Cyclocarya paliurus yellow tea and preparation method thereof

Abstract

The invention relates to the technical field of tea drinks, in particular to cyclocarya paliurus yellow tea and a preparation method thereof, and particularly relates to a cyclocarya paliurus leaf fermentation method and cyclocarya paliurus yellow tea formed by blending and mixing fermented cyclocarya paliurus leaves and black tea according to a certain proportion. The cyclocarya paliurus leaf fermentation method comprises the steps of withering, rolling, fermenting and drying. The water content of the withered cyclocarya paliurus leaves is 58-62 wt%; the cell destruction rate of the rolled cyclocarya paliurus leaves reaches 85% or above, and the strip forming rate of the leaves is 90% or above; the fermentation degree is 15-20%, 90% or more of the leaf color of the cyclocarya paliurus leaves after fermentation becomes copper red, and the liquor color is bright yellow; the drying comprises gross fire drying, spreading for cooling and complete fire drying which are performed in sequence; the moisture content after the first fire drying is 20wt%, and the moisture content after the full fire drying is 6wt%. The cyclocarya paliurus leaves are processed through a fermentation technology, the fermented cyclocarya paliurus leaves and the black tea are blended and mixed according to a certain proportion, the cyclocarya paliurus yellow tea which is unique in flavor and suitable for human health is formed, the cyclocarya paliurus yellow tea and the black tea are in synergistic interaction, the requirements of consumers for health functions are met, the acceptability of the public for the flavor of tea drinks is met, and the cyclocarya paliurus yellow tea is suitable for popularization and application. A new way is opened up for high-value utilization of the cyclocarya paliurus leaves.

Description

Technical Field

[0001] This invention relates to the field of tea beverage technology, and in particular to a Qingqianliu yellow tea and its preparation method. Background Technology

[0002] Tea-containing products include substitute teas made from tea leaves and flavored teas made from tea leaves with various edible substances or edible spices. Substitute teas refer to products made from the leaves, flowers, fruits, roots, and stems of edible plants, and consumed using a brewing (steeping) method similar to tea.

[0003] With the development of the times, modern people have increasingly higher requirements for quality of life, and are pursuing tea drinks that are both uniquely flavored and beneficial to health. Traditional processing methods for Qingqianliu leaf tea cannot meet the quality requirements of most tea drinkers, the single product has a small audience, and traditional processing methods cannot adapt to the requirements of modern production and life. Summary of the Invention

[0004] The purpose of this invention is to provide a Qingqianliu yellow tea and its preparation method. The method involves processing Qingqianliu leaves using a fermentation process, and then blending the fermented Qingqianliu leaves with black tea in a certain proportion to form a Qingqianliu yellow tea with a unique flavor that is beneficial to human health.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is to provide a method for fermenting Eucommia ulmoides leaves, comprising the following steps: withering, rolling, fermentation, and drying; The withered leaves of *Cyclocarya paliurus* have a moisture content of 58-62 wt%; the kneaded leaves have a cell destruction rate of over 85% and a leaf strip formation rate of over 90%; the fermentation degree is 15%-20%, and over 90% of the leaves turn copper-red after fermentation, with a bright yellow liquor; the drying process includes sequential initial drying, cooling, and final drying; the initial drying has a moisture content of 20 wt%, and the final drying has a moisture content of 6 wt%.

[0006] This invention utilizes a process of withering, rolling, fermentation, and drying to ferment the leaves of *Eucommia ulmoides*. By controlling the state of the product obtained in each process step, the effective components in the leaves are fully converted, significantly improving the content and bioavailability of active substances. At the same time, it improves the bitterness and grassy smell of the leaves, giving the product a unique sweet aroma and mellow taste. The finished product has a uniform color, tightly rolled strands, and stable quality, and has good health benefits, providing an effective way for the high-value utilization of *Eucommia ulmoides* leaves. Specifically, after withering, the moisture content of *Cyclocarya paliurus* leaves should be 58-62 wt% to ensure moderate softening. This facilitates the full destruction of cell walls during the subsequent rolling process and avoids leaf breakage due to excessive moisture or insufficient rolling due to insufficient moisture. After rolling, the cell destruction rate of *Cyclocarya paliurus* leaves should reach over 85%, and the leaf strip formation rate should be over 90%. This promotes the full exudation of juice from the leaves, providing sufficient substrate for the subsequent fermentation process while maintaining good appearance quality. After fermentation, over 90% of the *Cyclocarya paliurus* leaves should turn copper-red, indicating that the polyphenols are fully oxidized, the fermentation degree is appropriate, and the flavor compounds are completely transformed. The process of initial drying, cooling, and final drying reduces the moisture gradient of the *Cyclocarya paliurus* leaves, avoiding the loss of active ingredients due to rapid high-temperature drying that results in dry leaves on the outside but wet leaves on the inside. At the same time, cooling promotes the redistribution of moisture, ultimately yielding a finished product with uniform color, pure aroma, and stable quality.

[0007] Preferably, during the withering process, the following parameters are controlled: the fresh leaves of *Eucommia ulmoides* are spread evenly with a thickness of 14-20 cm; the withering temperature is controlled at 28-32℃; the leaves are turned over every 30-60 minutes during the withering process; and the withering time is 4-5 hours.

[0008] Preferably, during the spreading process, tender leaves are spread thinly and old leaves are spread thickly, with the thin spreading thickness being 14-18cm and the thick spreading thickness being 20cm. Preferably, when the Cyclocarya paliurus leaves are spring Cyclocarya paliurus leaves, the moisture content of the withered Cyclocarya paliurus leaves is 58-60 wt%. Preferably, when the leaves of *Cyclocarya paliurus* are summer or autumn leaves, the moisture content of the withered leaves is 60-62 wt%.

[0009] By controlling the spreading thickness, temperature, and turning frequency, it is possible to ensure uniform water loss of Cyclocarya paliurus leaves and avoid leaf damage caused by localized overheating or excessively rapid water loss. A mild temperature of 28-32℃ is beneficial for promoting the activity of enzymes in the leaves while avoiding the loss of active ingredients due to high temperatures. Turning every 30-60 minutes effectively solves the problem of uneven temperature and humidity within the pile, promoting uniform wilting of the leaves. The wilting time of 4-5 hours is matched with the spreading thickness to ensure that the leaves reach the ideal degree of softening. The graded treatment method of spreading tender leaves thinly and older leaves thickly allows for adjustment of the water loss rate according to the maturity of the leaves, ensuring that leaves of different tenderness levels wither to a consistent degree, laying a good foundation for subsequent rolling and fermentation processes.

[0010] The differentiated moisture content control strategy fully considers the physiological characteristics of Eucommia ulmoides leaves in different seasons: In spring, the leaves are more tender and rich in internal substances, resulting in a faster rate of water loss. Therefore, controlling the moisture content at 58-60 wt% avoids excessive water loss that leads to brittle leaves and increased breakage during rolling. In summer and autumn, the leaves are relatively coarse and older, with a higher degree of fibrousness and a slower rate of water loss, making them less ideal raw materials for tea. This invention controls the moisture content at 60-62 wt% to ensure that the leaves are fully softened, facilitating the complete breakdown of cell walls during rolling, while avoiding excessive moisture content that could lead to difficulties in rolling or uneven fermentation. Through this precise seasonal moisture content control, the withering degree of the raw materials in different seasons can be matched with subsequent processes, thereby obtaining fermented Eucommia ulmoides leaf products with stable quality and harmonious flavor.

[0011] Preferably, the kneading is carried out at a temperature of 20-24℃ and a humidity of 85-95%; the kneading is carried out in two stages. After the first kneading, the kneading leaves are put into a de-clumping machine to de-clump, and then sieved through a 2-3 mesh screen. The material under the screen is used directly for fermentation, and the material over the screen is used for fermentation after a second kneading; the first kneading time is 50 minutes, and the second kneading time is 40 minutes.

[0012] By controlling the temperature and humidity environment during kneading (20-24℃, 85-95% humidity), the excessive activation of polyphenol oxidase during kneading can be effectively inhibited, preventing premature reddening of leaves while maintaining leaf toughness and reducing breakage. A grading process combining two kneading stages with de-clumping and sieving achieves precise kneading of the raw materials: the first kneading ensures most leaves achieve suitable cell destruction and strip formation rates; after sieving through a 2-3 mesh screen, the undersize material (fully kneaded leaves) can directly enter the fermentation process, avoiding over-kneading that could lead to flavor loss; the oversize material (coarser, older leaves) undergoes a second kneading stage, further enhancing cell destruction and ensuring the full release of fermentation substrates from the coarser leaves. This grading kneading process not only improves kneading efficiency but also enables differentiated treatment of leaves of varying tenderness, ensuring all raw materials reach the ideal pre-fermentation state, laying the foundation for uniformity and quality stability in subsequent fermentation processes.

[0013] Preferably, the fermentation is carried out at a temperature of 24-26°C and a humidity of over 95%. Preferably, during the fermentation process, the thickness of the spread leaves is 15-20cm; and the fermentation time is 3-5 hours.

[0014] By precisely controlling temperature and humidity parameters (24-26℃, humidity above 95%), a suitable microenvironment for endogenous enzyme activity is created. This ensures the full progress of enzymatic reactions, promoting the oxidation of polyphenols to form beneficial components such as theaflavins and thearubigins, while preventing excessive temperature from causing enzyme inactivation or over-fermentation. A leaf-spreading thickness of 15-20cm ensures relative stability of temperature and humidity within the fermentation pile and provides ample oxygen supply, promoting smooth aerobic fermentation while avoiding uneven fermentation or localized overheating caused by excessively thick stacks. A fermentation time of 3-5 hours, matched with the aforementioned process parameters, results in over 90% of the leaves turning copper-red, indicating appropriate polyphenol oxidation and sufficient transformation of flavor compounds. This preserves the active ingredients of *Eucommia ulmoides* leaves and develops a unique sweet aroma and mellow taste. This combination of fermentation process parameters ensures the controllability and consistency of the fermentation process, ultimately yielding a fermented *Eucommia ulmoides* leaf product with uniform color, harmonious flavor, and stable quality.

[0015] Preferably, the drying temperature is 110-120℃, and the heating rate is 3℃ / min; Preferably, the foot drying temperature is 80°C; Preferably, the cooling time is 20 minutes.

[0016] The initial drying temperature is 110-120℃, with a heating rate controlled at 3℃ / min. This rapidly deactivates enzyme activity and fixes the quality characteristics formed during fermentation. Gradient temperature control and cooling processes stabilize the quality of *Eucommia ulmoides* leaves and optimize their flavor compounds. The initial drying at 110-120℃ rapidly terminates residual enzyme activity during fermentation, preventing over-fermentation and quality deterioration, while simultaneously evaporating moisture to 20wt%, forming the initial shape of the dried tea. Cooling for 20 minutes allows for redistribution of moisture within the leaves, avoiding uneven quality caused by external dryness and internal moisture, creating uniform initial conditions for subsequent final drying. The final drying at a gentle 80℃ further reduces moisture to the safe storage standard of 6wt%, while avoiding the loss of volatile aroma compounds and destruction of active ingredients due to high temperatures. The final product is characterized by uniform color, tightly rolled leaves, pure aroma, and stable quality. This combination of drying process parameters ensures product quality stability and retention of active ingredients, providing reliable technical support for the industrial production of fermented *Eucommia ulmoides* leaves.

[0017] The second technical solution of the present invention is the fermented *Cyclocarya paliurus* leaves obtained by the above-mentioned fermentation method.

[0018] The third technical solution of the present invention is a kind of Qingqianliu yellow tea, the raw materials of which include the above-mentioned fermented Qingqianliu leaves and black tea.

[0019] Preferably, the mass ratio of the fermented Eucommia ulmoides leaves to black tea is 1:1; Preferably, the black tea is Xinyang black tea.

[0020] The fourth technical solution of the present invention, the preparation method of the above-mentioned Qingqianliu yellow tea, involves mixing the fermented Qingqianliu leaves and black tea, drying them at 60-65℃ until the moisture content is 5-8wt%, and then cooling them to obtain the Qingqianliu yellow tea.

[0021] The present invention discloses the following technical effects: 1. In the existing technology, most black tea or green tea is produced using Cyclocarya paliurus as raw material. However, the present invention provides a production process for yellow tea using Cyclocarya paliurus as raw material. Compared with black tea or green tea, the moderate fermentation of Cyclocarya paliurus yellow tea not only removes the astringent smell and taste of green tea, but also avoids the loss of some nutrients during the fermentation process.

[0022] 2. The fermented *Eucommia ulmoides* leaves produced by the process of this invention are intact, clearly distinguishable from the blocky or granular leaves produced by existing technologies. Intact *Eucommia ulmoides* leaves facilitate the extraction of beneficial substances during brewing, resulting in a more aesthetically pleasing and visually appealing tea that achieves a perfect balance of color, aroma, flavor, and shape, thus enhancing the commercial value of *Eucommia ulmoides* tea.

[0023] 3. This invention improves the taste of *Eucommia ulmoides* leaves through fermentation, enriches their nutritional components, significantly increases their effective substances, and noticeably reduces bitterness, resulting in a unique sweet aroma and mellow flavor. This invention blends fermented *Eucommia ulmoides* leaves with black tea to prepare *Eucommia ulmoides* yellow tea. The product not only possesses the health benefits of *Eucommia ulmoides* leaf tea, such as its antioxidant effects, but also achieves a harmonious blend of the unique sweet and mellow taste of fermented *Eucommia ulmoides* leaves and the rich and refreshing aroma of black tea, creating a multi-layered, harmonious, and pleasant flavor profile, thus enhancing the quality of *Eucommia ulmoides* yellow tea. Through a 1:1 mass ratio, the quality of *Eucommia ulmoides* leaves and black tea complement each other: fermented *Eucommia ulmoides* leaves provide health benefits and a mellow base, while black tea imparts a fresh aroma and traditional tea-like taste. The synergistic effect of both satisfies consumers' demand for health benefits and aligns with the public's acceptance of tea flavors, opening up new avenues for the high-value utilization of *Eucommia ulmoides* leaves. 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 embodiments 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 these drawings without creative effort.

[0025] Figure 1 This is a picture of the fermented Eucommia ulmoides leaves prepared in Example 1 of the present invention.

[0026] Figure 2 This is a photograph of the Qingqianliu yellow tea prepared in Example 1 of the present invention after being brewed and subjected to sensory evaluation testing. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] This invention provides a Qingqianliu yellow tea, which is made from Qingqianliu leaves and Xinyang black tea as raw materials.

[0033] The preparation method of Qingqianliu Yellow Tea according to the present invention includes the following steps: (1) After removing branches and other leaves from the fresh leaves of *Eucommia ulmoides*, the withering process is carried out using a spreading withering trough. During withering, the fresh leaves of *Eucommia ulmoides* are evenly spread in the withering trough, adopting the principle of "thin spreading for tender leaves and thick spreading for old leaves". The thickness of thin spreading should be 14-18cm, and the thickness of thick spreading should not exceed 20cm. When spreading, the leaves should be shaken and spread flat to make the fresh leaves fluffy and uniform in thickness and looseness, so as to facilitate uniform ventilation. (2) After the leaves in (1) are properly placed, the temperature is controlled at (28-32)℃ and hot air is introduced.

[0034] (3) During (2), the leaves should be turned over in a timely manner and the action should be quick. Turn the upper and lower layers of leaves over and loosen them to increase the air permeability of the leaf layer and make the withering even. Generally, turn over once every 1 hour. When turning over, stop blowing air. Leaves with rain and dew should be turned over once every 30 minutes before withering so that the moisture on the leaf surface can be lost.

[0035] (4) The withering process generally takes 4-5 hours. The moisture content of the withered leaves should be (58-62) wt%. The spring leaves of *Eucommia ulmoides* should be withered more heavily, with the moisture content controlled at (58-60) wt%, to eliminate the green taste of the leaves. The summer and autumn leaves of *Eucommia ulmoides* should be withered less heavily, with the moisture content controlled at (60-62) wt%, to ensure good freshness.

[0036] (5) After withering, kneading is carried out. The kneading temperature should be (20-24)℃, the relative humidity should be (85-95)%, and direct sunlight should be avoided to keep the indoor air fresh. In summer and autumn, when the temperature is high and the humidity is low, cold water or spray can be sprinkled on the floor of the kneading room to lower the room temperature and increase the relative humidity.

[0037] (6) When using a kneading machine, the amount of leaves added should be moderate. If too many leaves are added, the leaves will be obstructed from turning in the kneading drum, resulting in uneven kneading and increased leaf temperature.

[0038] (7) A two-stage kneading method is adopted. After the first kneading, the kneaded leaves are put into the de-clumping machine to break up the clumps. After passing through a (2-3) mesh sieve, the leaves that pass through the sieve are tightly rolled and directly enter the fermentation machine for fermentation. The leaves that pass through the sieve are loosely kneaded for the second kneading, generally for 50 minutes. The leaves that pass through the sieve are kneaded again for 40 minutes. The kneading time can be extended for older leaves. For leaves with high tenderness and good uniformity, they can be kneaded once. The criteria for judging the appropriate kneading are generally that the cell destruction rate reaches more than 85%, the leaf strip formation rate is more than 90%, the strips are tightly rolled, the tea juice overflows fully and adheres to the leaf surface, and the locally kneaded leaves turn red.

[0039] (8) After kneading, feed the product into the de-clumping machine. Master the ratio between the amount of material fed and the de-clumping effect, and determine the optimal amount of material fed. The de-clumping effect should be such that each blade can be dispersed, independent, and not clump together.

[0040] (9) After breaking up the block, use a fermentation box for fermentation production. The fermentation temperature should be (24-26)℃. The relative humidity of the fermentation box should reach more than 95%. Cover the fermentation tray with a damp cloth to achieve the purpose of keeping it moist.

[0041] (10) During fermentation, the thickness of the leaves should generally be (15-20) cm. It can be thinner in high temperatures and thicker in low temperatures. The leaves should be thicker in spring and thinner in summer and autumn. Note that the fermenting leaves should not be pressed tightly. The fermentation time is generally (3-5) hours, depending on the appropriate fermentation time. The sensory criteria for judging the appropriate fermentation time are: more than 90% of the leaf color turns copper red, the green smell gradually disappears, a fresh and strong floral and fruity fragrance is emitted, and the leaf veins and sap turn red.

[0042] (11) A two-stage drying method (initial drying and final drying) is adopted, with one cooling in between. The moisture content of the fermented leaves is about (50-60) wt%, requiring a high initial drying temperature. At the beginning of drying, the leaf temperature needs to rise from (20-30) ℃ to (70-80) ℃, which requires a process, while fermentation continues. To ensure fermentation quality, the initial heating rate needs to be controlled at 3 ℃ / min. Generally, the inlet temperature of the initial drying is required to be (110-120) ℃ to quickly inactivate oxidation; the final drying is around 80 ℃, with a smaller air volume and a longer time to fully develop aroma. Generally, a cooling period of 20 minutes is required between the initial and final drying, and the final drying adopts the "low-temperature slow drying" method. After the initial drying, the leaves feel slightly prickly to the touch, but are still soft, foldable but not broken, and can be easily loosened when released after being tightly squeezed. They have a mellow aroma, and the moisture content of the leaves is about 20 wt%, at which point the final drying can be carried out. After being thoroughly roasted, the leaves of the tea can be easily rubbed into powder by hand. The tea has a distinct aroma, and the leaves are tightly rolled and dark in color, with a moisture content of approximately 6 wt%.

[0043] (12) Spread out to cool, sort, select stems, and select carefully.

[0044] (13) Take the fermented Qingqianliu leaves and Xinyang black tea in step (12) and mix them in a 1:1 ratio; dry the mixed tea leaves at 60-65℃ until the moisture content is 5-8wt%, and then cool them to obtain the Qingqianliu yellow tea; the cooling process needs to ensure a cooling rate of 5℃ / min to prevent the tea leaves from deteriorating due to residual heat.

[0045] The fresh leaves of *Eucommia ulmoides* used in this embodiment of the invention were sourced from the *Eucommia ulmoides* base in Fushan Township, Shangcheng County, Xinyang City, Henan Province, owned by Henan Xinglin Agricultural Development Co., Ltd.; the Xinyang black tea was purchased from the market.

[0046] Example 1 A type of Qingqianliu yellow tea is made from Qingqianliu leaves (spring) and Xinyang black tea. The specific process is as follows: (1) After removing branches and other leaves from the fresh leaves of *Eucommia ulmoides*, the withering process is carried out using a spreading withering trough. During withering, the fresh leaves of *Eucommia ulmoides* are evenly spread in the withering trough, adopting the principle of "spreading tender leaves thinly and old leaves thickly". The thickness of the thin spreading is 15-16cm, and the thickness of the thick spreading is 18-20cm. When spreading, the leaves are shaken and flattened to make the fresh leaves fluffy and uniform in thickness and looseness, so as to facilitate uniform ventilation. (2) Based on (1), the temperature is controlled at 30±1℃ and hot air is introduced.

[0047] (3) During (2) process, turn the leaves over in a timely manner. The action should be quick, so that the upper and lower layers of leaves are turned over and shaken loose to increase the air permeability of the leaf layer and make the withering even. Generally, turn the leaves over once every 1 hour. When turning the leaves over, stop blowing air. Leaves with rain and dew should be turned over once every 30 minutes before withering so that the moisture on the leaf surface can be lost.

[0048] (4) After 4.5 hours of withering, the moisture content of the withered leaves is 60%.

[0049] (5) After withering, kneading is carried out at a temperature of 22±1℃ and a relative humidity of 90±2%. Avoid direct sunlight and keep the indoor air fresh.

[0050] (6) Use a kneading machine to knead the leaves. The amount of leaves should be moderate. Avoid adding too many leaves, which may cause the leaves to be obstructed in the kneading drum, resulting in uneven kneading or increased temperature of the kneading leaves.

[0051] (7) A two-stage kneading method is adopted. After the first kneading (50 min), the kneaded leaves are put into the de-clumping machine to break up the clumps. After passing through a 3-mesh sieve, the leaves that pass through the sieve are tightly rolled and fine, and directly enter the fermentation machine for fermentation. The leaves that pass through the sieve with a coarser surface are kneaded a second time (40 min). Older leaves can be kneaded for a longer time. For leaves with high tenderness and good uniformity, only one kneading is required. The criteria for judging the appropriate kneading are generally that the cell destruction rate reaches more than 85%, the leaf strip formation rate is more than 90%, the strips are tightly rolled, the tea juice overflows fully and adheres to the leaf surface, and the locally kneaded leaves turn reddish.

[0052] (8) After kneading, feed the product into the de-clumping machine. Master the ratio between the amount of material fed and the de-clumping effect, and determine the optimal amount of material fed. The de-clumping effect should be such that each blade can be dispersed, independent, and not clump together.

[0053] (9) After breaking up the block, use a fermentation box for fermentation production. The fermentation temperature should be 24-26℃. The relative humidity of the fermentation box should be above 95%. Cover the fermentation tray with a damp cloth to achieve the purpose of keeping it moist.

[0054] (10) During fermentation, the thickness of the leaves should be 17-18cm; fermentation time should be 4.5h to reach the appropriate level. The sensory criteria for judging the appropriate level of fermentation are: more than 90% of the leaves turn copper red, the green smell gradually disappears, a fresh and strong floral and fruity fragrance is emitted, and the veins and juice of the leaves turn red.

[0055] (11) A two-stage drying method (initial drying and final drying) is adopted, with one cooling in between. The moisture content of the fermented leaves is approximately (50-60)%. To ensure fermentation quality, the initial drying rate is controlled at 3℃ / min, and the inlet temperature of the initial drying is 115℃ to quickly inactivate oxidation. The final drying is at 80℃ with a small air volume for 30 minutes to fully develop aroma. The leaves are cooled for 20 minutes between the initial and final drying, and the final drying adopts a "low-temperature slow drying" method. After the initial drying, the leaves feel slightly prickly to the touch, but are still soft and do not break when folded. The leaves can be easily crumbled when released after being tightly squeezed, and have a mellow aroma. The moisture content of the leaves is approximately 20% before the final drying. After the final drying, the leaves can be easily crushed into powder by hand, with a distinct tea aroma, tightly rolled and dark-colored leaves, and a moisture content of approximately 6%.

[0056] (12) Spread out to cool, sort, select stems, and select carefully.

[0057] (13) The fermented Qingqianliu leaves and Xinyang black tea after the above steps are mixed in a mass ratio of 1:1; the mixed tea is dried at 65°C until the moisture content is 6% and then cooled to obtain the Qingqianliu yellow tea; the cooling process needs to ensure a cooling rate of 5°C / min to prevent the tea from deteriorating due to residual heat.

[0058] Example 1 of effect verification The fermented Eucommia ulmoides leaves obtained in step (12) of Example 1, the Eucommia ulmoides yellow tea obtained in step (13), the unfermented Eucommia ulmoides leaves, and Xinyang black tea were tested using the following methods: 1. Sensory evaluation test: A sensory evaluation team of 7 members (3 men and 4 women) was formed. Members received basic training, understood the basic flavor characteristics of *Eucommia ulmoides* leaves and black tea, and possessed a certain level of sensory sensitivity. They refrained from smoking, eating (except drinking water), and using scented cosmetics for one hour prior to the evaluation. During the evaluation process, a quiet environment was maintained, and evaluations were conducted independently.

[0059] The sensory evaluation was conducted in a quiet, odorless, and evenly lit dedicated sensory evaluation room. All teaware and teacups used were clean, odorless, and warm. Approximately 100g of representative sample was randomly selected from each finished product sample and placed in a teaware container. 150mL of boiling water was poured in, and the timer was immediately started. The tea was steeped for 5 minutes (this time is optimal for the full extraction of active ingredients and flavor), and the tea liquor was immediately strained into a teacup. After smelling the aroma, further evaluation was conducted.

[0060] The evaluation process is as follows: appearance → aroma → liquor color → taste → infused leaves, with a total score of 100 points. The average score of the evaluation results from each evaluator is taken. The sensory evaluation form is shown in Table 1.

[0061] Table 1 2. Total antioxidant capacity of total flavonoids in Eucommia ulmoides leaves (FRAP method) Basic process: Preparation of total flavonoid sample solution from Cyclocarya paliurus leaves: Flavonoids were extracted from Cyclocarya paliurus leaves by ethanol reflux method, and then diluted with anhydrous ethanol to prepare sample solutions of the corresponding concentrations.

[0062] Add FRAP working solution (prepared according to the experimental reagent instructions, with a volume ratio of 1:4) to the total flavonoid sample solution of Eucommia ulmoides leaves, mix and react for 5 min, measure absorbance at 593 nm, and calculate FeSO4 equivalent based on absorbance value and standard curve equation.

[0063] 3. Scavenging rate of total flavonoids from Eucommia ulmoides leaves against DPPH free radicals Basic process: Preparation of total flavonoids from Cyclocarya paliurus leaves: Flavonoids were extracted from Cyclocarya paliurus leaves by ethanol reflux method.

[0064] Experimental sample: The total flavonoids were extracted and diluted with anhydrous ethanol to obtain a sample solution of the corresponding concentration.

[0065] DPPH solution: Purchase DPPH solution and adjust to 0.1 mmol / L DPPH ethanol solution.

[0066] The experimental sample was added to DPPH solution (volume ratio 1:1), and the absorbance at 517 nm was measured as T1.

[0067] The experimental sample was added to anhydrous ethanol (volume ratio 1:1), and the absorbance at 517 nm was measured as T2.

[0068] Anhydrous ethanol was added to DPPH solution (volume ratio 1:1), and the absorbance at 517 nm was measured to be T0.

[0069] The calculation method is as follows: DPPH free radical scavenging rate = 1 - (T1 - T2) / T0 × 100%.

[0070] 4. Test Results: (1) Sensory evaluation results: Table 2 Figure 1 This is a picture of the fermented Eucommia ulmoides leaves prepared in Example 1 of the present invention.

[0071] Figure 2This is a photograph of the Qingqianliu yellow tea prepared in Example 1 of the present invention after being brewed and subjected to sensory evaluation testing.

[0072] Depend on Figure 1 and Figure 2 As can be seen, the fermented Eucommia ulmoides leaves prepared by this invention have intact leaf shape, and the soup is golden yellow after brewing.

[0073] (2) FRAP test results: Table 3 (3) Scavenging rate of total flavonoids from Eucommia ulmoides leaves against DPPH free radicals: Table 4 In summary, the fermented Eucommia ulmoides leaves and Eucommia ulmoides yellow tea provided by this invention meet consumers' demand for health benefits and are in line with the public's acceptance of tea flavors, opening up new avenues for the high-value utilization of Eucommia ulmoides leaves.

[0074] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for fermenting Eucommia ulmoides leaves, characterized in that, Includes the following steps: Withering, kneading, fermentation, and drying; The moisture content of the wilted Cyclocarya paliurus leaves was 58-62 wt%. After kneading, the cell destruction rate of the Cyclocarya paliurus leaves reached over 85%, and the leaf strip formation rate was over 90%. The fermentation degree is 15%-20%. After fermentation, more than 90% of the leaves of *Cyclocarya paliurus* turn copper-red, and the soup is bright yellow. The drying process includes sequential initial drying, cooling, and final drying. The moisture content after initial drying is 20 wt%, and the moisture content after final drying is 6 wt%.

2. The method for fermenting Eucommia ulmoides leaves according to claim 1, characterized in that, During the withering process, the following parameters are controlled: spread the fresh leaves of Eucommia ulmoides evenly with a thickness of 14-20cm; control the withering temperature at 28-32℃; turn the leaves over every 30-60 minutes during the withering process; and wither for 4-5 hours.

3. The method for fermenting Eucommia ulmoides leaves according to claim 2, characterized in that, During the spreading process, tender leaves are spread thinly and old leaves are spread thickly, with the thin spreading thickness being 14-18cm and the thick spreading thickness being 20cm. When the leaves of *Cyclocarya paliurus* are spring leaves, the moisture content of the withered leaves is 58-60 wt%. When the leaves of *Cyclocarya paliurus* are from summer and autumn, the moisture content of the withered leaves is 60-62 wt%.

4. The method for fermenting Eucommia ulmoides leaves according to claim 1, characterized in that, The kneading is carried out at a temperature of 20-24℃ and a humidity of 85-95%. The kneading is carried out in two stages. After the first kneading, the kneaded leaves are put into a de-clumping machine to de-clump and then sieved through a 2-3 mesh screen. The undersize material is used directly for fermentation, and the oversize material is used for fermentation after a second kneading. The first kneading time is 50 minutes, and the second kneading time is 40 minutes.

5. The method for fermenting Eucommia ulmoides leaves according to claim 1, characterized in that, The fermentation is carried out at a temperature of 24-26℃ and a humidity of over 95%; during the fermentation process, the leaf thickness is 15-20cm; and the fermentation time is 3-5 hours.

6. The method for fermenting Eucommia ulmoides leaves according to claim 1, characterized in that, The initial drying temperature is 110-120℃; the final drying temperature is 80℃; and the cooling time is 20 minutes.

7. A fermented *Cyclocarya paliurus* leaf obtained by the fermentation method according to any one of claims 1-6.

8. A type of Qingqianliu yellow tea, characterized in that, The raw materials include the fermented Eucommia ulmoides leaves and black tea as described in claim 7.

9. The Qingqianliu Yellow Tea according to claim 8, characterized in that, The mass ratio of fermented Eucommia ulmoides leaves to black tea is 1:1; and / or, the black tea is Xinyang black tea.

10. A method for preparing Qingqianliu yellow tea according to any one of claims 8-9, characterized in that, The fermented Eucommia ulmoides leaves and black tea are mixed and dried at 60-65℃ until the moisture content is 5-8wt%, and then cooled to obtain the Eucommia ulmoides yellow tea.

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