Processing method of high-green white tea

Abstract

The invention belongs to the technical field of tea production, and discloses a high-green white tea processing method which comprises the following steps: S1, thin spreading in a dark place: thin spreading fresh tea leaves on a green leaf cooling frame of a dark withering room for withering; s2, performing low-humidity precipitation: performing dehumidification by adopting equipment to reduce the air humidity in the withering chamber, and performing primary precipitation on the tea leaves; s3, performing low-temperature green keeping: during continuous dehumidification, reducing the indoor temperature by using refrigeration equipment, and performing second-time water reduction on the tea leaves; s4, negative-pressure green removal: performing third-time water reduction on the tea leaves through an indoor low-humidity air circulation negative-pressure air field; s5, performing low-oxygen color fixation: reducing the proportion of oxygen in indoor air while continuously dehumidifying, and performing fourth-time water reduction on the tea leaves; and S6, hot air fragrance enhancing: transferring the tea leaves to a drying chamber, and alternately using a hot-air blower and a dehumidifier until the water content of the tea leaves is below 7%, so as to obtain the high-green white tea. By controlling the temperature and humidity of the withering environment, reducing the oxygen concentration in the withering chamber and changing the air flowing direction of the withering chamber, the fresh leaves are uniformly withered, and the green-keeping and high-quality effects of the tea leaves are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of tea production, and in particular to a high-quality green white tea processing method. Background Art

[0002] White tea is a type of tea unique to my country and is a slightly fermented tea. In recent years, white tea has been favored by consumers, and production and sales have continued to grow. Processing white tea has become one of the ways to efficiently utilize tea resources at this stage. At present, most of the research on white tea processing technology focuses on high-quality Baihao Yinzhen and Bai Mudan, while there are few creations of processing technology for Gongmei and Shoumei grade white tea. In fact, white tea products with lower raw material grades such as Gongmei and Shoumei occupy most of the white tea consumer market. In the process of white tea processing, low-grade raw materials (one bud, three or four leaves) are more likely to wither unevenly. In case of high temperature, rainy and humid weather, the white tea produced often has problems such as reddish, brown and dull appearance, orange-yellow soup color, lack of freshness, and lack of purity of aroma, which directly affects the value of white tea made from this grade of raw materials. How to improve the appearance, color and internal quality of white tea through technological creation and assign value to low-grade raw white tea is worthy of in-depth study.

[0003] The traditional white tea processing technology is relatively simple, and is divided into two steps: withering and drying. The withering step is the key step in the formation of the unique quality of white tea. During the withering stage, macromolecules such as proteins and polysaccharides in fresh leaves are hydrolyzed into small molecules such as amino acids, monosaccharides and disaccharides under the action of enzymes, and substances such as chlorophyll and catechins are gradually oxidized, thus forming the unique quality of white tea. In the traditional white tea processing process, according to weather conditions, processing equipment and other conditions, the withering method can be divided into natural withering, sunlight withering and compound withering. Most white teas are mainly withered indoors, and the total withering time is generally more than 36 hours. In case of rainy and humid weather, the withering time will be appropriately extended to more than 72 hours. The technical parameters of traditional white tea withering are relatively simple, and are mainly adjusted by changing the thickness of the fresh leaves. They are greatly affected by weather conditions and lack artificial precision control of other indoor environmental conditions such as temperature and humidity. Therefore, the present invention proposes a high-green white tea processing method by controlling the temperature and humidity of the withering environment, reducing the oxygen concentration in the withering chamber, and changing the air flow direction in the withering chamber, so as to ensure uniform withering of fresh leaves, form a green and moist color of dry tea, and achieve the effect of high green and high quality. Summary of the invention

[0004] The purpose of the present invention is to provide a high-green white tea processing method, by controlling the temperature and humidity of the withering environment, reducing the oxygen concentration in the withering chamber, changing the air flow direction of the withering chamber, so that the fresh leaves can be withered evenly, and the effect of high green and high quality tea can be achieved, so as to solve the technical problem that it is difficult to achieve green and uniform color in the production of white tea.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A high-quality green white tea processing method comprises the following steps:

[0007] S1. Spread thinly in a dark withering room: Spread fresh tea leaves thinly on a drying tray and place on a drying rack in a dark withering room for withering;

[0008] S2. Low humidity precipitation: During the withering process, dehumidifiers and other equipment are used to continuously extract moisture from the withering room to dehumidify the air, reduce the humidity in the withering room, and perform the first precipitation treatment on the tea leaves;

[0009] S3. Low temperature to keep green: Use refrigeration or air conditioning to lower the indoor temperature while dehumidifying with dehumidifiers and other equipment. This second precipitation treatment of tea leaves can slow down the degree of chlorophyll oxidation.

[0010] S4, negative pressure to remove green air: by setting low humidity air to blow into the room in different directions, high humidity air is extracted from the room in the corresponding direction, forming a negative pressure wind field with low humidity wind circulation in the room, continuously extracting the humidity of leaves and promoting the disappearance of green air, which is the third precipitation treatment for tea leaves;

[0011] S5, low oxygen fixation: while extracting high humidity air from the room, reduce the proportion of oxygen in the indoor air, reduce leaf cell oxidation, and perform the fourth precipitation treatment on the tea leaves;

[0012] S6. Hot air aroma enhancement: After sieving the tea leaves evenly, transfer them to the drying room, gather them into piles and place them on the platform. Use the hot air blower and dehumidifier alternately until the moisture content of the tea leaves is below 7%, and obtain high green white tea.

[0013] Preferably, in step S1, the light-proof withering room is a room without sunlight, the lights are turned off during the withering process, and the thickness of the thin spread of fresh tea leaves is 2-3 cm.

[0014] Preferably, in step S2, the air humidity in the withering room is in the range of 55%-60%, and the water content of the leaves in the first precipitation needs to be controlled at 55%-57%.

[0015] Preferably, in step S3, before cooling, the dehumidifier needs to be kept running to make the indoor humidity reach about 55%, and the indoor temperature needs to be reduced to below 20°C.

[0016] Preferably, in step S3, the moisture content of the blades during the second precipitation needs to be controlled at 45%-50%.

[0017] Preferably, in step S4, the indoor temperature needs to be maintained below 23°C, and the moisture content of the leaves in the third precipitation needs to be controlled at 35%-40%.

[0018] Preferably, in step S5, reducing the oxygen ratio in the indoor air is specifically adding nitrogen into the withering chamber.

[0019] Preferably, in step S5, the moisture content of the blades in the fourth precipitation needs to be controlled at 20%-25%.

[0020] Preferably, in step S6, the temperature of the hot air blower is set to be above 35°C, and the humidity of the dehumidifier is set to be about 30%.

[0021] Preferably, in step S6, the hot air blower and the dehumidifier are used alternately, specifically, the hot air blower and the dehumidifier are used alternately every two days. After being used alternately 2-3 times, the tea leaves are put into an aluminum foil bag, and the bag is opened to continue processing until the moisture content of the tea leaves is below 7%.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. The present invention can make the white tea green and moist

[0024] During the processing of white tea, the oxidation of chlorophyll is promoted due to damage, temperature, humidity and light. It is often difficult to keep the green color of the leaves in the processing of low-grade raw white tea. Studies have shown that high temperatures above 80°C will promote the rapid conversion of chlorophyll into pheophytin; a long-term high humidity environment during withering will be detrimental to the formation of white tea color; sunlight will increase the temperature of the withered leaves and accelerate the degradation of chlorophyll. In the method provided by the present invention, low-temperature withering delays the degradation of chlorophyll and reduces the accumulation of melanin by inhibiting the activity and gene expression of chelatase, chlorophyllase and chlorophyll a oxygenase; the low humidity environment accelerates the dehydration of fresh leaf cells and helps to quickly fix the color of tea leaves; withering in a low-oxygen environment reduces the respiration rate of fresh leaves, reduces the oxidation of polyphenols and the formation of color-developing substances such as theaflavins; and a light-proof environment can reduce the degradation of chlorophyll. Through technical means such as low humidity, low temperature, low oxygen and light-proof, the damage to the green color of leaves can be reduced, forming a green and moist white tea color.

[0025] 2. Improve the quality of white tea

[0026] The method provided by the present invention not only makes the water loss and withering of the leaves balanced through negative pressure air circulation, but also reduces the concentration of green gas and other substance components in the fresh leaves, highlighting the fragrance quality of white tea. In addition, long-term low-temperature hot air aroma enhancement promotes the slow loss of water, reduces the Maillard reaction during drying, retains more sugars and amino acids, and helps to improve the quality of tea.

[0027] 3. Accelerate the withering process and improve the efficiency of white tea processing

[0028] During the implementation of the technology of the present invention, the humidity of the withering environment can be effectively controlled, the cell water loss rate can be accelerated, and the withering time of fresh leaves can be shortened. The total withering time of the traditional white tea processing method is more than 36 hours. The method of the present invention can control the total withering time to 22-24 hours (the aroma-enhancing stage is transferred to the drying room), saving more than 12 hours of withering time. In view of the fact that white tea processing is mainly withering, in actual production, the method of the present invention can ensure that the fresh leaves complete the withering process within 24 hours, provide withering equipment and space for the fresh leaves entering the factory the next day, realize the continuous daily production of large quantities of white tea, and improve the processing efficiency of white tea. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a comparison diagram of the appearance and color of the high green white tea of ​​Example 1 of the present invention and the traditional white tea of ​​Comparative Example 1 (A is the traditional white tea of ​​Comparative Example 1, and B is the high green white tea of ​​Example 1). DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0031] The present invention provides a high-quality green white tea processing method, comprising the following steps:

[0032] A high-quality green white tea processing method comprises the following steps:

[0033] S1. Spread thinly away from light: Spread the fresh tea leaves thinly on a drying tray with a thickness of 2-3 cm, and place it on a drying rack in a withering room away from sunlight for withering. Turn off the light during the withering process.

[0034] S2. Low humidity precipitation: During the withering process, use dehumidifiers and other equipment to continuously extract moisture from the withering room to reduce the air humidity in the withering room to 55%-60% until the moisture content of the leaves is 55%-57%.

[0035] S3. Keep green at low temperature: When the indoor humidity reaches 55% while the dehumidifier is continuously dehumidifying, use equipment such as refrigerators or air conditioners to lower the indoor temperature to below 23°C, which can slow down the oxidation of chlorophyll until the water content of the leaves is 45%-50%.

[0036] S4. Negative pressure to remove green air: By setting low-humidity air to the room in different directions, high-humidity air is extracted from the room in the corresponding direction, forming an indoor low-humidity wind circulation negative pressure wind field, continuously extracting the humidity of the leaves and promoting the dissipation of green air, keeping the indoor temperature below 20°C until the moisture content of the leaves is 35%-40%.

[0037] S5. Low oxygen fixation: While extracting high humidity air from the room, add nitrogen to the low humidity blower to reduce the oxygen ratio in the indoor air and reduce leaf cell oxidation until the water content of the leaves is 20%-25%.

[0038] S6. Hot air aroma enhancement: After sieving the tea leaves evenly, transfer them to the drying room, gather them into piles and place them on the platform. Set the hot air blower with the temperature above 35°C and the dehumidifier with the humidity set at about 30% alternately every two days. After alternating for 2-3 times, put the tea leaves into aluminum foil bags, open the bag and continue processing until the moisture content of the tea leaves is below 7%, thus obtaining high green white tea.

[0039] Example 1

[0040] A high-quality green white tea processing method comprises the following steps:

[0041] S1. Spread thinly in a dark withering room: Spread the fresh tea leaves thinly on a drying tray with a thickness of 2.5 cm and place on a drying rack in a dark withering room for withering.

[0042] S2. Low humidity precipitation: During the withering process, dehumidifiers and other equipment are used to continuously extract moisture from the withering room to reduce the air humidity in the withering room to about 58%, until the moisture content of the leaves is about 56%.

[0043] S3. Keep green at low temperature: When the indoor humidity reaches about 55% while the dehumidifier and other equipment are continuously dehumidifying, a refrigerator is used to lower the indoor temperature to below 20°C, which can slow down the oxidation of chlorophyll until the water content of the leaves is about 48%.

[0044] S4. Negative pressure to remove green air: By setting low-humidity air to the room in different directions, high-humidity air is extracted from the room in the corresponding direction, forming an indoor low-humidity wind circulation negative pressure wind field, continuously extracting the humidity of the leaves and promoting the dissipation of green air, keeping the indoor temperature below 23°C until the moisture content of the leaves is about 38%.

[0045] S5. Low oxygen color fixation: While extracting high humidity air from the room, add nitrogen to the low humidity blower to reduce the proportion of oxygen in the indoor air and reduce leaf cell oxidation until the water content of the leaves is about 23%.

[0046] S6. Hot air aroma enhancement: After sieving the tea leaves evenly, transfer them to the drying room, gather them into piles and place them on the platform. Set the temperature of the hot air blower to above 35°C and the humidity of the dehumidifier to about 30% alternately every two days. After alternating for 3 times, put the tea leaves into aluminum foil bags, open the bag and continue to process until the moisture content of the tea leaves is 7%. The whole process lasts for 25-30 days to obtain high green white tea.

[0047] Comparative Example 1

[0048] The traditional white tea processing method includes the following steps:

[0049] S1. Spreading leaves: Spread the fresh leaves on withering troughs, drying trays or water screens with a thickness of about 4 cm.

[0050] S2. Withering: Place the withering trough, airing tray or water sieve indoors for natural withering indoors. When the moisture content of the tea leaves is about 40%, combine the trays / sieves, that is, combine the two trays / sieves into one tray (if withering in the withering trough, close them together). Continue withering indoors until the moisture content of the withered leaves is about 12% and they are ready for drying. The total withering time is about 60 hours.

[0051] S3. Drying: Use an automatic dryer with a temperature set at about 85°C, and further dry for about 40 minutes until the moisture content reaches 7%.

[0052] Test example

[0053] 1. Comparison of the appearance and color of the high green white tea obtained in Example 1 and the traditional white tea obtained in Comparative Example 1

[0054] The appearance and color of the high green white tea obtained in Example 1 of the present invention are compared with the traditional white tea obtained in Comparative Example 1. Figure 1 , as well as the detection of pink color difference between dry tea made from high green white tea and traditional white tea.

[0055] The color difference detection method is as follows: the American X-Rite desktop spectrophotometer (Ci7XX0) is used for detection. Before the detection, the equipment is calibrated in the reflection measurement mode, and then the tea powder is transferred into a transparent glass tube, and the color difference is measured in the reflection mode. The various tea powders are measured three times. The experimental results are shown in Table 1, where L* (Lightness) represents the brightness of the color, ranging from 0 to 100, where 0 represents pure black and 100 represents pure white; a* (Green-Red Axis) represents the red-green color, ranging from -128 to +127, where -128 represents green and +127 represents red; b* (Blue-Yellow Axis) represents the yellow-blue color, ranging from -128 to +127, where -128 represents blue and +127 represents yellow.

[0056] Table 1 The difference in pink color between tea made by the comparative technology and the technology of the present invention

[0057] White tea sample L* a* b* Comparative Example 1 White Tea 51.46 0.31 8.83 Example 1 White Tea 58.28 -1.61 13.67

[0058] Depend on Figure 1From the color diagram of the two finished teas, it can be seen that the high green white tea produced by the white tea processing method provided by the present invention has a sandy green color that is moist and fresh, while the traditional white tea produced by the traditional process has a slightly darker green-brown color and is slightly dry. It can be seen that the present invention significantly improves the appearance color of the finished white tea.

[0059] From the color difference detection results in Table 1, it can be seen that the L value of the high green white tea prepared by the white tea processing method provided by the present invention is significantly higher than that of the traditional white tea prepared by the traditional process, and the color is brighter; and the a* value of the high green white tea obtained in Example 1 is negative, and the color is green, while the a* value of the traditional white tea obtained in Comparative Example 1 is positive, and the color is reddish; the b* value of the high green white tea obtained in this Example 1 is significantly higher than that of the traditional white tea obtained in Comparative Example 1, and the saturation is higher.

[0060] 2. Comparison of the sensory qualities of the high green white tea obtained in Example 1 and the traditional white tea obtained in Comparative Example 1

[0061] The sensory evaluation method was carried out in accordance with GB / T23776-2018 "Tea Sensory Evaluation Method", and the evaluation team was composed of 5 professional tea appraisers with experience in white tea evaluation. The five factors of appearance, soup color, aroma, taste, and leaf bottom were evaluated, and the comments and scores were combined with the weighted scoring method. The evaluation results are shown in Table 2.

[0062] Table 2 Sensory evaluation of two types of white tea

[0063]

[0064] As can be seen from Table 2, the total sensory quality score of the high green white tea produced by the white tea processing method provided by the present invention is higher than that of the traditional white tea produced by the traditional process, and the overall quality is better, which is mainly reflected in the fact that the high green white tea produced by the present invention has a high fragrance and a mellow and sweet taste.

[0065] 3. Comparison of the main biochemical components of the high green white tea obtained in Example 1 and the traditional white tea obtained in Comparative Example 1

[0066] The water extract content was determined according to GB / T 8305-2013 “Determination of tea water extract”; the total free amino acid content was determined according to the ninhydrin method in GB / T 8314-2013 “Determination of free amino acid content in tea”; the tea polyphenol content was determined by ferrous tartrate colorimetry; the tea soluble sugar content was determined according to the anthrone colorimetry. The test results are shown in Table 3.

[0067] Table 3 Content of main biochemical components of two kinds of white tea (%)

[0068]

[0069] As shown in Table 3, compared with traditional white tea, the present invention adopts low temperature and low oxygen technology to reduce the oxidation of tea polyphenols; and adopts long-term low temperature hot air to retain more amino acids and soluble sugar content, which is beneficial to improve the quality of white tea.

[0070] In summary, the present invention can reduce the damage of high temperature to leaf green by low humidity, low temperature, low oxygen and other technical means, so that the obtained white tea has green color; it can solve the technical problem that low-grade raw materials (one bud, three or four leaves) white tea processing is often difficult to keep the green color of leaves due to damage, temperature, humidity and light during the processing of white tea, and it can also avoid mechanical damage, resulting in the destruction of tea leaf cell structure, prompting polyphenol oxidase in cell fluid to fully combine with polyphenols to form color-developing substances such as theaflavins and thearubigins, and changing the color of white tea leaves. At the same time, the method provided by the present invention, through negative pressure air circulation, not only makes the leaf dehydration and withering balanced, but also reduces the concentration of material components such as green gas in fresh leaves, highlighting the fragrance quality of white tea. In addition, long-term low-temperature hot air aroma, promotes the slow loss of water, reduces the Maillard reaction during drying, retains more sugars and amino acids, and helps to improve the quality of tea leaves. In actual production, the method of the present invention can ensure that the fresh leaves complete the withering process within 24 hours (transfer to the drying room for aroma extraction), provide withering equipment and space for the fresh leaves entering the factory the next day, realize the continuous daily production of large quantities of white tea, and improve the processing efficiency of white tea.

[0071] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for processing high green white tea, characterized in that: The following steps are involved: S1. Spread thinly in a dark withering room: Spread fresh tea leaves thinly on a drying tray and place on a drying rack in a dark withering room for withering; S2. Low humidity precipitation: During the withering process, dehumidification equipment is used to continuously extract moisture from the withering room to reduce the air humidity in the withering room, which is the first precipitation treatment for tea leaves; S3, low temperature to keep green: while the dehumidification equipment is continuously dehumidifying, the refrigeration equipment is used to lower the indoor temperature, and the tea leaves are subjected to a second precipitation treatment; S4, negative pressure to remove green leaves: by setting low humidity air to blow into the room in different directions, high humidity air is extracted from the room in the corresponding direction, forming a negative pressure wind field with low humidity wind circulation in the room, continuously extracting the humidity of leaves and promoting the disappearance of green air, which is the third precipitation treatment for tea leaves; S5. Low oxygen color fixation: While extracting high humidity air from the room, reduce the proportion of oxygen in the indoor air, reduce leaf cell oxidation, and perform the fourth precipitation treatment on the tea leaves. S6. Hot air aroma enhancement: After sieving the tea leaves evenly, transfer them to the drying room, gather them into piles and place them on the platform. Use the hot air blower and dehumidifier alternately until the moisture content of the tea leaves is below 7%, and obtain high green white tea.

2. A high green white tea processing method according to claim 1, characterized in that: In step S1, the light-proof withering room is a room without sunlight, the lights are turned off during the withering process, and the fresh tea leaves are thinly spread to a thickness of 2-3 cm.

3. A high green white tea processing method according to claim 1, characterized in that: In step S2, the air humidity in the withering room ranges from 55% to 60%, and the water content of the leaves in the first precipitation needs to be controlled at 55% to 57%.

4. A high green white tea processing method according to claim 1, characterized in that: In step S3, before cooling down, the dehumidifier is kept running to make the indoor humidity reach about 55%, and the indoor temperature needs to be reduced to below 20°C.

5. A high green white tea processing method according to claim 1, characterized in that: In step S3, the moisture content of the blades in the second precipitation needs to be controlled at 45%-50%.

6. A high green white tea processing method according to claim 1, characterized in that: In step S4, the indoor temperature needs to be maintained below 23°C, and the water content of the leaves in the third precipitation needs to be controlled at 35%-40%.

7. A high green white tea processing method according to claim 1, characterized in that: In step S5, reducing the proportion of oxygen in the indoor air is specifically adding nitrogen into the withering chamber.

8. The method for processing high-quality green white tea according to claim 1, characterized in that: In step S5, the moisture content of the blades in the fourth precipitation needs to be controlled at 20%-25%.

9. A high green white tea processing method according to claim 1, characterized in that: In step S6, the temperature of the hot air blower is set to above 35°C, and the humidity of the dehumidification equipment is set to about 30%.

10. A high green white tea processing method according to claim 1, characterized in that: In step S6, the hot air blower and the dehumidifier are used alternately every two days. After 2-3 times of alternate use, the tea leaves are put into an aluminum foil bag, and the bag is opened to continue processing until the moisture content of the tea leaves is below 7%.

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