A low-astringency high-aroma original leaf tea refining process suitable for bottled cold-brewing and preserving the integrity of leaf shape

Abstract

The present application relates to the technical field of tea processing, and discloses a low-astringency high-aroma original leaf tea refining process suitable for bottled cold brewing and preserving leaf shape, which comprises fresh leaf screening, low-temperature withering, light rolling, fixation and temperature reduction, feedback type light rubbing in batches, gradient drying in batches, balanced moisture, secondary light setting, and grading screening. During the feedback type light rubbing in batches, unblocking, rapid temperature reduction, and standing for moisture are sequentially performed after each light rubbing, and sampling is performed for short-time cold brewing detection below 25 DEG C. Whether to continue light rubbing is determined according to the comparison result of the refractive index of the soluble solids in the cold brewing liquid and the corresponding rubbing end point range. After rubbing is completed, gradient drying in the order of initial drying, moisture balancing, re-drying, moisture balancing, and sufficient drying is adopted. The present application can match the rubbing degree with the cold water infusion state, take into account the original leaf integrity, cold brewing taste, and aroma, and improve the stability of the color and clarity of the tea soup during long-time cold brewing, and is suitable for the processing of bottled cold brewing original leaf tea.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, specifically to a refining process for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the shape of the leaves. Background Technology

[0002] With the development of ready-to-drink tea and cold-brewed tea beverages, the method of steeping tea leaves directly in bottled drinking water at low temperatures for a longer period of time has gradually gained popularity. Compared to short-time brewing with boiling or hot water, bottled cold brewing is typically carried out at a lower water temperature. The water-soluble components in the tea leaves are mainly extracted through the penetration of water into the leaves and the diffusion of soluble substances outward. For cold-brewed products that retain the original leaves in the bottle, in addition to the taste and aroma of the tea soup, it is also necessary to consider the integrity of the leaves during the steeping process, as well as the color and clarity of the tea soup. Therefore, the processing conditions of the tea raw materials have different requirements than those for conventional hot-brewed tea.

[0003] Current tea processing typically involves the following steps, depending on the type of tea and the requirements for hot water brewing: withering or spreading, shaking or oxidation, fixation, rolling, and drying. Withering or spreading reduces the moisture content of the fresh leaves and adjusts their shape; shaking promotes appropriate changes in the leaf edges and aroma formation; fixation inhibits enzymatic oxidation; rolling mechanically curls the leaves and promotes the extraction of internal substances during brewing; and drying further reduces moisture content and fixes the tea's quality. To ensure a relatively quick formation of a concentrated tea liquor during hot water brewing, current processing methods typically involve rolling for a fixed time, pressure, and number of times, followed by continuous or high-temperature drying to dehydrate and shape the leaves. These processing methods meet the requirements for use under conventional hot water brewing conditions.

[0004] However, when tea processed according to the above hot-brewing requirements is directly used for bottled cold brewing, the fixed degree of rolling is difficult to correspond to the actual extraction state under cold water conditions due to the lower water temperature and longer steeping time. Insufficient rolling results in slower extraction of tea leaves in cold water, leading to insufficient flavor and aroma in the tea soup; excessive rolling can cause the leaves to break and crumble, and may cause some flavor components to continue to extract during prolonged steeping, resulting in increased astringency later. Furthermore, when tea leaves clump together during rolling, and localized temperature and moisture conditions are inconsistent, using fixed rolling parameters makes it difficult to guarantee a consistent cold-brewing extraction state across different batches. Simultaneously, conventional continuous drying primarily aims for rapid dehydration and meeting hot-brewing quality requirements. Uneven moisture migration within the leaves can increase leaf brittleness, hindering the display of intact leaves in the bottle and potentially affecting the color and clarity of the tea soup during prolonged cold brewing. Therefore, the existing processing technology, which is mainly based on hot water brewing, cannot simultaneously meet the requirements of cold water immersion, leaf shape integrity, flavor harmony, and long-term soaking stability for bottled cold brewing. Corresponding improvements are needed to control the rolling endpoint and subsequent drying methods for bottled low-temperature cold brewing conditions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a refined processing technology for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the integrity of the leaf shape. This solves the problem that existing tea processing technologies are mainly designed for hot water brewing and are difficult to balance the appropriateness of cold water extraction, leaf shape integrity, low astringency and high aroma, as well as the stability of tea soup color and clarity during long-term steeping under bottled cold brewing conditions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a refining process for low-astringency, high-aroma whole-leaf tea suitable for bottled cold brewing and preserving the integrity of the leaf shape, comprising the following steps: S1. Fresh leaf selection and withering: Fresh tea leaves are selected and then subjected to low-temperature withering treatment. S2, Shaking: The withered tea leaves are lightly shaken and then left to stand. S3, Fixing: Fix the tea leaves after shaking, and then cool the tea leaves after fixing. S4. Feedback-type phased gentle kneading: After the tea leaves have cooled down, they are gently kneaded for the first time. After the first gentle kneading, the tea leaves are broken up, cooled down quickly, and allowed to stand and moisten evenly. Samples are taken from the tea leaves after they have been allowed to stand and moisten evenly. Short-term cold brewing test is conducted at a water temperature below 25℃ according to the preset tea-water mass ratio and preset steeping time to obtain the refractive index of soluble solids in the short-term cold brew liquid. The refractive index of the soluble solids is compared with the preset rolling endpoint range corresponding to the short-time cold brew test conditions; when the refractive index of the soluble solids is lower than the lower limit of the rolling endpoint range, the main tea leaves are lightly rolled again; after the next light rolling, the leaves are again broken up, rapidly cooled, and allowed to stand and moisten evenly, and tested under the same short-time cold brew test conditions; rolling is stopped when the refractive index of the soluble solids reaches the rolling endpoint range; S5. Segmented gradient drying: After the rolling is stopped, the tea leaves are sequentially subjected to initial drying, first inter-stage uniform drying, re-drying, second inter-stage uniform drying, and final drying, wherein the air inlet temperature of the initial drying, re-drying, and final drying decreases sequentially. S6. Balancing and Moisturizing, and Secondary Light Shaping: After the tea leaves are fully dried, they are balanced and moisturized, and then lightly shaped a second time. S7. Grading and screening: The tea leaves after the second light shaping are graded and screened to obtain bottled cold brew whole leaf tea.

[0007] According to the above technical solution, bottled cold-brewed whole-leaf tea is prepared through fresh leaf selection, low-temperature withering, light shaking, fixation and cooling, feedback-based multiple light rolling, segmented gradient drying, balanced moisture equalization, and secondary light shaping. Each light rolling is followed by breaking up clumps, rapid cooling, and static moisture equalization. The rolling endpoint is determined by the refractive index of soluble solids in the short-term cold-brewed liquid below 25℃, ensuring the rolling degree matches the cold water immersion state. This, combined with gradient drying and moisture equalization, balances leaf shape integrity, low astringency, high aroma, and tea liquor stability.

[0008] Preferably, in step S1, the fresh tea leaves include one bud and one leaf and one bud and two leaves, with a mass ratio of one bud and one leaf to one bud and two leaves of 60-80:20-40. After sieving out diseased, insect-damaged, reddened, mechanically damaged, old, and coarse leaves, the fresh tea leaves are spread out in a thickness of 3-5 cm for low-temperature withering. The ambient temperature for low-temperature withering is 18-24℃, the relative humidity is 62%-70%, the air velocity is 0.2-0.5 m / s, the withering time is 6-10 hours, and the moisture content of the tea leaves at the end of withering is 64.5%-69.5%.

[0009] Preferably, in step S2, the light shaking is performed 2 to 3 times, the shaking speed is 5 to 10 r / min, and the shaking time for each time is 2 to 4 min; between two adjacent shakings and after the last shaking, the plants are left to stand, with an ambient temperature of 20 to 24°C and a relative humidity of 65% to 75%, and a standing time of 25 to 50 min for each time.

[0010] Preferably, in step S3, a drum-type fixing device is used for fixing. The hot zone temperature of the fixing device is 120-145℃, the fixing time is 3-5 minutes, the temperature of the tea leaves after fixing is 76-92℃, and the moisture content of the tea leaves at the end of fixing is 56%-62%. After fixing, the tea leaves are cooled with air at 18-22℃, the air velocity is 0.8-2.0m / s, and the cooling time is 4-6 minutes, so that the temperature of the tea leaves is reduced to 24-28℃.

[0011] Preferably, in step S4, the kneading speed for each light kneading is 18-26 r / min, the average apparent pressure is 3-11 kPa, the single light kneading time is 2-5 min, and the cumulative number of light kneadings does not exceed 4 times; wherein, the average apparent pressure P is determined according to P=F / S, where F is the loading force applied by the kneading machine cover along the axial direction of the kneading drum, and S is the effective cross-sectional area of ​​the kneading drum.

[0012] Preferably, in step S4, after each gentle kneading, the tea leaves are de-clumped at a speed of 30-50 r / min for 1 minute; after de-clumping, the leaves are rapidly cooled with air at 18-22°C at a flow rate of 0.8-1.8 m / s for 3-5 minutes, reducing the leaf temperature to 23-27°C; after rapid cooling, the leaves are left to stand and be evenly moistened in an environment of 20-25°C and 65%-75% relative humidity for 12-20 minutes, and then samples are taken from the tea leaves after standing and being evenly moistened for the aforementioned short-time cold brew test.

[0013] Preferably, in step S4, 5 parts by weight of the tea leaves after they have been allowed to stand and become evenly moistened are taken, and 100 parts by weight of water at a temperature of 20°C are added. After stirring, the tea leaves are allowed to stand and soak for 15 minutes at 20°C. After soaking, solid-liquid separation is performed, and the refractive index of the soluble solids in the obtained short-time cold-brewed liquid is measured. The rolling endpoint range corresponding to the short-time cold-brew detection conditions is 0.35 to 0.65°Bx. When the refractive index of the soluble solids is lower than 0.35°Bx, the main tea leaves are lightly rolled again. When the refractive index of the soluble solids is 0.35 to 0.65°Bx, rolling is stopped.

[0014] Preferably, in step S4, the refractive index of soluble solids is used as the main control parameter for the end point of kneading, and the conductivity increment of the short-time cold-soaking liquid relative to the water used is used as an auxiliary monitoring parameter; the conductivity increment is the difference between the conductivity of the short-time cold-soaking liquid and the conductivity of the water used, and both the conductivity of the short-time cold-soaking liquid and the conductivity of the water used are converted to 25°C. Take 4 parts by weight of tea leaves that have been allowed to stand and become evenly moistened, add 100 parts by weight of water at 15°C, and let them stand and soak for 20 minutes at 15°C. The rolling endpoint range corresponding to the short-time cold-soaking test conditions is 0.30–0.55°Bx, and the conductivity increment auxiliary monitoring range is 80–280 μS / cm. When the soluble solids refractive index is below 0.30°Bx, perform another light rolling on the main tea leaves. Stop rolling when the soluble solids refractive index is 0.30–0.55°Bx. When the soluble solids refractive index is 0.30–0.55°Bx and the conductivity increment exceeds 80–280 μS / cm, resample from different positions of the main tea leaves, mix them, and retest. Stop rolling when the soluble solids refractive index obtained from the retest is still 0.30–0.55°Bx.

[0015] Preferably, in step S5, the initial drying air temperature is 68–82℃, the air velocity is 0.8–1.8 m / s, and the processing time is 12–20 min, reducing the tea moisture content to 29.5%–36.0%; the first stage of uniform humidity is achieved at an ambient temperature of 24–30℃ and a relative humidity of 60%–70%, for a time of 35–60 min; the re-drying air temperature is 55–68℃, the air velocity is 0.7–1.4 m / s, and the processing time is 15–25 min, reducing the tea moisture content to 15.0%–19.0%; the second stage of uniform humidity is achieved at an ambient temperature of 24–29℃ and a relative humidity of 58%–67%, for a time of 40–70 min; and the final drying air temperature is 50–60℃, the air velocity is 0.5–1.0 m / s, and the processing time is 22–38 min, reducing the tea moisture content to 5.0%–6.3%.

[0016] Preferably, in step S6, after the tea leaves are fully dried and cooled, they are equilibrated and moistened in an environment of 22-26℃ and 55%-65% relative humidity for 2.5-4 hours, and turned over once every 50-60 minutes during the equilibration and moistening process. After the equilibration and moistening is completed, a second light shaping is performed using air intake at 48-56℃, with an air velocity of 0.5-0.9 m / s and a processing time of 12-20 minutes. After the second light shaping, the leaves are cooled to obtain a moisture content of 4.9%-6.0% for the original tea leaves.

[0017] This invention provides a refining process for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the integrity of the tea leaves. It has the following beneficial effects: 1. In the rolling stage, this invention employs multiple light rolling processes, followed by de-clumping, rapid cooling, static humidification, and short-term cold brew testing. The refractive index of the soluble solids in the cold brew liquid determines whether to continue the next light rolling. This ensures that the rolling endpoint is determined by the actual cold water immersion state, avoiding excessive mechanical action caused by fixed-time or continuous heavy rolling. This balances cold water immersion capacity and leaf integrity, solving the problems of easily broken leaves, excessive broken tea, and continuous leaching of bitter substances after prolonged soaking when using traditional tea for bottled cold brewing.

[0018] 2. This invention continuously controls the water loss, aroma formation, and oxidation of fresh leaves through low-temperature gentle withering, light shaking, moderate fixation, and rapid cooling after fixation. This keeps the leaves in a suitable soft state before subsequent rolling and reduces the impact of unnecessary high temperature and continuous oxidation on the aroma, thereby improving the fragrance, floral aroma, and sweetness under cold brewing conditions. It also solves the problem of insufficient aroma release and dull flavor of traditional hot-brewed tea raw materials when steeped at low temperatures.

[0019] 3. This invention employs a segmented gradient drying process after kneading, including initial drying, inter-stage equalization of moisture, re-drying, re-equalization of moisture, and final drying. After final drying, it performs balanced equalization of moisture and a second light shaping, allowing the internal moisture of the leaves to gradually migrate and complete the shaping process. This reduces leaf brittleness and uneven drying caused by continuous high-temperature drying. At the same time, combined with the aforementioned moderate fixation and controlled kneading, it reduces the degree of deepening of the tea color and increase in turbidity during prolonged cold brewing, thus solving the problems of dark and cloudy tea color and unstable original leaf display after prolonged brewing of bottled cold brew tea. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the method steps of the present invention; Figure 2 This is a schematic diagram of the columnar comparison of Test Example 1 of the present invention; Figure 3 This is a schematic diagram of the columnar comparison of test example 2 of the present invention; Figure 4 This is a schematic diagram of the columnar comparison of test example 3 of the present invention; Figure 5 This is a schematic diagram of the columnar comparison of test example 4 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0022] Current tea processing techniques primarily determine the degree of withering, shaking, fixing, rolling, and drying based on hot water brewing conditions. Under bottled cold brewing conditions, tea needs to be continuously steeped in water below 25℃ for a longer period. The water temperature, steeping time, and the contact state between the tea and water all differ from conventional hot brewing. When tea processed according to hot brewing requirements is directly used for bottled cold brewing, it is prone to problems such as insufficient initial extraction followed by continuous extraction of bitter and astringent substances, leaf breakage, and a darkening of the tea liquor color and increased turbidity after prolonged steeping.

[0023] For bottled whole-leaf cold-brewed tea, the degree of rolling needs to meet two conditions simultaneously: on the one hand, it needs to generate sufficient cold water extraction capacity; on the other hand, it should not produce too many broken leaves or tea fragments due to excessive mechanical action, or cause the extraction to be too rapid during the long cold brewing stage. The tenderness of the fresh leaves, the degree of water loss during withering, the softness after fixation, and the moisture content of the batch all affect the actual degree of rolling under the same rolling time. Therefore, controlling the processing endpoint solely based on a fixed rolling time or a fixed number of rolling cycles is insufficient to directly reflect the actual extraction state of the tea under cold brewing conditions.

[0024] Based on the above, this invention incorporates a short-term cold-brewing test on top of light rolling. The refractive index of soluble solids in the currently rolled leaves under specified cold-brewing conditions is used as the criterion for determining whether to continue rolling. After each light rolling, the leaves are first broken up, rapidly cooled, and allowed to stand and evenly moisten, allowing the clumps of tea leaves to redistribute, reducing the temperature rise caused by rolling, and redistributing moisture between the surface and interior of the leaves before another short-term cold-brewing test. If the test value does not reach the specified range, the next light rolling is performed; once the specified range is reached, rolling is stopped.

[0025] After the rolling process, a segmented low-temperature gradient drying process is adopted, consisting of initial drying, inter-stage uniform wetting, re-drying, re-uniform wetting, and final drying. After final drying, balanced wetting and secondary light shaping are carried out to gradually dehydrate the tea leaves and complete the leaf shape shaping. The entire processing is based on the cold water immersion state, the integrity of the leaves, and the changes in the color and turbidity of the tea soup after long-term cold brewing as the process control basis.

[0026] The present invention will be described below with reference to specific embodiments. Operations not specifically described in the embodiments all employ conventional equipment and operating methods in the tea processing field.

[0027] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0028] The fresh tea leaves were harvested from the seasonal new shoots of tea trees in high-altitude tea gardens. The picking standard was one bud and one leaf or one bud and two leaves. After picking, diseased, insect-damaged, reddened, mechanically damaged, old, and coarse leaves were removed. In the examples and comparative examples, fresh leaves from the same picking batch were processed in groups. Each group used 100 parts by weight of fresh leaves as the starting material, of which 70 parts by weight were one bud and one leaf, and 30 parts by weight were one bud and two leaves. The initial moisture content of the fresh leaves was 76.8%.

[0029] The process water used is water that meets the requirements for drinking water, and the same batch of process water is used in the same group of comparative tests. The process water used for short-term cold bubble testing and long-term cold bubble testing is adjusted to the specified temperature before use.

[0030] The average apparent pressure P mentioned in the embodiment is calculated according to P=F / S, where F is the loading force applied by the kneading machine cover along the axial direction of the kneading drum, in N; and S is the effective cross-sectional area of ​​the kneading drum, in m². 2 P represents the average apparent pressure, expressed in Pa, and converted to kPa in the examples.

[0031] The actual temperature of the tea leaves during the fixation and drying process was measured using an infrared thermometer. Multiple measurements were taken at different locations immediately after the tea leaves were discharged, and the results were expressed as the range of multiple measurements taken in the same batch.

[0032] Preparation Example 1: This preparation example provides a short-time cold bubble detection method for feedback control of the kneading endpoint, including the following steps: Take 5 parts by weight of tea leaves that have undergone a single light kneading, breaking up clumps, rapid cooling, and standing to evenly moisten. Add 100 parts by weight of process water at a temperature of 20℃, ensuring the tea leaves are completely submerged. After adding water, stir at 60 rpm for 10 seconds, then stop stirring and let it steep at 20℃ for 15 minutes.

[0033] After soaking, a food-grade sieve with a pore size of 0.8 mm was used for the first solid-liquid separation. Then, the resulting cold-soaked liquid was passed through a food-grade filter with a pore size of 200 μm, and the filtrate was collected. The filtrate was tested within 3 minutes after filtration.

[0034] The refractive index of soluble solids in the filtrate was determined using a digital refractometer with a resolution of at least 0.01°Bx. Zero-point calibration was performed using the same process water before testing. Each sample was measured in triplicate, and the arithmetic mean was taken as the short-time cold-soak test value.

[0035] Under the aforementioned fixed testing conditions, 0.35–0.65°Bx was taken as the target cold-brewing extraction range. When the measured value was below 0.35°Bx, the main tea leaves underwent another short, light kneading; when the measured value was between 0.35 and 0.65°Bx, subsequent kneading was stopped; when the measured value was above 0.65°Bx, kneading was discontinued.

[0036] For the same processing batch, from the first test to the end of kneading, the same tea-to-water ratio, water temperature, soaking time, stirring method, filtration method and testing method are used, and the number of consecutive short-term light kneadings does not exceed 4 times.

[0037] Preparation Example 2: This preparation example provides a short-time cold bubble detection method that uses the refractive index of soluble solids to control the end point of kneading and uses conductivity increment for auxiliary monitoring, including the following steps: Take 4 parts by weight of tea leaves that have undergone a single light kneading, breaking up clumps, rapid cooling, and standing to evenly moisten. Add 100 parts by weight of process water at 15℃, stir at 60r / min for 15s, and then let it stand and soak at 15℃ for 20min.

[0038] After soaking, a food-grade sieve with a pore size of 0.8 mm was used for the first solid-liquid separation. Then, the resulting cold-soaked liquid was passed through a food-grade filter with a pore size of 200 μm. The liquid was tested within 3 minutes after filtration.

[0039] The refractive index of soluble solids in the filtrate was determined using a digital refractometer with a resolution of not less than 0.01°Bx. Each sample was measured in triplicate and the arithmetic mean was taken.

[0040] The conductivity of the filtrate was measured using a conductivity meter and uniformly converted to conductivity values ​​at 25℃. Blank conductivity was measured using the same batch of process water. The conductivity increment was calculated according to ΔC = C1 - C0, where ΔC is the conductivity increment in μS / cm; C1 is the conductivity of the cold-soaked solution converted to 25℃ in μS / cm; and C0 is the conductivity of the blank process water converted to 25℃ in μS / cm.

[0041] Under the above testing conditions, 0.30–0.55°Bx was taken as the main control range for the kneading endpoint, and 80–280 μS / cm was taken as the auxiliary monitoring range for conductivity increment.

[0042] When the refractive index is below 0.30°Bx, the main tea leaves continue to be kneaded for another short period of time; when the refractive index is between 0.30 and 0.55°Bx, kneading is stopped; when the refractive index is above 0.55°Bx, kneading is stopped.

[0043] When the refractive index is between 0.30 and 0.55°Bx and the conductivity increment exceeds 80–280 μS / cm, samples are taken again from different locations on the main tea leaves and mixed, and the test is repeated under the same conditions. If the refractive index remains between 0.30 and 0.55°Bx after the retest, rolling is stopped, and the conductivity increment is recorded.

[0044] For the same processing batch, fixed testing conditions are used, and the number of consecutive short-term light kneading times does not exceed 4.

[0045] Preparation Example 3: This preparation example provides a short-time cold bubble detection method for feedback control of the kneading endpoint under low temperature conditions, including the following steps: Take 3 parts by weight of tea leaves that have undergone a single light kneading, breaking up clumps, rapid cooling, and standing to evenly moisten. Add 100 parts by weight of process water at 10℃, stir at 60r / min for 20s, and then let it stand and soak at 10℃ for 25min.

[0046] After soaking, a food-grade sieve with a pore size of 0.8 mm was used for the first solid-liquid separation. The resulting cold-soaked liquid was then passed through a filter with a pore size of 200 μm, and the filtrate was collected. The filtrate was tested within 3 minutes after filtration.

[0047] The refractive index of soluble solids in the filtrate was determined using a digital refractometer with a resolution of not less than 0.01°Bx. Each sample was measured in triplicate, and the arithmetic mean was taken as the test result.

[0048] Under the above-mentioned fixed testing conditions, 0.22–0.45°Bx was taken as the target cold leaching range. When the test value was below 0.22°Bx, the next short, light kneading was continued; when the test value was between 0.22 and 0.45°Bx, kneading was stopped; when the test value was above 0.45°Bx, kneading was discontinued.

[0049] For the same processing batch, from the first test to the end of rolling, the fixed testing conditions of tea to process water mass ratio of 3:100, water temperature of 10℃, and soaking time of 25 minutes were used, and the number of consecutive short-term light rollings did not exceed 4 times.

[0050] Example 1: This embodiment provides a refining process for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the complete leaf shape, including the following steps: (1) Take 100 parts by weight of fresh tea leaves, including 70 parts by weight of one bud and one leaf and 30 parts by weight of one bud and two leaves. The initial moisture content of the fresh leaves is 76.8%. Remove diseased and insect-infested leaves, reddened leaves, mechanically damaged leaves, old leaves and coarse and hard leaves. Spread the selected fresh leaves evenly in a thickness of 4cm.

[0051] (2) The fresh leaves were placed in an indoor environment of 21℃ and 68% relative humidity for low-temperature and gentle withering. The air flow rate was 0.35m / s. The leaves were withered for 8 hours, and were turned gently once every 2 hours for a total of 3 times. The moisture content of the tea leaves was 67.0% at the end of withering.

[0052] (3) Place the withered leaves in a drum-type shaking machine for two light shakings. The drum speed is 8 r / min. The first shaking lasts for 3 minutes, followed by standing for 45 minutes in an environment of 22℃ and 72% relative humidity; the second shaking lasts for 3 minutes, followed by standing for 30 minutes in the same environment.

[0053] (4) After shaking, the tea leaves are fed into a drum-type fixation machine for moderate fixation. The temperature of the hot zone of the equipment is 135℃, and the actual leaf temperature of the tea is 84-88℃. The process lasts for 4 minutes, and the moisture content of the tea leaves is 59.0% at the end of fixation. After the fixation leaves are discharged, they are immediately spread out in a 3cm thickness and cooled with 20℃ air at a flow rate of 1.5m / s for 5 minutes to reduce the leaf temperature to 26℃. Then, they are left to stand for 10 minutes.

[0054] (5) Put the blanched leaves into the rolling machine, with the leaf load being 60% of the effective volume of the rolling machine. The first light rolling speed is 24 r / min, the average apparent pressure is 6 kPa, and the rolling is 4 min. The leaf temperature is controlled below 34℃.

[0055] Immediately after the first light kneading, the tea leaves are discharged and broken up using a low-speed de-clumping machine at 40 r / min for 1 minute. The broken-up tea leaves are spread out in a 3 cm thickness and cooled by air at 20℃ with a flow rate of 1.2 m / s for 4 minutes to reduce the leaf temperature to 25℃. Then, the leaves are left to stand and moisten evenly for 15 minutes in an environment of 22℃ and 72% relative humidity.

[0056] Short-time cold bubble testing was performed according to the method in Preparation Example 1. A second gentle kneading was performed when the first test value was below 0.35°Bx. The second gentle kneading speed was 22 r / min, the average apparent pressure was 8 kPa, and the kneading lasted for 3 minutes. After kneading, the leaf was broken up at 40 r / min for 1 minute, and then cooled with 20°C air at a flow rate of 1.2 m / s for 4 minutes until the leaf temperature dropped to 24°C. The leaf was then allowed to stand at 22°C and 72% relative humidity for 15 minutes to achieve uniform moisture absorption. Kneading was stopped when the second short-time cold bubble test value entered the range of 0.35–0.65°Bx.

[0057] (6) Perform segmented low-temperature gradient drying. The initial drying air temperature is 76℃, the actual temperature of the tea leaves is 55~62℃, the air velocity is 1.3m / s, and the treatment lasts for 15min to reduce the moisture content of the tea leaves to 32.0%; then, the leaves are left to stand at 28℃ and 68% relative humidity for 45min to achieve uniform moisture.

[0058] The re-drying air inlet temperature was 62℃, the actual temperature of the tea leaves was 47~54℃, the air velocity was 1.0m / s, and the treatment lasted for 18 minutes, reducing the moisture content of the tea leaves to 16.5%. Subsequently, the leaves were left to stand at 26℃ and 62% relative humidity for 50 minutes to achieve uniform moisture.

[0059] The air temperature for drying was 55℃, the actual temperature of the tea leaves was 43-49℃, the air velocity was 0.8m / s, and the treatment lasted for 28 minutes, which reduced the moisture content of the tea leaves to 5.6%.

[0060] (7) After the tea leaves are fully dried, they are cooled to 28°C using air at 24°C, and then placed in an environment at 24°C and 60% relative humidity for 3 hours to achieve uniform moisture balance. The tea leaves are piled up to a thickness of 10cm and gently turned over once every 60 minutes. After achieving uniform moisture balance, a second light shaping is performed with an air inlet temperature of 52°C, an actual tea leaf temperature of 40-46°C, an air velocity of 0.7m / s, and a treatment time of 15 minutes. After the treatment, the tea leaves are cooled to a core temperature of 30°C using air at 22°C. The resulting tea leaves have a moisture content of 5.4%.

[0061] (8) Use a sieve with a pore size of 2mm to remove tea dust and small debris, and then use low-speed sorting to remove leaves that are obviously broken and do not meet the requirements for finished product grading, so as to obtain bottled cold brew whole leaf tea.

[0062] Example 2: This embodiment provides a refining process for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the complete leaf shape, including the following steps: (1) 100 parts by weight of fresh leaves with the same composition as in Example 1 were screened and spread evenly with a thickness of 3 cm.

[0063] (2) In an environment of 18℃ and 62% relative humidity, withering was carried out at an air flow rate of 0.2m / s for 6 hours, with the leaves turned over lightly once every 2 hours for a total of 2 times. The moisture content of the tea leaves was 69.5% at the end of withering.

[0064] (3) Use a drum speed of 5r / min to perform two light shakings, each lasting 2min. After the first shaking, let it stand for 30min in an environment of 20℃ and 65% relative humidity, and after the second shaking, let it stand for 25min.

[0065] (4) Use a drum-type fixation machine for moderate fixation. The temperature of the hot zone of the equipment is 120℃, and the actual leaf temperature of the tea is 76~82℃. The treatment lasts for 3 minutes, and the moisture content of the tea leaves is 62.0% at the end of fixation. After fixation, use 18℃ air at a flow rate of 0.8m / s to cool down the leaves for 6 minutes, so that the leaf temperature drops to 24℃. Then let it stand for 8 minutes.

[0066] (5) The first light kneading speed is 18 r / min, the average apparent pressure is 3 kPa, kneading for 3 min, and the leaf temperature is controlled below 32℃. After kneading, break up the clumps at 30 r / min for 1 min, and use 18℃ air at a flow rate of 0.8 m / s to cool down for 5 min, so that the leaf temperature drops to 23℃. Then, let it stand in an environment of 20℃ and 65% relative humidity for 12 min to evenly moisten.

[0067] Short-time cold-bubble testing was performed according to Preparation Example 1. When the test value was below 0.35°Bx, a second light kneading was performed at a speed of 18 r / min and an average apparent pressure of 5 kPa for 2 minutes. Subsequently, the conditions after the first kneading were followed for de-caking, rapid cooling, and standing to achieve uniform moisture. Kneading was stopped when the second test value entered the range of 0.35–0.65°Bx.

[0068] (6) The initial drying air temperature is 68℃, the actual temperature of the tea leaves is 47-55℃, the air velocity is 0.8m / s, and the treatment time is 20min to reduce the moisture content to 36.0%. Then, the leaves are left to stand in an environment of 24℃ and 60% relative humidity for 60min to achieve uniform moisture content. The re-drying air temperature is 55℃, the actual temperature of the tea leaves is 42-49℃, the air velocity is 0.7m / s, and the treatment time is 25min to reduce the moisture content to 19.0%. Then, the leaves are left to stand in an environment of 24℃ and 58% relative humidity for 70min to achieve uniform moisture content. The final drying air temperature is 50℃, the actual temperature of the tea leaves is 39-45℃, the air velocity is 0.5m / s, and the treatment time is 38min to reduce the moisture content to 6.3%.

[0069] (7) Cool the fully dried tea to 28°C and equilibrate it in an environment of 22°C and 55% relative humidity for 4 hours, gently turning it once every 60 minutes. Then, use 48°C air intake for secondary light shaping, with the actual temperature of the tea leaves being 37-43°C and the air velocity being 0.5m / s, for 20 minutes. The moisture content of the tea leaves after cooling is 6.0%.

[0070] (8) Grade and screen according to the method of Example 1 to obtain bottled cold brew whole leaf tea.

[0071] Example 3: This embodiment provides a refining process for raw tea leaves that uses the refractive index of soluble solids to control the end point of kneading and uses the increase in electrical conductivity as an auxiliary monitoring method, including the following steps: (1) 100 parts by weight of fresh leaves with the same composition as in Example 1 were screened and spread evenly with a thickness of 5 cm.

[0072] (2) In an environment of 24℃ and 65% relative humidity, withering was carried out at an air flow rate of 0.5m / s for 10 hours, with the leaves turned over lightly every 2.5 hours for a total of 3 times. The moisture content of the tea leaves was 64.5% at the end of withering.

[0073] (3) Use a drum speed of 10r / min to perform three light shakings. After the first shaking for 3 minutes, let it stand for 50 minutes in an environment of 24℃ and 75% relative humidity; after the second shaking for 4 minutes, let it stand for 50 minutes; after the third shaking for 4 minutes, let it stand for 40 minutes.

[0074] (4) The temperature of the hot zone of the fixation equipment is 145℃, the actual leaf temperature of the tea is 86~92℃, the treatment is 5min, and the moisture content of the tea is 56.0% at the end of fixation. After the fixation leaves are discharged, they are cooled by air at 22℃ at a flow rate of 2.0m / s for 4min to reduce the leaf temperature to 28℃, and then left to stand for 12min.

[0075] (5) The first light kneading speed is 26 r / min, the average apparent pressure is 8 kPa, kneading for 5 min, and the leaf temperature is controlled below 35℃. After kneading, break up the clumps at 50 r / min for 1 min, and use 22℃ air at a flow rate of 1.8 m / s to cool down for 3 min, so that the leaf temperature drops to 27℃. Then, let it stand in an environment of 25℃ and 75% relative humidity for 20 min to evenly moisten.

[0076] The test was conducted according to the method described in Preparation Example 2. A second gentle kneading was performed when the refractive index was below 0.30°Bx. The second gentle kneading was performed at a speed of 25 r / min, an average apparent pressure of 11 kPa, and for 3 minutes. Afterward, the kneading was performed under the same conditions as after the first kneading: de-caking, rapid cooling, and static moisture equalization. Kneading was stopped when the refractive index entered the range of 0.30–0.55°Bx and the conductivity increment was between 80 and 280 μS / cm.

[0077] (6) The initial drying air temperature is 82℃, the actual temperature of the tea leaves is 58~65℃, the air velocity is 1.8m / s, and the treatment is 12min to reduce the moisture content to 29.5%. Then, it is left to stand in an environment of 30℃ and 70% relative humidity for 35min to achieve uniform moisture. The re-drying air temperature is 68℃, the actual temperature of the tea leaves is 51~58℃, the air velocity is 1.4m / s, and the treatment is 15min to reduce the moisture content to 15.0%. Then, it is left to stand in an environment of 29℃ and 67% relative humidity for 40min to achieve uniform moisture. The final drying air temperature is 60℃, the actual temperature of the tea leaves is 46~52℃, the air velocity is 1.0m / s, and the treatment is 22min to reduce the moisture content to 5.0%.

[0078] (7) After the tea leaves are fully dried, they are cooled to 28°C and then equilibrated and moistened in an environment of 26°C and 65% relative humidity for 2.5 hours, being gently turned over once every 50 minutes. Subsequently, a second light shaping is performed using air intake at 56°C, with the actual temperature of the tea leaves being 43-48°C and the air velocity being 0.9 m / s, for 12 minutes. The moisture content of the tea leaves obtained after cooling is 4.9%.

[0079] (8) Grade and screen according to the method of Example 1 to obtain bottled cold brew whole leaf tea.

[0080] Example 4: This embodiment provides a refining process for whole-leaf tea that uses multiple short-time cold brew detection feedbacks to determine the rolling endpoint, including the following steps: (1) 100 parts by weight of fresh leaves with the same composition as in Example 1 were screened and spread evenly with a thickness of 5 cm.

[0081] (2) In an environment of 20℃ and 70% relative humidity, withering was carried out at an air flow rate of 0.3m / s for 7 hours, with the leaves turned over lightly once every 2 hours for a total of 3 times. The moisture content of the tea leaves was 68.0% at the end of withering.

[0082] (3) Use a drum speed of 7r / min to perform two light shakings. After the first shaking for 2 minutes, let it stand for 40 minutes in an environment of 22℃ and 75% relative humidity; after the second shaking for 3 minutes, let it stand for 30 minutes.

[0083] (4) The temperature of the hot zone of the fixation equipment is 130℃, the actual leaf temperature of the tea is 80~86℃, the treatment is 4min, and the moisture content of the tea is 60.0% at the end of fixation. After fixation, the tea is cooled by air at 19℃ with a flow rate of 1.3m / s for 5min to reduce the leaf temperature to 25℃, and then left to stand for 10min.

[0084] (5) The first light kneading speed is 20 r / min, the average apparent pressure is 4 kPa, kneading for 3 min, and the leaf temperature is controlled below 33℃. After kneading, break up the clumps at 35 r / min for 1 min, and use 19℃ air at a flow rate of 1.0 m / s to cool down for 4 min, so that the leaf temperature drops to 24℃. Then, let it stand in an environment of 21℃ and 70% relative humidity for 15 min to evenly moisten.

[0085] The first short-time cold bubbling test was performed according to the method of Preparation Example 3. A second gentle kneading was performed when the test value was below 0.22°Bx.

[0086] The second light kneading was performed at a speed of 20 r / min, with an average apparent pressure of 6 kPa, for 2.5 minutes. After kneading, the mixture was broken up, rapidly cooled, and allowed to stand and moisten evenly as described above. A third light kneading was performed if the second detection value was still below 0.22°Bx.

[0087] The third light kneading was performed at a speed of 20 r / min, with an average apparent pressure of 8 kPa, for 2 minutes. After kneading, the dough was broken up, rapidly cooled, and allowed to stand until the moisture content was evenly distributed. Kneading was stopped when the third reading reached 0.22–0.45°Bx. The total effective kneading time was 7.5 minutes.

[0088] (6) The initial drying air temperature is 74℃, the actual temperature of the tea leaves is 52-60℃, the air velocity is 1.2m / s, and the treatment time is 17min to reduce the moisture content to 33.0%. Then, the leaves are left to stand in an environment of 27℃ and 66% relative humidity for 45min to achieve uniform moisture content. The re-drying air temperature is 60℃, the actual temperature of the tea leaves is 46-52℃, the air velocity is 0.9m / s, and the treatment time is 20min to reduce the moisture content to 17.0%. Then, the leaves are left to stand in an environment of 26℃ and 62% relative humidity for 55min to achieve uniform moisture content. The final drying air temperature is 54℃, the actual temperature of the tea leaves is 42-48℃, the air velocity is 0.7m / s, and the treatment time is 30min to reduce the moisture content to 5.7%.

[0089] (7) Cool the fully dried tea to 28℃, and equilibrate and evenly moisten it in an environment of 24℃ and 60% relative humidity for 3 hours, gently turning it once every 60 minutes; use 52℃ air intake for secondary light shaping, with the actual temperature of the tea leaves being 40~46℃ and the air velocity being 0.7m / s, for 15 minutes. The moisture content of the tea leaves obtained after cooling is 5.5%.

[0090] (8) Grade and screen according to the method of Example 1 to obtain bottled cold brew whole leaf tea.

[0091] Comparative Example 1: Compared with Example 1, the difference is that step (5) does not use feedback-type light kneading in multiple steps. Instead, the tea leaves that have been killed and cooled down are kneaded continuously once. The kneading speed is 24 r / min, the average apparent pressure is 8 kPa, and the kneading time is 7 min. After the kneading is completed, the process proceeds directly to step (6). All other steps are the same.

[0092] Comparative Example 2: Compared with Example 1, the difference is that step (5) uses three preset short-term light kneadings without short-term cold soaking tests. The first light kneading speed is 24 r / min, the average apparent pressure is 6 kPa, and the kneading time is 4 min; the second light kneading speed is 22 r / min, the average apparent pressure is 8 kPa, and the kneading time is 3 min; the third light kneading speed is 20 r / min, the average apparent pressure is 8 kPa, and the kneading time is 2 min; between adjacent kneadings, the process of breaking up clumps, rapid cooling, and allowing the mixture to stand and moisten is carried out in accordance with the method of Example 1. After completing the three light kneadings, the process proceeds directly to step (6), and the rest is the same.

[0093] Comparative Example 3: Compared with Example 1, the difference is that step (5) retains the short-time cold brew detection feedback control, but cancels the unblocking, rapid cooling and static moisture equalization between two adjacent light kneading. After the first light kneading, samples are taken from different positions of the kneaded leaves and mixed as test samples. Short-time cold brew detection is performed according to the method of Preparation Example 1. When the detection value is lower than 0.35°Bx, the main tea leaves are directly kneaded again until the detection value enters 0.35~0.65°Bx and then the kneading is stopped. The rest are the same.

[0094] Comparative Example 4: Compared with Example 1, the difference is that the two mechanical shaking actions in step (3) are cancelled, but the cumulative standing time of 75 min is retained as in step (3) of Example 1. After step (2) is completed, the withered leaves are placed in an environment of 22°C and 72% relative humidity for 75 min, and then step (4) is carried out directly, and the rest is the same.

[0095] Comparative Example 5: Compared with Example 1, the difference is that step (6) does not use the segmented low-temperature gradient drying consisting of initial drying, inter-stage equalization drying, re-drying, re-equalization drying and final drying, but adopts a continuous drying method. The rolled tea leaves are continuously dried at an air inlet temperature of 76℃ and an air flow rate of 1.3m / s until the moisture content reaches 5.6%. Then, equalization drying and secondary light shaping are carried out according to step (7) of Example 1, and the rest are the same.

[0096] Test Example 1: Finished Product Leaf Integrity and Broken Tea Content Test (1) Random samples were taken from the finished tea products obtained in Examples 1-4 and Comparative Examples 1-5, respectively. Three parallel samples were set up in each group, and 100g of each parallel sample was taken. Before the test, the tea samples were placed in a sealed container and equilibrated at 20-25℃ for 12h. During the sampling and transfer process, the tea leaves were not squeezed.

[0097] (2) The content of tea powder and broken tea shall be determined in accordance with the method specified in GB / T8311.

[0098] (3) Take another 100g of tea samples from each group for the determination of the percentage of intact leaves. Spread the tea samples flat in a sorting tray and sort out the tea leaves with continuous main body and no breakage from the tip to the base of the leaf. Tea leaves with only local defects at the leaf edge but continuous main body are counted as intact leaves. Weigh the mass of intact leaves m1 and record the total mass of the tested tea samples m0.

[0099] The percentage of intact leaves is calculated using the following formula: Intact leaf rate = m1 / m0 × 100%.

[0100] (4) Take another 5 parts by weight of tea sample and add 100 parts by weight of process water at 20℃. Let it stand and soak for 12 hours in a transparent glass container. After soaking, use a 0.8mm sieve to slowly separate the leaves. After draining for 5 minutes, record the leaf unfolding, breakage and debris shedding.

[0101] The percentage of whole leaves is an independent evaluation index established in this invention based on the continuity of the leaf body; the content of broken tea and powder content are determined according to the corresponding sieving methods. The portion not included in the above three items is an incomplete leaf with local breakage but whose particle size does not meet the criteria for broken tea. Therefore, the sum of the percentage of whole leaves, the content of broken tea, and the content of powder is not considered as a 100% mass balance relationship.

[0102] Table 1. Test data on leaf shape integrity of raw tea leaves obtained by different processes.

[0103] According to Table 1 and Figure 2 The data shows that the intact leaf rate in Examples 1-4 ranged from 88.9% to 93.4%, and the broken tea content ranged from 4.3% to 6.7%. Comparative Example 1, which used a single continuous rolling process, had an intact leaf rate of 76.8% and a broken tea content of 15.4%. Comparative Example 3, which retained feedback detection but eliminated the breaking up of clumps, rapid cooling, and static moisture equalization between adjacent rolling processes, had an intact leaf rate of 81.6% and a broken tea content of 11.9%. These data indicate that both multiple light rolling processes and inter-rolling treatments are related to the integrity of the finished leaf material.

[0104] During the rolling process, tea leaves are subjected to pressure, kneading, and friction. In continuous processing, the stress state between the outer and inner layers of the clump of tea leaves is not consistent. Some leaves continue to be subjected to mechanical action even after reaching the appropriate degree of rolling, which easily increases leaf edge damage and leaf breakage. Breaking up clumps between light rolling sessions allows the rolled leaf clusters to redistribute; rapid cooling reduces the temperature rise caused by mechanical friction; and allowing the leaves to stand and evenly moisten allows for the redistribution of moisture in different parts of the leaf after rolling. Completing these processes before deciding whether to proceed with the next rolling session reduces localized over-rolling caused by continuous mechanical action.

[0105] Based on the data from Example 1 and Comparative Example 2 in Table 1, both groups employed multiple light kneading techniques, along with inter-kneading de-clumping, cooling, and moisture equalization. Therefore, the difference in leaf integrity was less than the difference between Example 1 and Comparative Examples 1 and 3. This result closely matches the actual mechanical effects experienced by the tea leaves in both groups. The main function of short-time cold-infusion feedback control is not to directly increase the percentage of intact leaves in all processing batches, but rather to allow the kneading endpoint to be determined based on the current cold water immersion state of the tea leaves, preventing processing from proceeding at fixed times and durations when the tenderness, withering degree, and moisture content of the fresh leaves change after fixation.

[0106] Test Example 2: Leaching Performance Test under Different Cold Soaking Times (1) Take 5 parts by weight of tea samples obtained in Examples 1-4 and Comparative Examples 1-5 respectively, add 100 parts by weight of process water at 20℃, and let stand and cold steep in a 250mL transparent glass container with a lid. Set three time points: 4h, 8h and 12h respectively, and set 3 independent parallel samples at each time point.

[0107] (2) After the specified time is reached, the tea soup is passed through a 0.8 mm sieve and a 200 μm food-grade filter in sequence. The resulting filtrate is used for the determination of refractive index, tea polyphenols and caffeine, respectively.

[0108] (3) The refractive index of soluble solids was measured using a digital refractometer with a resolution of not less than 0.01°Bx. Zero-point calibration was performed using the same batch of process water before testing. Each parallel sample was measured three times consecutively and the arithmetic mean was taken.

[0109] (4) The tea polyphenols in the cold brew solution were determined according to the analytical principles and detection conditions specified in GB / T8313. The cold brew solution was appropriately diluted according to the detection range, and a standard curve was established using gallic acid standard solution. The mass concentration of tea polyphenols in the cold brew solution was calculated based on the absorbance, and the result was expressed in mg / L.

[0110] (5) The caffeine in the cold brew solution was determined according to the high performance liquid chromatography analysis principle and chromatographic conditions specified in GB / T8312. A standard curve was established using caffeine standard solution. The mass concentration of caffeine in the cold brew solution was calculated based on the peak area of ​​the sample. The result was expressed in mg / L.

[0111] Table 2. Cold brew extraction performance data of whole leaf tea obtained by different processes.

[0112] According to Table 2 and Figure 3 According to the data, in Examples 1-4, detectable substances were extracted during the 4-hour cold steeping period. As the cold steeping time was extended to 8 and 12 hours, the refractive index of soluble solids continued to increase. At 12 hours, the refractive index of Examples 1-4 ranged from 0.97 to 1.11°Bx, and the tea polyphenol concentration ranged from 451 to 527 mg / L. Comparative Example 1, which underwent continuous rolling once, had a refractive index of 1.42°Bx and a tea polyphenol concentration of 682 mg / L at 12 hours; the corresponding values ​​for Comparative Example 3, which underwent a recovery treatment without rolling, were 1.37°Bx and 641 mg / L.

[0113] Based on the sensory results in Table 3, Comparative Examples 1 and 3 showed higher bitterness and astringency scores at 12 hours. This change indicates that the degree of rolling in bottled cold-brewed whole-leaf tea cannot solely be used as a processing goal to increase extraction yield. Increased rolling intensity can promote water penetration into the leaf tissue and accelerate the migration of soluble substances into the aqueous phase. However, if the mechanical action exceeds the necessary level for cold-brew extraction, a high level of leaching will continue to occur during the prolonged steeping stage, resulting in a corresponding increase in the amount of tea polyphenols and components related to bitterness and astringency entering the aqueous phase.

[0114] Based on the data from Example 1 and Comparative Example 2 in Table 2, the two actual kneading procedures are similar. However, Comparative Example 2 completes the kneading according to a preset number of times, without using the current cold-infusion state of the tea leaves as a stopping condition. Therefore, this comparative example is used to reflect the difference in control logic between fixed-program kneading and feedback kneading, rather than to prove that significantly different single-batch results will inevitably occur under the same raw materials and kneading parameters.

[0115] When the maturity, initial moisture content, degree of withering water loss, and softness of fresh leaves change, the degree of tissue damage caused by the same rolling pressure and time will not be entirely consistent. Fixed programs can only control equipment operating parameters and cannot directly determine whether the tea leaves have acquired the extraction capacity suitable for low-temperature steeping. Short-time cold steeping tests directly use the refractive index formed under specified tea-to-water ratio, specified water temperature, and specified time conditions as the judgment basis, establishing a correspondence between the rolling endpoint and the actual cold water steeping state of the tea leaves.

[0116] Example 4 further employs a multiple-test method to determine the rolling endpoint. After each light rolling, the tea leaves are broken up, rapidly cooled, and allowed to stand and moisten evenly. Then, the cold water extraction state is evaluated under the same testing conditions. If the test value is below the set range, light rolling continues; once it enters the set range, rolling stops. Therefore, the actual number of rolling cycles is not predetermined but determined by the cold water extraction state of the tea leaves during processing.

[0117] Test Example 3: Sensory Evaluation of Cold-Brewed Tea (1) The evaluation environment, evaluator requirements and terminology used in the sensory evaluation shall refer to the relevant provisions of GB / T23776. Considering the actual use of the product of this invention, the tea soup for evaluation shall not be prepared under hot water brewing conditions, but under uniform cold brewing conditions.

[0118] (2) Take 5 parts by weight of tea sample and add 100 parts by weight of process water at 20℃, cover and let stand for 12 hours. After the specified time, separate the tea leaves with a 0.8mm sieve, and evaluate the tea soup at 20±2℃.

[0119] (3) An evaluation group consisting of 7 personnel trained in tea sensory evaluation was formed. Each sample was assigned a random three-digit code, and the evaluators were unaware of the corresponding implementation or comparative example. After evaluating every 3 samples, the evaluators rinsed their mouths with warm water for 5 minutes at intervals.

[0120] (4) Evaluate aroma, sweetness, bitterness, astringency, and off-flavors separately. Each item is scored out of 10. Higher scores for aroma and sweetness indicate more pronounced sensory characteristics; higher scores for bitterness, astringency, and off-flavors indicate more pronounced negative tastes or odors. The arithmetic mean of the scores from 7 evaluators is taken for each item.

[0121] (5) The aroma evaluation mainly focuses on the light, floral and fresh aroma formed under cold brewing conditions, and does not take the roasted aroma formed under high temperature brewing conditions as the evaluation basis for this test.

[0122] Table 3 Sensory evaluation data of raw leaf tea obtained by different processes after 12 hours of cold brewing.

[0123] According to Table 3 and Figure 4 According to the data, the aroma scores of Examples 1-4 ranged from 7.9 to 8.6, and the astringency scores ranged from 2.1 to 3.0. Comparative Example 4, where the mechanical shaking was eliminated, had an aroma score of 6.3, but its bitterness and astringency did not increase to the same extent as Comparative Examples 1 and 3. These results indicate that light directional shaking and rolling play different roles in the overall process.

[0124] After withering, the fresh leaves undergo a limited degree of shaking, which slightly mechanically affects the leaf edges, leading to aroma changes related to floral and delicate fragrances during the subsequent resting stage. The degree of shaking is limited by the rotation speed, time, and resting time, and further oxidation is then stopped by fixation. This process is not aimed at achieving a high degree of fermentation, but rather at adjusting the cold-brew aroma while maintaining the integrity of the leaf body. Even after eliminating shaking, the cold-brewed tea still extracts some aroma, but the aroma expression changes.

[0125] According to the data in Table 4, the ΔE values ​​for Examples 1-4, after being extended from 4h to 12h, ranged from 3.29 to 4.53, and the turbidity at 12h ranged from 5.9 to 7.8 NTU. The ΔE value for Comparative Example 1 was 10.66, and the turbidity at 12h was 21.7 NTU; the ΔE value for Comparative Example 3 was 9.73, and the turbidity at 12h was 18.8 NTU. Combined with the leaf shape results in Table 1, continuous or localized excessive mechanical action not only increased leaf breakage and tea fragmentation but also increased the chance of fine tissues and soluble substances entering the cold brew liquid. With prolonged steeping time, the turbidity and color of the tea infusion changed accordingly.

[0126] Changes in tea liquor color cannot be simply attributed to a single enzymatic reaction. Insufficient fixation or uneven heating may result in the incomplete deactivation of some oxidation-related enzymes. Simultaneously, the degree of tissue damage caused by rolling, the amount of fine particles entering the aqueous phase, the leaching of components such as tea polyphenols, and prolonged non-enzymatic oxidation in the aqueous environment all affect the color and turbidity of the tea liquor. This invention controls these factors through appropriate fixation, limiting the mechanical action of rolling, and subsequent segmented dehydration, rather than relying on a single process to control the liquor color.

[0127] Test Example 4: Test on Changes in Color and Turbidity of Cold-Brewed Tea (1) Take 5 parts by weight of tea samples obtained in Examples 1-4 and Comparative Examples 1-5 respectively, add 100 parts by weight of process water at 20°C, and let stand in a transparent glass container with a lid. Set two detection time points at 4h and 12h respectively, and set 3 independent parallel samples at each time point.

[0128] (2) After the specified time has elapsed, the tea leaves are slowly separated using a 0.8 mm sieve. This test does not use a 200 μm filter for secondary filtration in order to retain the fine suspended matter that enters the tea soup during the actual cold brewing process.

[0129] (3) Slowly add the tea soup into a 50mm optical path cuvette to avoid generating bubbles. Use a colorimeter to measure L, a, and b* under D65 light source and 10° observation angle conditions. Measure each sample 3 times and take the arithmetic mean.

[0130] (4) Take another sample of the same tea infusion and measure the turbidity using a scattering turbidimeter within 5 minutes after separating the tea leaves. The result is expressed as NTU. The instrument is calibrated with a standard turbidity solution before testing.

[0131] (5) Calculate the total color difference from 4h to 12h using the following formula:

[0132] in, , and These are the color values ​​of the 4-hour cold soaking solution. , and These are the color values ​​of the cold-soaked solution after 12 hours. To ensure that the basic data in the table can be cross-checked with ΔE, Table 4 also lists L, a, and b for 4 hours and 12 hours, as follows: *Recalculate based on the basic data in the table.

[0133] Table 4. Color and turbidity data of raw tea leaves obtained by different processes during cold brewing.

[0134] According to Table 4 and Figure 5The data from Example 1 and Comparative Example 5 show that the initial processing and kneading conditions are consistent between the two groups, but the drying procedures differ. Example 1 uses a segmented drying process: initial drying, resting for uniform wetting, re-drying, resting for uniform wetting again, and final drying. Comparative Example 5 uses continuous drying at 76°C to the target moisture content. The percentage of intact leaves, turbidity at 12 hours, and color difference from 4 to 12 hours in Comparative Example 5 are all different from those in Example 1.

[0135] This comparison involves both inter-stage moisture equalization and the subsequent drying temperature program; therefore, all differences cannot be attributed to a single moisture equalization operation. The overall effect of segmented low-temperature gradient drying is to gradually reduce the drying heat load as the moisture content of the tea leaves decreases, and to establish static moisture equalization between different drying stages, allowing the surface and interior moisture of the leaves to redistribute before continuing dehydration. Compared to continuously drying from a higher moisture content state to a lower moisture content state, this treatment method reduces the impact of continuously subjected low-moisture-content tea leaves to higher temperatures and uneven dehydration in the later stages.

[0136] The process of achieving equilibrium moisture content and secondary light shaping after full drying is continuous with the aforementioned segmented drying. During the equilibrium moisture content process, no water is actively added to the tea leaves; instead, they are left to stand under specified temperature and relative humidity conditions to allow the internal moisture distribution of the finished product to become more even. Subsequently, a secondary light shaping is performed using a lower heat load, followed by timely cooling. This step is used to further stabilize the moisture content and leaf shape of the finished product and is not interpreted as an independent chemical passivation reaction.

[0137] Based on the data in Tables 1-4, the short-time cold-brewing feedback and the kneading-in-place de-clumping, rapid cooling, and static moisture equalization methods in this invention address two different process problems. Short-time cold-brewing feedback is used to determine whether kneading needs to continue and when to stop; de-clumping, rapid cooling, and static moisture equalization are used to control the physical state of the tea leaves before the next kneading cycle. Using only feedback detection without kneading-in-place treatment cannot prevent the tea leaves from continuing to be subjected to mechanical action under conditions of clumping, localized temperature rises, and uneven moisture distribution; using only multiple kneading cycles and kneading-in-place treatment without cold-brewing detection cannot adjust the number of kneading cycles according to the actual cold water extraction state of different batches of tea leaves.

[0138] Therefore, the technical relationship of the rolling process in this invention is manifested in that after a short period of light rolling, the tea leaves are first restored to a state suitable for further rolling and testing, and then the results of a short-term cold brew under specified conditions are used to determine whether to continue mechanical processing. This control method differs from adjusting the rolling parameters in reverse based on the results of hot brew evaluation, and also differs from simply determining the rolling endpoint according to the equipment time, pressure, and number of times.

[0139] The initial low-temperature gentle withering, light directional shaking, and moderate fixation are used to create the appropriate moisture content and softness of the leaves for subsequent shape-preserving rolling, and to control aroma formation and oxidation levels. Feedback-based shape-preserving rolling is used to limit mechanical damage while ensuring cold water extraction. Segmented low-temperature gradient drying, inter-stage moisture equalization, and post-drying balanced moisture equalization, along with a secondary light shaping, are used to complete step-by-step dehydration and leaf shape shaping. Each process is connected according to the actual extraction requirements under bottle-bottling cold-brewing conditions.

[0140] The technical effects verifiable by the above results mainly include maintaining a high proportion of intact leaves in the finished product, controlling the continuous leaching of substances during long-term cold brewing, reducing the formation of excessive bitterness, preserving the aroma of cold brewing, and minimizing changes in the color and turbidity of the brew during 12 hours of cold brewing. The above tests focus on low-temperature, long-term immersion performance and do not directly equate 12-hour cold brewing stability with the commercial shelf-life stability of packaged products. The shelf life of the finished product in actual bottled beverages is also related to sterilization methods, filling conditions, packaging barrier properties, storage temperature, and microbial control conditions.

[0141] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A refining process for low-astringency, high-aroma whole-leaf tea suitable for bottled cold brewing and preserving the complete leaf shape, characterized in that: Includes the following steps: S1. Fresh leaf selection and withering: Fresh tea leaves are selected and then subjected to low-temperature withering treatment. S2, Shaking: The withered tea leaves are lightly shaken and then left to stand. S3, Fixing: Fix the tea leaves after shaking, and then cool the tea leaves after fixing. S4. Feedback-type phased gentle kneading: After the tea leaves have cooled down, they are gently kneaded for the first time. After the first gentle kneading, the tea leaves are broken up, cooled down quickly, and allowed to stand and moisten evenly. Samples are taken from the tea leaves after they have been allowed to stand and moisten evenly. Short-term cold brewing test is conducted at a water temperature below 25℃ according to the preset tea-water mass ratio and preset steeping time to obtain the refractive index of soluble solids in the short-term cold brew liquid. The refractive index of the soluble solids is compared with the preset kneading endpoint range corresponding to the short-time cold bubble detection conditions; When the refractive index of the soluble solids is lower than the lower limit of the rolling endpoint range, the main tea leaves are lightly rolled again; after the next light rolling, the leaves are broken up, rapidly cooled, and allowed to stand and moisten evenly, and tested under the same short-time cold brew testing conditions; when the refractive index of the soluble solids reaches the rolling endpoint range, the rolling is stopped. S5. Segmented gradient drying: After the rolling is stopped, the tea leaves are sequentially subjected to initial drying, first inter-stage uniform drying, re-drying, second inter-stage uniform drying, and final drying, wherein the air inlet temperature of the initial drying, re-drying, and final drying decreases sequentially. S6. Balancing and Moisturizing, and Secondary Light Shaping: After the tea leaves are fully dried, they are balanced and moisturized, and then lightly shaped a second time. S7. Grading and screening: The tea leaves after the second light shaping are graded and screened to obtain bottled cold brew whole leaf tea.

2. The refining process for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the integrity of the leaf shape, as described in claim 1, is characterized in that: In step S1, the fresh tea leaves include one bud and one leaf and one bud and two leaves, with a mass ratio of one bud and one leaf to one bud and two leaves of 60-80:20-40. After sieving out diseased, insect-damaged, reddened, mechanically damaged, old, and coarse leaves, the fresh tea leaves are spread out in a thickness of 3-5 cm for low-temperature withering. The ambient temperature for low-temperature withering is 18-24℃, the relative humidity is 62%-70%, the air velocity is 0.2-0.5 m / s, the withering time is 6-10 hours, and the moisture content of the tea leaves at the end of withering is 64.5%-69.5%.

3. The refining process for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the complete leaf shape, as described in claim 1, is characterized in that: In step S2, the light shaking is performed 2 to 3 times, with a shaking speed of 5 to 10 r / min and a shaking time of 2 to 4 min per time. Between two adjacent shakings and after the last shaking, the plants are allowed to stand for 25 to 50 min at an ambient temperature of 20 to 24°C and a relative humidity of 65% to 75%.

4. The refining process for low-astringency, high-aroma whole-leaf tea that is suitable for bottled cold brewing and preserves the complete leaf shape, as described in claim 1, is characterized in that: In step S3, a drum-type fixing device is used for fixing. The hot zone temperature of the fixing device is 120-145℃, the fixing time is 3-5 minutes, the temperature of the tea leaves after fixing is 76-92℃, and the moisture content of the tea leaves at the end of fixing is 56%-62%. After fixing, the tea leaves are cooled with air at 18-22℃, the air velocity is 0.8-2.0m / s, and the cooling time is 4-6 minutes, so that the temperature of the tea leaves is reduced to 24-28℃.

5. The refining process for low-astringency, high-aroma whole-leaf tea adapted for bottled cold brewing and preserving the complete leaf shape, as described in claim 1, is characterized in that: In step S4, the kneading speed for each light kneading is 18-26 r / min, the average apparent pressure is 3-11 kPa, the single light kneading time is 2-5 min, and the cumulative number of light kneadings does not exceed 4 times; wherein, the average apparent pressure P is determined according to P=F / S, where F is the loading force applied by the kneading machine cover along the axial direction of the kneading drum, and S is the effective cross-sectional area of ​​the kneading drum.

6. The refining process for low-astringency, high-aroma whole-leaf tea adapted for bottled cold brewing and preserving the complete leaf shape, as described in claim 5, is characterized in that: In step S4, after each gentle kneading, the tea leaves are de-clumped at a speed of 30-50 r / min for 1 minute. After de-clumping, the leaves are rapidly cooled with air at 18-22°C at a flow rate of 0.8-1.8 m / s for 3-5 minutes, reducing the leaf temperature to 23-27°C. After rapid cooling, the leaves are left to stand and moisten evenly for 12-20 minutes in an environment of 20-25°C and 65%-75% relative humidity. Samples are then taken from the tea leaves after standing and moistening evenly for the aforementioned short-time cold brew test.

7. The refining process for low-astringency, high-aroma whole-leaf tea adapted for bottled cold brewing and preserving the complete leaf shape, as described in claim 6, is characterized in that: In step S4, take 5 parts by weight of the tea leaves that have been allowed to stand and become evenly moistened, add 100 parts by weight of water at a temperature of 20°C, stir, and let it stand and soak for 15 minutes at 20°C. After soaking, perform solid-liquid separation and measure the refractive index of the soluble solids in the obtained short-time cold-brewed liquid. The rolling endpoint range corresponding to the short-time cold-brew detection conditions is 0.35 to 0.65°Bx. When the refractive index of the soluble solids is lower than 0.35°Bx, perform another light rolling on the main tea leaves. When the refractive index of the soluble solids is 0.35 to 0.65°Bx, stop rolling.

8. The refining process for low-astringency, high-aroma whole-leaf tea adapted for bottled cold brewing and preserving the complete leaf shape, as described in claim 6, is characterized in that: In step S4, the refractive index of soluble solids is used as the main control parameter for the end point of kneading, and the conductivity increment of the short-time cold-soaking liquid relative to the water used is used as an auxiliary monitoring parameter; the conductivity increment is the difference between the conductivity of the short-time cold-soaking liquid and the conductivity of the water used, and both the conductivity of the short-time cold-soaking liquid and the conductivity of the water used are converted to 25°C. Take 4 parts by weight of tea leaves that have been allowed to stand and become evenly moistened, add 100 parts by weight of water at 15°C, and let them stand and soak for 20 minutes at 15°C. The rolling endpoint range corresponding to the short-time cold-soaking test conditions is 0.30–0.55°Bx, and the conductivity increment auxiliary monitoring range is 80–280 μS / cm. When the soluble solids refractive index is below 0.30°Bx, perform another light rolling on the main tea leaves. Stop rolling when the soluble solids refractive index is 0.30–0.55°Bx. When the soluble solids refractive index is 0.30–0.55°Bx and the conductivity increment exceeds 80–280 μS / cm, resample from different positions of the main tea leaves, mix them, and retest. Stop rolling when the soluble solids refractive index obtained from the retest is still 0.30–0.55°Bx.

9. The refining process for low-astringency, high-aroma whole-leaf tea adapted for bottled cold brewing and preserving the complete leaf shape, as described in claim 1, is characterized in that: In step S5, the initial drying process involves an air inlet temperature of 68–82℃, an air velocity of 0.8–1.8 m / s, and a processing time of 12–20 min, reducing the tea moisture content to 29.5%–36.0%. The first stage of humidity equalization is conducted at an ambient temperature of 24–30℃ and a relative humidity of 60%–70%, for a duration of 35–60 min. The re-drying process involves an air inlet temperature of 55–68℃ and an air velocity of 0.7–1.4 m / s, for a processing time of 15–25 min, reducing the tea moisture content to 15.0%–19.0%. The second stage of humidity equalization is conducted at an ambient temperature of 24–29℃ and a relative humidity of 58%–67%, for a duration of 40–70 min. Finally, the final drying process involves an air inlet temperature of 50–60℃ and an air velocity of 0.5–1.0 m / s, for a processing time of 22–38 min, reducing the tea moisture content to 5.0%–6.3%.

10. The refining process for low-astringency, high-aroma whole-leaf tea adapted for bottled cold brewing and preserving the complete leaf shape, as described in claim 9, is characterized in that: In step S6, after the tea leaves are fully dried and cooled, they are equilibrated and moistened in an environment of 22-26℃ and 55%-65% relative humidity for 2.5-4 hours, and turned over once every 50-60 minutes during the equilibration and moistening process. After the equilibration and moistening is completed, a second light shaping is performed using air intake at 48-56℃, with an air velocity of 0.5-0.9 m / s and a processing time of 12-20 minutes. After the second light shaping, the leaves are cooled to obtain a moisture content of 4.9%-6.0% for the original tea leaves.

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