Method for improving instant solubility of coffee freeze-dried powder

Abstract

The invention relates to the technical field of coffee processing, in particular to a method for improving instant solubility of coffee freeze-dried powder. The method comprises the following steps: extracting coffee beans to obtain coffee liquid A; cooling the coffee liquid A to-5 DEG C to 10 DEG C, standing, and separating to obtain a water layer and an oil layer; the oil layer is subjected to reduced pressure evaporation to obtain aroma components; mixing the aroma component with the water layer to obtain coffee liquid C; the coffee liquid C is frozen and then freeze-dried, and the freeze-dried coffee powder is obtained. According to the method, the dissolution rate of the freeze-dried coffee powder can be effectively increased, after the freeze-dried coffee powder prepared through the method is added into normal-temperature water, the surface powder completely sinks within 3 seconds, then the powder in the water is completely dissolved within 7 seconds, the dissolution rate is remarkably superior to that of the freeze-dried coffee powder on the market at present, and coffee aroma components can be effectively reserved.

Description

Technical Field

[0001] The invention relates to the technical field of coffee processing, in particular to a method for improving the instant solubility of freeze-dried coffee powder. Background Art

[0002] Since its invention, instant coffee has evolved through three generations of product development: spray-dried coffee, aromatized coffee, and freeze-dried coffee. Based on the drying method, it can be categorized as spray-dried or freeze-dried. Spray-drying technology uses high-temperature, rapid evaporation to remove water from coffee liquid, producing a coffee extract. While this method is fast, cost-effective, and produces high yields, it requires high temperatures, which can easily cause flavor compounds in the coffee to escape, affecting the flavor and taste. Most instant coffees require hot water to dissolve, and even after dissolution, a layer of fine insoluble matter remains at the bottom of the bottle. Freeze-drying technology involves sublimating the water from the coffee extract under low-temperature, vacuum conditions to produce a dry coffee extract. Freeze-dried coffee dissolves quickly in hot water and, compared to spray-dried instant coffee, retains a greater degree of the coffee's original flavor while eliminating the problem of fine insoluble matter. In recent years, freeze-dried coffee has seen significant growth, becoming a mainstream product in the market. However, these products still suffer from slow dissolution rates. Currently available "3-second" instant products often dissolve in hot water within 3 seconds, but still produce a significant amount of oil in room-temperature water, requiring prolonged stirring to achieve complete dissolution. Therefore, achieving rapid and sufficient dissolution of freeze-dried coffee powder at room temperature is a critical technical challenge for freeze-dried coffee powder processors. Summary of the Invention

[0003] Based on the above content, the present invention provides a method for improving the solubility of freeze-dried coffee powder.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a method for improving the solubility of freeze-dried coffee powder, comprising the following steps:

[0006] Extracting coffee beans to obtain coffee liquid A;

[0007] Cooling the coffee liquid A to -5°C to 10°C and allowing it to stand to separate into an aqueous layer (coffee liquid B) and an oil layer;

[0008] The oil layer is evaporated under reduced pressure to obtain aroma components; the aroma components are mixed with the water layer to obtain coffee liquid C;

[0009] The coffee liquid C is frozen and then freeze-dried to obtain low-temperature instant coffee freeze-dried powder.

[0010] After extensive experiments, the present invention found that when the coffee liquid A is cooled to below -5°C, it will freeze, and the oil will stick to the ice crystals, and the oil-water separation effect cannot be achieved by standing. When the coffee liquid is cooled to above 10°C, such as 15°C and left to stand for 24 hours, although the oil separation can be achieved, the coffee taste will be greatly changed, affecting the flavor of the final prepared freeze-dried coffee powder.

[0011] In a preferred embodiment of the present invention, the step of crushing the coffee beans to a particle size of no more than 80 mesh is further included before extracting the coffee beans.

[0012] In a preferred embodiment of the present invention, the extraction is performed by grinding coffee beans and then adding them into water; the material-liquid ratio of the coffee beans to the water is 1 g:10 mL.

[0013] In a preferred embodiment of the present invention, the extraction method is ultrasonic extraction; the extraction temperature is 4°C to 80°C; further preferably, the extraction temperature is 20-80°C.

[0014] In some specific embodiments of the present invention, the extraction method is ultrasonic extraction. The present invention does not specifically limit the ultrasonic frequency and input power of ultrasonic extraction, and the ultrasonic frequency and input power of those skilled in the art can be used.

[0015] In a preferred embodiment of the present invention, the cooling method is two-stage cooling or direct cooling.

[0016] In a preferred embodiment of the present invention, the two-stage cooling is specifically to first cool to 10°C at a rate of 1°C / s, and then cool to -5°C at a rate of 15°C / h.

[0017] In a preferred embodiment of the present invention, the direct cooling is specifically to directly cool to -5 to 10°C at a rate of 1°C / s.

[0018] In a preferred embodiment of the present invention, the standing time is 6 to 48 hours.

[0019] In a preferred embodiment of the present invention, the vacuum degree of the reduced pressure evaporation is 10-30 kPa and the temperature is 30-50°C.

[0020] In a preferred embodiment of the present invention, the freezing cooling rate is 1 to 5°C / min.

[0021] In a preferred embodiment of the present invention, the freeze-drying temperature is -60°C to -30°C, the vacuum degree is 9 to 50 Pa, and the time is 24 to 48 hours.

[0022] Since the fatty chain structure in the oil molecule is a hydrophobic group, it repels water molecules, making it impossible for it to form a stable hydration layer in water and tends to aggregate together. The coffee extraction process extracts a large amount of oil, which causes the freeze-dried powder to dissolve slowly during the re-dissolution process. During the coffee extraction and coffee liquid storage process, long-term high temperature will destroy the flavor substances in the coffee liquid and easily cause the flavor substances in the coffee to escape, affecting the flavor and taste of the coffee. The present invention accelerates the separation of oil in the coffee liquid at low temperature (-5℃~10℃) by quickly cooling the coffee liquid B to -5℃~10℃ when preparing it, and further achieves full separation of oil and coffee water solution by standing at -5℃~10℃ for 6-48h. It can effectively retain the aroma components in the oil, and at the same time, the removal of oil will increase the dissolution rate of the freeze-dried coffee powder.

[0023] Since most of the aroma compounds in coffee are fat-soluble and easily dissolve in coffee oil, the coffee flavor compounds are also removed during the oil removal process. To preserve the coffee flavor compounds, the present invention uses evaporation at 30°C-50°C to recover the aroma compounds and then returns them to the coffee liquid, minimizing flavor loss while maintaining the dissolution rate of the freeze-dried coffee powder.

[0024] During the pre-freezing stage, a slow freezing rate can cause the system's materials to aggregate, forming large ice crystals. This can lead to microstructure agglomeration in the resulting freeze-dried coffee powder after freeze-drying, slowing its dissolution rate. However, rapid cooling increases the freezing rate. This method involves placing the coffee liquid in a quick-freeze chamber and freezing it at a controlled rate of 1-5°C / min, which helps form finer, more uniform ice crystals within the system, resulting in better solubility of the resulting freeze-dried coffee powder.

[0025] The present invention discloses the following technical effects:

[0026] The method of the present invention can effectively improve the dissolution rate of freeze-dried coffee powder. When the freeze-dried coffee powder prepared by the method of the present invention is added to water at room temperature, the powder on the surface sinks completely within 3 seconds, and then the powder in the water is completely dissolved within 7 seconds. The dissolution rate is significantly better than the freeze-dried coffee powder currently on the market, and the flavor is better retained. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. 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 any creative work.

[0028] Figure 1 The flavor retention of the freeze-dried coffee powder prepared in Example 1 and Comparative Example 1.

[0029] Figure 2 The flavor retention of the freeze-dried coffee powder prepared in Comparative Example 1 and Comparative Example 2.

[0030] Figure 3 The flavor retention of the freeze-dried coffee powder prepared in Comparative Example 1 and Example 3.

[0031] Figure 4 The flavor retention of the freeze-dried coffee powder prepared in Example 1 and Example 3.

[0032] Figure 5 The flavor retention of the freeze-dried coffee powder prepared in Example 2 and Comparative Example 4.

[0033] Figure 6 The dissolution effect of the freeze-dried coffee powder prepared in Example 1 and Comparative Example 1 in room temperature water for 1 minute is compared.

[0034] Figure 7 The dissolution effect of the freeze-dried coffee powder prepared in Example 1 in 25°C water in 3 seconds.

[0035] Figure 8 This is the dissolution effect of commercially available freeze-dried coffee powder in 25°C water for 3 seconds. DETAILED DESCRIPTION

[0036] 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 rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0037] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0038] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice 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 any conflict with any incorporated document, the contents of this specification shall prevail.

[0039] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0040] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0041] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0042] The coffee beans used in the embodiments of the present invention are washed beans purchased from Pu'er, Yunnan.

[0043] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] Coffee beans were ground to a particle size of 80 mesh. The ground coffee was added to water at a solid-liquid ratio of 1:10 (g / mL). Ultrasonic extraction was performed at 20°C, 40 kHz, and 3000W of power for 40 minutes. The coffee extract was then filtered to separate the coffee grounds from the coffee liquid A. Coffee liquid A was cooled from 20°C to 10°C at a rate of 1°C / s, then cooled from 10°C to -5°C in a cooling tank over 1 hour. The mixture was allowed to stand for 48 hours. After the oil and water were fully separated, the aqueous layer was collected as coffee liquid B. The upper oil layer was removed and evaporated under reduced pressure at 30°C and a vacuum of 10 kPa. The aroma components were collected and mixed with coffee liquid B to form coffee liquid C. Coffee liquid C was placed in a quick-freeze chamber and cooled at a rate of 5°C / min until the coffee liquid was completely frozen. Then the mixture was transferred to a freeze dryer and freeze-dried for 40 hours at -40°C and a vacuum degree of 20 Pa to obtain solid coffee, i.e., low-temperature instant coffee freeze-dried powder.

[0046] Example 2

[0047] Coffee beans were ground to a particle size of 80 mesh. The ground coffee was added to water at a material-liquid ratio of 1:10 (g / mL). Ultrasonic extraction was performed at 80°C, 40 kHz ultrasonic frequency, and 3000 W input power for 10 minutes. The coffee extract was then filtered to separate the coffee grounds from the coffee liquid A. Coffee liquid A was cooled from 80°C to 20°C at a rate of 6°C / s, then further cooled to -5°C in a cooling tank over 1.5 hours. The mixture was allowed to stand for 48 hours. After the oil and water were fully separated, the aqueous layer was collected as coffee liquid B. The upper oil layer was removed and evaporated under reduced pressure at 30°C and a vacuum of 10 kPa. The aroma components were collected and then mixed with coffee liquid B to form coffee liquid C. Coffee liquid C was placed in a quick-freeze chamber and cooled at a rate of 5°C / min until the coffee liquid was completely frozen. The coffee liquid was then transferred to a freeze dryer and freeze-dried at -40°C and a vacuum of 50 Pa for 48 hours to obtain solid coffee, i.e., low-temperature instant coffee freeze-dried powder.

[0048] Example 3

[0049] Coffee beans were ground to a particle size of 80 mesh. The ground coffee was added to water at a solid-liquid ratio of 1:10 (g / mL). Ultrasonic extraction was performed at 20°C, 40 kHz, and 3000W of power for 40 minutes. The coffee extract was then filtered to separate the coffee grounds from the coffee liquid A. Coffee liquid A was cooled from 20°C to -5°C at a rate of 1°C / s and allowed to stand for 48 hours. After the oil and water were fully separated, the aqueous layer was collected as coffee liquid B. The upper oil layer was removed and evaporated under reduced pressure at 30°C and a vacuum of 10 kPa. The aroma components were collected and then mixed with coffee liquid B to form coffee liquid C. Coffee liquid C was placed in a quick freezer and cooled at a rate of 5°C / min until the coffee liquid was completely frozen. The mixture was then transferred to a freeze dryer and freeze-dried for 40 hours at -40°C and a vacuum of 20 Pa to obtain solid coffee, i.e., low-temperature instant coffee freeze-dried powder (i.e., the only difference from Example 1 is that the coffee liquid A is cooled to -5°C in two stages instead of being cooled to -5°C directly).

[0050] Comparative Example 1

[0051] Coffee beans were ground to a particle size of 80 mesh. The ground coffee was added to water at a solid-liquid ratio of 1:10 (g / mL). Ultrasonic extraction was performed at 20°C, 40 kHz, and 3000W for 40 minutes. The coffee extract was then filtered to separate the coffee grounds, yielding coffee liquid A. This coffee liquid A was then placed in a quick-freeze chamber and cooled at a rate of 5°C / min until completely frozen. The coffee liquid was then freeze-dried in a freeze dryer at -40°C and a vacuum of 50 Pa for 48 hours to obtain a solid coffee, thus obtaining cold-brewed freeze-dried coffee powder.

[0052] Comparative Example 2

[0053] Coffee beans were ground into 80 meshes. The ground coffee was added to water at a material-liquid ratio of 1:10 (g / mL). The water temperature was 20°C, the ultrasonic frequency was 40KHz, and the input power was 3000W. Ultrasonic extraction was performed for 40 minutes. The coffee extract was separated from the coffee grounds by filtration to obtain coffee liquid A. Coffee liquid A was cooled from 20°C to 10°C at a rate of 1°C / s. Then, it was cooled from 10°C to -5°C in a cooling tank over 1 hour. It was allowed to stand for 48 hours. After the oil and water were fully separated, the water layer was collected as coffee liquid B. Coffee liquid B was placed in a quick-freezing storage and cooled at a rate of 5°C / min The mixture was cooled at a rate of 0.05° C. until the coffee liquid was completely frozen, and then transferred to a freeze dryer and freeze-dried for 40 h at -40° C. and a vacuum degree of 20 kPa to obtain solid coffee, i.e., low-temperature instant coffee freeze-dried powder (i.e., the only difference from Example 1 is that the steps of "taking the upper oil layer, evaporating it under reduced pressure at 30° C. and a vacuum degree of 10 kPa, collecting aroma components, and then mixing the aroma components with coffee liquid B to form coffee liquid C" are omitted, and coffee liquid B is directly freeze-dried to obtain low-temperature instant coffee freeze-dried powder).

[0054] Comparative Example 3

[0055] Coffee beans were ground to a particle size of 80 mesh. The ground coffee was added to water at a material-to-liquid ratio of 1:10 (g / mL). Ultrasonic extraction was performed at 20°C, a frequency of 40 kHz, and an input power of 3000 W for 40 minutes. The coffee extract was filtered to separate the coffee grounds from the coffee liquid, yielding coffee liquid A. The coffee was allowed to stand for 48 hours. After the oil and water were fully separated, the aqueous layer was collected as coffee liquid B. The upper oil layer was removed and evaporated under reduced pressure at 30°C and a vacuum of 10 kPa. The aroma components were collected and then mixed with coffee liquid B to form coffee liquid C. Coffee liquid C was placed in a quick-freeze chamber and cooled at a rate of 5°C / min until the coffee liquid was completely frozen. The coffee liquid C was then transferred to a freeze dryer and freeze-dried for 40 hours at -40°C and a vacuum of 20 Pa to yield solid coffee, i.e., a low-temperature instant coffee freeze-dried powder. (This differs from Example 1 only in that the cooling step is omitted when preparing coffee liquid B from coffee liquid A.)

[0056] Comparative Example 4

[0057] Coffee beans were ground into 80 mesh particles. The ground coffee was added to water at a material-liquid ratio of 1:10 (g / mL). The water temperature was 80°C, the ultrasonic frequency was 40KHz, the input power was 3000W, and ultrasonic extraction was performed for 10 minutes. The coffee extract was separated from the coffee grounds by filtration to obtain coffee liquid A. The coffee liquid A was naturally cooled from 80°C to 20°C, and then further cooled to -5°C in a cooling tank for 1.5 hours. It was allowed to stand for 48 hours. After the oil and water were fully separated, the water layer was collected as coffee liquid B. The upper oil layer was taken and evaporated under reduced pressure at 30°C and a vacuum degree of 10kPa to collect the aroma components. The aroma components are then mixed with coffee liquid B to form coffee liquid C. Coffee liquid C is placed in a quick-freeze chamber and cooled at a rate of 5°C / min until the coffee liquid is completely frozen. The coffee liquid is then transferred to a freeze dryer and freeze-dried for 48 hours at -40°C and a vacuum of 50 Pa to obtain solid coffee, i.e., low-temperature instant coffee freeze-dried powder (i.e., the only difference from Example 2 is that, when preparing coffee liquid B, "coffee liquid A is cooled from 80°C to 20°C at a rate of 6°C / s" is adjusted to "coffee liquid A is naturally cooled from 80°C to 20°C").

[0058] Effect Example 1

[0059] 1. Comparative test of flavor sensory properties of cold-brew freeze-dried coffee powder (i.e., freeze-dried coffee powder prepared in Examples 1 and 3 and Comparative Examples 1-3)

[0060] The sensory evaluation panel consisted of 10 individuals (5 men and 5 women), all qualified specialty coffee quality graders (Q-Graders) with the ability to accurately identify coffee quality. The sensory evaluation followed the sensory evaluation criteria established by the Specialty Coffee Association of America (SCA), assessing aroma, flavor, acidity, body, uniformity, clean cup, balance, and sweetness to determine the flavor attributes of the samples. All samples were provided at room temperature (20°C) and evaluated in random order.

[0061] Each treatment was tested in five independent replicates, and samples were collected for panelists to assess. Panelists 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.

[0062] (1) Flavor description

[0063] Example 1: Aroma: berries, nuts (the overall aroma is light); Taste: less bitter, balanced acidity, light body, clean and bright.

[0064] Example 3: Aroma: berries, nuts, Taste: less bitter, balanced acidity, full, light mellowness, clean and bright.

[0065] Comparative Example 1: Aroma: citrus, berry, nuts; Taste: less bitter, balanced acidity, full, soft, clean and bright.

[0066] Comparative Example 2: The aroma is obviously lost, the taste is relatively prominent, and the taste is relatively smooth, clean, and has a distinct sweet aftertaste.

[0067] Comparative Example 3: Coffee deteriorated and the aroma was completely lost

[0068] (2) Analysis of flavor evaluation results

[0069] Based on the sensory evaluation results of Examples 1 and 3 and Comparative Examples 1-3, the sensory evaluation of Comparative Example 1 reflects the flavor obtained by direct freeze-drying after cold extraction, which reflects the original flavor of the cold-extracted freeze-dried coffee powder. During the cold extraction process, Example 1 undergoes two cooling stages: first, rapid cooling to room temperature, then cooling to -5°C, followed by fat removal and recovery of the aroma dissolved in the fat. The resulting freeze-dried coffee powder better retains the coffee aroma, and compared to Comparative Example 1, Example 1 better preserves the flavor. Example 3, in which coffee liquid A is directly and rapidly cooled to -5°C, followed by fat removal and recovery of the aroma dissolved in the fat, does not undergo a two-stage cooling process. However, the rapid cooling reduces material changes in the thermal environment, resulting in better preservation of the coffee aroma. Compared to Example 1, both methods employ a cooling process, and therefore better preserve the coffee flavor, with little difference between the two. In Comparative Example 2, the aroma in the upper oil layer was not recovered, and the water layer (coffee liquid B) was directly freeze-dried. Compared with Comparative Example 1, the resulting freeze-dried coffee powder had a serious loss of flavor substances. In Comparative Example 3, coffee liquid A was not cooled in a low-temperature environment and was left at room temperature for 48 hours, causing the coffee liquid to deteriorate. The results are shown in the figure. Figure 1-4 And shown in Table 1.

[0070] Table 1 Statistics of flavor index results of cold brew coffee freeze-dried powder prepared in Examples 1 and 3 and Comparative Examples 1-3

[0071] aroma Flavor acidity body consistency Cleanliness Balance sweetness Example 1 7.75 8.75 7 7.75 9.5 9.25 8.25 8.75 Example 3 7.75 8.75 7 8.25 9.5 9 8.25 8.75 Comparative Example 1 8.75 8.75 7.5 8.75 9.5 9 8.25 8.75 Comparative Example 2 7 8.5 7 7.25 9 9 7.25 9 Comparative Example 3 0 0 0 0 9 0 0 0

[0072] 2. Comparative flavor sensory test of hot-extracted freeze-dried coffee powder (freeze-dried coffee powder prepared in Example 2 and Comparative Example 4) was conducted using the same method as the above-mentioned comparative flavor sensory test of cold-extracted freeze-dried coffee powder.

[0073] (1) Flavor description

[0074] Example 2: citrus, berries, nuts, taste: bright acidity, fruity acidity, slight bitterness, mellowness with a juicy texture, and relatively light sweetness.

[0075] Comparative Example 4: The aroma evaporated severely, and the oil was oxidized, with the flavor retained less than 60%. The sourness was weakened, the bitterness was more prominent, and the sweetness was comparable to caramel.

[0076] (2) Analysis of flavor evaluation results

[0077] Based on the cold extraction results, it can be seen that the coffee liquid can effectively retain the coffee flavor after rapid cooling and flavor recovery in the oil. Therefore, during the hot extraction process, this step is continued to ensure the retention of flavor substances. From the perspective of actual production, in the industrial production process, compared with cooling to -5°C in two stages and directly cooling to -5°C, the method of directly cooling to -5°C has higher requirements for the refrigerator, resulting in excessively high equipment costs. Therefore, the use of two-stage cooling is more suitable for reducing industrial costs. Example 2 refers to the above experimental results. After two stages of cooling, it is first rapidly cooled to room temperature and then cooled to -5°C. The oil is then removed and the aroma dissolved in the oil is recovered to obtain freeze-dried coffee powder. Comparative Example 4 uses the same method as Example 2, except that it does not undergo rapid cooling to room temperature, but is naturally cooled to room temperature and then cooled to -5°C. During the production process, 80°C is naturally cooled to room temperature, which takes a total of 5 hours. Since the coffee liquid stays in a high temperature environment for a long time, the hot-extracted freeze-dried powder obtained in Comparative Example 4 has a much different flavor than that in Example 2. The results are as follows Figure 5 and as shown in Table 2.

[0078] Table 2 Statistics of flavor index results of the hot-extracted coffee freeze-dried powder prepared in Example 2 and Comparative Example 4

[0079]

[0080] The above test results of cold-extracted and hot-extracted freeze-dried coffee powders confirmed that the freeze-dried coffee powder obtained by rapid cooling and recovery of the aroma substances of the oil can better preserve the flavor of the coffee.

[0081] 3. Solubility comparison experiment 1

[0082] 3 g of each of the freeze-dried coffee powders obtained in Examples 1-3 and Comparative Examples 1-4 were poured into 180 mL of room temperature water (25°C), allowed to settle, and the sinking of the coffee on the liquid surface was observed. The dissolution time was recorded. The results are shown in Tables 3 and Figure 6 As shown in Table 3, the solubility of freeze-dried coffee powder can be significantly improved by removing the oil.

[0083] Table 3 Comparison of the dissolution of freeze-dried coffee powder prepared in Examples 1-3 and Comparative Examples 1-4

[0084]

[0085] From the above content, it can be seen that the freeze-dried coffee powder prepared by the method of the present invention significantly improves the instant solubility of coffee while better retaining the coffee flavor.

[0086] 4. Solubility comparison experiment 2

[0087] Based on the experimental results above, 3g of each of the freeze-dried coffee powder obtained in Example 1 of the present invention and a commercially available cold-brew freeze-dried powder were added to 180mL of room-temperature water (25°C). The mixture was stirred to varying degrees, and the dissolution was observed and the dissolution time was recorded. The results are shown in Table 4. The freeze-dried coffee powder obtained in the present invention completely dissolved in room-temperature water in just 10 seconds, while the commercially available product required prolonged stirring to achieve dissolution. The dissolution rate of the present invention was superior to that of the commercially available product.

[0088] Table 4 Comparison results between Example 1 and commercially available cold-brew freeze-dried coffee powder

[0089]

[0090]

[0091] Figure 7 The dissolution effect of the freeze-dried coffee powder prepared in Example 1 in 25°C water in 3 seconds. Figure 8 This is the dissolution effect of commercially available freeze-dried coffee powder (a certain brand of commercial product C) in 25°C water for 3 seconds. Figure 7 and Figure 8 It can be seen that the freeze-dried coffee powder prepared in Example 1 of the present invention was essentially completely dissolved in 25°C water after 3 seconds, forming a clear liquid. The coffee liquid scooped from the bottom of the cup contained no insoluble matter. In contrast, the commercially available freeze-dried coffee powder completely sank in 25°C water after 3 seconds, with no floating freeze-dried powder on the water surface. However, a large amount of insoluble matter remained at the bottom of the water, and the coffee liquid scooped from the bottom of the cup contained a large amount of oily insoluble matter.

[0092] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for improving the solubility of freeze-dried coffee powder, characterized in that: The following steps are involved: Extracting coffee beans to obtain coffee liquid A; Cooling the coffee liquid A to -5°C to 10°C and allowing it to stand to separate into an aqueous layer and an oil layer; The oil layer is evaporated under reduced pressure to obtain aroma components; the aroma components are mixed with the water layer to obtain coffee liquid C; The coffee liquid C is frozen and then freeze-dried to obtain the freeze-dried coffee powder.

2. The method for improving the solubility of freeze-dried coffee powder according to claim 1, wherein: The extraction method is ultrasonic extraction; the extraction temperature is 4°C to 80°C.

3. The method for improving the solubility of freeze-dried coffee powder according to claim 1, wherein: The cooling method is two-stage cooling or direct cooling.

4. The method for improving the solubility of freeze-dried coffee powder according to claim 3, wherein: The two-stage cooling process is as follows: firstly cooling the temperature to 10°C at a rate of 1°C / s, and then cooling the temperature to -5°C at a rate of 15°C / h.

5. The method for improving the instant solubility of freeze-dried coffee powder according to claim 3, characterized in that: The direct cooling is specifically to directly cool to -5 to 10°C at a rate of 1°C / s.

6. The method for improving the solubility of freeze-dried coffee powder according to claim 1, wherein: The standing time is 6 to 48 hours.

7. The method for improving the solubility of freeze-dried coffee powder according to claim 1, wherein: The vacuum degree of the reduced pressure evaporation is 10-30 kPa, and the temperature is 30-50°C.

8. The method for improving the solubility of freeze-dried coffee powder according to claim 1, wherein: The freezing temperature reduction rate is 1-5°C / min.

9. The method for improving the solubility of freeze-dried coffee powder according to claim 1, wherein: The freeze-drying temperature is -60°C to -30°C, the vacuum degree is 9 to 50 Pa, and the time is 24 to 48 hours.

Images