Processing method for removing astringency and preserving fragrance of selenium-rich tea cake
Patent Information
- Application Number
- CN202611278004.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-21
- Publication Date
- 2026-10-30
AI Technical Summary
该工艺存在一定不足：蒸压工序中，高温蒸汽处理导致茶叶中有机硒（主要为硒代蛋氨酸和硒代半胱氨酸）分解挥发，硒保留率降低；茶饼原料中酯型儿茶素（EGCG、ECG）含量高，未经充分转化即压饼成型，成品茶饼涩味重、收敛性强，需长期陈化（3-5年）才能改善口感；其次，高温蒸汽处理和长时间热风干燥破坏了茶叶特征香气成分，成品香气平淡、青草气或熟闷味突出，香气品质下降
（1）本发明采用单宁酶、纤维素酶和β-葡萄糖苷酶复合酶系进行脱涩预处理。单宁酶选择性水解酯型儿茶素的没食子酸酯键，将EGCG转化为EGC和没食子酸，将ECG转化为EC和没食子酸，EGCG和ECG降低率达40-55%，涩味下降；纤维素酶适度破坏细胞壁纤维素骨架，促进脱涩酶液和后续稳态化液的渗透效率；β-葡萄糖苷酶在酶解过程中释放结合态香气前体，为后续保香奠定基础。
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This invention belongs to the field of tea processing technology, specifically relating to a method for processing selenium-enriched tea cakes to remove astringency and preserve aroma. Background Technology
[0002] Selenium is an essential trace element for the human body, possessing various physiological functions such as anti-oxidation, enhanced immunity, and prevention of cardiovascular diseases. Approximately 72% of my country's soil is selenium-deficient, making selenium supplementation through selenium-enriched agricultural products an economical and effective approach. Tea, with its wide consumer base and excellent selenium accumulation capacity, is an ideal carrier of selenium. Tea cakes (compressed tea) are an important form of tea product due to their ease of transportation, storage, and aging. Selenium-enriched tea cakes, in particular, combine the rich flavor of tea cakes with the nutritional and health benefits of selenium, leading to a year-on-year increase in market demand.
[0003] The current processing method for selenium-enriched compressed tea (tea cakes) follows the traditional compressed tea process: fresh leaves, fixation, rolling, sun-drying (or oven-drying), steaming to soften, pressing into cakes, drying, and aging. This process has certain shortcomings: during the steaming and pressing process, the high-temperature steam treatment causes the organic selenium (mainly selenomethionine and selenocysteine) in the tea leaves to decompose and volatilize, reducing the selenium retention rate; the raw materials for the tea cakes have a high content of ester-type catechins (EGCG, ECG), and if they are pressed into cakes without sufficient conversion, the finished tea cakes will have a strong astringent taste and require long-term aging (3-5 years) to improve their flavor; secondly, the high-temperature steam treatment and long-term hot air drying damage the characteristic aroma components of the tea leaves, resulting in a bland aroma, a prominent grassy or musty smell, and a decline in aroma quality.
[0004] To address the aforementioned issues, existing improvement technologies mainly focus on: reducing the astringency of tea cakes through raw material screening (selecting low-astringency tea tree varieties), but the selection of varieties is limited and cannot simultaneously take into account selenium-rich characteristics; using artificial temperature and humidity controlled aging to accelerate the fading of astringency, but the cycle still requires 6-12 months and is energy-intensive; and using microwave drying instead of hot air drying to improve aroma, but microwave drying is uneven and prone to local scorching, and the improvement in selenium retention rate is limited.
[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention
[0006] The purpose of this invention is to provide a method for processing selenium-enriched tea cakes to remove astringency and preserve aroma, so as to solve the problems existing in the prior art.
[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for processing selenium-enriched tea cakes to remove astringency and preserve aroma includes the following steps: S1. Spray the kneaded selenium-enriched tea leaves evenly with a compound deastringency enzyme solution, the amount of which is 6-12% of the tea leaf mass. After spraying, place the tea leaves in an enzymatic hydrolysis reaction chamber, control the temperature at 30-35℃ and the relative humidity at 85-90%, and let them stand for enzymatic hydrolysis for 1-3 hours. The compound deastringency enzyme solution is composed of tanninase, cellulase, β-glucosidase and phosphate buffer. S2. The enzymatically hydrolyzed tea leaves are placed in a negative pressure osmosis tank, and a selenium stabilization solution is added at a material-to-liquid ratio of 1:08-1.2. The tank is maintained at a vacuum of -0.07 to -0.09 MPa for 10-20 minutes, then slowly restored to atmospheric pressure and soaked for another 20-40 minutes. The selenium stabilization solution is composed of sodium alginate, reduced glutathione, trehalose, cysteine, and purified water. S3. Remove the tea leaves and drain them. Spray them evenly with a calcium chloride solution with a mass concentration of 0.5-1.5%, and spray the amount of solution at 3-6% of the mass of the tea leaves. Let it stand for 10-20 minutes to allow sodium alginate to cross-link with calcium ions to form a microgel network, which will stably embed selenium inside the tea leaf tissue. S4. The obtained tea leaves are placed into a steam press molding machine and treated with saturated steam at a low temperature of 90-95℃ for 40-60 seconds to soften the tea leaves. Then, the tea leaves are pressed into shape using a gradient pressure method. S5. Dry the tea cake in sections.
[0008] Furthermore, in step S1, the compound deastringent enzyme solution is composed of the following components by mass percentage: 0.05-0.20% tanninase, 0.02-0.08% cellulase, 0.01-0.05% β-glucosidase, and the balance is phosphate buffer with a pH of 5.0-5.5.
[0009] Furthermore, the tanninase activity is ≥500 U / g, the cellulase activity is ≥10000 U / g, and the β-glucosidase activity is ≥100 U / g.
[0010] Furthermore, in step S2, the selenium stabilization solution is composed of the following components by mass percentage: sodium alginate 0.8-2.0%, reduced glutathione 0.2-0.6%, trehalose 0.5-1.5%, cysteine 0.1-0.3%, and the balance being purified water.
[0011] Furthermore, in step S4, the gradient pressure method is specifically as follows: initial pressure of 5-8 MPa held for 5-10 s, pressure released for 2-3 s, medium pressure of 10-12 MPa held for 10-15 s, pressure released for 2-3 s, and final pressure of 12-15 MPa held for 20-30 s; the mold temperature is controlled at 35-45℃ during the pressing process.
[0012] Furthermore, in step S5, the segmented drying specifically involves: Low temperature and high humidity equilibrium stage: temperature 18-22℃, relative humidity 60-65%, time 12-24h, the moisture content of the tea cake drops to 20-24%; Medium-temperature and medium-humidity transformation stage: temperature 28-32℃, relative humidity 55-60%, time 24-36h, the moisture content of the tea cake drops to 15-18%; Low-temperature and low-humidity aroma enhancement stage: temperature 35-40℃, relative humidity 40-50%, time 12-18h, the moisture content of the tea cake is reduced to 10-12%; Low-temperature rehydration equilibrium stage: temperature 22-25℃, relative humidity 50-55%, time 24-48h, the moisture content of the tea cake is balanced to 9-11%.
[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses a complex enzyme system of tanninase, cellulase and β-glucosidase for deastringency pretreatment. Tanninase selectively hydrolyzes the gallic acid ester bonds of ester-type catechins, converting EGCG into EGC and gallic acid, and ECG into EC and gallic acid. The reduction rate of EGCG and ECG reaches 40-55%, and the astringency is reduced. Cellulase moderately destroys the cell wall cellulose skeleton, promoting the penetration efficiency of the deastringency enzyme solution and the subsequent stabilization solution. β-glucosidase releases bound aroma precursors during enzymatic hydrolysis, laying the foundation for subsequent aroma preservation.
[0014] (2) This invention employs a strategy of negative pressure permeation of a composite stabilizing solution containing sodium alginate, glutathione, trehalose, and cysteine, along with calcium ion crosslinking and solidification. Negative pressure permeation allows the stabilizing solution to penetrate deep into the intercellular spaces and cells of the mesophyll, where sodium alginate and calcium ions crosslink and solidify. 2+ Cross-linking forms a three-dimensional microgel network, physically embedding organic selenium within the gel network; the free sulfhydryl groups of glutathione and cysteine form Se-S covalent bonds with selenoamino acids to achieve chemical fixation; trehalose acts as a disaccharide protectant to stabilize the conformation of selenoproteins. The selenium retention rate after calcium ion cross-linking and curing reaches 75-86%.
[0015] (3) The finished tea cake of this invention has a significantly reduced astringency, a mellow and sweet taste, and no green or musty taste; the tea soup is bright yellow-green or bright orange-yellow; the water extract content is ≥38%, and the phenol-to-amino acid ratio is controlled within the suitable range of 6-9. The tea cake can be consumed directly without long-term aging, which greatly shortens the product's market cycle. Detailed Implementation
[0016] The technical solution of this invention patent will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.
[0017] The fresh leaves of the selenium-rich tea come from the selenium-rich tea producing area of Enshi, Hubei (one bud and two leaves or one bud and three leaves, with a total selenium content of 0.45mg / kg dry weight). They are processed into sun-dried green tea using traditional green tea techniques and used as raw materials for tea cakes.
[0018] Example 1 A method for processing selenium-enriched tea cakes to remove astringency and preserve aroma includes the following steps: S1. Take 50 kg of sun-dried green tea leaves and evenly spray 3 kg of compound deastringency enzyme solution. After spraying, place the tea leaves in an enzymatic hydrolysis reaction chamber, control the temperature at 30℃ and the relative humidity at 85%, and let them stand for 1 hour for enzymatic hydrolysis. The compound deastringency enzyme solution consists of the following components by mass percentage: 0.05% tanninase, 0.02% cellulase, 0.01% β-glucosidase, and the balance is phosphate buffer solution with a pH of 5.0; the tanninase activity is 500 U / g, the cellulase activity is 10000 U / g, and the β-glucosidase activity is 100 U / g. S2. The enzymatically hydrolyzed tea leaves are placed in a negative pressure osmosis tank, and a selenium stabilization solution is added at a material-to-liquid ratio of 1:08. The tank is maintained at a vacuum of -0.07 MPa for 10 minutes, then slowly restored to normal pressure and soaked for another 20 minutes. The selenium stabilization solution consists of the following components by mass percentage: sodium alginate 0.8%, reduced glutathione 0.2%, trehalose 0.5%, cysteine 0.1%, and the remainder is purified water. S3. Remove the tea leaves and drain them. Spray 1.5 kg of 0.5% calcium chloride solution evenly and let it stand for 10 minutes to allow sodium alginate to cross-link with calcium ions to form a microgel network, thus stably embedding selenium inside the tea leaf tissue. S4. The obtained tea leaves are placed into a steam pressing machine and softened by treating them with 90℃ low-temperature saturated steam for 40s. Then, they are pressed into shape using a gradient pressure method: initial pressure of 5MPa held for 5s, pressure released for 2s, medium pressure of 10MPa held for 10s, pressure released for 2s, and final pressure of 12MPa held for 20s. The mold temperature is controlled at 35℃ during the pressing process. S5. Drying the tea cake in sections: Low temperature and high humidity equilibrium stage: temperature 18℃, relative humidity 60%, drying until the moisture content of the tea cake drops to 20%; Medium-temperature and medium-humidity transformation stage: temperature 28℃, relative humidity 55%, drying until the moisture content of the tea cake drops to 15%; Low-temperature and low-humidity aroma enhancement stage: drying at 35℃ and 40% relative humidity until the moisture content of the tea cake drops to 10%; Low-temperature rehydration equilibrium stage: temperature 22℃, relative humidity 50%, dry until the moisture content of the tea cake reaches equilibrium at 9%.
[0019] Example 2 A method for processing selenium-enriched tea cakes to remove astringency and preserve aroma includes the following steps: S1. Take 50 kg of sun-dried green tea leaves and evenly spray 6 kg of compound deastringency enzyme solution. After spraying, place the tea leaves in an enzymatic hydrolysis reaction chamber, control the temperature at 35℃ and the relative humidity at 90%, and let them stand for 3 hours for enzymatic hydrolysis. The compound deastringency enzyme solution consists of the following components by mass percentage: 0.20% tanninase, 0.08% cellulase, 0.05% β-glucosidase, and the balance is phosphate buffer solution with a pH of 5.5; the tanninase activity is 500 U / g, the cellulase activity is 10000 U / g, and the β-glucosidase activity is 100 U / g. S2. The enzymatically hydrolyzed tea leaves are placed in a negative pressure osmosis tank, and a selenium stabilization solution is added at a material-to-liquid ratio of 1:1.2. The mixture is kept under a vacuum of -0.09 MPa for 20 minutes, then slowly restored to atmospheric pressure and soaked for another 40 minutes. The selenium stabilization solution consists of the following components by mass percentage: sodium alginate 2.0%, reduced glutathione 0.6%, trehalose 1.5%, cysteine 0.3%, and the remainder is purified water. S3. Remove the tea leaves and drain them. Spray 3 kg of 1.5% calcium chloride solution evenly and let it stand for 20 minutes to allow sodium alginate to cross-link with calcium ions to form a microgel network, thus stably embedding selenium inside the tea leaf tissue. S4. The obtained tea leaves are placed into a steam pressing machine and softened by treating them with -95℃ low-temperature saturated steam for 60s. Then, they are pressed into shape using a gradient pressure method: initial pressure of 8MPa held for 10s, pressure released for 3s, medium pressure of 12MPa held for 15s, pressure released for 3s, and final pressure of 15MPa held for 30s. The mold temperature is controlled at 45℃ during the pressing process. S5. Drying the tea cake in sections: Low temperature and high humidity equilibrium stage: temperature 22℃, relative humidity 65%, drying until the moisture content of the tea cake drops to 24%; Medium-temperature and medium-humidity transformation stage: temperature 32℃, relative humidity 60%, drying until the moisture content of the tea cake drops to 18%; Low-temperature and low-humidity aroma enhancement stage: drying at 40℃ and 50% relative humidity until the moisture content of the tea cake drops to 12%; Low-temperature rehydration equilibrium stage: temperature 25℃, relative humidity 55%, dry until the moisture content of the tea cake reaches equilibrium at 11%.
[0020] Example 3 A method for processing selenium-enriched tea cakes to remove astringency and preserve aroma includes the following steps: S1. Take 50 kg of sun-dried green tea leaves and evenly spray 5 kg of compound deastringency enzyme solution. After spraying, place the tea leaves in an enzymatic hydrolysis reaction chamber, control the temperature at 33℃ and the relative humidity at 88%, and let them stand for enzymatic hydrolysis for 2 hours. The compound deastringency enzyme solution consists of the following components by mass percentage: 0.12% tanninase, 0.04% cellulase, 0.025% β-glucosidase, and the balance is phosphate buffer solution with a pH of 5.2; the tanninase activity is 500 U / g, the cellulase activity is 10000 U / g, and the β-glucosidase activity is 100 U / g. S2. The enzymatically hydrolyzed tea leaves are placed in a negative pressure osmosis tank, and a selenium stabilization solution is added at a material-to-liquid ratio of 1:1.0. The mixture is kept under a vacuum of -0.08 MPa for 15 minutes, then slowly restored to atmospheric pressure and soaked for another 30 minutes. The selenium stabilization solution consists of the following components by mass percentage: sodium alginate 1.4%, reduced glutathione 0.4%, trehalose 1.0%, cysteine 0.2%, and the remainder is purified water. S3. Remove the tea leaves and drain them. Spray 2.5 kg of 1.0% calcium chloride solution evenly and let it stand for 15 minutes to allow sodium alginate to cross-link with calcium ions to form a microgel network, thus stably embedding selenium inside the tea leaf tissue. S4. The obtained tea leaves are placed into a steam pressing machine and softened by treating with saturated steam at 93℃ for 50s. Then, the tea leaves are pressed into shape using a gradient pressure method: initial pressure of 6MPa held for 8s, pressure release for 3s, medium pressure of 11MPa held for 12s, pressure release for 3s, and final pressure of 14MPa held for 25s. The mold temperature is controlled at 40℃ during the pressing process. S5. Drying the tea cake in sections: Low temperature and high humidity equilibrium stage: temperature 20℃, relative humidity 62%, drying until the moisture content of the tea cake drops to 22%; Medium-temperature and medium-humidity transformation stage: temperature 30℃, relative humidity 58%, drying until the moisture content of the tea cake drops to 16%; Low-temperature and low-humidity aroma enhancement stage: temperature 38℃, relative humidity 45%, drying until the moisture content of the tea cake drops to 10.5%; Low-temperature rehydration equilibrium stage: temperature 24℃, relative humidity 52%, drying until the moisture content of the tea cake reaches equilibrium at 9.8%.
[0021] Comparative Example 1 Sun-dried green tea is directly steamed and pressed using traditional methods: 100℃ saturated steam treatment for 90s, one-time pressing (15MPa / 30s), mold temperature 50℃, and hot air drying (initial drying at 55℃ / 6h; final drying at 40℃ / 12h).
[0022] Comparative Example 2 Except for step S1, which is replaced with pure water spraying (without tanninase, cellulase and β-glucosidase), the rest of the operation is the same as in Example 3.
[0023] Comparative Example 3 The sun-dried green tea leaves are directly steamed and pressed in S4 without being permeated by selenium stabilization solution or cross-linked with calcium ions. The remaining operations are the same as in Example 3.
[0024] Comparative Example 4 Except for step S4, which is changed to traditional high-temperature steam pressing (100℃ saturated steam treatment for 90s, one pressing of cake at 15MPa / 30s, mold temperature 50℃), the rest of the operation is the same as in Example 3.
[0025] Comparative Example 5 Except for step S5, which is changed to traditional two-stage hot air drying (initial drying at 55℃ / 6h; final drying at 40℃ / 12h), the rest of the operation is the same as in Example 3.
[0026] Selenium retention rate The total selenium content of the samples was determined according to GB 5009.93-2017, "National Food Safety Standard - Determination of Selenium in Food" (Hydride Atomic Fluorescence Spectrometry). The samples were digested with a mixture of nitric acid and perchloric acid, and the results are shown in Table 1.
[0027] Selenium retention rate (%) = Selenium content of finished tea cake / Selenium content of sun-dried green tea × 100%.
[0028] As shown in Table 1, the selenium retention rates of Examples 1-3 were all ≥77%, significantly higher than that of Comparative Example 1. The selenium retention rate of Comparative Example 3 (selenium-deficient stabilization and cross-linking curing) decreased to 64.4%. The selenium retention rate of Comparative Example 4 (high-temperature autoclaving) was 73.3%, lower than that of Example 3, indicating that low-temperature autoclaving is beneficial for selenium retention.
[0029] Table 1 Selenium Retention Rate
[0030] Determination of main quality components Tea polyphenols were determined according to GB / T 8313-2018 (Folin-Ciocalteu method); ester-type catechins (EGCG, ECG) and non-ester-type catechins (EGC, EC) were determined using HPLC-UV method (C18 reversed-phase column, detection at 278 nm); free amino acids were determined according to GB / T 8314-2013 (ninhydrin colorimetric method); and water extracts were determined according to GB / T 8305-2013. The results are shown in Table 2.
[0031] Table 2 Main Quality Components
[0032] Note: The reduction rate of ester-type catechins is calculated based on the EGCG+ECG content of Comparative Example 1 (traditional process).
[0033] Table 2 shows that the EGCG+ECG reduction rate in Examples 1-3 was ≥40%, significantly lower than that in Comparative Example 1. In Comparative Example 2 (enzyme-deficient solution), the EGCG+ECG reduction rate was only 5.1%, indicating that the selective hydrolysis of ester-type catechins by tannin enzymes is key to astringency removal. Comparative Examples 3 and 4, having undergone S1 enzymatic hydrolysis, also showed a significant reduction in ester-type catechins, indicating that the astringency removal effect of S1 is not affected by subsequent process changes. In Comparative Example 5, due to the high drying temperature, some ester-type catechins underwent isomerization degradation, resulting in a reduction rate of only 24.1%, which is far lower than the astringency removal effect of enzymatic methods.
[0034] The phenol-to-amino acid ratio of Example 3 (6.0) is within the suitable range for high-quality green tea (<8), while the phenol-to-amino acid ratio of Comparative Example 1 (8.6) is too high, indicating a strong astringent taste and insufficient freshness.
[0035] In summary, this invention employs a complex enzyme system of tanninase, cellulase, and β-glucosidase for astringency removal pretreatment. Tanninase selectively hydrolyzes the gallic acid ester bonds of ester-type catechins, converting EGCG to EGC and gallic acid, and ECG to EC and gallic acid, with a reduction rate of 40-55% in EGCG and ECG, resulting in a decrease in astringency. Cellulase moderately disrupts the cell wall cellulose skeleton, promoting the penetration efficiency of the astringency removal enzyme solution and subsequent stabilization solution. β-glucosidase releases bound aroma precursors during enzymatic hydrolysis, laying the foundation for subsequent aroma preservation.
[0036] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.
Claims
1. A method for processing selenium-enriched tea cakes to remove astringency and preserve aroma, characterized in that, Includes the following steps: S1. Spray the kneaded selenium-enriched tea leaves evenly with a compound deastringency enzyme solution, the amount of which is 6-12% of the tea leaf mass. After spraying, place the tea leaves in an enzymatic hydrolysis reaction chamber, control the temperature at 30-35℃ and the relative humidity at 85-90%, and let them stand for enzymatic hydrolysis for 1-3 hours. The compound deastringency enzyme solution is composed of tanninase, cellulase, β-glucosidase and phosphate buffer. S2. The enzymatically hydrolyzed tea leaves are placed in a negative pressure osmosis tank, and a selenium stabilization solution is added at a material-to-liquid ratio of 1:08-1.
2. The tank is maintained at a vacuum of -0.07 to -0.09 MPa for 10-20 minutes, then slowly restored to atmospheric pressure and soaked for another 20-40 minutes. The selenium stabilization solution is composed of sodium alginate, reduced glutathione, trehalose, cysteine, and purified water. S3. Remove the tea leaves and drain them. Spray them evenly with a calcium chloride solution with a mass concentration of 0.5-1.5%, and spray the amount of solution at 3-6% of the mass of the tea leaves. Let it stand for 10-20 minutes to allow sodium alginate to cross-link with calcium ions to form a microgel network, which will stably embed selenium inside the tea leaf tissue. S4. The obtained tea leaves are placed into a steam press molding machine and treated with saturated steam at a low temperature of 90-95℃ for 40-60 seconds to soften the tea leaves. Then, the tea leaves are pressed into shape using a gradient pressure method. S5. Dry the tea cake in sections.
2. The method for processing selenium-enriched tea cakes to remove astringency and preserve aroma according to claim 1, characterized in that, In step S1, the compound deastringent enzyme solution is composed of the following components by mass percentage: 0.05-0.20% tanninase, 0.02-0.08% cellulase, 0.01-0.05% β-glucosidase, and the balance is phosphate buffer with a pH of 5.0-5.
5.
3. The method for processing selenium-enriched tea cakes to remove astringency and preserve aroma according to claim 2, characterized in that, The tanninase activity is ≥500U / g, the cellulase activity is ≥10000U / g, and the β-glucosidase activity is ≥100U / g.
4. The method for processing selenium-enriched tea cakes to remove astringency and preserve aroma according to claim 1, characterized in that, In step S2, the selenium stabilization solution is composed of the following components by mass percentage: sodium alginate 0.8-2.0%, reduced glutathione 0.2-0.6%, trehalose 0.5-1.5%, cysteine 0.1-0.3%, and the balance being purified water.
5. The method for processing selenium-enriched tea cakes to remove astringency and preserve aroma according to claim 1, characterized in that, In step S4, the gradient pressure method is as follows: initial pressure of 5-8 MPa is maintained for 5-10s, pressure is released for 2-3s, medium pressure of 10-12 MPa is maintained for 10-15s, pressure is released for 2-3s, and final pressure of 12-15 MPa is maintained for 20-30s; the mold temperature is controlled at 35-45℃ during the pressing process.
6. The method for processing selenium-enriched tea cakes to remove astringency and preserve aroma according to claim 1, characterized in that, In step S5, the segmented drying specifically involves: Low temperature and high humidity equilibrium stage: temperature 18-22℃, relative humidity 60-65%, time 12-24h, the moisture content of the tea cake drops to 20-24%; Medium-temperature and medium-humidity transformation stage: temperature 28-32℃, relative humidity 55-60%, time 24-36h, the moisture content of the tea cake drops to 15-18%; Low-temperature and low-humidity aroma enhancement stage: temperature 35-40℃, relative humidity 40-50%, time 12-18h, the moisture content of the tea cake is reduced to 10-12%; Low-temperature rehydration equilibrium stage: temperature 22-25℃, relative humidity 50-55%, time 24-48h, the moisture content of the tea cake is balanced to 9-11%.