Method for preparing black brick tea from aged green tea

Abstract

The invention provides a method for preparing black brick tea by using aged green tea, the aged green tea is selected to be blended with Yunnan large-leaf sunned raw tea and / or tea stems, a production process of Pu'er tea is adopted, and the black brick tea is prepared through blending, water spraying, pile fermentation, weighing, boxing, steaming, brick making, drying and aging. The Pu'er tea prepared by the preparation method disclosed by the invention has the fragrance of green tea, the proportion of necessary and functional free amino acids, the content of microbial secondary metabolism active components, the content of water extract and the antioxidant activity are obviously increased, and the nutritional value, the functional value and the economic value of the raw materials are obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of tea processing, and in particular relates to a method for preparing black brick tea by utilizing aged green tea. Background Art

[0002] Tea is an important cash crop, and the tea industry is a traditional advantageous and characteristic industry in my country. According to the "2023 China Tea Production and Marketing Situation Report" compiled by the China Tea Circulation Association, the total tea production in China in 2023 will be 3.339 million tons, of which green tea will be 1.934 million tons, accounting for 57.9% of the total production. Green tea is the only non-fermented tea among the six major tea systems in my country. Its raw materials are mainly the tender buds of small-leaf tea trees, which are made by killing, rolling and drying. Green tea is generally made of spring tea. Due to its seasonal characteristics, green tea needs to be stored in warehouses for a considerable period of time from the completion of production to the end of sales. According to statistics from 2011 to 2021, China's tea inventory is nearly 3 million tons, of which green tea accounts for about 2 / 3. As a non-fermented tea, the quality of green tea will change greatly with the extension of storage time, and the color, aroma and taste of the tea will change greatly, resulting in reduced product quality and becoming "aged green tea" with low economic value. Moreover, in order to further guide and standardize the storage and shelf life of green tea products in my country, the Hangzhou Tea Research Institute of the China National Federation of Supply and Marketing Cooperatives and relevant units have formulated the China Tea Circulation Association Group Standard - Green Tea Shelf Life (T / CTMA028-2021), which stipulates that the shelf life of green tea at low temperature (<10°C) is only 36 months. Therefore, how to utilize aged green tea, especially green tea whose storage years are close to the shelf life, to improve its economic value is an urgent problem to be solved in the field of tea processing technology in my country. Pu'er tea is a unique geographical indication product in Yunnan, and its sales reached 2.85 billion in 2022. Pu'er tea is a post-fermented tea made from large-leaf sun-dried green tea from Yunnan, refined through processes such as tide, pile fermentation, aging and drying. Pu'er tea is a black tea, which undergoes a natural fermentation aging process during storage. During this process, the endogenous microorganisms produced by Pu'er tea interact with the ingredients contained in tea leaves, such as theaflavins, theabrownins, tea polyphenols, and water-soluble sugars, giving Pu'er tea a unique taste, aroma, and soup color. Not only that, the active ingredients it produces have a variety of effects, such as anti-diabetes, anti-hyperlipidemia, and regulating intestinal flora. Therefore, Pu'er tea is completely different from green tea, and its economic and edible value will increase with the increase in storage years. Summary of the invention

[0003] Technical problem to be solved: In view of the problem that the inventory of aged green tea is large and the quality and economic value decrease with the increase of storage years, the present invention provides a method for preparing black brick tea using aged green tea, wherein aged green tea is selected and blended with Yunnan large-leaf sun-dried green raw tea and / or tea stems, and the production process of Pu'er tea is adopted, and the tea is made through blending, tide water, pile fermentation, weighing, boxing, steaming, brick making, drying and aging. The prepared product has the "golden flower" unique to black tea, namely, Eurotium cristatum, and the soup color and taste of Pu'er tea, and has the fragrance of green tea, and the functional free amino acids, microbial secondary metabolic active ingredients, water extract content and antioxidant activity are significantly increased, thereby significantly improving the nutritional value, efficacy value and economic value of the raw materials.

[0004] Technical solution: A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: blending aged green tea with Yunnan large-leaf sun-dried green tea and / or tea stems to obtain blended tea leaves; S2. Tide: After sprinkling water on the blended tea leaves, wait for 5-8 hours to obtain the tea leaves after the tide; S3. Piling: Put the tea leaves after the tide into a bamboo basket and ferment them at 30-50°C for 3-15 days to obtain the tea leaves after the pile; S4. Packing: Put the piled tea leaves into the iron cylinder and flatten them; S5. Steaming: Place the iron cylinder on the steam generator and steam for 8-10 seconds to obtain steamed tea leaves; S6. Brick making: Put the steamed tea leaves into a brick press and press them into tea bricks; S7. Drying: After the temperature of the tea brick drops to 50 ° C, transfer it to the drying room and dry the tea brick at 40-60 ° C for 10-15 days to obtain a dried tea brick; S8. Aging: Place the dried tea bricks in an environment of 30-40°C and 40-50% RH and ferment for 6-7 days to obtain black brick tea. Furthermore, the aged green tea in step S1 includes but is not limited to small-leaf tea produced in Zhejiang. Furthermore, the small-leaf tea varieties include Wuniuzao, Jiukeng and Longjing. Furthermore, the aged green tea in step S1 is green tea with one bud and one leaf or one bud and two leaves picked during the Spring Festival and prepared according to traditional green tea technology, and the storage time includes but is not limited to 3 years or more. Furthermore, in step S1, the proportion of Yunnan large-leaf sun-dried green tea and / or tea stems added is not higher than 30%. Furthermore, the Yunnan large-leaf sun-dried green tea in step S1 includes green tea with one bud and three leaves or one bud and four leaves picked in spring and summer and dried in the sun, and the water content is controlled to be below 15%. Furthermore, in step S2, the amount of water sprayed is 42.8-66.7% of the amount of tea leaves, so that the humidity of the tea leaves is maintained at 30-40% RH. Furthermore, during the drying period in step S8, the drying room is opened for 2 hours every 3 days to allow the water vapor in the drying room to dissipate, and this is repeated 3-5 times. Beneficial effects: 1. The present invention blends aged green tea with Yunnan large-leaf sun-dried raw tea, and can utilize polyphenol oxidase and endogenous microorganisms in the large-leaf sun-dried raw tea to promote the quality transformation of green tea into dark tea during the fermentation process. The endogenous microorganisms will interact with theaflavins, theabrownins, tea polyphenols, water-soluble sugars and other components contained in the tea leaves, so that the prepared dark tea presents a unique taste, aroma and soup color; 2. When the blended tea leaves are subjected to tidal treatment, the tea leaves are placed on a waterproof cloth for sun exposure to ensure that the aged green tea and the sun-dried raw tea can fully absorb water, which is beneficial to the later fermentation; 3. The present invention uses bamboo baskets for fermentation. On the one hand, a small volume container is used for fermentation, which is simple to operate. When the tea pile is fermented by the triple effects of endogenous microorganisms, moisture, heat and enzymes, the fermentation conditions are more controllable and the quality is more stable. On the other hand, the use of bamboo baskets for fermentation improves the traditional method of piling Pu'er tea on the ground, thereby improving the sanitary quality of the tea leaves. 4. After the tea bricks are pressed, the present invention further dries them in a drying room to reduce the moisture content in the tea bricks, thereby avoiding the growth of bacteria and facilitating the fermentation and aging in the later stage; 5. The tea brick prepared by the present invention has the unique "golden flower" of dark tea, namely, the cosmidia cristata. During the subsequent storage, the substances in the tea brick can be further transformed, so that the dark tea has the advantage of higher economic value as it ages, which solves the problem that the inventory of aged green tea is large, and the quality and economic value decrease with the increase of storage years. The cosmidia cristata present in the present invention is not only the key factor in forming the unique soup color, taste and aroma of dark tea, but also the metabolites produced by it are also the important reasons why dark tea has the physiological effects of anti-oxidation, antibacterial, anti-inflammatory, hypoglycemic, antihypertensive and hypotensive. 6. The tea brick prepared by the present invention has the color and taste of Pu'er tea after brewing, and has the fragrance of green tea, and can increase the content of water extract, antioxidant activity, the ratio of essential and functional free amino acids and the content of active microbial secondary metabolites, which significantly improves the nutritional value, efficacy value and economic benefits of the raw materials. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a physical picture of the Eurotium cristatum of the black brick tea prepared in Example 2; Figure 2 The actual pictures are of 100% Zhejiang aged Longjing and black brick tea prepared in Examples 1-3, wherein A is 100% Zhejiang aged Longjing; B is Example 1; C is Example 2; D is Example 3; Figure 3 The figures are of dry tea, tea leaves and tea soup color, among which A is 100% Zhejiang aged Longjing tea without fermentation; B is comparative example 1 fermented and aged for 3 months; C is example 2 fermented and aged for 3 months; D is example 1 fermented and aged for 12 months; Figure 4 This is a non-target metabolomics analysis diagram of the black brick tea prepared in Example 2, where A is the orthogonal partial least squares method (OPLS-DA), unfermented (left side), fermented and aged for 3 months (right side); B is the important characteristic compound. DETAILED DESCRIPTION The present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are explanations of the present invention and the present invention is not limited to the following embodiments: Example 1 A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: 27kg of aged Longjing tea produced in Qingtian, Zhejiang, stored for 3 years, and 3kg of large-leaf sun-dried green tea picked in spring in Yunnan were blended to obtain blended tea leaves; S2. Tide: Place 30kg of blended tea on a waterproof cloth, spray 13kg of water, wait for 5 hours, maintain the humidity of the tea at 30% RH, until the tea fully absorbs water and becomes soft, and obtain the tea after the tide; S3. Wet pile: The tea leaves after the tide are placed in bamboo baskets and fermented at a temperature of 35 ° C for 5 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electric heating steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 10 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to a drying room set at a temperature of 50 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 4 times to obtain dried tea bricks; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 7 days to obtain black brick tea. Example 2 A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: 27kg of aged Longjing tea produced in Qingtian, Zhejiang, stored for 3 years, 1.5kg of large-leafed sun-dried green tea picked in spring in Yunnan, and 1.5kg of tea stems were blended to obtain blended tea leaves; S2. Tide: Place 30kg of blended tea on a waterproof cloth, spray 13kg of water, wait for 6 hours, maintain the humidity of the tea at 30% RH, until the tea fully absorbs water and becomes soft, and obtain the tea after the tide; S3. Wet pile: The tea leaves after the tide were placed in bamboo baskets and fermented at a temperature of 35 ° C for 10 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electrically heated steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 8 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to the drying room set at a temperature of 60 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 4 times to obtain dried tea bricks; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 6 days to obtain black brick tea. Example 3 A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: 21kg of aged Longjing tea produced in Qingtian, Zhejiang, stored for 3 years, 4.5kg of large-leafed sun-dried green tea picked in spring in Yunnan, and 4.5kg of tea stems were blended to obtain blended tea leaves; S2. Tide: Place 30kg of blended tea on a waterproof cloth, spray 16kg of water, wait for 8h, maintain the humidity of the tea at 35%RH, until the tea fully absorbs water and becomes soft, and obtain the tea after the tide; S3. Wet pile: The tea leaves after the tide are placed in bamboo baskets and fermented at a temperature of 35 ° C for 6 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electrically heated steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 8 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to the drying room set at a temperature of 60 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 5 times to obtain a dried tea brick; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 6 days to obtain black brick tea. Example 4 A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: 30kg of aged Wuniuzao produced in Qingtian, Zhejiang, stored for 3 years, was blended with 6kg of large-leaf sun-dried green tea picked in autumn in Yunnan to obtain blended tea leaves; S2. Tide: Place 36 kg of blended tea leaves on a waterproof cloth, spray 19.4 kg of water, wait for 5 hours, maintain the humidity of the tea leaves at 35% RH, until the tea leaves fully absorb water and become soft, and obtain the tea leaves after the tide; S3. Wet pile: The tea leaves after the tide are placed in bamboo baskets and fermented at a temperature of 35 ° C for 4 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electric heating steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 10 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to a drying room set at a temperature of 50 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 5 times to obtain a dried tea brick; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 7 days to obtain black brick tea. Example 5 A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: 30kg of aged Wuniuzao produced in Qingtian, Zhejiang, stored for 3 years, was blended with 10kg of large-leaf sun-dried green tea picked in autumn in Yunnan to obtain blended tea leaves; S2. Tide: Place 40kg of blended tea on a waterproof cloth, spray 21.5kg of water, wait for 5 hours, maintain the humidity of the tea at 35% RH, until the tea fully absorbs water and becomes soft, and obtain the tea after the tide; S3. Wet pile: The tea leaves after the tide are placed in bamboo baskets and fermented at a temperature of 35 ° C for 5 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electrically heated steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 8 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to a drying room set at a temperature of 50 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 5 times to obtain a dried tea brick; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 6 days to obtain black brick tea. Example 6 A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: 30kg of aged Wuniuzao produced in Qingtian, Zhejiang, stored for 3 years, 6kg of large-leafed sun-dried green tea picked in spring in Yunnan, and 6kg of tea stems were blended to obtain good tea leaves; S2. Tide: Place 42kg of blended tea on a waterproof cloth, spray 28kg of water, wait for 6 hours, maintain the humidity of the tea at 40% RH, until the tea fully absorbs water and becomes soft, and obtain the tea after the tide; S3. Wet pile: The tea leaves after the tide are placed in bamboo baskets and fermented at a temperature of 35 ° C for 12 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electrically heated steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 9 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to a drying room set at a temperature of 50 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 5 times to obtain a dried tea brick; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 7 days to obtain black brick tea. Comparative Example 1 The difference between this comparative example and Example 1 is that aged green tea is directly used to prepare black brick tea, as follows: S1. Blending: weigh 30 kg of aged Longjing tea produced in Qingtian, Zhejiang, stored for 3 years; S2. Tide: Place 30 kg of tea leaves on a waterproof cloth, spray 13 kg of water, wait for 5 hours, maintain the humidity of the tea leaves at 30% RH, until the tea leaves fully absorb water and become soft, and obtain the tea leaves after the tide; S3. Wet pile: The tea leaves after the tide are placed in bamboo baskets and fermented at a temperature of 35 ° C for 5 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electric heating steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 10 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to a drying room set at a temperature of 50 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 4 times to obtain dried tea bricks; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 7 days to obtain black brick tea. Comparative Example 2 The difference between this comparative example and Example 1 is that the black brick tea is prepared by using the fried green tea produced in the current year, as follows: A method for preparing black brick tea using fried green tea produced in the current year, comprising the following steps: S1. Weighing: weigh 30kg of stir-fried Qinglongjing produced in Qingtian, Zhejiang Province; S2. Tide: Place the stir-fried green tea on a waterproof cloth, spray 13 kg of water, wait for 5 hours, maintain the humidity of the tea at 30% RH, until the tea fully absorbs water and becomes soft, and obtain the tea after the tide; S3. Wet pile: The tea leaves after the tide are placed in bamboo baskets and fermented at a temperature of 35 ° C for 5 days to obtain tea leaves after Wet pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electric heating steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 10 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to a drying room set at a temperature of 50 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 4 times to obtain dried tea bricks; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 7 days to obtain black brick tea. Comparative Example 3 The difference between this comparative example and Example 1 is that the dark brick tea is prepared directly using large-leaf sun-dried green tea picked in spring in Yunnan, as follows: A method for preparing black brick tea using aged green tea, comprising the following steps: S1. Blending: weigh 30kg of large-leaf sun-dried green tea picked during the Spring Festival in Yunnan; S2. Tide: Place weighed tea leaves on a waterproof cloth, spray 13 kg of water, wait for 5 hours, and maintain the humidity of the tea leaves at 30% RH until the tea leaves fully absorb water and become soft, thus obtaining the tea leaves after the tide; S3. Piling: Put the tea leaves after the tide into a bamboo basket and ferment them at a temperature of 35°C for 5 days to obtain the tea leaves after the pile; S4. Loading box: weigh 500g of tea leaves after the pile is placed in a cylindrical iron cylinder with a diameter of 20cm and a height of 30cm, and level it; S5. Steaming: Use an electric heating steam generator to generate steam, output steam at about 100°C through a pipeline, place the cylindrical iron cylinder filled with tea leaves on the steam generator, and steam for 10 seconds to make the leaves absorb moisture and soften, thereby obtaining steamed tea leaves; S6. Brick making: The steamed tea leaves are placed in a 500g brick-making machine mold and pressed into tea bricks using a brick press; S7. Drying: After the temperature of the tea brick drops to 50 ° C, the prepared tea brick is transferred to a drying room set at a temperature of 50 ° C, and after drying for 3 days, the drying room is opened for 2h to dissipate the water vapor in the drying room, and then the drying room is closed, and then dried for 3 days, and then the drying room is opened for 2h to disperse the water vapor in the drying room, and this is repeated 4 times to obtain dried tea bricks; S8. Aging: Place the dried tea bricks in an environment of 30°C and 50% RH and ferment for 7 days to obtain black brick tea. Performance measurement: 1. Eurotium cristatum Figure 1 This is a real picture of the Eurotium cristatum in the black brick tea prepared in Example 2. 100% Zhejiang aged Longjing and the black brick tea prepared in Examples 1-3 were observed for Eurotium cristatum. Figure 2 It can be seen that there are obvious differences in the number of Eurotium coronarius in dark tea produced by different blending methods. Through comparison of several blending methods, it was found that the number of Eurotium coronarius produced in dark tea blended with Yunnan large-leaf sun-dried green tea and tea stems was significantly higher ( Figure 2 B, C, D), and all use Zhejiang produced aged Longjing ( Figure 2 A) The presence of Eurotium cristatum is almost invisible to the naked eye, indicating that the Yunnan large-leaf sun-dried green tea and tea stems play an important role in the production of Eurotium cristatum, especially in the black tea with 5% tea stems added, which has the largest amount of Eurotium cristatum. 2. Free amino acids Table 1 Free amino acid content of black brick tea produced by different blending methods Note: Sample A, 100% Zhejiang aged Longjing tea, unfermented; Sample B, 100% Zhejiang aged Longjing tea, fermented and aged for 3 months (Comparative Example 1); Sample C, 90% Zhejiang aged Longjing tea, 5% Yunnan large-leaf sun-dried green tea and 5% tea stems, blended and fermented and aged for 3 months (Example 2); Sample D, 90% Zhejiang aged Longjing tea, 10% Yunnan large-leaf sun-dried green tea, blended and fermented and aged for 12 months (Example 1). As can be seen from Table 1, a total of 24 free amino acids were detected in the four samples, including 7 essential amino acids, 10 non-essential amino acids and 7 non-protein amino acids. The free amino acid content of sample B, which was 100% Zhejiang aged Longjing fermented and aged for 3 months, was similar to that of sample A, which was 100% Zhejiang aged Longjing unfermented. However, the total free amino acid content of samples C and D, which were added with Yunnan large-leaf sun-dried green tea and tea stems, decreased significantly with the increase of aging time, especially the free amino acid content of sample D, which was only 2161.6 μg / g, and its amount was only 22.1% of that of unfermented sample A. This result is similar to the trend of free amino acids in the fermentation process of Pu'er tea, which may be caused by the Maillard reaction and the utilization of free amino acids by microorganisms such as Eurotium guanidinum during the fermentation process. By comparing the composition of free amino acids in sample A and sample D, it was found that after aging and fermentation, although the total amount of free amino acids decreased, the proportion of essential amino acids increased from 18.6% to 21.1%, indicating that the amino acid composition was significantly improved. In addition, after aging and fermentation, the content and proportion of total flavor amino acids decreased significantly, while the proportion of functional non-protein amino acids increased significantly, such as taurine, citrulline, β-alanine, and 2-aminobutyric acid increased from 1.12%, 0.42%, 0.54%, and 0.55% to 17.96%, 0.72%, 1.67%, and 1.86%, respectively, indicating that flavor amino acids were metabolized by microorganisms such as Eurotium guanidinum to produce new active ingredients. In particular, the content and proportion of taurine increased significantly. Taurine is an active substance that regulates the normal physiological activities of the body. It has a wide range of biological functions such as anti-inflammatory, analgesic, hypoglycemic, improving the body's immunity, and protecting myocardial cells. In addition, citrulline is the prerequisite for the gas signal molecule NO, which plays an important role in cardiac metabolic health; β-alanine has the ability to enhance anaerobic capacity, prolong the fatigue limit of athletes, and has anti-fatigue activity; 2-aminobutyric acid can increase the level of intracellular glutathione by activating AMPK and protect against oxidative stress. 3. Dry tea, tea leaves and tea soup color Select the four samples in Table 1. Figure 3 It can be seen that the leaf bottom color and soup color of sample B, which was fermented by 100% Zhejiang aged Longjing for 3 months, are similar to those of sample A, which is unfermented by 100% Zhejiang aged Longjing. The leaf bottom is yellow-green, and the soup color is bright yellow. As the aging time increases, the leaf bottom of samples C and D, which are added with Yunnan large-leaf sun-dried green tea and tea stems, turns green-brown, and the soup color also shows the bright red color of Pu'er tea. This result shows that after aging and fermentation by this process, the theabrownin increases under the action of microorganisms such as Aspergillus guanidinus, and the color of the tea soup deepens. During the aging and fermentation process, the peroxidase and laccase produced by microorganisms such as Aspergillus guanidinus can convert tea polyphenols into theaflavins, thearubigins and theabrownins, thereby reducing the astringency of tea leaves and forming the soup color and taste characteristics of Pu'er black tea. 4. Water extract content The determination was carried out according to the method specified in GB / T 8305-2013 “Determination of tea extract”. Table 2 Water extract content of black brick tea prepared in Examples 1-6 and Comparative Examples 1-3 Water extract content (%) Water extract content (%) Example 1 50.4 Example 6 49.2 Example 2 49.0 Comparative Example 1 39.7 Example 3 49.2 Comparative Example 2 44.2 Example 4 50.0 Comparative Example 3 47.4 Example 5 47.7 As can be seen from Table 2, the water extract content of the black brick tea prepared in Examples 1-6 is 47.7-50.4%, and Comparative Example 1 directly uses aged green tea to prepare black brick tea, and the water extract content is relatively low at 39.7%; Comparative Example 2 uses the current year's fried green tea to prepare black brick tea, and the water extract content is 44.2%, which is similar to the water extract content in the embodiments; Comparative Example 3 directly uses large-leaf sun-dried green tea picked in spring in Yunnan to prepare black brick tea, and the water extract content is 47.4%. Therefore, it can be seen that the black brick tea prepared by blending aged green tea with Yunnan large-leaf sun-dried green tea and / or tea stems in the present invention has an increased water extract content. 5. Antioxidant Activity The black brick tea prepared in Examples 1-6 and Comparative Examples 1-3 was ground, 0.3 g of the ground tea sample was taken, 45 mL of 50% ethanol solution was added, ultrasonic extraction was performed for 30 min, and the volume was adjusted to 100 mL after filtration to obtain a test sample. 1) DPPH free radical scavenging activity Add 495 μL DPPH ethanol solution and 5 μL test sample to a 1.5 mL centrifuge tube, place in a 37°C water bath for 30 min, and measure at 517 nm using an ELISA reader. The free radical scavenging rate of each sample was measured three times in parallel, and the experimental results were expressed as the average ± standard error of the three measurements, and the calculation formula is as follows: Clearance rate (%) = (A0-A x ) / A0×100% Where A0 is the absorbance value of the control group; A x is the absorbance value of the test sample group. 2) ABTS free radical scavenging activity Adjust the absorbance of the ABTS storage solution to 0.72±0.02 working solution. Add 498μL working solution and 2μL tea test sample to a 1.5mL centrifuge tube, react at room temperature in the dark for 6 minutes, and measure at 734nm using an ELISA reader. The free radical scavenging rate of each sample was measured three times in parallel, and the experimental results were expressed as the average ± standard deviation of the three measurements, and the calculation formula was the same as DPPH. Table 3 Antioxidant activity of black brick tea prepared in Examples 1-6 and Comparative Examples 1-3 DPPH free radical scavenging rate (%) ABTS free radical scavenging rate (%) Example 1 62.0±2.5 64.8±2.7 Example 2 84.6±2.6 90.9±3.2 Example 3 85.2±4.6 88.8±2.8 Example 4 63.1±2.6 69.4±1.6 Example 5 70.6±1.8 76.0±3.5 Example 6 80.6±0.7 73.4±1.0 Comparative Example 1 60.1±1.3 62.6±3.3 Comparative Example 2 78.3±2.9 72.5±2.7 Comparative Example 3 70.9±3.5 67.0±1.7 As can be seen from Table 3, the black brick tea prepared in Examples 1-6 has good antioxidant activity, wherein the DPPH free radical scavenging rate is between 62.0-85.2%, and the ABTS free radical scavenging rate is between 64.8-90.9%; while in Comparative Example 1, aged green tea is directly used to prepare black brick tea, and the DPPH and ABTS free radical scavenging rates are the lowest; in Comparative Example 2, the fried green tea produced in the current year is used to prepare black brick tea, and the DPPH free radical scavenging rate is 78.3%, and the ABTS free radical scavenging rate is 72.5%, and the antioxidant effect is lower than that of Examples 2 and 3, and the aged green tea used in the present invention is more economically valuable; in Comparative Example 3, large-leaf sun-dried green tea picked in spring in Yunnan is directly used to prepare black brick tea, and the DPPH free radical scavenging rate is between 70.9%, and the ABTS free radical scavenging rate is 67.0%, which is lower than that of Examples 2, 3 and 6. Therefore, it can be seen that the black brick tea prepared by blending aged green tea with Yunnan large-leaf sun-dried green tea and / or tea stems in the present invention has increased antioxidant activity. 6. Non-targeted metabolomics analysis Through non-target metabolomics analysis of 90% Zhejiang aged Longjing tea, 5% Yunnan large-leaf sun-dried green tea and 5% tea stem blended unfermented and fermented aged for 3 months, the results showed that the samples before and after fermentation were clearly divided into two groups ( Figure 4 A), indicating that under the action of microorganisms, the tea components have undergone significant changes. Figure 4 From the compounds marked in B, it can be seen that the key components of the differential metabolites are mainly organic acids such as reduced glutathione (L-glutathione, reduced), propionic acid, succinate, phenylacetyl-l-glutamine, sugars such as 2-deoxyribose 5-phosphate, lipids such as trans-traumatic acid, etc., indicating that under the metabolism of microorganisms, the proteins, sugars, lipids and other components contained in tea leaves have undergone significant effects. In addition, some functional metabolites have increased significantly under the action of microorganisms, such as the content of reduced glutathione, which has increased by 13 times compared with before fermentation. Reduced glutathione is a recognized active molecule with multiple functions including anti-oxidation, DNA repair, detoxification, anti-aging, and prevention of neurodegenerative diseases. 7. Sensory evaluation Referring to GB / T 23776-2018 "Tea Sensory Evaluation Method", the black brick tea prepared in Example 2 and Comparative Examples 1-3 was subjected to sensory evaluation, and the results are as follows: Table 4 Sensory evaluation results of black brick tea prepared in Example 2 and Comparative Examples 1-3 As can be seen from Table 4, the black brick tea prepared by blending aged green tea with large-leaf sun-dried green tea and tea stems picked in spring in Yunnan Province in Example 2 of the present invention is similar to Comparative Example 3, and is higher than the black brick tea prepared by using fried green tea produced in the current year (Comparative Example 2), and the present invention has more economic and social benefits. The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing black brick tea using aged green tea, characterized in that: The following steps are involved: S1. Blending: blending aged green tea with Yunnan large-leaf sun-dried green tea and / or tea stems to obtain blended tea leaves; S2. Tide: After sprinkling water on the blended tea leaves, wait for 5-8 hours to obtain the tea leaves after the tide; S3. Piling: Put the tea leaves after the tide into a bamboo basket and ferment them at 30-50°C for 3-15 days to obtain the tea leaves after the pile; S4. Packing: Put the piled tea leaves into the iron cylinder and flatten them; S5. Steaming: Place the iron cylinder on the steam generator and steam for 8-10 seconds to obtain steamed tea leaves; S6. Brick making: Put the steamed tea leaves into a brick press and press them into tea bricks; S7. Drying: After the temperature of the tea brick drops to 50 ° C, transfer it to the drying room and dry the tea brick at 40-60 ° C for 10-15 days to obtain a dried tea brick; S8. Aging: Place the dried tea bricks in an environment of 30-40°C and 40-50% RH and ferment for 6-7 days to obtain black brick tea.

2. The method for preparing black brick tea by using aged green tea according to claim 1, characterized in that: The aged green tea in step S1 includes but is not limited to small-leaf tea produced in Zhejiang.

3. A method for preparing black brick tea using aged green tea according to claim 2, characterized in that: The small-leaf tea varieties include Wuniuzao, Jiukeng and Longjing.

4. The method for preparing black brick tea by using aged green tea according to claim 2, characterized in that: The aged green tea in step S1 is green tea with one bud and one leaf or one bud and two leaves picked during the Spring Festival and prepared according to the traditional green tea process, and the storage time includes but is not limited to 3 years and above.

5. The method for preparing black brick tea by using aged green tea according to claim 1, characterized in that: In the step S1, the proportion of the Yunnan large-leaf sun-dried green tea and / or tea stems added is not higher than 30%.

6. The method for preparing black brick tea by using aged green tea according to claim 4, characterized in that: The Yunnan large-leaf sun-dried green tea in step S1 includes green tea with one bud and three leaves or one bud and four leaves picked in spring and summer and dried in the sun, and the water content is controlled to be below 15%.

7. The method for preparing black brick tea by using aged green tea according to claim 1, characterized in that: In step S2, the amount of water sprayed is 42.8-66.7% of the amount of tea leaves, so that the humidity of the tea leaves is maintained at 30-40% RH.

8. The method for preparing black brick tea by using aged green tea according to claim 1, characterized in that: During the drying period in step S7, the drying room is opened for 2 hours every 3 days to allow the water vapor in the drying room to dissipate, and this is repeated 3-5 times.

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