Process for microbe-assisted water extraction of theaflavin
By using Aspergillus fumigatus and Streptococcus thermophilus fermentation microorganisms, tea leaves are fermented, fermentation conditions are optimized and fermentation promoters are added, and the problems of excessive ethyl acetate in theaflavin extraction are solved, achieving high efficiency and low The cost of theaflavin extraction is suitable for industrial applications.
Patent Information
- Application Number
- CN202411361373.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-27
- Publication Date
- 2024-12-27
Smart Images
Figure BDA0005065016380000081 
Figure BDA0005065016380000091
Abstract
Description
Technical Field
[0001] The invention relates to a process for extracting theaflavins by water with the assistance of microorganisms, and belongs to the technical field of theaflavins extraction. Background Art
[0002] Theaflavins are a general term for a class of compounds with benzophenones that are soluble in ethyl acetate and formed by the oxidation of polyphenols. They are important quality and functional ingredients in tea, especially black tea. They have multiple biological activities and pharmacological effects such as lowering blood lipids and blood pressure, anti-oxidation, anti-radiation, anti-bacterial, and anti-cancer, and are known as the "soft gold in tea". Due to their important pharmacological effects, they are increasingly being studied and valued by people, and have broad application prospects in the fields of food, daily chemicals, and medical health care. Therefore, the extraction and preparation methods of theaflavins have also become a research hotspot in recent years.
[0003] The patent application with the patent publication number CN 110305096A discloses a method for producing theaflavins by using the pruned branches and leaves of Anji white tea, which includes the steps of preparing a buffer solution, preparing an enzyme solution, preparing a substrate solution, fermenting, filtering, extracting, and concentrating and drying to obtain theaflavins. The present invention adopts a two-liquid phase fermentation method to produce theaflavins, and improves the enzyme conversion rate by optimizing the enzyme solution, buffer solution, enzymatic reaction system and other conditions. However, the two-liquid phase fermentation method has the problem of too much ethyl acetate and easy residue of ethyl acetate. A patent application with patent publication number CN 110305096A discloses a method for extracting theaflavins by countercurrent ultrasonic method. The extraction steps are as follows: put black tea powder in a countercurrent ultrasonic reactor and add deionized water to soften it; then place the reactor in ultrasonic wave and irradiate it under a certain pressure for 60 to 70 seconds, and then extract it with ethanol-water solution; filter, concentrate and dry to obtain theaflavins extract. The extraction method of the invention is easy to implement, environmentally friendly, has a short extraction time and high extraction efficiency. However, the invention requires operating conditions such as ultrasonic wave and pressurization, resulting in a high production cost.
[0004] At present, there are roughly three methods for preparing theaflavins: extraction, chemical oxidation, and enzymatic oxidation. However, these three methods all have different problems. The microbial fermentation method is a green, environmentally friendly, mild, and low-cost production method. In recent years, the use of microbial fermentation methods to extract active ingredients from plants has received more and more attention, but there are currently few studies on the use of microbial fermentation methods to produce theaflavins. Therefore, based on the problems existing in the prior art, a method of fermenting theaflavins in tea leaves using microbial fermentation methods has been developed, and then extracting theaflavins with a high yield has been obtained, which is conducive to the early realization of the industrial development of theaflavins. Summary of the invention
[0005] In view of the problems existing in the prior art, the present invention provides a process for extracting theaflavins by water assisted by microorganisms. The present invention selects Aspergillus fumigatus CICC 40232 and Streptococcus thermophilus CICC 6218 as fermentation microorganisms, and ferments tea leaves by a microbial fermentation method. The fermentation process is green and mild. The inoculation amount of Aspergillus fumigatus and Streptococcus thermophilus, the fermentation time and temperature, the moisture content and other conditions during the fermentation process are optimized, and a specific fermentation promoter and copper salt are added to regulate the generation process of theaflavins, so as to obtain theaflavins with high yield and purity.
[0006] The present invention provides a process for extracting theaflavins by water with the assistance of microorganisms, comprising the following extraction steps:
[0007] (1) Grinding the debranched and dried tea leaves and passing them through a 60-100 mesh sieve to obtain tea powder, adding a fermentation promoter to the powder, mixing and sterilizing, and then adding a microbial flora liquid, sterile water and copper salt to obtain a solid fermentation medium with a water content of 30-40 wt %, and fermenting for 8-16 hours in an aerobic environment at 20-40° C. and 70-80% humidity to obtain fermented tea powder;
[0008] (2) adding 20-30 times by weight of pure water to the fermented tea powder of step (1), heating and reflux extraction for 30-40 minutes, filtering under reduced pressure, cooling, adding an antioxidant to the obtained filtrate, filtering, concentrating, and vacuum freeze-drying to obtain theaflavins.
[0009] In some embodiments, the fermentation promoter includes catechol, catechin and oligofructose in a mass ratio of (5-6):(1-1.5):1.
[0010] Preferably, the fermentation promoter comprises catechol, catechin and oligofructose in a mass ratio of 5.5:1.25:1.
[0011] In some embodiments, the fermentation promoter is used in an amount of 1-2 wt % of the tea powder.
[0012] Preferably, the fermentation promoter is used in an amount of 1.5 wt % of the tea powder.
[0013] In some embodiments, the concentration of copper ions in the copper salt in the solid fermentation medium is 4-8 mmol / kg.
[0014] Preferably, the concentration of copper ions in the copper salt in the solid fermentation medium is 6.5 mmol / kg.
[0015] In some embodiments, the copper salt is sterilized and then dissolved in sterile water before being added to the tea powder.
[0016] In some embodiments, the microbial flora liquid includes Aspergillus fumigatus CICC 40232 seed liquid and Streptococcus thermophilus CICC 6218 seed liquid.
[0017] In some embodiments, the quantitative ratio of Aspergillus fumigatus CICC 40232 and Streptococcus thermophilus CICC6218 in the microbial flora liquid is (2-3):1.
[0018] Preferably, the quantitative ratio of Aspergillus fumigatus CICC 40232 to Streptococcus thermophilus CICC 6218 in the microbial flora liquid is 2.5:1.
[0019] In some embodiments, the concentration of the microbial flora liquid is (1-10)×10 7 CFU / mL, and the added amount is 8-15wt% of the tea powder.
[0020] Preferably, the concentration of the microbial flora liquid is (2-9)×10 7 CFU / mL, and the added amount was 12wt% of the tea powder.
[0021] In some embodiments, the heating is to a temperature of 60-75°C.
[0022] Preferably, the heating temperature is 70°C.
[0023] In some embodiments, the concentration of the antioxidant in the filtrate is 35-45 mg / kg, and the antioxidant is a food grade antioxidant.
[0024] Preferably, the concentration of the antioxidant in the filtrate is 40 mg / kg.
[0025] In some embodiments, the filtration operation is performed by sequentially using a microfiltration membrane and an ultrafiltration membrane.
[0026] Theaflavins are an important water-soluble pigment produced during tea fermentation, which is formed by the oxidation polymerization of tea polyphenols under the catalysis of polyphenol oxidase. The present invention uses a microbial fermentation method to ferment tea leaves, and the fermentation process is green and mild, and theaflavins with high yield and purity are obtained.
[0027] The present invention selects Aspergillus fumigatus CICC 40232 and Streptococcus thermophilus CICC 6218 as fermentation microorganisms, and constructs a microbial flora liquid by a specific ratio, and ferments tea powder in the presence of a fermentation promoter to obtain theaflavins with high yield and purity. Aspergillus fumigatus CICC 40232 is a fungus that can produce polyphenol oxidase, which can catalyze the oxidative polymerization reaction of tea polyphenols to produce theaflavins, while Streptococcus thermophilus is a bacterium that can still maintain activity under high temperature conditions, and the metabolites produced by it during the fermentation process may promote the production of theaflavins. The applicant has found that using the two to ferment tea powder at the same time can significantly increase the yield of theaflavins. This may be because the polyphenol oxidase produced by Aspergillus fumigatus during the fermentation process can efficiently catalyze the oxidation of tea polyphenols in tea leaves to form o-benzoquinone intermediates, which are further polymerized to form theaflavins; and Streptococcus thermophilus may provide favorable conditions for the oxidation of tea polyphenols by polyphenol oxidase by changing the pH value of the fermentation environment or secreting certain metabolites during the fermentation process, thereby increasing the yield of theaflavins. In addition, there may be a synergistic effect in the co-fermentation of Aspergillus fumigatus and Streptococcus thermophilus. The metabolic pathways of the two can complement each other and jointly promote the production of theaflavins. The lactic acid produced by Streptococcus thermophilus may reduce the pH value of the fermentation environment, thereby increasing the activity of PPO and the yield of theaflavins. At the same time, the enzymes produced by Aspergillus fumigatus may further modify theaflavins molecules and increase their biological activity.
[0028] The present invention also optimizes the inoculation amount, fermentation time, temperature, moisture content and other conditions of Aspergillus fumigatus and Streptococcus thermophilus during the fermentation process, and adds a specific fermentation promoter to regulate the production process of theaflavins and improve the yield of theaflavins. The present invention compounds catechol, catechins and oligofructose according to a certain ratio, and adds the obtained fermentation promoter to the fermentation medium, which can promote the secretion of polyphenol oxidase by Aspergillus fumigatus and Streptococcus thermophilus during the fermentation process, and adds a certain amount of copper ions to improve the catalytic activity of polyphenol oxidase, further promoting the oxidation of tea polyphenols and the production of theaflavins.
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] 1. The present invention selects Aspergillus fumigatus CICC 40232 and Streptococcus thermophilus CICC 6218 as fermentation microorganisms, and uses a microbial fermentation method to ferment tea leaves. The fermentation process is green and mild. Through the process control of the fermentation conditions, theaflavins with high yield and purity are finally obtained.
[0031] 2. The present invention adds a fermentation promoter obtained by compounding catechol, catechins and oligofructose into a fermentation medium, promotes the secretion of polyphenol oxidase by Aspergillus fumigatus and Streptococcus thermophilus during the fermentation process, and adds a certain amount of copper ions to further improve the catalytic activity of polyphenol oxidase, thereby promoting the oxidation of tea polyphenols and the production of theaflavins. DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0033] In order to better illustrate the specific implementation mode of the present invention, further examples are given below.
[0034] The "normal temperature concentration", "vacuum freeze drying" and "reduced pressure filtration" in the present invention are all well-known operations to those skilled in the art, and the specific operation steps can be selected according to the actual production conditions.
[0035] The Aspergillus fumigatus used in the present invention is Aspergillus fumigatus CICC 40232, the thermophilic Streptococcus used is thermophilic Streptococcus CICC6218; the oligofructose used is purchased from Shanxi Jinnian Biotechnology Co., Ltd.; the black tea used is the black tea produced by the company; the antioxidant used is ascorbic acid; the microfiltration membrane and ultrafiltration membrane used are purchased from Maiborui Filtration Group Co., Ltd.
[0036] Preparation Example 1
[0037] Preparation of Aspergillus fumigatus seed solution:
[0038] In a sterile environment, the preserved Aspergillus fumigatus was inoculated into 500 mL of sterilized liquid culture medium, cultured at 37 °C for 3 days, and then centrifuged at 6000 r / min to obtain the cells, which were diluted with sterile water to 9 × 10 7 CFU / mL, and Aspergillus fumigatus seed liquid was obtained.
[0039] The formula of the liquid culture medium used was: 1 kg of deionized water, 30.0 g of sucrose, 3.0 g of NaNO3, 0.5 g of MgSO4·7H2O, 0.5 g of KCl, 0.01 g of FeSO4·4H2O, and 1.0 g of K2HPO4, and the pH was adjusted to 6.5.
[0040] Preparation Example 2
[0041] Preparation of thermophilic Streptococcus seed solution:
[0042] Under a sterile environment, 100 μL of bacterial solution was drawn from the glycerol tube containing thermophilic Streptococcus, and evenly spread on the LB plate medium by the plate streak method. The plate was inverted and cultured at 37°C. After the colonies grew, a single colony was picked and inoculated into 500 mL of sterilized liquid culture medium. The culture was shaken at 37°C for 20 h, and centrifuged at 6000 r / min to obtain the bacteria. The bacteria were diluted with sterile water to 9×10 7 CFU / mL, and obtain the thermophilic Streptococcus seed liquid.
[0043] The formula of the liquid culture medium used is: 1 kg of deionized water, 15.0 g of tryptone, 5.0 g of soy peptone, 5.0 g of NaCl, and 50.0 mL of defibrinated sheep blood is added after sterilization.
[0044] Example 1
[0045] A process for extracting theaflavins with water assisted by microorganisms comprises the following extraction steps:
[0046] (1) Grinding 1 kg of debranched and dried black tea and passing it through a 60-mesh sieve to obtain black tea powder, adding 1.5 wt % of a fermentation accelerator to the black tea powder, mixing well, sterilizing at 120° C. for 20 min, and then adding 15 wt % of a microbial flora liquid, 25 wt % of sterile water and copper chloride (so that the concentration of copper ions in the solid fermentation medium is 8 mmol / kg) to obtain a solid fermentation medium with a water content of 40 wt %, and fermenting for 16 h in an aerobic environment at 20° C. and 70% humidity to obtain fermented tea powder;
[0047] (2) Add 20 times the mass of pure water to the fermented tea powder of step (1), heat to 75°C, reflux extraction for 30 minutes, filter under reduced pressure, cool the filtrate, add an antioxidant to the obtained filtrate to make the antioxidant concentration of 35 mg / kg, perform microfiltration and ultrafiltration (the treatment temperature, pressure and flow rate are 20°C, 0.2 MPa, and 20 kg / h, respectively), concentrate at room temperature, and vacuum freeze-dry to obtain theaflavins.
[0048] The microbial flora liquid used was composed of the Aspergillus fumigatus seed liquid of Preparation Example 1 and the Streptococcus thermophilus seed liquid of Preparation Example 2 in a volume ratio of 2.5:1;
[0049] The fermentation promoter used is composed of catechol, catechin and oligofructose in a mass ratio of 5.5:1.5:1.
[0050] Example 2
[0051] A process for extracting theaflavins with water assisted by microorganisms comprises the following extraction steps:
[0052] (1) 1 kg of debranched and dried black tea is ground and passed through a 100-mesh sieve to obtain black tea powder. Based on the black tea powder, 1 wt% of a fermentation accelerator is added thereto, mixed evenly, sterilized at 120° C. for 20 min, and then 8 wt% of a microbial flora liquid, 22 wt% of sterile water and copper chloride (so that the concentration of copper ions in the solid fermentation medium is 4 mmol / kg) are added to obtain a solid fermentation medium with a water content of 30 wt%, and fermented for 8 h in an aerobic environment at 40° C. and 80% humidity to obtain fermented tea powder;
[0053] (2) adding 30 times by weight of pure water to the fermented tea powder of step (1), heating to 60°C, reflux extraction for 40 min, filtering under reduced pressure, cooling the filtrate, adding an antioxidant to the obtained filtrate to make the antioxidant concentration 45 mg / kg, performing microfiltration and ultrafiltration (the treatment temperature, pressure and flow rate are 20°C, 0.2 MPa and 20 kg / h, respectively), concentrating at room temperature, and vacuum freeze-drying to obtain theaflavins.
[0054] The microbial flora liquid used was composed of the Aspergillus fumigatus seed liquid of Preparation Example 1 and the Streptococcus thermophilus seed liquid of Preparation Example 2 in a volume ratio of 2.5:1;
[0055] The fermentation promoter used is composed of catechol, catechin and oligofructose in a mass ratio of 5.5:1.5:1.
[0056] Example 3
[0057] A process for extracting theaflavins with water assisted by microorganisms comprises the following extraction steps:
[0058] (1) 1 kg of debranched and dried black tea is ground and passed through an 80-mesh sieve to obtain black tea powder. Based on the black tea powder, 1.25 wt % of a fermentation accelerator is added thereto, mixed evenly, sterilized at 120° C. for 20 min, and then 12 wt % of a microbial flora liquid, 23 wt % of sterile water and copper chloride (so that the concentration of copper ions in the solid fermentation medium is 6.5 mmol / kg) are added to obtain a solid fermentation medium with a water content of 35 wt %, and fermented for 12 h in an aerobic environment at 30° C. and 75% humidity to obtain fermented tea powder;
[0059] (2) Add 25 times the mass of pure water to the fermented tea powder of step (1), heat to 70°C, reflux extraction for 35 minutes, filter under reduced pressure, cool the filtrate, add an antioxidant to the obtained filtrate to make the antioxidant concentration 40 mg / kg, perform microfiltration and ultrafiltration (treatment temperature, pressure and flow rate are 20°C, 0.2 MPa, 20 kg / h, respectively), concentrate at room temperature, and vacuum freeze-dry to obtain theaflavins.
[0060] The microbial flora liquid used was composed of the Aspergillus fumigatus seed liquid of Preparation Example 1 and the Streptococcus thermophilus seed liquid of Preparation Example 2 in a volume ratio of 2.5:1;
[0061] The fermentation promoter used is composed of catechol, catechin and oligofructose in a mass ratio of 5.5:1.5:1.
[0062] Example 4
[0063] A process for microbial-assisted water extraction of theaflavins, the specific implementation method is the same as that of Example 3, except that the microbial flora liquid used is composed of the Aspergillus fumigatus seed liquid of Preparation Example 1 and the Streptococcus thermophilus seed liquid of Preparation Example 2 in a volume ratio of 1:1.
[0064] Example 5
[0065] A process for extracting theaflavins by water with the assistance of microorganisms, the specific implementation method is the same as that of Example 3, except that the fermentation promoter used is composed of catechol, catechins and oligofructose in a mass ratio of 4:1.5:1.
[0066] Example 6
[0067] A process for extracting theaflavins by water with the assistance of microorganisms, the specific implementation method is the same as that of Example 3, except that the fermentation promoter used is composed of catechol and oligofructose in a mass ratio of 5.5:1.
[0068] Example 7
[0069] A process for extracting theaflavins by water with the assistance of microorganisms, the specific implementation method is the same as that of Example 3, except that the fermentation promoter used is composed of catechins and oligofructose in a mass ratio of 1.5:1.
[0070] Comparative Example 1
[0071] A process for extracting theaflavins with water assisted by microorganisms, the specific implementation method is the same as that of Example 3, except that copper chloride is not added.
[0072] Comparative Example 2
[0073] A process for extracting theaflavins by water with the assistance of microorganisms, the specific implementation method is the same as that of Example 3, except that no fermentation promoter is added.
[0074] Comparative Example 3
[0075] A process for microbial-assisted water extraction of theaflavins, the specific implementation method is the same as that of Example 3, except that an equal mass of Aspergillus fumigatus seed liquid of Preparation Example 1 is used instead of the microbial flora liquid.
[0076] Comparative Example 4
[0077] A process for extracting theaflavins by water with the assistance of microorganisms is provided. The specific implementation method is the same as that of Example 3, except that the thermophilic Streptococcus seed liquid of Preparation Example 2 of the same mass is used instead of the microbial flora liquid.
[0078] Comparative Example 5
[0079] A theaflavins extraction process comprises the following extraction steps:
[0080] 1 kg of debranched and dried black tea was ground and passed through an 80-mesh sieve to obtain black tea powder. 25 times by mass of pure water was added to the black tea powder, heated to 80°C, refluxed for 40 minutes, filtered under reduced pressure, and the filtrate was cooled. An antioxidant was added to the obtained filtrate to make the antioxidant concentration of 40 mg / kg, and microfiltration and ultrafiltration were performed (the treatment temperature, pressure and flow rate were 20°C, 0.2 MPa, and 20 kg / h, respectively), concentrated at room temperature, and vacuum freeze-dried to obtain theaflavins.
[0081] Performance Testing
[0082] 1. Polyphenol oxidase activity test: The fermented tea powder obtained in Examples 1-7 and Comparative Examples 1-4 was tested for polyphenol oxidase activity at 4 and 8 hours respectively. The operation steps were as follows: 1 g of fermented tea powder was added with 5 mL of deionized water, shaken at 500 r / min for 15 min, and then allowed to stand for 30 min. 1 mL of supernatant was taken, and 3 mL of 0.1 mol / L phosphate buffer solution with a pH of 6.0 and 1 mL of 0.1 mol / L catechol solution were added thereto in sequence. The mixture was mixed evenly, and the absorbance value (OD) was measured at a wavelength of 600 nm. 600 The absorbance value change was recorded every 30 seconds for 10 minutes; 1 mL of deionized water, 3 mL of 0.1 mol / L phosphate buffer solution with pH = 6.0, and 1 mL of 0.1 mol / L catechol solution were used as blank controls.
[0083] The calculation formula of polyphenol oxidase activity is as follows:
[0084] Enzyme activity = 1 / V × ΔOD 600 / ΔT×10 3 ,
[0085] Where V represents the volume of the supernatant in mL; ΔOD 600 is the change in absorbance value; ΔT is the reaction time, in min.
[0086] 2. Theaflavin quality: weigh using a balance.
[0087] 3. Test of the content of thea saponin: The theaflavins obtained in the examples of the present invention and the comparative examples were tested by HPLC. The HPLC used was Shimadzu high performance liquid chromatograph LC-10Avp, the chromatographic column was Hypersil BDS (C18, 5μ, 4.6x250mm), the mobile phase A was 2v / v% acetic acid aqueous solution, the mobile phase B was acetonitrile-ethyl acetate with a volume ratio of 21:3, gradient elution, the mobile phase B linear gradient changed from 18% to 30% within 30min, the flow rate was 0.9mL / min, the column temperature was 40°C, the detection wavelength was 280nm, and the injection volume was 10μL; the standard curve was constructed by the external standard method for quantification.
[0088] Specific test data are shown in Table 1.
[0089] Table 1
[0090]
[0091]
[0092] As shown in Table 1, the polyphenol oxidase activity in Examples 1-3 is relatively high, and the yield and purity of the prepared theaflavins are also relatively high. Compared with Example 3, the ratio of fermented microorganisms in Example 4 is changed, Aspergillus fumigatus seed liquid is used instead of microbial flora liquid in Comparative Example 3, and Streptococcus thermophilus seed liquid is used instead of microbial flora liquid in Comparative Example 4, which will lead to a decrease in polyphenol oxidase activity, change the fermentation effect of black tea, and affect the dissolution of theaflavins; the ratio or composition of the fermentation promoter used in Examples 5-7 is changed, and no fermentation promoter is added in Comparative Example 2, which changes the fermentation degree of black tea by microorganisms, and reduces the generation and dissolution rate of theaflavins; copper chloride is not added in Comparative Example 1, and the polyphenol oxidase activity is relatively low, which weakens the oxidation effect of tea polyphenols and reduces the generation of theaflavins; the black tea in Comparative Example 5 is not directly extracted from theaflavins by microbial fermentation, and the original theaflavins extraction rate and purity in the black tea are not high, which are significantly lower than those in other Examples and Comparative Examples.
[0093] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.
Claims
1. A process for extracting theaflavins by water assisted by microorganisms, characterized in that: The extraction steps include: (1) Grinding the debranched and dried tea leaves and passing them through a 60-100 mesh sieve to obtain tea powder, adding a fermentation promoter to the powder, mixing and sterilizing, and then adding a microbial flora liquid, sterile water and copper salt to obtain a solid fermentation medium with a water content of 30-40 wt %, and fermenting for 8-16 hours in an aerobic environment at 20-40° C. and 70-80% humidity to obtain fermented tea powder; (2) adding 20-30 times by weight of pure water to the fermented tea powder of step (1), heating and reflux extraction for 30-40 minutes, filtering under reduced pressure, cooling, adding an antioxidant to the obtained filtrate, filtering, concentrating, and vacuum freeze-drying to obtain theaflavins.
2. The process for extracting theaflavins according to claim 1, characterized in that: The fermentation promoter comprises catechol, catechin and oligofructose in a mass ratio of (5-6):(1-1.5):
1.
3. The process for extracting theaflavins according to claim 2, characterized in that: The fermentation accelerator is used in an amount of 1-2 wt % of the tea powder.
4. The process for extracting theaflavins according to claim 1, characterized in that: The concentration of copper ions in the copper salt in the solid fermentation medium is 4-8 mmol / kg.
5. The process for extracting theaflavins according to claim 1, characterized in that: The microbial flora liquid includes Aspergillus fumigatus CICC 40232 seed liquid and Streptococcus thermophilus CICC 6218 seed liquid.
6. The process for extracting theaflavins according to claim 5, characterized in that: The quantitative ratio of Aspergillus fumigatus CICC 40232 and Streptococcus thermophilus CICC 6218 in the microbial flora liquid is (2-3):
1.
7. The process for extracting theaflavins according to claim 5, characterized in that: The concentration of the microbial flora liquid is (1-10)×10 7 CFU / mL, and the added amount is 8-15wt% of the tea powder.
8. The process for extracting theaflavins according to claim 1, characterized in that: The heating temperature is 60-75°C.
9. The process for extracting theaflavins according to claim 1, characterized in that: The concentration of the antioxidant in the filtrate is 35-45 mg / kg, and the antioxidant is a food-grade antioxidant.
10. The process for extracting theaflavins according to claim 1, characterized in that: The filtering operation is to use a microfiltration membrane and an ultrafiltration membrane in sequence.