Black tea and preparation method thereof
Through the optimization of segmented withering, rolling and fermentation processes, the problems of high caffeine content and single aroma in black tea are solved, and caffeine reduction and mellowness increase in tea soup are achieved, forming a unique flower and fruit aroma and improving the quality of black tea.
Patent Information
- Application Number
- CN202510697123.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-28
- Publication Date
- 2025-07-18
AI Technical Summary
In the existing black tea preparation process, the caffeine content is high, which affects the applicable population of tea. It has a single aroma and is difficult to meet the market diversity needs. The enzymatic oxidation reaction in traditional processes strongly affects the quality of tea.
The process of segmented withering, segmented withering, fermentation and drying is adopted, including low-temperature and high-humidity withering, high-speed low-temperature kneading and moderate fermentation, combined with rapid high-temperature leaching, control the fermentation time and temperature, and optimize the formation of tea ingredients.
Effectively reduce the caffeine content, improve the mellowness and luster of the tea soup, retain fresh leaf active substances, form a unique flower and fruit aroma, and enhance the sensory quality of black tea.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of tea processing, and particularly relates to a black tea and a preparation method thereof. Background Art
[0002] Black tea is one of the main tea categories produced and exported in China and is the most consumed tea category in the world, accounting for more than 70% of the world tea market. The preparation process of black tea is: withering, rolling, fermentation, and drying. Although the traditional process endows black tea with a unique flavor, in the face of the changing market demand, innovation and improvement have become the key to enhancing competitiveness. Nowadays, the Gongfu black tea made by traditional processes faces challenges such as a single aroma, a dull smell caused by excessive "fermentation", and product homogenization among different tea production areas. Consumers' pursuit of diversity in aspects such as aroma and taste in the drinking experience of black tea promotes further exploration of the black tea preparation process.
[0003] Caffeine is a xanthine alkaloid compound and has the effects of refreshing and anti-fatigue. As one of the main flavor substances in tea, caffeine accounts for 2% - 5% of the total dry matter content of tea. Regular intake of high doses of caffeine can stimulate the central nervous system, affect sleep, increase blood pressure, increase the prevalence of rheumatoid arthritis, cause premature birth of infants, etc. Therefore, it is necessary to reduce the caffeine content to a certain extent in the preparation of black tea for a wider range of people to drink.
[0004] However, the young tissues of tea leaves contain polyphenol oxidase with strong activity, and an overly strong enzymatic oxidation reaction will occur during withering and shaking, which is not conducive to the generation of black tea aroma; on the other hand, while the existing technology uses hot water extraction to reduce the caffeine content of black tea, it will affect the activity of polyphenol oxidase in fresh tea leaves, and it is difficult for the enzyme activity to meet the requirements for making black tea during rolling and fermentation, and the taste of black tea is affected; the content of polyphenols, catechins, and caffeine in black tea is relatively high, while the content of precursors for forming aromatic substances, sugars, and ether extracts is relatively low, which is also not conducive to the development of tea aroma.
[0005] Therefore, how to explore a black tea preparation process that takes into account low caffeine and unique aroma and flavor has become a new research direction. Summary of the Invention
[0006] In view of the above deficiencies, the present invention provides a black tea and a preparation method thereof. Through four processes of segmented withering, segmented rolling, fermentation, and drying, it effectively promotes the formation of aroma precursor substances, enhances the thickness and brightness of the tea soup, retains the active substances in fresh tea leaves, and at the same time can better reduce the caffeine content. The specific technical solutions are as follows:
[0007] A preparation method of black tea, comprising the following steps:
[0008] S1. Withering
[0009] The freshly picked tea leaves are withered, including primary withering and secondary withering. The specific methods are as follows: The freshly picked tea leaves are evenly spread out flat in a withering trough. For the primary withering, the temperature is controlled at 15 - 20°C and the humidity at 60 - 70%, and the withering lasts for 16 - 20 hours. Then, the blower is turned on for secondary withering. The wind speed is 5 - 7 m / s, the hot air temperature is 30 - 35°C, the humidity is 60%, and the withering time is 3 - 5 hours, obtaining withered tea leaves.
[0010] S2. Rolling
[0011] The withered tea leaves from step S1 are rolled, including primary rolling and secondary rolling. The specific methods are as follows: The withered tea leaves are placed in a rolling machine for primary rolling, and then the tea leaves are taken out and spread out to dry under natural conditions for 5 - 10 minutes. Then, secondary rolling is carried out to obtain rolled tea leaves.
[0012] S3. Fermentation
[0013] The rolled tea leaves obtained in step S2 are placed in a black tea fermentation machine for fermentation. The temperature inside the machine is 25 - 30°C, the relative humidity is 88 - 93%, and the fermentation time is 4 hours - 4 hours and 40 minutes. The fermentation ends when the rolled tea leaves turn uniformly red and have no peculiar smell, obtaining fermented tea leaves.
[0014] S4. Drying
[0015] The fermented tea leaves from step S3 are subjected to rough drying and thorough drying. The rough drying temperature is 100 - 115°C, and the rough drying time is 8 - 10 minutes. The thorough drying temperature is 110 - 115°C, and the thorough drying time is 8 - 12 minutes, controlling the moisture content after drying to be below 7%.
[0016] S5. Packaging
[0017] The dried black tea leaves are weighed by an electronic pricing scale, packaged, and then sealed by a continuous ink jet coding and sealing machine to obtain the finished black tea leaves, which are stored in a dry and odorless warehouse at an ambient temperature below 30°C and a relative humidity below 70%.
[0018] Preferably, in step S1, for the primary withering, the water loss rate of the tea leaves is controlled to 20 - 24%, and for the secondary withering, the water loss rate of the tea leaves is controlled to 38 - 42%.
[0019] Preferably, in step S1, after the secondary withering, extraction is also included. The extraction temperature is 90 - 100°C, and the time is 50 - 70 seconds.
[0020] Preferably, in the extraction process, the mass ratio of the withered tea leaves to hot water is 1:15 - 18.
[0021] Preferably, in the step S2, the rotation speed of the first rolling is 20-25 r / min, the temperature of the first rolling is 13-17 °C, and the time of the first rolling is 70-80 min.
[0022] Preferably, in the step S2, the rotation speed of the second rolling is 70-80 r / min, the temperature of the second rolling is 30-33 °C, and the time of the second rolling is 15-20 min.
[0023] Preferably, in the step S1, the thickness of the withered leaves in the withering trough is 3-5 cm.
[0024] The present invention also provides a black tea prepared by the above preparation method.
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0026] 1. The black tea preparation method provided by the present invention, through the processes of segmented withering, segmented rolling, fermentation, and drying, effectively promotes the formation of aroma precursor substances, enhances the thickness and brightness of the tea soup, retains the active substances in the fresh leaves, and at the same time can better reduce the content of caffeine.
[0027] 2. During extraction, as the temperature of the hot water increases, caffeine will quickly dissolve and leach out in the hot water, resulting in a continuous decrease in the caffeine content in the tea leaves and an increase in the removal rate. However, high temperature will inactivate polyphenol oxidase, so that catechins cannot be oxidized into theaflavins, affecting the color of black tea and causing a decline in the sensory quality of black tea; as the extraction time increases, the tea leaves shrink due to temperature rise, resulting in a decrease in the caffeine removal rate in the tea leaves and a darker color of the tea soup affecting the brightness, while too low extraction temperature and too short extraction time cannot achieve the effect of effectively removing caffeine. The present invention uses rapid high-temperature extraction after secondary withering, which not only retains the active substances in the fresh leaves but also reduces the content of caffeine without affecting the brightness of the tea soup.
[0028] 3. The present invention uses segmented withering, first slowly losing water by 20-24% at low temperature and high humidity, and then heating and blowing air to accelerate the water loss rate to 38-42%, effectively promoting the formation of aroma precursor substances and enhancing the thickness of the tea soup. Combining with the rolling stage, high-speed rolling at 70-80 r / min at 13-17 °C for 70-80 min in the first time and low-speed rolling at 20-25 r / min at 30-33 °C for 15-20 min in the second time are adopted to achieve a cell breakage rate of more than 80%, improve the enzymatic oxidation efficiency, and enable the content of theaflavins and thearubigins to reach a more appropriate content, with a higher amino acid content, improving the freshness of the tea soup, making the finished tea soup red and bright, with a strong sweet aroma and no grassy taste, and providing a good foundation for the subsequent fermentation process.
[0029] 4. The present invention controls the fermentation at 25-30°C for 4h-4h40min, reducing the cumbersome multi-stage fermentation process. It is not the case that the more complex the fermentation process and the longer the fermentation time and the higher the temperature, the better the quality of the tea obtained. The moderate light fermentation of the present invention can, to a certain extent, prevent the further conversion of terpenoid substances, better retain the fresh fragrance of the tea, and have a floral and fruity aroma. The floral and fruity aroma is rich and persistent, and the aftertaste is strong. If the fermentation time is too short, the aroma is miscellaneous and has a grassy smell, the taste is strongly stimulating and lacks mellow taste. Similarly, if the fermentation process is too complex and the fermentation time is too long, sourness will also be produced, and the color of the tea soup is dull. Detailed Embodiments
[0030] The following describes the detailed embodiments of the present invention in detail, but it should be understood that the protection scope of the present invention is not limited by the detailed embodiments. Unless otherwise defined, all the professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.
[0031] Example 1
[0032] A method for preparing black tea in this example includes the following steps:
[0033] S1. Withering
[0034] The freshly picked leaves are withered, including primary withering and secondary withering. The specific method is as follows: The freshly picked leaves are evenly spread out flat in the withering trough. The thickness of the spread leaves in the withering trough is 4 cm, and then primary withering is carried out. The temperature for primary withering is controlled at 18°C, the humidity is 65%, and the withering time is 18 h. The water loss rate of the tea leaves is controlled to 22% during primary withering; then the blower is turned on for secondary withering. The wind speed is 6 m / s, the hot air temperature is 32°C, the humidity is 60%, and the withering time is 4 h. The water loss rate of the tea leaves is controlled to 40% during secondary withering. After secondary withering, extraction is carried out. The extraction temperature is 95°C and the time is 60 s to obtain withered tea leaves;
[0035] S2. Rolling
[0036] The withered tea leaves in step S1 are rolled, including primary rolling and secondary rolling. The specific method is as follows: The withered tea leaves are placed in a rolling machine for primary rolling. The rotation speed for primary rolling is 22 r / min, the temperature for primary rolling is 15°C, and the time for primary rolling is 75 min. Then the tea leaves are taken out and spread out to dry for 8 min under natural conditions; then secondary rolling is carried out. The rotation speed for secondary rolling is 75 r / min, the temperature for secondary rolling is 32°C, and the time for secondary rolling is 18 min to obtain rolled tea leaves;
[0037] S3. Fermentation
[0038] Place the rolled tea leaves obtained in step S2 in a black tea fermentation machine for fermentation. The temperature inside the machine is 27°C, the relative humidity is 90%, and the fermentation time is 4 hours. The fermentation ends when the rolled tea leaves turn uniformly red and have no abnormal smell, obtaining fermented tea leaves;
[0039] S4. Drying
[0040] Carry out primary drying and final drying on the fermented tea leaves in step S3; the primary drying temperature is 110°C and the primary drying time is 9 minutes; the final drying temperature is 112°C and the final drying time is 10 minutes, controlling the moisture content after drying to be 5%.
[0041] S5. Packaging
[0042] Weigh the dried black tea leaves with an electronic weighing scale, package them, and then seal them with a continuous ink coding and sealing machine to obtain the finished black tea leaves, which are stored in a dry and odorless warehouse at an ambient temperature of 25°C and a relative humidity of 55%.
[0043] Example 2
[0044] A method for preparing black tea in this example includes the following steps:
[0045] S1. Withering
[0046] Carry out withering on the leached tea leaves, including primary withering and secondary withering. The specific method is as follows: Spread the leached tea leaves evenly on the withering trough, and the thickness of the tea leaves spread in the withering trough is 3 cm. Then carry out primary withering, controlling the temperature at 15°C and the humidity at 60% for 20 hours, and controlling the water loss rate of the tea leaves to 20% during primary withering; then turn on the blower for secondary withering, with a wind speed of 5 m / s, a hot air temperature of 35°C, a humidity of 60%, and a withering time of 3 hours. Control the water loss rate of the tea leaves to 38% during secondary withering. After secondary withering, carry out secondary leaching at a leaching temperature of 90°C and a time of 40 s to obtain withered tea leaves;
[0047] S2. Rolling
[0048] Carry out rolling on the withered tea leaves in step S1, including primary rolling and secondary rolling. The specific method is as follows: Place the withered tea leaves in a rolling machine for primary rolling, with a primary rolling speed of 20 r / min, a primary rolling temperature of 13°C, and a primary rolling time of 70 minutes. Then take out the tea leaves and air them for 10 minutes under natural conditions; then carry out secondary rolling, with a secondary rolling speed of 70 r / min, a secondary rolling temperature of 30°C, and a secondary rolling time of 20 minutes to obtain rolled tea leaves;
[0049] S3. Fermentation
[0050] Place the rolled tea leaves obtained in step S2 into a black tea fermenter for fermentation. The temperature inside the machine is 25°C, the relative humidity is 88%, and the fermentation time is 4 hours and 40 minutes. The fermentation ends when the rolled tea leaves turn uniformly red and have no abnormal smell, obtaining fermented tea leaves.
[0051] S4. Drying
[0052] Perform primary drying and final drying on the fermented tea leaves in step S3. The primary drying temperature is 100°C and the primary drying time is 10 minutes. The final drying temperature is 110°C and the final drying time is 12 minutes, controlling the moisture content after drying to 5%.
[0053] S5. Packaging
[0054] Weigh the dried black tea leaves with an electronic weighing scale, package them, and then seal them with a continuous ink coding and sealing machine to obtain the finished black tea leaves, which are stored in a dry and odorless warehouse at an environmental temperature of 25°C and a relative humidity of 55%.
[0055] Comparative Example 1
[0056] The withering step of this comparative example is as follows: Evenly spread the picked fresh leaves on the withering trough. The thickness of the leaves spread in the withering trough is 4 cm, and then turn on the blower for withering. The wind speed is 6 m / s, the hot air temperature is 32°C, the humidity is 60%, and the withering time is 12 hours, controlling the water loss rate of the tea leaves to 40%.
[0057] The remaining processes are the same as those in Example 1.
[0058] Comparative Example 2
[0059] The rolling step of this comparative example is as follows: Place the withered tea leaves in a rolling machine for rolling. The rolling speed is 60 r / min, the rolling temperature is room temperature, and the rolling time is 93 minutes.
[0060] The remaining processes are the same as those in Example 1.
[0061] Comparative Example 3
[0062] The leaching step of this comparative example is as follows: After the secondary withering is completed, perform leaching. The leaching temperature is 90°C and the time is 2 minutes.
[0063] The remaining processes are the same as those in Example 1.
[0064] Comparative Example 4
[0065] The fermentation step of this comparative example is as follows: Place the rolled tea leaves in a black tea fermenter for fermentation. First, control the fermentation temperature to 35°C and the humidity to 95%, and the fermentation time is 1 hour. Then, adjust the fermentation temperature to 20°C and the humidity to 60%, and ferment for 5 hours.
[0066] The remaining processes are the same as those in Example 1.
[0067] Comparative Example 5
[0068] The fermentation steps in this comparative example are as follows:
[0069] The rolled tea leaves obtained in step S3 are placed in a black tea fermenter for fermentation. The temperature inside the machine is 20°C, the relative humidity is 90%, and the fermentation time is 2 h;
[0070] The remaining processes are the same as those in Example 1.
[0071] I. Sensory evaluation
[0072] Weigh 3.0 g of the black tea samples prepared in Examples 1-2 and Comparative Examples 1-5. The mass ratio of tea to water is 1:50. Place them in a 150 mL evaluation tea cup, fill it with boiling water, cover the cup, start timing, and the brewing time is 5 min. Filter out the tea soup. Refer to the "Method for Sensory Evaluation of Tea (GB / T 23776-2018)", and conduct sensory evaluations on the color, aroma, and taste of the black tea samples prepared in Examples 1-2 and Comparative Examples 1-5 respectively. As shown in Table 1 below.
[0073] Table 1
[0074]
[0075]
[0076] II. Determination of caffeine removal rate
[0077] (1) Preparation of standard solution. Weigh 125 mg of caffeine (purity not less than 99%), add ethanol and distilled water in a ratio of 1:4, dissolve and make up the volume to 250 mL, shake well. Pipette 1.0, 2.0, 5.0, 10.0 mL of the above standard stock solution, and make up the volume to 50 mL with distilled water respectively as a series of standard solutions.
[0078] (2) Preparation of treatment solution. Weigh 1.0 g of the prepared black tea sample, grind it and place it in a 500 mL beaker, add 4.5 g of magnesium oxide, add 300 mL of boiling water, heat it in a boiling water bath for 20 min, and shake the flask well every 5 min. After the boiling water bath is completed, immediately transfer it to a suction filter for filtration, transfer the filtrate into a 500 mL volumetric flask, cool it and make up the volume with distilled water, mix well to prepare the treatment solution for testing.
[0079] (3) Draw a standard curve. Take an appropriate amount of caffeine standard solution and place it in an HPLC injection vial. Respectively, with the mass concentrations of the caffeine standard solution being 5, 10, 25, and 50 μg / mL, and according to the high-performance liquid chromatography conditions: detection wavelength: ultraviolet detector, wavelength 280 nm; mobile phase: add 600 mL of methanol to 1400 mL of distilled water, mix well, and filter through a 0.45 μm membrane; flow rate 0.5 - 1.5 mL / min, column temperature 40 °C, injection volume 10 - 20 μL for determination. Obtain the regression equation of the standard curve, and determine the caffeine content with reference to GB / T 8312—2013, and calculate the caffeine removal rate. As shown in Table 2 below.
[0080] Caffeine removal rate = (caffeine content before treatment - caffeine content after treatment) ÷ caffeine content before treatment × 100%
[0081] Table 2
[0082] Caffeine removal rate (%) Example 1 68.5 Example 2 67.5 Comparative Example 1 67.2 Comparative Example 2 66.8 Comparative Example 3 51.3 Comparative Example 4 67.0 Comparative Example 5 66.9
[0083] In summary, the black tea preparation method provided by the present invention, through the processes of segmented withering, segmented rolling, fermentation, and drying, effectively promotes the formation of aroma precursor substances, enhances the thickness and brightness of the tea soup, retains the active substances in fresh leaves, and at the same time can better reduce the caffeine content. During extraction, as the temperature of hot water increases, caffeine will quickly dissolve and leach in hot water, causing the caffeine content in tea leaves to continuously decrease and the removal rate to increase. However, high temperature will inactivate polyphenol oxidase, resulting in catechins not being oxidized into theaflavins, affecting the color of black tea and causing a decline in the sensory quality of black tea; as the extraction time increases, the tea leaves shrink due to temperature rise, leading to a decrease in the caffeine removal rate in tea leaves and the color of the tea soup becoming darker, affecting the brightness, while too low extraction temperature and too short extraction time cannot achieve the effect of effectively removing caffeine. The present invention achieves rapid high-temperature extraction after secondary withering, which not only retains the active substances in fresh leaves but also reduces the caffeine content without affecting the brightness of the tea soup. The segmented withering of the present invention first slowly loses water at a low temperature and high humidity by 20-24%, and then heats and blows air to accelerate the water loss rate to 38-42%, effectively promoting the formation of aroma precursor substances and enhancing the thickness of the tea soup. Combined with the rolling stage, it uses high-speed rolling at 70-80 r / min and low temperature of 13-17°C for 70-80 min for the first time, and low-speed rolling at 20-25 r / min and high temperature of 30-33°C for 15-20 min for the second time, achieving a cell breakage rate of over 80%, improving the enzymatic oxidation efficiency, and enabling the content of theaflavins and thearubigins to reach a more suitable level. The amino acid content is relatively high, improving the freshness of the tea soup, making the finished tea soup red and bright, with a strong sweet aroma and no grassy taste, and providing a good basis for the subsequent fermentation process. The present invention controls the fermentation at 25-30°C for 4 h - 4 h 40 min, reducing the cumbersome multi-stage fermentation process. It is not that the more complex the fermentation process, the longer the fermentation time, and the higher the temperature, the better the quality of the obtained tea. The moderate and mild fermentation of the present invention can, to a certain extent, prevent the further conversion of terpenoids, better retain the fresh aroma of the tea, and have a floral and fruity aroma. The floral and fruity aroma is rich and long-lasting, and the aftertaste is relatively strong. If the fermentation time is too short, the aroma is mixed and has a grassy smell, the taste is strongly stimulating and lacks mellow taste. Similarly, too complex a fermentation process and too long a fermentation time will also produce a sour taste, and the color of the tea soup is dull.
[0084] The foregoing description of specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and obviously, many changes and variations are possible in light of the above teachings. The purpose of selecting and describing exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the present invention, as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.
Claims
1. A method for preparing black tea, characterized in that, It includes the following steps: S1. Withering The freshly picked tea leaves are withered, including primary withering and secondary withering. The specific method is as follows: The freshly picked tea leaves are evenly spread out flat in a withering trough. For primary withering, the temperature is controlled at 15 - 20°C, the humidity is 60 - 70%, and the withering time is 16 - 20 h; then the blower is turned on for secondary withering, the wind speed is 5 - 7 m / s, the hot air temperature is 30 - 35°C, and the withering time is 3 - 5 h, obtaining withered tea leaves; S2. Rolling The withered tea leaves in step S1 are rolled, including primary rolling and secondary rolling. The specific method is as follows: The withered tea leaves are placed in a rolling machine for primary rolling, and then the tea leaves are taken out and spread out to dry in natural conditions for 5 - 10 min; then secondary rolling is carried out to obtain rolled tea leaves; S3. Fermentation The rolled tea leaves obtained in step S2 are placed in a black tea fermentation machine for fermentation. The temperature inside the machine is 25 - 30°C, the relative humidity is 88 - 93%, and the fermentation time is 4 h - 4 h 40 min, obtaining fermented tea leaves; S4. Drying The fermented tea leaves in step S3 are subjected to primary drying and final drying. The primary drying temperature is 100 - 115°C, and the primary drying time is 8 - 10 min; the final drying temperature is 110 - 115°C, and the final drying time is 8 - 12 min, controlling the moisture content after drying to be below 7%.
2. The preparation method of a black tea according to claim 1, wherein, In step S1, the water loss rate of the tea leaves is controlled to 20 - 24% during primary withering and 38 - 42% during secondary withering.
3. The preparation method of a black tea according to claim 1, characterized in that, In step S1, it also includes extraction after the end of secondary withering. The extraction temperature is 90 - 100°C, and the time is 50 - 70 s.
4. The preparation method of a black tea according to claim 3, characterized in that, In the extraction treatment, the mass ratio of the withered tea leaves to hot water is 1:15 - 18.
5. A method for preparing black tea according to claim 1, characterized in that, In step S2, the rotation speed of primary rolling is 20 - 25 r / min, the temperature of primary rolling is 13 - 17°C, and the time of primary rolling is 70 - 80 min.
6. The preparation method of a black tea according to claim 1, characterized in that, In step S2, the rotation speed of secondary rolling is 70 - 80 r / min, the temperature of secondary rolling is 30 - 33°C, and the time of secondary rolling is 15 - 20 min.
7. A method for preparing black tea according to claim 1, characterized in that, In step S1, the thickness of the tea leaves spread in the withering trough is 3 - 5 cm.
8. A black tea prepared by the preparation method according to any one of claims 1 - 7.