Yellow tea with high theaflavin stability as well as preparation method and application of yellow tea

Abstract

The invention discloses yellow tea with high stability of theaflavin as well as a preparation method and application thereof, and the yellow tea with high stability of theaflavin is obtained through enhanced fermentation and green leaf rocking treatment and by utilizing a steam explosion technology. A proper amount of yellow tea is taken and smashed, clear extract liquor is obtained through an ultrasonic extraction technology and a nanofiltration technology, the extract liquor and white spirit are mixed in proportion to form the tea wine, high performance liquid chromatography is used for determination, theaflavin is increased by 2.2 times, and stability of theaflavin in the yellow tea wine is determined to be improved through a stability experiment. The content and stability of theaflavin in the yellow tea are improved through enhanced fermentation, rocking and steam explosion treatment, the tea wine is rich in flavor level and golden yellow and transparent in color through the nanofiltration technology and the optimal proportion, the unique flavor and nutritional value of the yellow tea can be effectively improved, and the tea wine has better sensory quality and high health-care value.

Description

Technical Field

[0001] The invention belongs to the technical field of tea processing, and particularly relates to yellow tea with high theaflavins stability, and a preparation method and application thereof. Background Art

[0002] Yellow tea is one of the six traditional teas in China, with a unique flavor and nutritional value. Among them, theaflavins (TFs) are one of the important active ingredients in yellow tea. In recent years, studies have found that they have broad application prospects in many fields such as food and beverages, health products, cosmetics, and medicine. They have multiple physiological functions such as antioxidant, lipid-lowering, digestion-promoting, and anti-tumor.

[0003] However, during the production and storage of yellow tea wine, theaflavins are less stable and easily degrade, resulting in a decrease in the quality and nutritional value of the wine. The formation mechanism of theaflavins indicates that, compared with traditional natural fermentation, enhanced fermentation significantly increases the content of tea polyphenols, theabrownins, and soluble sugars, significantly increasing the content of theaflavins through enhanced fermentation. Shaking the tea leaves promotes the transformation of substances within the tea, providing more substrates and active ingredients for the formation of theaflavins, thus affecting the formation of theaflavins. Therefore, increasing the theaflavin content in yellow tea through enhanced fermentation and shaking the leaves is one of the keys to improving the quality of the wine. Combining enhanced fermentation, shaking the leaves with steam explosion, ultrasonic extraction, and nanofiltration techniques can significantly increase the theaflavin content in yellow tea while optimizing the quality of the wine.

[0004] The stability of theaflavins in existing yellow tea wine production methods is poor, affecting the quality and marketability of the wine. Therefore, developing a method to improve the stability of theaflavins in yellow tea and yellow tea wine is of great significance for improving the quality of yellow tea wine. Summary of the Invention

[0005] In light of these shortcomings, and to enhance the theaflavins content in yellow tea and improve the sensory quality and health benefits of tea wine, the present invention provides a method for improving the stability of theaflavins in yellow tea wine. By intensifying fermentation and shaking, as well as steam explosion, ultrasound-assisted extraction, and nanofiltration techniques, combined with an optimized cold extract to tea wine ratio, the theaflavins content and stability are significantly increased.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for improving the stability of theaflavins in yellow tea wine, comprising:

[0008] (1) Select fresh yellow tea leaves from the same tea garden, of the same variety, and picked at the same time.

[0009] (2) Wither the fresh yellow tea leaves moderately to make the water loss rate of the tea leaves reach 30%.

[0010] (3) The withered yellow tea leaves are withered at a temperature of 150°C for 5 minutes.

[0011] (4) Place the yellow tea leaves after withering in a shaking machine at a temperature of 22°C and a relative humidity of 65% for 40-50 minutes, with an 8-minute pause every 12 minutes. During the shaking process, the tea cell tissue is slightly damaged, which promotes full contact between polyphenols and enzymes, accelerates the oxidative polymerization reaction of catechins, and thus promotes the production of theaflavins.

[0012] (5) Pichia pastoris was inoculated into YPD liquid medium (Shanghai Sangon Biotechnology Co., Ltd.), cultured at 28°C with shaking for 24 h, and diluted to 1×10 with sterile saline after counting. 6 CFU / mL; 10 mL of the diluted bacterial solution was centrifuged at 3000 r / min for 5 min to collect the bacteria, which were then mixed with sterilized wheat bran at a ratio of 1:5 (w / w). An appropriate amount of sterile water was added to make the substrate humidity 60%, and the mixture was incubated at 28°C for 24 h to prepare a solid bacterial agent for later use;

[0013] (6) The yellow tea leaves after shaking were mixed evenly with the solid bacterial agent in a mass ratio of 10:1 to form a fermentation matrix. A breathable fermentation tray was used with a thickness of 5 cm and placed in a constant temperature fermentation room at 30°C. The fermentation time was 8 days. The matrix humidity was maintained at 60% by regularly spraying sterile water. The matrix was turned over every 12 hours to promote uniform oxygen distribution. During the fermentation process, 0.2% yeast nutrient was sprayed every 24 hours.

[0014] (7) After the fermentation is completed, the tea leaves are dried in an oven at 60°C to a moisture content of ≤8%, thereby obtaining yellow tea that has undergone enhanced fermentation and shaking treatment.

[0015] (8) The yellow tea obtained in step (7) is subjected to steam explosion treatment, with the steam explosion pressure controlled to 0.8 MPa, the steam explosion time to 3 min, and the steam explosion temperature to 130° C., and the yellow tea is cooled to room temperature after the steam explosion to obtain steam-exploded yellow tea.

[0016] (9) The steam-exploded yellow tea was crushed and sieved with 80 mesh to obtain yellow tea powder.

[0017] (10) Ultrasonic-assisted extraction technology was used. 2.00 g of tea powder was weighed and distilled water was added at a solid-liquid ratio of 1:40 (g / mL). The mixture was placed in a 4 °C refrigerator and allowed to stand for 5 h. After standing, the mixture was placed in an ultrasonic processor with an ultrasonic power of 200 W, an ultrasonic time of 30 min, and an ultrasonic temperature of 40 °C.

[0018] (11) The ultrasonic extract was centrifuged at 5000 r / min for 10 min and the supernatant was collected.

[0019] (12) The supernatant was filtered using nanofiltration technology with a nanofiltration membrane pore size of 10 nm and an operating pressure of 1.0 MPa to obtain a clear yellow tea cold extract.

[0020] (13) Yellow tea cold extract and base wine were mixed in a ratio of 9:2.5 (v / v) to obtain tea wine.

[0021] (14) The tea wine was stored in a refrigerator at 4°C, and the theaflavins content was measured regularly to evaluate its stability.

[0022] The present invention also discloses a method for detecting theaflavin content, comprising:

[0023] Theaflavin content was determined using high-performance liquid chromatography (HPLC). A C18 column was used, with a mobile phase of methanol-water (70:30, v / v), a flow rate of 1.0 mL / min, and a detection wavelength of 278 nm. The results showed that the theaflavin content in the tea leaves increased by 2.1 times, and the retention rate of theaflavin in the tea wine reached 85% after three months, significantly improving the stability of theaflavin in the tea wine.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] During the experiment, the present application found that shaking treatment, enhanced fermentation and steam explosion technology can significantly increase the content of theaflavins in tea leaves. The impurities in the yellow tea cold extract are effectively removed by nanofiltration technology, and the stability of theaflavins in tea wine is effectively improved by optimizing the ratio of yellow tea cold extract and base wine. It has been verified that compared with traditional natural fermentation, the enhanced fermentation significantly increases the content of tea polyphenols, theabrownins and soluble sugars, and the enhanced fermentation significantly increases the content of theaflavins. Shaking can promote the transformation of substances in tea leaves, provide more substrates and active ingredients for the formation of theaflavins, and affect the formation of theaflavins. Appropriate shaking causes damage to the cell tissue at the edge of the tea leaves and produces enzymatic browning, which significantly increases the content of theaflavins. The application of steam explosion technology makes it easier to dissolve the active ingredients in tea leaves. Ultrasonic extraction technology is used to further improve the extraction efficiency of theaflavins, and nanofiltration technology is used to effectively remove impurities from the extract. The optimal ratio of yellow tea soup and base wine is accurately determined, so that theaflavins achieve optimal solubility and stability in the tea wine system, optimizing the flavor and taste of the tea wine. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments.It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention.In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.Unindicated specific conditions in the embodiment are carried out according to the conditions of normal conditions or manufacturer's advice.Reagents used or instruments are not indicated by manufacturers, and are conventional products that can be obtained by commercial purchase.

[0027] Example 1

[0028] (1) Select fresh yellow tea leaves from the same tea garden, of the same variety, and picked at the same time.

[0029] (2) The fresh yellow tea leaves are moderately withered to make the water loss rate of the tea reach 30%.

[0030] (3) After withering, the temperature is 150℃ and the time is 5 minutes.

[0031] (4) Place the yellow tea leaves after withering in a shaking machine with a shaking temperature of 22°C and a relative humidity of 65% for 45 minutes, with a pause of 8 minutes every 12 minutes.

[0032] (5) Pichia pastoris was inoculated into YPD liquid medium and cultured at 28°C with shaking for 24 h. After counting, the culture was diluted to 1×10 6 CFU / mL; 10 mL of the diluted bacterial solution was centrifuged at 3000 r / min for 5 min to collect the bacteria, which were then mixed with sterilized wheat bran at a ratio of 1:5 (w / w). An appropriate amount of sterile water was added to make the substrate humidity 60%, and the mixture was incubated at 28°C for 24 h to prepare a solid bacterial agent for later use;

[0033] (6) The yellow tea leaves after shaking were mixed evenly with the solid bacterial agent in a mass ratio of 10:1 to form a fermentation matrix. A breathable fermentation tray was used with a thickness of 5 cm and placed in a constant temperature fermentation room at 30°C. The fermentation time was 8 days. The matrix humidity was maintained at 60% by regularly spraying sterile water. The matrix was turned over every 12 hours to promote uniform oxygen distribution. During the fermentation process, 0.2% yeast nutrient was sprayed every 24 hours.

[0034] (7) After the fermentation is completed, the tea leaves are dried in an oven at 60°C to a moisture content of ≤8%, thereby obtaining yellow tea that has undergone enhanced fermentation and shaking treatment.

[0035] (8) The yellow tea obtained in step (7) is subjected to steam explosion treatment, with the steam explosion pressure controlled to 0.8 MPa, the steam explosion time to 3 min, and the steam explosion temperature to 130° C., and the yellow tea is cooled to room temperature after the steam explosion to obtain steam-exploded yellow tea.

[0036] (9) The steam-exploded yellow tea was crushed and sieved with 80 mesh to obtain yellow tea powder.

[0037] (10) Weigh 2.00 g of tea powder and add distilled water at a material-liquid ratio of 1:40 (g / mL). The mixture is placed in a refrigerator at 4°C for 5 h. After standing, the mixture is placed in an ultrasonic processor at a power of 200 W, a time of 30 min, and a temperature of 40°C.

[0038] (11) The ultrasonic extract was centrifuged at 5000 r / min for 10 min and the supernatant was collected.

[0039] (12) The supernatant was filtered using nanofiltration technology with a nanofiltration membrane pore size of 10 nm and an operating pressure of 1.0 MPa to obtain a clear yellow tea cold extract.

[0040] (13) Yellow tea cold extract and base wine were mixed in a ratio of 9:2.5 (v / v) to obtain tea wine.

[0041] (14) The tea wine was stored in a refrigerator at 4°C, and the theaflavins content was measured regularly to evaluate its stability.

[0042] Comparative Example 1

[0043] (1) Select fresh yellow tea leaves from the same tea garden, of the same variety, and picked at the same time.

[0044] (2) The fresh yellow tea leaves are moderately withered to make the water loss rate of the tea reach 30%.

[0045] (3) After withering, the temperature is 150℃ and the time is 5 minutes.

[0046] (4) Pichia pastoris was inoculated into YPD liquid medium and cultured at 28°C with shaking for 24 h. After counting, the culture was diluted to 1×10 6 CFU / mL. Take 10 mL of the diluted bacterial solution and centrifuge at 3000 rpm for 5 minutes to collect the bacteria. Mix the bacteria with sterilized wheat bran at a ratio of 1:5 (w / w). Add an appropriate amount of sterile water to bring the substrate humidity to 60%. Incubate at 28°C for 24 hours to prepare a solid inoculum for later use.

[0047] (5) The yellow tea leaves after withering were mixed with the solid microbial agent in a mass ratio of 10:1 to form a fermentation matrix. A permeable fermentation tray was used with a thickness of 5 cm and placed in a constant temperature fermentation room at 30°C. The fermentation time was 8 days. The matrix humidity was maintained at 60% by regularly spraying sterile water. The matrix was turned over every 12 hours to promote uniform oxygen distribution. During the fermentation process, 0.2% yeast nutrient was sprayed every 24 hours.

[0048] (6) After the fermentation is completed, the tea leaves are placed in an oven at 60°C and dried to a moisture content of ≤8% to obtain yellow tea subjected to enhanced fermentation.

[0049] (7) The yellow tea obtained in step (6) is subjected to steam explosion treatment, with the steam explosion pressure controlled to 0.8 MPa, the steam explosion time to 3 min, and the steam explosion temperature to 130° C., and the yellow tea is cooled to room temperature after the steam explosion to obtain steam-exploded yellow tea.

[0050] (8) The steam-exploded yellow tea was crushed and sieved with 80 mesh to obtain yellow tea powder.

[0051] (9) Weigh 2.00 g of tea powder and add distilled water at a material-liquid ratio of 1:40 (g / mL). The mixture is placed in a refrigerator at 4°C for 5 h. After standing, the mixture is placed in an ultrasonic processor at a power of 200 W, a time of 30 min, and a temperature of 40°C.

[0052] (10) The ultrasonic extract was centrifuged at 5000 r / min for 10 min and the supernatant was collected.

[0053] (11) The supernatant was filtered using nanofiltration technology with a nanofiltration membrane pore size of 10 nm and an operating pressure of 1.0 MPa to obtain a clear yellow tea cold extract.

[0054] (12) Yellow tea cold extract and base wine are mixed in a ratio of 9:2.5 (v / v) to obtain tea wine.

[0055] (13) The tea wine was stored in a refrigerator at 4°C, and the theaflavins content was measured regularly to evaluate its stability.

[0056] Comparative Example 2

[0057] (1) Select fresh yellow tea leaves from the same tea garden, of the same variety, and picked at the same time.

[0058] (2) The fresh yellow tea leaves are moderately withered to make the water loss rate of the tea reach 30%.

[0059] (3) After withering, the temperature is 150℃ and the time is 5 minutes.

[0060] (4) Place the yellow tea leaves after withering in a shaking machine with a shaking temperature of 22°C and a relative humidity of 65% for 45 minutes, with a pause of 8 minutes every 12 minutes.

[0061] (5) After shaking, the tea leaves are dried in an oven at 60°C to obtain yellow tea treated with shaking.

[0062] (6) The yellow tea obtained in step (5) is subjected to steam explosion treatment, with the steam explosion pressure controlled to 0.8 MPa, the steam explosion time to 3 min, and the steam explosion temperature to 130° C., and the yellow tea is cooled to room temperature after the steam explosion to obtain steam-exploded yellow tea.

[0063] (7) Grind the steam-exploded yellow tea and sieve it through an 80-mesh sieve to obtain yellow tea powder.

[0064] (8) Weigh 2.00 g of tea powder and add distilled water at a material-liquid ratio of 1:40 (g / mL). The mixture is placed in a refrigerator at 4°C for 5 h. After standing, the mixture is placed in an ultrasonic processor at a power of 200 W, a time of 30 min, and a temperature of 40°C.

[0065] (9) Centrifuge the ultrasonic extract at 5000 r / min for 10 min and collect the supernatant.

[0066] (10) The supernatant was filtered using nanofiltration technology with a nanofiltration membrane pore size of 10 nm and an operating pressure of 1.0 MPa to obtain a clear yellow tea cold extract.

[0067] (11) Yellow tea cold extract and base wine are mixed in a ratio of 9:2.5 (v / v) to obtain tea wine.

[0068] (12) The tea wine was stored in a refrigerator at 4°C, and the theaflavins content was measured regularly to evaluate its stability.

[0069] Comparative Example 3

[0070] (1) Select fresh yellow tea leaves from the same tea garden, of the same variety, and picked at the same time.

[0071] (2) The fresh yellow tea leaves are moderately withered to make the water loss rate of the tea reach 30%.

[0072] (3) After withering, the temperature is 150℃ and the time is 5 minutes.

[0073] (4) Place the yellow tea leaves after withering in a shaking machine with a shaking temperature of 22°C and a relative humidity of 65% for 45 minutes, with a pause of 8 minutes every 12 minutes.

[0074] (5) Pichia pastoris was inoculated into YPD liquid medium and cultured at 28°C with shaking for 24 h. After counting, the culture was diluted to 1×10 6 CFU / mL; 10 mL of the diluted bacterial solution was centrifuged at 3000 r / min for 5 min to collect the bacteria, which were then mixed with sterilized wheat bran at a ratio of 1:5 (w / w). An appropriate amount of sterile water was added to make the substrate humidity 60%, and the mixture was incubated at 28°C for 24 h to prepare a solid bacterial agent for later use;

[0075] (6) The yellow tea leaves after shaking were mixed evenly with the solid bacterial agent in a mass ratio of 10:1 to form a fermentation matrix. A breathable fermentation tray was used with a thickness of 5 cm and placed in a constant temperature fermentation room at 30°C. The fermentation time was 8 days. The matrix humidity was maintained at 60% by regularly spraying sterile water. The matrix was turned over every 12 hours to promote uniform oxygen distribution. During the fermentation process, 0.2% yeast nutrient was sprayed every 24 hours.

[0076] (7) After the fermentation is completed, the tea leaves are dried in an oven at 60°C to a moisture content of ≤8%, thereby obtaining yellow tea that has undergone enhanced fermentation and shaking treatment.

[0077] (8) The yellow tea obtained in step (7) was pulverized and sieved through an 80-mesh sieve to obtain yellow tea powder. 2.00 g of the tea powder was weighed and distilled water was added at a material-to-liquid ratio of 1:40 (g / mL). The mixture was placed in a 4°C refrigerator and allowed to stand for 5 hours. After standing, the mixture was placed in an ultrasonic processor with an ultrasonic power of 200 W, an ultrasonic time of 30 minutes, and an ultrasonic temperature of 40°C.

[0078] (9) Centrifuge the ultrasonic extract at 5000 r / min for 10 min and collect the supernatant.

[0079] (10) The supernatant was filtered using nanofiltration technology with a nanofiltration membrane pore size of 10 nm and an operating pressure of 1.0 MPa to obtain a clear yellow tea cold extract.

[0080] (11) Yellow tea cold extract and base wine are mixed in a ratio of 9:2.5 (v / v) to obtain tea wine.

[0081] (12) The tea wine was stored in a refrigerator at 4°C, and the theaflavins content was measured regularly to evaluate its stability.

[0082] Comparative Example 4

[0083] (1) Select fresh yellow tea leaves from the same tea garden, of the same variety, and picked at the same time.

[0084] (2) The fresh yellow tea leaves are moderately withered to make the water loss rate of the tea reach 30%.

[0085] (3) After withering, the temperature is 150℃ and the time is 5 minutes.

[0086] (4) The yellow tea leaves after withering are directly dried in an oven at 60°C to obtain unfermented yellow tea.

[0087] (5) Grind the dried yellow tea and sieve it through an 80-mesh sieve to obtain yellow tea powder.

[0088] (6) Weigh 2.00 g of tea powder and add distilled water at a material-liquid ratio of 1:40 (g / mL). Place the mixture in a refrigerator at 4°C for 5 hours. After standing, place the mixture in an ultrasonic processor at a power of 200 W, a time of 30 minutes, and a temperature of 40°C.

[0089] (7) Centrifuge the ultrasonic extract at 5000 r / min for 10 min and collect the supernatant.

[0090] (8) The supernatant was filtered using nanofiltration technology with a nanofiltration membrane pore size of 10 nm and an operating pressure of 1.0 MPa to obtain a clear yellow tea cold extract.

[0091] (9) The yellow tea cold extract and base wine are mixed in a ratio of 9:2.5 (v / v) to obtain tea wine.

[0092] (10) The tea wine was stored in a refrigerator at 4°C, and the theaflavins content was measured regularly to evaluate its stability.

[0093] Experimental Example 1

[0094] Yellow tea cold brew optimization experiment

[0095] The yellow tea cold extract from Example 1 was subjected to a single-factor experiment to investigate the solid-liquid ratio, extraction temperature, and extraction time. The solid-liquid ratios were 1:20, 1:40, 1:60, 1:80, and 1:100; the extraction temperatures were 0°C, 4°C, 15°C, 25°C, and 35°C; and the extraction times were 3 hours, 4 hours, 5 hours, 6 hours, and 7 hours. Based on the single-factor experiments, an orthogonal experiment was conducted to determine the optimal extraction parameters for the yellow tea extract. The orthogonal experimental design factor levels were designed based on the results of the single-factor experiments.

[0096] The optimal conditions for yellow tea cold extraction optimization experiments were as follows: solid-liquid ratio 1:40, extraction temperature 4°C, and extraction time 5 hours.

[0097] Experimental Example 2

[0098] Tea and wine blending experiment

[0099] Yellow tea cold-brew liquid was blended with base liquor in a specific ratio. A single-factor experiment was conducted to test the base liquor and yellow tea cold-brew liquid amounts used in the tea-wine blend. The base liquor amounts were 80ml, 90ml, 100ml, 110ml, and 120ml, while the yellow tea cold-brew liquid amounts were 10ml, 15ml, 20ml, 25ml, and 30ml. Based on the single-factor experiment, an orthogonal experiment was conducted to test two influencing factors and determine the optimal tea-wine blend ratio. The orthogonal experimental design factor levels were designed based on the results of the single-factor experiment.

[0100] Through the tea and wine blending experiment, it was found that the tea and wine blending effect is best when the base wine volume is 90ml and the yellow tea cold extract volume is 25ml.

[0101] Test Example 1

[0102] Stability test

[0103] The tea wines prepared in Example 1 and Comparative Examples 1-4 were stored in a refrigerator at 4°C, and the theaflavins content was measured regularly to evaluate their stability. The theaflavins content was determined using high performance liquid chromatography (HPLC) using a C18 column, a mobile phase of methanol-water (70:30, v / v), a flow rate of 1.0 mL / min, and a detection wavelength of 278 nm. The details are shown in Table 1:

[0104] Table 1 Determination of theaflavin content in Example 1 and Comparative Example

[0105]

[0106]

[0107] In summary, enhanced fermentation, shaking, and steam explosion treatments significantly increased the theaflavins content in yellow tea. The optimal cold-extract yellow tea ratio was 1:40, 4°C, and 5 hours, and the optimal tea-wine blend ratio was 9:2.5 (v / v). Under these conditions, nanofiltration technology and optimized tea-wine ratios significantly improved the stability of theaflavins in the tea-wine system. Compared to traditional natural fermentation, enhanced fermentation significantly increased the contents of tea polyphenols, theabrownins, and soluble sugars. Shaking promoted the transformation of tea substances, providing more substrates and active ingredients for the formation of theaflavins. Steam explosion facilitated the dissolution of theaflavins from the tea leaves. In the tea-wine system obtained through nanofiltration and optimized ratios, the retention rate of theaflavins reached 85% after three months of storage.

[0108] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing yellow tea with high theaflavins stability, comprising: (1) Select high-quality yellow tea leaves from the same tea garden, the same variety, and picked at the same time; (2) subjecting the fresh yellow tea leaves to withering, fixing and shaking treatments in sequence to obtain shaken yellow tea leaves for later use; (3) The shaken yellow tea leaves and the solid microbial agent were mixed evenly in a mass ratio of 10:1 to form a fermentation matrix. A permeable fermentation tray was used with a thickness of 5 cm. The fermentation was carried out in a constant temperature fermentation room at 30°C for 8 days. Sterile water was sprayed regularly to maintain the matrix humidity at 60%. The matrix was turned over every 12 hours and 0.2% yeast nutrient was sprayed every 24 hours. (4) After the fermentation is completed, the tea leaves are sequentially dried, steam-exploded, cooled, crushed, and sieved to obtain yellow tea with high theaflavins stability.

2. The preparation method according to claim 1, wherein: The fixing treatment temperature in step (2) is 150° C. and the time is 5 min; The shaking treatment temperature is 22° C., the relative humidity is 65%, the time is 40-50 minutes, and there is a pause of 8 minutes every 12 minutes.

3. The preparation method according to claim 1, wherein: The solid bacterial agent in step (3) is obtained by the following method: Pichia pastoris was inoculated into YPD liquid medium and cultured at 28°C with shaking for 24 h. After counting, the culture was diluted to 1×10 6 CFU / mL; Take 10 mL of diluted bacterial solution and centrifuge at 3000 rpm for 5 min to collect the bacteria; The bacteria were mixed with sterilized wheat bran in a mass ratio of 1:5, and an appropriate amount of sterile water was added to make the substrate humidity 60%. The mixture was cultured at 28°C for 24 hours to obtain a solid bacterial agent.

4. The preparation method according to claim 1, wherein: The yeast nutrient in step (3) includes: ammonium sulfate and potassium dihydrogen phosphate.

5. The preparation method according to claim 1, wherein: The drying temperature in step (4) is 60° C., and the mixture is dried to a moisture content of ≤8%. The steam explosion treatment pressure is 0.8 MPa, the steam explosion time is 3 minutes, and the steam explosion temperature is 130°C; The cooling treatment temperature is cooling to room temperature; The sieving particle size is 80 mesh.

6. Yellow tea with high theaflavins stability prepared according to the preparation method according to any one of claims 1 to 5.

7. Use of the yellow tea with high theaflavins stability according to claim 6 in preparing yellow tea wine.

8. The use according to claim 7, wherein: The yellow tea wine is prepared by the following method: (1) Weigh 2.00 g of yellow tea powder, add 40 times the amount of distilled water, and place in a refrigerator at 4°C for 5 hours. Then, ultrasonicate the mixture for 30 minutes at an ultrasonic power of 200 W and an ultrasonic temperature of 40°C to obtain a yellow tea extract; (2) The yellow tea extract was centrifuged at a speed of 5000 r / min for 10 min, and the supernatant was filtered using nanofiltration technology with a nanofiltration membrane pore size of 10 nm and an operating pressure of 1.0 MPa to obtain a yellow tea cold extract; (3) The yellow tea cold extract and the base wine are mixed in a volume ratio of 9:2.5 to obtain a yellow tea wine.

9. Yellow tea wine prepared according to the use of claim 8.

10. A method for detecting the theaflavins content in the yellow tea according to claim 6 or the yellow tea wine according to claim 9, comprising: The theaflavins content was determined by high performance liquid chromatography using a C18 column, a methanol-water mixed solution as the mobile phase, a flow rate of 1.0 mL / min, and a detection wavelength of 278 nm.

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