High-aroma cold-soluble instant black tea and preparation method thereof

Abstract

The application relates to the technical field of tea deep processing, in particular to a high-aroma cold-soluble instant black tea and a preparation method thereof, the preparation method comprising the following steps: (1) naturally withering fresh tea tree leaves; (2) performing 3D airflow dynamic fermentation on the withered leaves; (3) performing high-pressure bubble and low-frequency ultrasonic low-temperature extraction on the fermented leaves in step (2); (4) centrifuging the extracted liquid and taking supernatant; (5) performing reverse osmosis membrane concentration on the supernatant; and (6) performing spray drying on the concentrated liquid to obtain instant black tea powder. Through optimization of the process, the instant black tea prepared by the application can be dissolved in cold water, the solubility of the black tea is improved, the product has the characteristics of flower and fruit aroma, full and rich sweet aroma and thick taste due to the unique process, and can be applied to more fields.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tea deep processing, and particularly relates to a high-aroma cold-soluble instant black tea and a preparation method thereof. BACKGROUND

[0002] Instant black tea generally refers to instant powder produced through the processes of extraction, filtration, concentration and drying, etc. using black tea dry leaves as raw materials.

[0003] The production process of black tea dry leaves mainly includes withering, rolling, fermentation and drying. Polyphenols exist in the vacuoles of fresh leaves, and polyphenol oxidase is generally considered to exist in chloroplasts. When the vacuole membrane of fresh leaves is damaged due to rolling, the vacuole juice is forced out, and polyphenols are free to diffuse into the protoplasm, and contact with polyphenol oxidase and oxygen gathered in chloroplasts and mitochondria, resulting in rapid enzymatic oxidation. Therefore, rolling is a necessary condition for fermentation. However, polyphenols are also natural precipitants and inhibitors of enzymes, which can greatly reduce the activity of enzymes, thereby inhibiting the pathway of enzyme-catalyzed reaction to form aroma. Therefore, the aroma components of black tea produced through rolling are relatively single, and the aroma concentration is also low. The essence of fermentation is the enzymatic oxidation and polymerization of polyphenols to form colored substances such as theaflavins and thearubigins. Generally, the fermented leaves are filled in a large container, stacked to a thickness of 20-40 cm, covered with wet cloth, and given temperature to promote fermentation. Because the rolling leaves are damaged to a large extent, the fermentation is usually carried out under relatively intense conditions, and therefore the control of fermentation time and fermentation endpoint is highly dependent on the experience of workers. In addition, stacking is easy to cause uneven fermentation, leading to over-fermentation or under-fermentation. Under-fermentation easily leads to residual green aroma, and over-fermentation easily leads to deterioration of aroma, thereby affecting the overall aroma quality of black tea.

[0004] Excessive fermentation also leads to excessive accumulation of theaflavins and thearubigins, which can easily form complexes with caffeine through hydrogen bonding. As the complexes continue to grow, they form cold-water insoluble substances, also known as tea cream. Tea cream dissolves in hot water in a free state, so the extraction temperature of instant black tea is close to 100 DEG C. However, instant black tea produced by high-temperature extraction can only be dissolved in hot water, and cannot achieve cold-water instant dissolution. The general method for producing cold-dissolving instant black tea in the industry is to reduce the extraction temperature and discard part of the tea cream to improve the cold-water solubility. The disadvantage is that the extraction is not sufficient, resulting in a thin product taste, weak aroma, light soup color and low yield. The drying process of tea leaves causes a large amount of volatile aromatic substances, resulting in high fire aroma or even burnt fire aroma. High temperature also causes partial leaf carbonization and hardening, further affecting the turbidity and cold-water solubility of instant black tea. Therefore, tea leaf drying is also an unfavorable step for instant black tea. In summary, starting from tea fresh leaves, improving the production process and innovating the development of a high-aroma and cold-water instant instant black tea with cold-water instant dissolution are very valuable according to the characteristics of the target instant black tea. SUMMARY

[0005] In order to solve the above problems, on the basis of the existing preparation of instant black tea, the application provides a high-aroma cold-dissolving instant black tea and a preparation method thereof.

[0006] The first aspect of the application provides a preparation method of a high-aroma cold-dissolving instant black tea, comprising the following preparation steps:

[0007] (1) obtaining withering leaves by naturally withering tea fresh leaves, the withering leaves having a water content of 45-55%;

[0008] (2) performing 3D airflow dynamic fermentation on the withering leaves, the airflow flow rate of the mixed gas being 10-20 m / s, the gas pressure being 0.6-1.0 MPa, the fermentation temperature being 15-30 DEG C, and the fermentation humidity being 70-80%; the mixed gas comprises oxygen and air, and the mass ratio of oxygen to air is 3:6-9;

[0009] (3) performing high-pressure bubble assisted low-frequency ultrasonic low-temperature extraction on the fermented leaves obtained in step (2), the wave band of the low-frequency ultrasonic being 20-30 KHz, and the energy output being 200-400 W; during the ultrasonic treatment, mixed gas is continuously added to the extraction liquid, the mixed gas comprising oxygen and air, and the mass ratio of oxygen to air being 3:6-9;

[0010] (4) centrifuging the extraction liquid obtained in step (3) to obtain supernatant;

[0011] (5) concentrating the supernatant by reverse osmosis membrane to 18-25 Brix to obtain a concentrate;

[0012] (6) the concentrated liquid is spray dried.

[0013] Further, the wilting condition in step (1) is: temperature 28-32 DEG C, humidity 60-70%, leaf thickness 10-20 cm, time 14-18 h.

[0014] Further, the mixed gas treatment condition in step (2) is: treatment time 30 min-1 h, standing time 30 min-2 h, cycle treatment 5-20 times.

[0015] Further, the gas flow pressure in step (3) is 0.1-0.5 Mpa, and the gas flow speed is 20-40 ml / min.

[0016] Further, the extraction temperature in step (3) is 40-50 DEG C, the extraction time is 20-60 min, the extraction solvent is water, and the mass ratio of the fermented leaf to water is 1:7-10.

[0017] Further, the centrifugation temperature in step (4) is 25-35 DEG C, the rotation speed is 3000-4000 r / min, and the time is 10-30 min.

[0018] Further, the concentration temperature in step (5) is 20-30 DEG C.

[0019] Further, the concentrated liquid is spray dried to a moisture content of less than 5% in step (6).

[0020] Further, the inlet air temperature of the spray drying is 150-200 DEG C, and the outlet air temperature is 60-80 DEG C.

[0021] The second aspect of the application provides a high-aroma cold-soluble instant black tea powder prepared by the above method.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] 1. The present application uses 3D air flow dynamic fermentation process instead of traditional kneading and fermentation process. The withering leaves are put into 3D air flow dynamic fermentation machine, high pressure mixed gas is introduced, and the impact force of air flow on fresh leaves, the friction force between fresh leaves, and the collision force between fresh leaves and the inner wall of the fermentation machine are used to fully activate the various bioactive enzymes in the cells of fresh leaves. After a period of collision, the leaves are allowed to stand for a period of fermentation. The fermentation process has mixed gas introduced, and the temperature and humidity are controlled, so that the fermentation is carried out in an environment with increased oxygen and variable temperature and humidity. According to the tenderness of tea leaves, the fermentation degree of target black tea, and the aroma style, different air flow impact forces, standing times, and cycle times are set. The use of 3D air flow dynamic fermentation instead of conventional process kneading and fermentation avoids the inhibition of polyphenols in the cytoplasm to enzymes during kneading, makes the fermentation more uniform, and the generation of aroma substances more sufficient, greatly improving the types and height of black tea aroma.

[0024] 2. In order to avoid the influence of tea drying process on the turbidity of instant black tea, the fermented tea is not dried, but directly extracted by high pressure bubble and low frequency ultrasonic low temperature. The main basis of ultrasonic extraction is the cavitation effect of ultrasonic. When high energy ultrasonic wave acts, the medium is torn into many small cavities, these small cavities are closed instantaneously, and the instantaneous pressure as high as several thousand atmospheres is generated, that is, cavitation phenomenon. The cavitation effect will be weakened under traditional high frequency ultrasonic, and the high frequency ultrasonic increases the thermal effect of the extraction process, which will have a certain destructive effect on the aroma and some flavoring substances in the black tea. Therefore, the extraction process of the present application uses low frequency ultrasonic 20-30KHz to maximize the cavitation effect of ultrasonic, while reducing the thermal damage effect on the loss of tea aroma. During the extraction process, exogenous mixed oxygen is continuously introduced into the extraction liquid to increase the number of microcavities and enhance the generation of cavitation effect, improve the extraction effect, and high pressure bubble uses air and oxygen mixture to increase the oxygen content in the mixed gas, which can efficiently extract and continuously oxidize the black tea extract. Finally, the instant black tea obtained by this process has more mellow aroma and brighter soup color.

[0025] 3. The extraction liquid concentration process uses reverse osmosis membrane concentration to avoid the production of high molecular polymers in the black tea extract due to long time high temperature treatment. Finally, the black tea extract is dried and aroma is extracted by short time spray drying process, which locks the floral and fruity aroma generated during fermentation of black tea, and promotes the formation of sweet aroma of black tea. The instant black tea produced by this process can be dissolved in cold water, which not only improves the solubility of black tea, but also has floral and fruity aroma, sweet and full-bodied aroma, and rich taste due to the unique process, which can be applied to more fields. DETAILED DESCRIPTION

[0026] The technical solutions of the present application will be described clearly and completely below in connection with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0027] Embodiment 1

[0028] The present embodiment provides a high-aroma cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0029] (1) Withering: temperature: 30℃, humidity: 62%; leaf thickness: 15cm, time: 15h. Withered leaf moisture content: 52%.

[0030] (2) 3D airflow dynamic fermentation: mixed gas airflow pressure: 0.8Mpa, airflow speed: 15m / s, fermentation temperature: 25℃, fermentation humidity: 75%, processing time: 35min, standing time: 40min, cycle processing: 8 times; mixed gas composition: oxygen: air = 3:6.

[0031] (3) High-pressure bubble combined with low-frequency ultrasonic low-temperature extraction: ultrasonic band 20KHz, energy output 350W, extraction temperature 45℃, tea-water ratio 1:7, ultrasonic extraction time: 30min. High-pressure mixed gas airflow pressure 0.4Mpa, airflow speed 30ml / min, mixed gas composition: oxygen: air = 3:6.

[0032] (4) Centrifugation: temperature: 30℃, speed: 3000r / min, time: 15min.

[0033] (5) Reverse osmosis membrane concentration: temperature: 30℃, concentration: 22Brix.

[0034] (6) Spray drying: inlet air temperature 180℃, outlet air temperature 75℃, moisture content 4%, to obtain the high-aroma cold-soluble instant black tea.

[0035] Embodiment 2

[0036] The present embodiment provides a high-aroma cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0037] (1) Withering: temperature: 28℃, humidity: 65%; leaf thickness: 12cm, time: 16h. Withered leaf moisture content: 50%.

[0038] (2) 3D airflow dynamic fermentation: mixed gas airflow pressure: 0.9 Mpa, airflow speed: 18 m / s, fermentation temperature: 20℃, fermentation humidity: 78%, processing time: 50 min, standing time: 60 min, cycle processing: 10 times; mixed gas composition: oxygen: air = 3:8.

[0039] (3) High-pressure bubble cooperates with low-frequency ultrasonic low-temperature extraction: ultrasonic wave band 25 KHz, energy output 300 W, extraction temperature 40℃, tea-water ratio 1:8, ultrasonic extraction time: 20 min. High-pressure mixed gas airflow pressure 0.5 Mpa, airflow speed 20 ml / min, mixed gas composition: oxygen: air = 3:8.

[0040] (4) Centrifugation: temperature: 35℃, speed: 3500 r / min, time: 20 min.

[0041] (5) Reverse osmosis membrane concentration: temperature: 35℃, concentration: 22 Brix.

[0042] (6) Spray drying: inlet air temperature 190℃, outlet air temperature 70℃, moisture content 4%, to obtain the high-aroma cold-soluble instant black tea.

[0043] Example 3

[0044] The embodiment provides a high-aroma cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0045] (1) Withering: temperature: 30℃, humidity: 65%; leaf thickness 10 cm, time: 14 h. Withered leaf moisture content: 52%.

[0046] (2) 3D airflow dynamic fermentation: mixed gas airflow pressure: 0.8 Mpa, airflow speed: 10 m / s, fermentation temperature: 28℃, fermentation humidity: 70%, processing time: 30 min, standing time: 90 min, cycle processing: 12 times; mixed gas composition: oxygen: air = 3:9.

[0047] (3) High-pressure bubble cooperates with low-frequency ultrasonic low-temperature extraction: ultrasonic wave band 20 KHz, energy output 350 W, extraction temperature 35℃, tea-water ratio 1:10, ultrasonic extraction time: 20 min. High-pressure mixed gas airflow pressure 0.3 Mpa, airflow speed 20 ml / min, mixed gas composition: oxygen: air = 3:9.

[0048] (4) Centrifugation: temperature: 35℃, speed: 4000 r / min, time: 10 min.

[0049] (5) Reverse osmosis membrane concentration: temperature: 35℃, concentration: 25 Brix.

[0050] (6) Spray drying: inlet temperature 190 °C, outlet temperature 75 °C, moisture content 4%, to obtain the high-aroma cold-soluble instant black tea.

[0051] Comparative Example 1

[0052] The present comparative example provides a cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0053] (1) Withering: temperature: 28 °C, humidity: 60%; leaf thickness: 15 cm, time: 15 h. Withered leaf moisture content: 58%.

[0054] (2) Rolling: tea leaves are placed in a rolling machine, rolling chamber temperature: 25 °C, humidity: 75%, rolling time: 50 min, re-rolling time: 20 min.

[0055] (3) Fermentation: tea leaves are stacked in a fermentation chamber, stacking thickness: 25 cm, fermentation time: 2.5 h, fermentation chamber temperature controlled at: 25 °C.

[0056] (4) Ultrasonic extraction: ultrasonic band 40 KHz, energy output 300 W, extraction temperature 50 °C, tea-water ratio 1:9, ultrasonic extraction time: 25 min.

[0057] (5) Centrifugation: temperature: 20 °C, speed: 5000 r / min, time: 30 min.

[0058] (6) Reverse osmosis membrane concentration: concentration temperature 40 °C, concentration: 25 Brix.

[0059] (7) Spray drying: inlet temperature: 180 °C, outlet temperature: 75 °C, moisture content 4%, to obtain the cold-soluble instant black tea.

[0060] Comparative Example 2

[0061] The present comparative example provides a cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0062] (1) Withering: temperature: 28 °C, humidity: 60%; leaf thickness: 15 cm, time: 13 h. Withered leaf moisture content: 55%.

[0063] (2) Rolling: tea leaves are placed in a rolling machine, rolling chamber temperature: 25 °C, humidity: 75%, rolling time: 50 min, re-rolling time: 20 min.

[0064] (3) Fermentation: tea leaves are stacked in a fermentation chamber, stacking thickness: 25 cm, fermentation time: 2.0 h, fermentation chamber temperature controlled at: 25 °C.

[0065] (4) Ultrasonic extraction: ultrasonic wave band 40 KHz, energy output 250 W, extraction temperature 60 °C, tea-water ratio 1:10, ultrasonic extraction time: 30 min.

[0066] (5) Centrifugation: centrifugation temperature: 20 °C, rotation speed: 5000 r / min, time: 20 min.

[0067] (6) Reverse osmosis membrane concentration: concentration temperature 40 °C, concentration: 25 Brix.

[0068] (7) Freeze-drying: pre-freezing at -20 °C for 24 h, then freeze-drying, cold trap temperature -70 °C, freeze-drying for 48 h, moisture content 4%, to obtain the cold-soluble instant black tea.

[0069] Comparative Example 3

[0070] This comparative example provides a cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0071] (1) Withering: temperature: 28 °C, humidity: 68%, leaf thickness: 15 cm, time: 15 h. Withered leaf moisture content: 62%.

[0072] (2) Rolling: tea leaves are placed in a rolling machine, rolling chamber temperature: 30 °C, humidity: 75%, rolling time: 45 min, re-rolling time: 15 min.

[0073] (3) Fermentation: tea leaves are stacked in a fermentation chamber, stacking thickness: 30 cm, fermentation time: 2.5 h, fermentation chamber temperature controlled at: 28 °C.

[0074] (4) High-pressure bubble combined with low-frequency ultrasonic low-temperature extraction: ultrasonic wave band 22 KHz, energy output 380 W, extraction temperature 38 °C, tea-water ratio 1:9, ultrasonic extraction time: 25 min. High-pressure mixed gas flow pressure 0.4 Mpa, gas flow speed 30 ml / min, mixed gas composition: oxygen: air = 3:6.

[0075] (5) Centrifugation: centrifugation temperature: 25 °C, rotation speed: 4000 r / min, time: 20 min.

[0076] (6) Reverse osmosis membrane concentration: concentration temperature 35 °C, concentration: 25 Brix.

[0077] (7) Spray drying: inlet air temperature: 190 °C, outlet air temperature: 80 °C, moisture content 4%, to obtain the cold-soluble instant black tea.

[0078] Comparative Example 4

[0079] This comparative example provides a cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0080] (1) withering: temperature: 30°C, humidity: 65%; leaf thickness 10 cm, time: 14 h. Withered leaf moisture content: 52%.

[0081] (2) 3D airflow dynamic fermentation: fermentation temperature: 28°C, fermentation humidity: 70%, processing time: 30 min, standing time: 90 min, cycle processing: 12 times, mixed gas airflow pressure: 0.8 Mpa, airflow speed: 10 m / s.

[0082] (3) ultrasonic extraction: ultrasonic band 40 KHz, energy output 350 W, extraction temperature 50°C, tea-water ratio 1:9, ultrasonic extraction time: 25 min.

[0083] (4) centrifugation: centrifugation temperature: 35°C, speed: 4000 r / min, time: 10 min.

[0084] (5) reverse osmosis membrane concentration: temperature: 35°C, concentration: 25 Brix.

[0085] (6) spray drying: inlet air temperature 190°C, outlet air temperature 75°C, moisture content 4%, to obtain the cold-soluble instant black tea.

[0086] Comparative Example 5

[0087] This comparative example provides a cold-soluble instant black tea and a preparation method thereof, and the specific preparation steps are as follows:

[0088] (1) withering: temperature: 30°C, humidity: 65%; leaf thickness 10 cm, time: 14 h. Withered leaf moisture content: 52%.

[0089] (2) 3D airflow dynamic fermentation: fermentation temperature: 28°C, fermentation humidity: 70%, processing time: 30 min, standing time: 90 min, cycle processing: 12 times, mixed gas airflow pressure: 0.8 Mpa, airflow speed: 10 m / s.

[0090] (3) low-frequency ultrasonic low-temperature extraction: ultrasonic band 20 KHz, energy output 350 W, extraction temperature 35°C, tea-water ratio 1:10, ultrasonic extraction time: 20 min.

[0091] (4) centrifugation: temperature: 35°C, speed: 4000 r / min, time: 10 min.

[0092] (5) reverse osmosis membrane concentration: temperature: 35°C, concentration: 25 Brix.

[0093] (6) spray drying: inlet air temperature 190°C, outlet air temperature 75°C, moisture content 4%, to obtain the high-aroma cold-soluble instant black tea.

[0094] The sensory and physicochemical indexes of the cold-soluble instant black tea prepared in the above examples and comparative examples were detected:

[0095] (1) Sensory index: 0.4 g of sample was taken in a sensory evaluation bowl, and 20±1℃ cold water was added to 200 g. Five sensory evaluation personnel with senior tea evaluation certificate were invited to smell the aroma, observe the color and solubility of the tea soup, and taste the flavor. The evaluation results were expressed in the form of comments and scores.

[0096] (2) Physicochemical index:

[0097] Yield: the weight of the instant tea powder / the weight of the fresh tea leaves*100%.

[0098] Turbidity: the tea soup was placed in a turbidimetry detection container, and the direct reading was taken.

[0099] The index detection results are shown in Table 1.

[0100] Table 1 Sensory and physicochemical indexes of instant black tea of each example

[0101]

[0102] The above results show that the instant black tea powder prepared by the method of the application (Examples 1-3) has the characteristics of red and bright soup color, strong and high fruit-flower aroma, full sweet aroma, thick flavor, clear and transparent cold water solubility, and low turbidity value, and the yield of the product is also high.

[0103] Compared with the examples, the conventional fermentation process is used in the preparation method of Comparative Example 1, and the obtained instant black tea basically has no fruit-flower aroma. Because of the high-frequency microwave low-temperature extraction, the product has a shallow soup color, weak sweet aroma, and thin flavor, and the yield is also low. Because the conventional fermented black tea is subjected to spray drying, it is easy to cause poor clarity of the instant black tea, and cold water instant solubility cannot be achieved.

[0104] Compared with the examples, the processing method of Comparative Example 2 optimizes the processing method of Comparative Example 1, and uses freeze drying instead of spray drying, so that the whole processing of the instant black tea is carried out under low temperature conditions, and the clarity of the product is obviously improved, but the sensory evaluation is not much different from that of Comparative Example 1.

[0105] Compared with the examples, the processing method of Comparative Example 3 optimizes the processing method of Comparative Example 1, and uses the high-pressure bubble synergistic low-frequency ultrasonic low-temperature extraction technology in the application, so that the yield of the product increases, the soup color becomes bright red, and the flavor becomes mellow. However, because of the influence of the conventional fermentation process, the aroma and clarity of the product are not improved, which shows the necessity of the 3D airflow dynamic fermentation of the application.

[0106] Compared with the examples, the preparation method of Comparative Example 4 optimizes the processing method of Comparative Example 1, and the 3D airflow dynamic fermentation and high-frequency ultrasonic extraction technology in the application are used, so that the extraction yield of the product is obviously increased, the soup color becomes bright red, the taste becomes mellow, and the cold water solubility is good, but there is still a gap compared with the effect of the application, which shows the necessity of high-pressure bubble synergistic low-frequency ultrasonic low-temperature extraction in the application.

[0107] Compared with the examples, the preparation method of Comparative Example 5 is basically the same as that of the examples, except that high-pressure bubble synergistic extraction is not used during extraction. The results show that the instant black tea soup color is lighter, the aroma is slightly weaker, and the taste is slightly less thick, which shows the necessity of high-pressure bubble synergistic extraction in the application.

Claims

1. A method for preparing high-fragrance cold-soluble instant black tea, characterized in that: The following steps are involved: (1) naturally withering fresh tea leaves to obtain withered leaves, wherein the water content of the withered leaves is 45-55%; (2) subjecting the withered leaves to 3D airflow dynamic fermentation, with a mixed gas airflow velocity of 10-20 m / s, a gas pressure of 0.6-1.0 MPa, a fermentation temperature of 15-30° C., and a fermentation humidity of 70-80%, wherein the mixed gas comprises oxygen and air, and the mass ratio of oxygen to air is 3:6-9; (3) subjecting the fermented leaves obtained in step (2) to low-temperature extraction using high-pressure bubbles in combination with low-frequency ultrasound, wherein the low-frequency ultrasound has a wavelength of 20-30 kHz and an energy output of 200-400 W; and continuously adding a mixed gas to the extract during the ultrasonic treatment, wherein the mixed gas comprises oxygen and air, and the mass ratio of oxygen to air is 3:6-9; (4) centrifuging the extract obtained in step (3) and taking the supernatant; (5) concentrating the supernatant to 18-25 Brix using a reverse osmosis membrane to obtain a concentrate; (6) spray drying the concentrate.

2. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1, wherein: The withering conditions in step (1) are: temperature 28-32° C., humidity 60-70%, leaf thickness 10-20 cm, and time 14-18 h.

3. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1, wherein: The mixed gas treatment time in step (2) is 30 min-1 h, the standing time is 30 min-2 h, and the cycle treatment is 5-20 times.

4. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1, wherein: The air flow pressure of the continuously added mixed gas in step (3) is 0.1-0.5 MPa, and the air flow speed is 20-40 ml / min.

5. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1, wherein: The extraction temperature in step (3) is 40-50° C., the extraction time is 20-60 min, the extraction solvent is water, and the mass ratio of the fermented leaves to water is 1:7-10.

6. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1, wherein: The centrifugation temperature in step (4) is 25-35° C., the rotation speed is 3000-4000 r / min, and the time is 10-30 min.

7. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1, wherein: The concentration temperature in step (5) is 20-30°C.

8. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1, wherein: Step (6) spray-drying the concentrate until the moisture content is less than 5%.

9. The method for preparing the high-aroma cold-dissolving instant black tea powder according to claim 1 or 8, characterized in that: The inlet air temperature of the spray drying is 150-200°C, and the outlet air temperature is 60-80°C.

10. A high-aroma cold-dissolve instant black tea powder, characterized in that: The product is prepared by the method according to any one of claims 1 to 9.

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