Preparation method of flat famous green tea, composite leaf surface preparation, preparation method and application thereof

Abstract

This invention provides a compound leaf preparation for improving the quality of fresh summer tea leaves, its preparation method, application, and a corresponding method for preparing flat-shaped premium green tea, belonging to the field of tea production technology. The compound leaf preparation consists of a metabolic regulation composition, an environmentally responsive composite nanocarrier, and adjuvants. The metabolic regulation composition includes exogenous amino acids, carotenoid precursors, and methyl jasmonic acid analogs. The nanocarrier is a PNIPAM-TiO2 complex, capable of encapsulating the metabolic regulation composition at temperatures ≥28℃ and ultraviolet intensity ≥30W / m². 2 Time-responsive release. This invention improves the quality of summer tea leaves from the source. Using these high-quality fresh leaves as raw materials, and through appropriate withering, fixation, shaping, and aroma-enhancing processes, a flat-shaped premium green tea with a fresh, mellow taste and a prominent chestnut aroma can be produced, realizing the high-value utilization of summer tea resources.

Description

Technical Field

[0001] This invention belongs to the field of tea production technology, specifically relating to a method for preparing a flat-shaped premium green tea, a compound leaf preparation, its preparation method, and its application. Background Technology

[0002] The composition of secondary metabolites in fresh tea leaves is a core factor determining the flavor, quality, and market value of finished tea. Spring tea leaves, rich in free amino acids and low in bitter substances such as ester-type catechins, possess a superior "fresh, crisp, and mellow" flavor, making them a core raw material for renowned flat-shaped green teas like Meitan Cuiya. However, summer tea leaves, affected by adverse environmental conditions such as high temperatures and strong sunlight, experience a significant imbalance in their internal secondary metabolic network. Carbon metabolism flows are heavily shifted towards the flavonoid biosynthesis pathway, leading to excessive accumulation of bitter substances such as ester-type catechins and caffeine. This also directly inhibits the synthesis of free amino acids and terpenoid aroma precursors, ultimately resulting in summer tea leaves and finished tea generally exhibiting quality shortcomings such as "heavy bitterness, insufficient freshness, and weak aroma," severely restricting the utilization rate and economic added value of summer tea resources.

[0003] As a typical representative of China's flat-shaped premium green tea, Meitan Cuiya tea traditionally has stringent requirements for raw material quality. The processing raw materials are strictly limited to tender spring tea buds harvested around the Qingming Festival. Summer fresh leaves are rarely used for high-end product processing due to the aforementioned quality defects. In recent years, research on improving the quality of summer tea has largely focused on optimizing parameters in processing techniques such as fixation, shaping, and aroma enhancement. However, these techniques are "post-processing remedial measures," only able to make limited transformations and controls on the components of fresh leaves during processing, and cannot fundamentally improve the inherent characteristics of summer tea leaves: a high proportion of bitter and astringent substances, and insufficient freshness and aroma.

[0004] Based on this, this application urgently needs to provide a compound leaf preparation and its preparation method and application, as well as a matching method for preparing flat-shaped premium green tea, in order to alleviate or solve the technical problems of low utilization rate of summer tea resources and limited economic added value in the above-mentioned commonly used technologies. Summary of the Invention

[0005] In order to solve the technical problems of high proportion of bitter substances and insufficient fresh aroma substances in summer tea fresh leaves in the above-mentioned commonly used technologies, the present invention provides a compound leaf preparation for improving the quality of summer tea fresh leaves, which is composed of a metabolic regulation composition, a composite nanocarrier and an adjuvant, wherein the composite nanocarrier encapsulates the metabolic regulation composition. The metabolic regulation composition includes exogenous amino acids, aroma precursors and natural inducers. The exogenous amino acids are selected from at least one of L-glutamic acid and L-arginine. The aroma precursor is a carotenoid precursor. The natural inducer is selected from at least one of propyl jasmonate and isobutyl jasmonate. The composite nanocarrier is subjected to a temperature ≥28℃ and an ultraviolet intensity ≥30W / m. 2 Time-specific response.

[0006] The compound leaf preparation provided by this invention effectively solves the quality defects caused by metabolic imbalance in fresh summer tea leaves.

[0007] The core of this formulation lies in its encapsulated exogenous amino acids and natural inducers, which can intervene in the secondary metabolism of tea trees from the source. Under the high temperature and strong light conditions of summer, they work synergistically to guide the metabolic resources of tea trees from the path of excessive synthesis of bitter substances (such as ester-type catechins) to a path of synthesizing fresh amino acids and aroma precursors, thereby improving the biochemical basis of fresh leaves before harvesting.

[0008] To achieve precise intervention, the formulation utilizes nanocarriers that specifically respond to temperature (≥28℃) and ultraviolet light (≥30W / m²). This design ensures that the active ingredient is triggered for release only under the target stress conditions, achieving synchronization with the physiological stress period of the tea plant, and maintaining a stable regulatory effect through a sustained-release mode, thus avoiding the waste of effective ingredients.

[0009] Ultimately, the internal quality of summer tea leaves treated with this formulation was systematically optimized: the accumulation of bitter and astringent substances was inhibited, while the content of fresh-tasting amino acids and aroma precursors was significantly increased. This provides a crucial guarantee of high-quality raw materials for the subsequent production of high-end flat-shaped green teas with harmonious aroma and taste (such as Meitan Cuiya) from summer tea raw materials, breaking through the core bottleneck of high-value utilization of summer tea resources.

[0010] Furthermore, the mass fraction of each component in the composite leaf preparation is as follows: exogenous amino acids 5%-15%, aroma precursors 3%-8%, natural inducers 0.5%-2%, composite nanocarriers 60%-80%, and adjuvants 5%-10%.

[0011] Furthermore, the composite nanocarrier is a PNIPAM-TiO2 composite nanocarrier, wherein the mass ratio of PNIPAM to TiO2 in the PNIPAM-TiO2 composite nanocarrier is 4-6:1, the particle size of TiO2 nanoparticles is 20-50 nm, and the particle size of the composite nanocarrier is 50-200 nm.

[0012] Furthermore, the carotene precursor is selected from at least one of β-carotene and lutein; the natural inducer is selected from at least one of propyl jasmonic acid and isobutyl jasmonic acid. The additive is selected from at least two of Tween-80, sodium lignosulfonate, and xanthan gum.

[0013] Furthermore, the additives include Tween-80, sodium lignosulfonate, and xanthan gum in a mass ratio of 2-4:1-3:1-3.

[0014] This invention provides a method for preparing a compound foliar preparation for improving the quality of fresh summer tea leaves as described in any of the preceding claims, comprising the following steps: PNIPAM monomer, TiO2 nanoparticles, and crosslinking agent were dispersed in an aqueous solvent to obtain an aqueous phase; The metabolic regulation composition was dissolved in an oily solvent to obtain an oil-phase core material; Under high-speed shearing conditions, the oil phase core material is injected into the aqueous phase to obtain an oil / water microemulsion; Add a polymerization initiator to the oil / water microemulsion to polymerize PNIPAM monomers at the oil-water interface and encapsulate TiO2 nanoparticles to form a PNIPAM-TiO2 composite nanocarrier encapsulating the metabolic regulation composition. The composite nanocarrier was collected and purified, and then dispersed in water with adjuvants to form the composite leaf preparation.

[0015] Furthermore, the addition of the polymerization initiator to the oil / water microemulsion includes: obtaining a mixture of the oil / water microemulsion and the polymerization initiator, and then treating it at a temperature of 55-65°C for 3.5-4.5 hours.

[0016] This invention provides an application of a compound foliar preparation for improving the quality of fresh summer tea leaves as described in any of the preceding claims, or a compound foliar preparation prepared by the method described above, comprising the following steps: Spray the aforementioned compound foliar preparation on fresh tea leaves in summer to ensure even coverage on both sides of the leaves; the timing of spraying is 5-7 days before harvesting; Under conditions where the ambient temperature is ≥28℃ and the ultraviolet intensity is ≥30W / m², the porosity of the composite nanocarrier shell increases from 8-12% to 30-45%, slowly releasing the metabolic regulation composition.

[0017] The application method defined in this invention achieves effective field regulation of summer tea tree metabolic behavior by combining precise field operations with the responsive characteristics of the formulation.

[0018] This method clarifies the critical window period, dosage, and application method for the formulation, ensuring that the active ingredients can fully act on the functional leaves of the tea plant. When the typical high temperature and strong light conditions of summer trigger the response mechanism of the nanocarrier, its structure undergoes controllable changes, achieving a slow and continuous release of the active ingredients. In this process, the components work synergistically: amino acid precursors directly supplement nitrogen metabolism and regulate carbon-nitrogen balance; natural inducers activate endogenous signaling pathways and guide metabolic flow; and carotenoid precursors serve as reserve raw materials for subsequent aroma conversion.

[0019] This environment-triggered in-situ slow-release and metabolic-guided process optimizes the metabolic network of tea trees during their critical growth period before harvesting. The end result is an effective mitigation of the inherent defects of summer tea leaves—excessive bitterness and insufficient freshness and aroma—from the raw material perspective, laying a direct material foundation for the subsequent processing of high-quality summer tea products.

[0020] This invention provides a method for preparing a flat-shaped premium green tea, comprising the following steps: Take one bud and one leaf or newly unfolded fresh leaf that sprouts in summer from the small-leaf tea tree after being treated as described above, and place it in an environment of 28-32℃ to dry for 4 hours until the moisture content of the fresh leaf drops to 65%-70%. Place the dried fresh leaves in the blanching equipment, control the temperature at 170-190℃, and the blanching time at 5-7 minutes; After blanching, the fresh leaves are immediately transferred to a leaf-shaping machine, with the temperature set at 75-85℃ and the leaf-shaping time at 5-7 minutes. After the tea leaves are shaped, they are fed into an aroma-enhancing device, with the temperature controlled at 125-135℃ and the aroma-enhancing time at 4-6 minutes. After the tea leaves are infused with aroma, they are naturally cooled to room temperature, then sieved to remove broken pieces and impurities, resulting in a flat-shaped premium green tea product.

[0021] The core technical effect of the flat-shaped premium green tea preparation method provided by this invention lies in the precise matching and synergy with the aforementioned high-quality summer tea fresh leaf raw materials that have undergone metabolic regulation.

[0022] This method is not a simple application of traditional spring tea processing techniques, but rather an adaptation and optimization of key process parameters to address the new characteristics of processed summer fresh leaves: "relatively reduced bitterness and astringency, and increased freshness and aroma precursors." Proper withering facilitates the formation of flavor precursors, while precise control of the temperature and time windows for fixing, shaping, and aroma enhancement efficiently deactivates enzymes, shapes the leaves, and particularly emphasizes promoting the transformation and fixation of accumulated aroma precursors, while avoiding excessive heat that could lead to the loss of quality components.

[0023] Therefore, this method, together with the raw material pretreatment technology, constitutes a coherent technical system. It can fully transform the potential of summer tea leaves that have undergone source metabolic improvement into the sensory quality of the finished tea, and ultimately stably produce flat-shaped premium green tea with the characteristics of "distinct chestnut or light fragrance, fresh and mellow taste, and moderate astringency", thus realizing the high-value utilization of summer tea resources. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0025] Figure 1 This is a comparative table showing the results of the investigation on the content of ester-type and non-ester-type catechins for different treatment times in three key stages: fixation (180℃, 0, 2, 4, 6, 8 min), shaping (80℃, 0, 2, 4, 6, 8 min), and aroma enhancement (130℃, 0, 5, 10, 15, 20 min) in Example 3 of the present invention.

[0026] Figure 2 These are actual product images of the present invention with different blanching times, strip-forming times, and aroma-enhancing times. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0029] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0030] This invention provides a compound foliar formulation for improving the quality of fresh summer tea leaves. The formulation comprises a metabolic regulating composition, a composite nanocarrier, and adjuvants, wherein the composite nanocarrier encapsulates the metabolic regulating composition. The metabolic regulation composition includes exogenous amino acids, aroma precursors and natural inducers. The exogenous amino acids are selected from at least one of L-glutamic acid and L-arginine. The aroma precursor is a carotenoid precursor and the natural inducer is a natural inducer. The composite nanocarrier exhibits a specific response at temperatures ≥28℃ and UV intensity ≥30W / m².

[0031] For ease of understanding, the following explains some key terms in this embodiment: The compound foliar preparation is designed to deliver active ingredients to the leaves of tea plants through foliar spraying, thereby regulating the physiological metabolic processes of tea plants and improving the quality of fresh summer tea leaves.

[0032] Metabolic regulatory compounds refer to substances that can directly participate in or promote the secondary metabolic pathways of tea plants. Metabolic precursors are the starting or intermediate products for the synthesis of specific flavor substances in tea plants, while inducers can activate or regulate the activity of related metabolic enzymes, working together on the endogenous metabolic network of tea plants.

[0033] Composite nanocarriers are microscopic carriers with intelligent release capabilities. These carriers can sense and respond to specific environmental stimuli, such as temperature or ultraviolet intensity, thereby altering their structure or porosity to achieve precise controlled release of the encapsulated material.

[0034] Exogenous amino acids, as the basic building blocks of protein synthesis in tea plants, are also important precursors for the fresh and flavorful substances in tea leaves. Supplementing with these amino acids can promote the synthesis of more compounds related to freshness and flavor in tea plants.

[0035] Aroma precursors are compounds that undergo a series of enzymatic reactions within the tea plant, ultimately transforming into volatile substances with specific aroma characteristics. Supplementing with these precursors aims to enhance the aroma complexity and intensity of fresh summer tea leaves.

[0036] Natural inducers are molecules that can mimic endogenous signaling molecules in plants, inducing or enhancing the activation of specific metabolic pathways in tea plants, such as promoting the biosynthesis of aroma substances or regulating the accumulation of bitter substances.

[0037] The core defect in the quality of summer tea leaves lies in their internal metabolic imbalance, specifically manifested as abnormal accumulation and insufficient synthesis of key flavor compounds. Among them, bitterness and astringency mainly originate from excessive ester-type catechins and caffeine; while insufficient freshness and weak aroma are directly related to low levels of free amino acids (especially theanine) and a lack of aroma precursors such as terpenes (e.g., carotenoids), respectively.

[0038] In this regard, based on the aforementioned exogenous amino acid being selected from at least one of L-glutamic acid and L-arginine, this application further proposes that the carotene precursor be selected from at least one of β-carotene and lutein, and that the natural inducer be selected from at least one of propyl jasmonic acid and isobutyl jasmonic acid.

[0039] The preferred carotenoid precursor is β-carotene or lutein, or a combination of both. Carotenoids are important biosynthetic precursors for various aroma compounds in fresh tea leaves, especially ionones (which impart chestnut and floral aromas). Supplementing with these precursors aims to enhance the aroma compound synthesis potential of fresh leaves from the raw material stage, addressing the issue of "weak aroma" in summer tea. β-carotene and lutein can be obtained through chemical synthesis or extracted from natural plants (such as algae and marigolds), and added to the formulation in high-purity form to ensure their biotransformation efficiency.

[0040] The preferred natural inducer is propyl jasmonate or isobutyl jasmonate, or a combination of both. As a mimic of endogenous plant signaling molecules, it can activate the tea plant's own defense and secondary metabolic responses. Its dual function lies in two aspects: firstly, inducing or enhancing the biosynthetic pathways of aroma substances such as terpenes, synergistically improving aroma potential; secondly, through signal regulation, it may help guide carbon metabolic flow, thereby inhibiting the excessive accumulation of bitter substances such as ester-type catechins. Therefore, its application directly addresses the dual shortcomings of "heavy bitterness" and "insufficient aroma."

[0041] The exogenous amino acids (such as L-glutamic acid and L-arginine) can be directly used as precursors for nitrogen metabolism. Exogenous supplementation can effectively promote the synthesis of theanine and other free amino acids in tea plants, increasing the absolute content of fresh and flavorful substances in fresh leaves.

[0042] Furthermore, the composite nanocarrier is designed to encapsulate this metabolic regulatory composition. The encapsulation process can be achieved through various techniques, such as emulsion polymerization to encapsulate the active ingredient within the nanocarrier, or co-precipitation to form a shell around the active ingredient using the nanocarrier material. Thus, the active ingredient is physically isolated from the external environment, thereby prolonging its stability and activity on the leaf surface.

[0043] This composite nanocarrier is designed to respond specifically to certain environmental conditions, namely, at temperatures ≥28°C and under specific UV intensities. For example, the nanocarrier can be composed of a thermosensitive polymer material that undergoes a phase transition upon reaching a specific temperature threshold, exhibiting a significant increase in porosity, particularly when combined with UV intensities ≥30 W / m². Simultaneously, the nanocarrier can also contain UV-sensitive components, whose hydrophilicity is optimized when the UV intensity reaches a set value, further promoting the release of the encapsulated material. This dual-response mechanism ensures the effective release of active ingredients under the specific adverse conditions required for summer tea growth.

[0044] The composite leaf preparation proposed in this application utilizes a composite nanocarrier to intelligently release a metabolic regulation composition under high temperature and strong sunlight conditions in summer, effectively regulating the secondary metabolic network of summer tea leaves. This promotes the synthesis of free amino acids and aroma precursors while alleviating the excessive accumulation of bitter substances, fundamentally improving the quality shortcomings of summer tea leaves, such as excessive bitterness, insufficient freshness, and weak aroma, thereby enhancing the resource utilization rate and economic added value of summer tea.

[0045] However, if the proportions of the components are not appropriate, the synergistic effect of the preparation may be poor, affecting the effective release and absorption of active ingredients, thus failing to fully exert its expected effect of improving the quality of summer tea, and even causing a waste of resources.

[0046] In this regard, this application further proposes an optimized mass fraction range for each component in the composite leaf preparation, namely, the mass fraction of each component in the composite leaf preparation is: exogenous amino acids 5%-15%, aroma precursors 3%-8%, natural inducers 0.5%-2%, composite nanocarriers 60%-80%, and adjuvants 5%-10%.

[0047] The mass fraction of exogenous amino acids is set at 5%-15%. As important precursors in the metabolic pathway of tea plants, the content of exogenous amino acids within this range can ensure that tea plants have sufficient raw materials for synthesis, effectively promote the accumulation of quality components such as tea polyphenols and amino acids, and avoid metabolic burden or waste of resources caused by excessive amounts.

[0048] The mass fraction of aroma precursors is set at 3%-8%. Aroma precursors, such as carotenoid precursors, are key substances in the formation of tea aroma. Within this mass fraction range, it can be ensured that the tea plant has enough aroma precursors to transform into various aroma components during subsequent processing, significantly improving the aroma quality of the tea, without the aroma being insufficient due to too low a content, or unnecessary costs due to too high a content.

[0049] The mass fraction of natural inducers was set at 0.5%-2%. Natural inducers, such as [specific incomplete], can effectively induce tea plants to initiate secondary metabolic pathways, promoting the synthesis and accumulation of specific flavor compounds. Within this concentration range, their inducing effect can be fully utilized, enhancing the tea plant's response to environmental stress, while avoiding potential physiological stress responses in plants caused by excessively high concentrations.

[0050] The mass fraction of the composite nanocarrier is set at 60%-80%. The composite nanocarrier is the core component for encapsulating and controlling the release of the metabolic regulation composition. Its high proportion ensures sufficient encapsulation capacity, enabling the active ingredients to be effectively protected and achieving precise and continuous sustained release under specific environmental conditions (such as temperature ≥28℃ and UV intensity ≥30W / m²), thereby prolonging the action time of the active ingredients and improving utilization efficiency.

[0051] The adjuvant's mass fraction is set at 5%-10%. The adjuvant is used to improve the physicochemical properties of the compound foliar formulation, such as wettability, spreadability, and permeability. Within this mass fraction range, the adjuvant ensures that the formulation adheres evenly to the surface of the tea leaves, promoting the effective absorption of active ingredients, while avoiding potential adverse effects or residue problems on the leaves due to excessive adjuvant content.

[0052] The preferred adjuvants are at least two of Tween-80, sodium lignosulfonate, and xanthan gum. Adjuvants play multiple key roles in foliar formulations, including improving the wettability, spreadability, penetration, suspension stability, and adhesion to leaves. Tween-80, as a nonionic surfactant, significantly reduces the surface tension of the formulation, allowing it to form a uniform liquid film on the tea leaf surface, improving wettability and spreadability, thereby promoting the effective penetration and absorption of active ingredients. Sodium lignosulfonate, as a natural polymeric dispersant and binder, helps to stably disperse the composite nanocarrier and metabolic regulation composition in aqueous solution, preventing sedimentation or aggregation, while enhancing the adhesion of the formulation to leaves and reducing losses caused by rain or wind. Xanthan gum, as a highly efficient biopolymer thickener and suspending agent, increases the viscosity of the formulation, further improving the suspension stability of the nanocarrier and active ingredients, ensuring the uniformity of the formulation during storage and spraying, and prolonging the residence time of the formulation on leaves, creating favorable conditions for the slow release of active ingredients. These adjuvants are typically purchased in industrial or food-grade form and added to the formulation in specific proportions, then thoroughly stirred and mixed to ensure uniform dispersion.

[0053] In some preferred embodiments, the mass ratio of Tween-80, sodium lignosulfonate, and xanthan gum is 2-4:1-3:1-3. This specific mass ratio is obtained through optimization and screening to achieve synergistic effects among the components for optimal adjuvant efficacy. For example, a mass ratio of Tween-80 between 2 and 4 provides sufficient wetting and emulsifying capabilities; a mass ratio of sodium lignosulfonate between 1 and 3 effectively disperses the nanocarrier and prevents its aggregation; and a mass ratio of xanthan gum between 1 and 3 provides suitable viscosity to maintain the suspension stability of the formulation. This precise formulation ensures excellent performance during storage, application, and action.

[0054] However, in practical applications, the key challenge to ensure the efficacy of formulations lies in how to select and construct a nanocarrier that can stably encapsulate active ingredients and precisely control their efficient and specific release under specific high temperature and strong ultraviolet light environments.

[0055] In this regard, this application further proposes that the composite nanocarrier is a PNIPAM-TiO2 composite nanocarrier, wherein the mass ratio of PNIPAM to TiO2 in the PNIPAM-TiO2 composite nanocarrier is 4-6:1, the particle size of TiO2 nanoparticles is 20-50 nm, and the particle size of the composite nanocarrier is 50-200 nm.

[0056] Specifically, PNIPAM (poly-N-isopropylacrylamide) is a typical thermosensitive polymer that undergoes a hydrophilic-hydrophobic transition at specific temperatures, resulting in a rapid shrinkage or expansion of its volume. TiO2 (titanium dioxide) is a photocatalytic material with excellent ultraviolet absorption and photosensitivity. PNIPAM provides thermosensitivity, ensuring structural changes occur when a specific temperature threshold is reached; TiO2 provides photosensitivity, enabling a response even under ultraviolet irradiation, thus achieving synergistic sensing and response to the high temperature and strong ultraviolet environment in summer tea fields.

[0057] This composite nanocarrier can be prepared by various methods, such as emulsion polymerization, precipitation polymerization or template method, in which PNIPAM can be used as the shell material and TiO2 nanoparticles can be embedded in it or used as the core.

[0058] Furthermore, the mass ratio of PNIPAM to TiO2 in the PNIPAM-TiO2 composite nanocarrier is 4-6:1. The PNIPAM content affects the temperature response sensitivity and volume change amplitude of the capsule, while the TiO2 content affects its ultraviolet absorption capacity and photocatalytic activity. A reasonable ratio ensures that the nanocarrier achieves optimal structural changes and active ingredient release efficiency under target environmental conditions (temperature ≥28℃ and ultraviolet intensity ≥30W / m²). Excessively high or low ratios may lead to insufficient response or decreased stability. This ratio can be achieved by precisely controlling the amount of PNIPAM monomer and TiO2 nanoparticles fed into the polymerization reaction.

[0059] Furthermore, the TiO2 nanoparticles have a particle size of 20-50 nm. The particle size of the TiO2 nanoparticles significantly affects their photoresponse characteristics and dispersion stability in the composite nanocarrier. Within this particle size range, TiO2 nanoparticles possess a large specific surface area and quantum size effect, enabling them to more effectively absorb ultraviolet light and generate photocatalytic activity, thereby enhancing the ultraviolet response capability of the nanocarrier. Simultaneously, a suitable particle size also helps TiO2 to be uniformly dispersed in the PNIPAM matrix, avoiding agglomeration and ensuring the structural integrity and response uniformity of the composite nanocarrier.

[0060] TiO2 nanoparticles with a particle size of 20-50 nm can be obtained by various synthesis methods such as hydrothermal method, sol-gel method or vapor deposition method, and the particle size distribution can be ensured to be within the target range through subsequent screening or classification.

[0061] Meanwhile, the composite nanocarrier has a particle size of 50-200 nm. The overall particle size of the nanocarrier is crucial for its adhesion, penetration, and release kinetics of active ingredients on the blade surface. Nanocarriers with a particle size in the range of 50-200 nm can ensure sufficient specific surface area to achieve efficient surface response and release of active ingredients, while avoiding agglomeration or difficulty in recovery due to excessively small particle size, or affecting uniform coverage and adhesion on the blade surface due to excessively large particle size.

[0062] The key challenge in achieving the desired effect is to efficiently and stably prepare this complex and uniquely functional composite leaf preparation, especially ensuring the formation of nanocarriers, effective encapsulation of active ingredients, and uniform mixing of all components.

[0063] In this regard, this application further proposes a method for preparing a compound foliar formulation for improving the quality of fresh summer tea leaves, the steps of which include: PNIPAM monomer, TiO2 nanoparticles, and crosslinking agent were dispersed in an aqueous solvent to obtain an aqueous phase; The metabolic regulation composition was dissolved in an oily solvent to obtain an oil-phase core material; Under high-speed shearing conditions, the oil phase core material is injected into the aqueous phase to obtain an oil / water microemulsion; A polymerization initiator is added to the oil / water microemulsion to carry out a thermally initiated free radical polymerization reaction, so that PNIPAM monomers are polymerized at the oil-water interface and encapsulate TiO2 nanoparticles to form a PNIPAM-TiO2 composite nanocarrier encapsulating the metabolic regulation composition. The composite nanocarrier was collected and purified, and then dispersed in water with adjuvants to form the composite leaf preparation.

[0064] Furthermore, the crosslinking agent can be N,N'-methylenebisacrylamide; the polymerization initiator can be ammonium persulfate; the oily solvent can be chloroform; the aqueous solvent can be water; and the surfactant can be sodium dodecyl sulfate.

[0065] The mass ratio of PNIPAM monomer to TiO2 nanoparticles is 4-6:1, and the mass concentration of PNIPAM monomer in the aqueous phase is about 10 to 20 g / L; the amount of crosslinking agent can be 1% to 2% of the mass of PNIPAM monomer; the amount of surfactant is 0.5% to 1.5% of the total mass of the aqueous phase.

[0066] The volume ratio of the oil phase to the water phase can be from 1:15 to 1:25.

[0067] The total mass concentration of the metabolic regulation composition in chloroform is preferably 20-50 g / L.

[0068] The amount of the polymerization initiator is 0.1% to 0.4% of the mass of the PNIPAM monomer.

[0069] Furthermore, the free radical polymerization reaction is carried out at a temperature of 55-65°C for a duration of 3.5-4.5 h.

[0070] Furthermore, the process of obtaining an aqueous phase comprising PNIPAM monomer, TiO2 nanoparticles, and a crosslinking agent dispersed in an aqueous solvent includes: placing the mixture of PNIPAM monomer, TiO2 nanoparticles, crosslinking agent, and aqueous solvent in an ultrasonic cell disruptor or a high-speed shear disperser and treating it at room temperature for 10-30 minutes until the TiO2 nanoparticles are uniformly dispersed without obvious agglomeration, resulting in a homogeneous, translucent, or milky white aqueous solution.

[0071] Furthermore, the step of dissolving the metabolic regulation composition in an oily solvent to obtain the oil-phase core material comprises weighing exogenous amino acids (such as L-glutamic acid), carotenoid precursors (such as β-carotene), and natural inducers (such as propyl jasmonic acid). These three components are then dissolved together in the oily solvent chloroform, and thoroughly stirred or sonicated to form a clear oil-phase core material solution.

[0072] Furthermore, the step of injecting the oil phase core material into the aqueous phase under high-speed shearing conditions to obtain an oil / water microemulsion includes: slowly adding the oil phase core material solution obtained in S2 to the aqueous phase solution obtained in S1 dropwise under continuous high-speed shearing (e.g., a rotation speed of 8000-12000 rpm). The volume ratio of the oil phase to the aqueous phase is controlled to be 1:15 to 1:25. After the dropwise addition is complete, high-speed shearing continues for 5-15 minutes to form a uniform and stable milky white oil / water (O / W) microemulsion.

[0073] Furthermore, the step of adding a polymerization initiator to the oil / water microemulsion to conduct a thermally initiated free radical polymerization reaction, causing PNIPAM monomers to polymerize at the oil-water interface and encapsulate TiO2 nanoparticles to form a PNIPAM-TiO2 composite nanocarrier encapsulating the metabolic regulation composition, includes: adding ammonium persulfate, a polymerization initiator, to the microemulsion obtained in S3, at an amount of 0.1%-0.4% of the PNIPAM monomer mass. Nitrogen or argon gas is then introduced for 15-30 minutes to remove oxygen from the system. Subsequently, under an inert atmosphere, the reaction system is placed in a constant temperature water bath at 55-65°C, and the thermally initiated free radical polymerization reaction is continuously stirred for 3.5-4.5 hours. During this process, the PNIPAM monomers dissolved in the aqueous phase polymerize at the oil-water interface and combine with the coexisting TiO2 nanoparticles to form a cross-linked PNIPAM-TiO2 composite shell on the surface of the oil droplets, thereby encapsulating the oil phase core material (metabolic regulation composition) inside the nanocapsule to form the PNIPAM-TiO2 composite nanocarrier.

[0074] Furthermore, the collection and purification of the composite nanocarrier, followed by dispersion with adjuvants in water to form the composite foliar formulation, may include: after the polymerization reaction is complete, cooling the reaction system to room temperature. Collecting the solid precipitate by centrifugation (e.g., 10000-15000 rpm, 15-30 minutes). To remove unreacted monomers, residual surfactants, initiators, and unencapsulated active ingredients, washing the precipitate alternately with deionized water and ethanol 3-5 times until the supernatant is clear and no significant active ingredient peaks are detected by high-performance liquid chromatography (HPLC). The washed precipitate is redispersed in a small amount of deionized water to obtain a concentrated dispersion of the purified nanocarrier. A solid powder can be obtained by freeze-drying for easy storage.

[0075] The nanocarrier concentrated dispersion (or redispersed solid powder) is mixed with the adjuvant and homogenized (e.g., by high-speed stirring or high-pressure homogenization) to obtain the composite foliar formulation. The adjuvant is selected from at least two of Tween-80, sodium lignosulfonate, and xanthan gum, and its total addition accounts for 5%-10% of the final formulation mass. The specific ratio can be adjusted according to the requirements of wettability, adhesion, and stability (e.g., the mass ratio of Tween-80:sodium lignosulfonate:xanthan gum is 2-4:1-3:1-3).

[0076] For example, deionized water can be added to the compound foliar preparation to a predetermined volume so that its total solid content is controlled at 2%-10%.

[0077] In actual agricultural production, a key issue that needs to be addressed is how to accurately apply this compound foliar preparation to ensure that its environmental response characteristics are fully utilized and that the active ingredients are efficiently absorbed and utilized in fresh tea leaves, thereby maximizing its effect on improving the quality of summer tea. Improper application may lead to untimely release or low utilization of active ingredients, affecting the overall effect.

[0078] To address this, this application further proposes a method for applying the aforementioned compound foliar preparation, aiming to optimize its application effect on fresh tea leaves in summer. The method involves spraying the compound foliar preparation onto fresh tea leaves in summer, ensuring uniform coverage on both sides of the leaves. Specifically, the spraying timing is set 5-7 days before harvesting to ensure sufficient time for the active ingredients to be absorbed, transported, and exert their effects on the tea leaves, thereby achieving optimal quality improvement at harvest time. The spraying volume is controlled within the range of 50-150 mL per square meter. This optimized dosage ensures a sufficient supply of active ingredients while avoiding waste or adverse effects on the tea leaves. The number of sprays can be 1-2 times. If two sprays are performed, the interval between the two sprays is 3-5 days. This staggered application strategy helps maintain a continuous supply of active ingredients and prolongs their duration of action to meet the rapid growth and metabolic needs of tea leaves under the high temperature and humidity conditions of summer.

[0079] It should be noted that the compound foliar formulation can be diluted to a solid content of 2%-10% before spraying. For example, the high-concentration original of the compound foliar formulation can be diluted with water to prepare a spraying working solution with a total solid content of 2%-10% for the nanocarrier. Crucially, this occurs in summer when the ambient temperature is ≥28℃ and the ultraviolet radiation intensity is ≥30W / m². 2 In this scenario, the composite nanocarrier will respond specifically, with its shell porosity significantly increasing from 8-12% to 30-45%. This increase in porosity allows the metabolic regulatory composition encapsulated within the nanocarrier to be released slowly and continuously.

[0080] While the quality of fresh tea leaves improved after treatment with compound foliar preparations in summer, improper subsequent processing, especially for the preparation of flat-shaped premium green tea, may prevent the full realization of its potential quality advantages, and even lead to the aroma, taste, and appearance failing to meet expected standards. Therefore, how to transform treated high-quality fresh leaves into high-quality flat-shaped premium green tea is a key issue that needs to be addressed.

[0081] In response, this application proposes a method for preparing a flat-shaped premium green tea, which includes the following steps: First, select one bud and one leaf or newly unfolded fresh leaves that sprout in summer from small-leaf tea trees treated using the above-mentioned method as raw materials. Due to the application of compound foliar preparations in the early stages, the internal substances of these fresh leaves, especially the metabolic regulatory compounds related to aroma and flavor, have been effectively accumulated and optimized. Subsequently, these fresh leaves are spread out in an environment of 28-32℃ for 4 hours until the moisture content of the fresh leaves decreases to 65%-70%. Spreading out is the initial step in green tea processing; its purpose is to increase the permeability of the cell membranes of the fresh leaves through moderate water loss, activate some enzyme activities, and simultaneously release the grassy aroma, preparing for subsequent fixation and shaping. Spreading out within this temperature and time range ensures that the moisture of the fresh leaves is evenly lost, avoiding excessive drying or fermentation, thereby preserving the active ingredients and good condition of the fresh leaves.

[0082] Next, the dried fresh leaves are quickly placed in the blanching equipment, and the temperature of the equipment is controlled at 170-190℃ for 3-5 minutes.

[0083] After initial processing (killing the green leaves), the fresh leaves must be immediately transferred to a shaping machine for shaping. The machine temperature is set at 75-85℃, and the shaping time is 3-5 minutes. Following this, the shaped tea leaves are fed into an aroma-enhancing device, with the temperature controlled at 125-135℃, and the aroma-enhancing time is 5-7 minutes. Finally, the aroma-enhanced tea leaves are allowed to cool naturally to room temperature, and then sieved to remove any broken pieces and impurities, ultimately producing a flat-shaped premium green tea product. Natural cooling helps stabilize and maintain the tea's aroma, preventing aroma loss due to rapid cooling. Sieving ensures the purity and consistency of the finished product, meeting the quality requirements of premium green tea.

[0084] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided: Example 1 Preparation of compound leaf preparations.

[0085] Aqueous phase preparation: 10.0 g of N-isopropylacrylamide (NIPAM) monomer, 2.0 g of hydrophobically modified anatase TiO2 nanoparticles (average particle size 35 nm) (PNIPAM:TiO2 mass ratio = 5:1), 0.15 g of crosslinking agent N,N'-methylenebisacrylamide (BIS) (1.5% of the NIPAM monomer mass), and 0.75 g of emulsifier sodium dodecyl sulfate (SDS) (approximately 0.5% of the expected aqueous phase mass) were added to 500 mL of deionized water. The mixture was ultrasonically dispersed in an ice-water bath (300 W, intermittent mode) for 20 minutes to obtain a uniform milky white aqueous dispersion (PNIPAM concentration 20 g / L).

[0086] Preparation of the oil phase core material: Weigh 6.0g of L-glutamic acid (exogenous amino acid), 3.0g of β-carotene (carotenoid precursor), and 0.6g of propyl jasmonic acid (natural inducer), for a total mass of 9.6g. Dissolve in 50mL of chloroform and sonicate to obtain a clear oil phase. The total concentration of the active ingredient in chloroform is approximately 192g / L.

[0087] Fine emulsion preparation: Under vigorous stirring in a high-speed shear press (12000 rpm), the oil phase was slowly added dropwise to the aqueous phase. The volume ratio of the oil phase to the aqueous phase was controlled at 1:20. After the addition was complete, shearing was continued for 10 minutes to obtain a stable O / W type fine emulsion.

[0088] Interfacial polymerization and encapsulation: After purging the emulsion with nitrogen to remove oxygen for 30 minutes, 0.02 g of water-soluble initiator ammonium persulfate (APS) (0.2% of the mass of NIPAM monomer) was added. The reaction was carried out under nitrogen protection in a constant temperature water bath at 60°C with stirring for 4.0 hours.

[0089] Preparation of purified and concentrated raw materials: After cooling, the reaction solution was centrifuged (15000 rpm, 30 min) to collect the precipitate. The precipitate was washed three times alternately with deionized water and ethanol to remove unreacted monomers and unencapsulated components. After freeze-drying, a light yellow powdery composite nanocarrier (composite leaf preparation) was obtained.

[0090] Preparation of spraying working solution: Take 3.0g of the above-mentioned nano-carrier powder and mix it with the adjuvants (Tween-80 0.12g, sodium lignosulfonate 0.06g, xanthan gum 0.06g, mass ratio 2:1:1), add deionized water to make up to 100mL, and homogenize at high speed to obtain a sprayable working solution with a total solid content of about 3% and good fluidity.

[0091] Results: The dry particle size of the composite nanocarrier is approximately 120-180 nm, and its hydrodynamic diameter (Dh) in water is 185 ± 20 nm.

[0092] Differential scanning calorimetry (DSC) was used to test the purified nanocarrier powder. The results showed that the lower critical dissolution temperature (LCST) of the PNIPAM shell was 29.5 ± 0.5 °C, which means that by controlling the amount of crosslinking agent BIS at 1.5%, the carrier response threshold was successfully and precisely controlled within the range of ≥28 °C.

[0093] The surface wettability of the carrier film before and after UV irradiation (35 W / m², 30 min) was compared using a contact angle meter. The results showed that the water contact angle decreased from 75° before irradiation to 42° after irradiation, proving that the TiO2 component was effectively activated under the target UV intensity, producing a significant photo-induced hydrophilic effect.

[0094] Analysis example 1 To elucidate the structural changes and release mechanism of the carrier under response conditions, a comparative analysis was performed on the nanocarrier powder prepared in Example 1. The sample was divided into two portions: one portion was stored at 20°C in the dark (non-responsive state), and the other portion was placed at 30°C and subjected to 35 W / m². 2 After 2 hours of UV irradiation (response state), scanning electron microscopy (SEM) revealed a more pronounced wrinkling and porous structure on the surface of the responsive sample. Further analysis showed that the shell porosity significantly increased from approximately 10% in the non-response state to approximately 35% in the responsive state. This result directly confirms the synergistic effect of ≥30 W / m² at temperatures ≥28℃. 2 The intensity of ultraviolet radiation fundamentally altered the permeability of the carrier shell.

[0095] Release was simulated using dialysis (molecular weight cutoff 3500). L-glutamate was used as the model molecule for the metabolic regulatory composition, and its cumulative release rate was determined under four conditions: Group A (25℃, protected from light): 11.2% release after 24 hours, release was slow and steady.

[0096] Group B (25℃, 35W / m) 2 UV): 18.5% was released in 24 hours, indicating that UV light alone can slightly promote the release.

[0097] Group C (30℃, protected from light): 32.8% release in 24 hours, indicating that high temperature alone significantly accelerates the release.

[0098] Group D (30℃, 35W / m) 2 UV): 58.6% was released over 24 hours, exhibiting a slow-release characteristic. This data strongly demonstrates a significant synergistic triggering effect between temperature and ultraviolet radiation, and that the release mode is controlled slow release rather than burst release.

[0099] Example 2 The compound foliar preparation was applied to improve the quality of fresh summer tea leaves.

[0100] In summer (July), fresh tea leaves of small-leaf tea varieties in Meitan County were sprayed with the working solution prepared in Example 1. The solution was sprayed twice, once on the afternoon of the 7th and 4th day before harvesting, at a rate of 100 mL / m², ensuring uniform coverage of the leaves. A control group (CK) was established by spraying an equal volume of water. Each treatment was replicated in triplicate.

[0101] Three days after the second spraying (one day before harvest), standard fresh leaves with one bud and one leaf were collected and flash-frozen in liquid nitrogen. The following four key indicators were tested to evaluate the synergistic efficacy of the components described in this invention: Key substances for bitterness: Ester-type catechins (EGCG) were quantified using high performance liquid chromatography (HPLC).

[0102] The core components of the fresh and crisp flavor were: theanine was quantified by HPLC; and the total amount of free amino acids was determined by an amino acid analyzer.

[0103] Aroma synthesis potential index: Total carotenoids were determined by spectrophotometry.

[0104] Results: As shown in the table below, compared with the control group, the intrinsic quality components of summer tea leaves underwent significant changes in the expected direction after treatment with the formulation of this invention: Table 1. Changes in key quality components of summer tea fresh leaves The experimental conditions for the control group were the same as those for the treatment group, as follows: equal amounts of water were sprayed twice, once on the afternoon of the 7th day and again on the 4th day before harvesting, at a rate of 100 mL / m². 2 Ensure even leaf coverage. Each treatment was replicated in triplicate, with all other field management practices consistent. Standard fresh leaves (one bud and one leaf) were collected on the third day after the second spray (one day before harvest) and flash-frozen in liquid nitrogen for preservation.

[0105] Example 3 Prepare flat-shaped premium green tea.

[0106] The raw material used was a fresh leaf with one bud and one leaf treated with the compound foliar preparation of the present invention as described in Example 2. The core characteristics of this raw material (based on the data from Example 2) are: a significant decrease in the content of ester-type catechins (EGCG), and a significant increase in the content of theanine, total free amino acids, and total carotenoids.

[0107] Spreading and drying: Spread the fresh leaves evenly and thinly on a bamboo tray and place them in a clean environment at 30℃ for 4 hours to allow the moisture content of the fresh leaves to naturally decrease to 68%.

[0108] Blanching: Use a drum blanching machine, control the pan temperature at 180℃, and the blanching time is 6 minutes.

[0109] Shaping: Immediately after blanching, transfer the green leaves to a multi-functional shaping machine, set the pot temperature to 80℃, and shape for 6 minutes until the leaves are flat and straight.

[0110] Aroma Enhancement: Place the tea leaves in an aroma enhancement machine and enhance the aroma at 130℃ for 5 minutes until the tea leaves are fully dry and the aroma is apparent.

[0111] Cooling and sieving: After the aroma is enhanced, the tea leaves are naturally cooled to room temperature and then sieved through a 60-mesh sieve to remove fragments and impurities, resulting in a flat-shaped premium green tea product.

[0112] like Figure 1As shown, during the processing, three key steps were set: fixation (180℃, 0, 2, 4, 6, 8 min), shaping (80℃, 0, 2, 4, 6, 8 min), and aroma enhancement (130℃, 0, 5, 10, 15, 20 min). (AB) represented different fixation times for ester-type and non-ester-type catechins; (CD) represented different shaping times for ester-type and non-ester-type catechins; and (EF) represented different aroma enhancement times for ester-type and non-ester-type catechins. The results showed that when the process parameters were set to fixation time of 6 min, shaping time of 6 min, and aroma enhancement time of 5 min, the EGCG content in the finished tea could be reduced to the lowest level, achieving effective control over the bitter and astringent substances in tea.

[0113] Figure 2 The images show actual products of this invention with different fixation times, tidying times, and aroma-enhancing times. Fixating refers to fixing, tidying refers to tidying, and drying refers to aroma-enhancing.

[0114] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A compound foliar preparation for improving the quality of fresh summer tea leaves, characterized in that, The composition comprises a metabolic regulation composition, a composite nanocarrier, and an auxiliary agent, wherein the composite nanocarrier encapsulates the metabolic regulation composition. The metabolic regulation composition includes exogenous amino acids, aroma precursors and natural inducers. The exogenous amino acids are selected from at least one of L-glutamic acid and L-arginine. The aroma precursor is a carotenoid precursor. The natural inducer is selected from at least one of propyl jasmonate and isobutyl jasmonate. The composite nanocarrier is subjected to a temperature ≥28℃ and an ultraviolet intensity ≥30W / m. 2 Time-specific response.

2. The compound foliar preparation for improving the quality of fresh summer tea leaves according to claim 1, characterized in that, The mass fractions of each component in the compound foliar preparation are as follows: exogenous amino acids 5%-15%, aroma precursors 3%-8%, natural inducers 0.5%-2%, composite nanocarriers 60%-80%, and adjuvants 5%-10%.

3. The compound foliar preparation for improving the quality of fresh summer tea leaves according to claim 1, characterized in that, The composite nanocarrier is a PNIPAM-TiO2 composite nanocarrier, and the mass ratio of PNIPAM to TiO2 nanoparticles in the PNIPAM-TiO2 composite nanocarrier is 4-6:

1.

4. The compound foliar preparation for improving the quality of fresh summer tea leaves according to claim 3, characterized in that, The TiO2 nanoparticles have a particle size of 20-50 nm, and the composite nanocarrier has a particle size of 50-200 nm.

5. The compound foliar preparation for improving the quality of fresh summer tea leaves according to claim 2, characterized in that, The carotene precursor is selected from at least one of β-carotene and lutein; The additive is selected from at least two of Tween-80, sodium lignosulfonate, and xanthan gum.

6. The compound foliar preparation for improving the quality of fresh summer tea leaves according to claim 5, characterized in that, The additives include Tween-80, sodium lignosulfonate, and xanthan gum in a mass ratio of 2-4:1-3:1-3.

7. A method for preparing a compound foliar preparation for improving the quality of fresh summer tea leaves according to any one of claims 1-6, characterized in that, Including the following steps: PNIPAM monomer, TiO2 nanoparticles, crosslinking agent, and surfactant are dispersed in an aqueous solvent to obtain an aqueous phase; The metabolic regulation composition was dissolved in an oily solvent to obtain an oil-phase core material; Under high-speed shearing conditions, the oil phase core material is injected into the aqueous phase to obtain an oil / water microemulsion; Add a polymerization initiator to the oil / water microemulsion to polymerize PNIPAM monomers at the oil-water interface and encapsulate TiO2 nanoparticles to form a PNIPAM-TiO2 composite nanocarrier encapsulating the metabolic regulation composition. The composite nanocarrier was collected and purified, and then dispersed in water with adjuvants to form the composite leaf preparation.

8. The preparation method according to claim 7, characterized in that, The addition of the polymerization initiator to the oil / water microemulsion includes: obtaining a mixture of the oil / water microemulsion and the polymerization initiator, and then treating it at a temperature of 55-65°C for 3.5-4.5 hours.

9. The application of a compound foliar preparation for improving the quality of fresh summer tea leaves as described in any one of claims 1-6, or a compound foliar preparation prepared by the method described in claim 7 or 8, characterized in that, Including the following steps: Spray the aforementioned compound foliar preparation on fresh tea leaves in summer to ensure even coverage on both sides of the leaves; the timing of spraying is 5-7 days before harvesting; When the ambient temperature is ≥28℃ and the ultraviolet intensity is ≥30W / m 2 In this case, the porosity of the composite nanocarrier shell increases from 8-12% to 30-45%, allowing for the slow release of the metabolic regulation composition.

10. A method for preparing a flat-shaped premium green tea, characterized in that, Including the following steps: Take one bud and one leaf or newly unfolded fresh leaf from the small-leaf tea tree that sprouts in summer after being treated by the application method described in claim 9, and place it in an environment of 28-32℃ to dry for 4 hours until the moisture content of the fresh leaf drops to 65%-70%; Place the dried fresh leaves in the blanching equipment, control the temperature at 170-190℃, and the blanching time at 5-7 minutes; After blanching, the fresh leaves are immediately transferred to a leaf-shaping machine, with the temperature set at 75-85℃ and the leaf-shaping time at 5-7 minutes. After the tea leaves are shaped, they are fed into an aroma-enhancing device, with the temperature controlled at 125-135℃ and the aroma-enhancing time at 4-6 minutes. After the tea leaves are infused with aroma, they are naturally cooled to room temperature, then sieved to remove broken pieces and impurities, resulting in a flat-shaped premium green tea product.

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