Fermented floral green tea and method for preparing the same

Abstract

This invention discloses a floral-scented green tea induced by dual-strain synergistic fermentation, its preparation method, and a milk tea, relating to the field of food processing technology. The preparation method of this floral-scented green tea employs a composite process of "first fermentation to generate aroma, then adsorption and fixation of aroma." Specific microorganisms metabolize soluble polysaccharides in tea leaves as nutrients, while added fresh flower cell sap serves as a nutrient and specific substrate to induce aroma production. This achieves a synergistic enhancement of the flavor of the tea soup by the "self-generated" or "induced" floral aroma substances during the fermentation process.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to tea fermentation processing technology, and more particularly to a floral-scented green tea based on aroma-inducing fermentation by two bacteria, its preparation process, and a method for preparing milk tea using this floral-scented green tea. Background Technology

[0002] Floral green tea, combining the freshness of green tea with the elegance of floral aromas, holds an important position in the global tea market. Currently, floral green teas on the market are mainly divided into two categories: The first category is traditional scented tea, which uses green tea leaves mixed with fresh flowers (such as jasmine, osmanthus, and gardenia) in a specific ratio. The tea leaves absorb the aroma released by the flowers through their physical adsorption properties, and after repeated scenting processes, the flower residue is removed; a representative product is jasmine tea. The second category is craft flower tea / scented tea, which imparts floral aromas by spraying edible flavorings onto the tea leaves or by directly adding dried flower petals; representative products include various tea bags containing flavored tea.

[0003] The traditional scenting process has the following inherent defects: (1) Strong aroma dependence and poor stability: Traditional scenting relies entirely on the yield and aroma quality of fresh flowers, and the production cost fluctuates greatly due to weather and origin; the aroma quality depends on human experience and is difficult to standardize between batches.

[0004] (2) The aroma is shallow and the heat resistance is poor: The pore structure of green tea leaves is limited and the physical adsorption capacity is weak. The absorption rate of floral aroma is only 30%-40%. Moreover, the adsorbed aroma is an external attachment, which is very easy to volatilize and dissipate during subsequent processing (such as high temperature steam, hot water brewing or heating and stirring in the production of hot milk tea). This results in the finished milk tea having a weak aroma, which often requires the addition of flavorings to make up for it later.

[0005] (3) Limited flavor: Existing processes only focus on "fragrance enhancement" without improving the bitterness and grassy taste of green tea itself. High content of tea polyphenols (especially ester-type catechins) results in a heavy astringency in the tea soup, making it less smooth when used to prepare milk tea. In addition, the traditional piling and scenting process is difficult to control precisely, which can easily produce a "stale" or overly fermented taste.

[0006] (4) Resource waste and environmental pressure: The flowers after traditional scenting become waste, which has high processing costs, and the limited flowering period makes production distinctly seasonal.

[0007] A few studies have attempted to improve tea flavor using microbial fermentation. For example, fermenting tea with a single strain (such as brewer's yeast) can generate some aroma compounds to a certain extent, but single-strain fermentation suffers from low aroma production efficiency, insignificant improvement in bitterness and astringency, and limited aroma variety. Other studies have simply mixed strains for fermentation, but without precise control over the fermentation sequence (anaerobic-aerobic phase), the microbial proliferation and secondary metabolic aroma production phases interfere with each other, resulting in unsatisfactory overall results.

[0008] Therefore, there is an urgent need to develop a new process that can generate or induce the production of floral aroma substances within tea leaves without relying on a large amount of fresh flowers, while significantly improving the bitterness and mellowness of the tea soup, and producing a floral green tea base that exhibits excellent aroma persistence and product stability in subsequent milk tea processing. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a method for preparing floral green tea by synergistic fermentation of two bacteria to induce aroma production, so as to overcome the defects of traditional scenting process such as high dependence on fresh flowers, poor heat resistance of aroma, difficulty in improving bitterness and astringency, and long production cycle, and realize the synergistic enhancement of floral aroma substances and tea soup flavor by "self-generated" or "induced generation" during the fermentation process of green tea.

[0010] The further technical problem to be solved by the present invention is to provide a method for preparing milk tea using floral green tea prepared by the above method, so as to obtain a milk tea product with a long-lasting floral aroma, a mellow and smooth taste and excellent product stability without the need for additional flavoring.

[0011] To address the aforementioned technical problems, this patent proposes a composite process of "first fermentation to generate aroma, then adsorption and fixation of aroma." This process utilizes a specific microbial strain (Saccharomyces cerevisiae) to metabolize soluble polysaccharides in tea leaves, using added fresh flower cell sap as nutrients and a specific substrate to induce aroma production. During fermentation, the β-glucosidase produced by the Saccharomyces cerevisiae hydrolyzes glycoside precursors in the tea leaves, releasing free terpene alcohols as aroma compounds. Simultaneously, lactic acid bacteria and Saccharomyces cerevisiae work synergistically during fermentation. Lactic acid produced by the lactic acid bacteria lowers the pH of the environment, activating the activity of the β-glucosidase produced by the Saccharomyces cerevisiae, and also complexing with polyphenols in the tea leaves, reducing bitterness and increasing the richness of the flavor. The specific technical solution of this invention is as follows.

[0012] A method for preparing floral-scented green tea induced by synergistic fermentation of two microorganisms is provided, comprising the following steps: S1. Pre-treatment of tea leaves: Select fresh green tea leaves, and after fixing and initial rolling, obtain preliminary tea leaves with a moisture content of 25%-35%. Place the preliminary tea leaves in an environment of 30-35℃ for later use. S2. Fermentation broth preparation: Aroma-producing yeast and lactic acid bacteria are inoculated into the culture medium for activation culture until the viable cell concentration reaches 1×10⁻⁶. 8 Fermentation broth was prepared by adding CFU / mL or higher; wherein the culture medium was a sterile aqueous solution containing fresh flower cell sap and sucrose, the amount of fresh flower cell sap added was 5%-10% of the mass of sterile water, and the amount of sucrose added was 2%-5% of the mass of sterile water; the inoculation mass ratio of aroma-producing yeast to lactic acid bacteria was (0.8-1.0):(0.8-1.0); the activation culture conditions were: temperature 26-30℃, time 12-24 hours; S3. Co-fermentation and scenting: The initial tea leaves from step S1 and the fermentation liquid from step S2 are mixed evenly at a mass ratio of (8-10):(1-3), and placed in a sealed fermentation container. Anaerobic-aerobic alternating fermentation is carried out under conditions of 28-32℃ and relative humidity ≥90%. The anaerobic-aerobic alternating fermentation includes: firstly, the first stage of anaerobic fermentation is carried out for 18-30 hours under anaerobic conditions, and then sterile air or oxygen is introduced to carry out the second stage of aerobic fermentation for 18-30 hours under aerobic conditions. S4. Inactivation and Drying: After fermentation, the fermentation product is inactivated to terminate fermentation, and then dried until the moisture content is ≤5%, thus obtaining the floral green tea.

[0013] Preferably, in step S2, the aroma-producing yeast is brewer's yeast (Saccharomyces cerevisiae). Saccharomyces cerevisiae The lactic acid bacteria mentioned are *Lactobacillus plantarum* (…). Lactobacillus plantarum ).

[0014] Preferably, in step S2, the fresh flower cell sap is selected from one or more of rose cell sap, jasmine cell sap, osmanthus cell sap, and gardenia cell sap.

[0015] The present invention preferably uses a combination of "Saccharomyces cerevisiae and Lactobacillus plantarum" and "fresh flower cell sap" as inducing substrates. However, those skilled in the art will understand that other aroma-producing yeasts with high β-glucosidase production capacity (such as Kluyveromyces kluyveromyces) or other lactic acid bacteria that can produce organic acids for synergistic effects (such as Streptococcus thermophilus), as well as cell sap from edible flowers (such as rose, osmanthus, gardenia, etc.) can be substituted based on the principles of the present invention and achieve essentially the same inventive purpose. All of these should fall within the protection scope of the present invention.

[0016] Preferably, in step S2, the amount of fresh flower cell sap added is 8%-10% of the mass of sterile water, the amount of sucrose added is 3%-5% of the mass of sterile water, and the inoculation mass ratio of aroma-producing yeast to lactic acid bacteria is 1.0:1.0.

[0017] Preferably, in step S3, the temperature for both the first-stage anaerobic fermentation and the second-stage aerobic fermentation is 30-32℃, the first-stage anaerobic fermentation time is 20-26 hours, and the second-stage aerobic fermentation time is 20-26 hours. During this process, *Saccharomyces cerevisiae* and *Lactobacillus plantarum* use soluble sugars in the tea leaves and added fresh flower cell sap as nutrients for metabolism. The β-glucosidase produced by *Saccharomyces cerevisiae* hydrolyzes glycoside precursors in the tea leaves, releasing free terpene alcohol aroma compounds (such as linalool, geraniol, and other natural floral aroma components). Simultaneously, the lactic acid produced by lactic acid bacteria fermentation and its metabolic activity complex with polyphenols in the tea leaves, reducing bitterness and increasing the richness of the flavor. In this stage, the tea leaves serve both as a fermentation carrier for microorganisms and continuously absorb the aromas produced during the metabolic process.

[0018] Preferably, in step S3, the mass ratio of the initial tea base to the fermentation liquid is 10:(1-3).

[0019] Preferably, the anaerobic conditions described in step S3 are achieved by introducing nitrogen or carbon dioxide into a sealed fermentation vessel.

[0020] Preferably, in step S4, the inactivation treatment is instantaneous high-temperature steam treatment at 85-95°C for 10-15 seconds; the drying is low-temperature vacuum drying.

[0021] In some specific embodiments, the method for preparing floral-scented green tea induced by dual-strain synergistic fermentation specifically includes: S1. Select fresh green tea leaves with one bud and two leaves or one bud and three leaves. After fixing and initial rolling, obtain a primary tea blank with a moisture content of 25%-35%. Place the primary tea blank in an environment with a temperature of 30-35℃ and a relative humidity of ≥90% for later use. S2. Take sterile water, add 5%-10% fresh flower cell sap and 2%-5% sucrose (by weight of sterile water), mix well and sterilize to obtain the culture medium; inoculate *Saccharomyces cerevisiae* and *Lactobacillus plantarum* at a mass ratio of (0.8-1.0):(0.8-1.0) into the culture medium, and activate and culture at 26-30℃ for 12-24 hours until the viable cell concentration reaches 1×10⁻⁶. 8 Fermentation broth was prepared with a concentration of CFU / mL or higher. S3. Mix the initial tea leaves from step S1 with the fermentation liquid from step S2 at a mass ratio of (8-10):(1-3), and put them into a sealed fermentation tank. Control the fermentation temperature at 28-32℃ and the relative humidity at ≥90%. First, fill the tank with nitrogen or carbon dioxide to replace the air and ferment for 18-30 hours under anaerobic conditions. Then, introduce sterile air and continue fermenting for 18-30 hours under aerobic conditions. S4. After fermentation, the tea is inactivated by steam at 85-95℃ for 10-15 seconds, and then dried under low temperature vacuum until the moisture content is ≤5%, thus obtaining the floral green tea.

[0022] The present invention also provides a floral-scented green tea, which is prepared by the above-mentioned method for preparing floral-scented green tea by synergistic fermentation of two bacteria to induce aroma production.

[0023] The floral-scented green tea prepared according to the present invention exhibits excellent stability in milk tea preparation, and the mechanism is as follows: Ester-type catechin degradation: During lactic acid bacteria fermentation, some ester-type catechins (such as EGCG) undergo hydrolysis or complexation, resulting in a reduction of more than 30% in their content. Ester-type catechins are the main substances that bind to milk proteins to form precipitates; their reduced content directly reduces the sites for precipitate formation.

[0024] Changes in the structure of tea polyphenols: During fermentation, tea polyphenols undergo a complexation reaction with lactic acid to form a soluble complex, which reduces the direct binding ability of tea polyphenols to milk proteins.

[0025] pH adjustment: The acid produced by lactic acid bacteria slightly lowers the pH of the tea infusion, which is conducive to the formation of a more stable dispersion system of tea polyphenols and milk proteins under acidic conditions.

[0026] This invention achieves a significant synergistic effect through the synergistic action of aroma-producing yeast and lactic acid bacteria, specific induction from fresh flower cell sap, sequential control of anaerobic-aerobic alternating fermentation, and the organic combination of the above three elements. The aroma-producing yeast (Saccharomyces cerevisiae) provides highly active β-glucosidase, hydrolyzing glycoside precursors in tea leaves to release terpenoids, natural aroma aglycones. The lactic acid bacteria (Lactobacillus plantarum) metabolize and produce acid, lowering the environmental pH to 4.5-5.5 (the optimal pH range for β-glucosidase), activating and enhancing β-glucosidase activity. Simultaneously, lactic acid complexes with tea polyphenols, reducing astringency. Glycoside precursors and trace elements in the fresh flower cell sap provide specific inducing substrates for microbial metabolism, directionally strengthening the aroma-producing pathway. The anaerobic stage preferentially promotes rapid cell proliferation, while the aerobic stage activates secondary metabolism for efficient aroma production, achieving the optimal temporal solution of "first bacterial growth, then aroma production."

[0027] This invention also provides a method for preparing floral-scented green tea milk tea, comprising the following steps: (1) Tea extraction: Mix the above-mentioned floral green tea with process water at a mass ratio of 1:(20-40), and extract at a low temperature of 40-50℃ for 30-60 minutes to obtain tea soup; (2) Mixing raw materials: By weight, mix 45-50 parts of raw milk, 25-30 parts of light cream, 25-30 parts of the tea soup and 0.1-0.3 parts of stabilizer and stir evenly; (3) Homogenization: Heat the mixture from step (2) to 55-60℃ and keep it at that temperature for 5-10 minutes. Then perform two-stage homogenization treatment, with a first-stage pressure of 20-25 MPa and a second-stage pressure of 4-5 MPa. (4) Sterilization and cooling: The homogenized liquid is subjected to ultra-high temperature instantaneous sterilization (UHT) with sterilization parameters of 135-145℃ for 4-40 seconds, and then rapidly cooled to below 30℃; (5) Aseptic filling: The cooled milk tea is aseptically filled to obtain the floral green tea milk tea.

[0028] Preferably, in step (1), the mass ratio of the floral green tea to the process water is 1:(25-35), the extraction temperature is 42-48℃, and the extraction time is 35-50 minutes.

[0029] Preferably, in step (2), the stabilizer is microcrystalline cellulose, and the amount added is 0.15-0.25 parts.

[0030] Preferably, in step (3), the two-stage homogenization process is two homogenizations, with the first-stage pressure being 20-25 MPa and the second-stage pressure being 4-5 MPa.

[0031] Preferably, in step (4), the parameters for ultra-high temperature instantaneous sterilization are 138-142℃, 10-20 seconds, and cooling to 25-30℃.

[0032] In some specific embodiments, the preparation method of the floral green tea milk tea includes the following steps: (1) Tea extraction: The floral green tea and process water are mixed at a mass ratio of 1:30, and extracted at a low temperature of 45°C for 40 minutes. The tea soup is then filtered. (2) Mixing raw materials: Take 45 parts of raw milk, 30 parts of light cream, 25 parts of tea and 0.2 parts of microcrystalline cellulose by weight, and stir for 30 seconds to mix evenly; (3) Homogenization: Heat the mixture to 60°C and keep it at that temperature for 5 minutes. Then perform two-stage homogenization. The first-stage pressure for each homogenization is 20 MPa and the second-stage pressure is 5 MPa. (4) Sterilization and cooling: The homogenized liquid is subjected to ultra-high temperature instantaneous sterilization with sterilization parameters of 140°C for 15 seconds, and then cooled to 25°C; (5) Aseptic filling: The cooled milk tea is aseptically filled to obtain the floral green tea milk tea.

[0033] The present invention also provides a floral green tea milk tea, which is prepared by the above-described preparation method.

[0034] Compared with the prior art, the technical solution of the present invention has the following significant advantages: (1) Significantly improved aroma persistence: After brewing traditional scented tea with hot water at 85℃ for 1 hour, the aroma retention rate is less than 40%; after brewing the fermented green tea prepared by this invention under the same conditions for 1 hour, GC-MS analysis shows that the retention rate of the main floral aroma components (terpenoids, linalool, etc.) can reach more than 75%. When used to make hot milk tea, no additional flavoring is needed, and a distinct and lasting natural floral aroma can be smelled at the mouth of the cup.

[0035] (2) The bitterness and astringency are greatly reduced, and the mellowness and richness of the taste are significantly increased: According to the test, the process of the present invention reduces the content of ester-type catechins in tea by more than 30%, while increasing the content of lactic acid and free amino acids. The astringency of the tea soup is greatly reduced, and the freshness and mellowness are significantly improved. The prepared milk tea is smooth and has no astringent taste.

[0036] (3) The production cycle is greatly shortened and the raw material utilization rate is high: The traditional multiple scenting process takes 7-15 days and consumes a large amount of fresh flowers. The present invention uses a controllable fermentation tank for fermentation, shortening the production cycle to 36-60 hours, and only requires a small amount of fresh flower cell liquid (the amount used is only about 1 / 10 of that used in traditional scenting), which greatly reduces the dependence on the seasonality and quantity of fresh flowers, and reduces production costs and environmental pressure.

[0037] (4) Good batch stability of products: The parameters of the microbial fermentation process are controllable. Standardized flavor output can be achieved by adjusting the temperature, time and ventilation conditions, overcoming the shortcomings of traditional scenting which is greatly affected by natural conditions and has inconsistent flavor across batches.

[0038] (5) The stability of milk tea products was significantly improved unexpectedly: Milk tea prepared using the floral green tea of ​​this invention did not show any stratification or sedimentation during the 30-day observation period under the accelerated temperature test at 55℃; while milk tea prepared using traditional scented green tea showed obvious tea sedimentation and stratification on the 9th day under the same conditions. This improvement in stability is due to the complexation reaction between the acid produced by lactic acid bacteria metabolism and tea polyphenols during fermentation, as well as the degradation of ester-type catechins, which changed the binding characteristics of tea polyphenols and milk proteins, and is an unexpected technical effect. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 The milk tea bags used in Example 1 and Comparative Examples 1-5 for accelerated stability testing are shown. Detailed Implementation

[0041] To make the present invention clearer, the technical solution of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0042] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0043] In this invention, unless otherwise explicitly specified and limited, all raw materials and microbial strains are varieties permitted for use in the food industry and can be purchased commercially. Unless otherwise specified, all percentages used in the embodiments of this invention are mass percentages.

[0044] Example 1 This embodiment provides a method for preparing floral-scented green tea induced by dual-strain synergistic fermentation and a method for preparing milk tea thereafter. The specific steps are as follows: S1. Pre-treatment of tea leaves: Select fresh green tea leaves with one bud and two leaves in summer, and after fixing and initial rolling, obtain the initial tea leaves with a moisture content of 25%. Place the tea leaves in an environment with a temperature of 30℃ and a relative humidity of ≥90% for later use.

[0045] S2. Fermentation broth preparation: ① Culture medium preparation: Take 1000g of sterile water and put it into a sterile conical flask. Add 80g of jasmine cell sap (8% of the mass of sterile water) and 50g of sucrose (5% of the mass of sterile water). Mix well and sterilize at 115℃ for 15 minutes. Cool and set aside.

[0046] ②Inoculation: Inoculate the above culture medium with Saccharomyces cerevisiae and Lactobacillus plantarum at a mass ratio of 1.0:1.0, with the total inoculation amount being 3% of the mass of the culture medium.

[0047] ③ Activation culture: Place the inoculated culture medium in a 28℃ constant temperature incubator and incubate for 18 hours. During this period, take samples every 3 hours to test the viable cell concentration until the viable cell concentration reaches 1.2×10⁻⁶. 8 Stop culturing when CFU / mL is reached to obtain fermentation broth.

[0048] S3, Co-fermentation and scenting: Mix 1000g of the initial tea base from step S1 with 200g of the fermentation liquid from step S2 (tea base: fermentation liquid = 10:2) evenly, and put them into a sealed fermentation tank, controlling the temperature inside the tank at 30℃ and the relative humidity at ≥90%.

[0049] ① First stage anaerobic fermentation: Nitrogen gas is introduced into the tank to replace the air and then sealed. Static fermentation is carried out for 24 hours at 30°C under anaerobic conditions.

[0050] ② Second stage aerobic fermentation: After the anaerobic fermentation is completed, sterile air is introduced at a rate of 0.5 vvm (the volume of air introduced per minute per volume of fermentation liquid), and fermentation continues for 24 hours under aerobic conditions at 30℃.

[0051] S4. Inactivation and drying: ① Inactivation: After fermentation, the fermentation product is passed through 90℃ saturated steam for instantaneous high-temperature inactivation for 10 seconds to terminate fermentation.

[0052] ②Drying: Place the inactivated tea leaves in a vacuum drying oven and dry them at a vacuum degree of -0.095MPa and a temperature of 45℃ until the moisture content is 4%, thus obtaining jasmine-scented green tea.

[0053] S5. Preparation of Jasmine Scented Green Tea Milk Tea: ① Tea extraction: Mix the floral green tea obtained in step S4 with process water at 40-50℃ at a mass ratio of 1:30, extract at a constant temperature of 45℃ for 40 minutes, and filter through a 200-mesh filter to obtain tea soup.

[0054] ② Mixing ingredients: By weight, take 45 parts raw milk, 30 parts light cream, 25 parts tea and 0.2 parts microcrystalline cellulose, and stir for 30 seconds to mix evenly.

[0055] ③ Homogenization: Heat the mixture to 60℃ and hold for 5 minutes, then perform two-stage homogenization: the first homogenization is performed at a pressure of 20MPa and 5MPa; the second homogenization is performed at a pressure of 20MPa and 5MPa. After homogenization, the mixture is pumped into a temporary storage tank.

[0056] ④UHT sterilization and cooling: The homogenized milk tea liquid is subjected to ultra-high temperature instantaneous sterilization through a plate heat exchanger with sterilization parameters of 140℃ and 15 seconds; then it is rapidly cooled to 25℃.

[0057] ⑤ Aseptic filling: The cooled milk tea is filled into sterilized bottles under aseptic conditions, sealed and packaged to obtain jasmine-scented green tea milk tea.

[0058] Comparative Example 1 This comparative example uses the traditional scenting process to prepare jasmine tea, without involving microbial fermentation.

[0059] 1. Tea base processing: Select fresh green tea leaves with one bud and two leaves in summer, and after fixing, initial rolling, re-drying and cooling, obtain tea base with a moisture content of 5% and a temperature of 30℃.

[0060] 2. Fresh flower care: Pick jasmine flowers that are about to bloom in the afternoon, spread them out to cool and dissipate heat, then sift them to remove green buds, calyxes and impurities.

[0061] 3. Mixing tea leaves and jasmine flowers: Mix the tea leaves and fresh jasmine flowers evenly at a ratio of 100kg:150kg.

[0062] 4. Static Scenting (Pile Scenting): Pile the mixed camellia flower mixture into a pile about 30cm high, with an initial pile temperature of 28℃ and a total scenting time of 15 hours. During the scenting process, when the pile temperature rises to 38℃, turn the pile over to cool it down to 28℃ and continue scenting until the total time is reached.

[0063] 5. Scenting and Re-firing: After the scenting process is completed, the flower residue is sifted out, and the tea leaves are roasted in an oven at 80-90℃ for 2-3 hours until the moisture content of the tea leaves is 4%, thus obtaining traditional jasmine tea.

[0064] 6. Milk tea preparation: Same as step S5 in Example 1.

[0065] Comparative Example 2 The difference between this comparative example and Example 1 is that only Saccharomyces cerevisiae was inoculated into the fermentation broth, and Lactobacillus plantarum was not inoculated.

[0066] In S2, only brewer's yeast is inoculated (the inoculation amount is increased year-on-year, while the total inoculation amount remains unchanged); the remaining steps are the same as in Example 1.

[0067] Comparative Example 3 The difference between this comparative example and Example 1 is that fresh flower cell sap is not added to the culture medium; instead, an equal amount of sterile water is used.

[0068] Jasmine cell sap is not added in the preparation of S2 culture medium; the remaining steps are the same as in Example 1.

[0069] Comparative Example 4 The difference between this comparative example and Example 1 is that the entire fermentation process involves only anaerobic fermentation, without anaerobic-aerobic alternation.

[0070] In S3, the alternating anaerobic-aerobic fermentation was changed to continuous anaerobic fermentation at 30°C under anaerobic conditions for 48 hours; the remaining steps were the same as in Example 1.

[0071] Comparative Example 5 The difference between this comparative example and Example 1 is that the fermentation process only involves aerobic fermentation and does not involve anaerobic-aerobic alternation.

[0072] In S3, the anaerobic-aerobic alternating fermentation was changed to introducing sterile air and continuous aerobic fermentation at 30°C under aerobic conditions for 48 hours; the remaining steps were the same as in Example 1.

[0073] In order to objectively evaluate the technical effects of the various embodiments and comparative examples of the present invention, the effects of floral fragrance substances, tea soup mellowness, tea soup aroma intensity, and sensory evaluation of milk tea were carried out.

[0074] 1) The results of the detection of floral fragrance substances in the floral green tea prepared in Example 1 and Comparative Examples 1-5 are shown in Table 1.

[0075] Table 1 The floral-scented green teas prepared in Example 1 and Comparative Example 1 were steeped in hot water at 85°C for 1 hour. The content of floral-scented substances in the floral-scented green teas was detected, and the results are shown in Table 2.

[0076] Table 2 Loss calculation method: Loss = (sum of terpenoid compounds and jasmine fragrance characteristic compounds in Table 1 - sum of terpenoid compounds and jasmine fragrance characteristic compounds in Table 2) / sum of terpenoid compounds and jasmine fragrance characteristic compounds in Table 1 * 100%.

[0077] 2) Table 2 shows a comparison of the tea soup mellowness of the floral green teas prepared in Example 1 and Comparative Examples 1-5.

[0078] Table 3 3) Sensory evaluation of the tea infusion and milk tea from Example 1 and Comparative Examples 1-5. Ten professionally trained sensory evaluators (half male and half female, aged 25-45) were invited to conduct blind tastings and scores of the tea and milk tea products. The tea evaluation was conducted after brewing at 85℃ for one hour, while the milk tea evaluation was conducted after cooling to 50±2℃. A 9-point scale (1 = very poor, 9 = excellent) was used, with the average value of each indicator taken. The tea evaluation indicators included: floral aroma intensity, floral aroma persistence, body, bitterness, and aftertaste. The milk tea evaluation indicators included: flavor, mouthfeel, and tea taste.

[0079] The sensory evaluation results of the tea infusion are shown in Table 4.

[0080] Table 4 Note: The bitterness rating is an inverse indicator; the lower the score, the better the taste.

[0081] The sensory evaluation results of the milk tea are shown in Table 5.

[0082] Table 5 4) Accelerated stability test of milk tea The milk tea from Example 1 and Comparative Examples 1-5 was packaged into transparent bags of the same size (e.g., ...). Figure 1 (As shown), after sealing, the samples were placed in a constant temperature incubator at 55±1℃ for accelerated stability observation. The precipitation and stratification of the tea in the samples were observed and recorded at fixed times each day for 30 days. The number of days on which visible precipitation first appeared and the number of days on which stratification was clearly defined were recorded.

[0083] The results of the accelerated stability test of milk tea are shown in Table 6.

[0084] Table 6 As shown in Table 5, the milk tea prepared in Example 1 of this invention did not exhibit any precipitation or stratification during the 30-day observation period under accelerated testing at 55℃, demonstrating excellent system stability. Comparative Example 1 showed obvious stratification on day 9; Comparative Examples 2-5 showed slight precipitation on days 15 and 17, but no obvious stratification occurred during the observation period. The stability of Comparative Examples 2-5 was significantly improved compared to Comparative Example 1, but still not as good as Example 1.

[0085] Example 2 This embodiment provides a method for preparing floral-scented green tea induced by dual-strain synergistic fermentation and a method for preparing milk tea thereafter. The specific steps are as follows: S1. Pre-treatment of tea leaves: Select fresh green tea leaves with one bud and three leaves in autumn, and after fixing and initial rolling, obtain the initial tea leaves with a moisture content of 25%. Place the tea leaves in an environment with a temperature of 30℃ for later use.

[0086] S2. Fermentation broth preparation: ① Culture medium preparation: Take 1000g of sterile water, add 50g of rose cell sap (accounting for 5% of the mass of sterile water) and 20g of sucrose (accounting for 2% of the mass of sterile water), mix well and sterilize at 115℃ for 15 minutes.

[0087] ②Inoculation: Inoculate with Saccharomyces cerevisiae and Lactobacillus plantarum at a mass ratio of 0.8:0.8.

[0088] ③ Activation culture: Incubate at 26℃ for 24 hours until the viable bacterial concentration reaches 1.0 × 10⁻⁶. 8 CFU / mL.

[0089] S3. Co-fermentation and scenting: The mass ratio of tea leaves to fermentation liquid is 8:1. First stage: anaerobic fermentation: 28℃, 18 hours; Second stage: aerobic fermentation: 28℃, 18 hours.

[0090] S4. Inactivation and drying: Inactivation parameters are 85℃ for 15 seconds; dry to a moisture content of 5%.

[0091] S5. Milk Tea Preparation: The extraction ratio of tea leaves to water is 1:20, the extraction temperature is 40℃, and the extraction time is 30 minutes. Ingredient Mixing: 50 parts raw milk, 25 parts light cream, 25 parts tea broth, and 0.1 parts microcrystalline cellulose. Homogenization temperature is 55℃, and the temperature is maintained for 10 minutes. UHT sterilization parameters are 135℃ for 40 seconds.

[0092] The remaining steps and conditions are the same as in Example 1.

[0093] Example 3 This embodiment provides a method for preparing floral-scented green tea induced by dual-strain synergistic fermentation and a method for preparing milk tea thereafter. The specific steps are as follows: S1. Pre-treatment of tea leaves: Select fresh green tea leaves with one bud and three leaves in summer, and after fixing and initial rolling, obtain the initial tea leaves with a moisture content of 35%. Place the tea leaves in an environment with a temperature of 35℃ for later use.

[0094] S2. Fermentation broth preparation: ① Culture medium preparation: Take 1000g of sterile water, add 100g of osmanthus cell sap (accounting for 10% of the mass of sterile water) and 50g of sucrose (accounting for 5% of the mass of sterile water), mix well and sterilize at 115℃ for 15 minutes.

[0095] ②Inoculation: Inoculate with Saccharomyces cerevisiae and Lactobacillus plantarum at a mass ratio of 1.0:1.0.

[0096] ③ Activation culture: Incubate at 30℃ for 12 hours until the viable bacterial concentration reaches 1.5 × 10⁻⁶. 8 CFU / mL.

[0097] S3. Co-fermentation and scenting: The mass ratio of tea leaves to fermentation liquid is 10:3. First stage: anaerobic fermentation: 32℃, 30 hours; Second stage: aerobic fermentation: 32℃, 30 hours.

[0098] S4. Inactivation and drying: Inactivation parameters are 95℃ for 10 seconds; dry to a moisture content of 3%.

[0099] S5. Milk Tea Preparation: The extraction ratio of tea leaves to water is 1:40, the extraction temperature is 50℃, and the extraction time is 60 minutes. Ingredient Mixing: 45 parts raw milk, 30 parts light cream, 30 parts tea broth, and 0.3 parts microcrystalline cellulose. Homogenization temperature: 60℃, incubation time: 5 minutes. UHT sterilization parameters: 145℃, 4 seconds.

[0100] The remaining steps and conditions are the same as in Example 1.

[0101] Example 4 This embodiment provides a method for preparing floral-scented green tea induced by dual-strain synergistic fermentation and a method for preparing milk tea thereafter. The specific steps are as follows: S1. Pre-treatment of tea leaves: Select fresh green tea leaves with one bud and two leaves in autumn, and after fixing and initial rolling, obtain the initial tea leaves with a moisture content of 30%. Place the tea leaves in an environment with a temperature of 32℃ for later use.

[0102] S2. Fermentation broth preparation: ① Culture medium preparation: Take 1000g of sterile water, add 70g of gardenia cell sap (accounting for 7% of the mass of sterile water) and 35g of sucrose (accounting for 3.5% of the mass of sterile water), mix well and sterilize at 115℃ for 15 minutes.

[0103] ②Inoculation: Inoculate with Saccharomyces cerevisiae and Lactobacillus plantarum at a mass ratio of 0.9:0.9.

[0104] ③ Activation culture: Incubate at 28℃ for 20 hours until the viable bacterial concentration reaches 1.1×10⁻⁶. 8 CFU / mL.

[0105] S3. Co-fermentation and scenting: The mass ratio of tea leaves to fermentation liquid is 9:2. First stage: anaerobic fermentation, 30℃, 24 hours; Second stage: aerobic fermentation, 30℃, 24 hours.

[0106] S4. Inactivation and drying: Inactivation parameters are 90℃ for 12 seconds; dry to a moisture content of 4%.

[0107] S5. Milk Tea Preparation: The extraction ratio of tea leaves to water is 1:30, the extraction temperature is 45℃, and the extraction time is 45 minutes. Ingredient Mixing: 48 parts raw milk, 27 parts light cream, 27 parts tea broth, and 0.2 parts microcrystalline cellulose. Homogenization temperature: 58℃, incubation time: 8 minutes; primary pressure: 22MPa; secondary pressure: 4.5MPa. UHT sterilization parameters: 140℃, 20 seconds.

[0108] The remaining steps and conditions are the same as in Example 1.

[0109] Example 5 The difference between this embodiment and Example 1 is that: the effect of different inoculation ratios of Saccharomyces cerevisiae and Lactobacillus plantarum (0.8:1.0 and 1.0:0.8) on the fermentation effect is tested to verify the feasibility of the process under different strain ratios.

[0110] Group 5-1 (Saccharomyces cerevisiae:Lactobacillus plantarum = 1.0:0.8): The inoculation ratio in S2 was adjusted to Saccharomyces cerevisiae:Lactobacillus plantarum = 1.0:0.8; the mass ratio of tea base to fermentation liquid in S3 was 10:2; the first stage of anaerobic fermentation was carried out at 30°C for 24 hours; the second stage of aerobic fermentation was carried out at 30°C for 24 hours; the remaining steps were the same as in Example 1.

[0111] Group 5-2 (Saccharomyces cerevisiae:Lactobacillus plantarum = 0.8:1.0): The inoculation ratio in S2 was adjusted to Saccharomyces cerevisiae:Lactobacillus plantarum = 0.8:1.0; the mass ratio of tea base to fermentation liquid in S3 was 10:2; the first stage of anaerobic fermentation was carried out at 30°C for 24 hours; the second stage of aerobic fermentation was carried out at 30°C for 24 hours; the remaining steps were the same as in Example 1.

[0112] Example 6 The difference between this embodiment and Embodiment 1 is that this embodiment tests the effect of different mass ratios of tea leaves and fermentation liquid on the fermentation effect.

[0113] Group 6-1 (tea base: fermentation liquid = 10:1): The mass ratio of tea base to fermentation liquid is adjusted to 10:1; the remaining steps are the same as in Example 1.

[0114] Group 6-2 (tea base: fermentation liquid = 8:3): The mass ratio of tea base to fermentation liquid is adjusted to 8:3; the remaining steps are the same as in Example 1.

[0115] Example 7 The difference between this embodiment and Embodiment 1 is that: a mixed fresh flower cell sap is used as an induction substrate to test the feasibility of a combined induction process using multiple fresh flower cell saps.

[0116] In the preparation of S2 culture medium, 80g of jasmine cell sap was replaced with 40g of jasmine cell sap and 40g of rose cell sap; the remaining steps were the same as in Example 1.

[0117] Sensory evaluations and accelerated stability tests were performed on the tea infusions and milk teas from Examples 2-6. The methods for sensory evaluation and accelerated stability tests were the same as those in Example 1.

[0118] The sensory evaluation results of the tea infusions in Examples 2-6 are shown in Table 7.

[0119] Table 7 The sensory evaluation results of the milk tea in Examples 2-7 are shown in Table 8.

[0120] Table 8 The results of the accelerated stability test of milk tea in Examples 2-7 are shown in Table 9.

[0121] Table 9 Based on the test data of the above embodiments and comparative examples, it can be seen that the present invention achieves the synergistic enhancement of floral aroma substances and tea flavor in green tea during the fermentation process by organically combining three core technical features: the synergistic effect of aroma-producing yeast (Saccharomyces cerevisiae) + lactic acid bacteria (Lactobacillus plantarum), the specific induction of fresh flower cell sap, and the time-sequence control of anaerobic-aerobic alternating fermentation.

[0122] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing floral-scented green tea induced by synergistic fermentation of two microorganisms, characterized in that, Includes the following steps: S1. Pre-treatment of tea leaves: Select fresh green tea leaves, and after fixing and initial rolling, obtain preliminary tea leaves with a moisture content of 25%-35%. Place the preliminary tea leaves in an environment of 30-35℃ for later use. S2. Fermentation broth preparation: Aroma-producing yeast and lactic acid bacteria are inoculated into the culture medium for activation culture until the viable cell concentration reaches 1×10⁻⁶. 8 Fermentation broth was prepared by adding CFU / mL or higher; wherein the culture medium was a sterile aqueous solution containing fresh flower cell sap and sucrose, the amount of fresh flower cell sap added was 5%-10% of the mass of sterile water, and the amount of sucrose added was 2%-5% of the mass of sterile water; the inoculation mass ratio of aroma-producing yeast to lactic acid bacteria was (0.8-1.0):(0.8-1.0); the activation culture conditions were: temperature 26-30℃, time 12-24 hours; S3. Co-fermentation and scenting: The initial tea leaves from step S1 and the fermentation liquid from step S2 are mixed evenly at a mass ratio of (8-10):(1-3), and placed in a sealed fermentation container. Anaerobic-aerobic alternating fermentation is carried out under conditions of 28-32℃ and relative humidity ≥90%. The anaerobic-aerobic alternating fermentation includes: firstly, the first stage of anaerobic fermentation is carried out for 18-30 hours under anaerobic conditions, and then sterile air or oxygen is introduced to carry out the second stage of aerobic fermentation for 18-30 hours under aerobic conditions. S4. Inactivation and Drying: After fermentation, the fermentation product is inactivated to terminate fermentation, and then dried until the moisture content is ≤5%, thus obtaining the floral green tea.

2. The method for preparing floral-scented green tea by synergistic fermentation of two microorganisms to induce aroma production according to claim 1, characterized in that, In step S2, the aroma-producing yeast is brewer's yeast; the lactic acid bacteria is Lactobacillus plantarum.

3. The method for preparing floral-scented green tea induced by dual-strain synergistic fermentation according to claim 1, characterized in that, In step S2, the fresh flower cell sap is selected from one or more of the following: rose cell sap, jasmine cell sap, osmanthus cell sap, and gardenia cell sap.

4. The method for preparing floral-scented green tea by synergistic fermentation induced by two microorganisms according to claim 1, characterized in that, In step S3, the temperature of the first stage of anaerobic fermentation and the second stage of aerobic fermentation are both 30-32℃, the time of the first stage of anaerobic fermentation is 20-26 hours, and the time of the second stage of aerobic fermentation is 20-26 hours.

5. The method for preparing floral-scented green tea by synergistic fermentation induced by two microorganisms according to claim 1, characterized in that, In step S4, the inactivation treatment is instantaneous high-temperature steam treatment at 85-95℃ for 10-15 seconds; the drying is low-temperature vacuum drying.

6. A floral-scented green tea, characterized in that, The aroma-inducing floral green tea is prepared by the method of dual-strain synergistic fermentation induced by any one of claims 1 to 5.

7. A method for preparing floral-scented green tea milk tea, characterized in that, Includes the following steps: (1) Tea extraction: The floral green tea described in claim 6 is mixed with process water at a mass ratio of 1:(20-40), and extracted at a low temperature of 40-50℃ for 30-60 minutes to obtain tea soup; (2) Mixing raw materials: By weight, mix 45-50 parts of raw milk, 25-30 parts of light cream, 25-30 parts of the tea soup and 0.1-0.3 parts of stabilizer and stir evenly; (3) Homogenization: Heat the mixture from step (2) to 55-60℃ and keep it at that temperature for 5-10 minutes. Then perform two-stage homogenization treatment, with a first-stage pressure of 20-25 MPa and a second-stage pressure of 4-5 MPa. (4) Sterilization and cooling: The homogenized liquid is subjected to ultra-high temperature instantaneous sterilization with sterilization parameters of 135-145℃ for 4-40 seconds, and then rapidly cooled to below 30℃; (5) Aseptic filling: The cooled milk tea is aseptically filled to obtain the floral green tea milk tea.

8. The method for preparing floral-scented green tea milk tea according to claim 7, characterized in that, In step (2), the stabilizer is microcrystalline cellulose, and the amount added is 0.15-0.25 parts.

9. The method for preparing floral-scented green tea milk tea according to claim 7, characterized in that, In step (3), the two-stage homogenization process is two homogenizations, with the first-stage pressure being 20-25 MPa and the second-stage pressure being 4-5 MPa.

10. A floral-scented green tea milk tea, characterized in that, It is prepared by the preparation method according to any one of claims 7 to 9.

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