figure, the concentrated liquid of the present invention represents Example 1, and the coffee liquid obtained by sterilizing at 121° C. for 30 minutes represents Comparative Example 2).

[0089] The flavor retention of the coffee concentrate prepared in Example 1 and Comparative Example 3 is as follows: Figure 3 As shown (in the figure, the concentrated liquid of the present invention represents Example 1, and the coffee liquid obtained by insufficient sterilization represents Comparative Example 3).

[0090] The flavor retention of the cold brew stock solution and coffee concentrate prepared in Comparative Examples 4 and 7 is as follows: Figure 4 As shown (the cold-extracted stock solution in the figure represents Comparative Example 4, and the concentrated solution obtained by rapid cooling and separation represents Comparative Example 7).

[0091] The flavor retention of the cold brew stock solution and coffee concentrate prepared in Comparative Examples 4 and 6 is as follows: Figure 5 As shown (the cold-extracted stock solution in the figure represents comparative example 4, and the concentrated solution obtained by slowly cooling without stirring represents comparative example 6).

[0092] The flavor retention of the cold brew stock solution and coffee concentrate prepared in Comparative Examples 4 and 5 is as follows: Figure 6 As shown (in the figure, the cold-extracted stock solution represents Comparative Example 4, and the membrane concentrated solution represents Comparative Example 5).

[0093] The flavor retention of the cold brew stock solution and coffee concentrate prepared in Comparative Example 4 and Example 1 is as follows: Figure 7 As shown (in the figure, the cold-extracted stock solution represents comparative example 4, and the concentrated solution of the present invention represents example 1).

[0094] The flavor retention of the cold brew stock solution and coffee concentrate prepared in Comparative Examples 4 and 8 is as follows: Figure 8 As shown (in the figure, the cold-extracted stock solution represents Comparative Example 4, and the concentrate without oil addition represents Comparative Example 8).

[0095] The flavor index results of the coffee concentrates and cold-brew stock solutions prepared in Example 1 and Comparative Examples 1-8 are statistically shown in Table 1.

[0096] Table 1

[0097] ,

[0098] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a coffee concentrate, characterized in that: The following steps are involved: The coffee beans are crushed and added into water for ultrasonic extraction, and then filtered to obtain coffee extract and coffee grounds; The coffee grounds are added into an ethanol solution for extraction, and then concentrated under reduced pressure to remove the ethanol to obtain coffee oil; The coffee oil and the coffee extract are uniformly mixed at room temperature, cooled, and allowed to stand to obtain a coffee oil layer and a coffee liquid layer; Concentrating the coffee liquid layer and mixing it with the coffee oil layer to obtain the coffee concentrated liquid; The temperature of the ultrasonic extraction is 0-30°C and the time is 10-60min; The ethanol solution is an ethanol aqueous solution with a volume concentration of 80%-95%; The cooling is specifically to cool to 0-8°C at a cooling rate of 3-5°C / h; The standing time is 8-12 hours; The coffee liquid layer is filtered through a ceramic membrane and concentrated through a reverse osmosis membrane to a mass concentration of 7% to 30%; After the coffee liquid layer is concentrated and mixed with the coffee oil layer, the steps of degassing, nitrogen filling and packaging are also included; after the packaging, the step of water bath sterilization is also included; The water bath sterilization is 60-85° C. water bath sterilization for 35-60 min, or 90-100° C. water bath sterilization for 30-45 min.

2. The method for preparing coffee concentrate according to claim 1, characterized in that: The temperature for removing ethanol by concentration under reduced pressure is 30-60°C.

3. The coffee concentrate prepared according to the preparation method according to claim 1 or 2.

4. A method for retaining floral and fruity aroma components in coffee concentrate, characterized in that: The method for preparing the coffee concentrate according to claim 1 or 2.

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