Processing method for acicular green tea

Abstract

A processing method for needle-shaped green tea, comprising the steps of spreading, fixation, primary rolling, enzyme-added re-rolling, dehydration, shaping, and drying. The fixation is divided into three-stage treatment, and tannase is added during the re-rolling process for synchronous enzymatic hydrolysis. Specifically, an aqueous tannase solution with a mass concentration of 0.4-0.6% and an enzyme activity of 500 U / g is added, and the addition amount of the aqueous tannase solution is 1-3% of the mass of the tea leaves. In the present invention, through the continuous fixation method of high-temperature steam fixation - hot-air fixation - microwave fixation, the generation of brown pyropheophytin is reduced, the color of the fresh leaves is greatly maintained, and the conversion of tea protein to amino acid is promoted. Combining with the enzymatic hydrolysis treatment of adding tannase during re-rolling, it promotes the subsequent rolling to prepare a fine, straight, and compact needle-shaped structure, reduces the appearance of flat and broken shapes, and through the combination of shaping with high-temperature low-frequency - medium-temperature medium-frequency - low-temperature high-frequency and the three-step drying process, effectively promotes the fresh fragrance of the tea, the green and bright tea soup, and the mellow and refreshing taste.

Description

Technical Field

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

[0002] Green tea, with the quality characteristics of green leaves and green tea, is the largest type of tea produced and consumed in my country. Green tea is the most basic type of tea processing. Other types of processing are developed by improving the green tea techniques and retaining their characteristics. Green tea accounts for the largest proportion of Chinese tea, accounting for more than 60%, and is also the essence of tea processing technology. The processing technology of green tea mainly includes picking, drying, killing green, rolling and drying. Green tea can be divided into bud tea, needle-shaped tea, flat tea, curved tea, spiral tea, bead-shaped tea, orchid-shaped tea, etc. Among them, needle-shaped tea is formed by rolling, straightening and other key processes in the process of green tea processing, which makes green tea have a unique and beautiful appearance like pine needles, which is deeply loved by consumers. However, in actual production, needle-shaped green tea often has the characteristics of heavy flat strips, more broken pieces, dark color of dry tea, yellow-green soup color, astringent taste, low and dull aroma or obvious high-fire aroma, resulting in sudden changes in product style and reduced commodity value.

[0003] The root cause of the above problems is mainly due to the lack of process technology. First, the traditional method of killing green tea is inefficient and the degree of killing green tea is difficult to control. The southwestern tea region is the origin of my country's famous green tea in the morning market, but the roller method is generally used for withering, which is prone to insufficient withering, excessive moisture content and uneven moisture distribution, resulting in the failure of the green phytol with a strong grassy aroma to completely volatilize or convert into the fragrant trans-green phytol, and at the same time causing the tea soup to taste astringent and have a strong green aroma. Secondly, due to the unsatisfactory control of moisture, flat strips or broken shapes will be formed during the rolling process, and the needle-shaped structure will not be maintained ideally, and it is easy to cause the color of the tea to be dark and the aroma to lose the fragrance of the tea itself. Thirdly, drying is a key process for determining the quality of tea. Traditional drying methods all use high-then-low temperature control to achieve the effect of quickly fixing the quality of tea. However, if the temperature and time are not properly controlled, it is very easy to cause the fragrance of the tea to dissipate and the roasted aroma to be obvious. At the same time, under the action of heat, the sugar and amino acid flavor substances in the tea are prone to caramelization, making the tea soup bitter. Summary of the invention

[0004] Based on the above technical problems, the purpose of the present invention is to provide a processing method for needle-shaped green tea, which effectively forms a straight, tight and fine needle-shaped appearance structure with emerald green color, while retaining the fragrance of the tea leaves, with green and bright leaves and complete bottom, thereby improving the overall quality of the green tea.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A processing method for needle-shaped green tea, comprising the steps of spreading for withering, fixation, primary rolling, enzyme-added re-rolling, dehydration, shaping by straightening, and drying, characterized in that: the fixation is divided into three-stage treatment. In the first stage, steam fixation is adopted, in the second stage, hot air fixation is adopted, and in the third stage, microwave fixation is adopted. The steam temperature for steam fixation in the fixation is 455-460°C, and the fixation time is 30-38 s. Immediately after the steam fixation ends, hot air fixation is carried out. The hot air temperature is 115-120°C, and the time is 40-50 s. After the hot air fixation ends, it is cooled to room temperature with cold air, and then the third-stage microwave fixation is carried out. The microwave power is 13.5 kW, and the time is 50-65 s. The enzyme-added re-rolling is to add tannase during the re-rolling process for synchronous enzymatic hydrolysis.

[0007] After the fixation ends, the water content of the tea leaves is between 57% and 59%.

[0008] In the present invention, by adjusting the fixation method and carrying out high-temperature fixation above 455°C, the fixation rate is improved. The relatively high steam temperature has extremely strong penetration, which promotes the rapid inactivation of enzyme substances such as polyphenol oxidase and peroxidase in the fresh leaves, reduces the generation of brown pheophytin, and greatly maintains the color of the fresh leaves. Then, through hot air fixation, the excessive water remaining on the leaf surface during the steam fixation process is removed. At the same time, after treatment at a relatively high temperature and then reducing the temperature, thermal reactions occur under a large temperature difference, increasing the hydrolysis of protein substances into amino acid substances, so as to achieve the loss of low-boiling-point green flavor aroma substances and the increase of precursor substances of the fresh aroma type. At the same time, after two-stage fixation with a large temperature difference, the problem of uneven water distribution between the leaf surface and the leaf stalk will occur, resulting in uncontrollable crushing of tea cells during the subsequent rolling process. Therefore, finally, through microwave fixation, while consolidating the first two steps of fixation, the temperature is increased from the inside of the leaves by microwave, achieving rapid fixation while promoting the redistribution of water in the tea leaves and leaf stalks. The water is more evenly distributed in the tea leaves, which is beneficial to the development of the rolling process, improves the rolling efficiency, and ensures the uniform crushing of cells.

[0009] Further, there is a hot air dehydration step between the primary rolling and the re-rolling. The hot air temperature is 90-100°C, and the dehydration time is 190-240 s, and the dehydration is carried out until the water content of the tea leaves is 50-54%.

[0010] Further, during re-rolling, an aqueous tannase solution with a mass concentration of 0.4-0.6% and an enzyme activity of 500 U / g is added to the tea leaves, and the addition amount of the aqueous tannase solution is 1-3% of the mass of the tea leaves.

[0011] During the hydrolysis process, tannase can decompose the ester catechins in tea leaves, which have strong bitterness and astringency and are easily oxidized, and convert them into simple catechins such as GA and EGC. While reducing the bitterness of the tea soup, it ensures that the catechin content in the tea does not decrease, and at the same time increases the content of certain amino acids, improving the smoothness of the tea soup. However, it was found that when hydrolyzing with tannase protease during the rolling process, macromolecules such as proteins, cellulose, and starch in the tea leaves are prone to complexation reactions with tannase proteins, affecting the activity of tannase and reducing the hydrolysis effect. After the decomposition of ester catechins, they are not well converted into simple catechins, and the effect on the content of amino acids is not obvious either.

[0012] In the present invention, due to the combined use of high-temperature steam fixation and hot-air fixation with a large temperature difference during fixation, macromolecules such as proteins and cellulose in the tea leaves are effectively decomposed. When adding tannase during subsequent rolling, this technical problem is effectively solved, ensuring the activity of tannase and improving the hydrolysis efficiency. Moreover, by adding an aqueous solution of tannase during the rolling process, a certain degree of redistribution of the moisture in the tea leaves is formed, which, in cooperation with the subsequent variable-temperature and variable-frequency shaping means, achieves an efficient effect of shaping and enhancing the fragrance.

[0013] Furthermore, the shaping is carried out in a variable-temperature and variable-frequency manner. Specifically, the tea leaves are shaped at a temperature of 160 °C and a frequency of 180 times / min for 4 min, then at a temperature of 150 °C and a frequency of 190 times / min for 7 min, and finally at a temperature of 140 °C and a frequency of 200 times / min for 4 min.

[0014] Furthermore, the drying is carried out in three steps. The temperature in the first step of drying is 105 - 115 °C, the drying time is 4 - 6 min, and the cooling and moisture regain time is 1 - 2 h. The temperature in the second step of drying is 90 - 100 °C, the drying time is 4 - 6 min, and the cooling and moisture regain time is 8 - 10 h. The temperature in the third step of drying is 75 - 85 °C, and the drying time is 7 - 10 min.

[0015] Most specifically, a processing method for needle-shaped green tea is characterized by the following steps:

[0016] S1. Spreading: Picking the new shoots of tea trees with one bud and one leaf or one bud and two leaves as fresh tea leaves, spreading them with a thickness of 4 - 5 cm, and spreading for 2 - 4 h;

[0017] S2. Fixation: Fixing the fresh tea leaves in turn by steam fixation, hot-air fixation, and microwave fixation. The steam temperature for steam fixation is 455 - 460 °C, the fixation time is 30 - 38 s. Immediately after the steam fixation, hot-air fixation is carried out. The hot-air temperature is 115 - 120 °C, and the time is 40 - 50 s. After the hot-air fixation, it is cooled to room temperature with cold air, and then the third-stage microwave fixation is carried out. The microwave power is 13.5 kW, and the time is 50 - 65 s. After the fixation, it is cooled;

[0018] S3. Primary rolling: Use a rolling machine to roll the tea leaves after de-enzyming for 10 - 15 minutes, and immediately break up the rolled tea leaves;

[0019] S4. Hot air dehydration: Conduct dehydration treatment through a hot air dehydration device, with the hot air temperature being 90 - 100 °C and the dehydration time being 3 - 5 minutes;

[0020] S5. Secondary rolling: Use the same method as the primary rolling to conduct a second rolling on the tea leaves after hot air dehydration for 10 - 15 minutes. During the secondary rolling, add an aqueous solution of tannase with a mass concentration of 0.4 - 0.6% and an enzyme activity of 500 U / g, and the addition amount is 1 - 3% of the tea leaf mass. Immediately break up the tea leaves after rolling, and then let them stand for 30 minutes;

[0021] S6. Shaping: First, process at 160 °C and a frequency of 180 times / minute for 4 minutes, then process at 150 °C and a frequency of 190 times / minute for 7 minutes, and finally raise the temperature to 140 °C and a frequency of 200 times / minute for 4 minutes to conduct shaping. After completion, cool with cold air;

[0022] S7. Drying: Adopt three-step drying treatment. The temperature of the first step of drying is 105 - 115 °C, and the drying time is 4 - 6 minutes, with a cooling and moisture regain of 1 - 2 hours. The temperature of the second step of drying is 90 - 100 °C, and the drying time is 4 - 6 minutes, with a cooling and moisture regain of 8 - 10 hours. The temperature of the third step of drying is 75 - 85 °C, and the drying time is 7 - 10 minutes;

[0023] S8. Obtain the final finished product through air separation, color sorting, stalk picking, and impurity removal.

[0024] By combining "temperature-variable and frequency-variable shaping" with "three-step low-temperature drying", the effect of solidifying shape and enhancing fragrance is effectively achieved. Using temperature-variable and frequency-variable shaping avoids the damage to chlorophyll and the like in tea leaves caused by high temperature and high frequency. On the premise of the temperature-variable and frequency-variable shaping method, drying is carried out in a way of gradually decreasing the temperature in three steps. Compared with the traditional one-step drying or two-step drying method of first high and then low, it effectively ensures that the needle shape is not damaged by subsequent processes, and at the same time can effectively avoid the demagnesiation of chlorophyll, thereby reducing the occurrence of the "Maillard" reaction in tea leaves, which is beneficial to the green tea to maintain the flavor characteristics of green appearance color, clear green soup, elegant fragrance, and mellow taste.

[0025] The present invention has the following technical effects:

[0026] In the present invention, through the continuous tea-killing method of high-temperature steam tea-killing - hot-air tea-killing - microwave tea-killing, the generation of brown pyropheophytin is reduced, the color of fresh tea leaves is greatly maintained, the conversion of tea leaf protein into amino acids is promoted, the subsequent rolling is facilitated to prepare a fine, straight, firm and compact needle-shaped structure, the appearance of flat and broken shapes is reduced, and through the combination of shaping by high-temperature and low-frequency - medium-temperature and medium-frequency - low-temperature and high-frequency and the three-step drying process, the fresh fragrance of tea is effectively promoted, the tea soup is green and bright, and the taste is mellow and refreshing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : Pictures of needle-shaped green tea prepared in Example 1 and Comparative Example 2.

[0028] Figure 2 : Pictures of the tea soup brewed from the needle-shaped green tea prepared in Example 1 and Comparative Example 2.

[0029] Figure 3 : Pictures of the leaf bottoms of the needle-shaped green tea after brewing in Example 1 and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above content of the present invention.

[0031] Example 1

[0032] A processing method for needle-shaped green tea is carried out according to the following steps:

[0033] S1. Spreading: Picking the new shoots of tea trees with one bud and one leaf or one bud and two leaves as fresh tea leaves, spreading them with a thickness of 4 - 5 cm, and spreading for 3 h;

[0034] S2. Tea-killing: Sequentially using steam tea-killing, hot-air tea-killing and microwave tea-killing methods to tea-kill fresh tea leaves. The steam temperature for steam tea-killing is 460 °C, the tea-killing time is 35 s. Immediately after the steam tea-killing is completed, hot-air tea-killing is carried out. The hot-air temperature is 120 °C and the time is 45 s. After the hot-air tea-killing is completed, it is cooled to room temperature with cold air, and then the third-stage microwave tea-killing is carried out. The microwave power is 13.5 kW and the time is 60 s. After the tea-killing is completed, the water content of the tea leaves is 58%;

[0035] S3. Primary rolling: Using a rolling machine to roll the tea leaves after tea-killing for 12 min, and immediately breaking up the rolled tea leaves;

[0036] S4. Hot-air dehydration: Carrying out dehydration treatment through a hot-air dehydration device, with a hot-air temperature of 95 °C and a dehydration time of 4 min;

[0037] S5. Secondary kneading: The tea leaves after hot air dehydration are kneaded for the second time by the same means as the primary kneading. During the secondary kneading, an aqueous tannase solution with a mass concentration of 0.5% and an enzyme activity of 500 U / g is added to the tea leaves. The addition amount of the aqueous tannase solution is 2% of the mass of the tea leaves. After kneading, the lumps are immediately loosened, and then left to stand for 30 min;

[0038] S6. Shaping and straightening: First, it is processed at 160 °C and a frequency of 180 times / min for 4 min, then at 150 °C and a frequency of 190 times / min for 7 min, and finally heated to 140 °C and processed at a frequency of 200 times / min for 4 min for shaping and straightening. After completion, it is cooled with cold air, and the moisture content of the tea leaves is 52%;

[0039] S7. Drying: Three-step drying treatment is adopted. The temperature of the first step of drying is 110 °C, the drying time is 5 min, and it is cooled and returned to normal moisture for 1.5 h. The temperature of the second step of drying is 90 °C, the drying time is 5 min, and it is cooled and returned to normal moisture for 8 h. The temperature of the third step of drying is 80 °C, the drying time is 7 min, and then it is cooled;

[0040] S8. Remove the light and single pieces, tea stalks, heavy and solid foreign matters, etc. through an air separator, select the yellow tea, dark tea strips, etc. through a tea color sorter, and use a step-by-step tea stalk picking machine to pick the tea with a length of less than 1.5 cm, pick out the impurities and the tea that does not conform to the appearance quality of the product to obtain the final finished product.

[0041] In terms of color, the quality of the tea is reflected as "three greens", namely, the tea is green, the tea soup is green, and the tea bottom is green. As Figure 1 shown, the left figure is the shaped green tea leaves prepared in Example 1 of the present invention, and the right figure is the shaped green tea leaves prepared by two-step drying in Comparative Example 2. It can be clearly seen that the color of the tea leaves prepared in Example 1 is greener and more moist, while the color of the tea leaves prepared in Comparative Example 2 is yellowish and less moist. Using the same brewing method to brew the tea leaves prepared in Example 1 and Comparative Example 2, the results of the tea soup are as Figure 2 shown. The tea soup brewed from the tea leaves prepared in Example 1 is yellowish green and bright (left figure), while the color of the tea soup brewed from the tea leaves prepared in Comparative Example 2 is relatively light (right figure). The tea bottom after soaking is as Figure 3 shown. The tea bottom in Example 1 is yellowish green and tender and bright in color (left figure), while the tea bottom in Comparative Example 2 is yellowish and dull (right figure).

[0042] When evaluating the color and luster, the lab colorimetric method is adopted for color and luster analysis. Usually, comparisons are made through the data of L value, a value, and b value. Among them, the L value represents the surface brightness of the tea leaves, and the larger the value, the higher the brightness. The a value represents the degree of greenness of the tea leaves. The smaller the a value, the stronger the greenness of the color and luster. As the a value increases, the color shows a changing trend from dark green to gray to bright pink. The b value represents the degree of yellowness of the tea leaves. The larger the b value, the stronger the yellowness. As the b value increases, the color shows a changing trend from bright blue to gray to yellow.

[0043] Compared with Example 1, with other conditions unchanged, by adjusting the temperature and time of the third drying step in the drying process, the effects on the color and luster and quality of the tea leaves are detected. The results are shown in Table 1, where the control group is the initial data corresponding to the tea leaves after the second drying treatment in Example 1.

[0044] Table 1: Effects of the third drying at different temperatures and drying times on the color and luster and quality of needle-shaped green tea

[0045]

[0046] The control group is actually the L, a, and b data of the tea leaves measured after completing the second drying. It can be seen from the table that as time extends, the L value under low-temperature drying at 70°C generally shows a trend of first decreasing and then increasing, with occasional fluctuations; while the L value at 80°C and 90°C shows a wavy fluctuation. As time extends, the a value generally shows a trend of first decreasing and then increasing at each temperature. At 90°C, the longer the drying time, the larger the a value. At the same drying time, the a value corresponding to 90°C has the largest increase, indicating that high temperature is likely to cause the color and luster of green tea to turn red. At each temperature, as time extends, the b value generally shows a wavy changing trend and all increase after drying, indicating that drying makes the color and luster of the formed green tea turn yellow.

[0047] Through the above comparisons, it can be seen that during the third drying process, when drying at 80°C for 7 minutes, the color and luster effect of the obtained tea leaves is the most ideal. When the temperature exceeds 90°C, the color and luster effects of the processed tea leaves are all poor. During the experiment, temperatures higher than 90°C were also tried, and it was found that as the temperature increases and time extends, the negative impact on the color and luster of the tea leaves is greater. When the temperature is as low as 70°C or even lower, the tea leaves cannot be dried well, and the impact on the color and luster of the tea leaves is not ideal.

[0048] Compared with Example 1, with other conditions unchanged, by changing the moisture regain time before the third drying step, the effects on the color and luster and quality of the tea leaves are detected. The results are shown in Table 2, where the control group is the initial data corresponding to the tea leaves after the second drying treatment in Example 1.

[0049] Table 2:

[0050] Moisture regain time L* a* b* Control 27.52±0.28 0.09±0.06 6.02±0.47 0 min 26.02±0.51 0.22±0.05 5.69±0.35 120 min 26.42±0.39 0.19±0.06 5.71±0.23 240 min 26.85±0.31 0.14±0.08 5.84±0.36 360 min 27.26±0.43 0.08±0.09 6.10±0.28 480 min 27.69±0.50 0.05±0.08 6.49±0.39 600 min 27.55±0.46 0.07±0.05 6.52±0.17 720 min 27.46±0.86 0.08±0.02 6.39±0.54 840 min 27.24±0.49 0.09±0.02 6.28±0.72

[0051] As can be seen from the above table, when the rewetting time increases from 0 to 6 h, although the L value shows an upward trend, it is lower than the L value at the end of the second-stage drying. By comparing the effects of different rewetting times on the color of tea leaves, it can be known that when the rewetting time is more than 8 h, as the time prolongs, the L value only shows a downward trend, and the a value and b value show an upward trend. However, when the rewetting time is 8 - 12 h, the effects on the L, a, and b values are all beneficial.

[0052] Comparative Example 1:

[0053] Compared with Example 1, in this solution, the temperature of steam fixation in the fixation step is as low as 140 °C, and the fixation time is 35 s. Then, the hot air temperature is 120 °C and the time is 45 s. After the hot air fixation ends, it is cooled to room temperature with cold air, and then the third-stage microwave fixation is carried out with a microwave power of 13.5 kW and a time of 60 s; the remaining steps are the same as those in Example 1.

[0054] Comparative Example 2

[0055] Compared with Example 1, in this solution, drying is carried out in two steps. The drying temperature in the first step is 110 °C and the drying time is 5 min. The drying temperature in the second step is 90 °C until the water content of the tea leaves is 5 - 6%; the remaining steps are the same as those in Example 1.

[0056] Comparative Example 3

[0057] In this solution, different variable temperature and variable frequency means are tried for shaping the tea strips, and the remaining steps are the same as those in Example 1 to reflect the effects of different variable temperature and variable frequency shaping of the tea strips combined with three-stage temperature-controlled drying on the final physical and chemical components and visual quality of the tea leaves. The specific variable temperature and variable frequency are shown in Table 3.

[0058] Table 3:

[0059]

[0060] With the processing time fixed, by adjusting the temperature and frequency during the shaping of the tea strips, the color of the prepared tea products is analyzed, and the results are shown in Table 4.

[0061] Table 4: Changes in the color of needle-shaped green tea prepared by different solutions

[0062] Treatment L a b Comparative example 1 26.72±0.16 0.15±0.38 6.42±0.50 Comparative example 2 27.26±0.33 0.16±0.27 6.36±0.68 Stir-frying 1 26.29±0.36 0.16±0.15 6.32±0.31 Stir-frying 2 26.34±0.45 0.12±0.22 6.39±0.42 Stir-frying 3 26.75±0.29 0.14±0.51 6.25±0.26 Stir-frying 4 26.59±0.42 0.10±0.12 6.41±0.54 Stir-frying 5 26.40±0.18 0.11±0.45 6.50±0.23 Stir-frying 6 26.83±0.29 0.14±0.22 6.44±0.30 Example 1 27.60±0.42 0.07±0.10 6.68±0.28 Stir-frying 7 27.12±0.36 0.09±0.27 6.52±0.46

[0063] As can be seen from the above table, for the shaping method, the temperature is first set at 160°C with a frequency of 180 times / min, then at 150°C with a frequency of 190 times / min, and finally at 140°C with a frequency of 200 times / min. Such a variable-temperature and variable-frequency shaping method of high temperature and low frequency - medium temperature and medium frequency - low temperature and high frequency results in relatively good overall color of the tea leaves. Secondly, the method of high temperature and high frequency - medium temperature and high frequency - low temperature and high frequency in shaping 7 also shows good results. The other variable-temperature and variable-frequency shaping methods do not achieve good effects. It can be seen that only by combining different variable-temperature and variable-frequency shaping methods with a three-step drying process can the tea leaves in Example 1 present good color. When using the above shaping method and then selecting the drying method of high temperature first and then low temperature in Comparative Example 2 for processing the tea leaves, it is found that the overall color effect of the tea leaves prepared by high temperature and high frequency - medium temperature and medium frequency - high temperature and high frequency in shaping 5 is the best, with specific L value of 26.98±0.52, a value of 0.14±0.32, and b value of 6.26±0.21.

[0064] Example 2

[0065] A processing method for acicular green tea is carried out according to the following steps:

[0066] S1. Spreading: Picking the new shoots of tea trees with one bud and one leaf or one bud and two leaves as fresh tea leaves, spreading them with a thickness of 4 - 5 cm, and spreading for 2 - 4 h;

[0067] S2. Fixing: Fixing the fresh tea leaves by using steam fixing, hot air fixing and microwave fixing in sequence. The steam temperature for steam fixing is 455°C, and the fixing time is 30 s. Immediately after steam fixing, hot air fixing is carried out. The hot air temperature is 120°C, and the time is 40 s. After hot air fixing, it is cooled to room temperature with cold air, and then the third-stage microwave fixing is carried out. The microwave power is 13.5 kW, and the time is 65 s. After fixing, the water content of the tea leaves is 59%;

[0068] S3. Primary rolling: Rolling the fixed tea leaves with a rolling machine for 10 min, and immediately breaking up the rolled tea leaves;

[0069] S4. Hot air dehydration: Conducting dehydration treatment through a hot air dehydration device, with the hot air temperature being 100°C and the dehydration time being 3 min;

[0070] S5. Re-rolling: Conducting the second rolling on the tea leaves after hot air dehydration by using the same method as in primary rolling. During re-rolling, an aqueous solution of tannase with a mass concentration of 0.6% and an enzyme activity of 500 U / g is added to the tea leaves, and the addition amount is 3% of the tea leaf mass. After rolling, break up the tea leaves immediately, and then let it stand for 30 min;

[0071] S6. Shaping: First, process at 160°C and a frequency of 180 times / min for 4 minutes, then process at 150°C and a frequency of 190 times / min for 7 minutes, and finally raise the temperature to 140°C and process at a frequency of 200 times / min for 4 minutes for shaping. After that, cool with cold air to complete the shaping.

[0072] S7. Drying: Use three-step drying. The temperature for the first step of drying is 115°C, the drying time is 4 minutes, followed by 1 hour of cooling and moisture regain. The temperature for the second step of drying is 100°C, the drying time is 4 minutes, followed by 10 hours of cooling and moisture regain. The temperature for the third step of drying is 75°C, the drying time is 10 minutes, and then cool.

[0073] S8. Remove light and single pieces, tea stalks, heavy and solid foreign matters, etc. through an air separator, select yellow tea, dark tea strips, etc. with a tea color sorter, use a step-by-step tea stalk picking machine to pick tea with a length of less than 1.5 cm, pick out impurities and tea that does not conform to the appearance quality of the product to obtain the final finished product.

[0074] Example 3

[0075] A processing method for needle-shaped green tea is carried out according to the following steps:

[0076] S1. Spreading: Pick the new shoots of tea trees with one bud and one leaf or one bud and two leaves as fresh tea leaves, and spread them with a thickness of 4 - 5 cm for 2 - 4 hours.

[0077] S2. Fixing: Fix the fresh tea leaves by using steam fixing, hot air fixing and microwave fixing in sequence. The steam temperature for steam fixing is 460°C, the fixing time is 38 s. Immediately after the steam fixing ends, carry out hot air fixing. The hot air temperature is 115°C and the time is 50 s. After the hot air fixing ends, cool with cold air to room temperature, and then carry out the third stage of microwave fixing. The microwave power is 13.5 kW and the time is 50 s. After the fixing ends, the water content of the tea leaves is 57%.

[0078] S3. Primary rolling: Use a rolling machine to roll the fixed tea leaves for 15 minutes, and immediately break up the rolled tea leaves.

[0079] S4. Hot air dehydration: Carry out dehydration treatment through a hot air dehydration device. The hot air temperature is 90°C and the dehydration time is 5 minutes.

[0080] S5. Secondary rolling: Use the same method as the primary rolling to carry out the second rolling on the tea leaves after hot air dehydration. During the secondary rolling, add an aqueous solution of tannase with a mass concentration of 0.4%, an enzyme activity of 500 U / g, and the addition amount is 1% of the tea leaf mass. Immediately break up the tea leaves after the rolling ends, and then let it stand for 30 minutes.

[0081] S6. Shaping the tea strips: First, process at 160°C and a frequency of 180 times / min for 4 minutes, then process at 150°C and a frequency of 190 times / min for 7 minutes, and finally raise the temperature to 140°C and process at a frequency of 200 times / min for 4 minutes to shape the tea strips. After that, cool with cold air;

[0082] S7. Drying: Adopt three-step drying treatment. The temperature of the first step of drying is 105°C, and the drying time is 6 minutes, followed by cooling and moisture regain for 2 hours. The temperature of the second step of drying is 95°C, and the drying time is 6 minutes, followed by cooling and moisture regain for 8 hours. The temperature of the third step of drying is 85°C, and the drying time is 8 minutes, then cool;

[0083] S8. Remove the light and single pieces, tea stalks, heavy and solid foreign matters, etc. through an air separator, select the yellow tea, dark tea strips, etc. through a tea color sorter, and use a stepped tea stalk picking machine to pick the tea with a length of less than 1.5 cm, pick out the impurities and the tea that does not conform to the appearance quality of the product to obtain the final product.

[0084] By detecting the contents of gallic acid (GA), caffeine (CAF), gallocatechin (GC), epigallocatechin (EGC), catechin (C), epigallocatechin gallate (EGCG), and epicatechin gallate (ECG) in the tea soup soaked from the tea prepared by different schemes, the detection results are shown in Table 5.

[0085] Table 5: Comparison of catechin contents in needle-shaped green tea prepared by different schemes (%)

[0086] Each scheme GA GC EGC C EGCG CAF ECG Comparative example 1 0.07±0.02 0.27±0.12 3.24±0.22 0.22±0.01 10.86±0.23 4.29±0.15 2.28±0.04 Comparative example 2 0.10±0.03 1.58±0.1 3.65±0.41 0.31±0.06 10.18±0.5 4.13±0.25 2.16±0.18 Example 1 0.18±0.04 2.37±0.23 4.55±0.05 0.49±0.02 9.78±0.32 4.41±0.17 2.08±0.15 Example 2 0.19±0.03 2.34±0.30 4.46±0.11 0.45±0.01 10.09±0.47 4.46±0.12 2.02±0.20 Example 3 0.19±0.06 2.28±0.33 4.51±0.06 0.47±0.02 10.12±0.39 4.50±0.29 2.05±0.31 Stir-frying 1 0.04±0.01 0.51±0.42 3.71±0.84 0.22±0.05 11.53±0.62 4.09±0.16 2.57±0.25 Stir-frying 2 0.06±0.01 0.94±0.09 3.59±0.56 0.25±0.01 11.8±0.54 4.02±0.18 2.48±0.08 Stir-frying 3 0.11±0.02 1.46±0.42 3.92±0.19 0.25±0.08 11.04±0.26 4.28±0.32 2.61±0.02 Stir-frying 4 0.15±0.01 1.83±0.46 4.10±0.33 0.28±0.04 11.02±0.23 4.10±0.02 2.41±0.03 Stir-frying 5 0.12±0.02 1.78±0.48 4.15±0.16 0.38±0.01 10.89±0.58 4.22±0.19 2.26±0.26 Stir-frying 6 0.15±0.01 1.94±0.36 4.02±0.21 0.30±0.06 10.56±0.46 4.17±0.19 2.39±0.14 Stir-frying 7 0.13±0.03 2.06±0.51 4.15±0.32 0.36±0.05 10.54±0.37 4.33±0.24 2.40±0.18

[0087] It can be seen that in Comparative Example 1, a relatively low temperature of 140°C was used for steam fixation during the fixation process. The contents of epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) in the prepared green tea were higher than those in the examples, and the contents of gallic acid (GA), catechin (C), and epigallocatechin (EGC) were all at relatively low levels. It can be seen that due to the lack of good decomposition of macromolecules such as proteins and cellulose in the early stage, the tannase was complexed with the macromolecules and its activity was inhibited to a certain extent, resulting in a decrease in the ability of tannase to decompose ester-type catechins to generate substances such as GA and EGC. And the drying process was a two-step drying method of high temperature first and then low temperature, and the content level of catechins in the prepared green tea was not high either. When using different variable temperature and variable frequency tea strip shaping methods, the content of catechins in the prepared green tea was at a relatively high level by combining the tea strip shaping method of high temperature and low frequency - medium temperature and medium frequency - low temperature and high frequency with the three-step drying process.

[0088] Detection method:

[0089] (1) For the detection of the main physical and chemical components of tea, the determination of water extract was carried out in accordance with GB / T 8305-2002; the determination of polyphenols was carried out in accordance with GB / T 8313-2008; the determination of amino acids was carried out in accordance with GB / T 8314-2013; the determination of caffeine was carried out in accordance with GB / T 8312-2013; the determination of soluble sugar was carried out by the sulfuric acid-anthrone colorimetric method; the determination of chlorophyll was carried out by spectrophotometry.

[0090] (2) For the detection of the sensory quality of tea, referring to GB / T 23776-2009, three senior tea tasters scored respectively, and then the average score was calculated.

[0091] Combined with existing research, needle-shaped green tea was made by the processes of each scheme, and the effects on the sensory quality and main physical and chemical components (contents of tea polyphenols, amino acids, caffeine, soluble sugar, chlorophyll and water extract) of each needle-shaped green tea were analyzed. 100 g was taken from each tea sample and repeated 3 times. The test results are shown in Table 6 below.

[0092] Table 6: Comparison of the contents of physical and chemical components of needle-shaped green tea prepared by different schemes (%)

[0093]

[0094] It can be seen that the contents of tea polyphenols, amino acids, caffeine, soluble sugar, water extract and total chlorophyll of the needle-shaped green tea prepared in the present invention are significantly different from those of the green tea prepared by the low-temperature steam fixation in Comparative Example 1, the two-step drying process in Comparative Example 2 and the different temperature-changing and frequency-changing shaping methods in Comparative Example 3.

[0095] Through the visual comparison of the appearance, color, taste, etc. of tea leaves, tea soup and tea residues, the results are shown in Table 7.

[0096] Table 7: Comparison of the sensory quality of needle-shaped green tea prepared by different schemes

[0097]

[0098] As can be seen from the above table, the needle-shaped green tea prepared in Examples 1-3 of the present invention has relatively excellent effects in terms of appearance, color, tea soup and taste, and the overall score is also relatively high. The prepared tea leaves maintain their thin, straight and tight needle-shaped structure, with bright and moist green color, the brewed tea soup is green and bright in color, showing a sweet fragrance and a mellow and refreshing taste.

Claims

1. A processing method for needle-shaped green tea, comprising the steps of spreading, fixing, primary rolling, secondary rolling, dehydration, shaping, and drying, characterized in that: The fixation is divided into three stages. In the first stage, steam fixation is used. In the second stage, hot air fixation is used. In the third stage, microwave fixation is used. The steam temperature for steam fixation in the fixation process is 455 - 460 °C, and the fixation time is 30 - 38 s. Immediately after the steam fixation ends, hot air fixation is carried out. The hot air temperature is 115 - 120 °C, and the time is 40 - 50 s. After the hot air fixation ends, it is cooled to room temperature with cold air, and then the third-stage microwave fixation is carried out. The microwave power is 13.5 kW, and the time is 50 - 65 s. The shaping is carried out in a way of variable temperature and variable frequency. Specifically, the leaves are shaped at 160 °C and a frequency of 180 times / min for 4 min, then at 150 °C and a frequency of 190 times / min for 7 min, and finally at 140 °C and a frequency of 200 times / min for 4 min. The drying is carried out in three steps. The temperature for the first step of drying is 105 - 115 °C, and the drying time is 4 - 6 min. After that, it is cooled and allowed to return to moisture for 1 - 2 h. The temperature for the second step of drying is 90 - 100 °C, and the drying time is 4 - 6 min. After that, it is cooled and allowed to return to moisture for 8 - 10 h. The temperature for the third step of drying is 75 - 85 °C, and the drying time is 7 - 10 min, then it is cooled.

2. The processing method of a needle-shaped green tea according to claim 1, characterized in that: There is also a hot air dehydration step between the first kneading and the second kneading. The hot air temperature is 90 - 100 °C, and the dehydration time is 190 - 240 s. The dehydration is carried out until the water content of the tea leaves reaches 50 - 54%.

3. A processing method for needle-shaped green tea, characterized in that, The steps are as follows: S1. Spreading: Picking one bud with one or two leaves of the tea tree shoot as fresh tea leaves for spreading, with a spreading thickness of 4 - 5 cm and a spreading time of 2 - 4 h; S2. Fixation: The fresh tea leaves are fixed in turn by steam fixation, hot air fixation and microwave fixation. The steam temperature for steam fixation is 455 - 460 °C, and the fixation time is 30 - 38 s. Immediately after the steam fixation ends, hot air fixation is carried out. The hot air temperature is 115 - 120 °C, and the time is 40 - 50 s. After the hot air fixation ends, it is cooled to room temperature with cold air, and then the third-stage microwave fixation is carried out. The microwave power is 13.5 kW, and the time is 50 - 65 s. After the fixation ends, it is cooled; S3. First kneading: Kneading the fixed tea leaves with a kneading machine for 10 - 15 min, and immediately breaking up the kneaded tea leaves; S4. Hot air dehydration: Dehydration treatment is carried out through a hot air dehydration device. The hot air temperature is 90 - 100 °C, and the dehydration time is 3 - 5 min; S5. Second kneading: Kneading the tea leaves after hot air dehydration by the same method as the first kneading. When kneading, an aqueous solution of tannase with a mass concentration of 0.4 - 0.6% and an enzyme activity of 500 U / g is added, and the addition amount is 1 - 3% of the tea leaf mass. Immediately after the kneading ends, break up the tea leaves, and then let it stand for 30 min; S6. Shaping: First, process at 160 °C and a frequency of 200 times / min for 4 min, then at 150 °C and a frequency of 190 times / min for 7 min, and finally heat up to 160 °C and a frequency of 200 times / min for 4 min to carry out shaping. After the end, it is cooled with cold air; S7. Drying: Three-step drying treatment is adopted. For the first step of drying, the temperature is 105 - 115 °C, the drying time is 4 - 6 min, followed by cooling and moisture regain for 1 - 2 h. For the second step of drying, the temperature is 90 - 100 °C, the drying time is 4 - 6 min, and then cooling and moisture regain for 8 - 10 h. For the third step of drying, the temperature is 75 - 85 °C, the drying time is 7 - 10 min, and then cooling; S8. The final product is obtained after air separation, color sorting, stem picking, and impurity removal.

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