Bean-flavor Longjing raw material tea processing method based on novel powder light coupling magnetic induction tedding technology

Abstract

The invention provides a bean-flavor Longjing raw material tea processing method based on a novel powder light coupling magnetic induction tedding technology. The method comprises the following core steps: uniformly spreading withered fresh Longjing raw material tea leaves on a tedding frame; a powder light wave band light source (600-680 nm) with the specific wavelength and light intensity is adopted for conducting intermittent irradiation on the leaf layer; meanwhile, an alternating weak magnetic field (the frequency is 5-50 Hz, and the strength is 1-10 mT) is applied to the lower portion of the leaf layer; leaf layer temperature, humidity and leaf surface color change are monitored in real time through a sensor, and optomagnetic coupling parameters are dynamically adjusted until the tea leaves are properly tedded. According to the method, moisture migration, enzyme activity excitation and directional conversion of flavor precursor substances in the tea leaves are synergistically promoted through the photo-magnetic coupling effect, precise, uniform and efficient control of the tedding process is achieved, and the bean fragrance quality of the Longjing raw material tea is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of tea processing technology, specifically relating to a method for spreading Longjing raw tea leaves based on physical field control, and in particular a method for precisely controlling the spreading process of Longjing raw tea leaves by utilizing the coupling effect of light and magnetic field. Background Technology

[0002] Withering is a crucial step in the production of Longjing tea, bridging the preceding and following stages. Traditional withering relies mainly on natural conditions, where the slow evaporation of moisture triggers a series of slow biochemical reactions within the fresh leaves, laying the foundation for subsequent fixation. However, traditional methods are greatly affected by weather, temperature, and humidity, resulting in poor uniformity of withering, varying processing times (usually 6-10 hours), inconsistent quality, and heavy reliance on the experience of the tea master.

[0003] In the existing technology, some devices and methods have emerged that attempt to improve the withering process. For example, patent CN201710329730.X discloses a withering room with controllable temperature and humidity, which creates a stable environment through an air conditioning system. However, this method only controls the macroscopic environment, and its active regulation of the internal material transformation of tea leaves is weak, and its energy consumption is high. Other studies have attempted to treat tea leaves using a single physical field, such as far-infrared rays or specific blue light, but the effect on promoting uniformity and aroma quality is limited, with problems such as poor aroma enhancement and insufficient synergistic effect.

[0004] Therefore, how to provide a new method that can actively, accurately, and uniformly control the withering process of Longjing raw tea, reduce environmental dependence, and improve aroma quality and stability has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a processing method for Longjing tea raw materials based on a new powder-optical coupled magnetic induction withering technology. This method uses the coupling effect of powder and light with an alternating weak magnetic field to synergistically regulate the physiological and biochemical processes of tea leaves, achieving rapid, uniform, and precise withering, thereby stabilizing and improving the color, aroma, and taste quality of Longjing raw tea.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A processing method for bean-scented Longjing tea raw materials based on a new powder-optical coupled magnetic induction withering technology, the core of which lies in constructing a physical field control environment coupled with light and magnetism. Specific steps include: Leaf spreading: The moderately withered fresh Longjing tea leaves (usually one bud and two or three newly unfolded leaves) are evenly and loosely spread on a specially designed powder-light coupled magnetic induction spreading device. This spreading device features a light-transmitting surface that does not affect the magnetic field. Specifically, the spreading device has a multi-layered structure, using iron partitions to separate the layers. Each layer is independently equipped with a powder-light irradiation device, a magnetic field generating device, and a temperature and humidity sensing and monitoring device, achieving independent and precise control of each layer. The powder-light irradiation device uses powder-light LED tubes, the magnetic field generating device includes a magnetic heating element, and the temperature and humidity sensing and monitoring device includes temperature and humidity sensors.

[0007] Light irradiation: Activate the light irradiation LED array located above the leaf layer. Select light in the 600-680 nm wavelength range. This wavelength has moderate photon energy, which can be partially absorbed by the mesophyll cells, gently raising the leaf temperature and promoting the activity of proteases, ester oxygenases, and amylases, without causing photoinhibition or excessive heat generation that could lead to "over-greening". Intermittent irradiation is used to simulate the natural diurnal rhythm of light, giving the tea leaves a physiological recovery period, which is beneficial for the accumulation of flavor compounds.

[0008] Magnetic induction treatment: The electromagnetic coil embedded in the leaf-spreading rack is activated simultaneously to generate a low-frequency alternating weak magnetic field perpendicular to the leaf surface. The magnetic field can affect cell membrane potential and ion channels non-thermally, increasing membrane permeability and promoting the migration and exchange of intracellular water and flavor substances. The magnetic field couples with the light field to produce a synergistic effect.

[0009] Intelligent control: The system integrates temperature and humidity sensors and machine vision cameras. The sensors monitor the temperature and relative humidity of the leaf microenvironment in real time; the camera captures changes in leaf color. The central controller dynamically adjusts the light cycle, light intensity, and magnetic field frequency and intensity based on the preset process curve and real-time feedback data, ensuring that the spreading process always proceeds along the optimal path.

[0010] Endpoint determination: When the system determines that the water loss rate of fresh leaves reaches 18%-22%, and the leaf color changes from bright green to dark green, the luster disappears, the leaf texture softens slightly, and the fragrance persists, the processing will automatically stop, completing the withering process. The total processing time can be shortened to 3-5 hours, and the uniformity is better.

[0011] Processing finished Longjing raw tea: Spread the green leaves into continuous shaping and fixing (fixing temperature 280 ℃-320 ℃, 5 min), winnowing, continuous flattening (170 ℃-190 ℃, 4 min), aroma enhancement (80 ℃-100 ℃, 30 min-40 min), to obtain Longjing raw tea.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1) Quality Improvement and Stability: The photomagnetic coupling effect can more effectively activate and guide the enzymatic reactions and biochemical transformation pathways inside the tea leaves, promote the formation and accumulation of flavor substances such as amino acids, soluble sugars, and simple catechins, and lay a better material foundation for the formation of the "fresh, sweet and mellow" taste and "tender and fragrant bean aroma" of Longjing raw tea, and significantly improve batch stability.

[0013] 2) High efficiency and uniformity: The physical field energy has strong penetrating power and can act on both the surface and inner layers of tea leaves simultaneously, overcoming the unevenness problem of "dry surface and wet interior" in traditional methods. Processing time is significantly shortened, and production efficiency is improved.

[0014] 3) Environmentally friendly and intelligent: It reduces the heavy reliance of traditional processes on specific weather and locations, and can be carried out indoors. Closed-loop control is achieved through sensor feedback, which reduces the reliance on human experience. The process is highly replicable and easy to standardize and upgrade to intelligent systems.

[0015] 4) Energy saving and safety: The powder LEDs and weak magnetic field generators used have low energy consumption and no chemical residues, and belong to clean and safe physical processing technology. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the method for implementing the present invention; Figure 2 This is a schematic diagram of the powder-optical coupled magnetic induction spreading device of the present invention; In the diagram, 1-temperature and humidity sensor, 2-powder LED tube, 3-iron partition, 4-image acquisition camera, 5-magnetic heating coil layer, 6-pulley. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments.

[0018] Example 1

[0019] Fresh leaves of the Longjing 43 tea tree variety (one bud and three leaves) were picked and evenly spread in a thickness of about 3 cm on the first layer of the powder-light coupled magnetic induction spreading device. The system was started and the initial parameters were set as follows: the powder light (main wavelength 630 nm) irradiation mode was cycled on for 15 minutes and off for 10 minutes, with a light intensity of 300 lux; the alternating magnetic field frequency was 30 Hz, the intensity was 5 mT, and the direction was vertically upward.

[0020] During the spreading process, the sensor monitored the temperature at the center of the leaf layer and maintained it at 25±1 ℃. When the image analysis system detected that the green channel value of the leaf surface dropped to 75% of the initial value (about 4 hours later), the system automatically adjusted the light mode to be on for 10 minutes and off for 15 minutes, and the light intensity was reduced to 220 lux; the magnetic field frequency was adjusted to 12 Hz and the intensity was reduced to 2 mT.

[0021] After approximately 1 hour of continued treatment, the system detected a water loss rate of 20.8%, and the leaves became dark green with a distinct fragrance, at which point all treatments were automatically stopped. The total time for spreading the leaves was 4.5 hours.

[0022] The green leaves are spread out and subjected to continuous shaping and fixing (fixing temperature 280 ℃-320 ℃, 5 min), winnowing, continuous flattening (170 ℃-190 ℃, 4 min), and aroma enhancement (80 ℃-100 ℃, 30 min-40 min) to obtain Longjing raw tea.

[0023] Example 2

[0024] Fresh leaves of the Longjing 43 tea tree variety (one bud and three leaves) were picked and evenly spread in a thickness of about 3 cm on the first layer of the powder-light coupled magnetic induction spreading device. The system was started and the initial parameters were set as follows: the powder light (main wavelength 630 nm) irradiation mode was cycled on for 15 minutes and off for 10 minutes, with a light intensity of 350 lux; the alternating magnetic field frequency was 33 Hz, the intensity was 6 mT, and the direction was vertically upward.

[0025] During the spreading process, the sensor monitored the temperature at the center of the leaf layer and maintained it at 25±1 ℃. When the image analysis system detected that the green channel value of the leaf surface dropped to 75% of the initial value (about 4 hours later), the system automatically adjusted the light mode to be on for 10 minutes and off for 15 minutes, and the light intensity was reduced to 260 lux; the magnetic field frequency was adjusted to 13 Hz and the intensity was reduced to 3 mT.

[0026] After approximately 1 hour of continued treatment, the system detected a water loss rate of 20.5%, and the leaves became dark green with a distinct fragrance, at which point all treatments were automatically stopped. The total time for spreading the leaves was approximately 4.3 hours.

[0027] The green leaves are spread out and subjected to continuous shaping and fixing (fixing temperature 280 ℃-320 ℃, 5 min), winnowing, continuous flattening (170 ℃-190 ℃, 4 min), and aroma enhancement (80 ℃-100 ℃, 30 min-40 min) to obtain Longjing raw tea.

[0028] Example 3

[0029] Fresh leaves of the Longjing 43 tea tree variety (one bud and three leaves) were picked and evenly spread in a thickness of about 3 cm on the first layer of the powder-light coupled magnetic induction spreading device. The system was started and the initial parameters were set as follows: the powder light (main wavelength 630 nm) irradiation mode was cycled on for 15 min and off for 10 min, with a light intensity of 450 lux; the alternating magnetic field frequency was 40 Hz, the intensity was 9 mT, and the direction was vertically upward.

[0030] During the spreading process, the sensor monitored the temperature at the center of the leaf layer and maintained it at 25±1 ℃. When the image analysis system detected that the green channel value of the leaf surface dropped to 75% of the initial value (about 4 hours later), the system automatically adjusted the light mode to be on for 10 minutes and off for 15 minutes, and the light intensity was reduced to 230 lux; the magnetic field frequency was adjusted to 18 Hz and the intensity was reduced to 6 mT.

[0031] After approximately 1 hour of continued treatment, the system detected a water loss rate of 19.6%, and the leaves became dark green with a distinct fragrance, at which point all treatments were automatically stopped. The total time for spreading the leaves was approximately 3.8 hours.

[0032] The green leaves are spread out and subjected to continuous shaping and fixing (fixing temperature 280 ℃-320 ℃, 5 min), winnowing, continuous flattening (170 ℃-190 ℃, 4 min), and aroma enhancement (80 ℃-100 ℃, 30 min-40 min) to obtain Longjing raw tea.

[0033] Comparative Example Fresh leaves of the Longjing 43 tea tree variety, consisting of one bud and three leaves, were picked and evenly spread on the first layer of a multi-layered withering rack to a thickness of approximately 3 cm. After 7.5 hours of treatment, the water loss rate reached 21.3%.

[0034] The green leaves are spread out and subjected to continuous shaping and fixing (fixing temperature 280 ℃-320 ℃, 5 min), winnowing, continuous flattening (170 ℃-190 ℃, 4 min), and aroma enhancement (80 ℃-100 ℃, 30 min-40 min) to obtain Longjing raw tea.

[0035] The sensory quality of the Longjing raw tea obtained in Examples 1-3 and the comparative example was evaluated using the following methods: Sensory evaluation of the raw tea was conducted using a three-factor evaluation method, including three quality factors: tea liquor color, aroma, and taste. 3.0 g of Longjing raw tea was weighed and placed in a 150 mL evaluation cup, filled with boiling water, and timed for 4 minutes. The tea liquor was then filtered, leaving the tea leaves in the cup. A coded evaluation method was used to sequentially evaluate the tea liquor color, aroma, and taste of the Longjing raw tea. The total evaluation score was 100 points, with the following scoring coefficients for each quality factor: liquor color (20%), aroma (40%), and taste (40%).

[0036] Y = A × a + B × b + C × c Y: Total score for sensory evaluation.

[0037] B and C represent the three quality factors: color, aroma, and taste, respectively.

[0038] a, b, and c: represent the rating coefficients of the three quality factors mentioned above, respectively.

[0039] The sensory quality evaluation results are shown in Table 1.

[0040] Table 1. Sensory quality evaluation results of Longjing raw tea obtained in Examples 1-3 and comparative examples.

[0041] According to the sensory quality evaluation results in Table 1, compared with the comparative examples, the Longjing raw tea of ​​Examples 1-3 of the present invention has a green color, a higher bean aroma, and a mellow and sweet taste. The sensory evaluation scores are significantly higher than those of Longjing raw tea processed by the traditional withering method.

[0042] The aroma compounds in the Longjing raw tea prepared in Examples 1-3 and the comparative examples were determined by GC-MS. The specific determination method is as follows: (1) Extraction of Longjing raw tea samples Take the sample from the -80 °C freezer (unless otherwise specified, the sample is assumed to be a solid fresh sample) and grind it with liquid nitrogen. Vortex mix thoroughly. Weigh approximately 500 mg (1 mL liquid) of each sample into a headspace vial. Add saturated NaCl solution and 20 μL (10 μg / mL) internal standard solution to each vial. Perform sample extraction using fully automated headspace solid-phase microextraction (HS-SPME) for GC-MS analysis.

[0043] (2) Headspace solid-phase microextraction treatment Under constant temperature of 60 °C, the sample was shaken for 5 min, and a 120 µm DVB / CWR / PDMS extraction tip was inserted into the headspace vial for headspace extraction for 15 min. The sample was then desorbed at 250 °C for 5 min, followed by GC-MS separation and identification. The extraction tip was aged at 250 °C for 5 min in a Fiber Conditioning Station before sampling. Note: New extraction tips were aged in a Fiber Conditioning Station for 2 h before extraction. An SPME arrow was used, which has a sensitivity up to 10 times that of traditional SPME fiber tips.

[0044] (3) Chromatographic conditions: DB-5MS capillary column (30 m × 0.25 mm × 0.25 μm, Agilent J&W Scientific, Folsom, CA, USA), carrier gas: high-purity helium (purity not less than 99.999%), constant flow rate: 1.2 mL / min, injection port temperature: 250 °C, splitless injection, solvent delay: 3.5 min. Temperature program: 40 °C, hold for 3.5 min, increase to 100 °C at 10 °C / min, then increase to 180 °C at 7 °C / min, and finally increase to 280 °C at 25 °C / min, hold for 5 min.

[0045] (4) Mass spectrometry conditions: Electron impact ion source (EI), ion source temperature 230 °C, quadrupole temperature 150 °C, mass spectrometry interface temperature 280 °C, electron energy 70 eV, scanning mode selected ion detection mode (SIM), qualitative and quantitative ion precise scanning (GB23200.8-2016).

[0046] The aroma test results are shown in Table 2.

[0047] Table 2. Content of aroma substances in Longjing raw tea obtained in Examples 1-3 and comparative examples.

[0048] According to Table 2, which lists the aroma compounds in Longjing raw tea, compared to the comparative example, the Longjing raw tea from Examples 1-3 of this invention contains higher levels of β-linalool, limonene, β-myrcene, 6-methyl-5-hepten-2-one, dehydrolinalool, benzaldehyde, and β-cyclocitral, while the contents of α-terpinene, trans-β-ocimene, 2-methylbutanal, β-phellandrene, decanal, 4-terpene alcohol, isoterpinene, β-phellandrene, decanal, 4-terpene alcohol, and isoterpinene are lower than those in the comparative example.

Claims

1. A processing method for bean-scented Longjing tea raw materials based on a new powder-optical coupled magnetic induction withering technology, characterized in that... Includes the following steps: 1) Spreading the leaves: Spread the fresh tea leaves evenly on the powder-photocoupled magnetic induction spreading device, with a leaf thickness of 2-5 cm; 2) Powder irradiation: Turn on the powder irradiation device set above the powder-coupled magnetic induction spreading device, and periodically irradiate the leaf layer with a light beam with a wavelength range of 600-680 nm and a light intensity of 100-500 lux. The irradiation time of each cycle is 10-30 min, and the interval time is 5-15 min. 3) Magnetic induction treatment: Simultaneously activate the magnetic field generator integrated inside the powder-optical coupling magnetic induction spreading device to apply an alternating weak magnetic field with a frequency of 5-50 Hz and a magnetic induction intensity of 1-10 mT to the leaf layer. 4) Intelligent control and endpoint determination: The temperature and humidity sensors and image acquisition devices set in the spreading area monitor the state parameters of the leaf layer in real time; the light parameters of the powder irradiation and the magnetic field parameters of the magnetic induction processing are dynamically adjusted according to the monitored state parameters; the spreading is completed when the water loss rate of the fresh leaves reaches 15%-25%, the leaf color turns dark green and the aroma is revealed, and the spreading is obtained. 5) Subsequent processing: The withered leaves are sequentially subjected to strip-cutting, wind selection, continuous flattening and aroma enhancement to obtain bean-scented Longjing raw tea.

2. The processing method for bean-scented Longjing raw tea based on the new powder-optical coupled magnetic induction withering technology as described in claim 1, characterized in that, The powder irradiation device uses an LED light source with a main wavelength of 630 nm ± 10 nm.

3. The processing method for bean-scented Longjing raw tea based on the new powder-optical coupled magnetic induction withering technology as described in claim 1, characterized in that, The specific method for dynamically adjusting the illumination parameters for powder irradiation is as follows: Based on the temperature at the center of the leaf layer monitored by the temperature and humidity sensor, the illumination mode is dynamically adjusted. When the temperature at the center of the leaf layer is below 22℃, continuous irradiation mode is used; When the temperature at the center of the leaf layer is between 22-28℃, the periodic intermittent irradiation mode is adopted. When the temperature at the center of the leaf layer exceeds 28°C, irradiation should be suspended and ventilation should be increased.

4. The processing method for bean-scented Longjing raw tea based on the new powder-optical coupled magnetic induction withering technology as described in claim 1, characterized in that, The direction of the alternating weak magnetic field is perpendicular to the leaf plane, and its magnetic field frequency is related to the on-off rhythm of the illumination: during the illumination period, the magnetic field frequency is set to 20-50 Hz; during the illumination period, the magnetic field frequency is adjusted to 5-20 Hz.

5. The processing method for bean-scented Longjing raw tea based on the new powder-optical coupled magnetic induction withering technology as described in claim 1, characterized in that, The light and magnetic field parameters are dynamically adjusted based on the state parameters. Specifically, this includes: acquiring leaf images through an image acquisition device and analyzing the RGB values ​​of the leaf color; when the green channel value of the leaf color drops to 70%-80% of its initial value and the red channel value rises, it is determined that the spreading process is close to the appropriate level, and the light intensity of the powder irradiation and the magnetic field intensity of the magnetic induction processing are gradually reduced.

6. The processing method for bean-scented Longjing raw tea based on the new powder-optical coupled magnetic induction withering technology as described in claim 1, characterized in that, The powder-optical coupled magnetic induction spreading device has a multi-layer structure, with each layer independently equipped with the powder irradiation device, magnetic field generating device, and temperature and humidity sensing and monitoring device, so as to achieve independent and precise control of each layer.

7. The processing method for bean-scented Longjing raw tea based on the new powder-optical coupled magnetic induction withering technology as described in claim 1, characterized in that, The temperature for fixing the strips is 280℃-320℃ for 5 minutes; the temperature for flattening is 170℃-190℃ for 4 minutes; and the temperature for enhancing aroma is 80℃-100℃ for 30-40 minutes.

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