Tea leaf de-enzyming method by sealing and moisturizing fresh leaf with water vapor

Abstract

The application provides a tea leaf fixation method using fresh leaf water vapor sealing and moisturizing, and relates to the technical field of tea processing. The method comprises placing tea fresh leaves in a fixation space provided with an openable and closable steam exhaust channel for heating, and closing the steam exhaust channel. The moisture of the tea fresh leaves is vaporized by heat to form water vapor, which accumulates in the fixation space. The tea leaf fixation method using fresh leaf water vapor sealing and moisturizing detects the pair disturbance during the fixation process of the tea fresh leaves in a sealed and moisturized state. The second steam exhaust is triggered according to the water vapor partial pressure recovery state after the first steam exhaust. The first recovery time and the second recovery time are compared to determine the water release change of the tea fresh leaves in the current fixation stage. The end time of the fixation in the sealed and moisturized state is controlled according to the water release change. The method reduces the influence of the water content and water migration speed difference of different batches of tea fresh leaves on the end point judgment, and makes the end condition of the fixation in the sealed and moisturized state correspond to the actual water release state of the tea fresh leaves.

Description

Technical Field

[0001] This invention relates to the field of tea processing technology, specifically to a method for fixing tea leaves by utilizing the moisture of fresh leaves in a sealed environment. Background Technology

[0002] Fixing (or killing the green) is a crucial step in tea processing, primarily used to inhibit enzyme activity in fresh leaves, control changes in internal substances, and cause some moisture loss. After fixing, the leaves gradually soften and can proceed to subsequent processes such as rolling, shaping, and drying. Current tea fixing methods mainly include pan-fired fixing, drum fixing, hot air fixing, and steam fixing. Pan-fired and drum fixing utilize a heated pan or drum to transfer heat to the fresh leaves; hot air fixing uses flowing hot air to heat the leaves; and steam fixing uses high-temperature steam to raise the temperature of the leaves. After the fresh leaves enter the fixing equipment, the moisture in the leaves vaporizes and is released into the fixing space. As heating continues, the temperature of the fresh leaves gradually increases, and the leaf tissue changes accordingly. In actual production, operators adjust the fixing temperature, fixing time, equipment speed, and ventilation based on the tea variety, maturity, moisture content, and amount of leaves used. Some fixing equipment is equipped with a dehumidification structure, through which the moisture generated during fixing is discharged, maintaining appropriate temperature and humidity conditions inside the equipment.

[0003] Existing blanching methods that use a closed-loop, humidified approach often determine the timing of termination based on preset time, set humidity, or the degree of moisture leakage. However, different batches of fresh leaves have varying moisture content and water migration rates, making it difficult to accurately determine the timing of termination for the closed-loop, humidified stage based solely on these conditions, as the actual water release state of the fresh leaves varies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for fixing tea leaves using the moisture of fresh leaves in a sealed environment. The technical problem this invention aims to solve is: how to solve the problem of difficulty in accurately reflecting the actual water release state of different batches of fresh tea leaves, which leads to the difficulty in determining the timing of the sealing and moisturizing fixing process, by using a paired disturbance detection process triggered by the recovery response of the moisture partial pressure of the fresh tea leaves themselves.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for fixing tea leaves using the moisture vapor of fresh leaves in a sealed environment, comprising:

[0006] S1. Place the fresh tea leaves in a fixation space equipped with an openable and closable steam exhaust channel for heating. Close the steam exhaust channel. The moisture in the fresh tea leaves will vaporize due to the heat and form water vapor that accumulates in the fixation space. Keep the steam exhaust channel closed and continue to heat the fresh tea leaves to perform a sealed and moisturizing fixation.

[0007] S2. During the sealed and moisturizing fixation process, paired disturbance detection is performed. The first steam exhaust is performed based on the water vapor partial pressure before the first steam exhaust to remove the water vapor in the fixation space until the water vapor partial pressure decreases by a preset disturbance ratio relative to the water vapor partial pressure before the first steam exhaust, and then the steam exhaust channel is closed. From the time the steam exhaust channel is closed, the water vapor partial pressure recovery process during the continued heating and water release of the fresh tea leaves is detected. The increase in water vapor partial pressure relative to the water vapor partial pressure when the steam exhaust channel is closed after the first steam exhaust is taken as the first water vapor partial pressure recovery amount. The first recovery time required for the first water vapor partial pressure recovery amount to reach the preset recovery ratio of the water vapor partial pressure reduction caused by the first steam exhaust is obtained. The preset recovery ratio is greater than 0 and less than 1.

[0008] S3. When the first water vapor partial pressure recovery amount reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the first exhaust, the second exhaust is performed, and the water vapor in the blanching space is discharged based on the water vapor partial pressure before the second exhaust, until the water vapor partial pressure is reduced by the preset disturbance ratio relative to the water vapor partial pressure before the second exhaust, and then the exhaust channel is closed.

[0009] S4. After the second steam exhaust is closed, the water vapor partial pressure recovery process is detected. The increase in water vapor partial pressure relative to the water vapor partial pressure when the exhaust channel is closed after the second steam exhaust is taken as the second water vapor partial pressure recovery amount. The second recovery time required for the second water vapor partial pressure recovery amount to reach the preset recovery ratio of the water vapor partial pressure reduction caused by the second steam exhaust is obtained. When the second recovery time is less than a preset multiple of the first recovery time, the closed moisturizing blanching process continues, and the paired disturbance detection is performed again in the subsequent closed moisturizing blanching process. When the second recovery time reaches or exceeds the preset multiple of the first recovery time, the closed moisturizing blanching process ends.

[0010] S5. After the closed-loop moisturizing fixation is completed, the steam exhaust channel is opened to continue heating and steam exhausting the fresh tea leaves.

[0011] Preferably, no external moisture or steam is added to the blanching space during the sealed and moisturizing blanching process.

[0012] Preferably, the water vapor partial pressure is determined based on the temperature and relative humidity within the withering space, and both the temperature and relative humidity are detected in the gas phase region above the fresh tea leaves.

[0013] Preferably, the preset disturbance ratio is 10%-30%.

[0014] Preferably, the preset recovery ratio is 40%-70%, the first recovery time ends when the first water vapor partial pressure recovery amount first reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the first exhaust steam, and the second recovery time ends when the second water vapor partial pressure recovery amount first reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the second exhaust steam.

[0015] Preferably, the opening degree of the exhaust passage is the same during the first exhaust period and the second exhaust period.

[0016] Preferably, the preset multiple is 1.15-1.60.

[0017] Preferably, the same heating power for fresh tea leaves is used during the acquisition of the first water vapor partial pressure recovery amount and the second water vapor partial pressure recovery amount.

[0018] This invention provides a method for fixing tea leaves using the moisture vapor from fresh leaves in a sealed environment. It has the following beneficial effects:

[0019] This tea fixation method, utilizing the moisture-retaining properties of fresh tea leaves, employs paired disturbance detection during the closed-loop fixation process. A second steam release is triggered by the recovery of the water vapor partial pressure after the first release, and the recovery times are compared to determine the water release changes of the tea leaves at the current fixation stage. Based on this, the termination time of the closed-loop fixation is controlled. This method reduces the impact of differences in moisture content and water migration rate between different batches of fresh tea leaves on the endpoint determination, ensuring that the termination conditions of the closed-loop fixation correspond to the actual water release state of the fresh tea leaves.

[0020] Two steam exhaust processes with the same perturbation ratio are used, and the first and second recovery times are determined with the same recovery ratio, ensuring uniform comparison conditions for the two water vapor partial pressure recovery processes. The second steam exhaust is triggered by the first water vapor partial pressure recovery process, and the second recovery time reflects the change in water release from the tea leaves after the first steam exhaust. The comparison between the first and second recovery times is used to identify changes in the water release capacity of the tea leaves, reducing deviations caused by determining the end time solely based on preset time, set humidity, or water vapor overflow status. Attached Figure Description

[0021] Figure 1 This is an overall flowchart of the method of the present invention;

[0022] Figure 2 This is a flowchart of the paired disturbance detection process of the present invention;

[0023] Figure 3 This is a schematic diagram of the blanching system of the present invention. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention have been clearly and completely described. 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.

[0025] Example 1

[0026] like Figure 1-3 As shown, this embodiment of the invention provides a method for fixing tea leaves using the moisture vapor of fresh leaves in a sealed environment, comprising:

[0027] S1. Place the fresh tea leaves in a fixation chamber equipped with an openable and closable steam venting channel for heating. Close the steam venting channel, and the moisture in the fresh tea leaves will vaporize and accumulate in the fixation chamber. Keep the steam venting channel closed and continue heating the fresh tea leaves for a sealed and moisturizing fixation process. Do not add external moisture or steam to the fixation chamber during this process.

[0028] S2. During the closed-loop, moisturizing fixation process, paired disturbance detection is performed. The first steam exhaust is conducted based on the water vapor partial pressure before the first exhaust, removing water vapor from the fixation space until the water vapor partial pressure decreases by a preset disturbance ratio relative to the water vapor partial pressure before the first exhaust, at which point the exhaust channel is closed. From the time the exhaust channel is closed, the water vapor partial pressure recovery process during the continued heating and moisture release of the tea leaves is monitored. The increase in water vapor partial pressure relative to the water vapor partial pressure at the time the exhaust channel is closed after the first exhaust is taken as the first water vapor partial pressure recovery amount. The first recovery time required for the first water vapor partial pressure recovery amount to reach the preset recovery ratio of the water vapor partial pressure decrease caused by the first exhaust is obtained. The preset recovery ratio is greater than 0 and less than 1. The water vapor partial pressure is determined based on the temperature and relative humidity within the fixation space, both of which are detected in the gas phase region above the tea leaves. The preset disturbance ratio is 10%-30%. The preset recovery ratio is 40%-70%. The first recovery time ends when the first water vapor partial pressure recovery amount first reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the first exhaust steam. The second recovery time ends when the second water vapor partial pressure recovery amount first reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the second exhaust steam.

[0029] S3. When the first water vapor partial pressure recovery reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the first exhaust, a second exhaust is performed. The water vapor in the blanching space is discharged based on the water vapor partial pressure before the second exhaust until the water vapor partial pressure is reduced by a preset disturbance ratio relative to the water vapor partial pressure before the second exhaust, at which point the exhaust passage is closed. The exhaust passage opening is the same during the first exhaust and the second exhaust.

[0030] S4. After the second steam exhaust is completed and the exhaust channel is closed, the moisture partial pressure recovery process is monitored. The increase in moisture partial pressure relative to the pressure at the time the exhaust channel was closed after the second steam exhaust is taken as the second moisture partial pressure recovery amount. The second recovery time required for the second moisture partial pressure recovery amount to reach the preset recovery ratio of the moisture partial pressure reduction caused by the second steam exhaust is obtained. When the second recovery time is less than a preset multiple of the first recovery time, the closed-loop moisturizing fixation process continues, and paired disturbance detection is performed again during subsequent closed-loop moisturizing fixation processes. When the second recovery time reaches or exceeds a preset multiple of the first recovery time, the closed-loop moisturizing fixation process ends. The preset multiple is 1.15-1.60. The same heating power for fresh tea leaves is used during the acquisition of the first and second moisture partial pressure recovery amounts.

[0031] S5. After the closed-loop moisturizing fixation is completed, open the steam exhaust channel to continue heating and steam exhausting the fresh tea leaves.

[0032] The preset disturbance ratio is set at 10%-30%, which can reduce the excessive alteration of the original sealed and humidified environment during the exhaust process while forming a recognizable change in water vapor partial pressure. The preset recovery ratio is set at 40%-70%, which ensures that the second exhaust is in the stage where the water vapor partial pressure has not fully recovered from the first exhaust, reducing the impact of short-term airflow disturbance and near-complete recovery on the detection results.

[0033] The same disturbance ratio is used for both exhaust cycles, and the recovery time is determined by the same recovery ratio, so that the first recovery time and the second recovery time have a unified basis for comparison.

[0034] The preset multiplier is 1.15-1.60, used to identify stages where the second recovery time has clearly extended relative to the first recovery time. This range reduces premature termination due to slight fluctuations and avoids delayed termination of the occlusive moisturizing process.

[0035] The preset disturbance ratio, preset recovery ratio, and preset multiple correspond to the disturbance establishment, the second exhaust timing, and the termination judgment, respectively. Together, they form a dynamic self-reference detection relationship for the same batch of fresh tea leaves.

[0036] Example 2

[0037] This embodiment uses tender leaf raw materials with high water content to verify the endpoint control of closed moisturizing under rapid water release conditions.

[0038] 1. Preparation of raw materials and equipment

[0039] Select fresh tea leaves with one bud and one to two leaves. The initial moisture content of the fresh tea leaves is 79.1%, and the amount of leaves added each time is 4.0 kg.

[0040] The blanching equipment adopts a horizontal drum structure. The effective volume of the blanching space is 0.18 m³, the drum speed is 12 r / min, and the drum wall is electrically heated. The inner diameter of the exhaust channel is 30 mm, and an electric butterfly valve is installed in the exhaust channel. During the first and second exhausts, the butterfly valve opening is 50%.

[0041] A temperature sensor and a relative humidity sensor are installed 120mm above the fresh tea leaves, with the horizontal distance between the detection position and the exhaust channel being 180mm. The temperature detection accuracy is ±0.3℃, and the relative humidity detection accuracy is ±1.5%RH, with a sampling period of 1s. The controller determines the partial pressure of water vapor based on the real-time temperature, relative humidity, and the saturated water vapor pressure at the corresponding temperature.

[0042] The moisture content of fresh tea leaves was calculated on a wet basis. 20.0 g of sample was taken each time and dried at 105℃ to constant weight.

[0043] 2. Determination of detection parameters

[0044] After mixing the same batch of fresh tea leaves, they were randomly divided into groups of 4.0 kg each. Each parameter group was tested using independent fresh tea leaves, and each group was repeated 3 times.

[0045] When selecting the preset disturbance ratio, the heating power is 2.6kW and the preset recovery ratio is 55%. The first steam venting is performed 90 seconds after the exhaust passage is closed.

[0046] When selecting the preset recovery ratio, the preset perturbation ratio is 20% for all conditions, and the other conditions remain the same.

[0047] Table 1: Detection results for different preset disturbance ratios and preset recovery ratios.

[0048] Parameter type Parameter value Recovery time coefficient of variation Supplementary test results Preset perturbation ratio 5% 12.4% The vapor phase temperature drops by 0.8℃ during the first exhaust phase. Preset perturbation ratio 10% 5.2% The vapor phase temperature drops by 1.5℃ during the first exhaust phase. Preset perturbation ratio 20% 3.7% The vapor phase temperature drops by 3.0℃ during the first exhaust phase. Preset perturbation ratio 30% 4.6% The vapor phase temperature drops by 4.3℃ during the first exhaust phase. Preset perturbation ratio 40% 4.1% The vapor phase temperature drops by 6.5℃ during the first exhaust phase. Preset recovery ratio 20% 10.8% The average ratio of the two recovery times was 1.06. Preset recovery ratio 40% 4.9% The average ratio of the two recovery times was 1.12. Preset recovery ratio 55% 3.5% The average recovery time ratio was 1.18. Preset recovery ratio 70% 4.4% The average ratio of the two recovery times was 1.16. Preset recovery ratio 90% 5.1% The average recovery time ratio was 1.05.

[0049] When the preset disturbance ratio is 5%, the recovery time fluctuates significantly; when the preset disturbance ratio is 40%, the decrease in gas phase temperature during exhaust increases. When the preset recovery ratio is 20%, the second recovery time exhibits significant dispersion; when the preset recovery ratio is 90%, the difference between the two recovery times decreases.

[0050] The official wrap-up uses a preset perturbation ratio of 20% and a preset recovery ratio of 55%, with the preset multiplier set to 1.25.

[0051] 3. Sealed and moisturized blanching

[0052] 4.0 kg of fresh tea leaves are placed into the processing chamber. The drum rotates at 12 r / min, and the heating power is set to 2.6 kW.

[0053] Close the vent and continue heating for 90 seconds. Do not add external moisture or steam during the sealed and humidified period.

[0054] At 90 seconds, the vapor temperature above the fresh tea leaves was 50.0℃, the relative humidity was 87.4%, and the corresponding water vapor partial pressure was 10.80 kPa. After the temperature and relative humidity remained within the sensor's detection accuracy range for 10 consecutive seconds, the first paired disturbance detection began.

[0055] 4. Paired disturbance detection

[0056] During the first test, the partial pressure of water vapor before the first exhaust was 10.80 kPa. After opening the exhaust channel, the partial pressure of water vapor dropped to 8.64 kPa, and then the exhaust channel was closed. The reduction in partial pressure of water vapor caused by the first exhaust was 2.16 kPa.

[0057] Continue heating at 2.6kW. When the first water vapor partial pressure recovery reaches 1.19kPa, the first recovery time is 18s, and the second steam exhaust is immediately initiated.

[0058] The partial pressure of water vapor before the second exhaust is 9.83 kPa. The exhaust channel is opened, and the partial pressure of water vapor drops to 7.86 kPa before the exhaust channel is closed. The second recovery time is 20 seconds when the second partial pressure of water vapor recovers to 1.08 kPa.

[0059] After obtaining the second recovery time, keep the exhaust passage closed and continue heating for 30 seconds before performing the next paired disturbance detection. Subsequent detections will use the same time interval and heating power.

[0060] Table 2: Results of paired disturbance detection of tender leaves with high water content.

[0061] Number of tests Water vapor partial pressure before the first exhaust steam Water vapor partial pressure after the first exhaust First recovery time Water vapor partial pressure before the second exhaust steam Water vapor partial pressure after the second exhaust Second recovery time Time ratio 1st time 10.80 kPa 8.64 kPa 18s 9.83 kPa 7.86 kPa 20s 1.11 2nd time 10.20 kPa 8.16 kPa 22s 9.28 kPa 7.42 kPa 25s 1.14 3rd 9.70 kPa 7.76 kPa 25s 8.83 kPa 7.06 kPa 32s 1.28

[0062] The time ratios obtained from the first two tests were both less than 1.25, so the closed-environment humidification process continued. The time ratio obtained from the third test was 1.28, reaching the preset multiple, so the closed-environment humidification process ended.

[0063] All three tests reached the preset recovery amount within 61 seconds, and there were no instances where the recovery amount could not reach the set value.

[0064] 5. Exhaust steam and result detection

[0065] After the sealed and moisturizing blanching process is completed, open the exhaust channel and continue heating and exhausting for 80 seconds while maintaining a heating power of 2.6kW.

[0066] Three independent experiments were conducted under the same conditions. In all three experiments, the closed-loop, moisturizing fixation process ended after the third paired disturbance detection, with time ratios of 1.28, 1.26, and 1.29, respectively. The moisture content of the fresh tea leaves after fixation was 62.1%, 61.8%, and 62.5%, respectively.

[0067] Fifty tea leaves were randomly selected from each batch, and the main stem was bent 180°. The number of broken leaves was recorded. The leaf stem breakage rates obtained in the three experiments were 4%, 6%, and 4%, respectively. One hundred tea leaves were randomly selected from each batch, and no tea leaves were found with browning area exceeding 10% of the leaf area.

[0068] Experimental results show that when using a preset perturbation ratio of 20% and a preset recovery ratio of 55%, the two water vapor partial pressure recovery processes maintain good detection stability. In all three independent experiments, the closed-loop moisturizing blanching process ended after the third paired perturbation detection, with the time ratio at termination concentrated between 1.26 and 1.29. After blanching, the moisture content and leaf stalk breakage rate remained close. Therefore, the method of this invention can determine the timing of ending the closed-loop moisturizing process based on the changes in the water release response of high-moisture-content young leaves.

[0069] Example 3

[0070] This embodiment uses fresh tea leaves with low moisture content after being spread out to verify the endpoint control of closed moisturizing under slow water release conditions.

[0071] 1. Preparation of raw materials and equipment

[0072] Select fresh tea leaves with one bud and three leaves of similar maturity and spread them out for 3.5 hours. The initial moisture content after spreading is 68.6%, and the amount of leaves added each time is 4.0 kg.

[0073] The blanching equipment adopts a horizontal drum structure. The effective volume of the blanching space is 0.18 m³, the drum speed is 12 r / min, and the drum wall is electrically heated. The inner diameter of the exhaust channel is 30 mm. During the first and second exhausts, the electric butterfly valve is opened to 50%.

[0074] Temperature and relative humidity sensors are installed 120mm above the fresh tea leaves, with a horizontal distance of 180mm between the sensor location and the exhaust channel. The temperature detection accuracy is ±0.3℃, and the relative humidity detection accuracy is ±1.5%RH, with a sampling period of 1s. The water vapor partial pressure is determined based on real-time temperature, relative humidity, and the saturated water vapor pressure at the corresponding temperature.

[0075] The method for determining moisture content is the same as in Example 2.

[0076] 2. Determining the preset multiplier

[0077] After mixing the fresh tea leaves from the same batch, they were randomly divided into groups of 4.0 kg each. The preset disturbance ratio was set to 25%, the preset recovery ratio was set to 65%, and the heating power was set to 2.8 kW.

[0078] The first paired disturbance detection begins 120 seconds after the exhaust passage is closed. After each second recovery time is obtained, the exhaust passage is kept closed and heating continues for 35 seconds before the next detection is performed.

[0079] The preset multipliers were set to 1.10, 1.15, 1.35, 1.50, 1.60, and 1.70, respectively, and each group was tested three times using independent fresh tea leaves. After the termination condition was reached, the steam was continued to be exhausted for 95 seconds.

[0080] Table 3: Results of blanching at different preset multipliers.

[0081] Preset multiplier Number of tests terminated Moisture content after blanching Leaf stalk breakage rate Brown leaf ratio 1.10 1 65.7% 22% 0 1.15 2 63.8% 10% 0 1.35 3 62.4% 6% 0 1.50 3 61.3% 4% 2% 1.60 4 59.9% 6% 4% 1.70 5 57.5% 8% 18%

[0082] When the preset multiplier is 1.10, the sealed moisturizing process ends earlier, and the leaf stalk breakage rate is 22%. When the preset multiplier is 1.70, the proportion of browned leaves increases to 18%. The preset multiplier for the final curing is 1.50.

[0083] 3. Sealed and moisturized blanching

[0084] 4.0 kg of fresh tea leaves were placed into the processing chamber. The drum speed was set to 12 r / min, and the heating power was set to 2.8 kW.

[0085] Close the vent and continue heating for 120 seconds. Do not add external moisture or steam during the sealed and humidified period.

[0086] At 120s, the gas phase temperature was 45.0℃, the relative humidity was 81.4%, and the corresponding water vapor partial pressure was 7.80kPa. After the temperature and relative humidity did not change beyond the sensor's detection accuracy range for 10 consecutive seconds, the first pairwise disturbance detection began.

[0087] 4. Paired disturbance detection

[0088] During the first test, the partial pressure of water vapor before the first exhaust was 7.80 kPa. After opening the exhaust channel, the partial pressure of water vapor dropped to 5.85 kPa, and then the exhaust channel was closed.

[0089] Continue heating at 2.8kW. When the first water vapor partial pressure recovery reaches 1.27kPa, the first recovery time is 31s, and the second exhaust steam is then vented.

[0090] The partial pressure of water vapor before the second exhaust is 7.12 kPa. The exhaust channel is opened, and the water vapor partial pressure drops to 5.34 kPa before the exhaust channel is closed. The second recovery time is 35 seconds when the second water vapor partial pressure recovers to 1.16 kPa.

[0091] After obtaining the second recovery time, keep the exhaust passage closed and continue heating for 35 seconds before performing the next paired disturbance detection. Subsequent detections will use the same time interval and heating power.

[0092] Table 4: Results of paired disturbance detection of fresh tea leaves with low moisture content.

[0093] Number of tests Water vapor partial pressure before the first exhaust steam Water vapor partial pressure after the first exhaust First recovery time Water vapor partial pressure before the second exhaust steam Water vapor partial pressure after the second exhaust Second recovery time Time ratio 1st time 7.80 kPa 5.85 kPa 31s 7.12 kPa 5.34 kPa 35s 1.13 2nd time 7.55 kPa 5.66 kPa 35s 6.89 kPa 5.17 kPa 44s 1.26 3rd 7.21 kPa 5.41 kPa 39s 6.58 kPa 4.94 kPa 61s 1.56

[0094] The time ratios obtained from the first two tests were both less than 1.50. The time ratio obtained from the third test was 1.56, reaching the preset multiple, and the closed-loop humidification sterilization was terminated.

[0095] All three tests reached the preset recovery amount, with the longest recovery time being 61 seconds.

[0096] 5. Exhaust steam and result detection

[0097] Open the exhaust passage and maintain a heating power of 2.8kW to continue heating and exhausting for 95 seconds.

[0098] Three independent experiments were conducted under the same conditions. In all three experiments, the closed-loop, moisturizing fixation process ended after the third paired disturbance detection, with time ratios of 1.56, 1.52, and 1.58, respectively. The moisture content of the fresh tea leaves after fixation was 60.6%, 60.2%, and 61.0%, respectively.

[0099] The leaf stalk breakage rate and the proportion of browned leaves were detected using the same method as in Example 2. The leaf stalk breakage rates obtained from the three experiments were 4%, 6%, and 4%, respectively, and no tea leaves with browned leaf area exceeding 10% of the leaf area were found in any of them.

[0100] Experimental results show that when the preset multiplier is between 1.15 and 1.60, the leaf stalk breakage rate and the proportion of browned leaves after fixation remain at a low level. In the formal experiment, 1.50 was used as the preset multiplier. In all three independent experiments, the closed-loop fixation was terminated after the third paired perturbation detection, with a termination time ratio of 1.52-1.58. Therefore, the method of this invention can determine the timing for ending the closed-loop fixation based on the changes in the recovery response of slowly releasing tea leaves after two consecutive cycles.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for fixing tea leaves using moisture from fresh leaves in a sealed environment, characterized in that, include: S1. Place the fresh tea leaves in a fixation space equipped with an openable and closable steam exhaust channel for heating. Close the steam exhaust channel. The moisture in the fresh tea leaves will vaporize due to the heat and form water vapor that accumulates in the fixation space. Keep the steam exhaust channel closed and continue to heat the fresh tea leaves to perform a sealed and moisturizing fixation. S2. During the sealed and moisturizing fixation process, paired disturbance detection is performed. The first steam exhaust is performed based on the water vapor partial pressure before the first steam exhaust to remove the water vapor in the fixation space until the water vapor partial pressure decreases by a preset disturbance ratio relative to the water vapor partial pressure before the first steam exhaust, and then the steam exhaust channel is closed. From the time the steam exhaust channel is closed, the water vapor partial pressure recovery process during the continued heating and water release of the fresh tea leaves is detected. The increase in water vapor partial pressure relative to the water vapor partial pressure when the steam exhaust channel is closed after the first steam exhaust is taken as the first water vapor partial pressure recovery amount. The first recovery time required for the first water vapor partial pressure recovery amount to reach the preset recovery ratio of the water vapor partial pressure reduction caused by the first steam exhaust is obtained. The preset recovery ratio is greater than 0 and less than 1. S3. When the first water vapor partial pressure recovery amount reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the first exhaust, the second exhaust is performed, and the water vapor in the blanching space is discharged based on the water vapor partial pressure before the second exhaust, until the water vapor partial pressure is reduced by the preset disturbance ratio relative to the water vapor partial pressure before the second exhaust, and then the exhaust channel is closed. S4. After the second steam exhaust is closed, the water vapor partial pressure recovery process is detected. The increase in water vapor partial pressure relative to the water vapor partial pressure when the exhaust channel is closed after the second steam exhaust is taken as the second water vapor partial pressure recovery amount. The second recovery time required for the second water vapor partial pressure recovery amount to reach the preset recovery ratio of the water vapor partial pressure reduction caused by the second steam exhaust is obtained. When the second recovery time is less than a preset multiple of the first recovery time, the closed moisturizing blanching process continues, and the paired disturbance detection is performed again in the subsequent closed moisturizing blanching process. When the second recovery time reaches or exceeds the preset multiple of the first recovery time, the closed moisturizing blanching process ends. S5. After the closed-loop moisturizing fixation is completed, the steam exhaust channel is opened to continue heating and steam exhausting the fresh tea leaves.

2. The method for fixing tea leaves using moisture from fresh leaves in a sealed environment according to claim 1, characterized in that: During the sealed and moisturizing blanching process, no external moisture or steam is added to the blanching space.

3. The method for fixing tea leaves using moisture from fresh leaves in a sealed environment according to claim 1, characterized in that: The partial pressure of water vapor is determined based on the temperature and relative humidity within the fixation space, and both the temperature and relative humidity are detected in the gas phase region above the fresh tea leaves.

4. The method for fixing tea leaves using moisture from fresh leaves in a sealed environment according to claim 1, characterized in that: The preset perturbation ratio is 10%-30%.

5. The method for fixing tea leaves using moisture from fresh leaves in a sealed environment according to claim 1, characterized in that: The preset recovery ratio is 40%-70%, the first recovery time ends when the first water vapor partial pressure recovery amount first reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the first exhaust steam, and the second recovery time ends when the second water vapor partial pressure recovery amount first reaches the preset recovery ratio of the water vapor partial pressure reduction caused by the second exhaust steam.

6. The method for fixing tea leaves using moisture from fresh leaves in a sealed environment according to claim 1, characterized in that: The opening degree of the exhaust passage is the same during the first exhaust period and the second exhaust period.

7. The method for fixing tea leaves using moisture from fresh leaves in a sealed environment according to claim 1, characterized in that: The preset multiple is 1.15-1.

60.

8. The method for fixing tea leaves using moisture from fresh leaves in a sealed environment according to claim 1, characterized in that: The same heating power for fresh tea leaves was used during the acquisition of the first water vapor partial pressure recovery amount and the second water vapor partial pressure recovery amount.

Images