CN116158478A - High-quality black tea and preparation process thereof - Google Patents

Abstract

The invention discloses a high-quality black tea and a preparation process thereof, comprising the following steps: withering and high-temperature washing: placing the withered tea leaves on a filter screen, and continuously flushing with hot water at 80-90 ℃ for 30-50 seconds; hot air dehumidifying; twisting; fermenting; high-temperature stewing: uniformly spreading the fermented tea leaves to be 1-1.5 cm thick, then introducing water vapor with the temperature of 80-90 ℃, and sealing the container for 20-30 seconds; drying; the method has the technical principle that the caffeine contained in the tea green is removed by scouring of boiling water by utilizing the characteristic that the caffeine is easy to dissolve in the boiling water through high-temperature flushing, and then the content of the caffeine in the tea after fermentation can be further removed by high-temperature steam soaking for a plurality of seconds, so that the prepared black tea caffeine is less than 1%, the retention rate of other main components is about 90%, the original fragrance of the black tea is maintained, the soup color is thick and bright, the cold soup is not turbid, and the method is more suitable for clear drinking and the like.

Description

A kind of high-quality black tea and its preparation process

technical field

The invention relates to the field of black tea preparation, in particular to a high-quality black tea and a preparation process thereof.

Background technique

Black tea belongs to the fermented tea category, which is made from the buds and leaves of tea trees through typical processes such as withering, rolling, fermenting, and drying. . In addition to the three primary metabolites of sugar, lipid, and protein in tea, there are also secondary metabolites such as alkaloids, polyphenols, and theanine. Caffeine is the main component of tea taste substances. In addition to the bitter taste of caffeine, it can also form complexes with theaflavins and thearubigins by hydrogen bonds to improve the quality of tea soup. Caffeine has a positive impact on human psychomotor and cognitive abilities, including low habitual intake Increase alertness, energy and excitement in the case of moderate doses of caffeine. Although caffeine is an important component of the taste of tea, it does not mean that the more it contains, the better. On the contrary, high doses of caffeine can cause symptoms such as increased blood pressure, Negative effects such as nervousness, palpitations, restlessness, insomnia and embryonic deformities, long-term consumption will make people feel dependent, so it is not conducive to long-term consumption, and it is not conducive to children, pregnant women, the elderly and people with neurasthenia. To improve the quality of black tea generally lies in the pursuit of high content of alkaloids, polyphenols, theanine and other substances in black tea, but a low-caffeine black tea that retains the original aroma of black tea and can give full play to its health benefits can satisfy more people Therefore, low caffeine is an important factor in determining the high quality of black tea, and low caffeine black tea products are getting more and more attention from the market.

Chinese patent CN105211354B, the process includes the steps of fresh leaf selection, drying, shaking, cool green, dehydration treatment, rolling, fermentation, drying and aroma enhancement. The black tea product prepared by this process has beautiful appearance, sweet and mellow taste, and reduced astringency. The present invention can effectively improve the appearance quality of black tea (especially flower-fragrance Gongfu black tea). When the aroma formation and dehydration are not synchronized, the method of low-temperature rapid dehydration after shaking the green tea is adopted, which not only retains the aroma of the tea, but also makes the fresh leaves Part of the water is removed to ensure that the kneading is not broken, which is conducive to the smooth development of the subsequent process. The invention can effectively improve the taste of black tea, and after low-temperature rapid dehydration treatment, light pressure and long-time kneading are used to reduce the degree of leaf cell breakage without affecting the breakage rate, and obviously improve the taste and mouthfeel of the product.

Chinese patent CN108402219B discloses a method for preparing black tea, which includes the following steps: picking single buds, one bud and one leaf tea leaves, and spreading them on the withering tank to wither; then shaking the green tea for 2-3 times, and rolling the tea leaves for 30 -90min; then carry out fermentation, the fermentation process is divided into 2-3 times; the first fermentation: put the tea leaves kneaded in step 3 on the sieve fermentation tank, and carry out fermentation under the conditions of 28-35°C and humidity ≥ 92% The fermentation time lasts for 4-7 hours; after the fermentation is completed, take out the tea leaves and dry them for the first time at 25-32°C; Layer, ferment for 3-7 hours under the conditions of 25-36°C and humidity ≥ 95%; after the second fermentation is completed, directly dry or carry out the second water loss and the third fermentation. Finally, the tea leaves are taken out and placed on a sieve trough for drying to obtain finished black tea with a moisture content of 4-7%.

As can be seen from the above processing methods, the current black tea production process, conventional methods in the prior art usually include: (1) withering: the fresh leaves are evenly and thinly spread on the withering curtain to wither naturally, so that the moisture content of the withered leaves is reduced, and the green grass gas is reduced; (2) ) Kneading: currently kneading is usually done with a kneading machine, pressurized according to the principle of light, heavy and light pressure, and kneaded until the tea sticks are tightly rolled, the tea juice overflows, and sticks to the tea surface; (3) Fermentation: the kneaded leaves Evenly and loosely piled up, fermented on the fermentation rack, and the fermentation was stopped when the leaves were yellow-red and had a pleasant aroma; (4) Titian: put the fermented tea leaves into the tea flavoring machine and dry them for a certain period of time to obtain black tea finished product. In the preparation of black tea, if shaking the green is not enough, it will lead to incomplete drainage and easy to cause dead green, which will reduce the yield of tea leaves. If the fermentation time is too long, it will lead to over-fermentation of black tea, resulting in red and dark leaves and low aroma. In the case of light, although the increase of black tea alkaloids, polyphenols, theanine and other substances is improved, as a new low-caffeine black tea that retains the original aroma of black tea and can also give full play to its health benefits, it can satisfy more people. Crowd is to the demand of tealeaves, therefore, the high-quality black tea of a kind of low caffeine is developed to have development prospect and popularization significance very much.

Contents of the invention

The object of the present invention is to provide a kind of high-quality black tea with low caffeine and its preparation process aiming at the problems existing in the prior art.

In order to achieve the above purpose, the technical scheme adopted is:

A kind of high-quality black tea and preparation technology thereof, comprises the following steps:

Step 1, withering: Select tea greens with high tenderness and good uniformity, spread them on the withering rack, and naturally wither at room temperature for 2 days;

Step 2, high-temperature rinsing: put the withered green tea on the filter screen, and rinse with hot water at 80-90°C for 30-50 seconds;

Step 3, hot air dehumidification: dehumidify the green tea obtained by simmering at high temperature through hot air, the temperature of the hot air is 70-75°C, and the time is 3-5 minutes;

Step 4, kneading: put the dehumidified tea into the kneading machine for kneading, and knead with light and heavy pressure, and kneading time is 5-8 minutes; after the first kneading, put the kneaded leaves into the deblocking machine, 2~3 mesh sieve, the leaves under the sieve are tight and fine, and directly enter the fermentation room for fermentation; the sieve surface is rough and loose, and the leaves are kneaded for the second time;

Step 5, Fermentation: After kneading, the leaf thickness of the rolled tea leaves is generally 6~8cm, and the fermentation is carried out; during the fermentation process, more than 90% of the leaf color turns copper red, the green gas gradually disappears, and the fermentation is stopped when there is a fresh and elegant tea fragrance;

Step 6, high-temperature immersion: Spread the fermented tea leaves evenly to a thickness of 1-1.5cm, then pass in steam at a temperature of 80-90°C, and seal the container for 20-30 seconds;

Step 7, drying: dry the stewed tea leaves twice, the first time keep the temperature at 180~200℃ and dry until the water content of the tea leaves is 20~30%, let it dry for 15~20 minutes; the second time keep the temperature Dry at 120-140°C until the water content of the tea leaves is 0-5%, and let it dry for 20-30 minutes.

Preferably, withering in the step 1 spreads the layer thickness of dark green to be 1～1.5cm thick.

Preferably, in the step 3, the hot air dehumidification reduces the water content of the green tea to 65-75%.

Preferably, in the step 4, the amount of tea contained in the kneading control is half of the height of the tea barrel of the kneading machine.

Preferably, in the step 4, the temperature of the kneading room is controlled between 15-25° C., and the relative humidity is 80-90%, so as to maintain indoor air circulation.

Preferably, the fermentation temperature in step 5 is 25-27°C, and the relative humidity is 85-95%.

The beneficial effects of adopting the above scheme are as follows: the main technical principle of the present invention is that, firstly, after the green tea is naturally withered, the caffeine contained in the green tea is washed away by boiling water by washing at high temperature, utilizing the characteristic that caffeine is easily soluble in boiling water, Secondly, after fermentation, the high-temperature steam is used to immerse for a few seconds, and the surface of the tea leaves is soaked in the high-temperature steam flowing process. After drying, the content of caffeine in the fermented tea can be further removed. By changing the traditional black tea preparation process, the preparation To obtain low-caffeine black tea, the prepared black tea has less than 1% caffeine, about 90% of other main ingredients, and retains the original aroma of black tea. The soup is red and bright, and the cold soup is not cloudy.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in combination with specific embodiments of the present invention. The described embodiments are only some, not all, embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

A kind of high-quality black tea and preparation technology thereof, comprises the following steps:

Step 1, withering: Select tea greens with high tenderness and good uniformity, spread them on the withering rack, and naturally wither at room temperature for 2 days;

Step 2, high-temperature rinsing: put the withered green tea on the filter screen, and rinse it with hot water at 80°C for 30 seconds;

Step 3, hot air dehumidification: dehumidify the green tea obtained by simmering at high temperature through hot air, the temperature of the hot air is 70°C, and the time is 3 minutes;

Step 4, kneading: put the dehumidified tea into the kneading machine for kneading, and knead with light and heavy pressure, and kneading time is 5-8 minutes; after the first kneading, put the kneaded leaves into the deblocking machine, 2~3 mesh sieve, the leaves under the sieve are tight and fine, and directly enter the fermentation room for fermentation; the sieve surface is rough and loose, and the leaves are kneaded for the second time;

Step 5, Fermentation: After kneading, the leaf thickness of the rolled tea leaves is generally 6~8cm, and the fermentation is carried out; during the fermentation process, more than 90% of the leaf color turns copper red, the green gas gradually disappears, and the fermentation is stopped when there is a fresh and elegant tea fragrance;

Step 6, high-temperature steeping: Spread the fermented tea evenly to a thickness of 1-1.5 cm, then pass in steam at a temperature of 80°C, and seal the container for 20 seconds;

Step 7, drying: drying the stewed tea leaves twice, the first time keeping the temperature at 180°C and drying until the water content of the tea leaves is 30%, and drying for 20 minutes; the second time keeping the temperature at 120°C and drying to The water content of the tea leaves is 5%, and the tea leaves are dried for 30 minutes.

Withering in said step 1, the layer thickness of tea greens is 1-1.5cm thick.

In described step 3, hot air dehumidification makes the green tea water content drop to 65%.

In described step 4, knead and control the amount of loaded tea to be half of the height of the kneading machine's tea bucket.

In the step 4, the temperature of the kneading chamber is controlled between 15° C. and the relative humidity is 80%, so as to keep the indoor air circulation.

The temperature of fermentation in the step 5 is 25° C., and the relative humidity is 85%.

Example 2

A kind of high-quality black tea and preparation technology thereof, comprises the following steps:

Step 1. Withering: Select tea greens with high tenderness and good uniformity, spread them on the withering rack, and naturally wither at room temperature for 2 days;

Step 2, high-temperature washing: put the withered tea greens on the filter screen, and rinse them with hot water at 85°C for 40 seconds;

Step 3, hot air dehumidification: dehumidify the green tea obtained by stewing at high temperature through hot air, the temperature of the hot air is 73°C, and the time is 4 minutes;

Step 4, kneading: Put the dehumidified tea leaves into the kneading machine for kneading, and knead with light and heavy pressure, and the kneading time is 6 minutes; after the first kneading, put the kneaded leaves into the deblocking and decomposing machine. 3-mesh sieve, the leaves under the sieve are tight and fine, and directly enter the fermentation room for fermentation; the sieve surface is coarse and loose, and the leaves are kneaded for the second time;

Step 5. Fermentation: After kneading, the leaf thickness of the rolled tea leaves is generally 6-8cm, and the fermentation is carried out; during the fermentation process, more than 90% of the leaf color turns copper red, and the green gas gradually disappears, and the fermentation is stopped when there is a fresh and elegant tea fragrance;

Step 6. Stewing and steeping at high temperature: Spread the fermented tea leaves evenly to a thickness of 1-1.5 cm, then pass in steam at a temperature of 85°C, and seal the container for 20-30 seconds;

Step 7. Drying: Dry the stewed tea leaves in two times. For the first time, keep the temperature at 190°C and dry until the water content of the tea leaves is 25%, and let it dry for 18 minutes; The water content of the tea leaves is 3.5%, and the tea leaves are dried for 25 minutes.

Withering in said step 1, the layer thickness of tea greens is 1-1.5cm thick.

In the described step 3, the hot air dehumidification makes the green tea water content down to 70%.

In described step 4, knead and control the amount of loaded tea to be half of the height of the kneading machine's tea bucket.

In the step 4, the temperature of the kneading chamber is controlled between 20°C and the relative humidity is 85%, so as to keep the indoor air circulation.

The temperature of fermentation in the step 5 is 26° C., and the relative humidity is 90%.

Example 3

A kind of high-quality black tea and preparation technology thereof, comprises the following steps:

Step 1, withering: Select tea greens with high tenderness and good uniformity, spread them on the withering rack, and naturally wither at room temperature for 2 days;

Step 2, high-temperature rinsing: put the withered green tea on the filter screen, and rinse with hot water at 90°C for 50 seconds;

Step 3, hot air dehumidification: dehumidify the green tea obtained by stewing at high temperature through hot air, the temperature of the hot air is 75°C, and the time is 5 minutes;

Step 4, kneading: Put the dehumidified tea leaves into the kneading machine for kneading, and knead with light and heavy pressure, and the kneading time is 8 minutes; 3-mesh sieve, the leaves under the sieve are tight and fine, and directly enter the fermentation room for fermentation; the sieve surface is coarse and loose, and the leaves are kneaded for the second time;

Step 5, Fermentation: After kneading, the leaf thickness of the rolled tea leaves is generally 6~8cm, and the fermentation is carried out; during the fermentation process, more than 90% of the leaf color turns copper red, the green gas gradually disappears, and the fermentation is stopped when there is a fresh and elegant tea fragrance;

Step 6, high-temperature steeping: spread the fermented tea evenly to a thickness of 1-1.5 cm, then pass in steam at a temperature of 90°C, and seal the container for 30 seconds;

Step 7, drying: drying the stewed tea leaves twice, the first time keeping the temperature at 200°C and drying until the water content of the tea leaves is 20%, and drying for 15 minutes; the second time keeping the temperature at 140°C and drying to The water content of the tea leaves is 1%, and it is ready to dry for 20 minutes.

Withering in said step 1, the layer thickness of tea greens is 1-1.5cm thick.

In described step 3, the hot air dehumidification makes the green tea water content down to 75%.

In described step 4, knead and control the amount of loaded tea to be half of the height of the kneading machine's tea bucket.

In the step 4, the temperature of the kneading chamber is controlled between 25° C. and the relative humidity is 90%, so as to keep the indoor air circulation.

The temperature of fermentation in the step 5 is 27° C., and the relative humidity is 95%.

Comparative example 1: comprising the following steps:

Step 1. Withering: Select tea greens with high tenderness and good uniformity, spread them on the withering rack, and naturally wither at room temperature for 2 days;

Step 2, high-temperature washing: put the withered green tea on the filter screen, and continue washing with hot water at 60°C for 20 seconds;

Step 3, hot air dehumidification: dehumidify the green tea obtained by stewing at high temperature through hot air, the temperature of the hot air is 73°C, and the time is 4 minutes;

Step 4, kneading: Put the dehumidified tea leaves into the kneading machine for kneading, and knead with light and heavy pressure, and the kneading time is 6 minutes; after the first kneading, put the kneaded leaves into the deblocking and decomposing machine. 3-mesh sieve, the leaves under the sieve are tight and fine, and directly enter the fermentation room for fermentation; the sieve surface is coarse and loose, and the leaves are kneaded for the second time;

Step 5. Fermentation: After kneading, the leaf thickness of the rolled tea leaves is generally 6-8cm, and the fermentation is carried out; during the fermentation process, more than 90% of the leaf color turns copper red, and the green gas gradually disappears, and the fermentation is stopped when there is a fresh and elegant tea fragrance;

Step 6. Stewing and steeping at high temperature: Spread the fermented tea leaves evenly to a thickness of 1-1.5 cm, then pass in steam at a temperature of 60°C, and seal the container for 15 seconds;

Step 7. Drying: Dry the stewed tea leaves in two times. For the first time, keep the temperature at 190°C and dry until the water content of the tea leaves is 25%, and let it dry for 18 minutes; The water content of the tea leaves is 3.5%, and the tea leaves are dried for 25 minutes.

Withering in said step 1, the layer thickness of tea greens is 1-1.5cm thick.

In the described step 3, the hot air dehumidification makes the green tea water content down to 70%.

In described step 4, knead and control the amount of loaded tea to be half of the height of the kneading machine's tea bucket.

In the step 4, the temperature of the kneading chamber is controlled between 20°C and the relative humidity is 85%, so as to keep the indoor air circulation.

The temperature of fermentation in the step 5 is 26° C., and the relative humidity is 90%.

Comparative example 2: comprising the following steps:

Step 1. Withering: Select tea greens with high tenderness and good uniformity, spread them on the withering rack, and naturally wither at room temperature for 2 days;

Step 2. High-temperature washing: put the withered tea greens on the filter screen, and rinse them with hot water at 100°C for 60 seconds;

Step 3, hot air dehumidification: dehumidify the green tea obtained by stewing at high temperature through hot air, the temperature of the hot air is 73°C, and the time is 4 minutes;

Step 4, kneading: Put the dehumidified tea leaves into the kneading machine for kneading, and knead with light and heavy pressure, and the kneading time is 6 minutes; after the first kneading, put the kneaded leaves into the deblocking and decomposing machine. 3-mesh sieve, the leaves under the sieve are tight and fine, and directly enter the fermentation room for fermentation; the sieve surface is coarse and loose, and the leaves are kneaded for the second time;

Step 5. Fermentation: After kneading, the leaf thickness of the rolled tea leaves is generally 6-8cm, and the fermentation is carried out; during the fermentation process, more than 90% of the leaf color turns copper red, and the green gas gradually disappears, and the fermentation is stopped when there is a fresh and elegant tea fragrance;

Step 6. Stewing and steeping at high temperature: Spread the fermented tea leaves evenly to a thickness of 1-1.5 cm, then pass in steam at a temperature of 100°C, and seal the container for 40 seconds;

Step 7. Drying: Dry the stewed tea leaves in two times. For the first time, keep the temperature at 190°C and dry until the water content of the tea leaves is 25%, and let it dry for 18 minutes; The water content of the tea leaves is 3.5%, and the tea leaves are dried for 25 minutes.

Withering in said step 1, the layer thickness of tea greens is 1-1.5cm thick.

In the described step 3, the hot air dehumidification makes the green tea water content down to 70%.

In described step 4, knead and control the amount of loaded tea to be half of the height of the kneading machine's tea bucket.

In the step 4, the temperature of the kneading chamber is controlled between 20°C and the relative humidity is 85%, so as to keep the indoor air circulation.

The temperature of fermentation in the step 5 is 26° C., and the relative humidity is 90%.

Experimental example 1

The sensory quality of the black tea product prepared by the process of the above-mentioned examples 1-3, the black tea product prepared by the process of comparative example 1-2, and the control example (Zunyi black tea sold in the market) is compared, as shown in Table 1:

sample shape color aroma soup color taste Example 1 The rope is tightly knotted and slightly soft uniform sweet aroma Red thick bright cold soup is not cloudy Sweet and mellow, mild astringency Example 2 The rope is tightly knotted and slightly soft uniform sweet aroma Red thick bright cold soup is not cloudy Sweet and mellow, mild astringency Example 3 The rope is tightly knotted and slightly soft uniform sweet aroma Red thick bright cold soup is not cloudy Sweet and mellow, mild astringency Comparative example 1 Hard Uneven withered and yellow strong aroma The red thick deep cold soup has a small amount of complexes and is not cloudy Fragrance thin and astringent Comparative example 2 Coarse and loose light color light aroma Red clear cold soup is not cloudy lighter Comparative example The rope is tightly knotted and slightly stiff brighten high aroma The red is thick and slightly golden, the cold soup has complexes, and the cold soup is muddy Mellow, sweet and smooth, slightly astringent

Table 1

Experimental example 2

The black tea product prepared by the above-mentioned process of Example 1-3 and the black tea product prepared by the process of Comparative Example 1-2, as well as the control example (Zunyi black tea on the market) were subjected to caffeine, free amino acids, tea polyphenols, water extracts, etc. The content is measured, see Table 2:

sample Caffeine (%) Free amino acids(%) Tea polyphenols (%) Water extract (%) Example 1 0.64 3.15 5.98 36.4 Example 2 0.57 3.11 5.7 35.3 Example 3 0.42 3.06 5.61 34.1 Comparative example 1 1.81 3.13 5.98 38.6 Comparative example 2 0.36 2.31 4.43 31.5 Comparative example 3.28 3.34 6.29 40.5

According to the results of the test, it can be seen from Table 1 that the black tea products prepared by the process examples 1-3 of the present invention are slightly softer in appearance than the control example (the Zunyi black tea on sale in the market), but the structure is complete and the strands Tight knot, the aroma is relatively sweet, not as strong as the control example, the soup is red, thick and bright, the cold soup has no complexes, is not turbid, and the taste is obviously less astringent than the control example. Combined with the determination of the main component content, the table 2 It can be seen that the black tea caffeine prepared by the black tea products prepared by the process examples 1-3 of the present invention is less than 1%, and the retention rate of free amino acids, tea polyphenols, and water extracts is about 90% compared with the control example.

Comparative example 1-2 is as the preparation method of the present invention, and comparative example 1 has reduced the temperature of step 2 high-temperature rinsing and less rinsing time, has reduced the temperature of step 6 high-temperature immersion and less immersion time, from table 1 As can be seen from the results in Table 2, the content of caffeine has not been effectively removed, resulting in uneven color, thin fragrance, heavy astringent taste, and insufficient fermentation; Comparative Example 2 increases the temperature and increase in the temperature of step 2 high-temperature washing The rinse time was increased, the temperature of step 6 high-temperature immersion was increased and the immersion time was increased. As can be seen from the results in Table 1 and Table 2, although the content of caffeine was effectively removed, the content of other main components was also lower than that of Normal data; it can be drawn that the black tea product prepared by the process of Example 1-3, the black tea prepared by the process of the present invention has the characteristics of caffeine, and can meet the requirements of other main components with a retention rate of about 90%, and keep the original black tea Aroma, the soup is red and bright, and the cold soup is not cloudy, which is more suitable for clear drinks.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only includes an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (6)

1. a kind of high-quality black tea and preparation technology thereof, is characterized in that, comprises the following steps: Step 1, withering: Select tea greens with high tenderness and good uniformity, spread them on the withering rack, and naturally wither at room temperature for 2 days; Step 2, high-temperature rinsing: put the withered green tea on the filter screen, and rinse with hot water at 80-90°C for 30-50 seconds; Step 3, hot air dehumidification: dehumidify the green tea obtained by simmering at high temperature through hot air, the temperature of the hot air is 70-75°C, and the time is 3-5 minutes; Step 4, kneading: put the dehumidified tea into the kneading machine for kneading, and knead with light and heavy pressure, and kneading time is 5-8 minutes; after the first kneading, put the kneaded leaves into the deblocking machine, 2~3 mesh sieve, the leaves under the sieve are tight and fine, and directly enter the fermentation room for fermentation; the sieve surface is rough and loose, and the leaves are kneaded for the second time; Step 5, Fermentation: After kneading, the leaf thickness of the rolled tea leaves is generally 6~8cm, and the fermentation is carried out; during the fermentation process, more than 90% of the leaf color turns copper red, the green gas gradually disappears, and the fermentation is stopped when there is a fresh and elegant tea fragrance; Step 6, high-temperature immersion: Spread the fermented tea leaves evenly to a thickness of 1-1.5cm, then pass in steam at a temperature of 80-90°C, and seal the container for 20-30 seconds; Step 7, drying: dry the stewed tea leaves twice, the first time keep the temperature at 180~200℃ and dry until the water content of the tea leaves is 20~30%, let it dry for 15~20 minutes; the second time keep the temperature Dry at 120-140°C until the water content of the tea leaves is 0-5%, and let it dry for 20-30 minutes. 2. A kind of high-quality black tea and its preparation process according to claim 1, characterized in that: in said step 1, wither and spread the green tea with a layer thickness of 1 to 1.5 cm. 3. A kind of high-quality black tea and its preparation process according to claim 1, characterized in that: in said step 3, the hot air dehumidification reduces the water content of the green tea to 65-75%. 4. A kind of high-quality black tea and its preparation process according to claim 1, characterized in that: in said step 4, the amount of tea contained in the kneading control is half of the height of the tea barrel of the kneading machine. 5. A kind of high-quality black tea and its preparation process according to claim 1, characterized in that: in the step 4, the temperature of the rolling room is controlled between 15-25°C, the relative humidity is 80-90%, and the indoor air circulation is maintained . 6. A kind of high-quality black tea and its preparation process according to claim 1, characterized in that: the temperature of fermentation in the step 5 is 25-27°C, and the relative humidity is 85-95%.