Preparation method of eucommia strigose hydrangea juvenile tea

Abstract

The invention discloses a preparation method of eucommia strigose hydrangea juvenile tea, which belongs to the technical field of tea leaf processing, and comprises the following steps: picking, spreading, shearing, de-enzyming, winnowing, rolling, gross fire treatment, full fire treatment and cooling. According to the method disclosed by the invention, a hot air-cold air circulation process, a microwave fixation process and a high-temperature-low-temperature drying process are combined, and moisture of key processes is controlled, so that the prepared eucommia strigose hydrangea juvenile tea leaves are free of obvious grass smell, light in smell, sweet and fragrant, and lasting in fragrance; the tea soup is clear in color and free of precipitates; tea soup is fresh and refreshing in taste and obvious in sweetness; the flavor quality is good; according to the process, the utilization rate of eucommia ulmoides and the quality of eucommia ulmoides tea are improved, and the additional value of the eucommia ulmoides industry is favorably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of tea processing, and particularly relates to a preparation method of eucommia sweet tea. Background Art

[0002] Eucommia ulmoides Oliver, a plant belonging to the Eucommia genus of the Eucommiaceae family, is a tree species endemic to my country. It has a long history of medicinal and edible use and is known as "plant gold." Listed as a superior herb in the *Shennong Bencao Jing* (Shennong's Classic of Materia Medica), its bark, leaves, male flowers, and fruits are all rich in natural active ingredients, possessing immense medicinal value and promising prospects for comprehensive utilization and development. Eucommia tea is generally made from Eucommia leaves or male flowers using traditional tea-making techniques. It is a health-promoting tea beverage with a slightly bitter taste followed by a sweet aftertaste, and is believed to have effects such as weight loss, anti-aging, fatigue relief, and metabolism promotion.

[0003] Chinese patent document CN102657274A discloses a method for producing Eucommia ulmoides male flower tea, including the following steps: material selection, withering, fixation, drying, aroma enhancement, and packaging. The fixation process uses a steam-heated fixation machine for 2.5 minutes. However, Eucommia ulmoides tea produced using traditional green tea processing techniques such as drum fixation and steam fixation suffers from problems such as a yellowish-black tea color, cloudy tea liquor, a pronounced grassy aroma, and loss of active ingredients. The long duration and high temperature of drum fixation and steam fixation easily lead to the rapid loss of chlorogenic acid, chlorophyll, amino acids, and flavonoids in Eucommia ulmoides tea, affecting its efficacy and taste.

[0004] Chinese patent document CN107439716A discloses a fixation process for high-quality Eucommia ulmoides compound tea. This process includes a first fixation treatment, a second fixation treatment, and a third fixation treatment. The first fixation treatment is carried out in a steam fixation machine, followed by drying (moisture content not exceeding 15%) and a second microwave fixation treatment. Finally, a soaking-freezing treatment and a third microwave fixation treatment are performed in a microwave processing instrument. On the one hand, this fixation process is complex, targeting a compound tea of ​​Eucommia ulmoides leaves and green tea leaves. On the other hand, the main purpose of fixation is to destroy and deactivate the oxidase activity in the fresh leaves through high temperature, inhibiting the enzymatic oxidation of tea polyphenols and other substances, and evaporating some of the moisture from the fresh leaves. In this invention, the steam fixation process achieves this effect. While the second and third microwave fixation treatments are called fixation, they are actually closer to a drying process.

[0005] The raw materials and processing techniques significantly influence the flavor quality of Eucommia tea. The amino acids in tea are crucial for the freshness and refreshing flavor of the tea. The content of soluble sugars and sweet amino acids is closely related to the sweetness of the tea. Sweetness is a key evaluation factor in tea, balancing bitterness and astringency, enriching the tea's flavor, and enhancing its depth. Therefore, there is a need to develop a method for preparing Eucommia tea that is high in soluble sugars and sweet amino acids, low in green compounds, and bright and transparent. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing Eucommia ulmoides sweet tea. The Eucommia ulmoides sweet tea prepared by this method has no obvious grassy smell, the tea soup is clear and free of sediment, and it has a high content of soluble sugars and sweet amino acids.

[0007] The specific technical solutions adopted are as follows:

[0008] A method for preparing Eucommia ulmoides sweet tea includes the following steps:

[0009] S1 Harvesting: Harvest fresh young leaves or sprouting leaves of Eucommia ulmoides in spring or autumn;

[0010] S2 Spreading: Place the harvested Eucommia ulmoides leaves on a perforated frame and spread them out so that the moisture content of the Eucommia ulmoides leaves reaches 65%-70%;

[0011] S3 Cutting: Wash the spread-out Eucommia ulmoides leaves and cut them into strips;

[0012] S4 Blanching: Use a microwave blanching and drying machine to blanch the Eucommia ulmoides leaves. The microwave power is 6kW, the conveying speed is 350-450r / min, and the blanching time is 60-90s, so that the moisture content of the Eucommia ulmoides leaves reaches 38%-42%.

[0013] S5 air classifier: Air classifier is used to remove impurities;

[0014] S6 Rolling: Using a rolling machine, roll the leaves using a light-heavy-light principle. Lightly roll for 15-20 minutes, heavily roll for 25-30 minutes, lightly roll for 10-15 minutes, and then roll without air for 2-3 minutes to roll the Eucommia leaves into rolls. Using the surface of the tea leaves as a reference, a rolling depth of 1-2 cm is considered light rolling; a rolling depth of 4-6 cm is considered heavy rolling.

[0015] S7 Initial Drying Process: The rolled Eucommia ulmoides leaves are subjected to initial drying in a drying oven to bring the moisture content of the Eucommia ulmoides tea to 25%-30%.

[0016] S8 Full-heat treatment: The Eucommia ulmoides leaves after the initial heat treatment are subjected to full-heat treatment in a drying oven to reduce the moisture content of the Eucommia ulmoides tea to less than 5%.

[0017] S9 Cooling: Close the drying chamber, introduce nitrogen gas into the drying chamber, and allow it to cool naturally to obtain the finished Eucommia sweet tea.

[0018] Preferably, select 4-5 year old Eucommia trees with similar growth. When harvesting, only select Eucommia leaves from the sunny side of the tree. Use a breathable and spacious container such as a bamboo basket to prevent the leaves from being crushed and damaged. Use pruning shears to remove as many petioles as possible. Harvest between 9-10 am and immediately place the harvested leaves in a sealed plastic bag and refrigerate at 4℃.

[0019] The standard for picking Eucommia ulmoides sprouting leaves is that the leaves are 3-5cm long, 1-4cm wide, soft, and light green in color, and one bud and one leaf should be picked at a time; the standard for picking young Eucommia ulmoides leaves is that the leaves are 5-10cm long, 4-6cm wide, relatively hard, and green in color.

[0020] Preferably, the spreading thickness does not exceed 2.5 cm. During the spreading process, the Eucommia ulmoides leaves are subjected to a "hot air-cold air" circulation treatment. Specifically, during the "hot air-cold air" circulation treatment, the hot air temperature is 35℃ and lasts for 10-15 minutes; the cold air temperature is 25℃ and lasts for 45-50 minutes. The circulation is repeated once every hour for a total of 3-6 hours.

[0021] Preferably, in step S4, during the fixation process, a microwave fixation and drying machine is used to fix the Eucommia ulmoides leaves. The Eucommia ulmoides leaves are laid flat on the conveyor belt of the machine, covered with non-woven fabric, the microwave fixation and drying machine is started, the power is adjusted to 6kW, the conveyor belt speed is adjusted to 400r / min, the fixation time is 85 seconds, and the fixed tea leaves are collected.

[0022] Furthermore, the thickness of the Eucommia ulmoides leaf strips laid flat on the machine conveyor belt should not exceed 3.5 cm.

[0023] Preferably, during the initial heat treatment, the temperature is 100-105℃ and the time is 60-75min.

[0024] Preferably, during the heat treatment process, the temperature is 75-85℃ and the time is 90-120 minutes.

[0025] During the cooling process in step S9, nitrogen gas at 20-25°C is introduced into the drying oven.

[0026] The initial drying process involves a temperature of 100-105℃, at which point a large amount of free water in the Eucommia tea evaporates, resulting in significant heat loss. Functional components such as chlorogenic acid remain relatively stable. The final drying process adjusts the temperature to 75-85℃, which dries the bound water in the tea leaves. Temperatures above 85℃ cause slow evaporation of bound water, and excess heat can easily damage components like chlorogenic acid and chlorophyll. Therefore, drying within the 75-85℃ range ensures that the moisture content of the Eucommia tea is less than 5% while avoiding the loss of functional components. Finally, allowing the Eucommia tea to cool naturally in a nitrogen stream at room temperature prevents the water vapor inside the drying chamber from being absorbed by the Eucommia, causing the tea to regain moisture and reducing its flavor.

[0027] Preferably, based on the mass of the Eucommia sweet tea, the soluble sugar content in the Eucommia sweet tea is ≥18.46%, the sweet amino acid content is ≥0.58 mg / g, and the volatile compound content is ≤46.62 μg / kg.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The method of this invention combines a hot-air-cold-air circulating process, a microwave fixation process, and a high-temperature-low-temperature drying process, and controls the moisture content of key processes. Under the hot-air-cold-air circulating environment, the grassy smell of Eucommia ulmoides leaves will rapidly decrease, and the leaves will curl slightly, which is conducive to the formation of sweet aroma substances. In the subsequent microwave fixation process, a low-power, short-time fixation method can be used, which is more conducive to the preservation of functional substances in Eucommia ulmoides leaves. The high-temperature-low-temperature drying not only preserves the functional substances in Eucommia ulmoides tea from damage, but also achieves the effect of enhancing aroma. The tea prepared according to the method of this invention has no obvious grassy smell, has a sweet aroma when lightly smelled and the aroma is long-lasting; the tea soup is clear and bright without sediment; the tea soup is fresh and refreshing on the palate with obvious sweetness; the flavor and quality are excellent; the method of this invention significantly improves the aroma, taste and color of Eucommia ulmoides tea, and increases product quality.

[0030] (2) The process of the present invention improves the utilization rate of Eucommia ulmoides and the quality of Eucommia ulmoides tea, which helps to increase the added value of the Eucommia ulmoides industry. Attached Figure Description

[0031] Figure 1 The graph shows the relative content of soluble sugars in samples S1, S2 and S3. a, b and c indicate significant differences among the samples at the 5% level. Detailed Implementation

[0032] The present invention will be further described below with reference to the following examples and accompanying drawings. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0033] Example 1

[0034] In this embodiment, the preparation method of Eucommia sweet tea includes the following steps:

[0035] Step 1, Harvesting: Harvest fresh Eucommia ulmoides young leaves or sprouting leaves in spring or autumn; the harvesting standards are: sprouting leaves (leaf length 3-5cm, leaf width 1-4cm, soft leaf texture, light green color, one bud and one leaf as the standard when harvesting), young leaves (leaf length 5-10cm, leaf width 4-6cm, relatively hard leaf texture, green color).

[0036] Step 2: Spreading: Place the harvested Eucommia ulmoides leaves on a perforated frame and spread them out (the thickness should not exceed 2.5 cm). During the spreading process, the leaves are subjected to a "hot air-cold air" circulation treatment. The hot air temperature is 35℃ for 10 minutes, and the cold air temperature is 25℃ for 50 minutes. This circulation is repeated once every hour for a total of 6 hours. This process allows water vapor and heat to dissipate from the surface of the Eucommia ulmoides leaves, promotes aroma formation, and ensures that the moisture content of the leaves reaches 65%-70%.

[0037] Step 3, Cutting: Wash the spread-out Eucommia leaves and place them in a leaf cutter to cut them into thin strips (about 0.5cm wide);

[0038] Step 4, Fixation: Use the 6CW-6E microwave tea fixation and drying machine to fix the Eucommia ulmoides leaves. Spread the Eucommia ulmoides leaves flat on the machine's conveyor belt, with a thickness not exceeding 3.5 cm. Cover the Eucommia ulmoides leaves with non-woven fabric. Start the microwave tea fixation and drying machine, adjust the power to 6kW, and adjust the conveyor belt speed to 400r / min. The fixation time is 85 seconds. Use a tray to catch the fixed Eucommia ulmoides leaves at the discharge port of the microwave fixation machine. The moisture content of the Eucommia ulmoides leaves should reach 38%-42%.

[0039] Step 5, Air Separation: Impurities are removed by air separation in an air separator;

[0040] Step Six: Rolling: Use a 6C12-30 rolling machine to roll the leaves. The amount of leaves should be 6-8 kg, and the rolling time should be 60 minutes. A rolling cover compression depth of 1-2 cm is light rolling; a rolling cover compression depth of 4-6 cm is heavy rolling. Use the light-heavy-light principle to roll the leaves. Light rolling for 15 minutes, heavy rolling for 28 minutes, light rolling for 15 minutes, and air rolling for 2 minutes to make the Eucommia leaves roll into uniform rolls.

[0041] Step 7, Initial Drying Treatment: Use a drying oven to perform initial drying treatment on the rolled Eucommia ulmoides leaves. The temperature of the drying oven is 105℃ and the drying time is 75 minutes; so that the moisture content of the Eucommia ulmoides tea reaches 25%-30%.

[0042] Step 8, Final Drying: Use a drying oven to perform final drying on the Eucommia ulmoides leaves after the initial drying. The temperature of the drying oven is 75℃ and the drying time is 100 minutes, so that the moisture content of the Eucommia ulmoides tea is less than 5%.

[0043] Step 9: Cooling: Close the drying oven and introduce room temperature (20-25℃) nitrogen gas into the drying oven to allow the Eucommia tea to cool naturally, thus obtaining the finished Eucommia sweet tea, which is denoted as sample S1.

[0044] Comparative Example 1

[0045] In this comparative example, the preparation method of Eucommia ulmoides sweet tea differs from that of Example 1 in that: natural spreading in step two and drum fixing in step four. Natural spreading means spreading the tea for 6 hours in a well-ventilated environment with a humidity of 55-65% and a temperature of 23-26℃; the drum fixing parameters are 350℃, rotation speed of 20r / min, and time of 180s, to obtain the finished Eucommia ulmoides tea, which is denoted as sample S2.

[0046] Comparative Example 2

[0047] In this comparative example, the preparation method of Eucommia ulmoides sweet tea differs from that of Example 1 in that: natural spreading in step two and steam fixation in step four. Natural spreading means spreading the tea in a well-ventilated environment with a humidity of 55-65% and a temperature of 23-26℃ for 6 hours; steam fixation uses a steam fixation pot at a temperature of 120℃ for 2 minutes to obtain the finished Eucommia ulmoides tea, which is denoted as sample S3.

[0048] Sample Analysis

[0049] (1) Sensory evaluation

[0050] Sensory evaluation was conducted on samples S1, S2, and S3. The sensory evaluation was carried out according to the green tea standard in (GB / T 23776-2018), and the samples were brewed, evaluated, and scored. The results are shown in Table 1.

[0051] Table 1 Sensory evaluation results of samples S1, S2 and S3

[0052]

[0053] The sensory evaluation results of samples S1, S2, and S3 are shown in Table 1. In the taste category, sample S1, prepared in Example 1, scored 98 points, significantly higher than sample S2's 65 points and sample S3's 70 points, with a lead of 50% and 40%, respectively. Considering all five influencing factors, sample S1 scored 97.19 points, significantly higher than sample S2's 76.28 points and sample S3's 80.64 points. Sweetness is one of the important evaluation factors for tea infusion; the results show that sample S1 highlighted the sweet quality characteristics of the tea infusion, while the others were mainly characterized by grassy and bitter tastes.

[0054] The results above show that the Eucommia ulmoides sweet tea prepared by the present invention has the following advantages: Taste: prominent sweet aroma, taste evaluation results improved by 40%-50%; sweet taste value improved by 25%-28%; bitter and astringent taste values ​​decreased by 50%-60%; sweet amino acid content increased by 20%-25%; soluble sugar content increased by up to 49%.

[0055] (2) Electronic tongue detection

[0056] The sensor response values ​​of tea infusions prepared from samples S1, S2, and S3 were collected using an electronic tongue to determine the taste value of the tea infusions. The steps are as follows: Take about 40 mL of the tea infusion preparation solution from the above sensory evaluation process, for a total of 3 portions, and pour them into a special measuring cup. Place the cup on the electronic tongue autosampler. The data acquisition sequence is to alternate between the calibration solution and the tea infusion to be tested. Repeat the measurement 3 times and calculate the average value of the 3 measurements as the raw data of each sensor response value. Then, the taste value is converted to obtain the corresponding taste value. The results are shown in Table 2.

[0057] Table 2 Electronic tongue test results of samples S1, S2 and S3

[0058]

[0059] As shown in the table above, taste analysis using an electronic tongue reveals significant differences in the abundance of sweetness, astringency, bitterness, and aftertaste-astringency in Eucommia tea produced using different processes. The taste values ​​for sourness, saltiness, and aftertaste-bitterness are below the human taste threshold, making the differences imperceptible during consumption. The data indicates that sample S1 has a 28% and 25% higher sweetness value than samples S2 and S3, respectively; bitterness values ​​are reduced by 55% and 54%, respectively; astringency values ​​are reduced by 59% and 60%, respectively; and aftertaste-astringency values ​​are reduced by 50% and 54%, respectively. The reduced bitterness and astringency values ​​further highlight the sweetness of the tea soup.

[0060] (3) Amino acid content test

[0061] The content of soluble amino acids is a key factor in the quality of Eucommia ulmoides tea and an important indicator for evaluating its quality. It is also a significant factor affecting the flavor of the tea infusion. Amino acids can be categorized according to their flavor into flavor-related, fresh, sweet, aromatic, and bitter categories. There is some overlap in the types of amino acids within these categories, which can explain, to some extent, the contribution of amino acids to the flavor of the tea infusion. Therefore, liquid chromatography-mass spectrometry (LC-MS) was used to determine the amino acid composition of three tea samples (S1, S2, and S3), and sweet amino acids were screened out. The results are shown in Table 3.

[0062] Table 3 Relative content of sweet amino acids in samples S1, S2 and S3 (mg / g)

[0063]

[0064] The results are shown in the table above. Serine, glycine, alanine and threonine are sweet amino acids, and their relative content has a significant advantage in sample S1. The total sweet amino acid content of sample S1 is 0.64 mg / g, which is higher than 0.41 mg / g of sample S2 and 0.50 mg / g of sample S3, with an increase of 20%-25%.

[0065] (4) Soluble sugar content test

[0066] Soluble sugars are the most important flavor compounds in tea infusion, dominating its sweetness. The soluble sugar content of samples S1, S2, and S3 was determined using the anthrone colorimetric method, and the results are as follows: Figure 1 As shown in the figure, the soluble sugar content of sample S1 reached 19.62%, significantly higher than the 10.07% and 11.62% of samples S2 and S3, respectively. The process of the present invention can increase the soluble sugar content of Eucommia tea by more than 40%, further highlighting the sweet taste of Eucommia tea.

[0067] (5) Aroma component determination

[0068] Aroma components, a collective term for volatile substances in tea, are one of the most important factors affecting tea quality. In sensory evaluation, aroma contributes 25% to 35% of the overall sensory evaluation. Gas chromatography-mass spectrometry was used to identify the aroma components of samples S1, S2, and S3, and aroma components associated with grassy notes were screened. The results are shown in Table 4.

[0069] Table 4. Relative contents (μg / kg) of volatile compounds in samples S1, S2, and S3

[0070]

[0071] As shown in the table above, the levels of all grassy compounds in Eucommia ulmoides tea S1 were significantly reduced, while the processing method of sample S2 was less effective in removing the grassy odor from Eucommia ulmoides tea. The processing method of Eucommia ulmoides tea S1 significantly reduced the content of compounds with "grassy" characteristics, such as (Z)-3-hexen-1-ol and methyl salicylate, which are present in high concentrations in fresh leaves, by 60% and 50% respectively, with a 100% removal rate of hexanal. Other grassy compounds, such as isoamyl alcohol, heptanal, and linalool oxide, were also removed with a 20%-50% removal rate. This indicates that the process of this invention achieves a 50%-60% removal rate of characteristic grassy substances in fresh leaves, and a 100% removal rate of individual grassy substances, resulting in sample S1 with no obvious grassy odor.

[0072] (6) Tea liquor color detection

[0073] The color difference of three tea samples (S1, S2, and S3) was analyzed using a CM-5 colorimeter (Konica Minolta Holdings, Inc.). The procedure was as follows: 3.0g of tea sample was randomly weighed into a tasting cup → boiling water was poured in and the cup was covered for brewing (5 min) → the tea liquor was filtered out (rapidly cooled to room temperature) → the colorimeter was calibrated → the color difference value was measured. The L* (brightness), a*, and b* values ​​were then recorded. A negative a* value indicates a greenish tint to the tea liquor, while a positive a* value indicates a reddish tint; a higher b* value indicates a yellower tea liquor. The results are shown in Table 5.

[0074] Table 5 shows the L*, a*, and b* values ​​for samples S1, S2, and S3.

[0075]

[0076] According to the data in the table, a higher L* value indicates better and brighter tea liquor. The Eucommia ulmoides tea sample S1 obtained in Example 1 has a higher L* value by 8%-10% compared to samples S2 and S3, which matches the bright liquor characteristic of sample S1 in the evaluation results. Sample S1 has the highest a* value and the lowest b* value compared to S2 and S3, exhibiting a light greenish-yellow color in its tea liquor, appearing transparent and water-like to the naked eye. This demonstrates that the Eucommia ulmoides sweet tea liquor prepared by the process of this invention has a bright, transparent, and clear liquor, resembling water.

[0077] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing Eucommia ulmoides sweet tea, characterized in that: The following steps are involved: S1 picking: picking fresh young leaves or sprouting leaves of Eucommia ulmoides in spring or autumn; S2: Spreading: placing the harvested Eucommia leaves on a hollow rack to make the moisture content of the Eucommia leaves reach 65%-70%; S3 cutting: wash the spread Eucommia leaves and cut them into strips; S4: Use a microwave drying machine to dry the Eucommia ulmoides leaves, with a microwave power of 6kW, a transmission speed of 350-450r / min, and a drying time of 60-90s, so that the moisture content of the Eucommia ulmoides leaves reaches 38%-42%; S5 air separation: air separation and impurity removal in the air separator; S6 rolling: Use the rolling machine to roll the leaves according to the principle of light and heavy. Roll the leaves with light pressure for 15-20 minutes, roll the leaves with heavy pressure for 25-30 minutes, roll the leaves with light pressure for 10-15 minutes, and roll the leaves with air pressure for 2-3 minutes to make the leaves roll. Based on the surface of the tea leaves, the rolling cover should be squeezed to a depth of 1-2 cm for light rolling; the rolling cover should be squeezed to a depth of 4-6 cm for heavy rolling. S7: Rough fire treatment: Use a drying oven to perform rough fire treatment on the rolled Eucommia ulmoides leaves to make the moisture content of Eucommia ulmoides tea reach 25%-30%; S8 Full-fire treatment: Use a drying oven to fully fire the Eucommia ulmoides leaves after rough-fire treatment, so that the moisture content of the Eucommia ulmoides tea is less than 5%; S9 Cooling: Close the drying oven, introduce nitrogen into the drying oven, and allow it to cool naturally to obtain a finished product of Eucommia sweet tea.

2. The method for preparing Eucommia ulmoides sweet tea according to claim 1, characterized in that: The picking standard for the sprouting leaves of Eucommia ulmoides is that the leaf length is 3-5cm, the leaf width is 1-4cm, the leaf texture is soft, the color is light green, and there is one core and one leaf; the picking standard for the young leaves of Eucommia ulmoides is that the leaf length is 5-10cm, the leaf width is 4-6cm, the leaf texture is hard, and the color is green.

3. The method for preparing Eucommia ulmoides sweet tea according to claim 1, characterized in that: The spreading thickness shall not exceed 2.5 cm. During the spreading process, the Eucommia leaves shall be subjected to a "hot air-cold air" circulation treatment.

4. The method for preparing Eucommia sweet tea according to claim 3, characterized in that: During the "hot air-cold air" cycle treatment process, the hot air temperature is 35℃, which lasts for 10-15 minutes; the cold air temperature is 25℃, which lasts for 45-50 minutes. The cycle is repeated once every hour for a total of 3-6 hours.

5. The method for preparing Eucommia sweet tea according to claim 1, characterized in that: During the withering process in step S4, a tea microwave withering dryer is used to wither the Eucommia leaf strips, the Eucommia leaf strips are spread flat on the conveyor belt of the machine, the Eucommia leaf strips are covered with non-woven fabric, the tea microwave withering dryer is started, the power is adjusted to 6 kW, and the conveyor belt transmission speed is adjusted to 400 r / min, the withering time is 85 seconds, and the withered tea leaves are collected.

6. The method for preparing Eucommia sweet tea according to claim 5, characterized in that: The thickness of the Eucommia leaf strips laid flat on the conveyor belt of the machine shall not exceed 3.5 cm.

7. The method for preparing Eucommia ulmoides sweet tea according to claim 1, characterized in that: During the rough fire treatment process, the temperature is 100-105℃ and the time is 60-75min.

8. The method for preparing Eucommia ulmoides sweet tea according to claim 1, characterized in that: During the full fire treatment process, the temperature is 75-85℃ and the time is 90-120min.

9. The method for preparing Eucommia sweet tea according to claim 1, characterized in that: During the cooling process in step S9, nitrogen gas at 20-25° C. is introduced into the drying oven.

10. The method for preparing Eucommia ulmoides sweet tea according to claim 1, characterized in that: Calculated based on the mass of Eucommia sweet tea, the soluble sugar content in Eucommia sweet tea is ≥18.46%, the sweet amino acid content is ≥0.58 mg / g, and the volatile compound content is ≤46.62 μg / kg.

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