Wuniu early-mixing drinking tea and preparation method thereof

Abstract

The invention relates to the technical field of mixed drinking tea beverages, and provides Wuniu early mixed drinking tea and a preparation method thereof. The preparation method comprises the following steps: carrying out pretreatment and deoxidation treatment on drinking water to obtain low-dissolved-oxygen softened water; wuniuzao black tea original leaves are subjected to fractional extraction with low-dissolved-oxygen softened water, and a tea base is obtained; preparing pretreated waxberry juice and early-fragrant pomelo juice; blending a tea base, the pretreated waxberry juice, early-fragrant pomelo juice, a sweetening agent, old wine sweat and low-dissolved-oxygen softened water to obtain mixed tea juice; and performing homogenization treatment and sterilization treatment on the mixed tea juice, and performing filling and sealing to obtain the Wuniu early-blending drinking tea. According to the preparation method disclosed by the invention, the problem of insufficient stability is solved on the premise of no preservatives, antioxidants and stabilizers through combination of various means such as water demineralization and deoxidation, segmented tea extraction, advanced deoxidation and anti-browning treatment of fruit juice, inert gas oxygen-controlled mixing and the like, and the color and flavor stability of the product in the shelf life storage process is improved.

Description

Technical Field

[0001] This invention relates to the technical field of Wuniuzao Tiaoyin tea beverages, and more specifically, to a Wuniuzao Tiaoyin tea and its preparation method. Background Technology

[0002] Blended teas are typically made by combining tea infusion with flavoring ingredients such as fruit juice, offering both tea and fruit aromas, aligning with current trends in ready-to-drink beverages. Yongjia Wuniuzao, often simply referred to as "Wuniuzao," is a representative of my country's early-ripening green teas, renowned for its exceptionally early market availability and fresh, crisp flavor.

[0003] In terms of taste, its extremely fresh and crisp flavor is the most prominent characteristic of Wuniuzao tea. Blending it with fruit juice to prepare tea-like beverages is an industrial beverage technology route that offers advantages in flavor, nutrition, and functionality.

[0004] As consumers increasingly prefer products with simpler formulas and fewer or no additives, the market is placing higher demands on ready-to-drink tea beverages that can maintain good quality without relying on additives such as preservatives, antioxidants, and stabilizers. However, existing blended teas generally suffer from insufficient stability during industrial production and shelf-life storage, especially prone to oxidative browning, which leads to darkening and browning of color and aroma loss, thus affecting sensory quality and product consistency.

[0005] The tea and fruit juice system contains easily oxidized components such as tea polyphenols, fruit juice polyphenols, and anthocyanins. During industrial processing steps such as extraction, blending, homogenization, sterilization, and bottling, these components inevitably undergo heating, shearing, and transport. If the dissolved oxygen content in the system is too high, or if oxygen is re-introduced due to contact with air during blending and bottling, these easily oxidized components will undergo oxidation, further leading to browning and flavor deterioration. Simultaneously, insufficient control of calcium and magnesium ions in the process water may induce colloidal instability, causing turbidity, sedimentation, or a rough, astringent taste, further reducing shelf-life quality stability. This problem is particularly pronounced for green tea beverages like Wuniuzao, which are characterized by their sweet and fresh taste.

[0006] To address the aforementioned issues, existing technologies typically rely on adding antioxidants, stabilizers, or preservatives to delay browning, improve system stability, and control microbial risks. However, such solutions increase formulation complexity, which does not align with the trend towards products with no or minimal additives. Furthermore, under conditions of heat processing and long-term storage, phenomena such as color drift and aroma decay may still occur, making it difficult to achieve stable and reproducible industrial-scale quality control.

[0007] Therefore, there is an urgent need for a method for preparing Wuniu Zaocha tea that can improve the color and flavor stability of the product during shelf-life storage without the use of preservatives, antioxidants, or stabilizers. Summary of the Invention

[0008] One of the problems solved by the present invention is how to provide a Wuniuzao blended tea.

[0009] To solve at least one of the above problems, the present invention provides a preparation method for Wuniuzao blended tea, and the preparation method includes: S100. Pretreat and deoxygenate the drinking water to obtain low-dissolved-oxygen softened water; S200. Take the original leaves of Wuniuzao black tea and perform graded extraction with low-dissolved-oxygen softened water to obtain the first-stage tea soup and the second-stage tea soup, and compound them according to the volume ratio of the first-stage tea soup to the second-stage tea soup of 1:(1 - 4) to obtain a tea base; S300. Perform anti-browning pretreatment on the bayberry juice to obtain pretreated bayberry juice; prepare early-fragrant pomelo juice; S400. Add the tea base, pretreated bayberry juice, early-fragrant pomelo juice, sweetener, old rice wine sweat, and low-dissolved-oxygen softened water into a closed mixing tank under oxygen-controlled conditions for blending treatment to obtain a blended tea juice; S500. Perform homogenization treatment and sterilization treatment on the blended tea juice, and then perform filling and sealing to obtain Wuniuzao blended tea.

[0010] In the above technical solution, in S100, the pretreatment includes at least one of softening treatment and demineralization treatment; calculated by CaCO3, the total hardness of the drinking water after pretreatment is 5 - 30 mg / L, and the total concentration of Ca 2+ and Mg 2+ is 1 - 12 mg / L; and / or the deoxygenation treatment includes at least one of vacuum degassing, membrane deoxygenation, or inert gas bubbling deoxygenation, so that the dissolved oxygen DO ≤ 2.0 mg / L.

[0011] In the above technical solution, in S200, the extraction conditions for the first-stage tea soup are 88 - 95 °C and 1 - 3 min; and / or the extraction conditions for the second-stage tea soup are 72 - 85 °C and 4 - 8 min.

[0012] In the above technical solution, in S300, the anti-browning pretreatment includes: adding an oxygen-consuming enzyme system to the bayberry juice for oxygen-consuming treatment to reduce the dissolved oxygen DO of the bayberry juice to ≤ 1.0 mg / L to obtain pretreated bayberry juice.

[0013] In the above technical solution, the oxygen-consuming enzyme system is provided on the carrier in an immobilized form, the oxygen-consuming enzyme system includes ascorbic acid oxidase, and the carrier includes at least one of resin, silica gel, and alginate gel.

[0014] In the above technical solution, in S400, the oxygen control conditions include: replacing the space inside the sealed mixing tank with an inert gas before feeding, followed by immediate sealed mixing, and adjusting the pH of the mixed tea juice to 3.2-3.8, and the dissolved oxygen (DO) of the mixed tea juice ≤ 1.5 mg / L.

[0015] In the above technical solution, the homogenization pressure in S500 is 15-30 MPa; the sterilization treatment includes ultra-high temperature instantaneous sterilization or pasteurization.

[0016] In the above technical solution, based on the volume of the beverage, Wuniu Zao Tiao Tea includes: 50-80% tea base, 10-30% pre-treated bayberry juice, 3-20% early-ripening pomelo juice, 0.5-5% sweetener, 0.8-2.0% aged rice wine, and the remainder of low-dissolved oxygen softened water.

[0017] In the above technical solution, in S200, the tea base is cooled to below 15°C after compounding and then filtered.

[0018] The present invention also provides a Wuniuzao decoction tea, which is obtained by the preparation method of any of the above technical solutions.

[0019] Beneficial effects This invention provides a method for preparing Wuniuzao (a type of Chinese herbal tea) and its preparation. The method uses low-oxygen softened water as the base water and combines segmented extraction, deoxygenated fruit juice pretreatment, closed-loop oxygen-controlled blending, pH window regulation, homogenization sterilization, and sealed bottling processes. Without the need for additional antioxidants, preservatives, or stabilizers, this method improves the color and flavor stability of Wuniuzao tea during industrial preparation and shelf-life storage. By deoxygenating the process water and using inert gas replacement and immediate closed mixing during the blending process, the initial dissolved oxygen of the system is reduced and oxygen re-dissolution is inhibited. Simultaneously, the bayberry juice undergoes deoxygenation treatment using an oxygen-consuming enzyme system, reducing the oxygen load on the juice. These low-oxygen boundary conditions weaken the oxidation pathways of tea polyphenols, bayberry polyphenols, and anthocyanins, reducing the browning reaction rate from the source and improving the color stability of the finished product during processing and storage. The method also controls the calcium content of the water through softening or demineralization treatment. 2+ Mg 2+The use of equal-hardness ions weakens the complexation, bridging, and aggregation of polyphenols with divalent ions, reducing the probability of colloidal instability, turbidity, and precipitation in the compound system. Segmented extraction separates the rapid acquisition of high-quality aroma and refreshing components in the initial stage from the gentle replenishment in the subsequent stage, and these are then blended in proportion to form the tea base. This ensures the tea flavor structure and concentration while reducing the introduction of bitter substances such as highly polymerized polyphenols. Low-hardness water further reduces the astringency amplification effect, resulting in a more delicate, refreshing, and harmonious taste. A low-oxygen environment reduces aroma oxidation loss and the formation of musty flavors. Aged wine provides volatile aroma components and, through ethanol, synergistically improves aroma release and retention. Grapefruit juice provides a refreshing top note and acidity balance, forming a stable complex aroma structure. Simultaneously, low-oxygen softened water serves as the basic medium throughout extraction and blending, reducing batch-to-batch variations caused by process fluctuations. In summary, this invention achieves color stability, flavor retention, and system stability of Wuniuzao tea under conditions free of preservatives, antioxidants, and stabilizers through the synergistic effects of low-oxygen, low-hardness water quality control, segmented extraction, fruit juice oxygen reduction, closed-loop oxygen control and blending, pH window, and homogenization sterilization. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, a detailed description of specific embodiments of the present invention will be provided below.

[0022] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available. Experimental methods in the following examples that do not specify particular conditions should be performed according to conventional methods and conditions, or as selected in the product instructions.

[0023] This invention provides a Wuniu Zaocha (a type of tea) to address the risk of oxidative browning and improve the color and flavor stability of the product during shelf life storage without the use of preservatives, antioxidants, or stabilizers. The Wuniu Zaocha comprises: a tea base, pretreated bayberry juice, early-ripening pomelo juice, a sweetener, aged rice wine, and the remainder of low-oxygen softened water.

[0024] This invention introduces low-dissolved oxygen softened water as the base water for extraction and blending during the preparation process, reducing the risk of oxidation-driven forces and ion-induced instability from the source. The low-dissolved oxygen environment reduces the oxidation of tea polyphenols, myricetin, anthocyanins, and other components, weakening the initiation conditions of the oxidation chain reaction, thereby reducing the browning rate and improving color retention. Softening or demineralization treatment can reduce calcium... 2+ With Mg 2+The reduced content of divalent ions decreases their complexing, bridging, and aggregation effects on polyphenol systems, lowering the probability of turbidity and precipitation. It also reduces the promoting effect of metal ions on partial oxidation reactions, resulting in a fresher flavor and lower astringency. In fruit juice-tea blends, the high proportion of the aqueous phase means that the dissolved oxygen and ion background of the water determine the oxidation rate and colloidal stability window. Using low-oxygen softened water can improve the consistency of color, aroma, and taste of the product during room temperature storage without relying on additional chemical antioxidants.

[0025] In practice, low-oxygen softened water is obtained through pretreatment and deoxygenation. The pretreatment stage reduces hardness ion levels through softening or demineralization, ensuring a low-ionic-strength environment for the polyphenol system during subsequent tea extraction and blending. This reduces turbidity and sedimentation, improves clarity, and enhances the smoothness and freshness of the taste. The deoxygenation stage lowers dissolved oxygen content through vacuum degassing, membrane deoxygenation, or inert gas bubbling. This reduces oxidative loss of tea polyphenols during the initial extraction stage and lowers the background value of oxygen re-dissolution during blending, thus inhibiting the oxidative browning of anthocyanins and polyphenols in the fruit juice. Using low-oxygen softened water for extraction and blending replenishment provides stable and consistent low-oxygen, low-hardness conditions throughout the process, thereby improving batch stability and shelf-life consistency.

[0026] Furthermore, pretreatment reduces the total hardness of drinking water (CaCO3) to 5-30 mg / L. This hardness range is used to adjust the process water to a soft water range, reducing the complexation and aggregation effect of divalent ions on tea polyphenols and amplifying the astringent taste, while avoiding the thin taste caused by extreme deionization. Deoxygenation treatment reduces dissolved oxygen (DO) to ≤2.0 mg / L. Dissolved oxygen is a direct participant in the oxidation reaction of polyphenols and anthocyanins; this threshold effectively reduces the probability of oxidation reaction initiation during extraction and blending, minimizing oxidative browning and vitamin loss, providing a lower initial oxygen load for subsequent closed blending, and reducing quality fluctuations caused by oxygen redissolution. This approach balances the challenges of industrial implementation with stability requirements and can be stably achieved under common deoxygenation conditions. 2+ With Mg 2+ As the main hardness ion, it is an important factor that causes polyphenol complexation precipitation, colloidal instability and rough taste. Controlling its total concentration at 1-12 mg / L can further reduce the risk of aggregation caused by polyphenol-metal ion complexation or bridging in the tea and fruit juice blending system, reduce turbidity, precipitation and delayed astringency, thereby improving the appearance clarity and taste smoothness of the finished product, and enhancing the stability of the system during storage.

[0027] During tea extraction, dissolved oxygen and divalent metal ions in the extraction medium jointly affect the color, aroma, and colloidal stability of the tea infusion. This invention uses low-oxygen softened water as the extraction medium. Compared to ordinary drinking water, its advantages lie not only in its low dissolved oxygen content but also in the targeted control of hardness ions such as calcium and magnesium. This effectively inhibits oxidation reactions and complexation instability while maintaining extraction efficiency. Specifically, lower dissolved oxygen reduces the probability of oxidation initiation of easily oxidized substances such as tea polyphenols during the extraction stage, inhibiting browning and aroma deterioration of the tea infusion under high-temperature conditions. Simultaneously, the reduction in calcium and magnesium ions weakens their complexation and bridging effects with tea polyphenols, pectin-like substances, and protein impurities, reducing the risk of turbidity and precipitation in subsequent compounding systems and improving the roughness and astringency of the taste. In contrast, while pure water has extremely low hardness, its dissolved oxygen is usually high, which easily accelerates the oxidation of the tea infusion during extraction, leading to a darker color and loss of aroma.

[0028] Furthermore, the dissolution rate of tea components varies significantly and is temperature-sensitive. Some low-molecular-weight substances that contribute to freshness and aroma dissolve rapidly at high temperatures, while high-polymer polyphenols, some pigments, and components that may cause a harsh taste, associated with bitterness, astringency, and darkening of the tea liquor, tend to dissolve in greater proportions under prolonged or intense conditions. Conventional single-stage extraction often involves a trade-off between extraction rate and flavor purity. While increasing the temperature or extending the extraction time can increase the total amount of soluble substances, it can also easily lead to increased bitterness, excessively dark tea liquor, loss of aroma, and accelerated oxidation.

[0029] Considering the above, in a specific embodiment of the present invention, Wuniuzao black tea leaves are subjected to graded extraction using low-dissolved oxygen softened water to obtain a first-stage tea infusion and a second-stage tea infusion. These are then blended at a volume ratio of 1:(1-4) to obtain a tea base. The graded extraction separates and controls the rapid extraction of high-quality flavor components in the first stage with the gentle replenishment of residual effective components in the second stage. Specifically, the first stage of extraction aims to quickly release the tea aroma and refreshing sensation, while the second stage replenishes soluble solids under relatively mild conditions, avoiding the introduction of excessive bitter substances and oxidation side reactions due to the pursuit of extraction rate. Therefore, compared with single-stage extraction, graded extraction can maintain the flavor concentration of the tea base while reducing the proportion of bitterness and harshness, providing a purer and more stable tea base for subsequent blending with fruit juice. This method allows the tea infusion to combine the richness of high-temperature extraction with the freshness of medium-temperature extraction, reducing astringency and excessive bitterness, thus making it more suitable for blending with fruit juice in terms of flavor balance and tea polyphenol composition.

[0030] Furthermore, the extraction conditions for the first stage of tea infusion are 88-95℃ for 1-3 minutes. Within this temperature range, the tea cell structure rapidly swells, and aromatic precursors and easily soluble flavor substances quickly diffuse into the aqueous phase, thus achieving a high level of aroma and freshness in a relatively short time. Limiting the extraction time to 1-3 minutes avoids excessive oxidation and polymerization of tea polyphenols under high temperatures, as well as excessive dissolution of highly polymerized polyphenols, which can lead to increased astringency and a darker liquor color. The extraction conditions for the second stage of tea infusion are 72-85℃ for 4-8 minutes. Appropriately lowering the temperature helps to slow down oxidation and thermal deterioration, reducing the musty taste and harshness that may result from the later extraction stages. Extending the extraction time appropriately replenishes the soluble solids and some flavor substances that were not fully dissolved in the first stage, enhancing the body and thickness of the tea base. Through staged extraction, the overall extraction process ensures both the preservation of the tea flavor structure and control of bitterness, astringency, and browning trends, making it suitable for subsequent blending with acidic fruit juice systems where a clear, low-astringency, and aroma-retaining tea base is required.

[0031] Furthermore, the two tea infusions have distinct characteristics in terms of flavor emphasis and composition. The first infusion has a more prominent aroma and a refreshing taste, but its concentration and body may be insufficient. The second infusion has a higher content of soluble solids and a thicker body, but its bitterness, astringency, and color tend to be stronger. By blending the first and second infusions at a volume ratio of 1:(1-4), the overall balance of aroma, body, astringency, and color of the tea base can be flexibly adjusted. When the proportion of the second infusion is lower, the refreshingness and aroma are emphasized more. When the proportion of the second infusion is increased, the main flavor and concentration of the tea are enhanced, but it is still diluted and modified by the aroma and refreshing characteristics of the first infusion, thus avoiding the harshness caused by using the second infusion alone. Furthermore, blending helps reduce the impact of batch differences in raw materials on the finished product; the two tea infusions have different sensitivities to the original leaf state due to different extraction kinetics. Blending in proportion can achieve component homogenization, improve the batch consistency of the tea base, and provide a more controllable basic flavor and stability window for subsequent blending with flavor components such as bayberry juice and grapefruit juice.

[0032] Bayberry juice is rich in polyphenols such as anthocyanins, phenolic acids, and flavonoids, exhibiting a vibrant reddish-purple color and a rich fruity aroma. However, its system is highly sensitive to oxygen. During processing steps such as crushing, juicing, filtering, conveying, and mixing, dissolved oxygen and contact with air significantly promote the oxidation of polyphenols and anthocyanins, causing the color to gradually change from reddish-purple to dark red and even brownish-red, accompanied by a decline in fruity aroma and a dulling of taste. In addition, enzymes such as polyphenol oxidase that may remain in bayberry juice can trigger enzymatic browning in the presence of dissolved oxygen. Therefore, pre-treating bayberry juice to prevent browning before blending with the tea base, in order to reduce dissolved oxygen and inhibit the oxidation chain reaction, is a crucial step in ensuring the color and flavor stability of the finished Wuniuzao tea.

[0033] In practice, bayberry juice can be obtained by selecting, washing, crushing, pulping, and pressing fresh or frozen bayberries. The juice can be further purified by coarse filtration or clarification to remove peel fragments and large suspended solids. Subsequently, an immobilized oxygen-consuming enzyme carrier is packed into a treatment column or placed in a closed reaction vessel, allowing the bayberry juice to contact it in a circulating or continuous flow. Under gentle stirring and circulation conditions, the oxygen-consuming enzyme system catalyzes the consumption of dissolved oxygen (DO), reducing the DO in the bayberry juice to ≤1.0 mg / L. After treatment, the immobilized carrier can be physically separated from the bayberry juice, reducing the oxygen content without introducing solid impurities, thus obtaining pretreated bayberry juice. The oxygen-consuming enzyme system is preferably loaded onto a carrier in an immobilized form. The carrier includes at least one of resin, silica gel, alginate gel, or porous membrane material, and the oxygen-consuming enzyme system includes ascorbic acid oxidase.

[0034] In one embodiment, the oxygen-consuming enzyme system uses ascorbic acid, naturally present in bayberry juice, as an electron donor to consume dissolved oxygen. To ensure the stability and repeatability of the oxygen-consuming treatment, the ascorbic acid content of the bayberry juice can be measured before treatment and ensured to be no less than the theoretical oxygen consumption equivalent required to achieve the target dissolved oxygen. When the ascorbic acid content in the bayberry juice is insufficient to reduce DO to ≤1.0 mg / L, vacuum degassing, membrane deoxygenation, or inert gas bubbling deoxygenation can be used to pre-deoxygenate the bayberry juice to ensure that the DO of the pre-treated bayberry juice meets the control target of ≤1.0 mg / L.

[0035] As the core source of flavor and color for this Wuniu Zaocha tea, bayberry juice's natural anthocyanins impart a bright reddish-purple hue to the beverage, forming a complex color system together with the tea pigments in the black tea base. Its organic acids and aromatic components provide a sweet and sour taste and fruity aroma, enhancing the overall flavor profile and complementing the tea aroma. Simultaneously, bayberry polyphenols and tea polyphenols together constitute the antioxidant basis of the beverage, but also make the system more susceptible to browning triggered by oxygen. Using an oxygen-consuming enzyme system for oxygen-reducing pretreatment of bayberry juice can break the oxidation chain at the reactant end. Whether browning of bayberry juice occurs through the auto-oxidation of polyphenols and anthocyanins or enzymatic oxidation, dissolved oxygen is the core limiting factor. When DO is reduced to ≤1.0 mg / L, the initiation probability and rate of the oxidation reaction are significantly reduced, thereby reducing the oxidative degradation of anthocyanins and the formation of browning polymerization products, helping to maintain the bright reddish-purple color of the bayberry juice; at the same time, it reduces aroma loss and the development of a stale taste caused by oxidation, resulting in a fuller fruity aroma. Pre-reducing the oxygen load of the bayberry juice can also decrease the total dissolved oxygen background value of the blended system, synergizing with the low-temperature oxygen system of the tea base, making the finished product less prone to continuous browning during sterilization and storage. Furthermore, compared to directly adding free enzymes, using an immobilized oxygen-consuming enzyme system offers advantages such as easy carrier separation, reusability, minimal impact on system clarity, and reduced enzyme residue risk, making it more suitable for industrial continuous processing and consistent quality control.

[0036] Early-ripening pomelo juice can be prepared as follows: Select and wash early-ripening pomelos, peel them, remove the pulp and membrane, and remove the seeds and the white inner peel with a significant bitter taste; crush the pulp, pulp it, and press it to extract the juice; perform coarse filtration or centrifugation to remove larger suspended solids, and temporarily store it at low temperature for later use.

[0037] Grapefruit juice provides the system with natural acidity, which can reduce reliance on additional preservatives to some extent. At the same time, its unique citrus aroma and acidity enhance the overall flavor profile and work synergistically with the sweet and sour taste of bayberry, creating a more balanced flavor. The slightly bitter-sweet aroma of grapefruit neutralizes the intense tartness of bayberry. The acidic environment also helps stabilize anthocyanins, preventing browning or discoloration during long-term storage.

[0038] Furthermore, the volatile aromas of grapefruit enhance the overall fragrance and freshness of the beverage, creating a complex aroma profile that blends with the berry notes of bayberry and the aroma of black tea. The moderate acidity and refreshing sensation provided by grapefruit juice can enhance the aftertaste and cleanliness of the mouth without significantly increasing the sugar content, and also plays a sensory balancing role against the astringency of the tea. In acidic blending systems, a suitable proportion of grapefruit juice helps maintain the pH of the finished product within a range conducive to anthocyanin stability, thus aligning with the color retention goals of bayberry juice. Grapefruit flavor components also create layers of flavor, reducing the cloying sweetness and tartness that might result from a single berry flavor, making the finished product more enjoyable to drink.

[0039] The Wuniu Zao Tiaoyin Tea of ​​this invention also includes aged rice wine. The preparation method of aged rice wine may include: separating the fermented mash into solid and liquid components or directly feeding it into a distillation vessel, distilling it under heating conditions, collecting the pre-distillate to obtain a high-alcohol distillate, allowing it to stand for clarification, filtering to remove impurities, and storing it under sealed conditions for later use. Preferably, the alcohol content is in the range of 50-75% vol.

[0040] It is understandable that the purpose of adding aged ethanol is to achieve a synergistic effect of building complex aromas, smoothing flavors, and maintaining aromas during storage. Aged ethanol contains a relatively rich amount of volatile flavor compounds, which, when combined with the roasted and sweet aromas of black tea and the fruity aromas of bayberry and grapefruit, can significantly enhance the aroma intensity and complexity of the beverage, making the aroma more three-dimensional and distinctive. A small amount of ethanol in the beverage system can change the distribution behavior of aroma substances between the aqueous and gas phases, increasing the release and retention of some hydrophobic aroma components; at the same time, ethanol can reduce the sharpness of acidity and mask astringency to a certain extent, making the sweet and sour taste more harmonious with the tea flavor, improving the smoothness and aftertaste. As a co-solvent, ethanol can improve the solubility stability of some aroma substances in the system, reducing the irreversible loss of volatile aromas during processing and storage; in addition, in the low dissolved oxygen system and acidic environment of this invention, trace amounts of ethanol also have a certain inhibitory effect on microbial growth, which helps maintain flavor consistency throughout the shelf life. Therefore, the introduction of aged wine sweat as a flavor enhancement and flavor balancing component can improve the aroma level, mouthfeel roundness, and flavor retention during storage without significantly changing the main tea and fruit flavor of the beverage.

[0041] Sweeteners include one or more of sucrose, fructose syrup, erythritol, xylitol, sucralose, acesulfame potassium, aspartame, neotame, steviol glycosides, and mogrosides. The function of the sweeteners is the same as that of the prior art, and will not be described in detail here.

[0042] In the S400 process, tea base, pretreated bayberry juice, early-ripening pomelo juice, sweetener, aged rice wine juice, and low-dissolved oxygen softened water are added to a sealed mixing tank under controlled oxygen conditions for blending to obtain a mixed tea juice. This step aims to achieve uniform dispersion and harmonious balance of various flavor components, while maintaining a low-oxygen environment in the system as much as possible to reduce the probability of oxidative browning of polyphenols and anthocyanins. The blended tea juice has uniform components and controllable pH, providing a stable liquid base for subsequent homogenization and sterilization processes, thereby reducing differences in color and taste caused by process fluctuations.

[0043] It is understandable that this Wuniu Zao blended tea system contains easily oxidized components such as tea polyphenols, bayberry polyphenols, and anthocyanins. Dissolved oxygen is a key factor driving its oxidative browning and aroma decay. If air is introduced or oxygen re-dissolves during the blending process, it will significantly increase the oxygen load of the system, thereby accelerating the oxidation reaction in the subsequent homogenization shearing and sterilization heating stages, resulting in darker color, deeper browning, weakened fruity aroma, and a duller taste. Oxidation may also promote polyphenol polymerization, enhance astringency, and induce colloidal instability. Therefore, the purpose of controlling oxygen is to reduce the chance of oxygen participating in the reaction from the source of the process, so that the subsequent heat treatment mainly plays a sterilization role rather than aggravating oxidative deterioration, thereby improving the color, aroma, and taste stability of the finished product during its shelf life.

[0044] In practice, the space inside the sealed mixing tank is purged with an inert gas before adding the raw materials, followed immediately by sealing and mixing. This operation rapidly reduces the oxygen partial pressure in the gas phase inside the tank, creating a low-oxygen environment at the gas-liquid interface and reducing oxygen dissolution into the liquid phase. Simultaneously, immediate sealing prevents the re-intake of air after purging and reduces oxygen mass transfer caused by air bubbles during stirring. This significantly reduces the initial oxygen load of the mixed tea liquor, inhibits the triggering of polyphenol and anthocyanin oxidation reactions, and mitigates the accelerated oxidation effect in subsequent heat treatment stages. Adjusting the pH of the mixed tea liquor to the range of 3.2-3.8 provides a more stable anthocyanin structure under these acidic conditions, helping to reduce color changes and browning tendencies. Simultaneously, the activity and reaction rate of some oxidation-related enzymes are inhibited, reducing the possibility of enzymatic browning. Moderate acidity enhances the refreshing taste of beverages and balances with sweetness, resulting in a harmonious tea-fruit flavor. Within this pH range, anthocyanins remain in a relatively stable form while avoiding degradation and colloidal instability caused by excessively low pH during heat processing and storage, thus maintaining a balance of tea-fruit flavor. The combination of inert gas replacement and pH control creates a synergistically stable low-oxygen and acidic environment, making the blended tea more resistant to further processing and long-term storage in terms of color, aroma, and taste.

[0045] In the S500 process, homogenization enhances the system's physical stability and taste consistency, while sterilization and sealing ensure microbial safety and shelf-life stability. Blended tea contains tea colloids, fruit juice colloids, and trace amounts of volatile flavor compounds. Without homogenization, long-term storage may lead to stratification, turbidity, flocculation, or a rough texture. Insufficient sterilization and sealing can expose even acidic beverages to yeast or acid-resistant bacteria contamination, resulting in gas production, turbidity, or flavor deterioration. The combined process of homogenization, sterilization, and sealing maximizes the consistency of color and flavor in Wuniuzao tea while ensuring product safety and inhibiting ongoing browning and system instability during storage.

[0046] Furthermore, the homogenization process employs a pressure of 15-30 MPa to further refine and uniformly disperse the colloids and fine particles in the mixed tea juice, reducing particle size and distribution range, thereby enhancing the physical stability of the system and reducing sedimentation, flocculation, and stratification tendencies. Simultaneously, homogenization improves the smoothness and fineness of the taste, resulting in a more balanced perception of sweetness, sourness, and astringency, and improving batch-to-batch consistency. Within this pressure range, both dispersion and protection of flavor compounds are typically achieved, significantly improving stability while avoiding excessive shear that could lead to aroma loss or excessive foaming. Sterilization utilizes ultra-high temperature (UHT) sterilization or pasteurization processes, using heat to inactivate microorganisms, achieving commercial sterility or the prescribed microbial control levels. For this type of acidic tea-fruit blend system, UHT sterilization achieves efficient sterilization within a very short heat treatment time, reducing the cooked taste and color deterioration caused by prolonged heating; pasteurization, on the other hand, controls acid-resistant microorganisms at relatively mild temperatures and allows for stable shelf life through hot filling or post-sterilization processes.

[0047] Example 1 This embodiment provides a Wuniu Zao Tiao Yin Tea and its preparation method, the preparation method including: S100. Drinking water, after ion exchange softening and reverse osmosis demineralization treatment, should have a total hardness of 12 mg / L (calculated as CaCO3). 2+ With Mg 2+ The total concentration was 3.5 mg / L; subsequently, a hollow fiber membrane contactor was used for membrane deoxygenation treatment to reduce the dissolved oxygen (DO) in the water to 1.2 mg / L, resulting in low dissolved oxygen softened water. S200. Take Wuniuzao black tea leaves and perform graded extraction with a volume ratio of tea leaves to low dissolved oxygen softened water of 1:30. The first stage is carried out at a temperature of 92℃ for 2 minutes to obtain the first tea infusion; the second stage is carried out at a temperature of 80℃ for 6 minutes to obtain the second tea infusion. The first and second tea infusions are combined at a volume ratio of 1:3, cooled to 10℃ through a plate heat exchanger, and filtered through a 150μm filter to obtain the tea base. S300, bayberries are washed, crushed, pulped, and juiced by pressing. After coarse filtration, bayberry juice is obtained. An immobilized oxygen-consuming enzyme system is packed into a stainless steel column reactor. The carrier is a composite of alginate gel beads and porous resin with a particle size of 2-4 mm, loaded with ascorbic acid oxidase. The bayberry juice is circulated through the reaction column at 15℃ and a flow rate of 1.0 BV / h until the DO is 0.8 mg / L, to obtain pretreated bayberry juice. Remove the outer peel and inner white membrane of the early-ripening pomelo, remove the seeds, crush the pulp and press to extract the juice, then filter it coarsely to obtain early-ripening pomelo juice; S400, by beverage volume, add: 60% tea base, 18% pretreated bayberry juice, 10% early-ripening pomelo juice, 2.5% sucrose, 1.2% aged rice wine (60% vol), and the remainder is low-oxygen softened water to bring it to 100%; purge the tank with nitrogen, add the above components to the sealed mixing tank under controlled oxygen conditions, then immediately seal and stir for 10 minutes, adjust the pH to 3.5 with citric acid to obtain the mixed tea juice, the DO of the mixed tea juice is 0.9 mg / L; S500, mixed tea juice is homogenized at 25MPa, sterilized at 135℃ for 30 seconds, and then aseptically cold-filled and sealed to obtain the finished Wuniuzao tea.

[0048] Example 2 This embodiment provides a Wuniu Zao Tiao Yin Tea and its preparation method, the preparation method including: S100. Take drinking water, after softening treatment, to achieve a total hardness of 25 mg / L (calculated as CaCO3). 2+ With Mg 2+ The total concentration was 8 mg / L; then, the dissolved oxygen (DO) in the water was reduced to 1.8 mg / L by vacuum degassing at -0.08 MPa for 10 min and nitrogen bubbling for 5 min, resulting in low dissolved oxygen softened water. S200. Take Wuniuzao black tea leaves and perform graded extraction with a volume ratio of tea leaves to low dissolved oxygen softened water of 1:30. The first stage is carried out at a temperature of 90℃ for 3 minutes to obtain the first tea infusion; the second stage is carried out at a temperature of 75℃ for 8 minutes to obtain the second tea infusion. The first and second tea infusions are combined at a volume ratio of 1:2, cooled to 12℃ through a plate heat exchanger, and filtered through a 150μm filter to obtain the tea base. S300 and early-ripening pomelo juice are the same as in Example 1; pretreated bayberry juice is the same as in Example 1, except that: the carrier is porous silica particles, and the DO of the pretreated bayberry juice is 1 mg / L. S400, by beverage volume, add: 70% tea base, 10% pretreated bayberry juice, 8% early-ripening grapefruit juice, 1.2% erythritol and sucralose, 0.8% aged wine broth, and the remainder is low-oxygen softened water to make up to 100%; purge the tank with nitrogen, add the above components to the sealed mixing tank under controlled oxygen conditions, then immediately seal and stir for 10 minutes, adjust the pH to 3.7 with citric acid to obtain the mixed tea juice, the DO of the mixed tea juice is 1.2 mg / L; S500, the mixed tea juice is homogenized at 18MPa, pasteurized at 92℃ for 10min, and aseptically hot-filled and sealed to obtain the finished Wuniuzao tea.

[0049] Example 3 This embodiment provides a Wuniu Zao Tiao Yin Tea and its preparation method, the preparation method including: S100, Same as Example 1, Low dissolved oxygen softened water, calculated as CaCO3, has a total hardness of 5 mg / L, Ca 2+ With Mg 2+ The total concentration was 1.2 mg / L, and the dissolved oxygen (DO) concentration decreased to 0.9 mg / L. S200. Take Wuniuzao black tea leaves and perform graded extraction with a volume ratio of tea leaves to low dissolved oxygen softened water of 1:30. The first stage is at a temperature of 95℃ for 1 minute to obtain the first tea infusion; the second stage is at a temperature of 85℃ for 4 minutes to obtain the second tea infusion. The first and second tea infusions are combined at a volume ratio of 1:1, cooled to 8℃ by a plate heat exchanger, and filtered through a 100μm filter to obtain the tea base. S300, same as in Example 1, pre-treated bayberry juice with DO of 0.6 mg / L, yielded; Remove the outer peel and inner white membrane of the early-ripening pomelo, remove the seeds, crush the pulp and press to extract the juice, then filter it coarsely to obtain early-ripening pomelo juice; S400, by beverage volume, add: 50% tea base, 25% pretreated bayberry juice, 18% early-ripening grapefruit juice, 3% xylitol, 2% aged rice wine, and the remainder is low-oxygen softened water to make up to 100%; purge the tank with nitrogen, add the above components to the sealed mixing tank under controlled oxygen conditions, then immediately seal and stir for 10 minutes, adjust the pH to 3.2 with citric acid to obtain the mixed tea juice, the DO of the mixed tea juice is 0.7 mg / L; S500, mixed tea juice is homogenized at 30MPa, sterilized at 135℃ for 20 seconds, and then aseptically cold-filled and sealed to obtain the finished Wuniuzao tea.

[0050] Example 4 This embodiment provides a Wuniu Zao Tiao Yin Tea and its preparation method, the preparation method including: S100, same as in Example 1; S200. Take Wuniuzao black tea leaves and perform graded extraction with a volume ratio of tea leaves to low dissolved oxygen softened water of 1:30. The first stage is at a temperature of 88℃ for 3 minutes to obtain the first tea infusion; the second stage is at a temperature of 72℃ for 8 minutes to obtain the second tea infusion. The first and second tea infusions are combined at a volume ratio of 1:4, cooled to 8℃ by a plate heat exchanger, and filtered through a 100μm filter to obtain the tea base. S300, same as in Example 1; S400: Add by volume of the drink: 80% tea base, 15% pre-treated bayberry juice, 3% early sweet pomelo juice, 0.5% fructose syrup, 0.8% aged liquor sweat, and the balance is made up to 100% with low-dissolved oxygen softened water; displace the inside of the tank with nitrogen, add the above components into a closed mixing tank under oxygen-controlled conditions, and then immediately mix them by stirring for 10 min, fine-tune the pH to 3.8 with citric acid to obtain mixed tea juice, and the DO of the mixed tea juice is 0.7 mg / L; S500: The mixed tea juice is homogenized at 15 MPa, pasteurized at 95 °C for 10 min, and aseptically hot-filled and sealed to obtain the finished product of Wuniuzao flavored tea.

[0051] Comparative Example 1 This comparative example provides a Wuniuzao flavored tea and its preparation method. The preparation method is as shown in Example 1, except that: there is no S100, that is, drinking water is used, and its total hardness is 160 mg / L, and the total concentration of Ca 2+ and Mg 2+ is 45 mg / L, and the DO is 7.5 mg / L.

[0052] Comparative Example 2 This comparative example provides a Wuniuzao flavored tea and its preparation method. The preparation method is as shown in Comparative Example 1, except that: in S400, 0.02% of potassium sorbate is further added.

[0053] Comparative Example 3 This comparative example provides a Wuniuzao flavored tea and its preparation method. The preparation method is as shown in Example 1, except that: in S400, 0.03% of ascorbic acid is additionally added.

[0054] Comparative Example 4 This comparative example provides a Wuniuzao flavored tea and its preparation method. The preparation method is as shown in Example 1, except that: in S100, vacuum degassing and nitrogen bubbling are used to make the DO 1.2 mg / L, but no pretreatment is carried out, that is, the total hardness of the drinking water is still 160 mg / L, and the total concentration of Ca 2+ and Mg 2+ is 45 mg / L.

[0055] Comparative Example 5 This comparative example provides a Wuniuzao flavored tea and its preparation method. The preparation method is as shown in Example 1, except that: in S100, no deoxidation treatment is carried out.

[0056] Comparative Example 6 This comparative example provides a Wuniuzao flavored tea and its preparation method. The preparation method is as shown in Example 1, except that: in S300, the bayberry juice is not treated with immobilized oxygen-consuming enzyme.

[0057] Comparative Example 7 This comparative example provides a Wuniu Zao Tiao tea and its preparation method. The preparation method is as shown in Example 1, except that: in S400, nitrogen replacement is not performed, and an open stirring tank is used for mixing, and the DO after mixing is 3.5 mg / L.

[0058] Comparative Example 8 This comparative example provides a Wuniu Zao Tiao tea and its preparation method, which is as shown in Example 1, except that: in S400, citric acid is used to finely adjust the pH to 4.2.

[0059] Comparative Example 9 This comparative example provides a Wuniu Zao Tiao tea and its preparation method, which is as shown in Example 1, except that: in S400, citric acid is used to finely adjust the pH to 2.9.

[0060] Performance testing The Wuniuzao Tiaoyin Tea prepared in Examples 1-4 and Comparative Examples 1-9 was subjected to the following performance tests, and the results are as follows: Browning Index (BI): The sample was equilibrated to room temperature at 25°C, centrifuged at 4000 rpm for 10 min, and the supernatant was collected. The absorbance A at 420 nm was measured using a UV-Vis spectrophotometer. 420 A 420 As the browning index (BI); Color difference ΔE: Brightness, red-green value, and yellow-blue value were measured using a colorimeter. The color difference ΔE after storage was calculated using the 0-day sample as a control. Turbidity: The turbidity of the sample was measured and recorded using a turbidimeter after 30 days of storage at 37°C. Anthocyanin retention rate: The total anthocyanin content was determined by pH difference method, and the retention rate at 30 days was calculated with the content at 0 days as 100%. Precipitation amount: After storing the sample at 25℃ in the dark for 30 days, take 100mL of the sample and centrifuge at 4000rpm for 10min. Discard the supernatant, dry the precipitate at 60℃ to constant weight, weigh it and calculate the precipitation amount.

[0061] Table 1 Examples 1-4 showed significantly better performance than Comparative Example 1, which used ordinary water, in key indicators such as color difference, browning index growth, turbidity, sedimentation amount, and anthocyanin retention rate; and achieved or exceeded the overall stability performance of Comparative Examples 2-3, which added ascorbic acid and potassium sorbate, without the need for the addition of preservatives, antioxidants, or stabilizers.

[0062] Table 2 The color change and functional component decay rate of Example 1 were much lower than those of the comparative example, indicating that the protective effect of the present invention lasts throughout the entire shelf life, rather than being effective in the short term.

[0063] Table 3 Example 1 and Comparative Examples 1-3 were stored at 25°C for 60 days. The sensory evaluation after storage is shown in Table 3 above. Example 1 maintained an extremely high level of sensory quality, proving its excellent flavor stability; while Comparative Example 1 had basically lost its commercial value.

[0064] As shown in Tables 1-3, Examples 1-4 exhibited lower browning index growth, smaller color difference changes, lower turbidity and precipitation formation under both accelerated and room temperature storage conditions, while maintaining a higher anthocyanin retention rate. In summary, this invention achieves improved stability of Wuniuzao tea under conditions without preservatives, antioxidants, or stabilizers through the synergistic effect of key processes such as low-oxygen softened water, segmented extraction, pre-treatment with reduced oxygen at the juice end, and closed-loop oxygen control. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of this invention; therefore, the scope of protection of this invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing Wuniuzao tea, characterized in that, Includes the following steps: S100: Pre-treatment and deoxygenation of drinking water to obtain low dissolved oxygen softened water; S200. Take the original leaves of Wuniuzao black tea and use the low dissolved oxygen softened water for graded extraction to obtain the first tea soup and the second tea soup. Then, blend the first tea soup and the second tea soup in a volume ratio of 1:(1-4) to obtain the tea base. S300. Pretreated bayberry juice by anti-browning pretreatment; prepare early-fragrant pomelo juice. S400, the tea base, the pretreated bayberry juice, the early-ripening pomelo juice, the sweetener, the aged wine juice, and the low-dissolved oxygen softened water are added to a sealed mixing tank under controlled oxygen conditions for blending and processing to obtain a mixed tea juice; S500. The mixed tea juice is homogenized, sterilized, and then bottled and sealed to obtain the Wuniuzao tea.

2. The preparation method according to claim 1, characterized in that, In S100, The pretreatment includes at least one of softening treatment and demineralization treatment; based on CaCO3, the pretreatment reduces the total hardness of the drinking water to 5-30 mg / L. 2+ With Mg 2+ Total concentration of 1-12 mg / L; and / or The deoxygenation treatment includes at least one of vacuum degassing, membrane deoxygenation, or inert gas bubbling deoxygenation, to achieve dissolved oxygen (DO) ≤ 2.0 mg / L.

3. The preparation method according to claim 1, characterized in that, In S200, The extraction conditions for the first tea infusion were 88-95℃ for 1-3 minutes; and / or The extraction conditions for the second stage of tea infusion are 72-85℃ for 4-8 minutes.

4. The preparation method according to claim 1, characterized in that, In S300, the anti-browning pretreatment includes: adding an oxygen-consuming enzyme system to the bayberry juice for oxygen-consuming treatment, so that the dissolved oxygen (DO) of the bayberry juice is reduced to ≤1.0 mg / L, to obtain the pretreated bayberry juice.

5. The preparation method according to claim 4, characterized in that, The oxygen-consuming enzyme system is immobilized on a carrier, and the oxygen-consuming enzyme system includes ascorbic acid oxidase. The carrier includes at least one of resin, silica gel, and alginate gel.

6. The preparation method according to claim 1, characterized in that, In S400, the oxygen control conditions include: replacing the space inside the sealed mixing tank with an inert gas before adding the material, followed by immediate sealed mixing, and adjusting the pH of the mixed tea juice to 3.2-3.8, and the dissolved oxygen (DO) of the mixed tea juice to ≤1.5 mg / L.

7. The preparation method according to claim 1, characterized in that, In the S500, The homogenization pressure during the homogenization process is 15-30 MPa; The sterilization process includes ultra-high temperature instantaneous sterilization or pasteurization.

8. The preparation method according to claim 1, characterized in that, Based on beverage volume, the Wuniu Zao Tiaoyin Tea includes: 50-80% of the tea base, 10-30% of the pretreated bayberry juice, 3-20% of the early-ripening pomelo juice, 0.5-5% of the sweetener, 0.8-2.0% of the aged wine sweat, and the balance of the low-dissolved oxygen softened water.

9. The preparation method according to any one of claims 1 to 8, characterized in that, In S200, the tea base is cooled to below 15°C after compounding and then filtered.

10. A kind of Wuniu Zaocha (a type of herbal tea), characterized in that, The Wuniu Zao Tiao Yin Tea is obtained by the preparation method as described in any one of claims 1 to 9.

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