Preparation process and product of cocoa-flavored black tea

Abstract

This invention relates to the field of tea processing technology, specifically disclosing a preparation process and product of cocoa-flavored black tea. The preparation process comprises, in sequence, a first withering, shaking, a second withering, rolling, fermentation, drying, and roasting. This invention effectively utilizes fresh tea leaves from tea trees, a mixture of old and young leaves harvested by tea-picking machines, to produce a black tea with excellent flavor and taste, a rich cocoa aroma, and consistent quality. The preparation process of this invention requires less manual labor and is easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, specifically a preparation process and product of cocoa-flavored black tea. Background Technology

[0002] Black tea belongs to the six major tea categories in China and is one of my country's most important export commodities, ranking among the top in global tea exports and enjoying widespread consumer popularity. With the development of my country's tea industry, the development and utilization of high-quality tea is receiving increasing attention. High-quality tea is typically made from tender leaves or buds because as leaves age, the levels of water-soluble functional components and flavor compounds such as tea polyphenols and catechins gradually decrease. The number of tender leaves on a tea tree is limited; after harvesting one bud and one leaf, or one bud and two leaves, a large number of mature leaves remain. How to utilize these mature leaves to produce high-quality tea has become a pressing issue that needs to be addressed.

[0003] Traditional black tea is typically made from tender leaves of the tea plant, typically one bud and one leaf, one bud and two leaves, or one bud and three leaves. The process involves withering, rolling, fermentation, baking, and re-baking. The reason for using tender leaves is that black tea is a fermented tea, and the fermentation process involves the oxidation of tea polyphenols. However, the older the tea leaves, the lower the polyphenol content, which is detrimental to fermentation and the formation of flavor compounds such as theaflavins, thearubigins, and theabrownins. Therefore, if more mature leaves, such as one bud and four or five leaves, are used, the resulting black tea will have a bitter and astringent taste, lower freshness, and a weak, dull aroma.

[0004] A tea-harvesting machine is a machine used to harvest tea leaves from the top of tea trees. Based on the harvesting method, they are divided into selective and non-selective tea-harvesting machines. Selective tea-harvesting machines pick only the tender leaves while preserving the older leaves by breaking or rubbing them. However, due to their low production efficiency and high requirements for tea garden operating conditions, selective tea-harvesting machines have not been widely adopted. Most tea gardens still use manual harvesting or non-selective tea-harvesting machines. Manual harvesting can collect fresh, tender leaves, but it is time-consuming and labor-intensive. While non-selective tea-harvesting machines can efficiently collect tea leaves, they cannot select the leaves, resulting in a mixture of old and tender leaves of varying quality and a lower overall tea quality. Therefore, non-selective tea-harvesting machines are currently generally used for producing low- to mid-range teas, while high-end teas typically still rely on manual harvesting.

[0005] In summary, the present invention aims to overcome the above difficulties and prepare a high-end black tea with excellent flavor and stable quality by using a mixture of old and young leaves harvested by a non-selective tea-harvesting machine. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a preparation process and product of cocoa-flavored black tea, so as to at least achieve that the preparation process is easy to industrialize and low in cost, and the black tea produced has a bright red color and a rich cocoa aroma after brewing.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A process for preparing cocoa-flavored black tea includes the following steps:

[0009] S1) First withering: Take a mixture of old and young leaves and lay them flat in the withering trough for withering, so that the leaves lose water to a moisture content of 68-70%;

[0010] S2) Shaking: Put the tea leaves after the first withering into a shaking machine for shaking;

[0011] S3) Second withering: Spread the tea leaves obtained after shaking evenly in the withering trough, so that the leaves lose water to a moisture content of 65-68%;

[0012] S4) Rolling: Roll the tea leaves after the second withering until the cell breakage rate is 70-73%;

[0013] S5) Fermentation: Ferment the kneaded tea leaves for 3-4 hours under conditions of 90-95% humidity and 28-30℃.

[0014] S6) Drying: Dry the fermented tea leaves at 80-100℃ until the moisture content is 25-35%;

[0015] S7) Stir-frying: Stir-fry the dried tea leaves until the moisture content is 4-6%.

[0016] Furthermore, in step S1, the mixed old and young leaves are tea leaves harvested using a non-selective tea-harvesting machine.

[0017] Furthermore, in step S7, the frying is carried out in a drum-type tea frying machine, and the drum of the drum-type tea frying machine rotates during frying.

[0018] Furthermore, the roasting process is divided into two stages. In the first stage, under intermittent blowing conditions, the temperature is controlled at 80-90℃ and roasted until the moisture content is 15-20%. In the second stage, under non-blowing conditions, the temperature is controlled at 90-150℃ and roasted until the moisture content is 4-6%.

[0019] It is worth noting that the characteristic flavor and aroma of the cocoa-flavored black tea prepared by this invention are mainly formed during the drying stage, with the second stage of roasting being particularly crucial. In the early stages of drying, the chemical components of tea undergo the Maillard reaction, where carbonyl compounds (such as sugars) and amino compounds (such as amino acids) condense and polymerize to form melanin-like substances. Sugars, especially monosaccharides, in the absence of amino compounds, undergo browning reactions when heated above their melting point (generally 140–170°C) due to dehydration and degradation; this reaction is called caramelization. Caramelization has two directions: one is dehydration to obtain caramel (caramel color) and other products; the other is pyrolysis to obtain volatile aldehydes and ketones, which can further condense and polymerize to ultimately yield some dark-colored substances. The combined products of the Maillard and caramelization reactions have a flavor and aroma similar to roasted coffee beans. Since both tea leaves and cocoa beans contain a significant amount of polyphenols such as catechins, epicatechins, and tea polyphenols, this invention combines cocoa bean roasting methods with improved black tea drying processes to obtain a black tea with a unique flavor. Specifically, this invention divides the roasting process into two stages. In the first stage, the main purpose is to accelerate the evaporation of moisture from the tea leaves and promote the Maillard reaction. In the second stage, when the roasting temperature is raised to 90-150℃, the phenols and ketones in the tea leaves undergo a condensation reaction with amino acids, thereby producing special cocoa flavor compounds.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention can effectively utilize the mixed old and young leaves picked by the tea-picking machine to prepare a black tea with excellent flavor and taste, a rich cocoa aroma, and consistent quality.

[0022] 2. The preparation process of this invention requires less manual labor for tea picking, is easy to industrialize, and improves the economic benefits of the tea industry. Detailed Implementation

[0023] The technical solution of the present invention will be described in further detail below, but the scope of protection of the present invention is not limited to the following description.

[0024] Example 1

[0025] In early June, tea trees in a tea garden (Yanmen Village, Dacheng Town, Pingshan County, Yibin City, Sichuan Province) were harvested using a tea-picking machine, yielding 50.8 kg of mixed leaves, containing varying amounts of one bud and one to six leaves. The mixed leaves were spread flat in a withering trough and underwent a first withering at room temperature for 5 hours (at which point the leaf moisture content was 68-70%). The leaves were then placed in a shaking machine for withering using a medium-intensity shaking mode (50 revolutions for the first shake, 100 revolutions for the second, and 150 revolutions for the third). After shaking, the leaves were placed back in the withering trough and allowed to wither naturally at room temperature for 3 hours (at which point the leaf moisture content was 65-68%). The leaves were then removed and rolled using a rolling machine (6CR-25 model) for 90 minutes, with pressure applied in a cycle of light, medium, and heavy rolling to ensure a cell breakage rate of over 70% after rolling. The rolled leaves were then placed in… Fermentation was carried out in a fermentation chamber at a controlled temperature of 25℃ and humidity of 95% for 4 hours. After fermentation, the tea leaves were placed in a rotary tea dryer (model 6CH-6) and dried at 90℃ until the moisture content reached 25-35%. Then, the tea leaves were placed in a drum-type tea frying machine (model SD-100) and fried at 85℃ and 30 rpm with intermittent airflow. A small amount of tea was taken out every 30 minutes to measure the moisture content. When the moisture content dropped below 20%, airflow was stopped, the speed was gradually reduced, and the temperature was gradually increased to 150℃. A small amount of tea was taken out every 30 minutes to measure the moisture content. When the moisture content fell below 6%, frying was stopped, and the tea was removed and quickly cooled. Tea brewed from this tea has a rich cocoa aroma and flavor.

[0026] Example 2

[0027] In early June, tea trees in the tea garden (Yanmen Village, Dacheng Town, Pingshan County, Yibin City, Sichuan Province) were manually harvested, yielding 50.3 kg of tender leaves with one bud and one leaf and two leaves. A cocoa-flavored black tea was prepared using the same method as in Example 1.

[0028] Example 3

[0029] In early June, tea trees in the tea garden (Yanmen Village, Dacheng Town, Pingshan County, Yibin City, Sichuan Province) were manually harvested, yielding 50.5 kg of old leaves with one bud and four, five, and six leaves. A cocoa-flavored black tea was prepared using the same method as in Example 1.

[0030] Comparative Example 1

[0031] Take the mixed leaves harvested in Example 1 and prepare black tea using the traditional "withering-rolling-fermentation-baking" process. The specific method is as follows:

[0032] ① Lay the mixed leaves flat in the withering trough and allow them to wither naturally at room temperature for 5 hours;

[0033] ② After withering, the tea leaves are rolled using a rolling machine (6CR-25 type) for 90 minutes, with pressure applied in a cycle of light, medium and heavy rolling.

[0034] ③ Place the kneaded tea leaves into the fermentation room and ferment them at a temperature of 25℃ and a humidity of 95% for 4 hours;

[0035] ④ After fermentation, the tea leaves are first dried at 120℃ to a moisture content of 40% in a rotary tea dryer (6CH-6 type), then cooled to 90℃ for re-drying to a moisture content of 20%, and finally placed in an aroma-enhancing machine for slow drying at a low temperature of 80℃ until the moisture content is 5%.

[0036] Comparative Example 2

[0037] Take the tender leaves of one bud and one leaf and two leaves harvested in Example 2, and prepare black tea using the traditional "withering-rolling-fermentation-baking" process, the same as in Comparative Example 1.

[0038] Comparative Example 3

[0039] Take the old leaves with one bud and four, five, and six leaves harvested in Example 3, and prepare black tea using the traditional "withering-rolling-fermentation-baking" method, the same as in Comparative Example 1.

[0040] Experimental Example 1

[0041] Tea infusions were prepared using tea leaves from Examples 1-3 and Comparative Example 1. Sensory evaluation of the resulting tea infusions was conducted according to the national standard "Sensory Evaluation Method for Tea" (GB / T 23776—2009). The results are as follows:

[0042]

[0043] The experimental results show that black tea prepared using the traditional "withering-rolling-fermentation-baking" method has high requirements for tea leaves. Black tea made from tender leaves with one bud and one or two leaves is of higher quality, while black tea made from old leaves or a mixture of new and old leaves shows a significant decrease in quality. However, black tea prepared using the method of this invention is of extremely high and uniform quality, regardless of whether tender leaves, old leaves, or mixed tea leaves are used. Therefore, mixed tea leaves collected by non-selective tea harvesting machines can be used as raw materials, greatly reducing the labor costs of black tea preparation.

[0044] Experiment Example 2

[0045] Physicochemical analysis was performed on the tea leaves from Example 1 and Comparative Example 1. The concentrations of water extract, tea polyphenols, amino acids, caffeine, and soluble sugars were detected according to the standards of "Determination of Tea Water Extract" (GB / T 8305—2013) and "Detection Method of Tea Polyphenols and Catechins in Tea" (GB / T 8313—2018). The concentrations of theaflavins, thearubigins, and theabrownins were accurately determined using the anthrone colorimetric method. 2,6-Dimethylpyrazine and trimethylpyrazine were detected by gas chromatography. The chromatographic conditions were as follows: DB-WAX column (30m × 0.25mm, 0.25μm); temperature program: 45℃ for 1 min, then increased to 230℃ at a rate of 6℃ / min and held for 6 min; carrier gas: He at a flow rate of 1.5 mL / min; injection port temperature: 250℃; desorption time: 1 min; splitless injection; standards: 2,6-Dimethylpyrazine (99%, Adamas) and trimethylpyrazine (99%, Adamas).

[0046] The test results are as follows:

[0047]

[0048] The experimental results show that the content of tea polyphenols and 2,6-dimethylpyrazine and trimethylpyrazine in the black tea produced by the method of this invention is significantly higher than that in black tea produced by the traditional method. Pyrazine compounds such as 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, trimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine are recognized sources of cocoa aroma. Compared with black tea prepared by the traditional method, the black tea of ​​this invention has a significant increase in pyrazine compounds, proving that the black tea of ​​this invention has a special cocoa-like flavor and aroma. Tea polyphenols are key to tea aroma, and their content directly affects the flavor of the product. Therefore, the black tea prepared by this invention has a rich flavor and a unique cocoa aroma.

[0049] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A preparation process for cocoa-flavored black tea, characterized in that, Includes the following steps: S1) First withering: Take a mixture of old and young leaves and lay them flat in the withering trough for withering, so that the leaves lose water to a moisture content of 68-70%; S2) Shaking: Put the tea leaves after the first withering into a shaking machine for shaking; S3) Second withering: Spread the tea leaves obtained after shaking evenly in the withering trough, so that the leaves lose water to a moisture content of 65-68%; S4) Rolling: Roll the tea leaves after the second withering until the cell breakage rate is 70-73%; S5) Fermentation: Ferment the kneaded tea leaves for 3-4 hours under conditions of 90-95% humidity and 28-30℃. S6) Drying: Dry the fermented tea leaves at 80-100℃ until the moisture content is 25-35%; S7) Stir-frying: Stir-fry the dried tea leaves until the moisture content is 4-6%; In step S7, the frying is carried out in a drum-type tea frying machine; The frying process is divided into two stages. In the first stage, under intermittent blowing conditions, the temperature is controlled at 85°C for frying until the moisture content is 15-20%. In the second stage, without blowing air, the temperature is controlled at 150℃ for stir-frying until the moisture content is 4-6%.

2. The preparation process according to claim 1, characterized in that: In step S1, the mixed old and young leaves are tea leaves harvested using a non-selective tea-harvesting machine.

3. Cocoa-flavored black tea prepared by any one of the preparation processes described in claims 1-2.

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