Preparation technology of selenium-enriched gynostemma pentaphylla Fuzhuan tea

Abstract

The invention discloses a preparation process of selenium-enriched gynostemma pentaphylla Fuzhuan tea. The preparation process comprises the following steps: selecting materials, spreading and airing, deactivating enzymes, rolling, adding selenium, carrying out pile fermentation on mucor, drying, ageing, steaming tea for the second time, pressing, shaping and growing fungus, and ageing for the second time. By adopting the mucor pile fermentation, on one hand, the added inorganic selenium is converted into organic selenium, and the organic selenium is tightly combined with the tea leaves, so that the loss of the selenium element is avoided; and on the other hand, the process of combining mucor pile fermentation with high-temperature instantaneous fixation reduces the degradation effect of gypenoside glycosidase on gypenoside, retains most of gypenoside in the gynostemma pentaphyllum, and improves the health-care effect of the gynostemma pentaphyllum Fuzhuan tea.

Description

Technical Field

[0001] The invention belongs to the technical field of food, and in particular relates to a preparation process of selenium-enriched Gynostemma pentaphyllum Fu tea. Background Art

[0002] Gynostemma pentaphyllum (Gynostemmapentaphyllum) is a perennial herbaceous vine belonging to the genus Gynostemma in the Cucurbitaceae family. Widely distributed in my country, it boasts abundant resources and strong adaptability. Its bitter and slightly sweet flavor is known for its heat-clearing and detoxifying properties, cough-relieving and phlegm-resolving properties, qi-boosting and body fluid-promoting properties, and spleen-strengthening and tranquilizing properties. Its primary active ingredient is gypenosides (GPS), which also contain polysaccharides, flavonoids, terpenes, amino acids, trace elements, and vitamins. These properties have anti-tumor and free radical scavenging and antioxidant properties, slowing cell aging, promoting metabolism, lowering blood sugar and lipids, protecting the liver, cardiovascular system, and enhancing immunity. Gynostemma pentaphyllum, a plant with both medicinal and edible properties, has been widely used in medicine, food, healthcare, daily necessities, and feed processing, offering promising development prospects and market applications.

[0003] Selenium is an essential trace element for humans and animals, with numerous important biological functions. It is essential for maintaining immune system homeostasis and delaying aging, among other physiological functions. Selenium deficiency not only contributes to Keshan disease and Kashin-Beck disease but also increases the risk of cardiovascular, endocrine, nervous, reproductive, and musculoskeletal diseases. The development of selenium-rich functional foods has broad application value and market prospects.

[0004] Compared to its inorganic form, the organic form of selenium boasts higher absorption rates, stronger biological activity, and less environmental pollution. Therefore, research on the organic conversion of selenium is a hot topic in selenium research. Biological conversion of selenium to organic selenium offers a simple and economical approach, facilitating its widespread application in practical production. Currently, selenium-enriched tea in my country is produced by growing tea plants on selenium-rich soil, where the plants convert inorganic selenium in the soil into organic selenium. However, in approximately 72% of regions, soil selenium concentrations are less than 0.1 mg / kg, and much of my country is selenium-deficient. Consequently, research has focused on spraying selenium onto planted tea leaves, allowing the plants to absorb inorganic selenium and convert it into organic selenium. However, this approach suffers from low leaf absorption and conversion rates and significant losses during the spraying process, hindering the development of selenium-enriched tea. Research has also reported on producing selenium-enriched tea by directly spraying selenium onto picked tea leaves. However, spraying inorganic selenium is toxic to humans, and spraying organic selenium not only increases production costs but also prevents it from adhering to the tea leaves, remaining attached to their surface and easily lost during production, storage, and washing, resulting in low selenium concentrations.

[0005] During the production of Fu's tea, fermentation occurs, and gypenosyl glycosidase is released from Gynostemma pentaphyllum. Gynostemma pentaphyllum glycosidase gradually decomposes gypenosyl glycosidase, reducing the gypenosyl glycosidase content in Gynostemma pentaphyllum Fu's tea, thereby affecting the health-care effects of Gynostemma pentaphyllum tea. Although long-term high temperature can inactivate gypenosyl glycosidase, long-term high temperature can also cause the decomposition of gypenosyl glycosidase, which also affects the subsequent flower-blooming process and the overall mouthfeel of the tea. Therefore, a method for reducing the decomposition of gypenosyl glycosidase in the production of Fu's tea is needed. Summary of the Invention

[0006] The present invention aims to provide a process for preparing selenium-enriched Gynostemma pentaphyllum Fucha. The method involves adding inorganic selenium and Mucor spores before fermentation of the Gynostemma pentaphyllum tea. Mucor absorbs inorganic selenium during the fermentation process and converts it into organic selenium. Mucor hyphae penetrate the interior of the tea leaves, securing them to the tea leaves and thereby tightly binding the selenium to the tea. The protease produced by Mucor degrades gypenosyl saponins, effectively reducing the decomposition of gypenosyl saponins during the Gynostemma pentaphyllum Fucha production process. The method also utilizes a high-temperature instantaneous withering method, effectively preventing the destruction of gypenosyl saponins by prolonged high temperatures.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation process of selenium-enriched Gynostemma pentaphyllum Fu tea comprises the following steps:

[0009] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea;

[0010] S2. Place the mixed tea leaves in an open air ventilated environment and dry them;

[0011] S3. The mixed tea leaves are placed in a warm box for fixing;

[0012] S4. The mixed tea leaves are rolled while hot;

[0013] S5. Add inorganic selenium to the mixed tea leaves and mix well;

[0014] S6. Mucor spores were added to the mixed tea leaves after adding inorganic selenium for fermentation; the tea leaves were piled into a certain shape and fermented until the leaves turned yellow and translucent;

[0015] S7. The mixed tea leaves are dried to obtain semi-finished tea;

[0016] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0017] S9. The semi-finished tea after aging is placed into the fermentation machine for secondary steaming;

[0018] S10. The semi-finished tea after the second steaming is pressed into tea bricks;

[0019] S11. After the tea brick is cooled, it is flowered and then dried;

[0020] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0021] Preferably, in S2, the airing time is 3 to 8 hours.

[0022] Preferably, in said S3, the fixing in the incubator comprises: keeping the temperature at 220°C to 260°C for 30 to 50 seconds; adjusting the temperature to 10 to 20°C for 30 to 50 seconds; and adjusting the temperature to 60°C to 100°C for 30 to 50 seconds.

[0023] Preferably, in S4, the kneading time is 3 to 10 minutes.

[0024] Preferably, in said S5, the amount of inorganic selenium added is 1-15 mg / kg of mixed tea leaves; said inorganic selenium includes sodium selenite and sodium selenate.

[0025] Preferably, in S6, the temperature of the fermentation is 20-30°C and the time is 5-15h; the amount of the mold spores added is 10 4 ~3×10 4 Pieces / kg of mixed tea.

[0026] Preferably, in said S7, the drying standard is 5% to 8% moisture.

[0027] Preferably, in said S9, the tea steaming temperature is 120-180°C, the pressure is 0.2-1.0 Pa, and the time is 10-20 s.

[0028] Preferably, in S10, the pressing time is 2 to 10 seconds.

[0029] Preferably, in said S11, the temperature after cooling is 20-30°C, the blooming time is 5-15 days, the blooming temperature is 26-32°C, and the humidity is 60%-70%; the drying temperature is 35-45°C, and the time is 5-15 days.

[0030] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0031] This method overcomes the problem of selenium-enriched tea being difficult to grow in selenium-deficient areas. It also addresses the existing problem of organic or inorganic selenium directly added to tea, which prevents it from being firmly incorporated into the tea leaves and causing selenium loss during production, storage, and tea washing. It also addresses the issue of gypenosides being easily hydrolyzed by gypenosides glycosidase during the production of gypenosides. The process is simple, economical, and suitable for large-scale production.

[0032] The present invention adds inorganic selenium and Mucor spores before the fermentation of Gynostemma pentaphyllum tea. On the one hand, Mucor absorbs inorganic selenium during the fermentation process and converts it into organic selenium. The hyphae of Mucor enters the interior of the tea leaves, so that the Mucor is fixed on the tea leaves, thereby enabling the selenium element to be closely combined with the tea. On the other hand, the protease produced by Mucor degrades the gypenosalpinoside glycosidase, thereby effectively reducing the decomposition of Gynostemma pentaphyllum soap during the production process of Gynostemma pentaphyllum Fucha. The high-temperature instantaneous fixing method is adopted, which also effectively avoids the destruction of gypenosalpinoside by long-term high temperature. The Gynostemma pentaphyllum Fucha produced by the method of the present invention has a high selenium content that is not easily lost, a higher gypenosalpinoside content, and can better exert the health-care effect of Gynostemma pentaphyllum. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of the preparation process of selenium-enriched Gynostemma pentaphyllum Fu tea.

[0034] Figure 2 This is the standard curve of selenium content.

[0035] Figure 3 This is the standard curve of ginsenoside Rb1. DETAILED DESCRIPTION

[0036] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0037] The main compounds used in the examples and comparative examples were all commercially available products and were not subjected to any further purification treatment.

[0038] Mucor (Actinomucor elegans) was purchased from Shanghai Microbiological Collection Center, strain number: SHBCCD19920.

[0039] Example 1

[0040] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0041] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 5 hours until they are dry.

[0042] S3. Place the mixed tea leaves in a thermostat at 240°C for 40 seconds, 16°C for 40 seconds, and 80°C for 40 seconds to fix the green tea leaves.

[0043] S4. Roll the mixed tea leaves while hot for 6 minutes.

[0044] S5. Add 20 mL of 0.5 mg / mL sodium selenite per kilogram of rolled mixed tea leaves and mix thoroughly.

[0045] S6. Add 20 mL of 2×10 4 Mix the suspension of Mucor spores evenly, pile them into a rectangular shape, and ferment them at room temperature of 25℃, turning the pile over every 6 hours for a total of 10 hours until the leaves turn yellow and translucent.

[0046] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 6%, and obtain semi-finished tea.

[0047] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0048] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 140°C and 0.5 Pa for 15 seconds for secondary steaming.

[0049] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 5 seconds.

[0050] S11. After the tea brick is cooled to 25°C, it is allowed to bloom for 10 days at room temperature of 28°C and humidity of 65%, and Eurotium cristatum is cultured, followed by drying at 40°C for 10 days.

[0051] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0052] Example 2

[0053] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0054] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 3 hours.

[0055] S3. Place the mixed tea leaves in a thermostat at 220°C for 30 seconds, 10°C for 30 seconds, and 60°C for 30 seconds to fix the green tea leaves.

[0056] S4. Roll the mixed tea leaves while hot for 3 minutes.

[0057] S5. Add 20 mL of 0.05 mg / mL sodium selenite per kilogram of rolled mixed tea leaves and mix thoroughly.

[0058] S6. Add 20 mL of 2×10 4 Mix the suspension of Mucor spores evenly, pile them into a rectangular shape, and ferment them at room temperature of 25℃, turning the pile over every 4 hours for a total of 5 hours until the leaves turn yellow and translucent.

[0059] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 4%, and obtain semi-finished tea.

[0060] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0061] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 120°C and 0.2 Pa for 10 seconds for secondary steaming.

[0062] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 2 seconds.

[0063] S11. After the tea brick is cooled to 20°C, it is allowed to bloom for 5 days at room temperature of 26°C and humidity of 60%, and Eurotium cristatum is cultured, followed by drying at 35°C for 5 days.

[0064] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0065] Example 3

[0066] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0067] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 8 hours until they are dry.

[0068] S3. Place the mixed tea leaves in a thermostat at 260°C for 50 seconds, 20°C for 50 seconds, and 100°C for 50 seconds to fix the green tea leaves.

[0069] S4. Roll the mixed tea leaves while hot for 10 minutes.

[0070] S5. Add 20 mL of 0.75 mg / mL sodium selenite per kilogram of rolled mixed tea leaves and mix thoroughly.

[0071] S6. Add 20 mL of 2×10 4 Mix the suspension of Mucor spores evenly, pile them into a rectangular shape, and ferment them at room temperature of 25℃, turning the pile over every 8 hours for a total of 15 hours until the leaves turn yellow and translucent.

[0072] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 8%, and obtain semi-finished tea.

[0073] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0074] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 180°C and 1.0 Pa for 20 seconds for secondary steaming.

[0075] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 10 seconds.

[0076] S11. After the tea brick is cooled to 30°C, it is allowed to bloom for 15 days at room temperature of 28°C and humidity of 70%, and Eurotium cristatum is cultured, followed by drying at 45°C for 15 days.

[0077] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0078] Example 4

[0079] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0080] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 5 hours until they are dry.

[0081] S3. Place the mixed tea leaves in a thermostat at 240°C for 40 seconds, 16°C for 40 seconds, and 80°C for 40 seconds to fix the green tea leaves.

[0082] S4. Roll the mixed tea leaves while hot for 6 minutes.

[0083] S5. Add 20 mL of 0.5 mg / mL sodium selenate per kilogram of rolled mixed tea leaves and mix thoroughly.

[0084] S6. Add 20 mL of 2×10 4 Mix the suspension of Mucor spores evenly, pile them into a rectangular shape, and ferment them at room temperature of 25℃, turning the pile over every 6 hours for a total of 10 hours until the leaves turn yellow and translucent.

[0085] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 6%, and obtain semi-finished tea.

[0086] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0087] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 140°C and 0.5 Pa for 15 seconds for secondary steaming.

[0088] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 5 seconds.

[0089] S11. After the tea brick is cooled to 25°C, it is allowed to bloom for 10 days at room temperature of 28°C and humidity of 65%, and Eurotium cristatum is cultured, followed by drying at 40°C for 10 days.

[0090] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0091] Example 5

[0092] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0093] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 5 hours until they are dry.

[0094] S3. Place the mixed tea leaves in a thermostat at 240°C for 40 seconds, 16°C for 40 seconds, and 80°C for 40 seconds to fix the green tea leaves.

[0095] S4. Roll the mixed tea leaves while hot for 6 minutes.

[0096] S5. Add 20 mL of 0.5 mg / mL sodium selenite per kilogram of rolled mixed tea leaves and mix thoroughly.

[0097] S6. Add 20 mL of 10 per kg of mixed tea leaves after adding inorganic selenium. 4 Mix the suspension of 100 Mucor spores evenly, pile them into a rectangular shape, and ferment them at room temperature of 25℃, turning the pile over every 6 hours for a total of 10 hours until the leaves turn yellow and translucent.

[0098] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 6%, and obtain semi-finished tea.

[0099] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0100] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 140°C and 0.5 Pa for 15 seconds for secondary steaming.

[0101] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 5 seconds.

[0102] S11. After the tea brick is cooled to 25°C, it is allowed to bloom for 10 days at room temperature of 28°C and humidity of 65%, and Eurotium cristatum is cultured, followed by drying at 40°C for 10 days.

[0103] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0104] Example 6

[0105] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0106] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 5 hours until they are dry.

[0107] S3. Place the mixed tea leaves in a thermostat at 240°C for 40 seconds, 16°C for 40 seconds, and 80°C for 40 seconds to fix the green tea leaves.

[0108] S4. Roll the mixed tea leaves while hot for 6 minutes.

[0109] S5. Add 20 mL of 0.5 mg / mL sodium selenite per kilogram of rolled mixed tea leaves and mix thoroughly.

[0110] S6. Add 20 mL of 3×10 4 Mix the suspension of Mucor spores evenly, pile them into a rectangular shape, and ferment them at room temperature of 25℃, turning the pile over every 6 hours for a total of 10 hours until the leaves turn yellow and translucent.

[0111] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 6%, and obtain semi-finished tea.

[0112] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0113] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 140°C and 0.5 Pa for 15 seconds for secondary steaming.

[0114] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 5 seconds.

[0115] S11. After the tea brick is cooled to 25°C, it is allowed to bloom for 10 days at room temperature of 28°C and humidity of 65%, and Eurotium cristatum is cultured, followed by drying at 40°C for 10 days.

[0116] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0117] Comparative Example 1

[0118] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0119] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 5 hours until they are dry.

[0120] S3. Place the mixed tea leaves in a thermostat at 240°C for 40 seconds, 16°C for 40 seconds, and 80°C for 40 seconds to fix the green tea leaves.

[0121] S4. Roll the mixed tea leaves while hot for 6 minutes.

[0122] S5. Add 20 mL of sterile water to each kilogram of rolled mixed tea leaves and mix thoroughly.

[0123] S6. Add 2×10 4 Mix the spores of Mucor, pile them into a rectangular shape, keep the room temperature at 25℃, turn the pile over every 6 hours, and ferment for a total of 10 hours until the leaves turn yellow and translucent.

[0124] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 6%, and obtain semi-finished tea.

[0125] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0126] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 140°C and 0.5 Pa for 15 seconds for secondary steaming.

[0127] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 5 seconds.

[0128] S11. After the tea brick is cooled to 25°C, it is allowed to bloom for 10 days at room temperature of 28°C and humidity of 65%, and Eurotium cristatum is cultured, followed by drying at 40°C for 10 days.

[0129] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0130] Comparative Example 2

[0131] S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea.

[0132] S2. Place the mixed tea leaves in an open air and ventilated environment to dry for 5 hours until they are dry.

[0133] S3. Place the mixed tea leaves in a thermostat at 240°C for 40 seconds, 16°C for 40 seconds, and 80°C for 40 seconds to fix the green tea leaves.

[0134] S4. Roll the mixed tea leaves while hot for 6 minutes.

[0135] S5. Add 20 mL of 0.5 mg / mL sodium selenite per kilogram of rolled mixed tea leaves and mix thoroughly.

[0136] S6. Add 20 mL of sterile water per kg of mixed tea leaves to the mixed tea leaves after inorganic selenium addition, mix well, pile into a rectangular shape, and ferment at room temperature of 25°C, turning the pile every 6 hours for a total of 10 hours until the leaves turn yellow and translucent.

[0137] S7. Place the mixed tea leaves in a dryer and dry them. Take them out when the moisture content reaches 6%, and obtain semi-finished tea.

[0138] S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year;

[0139] S9. Place the aged semi-finished tea into a fermentation machine and steam it at 140°C and 0.5 Pa for 15 seconds for secondary steaming.

[0140] S10. The semi-finished tea after the second steaming is pressed into tea bricks using a 60-ton hydraulic press for 5 seconds.

[0141] S11. After the tea brick is cooled to 25°C, it is allowed to bloom for 10 days at room temperature of 28°C and humidity of 65%, and Eurotium cristatum is cultured, followed by drying at 40°C for 10 days.

[0142] S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

[0143] Experimental Example 1: Determination of Selenium Content

[0144] Determination of total selenium content: Accurately weigh 1g of tea sample using an analytical balance and place it in a beaker. Add 50mL of distilled water and soak for 20 minutes. Filter the tea leaves and dry them at 50°C. Add 20mL of a 4+1 mixed acid (nitric acid to perchloric acid, 4:1 by mass) to the tea leaves and digest them on a hot plate at 185°C. Heat until the solution becomes clear and colorless with white smoke and is nearly dry. After cooling, add 5mL of 1:1 hydrochloric acid to the remaining digestion solution and continue on a hot plate to remove the acid until nearly dry. After cooling, add 5mL of concentrated hydrochloric acid and dilute to 25mL with ultrapure water. Dilute 10-fold with 20% hydrochloric acid and determine the total selenium content in the tea leaves using an atomic fluorescence spectrometer. Simultaneously test a blank sample.

[0145] Determination of inorganic selenium: Accurately weigh 4g of sample into a beaker using an analytical balance. Add 200mL of distilled water and soak for 20 minutes. After filtering, dry the tea leaves at 50°C and transfer them to a graduated stoppered test tube. Add 20mL of 1:1 hydrochloric acid and mix thoroughly in an ultrasonicator for 30 minutes. Then, place in a boiling water bath for 30 minutes, cool, and filter. Place 5mL of the filtrate in a beaker, add 10mL of the 4+1 mixed acid, and digest on a hot plate at 185°C. Heat until the solution becomes clear and colorless with the emission of white smoke and is nearly dry. After the treated solution cools, add 5mL of 1:1 hydrochloric acid and continue on a hot plate to remove the acid until nearly dry. After the treated solution cools, add 5mL of concentrated hydrochloric acid and dilute to 25mL with ultrapure water. Determine the inorganic selenium content of the tea leaves using an atomic fluorescence spectrophotometer, while also testing a blank sample.

[0146] Pipette 20mL of 1000mg / L selenium standard solution into a 100mL volumetric flask, add 20mL of concentrated hydrochloric acid, and dilute with ultrapure water to a selenium standard intermediate solution with a mass concentration of 0.2mg / L. Then, prick 10mL of the intermediate solution into a 100mL volumetric flask, add 18mL of concentrated hydrochloric acid, and dilute with ultrapure water to a selenium standard working solution with a mass concentration of 0.02mg / L. During detection, the instrument automatically dilutes to different mass concentrations of 2, 4, 8, 16, and 20μg / L. Use the measured fluorescence intensity as the ordinate and the corresponding mass concentration as the abscissa to draw a standard curve, and calculate the regression equation and correlation coefficient (such as Figure 2 ). Calculate the selenium content in the sample based on the obtained standard curve (as shown in Table 1)

[0147] Table 1: Selenium content in Gynostemma pentaphyllum tea

[0148] Group <![CDATA[Total selenium content mg·kg -1 > <![CDATA[Inorganic selenium content mg·kg -1 > <![CDATA[Organic selenium content mg·kg -1 > Example 1 3.623 0.614 3.009 Example 2 3.417 0.578 2.839 Example 3 3.439 0.581 2.858 Example 4 3.598 0.602 2.996 Example 5 3.176 0.567 2.609 Example 6 3.611 0.625 2.986 Comparative Example 1 0.041 0.038 0.003 Comparative Example 2 1.574 1.499 0.075

[0149] The organic selenium content is equal to the total selenium content minus the inorganic selenium content. The test results show that a certain amount of inorganic selenium and Mucor spores are added before the fermentation. During the fermentation process, the inorganic selenium added can be converted into organic selenium due to the absorption and conversion of Mucor, and the organic selenium obtained by conversion is tightly connected to the tea leaves. After soaking in water before detection, there is still a high organic selenium content. Example 1 is the optimal process scheme. The difference between Examples 2 to 6 and Example 1 is the change in process parameters. The change in these parameters has little effect on the content of organic selenium. Comparative Example 1 is a comparison without adding inorganic selenium, and Comparative Example 2 is a comparison without adding Mucor. The results show that in the tea leaves without adding Mucor, most of the inorganic selenium has been lost after soaking, and a small amount of inorganic selenium can be detected, while almost no organic selenium is contained. This shows that the addition of Mucor is crucial to the selenium-enriched process of Gynostemma pentaphyllum Fu tea, and Mucor is the key factor in converting the added inorganic selenium into organic selenium.

[0150] Experimental Example 2: Determination of Gynostemma pentaphyllum total saponin content

[0151] Take Gynostemma pentaphyllum tea, dry it, grind it, and pass it through a 0.250mm pore size (60 mesh) standard sieve. Accurately weigh 1g of Gynostemma pentaphyllum powder and place it in a round-bottom flask. Add 50mL of 75% ethanol and reflux extract at 80°C twice, each time for 1 hour. After cooling, centrifuge and combine the extracts. Concentrate the extracts to dryness using a rotary evaporator in a vacuum vacuum. Add water to the residue and bring the volume to a 100mL volumetric flask. Transfer 1mL of the supernatant to a chromatography column filled with macroporous adsorption resin. Wash the column with 25mL of water, discard the eluent, and elute with 25mL of 70% ethanol. Collect the eluent and transfer it to a rotary evaporator to dry it. Dissolve it in 5mL of methanol and filter to obtain the sample solution. Transfer 1mL to a stoppered test tube and evaporate it to dryness using a nitrogen purge. This will be used for color development. After the solvent has evaporated, add 0.4 mL of vanillin glacial acetic acid solution, rotate the test tube to dissolve the residue, add 1.6 mL of perchloric acid, incubate in a 60°C water bath for 10 minutes, take out and cool in an ice bath for 3 minutes, accurately add 5 mL of glacial acetic acid, shake well, and perform colorimetry at a wavelength of 550 nm.

[0152] Preparation of standard curve: Accurately measure 20, 40, 60, 80, 100 and 120 μL of ginsenoside Rb1 standard solution (2 mg / mL) and place them in stoppered test tubes respectively. Volatilize them in a nitrogen blower at 60°C, add 0.4 mL of vanillin glacial acetic acid solution, rotate the test tube to dissolve the residue, add 1.6 mL of perchloric acid, and place in a 60°C water bath for 10 minutes. Take out and cool in an ice bath for 3 minutes. Accurately add 5 mL of glacial acetic acid, shake well, and perform colorimetry at a wavelength of 550 nm. Regression calculation is performed with absorbance (A) as the ordinate and ginsenoside Rb1 content (mg) as the abscissa, and a regression equation is established (such as Figure 3 The total saponin content of Gynostemma pentaphyllum in the sample was calculated according to the obtained standard curve (as shown in Table 2).

[0153] Table 2: Total saponin content in Gynostemma pentaphyllum tea

[0154] Group absorbance <![CDATA[Total gypenoside content g·100g -1 > Example 1 0.72 9.60 Example 2 0.711 9.48 Example 3 0.715 9.53 Example 4 0.719 9.59 Example 5 0.592 7.89 Example 6 0.674 8.99 Comparative Example 1 0.726 9.68 Comparative Example 2 0.353 4.71

[0155] The gypenosin content detection experiment showed that the gypenosin content in the gypenosin tea fermented with Mucor spores (Example 1) was higher than that in the gypenosin tea without Mucor spores (Comparative Example 2), which was related to the inhibition of gypenosin glycosidase by protease produced by Mucor.

[0156] In summary, adding a certain amount of Mucor spores before pile fermentation can not only convert the added inorganic selenium into organic selenium that is tightly combined with tea leaves, thereby obtaining selenium-rich Gynostemma pentaphyllum Fu tea in selenium-deficient areas and reducing production costs, but also protect the key component of Gynostemma pentaphyllum, gypenosides, from hydrolysis by gypenosides glycosidase, which plays a key role in increasing the content of gypenosides, which is also beneficial to the health care effects of Gynostemma pentaphyllum Fu tea.

[0157] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A preparation process for selenium-enriched Gynostemma pentaphyllum tea, characterized in that: The steps include: S1. Select tea leaves with one bud and two leaves to one bud and four leaves and mix them with Gynostemma pentaphyllum as mixed tea; S2. Place the mixed tea leaves in an open air ventilated environment and dry them; S3. The mixed tea leaves are placed in a warm box for fixing; S4. The mixed tea leaves are rolled while hot; S5. Add inorganic selenium to the mixed tea leaves and mix well; S6. Mucor spores were added to the mixed tea leaves after adding inorganic selenium for fermentation; S7. The mixed tea leaves are dried to obtain semi-finished tea; S8. The dried semi-finished tea is piled in a ventilated, dry, odor-free environment for one year; S9. The semi-finished tea after aging is placed into the fermentation machine for secondary steaming; S10. The semi-finished tea after the second steaming is pressed into tea bricks; S11. After the tea brick is cooled, it is flowered and then dried; S12. The dried tea bricks are piled up in a ventilated, dry, and odor-free environment for one year to be converted into finished tea.

2. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S2, the airing time is 3 to 8 hours.

3. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S3, the fixing process in the incubator includes: keeping the temperature at 220°C to 260°C for 30 to 50 seconds; adjusting the temperature to 10 to 20°C for 30 to 50 seconds; and adjusting the temperature to 60°C to 100°C for 30 to 50 seconds.

4. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S4, the kneading time is 3 to 10 minutes.

5. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S5, the amount of inorganic selenium added is 1-15 mg / kg of mixed tea leaves; the inorganic selenium includes sodium selenite and sodium selenate.

6. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S6, the temperature of the fermentation is 20-30°C and the time is 5-15h; the amount of the mold spores added is 10 4 ~3×10 4 Pieces / kg of mixed tea.

7. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S7, the drying standard is 5% to 8% moisture.

8. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S9, the tea steaming temperature is 120-180°C, the pressure is 0.2-1.0 Pa, and the time is 10-20 s.

9. The preparation process of a selenium-enriched Gynostemma pentaphyllum tea according to claim 1, characterized in that: In S10, the pressing time is 2 to 10 seconds.

10. The preparation process of a selenium-enriched Gynostemma pentaphyllum Fu tea according to claim 1, characterized in that: In S11, the temperature after cooling is 20-30°C, the flowering time is 5-15 days, the flowering temperature is 26-32°C, and the humidity is 60%-70%; the drying temperature is 35-45°C, and the time is 5-15 days.

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