A multi-stage fermentation method for improving the taste of longjing tea

Abstract

The application discloses a multi-stage fermentation method for improving Longjing tea taste, comprising the following steps: S1. placing picked fresh leaves in a withering groove, and performing alternating treatment of strong and weak wind speeds to obtain fixed green tea; S2. performing segmented temperature control fixation of the fixed green tea to obtain rolled tea; S3. rolling the rolled tea to obtain rolled tea; S4. firstly spreading the rolled tea by using a conveyor with a screen plate, then performing atomization fumigation on the spread rolled tea, finally placing the atomization fumigated rolled tea in a fermentation chamber for fermentation, and obtaining fermented tea after the fermentation; and performing post-treatment and processing on the obtained fermented tea for standby use. The fermentation method can effectively reduce the grassy taste and bitterness of the Longjing tea, induce aroma, make the taste sweet and mellow, effectively improve the taste and taste of the Longjing tea, and provide more products for promoting the development of tea culture, so as to meet the needs of different consumers in the market.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, specifically a multi-stage fermentation method for improving the flavor of Longjing tea. Background Technology

[0002] Longjing tea is a traditional Chinese famous tea. The traditional processing method of Longjing tea involves using high temperatures to deactivate enzymes, thus preventing the oxidation of polyphenols and preserving the natural color of the fresh leaves. In the processing of Longjing tea, the "kill-green" step is used to quickly deactivate enzymes, aiming to prevent the bio-oxidation of tea polyphenols, maintaining the tea leaves' bright green appearance, fresh taste, and preventing them from turning red. Kill-green is a crucial step in the processing of Longjing tea; its quality directly affects subsequent processing and has a significant impact on the appearance, color, and quality of the finished tea.

[0003] It is evident that if the temperature for fixing is not properly controlled in traditional processing methods, it will not only affect the appearance and color of the finished tea, but also its quality. Furthermore, insufficient fixing will intensify the bitterness and astringency of the finished tea, thus affecting the flavor of Longjing tea.

[0004] As is well known, fermented tea refers to tea that has undergone a "fermentation" process in its production. After the tea buds and leaves have undergone initial processing such as withering, rolling, fermentation, and drying to make raw tea, the tea that is then refined is fermented tea.

[0005] Because tea contains polyphenols, which have astringent properties and can irritate the stomach, especially on an empty stomach, fermented tea is different. Fermented tea undergoes fermentation and baking, during which polyphenols undergo enzymatic oxidation. This reduces the polyphenol content and thus decreases its irritation to the stomach. Furthermore, the oxidation products of these polyphenols can promote digestion. Therefore, fermented tea not only does not harm the stomach but can actually nourish it. Regular consumption can reduce inflammation, protect the gastric mucosa, and offer certain health benefits.

[0006] In tea processing, for fermented tea, fermentation essentially involves controlling biological oxidation, i.e., enzymatic reactions. Its main purpose is to improve taste, reduce bitterness, and enrich aroma, causing a large amount of the originally bitter tea polyphenols to oxidize. The higher the degree of fermentation, the smoother the tea soup and the lower its bitterness. Therefore, to improve the flavor of Longjing tea and provide a processing method different from traditional Longjing tea, products obtained using this method can meet the needs of different consumers in the market, which is essential. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to address the problems existing in the background art, and thus provide a fermentation method. Using this fermentation method, through a specific processing technology, the enzymatic oxidation of polyphenols and the transformation of aroma precursors can be accelerated, thereby promoting better fermentation of tea leaves. Specifically, it is a multi-stage fermentation method to improve the flavor of Longjing tea.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a multi-stage fermentation method for improving the flavor of Longjing tea, wherein the fermentation method includes the following steps: S1. Spread the freshly picked leaves evenly in the withering trough, with a thickness of 4-6 cm, and subject them to alternating strong and weak wind speeds to obtain the withered tea leaves; S2. Place the obtained green tea leaves into a greening machine for segmented temperature-controlled greening, and after greening, the rolled tea leaves are obtained; S3. The obtained rolled tea leaves are rolled using a vacuum low-temperature rolling method to obtain rolled tea leaves; S4. The obtained kneaded tea leaves are first spread out using a conveyor with a mesh plate, with a spreading thickness of 5-8cm. Then, the spread kneaded tea leaves are steamed by mist. After mist steaming, they are finally placed in a fermentation chamber for step-by-step variable temperature fermentation. After fermentation, fermented tea is obtained. The obtained fermented tea is then processed for post-processing and ready for use.

[0009] Furthermore, in the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention, the specific process of alternating strong and weak wind speed treatment in step S1 is as follows: first, the tea is treated with wind speed of 0.5-1.5 m / s for 8-12 minutes, then left to stand for 2-3 minutes, and then treated with wind speed of 3.5-5.0 m / s for 12-15 minutes, then left to stand for 1.5-2.5 minutes, and the wind speed is repeated 3-4 times.

[0010] Furthermore, in the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention, in step S2, the segmented temperature-controlled fixation includes three fixation stages: the first stage of steam fixation, the second stage of steam fixation, and the third stage of hot air fixation.

[0011] Furthermore, the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention is adopted. The first stage of steam fixation involves placing the fixation tea leaves in a steam fixation device and passing saturated steam for treatment at a temperature of 105-115℃ for 1-3 minutes. The second stage of steam fixation involves adjusting the steam temperature to 90-100℃ after the first stage of steam fixation and continuing treatment for 2-5 minutes. The third stage of hot air fixation involves using hot air at a temperature of 85℃ for quick drying for 1-2 minutes after the second stage of steam fixation.

[0012] Furthermore, in the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention, the specific process of the vacuum low-temperature kneading method in step S3 is as follows: the pressure is controlled at -0.08 MPa, the temperature is controlled at 30-35℃, and the kneading time is 10-15 min.

[0013] Furthermore, in the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention, in step S4, the atomization steaming is performed by atomizing the compound fermentation liquid and then steaming the spread and rolled tea leaves at a temperature of 25-30°C.

[0014] Furthermore, the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention is adopted. The specific treatment process of the atomization fumigation is as follows: under the condition of 25-30℃, the tea is first fumigated at a speed of 1.0-1.5 mL / s for 40-60 min, then left to stand for 8-12 min, and then fumigated at a speed of 2.0-3.0 mL / s for 20-30 min, then left to stand for 5-10 min. This process is repeated 2-4 times.

[0015] Furthermore, using the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention, the compound fermentation liquid is prepared by crushing agarwood leaves and honeysuckle at a mass ratio of (8-10):1 to obtain a mixed powder. The mixed powder is then mixed with water at a material-to-liquid ratio of 1:(15-20) g / mL under ultrasonic power of 500-800W and temperature of 50-60℃ for 1-2 hours. After extraction, the mixture is filtered to obtain the compound fermentation liquid. Since the compound fermentation liquid is obtained from the extraction of agarwood leaves and honeysuckle, this method... Furthermore, in the multi-stage fermentation method for improving the flavor of Longjing tea described in this invention, in step S4, the specific process of the stepped variable temperature fermentation is as follows: first, fermentation is carried out for 1.5 to 2.5 hours at a temperature of 10 to 15°C and a humidity of 85 to 90%, and then fermentation is carried out for 2.5 to 3.5 hours at a temperature of 25 to 30°C and a humidity of 70 to 80%.

[0016] Before fermentation, a compound fermentation liquid is used for atomized fumigation. This compound fermentation liquid is extracted from agarwood leaves and honeysuckle. Agarwood leaves are rich in flavonoids, phenols, and endogenous oxidases; while honeysuckle contains chlorogenic acid and luteolin. After fermentation, it releases a large amount of exogenous polyphenol oxidase, peroxidase, and tanninase. Spraying this liquid onto the tea leaves through atomization compensates for the tea leaves' insufficient enzyme activity, accelerates the oxidation of catechins to theaflavins and thearubigins, thereby reducing the residue of bitter ester-type polyphenols.

[0017] Therefore, it can be seen that the compound fermentation liquid extracted and fermented from agarwood leaves and honeysuckle is rich in polyphenol oxidase, flavonoids, chlorogenic acid and natural antibacterial organic acids. When sprayed on tea during the fermentation stage, it can enhance the endogenous enzymatic reaction of tea, promote the full oxidation of tea polyphenols and their directional conversion into theaflavins and thearubigins. At the same time, it can also inhibit the growth of fermentation bacteria, eliminate grassy smell and musty odor, and give the finished product a compound floral aroma of agarwood. The resulting tea has the drinking value of clearing heat and moisturizing dryness, anti-oxidation, and calming and soothing. The fermentation uniformity and stability of the finished product are significantly improved.

[0018] The multi-stage fermentation method for improving the flavor of Longjing tea described in this invention has the following advantages compared with the prior art: This invention, through a specific processing method, can promote the full oxidation and transformation of the polyphenols and other internal substances in Longjing tea during processing, while also better preserving the effective components in Longjing tea. This, in turn, enhances the flavor and aroma of Longjing tea, resulting in a Longjing tea with a mellow taste, a rich red liquor, and a strong and lasting floral aroma, thereby effectively improving the aroma and quality of Longjing tea.

[0019] Therefore, the fermentation method described in this invention, through specific withering, temperature-controlled fixation, and rolling, followed by atomized steaming of the rolled tea leaves, can accelerate the enzymatic oxidation of polyphenols and other polyphenolic substances, as well as the transformation of aroma precursors. This promotes better fermentation of the tea leaves, effectively reducing the grassy and bitter taste of Longjing tea, inducing aroma, and enhancing its sweet and mellow flavor. It can also effectively improve the taste and flavor of Longjing tea, providing more products to promote the development of tea culture and meet the needs of different consumers in the market. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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. Example 1

[0021] A multi-stage fermentation method for improving the flavor of Longjing tea, the fermentation method comprising the following steps: S1. Spread the freshly picked leaves evenly in the withering trough to a thickness of 4cm, and perform alternating strong and weak wind speed blowing treatment to obtain the withered tea leaves; wherein, the specific process of the alternating strong and weak wind speed blowing treatment is as follows: first blow at a wind speed of 0.5m / s for 12min, let stand for 3min, then blow at a wind speed of 3.5m / s for 15min, let stand for 2.5min, and repeat the blowing 3 times; S2. The obtained withered tea leaves are placed in a withering machine for segmented temperature-controlled withering, resulting in rolled tea leaves. The segmented temperature-controlled withering includes three stages: the first stage of steam withering, the second stage of steam withering, and the third stage of hot air withering. In the first stage of steam withering, the withered tea leaves are placed in a steam withering equipment and treated with saturated steam at a temperature of 105°C for 3 minutes. In the second stage of steam withering, after the first stage of steam withering is completed, the steam temperature is adjusted to 90°C and the treatment continues for 5 minutes. In the third stage of hot air withering, after the second stage of steam withering is completed, hot air at a temperature of 85°C is used for rapid drying for 1 minute. S3. The obtained rolled tea leaves are rolled using a vacuum low-temperature rolling method to obtain rolled tea leaves; wherein, the specific process of the vacuum low-temperature rolling method is as follows: the pressure is controlled at -0.08MPa, the temperature is controlled at 30℃, and the rolling time is 15min. S4. The obtained rolled tea leaves are first spread out using a conveyor with a mesh plate to a thickness of 5cm. Then, the rolled tea leaves are subjected to atomized fumigation. The atomized fumigation is carried out by atomizing the compound fermentation liquid and fumigating the rolled tea leaves at a temperature of 25℃. The specific process of atomized fumigation is as follows: first, fumigate at a speed of 1.0mL / s for 60min, let stand for 12min, then fumigate at a speed of 2.0mL / s for 30min, let stand for 10min, and repeat the operation twice. The compound fermentation liquid is prepared by crushing agarwood leaves and honeysuckle at a mass ratio of 8:1 to obtain a mixed powder. The mixed powder is then mixed with water at a material-to-liquid ratio of 1:15g / mL and extracted at an ultrasonic power of 500W and a temperature of 50℃ for 1h. After extraction, the mixture is filtered to obtain the compound fermentation liquid. After atomized fumigation, the tea is placed in a fermentation chamber for step-by-step variable-temperature fermentation. The resulting fermented tea undergoes further processing for later use. Specifically, the step-by-step variable-temperature fermentation process involves first fermenting at 10°C and 85% humidity for 2.5 hours, then raising the temperature to 30°C and lowering the humidity to 70% for another 2.5 hours. Example 2

[0022] A multi-stage fermentation method for improving the flavor of Longjing tea, the fermentation method comprising the following steps: S1. Spread the freshly picked leaves evenly in the withering trough to a thickness of 5cm, and perform alternating strong and weak wind speed blowing treatment to obtain the withered tea leaves; wherein, the specific process of the alternating strong and weak wind speed blowing treatment is as follows: first blow at a wind speed of 1.0m / s for 10min, let stand for 2.5min, then blow at a wind speed of 4.5m / s for 13min, let stand for 2min, and repeat the blowing 4 times; S2. The obtained withered tea leaves are placed in a withering machine for segmented temperature-controlled withering, resulting in rolled tea leaves. The segmented temperature-controlled withering includes three stages: the first stage of steam withering, the second stage of steam withering, and the third stage of hot air withering. In the first stage of steam withering, the withered tea leaves are placed in a steam withering equipment and treated with saturated steam at a temperature of 110°C for 2 minutes. In the second stage of steam withering, after the first stage of steam withering is completed, the steam temperature is adjusted to 95°C and the treatment continues for 3 minutes. In the third stage of hot air withering, after the second stage of steam withering is completed, hot air at a temperature of 85°C is used for rapid drying for 1.5 minutes. S3. The obtained rolled tea leaves are rolled using a vacuum low-temperature rolling method to obtain rolled tea leaves; wherein, the specific process of the vacuum low-temperature rolling method is as follows: the pressure is controlled at -0.08MPa, the temperature is controlled at 32℃, and the rolling time is 12min. S4. The obtained rolled tea leaves are first spread out using a conveyor with a mesh plate to a thickness of 5cm. Then, the rolled tea leaves are subjected to atomized fumigation. The atomized fumigation is carried out by atomizing the compound fermentation liquid and fumigating the rolled tea leaves at a temperature of 28℃. The specific process of atomized fumigation is as follows: first, fumigate at a speed of 1.2mL / s for 50min, let stand for 10min, then fumigate at a speed of 2.5mL / s for 25min, let stand for 8min, and repeat the operation 3 times. The compound fermentation liquid is obtained by crushing agarwood leaves and honeysuckle at a mass ratio of 9:1 to obtain a mixed powder. The mixed powder is then mixed with water at a material-to-liquid ratio of 1:18g / mL and extracted at an ultrasonic power of 600W and a temperature of 55℃ for 1h. After extraction, the mixture is filtered to obtain the compound fermentation liquid. After being steamed by atomization, the tea is finally placed in a fermentation chamber for step-by-step variable-temperature fermentation. After fermentation, fermented tea is obtained, which is then processed for later use. The specific process of step-by-step variable-temperature fermentation is as follows: first, fermentation is carried out for 2 hours at a temperature of 12℃ and a humidity of 90%, and then the temperature is raised to 28℃ and the humidity is lowered to 75% for 3 hours. Example 3

[0023] A multi-stage fermentation method for improving the flavor of Longjing tea, the fermentation method comprising the following steps: S1. Spread the freshly picked leaves evenly in the withering trough to a thickness of 6cm, and perform alternating strong and weak wind speed blowing treatment to obtain the withered tea leaves; wherein, the specific process of the alternating strong and weak wind speed blowing treatment is as follows: first blow at a wind speed of 1.5m / s for 8min, let stand for 2min, then blow at a wind speed of 5.0m / s for 12min, let stand for 1.5min, and repeat the blowing 4 times; S2. The obtained withered tea leaves are placed in a withering machine for segmented temperature-controlled withering, resulting in rolled tea leaves. The segmented temperature-controlled withering includes three stages: the first stage of steam withering, the second stage of steam withering, and the third stage of hot air withering. In the first stage of steam withering, the withered tea leaves are placed in a steam withering equipment and treated with saturated steam at a temperature of 115°C for 1 minute. In the second stage of steam withering, after the first stage of steam withering is completed, the steam temperature is adjusted to 100°C and the treatment continues for 2 minutes. In the third stage of hot air withering, after the second stage of steam withering is completed, hot air at a temperature of 85°C is used for rapid drying for 2 minutes. S3. The obtained rolled tea leaves are rolled using a vacuum low-temperature rolling method to obtain rolled tea leaves; wherein, the specific process of the vacuum low-temperature rolling method is as follows: the pressure is controlled at -0.08MPa, the temperature is controlled at 35℃, and the rolling time is 10min. S4. The obtained rolled tea leaves are first spread out using a conveyor with a mesh plate to a thickness of 5cm. Then, the rolled tea leaves are subjected to atomized fumigation. The atomized fumigation is carried out by atomizing the compound fermentation liquid and fumigating the rolled tea leaves at a temperature of 25℃. The specific process of atomized fumigation is as follows: first, fumigate at a speed of 1.5mL / s for 40min, let stand for 8min, then fumigate at a speed of 3.0mL / s for 20min, let stand for 5min, and repeat the operation 4 times. The compound fermentation liquid is obtained by crushing agarwood leaves and honeysuckle at a mass ratio of 10:1 to obtain a mixed powder. The mixed powder is then mixed with water at a material-to-liquid ratio of 1:20g / mL and extracted at an ultrasonic power of 800W and a temperature of 60℃ for 2h. After extraction, the mixture is filtered to obtain the compound fermentation liquid. After atomized fumigation, the tea is placed in a fermentation chamber for step-by-step variable-temperature fermentation to obtain fermented tea. The fermented tea is then further processed for later use. The specific process of step-by-step variable-temperature fermentation is as follows: first, fermentation is carried out at a temperature of 15℃ and a humidity of 90% for 1.5 hours; then, the temperature is increased to 25℃ and the humidity is decreased to 80% for 3.5 hours.

[0024] The fermentation method provided by this invention is a conventional method unless otherwise specified, and the materials and reagents used are commercially available unless otherwise specified.

[0025] The fermentation method described in this invention employs specific and rational withering, fixation, rolling, misting and steaming, and variable-temperature fermentation processes. After fixation, rolling promotes cell wall breaking. Subsequent misting and variable-temperature fermentation effectively promote the conversion of polyphenols, thereby reducing the polyphenol content in the prepared Longjing tea. This effectively reduces bitterness and green tea taste, resulting in a richer aroma and sweeter, more mellow flavor after brewing, thus effectively enhancing the aroma and quality of Longjing tea.

[0026] Therefore, the fermentation method described in this invention can not only effectively reduce the grassy and bitter taste of Longjing tea and induce its aroma and sweetness, but also effectively improve the taste and flavor of Longjing tea. This can provide more products to promote the development of tea culture and meet the needs of different consumers in the market.

[0027] Other aspects of this invention that are not detailed herein are all conventional techniques known to those skilled in the art.

[0028] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0029] The scope of protection of this invention is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of this invention shall fall within the scope of protection of this invention.

Claims

1. A multi-stage fermentation method for improving the flavor of Longjing tea, characterized in that: The fermentation method includes the following steps: S1. Spread the freshly picked leaves evenly in the withering trough, with a thickness of 4-6cm, and subject them to alternating strong and weak wind speeds to obtain the tea leaves to be processed for fixation; S2. Place the obtained green tea leaves into a greening machine for segmented temperature-controlled greening, and after greening, obtain the green tea leaves to be rolled; S3. The obtained rolled tea leaves are rolled using a vacuum low-temperature rolling method to obtain rolled tea leaves; S4. The obtained kneaded tea leaves are first spread out using a conveyor with a mesh plate, with a spreading thickness of 5-8cm. Then, the spread kneaded tea leaves are steamed by mist. After mist steaming, they are finally placed in a fermentation chamber for step-by-step variable temperature fermentation. After fermentation, fermented tea is obtained. The obtained fermented tea is then processed for post-processing and ready for use.

2. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 1, characterized in that: In step S1, the specific process of alternating strong and weak wind speed blowing is as follows: first, blow at a wind speed of 0.5 to 1.5 m / s for 8 to 12 minutes, let stand for 2 to 3 minutes, then blow at a wind speed of 3.5 to 5.0 m / s for 12 to 15 minutes, let stand for 1.5 to 2.5 minutes, and repeat the blowing 3 to 4 times.

3. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 1, characterized in that: In step S2, the segmented temperature-controlled blanching includes three blanching stages: the first stage of steam blanching, the second stage of steam blanching, and the third stage of hot air blanching.

4. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 3, characterized in that: The first stage of steam fixation involves placing the tea leaves in a steam fixation device and passing saturated steam through them at a temperature of 105–115°C for 1–3 minutes. The second stage of steam fixation involves adjusting the steam temperature to 90–100°C after the first stage of steam fixation and continuing the process for 2–5 minutes. The third stage of hot air fixation involves using hot air at 85°C for 1–2 minutes after the second stage of steam fixation.

5. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 1, characterized in that: In step S3, the specific process of the vacuum low-temperature kneading method is as follows: the pressure is controlled at -0.08MPa, the temperature is controlled at 30-35℃, and the kneading time is 10-15min.

6. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 1, characterized in that: In step S4, the atomized fumigation is performed by atomizing the compound fermentation liquid and then fumigating the spread and rolled tea leaves at a temperature of 25-30°C.

7. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 6, characterized in that: The specific process of the atomized fumigation is as follows: under the condition of 25-30℃, first fumigate at an atomization rate of 1.0-1.5mL / s for 40-60min, let stand for 8-12min, then fumigate at an atomization rate of 2.0-3.0mL / s for 20-30min, let stand for 5-10min, and repeat the operation 2-4 times.

8. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 6, characterized in that: The compound fermentation liquid is prepared by crushing agarwood leaves and honeysuckle at a mass ratio of (8-10):1 to obtain a mixed powder. The mixed powder is then mixed with water at a material-to-liquid ratio of 1:(15-20) g / mL and extracted for 1-2 hours under ultrasonic power of 500-800W and temperature of 50-60℃. After extraction, the mixture is filtered to obtain the compound fermentation liquid.

9. The multi-stage fermentation method for improving the flavor of Longjing tea according to claim 1, characterized in that: In step S4, the specific process of the stepped variable temperature fermentation is as follows: first, fermentation is carried out for 1.5 to 2.5 hours at a temperature of 10 to 15°C and a humidity of 85 to 90%, and then fermentation is carried out for 2.5 to 3.5 hours at a temperature of 25 to 30°C and a humidity of 70 to 80%.