Vacuum freeze-dried coffee ball preparation process

Abstract

This invention belongs to the field of vacuum freeze-drying coffee, specifically a process for preparing vacuum freeze-dried coffee balls. The process includes the following steps: S1: Pre-freezing coffee extract by dripping it into liquid nitrogen to obtain coffee ice balls; S2: Freezing the coffee ice balls in a freeze dryer to obtain freeze-dried coffee balls. This method uses liquid nitrogen for pre-freezing, which is simple to operate. Forming ice balls at the ultra-low temperature of liquid nitrogen before vacuum freeze-drying not only shortens the freeze-drying time but also maximizes the preservation of the coffee's flavor components.

Description

Technical Field

[0001] This invention belongs to the field of vacuum freeze-drying coffee, specifically the process for preparing vacuum freeze-dried coffee balls. Background Technology

[0002] Vacuum freeze drying is a process that uses a vacuum freeze dryer to remove moisture from solidified materials by direct sublimation under low temperature and vacuum. The entire freeze drying process can generally be divided into three stages: pre-freezing, primary drying (main sublimation and main drying), and secondary drying.

[0003] Traditional freeze-dried coffee powder is made by quickly freezing coffee extract and then vacuum freeze-drying it. After drying, it is ground to obtain freeze-dried coffee particles of varying shapes, which are then weighed and packaged. In this method, the thick layers of coffee ice prevent sublimation, resulting in a very long freeze-drying time, typically over 20 hours, and the freeze dryer consumes a great deal of energy. To address this issue, some processes advance the grinding process, grinding the coffee into ice crystals after the quick-freezing stage before vacuum freeze-drying, partially solving the problem of the long freeze-drying time. However, this process prolongs the freezing process of the coffee liquid and also leads to a loss of coffee flavor. Summary of the Invention

[0004] This invention addresses the above-mentioned technical problems by providing a vacuum freeze-drying process for preparing coffee balls. This process not only shortens the freeze-drying time but also preserves the coffee flavor to a great extent.

[0005] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows:

[0006] The process for preparing vacuum freeze-dried coffee balls includes the following steps:

[0007] S1: Pre-freeze the coffee extract by dripping it into liquid nitrogen to obtain coffee ice balls;

[0008] S2: Send the coffee ice ball into a freeze dryer for freeze drying to obtain freeze-dried coffee balls.

[0009] Preferably, in step S1, the coffee extract is added to liquid nitrogen at a volume of 1-200 microliters; more preferably, the coffee concentrate is added to liquid nitrogen at a volume of 1-100 microliters; and even more preferably, the coffee concentrate is added to liquid nitrogen at a volume of 1-50 microliters. In practice, larger drops will break into smaller droplets upon contact with liquid nitrogen, ultimately forming coffee balls of varying sizes, which affects the appearance.

[0010] Preferably, the liquid nitrogen mentioned in S1 is liquid nitrogen at -196°C.

[0011] As a preferred option, the coffee ice balls in S2 are fed into a freeze dryer for freeze drying. The freeze drying conditions are as follows: the main drying temperature is -40℃ to -10℃, the main drying time is 2 to 8 hours, and after removing free water, they enter the secondary drying process. The secondary drying temperature is 20℃ to 35℃, and the time is 1 to 4 hours. Time and temperature are inversely proportional; the higher the temperature, the shorter the time.

[0012] Further optimization involves feeding the coffee ice balls in S2 into a freeze dryer for freeze drying. The freeze drying conditions are: primary drying at -15°C and 20 Pa for 4 hours, followed by secondary drying at 25°C and 5 Pa for 2 hours. Under the optimal parameter settings, the process achieves the shortest time and lowest energy consumption, primarily while preserving the flavor.

[0013] Furthermore, this process is applicable to preparation processes using tea as the raw material; simply replace the coffee extract with a tea extract.

[0014] Furthermore, this process is applicable to preparation processes using Dendrobium as the raw material; simply replace the coffee extract with Dendrobium extract obtained from Dendrobium.

[0015] The coffee extract is a commercially available product; it can also be obtained by direct extraction from coffee beans. The extraction method does not affect the final product; common methods such as cold brew, hot brew, and hot brew espresso are all acceptable. The concentration of the coffee extract also has no impact on the final product and can be adjusted according to requirements.

[0016] Pre-freezing is achieved by dripping a specific volume (e.g., 1-200 microliters) of coffee extract into liquid nitrogen. At -196°C, the coffee droplets rapidly solidify into coffee ice balls. These ice balls are then freeze-dried, significantly reducing the freeze-drying time. Firstly, the coffee ice balls, already frozen at ultra-low temperatures in liquid nitrogen, no longer require pre-freezing and can be directly sublimated. Secondly, the spherical shape provides the largest specific surface area, further minimizing the sublimation process.

[0017] Furthermore, upon contact with liquid nitrogen, the rapid vaporization of the nitrogen encapsulates the coffee droplets, causing them to quickly tumble and form spherical droplets on the nitrogen surface. Simultaneously, the lipids in the coffee solution are distributed on the outer surface of these spherical droplets due to surface tension and the hydrophobic interaction between lipids and water, while the hydrophilic substances remain inside the spheres. Therefore, under controlled processing, when coffee droplets are introduced into liquid nitrogen, they form spherical coffee ice spheres with lipids distributed on the surface. These ice spheres not only shorten the freeze-drying time, but the lipid encapsulation also better preserves flavor compounds.

[0018] Compared with the prior art, the positive effects of the present invention are reflected in:

[0019] Liquid nitrogen is easy to operate. After forming ice balls through the ultra-low temperature of liquid nitrogen, it is then vacuum freeze-dried, which not only shortens the freeze-drying time but also preserves the flavor components of coffee to the greatest extent. Attached Figure Description

[0020] Figure 1 The image shows the freeze-dried coffee balls prepared in Example 1. The coffee balls are broken into two halves after freeze-drying. The inner core of the ball is dark brown, and the outer surface is a light-colored layer.

[0021] Figure 2 The vacuum freeze-dried coffee balls prepared in Comparative Example 2;

[0022] Figure 3 The vacuum freeze-dried coffee balls prepared in Comparative Example 3;

[0023] Figure 4 The image shows the flavor composition rating charts for Examples 1, 2, and the coffee concentrate. Detailed Implementation

[0024] To facilitate understanding of the present invention, specific embodiments are described below. However, this should not be construed as limiting the scope of the invention to the following embodiments.

[0025] In this application, the technique for preparing coffee concentrate from coffee beans is existing technology, such as conventional extraction techniques.

[0026] Example 1:

[0027] 65g of commercially available roasted coffee beans were thoroughly ground and extracted to obtain 1L of coffee extract (coffee concentrate). 20 μL of this extract was dropped into liquid nitrogen (-196°C) to obtain coffee ice balls (this can be done using a pipette, dropper, dispenser, automated pipetting station, etc.). These coffee ice balls were then freeze-dried to obtain freeze-dried coffee balls. During freeze-drying, the machine was pre-frozen to the main drying temperature or below before transferring the coffee balls into the freeze dryer for vacuum freeze-drying. The vacuum freeze-drying conditions were: -15°C, 20 Pa, 4 hours for the main drying, followed by a second drying at 25°C, 5 Pa, 2 hours. After freeze-drying, freeze-dried coffee balls with a diameter of approximately 2mm were obtained. The outer surface of these freeze-dried coffee balls (spheres) was light-colored and oily, while the interior contained a dark-colored hydrophilic substance.

[0028] Example 2:

[0029] 70g of commercially available roasted coffee beans were thoroughly ground and extracted to obtain 1L of coffee extract (coffee concentrate). The coffee extract was then dropped into liquid nitrogen in 30µL droplets to form coffee ice balls. These ice balls were then freeze-dried to obtain freeze-dried coffee balls. During freeze-drying, the machine was pre-frozen to or below the main drying temperature before transferring the coffee balls into the freeze dryer for vacuum freeze-drying. The vacuum freeze-drying conditions were: -20℃, 20Pa, 4 hours for the main drying, followed by a second drying at 20℃, 5Pa, 2 hours. After freeze-drying, the coffee balls were approximately 3mm in diameter. The outer surface of these freeze-dried coffee balls (spheres) was light-colored and oily, while the interior contained a dark-colored hydrophilic substance.

[0030] Example 3:

[0031] 75g of commercially available roasted coffee beans were thoroughly ground and extracted to obtain 1L of coffee extract (coffee concentrate). The coffee extract was then dropped into liquid nitrogen at 40µL droplets to form coffee ice balls. These ice balls were then freeze-dried to obtain freeze-dried coffee balls. During freeze-drying, the machine was pre-frozen to or below the main drying temperature before transferring the coffee balls into the freeze dryer for vacuum freeze-drying. The vacuum freeze-drying conditions were: -20℃, 20Pa, 4 hours for the main drying, followed by a second drying at 20℃, 5Pa, 2 hours. After freeze-drying, the coffee balls were approximately 3.7mm in diameter. The outer surface of these freeze-dried coffee balls (spheres) was light-colored and oily, while the interior contained a dark-colored hydrophilic substance.

[0032] Example 4:

[0033] 80g of commercially available roasted coffee beans were thoroughly ground and extracted to obtain 1L of coffee extract (coffee concentrate). The coffee extract was then dropped into liquid nitrogen in 50µL droplets to form coffee ice balls. These coffee ice balls were then freeze-dried to obtain freeze-dried coffee balls. During freeze-drying, the machine was pre-frozen to or below the main drying temperature before transferring the coffee balls into the freeze dryer for vacuum freeze-drying. The vacuum freeze-drying conditions were: -20℃, 20Pa, 4 hours for the main drying, followed by a second drying at 20℃, 5Pa, 2 hours. After freeze-drying, the coffee balls were approximately 4.5mm in diameter. The outer surface of these freeze-dried coffee balls (spheres) was light-colored and oily, while the interior contained a dark-colored hydrophilic substance.

[0034] Example 5:

[0035] 85g of commercially available roasted coffee beans were thoroughly ground and extracted to obtain 1L of coffee extract (coffee concentrate). This extract was then dropped into liquid nitrogen in 60µL droplets to form coffee ice balls. These ice balls were then freeze-dried to obtain freeze-dried coffee balls. During freeze-drying, the machine was pre-frozen to or below the main drying temperature before the coffee balls were transferred to the freeze dryer for vacuum freeze-drying. The vacuum freeze-drying conditions were: -20℃, 20Pa, 4 hours for the main drying, followed by a second drying at 20℃, 5Pa, 2 hours. After freeze-drying, the coffee balls were approximately 5.2mm in diameter. The outer surface of these freeze-dried coffee balls (spheres) was light-colored and oily, while the interior contained a dark-colored hydrophilic substance.

[0036] Example 6:

[0037] 85g of commercially available roasted coffee beans were thoroughly ground and extracted to obtain 1L of coffee extract (coffee concentrate). This extract was then dropped into liquid nitrogen in 70µL droplets to form coffee ice balls. These ice balls were then freeze-dried to obtain freeze-dried coffee balls. During freeze-drying, the machine was pre-frozen to or below the main drying temperature before the coffee balls were transferred to the freeze dryer for vacuum freeze-drying. The vacuum freeze-drying conditions were: -20℃, 20Pa, 4 hours for the main drying, followed by a second drying at 20℃, 5Pa, 2 hours. After freeze-drying, the coffee balls were approximately 6mm in diameter. The outer surface of these freeze-dried coffee balls (spheres) was light-colored and oily, while the interior contained a dark-colored hydrophilic substance.

[0038] Comparative Example 1:

[0039] The coffee concentrate from the example was dispensed into vials, frozen in a quick-freezing machine, and then the vials were sent to a freeze dryer for freeze drying. During freeze drying, the machine was pre-frozen to the main drying temperature or below, and the coffee pellets were transferred into the freeze dryer for vacuum freeze drying. The vacuum freeze drying conditions were: -20°C, 20 Pa, 4 hours for the main drying, followed by a second drying at 20°C, 5 Pa, 2 hours. After freeze drying, the product was removed from the freeze dryer as an extremely viscous liquid or a drastically shrunken "cake" state.

[0040] Comparative Example 2:

[0041] The preparation method is the same as in Example 1, except that the main drying temperature in Example 1 is changed to -45°C and the main drying time is 8 hours, while the other conditions remain the same. Finally, freeze-dried coffee balls are obtained. These freeze-dried coffee balls liquefy rapidly or partially liquefy after the machine is stopped.

[0042] Comparative Example 3:

[0043] The preparation method is the same as in Example 1, except that the main drying temperature in Example 1 is changed to -25°C and the main drying time is 1.5 hours, while all other conditions remain the same. Finally, freeze-dried coffee balls are obtained. After the freeze-dried coffee balls are shut down, they rapidly liquefy or partially liquefy.

[0044] test:

[0045] The coffee spheres obtained in Examples 1-6 were tested against the coffee products in the comparative examples. The specific results are shown in the table below:

[0046]

[0047] Flavor tests were conducted on Example 1, Example 2, and the coffee concentrate. Specific results are shown in [link to results]. Figure 4 .

[0048] As can be seen from the above, this method can prepare spherical freeze-dried coffee balls in a very short time with low energy consumption. Furthermore, the freeze-dried coffee balls prepared by this method not only have a beautiful, aesthetically pleasing spherical shape, but also dissolve rapidly in cold water without stirring or leaving any residue. Tests have shown that they maintain the same flavor profile as the original liquid extract.

[0049] The above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A process for the preparation of vacuum freeze-dried coffee pellets, characterized in that, It comprises the following steps: S1: drop the coffee extract into liquid nitrogen for pre-freezing to obtain coffee ice ball; S2: send the coffee ice ball into a freeze dryer for freeze-drying to obtain freeze-dried coffee ball; The freeze-drying condition is: the main drying temperature is-40℃ to-10℃, the main drying time is 2-8 hours, after removing free water, secondary drying is entered, the secondary drying temperature is 20℃ to 35℃, and the time is 1-4 hours; the time and the temperature are inversely proportional, the higher the temperature, the shorter the time.

2. The process for preparing a vacuum-frozen, freeze-dried coffee puck according to claim 1, wherein: The liquid nitrogen in S1 is-196℃ liquid nitrogen.

3. The process for preparing a vacuum-frozen coffee puck according to claim 1, wherein: In S2, the coffee ice ball is sent into a freeze dryer for freeze-drying, and the freeze-drying condition is-15℃, 20pa main drying for 4 hours, then the temperature is raised to 25℃, 5pa main drying for 2 hours.

4. The process of claim 1, wherein: In S1, when the coffee extract is dropped into liquid nitrogen, the volume is 1-50 microliters.

5. The process of claim 1, wherein: The coffee extract is a commercially available product.

6. Use of the process for the preparation of vacuum-frozen, freeze-dried coffee pellets according to any one of claims 1 to 4 in a process for the preparation of tea, characterized in that, The coffee extract in the preparation process of the vacuum freeze-dried coffee ball in any one of claims 1-4 is replaced by tea extract.

7. The use of the process for preparing vacuum freeze-dried coffee pellets according to any one of claims 1 to 4 in the process for preparing Dendrobium nobile Lindl, characterized in that, The coffee extract in the preparation process of the vacuum freeze-dried coffee ball in any one of claims 1-4 is replaced by Dendrobium extract.

Images