Baking method of dark oolong tea

Abstract

The application discloses a baking method of strong-flavor Chunmeng oolong tea, which has the following steps: in the first step, the lychee wood is burned in a smokeless stove, and the hot air and wood aroma required for baking are sent into a chain plate dryer through an air blower; in the second step, tea leaves are continuously put into the chain plate dryer for baking, the thickness of the tea leaves is 3-5 cm, the rotating speed is 70-120 r / min, the temperature of the hot air in the chain plate dryer is 110 DEG C, and the baking time is 6 h; in the third step, the baked tea leaves are sent to a dryer through a conveying belt for cooling, the cool air is sent into the dryer through an air blower, the rotating speed of the air blower is 1000-2500 r / min, and the rotating speed of the dryer is 70-120 r / min; and in the fourth step, the cooled tea leaves are sent into a uniform stacking room for uniform stacking, the temperature of the uniform stacking room is controlled to be 5-24 DEG C, the humidity is controlled to be 70-90%, and the light-proof cooling time is controlled to be 8 h, so that the strong-flavor Chunmeng oolong tea is obtained; and the baking method can further release aroma on the basis of fully exerting the characteristic flavor of Chunmeng oolong tea and forming characteristic baking aroma.

Description

Technical Field

[0001] This invention relates to the field of tea roasting technology, and in particular to a roasting method for a strong-aroma spring oolong tea. Background Technology

[0002] Tea is the world's second most consumed beverage after water. Tea leaves are rich in various secondary metabolites, such as catechins, theanine, caffeine, and aroma compounds, which collectively determine its unique flavor and quality. Although aroma compounds account for only 0.03% of the dry tea, they are a crucial factor in assessing the quality and market value of raw tea. Oolong tea is a unique tea category in my country, originating in Fujian. It possesses a distinctive floral and fruity aroma, making it highly popular among consumers, with aroma accounting for up to 35% of sensory evaluation. The 'Chun Gui' tea tree variety was developed through single-plant breeding from the natural hybrid offspring of 'Huang Yan', resulting in Minnan oolong tea with a natural jasmine fragrance that is rich and long-lasting. With rising living standards, strongly flavored oolong tea is increasingly favored by tea consumers.

[0003] Moreover, the applicant's previous research on the key aroma components that form the characteristic aroma quality of 'Chun Gui' oolong tea found that it has a high enrichment of indole components with a jasmine-like aroma, as well as high content of floral aroma components such as nerolidol and α-farnesene, which together constitute the characteristic aroma quality of Chun Gui oolong tea.

[0004] However, in actual production, due to insufficient mastery of key processing technologies for 'Chun Gui' oolong tea, only a small portion of high-quality 'Chun Gui' oolong tea products exhibit distinct aroma characteristics. Roasting is a crucial step in the production of 'Chun Gui' oolong tea. Therefore, developing a matching roasting method focused on stabilizing the aroma and quality of 'Chun Gui' oolong tea will facilitate its wider promotion and application, improve the quality and efficiency of related 'Chun Gui' oolong tea products, and play a significant role in enhancing the competitiveness of Minnan oolong tea, increasing the income of local tea farmers, and promoting rural revitalization. To meet market needs and promote the application of the Chun Gui tea variety, this project has been developed through active research, improvement, and trial production of roasting methods for Chun Gui oolong tea. Summary of the Invention

[0005] The purpose of this invention is to provide a roasting method for a strong-aroma spring oolong tea. This roasting method can fully bring out the characteristic flavor of spring oolong tea and further release its aroma to form a distinctive roasted aroma.

[0006] To achieve the above objectives, the solution of the present invention is:

[0007] A roasting method for a fragrant spring oolong tea, comprising the following steps:

[0008] The first step is to use lychee wood, place it in a smokeless stove for burning, and send the collected hot air and wood aroma of lychee wood into a chain plate dryer through an exhaust fan.

[0009] The second step involves continuously feeding the Chun Gui Oolong tea leaves from the tea storage hopper into a chain plate dryer for baking. The thickness of the tea leaves is 3-5cm, the rotation speed is 70-120r / min, the hot air temperature inside the chain plate dryer is 110℃, and the baking time is 6 hours.

[0010] The third step involves conveying the roasted tea leaves to a dryer for cooling via a conveyor belt. Cold air is then introduced by a blower with a speed of 1000-2500 r / min and a dryer speed of 70-120 r / min.

[0011] The fourth step involves conveying the cooled tea leaves to a blending room via a conveyor belt. The temperature in the blending room is controlled at 5-24℃ and the humidity at 70-90%. The cooling time in the dark is controlled at 8 hours to obtain a strong-aroma spring oolong tea.

[0012] In the second step, the Chun Gui Oolong tea leaves are refined, granular or curled Chun Gui Oolong tea leaves.

[0013] The standard for picking tea leaves for Chun Gui Oolong tea is to pick the leaves when they are open. Before baking, the tea leaves undergo a low-temperature withering and re-processing treatment. The tea leaves are first treated at a low temperature of 15℃, and then the tea leaves are re-processed. The re-processing involves shaking the tea leaves three times, for 2 minutes, 6 minutes and 10 minutes respectively.

[0014] In the second step, the tea leaves are placed 3cm thick during roasting, and the drying machine rotates at 70 rpm.

[0015] In the third step, the dryer rotates at 70 r / min and the blower rotates at 1000 r / min.

[0016] In the fourth step, the temperature of the uniform stacking room is controlled at 24°C and the humidity is controlled at 70%.

[0017] The tea leaves are conveyed via conveyor belts during the roasting process.

[0018] With the above structure, the roasting method of the strong-aroma Chun Gui Oolong tea of ​​the present invention can fully bring out the characteristic flavor of Chun Gui Oolong tea and the aroma quality characteristics of strong-aroma Oolong tea. The roasting method of the present invention uses a chain plate dryer, and the tea thickness is 3-5cm. The hot air temperature in the chain plate dryer is 110℃, the rotation speed is 70-120r / min, and the roasting time is 6h. The tea leaves flow between different layers of chain plates, and the heating is more uniform, which reduces the moisture content of the Oolong tea, volatilizes some low-boiling-point grassy aroma, enhances the tea aroma, and causes Maillard reaction to form pyrrole and pyrazine roasted aromas. Among them, the most important is that the characteristic aroma component indole is retained to the maximum extent, with the quality characteristics of natural jasmine fragrance, and a large amount of roasted aroma substances of strong-aroma Chun Gui Oolong tea are formed, which can maximize the characteristic aroma quality of Chun Gui Oolong tea. Attached Figure Description

[0019] Figure 1 A comparative chart showing the differences in key aroma components of Chun Gui Oolong tea under different roasting processes. Detailed Implementation

[0020] To further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

[0021] This invention discloses a roasting method for a strong-aroma spring oolong tea, comprising the following steps:

[0022] The first step is to use lychee wood, place it in a smokeless stove for burning, and send the collected hot air and wood aroma of lychee wood into a chain plate dryer through an exhaust fan.

[0023] The second step involves continuously feeding the Chun Gui Oolong tea leaves from the tea storage hopper into a chain plate dryer for baking. The thickness of the tea leaves is 3-5cm, the rotation speed is 70-120r / min, the hot air temperature inside the chain plate dryer is 110℃, and the baking time is 6 hours.

[0024] The third step involves conveying the roasted tea leaves to a dryer for cooling via a conveyor belt. Cold air is then introduced by a blower with a speed of 1000-2500 r / min and a dryer speed of 70-120 r / min.

[0025] The fourth step involves conveying the cooled tea leaves to a blending room via a conveyor belt. The temperature in the blending room is controlled at 5-24℃ and the humidity at 70-90%. The cooling time in the dark is controlled at 8 hours to obtain a strong-aroma spring oolong tea.

[0026] The roasting method of this invention for strong-aroma Chun Gui Oolong tea can fully bring out the unique flavor of Chun Gui Oolong tea and the aroma and quality characteristics of strong-aroma Oolong tea. The roasting method of this invention adopts a chain plate dryer with a tea thickness of 3-5cm. The hot air temperature in the chain plate dryer is 110℃, the rotation speed is 70-120r / min, and the roasting time is 6h. The tea leaves flow between different layers of chain plates, resulting in more uniform heating, which reduces the moisture content of the Oolong tea, volatilizes some low-boiling-point grassy aroma, enhances the tea aroma, and causes Maillard reaction to form pyrrole and pyrazine roasted aromas. Most importantly, the characteristic aroma component indole is retained to the maximum extent, exhibiting the quality characteristics of natural jasmine fragrance, and significantly forming roasted aroma substances of strong-aroma Chun Gui Oolong tea, which can maximize the characteristic aroma quality of Chun Gui Oolong tea. Moreover, the combination of blower and chain plate dryer for cooling can improve the cooling quality and efficiency.

[0027] In the second step of this invention, the Chun Gui Oolong tea leaves are refined, authentic granular or curled Chun Gui Oolong tea.

[0028] The picking standard for Chun Gui Oolong Tea of ​​this invention is open-face picking. Before baking, the tea leaves undergo low-temperature withering and re-processing. The tea leaves are first treated at a low temperature of 15℃, and then re-processed. The re-processing involves shaking the tea leaves three times, for 2 minutes, 6 minutes and 10 minutes respectively.

[0029] In the second step of this invention, the thickness of the tea leaves during roasting is 3 cm, and the rotation speed of the dryer is 70 r / min.

[0030] In the third step of this invention, the dryer rotates at 70 r / min and the blower rotates at 1000 r / min.

[0031] In the fourth step of this invention, the temperature of the uniform stacking room is controlled at 24°C and the humidity is controlled at 70%.

[0032] The tea leaves described in this invention are conveyed via conveyor belts during the roasting process.

[0033] Examples of the roasting method for the strong-aroma spring oolong tea of ​​the present invention

[0034] The first step is to use lychee wood, place it in a smokeless stove for burning, and send the collected hot air and wood aroma of lychee wood into a chain plate dryer through an exhaust fan.

[0035] The second step involves picking Chun Gui Oolong tea leaves according to the standard of "open-face picking". Before baking, the tea leaves undergo a low-temperature withering and re-withering process. The tea leaves are first treated at a low temperature of 15℃, and then the tea leaves are re-withered. The re-withering process involves shaking the tea leaves three times, for 2 minutes, 6 minutes and 10 minutes respectively. Then, the Chun Gui Oolong tea leaves are continuously fed from the tea storage hopper into a chain plate dryer for baking. The tea leaf thickness is 3cm, the rotation speed is 70r / min, the hot air temperature in the chain plate dryer is 110℃, and the baking time is 6 hours.

[0036] The third step involves conveying the roasted tea leaves to a dryer via a conveyor belt for cooling. A blower is used to deliver cold air for cooling, with the blower speed at 1000 r / min and the dryer speed at 70 r / min.

[0037] The fourth step involves conveying the cooled tea leaves to a blending room via a conveyor belt. The temperature in the blending room is controlled at 24°C and the humidity at 70%. The cooling time in the dark is controlled at 8 hours to obtain a strong-aroma spring oolong tea.

[0038] This invention combines a roasting method for the strong-aroma Chun Gui Oolong tea with a low-temperature withering and reprocessing method. The reprocessing method results in superior aroma quality for the Chun Gui Oolong tea, with the jasmine-like fragrance being the most prominent characteristic. Aroma testing results show that the relative content of indole, a characteristic aroma component of the low-temperature withering and reprocessing method, is the highest, reaching 32.15%. In addition, components such as nerolidol, geraniol butyrate, methyl nonyl ketone, ethyl nonanoate, and hexyl hexanoate are also significantly enriched in the low-temperature withering and reprocessing method.

[0039] 1. Aroma detection method for strong-aroma spring oolong tea according to the present invention.

[0040] 1.1 Test Materials

[0041] The fresh leaves of the 'Chun Gui' variety were harvested in the spring of 2023, with the harvest standard being "open-face picking." The raw materials were processed into light-aroma and traditional-style Minnan oolong teas using the Minnan oolong tea processing method. Two roasting methods were compared: low-temperature long-time (110℃, 6h) and high-temperature short-time (118℃, 4h). The low-temperature long-time (110℃, 6h) method yielded the best-aroma Chun Gui oolong tea.

[0042] 1.2 Reagents and Instruments

[0043] Experimental instruments: The main instruments and equipment include an 8890B-7000D gas chromatograph (Agi lent), a DB-5MS column (30m×0.25mm×0.25μm, Agi lent), a 120μm DVB / CWR / PDMS extraction head (Agi lent), and an MS105DU electronic precision balance (Mettler Toledo).

[0044] 1.3 Detection conditions

[0045] The method for determining aroma components in tea samples by combining HS-SPME with GC-TOF-MS is based on previous literature

[13] . Specifically, different treated tea samples are ground into uniform powder, and 0.5g is weighed into a 20mL headspace vial. Aroma substances are extracted using SPME, and data are collected from the extracted substances by GC-TOF-MS. SPME conditions: incubation at 60℃ for 5min, extraction for 15min. Gas chromatography conditions: injection port and ion source temperature is 250℃, transfer line temperature is 280℃, carrier gas is helium with a flow rate of 1.2mL·min-1, and splitless injection. Mass spectrometry conditions: electron impact ion source (EI), ion source temperature is 230℃, quadrupole temperature is 150℃, mass spectrometry interface temperature is 280℃, electron energy is 70eV, scanning mode is full scan mode, and mass scan range is 50-500amu.

[0046] 2. Test Results and Analysis

[0047] In all the processing steps of oolong tea, roasting is the final step and a crucial step in the formation of oolong tea quality. Volatile compounds in oolong tea are not only an important component of tea aroma but also significantly influence its sensory quality. Roasting, as the most important step in refining oolong tea, directly causes physicochemical reactions with these volatile compounds, fundamentally determining the quality of the oolong tea. This project investigated the effect of different roasting levels on the aroma quality of Minnan oolong tea processed from spring-processed tea. Using both lightly roasted and traditionally roasted spring-processed oolong tea as raw materials, the project set up two roasting methods: low-temperature long-time (110℃, 6h) and high-temperature short-time (118℃, 4h). The study showed that roasting weakens the characteristic aroma quality of spring-processed oolong tea while increasing the roasted aroma. In terms of aroma components, the characteristic aroma components of spring oolong tea, such as indole, are significantly reduced, while the roasting aroma components, such as 4,6-dimethyl-undecane, decane, tetradecane, 1-ethylpyrrole, (Z)-2-decenol, 2-butyltetrahydrofuran, and 2-ethyl-5-methylpyrazine, are significantly increased. Overall, the traditional roasting style combined with low-temperature, long-time roasting is more suitable for spring oolong tea.

[0048] From Figure 1 The study shows the differences in key aroma components of Chun Gui Oolong tea under different roasting processes.

[0049] The above embodiments are not intended to limit the product form and style of the present invention. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of the present invention.

Claims

1. A roasting method for a strong-aroma spring oolong tea, characterized in that, It includes the following steps: The first step is to use lychee wood, place it in a smokeless stove for burning, and send the collected hot air and wood aroma of lychee wood into a chain plate dryer through an exhaust fan. The second step involves continuously feeding the Chun Gui Oolong tea leaves from the tea storage hopper into a chain plate dryer for baking. The thickness of the tea leaves is 3-5cm, the rotation speed is 70-120r / min, the hot air temperature inside the chain plate dryer is 110℃, and the baking time is 6 hours. The third step involves conveying the roasted tea leaves to a dryer for cooling via a conveyor belt. Cold air is then introduced by a blower with a speed of 1000-2500 r / min and a dryer speed of 70-120 r / min. The fourth step involves conveying the cooled tea leaves to a blending room via a conveyor belt. The temperature in the blending room is controlled at 5-24℃ and the humidity at 70-90%. The cooling time in the dark is controlled at 8 hours to obtain a strong-aroma spring oolong tea. In the second step, the Chun Gui Oolong tea leaves are refined, authentic granular or curled Chun Gui Oolong tea leaves; the picking standard for Chun Gui Oolong tea leaves is open-face picking. Before baking, the tea leaves undergo low-temperature withering and re-withering treatment. The tea leaves are first treated at a low temperature of 15℃, and then the tea leaves are re-withered. The re-withering process involves shaking the leaves three times, for 2 minutes, 6 minutes and 10 minutes respectively. The hot air temperature inside the chain plate dryer is 110℃, and the baking time is 6 hours. The tea leaves flow between different layers of chain plates, and are heated evenly, which reduces the moisture content of the oolong tea, volatilizes some of the low-boiling-point grassy aroma, enhances the tea aroma, and causes Maillard reaction to form pyrrole and pyrazine roasting aroma.

2. The roasting method for a strong-aroma spring oolong tea as described in claim 1, characterized in that: In the second step, the tea leaves are placed 3cm thick during roasting, and the drying machine rotates at 70 rpm.

3. The roasting method for a strong-aroma spring oolong tea as described in claim 1, characterized in that: In the third step, the dryer rotates at 70 r / min and the blower rotates at 1000 r / min.

4. The roasting method for a strong-aroma spring oolong tea as described in claim 1, characterized in that: In the fourth step, the temperature of the uniform stacking room is controlled at 24°C and the humidity is controlled at 70%.

5. The roasting method for a strong-aroma spring oolong tea as described in claim 1, characterized in that: The tea leaves are conveyed via conveyor belts during the roasting process.

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