Mulberry leaf tea deep freezing and thawing treatment preparation process and deep freezing device

Abstract

The invention relates to the technical field of tea processing, in particular to a deep freezing and thawing treatment preparation process of mulberry leaf tea and a deep freezing device. The process comprises the steps of fresh leaf cleaning, fresh leaf spreading, shredding, deep freezing, ice melting, primary drying, spreading for cooling and moisture regaining, rolling and wrapping, variable-temperature dynamic heaping for yellowing and drying. The process is used together with a deep freezing device, withering operation is reduced, deep freezing and ice melting are used for replacing a fermentation process, and low-temperature enzymatic oxidation is combined, so that more aroma components are obtained, the rolling strip forming rate is high, the tea leaves are internally puffed, the appearance is tight and heavy, and the quality is better.

Description

Technical Field

[0001] The invention relates to the technical field of tea processing, in particular to a deep freeze-thaw treatment preparation process for mulberry leaf tea and a deep freezing device. Background Art

[0002] The veins of fresh mulberry leaves are thick, and the leaves are generally picked relatively rough and uneven, which brings unfavorable factors to processing and makes the quality stability uncontrolled. Mulberry leaf tea made according to the conventional green tea process often has problems such as strong green smell and bitter taste; while mulberry leaf tea made according to the black tea fermentation process often has various quality defects such as uneven fermentation.

[0003] Patent application "A method and equipment for preparing mulberry leaf tea" 2014101090081 discloses a method for preparing mulberry leaf tea. During the production process, the mulberry leaves are broken up and screened by corresponding equipment to avoid breakage and clumping. The main production steps are "picking - cleaning - drying - shredding - killing green - rolling - breaking up - drying". The purpose is to make full use of mulberry leaf resources, simplify the preparation process, ensure that the prepared mulberry leaf tea does not turn yellow, and improve the taste.

[0004] In order to improve the taste of mulberry leaf tea, the patent "A method for preparing fermented mulberry leaf tea" 2018114403773 discloses a method for preparing fermented mulberry leaf tea. Through soaking in a certain concentration of salt water and eluting with vinegar, a large amount of oxalic acid is removed and alkaloids are neutralized, thereby achieving deodorization. The process includes "mulberry leaf grading-cleaning-salting-washing-vinegar steaming-washing-fermentation-rinsing-rolling-medium temperature drying-high temperature baking".

[0005] Patent "A Method for Preparing Blood Sugar-Lowering Mulberry Leaf Tea" 2016110906670 discloses mulberry leaf tea with blood sugar-lowering effect. It mainly involves mixing mulberry leaves with ancient mulberry tree blood sugar-lowering compound liquid with blood sugar-lowering effect before fermentation to play a coordinating role. It is an expansion of the function of mulberry leaf tea based on raw material selection.

[0006] In order to further improve the quality of mulberry leaf tea, solve the problem of uneven fermentation in the existing fermented mulberry leaf tea preparation, and the process optimization problem of mulberry leaf tea involving the aforementioned fermentation step, the present application proposes a deep freeze-thaw treatment preparation process and a deep freezing device for mulberry leaf tea. Summary of the invention

[0007] The invention provides a deep freeze-thaw treatment preparation process for mulberry leaf tea and a deep freezing device, which reduces the withering operation, uses deep freezing and ice melting to replace the fermentation process, and combines with low-temperature enzymatic oxidation to obtain more aroma components, has a high rolling rate, expands the inside of the tea leaves, makes the appearance tight and heavy, has a black and oily color, and has better quality, thereby solving the problems existing in the prior art.

[0008] One of the technical solutions adopted by the present invention is:

[0009] A deep freeze-thaw treatment process for preparing mulberry leaf tea is provided, which is characterized by comprising the following steps:

[0010] (1) Cleaning fresh leaves: Rinse the fresh mulberry leaves with clean water, remove water droplets from the leaf surface, and blow dry the leaf surface with cold air;

[0011] (2) Fresh leaf spreading: The dried fresh leaves are spread naturally for 3-6 hours at a room temperature of 25°C until the moisture content of the fresh leaves reaches 70%-72%;

[0012] (3) Cutting into strips: Cut the fresh leaves into strips with a width of 3 mm to 5 mm.

[0013] (4) Deep freezing: deep freezing the fresh leaves cut into strips with liquid nitrogen for 5-10 minutes;

[0014] (5) Thawing: Spread the deep-frozen fresh leaves in a strip-like shape indoors to melt naturally, and blow cold air to remove moisture from the surface of the leaves until most of the leaves turn brown;

[0015] (6) Primary drying: Drying is carried out by high temperature, short time and fast drying, and the moisture content is controlled at 58%-62%;

[0016] (7) Cooling and moisture recovery: The newly dried leaves are spread out at room temperature to recover moisture for 15-30 minutes until the leaves are soft and easy to roll;

[0017] (8) Kneading → Wrapping and kneading: Kneading for 10-15 minutes using the alternating pressure of "light, heavy, light" until the strip forming rate reaches 85%-95%; wrapping and kneading into round, tight and heavy granules;

[0018] (9) Dynamic yellowing with variable temperature: the temperature is controlled at 45℃-60℃, the relative humidity is controlled at 70%-75%; the time is 3h-4h;

[0019] (10) Drying: Drying is carried out in two steps. The first step is high temperature and fast drying, with the temperature controlled at 110°C-115°C, until the particles feel prickly, and then they are taken off the machine and spread out to air for 20-30 minutes. The second step is drying until the particles are fully dry, with the moisture content controlled below 6%.

[0020] Furthermore, fresh mulberry leaves require: the upper part of the mulberry tree should be free of pollution and pests and diseases, the top of the branches should have 1 to 5 leaves of dark green buds and tender stems, and the tender stems should not be lignified.

[0021] Furthermore, the temperature of the high temperature and short time rapid drying in step (6) is 110° C.-120° C., and the time is 5-10 min.

[0022] Furthermore, step (8) is performed by kneading with a kneading machine; and kneading with a wrapping and kneading machine.

[0023] Furthermore, in step (9), the temperature is preferably controlled at 60°C in the first hour, and then gradually lowered to 45°C in the last 2-3 hours until the leaf color completely changes from green to dull yellow.

[0024] The present invention also provides the following technical solution 2:

[0025] A mulberry leaf tea deep freezing device is used for the liquid nitrogen deep freezing in the aforementioned step (4); the deep freezing device comprises a liquid nitrogen storage tank, a conveying system, a mesh material frame, a feeding mechanism, an exhaust device and a control system; the control system is used to receive a liquid nitrogen level monitoring signal in the liquid nitrogen storage tank and control the conveying system to replenish liquid nitrogen, control the opening and closing of the liquid nitrogen storage tank, control the feeding of the feeding mechanism, the opening of the liquid nitrogen storage tank and the exhaust of the exhaust device; the feeding mechanism conveys the mesh material frame through horizontal and vertical movement and places it into the opened liquid nitrogen storage tank.

[0026] Furthermore, the liquid nitrogen storage tank includes a deep freezing chamber, and an automatically opening and closing sealing cover is arranged on the top of the deep freezing chamber; a liquid storage chamber is arranged at the lower part of the deep freezing chamber, and liquid nitrogen is stored in the liquid storage chamber, and an automatically opening and closing cover is arranged on the top of the liquid storage chamber, and the cover is smaller than the inner diameter of the deep freezing chamber; an exhaust device is arranged on the side wall of the deep freezing chamber above the cover, and the exhaust device is used to discharge the exhaust gas in the space above the cover.

[0027] Furthermore, the deep freezing chamber is cylindrical and consists of an inner wall, an outer wall and a middle vacuum insulation layer; and the exhaust device is an exhaust pipe.

[0028] Furthermore, the feeding mechanism includes a frame, a horizontal slide is arranged on the frame, a slide plate is slidably arranged in the horizontal slide, a vertical slide is arranged on one side of the slide plate, a slider is arranged in the vertical slide, the slider is connected to a clamping mechanism to support the mesh material holding frame and drive it to move up and down along the vertical slide, and the clamping mechanism is released and separated from the mesh material holding frame after the mesh material holding frame is moved along the vertical slide to the bottom and enters the deep freezing chamber of the liquid nitrogen storage tank.

[0029] Furthermore, the horizontal slide is used to drive the slide supporting the mesh material holding frame to move horizontally to above the liquid nitrogen storage tank; the vertical slide is used to drive the second slide to move vertically away from or close to the top of the liquid nitrogen storage tank.

[0030] Furthermore, the clamping mechanism includes a cylinder body arranged on both sides of the second slide plate, the piston rod of the cylinder body is connected to an arc-shaped clamp, and the mesh material holding frame is supported by the two arc-shaped clamps.

[0031] Furthermore, a lifting support device is arranged on the inner bottom surface of the deep freezing chamber, and the lifting support device is used to rise, contact and support the mesh material holding frame lowered by the feeding mechanism, and drive the mesh material holding frame to descend to the bottom of the deep freezing chamber after the feeding mechanism releases the mesh material holding frame.

[0032] Furthermore, the control system may be a PLC controller.

[0033] Furthermore, the device also includes a conveying platform, which is arranged below the frame and is used to convey the mesh material frame. When the conveyor belt of the conveying platform conveys the mesh material frame to the vicinity of the liquid nitrogen storage tank, the clamping mechanism is respectively slid to the outside of the mesh material frame through the control and adjustment of the horizontal slide and the vertical slide, and then it is conveyed to the top of the liquid nitrogen storage tank. The setting of the conveying platform increases the flexibility of the device, and avoids the problem of manual operation and even frostbite.

[0034] Furthermore, an infrared sensor is arranged on the sealing cover, so that after sensing the mesh material holding frame above it, a signal is given to the control system to control the sealing cover and the lid in the deep freezing chamber to open simultaneously or in sequence, so as to facilitate the continued loading and unloading of materials, thereby increasing the automatic control effect of the entire device.

[0035] Furthermore, it also includes a timer and an alarm connected to the controller, which are used to time the freeze-thaw cycle. When the timing cycle is up, a reminder is given through the alarm.

[0036] Beneficial effects of the present invention:

[0037] The invention reduces withering by optimizing the preparation process, uses deep freezing and ice melting to replace the fermentation process of existing mulberry leaf tea preparation, and oxidizes polyphenols more fully in variable temperature (low temperature) enzymatic oxidation to obtain a large amount of theaflavins and more elegant aroma components; the moisture content of the initially dried and moistened leaves is precisely controlled in a suitable rolling state, and the rolling rate is high; the variable temperature dynamic yellowing, the contained substances are further heterostructured, and the green smell is removed; radio frequency drying is used in the drying process to make the drying more uniform, the tea leaves are puffed inside, and the quality is better. The product has a compact and heavy appearance, a black and oily color, a sweet and rich aroma, an orange-yellow soup color, a sweet and refreshing taste, and a bright red and yellow leaf bottom.

[0038] The device of the present invention realizes automatic feeding, discharging and deep freezing, thereby reducing the risk of frostbite; the liquid nitrogen is reused and the liquid nitrogen overflow is reduced, thereby improving the resource utilization rate; the liquid nitrogen can be automatically replenished, so that the liquid nitrogen in the liquid storage chamber is always in a normal state, thereby ensuring the quality of deep freezing; and the exhaust device discharges waste gas to reduce the risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0040] Figure 2 for Figure 1 Schematic diagram of the structure from top view;

[0041] Figure 3 for Figure 1 Schematic diagram of the internal structure of the liquid nitrogen storage tank;

[0042] Figure 4 This is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0043] Figure 5 This is a schematic diagram of the structure of Example 4 of the present invention.

[0044] Among them, 1 liquid nitrogen storage tank, 101 deep freezing chamber, 101 1 inner wall, 1012 outer wall, 1013 intermediate vacuum insulation layer, 102 sealing cover, 103 liquid storage chamber, 104 cover, 105 lifting support device, 106 support plate, 2 conveying system, 3 mesh material frame, 4 feeding mechanism, 401 rack, 402 horizontal slide, 403 slide plate, 404 vertical slide, 405 slider, 406 clamping mechanism, 4061 electric cylinder, 4062 arc clamp, 4063 connecting rod, 5 exhaust device, 6L type sliding lifting track. DETAILED DESCRIPTION

[0045] In order to clearly illustrate the technical features of the present invention, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0046] Example 1

[0047] A deep freeze-thaw treatment preparation process for mulberry leaf tea, the process flow is as follows:

[0048] Fresh leaves cleaning → removing moisture from the leaf surface - fresh leaves spreading - shredding - deep freezing - thawing - initial drying - rolling and twisting → wrapping and rolling - temperature-changing dynamic yellowing - drying. Among them, the requirements for fresh leaves are: picking the upper part of the mulberry tree without pollution, pests and diseases, dark green buds and leaves and tender stems with 1 to 5 leaves at the top of the branches, and the tender stems should not be lignified.

[0049] The above process specifically includes:

[0050] Step 1: Clean the fresh leaves → Remove moisture from the leaf surface: Use mulberry leaf cleaning equipment to rinse the leaves with clean water, then remove water droplets on the leaf surface and blow dry the leaf surface with cold air.

[0051] Step 2: Spread the fresh leaves: Spread the fresh leaves naturally for 3-6 hours, at room temperature of 25°C and relative humidity of about 60%, until the moisture content of the fresh leaves reaches 70%-72%.

[0052] Step 3: Cut into strips: Use a food cutter to cut the mulberry leaves into 3mm-5mm wide strips.

[0053] Step 4: Deep freezing: Place the fresh leaves cut into strips into a liquid nitrogen deep freezing device for deep freezing for 5-10 minutes.

[0054] Step 5: Thawing: Spread the deep-frozen fresh leaves in a thread-like shape indoors to melt naturally, and blow cold wind to remove the moisture on the surface of the fresh leaves; during deep freezing, the water in the vacuole of the fresh leaves quickly turns into ice crystals, causing the cell membrane to break. During the thawing process, the polyphenols in the vacuole are quickly enzymatically oxidized with polyphenol oxidase under variable temperature conditions, and the temperature range is generally 0℃-25℃. In the variable temperature (low temperature) enzymatic oxidation, the polyphenols are more fully oxidized to obtain a large amount of theaflavins and more elegant aroma components; the variable temperature enzymatic oxidation can be terminated when most of the leaves turn brown.

[0055] Step 6: Initial drying: Use high temperature, short-time rapid drying, the temperature should be controlled at 110℃-120℃, the time is 5-10min, to quickly inactivate the activity of polyphenol oxidase, and at the same time control the water content at 58%-62%.

[0056] Step 7. Spread out to cool and regain moisture: Spread out the newly dried leaves at room temperature to regain moisture for 15-30 minutes, and the buds and leaves will be soft and easy to roll.

[0057] Step 8. Kneading → Wrapping and kneading: Use a kneading machine to knead, and use the "light, heavy, light" alternating pressure method to knead for 10min-15min, until the strip formation rate reaches about 90%; use a wrapping and kneading machine to wrap and knead into round, tight and solid granules.

[0058] Step 9: Dynamic yellowing with variable temperature: Dynamic yellowing with variable temperature, the temperature is controlled at 45℃-60℃, the relative humidity is controlled at 70%-75%; the time is 3h-4h. The temperature should be controlled at 60℃ for the first hour, and then gradually lowered to 45℃ for the next 2-3 hours; the leaf color completely changes to no green, which is moderate yellowing.

[0059] Step 10: Drying: Drying is carried out in two steps. The first step is high temperature and fast, with the temperature controlled at 110℃-115℃, until the particles feel prickly, and then they are taken off the machine and spread out to air for 20min-30min. The second step is drying with a radio frequency dryer until the particles are fully dry, and the moisture content is controlled below 6%.

[0060] Example 2

[0061] An implementation of the liquid nitrogen deep freezing device used in the fourth step of the above-mentioned embodiment 1 is shown in Figure 1-3The liquid nitrogen deep freezing device comprises a liquid nitrogen storage tank 1, a conveying system 2, a mesh material frame 3, a feeding mechanism 4, an exhaust device 5 and a control system. The control system comprises a PLC controller. The controller receives a liquid nitrogen level monitoring signal in the liquid nitrogen storage tank 1 and controls the conveying system 2 to replenish liquid nitrogen, controls the opening and closing of the liquid nitrogen storage tank, controls the driving of the feeding mechanism 2 to feed, and controls the exhaust device 5 to exhaust or close. The feeding mechanism 4 conveys the mesh material frame 3 and moves it into the opened liquid nitrogen storage tank through horizontal and vertical movement.

[0062] The liquid nitrogen storage tank 1 includes a deep freezing chamber 101, which is composed of an inner wall 1011, an outer wall 1012 and an intermediate vacuum insulation layer 1013; an automatically opened and closed sealing cover 102 is arranged at the top of the deep freezing chamber, and the opening and closing of the sealing cover 102 is controlled by a controller. The sealing cover can be set to a horizontally rotating opening and closing type or an up and down rotating opening and closing type sealing cover structure, and an existing self-sealing cover structure that can achieve sealing is selected, which will not be described in detail here. A liquid storage chamber 103 is arranged at the lower part of the deep freezing chamber, and an automatically opened and closed lid 104 is arranged at the top of the liquid storage chamber. The lid is smaller than the inner diameter of the deep freezing chamber, and the automatic opening and closing of the lid is also controlled by the controller, which belongs to the existing setting structure. An exhaust device 5 is arranged on the side wall of the deep freezing chamber above the lid, and the exhaust device is an exhaust pipe, which is used to discharge the exhaust gas in the liquid nitrogen storage tank above the lid. The liquid nitrogen level in the liquid storage chamber 103 can be detected by an ultrasonic liquid level sensor, and the ultrasonic liquid level sensor is electrically connected to the controller.

[0063] Controlling the opening of the liquid nitrogen storage tank includes opening the sealing cover 102 and the lid 104 simultaneously or sequentially.

[0064] An infrared sensor (not shown in the figure) can be provided on the sealing cover, and the infrared sensor is connected to the controller. When the feeding mechanism conveys the mesh material frame to the top of the sealing cover, the infrared sensor senses the signal and transmits it to the controller. The controller controls the sealing cover and the lid 104 in the deep freezing chamber below to be opened together, so that the subsequent mesh material frame can continue to smoothly enter the liquid nitrogen storage tank.

[0065] The feeding mechanism 4 includes a frame 401, a horizontal slide 402 is arranged on the frame, a slide plate 403 is arranged to slide in the horizontal slide, a vertical slide 404 is arranged on one side of the slide, a slider 405 is arranged on the vertical slide, the slider is connected to a clamping mechanism 406 to support the mesh material frame 3 and drive the mesh material frame to move up and down along the vertical slide, and the clamping mechanism is released and separated from the mesh material frame after the mesh material frame is moved to the bottom along the vertical slide into the deep freezing chamber. This process has a taking action, specifically, a lifting support device 105 is arranged on the bottom surface of the deep freezing chamber, a support plate 106 is arranged on the top of the lifting support device, and the lifting device is used to rise, contact and support the bottom surface of the mesh material frame 3 lowered by the feeding mechanism, and the clamping mechanism is released after the mesh material frame is supported by the support plate 106 of the lifting device. Finally, the lifting device drives the mesh material frame to descend to the bottom of the deep freezing chamber together. The start control of the lifting device is also controlled by the controller.

[0066] The lifting device may adopt a cylinder structure, and the support plate is arranged at the top end of the cylinder piston rod.

[0067] The cylinder body can be a hydraulic cylinder, a pneumatic cylinder or an electric cylinder, and all are started by controlling the control thereof.

[0068] The clamping mechanism 406 comprises an electric cylinder 4061 disposed on both sides of the mesh material holding frame, the piston rod of the electric cylinder is connected to an arc-shaped clamp 4062, and the mesh material holding frame 3 is supported and clamped by the two arc-shaped clamps. The two electric cylinders slide along the vertical slideway through the connecting rod 4063. Specifically, the vertical slideway and the horizontal slideway both use a lead screw slideway, and the lead screw in the lead screw slideway is driven by a motor to rotate, driving the lead screw slider that is set on the lead screw to move, and then driving the clamping mechanism 406 and the slide plate 403 connected to the lead screw slider to move. Each motor is electrically connected to the controller.

[0069] When in use, put a proper amount of fresh leaves in the mesh material frame 3, fix it with the arc-shaped clamp 4062 of the clamping mechanism 406, and connect it with the slider of the vertical slide 404 of the feeding mechanism 4. Turn on the feeding mechanism, and place the mesh material frame above the liquid nitrogen storage tank 1 through horizontal and vertical adjustment. At this time, the controller controls the sealing cover 102 and the internal lid 104 to open together. The mesh material frame 3 continues to descend to its bottom and gradually enters the appropriate position at the top of the deep freezing chamber 102 under the drive of the vertical slide. Then, the controller controls the lifting support device 105 at the bottom of the liquid storage chamber 103 to rise, forming support for the bottom end of the mesh material frame. At the same time, the controller controls the electric cylinder 4061 of the clamping mechanism 406 to move, and the piston rod of the electric cylinder contracts, so that the arc-shaped clamp 4062 loosens the mesh material frame. Then, the lifting support device 105 is lifted and the lifting support device 105 is lifted. The device 105 is retracted and descends to the bottom of the liquid storage chamber with the mesh material frame. When the material discharge is completed, the sealing cover and the lid are closed at the same time through the controller, and the timing is started to realize the freeze-thaw operation for a certain time. After the set time, the alarm is sounded, and the lid 104 and the sealing cover 102 in the deep freezing chamber are controlled by the controller in sequence or at the same time. The lifting support device 105 lifts the mesh material frame 3 to the top of the liquid nitrogen storage tank, and then controls the feeding mechanism 4 to make the clamping mechanism clamp the mesh material frame again to complete the operation of leaving the liquid nitrogen storage tank; when the bottom end of the mesh material frame is separated from the liquid nitrogen storage tank, the liquid nitrogen storage tank is promptly controlled to be closed through the controller.

[0070] Example 3

[0071] See also Figure 4 , shows another embodiment of the liquid nitrogen deep freezing device. The structure is the same as the device structure of Example 2, except that a conveyor belt 5 is also provided below one side of the frame 401, and the conveyor belt is used to convey the mesh material frame 3 filled with materials. When the conveyor belt conveys the mesh material frame to the vicinity of the liquid nitrogen storage tank 1, the clamping mechanism 406 is slid to the outside of the mesh material frame through the horizontal slide and the vertical slide respectively, and then it is further conveyed to the top of the liquid nitrogen storage tank. The conveyor belt is provided to increase the flexibility of the device, and avoid the problem of frostbite that may be caused by direct manual operation.

[0072] As another embodiment of the liquid nitrogen deep freezing device, the device structure is the same as that of Example 1 or 2, except that in the setting of the feeding mechanism, the structure of the horizontal slide and the vertical slide can be replaced by other sliding structures, such as a sliding drive form of a worm gear.

[0073] In addition, as another embodiment of the liquid nitrogen deep freezing device, in order to make the adjustment flexible and intelligent, an electric convex strip or a convex block can be provided on the side wall of the upper space of the deep freezing chamber to realize the support before the lifting support device 105 is started, that is, after the feeding mechanism conveys the mesh material frame into the liquid nitrogen storage tank, it is first supported by the electric convex strip or the convex block, at which time, the clamping mechanism can be loosened and removed, and at the same time, the lifting support device rises to support the bottom surface of the mesh material frame, and then controls the electric convex strip or the convex block to be retracted along the thickness direction of the side wall of the liquid nitrogen storage tank, and the mesh material frame is brought downward into the liquid storage chamber through the lifting support device; and when discharging, first control to open the lid 104 above the liquid storage chamber, and keep the sealing cover 102 in the closed state; the mesh material frame is now lifted to the position above the electric convex strip by the lifting support device, and then the electric convex strip is turned on to support the mesh material frame, and then the lid 104 is closed, the sealing cover 102 is opened, and then the mesh material frame is removed and the sealing cover is closed. Compared with the structural form of the aforementioned embodiment, the arrangement of this structure is more flexible in the operation connection and coordination between the feeding mechanism and the lifting support device 105. Moreover, when discharging, the loss of liquid nitrogen can be minimized. Before the mesh material holding frame is supported by the electric convex strips, waiting to be clamped and leaving the liquid nitrogen storage tank, since the lifting support device has been retracted, the lid 104 in the deep freezing chamber can be controlled to be closed first, reducing the overflow of liquid nitrogen, and the overflowed liquid nitrogen retained in the upper space of the deep freezing chamber can be discharged through the exhaust pipe. Of course, in order to make the mesh material holding frame in this state better removed from the liquid storage tank, the clamping mechanism can be improved, and the clamping structure can be replaced with a hook-type structure.

[0074] Example 4

[0075] See also Figure 5 , showing another embodiment of the liquid nitrogen deep freezing device. The feeding mechanism of this structure is set as follows: an L-shaped sliding lifting track 6 is set parallel to each other on the outside of the liquid nitrogen storage tank 1, and a horizontal electric push rod (not shown in the figure) is transported on each L-shaped sliding lifting track through a slider or a chain, and each electric push rod is inserted into the openings on both sides of the top of the mesh material holding frame, thereby driving the mesh material holding frame to first rise along the L-shaped sliding lifting track, then move horizontally, and then descend to the top of the liquid nitrogen storage tank 1. The subsequent operation of feeding into the liquid nitrogen storage tank refers to the process of Example 2, the difference being that after the mesh material holding frame is taken over by the lifting support device, the electric push rod connected to the mesh material holding frame is separated from the mesh material holding frame by retraction.

[0076] The structural form of the feeding mechanism is not limited to the structures listed in the above embodiments. For example, the mesh material frame can be taken and placed by a robot or other structural forms to move the mesh material frame from bottom to top and then horizontally to above the liquid nitrogen storage tank.

[0077] In the description of the product structure of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0078] The above specific implementation manner cannot be used as a limitation on the protection scope of the present invention. For those skilled in the art, any substitution, improvement or change made to the implementation manner of the present invention falls within the protection scope of the present invention.

[0079] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A deep freeze-thaw treatment preparation process for mulberry leaf tea, characterized in that: The steps are as follows: (1) Cleaning fresh leaves: Rinse the fresh mulberry leaves with clean water, remove water droplets from the leaf surface, and blow dry the leaf surface with cold air; (2) Fresh leaf spreading: The dried fresh leaves are spread naturally for 3-6 hours at a room temperature of 25°C until the moisture content of the fresh leaves reaches 70%-72%; (3) Cutting into strips: Cut the fresh leaves into strips with a width of 3 mm to 5 mm. (4) Deep freezing: deep freezing the fresh leaves cut into strips with liquid nitrogen for 5-10 minutes; (5) Thawing: Spread the deep-frozen fresh leaves in a strip-like shape indoors to melt naturally, and blow cold air to remove moisture from the surface of the leaves until most of the leaves turn brown; (6) Primary drying: Drying is carried out by high temperature, short time and fast drying, and the moisture content is controlled at 58%-62%; (7) Cooling and moisture recovery: The newly dried leaves are spread out at room temperature to recover moisture for 15-30 minutes until the leaves are soft and easy to roll; (8) Kneading → Wrapping and kneading: Kneading for 10-15 minutes using the "light, heavy, light" alternating pressure method until the strip forming rate reaches 85%-95%; wrap and knead into round, tight and heavy granules; (9) Dynamic yellowing with variable temperature: the temperature is controlled at 45℃-60℃, the relative humidity is controlled at 70%-75%; the time is 3h-4h; (10) Drying: Drying is carried out in two steps. The first step is high temperature and fast drying, with the temperature controlled at 110°C-115°C, until the particles feel prickly, and then they are taken off the machine and spread out to air for 20-30 minutes. The second step is drying until the particles are fully dry, with the moisture content controlled below 6%.

2. The preparation process according to claim 1, characterized in that: The temperature of step (6) high temperature short time rapid drying is 110°C-120°C, and the time is 5-10 minutes.

3. The preparation process according to claim 1, characterized in that: Step (9) The temperature is preferably controlled at 60°C in the first hour, and then gradually lowered to 45°C in the last 2-3 hours until the leaf color completely changes from green to dull yellow.

4. A mulberry leaf tea deep freezing device, characterized in that: Used for deep freezing of liquid nitrogen in step (4) of claim 1; the deep freezing device comprises a liquid nitrogen storage tank, a conveying system, a mesh material frame, a feeding mechanism, an exhaust device and a control system; the control system is used to receive a liquid nitrogen level monitoring signal in the liquid nitrogen storage tank and control the conveying system to replenish liquid nitrogen, control the opening and closing of the liquid nitrogen storage tank, control the driving of the feeding mechanism to feed, the opening of the liquid nitrogen storage tank and the exhaust device to exhaust waste gas; the feeding mechanism conveys the mesh material frame through horizontal and vertical movement and places it in the opened liquid nitrogen storage tank.

5. The mulberry leaf tea deep freezing device according to claim 4, characterized in that: The liquid nitrogen storage tank comprises a deep freezing chamber, wherein an automatically opening and closing sealing cover is arranged on the top of the deep freezing chamber; a liquid storage chamber is arranged at the lower part of the deep freezing chamber, wherein liquid nitrogen is stored in the liquid storage chamber, and an automatically opening and closing cover is arranged on the top of the liquid storage chamber, wherein the cover is smaller than the inner diameter of the deep freezing chamber; and an exhaust device is arranged on the side wall of the deep freezing chamber above the cover, wherein the exhaust device is used for exhausting waste gas from the space above the cover.

6. The mulberry leaf tea deep freezing device according to claim 5, characterized in that: The deep freezing chamber is cylindrical and consists of an inner wall, an outer wall and a middle vacuum insulation layer; the exhaust device is an exhaust pipe.

7. The deep freezing device for mulberry leaf tea according to claim 4, characterized in that: The feeding mechanism includes a frame, a horizontal slide is arranged on the frame, a slide plate is slidably arranged in the horizontal slide, a vertical slide is arranged on one side of the slide plate, a slider is arranged in the vertical slide, the slider is connected to a clamping mechanism to support the mesh material holding frame and drive it to move up and down along the vertical slide, and the clamping mechanism is released and separated from the mesh material holding frame after the mesh material holding frame is moved along the vertical slide to the bottom and enters the deep freezing chamber of the liquid nitrogen storage tank.

8. The mulberry leaf tea deep freezing device according to claim 7, characterized in that: The horizontal slide is used to drive the slide supporting the mesh material holding frame to move horizontally to above the liquid nitrogen storage tank; the vertical slide is used to drive the second slide to move vertically away from or close to the top of the liquid nitrogen storage tank.

9. The mulberry leaf tea deep freezing device according to claim 7, characterized in that: The clamping mechanism comprises a cylinder body arranged on both sides of the second slide plate, a piston rod of the cylinder body is connected to an arc-shaped clamp, and the mesh material holding frame is supported by the two arc-shaped clamps.

10. The deep freezing device for mulberry leaf tea according to any one of claims 4 to 9, characterized in that: A lifting support device is arranged on the bottom surface of the deep freezing chamber, and the lifting support device is used for rising, contacting and supporting the mesh material holding frame lowered by the feeding mechanism, and driving the mesh material holding frame to descend to the bottom of the deep freezing chamber after the feeding mechanism releases the mesh material holding frame.

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