Preparation process of high-quality floating beam green tea

Abstract

The application provides a preparation process of high-quality floating beam green tea. A series of precise control means such as light enzyme cooperation withering, multiple coupling fixation, and vacuum aroma extraction drying are introduced, a breakthrough improvement is made on the basis of the core concept of traditional green tea fixation and enzyme inactivation, and finally a green tea processing system which can be standardized is formed while the quality of tea leaves is greatly improved.

Description

Technical Field

[0001] This invention belongs to the technical field of green tea processing, specifically relating to a preparation process for high-quality Fuliang green tea. Background Technology

[0002] Fuliang green tea, a historically renowned tea, typically follows a basic process of fresh leaf picking, withering, fixation, rolling, and drying. The core process, "fixation," aims to rapidly deactivate endogenous enzymes such as polyphenol oxidase in the fresh leaves using high temperatures, preventing enzymatic oxidation and thus creating the typical quality characteristic of green tea: "clear broth and green leaves." Guided by this traditional concept, the entire green tea processing technology system has long revolved around the core principle of "inhibiting enzyme activity," especially in the processes before fixation, where any operations that could lead to enzymatic oxidation must be strictly avoided.

[0003] However, this inherent technological paradigm largely limits the further improvement of green tea flavor and quality. First, in the crucial "withering" process, existing technologies mainly rely on the natural withering effect of ambient temperature and humidity. This passive and lengthy process aims only to moderately dehydrate and soften the fresh leaves, making it difficult to actively and effectively regulate and enrich aroma and flavor precursors. This results in inherent limitations in the variety and complexity of aromas in the finished tea. Second, to ensure complete enzyme inactivation, traditional fixation methods generally use a single heat source (such as pan-frying or drum firing). This easily leads to uneven heating, resulting in some leaves being under-fixed and developing a raw, astringent taste, or some leaves being overheated and developing a burnt or charred taste. At the same time, high temperatures also easily cause the volatilization and loss of a large number of low-boiling-point aromatic substances, making the tea aroma less pronounced and pure. Finally, in the drying stage, existing technologies mostly focus on rapid dehydration and shaping, often using high temperatures for one-time drying. Although this rough heat treatment method can efficiently remove moisture, it will inevitably exacerbate the transformation and loss of flavor substances in the tea leaves, resulting in a less mellow and full-bodied taste, and may introduce an unpleasant burnt smell.

[0004] As the tea market increasingly demands higher quality, a pressing technical challenge in the field is how to overcome traditional processing limitations and systematically enhance the richness of aroma, the freshness and mellowness of flavor, and reduce bitterness of green tea without altering its fundamental properties. Solving this problem requires a radical overhaul of existing processing concepts and the development of a novel green tea processing technology capable of actively shaping and precisely targeting flavor. This is crucial for propelling historically renowned teas like Fuliang green tea towards high-end status and achieving industrial upgrading. Summary of the Invention

[0005] This invention discloses a preparation process for high-quality Fuliang green tea to solve any of the above-mentioned or potential problems in the prior art. To solve the above-mentioned technical problems, the specific process of this invention is as follows:

[0006] (1) Fresh leaf picking: Pick fresh leaves with one bud and one leaf in the local area of ​​Fuliang that are just beginning to unfold;

[0007] (2) Fresh leaf spreading: The fresh leaves were spread out for 1 hour in an environment with a temperature of 22±1℃, a relative humidity of 65±5% and a slight breeze, with a spreading thickness of 1.5 to 2.0 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then, an enzyme solution equal to 4% of the total weight of fresh leaves was sprayed on the surface, followed by switching to red light with a wavelength of 670 nm at 60 μmol·m⁻¹. -2 ·s -1 Continue withering for another 3 hours until the water loss rate of the fresh leaves reaches 18% to 20%;

[0008] (3) Fixing: The withered leaves that have been laid out are subjected to microwave treatment, high-temperature hot air treatment and medium-temperature far-infrared radiation treatment in sequence.

[0009] (4) Rolling: After cooling the blanched leaves to 25-30℃, put them into a rolling machine for 10 minutes of pressureless rolling; then apply light to medium pressure and control the leaf temperature at 35-38℃ for 15 minutes; finally release all pressure and introduce 4℃ low-temperature cold air, and roll for 8 minutes in a pressureless cooling state to reduce the leaf temperature to below 20℃.

[0010] (5) Two-stage drying: First, dry the rolled leaves in hot air at 75-80℃ for 40 to 45 minutes to reduce the moisture content to 8% to 10%; then transfer them to a vacuum drying equipment and dry them at 50℃ and with an absolute pressure below -0.08MPa for 50 to 60 minutes until the final moisture content of the tea leaves is ≤5%.

[0011] Among them, (2) the enzyme solution in the fresh leaf spreading is obtained by mixing naringinase and tanninase in a mass ratio of 2:1.

[0012] The total concentration of the complex enzyme in the enzyme solution is 0.03-0.06 g / L.

[0013] The specific conditions for the blanching step are as follows: the withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, where they are first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 4 to 6 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 58% to 66%.

[0014] The advantages and beneficial effects of this invention are as follows:

[0015] 1. This invention breaks through traditional processes in green tea processing by employing a series of techniques, including "photo-enzyme synergy" withering, multi-coupling fixation, and vacuum aroma-enhancing drying, achieving a leapfrog improvement in quality. During the withering stage, naringinase and tanninase are introduced into a combined treatment during the window period of blue light preparation and red light maintenance. First, blue light activates metabolism and enhances membrane permeability to prepare high-quality substrates for enzymatic reactions, while red light continuously provides energy to promote the reaction. The two work together to precisely achieve "increased aroma and reduced astringency." Subsequently, a microwave-hot air-far-infrared stepped fixation method is used, with microwaves instantly deactivating enzymes and locking in flavor, and the far-infrared penetration effect ensuring uniform aroma penetration. Finally, a combination of medium-low temperature slow drying for solidification and vacuum low temperature aroma-enhancing drying effectively removes unpleasant odors while maximally preserving high-boiling-point aromatic substances. This systematically creates the unique advantages of this product: a high and pure aroma, a fresh, mellow, and sweet taste, significantly reduced astringency, and stable and excellent quality.

[0016] 2. The core of this process lies in the "fresh leaf spreading" stage. Traditional spreading is a passive dehydration process, while this invention transforms it into an active, targeted flavor-shaping stage by introducing exogenous enzyme treatment for precise intervention during the mid-spreading period. Specifically, we first pre-treat the fresh leaves with blue light of a specific wavelength. Blue light, as an effective physical stimulus, can activate the primary metabolism of tea cells, significantly promoting the accumulation of flavorful substances such as theanine and aromatic precursors, while moderately increasing cell membrane permeability, preparing abundant substrates and opening channels for subsequent enzymatic reactions. At this point, we spray an enzyme solution composed of naringinase and tanninase. Cell activity and membrane permeability are at their optimal levels, ensuring efficient contact between the exogenous enzyme and the endogenous substrate. The reason for choosing these two enzymes is that naringinase can efficiently hydrolyze flavonoid glycosides, represented by naringin, releasing free aglycones, which themselves or their derivatives often have pleasant floral and fruity aromas. It can also effectively degrade some bitter precursors. Tanninase, on the other hand, can specifically hydrolyze ester-type catechins that cause a strong astringency in tea, converting them into simple catechins and gallic acid, thus significantly reducing astringency and increasing the freshness of the tea. Immediately after spraying the enzyme solution, the light is switched to red light. Red light can maintain and optimize cellular metabolic activity, providing a stable energy source for the enzymatic reaction, thus providing a mild catalytic environment for this delicate biotransformation process, thereby promoting the targeted generation and accumulation of flavor compounds.

[0017] 3. A stepped fixation method using a triple coupling of "microwave-hot air-far-infrared" was employed in the fixation stage. This method offers the advantage of achieving rapid, uniform fixation with a high aroma profile. Microwave treatment, as the first step, utilizes its unique volumetric heating effect to instantly raise the temperature of the tea leaves both inside and out. This rapidly and thoroughly deactivates the activity of polyphenol oxidase, perfectly "locking in" the unique flavor profile created during the withering stage, solving the problem of external ripening and internal stunting in traditional fixation. The subsequent high-temperature hot air treatment quickly removes free water from the surface of the tea leaves, completing the initial dehydration. The final medium-temperature far-infrared stage utilizes the strong penetrating power and molecular resonance principle of far-infrared rays to simultaneously heat the internal moisture and organic molecules of the tea leaves, achieving uniform fixation from the inside out. This also effectively stimulates and fixes sweet and chestnut aromas, resulting in a superior aroma profile and higher purity.

[0018] 4. The final drying stage employs a two-stage drying process combining slow, medium-low temperature drying for solidification with low-temperature vacuum drying for aroma enhancement. The first stage, slow drying, provides ample time for the tea leaves to undergo internal transformation at a relatively mild temperature, allowing the Maillard reactions of sugars and amino acids to proceed fully, laying the foundation for the mellow and sweet flavor of the finished tea. The second stage, vacuum drying, takes place under negative pressure, significantly lowering the boiling point of water. This allows for the efficient removal of residual low-boiling-point unpleasant odor molecules (such as grassy or musty smells) from the tea leaves and those adsorbed in the pores at even lower temperatures, while maximizing the preservation of heat-sensitive high-boiling-point aromatic substances. The result is a finished tea with extremely high aroma purity, free of off-odors, and significantly enhanced richness and persistence of aroma.

[0019] 5. In summary, through the series of process improvements mentioned above, this process not only overcomes several technical bottlenecks in traditional green tea processing, but also successfully achieves the superior quality of Fuliang green tea, characterized by its high and rich aroma, fresh and mellow taste, extremely low astringency, and long-lasting aftertaste. It demonstrates significant technological advancement and broad application prospects. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the embodiments. The naringinase is food grade, with an enzyme activity of 10. 5 U / g, purchased from Guangzhou Kejin Biotechnology Co., Ltd., tanninase is food grade, enzyme activity 10. 5 U / g, purchased from Hubei Yihang Biotechnology Co., Ltd.

[0021] Example 1

[0022] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0023] (2) Fresh leaf spreading: Fresh leaves were spread out for 1 hour in an environment with a temperature of 22℃, a relative humidity of 65% and a slight breeze, with a spreading thickness of 1.75 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then 200 g of enzyme solution (the enzyme solution was obtained by mixing naringinase and tanninase at a mass ratio of 2:1, and the total concentration of the complex enzyme in the enzyme solution was 0.045 g / L) was sprayed on the surface, and then switched to red light with a wavelength of 670 nm at 60 μmol·m -2 ·s -1 Continue withering for 3 hours until the water loss rate of fresh leaves reaches 19%.

[0024] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 5 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 62%.

[0025] (4) Kneading: After cooling the blanched leaves to 28°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 36°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead them for 8 minutes in a pressureless cooling state, so that the leaf temperature drops below 20°C.

[0026] (5) Two-stage drying: First, dry the rolled leaves in hot air at 78°C for 43 minutes to reduce the moisture content to 9%; then transfer them to a vacuum drying device and dry them at 50°C and absolute pressure reduced to -0.085MPa for 55 minutes until the final moisture content of the tea leaves is 4.8%.

[0027] Example 2

[0028] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0029] (2) Fresh leaf spreading: The fresh leaves were spread out for 1 hour in an environment with a temperature of 21℃, a relative humidity of 60% and a slight breeze, with a spreading thickness of 1.5 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then 200 g of enzyme solution (the enzyme solution was obtained by mixing naringinase and tanninase at a mass ratio of 2:1, and the total concentration of the complex enzyme in the enzyme solution was 0.03 g / L) was sprayed on the surface, and then switched to red light with a wavelength of 670 nm at 60 μmol·m -2 ·s -1 Continue withering for 3 hours until the water loss rate of fresh leaves reaches 18%.

[0030] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 4 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 58%.

[0031] (4) Kneading: After cooling the blanched leaves to 25°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 35°C for kneading for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, kneading for 8 minutes in a pressureless cooling state to reduce the leaf temperature to below 20°C.

[0032] (5) Two-stage drying: First, dry the kneaded leaves in hot air at 75°C for 45 minutes to reduce the moisture content to 8%; then transfer them to a vacuum drying device and dry them at 50°C and absolute pressure reduced to -0.09MPa for 60 minutes until the final moisture content of the tea leaves is 4.5%.

[0033] Example 3

[0034] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0035] (2) Fresh leaf spreading: The fresh leaves were spread out for 1 hour in an environment with a temperature of 23℃, a relative humidity of 70% and a slight breeze, with a spreading thickness of 2.0 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then 200 g of enzyme solution (the enzyme solution was obtained by mixing naringinase and tanninase at a mass ratio of 2:1, and the total concentration of the complex enzyme in the enzyme solution was 0.06 g / L) was sprayed on the surface, and then switched to red light with a wavelength of 670 nm at 60 μmol·m -2 ·s -1 Continue withering for 3 hours until the fresh leaves lose 20% of their water content.

[0036] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 6 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 66%.

[0037] (4) Kneading: After cooling the blanched leaves to 30°C, put them into a kneading machine for 10 minutes of pressureless kneading; then apply light to medium pressure and control the leaf temperature at 38°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead for 8 minutes in a pressureless cooling state to reduce the leaf temperature to below 20°C.

[0038] (5) Two-stage drying: First, dry the rolled leaves in hot air at 80°C for 40 minutes to reduce the moisture content to 10%; then transfer them to a vacuum drying device and dry them at 50°C and absolute pressure reduced to -0.08MPa for 50 minutes until the final moisture content of the tea leaves is 5.0%.

[0039] Comparative Example 1

[0040] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0041] (2) Fresh leaf spreading: Spread the fresh leaves on a bamboo tray at room temperature (about 25°C) and natural humidity (about 70%), with a thickness of 2.0 cm. Do not expose them to light or treat them with enzymes during this period. Spread them naturally until the water loss rate reaches 20%, with a total time of about 10 hours.

[0042] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 5 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 62%.

[0043] (4) Kneading: After cooling the blanched leaves to 28°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 36°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead them for 8 minutes in a pressureless cooling state, so that the leaf temperature drops below 20°C.

[0044] (5) Two-stage drying: The rolled leaves were first dried in hot air at 78°C for 43 minutes to reduce the moisture content to 9%; then transferred to a vacuum drying device and dried for 55 minutes at 50°C and absolute pressure reduced to -0.085MPa until the final moisture content of the tea leaves was 4.8%. Comparative Example 2

[0045] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0046] (2) Fresh leaf spreading: Fresh leaves were spread out for 1 hour in an environment with a temperature of 22℃, a relative humidity of 65% and a slight breeze, with a spreading thickness of 1.75 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s-1 Irradiation at a high intensity for 4 hours; then directly switched to red light with a wavelength of 670 nm at 60 μmol·m -2 ·s -1 Continue withering for 3 hours until the water loss rate of fresh leaves reaches 19%.

[0047] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 5 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 62%.

[0048] (4) Kneading: After cooling the blanched leaves to 28°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 36°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead them for 8 minutes in a pressureless cooling state, so that the leaf temperature drops below 20°C.

[0049] (5) Two-stage drying: First, dry the rolled leaves in hot air at 78°C for 43 minutes to reduce the moisture content to 9%; then transfer them to a vacuum drying device and dry them at 50°C and absolute pressure reduced to -0.085MPa for 55 minutes until the final moisture content of the tea leaves is 4.8%.

[0050] Comparative Example 3

[0051] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0052] (2) Fresh leaf spreading: Fresh leaves were spread out for 1 hour in an environment with a temperature of 22℃, a relative humidity of 65% and a slight breeze, with a spreading thickness of 1.75 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then 200 g of enzyme solution (the enzyme solution was obtained by mixing naringinase and tanninase at a mass ratio of 1:1, and the total concentration of the complex enzyme in the enzyme solution was 0.045 g / L) was sprayed on the surface, followed by switching to red light with a wavelength of 670 nm at 60 μmol·m -2 ·s -1 Continue withering for 3 hours until the water loss rate of fresh leaves reaches 19%.

[0053] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 5 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 62%.

[0054] (4) Kneading: After cooling the blanched leaves to 28°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 36°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead them for 8 minutes in a pressureless cooling state, so that the leaf temperature drops below 20°C.

[0055] (5) Two-stage drying: First, dry the rolled leaves in hot air at 78°C for 43 minutes to reduce the moisture content to 9%; then transfer them to a vacuum drying device and dry them at 50°C and absolute pressure reduced to -0.085MPa for 55 minutes until the final moisture content of the tea leaves is 4.8%.

[0056] Comparative Example 4

[0057] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0058] (2) Fresh leaf spreading: Fresh leaves were spread out for 1 hour in an environment with a temperature of 22℃, a relative humidity of 65% and a slight breeze, with a spreading thickness of 1.75 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 The surface was irradiated with high intensity for 4 hours; then 200 grams of enzyme solution (the enzyme solution was obtained by mixing naringinase and tanninase at a mass ratio of 1:2, and the total concentration of the complex enzyme in the enzyme solution was 0.045 g / L) was sprayed on it, and then the light was switched to red light with a wavelength of 670 nm at 60 μmol·m -2 ·s -1 Continue withering for 3 hours until the water loss rate of fresh leaves reaches 19%.

[0059] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 5 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 62%.

[0060] (4) Kneading: After cooling the blanched leaves to 28°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 36°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead them for 8 minutes in a pressureless cooling state, so that the leaf temperature drops below 20°C.

[0061] (5) Two-stage drying: First, dry the rolled leaves in hot air at 78°C for 43 minutes to reduce the moisture content to 9%; then transfer them to a vacuum drying device and dry them at 50°C and absolute pressure reduced to -0.085MPa for 55 minutes until the final moisture content of the tea leaves is 4.8%.

[0062] Comparative Example 5

[0063] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0064] (2) Fresh leaf spreading: Fresh leaves were spread out for 1 hour in an environment with a temperature of 22℃, a relative humidity of 65% and a slight breeze, with a spreading thickness of 1.75 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then 200 g of enzyme solution (the enzyme solution was obtained by mixing naringinase and tanninase at a mass ratio of 2:1, and the total concentration of the complex enzyme in the enzyme solution was 0.045 g / L) was sprayed on the surface, and then switched to red light with a wavelength of 670 nm at 60 μmol·m -2 ·s -1 Continue withering for 3 hours until the water loss rate of fresh leaves reaches 19%.

[0065] (3) Blanching: Put all the withered leaves that have been spread out into the drum blanching machine and blanch them at 260℃ for 5 minutes at a time, so that the moisture content of the blanched leaves is reduced to 60%.

[0066] (4) Kneading: After cooling the blanched leaves to 28°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 36°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead them for 8 minutes in a pressureless cooling state, so that the leaf temperature drops below 20°C.

[0067] (5) Two-stage drying: First, dry the rolled leaves in hot air at 78°C for 43 minutes to reduce the moisture content to 9%; then transfer them to a vacuum drying device and dry them at 50°C and absolute pressure reduced to -0.085MPa for 55 minutes until the final moisture content of the tea leaves is 4.8%.

[0068] Comparative Example 6

[0069] (1) Fresh leaf picking: Pick 5.00 kg of fresh leaves with one bud and one leaf in the local area of ​​Fuliang.

[0070] (2) Fresh leaf spreading: Fresh leaves were spread out for 1 hour in an environment with a temperature of 22℃, a relative humidity of 65% and a slight breeze, with a spreading thickness of 1.75 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then 200 g of enzyme solution (the enzyme solution was obtained by mixing naringinase and tanninase at a mass ratio of 2:1, and the total concentration of the complex enzyme in the enzyme solution was 0.045 g / L) was sprayed on the surface, and then switched to red light with a wavelength of 670 nm at 60 μmol·m -2·s -1 Continue withering for 3 hours until the water loss rate of fresh leaves reaches 19%.

[0071] (3) Blanching: The withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 5 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 62%.

[0072] (4) Kneading: After cooling the blanched leaves to 28°C, put them into a kneading machine and knead them for 10 minutes without pressure; then apply light to medium pressure and control the leaf temperature at 36°C for 15 minutes; finally release all pressure and introduce 4°C low-temperature cold air, knead them for 8 minutes in a pressureless cooling state, so that the leaf temperature drops below 20°C.

[0073] (5) Drying: Dry the rolled leaves in a hot air dryer at 100°C for 60 minutes until the final moisture content of the tea leaves is 5%.

[0074] Experiment 1: Quality Inspection

[0075] Sample preparation: Take the dry tea sample (2g±0.01g) prepared in the above examples and comparative examples, take the sample according to the sampling requirements of GB / T8302-2013, grind it and determine the dry matter content (GB / T8303).

[0076] Water extract: Add 2g of ground sample to 200mL of boiling water, reflux for 45min (or 1h), filter, dry the residue to constant weight, and calculate the percentage of water extract.

[0077] Tea polyphenols and catechins: Extracted twice with 70% methanol in a 70°C water bath for 10 min, and the supernatants were combined. Polyphenols: Added Folin-Ciocalteu reagent, incubated at 37°C for 30 min, and the absorbance was measured at 765 nm, calculated according to GB / T8313. Catechins: HPLC-C18 column, gradient mobile phase (methanol / water), detection wavelength 278 nm.

[0078] Soluble sugars: Take 5g of sample, extract with boiling water, add anthrone-sulfuric acid reagent, boil in water for 10min, measure the photometric value at 620nm, and calculate the sugar content according to the standard curve.

[0079] Amino acids: Take 5g of sample, add 2% ninhydrin solution (pH 8.0), boil in water for 15min, cool and make up to volume, and measure the photometric value at 570nm. Calculate the total amino acid content (as theanine or glutamic acid) according to GB / T8314.

[0080] According to the sensory evaluation method for tea (GB / T23776-2018), the proportions of appearance, liquor color, aroma, taste, and infused leaf residue were 20%, 10%, 30%, 35%, and 5%, respectively.

[0081] The results are shown in Tables 1 and 2 below:

[0082] Table 1

[0083]

[0084] Table 2

[0085]

[0086] According to the data in Tables 1 and 2, Examples 1-3 are significantly superior to all comparative examples in all quality indicators. Specifically, they are richer in water extract, tea polyphenols, amino acids, and other internal substances, and their total sensory evaluation score is over 94 points. This is attributed to their "blue light induction-compound enzyme treatment-red light maintenance" withering process, which effectively activates cell metabolism, directionally hydrolyzes bitter substances, and promotes the generation of flavor precursors. In contrast, Comparative Example 1 has the lowest quality due to insufficient component transformation caused by traditional natural withering; Comparative Example 2 has limited effect due to the lack of enzyme treatment; Comparative Examples 3-4 have slightly inferior flavor enhancement effects compared to the examples due to improper enzyme ratios; and Comparative Examples 5-6 suffer from the loss of heat-sensitive flavor substances due to rough fixation or drying processes. In summary, the core advantage of this invention lies in the systematic integration of photoenzyme synergistic withering and step-by-step fixation and drying technologies, which achieves the active shaping and efficient locking of tea flavor substances. Ultimately, while significantly shortening the processing time, it achieves superior quality with high aroma, fresh and mellow taste, low astringency, and rich internal substances.

Claims

1. A preparation process for high-quality Fuliang green tea, characterized in that, The specific preparation process is as follows: (1) Fresh leaf picking: Pick fresh leaves with one bud and one leaf in the local area of ​​Fuliang that are just beginning to unfold; (2) Fresh leaf spreading: The fresh leaves were spread out for 1 hour in an environment with a temperature of 22±1℃, a relative humidity of 65±5% and a slight breeze, with a spreading thickness of 1.5 to 2.0 cm; then blue light with a wavelength of 460 nm was used at 80 μmol·m -2 ·s -1 Irradiated with high intensity for 4 hours; then, an enzyme solution equal to 4% of the total weight of fresh leaves was sprayed on the surface, followed by switching to red light with a wavelength of 670 nm at 60 μmol·m⁻¹. -2 ·s -1 Continue withering for another 3 hours until the water loss rate of the fresh leaves reaches 18% to 20%; (3) Fixing: The withered leaves that have been laid out are subjected to microwave treatment, high-temperature hot air treatment and medium-temperature far-infrared radiation treatment in sequence. (4) Rolling: After cooling the blanched leaves to 25-30℃, put them into a rolling machine for 10 minutes of pressureless rolling; then apply light to medium pressure and control the leaf temperature at 35-38℃ for 15 minutes; finally release all pressure and introduce 4℃ low-temperature cold air, and roll for 8 minutes in a pressureless cooling state to reduce the leaf temperature to below 20℃. (5) Two-stage drying: First, dry the rolled leaves in hot air at 75-80℃ for 40 to 45 minutes to reduce the moisture content to 8% to 10%; then transfer them to a vacuum drying device and dry them at 50℃ and with an absolute pressure below -0.08MPa for 50 to 60 minutes until the final moisture content of the tea leaves is ≤5%. The enzyme solution in the fresh leaf spreading process (2) is obtained by mixing naringinase and tanninase in a mass ratio of 2:

1. The specific conditions for the blanching step are as follows: the withered leaves that have been laid out are first treated in an 800-watt microwave device for 45 seconds; then they are transferred to a hot air-far-infrared composite blanching machine, first treated in pure hot air at 230°C for 90 seconds, and then treated with far-infrared radiation at 170°C with a peak wavelength of 4 to 6 micrometers for 5 minutes, so that the moisture content of the blanched leaves is reduced to 58% to 66%.

2. The preparation process according to claim 1, characterized in that, The total concentration of the complex enzyme in the enzyme solution is 0.03-0.06 g / L.

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