Fermentation microbial agent and fermentation method for red oolong tea
By using a composite bacterial agent of thermophilic Streptococcus, Eurotium cristatum and Pichia pastoris and a three-stage fermentation process, the problems of unstable bacterial flora, enzyme inactivation and unbalanced fermentation in red oolong tea fermentation were solved, and a stable increase in tea polysaccharides and flavor substances was achieved.
Patent Information
- Application Number
- CN202510809960.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-17
- Publication Date
- 2025-09-19
AI Technical Summary
Traditional red oolong tea fermentation relies on natural microorganisms, resulting in poor bacterial flora stability and large batch differences. High-temperature withering causes enzyme inactivation, and single-stage fermentation makes it difficult to coordinate the activity windows of polyphenol oxidase and hydrolase, affecting tea quality and production efficiency.
A composite bacterial agent composed of thermophilic Streptococcus, Eurotium cristatum and Pichia pastoris is used, combined with a three-stage gradient fermentation process, to directionally regulate the activity windows of hydrolases, polyphenol oxidases and esterases, avoiding the addition of exogenous enzymes.
The tea polysaccharide content and flavor stability are significantly improved, and batch stability is improved. The tea polysaccharide content reaches 17.57-18.34%, and the catechin content is 112-115 mg/g, which solves the problems of large batch differences, dependence on exogenous enzymes and single-stage fermentation defects in traditional processes.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of fermentation engineering, in particular to a red oolong tea fermentation agent and a fermentation method. Background Art
[0002] As a representative of semi-fermented tea, red oolong tea is deeply loved by consumers for its unique floral and fruity aroma and mellow taste. The fermentation process of traditional red oolong tea mainly relies on the synergistic effect of natural microbial communities and endogenous enzyme systems of tea leaves. However, due to the complex microbial composition and large fluctuations in environmental conditions, it leads to problems such as unstable product quality, long production cycle, and poor process controllability. In recent years, although some patented technologies have been used to try to optimize the fermentation process, the following problems still exist, which seriously restrict the standardized production and quality improvement of red oolong tea:
[0003] (1) Dependence on environmental microorganisms, poor bacterial flora stability leads to large batch differences. Traditional red oolong tea fermentation mostly adopts natural spreading or stacking fermentation, relying on wild microorganisms in the air (such as molds, yeasts, bacteria, etc.) to participate in polyphenol oxidation, protein degradation and aroma formation. However, the composition of environmental microorganisms is greatly affected by factors such as season, temperature and humidity, and geographical location, resulting in significant differences in the fermentation degree and flavor substance content of different batches of tea. Although the natural fermentation method can form a certain fermentation flavor, due to the lack of targeted regulation of the dominant strains, excessive reproduction of miscellaneous bacteria (such as toxin-producing strains such as Penicillium and Aspergillus) may occur during the fermentation process, which not only affects the safety of the tea, but also causes fluctuations in the content of aroma components between batches. In addition, the startup speed of natural fermentation is slow and the production efficiency is low;
[0004] (2) High-temperature post-withering fermentation causes enzyme inactivation, requiring exogenous addition of cellulase. High-temperature treatment irreversibly destroys endogenous enzymes in tea (such as polyphenol oxidase, β-glucosidase, etc.), resulting in reduced tea polyphenol conversion efficiency and insufficient fermentation flavor. To compensate for the loss of enzyme activity, existing solutions usually require additional addition of exogenous enzyme preparations (such as cellulase, pectinase, etc.), which not only increases production costs but also may introduce the risk of heterologous protein residues.
[0005] (3) Single-stage fermentation makes it difficult to coordinate the activity windows of polyphenol oxidase and hydrolase. The ideal fermentation of red oolong tea requires regulating the activity of different enzyme systems in stages: in the early stage, hydrolases (such as pectinases and proteases) are needed to degrade the cell wall structure and release flavor precursors; in the middle stage, polyphenol oxidase is relied upon to catalyze the oxidative polymerization of tea polyphenols to form theaflavins and thearubigins; and in the later stage, esterification enzymes are needed to promote the synthesis of aroma substances. However, existing technologies mostly use a single temperature condition for the entire fermentation process, which cannot meet the optimal working environment of different enzyme systems.
[0006] Therefore, in view of the limitations of the above existing technologies, how to fundamentally solve the dynamic balance problem among microorganisms, enzymes and substrates, and develop a fermentation technology that can directionally regulate the fermentation microbial community, optimize the enzyme activity window in stages, and avoid exogenous additions has become a difficult problem that the red oolong tea industry urgently needs to break through. Summary of the Invention
[0007] The present invention aims to provide a black oolong tea fermentation inoculum and fermentation method to address the aforementioned problems of the prior art. By targetedly regulating the microbial community and activating enzyme activity in stages, the present invention addresses the issues of large batch variability, reliance on exogenous enzymes, and single-stage fermentation in traditional processes, significantly increasing the content of tea polysaccharides and the stability of flavor compounds.
[0008] To achieve the above object, the present invention provides the following solutions:
[0009] The invention provides a red oolong tea fermentation bacterial agent, which comprises Streptococcus thermophilus, Eurotium cristatum and Pichia kudriavzevii.
[0010] Furthermore, the preparation method includes the following steps: culturing the thermophilic Streptococcus, Eurotium cristatum and Pichia kudrivis in LB liquid culture medium respectively, centrifuging and resuspending to obtain thermophilic Streptococcus agent, Eurotium cristatum agent and Pichia kudrivis agent; mixing the thermophilic Streptococcus agent, Eurotium cristatum agent and Pichia kudrivis agent to obtain a red oolong tea fermentation agent.
[0011] The present invention also provides a red oolong tea fermentation method, comprising the steps of using the red oolong tea fermentation agent to carry out fermentation during the fermentation stage.
[0012] Furthermore, the fermentation is a three-stage fermentation, and the three-stage fermentation includes the following steps:
[0013] The first stage: the inoculation amount of the red oolong tea fermentation agent is 0.3% w / t; the second stage: the inoculation amount of the red oolong tea fermentation agent is 0.5% w / t; the third stage: the inoculation amount of the red oolong tea fermentation agent is 0.2% w / t.
[0014] Furthermore, the fermentation time of the first stage is 2 hours; the fermentation time of the second stage is 1 hour; and the fermentation time of the third stage is 2 hours.
[0015] Furthermore, the temperature and humidity of the first stage fermentation are 27±2°C and 80±5% respectively; the temperature and humidity of the second stage fermentation are 35±2°C and 75±5% respectively; the temperature and humidity of the third stage fermentation are 25±2°C and 90±5% respectively.
[0016] Furthermore, oxygen is supplied throughout the fermentation process.
[0017] The present invention also provides a red oolong tea product prepared by the fermentation method.
[0018] The present invention also provides application of the red oolong tea fermentation agent in fermenting red oolong tea.
[0019] The present invention also provides the use of the red oolong tea fermentation agent in increasing the tea polysaccharide content of the red oolong tea.
[0020] The present invention discloses the following technical effects:
[0021] The present invention uses a composite bacterial agent (Streptococcus thermophilus + Eurotium cristatum + Pichia kudrida) combined with a three-stage gradient fermentation process to directional control the activity windows of hydrolases, polyphenol oxidases, and esterases, eliminating the need for exogenous enzyme addition; the results of the embodiment show that the tea polysaccharide content reaches 17.57-18.34% (the comparative example is only 12.74-14.35%), the catechin content is 112-115 mg / g (the comparative example is 83-94 mg / g), and the batch stability is significantly improved. The present invention solves the problems of large batch differences, dependence on exogenous enzymes, and single-stage fermentation defects in traditional processes by directional control of microbial communities and staged enzyme activity activation, significantly improving the content of tea polysaccharides and the stability of flavor substances. DETAILED DESCRIPTION
[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0023] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.
[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.
[0025] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.
[0026] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.
[0027] The present invention relates to the following strains:
[0028] Streptococcus thermophilus numbered SHBCC D15218 and Eurotium cristatum numbered SHBCC D15081 were purchased from Shanghai Collection Biotechnology Center; Pichia kudriavzevii numbered B94643 was purchased from Ningbo Mingzhou Biotechnology Co., Ltd.
[0029] The present invention relates to a culture medium formula as follows:
[0030] LB liquid medium: 5.0 g of tryptone, 10.0 g of yeast extract, 10.0 g of NaCl, 1000 mL of water, pH 7.2.
[0031] Example 1
[0032] 1. Preparation of black oolong tea fermentation agent
[0033] 100 μL of each bacterial suspension of Streptococcus thermophilus, Eurotium cristatum and Pichia kudridae were taken in sterile LB liquid medium, cultured at 60 ° C and 210 rpm for 24 h, centrifuged at 8000 rpm for 10 min, discarded the supernatant and collected the precipitate, washed 3 times with sterile PBS, and resuspended with 10 mL of sterile water to obtain Streptococcus thermophilus, Eurotium cristatum and Pichia kudridae inoculum. The OD of each inoculum was 0.05. 600 The values are all between 1.60-1.80.
[0034] Thermococcus, Eurotium cristatum and Pichia kudridae bacteria were mixed in LB liquid medium (equal volumes of Streptococcus, Eurotium cristatum and Pichia kudridae bacteria were added) to obtain red oolong tea fermentation bacteria. The number of viable bacteria in the red oolong tea fermentation bacteria could reach 8.5×10 9 cfu / mL.
[0035] The red oolong tea fermentation agent was inoculated into 10 mL of sterile LB liquid medium, and the shaking culture conditions were 60 ° C and 180 rpm. The culture was carried out for about 24 hours until the bacterial OD 600 The culture solution of each bacterial agent was centrifuged at 4°C and 10,000 rpm for 10 minutes, and resuspended in 10 mL of sterile water to obtain the composite bacterial agent seed solution for use.
[0036] 2. A fermentation method for red oolong tea
[0037] (1) Fresh leaves are picked when the new shoots are close to maturity and the terminal buds form stationary buds, and two leaves are picked;
[0038] (2) Withering: The fresh leaves collected are placed in a comprehensive tea-making machine. A bucket of fresh tea leaves weighs 300 kilograms. The leaves are continuously withered in the comprehensive tea-making machine by means of hot air from charcoal fire. The temperature is controlled within 35°C to make the fresh tea leaves evenly watered. When the moisture content reaches about 70%, the leaves are semi-soft, the base of the tea leaves is held in the hand, the front two leaves are drooping, the gloss of the leaves disappears, and the surface of the tea leaves is wrinkled, it is considered moderate.
[0039] (3) Shaking: The leaves after withering are shaken with a comprehensive green tea making machine for 6 rounds, with a total shaking time of 6 hours. In the early stage, the shaking time is short and light, and the shaking time is gradually prolonged in the middle and late stages. The standing time after each round of green tea making is gradually prolonged, and the changes in the fresh tea leaves are observed; rolling: The leaves after shaking are rolled with a 60-type black tea rolling machine until the leaves are rolled into strips; the rolling duration is 40 minutes; when rolling in the 60-type black tea rolling machine, a large amount of debris adheres to the rolling trough, and after being unloaded from the machine, it is mixed with the rolled leaves, and a dense sieve is required to remove the broken pieces; the dense sieve uses a 10-mesh screen to remove the broken pieces;
[0040] (4) Fermentation: The rolled leaves are placed in a fermentation chamber and fermented in three stages:
[0041] In the first stage, the fermentation was carried out at a temperature of 27° C. for 2 hours. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 was inoculated at an inoculation rate of 0.3% w / t. The relative humidity in the fermentation room was 80%, and sufficient oxygen was supplied.
[0042] In the second stage, the fermentation temperature was 35° C. for 1 hour. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 was inoculated at an inoculum amount of 0.5% w / wt. The relative humidity in the fermentation room was 75%, and sufficient oxygen was supplied.
[0043] The third stage is fermented at a temperature of 25° C. for 2 hours. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 is inoculated at an inoculation amount of 0.2% w / t. The relative humidity in the fermentation room is 90%, and sufficient oxygen is supplied.
[0044] (5) Fixing: After fermentation, the leaves are fixed with an oolong tea fixing machine. The pot temperature is controlled at 200℃ and the fixing time is 7 minutes. The best fixed leaves are those that can be easily loosened without forming a clumping mass and without water overflowing from the fingers.
[0045] (6) Drying: After the fixing process, the leaves are dried in a dryer in two steps. The first step is to control the temperature at 90°C for 30 minutes until the leaves are 50% dry and then stand for 1 hour. The second step is to control the temperature at 90°C for 1.5 hours until the leaves are 70% dry and then stand for 1 hour for cooling and bagging to obtain the prepared red oolong tea.
[0046] Example 2
[0047] 1. Preparation of black oolong tea fermentation agent
[0048] 100 μL of each bacterial suspension of Streptococcus thermophilus, Eurotium cristatum and Pichia kudridae were taken in sterile LB liquid medium, cultured at 60 ° C and 210 rpm for 24 h, centrifuged at 8000 rpm for 10 min, discarded the supernatant and collected the precipitate, washed 3 times with sterile PBS, and resuspended with 10 mL of sterile water to obtain Streptococcus thermophilus, Eurotium cristatum and Pichia kudridae inoculum. The OD of each inoculum was 0.05. 600 The values are all between 1.60-1.80.
[0049] Thermococcus, Eurotium cristatum and Pichia kudridae bacteria were mixed in LB liquid medium (equal volumes of Streptococcus, Eurotium cristatum and Pichia kudridae bacteria were added) to obtain red oolong tea fermentation bacteria. The number of viable bacteria in the red oolong tea fermentation bacteria could reach 7.5×10 9 cfu / mL.
[0050] The red oolong tea fermentation agent was inoculated into 10 mL of sterile LB liquid medium, and the shaking culture conditions were 60 ° C and 180 rpm. The culture was carried out for about 24 hours until the bacterial OD 600 The culture solution of each bacterial agent was centrifuged at 4°C and 10,000 rpm for 10 minutes, and resuspended in 10 mL of sterile water to obtain the composite bacterial agent seed solution for use.
[0051] 2. A fermentation method for red oolong tea
[0052] (1) Fresh leaves are picked when the new shoots are close to maturity and the terminal buds form stationary buds, and two leaves are picked;
[0053] (2) Withering: The fresh leaves collected are placed in a comprehensive tea-making machine. A bucket of fresh tea leaves weighs 300 kilograms. The leaves are continuously withered in the comprehensive tea-making machine by means of hot air from charcoal fire. The temperature is controlled within 35°C to make the fresh tea leaves evenly watered. When the moisture content reaches about 70%, the leaves are semi-soft, the base of the tea leaves is held in the hand, the front two leaves are drooping, the gloss of the leaves disappears, and the surface of the tea leaves is wrinkled, it is considered moderate.
[0054] (3) Shaking: The leaves after withering are shaken with a comprehensive green tea making machine for 6 rounds, with a total shaking time of 6 hours. In the early stage, the shaking time is short and light, and the shaking time is gradually prolonged in the middle and late stages. The standing time after each round of green tea making is gradually prolonged, and the changes in the fresh tea leaves are observed; rolling: The leaves after shaking are rolled with a 60-type black tea rolling machine until the leaves are rolled into strips; the rolling duration is 40 minutes; when rolling in the 60-type black tea rolling machine, a large amount of debris adheres to the rolling trough, and after being unloaded from the machine, it is mixed with the rolled leaves, and a dense sieve is required to remove the broken pieces; the dense sieve uses a 10-mesh screen to remove the broken pieces;
[0055] (4) Fermentation: The rolled leaves are placed in a fermentation chamber and fermented in three stages:
[0056] In the first stage, the fermentation was carried out at a temperature of 25° C. for 2 hours. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 was inoculated at an inoculation rate of 0.3% w / t. The relative humidity in the fermentation room was 75%, and sufficient oxygen was supplied.
[0057] In the second stage, the fermentation temperature was 33° C. for 1 hour. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 was inoculated at an inoculation rate of 0.5% w / t. The relative humidity in the fermentation room was 70%, and sufficient oxygen was supplied.
[0058] The third stage is fermented at a temperature of 23° C. for 2 hours. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 is inoculated at an inoculation amount of 0.2% w / t. The relative humidity in the fermentation room is 86%, and sufficient oxygen is supplied.
[0059] (5) Fixing: After fermentation, the leaves are fixed with an oolong tea fixing machine. The pot temperature is controlled at 200℃ and the fixing time is 7 minutes. The best fixed leaves are those that can be easily loosened without forming a clumping mass and without water overflowing from the fingers.
[0060] (6) Drying: After the fixing process, the leaves are dried in a dryer in two steps. The first step is to control the temperature at 90°C for 30 minutes until the leaves are 50% dry and then stand for 1 hour. The second step is to control the temperature at 90°C for 1.5 hours until the leaves are 70% dry and then stand for 1 hour for cooling and bagging to obtain the prepared red oolong tea.
[0061] Example 3
[0062] 1. Preparation of black oolong tea fermentation agent
[0063] 100 μL of each bacterial suspension of Streptococcus thermophilus, Eurotium cristatum and Pichia kudridae were taken in sterile LB liquid medium, cultured at 60 ° C and 210 rpm for 24 h, centrifuged at 8000 rpm for 10 min, discarded the supernatant and collected the precipitate, washed 3 times with sterile PBS, and resuspended with 10 mL of sterile water to obtain Streptococcus thermophilus, Eurotium cristatum and Pichia kudridae inoculum. The OD of each inoculum was 0.05. 600 The values are all between 1.60-1.80.
[0064] Thermococcus, Eurotium cristatum and Pichia kudridae bacteria were mixed in LB liquid medium (equal volumes of Streptococcus, Eurotium cristatum and Pichia kudridae bacteria were added) to obtain red oolong tea fermentation bacteria. The number of viable bacteria in the red oolong tea fermentation bacteria could reach 8×10 9 cfu / mL.
[0065] The red oolong tea fermentation agent was inoculated into 10 mL of sterile LB liquid medium, and the shaking culture conditions were 60 ° C and 180 rpm. The culture was carried out for about 24 hours until the bacterial OD 600 The culture solution of each bacterial agent was centrifuged at 4°C and 10,000 rpm for 10 minutes, and resuspended in 10 mL of sterile water to obtain the composite bacterial agent seed solution for use.
[0066] 2. A fermentation method for red oolong tea
[0067] (1) Fresh leaves are picked when the new shoots are close to maturity and the terminal buds form stationary buds, and two leaves are picked;
[0068] (2) Withering: The fresh leaves collected are placed in a comprehensive tea-making machine. A bucket of fresh tea leaves weighs 300 kilograms. The leaves are continuously withered in the comprehensive tea-making machine by means of hot air from charcoal fire. The temperature is controlled within 35°C to make the fresh tea leaves evenly watered. When the moisture content reaches about 70%, the leaves are semi-soft, the base of the tea leaves is held in the hand, the front two leaves are drooping, the gloss of the leaves disappears, and the surface of the tea leaves is wrinkled, it is considered moderate.
[0069] (3) Shaking: The leaves after withering are shaken with a comprehensive green tea making machine for 6 rounds, with a total shaking time of 6 hours. In the early stage, the shaking time is short and light, and the shaking time is gradually prolonged in the middle and late stages. The standing time after each round of green tea making is gradually prolonged, and the changes in the fresh tea leaves are observed; rolling: The leaves after shaking are rolled with a 60-type black tea rolling machine until the leaves are rolled into strips; the rolling duration is 40 minutes; when rolling in the 60-type black tea rolling machine, a large amount of debris adheres to the rolling trough, and after being unloaded from the machine, it is mixed with the rolled leaves, and a dense sieve is required to remove the broken pieces; the dense sieve uses a 10-mesh screen to remove the broken pieces;
[0070] (4) Fermentation: The rolled leaves are placed in a fermentation chamber and fermented in three stages:
[0071] In the first stage, the fermentation was carried out at a temperature of 26° C. for 2 hours. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 was inoculated at an inoculation rate of 0.3% w / t. The relative humidity in the fermentation room was 80%, and sufficient oxygen was supplied.
[0072] In the second stage, the fermentation temperature was 33° C. for 1 hour. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 was inoculated at an inoculation rate of 0.5% w / t. The relative humidity in the fermentation room was 75%, and sufficient oxygen was supplied.
[0073] The third stage is fermented at a temperature of 24° C. for 2 hours. During the fermentation, the seed solution of the composite bacterial agent prepared in step 1 is inoculated at an inoculation amount of 0.2% w / t. The relative humidity in the fermentation room is 90%, and sufficient oxygen is supplied.
[0074] (5) Fixing: After fermentation, the leaves are fixed with an oolong tea fixing machine. The pot temperature is controlled at 200℃ and the fixing time is 7 minutes. The best fixed leaves are those that can be easily loosened without forming a clumping mass and without water overflowing from the fingers.
[0075] (6) Drying: After the fixing process, the leaves are dried in a dryer in two steps. The first step is to control the temperature at 90°C for 30 minutes until the leaves are 50% dry and then stand for 1 hour. The second step is to control the temperature at 90°C for 1.5 hours until the leaves are 70% dry and then stand for 1 hour for cooling and bagging to obtain the prepared red oolong tea.
[0076] Comparative Example 1
[0077] The difference between this comparative example and Example 1 is that in "Step 1, Preparation of Red Oolong Tea Fermentation Inoculum", Eurotium cristatum is omitted. The remaining steps are the same as in Example 1.
[0078] Comparative Example 2
[0079] The difference between this comparative example and Example 1 is that in step 2, step (4) of the fermentation, the rolled leaves are placed in a fermentation chamber and fermented in one stage: fermented at a temperature of 27° C. for 5 hours. The remaining steps are the same as in Example 1.
[0080] Technical effect evaluation
[0081] The red oolong tea prepared in Examples 1-3, Comparative Example 1 and Comparative Example 2 were dried at 60°C and then pulverized to obtain red oolong tea powder, which was then subjected to relevant component detection and analysis:
[0082] (1) Determination of polysaccharide content: Determined by spectrophotometry;
[0083] (2) Determination of tea polyphenols: using ferrous tartrate colorimetric method;
[0084] (3) Catechin content detection method: detection was performed according to the method described in national standard GB 5009157.
[0085] The test results are shown in Table 1.
[0086] Table 1
[0087] Group Tea polysaccharide content% Tea polyphenols% Catechin content (mg / g) Example 1 18.34 22.35 115 Example 2 17.85 20.83 113 Example 3 17.57 21.19 112 Comparative Example 1 14.35 16.86 94 Comparative Example 2 12.74 14.35 83
[0088] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art shall fall within the scope of protection defined by the claims of the present invention.
Claims
1. A red oolong tea fermentation agent, characterized in that These include Streptococcus thermophilus, Eurotium cristatum, and Pichia kudriavzevii.
2. The red oolong tea fermentation agent according to claim 1, characterized in that The preparation method comprises the following steps: culturing the thermophilic streptococcus, the Eurotium cristatum and the Pichia kudrida in LB liquid culture medium respectively, centrifuging and resuspending to obtain the thermophilic streptococcus agent, the Eurotium cristatum agent and the Pichia kudrida agent; and mixing the thermophilic streptococcus agent, the Eurotium cristatum agent and the Pichia kudrida agent to obtain a red oolong tea fermentation agent.
3. A method for fermenting black oolong tea, characterized in that: The method comprises the step of using the red oolong tea fermentation agent according to claim 1 or 2 to carry out fermentation during the fermentation stage.
4. The fermentation method according to claim 3, characterized in that The fermentation is a three-stage fermentation, and the three-stage fermentation includes the following steps: The first stage: the inoculation amount of the red oolong tea fermentation agent is 0.3% w / t; the second stage: the inoculation amount of the red oolong tea fermentation agent is 0.5% w / t; the third stage: the inoculation amount of the red oolong tea fermentation agent is 0.2% w / t.
5. The fermentation method according to claim 4, characterized in that The first stage fermentation time is 2 hours; the second stage fermentation time is 1 hour; and the third stage fermentation time is 2 hours.
6. The fermentation method according to claim 4, characterized in that The temperature and humidity of the first stage fermentation are 27±2°C and 80±5% respectively; the temperature and humidity of the second stage fermentation are 35±2°C and 75±5% respectively; the temperature and humidity of the third stage fermentation are 25±2°C and 90±5% respectively.
7. The fermentation method according to claim 3, characterized in that Oxygen is supplied throughout the fermentation process.
8. A red oolong tea product, characterized in that: The product is prepared by the fermentation method according to any one of claims 3 to 7.
9. Use of the red oolong tea fermentation agent according to claim 1 or 2 in fermenting red oolong tea.
10. Use of the red oolong tea fermentation agent according to claim 1 or 2 in increasing the tea polysaccharide content of red oolong tea.