Fermented tea with compound flavor of tea fruit and preparation method thereof

Abstract

The application relates to the technical field of tea processing, and discloses a tea-fruit composite flavor fermented tea and a preparation method thereof. The method comprises the following steps: selecting tea base and performing steam softening and moisture adjusting treatment; crushing fruit raw materials, adding pectinase and cellulase to perform enzymolysis, and obtaining enzymolysis fruit pulp; mixing the tea base, the enzymolysis fruit pulp and a composite fermentation inoculum composed of lactobacillus plantarum, saccharomyces cerevisiae and eurotium cristatum, sequentially performing early micro-aerobic fermentation and late oxygen-controlled solid-state fermentation, and then performing low-temperature fragrance fixing and drying to obtain the tea-fruit composite flavor fermented tea. The application can promote the synergistic conversion of tea contents and fruit aroma precursor substances, the obtained product has tea aroma, fruit aroma and fermentation aroma, the taste is coordinated, the aroma is natural and persistent, the quality is stable, and the product is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, specifically to a fermented tea with a tea and fruit flavor and its preparation method. Background Technology

[0002] Fermented tea is a type of tea product that uses tea leaves as the main raw material and undergoes processes such as microbial fermentation, enzymatic transformation, or post-fermentation aging to develop a specific color, flavor, and aroma. With changing consumer demands, traditional single-flavor tea products are no longer sufficient to meet the needs of younger consumers who prefer fruity, fermented, refreshing, and low-irritant teas. Fermenting fruit with tea leaves utilizes the sugars, organic acids, aromatic precursors, and dietary fiber in the fruit to improve the tea fermentation substrate, resulting in a tea infusion with aromas of tea, fruit, and microbial fermentation, which has significant market development potential. Existing tea-fruit blended tea products are mostly prepared by simply blending tea leaves with dried fruit, fruit powder, or flavorings. They primarily rely on the layering of exogenous aromas to create flavor, lacking deep fermentation and transformation between tea leaves and fruits. This often results in problems such as a superficial aroma, short-lasting fragrance, separate flavors, and an unharmonious mouthfeel. Furthermore, fruit raw materials have high moisture and sugar-acid content. If directly mixed with tea leaves for fermentation, this can easily lead to excessive moisture in certain areas, contamination by other microorganisms, spoilage, uneven fermentation, and aroma loss after drying, affecting the stability of product quality. Furthermore, while some existing fermented tea processes incorporate microbial fermentation, the microbial strains are relatively simple, primarily focusing on the transformation of the tea's own internal components. They fail to adequately utilize the release of pectin, cellulose, and bound aroma precursors from fruit raw materials, resulting in limited integration of fruit and tea aromas. Simply increasing the amount of fruit added to enhance the fruit flavor can lead to problems such as masking the tea flavor, tea leaf clumping, difficulty in controlling fermentation temperature, and unstable moisture content in the finished product, hindering large-scale production. Therefore, it is necessary to provide a tea-fruit complex flavored fermented tea and its preparation method. By combining tea pretreatment, fruit enzymatic hydrolysis, compound microbial inoculation, segmented humidity-controlled fermentation, and low-temperature aroma fixation, tea polyphenols, amino acids, sugars, organic acids, and fruit aroma precursors undergo synergistic transformation. This results in a stable, harmonious, and natural tea-fruit complex flavor while maintaining the main flavor of the tea, and improves the controllability of the fermentation process and the consistency of product quality. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a tea and fruit flavored fermented tea and its preparation method, which solves the problems of floating aroma, short-lasting aroma, separation of tea and fruit flavors, uneven fermentation and insufficient quality stability of existing tea and fruit flavored tea products. The resulting product has the characteristics of tea aroma, fruit aroma and fermentation aroma, natural and lasting aroma, harmonious and mellow taste, controllable fermentation process and good batch stability.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a tea-fruit flavored fermented tea, comprising the following steps: S1. Pre-treatment of tea base: Select one or more of green tea, oolong tea, black tea or dark tea as tea base, remove impurities and then perform steam softening treatment. The steam temperature is 90-105℃ and the treatment time is 60-120s. Then adjust the moisture content of the tea base to 25-38%. S2. Preparation of fruit-flavored fermentation base: The fruit raw materials are crushed into fruit pulp, and pectinase and cellulase are added for enzymatic hydrolysis. The enzymatic hydrolysis temperature is 35-40℃ and the enzymatic hydrolysis time is 1-4h to obtain enzymatically hydrolyzed fruit pulp. S3. Preparation of tea and fruit compound fermentation material: The tea base obtained in step S1 and the enzymatically hydrolyzed fruit pulp obtained in step S2 are mixed at a mass ratio of 100:8-35, and a compound fermentation agent is added. After mixing evenly, the tea and fruit compound fermentation material is obtained. S4. Segmented humidity-controlled fermentation: The tea and fruit compound fermentation material obtained in step S3 is subjected to early microaerophilic fermentation and later oxygen-controlled solid fermentation. The early microaerophilic fermentation temperature is 25-32℃ and the time is 12-36h; the later oxygen-controlled solid fermentation temperature is 28-35℃ and the relative humidity is 70-90% for 36-96h. S5. Low-temperature aroma fixation and drying: The fermented material obtained in step S4 is subjected to low-temperature aroma fixation at 35-45℃ for 2-6 hours, and then dried at 45-60℃ until the moisture content is 5-9%, thus obtaining the tea and fruit compound flavor fermented tea.

[0005] Furthermore, in step S2, the fruit ingredients include one or more of the following: citrus, apple, pear, peach, berry, passion fruit, hawthorn, plum, jujube, or pomelo.

[0006] Further, in step S2, the amount of pectinase added is 0.03-0.20% of the fruit pulp mass, the amount of cellulase added is 0.02-0.15% of the fruit pulp mass, and the pH is controlled at 4.0-5.5 during enzymatic hydrolysis.

[0007] Furthermore, the compound fermentation agent in step S3 includes Lactobacillus plantarum, Saccharomyces cerevisiae, and Aspergillus cristatus, with a live bacteria ratio of 1-4:1-3:1, and the inoculation amount of the compound fermentation agent is 2-8% of the mass of the tea and fruit compound fermentation material.

[0008] Furthermore, the viable count of *Lactobacillus plantarum* in the compound fermentation agent is 1.0 × 10⁻⁶. 7 ~1.0×10 9 CFU / mL, viable count of Saccharomyces cerevisiae was 1.0 × 10⁻⁶. 6 ~1.0×10 8 CFU / mL, the number of spores of *Eurotium cristatum* was 1.0 × 10⁻⁶.5 ~1.0×10 7 CFU / mL.

[0009] Furthermore, in step S4, during the initial microaerophilic fermentation, the thickness of the tea and fruit compound fermentation material layer is 3-8 cm, the oxygen volume fraction is controlled at 3-12%, and the pH at the fermentation endpoint is controlled at 4.2-5.2.

[0010] Furthermore, in step S4, during the later stage of controlled oxygen solid-state fermentation, the thickness of the tea and fruit compound fermentation material layer is 5-12cm, and the material is turned over every 12-24 hours to ensure that the center temperature of the fermentation material does not exceed 38℃.

[0011] Compared with the prior art, the present invention has the following beneficial technical effects: This invention softens the tea leaves with steam and adjusts their moisture content, allowing the tea leaves to expand appropriately. This improves the adsorption, penetration, and uniform mixing of the tea leaves with fruit pulp and fermentation agents, avoiding problems such as excessively high local moisture content, clumping, uneven fermentation, or contamination by miscellaneous bacteria caused by directly mixing fruit raw materials. This provides a stable substrate for subsequent tea-fruit compound fermentation. This invention employs pectinase and cellulase to pre-hydrolyze fruit raw materials, which can disrupt the cell wall structure of fruits and release sugars, organic acids, soluble pectin, and bound aroma precursors. This allows the fruit raw materials to participate in microbial transformation as fermentation substrates, rather than merely as exogenous aroma additives. This improves the integration of fruit and tea aromas and addresses the problems of superficial aroma, short-lasting fragrance, and flavor separation in traditional tea-fruit blends. This invention employs a compound fermentation agent composed of *Lactobacillus plantarum*, *Saccharomyces cerevisiae*, and *Aurogonium cristatum*. *Lactobacillus plantarum* helps regulate the acidity of the fermentation system and create a mellow sourness; *Saccharomyces cerevisiae* promotes the conversion of sugars and generates alcoholic esters and aroma compounds; and *Aurogonium cristatum* promotes the conversion of tea polyphenols, proteins, and polysaccharides. The synergistic effect of these three agents results in a harmonious blend of tea aroma, fruity aroma, and fermented aroma in the tea liquor, while simultaneously reducing the harshness of the tea liquor and enhancing its smoothness and fullness. This invention combines early-stage microaerophilic fermentation with later-stage controlled-oxygen solid-state fermentation. By controlling oxygen, temperature, humidity, material layer thickness, and turning conditions at different stages, it ensures stable growth of beneficial microorganisms while inhibiting rancidity, mold, and over-fermentation, thus improving the controllability and batch consistency of the fermentation process. Subsequent low-temperature aroma fixation and medium-low temperature drying reduce the volatilization of fruity aromas and loss of tea aromas caused by high-temperature drying, resulting in a more natural and stable aroma in the finished product, with suitable moisture content, facilitating storage and industrial-scale production. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating the process of fermenting tea with a blend of tea and fruit flavors. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] The green tea base is first-grade loose green tea produced by Hunan Tea Industry Group Co., Ltd.; the oolong tea base is light-roasted oolong tea produced by Fujian Anxi Tieguanyin Group Co., Ltd.; and the black tea base is loose Anhua black tea produced by Hunan Baishaxi Tea Factory Co., Ltd. The citrus fruits, apples, hawthorns, passion fruit, pomelos, and dates are all selected from fresh, ripe, edible-grade fruits, and rotten, moldy, and mechanically damaged fruits are removed before use. The pectinase used was a food-grade pectinase preparation produced by Novozymes (China) Investment Co., Ltd., with an enzyme activity of not less than 30,000 U / g; the cellulase used was a food-grade cellulase preparation produced by Novozymes (China) Investment Co., Ltd., with an enzyme activity of not less than 10,000 U / g. Food-grade citric acid and food-grade sodium citrate were both food additive-grade products produced by Weifang Yingxuan Industrial Co., Ltd. Lactobacillus plantarum, commercially available Lactobacillus plantarum powder for food fermentation, manufactured by Chr. Hansen (China) Co., Ltd.; Saccharomyces cerevisiae, highly active dry yeast produced by Angel Yeast Co., Ltd.; and *Aurorus cristatus*, a strain of *Aurorus cristatus* preserved and activated in the tea science laboratory of Hunan Agricultural University. Before use, the above-mentioned microbial agents were activated on sterile culture media and adjusted to the required viable cell or spore counts as specified in the examples. Example 1 A method for preparing a fermented tea with a tea and fruit flavor includes the following steps: S1. Pre-treatment of tea base: Select green tea as tea base, remove broken pieces, tea stems and other impurities, and place it in a steam treatment device for steam softening treatment. The steam temperature is 90℃ and the treatment time is 60s. After steam treatment, spread it out to cool, and adjust the moisture content of the tea base to 25% by spraying water. S2. Preparation of Fruit-Flavored Fermentation Base: Citrus fruits were selected as the raw material. After washing, peeling, and deseeding, the fruit pulp was crushed. The initial pH of the fruit pulp was measured using a food-grade pH meter. When the pH of the fruit pulp was lower than 4.0, a 5% (w / w) food-grade sodium citrate solution was added dropwise while stirring to adjust the pH to 4.0. Subsequently, pectinase and cellulase were added to the fruit pulp for enzymatic hydrolysis. The amount of pectinase added was 0.03% of the fruit pulp mass, and the amount of cellulase added was 0.02% of the fruit pulp mass. The hydrolysis temperature was 35℃, and the hydrolysis time was 1 hour to obtain enzymatically hydrolyzed fruit pulp. The pH was measured every 30 minutes during the hydrolysis process. When the pH deviated from 4.0, it was finely adjusted using food-grade sodium citrate solution or food-grade citric acid solution to stabilize the pH of the hydrolysis system at 4.0. S3. Preparation of Tea and Fruit Compound Fermentation Material: The tea base obtained in step S1 and the enzymatically hydrolyzed fruit pulp obtained in step S2 are mixed at a mass ratio of 100:8. A compound fermentation agent is then added, and the mixture is stirred evenly to obtain the tea and fruit compound fermentation material. The compound fermentation agent consists of *Lactobacillus plantarum*, *Saccharomyces cerevisiae*, and *Aspergillus cristatus*, with a viable cell ratio of 1:1:1. The inoculum amount of the compound fermentation agent is 2% of the mass of the tea and fruit compound fermentation material. The viable cell count of *Lactobacillus plantarum* is 1.0 × 10⁻⁶. 7 CFU / mL, viable count of Saccharomyces cerevisiae was 1.0 × 10⁻⁶. 6 CFU / mL, the number of spores of *Eurotium cristatum* was 1.0 × 10⁻⁶. 5 CFU / mL. S4. Segmented Humidity-Controlled Fermentation: The tea and fruit compound fermented material obtained in step S3 is first subjected to early-stage microaerophilic fermentation. The material layer thickness is 3cm, the oxygen volume fraction is controlled at 3%, the fermentation temperature is 25℃, and the fermentation time is 12h. During the fermentation process, a representative sample of 10g of fermented material is taken every 6h, 50g of sterile water is added, and the extract is shaken and extracted for 5min. The pH of the extract is then measured using a pH meter. When the pH is lower than 4.2, the fermentation temperature is lowered or the early-stage microaerophilic fermentation is terminated early. When the pH is higher than 4.2, the early-stage microaerophilic fermentation time is appropriately extended until the pH of the early-stage microaerophilic fermentation endpoint is controlled at 4.2. Subsequently, the later-stage oxygen-controlled solid-state fermentation is carried out. The material layer thickness is 5cm, the fermentation temperature is 28℃, the relative humidity is 70%, and the fermentation time is 36h. The material is turned over every 12h to ensure that the center temperature of the fermented material does not exceed 38℃. S5. Low-temperature aroma fixation and drying: The fermented material obtained in step S4 is subjected to low-temperature aroma fixation at 35℃ for 2 hours, and then dried at 45℃ until the moisture content is 5%, thus obtaining the tea and fruit compound flavor fermented tea.

[0015] Example 2 A method for preparing a fermented tea with a tea and fruit flavor includes the following steps: S1. Pre-treatment of tea base: Select oolong tea as tea base, remove broken pieces, tea stems and other impurities, and place it in a steam treatment device for steam softening treatment. The steam temperature is 98℃ and the treatment time is 90s. After steam treatment, spread it out to cool, and adjust the moisture content of the tea base to 32% by spraying water. S2. Preparation of Fruit-Flavored Fermentation Substrate: Apples and hawthorns were selected as raw materials, with a mass ratio of 3:1. After washing and pitting, the fruit pulp was crushed. The initial pH of the fruit pulp was measured using a food-grade pH meter. When the pH of the fruit pulp was below 4.8, a 5% (w / w) food-grade sodium citrate solution was added dropwise while stirring to adjust the pH. When the pH of the fruit pulp was above 4.8, a 5% (w / w) food-grade citric acid solution was added dropwise while stirring to adjust the pH to 4.8. Subsequently, pectinase and cellulase were added to the fruit pulp for enzymatic hydrolysis. The amount of pectinase added was 0.10% of the fruit pulp mass, and the amount of cellulase added was 0.08% of the fruit pulp mass. The hydrolysis temperature was 38℃, and the hydrolysis time was 2.5 hours to obtain enzymatically hydrolyzed fruit pulp. The pH was measured every 30 minutes during the hydrolysis process, and the pH was fine-tuned using food-grade sodium citrate solution or food-grade citric acid solution based on the test results to maintain the pH of the hydrolysis system at 4.8. S3. Preparation of Tea and Fruit Compound Fermentation Material: The tea base obtained in step S1 and the enzymatically hydrolyzed fruit pulp obtained in step S2 are mixed at a mass ratio of 100:20. A compound fermentation agent is then added, and the mixture is stirred until homogeneous to obtain the tea and fruit compound fermentation material. The compound fermentation agent consists of *Lactobacillus plantarum*, *Saccharomyces cerevisiae*, and *Aspergillus cristatus*, with a viable count ratio of 2:2:1. The inoculum amount of the compound fermentation agent is 5% of the mass of the tea and fruit compound fermentation material. The viable count of *Lactobacillus plantarum* is 5.0 × 10⁻⁶. 8 CFU / mL, viable count of Saccharomyces cerevisiae was 5.0 × 10⁻⁶. 7 CFU / mL, the number of spores of *Eurotium cristatum* was 5.0 × 10⁻⁶. 6 CFU / mL. S4. Segmented Humidity-Controlled Fermentation: The tea and fruit compound fermented material obtained in step S3 is first subjected to early-stage microaerophilic fermentation. The material layer thickness is 5cm, the oxygen volume fraction is controlled at 8%, the fermentation temperature is 28℃, and the fermentation time is 24h. During the fermentation process, a representative sample of 10g of fermented material is taken every 6h, 50g of sterile water is added, and the extraction is performed by shaking for 5min. The pH of the extract is then measured using a pH meter. When the pH drops too quickly and is below 4.7, the fermentation temperature is appropriately reduced or the subsequent microaerophilic fermentation time is shortened. When the pH is above 4.7, microaerophilic fermentation is maintained and the fermentation time is extended so that the pH at the end of the early-stage microaerophilic fermentation is controlled at 4.7. Subsequently, the later-stage oxygen-controlled solid-state fermentation is carried out. The material layer thickness is 8cm, the fermentation temperature is 32℃, the relative humidity is 80%, and the fermentation time is 60h. The material is turned over every 18h to ensure that the center temperature of the fermented material does not exceed 38℃. S5. Low-temperature aroma fixation and drying: The fermented material obtained in step S4 is subjected to low-temperature aroma fixation at 40℃ for 4 hours, and then dried at 52℃ until the moisture content is 7%, thus obtaining the tea and fruit compound flavor fermented tea.

[0016] Example 3 A method for preparing a fermented tea with a tea and fruit flavor includes the following steps: S1. Pre-treatment of tea base: Select black tea as tea base, remove broken tea leaves, tea stems and other impurities, and place it in a steam treatment device for steam softening treatment. The steam temperature is 105℃ and the treatment time is 120s. After steam treatment, spread it out to cool, and adjust the moisture content of the tea base to 38% by spraying water. S2. Preparation of Fruit-Flavored Fermentation Base: Passion fruit, pomelo, and jujube were selected as fruit raw materials in a mass ratio of 2:2:1. After washing, peeling, and removing seeds or pits, the fruit pulp was crushed. The initial pH of the fruit pulp was measured using a food-grade pH meter. When the pH of the fruit pulp was lower than 5.5, a 5% (w / w) food-grade sodium citrate solution was added dropwise while stirring to adjust the pH to 5.5. Then, pectinase and cellulase were added to the fruit pulp for enzymatic hydrolysis. The amount of pectinase added was 0.20% of the mass of the fruit pulp, and the amount of cellulase added was 0.15% of the mass of the fruit pulp. The hydrolysis temperature was 40℃, and the hydrolysis time was 4 hours to obtain enzymatically hydrolyzed fruit pulp. The pH was measured every 30 minutes during the hydrolysis process. When the pH decreased, it was fine-tuned using a food-grade sodium citrate solution to maintain the pH of the hydrolysis system at 5.5. S3. Preparation of Tea and Fruit Compound Fermentation Material: The tea base obtained in step S1 and the enzymatically hydrolyzed fruit pulp obtained in step S2 are mixed at a mass ratio of 100:35. A compound fermentation agent is then added, and the mixture is stirred evenly to obtain the tea and fruit compound fermentation material. The compound fermentation agent consists of *Lactobacillus plantarum*, *Saccharomyces cerevisiae*, and *Aspergillus cristatus*, with a viable cell ratio of 4:3:1. The inoculum amount of the compound fermentation agent is 8% of the mass of the tea and fruit compound fermentation material. The viable cell count of *Lactobacillus plantarum* is 1.0 × 10⁻⁶. 9 CFU / mL, viable count of Saccharomyces cerevisiae was 1.0 × 10⁻⁶. 8 CFU / mL, the number of spores of *Eurotium cristatum* was 1.0 × 10⁻⁶. 7 CFU / mL. S4. Segmented Humidity-Controlled Fermentation: The tea and fruit compound fermented material obtained in step S3 is first subjected to early-stage microaerophilic fermentation. The material layer thickness is 8cm, the oxygen volume fraction is controlled at 12%, the fermentation temperature is 32℃, and the fermentation time is 36h. During the fermentation process, a representative sample of 10g of fermented material is taken every 6h, 50g of sterile water is added, and the extract is shaken and extracted for 5min. The pH of the extract is then measured using a pH meter. When the pH is below 5.2, the fermentation temperature is appropriately reduced, the microaerophilic fermentation time is shortened, or a small amount of food-grade sodium citrate solution is sprayed. When the pH is above 5.2, microaerophilic fermentation continues until the pH of the early-stage microaerophilic fermentation endpoint is controlled at 5.2. Subsequently, late-stage oxygen-controlled solid-state fermentation is carried out. The material layer thickness is 12cm, the fermentation temperature is 35℃, the relative humidity is 90%, and the fermentation time is 96h. The material is turned over every 24h to ensure that the center temperature of the fermented material does not exceed 38℃. S5. Low-temperature aroma fixation and drying: The fermented material obtained in step S4 is subjected to low-temperature aroma fixation at 45℃ for 6 hours, and then dried at 60℃ until the moisture content is 9%, thus obtaining the tea and fruit compound flavor fermented tea.

[0017] Comparative Example 1 The difference between this comparative example and Example 3 is that pectinase and cellulase are not added for enzymatic hydrolysis in step S2. Instead, passion fruit, grapefruit, and jujube are washed, peeled, seeded, or pitted and then directly crushed into fruit pulp. The initial pH of the fruit pulp is measured using a food-grade pH meter. When the pH of the fruit pulp is lower than 5.5, a 5% (w / w) food-grade sodium citrate solution is added dropwise while stirring to adjust the pH of the fruit pulp to 5.5 before it is directly mixed with the tea base. The composition of the remaining raw materials and the preparation conditions are the same as in Example 3.

[0018] Because the fruit raw materials were not enzymatically hydrolyzed, the cell wall structure of the fruit was not fully destroyed, resulting in insufficient release of bound aroma precursors, soluble pectin, and fermentable sugars. Consequently, the combination of fruit aroma and tea aroma was relatively weak, which could easily lead to insufficient release of fruit flavor and inadequate aroma integration.

[0019] Comparative Example 2 The difference between this comparative example and Example 3 is that only *Lactobacillus plantarum* is added as a fermentation agent in step S3, and *Saccharomyces cerevisiae* and *Aspergillus cristatus* are not added; the inoculation amount of *Lactobacillus plantarum* is the same as the total inoculation amount of the compound fermentation agent in Example 3, and the composition of other raw materials, pH control method and preparation conditions are the same as in Example 3. Because the fermentation agent has a single composition, the fermentation process mainly involves acidification. It lacks the alcohol esterification conversion of sugars by brewer's yeast and the synergistic conversion of tea polyphenols, proteins and polysaccharides by Aspergillus cristatus. As a result, the product is prone to problems such as a prominent acidity, insufficient fermentation aroma, and poor body and balance of the tea soup.

[0020] Comparative Example 3 The difference between this comparative example and Example 3 is that: in step S4, the segmented fermentation method combining early microaerophilic fermentation and later oxygen-controlled solid-state fermentation is not used. Instead, the tea and fruit compound fermented material obtained in step S3 is directly subjected to continuous solid-state fermentation at 35°C and 90% relative humidity for 132 hours, and the oxygen volume fraction is not controlled during the fermentation process. During the fermentation process, 10g of representative sample of fermented material is still taken every 6 hours, 50g of sterile water is added, and the pH of the extract is measured by a pH meter after shaking and extraction for 5 minutes. However, the fermentation temperature, fermentation time or fermentation stage is not adjusted according to the pH change. The composition of other raw materials and preparation conditions are the same as in Example 3. Because the process of beneficial bacteria adapting and multiplying is not carried out in stages, the temperature, humidity and oxygen distribution inside the fermentation material are uneven in the early stage of fermentation, which can easily lead to local over-humidity, uneven fermentation, rancidity or increased off-flavors. As a result, the product is relatively poor in terms of aroma stability, taste harmony and batch consistency.

[0021] To verify the quality stability, flavor harmony, and fermentation controllability of the tea-fruit flavored fermented tea obtained in this invention, samples from Examples 1-3 and Comparative Examples 1-3 were tested. Samples were taken for testing after drying and sealing for 24 hours. Each group of samples was measured in triplicate, and the average value was taken. I. Moisture Content Test Moisture content was determined according to the direct drying method in GB5009.3-2016 "National Food Safety Standard - Determination of Moisture in Food". Approximately 2.0 g of the pulverized and mixed sample was placed in a pre-dried weighing bottle to constant weight and dried at 101℃~105℃ to constant weight. The moisture content was calculated based on the difference in sample mass before and after drying. This indicator is used to evaluate the degree of drying and storage stability of the finished product. II. Water Extract Content Test The water extract content was determined according to GB / T8305-2013 "Determination of Water Extract Content in Tea". The pulverized sample was taken, boiled in water for thorough extraction, filtered, and the filtrate was evaporated to dryness and dried to constant weight. The percentage of water extract in the dry matter of the sample was calculated. This indicator is used to evaluate the release level of soluble flavor substances in tea infusion; a higher water extract content indicates better tea infusion thickness and flavor release ability. III. Tea Polyphenol Content Test The content of tea polyphenols was determined in accordance with GB / T8313-2018 "Determination Method of Tea Polyphenols and Catechins in Tea". IV. Test for total free amino acids The total amount of free amino acids was determined in accordance with GB / T8314-2013 "Determination of Total Free Amino Acids in Tea". V. Soluble sugar content test The soluble sugar content was determined using the anthrone-sulfuric acid colorimetric method. VI. Total Acidity Test The total acid content was determined using the conventional acid-base titration method for food acidity testing. The sample extract was titrated with 0.1 mol / L sodium hydroxide standard solution using phenolphthalein as an indicator until a faint red color persisted for 30 seconds. The total acid content was then calculated based on citric acid. This indicator is used to evaluate the degree of acidification during Lactobacillus plantarum fermentation and the harmony of the tea's acidity. VII. pH Test Take 5.0 g of sample, add 100 mL of boiled and cooled distilled water, and extract at 25 °C for 10 min. After filtration, measure the pH of the filtrate using a pH meter calibrated with standard buffer solutions of pH 4.00 and pH 6.86. Measure each sample three times and take the average value. This index is used to evaluate the acidity control at the fermentation endpoint. VIII. Sensory Evaluation Test Sensory evaluation was conducted according to GB / T23776-2018 "Sensory Evaluation Method for Tea", with scoring items set according to the characteristics of tea with a complex flavor profile. 3.0g of sample was steeped in 150mL of boiling water for 5 minutes, filtered, and then evaluated. An evaluation panel of 5 experienced tea evaluators assessed the tea from six aspects: appearance, liquor color, aroma, taste, infused leaves, and flavor harmony, with a maximum score of 100 points. The aroma evaluation focused on the naturalness of the fruity aroma, the purity of the fermentation aroma, and the duration of the aroma; the taste evaluation focused on the harmony of sweet and sour, body, bitterness, and the integration of tea and fruit flavors. IX. Microbiological Indicator Testing The total bacterial count was determined according to GB4789.2-2022 "National Food Safety Standard - Microbiological Examination of Food - Determination of Total Bacterial Count"; the mold and yeast counts were determined according to GB4789.15-2016 "National Food Safety Standard - Microbiological Examination of Food - Mold and Yeast Count". Samples were aseptically homogenized, serially diluted, and then inoculated and cultured. The counts were based on colony-forming units. This indicator is used to evaluate the hygienic stability of the finished product after drying and to assess the risk of abnormal microbial proliferation.

[0022] Table 1: Physicochemical Indicators Test

[0023] Table 2: Sensory Evaluation

[0024] Table 3: Microbiological Indicator Tests

[0025] As shown in Tables 1 to 3, the moisture content of the tea-fruit flavored fermented teas obtained in Examples 1-3 ranged from 5.8% to 7.6%, all within the suitable storage range. The content of water extract, free amino acids, and soluble sugars was generally higher than in the comparative examples, indicating that the present invention, through fruit enzymatic hydrolysis and compound fermentation, improved the release level of soluble flavor substances in the tea and fruit raw materials, thus improving the thickness, sweetness, and flavor harmony of the tea soup. Simultaneously, the total acid content and pH of Examples 1-3 were in a relatively balanced state, without the excessive acidification problems observed in Comparative Examples 2 and 3, indicating that segmented fermentation and pH control can make the acidity more mellow and natural.

[0026] Sensory evaluation results showed that Examples 1-3 scored 88.6-91.2 points, with aroma retention times of 18-22 minutes, significantly better than Comparative Examples 1-3. Comparative Example 1, lacking fruit enzymatic hydrolysis, exhibited insufficient fruit aroma release and reduced tea-fruit fusion; Comparative Example 2, using only *Lactobacillus plantarum* fermentation, had a more pronounced acidity and insufficient fermentation aroma; Comparative Example 3, lacking segmented humidity-controlled and oxygen-controlled fermentation, showed slight musty and unclean taste issues. Microbiological indicators further indicated that Examples 1-3 had low total bacterial counts, with mold and yeast both <10 CFU / g, demonstrating that the process of this invention improves the controllability of the fermentation process, reduces the risk of abnormal microbial proliferation, and results in products with better quality stability and hygiene safety.

[0027] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0029] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A method for preparing a fermented tea with a tea and fruit flavor, characterized in that, The steps include the following: S1. Pre-treatment of tea base: Select one or more of green tea, oolong tea, black tea or dark tea as tea base, remove impurities and then perform steam softening treatment. The steam temperature is 90-105℃ and the treatment time is 60-120s. Then adjust the moisture content of the tea base to 25-38%. S2. Preparation of fruit-flavored fermentation base: The fruit raw materials are crushed into fruit pulp, and pectinase and cellulase are added for enzymatic hydrolysis. The enzymatic hydrolysis temperature is 35-40℃ and the enzymatic hydrolysis time is 1-4h to obtain enzymatically hydrolyzed fruit pulp. S3. Preparation of tea and fruit compound fermentation material: The tea base obtained in step S1 and the enzymatically hydrolyzed fruit pulp obtained in step S2 are mixed at a mass ratio of 100:8-35, and a compound fermentation agent is added. After mixing evenly, the tea and fruit compound fermentation material is obtained. S4. Segmented humidity-controlled fermentation: The tea and fruit compound fermentation material obtained in step S3 is subjected to early microaerophilic fermentation and later oxygen-controlled solid fermentation. The early microaerophilic fermentation temperature is 25-32℃ and the time is 12-36h; the later oxygen-controlled solid fermentation temperature is 28-35℃ and the relative humidity is 70-90% for 36-96h. S5. Low-temperature aroma fixation and drying: The fermented material obtained in step S4 is subjected to low-temperature aroma fixation at 35-45℃ for 2-6 hours, and then dried at 45-60℃ until the moisture content is 5-9%, thus obtaining the tea and fruit compound flavor fermented tea.

2. The method for preparing tea with a combined tea and fruit flavor according to claim 1, characterized in that, In step S2, the fruit ingredients include one or more of the following: citrus, apple, pear, peach, berry, passion fruit, hawthorn, plum, jujube, or pomelo.

3. The method for preparing tea with a combined tea and fruit flavor fermentation according to claim 1, characterized in that, In step S2, the amount of pectinase added is 0.03-0.20% of the fruit pulp mass, the amount of cellulase added is 0.02-0.15% of the fruit pulp mass, and the pH is controlled at 4.0-5.5 during enzymatic hydrolysis.

4. The method for preparing tea with a compound flavor of tea and fruit according to claim 1, characterized in that, The compound fermentation agent in step S3 includes Lactobacillus plantarum, Saccharomyces cerevisiae, and Aspergillus cristatus, with a live bacteria ratio of 1-4:1-3:

1. The inoculation amount of the compound fermentation agent is 2-8% of the mass of the tea and fruit compound fermentation material.

5. The method for preparing tea with a compound flavor of tea and fruit according to claim 4, characterized in that, The viable count of *Lactobacillus plantarum* in the compound fermentation agent is 1.0 × 10⁻⁶. 7 ~1.0×10 9 CFU / mL, viable count of Saccharomyces cerevisiae was 1.0 × 10⁻⁶. 6 ~1.0×10 8 CFU / mL, the number of spores of *Eurotium cristatum* was 1.0 × 10⁻⁶. 5 ~1.0×10 7 CFU / mL.

6. The method for preparing tea with a combined tea and fruit flavor according to claim 1, characterized in that, In step S4, during the initial microaerophilic fermentation, the thickness of the tea and fruit compound fermentation material layer is 3-8 cm, the oxygen volume fraction is controlled at 3-12%, and the pH at the fermentation endpoint is controlled at 4.2-5.

2.

7. The method for preparing tea with a combined tea and fruit flavor according to claim 1, characterized in that, In step S4, during the later stage of controlled oxygen solid-state fermentation, the thickness of the tea and fruit compound fermentation material layer is 5-12cm, and the material is turned over every 12-24 hours to ensure that the center temperature of the fermentation material does not exceed 38℃.

8. A fermented tea with a tea and fruit flavor, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

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