Tea special fermentation process based on microbial flora regulation and control

Abstract

The invention discloses a special fermentation process for tea leaves, which comprises the following steps: screening lactic acid bacteria, saccharomycetes and fungi to construct a composite flora, and adjusting the ratio of black tea (2-3): (3-4): (1-2): (2-3): (3-4): (3-4) according to tea types (black tea): (1-2): (3-4): (1-2)). The method comprises the following steps: after fresh leaves are subjected to airing, fixation and rolling pretreatment, spraying a microbial inoculum according to the inoculum size of 5-8%, regulating and controlling the fermentation environment by sections by utilizing an intelligent system: the temperature of black tea is 26-30 DEG C, the temperature of dark tea is 28-35 DEG C, and the temperature of oolong is 22-28 DEG C, dynamically optimizing by combining the humidity of 65-85% and the oxygen concentration, and monitoring target components such as thearubigins, Fuzhuan brick elements and the like in real time through a near infrared spectrum. And stopping fermentation after reaching the standard. According to the process, microbial communities are directionally regulated and controlled, so that the accumulation efficiency of target flavor substances is improved by 30%-60%, the fermentation period is shortened by 20%-30%, the batch quality difference CV value is smaller than 8%, and a standardized scheme is provided for industrial production of black tea, dark green tea and oolong tea.

Description

Technical Field

[0001] This invention belongs to the field of tea processing technology, specifically relating to a fermentation process that achieves the targeted accumulation of tea's distinctive flavor compounds through targeted regulation of microbial flora composition and metabolic activity. This process is suitable for the industrial production of fermented or semi-fermented teas, such as black tea, dark tea, and oolong tea, significantly improving tea quality and stability while imparting unique flavor characteristics. This invention innovatively combines microbiome technology with intelligent control technology to construct a three-level regulatory system: strain screening, flora compounding, and environmental coupling. This provides a systematic solution for the precise control of the tea fermentation process. Background Art

[0002] 1. Limitations of Traditional Tea Fermentation Process

[0003] Tea fermentation is a key process in developing the distinctive qualities of tea. It is essentially a complex biochemical process involving the interaction between microbial communities and the tea matrix. Traditional fermentation techniques (such as black tea piling, dark tea fermentation, and oolong tea greening) primarily rely on natural inoculation or the simple addition of exogenous strains, resulting in the following technical bottlenecks:

[0004] (1) Imbalance in microbial community structure

[0005] During natural fermentation, microbial community succession is influenced by both environmental factors (temperature, humidity, oxygen) and substrate components (tea polyphenols, amino acids, carbohydrates), showing a dynamic growth and decline pattern of "bacteria-fungi-yeast". However, traditional processes lack a means to enrich dominant bacterial communities, resulting in:

[0006] The colonization efficiency of functional bacteria is low: for example, during the flowering process of dark tea, the spore germination rate of Eurotium cristatum is only 30%-40%, and is often inhibited by miscellaneous bacteria (such as Penicillium and Rhizopus);

[0007] Divergence of metabolic pathways: The ratio of tea polyphenol oxidation products (theaflavins, thearubigins, and theabrownins) is unbalanced. The proportion of theabrownins in black tea can easily exceed 30% (high-quality black tea should be less than 20%), resulting in a darker tea soup color and a rough taste.

[0008] (2) Lack of regulation of key enzyme activity

[0009] Polyphenol oxidase (PPO), β-glucosidase, lipoxygenase, etc. secreted by microorganisms are the core enzymes for the formation of flavor substances, but traditional processes cannot accurately regulate the expression of enzymes:

[0010] The peak time of β-glucosidase activity in natural fermentation is unstable (fluctuating between 24 and 48 hours), resulting in a 40% difference in the release of terpene aroma substances (such as linalool and nerol);

[0011] The activity of glutamate decarboxylase (GAD), which is required for lactic acid bacteria to produce GABA, is significantly affected by pH (optimum pH 5.0-5.5). However, the pH monitoring interval in traditional processes is as long as 6 hours, which easily misses the optimal window for enzymatic reaction.

[0012] (3) Standardization challenges in industrialized production

[0013] Statistics from a black tea production company show that the CV value (coefficient of variation) of sensory scores for different batches of products using traditional technology reaches 12%, and thearubigin content fluctuates by ±25%. The main reasons include:

[0014] Temperature and humidity differences in different areas of the fermentation workshop (temperature ± 3°C, humidity ± 10%);

[0015] Manual turning of the compost resulted in poor matrix uniformity (difference in tea polyphenol conversion rate > 15%).

[0016] 2. Deficiencies of Existing Microbial Regulation Technologies

[0017] In recent years, some studies have attempted to improve fermentation efficiency by inoculating a single bacterial species, but they only focused on the saccharification effect of a single bacterial species and ignored the synergistic effects of bacterial communities such as lactic acid bacteria and fungi, resulting in a single flavor level of fermented tea and a lack of the complex aroma of traditional fermented tea.

[0018] Another type of technology regulates microbial growth by controlling environmental parameters (such as temperature and oxygen concentration), but lacks targeted optimization for the specific microbial communities of different tea types. This makes it difficult to achieve precise accumulation of distinctive flavor compounds. For example, during the oolong tea production process, the "micro-damage-enzymatic reaction-microbial relay" mechanism required for edge cell oxidation cannot be achieved through simple temperature control.

[0019] 3. Motivation for the Development of the Invention

[0020] In response to the problems in the existing technology, such as vague microbial community structure, uncontrollable metabolic pathways, and inefficient accumulation of flavor substances, the present invention proposes a fermentation process based on "directional inoculation of composite microbial communities + dynamic regulation of environmental parameters". By analyzing the metabolic network of the core functional microbial communities of different tea types, a microbial preparation with synergistic effects is constructed, and combined with intelligent fermentation equipment, precise regulation of microbial community activity is achieved, thereby significantly improving the fermentation quality of tea, shortening the production cycle, and providing a standardized technical solution for the specialty tea industry. Summary of the Invention

[0021] The technical problem to be solved by the present invention is to provide a tea fermentation process with strong controllability, stable quality and the ability to directional generate characteristic flavor substances. By optimizing the composition of the microbial flora and the fermentation environment parameters, the efficient conversion of substrates such as tea polyphenols and amino acids can be achieved, thereby enhancing the richness and uniqueness of the aroma and taste of tea.

[0022] Specific goals include:

[0023] Increase the production of target flavor substances (such as black tea thearubigins, dark tea fuzhuansu, and oolong tea terpenes) by more than 30%;

[0024] The fermentation cycle is shortened by 20%-30% and energy consumption is reduced by more than 25%;

[0025] The CV values ​​of key physical and chemical indicators of different batches of products are <5%, and the CV values ​​of sensory scores are <8%.

[0026] In order to solve the above problems, the technical solution adopted by the present invention is as follows: a tea-specific fermentation process based on microbial flora regulation, including:

[0027] (1) Construction and optimization of complex microbial flora

[0028] 1. Core strain screening system

[0029] Establish a three-level screening model of "function-oriented-metabolomics-high-throughput sequencing":

[0030] Function-oriented screening: Isolation of target strains using selective media:

[0031] Lactic acid bacteria screening: MRS medium supplemented with 0.1% tea polyphenols was used to screen strains that were resistant to tea polyphenols and had a GABA production capacity of >100 mg / L.

[0032] Fungal screening: PDA medium supplemented with 1% tannic acid was used to screen strains with polyphenol oxidase activity > 20 U / mL;

[0033] Yeast screening: YPD medium was supplemented with 5% glucose, and strains with ester-producing ability (ethyl acetate detected by gas chromatography > 500 μg / L) were screened.

[0034] Metabolomics verification: LC-MS / MS was used to detect flavor precursors in the fermentation broth of the strains, and the strain combination that could significantly increase the content of thearubigins (black tea), fuzhuansu (dark tea), and linalool glycosides (oolong tea) was selected.

[0035] High-throughput sequencing analysis: 16S / ITS sequencing was performed on traditional high-quality fermented tea samples to analyze the symbiotic network of the core flora and determine the optimal ratio of dominant strains (Spearman correlation > 0.8).

[0036] 2. Optimization of the preparation process of composite microbial agents

[0037] Multi-stage expansion culture technology: using gradient amplification culture:

[0038] First-class strain: slant strain (storage period of 3 months at 4°C);

[0039] Secondary strain: 250mL shake flask culture (bacterial concentration reaches 1×10 8 CFU / mL);

[0040] Level 3 culture: culture in 5L fermenter (control the dissolved oxygen content at 20%-30%, pH 6.0-6.5).

[0041] Freeze-drying protection technology: Add protective agent (trehalose 10% + skim milk 5%), the survival rate of the freeze-dried bacteria is greater than 90%, and the number of viable bacteria is greater than 5×10 after 6 months of storage at room temperature. 9 CFU / g.

[0042] 3. Dynamic matching model

[0043] Establish a mathematical model for the ratio of microbial agents based on tea characteristics:

[0044] Y=0.3X1+0.4X2+0.3X3

[0045] Where Y is the predicted value of the target flavor substance, X1 is the proportion of lactic acid bacteria (volume %), X2 is the proportion of yeast, and X3 is the proportion of fungi. The response surface methodology was used to optimize the obtained values:

[0046] Black tea fermentation: X1 = 25%, X2 = 45%, X3 = 30% (maximum thearubigin production);

[0047] Dark tea fermentation: X1 = 15%, X2 = 30%, X3 = 55% (maximum amount of fuzhuansu produced);

[0048] Oolong tea making: X1 = 60%, X2 = 40%, X3 = 0% (optimal release of terpenes).

[0049] (2) Intelligent fermentation environment control system

[0050] 1. Multi-parameter coupling control model

[0051] Construct a four-dimensional control model including temperature (T), humidity (RH), oxygen concentration (O2), and matrix moisture content (MC):

[0052] Where M is the concentration of the target metabolite, and k1-k4 are the influence coefficients of environmental factors (determined by the Plackett-Burman test).

[0053] 2. Optimization of segmented control strategy

[0054]

[0055] 3. Intelligent monitoring and feedback system

[0056] An integrated multi-sensor array (temperature sensor PT100, humidity sensor HMP110, oxygen sensor OX-1) collects data every 2 minutes and inputs it into the PLC control system. A fuzzy PID algorithm is used to dynamically adjust the actuators (heating rod, humidifier, fan) to ensure that the parameter fluctuation range is:

[0057] Temperature ±0.5℃, humidity ±2%, oxygen concentration ±1%.

[0058] (3) Accurate fermentation endpoint determination technology

[0059] Establish a real-time monitoring model based on near-infrared spectroscopy (NIRS):

[0060] Collect tea samples at different fermentation stages and measure indicators such as thearubigins, theaflavins, and amino acids;

[0061] The correlation model between spectral data (900-1700 nm) and physicochemical indicators was established using the partial least squares (PLS) method, with a prediction error of <5%;

[0062] When the concentration of the target ingredient reaches the preset value (such as black tea thearubigins ≥ 12 mg / g), the termination program (microwave sterilization + forced cooling) is automatically triggered.

[0063] The present invention adopts the above structure to achieve the following beneficial effects:

[0064] (1) Significantly improve the quality stability and flavor uniqueness of tea

[0065] 1. Precisely control the accumulation of flavor substances: Through the coordinated regulation of targeted inoculation of composite microflora and environmental parameters, efficient accumulation of tea's characteristic flavor substances is achieved. During the fermentation of black tea, the content of thearubigins is increased by more than 40% compared with traditional processes, and the theaflavins / thearubigins ratio is stabilized in the high-quality range (0.25-0.35). The tea soup presents a bright golden ring, and the freshness of the taste is increased by 25%. During the flowering process of black tea, the content of fuzhuansu increases by 50%, and the coverage rate of the "golden flowers" of Aspergillus niger increases from 50% in the traditional process to more than 80%. At the same time, the gallic acid content is reduced by 25%, significantly improving the bitterness of the tea soup. When making oolong tea green, the total amount of terpene aroma substances (such as linalool and nerol) increases by 60%, forming a unique complex floral fragrance.

[0066] 2. Stable product quality: The intelligent control system achieves precise control of fermentation environment parameters, with temperature fluctuations of ±0.5°C, humidity fluctuations of ±2%, and oxygen concentration fluctuations of ±1%. The coefficient of variation (CV value) of key physical and chemical indicators of different batches of products is less than 5%, and the CV value of sensory scores is less than 8%. Compared with traditional processes, the difference between batches is reduced by more than 60%, effectively solving the problem of unstable quality in industrial production.

[0067] (2) Significantly improve production efficiency and reduce energy consumption

[0068] 1. Shortened Fermentation Cycle: By optimizing bacterial metabolic pathways and environmental conditions, the fermentation cycle has been significantly shortened. The fermentation time for black tea has been shortened from the traditional 36 hours to 20-24 hours, the flowering period for dark tea has been reduced from 72 hours to 48 hours, and the fermentation time for oolong tea has been shortened from 18 hours to 12 hours, increasing production efficiency by over 30%.

[0069] 2. Reduced energy consumption: Precise segmented temperature control and an intelligent ventilation system avoid the energy waste caused by improper temperature and humidity control in traditional processes. For example, using the process of this invention on a production line with an annual output of 500 tons of black tea reduces energy consumption by 30%, saving over 500,000 yuan in electricity costs annually.

[0070] (3) Enhance process universality and economic benefits

[0071] 1. Adaptability to the production of multiple tea types: The dynamic bacterial community ratio model and environmental control strategy established based on the metabolic characteristics of microorganisms of different tea types make this process suitable for a variety of tea types, including black tea, dark tea, and oolong tea. Parameters can also be flexibly adjusted according to the origin and variety of the raw materials. For example, increasing the proportion of lactic acid bacteria in small-leaf black tea can inhibit the production of bitter substances, demonstrating strong process universality.

[0072] 2. Improved Economic Benefits: While reducing production costs, high-quality products can increase market prices. Market research shows that tea produced using this process has an average selling price 20%-30% higher than traditional products. Furthermore, fermented tea residue can be processed into feed additives or organic fertilizer, achieving resource recycling and further increasing corporate profits.

[0073] (4) Promoting green and environmentally friendly production

[0074] This method suppresses bacterial growth through bacterial competition, replacing the use of chemical preservatives in traditional processes. This reduces the chemical oxygen demand (COD) in fermentation wastewater by 40% compared to traditional processes, alleviating wastewater treatment pressure. Furthermore, the shortened fermentation cycle and precise energy control reduce carbon emissions, aligning with the concept of green and sustainable development and contributing to the tea industry's low-carbon transformation. DETAILED DESCRIPTION

[0075] Example 1: Black tea fermentation process regulated by composite microflora

[0076] 1. Raw material preparation

[0077] 1. Fresh leaves: Yunnan large-leaf variety with one bud and two leaves, spread out to dry until the moisture content is 70%;

[0078] 2. Kneading: 55 type kneading machine, 3kg / time, light pressure kneading for 20 minutes, cell disruption rate 65%.

[0079] 2. Preparation of composite bacterial agents

[0080] 1. Strain activation: Lactobacillus plantarum CICC 2335, Saccharomyces cerevisiae AS2.1392, and Aspergillus niger CICC 2169 were inoculated into corresponding liquid culture medium and cultured with shaking at 28°C for 24 hours until the bacterial concentration reached 1×10 8 CFU / mL;

[0081] 2. Compound ratio: lactic acid bacteria: yeast: fungi = 2:3:1 (volume ratio), after mixing, dilute to a total bacterial concentration of 8×10 6 CFU / mL.

[0082] 3. Fermentation process control

[0083] 1. Inoculation: Spray the fungicide at 6% of the weight of the tea leaves, mix well and place on a plate with a thickness of 8cm;

[0084] 2. Temperature and humidity control:

[0085] 0-12h: temperature 28℃, humidity 70%, ventilation volume 0.5m 3 / (m 3 min);

[0086] 12-24h: Temperature 32℃, Humidity 75%, Ventilation 0.2m 3 / (m 3 min);

[0087] 3. Termination conditions: After 24 hours of fermentation, the tea red pigment OD540nm = 0.92, then the fermentation is terminated and microwave sterilization is carried out.

[0088] 4. Quality Analysis

[0089]

[0090] Results: The black tea soup of Example 1 was bright red, with a complex aroma of peach and caramel, a fresh and refreshing taste, and a bitterness significantly lower than that of traditional fermented tea.

[0091] Example 2: Dark Tea (Fuzhuan Tea) Directed Flowering Process

[0092] 1. Raw material preparation

[0093] 1. Dark tea: Grade 3 dark tea, crushed to a particle size of 2-5mm, with a moisture content of 18%;

[0094] 2. Autoclave treatment: Steam for 3 minutes and press into 3kg brick shape with a moisture content of 25%.

[0095] 2. Preparation of composite bacterial agents

[0096] 2. Strain selection: Strengthen the fungal ratio of lactic acid bacteria: yeast: fungi = 1:2:3 (volume ratio), where the fungi include Eurotium cristatum CICC 3125 (a new strain purchased from the Chinese Tea Academy strain bank);

[0097] 3. Bacterial agent concentration: total bacterial concentration 1×10 7 CFU / mL (the proportion of Eurotium cristatum spores is ≥40%).

[0098] 3. Fermentation process control

[0099] 1. Inoculation method: Spray the bacterial agent evenly on the surface of the autoclaved brick, with an inoculation volume of 5 mL per brick;

[0100] 2. Flowering room conditions:

[0101] 0-24h: temperature 30°C, humidity 85%, static anaerobic (oxygen concentration <5%);

[0102] 24-48h: Temperature 35℃, humidity 80%, open micro ventilation (0.1m 3 / (m 3 ·min)) promotes spore development;

[0103] 3. Termination conditions: After 48 hours, the coverage of "golden flowers" on the surface of the brick is ≥80%, and the content of Fuzhuansu is

[0104] 0.65mg / g.

[0105] 4. Quality Analysis

[0106]

[0107]

[0108] Results: The black tea brick "Golden Flower" of Example 2 is full and uniform, with a bright orange-red soup color, a mellow and sweet taste, and a unique fungus and flower fragrance. The gallic acid content is reduced by 25%, and the palatability is significantly improved.

[0109] Example 3: Microbial flora control process during the greening process of Oolong tea (Tieguanyin)

[0110] 1. Raw material preparation

[0111] 1. Fresh leaves: One bud and two leaves of Anxi Tieguanyin, spread out and air-dried for 8 hours until the moisture content reaches 68% and the weight loss rate reaches 12%; 2. Sun-drying: Sun-dry the leaves for 10 minutes, and control the leaf temperature at 28-30℃ to promote enzyme activation.

[0112] 2. Preparation of composite bacterial agents

[0113] 1. Strain combination: Lactobacillus plantarum CICC 2335: Saccharomyces cerevisiae AS2.1392 = 3:1 (volume ratio), bacterial agent concentration 1×10 7 CFU / mL;

[0114] 2. Special treatment: Add 0.05% β-glucosidase (enzyme activity ≥ 100U / mL) to the microbial agent to promote the release of glycoside aroma substances.

[0115] 3. Green process control

[0116] 1. Initial shaking: 30 rpm, 5 minutes, 15% cell damage rate at leaf margin;

[0117] 2. Inoculation: Spray the tea leaves with 5% of the tea weight and let them ferment for 2 hours, maintaining room temperature at 25°C and humidity at 75%.

[0118] 3. Second shaking: rotation speed 40rpm, time 8 minutes, breakage rate 30%, transfer to controlled room for staged fermentation:

[0119] 0-6h: temperature 22℃, humidity 70%, shaking once every hour (3 minutes / time);

[0120] 6-12h: Temperature 25℃, humidity 75%, shake twice per hour (5 minutes / time);

[0121] 4. End point determination: When the linalool content monitored by near-infrared monitoring is ≥50μg / kg, stop shaking and proceed to killing the green leaves (drum killing at 110℃ for 2 minutes).

[0122] 4. Quality Analysis

[0123]

[0124] Results: The aroma of the Tieguanyin dry tea in Example 3 is high and lasting, with a compound aroma of orchid and frankincense, a bright golden soup color, a fresh and sweet taste, and a bitterness that is 30% lower than that of the traditional process.

[0125] Example 4: Directed Fermentation Process of Small-leaf Black Tea (Qimen Black Tea)

[0126] 1. Adjustment of raw material differences

[0127] 1. Fresh leaves: Castanopsis keemunensis leaves with one bud and two leaves, spread out to air-dry until the moisture content is 72% and the cell breakage rate is 60% (the leaves of small-leaf varieties are thinner, so the rolling pressure is reduced by 10%).

[0128] 2. Adjustment of bacterial agent ratio: Increase the proportion of lactic acid bacteria by 10% (25% → 35%) to inhibit the production of bitter substances.

[0129] 2. Fermentation Parameter Optimization

[0130] 1. Sectional temperature control:

[0131] 0-8h: 26°C (promotes early colonization of lactic acid bacteria);

[0132] 8-20h: 28°C (balance of yeast and fungal metabolism);

[0133] 2. Oxygen concentration: 12% in the initial period (0-4h), 8% in the peak period (4-16h), and 5% in the decay period (16-20h).

[0134] 3. Quality Comparison

[0135]

[0136] Results: Example 4 Qihong tea liquor is bright red with a distinct golden ring and a unique "Qimen aroma" (rose + honey aroma). The theaflavins / thearubigins ratio is 0.28, which is in the optimal range for high-quality black tea (0.25-0.35).

[0137] The traditional natural fermentation process was adopted, and other conditions were the same as those in Example 2:

[0138] The flowering period was extended to 96 hours, the "golden flower" coverage rate was only 50%, and it was accompanied by 20% penicillium contamination; the content of tuckahoe brick was 0.35 mg / g, the content of gallic acid was 2.0 mg / g, the soup color was thick red and not bright, and the taste was rough and astringent.

[0139] Key technological innovations

[0140] (1) Analysis of the mechanism of bacterial synergy

[0141] Metagenomic analysis revealed that the composite bacterial consortium of the present invention exhibited significant metabolic pathway complementarity:

[0142] Lactic acid produced by lactic acid bacteria (lowering the environmental pH to 5.0-5.5) can activate the alcohol dehydrogenase of yeast and promote the synthesis of ester substances;

[0143] The cellulase and hemicellulase secreted by the fungi decompose the tea cell walls. The released glucose and amino acids provide carbon and nitrogen sources for lactic acid bacteria and yeast, forming a "substrate-product" cycle.

[0144] 2. The metabolic flow-guiding effect of environmental parameters

[0145] For every 1°C increase in fermentation temperature, thearubigin synthesis rate increases by 5% (peaking at 30°C), but temperatures exceeding 32°C can inactivate lactic acid bacteria. A 10% increase in humidity increases the germination rate of fungal spores by 20%, but excessive humidity (>85%) can easily lead to bacterial growth. The present invention uses a parameter combination determined through orthogonal experiments to increase the target metabolic flux to over 70% of the total metabolic flux.

[0146] (3) Engineering application of intelligent systems

[0147] The process of the present invention is applied to a production line with an annual output of 500 tons of black tea to achieve the following:

[0148] Labor costs are reduced by 40% (manual turning of the compost is eliminated, and temperature control is fully automatic);

[0149] Energy consumption is reduced by 30% (precise temperature control reduces heating time);

[0150] The product qualification rate increased from 85% to 98% (key indicator compliance rate).

[0151] The above description of the present invention and its embodiments is non-limiting. In short, if a person skilled in the art is inspired by the above description and designs an embodiment similar to the technical solution without departing from the purpose of the present invention, it should fall within the scope of protection of the present invention.

Claims

1. A tea-specific fermentation process based on microbial flora regulation, characterized in that: The following steps are involved: (1) screening a composite microbial flora comprising lactic acid bacteria, yeast, and fungi according to the target tea type, wherein the lactic acid bacteria include Lactobacillus plantarum CICC 2335, the yeast include Saccharomyces cerevisiae AS2.1392, and the fungi include Aspergillus niger CICC 2169 and Eurotium cristatum CICC 3125; (2) compounding the composite flora according to a specific volume ratio, wherein the volume ratio is adjusted according to different types of tea: 2-3:3-4:1-2 for black tea fermentation, 1-2:2-3:3-4 for dark tea fermentation, and 3-4:1-2:0 for oolong tea fermentation; (3) After pre-treating the tea leaves, inoculate the composite bacterial agent at 5% to 8% of the weight of the tea leaves; (4) The temperature, humidity, and oxygen concentration of the fermentation environment are regulated in sections through an intelligent control system. The fermentation temperature of black tea is 26-30°C, the blooming temperature of dark tea is 28-35°C, and the fermentation temperature of oolong tea is 22-28°C. (5) Use near-infrared spectroscopy to monitor the concentration of target flavor substances in real time and terminate fermentation when the preset value is reached.

2. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: The preparation of the composite bacterial agent includes the steps of slant culture, activation and expansion culture, and freeze-drying protection. The survival rate of the bacterial agent after freeze-drying is ≥90%, and the number of viable bacteria is ≥5×10 9 CFU / g; wherein the freeze-drying protective agent contains 10% trehalose and 5% skim milk.

3. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: The intelligent control system integrates the temperature and humidity sensor HMP110, the oxygen concentration sensor OX-1 and the PLC control module to achieve precise control of temperature fluctuations of ±0.5°C, humidity fluctuations of ±2%, and oxygen concentration fluctuations of ±1%.

4. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: The tea raw material pretreatment comprises spreading to air until the moisture content is 68%-72%, drum killing (treatment at 120 DEG C for 3 minutes) and rolling (cell breaking rate is 60%-70%).

5. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: The target flavor substances include thearubigins (OD540nm≥0.8) in black tea, fuzhuansu (≥0.5mg / g) in dark tea, and terpenes (linalool≥50μg / kg) in oolong tea. A correlation model between near-infrared spectral data (900-1700nm) and physical and chemical indicators was established using the partial least squares (PLS) method, with a prediction error of less than 5%.

6. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: During the initial fermentation period (0-6h), the temperature is 26±1℃, the humidity is 65%, and the oxygen concentration is 15%; during the peak period (6-18h), the temperature is 28±1℃, the humidity is 70%, and the oxygen concentration is 10%; during the decay period (18-24h), the temperature is 30±1℃, the humidity is 75%, and the oxygen concentration is 5%.

7. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: During the initial fermentation period (0-24h), the temperature is 28±1℃, the humidity is 80%, and the oxygen concentration is 5%; during the peak period (24-48h), the temperature is 32±1℃, the humidity is 85%, and the oxygen concentration is 3%; during the decay period (48-72h), the temperature is 35±1℃, the humidity is 80%, and the oxygen concentration is 1%.

8. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: During the initial stage (0-6h) of making oolong tea, the temperature is 22±1℃, the humidity is 70%, and the shaking frequency is 5 times / h; during the peak stage (6-12h), the temperature is 25±1℃, the humidity is 75%, and the shaking frequency is 8 times / h; during the decay stage (12-18h), the temperature is 28±1℃, the humidity is 80%, and the fermentation is static.

9. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: The screening of the composite bacterial community adopts a three-stage screening model: Function-oriented screening: Isolate target strains using selective culture media; Metabolomics validation: LC-MS / MS was used to detect flavor precursors in the fermentation broth; High-throughput sequencing analysis: 16S / ITS sequencing was performed on traditional high-quality fermented tea samples to determine the dominant strain ratio (Spearman correlation > 0.8).

10. The tea-flavored fermentation process based on microbial flora regulation according to claim 1, characterized in that: The method of inoculating the composite bacterial agent is: diluting the bacterial agent to 8×10 6 -1×10 7 After the inoculation, the tea leaves are evenly sprayed on the surface by spraying, and the thickness of the tea tray after inoculation is controlled as follows: 5-10cm for black tea, 20-30cm for dark tea, and 8-12cm for oolong tea.

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