A brewing process and quality evaluation method for high-quality tea soup

Abstract

This invention relates to a brewing process and quality evaluation method for high-quality tea infusion. The method involves weighing 1g of tea leaves, preheating ultrapure water at different temperatures, brewing the tea infusion at a tea-to-water ratio of 1:50 in a water bath at the same temperature at different time intervals, filtering immediately after each time, separating the tea infusion from the tea leaves, and collecting the tea infusion separately for testing. The chemical composition of selenium-enriched black tea, selenium-enriched green tea, ordinary black tea, and ordinary green tea are compared to explore the leaching patterns and sensory evaluation of quality components in selenium-enriched black tea and selenium-enriched green tea under different brewing conditions. By establishing a daily tea-drinking model, the antioxidant activity, hypoglycemic activity, and antibacterial activity of the tea infusion before and after digestion are measured. Compared with existing technologies, this invention establishes a quality evaluation method for different teas, optimizes the brewing process for high-quality tea infusion based on the leaching amount of quality components, sensory evaluation, and bioactivity, and provides guidance for consumers in selecting the optimal brewing conditions for teas that combine flavor and nutritional characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of tea applications, and particularly to a brewing process and quality evaluation method for high-quality tea soup. Background Art

[0002] The biological activity of tea lies in its rich active compound components. These substances not only bring rich taste to the tea soup, but also endow tea with various potential health benefits for the human body, and most of them are water-soluble organic substances. Taking tea polyphenols and catechins as examples, they have significant hypoglycemic and hypotensive activities, which help to maintain the metabolic balance of the human body. Flavonoids and theanine in tea are natural antioxidants, which can effectively delay the aging process and enhance immunity. Tea can also reduce the incidence of nervous system diseases and prevent the occurrence of different types of diseases such as cancer, metabolic syndrome, and cardiovascular diseases. Due to differences in variety, origin, and processing methods, the content of flavor substances in different types of tea varies. Generally speaking, the taste components in the tea soup mainly include: bitter and astringent polyphenolic compounds, caffeine, umami amino acids, soluble sugars, and pectin and other substances. The taste of the tea soup is the coordinated cooperation of various substances. Therefore, it is very necessary to study the dissolution rules of flavor substances in tea under different conditions to provide a theoretical basis for the deep processing of tea or daily drinking tea. Previous studies have found that with the increase of the tea-water ratio, brewing time, and temperature, the content of dissolved tea polyphenols, amino acids, caffeine, total sugar, theaflavins, theabrownins, and thearubigins is higher, and the taste of the tea soup presents an obvious taste and rich texture.

[0003] China has a long and diverse history of tea-drinking habits. Affected by factors such as geographical environment, history and culture, and ethnic habits, different tea-drinking customs have formed in different regions. Slow tea-drinking is more popular in South China, such as the morning tea culture in Guangdong, and the Gongfu tea is popular in Chaozhou and Shantou areas in Guangdong. The combination of tea and food is relatively common among ethnic minorities in China, such as Tibetan butter tea and Mongolian salty milk tea. In mountainous areas, it is common to use tea as medicine, such as the Tujia people in the areas of Hunan, Hubei, Guizhou, and Sichuan drinking pounded tea. Pounded tea is made by putting tea and ingredients into a pounding mortar and grinding them finely, and then pouring boiling water to brew. In addition, there are preferences and specific customs for choosing tea drinks in different regions. For example, jasmine tea is mostly drunk in Beijing, green tea is consumed more in Shanghai, oolong tea is popular in Fujian and Guangdong regions, and Pu'er tea is mainly consumed in the southwest region. This tea-drinking method emphasizes directly brewing tea with boiling water without adding any condiments to experience the original color and fragrance of tea. To sum up, when studying the influence of different tea-drinking methods on the dissolution rules of tea components, it is necessary to fully consider the tea-drinking habits of consumers in different regions. Summary of the Invention

[0004] The purpose of this invention is to provide a high-quality tea brewing process and quality evaluation method to solve the above-mentioned problems. Based on the national standard method for determining tea components, fitting and calculating the dissolution rate and dissolution time of tea components, and simulating daily tea drinking, this invention provides data for understanding the dissolution patterns of various components during the tea brewing process and provides a scientific basis for rationally selecting tea brewing conditions based on high biological activity.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] The purpose of this invention is to provide a brewing process and quality evaluation method for high-quality tea infusion, the method comprising the following steps:

[0007] S1. Pre-treat tea leaves of different years and varieties to obtain pre-treated tea leaves;

[0008] S2. The chemical content of the pretreated tea was determined and significance analysis was performed to verify the stability of different varieties of tea in different years.

[0009] S3. Brew the tea and prepare tea samples under different temperatures and time conditions;

[0010] S4. Calculate the dissolution rate of tea infusion samples obtained under different temperatures and time conditions. Through logarithmic fitting, with time as the independent variable and the component content dissolution rate as the dependent variable, obtain the dissolution rate fitting curve of tea infusion samples under different temperature conditions. Obtain the change in dissolution concentration of tea infusion samples under different temperatures and time conditions, and calculate the half-maximum dissolution time t of components in tea infusion samples under different conditions. 50 and complete dissolution time t 100 ;

[0011] S5. Sensory evaluation is used to score the taste, color, and aroma of tea soup under different temperatures and time conditions, and a sensory evaluation database of tea soup is constructed.

[0012] S6. Combine the dissolution rate fitting curves of tea samples under different temperature conditions obtained in step S4 with the sensory evaluation database of tea obtained in step S5 to establish a daily tea drinking model.

[0013] S7. The bioavailability of the daily tea drinking model was verified by measuring its hypoglycemic activity, antioxidant activity, and antibacterial activity through in vitro simulated digestion experiments.

[0014] Further, step S1 specifically includes the following process: place the tea leaves to be tested in a grinder and grind for 30 seconds, then add a small amount of tea leaves, stir evenly, grind again for about 60 seconds, filter with 200-mesh nylon cloth, obtain the pretreated tea leaves under drying conditions, store in a sealed bag, mark it, and store for short-term storage in a 4°C refrigerator for easy use in subsequent content determination experiments.

[0015] Further, in step S2, the chemical content determination of the pretreated tea includes one or more of the following determinations: determination of tea polyphenols in tea, determination of total soluble sugar content in tea, determination of total free amino acids in tea, determination of catechins in tea, determination of theanine and γ-aminobutyric acid in tea, determination of soluble protein content in tea, determination of total selenium content in tea, determination of chlorophyll content in tea, determination of tea pigment content in tea, and determination of total flavonoids in tea.

[0016] Further, step S3 includes the following process: weigh 1g of tea leaves, preheat ultrapure water at different temperatures, add 50mL of water at a tea-to-water ratio of 1:50, and brew the tea in a water bath at the same temperature at different time intervals. After the time is up, filter immediately to separate the tea soup from the tea leaves, and collect the tea soup for testing; the different temperatures include the following temperature conditions: 65℃, 75℃, 85℃, 100℃; the different time intervals include the following time intervals: 1min, 3min, 5min, 7min, 9min, 15min, 30min, 40min.

[0017] Furthermore, the tea leaves are selected from one or more of selenium-enriched black tea, ordinary black tea, selenium-enriched roasted green tea, and ordinary roasted green tea. The tea leaves are selected from one or more of 2021, 2022, and 2023.

[0018] Furthermore, in step S4, the dissolution rate of tea components measured at 100℃ for 40 minutes is defined as 100%, thereby calculating the dissolution rate of tea infusion samples obtained under different temperatures and time conditions.

[0019] Furthermore, in step S6, by combining the dissolution rate fitting curves of tea soup samples under different temperature conditions obtained in step S4 and the sensory evaluation database of tea soup obtained in step S5, a daily tea drinking model is established. The following conditions are selected as the daily tea drinking model: water temperature 100 degrees Celsius, tea-to-water ratio 1:50, 50 mL of water is added to each type of tea, and a total of four tea soups are brewed. The brewing time for the first, second, and third tea soups is designed to be 5 minutes, and the fourth tea soup is regarded as the last brew, with a brewing time of 1 hour.

[0020] Further, in step S7, the in vitro simulated digestion experiment includes one or more of the following: simulated saliva experiment, simulated gastric juice experiment, and simulated intestinal juice experiment. In step S7, the determination of in vitro hypoglycemic activity includes one or more of the following: determination of α-glucosidase inhibition rate activity and determination of α-amylase inhibition rate activity. In step S7, the determination of antioxidant activity includes one or more of the following: determination of DPPH· scavenging rate and performance of ABTS· free radical scavenging experiment.

[0021] Furthermore, based on methods such as determining tea components using national standard methods, fitting and calculating the dissolution rate and time of tea infusion components, and simulating daily tea drinking, data is provided to help people understand the dissolution patterns of various components during the tea brewing process, and to provide a scientific basis for rationally selecting tea brewing conditions based on high bioactivity. The main contents are as follows:

[0022] (1) To summarize the correlation patterns of quality components in twelve different years of (selenium-enriched) green tea and (selenium-enriched) black tea, the basic components and characteristic quality components of tea leaves from three years of ordinary green tea, selenium-enriched green tea, ordinary black tea, and selenium-enriched black tea were systematically tested using national standard methods. These components included tea polyphenols, soluble sugars, proteins, total free amino acids, theanine, catechins, total flavonoids, chlorophyll, tea pigments, and selenium content. By studying the influence of different years on the quality components of tea leaves and conducting significance analysis, the stability of tea quality across different years was verified.

[0023] (2) In order to study the effects of different brewing conditions such as time and temperature on the dissolution process of selenium-enriched green and black tea infusions and the dissolution characteristics of various components, linear fitting and calculation of the theoretical half-dissolution time t were used. 50 Complete dissolution time t 100 The optimal brewing conditions were determined, and a comprehensive score was given based on sensory evaluation, providing theoretical basis and data support for subsequent steps.

[0024] (3) Based on consumer lifestyle habits, national standard methods, and previous experimental conclusions, a simulated daily tea drinking model was constructed. Further, tea infusions were prepared at 100℃ for the first, second, and third infusions (all steeped for 5 minutes), and the final infusion (steeped for 1 hour). In vitro digestion was simulated, and the in vitro hypoglycemic activity, antioxidant activity, and in vitro antibacterial activity were measured to verify the bioavailability of the daily tea drinking model and maximize it under suitable conditions. Through in vitro simulated digestion experiments on tea leaves, and by measuring the tea infusion's activity against in vitro free radical scavenging, inhibition rate of sugar metabolism-related enzymes, and antibacterial activity, the antioxidant, hypoglycemic, and antibacterial activities of the tea infusion were determined. This screened the potential biological activities of the tea infusion, providing a reference for further in-depth research on the mechanisms of tea infusion digestion, absorption, and biological activity in the human body.

[0025] Furthermore, this invention relates to a brewing process and quality evaluation method for high-quality tea infusion. 1g of tea leaves are weighed, and ultrapure water at different temperatures (65℃, 75℃, 85℃, 100℃) is preheated. At a tea-to-water ratio of 1:50, 50mL of water is added to each type of tea. The tea infusion is then brewed in a water bath at the same temperature for time intervals of 1, 3, 5, 7, 9, 15, 30, and 40 minutes. After the designated time, the infusion is immediately filtered to separate the tea leaves from the tea infusion, and the tea infusion is collected separately for testing. The chemical compositions of selenium-enriched black tea (SeBT), selenium-enriched green tea (SeGT), ordinary black tea (BT), and ordinary green tea (GT) were compared. The extraction patterns and sensory evaluation of quality components in SeGT and SeBT under different brewing conditions were further explored. By establishing a daily tea-drinking model, the antioxidant activity, hypoglycemic activity, and antibacterial activity of the tea infusion before and after digestion were determined. In summary, brewing at 100℃ for 5 minutes effectively extracts the quality components of the tea leaves, while brewing at 85℃ for 5 minutes reduces the bitterness of the tea infusion.

[0026] Compared with the prior art, the beneficial effects of the present invention are reflected in the following aspects:

[0027] 1) The present invention proposes a brewing process and quality evaluation method for high-quality tea soup. Based on the national standard method for determining tea components, fitting and calculating the dissolution rate and dissolution time of tea soup components, and simulating daily tea drinking, it provides data for people to understand the dissolution rules of various components in the tea brewing process, and provides a scientific basis for rationally selecting tea brewing conditions based on high biological activity.

[0028] 2) The present invention proposes a brewing process and quality evaluation method for high-quality tea infusion, and establishes a quality evaluation method for different teas. Based on the extraction amount of quality components, sensory evaluation and bioactivity, the brewing process for high-quality tea infusion is optimized, providing guidance for selecting the best brewing conditions for teas that have both flavor and nutritional characteristics.

[0029] 3) The brewing process and quality evaluation method for high-quality tea soup proposed in this invention provide technical support for the brewing process and quality evaluation of high-quality tea soup. It has the advantages of data quantification, objective results, and high accuracy of judgment, and can be applied to select the best brewing conditions for tea with both flavor and nutritional characteristics. Attached Figure Description

[0030] Figure 1This is a schematic diagram illustrating the content of chemical components in tea leaves in an embodiment of the present invention, wherein: soluble sugar (A); total flavonoids (B); moisture (C); soluble protein (D); tea polyphenols (E); catechins and caffeine in green tea (F); catechins and caffeine in black tea (G); thea pigments in green tea (H); thea pigments in black tea (I); chlorophyll a and chlorophyll b in green tea (J) and chlorophyll a and chlorophyll b in black tea (K); selenium (L); total free amino acids (M) (* indicates a significant difference compared to other groups, *, p<0.05; **, p<0.01; ***, p<0.001).

[0031] Figure 2 The embodiments of the present invention illustrate the effects of different temperatures and times on the dissolution patterns of tea polyphenols (A), flavonoids (B), soluble sugars (C), free amino acids (D), caffeine (E), and L-theanine (F) in selenium-enriched green tea (SeGT) infusion; and the effects of different temperatures and times on the dissolution patterns of tea polyphenols (G), flavonoids (H), soluble sugars (I), free amino acids (J), caffeine (K), and L-theanine (L) in selenium-enriched black tea (SeBT) infusion.

[0032] Figure 3 Sensory evaluation radar charts of selenium-enriched green tea (A) and selenium-enriched black tea (B) in embodiments of the present invention; appearance of selenium-enriched green tea infusion (C) and selenium-enriched black tea infusion (D) at different brewing temperatures and times.

[0033] Figure 4 In the embodiments of the present invention, the DPPH free radical scavenging rate (A) and ABTS free radical scavenging rate (B) of tea infusions with different brewing times before and after digestion; the α-glucosidase inhibition rate (C) and α-amylase inhibition rate (D) of tea infusions with different brewing times before and after digestion (Note: 1-4 represent the first to fourth brewing times, AD represents after digestion, and **** represents p<0.0001).

[0034] Figure 5 This is a schematic diagram of the brewing process and quality evaluation method for high-quality tea in an embodiment of the present invention. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments, but this is by no means a limitation thereof. Any preparation methods, materials, structures, or compositional ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0036] Example 1

[0037] This embodiment provides a brewing process and quality evaluation method for high-quality tea infusion, the method comprising the following steps:

[0038] S1. Pre-treat tea leaves of different years and varieties to obtain pre-treated tea leaves. The specific process is as follows: Place the tea leaves to be tested in a grinder and grind for 30 seconds. Then add a small amount of tea leaves, stir evenly, grind for a second time for about 60 seconds, filter with 200-mesh nylon cloth, and obtain pre-treated tea leaves under dry conditions. Store in a sealed bag, mark it, and store for short-term storage in a 4°C refrigerator for easy use in subsequent content determination experiments.

[0039] S2. The chemical content of the pretreated tea was determined and significance analysis was performed to verify the stability of different tea varieties in different years. The chemical content determination of the pretreated tea included the following determinations: tea polyphenols, total soluble sugars, total free amino acids, catechins, theanine and γ-aminobutyric acid, soluble protein, total selenium, chlorophyll, tea pigments, and total flavonoids.

[0040] S3. Prepare tea samples by brewing tea at different temperatures and for different times. The specific process is as follows: Weigh 1g of tea leaves, preheat ultrapure water at different temperatures, add 50mL of water at a tea-to-water ratio of 1:50, and brew the tea in a water bath at the same temperature at different time intervals. After the time is up, filter immediately to separate the tea and tea leaves, and collect the tea for testing. The different temperatures include the following conditions: 65℃, 75℃, 85℃, and 100℃; the different time intervals include the following time intervals: 1min, 3min, 5min, 7min, 9min, 15min, 30min, and 40min.

[0041] S4. Calculate the dissolution rate of tea infusion samples obtained under different temperatures and time conditions. Through logarithmic fitting, with time as the independent variable and the component content dissolution rate as the dependent variable, obtain the dissolution rate fitting curve of tea infusion samples under different temperature conditions. Obtain the change in dissolution concentration of tea infusion samples under different temperatures and time conditions, and calculate the half-maximum dissolution time t of components in tea infusion samples under different conditions. 50 and complete dissolution time t 100 ;

[0042] S5. Sensory evaluation is used to score the taste, color, and aroma of tea soup under different temperatures and time conditions, and a sensory evaluation database of tea soup is constructed.

[0043] S6. Combine the dissolution rate fitting curves of tea samples under different temperature conditions obtained in step S4 with the sensory evaluation database of tea obtained in step S5 to establish a daily tea drinking model.

[0044] S7. Through in vitro simulated digestion experiments, including simulated saliva experiments, simulated gastric juice experiments, and simulated intestinal juice experiments, the in vitro hypoglycemic activity, antioxidant activity, and in vitro antibacterial activity were measured to verify the bioavailability of the daily tea drinking model.

[0045] In this embodiment, different types of tea were selected, namely selenium-enriched black tea, ordinary black tea, selenium-enriched roasted green tea, and ordinary roasted green tea. The different teas were selected from the years 2021, 2022, and 2023.

[0046] In step S4, the dissolution rate of tea components measured at 100℃ for 40 minutes is defined as 100%, thereby calculating the dissolution rate of tea infusion samples obtained under different temperatures and time conditions.

[0047] In step S6, the following conditions are selected as the daily tea drinking model: water temperature 100 degrees, tea-to-water ratio 1:50, a total of four tea infusions, the first, second and third tea infusions are designed to be brewed for 5 minutes, the fourth tea infusion is regarded as the last infusion, and the brewing time is designed to be 1 hour.

[0048] In step S6, the determination of in vitro hypoglycemic activity includes one or more of the following: determination of α-glucosidase inhibition rate activity and determination of α-amylase inhibition rate activity. In step S6, the determination of antioxidant activity includes one or more of the following: determination of DPPH· scavenging rate and performance of ABTS· free radical scavenging assay.

[0049] Determination of tea polyphenols in tea: The determination was performed using the spectrophotometric method as specified in GB / T 8313-2018 "Determination of tea polyphenols and catechins in tea".

[0050] Determination of total soluble sugar content in tea: The determination was performed using the phenol-sulfuric acid method as specified in SN / T 4260-2015.

[0051] Total free amino acids in tea: Refer to GB / T 8314-2013 "Determination of total free amino acids in tea".

[0052] Determination of catechins in tea: The determination was performed according to the spectrophotometric and high-performance liquid chromatography (HPLC) methods in GB / T 8313-2018, with appropriate modifications. Details are as follows:

[0053] Sample preparation: Weigh 1 g (accurate to 0.01 g) of tea powder into a 200 mL beaker, add 50 mL of 70% methanol solution preheated to 70 °C, stir well, and seal to prevent methanol evaporation. Extract in a 70 °C water bath for 1 h, shaking and filtering. After extraction, transfer to a 100 mL volumetric flask, cool, and dilute to the mark with water, mixing well. Filter through a 0.45 μm aqueous filter membrane, and then analyze using liquid chromatography.

[0054] Liquid chromatography conditions: High performance liquid chromatograph LC-20AT (Shimadzu, Tokyo, Japan) was used. Mobile phase A: ultrapure water, mobile phase B: methanol (0.1% formic acid), flow rate: 0.8 mL / min, column temperature: 35℃, injection volume: 40 μL, detection wavelength: 254 nm.

[0055] The time program settings for high performance liquid chromatography (HPLC) in the determination of catechins in tea are shown in Table 1.

[0056] Table 1. High Performance Liquid Chromatography (HPLC) Time Programs.

[0057]

[0058]

[0059] Determination of theanine and γ-aminobutyric acid in tea: Refer to GB / T 23193-2017 "Determination of theanine in tea by high performance liquid chromatography". Details are as follows:

[0060] Sample preparation: Weigh 1.0 g (accurate to 0.01 g) of tea powder into a 200 mL beaker and add 100 mL of boiling distilled water. Incubate in a 100℃ water bath for 30 min, filter, transfer to a 100 mL volumetric flask, cool, and dilute to the mark with water. Mix well. Filter through a 0.45 μm aqueous filter membrane, and then perform liquid chromatography analysis.

[0061] Liquid chromatography conditions: A high-performance liquid chromatograph (LC-20AT, Shimadzu, Tokyo, Japan) was used. Mobile phase A was ultrapure water, and mobile phase B was pure acetonitrile. Both phases were pre-filtered using two 0.45 μm membranes and sonicated for half an hour to remove air bubbles. The flow rate was set at 0.8 mL / min, column temperature at 35 °C, injection volume at 40 μL, and detection wavelength at 190 nm.

[0062] The high-performance liquid chromatography (HPLC) time program settings for the determination of theanine and γ-aminobutyric acid in tea are shown in Table 2.

[0063] Table 2. High Performance Liquid Chromatography (HPLC) Time Programs.

[0064]

[0065] Determination of soluble protein content in tea: The determination was performed using the Coomassie Brilliant Blue method as specified in SN / T 3926-2014.

[0066] Determination of total selenium content in tea: The selenium content was determined by atomic fluorescence spectrometry, referring to GB 5009.93-2017 "National Food Safety Standard - Determination of Selenium in Food".

[0067] Determination of chlorophyll content in tea: Refer to NY / T 3082-2017 "Determination of chlorophyll content in fruits, vegetables and their products by spectrophotometry" and make appropriate modifications.

[0068] Determination of the content of tea pigments in tea: The process for determining the content of theaflavins, thearubigins, and theabrownins is as follows: First, weigh and crush the tea leaves and mix them with boiling water; then, extract the tea powder in a boiling water bath for 10 minutes, stirring 2-3 times during extraction; after extraction, filter the solution while it is still hot and cool it to room temperature; collect the cooled extract, add ethyl acetate and shake for 5 minutes; after standing and separating the layers, keep the ethyl acetate layer and the aqueous layer separately; collect the ethyl acetate extract and dilute to volume with ethanol to obtain solution a; collect the ethyl acetate extract and mix it with 2.5% NaHCO3 solution, shake for 30 minutes. After standing for 3 seconds, discard the NaHCO3 aqueous layer and extract the ethyl acetate supernatant. Dilute to volume with 95% ethanol to obtain solution c. Mix the aqueous extract with saturated oxalic acid solution and water, and dilute to volume with 95% ethanol to obtain solution d. Separate the extract and n-butanol solution into containers, shake for 3 minutes, separate the aqueous layer, and mix the aqueous layer with saturated oxalic acid solution and distilled water. Dilute to volume with 95% ethanol to obtain solution b. Measure the absorbance A of each solution at 380 nm using a 1 cm cuvette with 95% ethanol as a blank control.

[0069] After determining the absorbance A of each solution using the spectrophotometric method, the formulas for calculating the contents of theaflavins, thearubigins, and theabrownins are as follows:

[0070] Theaflavins (%) = Ac × 2.25 / (m × w) × 100%

[0071] Thearubigin (%) = (2Aa + 2Ad - Ac - 2Ab) × 7.06 / (m × w) × 100%

[0072] Theabrownin (%)=7.06×2Ab / (m×w)×100%

[0073] In the formula, m is the mass of instant tea powder (g); w is the dry matter content of instant tea powder (%); Aa is the absorbance of solution a; Ab is the absorbance of solution b; Ac is the absorbance of solution c; Ad is the absorbance of solution d; 2.25 and 7.06 are conversion factors under the same operating conditions.

[0074] Determination of total flavonoids in tea: Sample preparation: Accurately weigh 0.1 g of 12 kinds of tea powder into 10 mL centrifuge tubes, add 3 mL of anhydrous ethanol, and extract by sonication for 60 min, shaking once every 20 min. Filter through a 0.45 μm filter membrane, and make up to 5 mL with anhydrous ethanol, then determine by ultraviolet spectrophotometer.

[0075] The sensory evaluation process for tea soup is as follows: A panel of 30 experienced professionals is selected to taste and score the tea soup under the different conditions described above. The specific scoring rules are shown in Table 3 below.

[0076] Table 3 Sensory Evaluation Scoring Criteria

[0077]

[0078]

[0079] In the process of establishing the daily tea drinking model, the leaching rate and leaching speed of the main components were comprehensively considered, along with daily tea drinking habits and the tea evaluation methods stipulated in the national standards. The following conditions were selected as the daily tea drinking model for subsequent research: water temperature of 100 degrees Celsius, tea-to-water ratio of 1:50, and a total of four tea infusions. In combination with consumers' living habits, the brewing time for the first, second, and third tea infusions was designed to be 5 minutes, and the fourth tea infusion was regarded as the last infusion, with a brewing time of 1 hour, to study whether the dissolution was sufficient.

[0080] The in vitro simulated digestion experiment includes the following procedures:

[0081] (1) Preparation of simulated saliva: KCl (15.1 mM), CaCl2(H2O)2 (1.5 mM), MgCl2(H2O)6 (0.15 mM), KH2PO4 (3.7 mM), (NH4)2CO3 (0.06 mM), NaHCO3 (13.6 mM) and HCl (1.1 mM) were mixed. 50 mL of tea sample solution, 15 mg α-amylase (1000 U / mg) and 100 mL of simulated saliva were mixed and incubated at 37 °C (pH = 7.0). After 0.5 h, 2 mL of the mixture was collected for further analysis.

[0082] (2) Preparation of simulated gastric juice: KCl (6.9 mM), CaCl2(H2O)2 (0.15 mM), MgCl2(H2O)6 (0.12 mM), KH2PO4 (0.9 mM), (NH4)2CO3 (0.5 mM), NaHCO3 (25.0 mM), NaCl (47.2 mM), and HCl (15.6 mM) were mixed. 30 mL of salivary digestive fluid, 0.04 g of pepsin (3000 U / g), and 30 mL of simulated gastric juice were mixed and rapidly adjusted to pH 3.0 to trigger simulated gastric digestion. After incubation at 37°C for 0.5 hours, 2 mL of the mixture was collected for further analysis.

[0083] (3) Preparation of simulated intestinal fluid: KCl (6.8 mM), CaCl2(H2O)2 (0.6 mM), MgCl2(H2O)6 (0.33 mM), KH2PO4 (0.8 mM), NaHCO3 (85 mM), NaCl (38.4 mM), and HCl (8.4 mM) were mixed in a solution. 30 mL of the digested sample, 0.245 g of bile salts, 0.3 g of trypsin (4000 U / g), and 30 mL of simulated intestinal fluid were mixed and rapidly adjusted to pH 7.0 to trigger simulated intestinal digestion. After incubation at 37°C for 0.5 hours, 2 mL of the mixture was obtained for further analysis.

[0084] All collected samples were first used for activity determination, then freeze-dried and coded individually.

[0085] The determination of DPPH· scavenging rate includes the following procedures:

[0086] Add 200 μL of sample solution to 10 mL test tubes. Add 3.8 mL of DPPH·ethanol solution (50.0 μg / mL) to test tube A and 3.8 mL of ethanol to test tube B. Shake thoroughly and react at room temperature in the dark for 30 min. After the reaction is complete, measure the absorbance at 517 nm. Use ethanol as a blank control (A0). Calculate the DPPH·scavenging rate (ID) using the following formula:

[0087] ID(%)=[1-(A1-A2) / A0]×100%

[0088] In the formula:

[0089] A1: Absorbance of 0.2 mL sample solution + 3.8 mL DPPH·ethanol solution; A2: Absorbance of 0.2 mL sample solution + 3.8 mL ethanol; A0: Absorbance of 0.2 mL ethanol + 3.8 mL DPPH·ethanol solution. The ABTS·free radical scavenging experiment includes the following procedures:

[0090] In test tube A, add 400 μL of sample solution and 3.6 mL of ABTS solution, respectively, and mix well. In test tube B, add 0.4 mL of ethanol solution and 3.6 mL of ABTS solution, and mix well. React at room temperature in the dark for 5 min. After the reaction is complete, measure the absorbance at a wavelength of 734 nm. Calculate the ABTS scavenging rate (P) using the following formula:

[0091] P(%)=(A0-A1) / A b ×100%

[0092] In the formula:

[0093] P: Scavenging rate; A0: Absorbance of the mixture of ABTS solution and sample solvent solution; A1: Absorbance of the mixture of ABTS solution and test solution.

[0094] The determination of α-glucosidase inhibitory activity includes the following procedures:

[0095] The procedure for determining the α-glucosidase inhibition rate of tea samples was as follows: First, a substrate solution PNPG (4-nitrophenyl-α-glucopyranoside) was prepared using 0.1 mol sodium phosphate buffer (pH 6.8). Then, 20 μL of α-glucosidase solution (1 U / μL) was added. After mixing the solutions, they were incubated at 37.5 °C for 10 minutes. After the reaction, 200 μL of saturated PNPG solution was added, and the mixture was incubated at 37.5 °C for another 20 minutes. The reaction was then terminated by adding 10 μL of 0.1 mol / L Na₂CO₃ solution. No α-glucosidase solution was added to the blank group, and no tea extract sample solution was added to the background group. Acarbose was used as a positive control. The absorbance was measured at 400 nm using sodium phosphate buffer (pH 6.8) as the zeroing solution. To evaluate the α-glucosidase inhibitory activity of the samples, the inhibition rate was calculated using the following formula:

[0096] Inhibition rate % = [A 空白- (A 样品 -A 背景 )]x100% / A 空白

[0097] The determination of α-amylase inhibition rate activity includes the following procedures:

[0098] Add 500 μL of tea infusion to 500 μL of 13 U / mL α-amylase solution (0.02 M sodium phosphate buffer, pH 6.9) and incubate in a test tube at 25 °C for 10 minutes. Then, add 500 μL of 1% soluble starch solution (previously dissolved in sodium phosphate buffer and boiled for 15 minutes) to each test tube and incubate for another 25 minutes. Finally, add 1 mL of DNS reagent and place the test tubes in a 100 °C water bath for 5 minutes. Dilute the mixture with 100 mL of distilled water. Read the absorbance at 520 nm. Results are expressed as a percentage of inhibition according to the following formula.

[0099] Inhibition rate % = [A 空白 -(A 样品 -A 背景 )]x100% / A 空白

[0100] The antibacterial properties test of tea infusion included the following procedures:

[0101] (1) Antimicrobial susceptibility testing (ASPT) tablets. ASPT tablets were prepared using a punch and sterilized by autoclaving. The tablets were then immersed in tea, penicillin solution (40 μg / mL), and sterile ultrapure water for 12 hours to observe the complete immersion of the tablets in different media. To ensure the accuracy of the experimental results, a blank control group and a positive control group were set up. Blank control group: sterile water was used as the immersion medium to exclude the influence of non-drug factors on the experimental results; Positive control group: penicillin solution (40 μg / mL) was used to verify the reliability of the experimental method.

[0102] (2) Activation and inoculation stage. Incubate the *E. coli* suspension overnight on a shaker. After activation, take 100 μL of a 10-1 concentration... 7 A CFU / mL E. coli suspension was prepared and evenly spread onto LB agar plates. Then, the soaked drug susceptibility testing tablets were placed on the plates containing the E. coli to ensure adequate contact between the drug and the bacterial strain.

[0103] (3) Bacterial culture. The experimental conditions were set at 37℃ in a constant temperature incubator for 24 hours to observe the inhibitory effect of the drug sensitivity tablets on Escherichia coli. After the experiment, the diameter of the inhibition zone was accurately measured with calipers, which was used as an indicator to evaluate the effectiveness of the drug sensitivity tablets.

[0104] Example 2

[0105] This embodiment, based on embodiment 1, includes the following:

[0106] Chemical composition (determination of chemical substance content)

[0107] 1. Main components in tea (specifically, the tested samples are 2021 selenium-enriched black tea (SeBT), 2021 selenium-enriched green tea (SeGT), 2021 ordinary black tea (BT), and 2021 ordinary green tea (GT); 2022 selenium-enriched black tea (SeBT), 2022 selenium-enriched green tea (SeGT), 2022 ordinary black tea (BT), and 2022 ordinary green tea (GT); and 2023 selenium-enriched black tea (SeBT), 2023 selenium-enriched green tea (SeGT), 2023 ordinary black tea (BT), and 2023 ordinary green tea (GT))

[0108] The components of tea leaves determine the quality of the tea infusion. The content of these components is influenced by various factors, such as the cultivation process, which affects the components during the tea's growth, including geographical environment, soil conditions, planting density, fertilization, pruning, and harvesting. Furthermore, tea processing techniques, such as fixing, rolling, and fermentation, also affect the components of the tea leaves after ripening and harvesting, leading to secondary changes.

[0109] like Figure 1 As shown in Figure A, the soluble sugar content in tea ranges from 1.12 ± 0.06% to 5.16 ± 0.12%. There are significant differences in the total soluble sugar content of the same type of tea from different years. Figure 1 B shows the total flavonoid content of tea. Flavonoids are the most abundant polyphenols in tea, possessing antioxidant, anti-inflammatory, anti-allergic, and antibacterial properties. The total flavonoid content in tea ranges from 0.36±0.05% to 0.83±0.05%. The total flavonoid content in normal black tea remained stable over three years and was lower than that in green tea. The total flavonoid content of selenium-enriched black tea differed between 2021 and 2023, while the total flavonoid content of selenium-enriched green tea and normal green tea fluctuated significantly. The stability order of total flavonoid content was: BT>SeBT>SeGT>GT. Significant differences in total flavonoid content were observed when comparing SeBT with BT and SeGT with GT within the same year. Considering different tea types, the total flavonoid content of BT was found to be lower than that of GT, which is attributed to the metabolic transformation that occurs during the fermentation of BT. During fermentation, the total flavonoid content gradually increased with increasing temperature, reaching a peak and then rapidly declining.

[0110] like Figure 1 As shown in Figure C, the moisture content of tea ranges from 1.63±0.25% to 5.60±0.47%. It is noteworthy that there are significant differences in moisture content among various teas from different years, with older teas having lower moisture content. The teas with the highest moisture content are all from the 2023 batch, with the 2023 selenium-enriched black tea having the highest moisture content at 5.60±0.47%. The soluble protein content in tea fluctuates between 0.56±0.07% and 1.16±0.05%. Figure 1D). Soluble protein is the most stable element among the basic components of tea. Generally speaking, the relative stability of the four core components in different years is in the following order: soluble protein, total flavonoids, moisture, and then total soluble sugars.

[0111] 2. Tea polyphenols, catechins, and caffeine

[0112] like Figure 1 As shown in Figure E, the polyphenol content in unfermented green tea is generally higher than that in fully fermented black tea. The polyphenol content of all green teas (including selenium-enriched green tea and normal green tea) ranges from approximately 9.43±0.15 to 16.27±0.83%, while the total polyphenol content of all black teas ranges from approximately 4.69±0.32 to 9.34±0.28%. Significant differences in polyphenol content exist between most years, except for a few (p<0.0001). During the fermentation process of black tea, suitable temperature and humidity provide favorable reaction conditions for polyphenol oxidase. Catechins undergo oxidative polymerization under the catalysis of polyphenol oxidase, forming key flavor compounds such as theaflavins and thearubigins. Catechins have various physiological activities beneficial to human health. Green tea, rich in catechins and caffeine, is a more effective sympathetic-mediated thermogenesis enhancer than caffeine itself, helping to better control obesity. Catechins are the main bitter and astringent substances and are key factors determining the body of the tea infusion. Catechins comprise eight monomers: catechin (+C), gallocatechin (GC), catechin gallate (CG), gallocatechin gallate (GCG), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). As a purine alkaloid, caffeine not only has a stimulating effect but also contributes to the flavor of tea. For example... Figure 1 As shown in Figure F, the content of various monomers varies in different teas, but EGCG is the most abundant catechin in most green teas. The highest EGCG content was found in selenium-enriched green tea in 2023, at 47.10±0.59 mg / g. The second most abundant monomer was caffeine. The highest caffeine content was found in normal green tea in 2021, at 32.55±1.38 mg / g, followed by selenium-enriched green tea in 2023 at 31.14±0.48 mg / g, while the lowest caffeine content was found in selenium-enriched green tea in 2022, at 26.91±1.02 mg / g. In black tea, the two most abundant monomers were +C and caffeine. The highest +C content was found in normal black tea in 2021, at 50.37±0.56 mg / g. Figure 1 G). The highest caffeine content was found in selenium-enriched black tea from 2022, at 38.13±1.03 mg / g, and the overall caffeine content remained stable. At low fermentation levels (10-15%), the caffeine content remained unchanged, while at high fermentation levels (85%), the caffeine content increased significantly.

[0113] 3.Tea pigment

[0114] The content of tea pigments, such as Figure 1 As shown in H and I, the total amount of tea pigments in green tea is lower than that in black tea, accounting for about 7%, while the total amount of tea pigments in black tea is between 13% and 16%. Among them, theaflavins are the most abundant tea pigments in green tea, accounting for about 5%. The content of theabrownins is between 2.10±0.39% and 2.57±0.12%, while the content of theaflavins is between 0.03% and 0.35%. In black tea, the content of theaflavins is between 5.39±0.58% and 7.39±0.24%, the content of theabrownins is between 7.16±0.58% and 9.43±0.34%, while theaflavins are relatively scarce. Chlorophyll is a natural pigment present in fresh tea leaves, of which chlorophyll b is the main form in plants. In green tea, the 2023 selenium-enriched green tea has the highest chlorophyll content, at 0.64±0.03%. Figure 1 The chlorophyll content of normal green tea in 2022 was the lowest, at 0.39±0.02%. For black tea, the chlorophyll content of selenium-enriched black tea in 2023 was the highest, at 0.51±0.05%, while the chlorophyll content of normal black tea in 2023 was the lowest, at 0.43±0.02%. Figure 1 K).

[0115] The composition of polyphenolic compounds varies among different types of tea. Green tea's main components are catechins and gallic acid, while black tea is dominated by theaflavins, thearubigins, and other polymers of catechins. During the fermentation of black tea, polyphenol oxidase catalyzes the conversion of catechins into theaflavins (TFs). Theaflavins primarily contribute to astringency, but their astringency threshold is significantly lower than that of catechins, contributing to the brightness of the black tea liquor. It is generally believed that the formation of low-molecular-weight oxidation products (such as theaflavins) marks the initial stage of thearubigin (TRs) development. Oxidation products, including theaflavins, can further condense to form dimers, trimers, and tetramers. Therefore, thearubigins are considered high-molecular-weight polymers of catechin oxidation products. The theaflavin / thearubigin ratio is an important quality indicator and is positively correlated with the brightness of the tea liquor.

[0116] 4. Selenium

[0117] Selenium, an essential trace element for the human body, possesses biological functions such as anti-cancer, anti-aging, antioxidant, and immune-enhancing effects, making it of great significance to human health. Figure 1As shown in Figure L, the selenium (Se) content in normal green tea was consistently detected between 2021 and 2023, ranging from 0.10±0.01 to 0.83±0.06 mg / kg. Similarly, the selenium content in normal black tea remained stable during the same period, fluctuating between 0.27±0.06 and 0.45±0.10 mg / kg. No significant annual differences in selenium content were observed among normal black teas, which may be attributed to the fact that the selenium in ordinary tea mainly originates from the environment and soil, rather than from exogenous selenium fertilizers.

[0118] The selenium content of selenium-enriched green tea varied significantly over the three years (p<0.0001). Notably, the highest selenium content was observed in 2023, reaching 7.66±0.39 mg / kg. Similarly, the selenium content in selenium-enriched black tea (SeBT) also fluctuated over the three years, with the highest content in 2022 at 3.19±0.20 mg / kg. The significant annual differences in selenium content in selenium-enriched tea may be attributed to manual application of glucosamine selenium fertilizer and the biotransformation of selenium in tea leaves. Furthermore, the application of selenium fertilizer can increase the content of most nutritional and functional components in tea, such as soluble sugars, tea polyphenols, catechins, flavonoids, soluble proteins, and amino acids.

[0119] 5. Total free amino acids, L-theanine, and γ-aminobutyric acid (GABA)

[0120] Tea contains various free amino acids, mainly including L-theanine (L-Theanine), aspartic acid (Asp), glutamic acid (Glu), asparagine (Asn), glutamine (Gln), glycine (Gly), histidine (His), threonine (Thr), alanine (Ala), serine (Ser), arginine (Arg), tryptophan (Trp), phenylalanine (Phe), and lysine (Lys). Among these, theanine accounts for about half of the total free amino acids. Theanine has a higher proportion of free amino acids in green tea, white tea, and black tea. Figure 1 As shown in M, the total free amino acid content in the four types of tea, ranked from highest to lowest, is as follows: selenium-rich green tea (1.23±0.42% in 2021, 1.04±0.06% in 2022, and 1.82±0.13% in 2023), ordinary green tea (1.44±0.22% in 2021, 1.23±0.13% in 2022, and 1.45±0.03% in 2023), ordinary black tea (0.82±0.07% in 2021, 0.81±0.05% in 2022, and 0.60±0.11% in 2023), and selenium-rich black tea (0.39±0.01% in 2021, 0.84±0.27% in 2022, and 0.39±0.08% in 2023).

[0121] Theanine is a unique amino acid found only in tea trees and mushrooms, and has been shown to have various health benefits for humans. Theanine can improve brain focus, learning ability, and memory. GABA is an important neurotransmitter with a major inhibitory effect on the central nervous system of mammals. Theanine and GABA can improve sleep disorders and maintain circadian rhythms. Furthermore, GABA has a blood pressure-lowering effect, and GABA tea has been shown to lower blood pressure in rats. The contents of L-theanine and GABA in four types of tea are shown in Table 1. The highest L-theanine content was found in ordinary green tea from 2021, at 10.23±0.22 mg / mL, while the lowest was found in ordinary black tea from 2022, at 4.80±0.55 mg / mL. GABA content was higher in green tea than in black tea, with the highest content in ordinary green tea from 2021 (1.41±0.02 mg / mL) and the lowest in ordinary black tea from 2023 (0.32±0.01 mg / mL). The contents of L-theanine and GABA in different teas are shown in Table 4.

[0122] Table 4. Content of L-theanine and GABA in different teas (mg / g)

[0123]

[0124] Extraction patterns of different active ingredients in selenium-enriched tea (dissolution rates of tea infusion samples obtained under different temperatures and time conditions).

[0125] 1. Tea polyphenols

[0126] Tea polyphenols are the main components of selenium-enriched green tea and selenium-enriched black tea, accounting for about 20% of the dry weight of tea leaves, and play a decisive role in the color, aroma, and taste of the tea infusion. Key components determining the bitterness and astringency of tea include alkaloids, catechins, anthocyanins, phenolic acids, flavonoid glycosides, and theaflavins. After brewing at 100℃ for 40 minutes, the concentration of tea polyphenols in selenium-enriched green tea was 201.30±1.85 mg / 100mL, while the concentration in selenium-enriched black tea was 160.40±1.46 mg / 100mL.

[0127] Figure 2Figures A and G illustrate the dissolution patterns of tea polyphenols in selenium-enriched black tea and selenium-enriched green tea at different temperatures, with brewing time as the independent variable and the amount of tea polyphenols dissolved as the dependent variable. Compared to selenium-enriched green tea, the dissolution process of tea polyphenols in selenium-enriched black tea is more significantly affected by temperature. Increasing temperature significantly increases the dissolution rate of tea polyphenols, and the dissolution rate of both types of tea gradually decreases with increasing brewing time. As brewing time increases, the difference in tea polyphenol concentration in the tea infusion gradually increases at different temperatures. Specifically, the tea polyphenol concentration after brewing at 100℃ for 40 minutes is twice that after brewing at 65℃. Logarithmic fitting curves show that after complete dissolution, the tea polyphenol content in selenium-enriched black tea is less than that in selenium-enriched green tea. This difference is due to the conversion of tea polyphenols into theaflavins and theabrownins during the fermentation process of black tea, leading to a decrease in tea polyphenol content. Excessive tea polyphenols in tea can cause the tea infusion to change from refreshing to bitter. Therefore, selenium-enriched black tea, with its lower amount of dissolved tea polyphenols, is more suitable for people who dislike the bitter taste of tea.

[0128] As shown in Table 5, the solubility of tea polyphenols after brewing at 100℃ for 40 minutes was defined as 100%, and the solubility was calculated based on this. Through logarithmic fitting, a fitting formula was obtained with time as the independent variable and tea polyphenol solubility as the dependent variable, to show the changes in the concentration of dissolved tea polyphenols in selenium-enriched black tea and selenium-enriched green tea under different time and temperature conditions. The half-dissolution time t of tea polyphenols was calculated. 50 and complete dissolution time t 100 (Table 6). When brewing selenium-enriched green tea at 100°C, it takes 4.47 minutes to dissolve 50% of the tea polyphenols. However, at 85°C, 75°C, and 65°C, it takes 7.66 minutes, 11.05 minutes, and 17.25 minutes, respectively. It is noteworthy that achieving 100% dissolution of tea polyphenols in selenium-enriched green tea at 75°C and 65°C is challenging. At 85°C, complete dissolution requires approximately 1.5 hours, a time impractical for everyday tea brewing.

[0129] For selenium-enriched black tea, it takes 6.39 minutes to dissolve 50% of the tea polyphenols at 100°C. At 85°C, 75°C, and 65°C, the same task requires 13.52 minutes, 35.70 minutes, and 112.97 minutes, respectively. Achieving complete dissolution of tea polyphenols in selenium-enriched black tea at 75°C and 65°C is equally difficult. At 85°C, complete dissolution of all tea polyphenols requires nearly 198.83 minutes, a time far exceeding the typical 15-minute brewing time, making 100% dissolution unlikely. However, this reduced dissolution may help lower the bitterness of the black tea, which could be a welcome result for those who prefer a milder tea flavor.

[0130] Table 5. Effects of different temperatures and times on the dissolution rate of tea polyphenols in SeGT and SeBT.

[0131]

[0132] Table 6. Fitting curves of tea polyphenol dissolution rate at different temperatures

[0133]

[0134] 2. Flavonoids

[0135] The concentration of flavonoids in the brewed selenium-enriched green tea was 0.36±0.02 mg / 100 mL, while the concentration of flavonoids in the brewed selenium-enriched black tea was 0.45±0.06 mg / 100 mL. Both were measured after brewing at 100℃ for 40 minutes. Figure 2 Figures B and H illustrate the dissolution patterns of flavonoids in selenium-enriched green tea and selenium-enriched black tea at different brewing temperatures, with brewing time as the independent variable and the amount of flavonoids dissolved as the dependent variable. Processing techniques significantly affect the quality components of tea. Even during the withering and drying stages of light fermentation in white tea, flavonoid glycosides are converted to flavonoid aglycones, and the content of water-soluble sugars increases, causing the tea's taste to change from bitter to slightly sweet. After fermentation, the amount of flavonoids dissolved in selenium-enriched black tea at 100℃ is higher than that in selenium-enriched green tea. Similar to tea polyphenols, the dissolution of flavonoids in selenium-enriched black tea is more significantly affected by temperature conditions than in selenium-enriched green tea. The dissolution rate of flavonoids in both teas gradually decreases over time, but the rate of decrease is significantly faster in selenium-enriched green tea than in selenium-enriched black tea. The difference in flavonoid concentration in the tea infusion at different temperatures gradually increases with brewing time; the flavonoid concentration after brewing at 100℃ for 40 minutes is twice that after brewing at 65℃.

[0136] As shown in Table 7, assuming a 100% solubility rate of flavonoids after brewing at 100℃ for 40 minutes, the solubility rates at different temperatures and brewing times were calculated. Through logarithmic fitting, a fitting equation was obtained with time as the independent variable and the solubility rate of flavonoids as the dependent variable, to show the changes in the concentration of flavonoids in selenium-enriched black tea and selenium-enriched green tea under different time and temperature conditions. The t-values ​​of flavonoids in the tea infusion at different brewing temperatures were also calculated. 50 and t 100 (Table 8). When brewing selenium-enriched green tea at 100℃, it takes only 3.66 minutes to dissolve 50% of the flavonoids, while at 85℃, 75℃, and 65℃, it takes 5.89 minutes, 12.37 minutes, and 15.59 minutes, respectively. When brewing selenium-enriched black tea at 100℃, it takes 6.34 minutes to dissolve 50% of the flavonoids, while at 85℃, 75℃, and 65℃, it takes 10.25 minutes, 18.45 minutes, and 71.73 minutes, respectively. Therefore, the dissolution rate of flavonoids in selenium-enriched green tea is faster than that in selenium-enriched black tea.

[0137] Table 7. Effects of different temperatures and times on the dissolution rate (%) of flavonoids in SeGT and SeBT.

[0138]

[0139]

[0140] Table 8. Fitted curves of flavonoid dissolution rate at different temperatures

[0141]

[0142] 3. Soluble sugars

[0143] The sweetness of tea infusion is directly related to its soluble sugar content. In some high-sugar green teas, soluble sugars account for 5-10% of the total soluble substances. Previous studies have shown that the soluble sugar content in tea leaves ranges from approximately 1.12 ± 0.06% to 5.16 ± 0.12%. After brewing at 100°C for 40 minutes, the soluble sugar concentrations in selenium-enriched green tea and selenium-enriched black tea were 90.92 ± 0.99 mg / 100 mL and 98.56 ± 1.10 mg / 100 mL, respectively. Generally, black tea contains higher levels of soluble sugars, including sucrose, fructose, glucose, and sorbitol, compared to green tea. Figure 2 Tables C and I illustrate the dissolution patterns of soluble sugars in selenium-enriched black tea and selenium-enriched green tea at different brewing temperatures, with brewing time as the independent variable and the amount of soluble sugar dissolved as the dependent variable. Specifically, temperature changes had no significant effect on the dissolution of soluble sugars in selenium-enriched black tea. The dissolution rate of soluble sugars in both selenium-enriched green tea and selenium-enriched black tea gradually decreased over time, and the rate of decrease was comparable. In the first 1-5 minutes of brewing, the concentration of soluble sugars in the tea infusion was similar at different brewing temperatures. However, from 5 minutes to 40 minutes, the difference in the concentration of soluble sugars in the tea infusion gradually increased at different brewing temperatures. As shown in Table 9, after brewing at 65℃ for 40 minutes, the dissolution rate of soluble sugars in the selenium-enriched green tea infusion reached 67.02%, exceeding the dissolution rates of tea polyphenols and flavonoids at the same temperature. As shown in Table 10, when brewing selenium-enriched green tea at 100℃, it takes 4.34 minutes to dissolve 50% of the soluble sugars, while at 85℃, 75℃, and 65℃, the time required is 5.24 minutes, 9.22 minutes, and 13.72 minutes, respectively. Furthermore, when brewing selenium-enriched black tea at 100℃, it takes 4.46 minutes to dissolve 50% of the soluble sugars, while at 85℃, 75℃, and 65℃, the time required is 5.24 minutes, 9.30 minutes, and 15.34 minutes, respectively.

[0144] Table 9. Effects of different temperatures and times on the dissolution rate of soluble sugars in SeGT and SeBT.

[0145]

[0146] Table 10 Fitting curves of soluble sugar dissolution rate at different temperatures

[0147]

[0148] 4. Free amino acids

[0149] Free amino acids in tea contribute to the rich flavor of tea infusion. Sensory evaluation scores for tea are significantly positively correlated with theanine and the proportions of sweet and umami amino acids. For example... Figure 2 As shown in D and J, the solubility of free amino acids in tea infusions at different brewing temperatures and durations was measured, and nonlinear dissolution curves of free amino acids were fitted based on the brewing time at each temperature. The results indicate that extending the brewing time increases the solubility of free amino acids in the tea infusion. Specifically, after brewing at 100℃ for 40 minutes, the concentration of free amino acids in selenium-enriched green tea infusions was 115.82 ± 0.58 mg / 100 mL, while the concentration in selenium-enriched black tea was 105.38 ± 0.72 mg / 100 mL.

[0150] Assuming a 100% dissolution rate after brewing at 100℃ for 40 minutes, a logarithmic fitting equation was calculated with the free amino acid dissolution rate as the dependent variable to show the changes in the concentration of free amino acids in selenium-enriched black tea and selenium-enriched green tea under different time and temperature conditions (Table 11). As shown in Table 12, when brewing selenium-enriched green tea at 100℃, it only takes 5.18 minutes to dissolve 50% of the free amino acids, while at 85℃, 75℃, and 65℃, it takes 7.88 minutes, 10.20 minutes, and 17.03 minutes, respectively. When brewing selenium-enriched black tea at 100℃, it only takes 4.02 minutes to dissolve 50% of the free amino acids, while at 85℃, 75℃, and 65℃, it takes 5.79 minutes, 8.05 minutes, and 12.88 minutes, respectively. In summary, compared with selenium-enriched green tea, selenium-enriched black tea dissolves free amino acids much faster.

[0151] Table 11 Effects of different temperatures and times on the dissolution rate of free amino acids in SeGT and SeBT

[0152]

[0153] Table 12 Fitting curves of ionized amino acid dissolution rate at different temperatures

[0154]

[0155] 5. Caffeine

[0156] Purine alkaloids, primarily caffeine and theobromine, are key compounds responsible for the unique bitterness of tea. It is generally believed that tea will exhibit a bitter taste when the caffeine concentration in the infusion reaches 500 μmol / L. The dissolved caffeine content in tea infusions was determined at different brewing temperatures and times, and nonlinear dissolution curves of caffeine dissolved content over time were fitted at each single temperature. Figure 2 (E and K). At a constant temperature, the caffeine content in the tea infusion increased with increasing brewing time. Specifically, after brewing for 40 minutes at 100℃, the caffeine concentrations in selenium-enriched green tea and selenium-enriched black tea were 76.52±0.34 mg / 100mL and 58.91±0.93 mg / 100mL, respectively. Regardless of temperature, both selenium-enriched black tea and green tea dissolved most rapidly within the first 1–3 minutes of brewing. Notably, this initial dissolution rate was faster than that of flavonoids and soluble sugars, but slower than that of tea polyphenols.

[0157] 100% caffeine dissolution rate is defined as the amount of caffeine dissolved after brewing at 100°C for 40 minutes. As shown in Table 13, selenium-enriched green tea dissolves more caffeine than selenium-enriched black tea, due to differences in processing methods, while the total caffeine content in green tea is lower than in black tea. As shown in Table 14, when brewing selenium-enriched green tea at 100°C, it takes 4.22 minutes to dissolve 50% of the caffeine, while brewing at 85°C, 75°C, and 65°C requires 6.79 minutes, 9.65 minutes, and 17.16 minutes, respectively. When brewing selenium-enriched black tea at 100°C, it takes 3.93 minutes to dissolve 50% of the caffeine, while brewing at 85°C, 75°C, and 65°C extends the dissolution time to 5.94 minutes, 11.26 minutes, and 28.45 minutes, respectively.

[0158] Table 13 Effects of different temperatures and times on the caffeine dissolution rate in SeGT and SeBT.

[0159]

[0160] Table 14 Fitting curves of caffeine dissolution rate at different temperatures

[0161]

[0162] L-Theanine

[0163] Theanine constitutes the largest proportion of free amino acids in green tea, white tea, black tea, and Pu-erh tea, accounting for 48% to 63% of the total free amino acids. Theanine plays a crucial role in imparting a fresh and crisp taste to tea infusions and can synergistically enhance this freshness with other free amino acids. However, when the concentration of theanine reaches 35 mg / 100 mL, a bitter taste emerges. The dissolved theanine content in tea infusions was measured at different brewing temperatures and durations, and nonlinear dissolution curves of theanine content over time were fitted at each single temperature. Figure 2 (F and L). Under the same temperature conditions, the brewing time of tea was positively correlated with the dissolved content of theanine. After brewing selenium-enriched green tea and selenium-enriched black tea at 100℃ for 40 minutes, the concentration of theanine in the tea soup reached 52.69±1.49mg / 100mL and 54.04±0.82mg / 100mL, respectively (Table 15).

[0164] By using logarithmic fitting to calculate the fitted equation with the theanine solubility rate as the dependent variable, the changes in the theanine solubility concentration during the brewing process of selenium-enriched black tea and selenium-enriched green tea were shown. As shown in Table 16, brewing selenium-enriched green tea at 100℃ for 4.30 minutes dissolves 50% of theanine, while brewing at 85℃, 75℃, and 65℃ requires 5.66 minutes, 8.79 minutes, and 11.32 minutes, respectively. Brewing selenium-enriched black tea at 100℃ for 4.43 minutes dissolves 50% of theanine, while brewing at 85℃, 75℃, and 65℃ requires 5.60 minutes, 8.12 minutes, and 13.08 minutes, respectively. It is worth noting that to maintain a pleasant taste without astringency, it is recommended that the brewing time for selenium-enriched green tea at 85℃ not exceed 15 minutes, or at 100℃ not exceed 10 minutes. For selenium-rich black tea, brewing time should not exceed 13 minutes at 85℃ or 9 minutes at 100℃ to ensure that the theanine content remains below 35mg / 100mL, thus avoiding bitterness in the tea.

[0165] Table 15 Effects of different temperatures and times on the dissolution rate of theanine in SeGT and SeBT

[0166]

[0167] Table 16 Fitting curves of theanine dissolution rate at different temperatures

[0168]

[0169] Sensory evaluation of tea infusion under different extraction temperatures and times (sensory evaluation was used to score the taste, color, and aroma of tea infusion under different temperature and time conditions, and a sensory evaluation database of tea infusion was constructed).

[0170] Figure 3Figures A and B show radar charts illustrating the sensory evaluations of selenium-enriched green tea and selenium-enriched black tea at different brewing temperatures and durations. Overall, 100℃ is considered the optimal brewing temperature for sensory evaluation. For selenium-enriched green tea, the only condition for a sensory evaluation score exceeding 95 is brewing at 100℃ for 5-7 minutes, while a score above 90 requires brewing at 100℃ for 3-9 minutes. Selenium-enriched black tea only achieves a sensory evaluation score exceeding 95 when brewed at 100℃ for 3-7 minutes. With appropriate brewing durations, both 100℃ and 85℃ can raise the sensory evaluation score of selenium-enriched black tea to above 90. Sensory evaluation scores are positively correlated with theanine, sweetness, and the proportion of umami amino acids. Based on the dissolution characteristics of tea liquor, when brewed at 100℃ for 5 minutes, most of the quality components of selenium-enriched black tea and selenium-enriched green tea showed a dissolution rate of 50%, which is consistent with the good scores in the sensory evaluation of aroma, color and taste. Therefore, the tea liquor at 100℃ showed a better sensory evaluation score.

[0171] In summary, steeping at 100℃ for 5 minutes effectively extracts the quality components of tea leaves, while steeping at 85℃ for 5 minutes reduces the bitterness of the tea. The bioactivity of the tea decreases with increasing steeping frequency and digestion time. Therefore, the following conditions were selected as a daily tea-drinking model for further research: water temperature 100 degrees Celsius, tea-to-water ratio 1:50, and a total of four infusions. Considering consumer habits, the steeping time for the first, second, and third infusions was designed to be 5 minutes, and the fourth infusion was considered the final infusion and steeped for 1 hour to study the adequacy of dissolution.

[0172] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A brewing process and quality evaluation method of high quality tea liquor, characterized in that, The method comprises the following steps: S1, pretreating tea leaves of different years and different varieties to obtain pretreated tea leaves; S2, determining the content of chemical substances of the pretreated tea leaves, and performing significance analysis to verify the stability of tea leaves of different varieties in different years; S3, brewing tea soup to prepare tea soup samples obtained under different temperature and time conditions; S4, calculating the dissolution rate of the tea soup sample obtained under different temperature and different time conditions, obtaining the dissolution rate fitting curve of the tea soup sample under different temperature conditions by logarithmic fitting with time as the independent variable and the dissolution rate of the ingredient content as the dependent variable, obtaining the dissolution concentration change of the tea soup sample under different temperature and different time conditions, and calculating the half-dissolution time t of the ingredient in the tea soup sample under different conditions 50 and the complete dissolution time t 100 ; S5, scoring the taste, color, and aroma of the tea soup under different temperature and time conditions by sensory evaluation to construct a tea soup sensory evaluation database; S6, combining the dissolution rate fitting curve of the tea soup samples under different temperature conditions obtained in step S4 with the tea soup sensory evaluation database obtained in step S5 to establish a daily tea drinking model.

2. The brewing process and quality evaluation method of a high-quality tea soup according to claim 1, characterized in that, Step S1 specifically comprises the following process: The tea leaves to be tested are crushed in a crusher for 30 seconds, and then a small amount of tea leaves is added, stirred evenly, crushed for 60 seconds again, filtered with a 200-mesh nylon cloth, and dried to obtain pretreated tea leaves, which are stored in a sealed bag, labeled, and stored in a 4°C refrigerator for short-term preservation for subsequent content determination experiments.

3. The brewing process and quality evaluation method of high quality tea liquor according to claim 1, characterized in that, In step S2, the determination of the content of chemical substances of the pretreated tea leaves comprises one or more of the following determinations: determination of tea polyphenols in tea leaves, determination of soluble total sugar content in tea leaves, determination of total free amino acid content in tea leaves, determination of catechins in tea leaves, determination of theanine and γ-aminobutyric acid in tea leaves, determination of soluble protein content in tea leaves, determination of total selenium content in tea leaves, determination of chlorophyll content in tea leaves, determination of tea pigment content in tea leaves, and determination of total flavonoids in tea leaves.

4. The brewing process and quality evaluation method of high quality tea liquor according to claim 1, characterized in that, Step S3 comprises the following process: 1 g of tea leaves is weighed, and ultrapure water at different temperatures is preheated, with a tea-to-water ratio of 1:50, 50 mL of water is added, and tea soup is brewed in a water bath at the same temperature at different time intervals, after which the tea soup is immediately filtered, separated from the tea leaves, and collected for testing; The different temperatures include the following temperature conditions: 65°C, 75°C, 85°C, and 100°C; The different time intervals include the following time intervals: 1 min, 3 min, 5 min, 7 min, 9 min, 15 min, 30 min, and 40 min.

5. The process for brewing and quality evaluation method of high quality tea liquor according to claim 4, characterized in that, The tea leaves are selected from one or more of selenium-enriched black tea, ordinary black tea, selenium-enriched roasted green tea, and ordinary roasted green tea.

6. The brewing process and quality evaluation method of a high-quality tea soup according to claim 1, characterized in that, In step S6, the dissolution rate fitting curve of the tea soup samples under different temperature conditions obtained in step S4 is combined with the tea soup sensory evaluation database obtained in step S5 to establish a daily tea drinking model, and the following conditions are selected as the daily tea drinking model: water temperature of 100 degrees, tea-to-water ratio of 1:50, a total of four tea soup brewing, first, second, and third tea soup brewing time of 5 minutes, and fourth tea soup brewing time of 1 hour.

7. The brewing process and quality evaluation method of a high-quality tea soup according to claim 1, characterized in that, After step S6, the following step is performed: S7, determining in vitro hypoglycemic activity, determining antioxidant activity, and determining in vitro antibacterial activity by in vitro simulation digestion experiment to verify the bioavailability of the daily tea drinking model.

8. The brewing process and quality evaluation method of a high-quality tea soup according to claim 7, characterized in that, In step S7, the in vitro simulated digestion experiment comprises one or more of a simulated saliva experiment, a simulated gastric juice experiment, and a simulated intestinal juice experiment.

9. The brewing process and quality evaluation method of a high-quality tea soup according to claim 7, characterized by, In step S7, the determination of in vitro hypoglycemic activity comprises one or more of determination of α-glucosidase inhibition rate activity and determination of α-amylase inhibition rate activity.

10. The brewing process and quality evaluation method of a high-quality tea soup according to claim 7, characterized in that, In step S7, the determination of antioxidant activity comprises one or more of determination of DPPH· clearance rate and ABTS· free radical clearance experiment.

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