Preparation method of health-preserving black tea rich in dendrobium polysaccharides

Abstract

The present application relates to the field of functional tea preparation technology, in particular to a health-preserving black tea rich in dendrobium polysaccharide and a preparation method thereof, comprising the following steps: pre-treating tea fresh leaves by spreading in the dark, subjecting fresh dendrobium strips to successively ultra-low temperature wall breaking, ultrasonic-assisted enzymatic hydrolysis and ultrafiltration purification to obtain a high-activity dendrobium polysaccharide enrichment liquid; subjecting the tea fresh leaves to primary withering by hot air, secondary withering under low oxygen after vacuum pulse spraying of the polysaccharide liquid; pulse gradient rolling of the tea leaves under a low-temperature environment, ultrasonic atomization supplementary spraying of the polysaccharide liquid in the heavy rolling stage; inoculation of the rolled and twisted leaves with a compound microbial inoculum, and fermentation under segmented temperature and oxygen control; and gradient drying by infrared, hot air and microwave. The present application solves the problems of polysaccharide loss and flavor fragmentation of existing dendrobium black tea, can efficiently enrich and stably retain dendrobium polysaccharide, realize deep and uniform loading of the polysaccharide, greatly improve the health-preserving value of the product, optimize the sensory quality of the black tea, coordinate the aroma and taste, and has strong controllability, is suitable for large-scale production, and takes into account the efficacy and drinking taste.

Description

Technical Field

[0001] This invention relates to the field of functional tea preparation technology, specifically a method for preparing health-preserving black tea rich in Dendrobium polysaccharides. Background Technology

[0002] Black tea, as my country's mainstream fully fermented tea, occupies a core position in the tea consumption market due to its mellow taste, rich flavor compounds, and broad consumer base. With the continuous improvement of national health consumption awareness, functional black tea, which combines drinking value with health benefits, has become an important direction for innovation and upgrading in the tea industry. Dendrobium officinale is a precious traditional Chinese medicinal and edible ingredient. Its core active ingredient is Dendrobium officinale polysaccharide, which possesses various physiological activities beneficial to the human body. The combined development of Dendrobium officinale and black tea is a research hotspot in the field of health tea.

[0003] Currently available technologies for preparing Dendrobium officinale black tea, such as those disclosed in patent documents CN105994764A and CN105325644A, mostly employ methods such as mixing Dendrobium officinale raw materials with fresh tea leaves to form strips, or physically blending Dendrobium officinale powder with finished black tea. These methods suffer from poor flavor integration between Dendrobium officinale and tea, low dissolution efficiency of Dendrobium officinale polysaccharides, and insufficient utilization of active ingredients during consumption. Some technologies achieve polysaccharide loading through soaking in water-extracted Dendrobium officinale extract or simple spraying, but these methods are not deeply integrated with the core processes of black tea preparation, such as withering, rolling, and fermentation. This results in uneven polysaccharide loading and an inability to effectively embed into tea cell cells. Consequently, during subsequent fermentation and high-temperature drying processes, Dendrobium officinale polysaccharides are prone to degradation and loss, leading to a significant reduction in biological activity.

[0004] Meanwhile, existing Dendrobium polysaccharide extraction processes mostly employ conventional hot water extraction, which suffers from insufficient cell wall disruption, low extraction rates of active polysaccharide components, and poor enrichment effects, failing to provide highly active polysaccharide raw materials for subsequent loading. Furthermore, existing processes often utilize natural fermentation, which has poor controllability, failing to guarantee the stable formation of black tea flavor and quality, and also hindering the stable solidification of Dendrobium polysaccharides. This results in low polysaccharide retention rates and insufficient shelf-life stability in the finished product during storage.

[0005] In summary, existing technologies cannot simultaneously achieve efficient and stable loading of highly active Dendrobium polysaccharides, improve the sensory quality of black tea, and synergistically exert health benefits, which seriously restricts the large-scale industrial development of Dendrobium health-preserving black tea. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for preparing health-promoting black tea rich in Dendrobium polysaccharides.

[0007] (II) Technical Solution A method for preparing a health-promoting black tea rich in Dendrobium polysaccharides includes the following steps: S1 Dual-Stage Cell Wall Breaking Targeted Enrichment Pretreatment: Select fresh tea leaves with one bud and two leaves before the Qingming Festival, and spread them out in a dark environment at 22-24℃ and 62%-68% relative humidity for 9-11 hours, with a thickness of 2.5-3.5cm; take fresh stems of 3-year-old Dendrobium officinale, remove the cuticle and cut into 1-2mm thin slices, and freeze them in liquid nitrogen at -18℃~-12℃ for 12-18 minutes to break the cell wall. After thawing, add purified water at a material-to-liquid ratio of 1:9-1:10, add compound enzyme preparation and use 200-300W ultrasonic assistance at 45-50℃ for 100-110 minutes of enzymatic hydrolysis. After enzyme inactivation, ultrafiltration is used to retain 30-100kDa of active components to obtain Dendrobium officinale polysaccharide enrichment solution. S2 Vacuum Pulsating Load-Based Segmented Withering: After spreading, the fresh tea leaves are first withered with hot air at 36-37℃ and a wind speed of 1.0-1.2m / s for 3.5-4 hours until the moisture content reaches 68%-72%. Then, a Dendrobium polysaccharide enrichment solution (16%-19% of the weight of the fresh tea leaves) is sprayed using a vacuum pulsating method, followed by a second withering in a low-oxygen environment at 29-31℃ and a relative humidity of 76%-79% for 2.5-3 hours until the moisture content of the withered leaves reaches 59%-61%. S3 Low-Temperature Pulse Pressure Rolling and Secondary Embedding: The withered material is rolled in a low-temperature environment of 18-22℃ using a light-heavy-light pulse gradient pressure rolling for 50-55 minutes. During the heavy rolling stage, Dendrobium polysaccharide enrichment solution, accounting for 6%-9% of the weight of fresh tea leaves, is sprayed twice by ultrasonic atomization until the tea leaf strip rate is ≥92% and the cell breakage rate is ≥78%. S4 dual-strain synergistic targeted segmented fermentation: After disintegration, the material is inoculated with a compound inoculum of Lactobacillus plantarum and Saccharomyces cerevisiae at a mass of 0.1%-0.2% of the material. Fermentation is first carried out in a micro-aerobic environment at 26-27℃ and 92%-94% relative humidity for 2.5-3 hours, and the pH of the system is adjusted to 5.1-5.4. Then the temperature is raised to 30-31℃ and 86%-89% relative humidity for 3.5-4 hours, until the leaves are evenly red and the aroma of flowers and fruits is harmonious with the fragrance of Dendrobium. S5 Infrared-Hot Air-Microwave Combined Gradient Drying: The fermented material is first dried at 46-49℃ using infrared low-temperature drying for 22-28 minutes to a moisture content of 31%-34%, then cooled at 20-22℃ for 15-20 minutes; next, it is dried with hot air at 76-79℃ to a moisture content of 12%-14%, then cooled for 10-15 minutes; finally, it is dried under microwave vacuum at 61-64℃ to a moisture content of 6.0%-6.5%. S6 Oxygen-Controlled Maillard Reaction Low-Temperature Curing: Dry materials are subjected to a slow Maillard reaction for 48-72 hours in a sealed environment at 36-39℃, relative humidity 42%-48%, and oxygen concentration 19%-20%, with ventilation for 5-8 minutes every 24 hours. The material is then allowed to cool naturally to room temperature to obtain the finished product.

[0008] Preferably, in step S1, the compound enzyme preparation comprises cellulase, pectinase, and The dextranase is compounded in a mass ratio of 4:2:1. The amount of the compound enzyme preparation added is 0.35%-0.45% of the mass of fresh Dendrobium slices. The ultrasonic-assisted frequency is 28-40kHz. After enzymatic hydrolysis, the enzyme is inactivated by a water bath at 95-100℃ for 8-10 minutes.

[0009] Preferably, in step S1, the Dendrobium polysaccharide enrichment solution contains ≥90mg / g of Dendrobium polysaccharide, has ≥85% of active polysaccharides in the molecular weight range of 30-100kDa, and has a DPPH free radical scavenging rate of ≥90%.

[0010] Preferably, in step S2, the parameters of the vacuum pulse spraying are: vacuum degree -0.06~-0.08MPa, pressure holding for 30-45s, atmospheric pressure immersion for 2-3min after breaking the vacuum, and the enrichment liquid spraying is completed by 2-3 cycles, and the oxygen concentration in the low oxygen environment is controlled at 12%-15%.

[0011] Preferably, in step S3, the pulsed gradient pressure kneading specifically comprises: light kneading without pressure for 12-13 minutes, intermittent pressure kneading for 28-30 minutes, depressurization for 30 seconds every 5 minutes of pressure application, light kneading without pressure for 10-12 minutes, with the pressure during the pressure kneading stage being 0.35-0.45 MPa, and the droplet size of the ultrasonic atomization spray being... .

[0012] Preferably, in step S4, the ratio of viable Lactobacillus plantarum to Saccharomyces cerevisiae in the compound microbial agent is 3:1, and the total number of viable bacteria in the compound microbial agent is ≥1×10⁻⁶. 9 CFU / g; the oxygen concentration in the micro-aerobic environment is controlled at 8%-10%, the fermentation material is spread to a thickness of 12-14cm, and it is turned over once every 50 minutes.

[0013] Preferably, in step S5, the infrared wavelength of the infrared drying is... The air velocity for hot air drying is 0.6-0.7 m / s, and the microwave power for microwave vacuum drying is 150-200 W, with a vacuum degree of -0.05 to -0.07 MPa.

[0014] Preferably, in step S6, 0.5%-1% of dried Dendrobium officinale flowers are placed simultaneously during the simmering process, the relative humidity in the sealed environment fluctuates by no more than ±5% throughout the process, and the water extract content of the material is ≥42% after the simmering is completed.

[0015] Preferably, the finished dried tea contains Dendrobium polysaccharide loading ≥30mg / g, Dendrobium polysaccharide dissolution rate ≥94% when brewed at room temperature for 5 minutes, tea turbidity ≤5NTU, and Dendrobium polysaccharide retention rate ≥95% after 6 months of sealed storage at room temperature.

[0016] Preferably, the fresh tea leaves are selected from Fuding Da Bai Cha, Qimen Zhuye variety or Yunnan Mengku Da Ye variety, and the pre-harvesting is completed within 4 hours after picking; the fresh Dendrobium officinale stems are selected from Huoshan Dendrobium officinale with semi-wild cultivation and polysaccharide content ≥30%.

[0017] (iii) Beneficial technical effects Compared with existing technologies, the beneficial effects of this invention are: Through optimized pretreatment processes, efficient cell wall disruption and targeted enrichment of active polysaccharides in Dendrobium officinale were achieved, significantly improving the extraction efficiency and proportion of active components of Dendrobium officinale polysaccharides. This effectively preserved the physiological activity of Dendrobium officinale polysaccharides, laying a high-quality raw material foundation for subsequent integration with black tea processing. By deeply integrating Dendrobium officinale polysaccharide loading with the core processes of black tea withering and rolling, uniform penetration and stable embedding of Dendrobium officinale polysaccharides within the tea tissue were achieved. This solved the problem of polysaccharides merely adhering to the surface of the tea leaves and being easily lost during processing in traditional methods, significantly improving the loading stability and retention rate of Dendrobium officinale polysaccharides in the finished product during storage.

[0018] Through an optimized segmented fermentation process, the fermentation process of black tea and the preservation of Dendrobium polysaccharide activity were synergistically regulated. This ensured the full transformation of flavor compounds in black tea and the stable formation of traditional quality, while effectively preventing the degradation and inactivation of Dendrobium polysaccharides during fermentation. Simultaneously, it achieved a deep and harmonious integration of the floral and fruity aromas of black tea with the delicate fragrance of Dendrobium, eliminating the problem of flavor fragmentation in traditional products and significantly enhancing the sensory drinking experience. Subsequent combined drying and low-temperature aroma-inhaling processes further solidified and stabilized the Dendrobium polysaccharides and optimized the product flavor, while also enhancing the shelf-life stability of the finished product. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for preparing health-preserving black tea rich in Dendrobium polysaccharides, as disclosed in this invention. Figure 2 This is a line graph comparing the polysaccharide retention rate and the DPPH free radical scavenging rate of the finished product after 6 months of sealing at room temperature with the examples and comparative examples; Figure 3 This is a bar chart comparing the polysaccharide loading of dried Dendrobium officinale tea and the polysaccharide dissolution rate after brewing at room temperature for 5 minutes in the examples and comparative examples; Figure 4 This is a radar comparison chart of the sensory quality and basic physicochemical properties of the finished products of the examples and comparative examples, after unifying the dimensions. Detailed Implementation

[0020] according to Figures 1 to 4 The specific embodiments of the present invention are as follows: The present invention will be further described in detail below with reference to specific embodiments and comparative examples. The following embodiments are only used to fully illustrate the technical solution of the present invention and to help understand the core concept of the present invention, and are not intended to limit the scope of protection of the present invention. Experimental operations and detection methods in the present invention that do not specify specific conditions are all performed according to conventional experimental conditions in the fields of tea processing and natural product extraction; the raw materials, reagents, instruments, and equipment used, unless otherwise specified, are all commercially available products conventional in the field.

[0021] The method for preparing health-promoting black tea rich in Dendrobium polysaccharides provided by this invention achieves targeted enrichment of highly active Dendrobium polysaccharides, stable embedding and loading within the tea leaves, preservation of activity during processing, synergistic fusion of flavor, and long-term shelf-life stability through six deeply coupled core processes. This method fully covers all the technical features of the claims, and the complete detailed process scheme is as follows: First, the raw materials are selected and pre-treated: the tea leaves are selected from Fuding Da Bai Cha, Qimen Zhuye variety or Yunnan Mengku Da Ye variety, and are one bud and two leaves before the Qingming Festival. The leaves are spread out for pre-treatment within 4 hours after picking to avoid oxidation and deterioration. The Dendrobium officinale is selected from 3-year-old Huoshan Dendrobium officinale stems with semi-wild cultivation and a dry polysaccharide content of ≥30% to ensure the activity of the raw materials.

[0022] S1 Dual-Stage Cell Wall Breaking Targeted Enrichment Pretreatment: Selected fresh tea leaves are spread out in a dark environment at 22-24℃ and 62%-68% relative humidity for 9-11 hours, with a thickness controlled at 2.5-3.5cm. Direct sunlight and mechanical damage are avoided throughout the process to complete the initial dehydration and initial transformation of the internal components of the fresh leaves. Simultaneously, Dendrobium officinale raw materials are processed by removing the surface cuticle of fresh Dendrobium officinale stems and slicing them into uniform thin slices of 1-2mm. After instantaneous freezing with liquid nitrogen, the slices are placed in an ultra-low temperature environment of -18℃ to -12℃ for 12-18 minutes to break the cell walls. The ice crystals formed by rapid freezing pierce the cell walls of Dendrobium officinale, achieving efficient cell wall breaking. After thawing, the Dendrobium officinale slices are added to purified water at a material-to-liquid ratio of 1:9-1:10, along with enzymes such as cellulase, pectinase, and... A compound enzyme preparation was prepared by combining glucanase in a mass ratio of 4:2:1. The amount of the compound enzyme preparation added was 0.35%-0.45% of the mass of fresh Dendrobium slices. With the assistance of ultrasound at 200-300W and 28-40kHz, the enzyme was enzymatically hydrolyzed in a constant temperature environment of 45-50℃ for 100-110 minutes. After the enzymatic hydrolysis was completed, the enzyme was inactivated by a water bath at 95-100℃ for 8-10 minutes. After inactivation, the solution was cooled to room temperature and the active components with a molecular weight cutoff of 30-100kDa were retained by ultrafiltration membrane to obtain Dendrobium polysaccharide enrichment solution. The Dendrobium polysaccharide enrichment solution contained Dendrobium polysaccharide content ≥90mg / g, the proportion of active polysaccharides in the molecular weight range of 30-100kDa was ≥85%, and the DPPH free radical scavenging rate was ≥90%, providing high-activity and high-purity polysaccharide raw materials for subsequent loading.

[0023] S2 Vacuum Pulsating Load-Based Segmented Withering: The spread-out fresh tea leaves are first placed in a hot air withering trough, where they undergo primary withering for 3.5-4 hours using hot air at 36-37℃ and a wind speed of 1.0-1.2 m / s, until the moisture content of the fresh tea leaves drops to 68%-72%, completing the initial water loss and withering process. Subsequently, a Dendrobium polysaccharide enrichment solution, comprising 16%-19% of the tea leaf weight, is sprayed using a vacuum pulsating method. Specific parameters for the vacuum pulsating spray are: vacuum degree controlled at -0.06~-0.08 MPa, pressure maintained for 30-45 seconds, followed by vacuum breaking. The enriched solution is sprayed by immersing under normal pressure for 2-3 minutes and circulating 2-3 times. Through the pulsating circulation of vacuum and normal pressure, the Dendrobium polysaccharide enriched solution can quickly penetrate into the interior of the tea tissue, avoiding the defect of conventional normal pressure spraying which only adheres to the surface of the leaves. After spraying, the fresh tea leaves are placed in a low-oxygen environment of 29-31℃, relative humidity of 76%-79%, and oxygen concentration of 12%-15% for a second withering for 2.5-3 hours, until the moisture content of the withered leaves stabilizes at 59%-61%, completing the segmented withering and achieving the first stable loading of Dendrobium polysaccharides.

[0024] S3 Low-Temperature Pulse-Pressure Rolling and Secondary Embedding: The withered material is sent to a low-temperature rolling workshop at 18-22℃, where a light-heavy-light pulse-gradient pressure rolling process is used, with a total rolling time of 50-55 minutes. The specific rolling procedure is as follows: First, light rolling without pressure for 12-13 minutes to initially form the tea leaves into strips; then, intermittent pressure rolling for 28-30 minutes, with pressure released for 30 seconds every 5 minutes of pressure to avoid excessive breakage of the tea leaves and cloudiness of the tea soup due to continuous pressure. The pressure during the heavy rolling stage is controlled at 0.35-0.45 MPa; finally, light rolling without pressure for 10-12 minutes to shape the tea strips, making them tight and uniform. During the heavy rolling stage, a Dendrobium polysaccharide enrichment solution, accounting for 6%-9% of the weight of the fresh tea leaves, is sprayed twice using ultrasonic atomization. The droplet size of the ultrasonic atomization is controlled within a certain range. This allows the enriched liquid to quickly embed into the tea cells while they are being broken, achieving a secondary stable embedding and loading of Dendrobium polysaccharides. After rolling, the tea leaves have a strip formation rate of ≥92% and a cell breakage rate of ≥78%, which not only ensures the foundation for subsequent fermentation of black tea but also achieves deep loading of polysaccharides.

[0025] S4 Dual-Strain Synergistic Targeted Segmented Fermentation: The kneaded material is thoroughly broken up to prevent clumping and uneven fermentation. Then, a compound microbial agent, comprising 0.1%-0.2% of the mass of the broken-up material, is inoculated. This compound microbial agent is composed of *Lactobacillus plantarum* and *Saccharomyces cerevisiae* at a viable cell ratio of 3:1. The total viable cell count of the compound microbial agent... After inoculation, the material is placed in a fermentation chamber and fermented for 2.5-3 hours in a micro-aerobic environment with a temperature of 26-27℃, a relative humidity of 92%-94%, and an oxygen concentration of 8%-10%. During fermentation, food-grade citric acid is used to adjust the pH of the system to 5.1-5.4, providing a suitable environment for the proliferation and metabolism of the compound microbial agent, while simultaneously achieving the initial transformation of the tea's internal components. Subsequently, the temperature is raised to 30-31℃ and the relative humidity is 86%-89%, and fermentation continues for 3.5-4 hours. During fermentation, the material is spread to a thickness of 12-14cm, and the material is turned over every 50 minutes to ensure uniform fermentation. After fermentation, the tea leaves are uniformly red, with a harmonious blend of floral and fruity aromas and the fresh fragrance of Dendrobium, free of grassy or fermentation odors. This process achieves the quality transformation of black tea through full fermentation while avoiding the degradation and inactivation of Dendrobium polysaccharides during fermentation.

[0026] S5 Infrared-Hot Air-Microwave Combined Gradient Drying: This method uses a three-stage combined gradient drying process to avoid the degradation of Dendrobium polysaccharides and flavor deterioration caused by single high-temperature drying. The first stage uses 46-49℃ and a specific wavelength... The material is first dried using infrared low-temperature drying for 22-28 minutes until the moisture content drops to 31%-34%, then cooled in a low-temperature environment of 20-22℃ for 15-20 minutes to allow the moisture inside the material to diffuse evenly. The second stage uses hot air drying at 76-79℃ and a wind speed of 0.6-0.7m / s until the moisture content drops to 12%-14%, followed by cooling for 10-15 minutes. The third stage uses microwave vacuum drying at 61-64℃, a microwave power of 150-200W, and a vacuum degree of -0.05~-0.07MPa until the moisture content of the material stabilizes at 6.0%-6.5%, completing the drying process. Through the combined drying of infrared, hot air, and microwave, rapid removal of moisture is achieved under low-temperature conditions, maximizing the preservation of the activity of Dendrobium polysaccharides while avoiding scorching of the tea leaves and loss of aroma.

[0027] S6 Oxygen-Controlled Maillard Reaction Low-Temperature Aroma-Enhancing Curing: The dried material is placed in a sealed aroma-enhancing chamber at 36-39℃, relative humidity 42%-48%, and oxygen concentration 19%-20%. Simultaneously, 0.5%-1% of dried Dendrobium officinale flowers (by weight of the material) are placed in the chamber for slow Maillard reaction aroma-enhancing curing for 48-72 hours. Ventilation is performed every 24 hours for 5-8 minutes during the aroma-enhancing process. The relative humidity fluctuation within the sealed environment does not exceed ±5%. After aroma-enhancing, the material is naturally cooled to room temperature to obtain the finished product. The resulting product has a water extract content ≥42%, a Dendrobium officinale polysaccharide loading ≥30mg / g in the dried tea, a Dendrobium officinale polysaccharide dissolution rate ≥94% when brewed at room temperature for 5 minutes, a tea turbidity ≤5NTU, and a Dendrobium officinale polysaccharide retention rate ≥95% after 6 months of sealed storage at room temperature. Example 1

[0028] The specific preparation steps of this invention are as follows in this embodiment: S1 Dual-Stage Cell Wall Breaking Targeted Enrichment Pretreatment: Fresh leaves of Fuding Da Bai tea (one bud and two leaves) harvested before the Qingming Festival are selected and sent to the pretreatment workshop within 3 hours of picking. They are spread out in a light-proof environment at 23℃ and 65% relative humidity for 10 hours, with a spreading thickness of 3cm, avoiding mechanical damage throughout the process. Simultaneously, fresh stems of 3-year-old Huoshan Dendrobium officinale (simulated wild cultivation) with a dried polysaccharide content of 32% are selected. After removing the surface cuticle, they are cut into 1.5mm uniform thin slices, instantly frozen with liquid nitrogen, and then placed in an ultra-low temperature environment at -15℃ for 15 minutes for cell wall breaking. After thawing, purified water is added at a material-to-liquid ratio of 1:9.5, along with enzymes such as cellulase and pectinase. A compound enzyme preparation of glucanase in a mass ratio of 4:2:1 was added at 0.4% of the mass of fresh Dendrobium slices. Enzymatic hydrolysis was performed at 48℃ for 105 min with 250W, 35kHz ultrasound assistance. After hydrolysis, the enzyme was inactivated by a 98℃ water bath for 9 min. After cooling to room temperature, an ultrafiltration membrane was used to retain the 30-100kDa active component, resulting in a Dendrobium polysaccharide enrichment solution. Analysis showed that the enrichment solution contained 95mg / g of Dendrobium polysaccharide, with 88% being 30-100kDa active polysaccharides, and a DPPH free radical scavenging rate of 93%.

[0029] S2 Vacuum Pulsating Load Segmented Withering: The spread-out fresh tea leaves are sent into a hot air withering trough and subjected to primary withering for 3.8 hours at 36.5℃ and 1.1m / s wind speed until the moisture content of the fresh tea leaves reaches 70%. Subsequently, a Dendrobium polysaccharide enrichment solution accounting for 18% of the mass of the fresh tea leaves is sprayed using a vacuum pulsating method at a vacuum degree of -0.07MPa for 40 seconds. After breaking the vacuum, the leaves are immersed at normal pressure for 2.5 minutes. This process is repeated twice to complete the spraying. After spraying, the fresh tea leaves are placed in a low-oxygen environment at 30℃, 78% relative humidity, and 13% oxygen concentration for secondary withering for 2.8 hours until the moisture content of the withered leaves reaches 60%.

[0030] S3 Low-Temperature Pulse Pressurized Kneading and Secondary Embedding: The withered material is sent to a 20℃ low-temperature kneading workshop and kneaded using a light-heavy-light pulse gradient pressurized kneading method for a total duration of 52 minutes. The specific procedure is as follows: 12.5 minutes of pressureless light kneading, 29 minutes of intermittent pressurized heavy kneading, with a pressure release of 30 seconds every 5 minutes of pressurization, a pressurization pressure of 0.4 MPa, and finally 10.5 minutes of pressureless light kneading. During the heavy kneading stage, Dendrobium polysaccharide enrichment solution is sprayed twice using ultrasonic atomization, with droplet size... Each time, the enriched solution was sprayed at 3.5% of the weight of the fresh tea leaves, with a total spraying amount of 7%. After rolling, the tea leaves had a strip formation rate of 94% and a cell breakage rate of 80%.

[0031] S4 Dual-Strain Synergistic Targeted Segmented Fermentation: After the kneaded material is fully broken up, it is inoculated with a compound microbial agent at 0.15% of the material mass. The compound microbial agent is a mixture of Lactobacillus plantarum and Saccharomyces cerevisiae at a live count ratio of 3:1, with a total live count of 2×10⁻⁶. 9CFU / g; After inoculation, the material was sent to the fermentation chamber and first fermented in a micro-aerobic environment of 26.5℃, 93% relative humidity, and 9% oxygen concentration for 2.8 hours. The pH of the system was adjusted to 5.2 using food-grade citric acid. Then, the temperature was raised to 30.5℃ and the relative humidity was 88% for 3.8 hours of fermentation. The material was spread out to a thickness of 13cm and turned over once every 50 minutes. After fermentation, the leaves were reddish-brown with a rich aroma of flowers and fruits, and the fragrance of Dendrobium was harmonious and without any off-odors.

[0032] S5 Infrared-Hot Air-Microwave Combined Gradient Drying: Fermented materials are first dried at 47℃ with a wavelength of... Infrared drying for 25 minutes until the moisture content is 32%, followed by cooling at 21°C for 18 minutes; then hot air drying at 77°C and 0.65 m / s until the moisture content is 13%, followed by cooling for 12 minutes; finally, microwave vacuum drying at 62°C, 180 W microwave power and -0.06 MPa until the moisture content is 6.2%.

[0033] S6 Oxygen-Controlled Maillard Reaction Low-Temperature Aroma Curing: The dried material is fed into a sealed aroma curing chamber at 37℃, relative humidity 45%, and oxygen concentration 19.5%, and 0.8% of the material mass of dried Dendrobium officinale flowers are added at the same time. The material is aroma cured for 60 hours, with ventilation every 24 hours for 6 minutes, and the humidity fluctuation throughout the process is ≤±3%. After the aroma curing is completed, the material is naturally cooled to room temperature to obtain the finished product. Example 2

[0034] The specific preparation steps using the process of the present invention in this embodiment are as follows: S1 Dual-Stage Cell Wall Breaking Targeted Enrichment Pretreatment: Fresh leaves of *Zanthoxylum bungeanum* (one bud and two leaves) harvested before the Qingming Festival were selected and placed in the pretreatment workshop within 4 hours of picking. They were then spread out in a light-protected environment at 22℃ and 62% relative humidity for 9 hours, with a spreading thickness of 2.5cm. Simultaneously, fresh stems of 3-year-old *Dendrobium officinale* (Huoshan Dendrobium) from semi-wild cultivation, with a dried polysaccharide content of 30%, were selected. After removing the surface cuticle, they were cut into 1mm thin slices, instantly frozen in liquid nitrogen, and then placed in an ultra-low temperature environment at -18℃ for 12 minutes to break down the cell walls. After thawing, purified water was added at a material-to-liquid ratio of 1:9, along with enzymes consisting of cellulase, pectinase, and... A compound enzyme preparation of glucanase in a mass ratio of 4:2:1 was added at 0.35% of the mass of fresh Dendrobium slices. Enzymatic hydrolysis was performed at 45℃ for 100 min with 200W, 28kHz ultrasound assistance. After hydrolysis, the enzyme was inactivated in a 95℃ water bath for 10 min. After cooling to room temperature, ultrafiltration was used to retain the 30-100kDa active component, resulting in a Dendrobium polysaccharide enrichment solution. Analysis showed that the enrichment solution contained 91 mg / g of Dendrobium polysaccharide, with 86% being 30-100kDa active polysaccharides, and a DPPH free radical scavenging rate of 91%.

[0035] S2 Vacuum Pulsating Load Segmented Withering: The spread-out fresh tea leaves are sent to a hot air withering trough and subjected to primary withering for 3.5 hours at 36℃ and 1.0 m / s until the moisture content of the fresh tea leaves reaches 72%. Subsequently, a Dendrobium polysaccharide enrichment solution accounting for 16% of the mass of the fresh tea leaves is sprayed using a vacuum pulsating method at a vacuum degree of -0.06 MPa for 30 seconds. After the vacuum is broken, the leaves are immersed at normal pressure for 2 minutes. This process is repeated twice to complete the spraying. After spraying, the fresh tea leaves are placed in a low-oxygen environment at 29℃, 76% relative humidity, and 12% oxygen concentration for secondary withering for 2.5 hours until the moisture content of the withered leaves reaches 61%.

[0036] S3 Low-Temperature Pulse Pressurized Kneading and Secondary Embedding: The withered material is sent to an 18℃ low-temperature kneading workshop and kneaded using a light-heavy-light pulse gradient pressurized kneading method for a total duration of 50 minutes. The specific procedure is as follows: 12 minutes of pressureless light kneading, 28 minutes of intermittent pressurized heavy kneading, with a 30-second depressurization every 5 minutes of pressurization, a pressurization pressure of 0.35 MPa, and finally 10 minutes of pressureless light kneading. During the heavy kneading stage, Dendrobium polysaccharide enrichment solution is sprayed twice using ultrasonic atomization, with droplet size... Each time, a 3% enriched solution based on the weight of fresh tea leaves is sprayed, with a total spraying amount of 6%. After rolling, the tea leaves have a strip formation rate of 92% and a cell breakage rate of 78%.

[0037] S4 Dual-Strain Synergistic Targeted Segmented Fermentation: After the kneaded material is fully broken up, it is inoculated with a compound microbial agent accounting for 0.1% of the material mass. The compound microbial agent is a mixture of Lactobacillus plantarum and Saccharomyces cerevisiae at a live count ratio of 3:1, with a total live count of 1.5 × 10⁻⁶. 9 CFU / g; After inoculation, the material was sent to the fermentation chamber and first fermented in a micro-aerobic environment of 26℃, 92% relative humidity, and 8% oxygen concentration for 2.5 hours. The pH of the system was adjusted to 5.1 using food-grade citric acid. Then, the temperature was raised to 30℃ and the relative humidity was 86% for 3.5 hours of fermentation. The material was spread out to a thickness of 12cm and turned over once every 50 minutes. After fermentation, the leaves were uniformly red, the flower and fruit aroma was pure, and the Dendrobium fragrance was harmonious.

[0038] S5 Infrared-Hot Air-Microwave Combined Gradient Drying: Fermented materials are first dried at 46℃ with a wavelength of... Infrared drying for 22 minutes until the moisture content is 34%, followed by cooling at 20°C for 15 minutes; then hot air drying at 76°C and 0.6 m / s until the moisture content is 14%, followed by cooling for 10 minutes; finally, microwave vacuum drying at 61°C, 150 W microwave power, and -0.05 MPa until the moisture content is 6.5%.

[0039] S6 Oxygen-Controlled Maillard Reaction Low-Temperature Aroma Curing: The dried material is sent into a sealed aroma curing chamber at 36℃, relative humidity 42%, and oxygen concentration 19%, and 0.5% of the material mass of dried Dendrobium officinale flowers are added at the same time. The aroma is cured for 48 hours, with ventilation every 24 hours for 5 minutes. The humidity fluctuation throughout the process is ≤±4%. After the aroma curing is completed, the material is naturally cooled to room temperature to obtain the finished product. Example 3

[0040] The specific preparation steps of the process of the present invention in this embodiment are as follows: S1 Dual-Stage Cell Wall Breaking Targeted Enrichment Pretreatment: Fresh leaves of Yunnan Mengku large-leaf variety, with one bud and two leaves, harvested before the Qingming Festival, were sent to the pretreatment workshop within 3.5 hours and spread out in a light-proof environment at 24℃ and 68% relative humidity for 11 hours, with a spreading thickness of 3.5cm. Simultaneously, fresh stems of 3-year-old Huoshan Dendrobium officinale, cultivated in a semi-wild environment, with a dried polysaccharide content of 33%, were selected. After removing the surface cuticle, they were cut into 2mm thin slices, instantly frozen with liquid nitrogen, and then placed in an ultra-low temperature environment at -12℃ for 18 minutes to break down the cell walls. After thawing, purified water was added at a material-to-liquid ratio of 1:10, along with enzymes consisting of cellulase, pectinase, and... A compound enzyme preparation of glucanase in a mass ratio of 4:2:1 was added at 0.45% of the mass of fresh Dendrobium slices. Enzymatic hydrolysis was performed at 50℃ for 110 min with 300W, 40kHz ultrasound assistance. After hydrolysis, the enzyme was inactivated by a 100℃ water bath for 8 min. After cooling to room temperature, ultrafiltration was used to retain the 30-100kDa active component, resulting in a Dendrobium polysaccharide enrichment solution. Analysis showed that the enrichment solution contained 96 mg / g of Dendrobium polysaccharide, with 89% being 30-100kDa active polysaccharides, and a DPPH free radical scavenging rate of 94%.

[0041] S2 Vacuum Pulsating Load Segmented Withering: The spread-out fresh tea leaves are sent to a hot air withering trough and subjected to primary withering for 4 hours at 37℃ and 1.2m / s hot air until the moisture content of the fresh tea leaves reaches 68%. Subsequently, a Dendrobium polysaccharide enrichment solution accounting for 19% of the mass of the fresh tea leaves is sprayed using a vacuum pulsating method at a vacuum degree of -0.08MPa, held at pressure for 45s, and then immersed at normal pressure for 3 minutes after the vacuum is broken. This process is repeated 3 times to complete the spraying. After spraying, the fresh tea leaves are placed in a low-oxygen environment at 31℃, 79% relative humidity, and 15% oxygen concentration for secondary withering for 3 hours until the moisture content of the withered leaves reaches 59%.

[0042] S3 Low-Temperature Pulse Pressurized Kneading and Secondary Embedding: The withered material is sent to a 22℃ low-temperature kneading workshop and kneaded using a light-heavy-light pulse gradient pressurized kneading method for a total duration of 55 minutes. The specific procedure is as follows: 13 minutes of pressureless light kneading, 30 minutes of intermittent pressurized heavy kneading, with a pressure release of 30 seconds every 5 minutes of pressurization, a pressurization pressure of 0.45 MPa, and finally 12 minutes of pressureless light kneading. During the heavy kneading stage, Dendrobium polysaccharide enrichment solution is sprayed twice using ultrasonic atomization, with droplet size... Each time, 4.5% of the enriched liquid by weight of fresh tea leaves is sprayed, with a total spraying amount of 9%; after rolling, the tea leaves have a strip formation rate of 95% and a cell breakage rate of 81%.

[0043] S4 Dual-Strain Synergistic Targeted Segmented Fermentation: After the kneaded material is fully broken up, it is inoculated with a compound microbial agent accounting for 0.2% of the material mass. The compound microbial agent is a mixture of Lactobacillus plantarum and Saccharomyces cerevisiae at a live count ratio of 3:1, with a total live count of 2.5 × 10⁻⁶.9 CFU / g; After inoculation, the material was sent to the fermentation chamber and first fermented in a micro-aerobic environment of 27℃, 94% relative humidity, and 10% oxygen concentration for 3 hours. The pH of the system was adjusted to 5.4 using food-grade citric acid. Then, the temperature was raised to 31℃ and the relative humidity to 89% for 4 hours of fermentation. The material was spread out to a thickness of 14cm and turned over once every 50 minutes. After fermentation, the leaves were red, uniform, and glossy, with a rich floral and fruity aroma, a prominent Dendrobium fragrance, and a harmonious and odorless taste.

[0044] S5 Infrared-Hot Air-Microwave Combined Gradient Drying: Fermented materials are first dried at 49℃ with a wavelength of... Infrared drying for 28 minutes until the moisture content is 31%, followed by cooling at 22°C for 20 minutes; then hot air drying at 79°C and 0.7 m / s until the moisture content is 12%, followed by cooling for 15 minutes; finally, microwave vacuum drying at 64°C, 200W microwave power and -0.07MPa until the moisture content is 6.0%.

[0045] S6 Oxygen-Controlled Maillard Reaction Low-Temperature Aroma Curing: The dried material is sent into a sealed aroma curing chamber at 39℃, relative humidity 48%, and oxygen concentration 20%, and 1% of the material mass of dried Dendrobium officinale flowers are added at the same time. The aroma is cured for 72 hours, with 8 minutes of ventilation every 24 hours, and the humidity fluctuation throughout the process is ≤±5%. After the aroma curing is completed, the material is naturally cooled to room temperature to obtain the finished product.

[0046] Comparative Example 1 This comparative example uses a conventional method of physical blending of Dendrobium officinale powder and finished black tea to prepare Dendrobium officinale black tea. The specific steps are as follows: Fresh leaves of Fuding Da Bai Cha (one bud and two leaves) before the Qingming Festival, the same as in Example 1, are selected. Following the conventional black tea preparation process, the leaves are spread out, withered by hot air, rolled, fermented naturally, dried in three stages by hot air, and then aged at room temperature to obtain the finished black tea. Fresh 3-year-old Dendrobium officinale stems from Huoshan, the same as in Example 1, are dried, ultra-finely pulverized, and passed through a 100-mesh sieve. The Dendrobium officinale powder is mixed evenly with the finished black tea at a ratio of 8% of the weight of the finished black tea to obtain the finished Dendrobium officinale black tea. All other basic process parameters are consistent with those in Example 1.

[0047] Comparative Example 2 This comparative example uses the conventional method of simply spraying Dendrobium extract in existing technologies, omitting the core innovative processes of this invention, such as vacuum pulsed loading, ultrasonic atomization secondary embedding, dual-strain synergistic targeted fermentation, infrared-hot air-microwave combined drying, and oxygen-controlled Maillard aroma extraction. The specific steps are as follows: S1 uses the same fresh tea leaves as in Example 1, which are laid out at room temperature as usual; Dendrobium officinale is extracted with hot water at 90℃ for 2 hours as usual to obtain Dendrobium officinale extract, without ultra-low temperature cell disruption, ultrasonic-assisted enzymatic hydrolysis, or ultrafiltration enrichment. S2 tea leaves are withered using conventional one-time hot air withering. During the withering process, Dendrobium extract is sprayed once at normal pressure, without vacuum pulsed spraying or segmented withering. S3 uses conventional continuous pressure kneading, without low temperature environment control, pulse pressure, or secondary atomized spraying of enrichment liquid; S4 uses conventional natural fermentation, without inoculation with compound microbial agents, without segmented temperature and oxygen control, and without pH adjustment; S5 uses conventional three-stage hot air drying, without infrared-microwave combined drying; S6 uses conventional room temperature sealed aroma-inhalation without temperature and oxygen control or the addition of Dendrobium officinale flowers for aroma enhancement; all other basic parameters are consistent with those in Example 1, resulting in the finished Dendrobium officinale black tea.

[0048] Comparative Example 3 Except for omitting the core processes of the two-stage cell wall disruption and targeted enrichment and the dual-strain synergistic targeted segmented fermentation of the present invention, the other process steps and parameters of this comparative example are completely consistent with those of Example 1. The specific steps are as follows: S1 Dendrobium officinale is extracted with conventional 90℃ hot water to obtain the extract, without ultra-low temperature cell wall disruption, ultrasonic-assisted enzymatic hydrolysis, or ultrafiltration enrichment; S4 is conventional natural fermentation, without inoculation with compound microbial agents, without segmented oxygen-controlled fermentation, or pH adjustment; the process steps and parameters of the remaining S2, S3, S5, and S6 are completely consistent with those of Example 1, and Dendrobium officinale black tea is obtained.

[0049] The core properties of the finished Dendrobium polysaccharides from the examples and comparative examples are compared in the table below: Table 1 The sensory quality and basic physicochemical properties of the finished products from the examples and comparative examples are compared in the table below: Table 2 The above two sets of performance comparison test data fully demonstrate that the health-preserving black tea rich in Dendrobium polysaccharides produced by the three embodiments of the present invention, based on the optimized whole-process innovative process, has all core indicators that are superior to the comparative products prepared by existing conventional processes.

[0050] From the perspective of the core performance of Dendrobium polysaccharides, the example far surpasses the comparative example, which uses physical blending, conventional extract spraying, and omits core innovative processes, in terms of dry tea polysaccharide loading, brewing dissolution rate, long-term storage retention rate, and bioactivity. This completely solves the pain points of existing technologies, such as severe polysaccharide loss, poor activity retention, and low dissolution efficiency. In terms of sensory quality and basic physicochemical indicators, the finished product of the example has a higher sensory score, a tighter appearance, a harmonious aroma, a mellow taste, and a clear and bright tea soup. It does not have the flavor fragmentation and turbidity problems of the comparative example. At the same time, it has a higher water extract content and a lower crude fiber content, resulting in better overall drinking quality and physicochemical stability.

[0051] The above comparison results fully demonstrate that the present invention achieves a synergistic improvement in health benefits and black tea quality through innovative coupling and precise control of each process, effectively making up for the core defects of existing Dendrobium black tea preparation technology. The technology has outstanding effects and strong practicality, and has significant technical creativity and industrialization value.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a health-promoting black tea rich in Dendrobium polysaccharides, characterized in that, Includes the following steps: S1 Dual-Stage Cell Wall Breaking Targeted Enrichment Pretreatment: Select fresh tea leaves with one bud and two leaves before the Qingming Festival, and spread them out in a dark environment at 22-24℃ and 62%-68% relative humidity for 9-11 hours, with a thickness of 2.5-3.5cm; take fresh stems of 3-year-old Dendrobium officinale, remove the cuticle and cut into 1-2mm thin slices, and freeze them in liquid nitrogen at -18℃~-12℃ for 12-18 minutes to break the cell wall. After thawing, add purified water at a material-to-liquid ratio of 1:9-1:10, add compound enzyme preparation and use 200-300W ultrasonic assistance at 45-50℃ for 100-110 minutes of enzymatic hydrolysis. After enzyme inactivation, ultrafiltration is used to retain 30-100kDa of active components to obtain Dendrobium officinale polysaccharide enrichment solution. S2 Vacuum Pulsating Load-Based Segmented Withering: After spreading, the fresh tea leaves are first withered with hot air at 36-37℃ and a wind speed of 1.0-1.2m / s for 3.5-4 hours until the moisture content reaches 68%-72%. Then, a Dendrobium polysaccharide enrichment solution (16%-19% of the weight of the fresh tea leaves) is sprayed using a vacuum pulsating method, followed by a second withering in a low-oxygen environment at 29-31℃ and a relative humidity of 76%-79% for 2.5-3 hours until the moisture content of the withered leaves reaches 59%-61%. S3 Low-Temperature Pulse Pressure Rolling and Secondary Embedding: The withered material is rolled in a low-temperature environment of 18-22℃ using a light-heavy-light pulse gradient pressure rolling for 50-55 minutes. During the heavy rolling stage, Dendrobium polysaccharide enrichment solution, accounting for 6%-9% of the weight of fresh tea leaves, is sprayed twice by ultrasonic atomization until the tea leaf strip rate is ≥92% and the cell breakage rate is ≥78%. S4 dual-strain synergistic targeted segmented fermentation: After disintegration, the material is inoculated with a compound inoculum of Lactobacillus plantarum and Saccharomyces cerevisiae at a mass of 0.1%-0.2% of the material. Fermentation is first carried out in a micro-aerobic environment at 26-27℃ and 92%-94% relative humidity for 2.5-3 hours, and the pH of the system is adjusted to 5.1-5.

4. Then the temperature is raised to 30-31℃ and 86%-89% relative humidity for 3.5-4 hours, until the leaves are evenly red and the aroma of flowers and fruits is harmonious with the fragrance of Dendrobium. S5 Infrared-Hot Air-Microwave Combined Gradient Drying: The fermented material is first dried at 46-49℃ using infrared low-temperature drying for 22-28 minutes to a moisture content of 31%-34%, then cooled at 20-22℃ for 15-20 minutes; next, it is dried with hot air at 76-79℃ to a moisture content of 12%-14%, then cooled for 10-15 minutes; finally, it is dried under microwave vacuum at 61-64℃ to a moisture content of 6.0%-6.5%. S6 Oxygen-Controlled Maillard Reaction Low-Temperature Curing: Dry materials are subjected to a slow Maillard reaction for 48-72 hours in a sealed environment at 36-39℃, relative humidity 42%-48%, and oxygen concentration 19%-20%, with ventilation for 5-8 minutes every 24 hours. The material is then allowed to cool naturally to room temperature to obtain the finished product.

2. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, In step S1, the compound enzyme preparation consists of cellulase, pectinase, and The dextranase is compounded in a mass ratio of 4:2:

1. The amount of the compound enzyme preparation added is 0.35%-0.45% of the mass of fresh Dendrobium slices. The ultrasonic-assisted frequency is 28-40kHz. After enzymatic hydrolysis, the enzyme is inactivated by a water bath at 95-100℃ for 8-10 minutes.

3. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, In step S1, the Dendrobium polysaccharide enrichment solution contains Dendrobium polysaccharide content ≥90mg / g, active polysaccharides in the molecular weight range of 30-100kDa account for ≥85%, and DPPH free radical scavenging rate ≥90%.

4. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, In step S2, the parameters of the vacuum pulse spraying are: vacuum degree -0.06~-0.08MPa, pressure holding for 30-45s, atmospheric pressure immersion for 2-3min after breaking the vacuum, and 2-3 cycles to complete the enrichment liquid spraying. The oxygen concentration in the low oxygen environment is controlled at 12%-15%.

5. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, In step S3, the pulsed gradient pressure kneading specifically consists of: light kneading without pressure for 12-13 minutes, intermittent pressure kneading for 28-30 minutes, depressurization for 30 seconds every 5 minutes of pressure application, light kneading without pressure for 10-12 minutes, with the pressure during the pressure kneading stage being 0.35-0.45 MPa, and the droplet size of the ultrasonic atomization spray being... .

6. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, In step S4, the ratio of viable Lactobacillus plantarum to Saccharomyces cerevisiae in the compound microbial agent is 3:1, and the total number of viable bacteria in the compound microbial agent is ≥1×10⁻⁶. 9 CFU / g; the oxygen concentration in the micro-aerobic environment is controlled at 8%-10%, the fermentation material is spread to a thickness of 12-14cm, and it is turned over once every 50 minutes.

7. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, In step S5, the infrared wavelength for infrared drying is... The air velocity for hot air drying is 0.6-0.7 m / s, and the microwave power for microwave vacuum drying is 150-200 W, with a vacuum degree of -0.05~-0.07 MPa.

8. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, In step S6, 0.5%-1% of dried Dendrobium officinale flowers are placed simultaneously during the simmering process. The relative humidity in the sealed environment fluctuates by no more than ±5% throughout the process. After the simmering is completed, the water extract content of the material is ≥42%.

9. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, The finished dried tea contains Dendrobium polysaccharide loading ≥30mg / g, Dendrobium polysaccharide dissolution rate ≥94% when brewed at room temperature for 5 minutes, tea turbidity ≤5NTU, and Dendrobium polysaccharide retention rate ≥95% after 6 months of sealed storage at room temperature.

10. The method for preparing health-preserving black tea rich in Dendrobium polysaccharides according to claim 1, characterized in that, The tea leaves are selected from the pre-Qingming fresh leaves of Fuding Da Bai Cha, Qimen Zhuye variety or Yunnan Mengku Da Ye variety, and the pre-processing is completed within 4 hours after picking; the Dendrobium officinale stems are selected from Huoshan Dendrobium officinale with semi-wild cultivation and polysaccharide content ≥30%.

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