Preparation process of a light-flavor floating beam black tea

Abstract

The application provides a preparation process of a Qingxiang type floating beam black tea. A multi-strain directional fermentation system composed of Hansenula debayii, Kuraishia sp. and Lactobacillus plantarum and supplemented with trehalose as a synergist is constructed to improve the problems of unstable quality and great flavor randomness of traditional black tea caused by relying on natural microbial flora. In the system, Hansenula debayii dominates the generation of sweet and sweet floral compounds, Kuraishia sp. releases more aroma precursors by secreting extracellular enzymes and improves the thickness of tea soup, and Lactobacillus plantarum inhibits miscellaneous bacteria and optimizes the metabolic environment by producing acid; at the same time, trehalose as a special carbon source ensures the rapid colonization and advantage establishment of the functional flora. The process can finally stably produce Qingxiang type floating beam black tea with high and elegant floral and fruity aroma, fresh and mellow taste, and bright orange-yellow soup color, and provides an effective path for the standardization and modernization upgrade of traditional black tea process.

Description

Technical Field

[0001] This invention belongs to the field of tea processing technology, specifically relating to a preparation process for a light-aroma type of Fuliang black tea. Background Technology

[0002] As one of the most consumed tea categories globally, the core quality of black tea lies in its unique fermentation process. Traditional black tea fermentation relies primarily on the combined action of the tea leaves' own endogenous enzymes and the complex and unstable microbial community naturally occurring in the environment. While this natural fermentation-dominated approach has historically fostered classic styles such as "Qimen aroma," it has revealed significant limitations in modern industrial production. First, the composition of the natural microbial community is easily affected by factors such as the tea garden's ecological environment, seasonal climate, and the hygiene conditions of the production workshop. This leads to significant differences in the fermentation process and metabolic products between different batches and from different origins, resulting in unstable product quality, slightly less uniform flavor, and difficulty in achieving standardized production and solidifying brand styles. Second, the natural fermentation process has low controllability. The degree of fermentation often depends on the tea master's personal experience and judgment, which involves considerable subjectivity and randomness. Insufficient fermentation can result in a lingering astringent taste, while over-fermentation can produce a dull, musty aroma, causing the tea to lose its freshness, vitality, and elegant characteristics. Furthermore, the natural fermentation cycle is usually long and inefficient, and there is a risk of contamination by harmful bacteria, affecting product safety.

[0003] The aforementioned problems severely restrict the further improvement of high-end black tea quality and the sustainable development of the modern tea industry. Therefore, how to achieve precise and targeted control of the black tea fermentation process to stably produce high-quality black tea with specific superior flavors has become a key technical challenge urgently needing to be solved in this field. The industry has attempted to improve fermentation by inoculating functional microorganisms (such as brewer's yeast), but the function of a single strain is limited, often only enhancing one aspect (such as ester production), making it difficult to comprehensively coordinate the formation of aroma, taste, and liquor color. Sometimes, it can even lead to new flavor imbalances due to a single metabolic pathway. This means that developing a multi-strain synergistic fermentation technology that can simulate and optimize the symbiotic relationship of natural microbial communities and achieve functional complementarity, along with corresponding fermentation promotion methods, is of paramount importance for breaking through existing technological bottlenecks and achieving a leap from "naturally formed" to "targeted design" of black tea flavor. This will not only ensure the superior quality and high stability of the product but also serve as a core driving force for upgrading traditional tea-making processes towards intelligence and standardization. Summary of the Invention

[0004] The purpose of this invention is to provide a preparation process for a light-aroma type of Fuliang black tea. By introducing a specific combination of microorganisms and precise process control, the fermentation process can be directionally regulated, thereby stably producing black tea products with a light and elegant aroma and a mellow and refreshing taste.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A preparation process for a light-aroma type of Fuliang black tea includes the following steps:

[0007] (1) Fresh leaf picking

[0008] In spring, fresh leaves of local tea tree varieties in Fuliang, with one bud and one leaf or one bud and two newly unfolded leaves, are harvested as raw materials to ensure the tenderness and uniformity of the raw materials.

[0009] (2) Withering

[0010] The harvested fresh leaves are withered. A withering trough is used, with the air temperature controlled at 30℃ to 35℃, and the withering time at 2 to 4 hours, so that the water loss rate of the fresh leaves reaches 35% to 40%. Withering should continue until the leaves become soft and begin to emit a pleasant aroma.

[0011] (3) Gently knead

[0012] The withered tea leaves are then placed in a rolling machine for rolling. The rolling machine speed is controlled between 50 and 60 revolutions per minute, and pressure is applied in three stages:

[0013] First, adjust the gap between the rolling machine lid and the tea surface to 5 to 8 centimeters. Roll the tea under very light pressure for 10 minutes to initially form strips. Next, lower the lid to maintain a gap of 1 to 3 centimeters and apply medium pressure to roll for 15 to 20 minutes to effectively break down the leaf cell tissue. Finally, raise the lid to restore the gap to 3 to 5 centimeters and continue rolling under light pressure for 5 to 10 minutes to refine the strips, prevent clumping, and reduce breakage. After rolling, immediately break up any clumps and cool the tea to room temperature for later use.

[0014] (1) Preparation of microbial agents

[0015] a. Preparation of high-concentration bacterial suspension:

[0016] Hansenula baryi suspension: Pure Hansenula baryi culture was inoculated into PDA medium (components: potato extract 5.0 g / L, glucose 20.0 g / L, agar 15.0 g / L) and cultured at 28°C to 30°C for 48 to 72 hours. Afterwards, the bacterial colony was scraped off with a sterile inoculation loop and suspended in sterile physiological saline. The cell concentration was precisely adjusted to 1 × 10⁻⁶ cells / mL using a hemocytometer. 8 CFU / mL.

[0017] *Cyclocarya spp.* suspension: Pure *Cyclocarya spp.* culture was inoculated into the above-mentioned PDA medium and cultured at 28°C to 30°C for 48 to 72 hours. The bacterial colony was collected using the same method and suspended in sterile physiological saline, adjusting the concentration to 1×10⁻⁶. 8 CFU / mL.

[0018] Lactobacillus plantarum suspension: Pure Lactobacillus plantarum culture was inoculated into MRS medium (components: peptone 10.0 g / L, beef extract 10.0 g / L, yeast extract 5.0 g / L, glucose 20.0 g / L) and incubated at 37°C for 24 to 48 hours. The bacterial colony was collected and suspended in sterile physiological saline, adjusted to a concentration of 1 × 10⁻⁶. 8 CFU / mL.

[0019] b. Prepare a sugar-containing compound bacterial solution:

[0020] Just before inoculation, the prepared *Hansenula haematobium* suspension, *Diplostomum tumefaciens* suspension, and *Lactobacillus plantarum* suspension were mixed at a volume ratio of 5:2:2. Then, a disaccharide, preferably trehalose, was added to the mixed bacterial solution at 0.5% of the dry weight of the tea leaves to be inoculated, as a synergist. The mixture was gently shaken to fully dissolve the synergist and mix it thoroughly with the bacterial solution, thus obtaining the sugar-containing compound bacterial solution for inoculation.

[0021] (5) Inoculation and fermentation

[0022] The prepared sugar-containing compound bacterial solution is sprayed evenly onto the cooled rolled leaves at a spraying rate of 0.7% to 0.9% (preferably 0.9%) of the dry weight of the rolled leaves, and the bacterial solution is thoroughly stirred to ensure even distribution.

[0023] The inoculated tea leaves are then piled into a 20 cm high fermentation heap, covered with sterilized, breathable fabric (such as linen), and placed in a fermentation chamber for temperature and humidity controlled fermentation. The fermentation process is divided into two stages: for the first 2 hours, the temperature is controlled at 28℃ to 30℃; after 2 hours, the temperature is raised to 32℃ to 34℃. Throughout the fermentation process, the relative humidity must be maintained between 85% and 90%, and the heap is turned every 2 hours to ensure uniform fermentation. The total fermentation time is 4 hours, and fermentation is terminated when the leaves turn copper-red and emit a fresh fruity aroma.

[0024] (6) Drying

[0025] After fermentation is complete, drying is immediately performed to terminate enzyme activity and the fermentation reaction. Drying is carried out in two steps:

[0026] Initial drying (rough drying): Use a high temperature of 110℃ to 120℃ to quickly dry the tea leaves for 10 to 15 minutes until they are about 70% to 80% dry, at which point the moisture content is about 15% to 20%.

[0027] Sufficient drying: After the leaves have cooled slightly, they are placed in a lower temperature range of 85°C to 95°C and slowly dried over a low heat for 15 to 20 minutes, until the moisture content of the tea leaves drops to below 6% and the tea leaves can be easily crushed into powder by hand.

[0028] (7) Refining and Flavoring

[0029] The fully dried tea leaves are sieved, winnowed, and sorted to remove impurities, grade, and standardize specifications. Subsequently, a brief aroma-enhancing treatment can be performed at 60℃ to 70℃ for approximately 20 minutes to further develop and fix the delicate aroma. The final product should be stored in sealed, moisture-proof, light-proof, and low-temperature conditions to maintain its excellent quality over the long term.

[0030] The advantages and beneficial effects of this invention are as follows:

[0031] 1. The core of the light-aroma type Fuliang black tea preparation process of the present invention lies in the introduction of a precision fermentation system composed of Hansenula de Barry yeast, Corydalis cylindrica and Lactobacillus plantarum, supplemented by trehalose as a synergist. The aim is to regulate the fermentation process in a targeted manner and overcome the problems of unstable quality and random flavor caused by the reliance on natural microbial flora in traditional black tea.

[0032] 2. During fermentation, the application of mixed strains creates a highly efficient and stable microbial environment. *Hansøe Baryia* efficiently produces volatile compounds with a sweet, floral aroma, such as phenylethanol and esters, providing a pleasant aroma base for black tea. *Diplostomum tumefaciens* not only metabolizes and produces abundant esters and alcohols, increasing the complexity and layering of the aroma, but more importantly, it typically has a strong ability to secrete extracellular enzymes (such as pectinase and cellulase). These enzymes gently break down the tea cell walls, releasing more sealed aroma precursors, providing richer "raw materials" for overall aroma formation, and also helping to improve the body of the tea liquor. The addition of *Lactobacillus plantarum* metabolizes and produces organic acids such as lactic acid and acetic acid during fermentation. These acidic substances subtly regulate the pH of the fermentation environment, inhibiting the growth of some unwanted bacteria (especially spoilage bacteria) to ensure the safety and purity of the fermentation process. Furthermore, a suitable acidic environment can influence the metabolic pathways of yeast, making it more inclined to produce the desired aroma components rather than fusel alcohols. At the same time, the slightly acidic taste brought by the metabolism of lactic acid bacteria can form a complex and harmonious flavor contrast with the sweet and mellow taste of the oxidation products of tea polyphenols, making the final tea soup taste fresh, refreshing and mellow, avoiding the overly strong and greasy yeast taste that may result from single yeast fermentation.

[0033] 3. Trehalose was chosen as a synergist based on its unique biochemical properties, serving as a high-quality carbon source for specific microorganisms such as *Hansenula polymorpha* and *Lactobacillus plantarum*. Applying it along with the mixed bacterial solution at the initial inoculation stage provides these functional microorganisms with initial fuel, enabling them to rapidly colonize and establish population dominance on the relatively complex substrate of tea. This allows them to dominate from the very beginning of fermentation, effectively crowding out and suppressing randomly introduced microorganisms, significantly improving the controllability and reproducibility of the fermentation process. Furthermore, trehalose may be converted through specific pathways during microbial metabolism, and it or its metabolic intermediates may participate in the aroma component formation network, positively contributing to the shaping of a refined and unique final aroma. This synergistic effect of "microbes-sugar" ensures that the functional microorganisms are vibrant from the outset, achieving "precise start-up" and "efficient advancement" of fermentation.

[0034] 4. In summary, this process constructs a multi-strain synergistic fermentation system with "Hansophila barleyi as the primary aroma producer, Diplostomum tumefaciens as the aroma enhancer and deconstructor, and Lactobacillus plantarum as the steady-state acidifier," and utilizes trehalose to provide exclusive nutritional support for the functional microbial communities, thus forming a highly efficient and targeted biotransformation platform for tea flavor substances. This platform can stably produce innovative Fuliang black tea with a delicate and high-pitched floral and fruity aroma, a fresh and mellow taste, and a bright orange-yellow liquor. It successfully transforms tea fermentation from a process dependent on the natural environment to a controllable and predictable process, improving the consistency and uniqueness of product quality while providing a clear and effective technical path for the modernization and upgrading of traditional black tea processing. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments. *Hansenula haematobium* was purchased from Shanghai Lianmai Biotechnology Co., Ltd., product number ATCC337311; *Cyclocarya paliurus* was purchased from Nuoan Gene Technology (Wuhan) Co., Ltd., strain number D13478; *Lactobacillus plantarum* was purchased from Shandong Qilu Chemical Technology Co., Ltd., product number ATCC. ® 8014 TM *

[0036] The preparation of the bacterial agent suspension is as follows:

[0037] Hansenula baryi suspension: Pure Hansenula baryi culture was inoculated into PDA medium (components: potato extract 5.0 g / L, glucose 20.0 g / L, agar 15.0 g / L) and cultured at 28°C to 30°C for 60 hours. Afterwards, the bacterial colony was scraped off with a sterile inoculation loop and suspended in sterile physiological saline. The cell concentration was precisely adjusted to 1 × 10⁻⁶ cells / mL using a hemocytometer. 8 CFU / mL.

[0038] *Cyclocarya spp.* suspension: Pure *Cyclocarya spp.* culture was inoculated into the above-mentioned PDA medium and cultured at 28°C to 30°C for 60 hours. The bacterial colony was collected using the same method and suspended in sterile physiological saline, adjusting the concentration to 1×10⁻⁶. 8 CFU / mL.

[0039] Lactobacillus plantarum suspension: Pure Lactobacillus plantarum culture was inoculated into MRS medium (components: peptone 10.0 g / L, beef extract 10.0 g / L, yeast extract 5.0 g / L, glucose 20.0 g / L) and incubated at 37°C for 36 hours. The bacterial colony was collected and suspended in sterile physiological saline, and the concentration was adjusted to 1×10⁻⁶. 8 CFU / mL.

[0040] Example 1

[0041] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0042] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0043] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0044] (4) Preparation of microbial agents:

[0045] Take 50 mL of Hansenula baicalensis suspension, 20 mL of Diplostomum tumefaciens suspension, and 20 mL of Lactobacillus plantarum suspension and mix them together. Add 4.5 g of trehalose to the mixed bacterial solution and shake to mix well to obtain a sugar-containing compound bacterial solution.

[0046] (5) Inoculation and Fermentation: Spray the sugar-containing compound bacterial solution evenly onto the cooled and rolled leaves (spraying amount accounts for 0.8% of the dry weight of the tea leaves). Pile the tea leaves into a fermentation pile 20 cm high and cover with sterilized linen. Control the fermentation temperature at 29℃ for the first 2 hours, and then raise the temperature to 33℃; maintain a humidity of 87.5% throughout the process; turn the pile over every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and exude a fresh fruity aroma.

[0047] (6) Drying: Initial drying temperature 115℃, time 12 minutes, until the moisture content is 17.5%; after cooling, final drying temperature 90℃, time 18 minutes, until the moisture content is 5.5%.

[0048] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0049] Example 2

[0050] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0051] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 30℃, and wither for 4 hours.

[0052] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 50 rpm. First, adjust the gap between the lid and the tea leaves to 8 cm and roll for 10 minutes; then adjust the gap to 3 cm and roll for 15 minutes; finally, adjust the gap to 5 cm and roll for 5 minutes. After rolling, immediately break up the clumps and cool to 26°C.

[0053] (4) Preparation of microbial agents:

[0054] Take 50 mL of Hansenula d'Barry yeast suspension, 20 mL of Cladosporium tumefaciens yeast suspension, and 20 mL of Lactobacillus plantarum suspension and mix them together. Add 4 g of trehalose to the mixed bacterial solution and shake to mix well to obtain a sugar-containing compound bacterial solution.

[0055] (5) Inoculation and Fermentation: Spray the sugar-containing compound bacterial solution evenly onto the cooled, rolled leaves at a rate of 0.7% of the dry weight of the tea leaves. Pile the tea leaves into a 20 cm high fermentation pile and cover with sterilized linen. Control the fermentation temperature at 28℃ for the first 2 hours, then raise the temperature to 32℃; maintain a humidity of 90% throughout the process; turn the pile every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and emit a fresh fruity aroma.

[0056] (6) Drying: Initial drying temperature 110℃, time 15 minutes, until the moisture content is 20%; after cooling, final drying temperature 85℃, time 20 minutes, until the moisture content is 5.8%.

[0057] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0058] Example 3

[0059] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0060] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 35℃, and wither for 2 hours.

[0061] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 60 rpm. First, adjust the gap between the lid and the tea leaves to 5 cm and roll for 10 minutes; then adjust the gap to 1 cm and roll for 20 minutes; finally, adjust the gap to 3 cm and roll for 10 minutes. After rolling, immediately break up the clumps and cool to 30°C.

[0062] (4) Preparation of microbial agents:

[0063] Take 50 mL of Hansenula d'Barry yeast suspension, 20 mL of Cladosporium tumefaciens yeast suspension, and 20 mL of Lactobacillus plantarum suspension and mix them together. Add 5 g of trehalose to the mixed bacterial solution and shake to mix well to obtain a sugar-containing compound bacterial solution.

[0064] (5) Inoculation and Fermentation: Spray the sugar-containing compound bacterial solution evenly onto the cooled, rolled leaves at a rate of 0.9% of the dry weight of the tea leaves. Pile the tea leaves into a 20 cm high fermentation pile and cover with sterilized linen. Control the fermentation temperature at 30℃ for the first 2 hours, then raise the temperature to 34℃; maintain a humidity of 85% throughout the process; turn the pile every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and emit a fresh fruity aroma.

[0065] (6) Drying: Initial drying temperature 120℃, time 10 minutes, until moisture content 15%; after cooling, final drying temperature 95℃, time 15 minutes, until moisture content 5.2%.

[0066] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0067] Comparative Example 1

[0068] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0069] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0070] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0071] (4) Fermentation: The cooled rolled leaves are piled into a 20 cm high fermentation pile and covered with sterilized linen. The fermentation temperature is controlled at 29℃ for the first 2 hours, and then the temperature is raised to 33℃; the humidity is 87.5% throughout the process; the pile is turned over once every 2 hours. The total fermentation time is 4 hours, until the leaves turn reddish-brown.

[0072] (5) Drying: The initial drying temperature is 115℃ and the time is 12 minutes, until the moisture content is 17.5%; after cooling, the final drying temperature is 90℃ and the time is 18 minutes, until the moisture content is 5.5%.

[0073] (6) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0074] Comparative Example 2

[0075] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0076] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0077] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0078] (4) Preparation of microbial agents:

[0079] a. Prepare a concentration of 1×10 8 CFU / mL Hansenula de Bary yeast suspension

[0080] b. Take 90 mL of Hansenbali yeast suspension, add 4.5 g of trehalose (equivalent to 0.5% of the dry weight of the rolled leaves) to the bacterial solution, shake and mix well to obtain a sugar-containing bacterial solution.

[0081] (5) Inoculation and Fermentation: Spray the sugar-containing bacterial solution evenly onto the cooled, rolled leaves at a rate of 0.8% of the dry weight of the tea leaves. Pile the tea leaves into a 20 cm high fermentation pile and cover with sterilized linen. Control the fermentation temperature at 29℃ for the first 2 hours, then raise the temperature to 33℃; maintain a humidity of 87.5% throughout the process; turn the pile over every 2 hours. The total fermentation time is 4 hours, until the leaves turn reddish-brown.

[0082] (6) Drying: Initial drying temperature 115℃, time 12 minutes, until moisture content 17.5%; after cooling, final drying temperature 90℃, time 18 minutes, until moisture content 5.5%.

[0083] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0084] Comparative Example 3

[0085] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0086] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0087] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0088] (4) Preparation of microbial agents:

[0089] Mix 50 mL of Hansenula baicalensis suspension and 20 mL of Diplostomum tumefaciens suspension, add 4.5 g of trehalose to the mixed bacterial solution, shake to mix well, and obtain a sugar-containing compound bacterial solution.

[0090] (5) Inoculation and Fermentation: Spray the sugar-containing compound bacterial solution evenly onto the cooled and rolled leaves (spraying amount accounts for 0.8% of the dry weight of the tea leaves). Pile the tea leaves into a fermentation pile 20 cm high and cover with sterilized linen. Control the fermentation temperature at 29℃ for the first 2 hours, and then raise the temperature to 33℃; maintain a humidity of 87.5% throughout the process; turn the pile over every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and exude a fresh fruity aroma.

[0091] (6) Drying: Initial drying temperature 115℃, time 12 minutes, until the moisture content is 17.5%; after cooling, final drying temperature 90℃, time 18 minutes, until the moisture content is 5.5%.

[0092] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0093] Comparative Example 4

[0094] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0095] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0096] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0097] (4) Preparation of microbial agents:

[0098] Mix 20 mL of *Streptomyces cuspidatum* suspension and 20 mL of *Lactobacillus plantarum* suspension, add 4.5 g of trehalose to the mixed bacterial solution, shake to mix well, and obtain a sugar-containing compound bacterial solution.

[0099] (5) Inoculation and Fermentation: Spray the sugar-containing compound bacterial solution evenly onto the cooled and rolled leaves (spraying amount accounts for 0.8% of the dry weight of the tea leaves). Pile the tea leaves into a fermentation pile 20 cm high and cover with sterilized linen. Control the fermentation temperature at 29℃ for the first 2 hours, and then raise the temperature to 33℃; maintain a humidity of 87.5% throughout the process; turn the pile over every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and exude a fresh fruity aroma.

[0100] (6) Drying: Initial drying temperature 115℃, time 12 minutes, until the moisture content is 17.5%; after cooling, final drying temperature 90℃, time 18 minutes, until the moisture content is 5.5%.

[0101] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0102] Comparative Example 5

[0103] (1) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0104] (2) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0105] (3) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0106] (4) Preparation of microbial agents:

[0107] Mix 50 mL of Hansenula d'Bary yeast suspension, 20 mL of Cladosporium tumefaciens suspension, and 20 mL of Lactobacillus plantarum suspension.

[0108] (5) Inoculation and Fermentation: Spray the compound bacterial solution evenly onto the cooled and rolled leaves (spraying amount accounts for 0.8% of the dry weight of the tea leaves). Pile the tea leaves into a fermentation pile 20 cm high and cover with sterilized linen. Control the fermentation temperature at 29℃ for the first 2 hours, and then raise the temperature to 33℃; maintain a humidity of 87.5% throughout the process; turn the pile over every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and exude a fresh fruity aroma.

[0109] (6) Drying: Initial drying temperature 115℃, time 12 minutes, until the moisture content is 17.5%; after cooling, final drying temperature 90℃, time 18 minutes, until the moisture content is 5.5%.

[0110] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0111] Comparative Example 6

[0112] The difference between this comparative example and Example 1 is that trehalose is replaced with sucrose in this comparative example; otherwise, it is the same as Example 1.

[0113] Comparative Example 7

[0114] (7) Fresh leaf picking: Pick 5.0 kg of fresh leaves with one bud and one leaf of local tea tree variety in Fuliang.

[0115] (8) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0116] (9) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0117] (10) Preparation of microbial agents:

[0118] Take 50 mL of Hansenula d'Barry yeast suspension, 20 mL of Cladosporium tumefaciens yeast suspension, and 20 mL of Lactobacillus plantarum suspension and mix them together. Add 8 g of trehalose to the mixed bacterial solution and shake to mix well to obtain a sugar-containing compound bacterial solution.

[0119] (11) Inoculation and Fermentation: Spray the sugar-containing compound bacterial solution evenly onto the cooled and rolled leaves (spraying amount accounts for 0.8% of the dry weight of the tea leaves). Pile the tea leaves into a fermentation pile 20 cm high and cover it with sterilized linen. Control the fermentation temperature at 29℃ for the first 2 hours, and then raise the temperature to 33℃; maintain a humidity of 87.5% throughout the process; turn the pile over every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and exude a fresh fruity aroma.

[0120] (12) Drying: Initial drying temperature 115℃, time 12 minutes, until the moisture content is 17.5%; after cooling, the final drying temperature 90℃, time 18 minutes, until the moisture content is 5.5%.

[0121] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0122] Comparative Example 8

[0123] (13) Fresh leaf picking: Pick 5.0 kg of fresh leaves of one bud and one leaf of local tea tree variety in Fuliang.

[0124] (14) Withering: Place the fresh leaves in the withering trough, control the air temperature to 32.5℃, and wither for 3 hours.

[0125] (15) Light rolling: Put the withered leaves into the rolling machine and set the speed to 55 rpm. First, adjust the gap between the lid and the tea leaves to 6.5 cm and roll for 10 minutes; then adjust the gap to 2.0 cm and roll for 18 minutes; finally, adjust the gap to 4.0 cm and roll for 8 minutes. After rolling, immediately break up the clumps and cool to 28°C.

[0126] (16) Preparation of microbial agents:

[0127] Take 50 mL of Hansenula d'Barry yeast suspension, 20 mL of Cladosporium clavatum suspension, and 20 mL of Lactobacillus plantarum suspension and mix them together. Add 2 g of trehalose to the mixed bacterial solution and shake to mix well to obtain a sugar-containing compound bacterial solution.

[0128] (17) Inoculation and Fermentation: Spray the sugar-containing compound bacterial solution evenly onto the cooled and rolled leaves (spraying amount accounts for 0.8% of the dry weight of the tea leaves). Pile the tea leaves into a fermentation pile 20 cm high and cover with sterilized linen. Control the fermentation temperature at 29℃ for the first 2 hours, and then raise the temperature to 33℃; maintain a humidity of 87.5% throughout the process; turn the pile over every 2 hours. The total fermentation time is 4 hours, until the leaves turn copper-red and exude a fresh fruity aroma.

[0129] (18) Drying: Initial drying temperature 115℃, time 12 minutes, until the moisture content is 17.5%; after cooling, final drying temperature 90℃, time 18 minutes, until the moisture content is 5.5%.

[0130] (7) Refining and aroma enhancement: After refining, the aroma is enhanced at 65℃ for 20 minutes to obtain the finished tea.

[0131] Based on the data results in Tables 1 and 2, the compound microbial agent co-fermentation process used in this embodiment shows significant advantages compared with the comparative examples: it successfully stabilized the TFRB ratio at an excellent level close to or above 1.0 (Examples 1-3: 0.97-1.07), which is much higher than all comparative examples (0.36-0.91). This is because the microenvironment constructed by specific microbial groups and trehalose can precisely regulate the polyphenol oxidation pathway, efficiently promote the generation of theaflavins and thearubigins and effectively inhibit their excessive conversion to theabrownins, thus laying the foundation for the "bright red" color and "strong, fresh and refreshing" taste of the tea soup; at the same time, the amino acid content of the embodiment (3.58%-3.65%) was the highest among all groups, reflecting the unique effect of this process in enhancing the freshness and rich nutritional value of the tea soup.

[0132] Experiment 1: Quality Inspection

[0133] Determination of catechin, amino acid and tea pigment content

[0134] The content of catechin components was determined according to GB / T8313-2018; the content of amino acid components was determined according to GB / T30987-2020.

[0135] The content of tea pigments was determined using a systematic analysis method.

[0136] TF (theaflavins), TR (thearubigins), and TB (theabrownins) were measured according to GB / T13738.2-2017. TFRB is the ratio of the sum of TF (theaflavins) and TR (thearubigins) to TB (theabrownins). All tests were performed in triplicate.

[0137] The results are shown in Table 1 and Table 2 below:

[0138] Table 1

[0139] Group Catechins / % amino acids / % Example 1 2.41 3.65 Example 2 2.36 3.62 Example 3 2.28 3.58 Comparative Example 1 1.57 2.26 Comparative Example 2 1.72 2.57 Comparative Example 3 1.95 2.84 Comparative Example 4 2.06 2.96 Comparative Example 5 2.18 3.29 Comparative Example 6 2.09 3.07 Comparative Example 7 2.34 3.55 Comparative Example 8 2.20 3.39

[0140] Table 2

[0141] Group Theaflavins Thearubigin Tea pigment TFRB Example 1 0.43 5.18 5.85 1.07 Example 2 0.41 5.72 5.98 1.02 Example 3 0.39 5.58 6.15 0.97 Comparative Example 1 0.18 3.25 9.45 0.36 Comparative Example 2 0.28 4.62 7.25 0.68 Comparative Example 3 0.30 4.68 7.12 0.70 Comparative Example 4 0.31 4.86 7.23 0.72 Comparative Example 5 0.31 4.71 6.98 0.72 Comparative Example 6 0.32 4.95 6.88 0.77 Comparative Example 7 0.37 5.35 6.31 0.91 Comparative Example 8 0.35 5.12 6.54 0.84

Claims

1. A preparation process for a light-aroma type of Fuliang black tea, characterized in that, Includes the following steps: Fresh leaf picking: Pick fresh leaves of one bud and one leaf or one bud and two newly unfolded leaves of local tea tree varieties in Fuliang; Withering: The fresh leaves are withered at an air temperature of 30°C to 35°C for 2 to 4 hours, until the water loss rate of the fresh leaves reaches 35% to 40%. Light rolling: Place the withered leaves in a rolling machine and, at a speed of 50 to 60 rpm, perform the following pressure controls in sequence: First, adjust the gap between the rolling machine cover and the tea surface to 5 to 8 cm and roll for 10 minutes; second, adjust the gap to 1 to 3 cm and roll for 15 to 20 minutes; finally, adjust the gap to 3 to 5 cm and roll for 5 to 10 minutes; immediately break up the clumps and cool after rolling to obtain rolled leaves; (4) Preparation of microbial agents: a. Prepare suspensions of *Hansophila d'Barry*, *Cyclophorus spp.*, and *Lactobacillus plantarum*, each with a concentration of 1×10⁻⁶. 8 CFU / mL; b. Before inoculation, the Hansenula d'Barry yeast suspension, the Cladosporium spp. suspension and the Lactobacillus plantarum suspension were mixed in a volume ratio of 5:2:2, and a disaccharide substance equivalent to 0.5% of the dry weight of the tea leaves to be inoculated was added to the mixed bacterial solution and mixed well to obtain a sugar-containing compound bacterial solution. (5) Inoculation and fermentation: The sugar-containing compound bacterial solution is sprayed evenly onto the cooled rolled leaves at a spraying rate of 0.7% to 0.9% of the dry weight of the rolled leaves, and then mixed evenly. The tea leaves are then piled into a fermentation pile with a height of 20 cm, covered with breathable fabric, and fermented in a fermentation room. The fermentation conditions are as follows: the temperature is controlled at 28°C to 30°C for the first 2 hours, and then the temperature is increased to 32°C to 34°C. The relative humidity is maintained at 85% to 90% throughout the process. The pile is turned over once every 2 hours. The total fermentation time is 4 hours. (6) Drying: The fermented tea leaves are dried in two steps: the initial drying temperature is 110℃ to 120℃, the time is 10 minutes to 15 minutes, and the moisture content is 15% to 20%; after cooling, the final drying is carried out at a temperature of 85℃ to 95℃ for 15 minutes to 20 minutes, until the moisture content of the tea leaves drops to below 6%. (7) Refining and aroma enhancement: The fully dried tea leaves are sieved, winnowed and sorted; then the aroma is enhanced at 60℃ to 70℃ for 20 minutes to obtain the light-aroma type Fuliang black tea.

2. The preparation process according to claim 1, characterized in that, The preparation process of the Hansenula baryi yeast suspension in step (4)a is as follows: Hansenula baryi yeast is inoculated into PDA medium and cultured at 28℃ to 30℃ for 48 to 72 hours. After that, the bacterial colony is collected and suspended in sterile physiological saline, and the concentration is adjusted to 1×10⁻⁶. 8 CFU / mL.

3. The preparation process according to claim 1, characterized in that, The preparation process of the *Cyclocarya paliurus* suspension in step (4)a is as follows: *Cyclocarya paliurus* is inoculated into PDA medium and cultured at 28°C to 30°C for 48 to 72 hours. After that, the bacterial colony is collected and suspended in sterile physiological saline, and the concentration is adjusted to 1×10⁻⁶. 8 CFU / mL.

4. The preparation process according to claim 1, characterized in that, The preparation process of the *Lactobacillus plantarum* suspension in step (4)a is as follows: *Lactobacillus plantarum* is inoculated into MRS medium and cultured at 37°C for 24 to 48 hours. After that, the bacterial colony is collected and suspended in sterile physiological saline, and the concentration is adjusted to 1×10⁻⁶. 8 CFU / mL; the MRS medium contains 10.0 g / L peptone, 10.0 g / L beef extract, 5.0 g / L yeast extract and 20.0 g / L glucose.

5. The preparation process according to claim 1, characterized in that, The disaccharide in step (4) is trehalose.

6. The preparation process according to claim 1, characterized in that, The amount of sugar-containing compound bacterial solution sprayed in step (5) is 0.9% of the dry weight percentage of the shredded leaves.