Processing method for improving quality of machine-picked leaf black tea in summer and autumn and black tea

Abstract

The application discloses a processing method for improving the quality of machine-picked black tea in summer and autumn and black tea, and relates to the technical field of black tea processing. The processing method comprises the following steps: S1, dispersing and spreading machine-picked black tea fresh leaves, carrying out withering treatment, and obtaining withered leaves; S2, carrying out rolling treatment on the withered leaves, wherein the rolling treatment comprises sequentially carrying out empty rolling treatment, light rolling treatment, heavy rolling treatment and light rolling treatment, and obtaining rolled leaves; S3, carrying out fermentation treatment on the rolled leaves, and obtaining fermented leaves; and S4, sequentially carrying out initial baking treatment, airing treatment and re-baking treatment on the fermented leaves, and obtaining a black tea product. The processing method can significantly improve the tea soup color and the red and bright degree of the leaf bottom, relieve the bitterness and astringency of the tea soup, and improve the sweet fragrance and mellow sweet and moist taste of the tea soup.

Description

Technical Field

[0001] This application relates to the field of black tea processing technology, and in particular to a processing method and black tea for improving the quality of machine-harvested leaf black tea in summer and autumn. Background Technology

[0002] Based on the harvesting season of fresh leaves, black tea can be divided into two categories: spring tea and summer / autumn tea. Summer / autumn tea resources are abundant, but due to climatic conditions and raw material characteristics, the fresh leaves of summer / autumn tea tend to have higher polyphenol content, lower amino acid content, and higher cellulose content. The quality of black tea produced from summer / autumn tea is generally lower than that of spring tea, exhibiting prominent problems such as bitterness and insufficient aroma, resulting in low economic benefits. To save costs, using tea-picking machines to replace manual harvesting has become a common practice in tea-producing areas during the summer and autumn seasons. However, machine harvesting has poor selectivity and identification of fresh leaves, resulting in low uniformity of harvested leaves. The raw material often contains leaves of varying maturity, size, and stem content, which negatively impacts subsequent processing.

[0003] To address the issue of mixed fresh leaf raw materials, some companies employ fresh leaf grading equipment for screening. Currently, the most widely used fresh leaf grading equipment in the industry is the drum-type fresh leaf grading machine. This equipment uses a drum woven from bamboo strips and covered with sieve holes, allowing the fresh leaves to be roughly graded as they roll within the drum. Additionally, some companies use air separation for preliminary grading, using airflow to separate leaves of different weights. However, these grading methods have significant shortcomings in practical application: firstly, fresh leaves easily get stuck on the drum and clog the sieves, leading to a substantial decrease in grading efficiency; secondly, the intense friction and collision between the fresh leaves and the machinery during rolling results in a high damage rate, and damaged leaves are prone to scorching edges, scorched buds, and reddening during subsequent spreading and withering, affecting the quality of the finished product; and thirdly, this type of equipment offers limited grading levels and has an indistinct grading effect, making it difficult to achieve the refined grading requirements for different grades of fresh leaf raw materials.

[0004] More importantly, the fresh leaf grading process itself faces a real cost dilemma in the processing of machine-harvested black tea in summer and autumn. Since the profit margin for summer and autumn tea is limited, adding a fresh leaf grading process means additional labor costs, equipment depreciation, and energy expenditures. At the same time, problems such as screen clogging and maintenance of the grading equipment further reduce production efficiency, making fresh leaf grading often considered unprofitable in actual production. Therefore, a large number of machine-harvested fresh leaves from summer and autumn are directly fed into processing without grading. This results in inconsistent water loss rates and oxidation levels in the withering, rolling, and fermentation processes due to the varying ages and sizes of the leaves, ultimately leading to uneven fermentation. The resulting black tea generally suffers from poor appearance, dull liquor, a single aroma, and a weak flavor, hindering the improvement of the quality of machine-harvested black tea from summer and autumn. Summary of the Invention

[0005] The main purpose of this application is to propose a processing method and a type of black tea that improves the quality of machine-harvested leaves in summer and autumn, aiming to solve the problems of coarse and loose appearance, dark liquor color, weak aroma and bitter taste of machine-harvested leaves in summer and autumn prepared in the prior art.

[0006] To achieve the above objectives, this application proposes a processing method for improving the quality of machine-harvested black tea leaves from summer and autumn, comprising the following steps: S1. Spread out the freshly harvested black tea leaves and wither them to obtain withered leaves; S2. The withered leaves are kneaded, and the kneading process includes sequentially performing air kneading, light kneading, heavy kneading and light kneading to obtain kneaded leaves. S3. The kneaded leaves are fermented to obtain fermented leaves; S4. The fermented leaves are subjected to initial drying, spreading and drying, and re-drying in sequence to obtain black tea products.

[0007] In one embodiment, in step S1: The spread thickness is 6-10 cm; and / or, The withering treatment is performed at a temperature of 26-30°C; and / or, The relative humidity of the withering treatment is 60%~65%; and / or, The withering treatment takes 5 to 7 hours.

[0008] In one embodiment, in step S2: The kneading process is performed at a temperature of 23~27℃; and / or, The kneading process is performed for 70-80 minutes; and / or, The kneading speed is 40~50 r / min.

[0009] In one embodiment, the kneading time is 20-80 minutes; and / or, The kneading process is performed for 5-15 minutes; and / or, The kneading process takes 10-20 minutes.

[0010] In one embodiment, the kneading time is 20-60 minutes.

[0011] In one embodiment, the kneading time is 20-40 minutes.

[0012] In one embodiment, in step S3: The fermentation treatment is performed at a temperature of 30-35°C; and / or, The relative humidity of the fermentation process is 90%~95%; and / or, The fermentation treatment time is 3-5 hours; and / or, The fermentation process involves piling the kneaded leaves to a height of 8-12 cm and then fermenting them, turning them over once every hour during the fermentation process.

[0013] In one embodiment, in step S4: The initial drying temperature is 105~115℃; and / or, The initial drying treatment time is 20-30 minutes; and / or, The initial drying treatment includes spreading the fermented leaves to a depth of 2-3 cm, drying until the moisture content is 25%-30%, and then stopping the drying process; and / or, The spreading thickness for the drying process is 3-5 cm; and / or, The drying time is 25-30 minutes; and / or, The temperature for the re-drying process is 75~80℃; and / or, The re-drying process takes 80-100 minutes; and / or, The re-drying process includes spreading the leaves, which have been air-dried, to a depth of 2-4 cm, drying them until the moisture content is 5%-6%, and then stopping the drying process.

[0014] This application also provides a black tea, which is obtained by the aforementioned processing method for improving the quality of machine-harvested black tea leaves in summer and autumn.

[0015] In one embodiment, the dry tea leaves of the black tea have a density of 1.2 to 1.6; and / or, The dry bulk density of the black tea is 75~105g / L.

[0016] The technical solution of this application introduces a "dry rolling" process into the traditional rolling process of black tea. By performing dry rolling at the initial stage of rolling, the leaves are allowed to unfold and experience light friction before being subjected to heavy pressure, promoting leaf softening and cell wall relaxation. This improves the uniformity of cell breakage in leaves of different tenderness and the efficiency of exudation of internal substances. This treatment helps to enhance enzymatic reaction activity, promote the accumulation of soluble sugars in tea leaves, and facilitate the appropriate conversion of flavonoids and catechins, thus improving their oxidation rate and conversion direction in the subsequent fermentation stage. As a result, the tea leaves are tightly rolled, the redness of the tea soup is significantly enhanced, the aroma is sweet, and the taste is mellow and sweet. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 These are images of the appearance of the black tea samples prepared in Examples 1-4 and Comparative Example 1 of this application; Figure 2 The graph shows the test results of the dry tea compactness of the black tea samples prepared in Examples 1-4 and Comparative Example 1 of this application. Figure 3 The graph shows the bulk density test results of the black tea samples prepared in Examples 1-4 and Comparative Example 1 of this application; Figure 4 The graph shows the test results of soluble sugar content in tea infusions prepared from black tea samples obtained in Examples 1-4 and Comparative Example 1 of this application. Figure 5 The graph shows the test results of the total flavonoid content of the tea infusions prepared from the black tea samples obtained in Examples 1-4 and Comparative Example 1 of this application; Figure 6 The graph shows the test results of the non-ester catechin, ester catechin, and total catechin content of the tea infusions prepared from the black tea samples prepared in Examples 1-4 and Comparative Example 1 of this application. Figure 7 The graph shows the test results of volatile aroma components in tea soup prepared from the black tea samples prepared in Examples 1-4 and Comparative Example 1 of this application.

[0019] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Based on the harvesting season of fresh leaves, black tea can be divided into two categories: spring tea and summer / autumn tea. Summer / autumn tea resources are abundant, but due to the influence of climate conditions and raw material characteristics, its processed quality is generally lower than that of spring tea. To save costs, using tea-picking machines to replace manual harvesting has become a common practice in tea-producing areas during the summer and autumn seasons. However, machine harvesting has poor selectivity and identification of fresh leaves, resulting in low uniformity of harvested leaves. The raw material often contains leaves of varying maturity, size, and stem content, which negatively impacts subsequent processing.

[0022] To address the issue of mixed fresh tea leaves, some companies employ fresh leaf grading equipment for screening. However, this method still has significant shortcomings in practical application. Firstly, fresh leaves easily get stuck on the drums, clogging the screens and drastically reducing grading efficiency. Secondly, the intense friction and collisions between the leaves and the machinery during drum rotation result in high damage rates. Damaged leaves are prone to scorching edges, bud burn, and reddening during subsequent spreading and withering, leading to premature leakage of cell sap and accelerated oxidation of polyphenols. This, in turn, affects the balance of fermentation and the normal transformation of aroma compounds, ultimately impacting the quality of the finished product. More importantly, the fresh leaf grading process itself faces a real cost dilemma in summer and autumn machine-harvested black tea processing. Given the limited profit margins of summer and autumn teas, adding a fresh leaf grading step means additional labor costs, equipment depreciation, and energy expenditure. Furthermore, the screen clogging, cleaning, and maintenance issues of the grading equipment further reduce production efficiency, making fresh leaf grading often considered unprofitable in actual production. Therefore, a large number of machine-harvested fresh leaves in summer and autumn are directly put into processing without grading. This results in inconsistent water loss rates and oxidation levels of leaves of varying ages and sizes during withering, rolling, and fermentation, ultimately leading to uneven fermentation. The resulting black tea generally has quality problems such as coarse and loose appearance, dull liquor color, single aroma, and thin taste, which restricts the improvement of the quality of machine-harvested black tea in summer and autumn.

[0023] In summary, in existing summer and autumn machine-harvested black tea processing technologies, the fresh leaf grading process is often omitted in actual production due to high costs, poor equipment grading efficiency, and high damage rates. This results in poor raw material uniformity throughout the entire processing, and uneven fermentation has become a long-standing technical challenge for the industry. Therefore, there is an urgent need for a technical solution that does not rely on fresh leaf grading equipment and directly addresses the problems of uneven fermentation and low quality in summer and autumn machine-harvested black tea at the processing technology level.

[0024] In view of this, this application proposes a processing method to improve the quality of machine-harvested black tea leaves in summer and autumn, comprising the following steps: S1, spreading out fresh machine-harvested black tea leaves and withering them to obtain withered leaves; S2, rolling the withered leaves, wherein the rolling process includes sequentially performing air rolling, light rolling, heavy rolling, and light rolling to obtain rolled leaves; S3, fermenting the rolled leaves to obtain fermented leaves; S4, sequentially performing initial drying, withering, and re-drying on the fermented leaves to obtain the black tea product.

[0025] In this application, the "empty rolling" process refers to allowing the tea leaves to roll and rub freely within the rolling machine drum without applying additional pressure. This process can initially shape the tea leaves, promote the convergence of physiological states of cells in different leaf positions, improve the uniformity of damage during subsequent pressure rolling, facilitate similar levels of enzymatic oxidation during fermentation, reduce quality differences within the same batch of tea, produce tighter tea leaves, enhance the mellowness and richness of the tea soup, promote the development of floral aromas, and improve the overall quality and sensory characteristics of the tea. Rolling is an essential step in black tea processing. Using an appropriate amount of empty rolling time to control the uniformity of black tea fermentation has the advantages of conveniently and cost-effectively improving the quality of summer and autumn black tea. Taking the 6CR-100 rolling machine as an example, light rolling means that after the rolling drum lid contacts the leaf surface, it is pressed down 4-6 cm, the rolling drum lid position is fixed, and rolling begins. Taking the 6CR-100 rolling machine as an example, heavy rolling means that after the rolling drum lid contacts the leaf surface, it is pressed down 10-15 cm, then rotated 4-6 times, the rolling drum lid position is fixed, and rolling begins.

[0026] In this application, a "dry rolling" process is introduced into the traditional rolling process of black tea. By performing dry rolling at the initial stage of rolling, the leaves are allowed to unfurl and experience light friction before being subjected to heavy pressure, promoting leaf softening and cell wall relaxation. This improves the uniformity of cell breakage and the efficiency of infusion of internal substances. This treatment also helps enhance enzymatic activity, promotes the accumulation of soluble sugars in the tea leaves, and facilitates the appropriate conversion of flavonoids and catechins, improving their oxidation rate and conversion direction in the subsequent fermentation stage. Consequently, the brightness and redness of the tea liquor are significantly enhanced.

[0027] In some embodiments, in step S1: the thickness of the spread leaves is 6-10 cm; and / or, the temperature of the withering treatment is 26-30°C; and / or, the relative humidity of the withering treatment is 60%-65%; and / or, the withering treatment time is 5-7 hours. Simultaneously controlling the thickness of the spread leaves and the temperature, humidity, and time of the withering treatment within the above ranges ensures effective air penetration through the leaf layer, preventing excessive thickness from hindering internal heat dissipation and moisture dissipation, resulting in a "stale" taste or uneven withering. It also prevents excessive thinness from causing rapid water loss, resulting in "dry edges" or scorched tips. Furthermore, it ensures that the leaf moisture content is reduced to a level that is soft like cotton, with tender stems that can be bent without breaking, and that when squeezed into a ball, it springs back easily when released. This provides the optimal physical basis for the subsequent rolling in step S2, ensuring that the leaves are neither easily broken nor difficult to form into strips.

[0028] The leaves can be rolled using a rolling machine. In some embodiments, in step S2: the rolling temperature is 23~27℃; and / or, the rolling time is 70~80min; and / or, the rolling speed is 40~50r / min. Simultaneously controlling the rolling temperature, time, and speed within the above range ensures that the tea leaves are fully tumbled, folded, and compressed within the rolling machine drum, causing appropriate cell wall rupture, and allowing tea juice to evenly overflow and adhere to the leaf surface, providing sufficient substrate for fermentation. This also minimizes broken tea leaves and excessively rapid reddening at high temperatures, preventing the black tea from becoming thin, sour, or even clumping.

[0029] In some embodiments, the air-rolling treatment lasts for 20-80 minutes; and / or, the light-rolling treatment lasts for 5-15 minutes; and / or, the heavy-rolling treatment lasts for 10-20 minutes. The main functions of air-rolling are to remove the grassy smell, raise the temperature, and initially shape the leaves, ensuring that the leaves reach the optimal state of consistent tea strip orientation and slight damage before entering the pressure stage. In the first light-rolling treatment, pressure is gradually applied to allow the leaves to adapt to mechanical force, initially damaging some cells and avoiding direct heavy-rolling that could cause the leaves to break instantly or form "dead knots." The heavy-rolling process involves continuous high-pressure rolling, allowing tea polyphenols and polyphenol oxidase to fully contact each other, resulting in a large amount of tea juice overflowing and adhering to the leaf surface. After the heavy-rolling process tightens the leaves, a second light-rolling process "loosens" and "tidies up" the leaves, breaking up any clumps that may have formed during the heavy-rolling process, making the leaves more round, straight, and uniform, and removing excess tea juice from the surface to prevent clumping and blackening during drying. At the same time, controlling the time of air kneading, light kneading, and heavy kneading within the above range avoids tea leaf breakage caused by "kneading all the way through" or "kneading for too long". This results in tightly rolled tea leaves with a significantly reduced content of broken tea (usually <3%), greatly increasing the yield of premium and first-grade tea.

[0030] For example, the time for kneading without kneading can be any range consisting of two values: 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or more. The time for kneading lightly can be any range consisting of two values: 5 min, 10 min, 15 min, or more; the time for kneading heavily can be any range consisting of two values: 10 min, 15 min, 20 min, or more.

[0031] In some embodiments, the air-rolling process is performed for 20-60 minutes. When the air-rolling time is 20-60 minutes, the sweetness and bitterness of the black tea product are increased, and the aroma is sweet. This process can significantly promote the formation of volatile floral and fruity aroma compounds such as linalool, leaf alcohol, methyl salicylate, and methyl heptenone, transforming the aroma from a single and thin fragrance to a complex sweet floral aroma. This effectively solves the problem of the single and weak aroma of traditional machine-harvested black tea.

[0032] In some embodiments, the kneading process is performed for 20 to 40 minutes. When the kneading time is 20 to 40 minutes, the black tea product has a better degree of compactness.

[0033] The optimal kneading time is 40 minutes. At this time, the tea soup is bright red, has a good aroma, a mellow and sweet taste, and the tea leaves are soft and bright red. This improves the overall sensory quality and product yield of the tea, and ultimately increases the utilization rate of fresh tea leaf resources in summer and autumn. It also provides a new technical solution for the quality improvement and industrial processing of summer and autumn black tea.

[0034] In some embodiments, in step S3: the fermentation temperature is 30-35°C; and / or the relative humidity of the fermentation is 90%-95%; and / or the fermentation time is 3-5 hours; and / or the fermentation includes piling the rolled leaves to 8-12 cm for fermentation, turning them over once every hour during the fermentation process. Simultaneously controlling the fermentation time, temperature, relative humidity, and frequency within the above ranges ensures good activity of polyphenol oxidase and peroxidase during the black tea fermentation process, resulting in the fastest and most controllable oxidation and polymerization rate of tea polyphenols. This allows for the rapid conversion of catechins into theaflavins and thearubigins, ensuring a bright red tea liquor with a sweet and mellow taste.

[0035] In some embodiments, in step S4: the temperature of the initial drying treatment is 105~115℃; and / or, the time of the initial drying treatment is 20~30min; and / or, the initial drying treatment includes spreading the fermented leaves to 2~3cm, drying until the moisture content is 25%~30%, and stopping the drying; and / or, the thickness of the spreading treatment is 3~5cm; and / or, the time of the spreading treatment is 25~30min; and / or, the temperature of the re-drying treatment is 75~80℃; and / or, the time of the re-drying treatment is 80~100min; and / or, the re-drying treatment includes spreading the leaves after the spreading treatment to 2~4cm, drying until the moisture content is 5%~6%, and stopping the drying. The initial drying conditions, within the aforementioned range, can ensure rapid deactivation of enzyme activity, lock in fermentation quality, and precisely target the optimal ratio of theaflavins and thearubigins formed during the S3 fermentation stage, ensuring a bright red tea liquor and a sweet and mellow taste. After the initial drying, the leaf surface is dry while the interior is moist. Controlling the withering conditions within the aforementioned range allows the internal moisture to diffuse to the surface using the effect of heat and moisture, i.e., "re-moistening," balancing the moisture content inside and outside the leaves. This also eliminates the thermal stress generated during the initial drying, preventing the leaves from breaking due to excessive temperature differences during the re-drying process, thus creating a uniform moisture base for the re-drying. Controlling the re-drying conditions within the aforementioned range can significantly reduce the breakage rate, resulting in tightly rolled and intact tea leaves in the finished product.

[0036] This application also provides a black tea, which is processed using the aforementioned method for improving the quality of machine-harvested black tea leaves from summer and autumn. Therefore, this black tea possesses all the beneficial effects of the processing method for improving the quality of machine-harvested black tea leaves from summer and autumn, which will not be elaborated upon here.

[0037] In some embodiments, the fineness of the black tea is 1.2 to 1.6; and / or, the bulk density of the black tea is 75 to 105 g / L. When the depth of the wrinkles and the bulk density of the dried black tea are controlled within the above ranges, the quality of the black tea product is better.

[0038] The technical solutions of this application will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain this application and are not intended to limit this application.

[0039] Example 1 A processing method for improving the quality of machine-harvested black tea leaves from summer and autumn includes the following steps: (1) Selection of tea leaves: The tea leaves are harvested in summer and autumn, and the machine-harvested fresh leaves of Fuding Da Bai tea tree are used as tea leaves (the grades range from one bud and one leaf to one bud and five leaves, mixed with paired leaves, fragmented leaves and single leaves).

[0040] (2) Withering: Spread the harvested fresh leaves evenly with a thickness of 8cm, with a withering temperature of 28℃, a relative humidity of 63%, and a withering time of 6h.

[0041] (3) Rolling: The withered leaves are placed in a rolling machine for rolling. The rolling temperature is 25℃, the rolling time is 75min, and the speed of the rolling drum is 45r / min. The rolling process includes 20min of empty rolling, 10min of light rolling, 15min of heavy rolling, and 10min of light rolling to obtain rolled leaves.

[0042] (4) Fermentation: The thickness of the rolled leaves is 10cm. The rolled leaves are fermented at 35℃ and 95% relative humidity for 4 hours. During fermentation, the leaves are turned over once every hour to obtain fermented leaves.

[0043] (5) Initial drying: Place the fermented leaves on a tea drying machine at 110℃ for 20 minutes, spread them out to a thickness of 2cm, until the tea leaves are slightly prickly to the touch and the moisture content is 28%, then stop drying to obtain the initial dried leaves.

[0044] (6) Cooling: Spread the initially dried leaves to a thickness of 3cm and let them dry for 30 minutes to regain moisture.

[0045] (7) Re-drying: Place the initially dried leaves in a roasting and aroma-enhancing machine for re-drying. Set the temperature to 80℃, the drying time to 90min, and the thickness of the leaves to 4cm. Stop drying when the moisture content is 6% to obtain the black tea product.

[0046] Example 2 The difference between Example 2 and Example 1 is that: The kneading time is 40 minutes.

[0047] Example 3 The difference between Example 3 and Example 1 is that: The kneading time is 60 minutes.

[0048] Example 4 The difference between Example 4 and Example 1 is that: The kneading time is 80 minutes.

[0049] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that: The empty kneading time is 0 minutes, meaning no empty kneading is performed.

[0050] Performance testing 1. Sensory evaluation Sensory evaluation was conducted on the black tea products prepared in Examples 1-4 and Comparative Example 1 according to the national standard GB / T 23776-2018 "Sensory Evaluation Method for Tea". The tea infusion preparation method was as follows: 3g of black tea product was put into a cylindrical evaluation cup and brewed with 150mL of boiling water at 100℃ for 5min to obtain the tea infusion. The results are shown in Table 1.

[0051] Table 1 Comparison of Sensory Evaluation Results

[0052] Table 1 shows that the sensory evaluation scores of the samples treated with air rolling were significantly higher than those of the samples without air rolling. In Examples 1-4, when the air rolling time was controlled between 20 and 80 minutes, the tea liquor, aroma, taste, and infused leaves of the black tea samples were all better. When the air rolling time was between 20 and 40 minutes, the appearance of the black tea samples was better. Overall, the sample in Example 2 had a tightly rolled appearance, a bright orange-red liquor, a sweet aroma, and a sweet taste, resulting in the best sensory evaluation.

[0053] 2. The tightness and density of the dry tea leaves The dry tea wrinkle depth and bulk density of the black tea samples prepared in Examples 1-4 and Comparative Example 1 were tested. The specific test methods are as follows: (1) Tightness of dry tea: The thickness and width of the widest part of the tea strips were measured using vernier calipers and a micrometer. Tightness was defined as the value obtained by dividing the width of the tea strip by the thickness. The smaller the value, the tighter the tea strip. The dry tea photos and calculation diagrams are shown below. Figure 1 As shown, the results of the fineness are as follows: Figure 2 As shown; (2) Bulk density: The bulk density of tea was determined using the volumetric method. The specific steps were as follows: Weigh the black tea sample and fill it into a 1000 mL graduated cylinder using the natural filling method. Allow the sample to fall naturally into the container, scrape off any excess tea leaves on the surface until it is flush with the rim of the container, and record the net weight of the tea leaves in the container. The bulk density was calculated using the following formula: Bulk density (g / L) = Net weight of tea leaves (g) / 1000 (mL) × 1000. Each sample was measured three times, and the arithmetic mean was taken as the bulk density value of the sample. The results are as follows: Figure 3 As shown.

[0054] like Figure 1 and Figure 2 As shown, in terms of the tightness of the dried tea leaves, Example 2 had the lowest tightness value, approximately 1.3, significantly lower than Comparative Example 1, Example 1, Example 3, and Example 4, indicating that the tea leaves of Example 2 were the tightest. The increased tightness indicates that the degree of cell dehydration and shrinkage in the leaves was more balanced during processing. The addition of the air-rolling process and the control of the air-rolling time allow the cell walls of the leaves to relax appropriately and release stress fully before being subjected to strong rolling pressure, indicating that the leaf tissue structure maintains good elasticity, which is conducive to improving the tightness of the dried tea leaves and enhancing the appearance quality.

[0055] like Figure 3 As shown, Example 2 also performed best in terms of bulk density, averaging approximately 99 g / L, significantly higher than other examples and comparative examples. The higher bulk density reflects the tightly rolled, dense structure and low gas content of the tea leaves, indicating good shaping during rolling and drying. The increased bulk density not only helps improve the appearance and packaging density of the dried tea, but also demonstrates that air rolling and its time control effectively prevent excessive leaf breakage and loosening, thereby improving the overall uniformity of the finished tea.

[0056] 3. Flavor Quality Analysis The black tea samples obtained in Examples 1-4 and Comparative Example 1 were used to prepare tea infusions according to GB / T 23776-2018 "Sensory Evaluation Methods for Tea". The taste and quality of each group of tea infusions were then tested. The specific test methods are as follows: (1) Soluble sugar content test: The soluble sugar content in tea infusion was determined by the anthrone-sulfuric acid colorimetric method. The specific steps were as follows: accurately pipette 1 ml of tea infusion sample, add 1 ml of water and 0.5 ml of anthrone reagent, mix well, slowly add 5 ml of concentrated sulfuric acid, shake well, react in a boiling water bath for 10 min, and then rapidly cool. Measure the absorbance at a wavelength of 620 nm. A standard curve was plotted using glucose as the standard, and the soluble sugar content in the sample was calculated based on the standard curve. The results were expressed as glucose equivalents. Figure 4 As shown; (2) Total flavonoid content test: Take 1 mL of tea infusion, add 0.5 mL of 5% sodium nitrite, shake well, and let stand for 6 min; then add 0.5 mL of 10% aluminum nitrate, shake well, and let stand for 6 min; finally add 4 mL of 4% sodium hydroxide, shake well, and let stand for 15 min to obtain a red-orange colorimetric solution; accurately transfer 200 μL of the red-orange colorimetric solution into a 96-well plate, set up 3 replicates, and measure the absorbance at a wavelength of 510 nm using an enzyme-linked immunosorbent assay (ELISA) reader. A standard curve was plotted using rutin as a standard, and the total flavonoid content in the sample was calculated based on the standard curve. The results are expressed as rutin equivalents. Figure 5 As shown; (3) Testing of non-esterified catechins, esterified catechins and total catechins: The content of tea polyphenols and catechins in tea was determined by appropriate modifications to GB / T 8313-2018 "Determination Method of Tea Polyphenols and Catechins in Tea", using high performance liquid chromatography (HPLC). The specific steps were as follows: the tea infusion was filtered through a 0.22 μm membrane and then injected for analysis. The chromatographic column was a C18 column. Mobile phase A was acetonitrile:acetic acid:ultrapure water = 6:1:193, mobile phase B was acetonitrile:acetic acid:ultrapure water = 6:1:139, and the detection wavelength was 278 nm. Based on the chromatographic peak areas of each catechin component, the contents of epicatechin (EC), catechin (C), epigallocatechin (EGC), gallocatechin (GC), epicatechin gallate (ECG), catechin gallate (CG), epigallocatechin gallate (EGCG), and gallocatechin gallate (GCG) were quantitatively determined using the external standard method. The contents of non-esterified catechins were the sum of the contents of EC, C, EGC, and GC; the contents of esterified catechins were the sum of the contents of ECG, CG, EGCG, and GCG; and the total catechin content was the sum of the contents of the eight catechin monomers. Results are as follows: Figure 6 As shown.

[0057] Analysis of flavor and quality components showed that the soluble sugar content in the tea soup increased significantly after the air-rolling process. Figure 4 The soluble sugar content varied significantly among the different treatment groups. Comparative Example 1 had the lowest soluble sugar content, approximately 60 mg / g; Examples 2 and 1 showed significantly higher levels, reaching approximately 70 mg / g and 72 mg / g respectively, with Example 2 showing the highest value and exhibiting a significant difference from the other groups. The soluble sugar contents of Examples 3 and 4 were approximately 68 mg / g and 62 mg / g, respectively. These results indicate that Example 2 of this application can effectively increase the accumulation of soluble sugars in tea samples, thereby improving the sweetness and overall flavor quality of the tea.

[0058] Reference Figure 5The total flavonoid content varied significantly among the treatment groups. Comparative Example 1 had the highest total flavonoid content, approximately 82 mg / g; Example 1 had approximately 75 mg / g; Example 2 had approximately 67 mg / g, slightly lower than the other groups; and Examples 3 and 4 had approximately 72 mg / g and 70 mg / g, respectively. It should be noted that flavonoids are closely related to the bitterness and astringency of tea; the higher the content, the more pronounced the bitterness and astringency. Therefore, Example 2 can maintain a relatively high content of quality components while moderately reducing the total flavonoid level, thereby effectively weakening the bitterness and astringency of the tea sample and improving the overall harmony of the tea's flavor.

[0059] Reference Figure 6 The contents of non-esterified catechins, esterified catechins, and total catechins showed a gradual decreasing trend in each treatment group. Comparative Example 1 had the highest total catechin content, approximately 149 mg / g. With prolonged kneading time, the total catechin content in Examples 1 and 2 decreased to approximately 136 mg / g and approximately 111 mg / g, respectively; Examples 3 and 4 further decreased to approximately 97 mg / g and approximately 85 mg / g. The trends in the changes of non-esterified and esterified catechins were consistent with the total content. These results indicate that Examples 1-4 of this application can effectively regulate the content of catechins, preventing excessive accumulation, and helping to optimize the proportion of phenolic substances in tea samples, thereby improving the smoothness and harmony of the tea flavor.

[0060] 4. Aroma component analysis The black tea samples obtained in Examples 1-4 and Comparative Example 1 were prepared into tea infusions according to GB / T 23776-2018 "Sensory Evaluation Methods for Tea". The volatile aroma components of each group of tea infusions were then tested. The testing method was as follows: headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was used to extract and analyze the volatile aroma components in the tea infusions. The specific steps were as follows: Accurately measure 10 mL of tea infusion sample and place it in a headspace vial. Add 10 ppm of internal standard ethyl decanoate and 2 g of sodium chloride. After sealing, equilibrate in a 50 °C water bath and perform headspace adsorption for 60 min. Then, insert the extraction head into the gas chromatograph injection port for desorption and injection. GC conditions: SH-Rxi-5Sil-MS capillary column (30m × 0.25mm × 0.25μm); high-purity helium (purity ≥99.999%) as carrier gas, flow rate 1.0mL / min, splitless injection mode. Temperature program conditions: initial temperature 50℃, hold for 5 min, increase to 230℃ at a rate of 3℃ / min, then increase to 250℃ at a rate of 10℃ / min and hold for 3 min. MS conditions: Ionization method was electron impact ionization (EI), ionization energy was 70 eV, ion source temperature was 250℃, mass scan range was 40~400 m / z, and data was acquired in full scan mode. Qualitative and quantitative methods: Mass spectra of each component obtained by GC-MS analysis were compared with the standard mass spectrometry library of the National Institute of Standards and Technology (NIST), and combined with the analysis of n-alkanes (C6~C4). 40 The retention indices (RIs) of each component were calculated based on the retention times under the same chromatographic conditions, and compared with the retention indices reported in the literature for confirmation, thus qualitatively identifying the volatile aroma components. The ethyl decanoate internal standard method was used for relative quantification of each aroma component, and its relative content was calculated based on the ratio of the peak area of ​​each component to the peak area of ​​the internal standard.

[0061] like Figure 7 As shown, there were significant differences in the content of various volatile aroma components among different treatment groups. The content of key aroma components in Examples 1-4 was higher than that in Comparative Example 1, which did not undergo air rolling treatment. Among them, the content of linalool, a key substance that imparts sweet and floral aroma characteristics to black tea, was increased by approximately 116% to 190% in the examples compared to Comparative Example 1, with the most significant increase in Example 1; the content of trans-2,4-decadienal, which provides fruity sweetness, was increased by approximately 108% to 134%; and the content of benzyl alcohol, which has a floral aroma, was increased by approximately 105% to 203%. The above results indicate that the air rolling process can effectively promote the transformation and accumulation of sweet and floral aroma precursors in machine-harvested black tea in summer and autumn.

[0062] It is worth noting that the content of trans-linalool oxide (furan), which has floral aroma characteristics, was significantly higher in all examples than in Comparative Example 1, with the content in Example 1 being more than four times that of Comparative Example 1. Based on the sensory evaluation results, the superior quality performance of Example 1, characterized by "increased sweetness and a slight floral aroma," is closely related to its high content of linalool and trans-linalool oxide (furan). In Examples 2-4, the content of this oxide was relatively low, and the sensory performance was predominantly "sweet," with less pronounced floral characteristics.

[0063] Comprehensive analysis results show that, by optimizing processing conditions, Examples 1-4 of this application promoted the activity of fatty acid oxidation and terpene metabolic pathways, enhanced the conversion efficiency of aroma precursors, and thus increased the accumulation levels of various key volatile components. The air-rolling process synergistically increases the content of sweet / floral aroma contributors such as linalool, trans-2,4-decadienal, and benzyl alcohol, and promotes the moderate oxidation of linalool to trans-linalool oxides (furans) with floral aroma characteristics, thereby effectively improving the defects of single aroma and insufficient sweetness in machine-harvested black tea from summer and autumn.

[0064] In summary, this application provides a process to improve the appearance, dark color, weak aroma, and bitter taste of machine-harvested black tea leaves from summer and autumn, resulting in tightly rolled leaves, a sweet aroma, and a mellow, sweet flavor. The implementation of this invention eliminates the need for sorting fresh leaves when producing machine-harvested black tea leaves from summer and autumn, achieving sensory qualities such as a bright orange-red liquor, a pronounced sweet aroma, and a sweet and mellow taste. This overcomes the inherent defects in color, aroma, and flavor of traditional machine-harvested black tea from summer and autumn, and enhances the utilization value of fresh tea leaf resources from summer and autumn.

[0065] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the patent protection scope of this application.

Claims

1. A processing method for improving the quality of summer-autumn plucked leaf black tea, characterized in that, Includes the following steps: S1. Spread out the freshly harvested black tea leaves and wither them to obtain withered leaves; S2. The withered leaves are kneaded, and the kneading process includes sequentially performing air kneading, light kneading, heavy kneading and light kneading to obtain kneaded leaves. S3. The kneaded leaves are fermented to obtain fermented leaves; S4. The fermented leaves are subjected to initial drying, spreading and drying, and re-drying in sequence to obtain black tea products.

2. The processing method of claim 1, wherein the processing method is characterized by, In step S1: The spread thickness is 6-10 cm; and / or, The withering treatment is performed at a temperature of 26-30°C; and / or, The relative humidity of the withering treatment is 60%~65%; and / or, The withering treatment takes 5 to 7 hours.

3. The processing method of claim 1, wherein the processing method is characterized by, In step S2: The kneading process is performed at a temperature of 23~27℃; and / or, The kneading process is performed for 70-80 minutes; and / or, The kneading speed is 40~50 r / min.

4. The processing method of claim 1, wherein the processing method is characterized by, The kneading time is 20-80 minutes; and / or, The kneading process is performed for 5-15 minutes; and / or, The kneading process takes 10-20 minutes.

5. The method of processing as claimed in claim 1, wherein the processing method is characterized by, The kneading process takes 20-60 minutes.

6. The method of processing as claimed in claim 1, wherein the processing method is characterized by, The kneading process takes 20-40 minutes.

7. The method of processing as claimed in claim 1, wherein the processing method is characterized by, In step S3: The fermentation treatment is performed at a temperature of 30-35°C; and / or, The relative humidity of the fermentation process is 90%~95%; and / or, The fermentation treatment time is 3-5 hours; and / or, The fermentation process involves piling the kneaded leaves to a height of 8-12 cm and then fermenting them, turning them over once every hour during the fermentation process.

8. The processing method of claim 1, wherein the processing method is characterized by, In step S4: The initial drying temperature is 105~115℃; and / or, The initial drying treatment time is 20-30 minutes; and / or, The initial drying treatment includes spreading the fermented leaves to a depth of 2-3 cm, drying until the moisture content is 25%-30%, and then stopping the drying process; and / or, The spreading thickness for the drying process is 3-5 cm; and / or, The drying time is 25-30 minutes; and / or, The temperature for the re-drying process is 75~80℃; and / or, The re-drying process takes 80-100 minutes; and / or, The re-drying process includes spreading the leaves, which have been air-dried, to a depth of 2-4 cm, drying them until the moisture content is 5%-6%, and then stopping the drying process.

9. A black tea, characterized by, The black tea is obtained by the processing method for improving the quality of machine-harvested black tea leaves in summer and autumn as described in any one of claims 1 to 8.

10. The black tea according to claim 9, wherein The dry tea leaves of the black tea have a density of 1.2 to 1.6; and / or, The dry bulk density of the black tea is 75~105g / L.

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