Fermentation process for regulating and controlling theaflavin content of black tea

Abstract

The invention belongs to the technical field of tea leaf processing, and provides a fermentation process for regulating and controlling the content of theaflavin in black tea, which comprises the following steps: fermenting withered and rolled tea leaves; fermenting for 40 to 80 minutes under the conditions that the temperature is 28 to 32 DEG C and the relative humidity is 90 to 95 percent; fermenting for 60 to 120 minutes under the conditions that the temperature is 24 to 26 DEG C and the relative humidity is 85 to 90 percent; fermenting for 20 to 40 minutes under the conditions that the temperature is 20 to 22 DEG C and the relative humidity is 80 to 85 percent; in the first stage and the second stage, oxygen-enriched air is intermittently introduced into the fermentation environment, so that the oxygen concentration is maintained at 23%-25%. According to the method disclosed by the invention, the generation and accumulation of theaflavin can be accurately regulated and controlled through the cooperation of multi-stage temperature change and dynamic oxygenation, the problems of unstable theaflavin content and large quality fluctuation of a traditional fermentation process are effectively solved, and the prepared black tea is high in theaflavin content, bright in liquor color, fresh and refreshing in taste and stable in quality and can be directionally regulated and controlled.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, and in particular to a fermentation process for regulating the theaflavins content in black tea. Background Technology

[0002] Black tea is one of the most widely consumed teas globally. Its quality characteristics primarily depend on secondary metabolites formed during fermentation, such as theaflavins, thearubigins (TRs), and theabrownins (TBs). Among these, theaflavins are key substances in forming the "golden ring" and "cloudiness after cooling" phenomena in black tea infusions, and are hailed as "soft gold" in tea. Their content directly determines the brightness of the tea's color, the freshness and intensity of its flavor. High theaflavin content is an important indicator of high-quality black tea.

[0003] Traditional black tea fermentation processes typically rely on experience for control, with significant fluctuations in environmental factors such as temperature, humidity, oxygen levels, and fermentation time. This leads to an uncontrollable fermentation process, resulting in unstable theaflavin content in the finished black tea and significant batch-to-batch quality variations. Theaflavins are intermediate products of the oxidative polymerization of catechins under the action of polyphenol oxidase (PPO) and peroxidase (POD). They are also unstable and further transform into thearubigins and theabrownins in the later stages of fermentation, leading to a decrease in freshness.

[0004] In existing technologies, although there are some methods to increase the content of theaflavins by controlling the fermentation temperature or time, most of the control methods are simple and cannot achieve precise and predictable dynamic control of the theaflavins content, making it difficult to carry out targeted production according to market demand for black tea with different flavors and liquor color characteristics.

[0005] Therefore, there is an urgent need to develop a new process that can precisely and stably regulate the generation and accumulation of theaflavins during the fermentation of black tea. Summary of the Invention

[0006] The purpose of this invention is to provide a fermentation process for regulating the theaflavins content of black tea, in order to solve the technical problems in the prior art.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a fermentation process for regulating the theaflavins content of black tea, comprising the following steps:

[0009] Ferment the withered and rolled tea leaves;

[0010] The fermentation process includes three stages:

[0011] First stage: Ferment for 40-80 minutes at a temperature of 28-32℃ and a relative humidity of 90-95%;

[0012] Second stage: Ferment for 60-120 minutes at a temperature of 24-26℃ and a relative humidity of 85-90%;

[0013] Third stage: Ferment for 20-40 minutes at a temperature of 20-22℃ and a relative humidity of 80-85%;

[0014] In the first and second stages, oxygen-enriched air is intermittently introduced into the fermentation environment to maintain the oxygen concentration at 23%-25%.

[0015] Preferably, the intermittent oxygen-enriched air supply mode is as follows: ventilate for 10 minutes, stop for 5 minutes, and repeat.

[0016] As a preferred method, the fermentation leaves should be stirred every 20-30 minutes during the fermentation process.

[0017] As a preferred method, the final content of theaflavins in black tea is controlled by adjusting the fermentation time of the second stage.

[0018] Preferably, a second-stage fermentation time of 60-90 minutes is used to prepare black tea with high theaflavin content; a second-stage fermentation time of 90-120 minutes is used to prepare black tea with medium theaflavin content.

[0019] Preferably, the oxygen-enriched air is provided by an oxygen generator or an oxygen cylinder.

[0020] The present invention also provides a black tea product prepared by the aforementioned fermentation process.

[0021] Preferably, the theaflavins content of the black tea product is higher than 1.5%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. Precise control: By dividing the fermentation process into three distinct stages and setting different temperature, humidity and oxygen conditions for each stage, the generation rate and conversion pathway of theaflavins can be precisely controlled, achieving "targeted" control of the theaflavin content in the final product.

[0024] 2. Stable quality: It overcomes the shortcomings of traditional fermentation, which is greatly affected by environmental factors. The process parameters are stable and controllable, ensuring a high degree of consistency and stability in the quality of different batches of black tea products.

[0025] 3. Improved quality: Through the "low-temperature enrichment" strategy, the further oxidation of theaflavins is effectively slowed down, and its fresh and refreshing flavor is preserved to the maximum extent. The resulting black tea has a bright golden color, a strong and refreshing taste, and a distinct "golden ring".

[0026] 4. High flexibility: By simply adjusting the duration of the second stage, a series of products with high and medium theaflavin content can be produced on the same process line to meet the diversified needs of the market and have broad application prospects. Detailed Implementation

[0027] This invention provides a fermentation process for regulating the theaflavins content of black tea, comprising the following steps:

[0028] Ferment the withered and rolled tea leaves;

[0029] The fermentation process includes three stages:

[0030] First stage: Ferment for 40-80 minutes at a temperature of 28-32℃ and a relative humidity of 90-95%;

[0031] Second stage: Ferment for 60-120 minutes at a temperature of 24-26℃ and a relative humidity of 85-90%;

[0032] Third stage: Ferment for 20-40 minutes at a temperature of 20-22℃ and a relative humidity of 80-85%;

[0033] In the first and second stages, oxygen-enriched air is intermittently introduced into the fermentation environment to maintain the oxygen concentration at 23%-25%.

[0034] In this invention, the intermittent oxygen-enriched air supply mode is as follows: ventilate for 10 minutes, stop for 5 minutes, and repeat the cycle.

[0035] In this invention, the fermentation leaves are stirred every 20-30 minutes during the fermentation process.

[0036] In this invention, the final content of theaflavins in black tea is controlled by adjusting the fermentation time of the second stage.

[0037] In this invention, when the second stage fermentation time is 60-90 minutes, it is used to prepare black tea with high theaflavin content; when the second stage fermentation time is 90-120 minutes, it is used to prepare black tea with medium theaflavin content.

[0038] In this invention, the oxygen-enriched air is provided by an oxygen generator or an oxygen cylinder.

[0039] The present invention also provides a black tea product prepared by the aforementioned fermentation process.

[0040] In this invention, the theaflavins content of the black tea product is higher than 1.5%.

[0041] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1: Preparation of black tea with high theaflavin content

[0043] Take one bud and two leaves of tea leaves, and after withering and thorough rolling, obtain rolled leaves.

[0044] Spread the kneaded leaves evenly in a temperature- and humidity-controlled fermentation box, with a leaf thickness of 10cm.

[0045] Phase 1: Set the temperature to 30℃ and humidity to 93% for 60 minutes. During this period, oxygen-enriched air (O2 concentration 24%) is introduced in a cycle of 10 minutes on, 5 minutes off, and stirred once every 30 minutes.

[0046] Phase 2: Set the temperature to 25°C and humidity to 88% for 70 minutes. Continue the same oxygen-enriched ventilation and agitation procedures (every 30 minutes).

[0047] Third stage: Set the temperature to 21℃ and humidity to 83% for 30 minutes. Stop oxygen supply and allow natural fermentation. Immediately transfer the fermented leaves to a dryer and dry them at 120℃ until the moisture content is below 6%, obtaining the finished black tea. Testing showed that the theaflavins content of this finished black tea was 1.68%.

[0048] Example 2: Preparation of black tea with medium theaflavin content

[0049] The steps are basically the same as in Example 1, except that the duration of the second stage is adjusted to 100 minutes.

[0050] Tests showed that the theaflavins content of the finished black tea was 1.25%.

[0051] Comparative example: Traditional natural fermentation process

[0052] Take the same batch of kneaded leaves and ferment them for 150 minutes at room temperature (fluctuating between 25-28℃) and natural humidity (fluctuating between 70-85%), stirring them manually twice during the process, and then drying them in the same way.

[0053] Tests showed that the theaflavins content of the finished black tea was 0.85%.

[0054] Effect comparison:

[0055] Sensory evaluation was conducted on the black teas prepared in Examples 1 and 2 and the comparative example. The results are shown in the table below:

[0056]

[0057] This invention divides the fermentation process into three distinct stages, setting different temperature, humidity, and oxygen conditions for each stage. This allows for precise control of the formation rate and conversion pathway of theaflavins, achieving targeted regulation of theaflavin content in the final product. It overcomes the shortcomings of traditional fermentation, which is greatly affected by environmental factors. The process parameters are stable and controllable, ensuring a high degree of consistency and stability in the quality of different batches of black tea. Through a "low-temperature enrichment" strategy, further oxidation of theaflavins is effectively slowed down, maximizing the preservation of their fresh flavor. The resulting black tea has a bright golden-yellow liquor, a strong and refreshing taste, and a distinct "golden ring." By simply adjusting the duration of the second stage, a series of products with high and medium theaflavin contents can be produced on the same production line, meeting diverse market demands and showing broad application prospects.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fermentation process for regulating the theaflavins content of black tea, characterized in that, Includes the following steps: Ferment the withered and rolled tea leaves; The fermentation process includes three stages: First stage: Ferment for 40-80 minutes at a temperature of 28-32℃ and a relative humidity of 90-95%; Second stage: Ferment for 60-120 minutes at a temperature of 24-26℃ and a relative humidity of 85-90%; Third stage: Ferment for 20-40 minutes at a temperature of 20-22℃ and a relative humidity of 80-85%; In the first and second stages, oxygen-enriched air is intermittently introduced into the fermentation environment to maintain the oxygen concentration at 23%-25%.

2. The fermentation process according to claim 1, characterized in that, The intermittent oxygen-enriched air supply mode is as follows: ventilate for 10 minutes, stop for 5 minutes, and repeat.

3. The fermentation process according to claim 1, characterized in that, During fermentation, the fermentation leaves should be stirred every 20-30 minutes.

4. The fermentation process according to claim 1, characterized in that, The final content of theaflavins in black tea can be controlled by adjusting the fermentation time in the second stage.

5. The fermentation process according to claim 4, characterized in that, When the second stage fermentation time is 60-90 minutes, it is used to prepare black tea with high theaflavin content; when the second stage fermentation time is 90-120 minutes, it is used to prepare black tea with medium theaflavin content.

6. The fermentation process according to any one of claims 5, characterized in that, The oxygen-enriched air is provided by an oxygen generator or oxygen cylinder.

7. A black tea product, characterized in that, Prepared by the fermentation process described in any one of claims 1-6.

8. The black tea product according to claim 7, characterized in that, The theaflavins content of the black tea product is higher than 1.5%.

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