CN112075492A - Corona discharge low-temperature plasma device, litchi fresh-keeping device and litchi fresh-keeping method - Google Patents

Abstract

The invention belongs to the field of fruit and vegetable preservation, and relates to a corona discharge low-temperature plasma device. The corona discharge low-temperature plasma device comprises: discharge area, transformer and pulse power supply, wherein: the discharge area is composed of a plurality of parallel columnar spaces with the same structure, the outermost layer of each columnar space is a hollow columnar glass tube, the low-voltage reticular electrode is tightly attached to the inner wall of the hollow columnar glass tube, the center of the columnar space is a high-voltage linear electrode, two ends of the hollow columnar glass tube are sealed by cover plates, and air holes are reserved on the cover plates; the high-voltage linear electrode of each columnar space in the discharge area is connected with one end of the transformer and one end of the pulse power supply through the electrode outgoing line, and the low-voltage reticular electrode of each columnar space is connected with the other end of the transformer and the other end of the pulse power supply through the electrode outgoing line to form a closed loop. The invention adopts a parallel corona discharge plasma device, occupies small area and has wide treatment area. The invention also discloses a device and a method for litchi preservation by corona discharge low-temperature plasma.

Description

Corona discharge low temperature plasma device, lychee fresh-keeping device and fresh-keeping method

technical field

The invention relates to the field of fresh-keeping of fruits and vegetables, in particular to a corona discharge low-temperature plasma device, a lychee fresh-keeping device and a fresh-keeping method.

technical background

The post-harvest quality of lychees undergoes dramatic changes, including browning of the peel, shriveled water loss, and poor taste. This change occurs the moment the lychee leaves the branch, mainly because the protective effect of the peel decreases after the lychee leaves the branch. Increased metabolism and microbial infestation. According to market research, the primary factor affecting the sales of lychees is the browning of the peel. According to scientific research, the occurrence of browning is mainly related to polyphenol oxidase (PPO) and peroxidase (POD). Low-temperature plasma technology has unique advantages in inhibiting browning. The low-temperature plasma acts on the surface of litchi to irreversibly change the structure of PPO and POD in the peel, which fundamentally solves the problem of enzymatic browning. In addition, low temperature plasma technology can degrade ethylene, resist softening and lignification, kill microorganisms, deodorize and remove agricultural residues.

At present, the commonly used lychee preservation technologies are low-temperature storage and combination of controlled atmosphere preservation, chemical preservation and other technical methods on the basis of low temperature. Low-temperature storage requires large-scale cold storage equipment, which consumes a lot of energy and occupies a large area; controlled atmosphere storage requires additional gas conditioning devices and multiple testing equipment, which is costly and unstable; chemical biological preservatives will lead to bad odor and chemical residues It affects the quality of fresh fruit. More importantly, the above technology cannot quickly realize the fresh-keeping treatment of lychees when they leave the branches.

SUMMARY OF THE INVENTION

In order to overcome the above shortcomings and deficiencies of the prior art, the present invention provides a corona discharge low temperature plasma device.

The invention also provides a corona discharge low-temperature plasma litchi fresh-keeping device.

The invention also provides a corona discharge low-temperature plasma litchi preservation method.

The present invention adopts the following technical scheme to realize:

A corona discharge low-temperature plasma device, comprising: a discharge area, a transformer and a pulse power supply, wherein: the discharge area is composed of a plurality of parallel and parallel columnar spaces with the same structure, and the outermost structure of each columnar space is a hollow columnar glass tube , the low-voltage mesh electrode is close to the inner wall of the hollow cylindrical glass tube, the center of the cylindrical space is a high-voltage wire electrode, the two ends of the hollow cylindrical glass tube are closed by a cover plate, and there are air holes on the cover plate; The grid electrode is connected to one end of the transformer and the pulse power supply through the electrode lead wire, and the low-voltage mesh electrode of each columnar space is connected to the other end of the transformer and the pulse power source through the electrode lead wire to form a closed loop.

Preferably, the pulse power supply outputs a microsecond pulse power supply with a voltage of 0-15kV, a pulse width of 1-20μs, and a frequency of 10-50kHz.

Preferably, the hollow cylindrical glass tube has an outer diameter of 40mm, an inner diameter of 30mm, and a length of 150mm; the low-voltage mesh electrode has a mesh aperture of 3mm, a length of 130mm, and a thickness of 1mm; the high-voltage wire electrode has an outer diameter of 0.5mm and a length of 150mm .

Preferably, the material of the low-voltage mesh electrode and the high-voltage wire electrode is steel or brass.

Preferably, the discharge area is composed of three parallel and parallel columnar spaces with the same structure, and the distance between each columnar space is 10 mm.

Preferably, the working principle of the corona discharge low-temperature plasma device is as follows: after starting the pulse power supply, the air entering the columnar space of the discharge area through the air hole is ionized near the high-voltage wire electrode and the low-voltage mesh electrode to generate high-energy active particles, and then high-energy active particles are generated. The particles gradually diffuse through the pores and come into contact with the lychee, so that the lychee can be kept fresh.

Preferably, the voltage range of the corona discharge plasma device is 0-15kV, the frequency is controlled at 10-50kHz, and the power is controlled at 50-500W; the corona discharge plasma device is treated for 8-10min to achieve a good litchi preservation effect.

A corona discharge low-temperature plasma litchi fresh-keeping device, comprising: a fresh-keeping container and a corona discharge low-temperature plasma device, the fresh-keeping container comprises a container body and a container cover, the container cover is equipped with a corona discharge low-temperature plasma device, and the container body and the container cover Snap closure;

The upper end of the container body distributes one or more cubic protrusions along the circumference of the container for snap closure with the container cover;

The container cover is a double-layer hollow structure, the two layers are separated by a plastic plate with holes, and the plastic plate can be removed; the upper layer is used to store the pulse power supply, the transformer, the lower layer is used to store the discharge area, and the hole is used to place the electrode lead wire; the container The upper end of the cover is provided with an opening for power supply replacement; the outer lower end of the container cover is provided with buckles at positions corresponding to the cubic protrusions of the container body, and the buckles are used for buckle-type closure with the container body.

Preferably, the fresh-keeping container includes: a fresh-keeping bucket, a fresh-keeping box, and a fresh-keeping box.

A corona discharge low-temperature plasma litchi fresh-keeping barrel, comprising: a barrel body, a plasma generating device and a barrel cover;

The barrel body is a cylinder, and the upper end of the barrel body distributes one or more cubic protrusions along the circumference for snap closure with the barrel cover;

The barrel cover is a double-layer hollow structure, and the two layers are separated by a plastic plate with holes, and the plastic plate can be disassembled; the upper layer is used to store the pulse power supply, the transformer, the lower layer is used to store the discharge area, and the hole is used to place the electrode lead wire; The upper end of the cover is provided with an opening for power supply replacement; the outer lower end of the barrel cover is provided with a buckle along the circumference at a position corresponding to the cubic protrusion of the barrel body for snap closure with the barrel body.

A corona discharge low-temperature plasma litchi preservation method, comprising:

(1) Litchi is placed in the container body, and the container cover that is equipped with corona discharge low-temperature plasma device is covered;

(2) Start the corona discharge plasma device in the container cover, set the voltage range of the corona discharge plasma device to 0-15kV, control the frequency to 10-50kHz, control the power to 50-500W, and treat the lychee sample for 8- 10min to achieve lychee preservation.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The present invention adopts corona discharge to generate low-temperature plasma, which has high energy efficiency, high activity of generated free radicals, large discharge area and small pressure loss. The corona discharge low-temperature plasma device of the invention is a parallel corona discharge plasma device, which occupies a small area and has a wide processing area.

(2) In the present invention, air is used as a plasma excitation gas source, and the obtained plasma oxidation active components are distributed in a sealed container, so that the lychee can be comprehensively and effectively preserved. Plasma treatment has unique advantages in lychee preservation. It can irreversibly passivate the enzymes that cause lychee browning, and solve the primary problem affecting lychee sales - discoloration. In addition, low-temperature plasma technology can degrade ethylene, resist softening and lignification, kill microorganisms, deodorize and remove agricultural residues, further enhancing the effect of lychee preservation.

(3) The present invention is convenient to move, and can be processed anytime and anywhere. Traditional fresh-keeping equipment is generally large in size and inconvenient to move, and can only be processed in designated places.

(4) The operating cost of the present invention is low. The pulsed power supply is used to treat lychees intermittently, which is gentle and energy-saving; the plasma is excited by atmospheric pressure air, which does not require additional vacuuming or the use of food-grade industrial standard gases, which reduces the user's cost and threshold for use.

(5) The higher-cost container cover of the present invention can be configured with multiple container bodies, and there is no need to use the container cover and the container body in one-to-one correspondence, which increases the processing capacity and reduces the purchase cost.

(6) The method of the present invention can prolong the shelf life of lychees by 2-3 days on the basis of traditional low-temperature fresh-keeping combined with low-temperature plasma fresh-keeping.

(7) Low-temperature plasma technology, as a safe and green new non-thermal processing technology, has broad application prospects in the field of litchi source preservation. The low-temperature plasma fresh-keeping device of the present invention can be applied to forest fields, realizes fresh-keeping at the source, and helps farmers increase income.

Description of drawings

FIG. 1 is a schematic structural diagram of a corona discharge low temperature plasma device in an embodiment of the present invention.

FIG. 2 is a second structural schematic diagram of a corona discharge low temperature plasma device in an embodiment of the present invention.

FIG. 3 is a schematic diagram of a corona discharge low-temperature plasma fresh-keeping barrel in an embodiment of the present invention.

FIG. 4 is a second schematic diagram of a corona discharge low-temperature plasma fresh-keeping barrel in an embodiment of the present invention.

Fig. 5 is the change situation of litchi browning index BI in one embodiment of the present invention.

Figure 6 shows the changes in the enzymatic activities of litchi peroxidase and polyphenol oxidase in an embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

Example 1

A corona discharge low temperature plasma device is a parallel corona discharge plasma device. As shown in Figures 1 and 2, it includes: a discharge area 9, a transformer 10, and a pulse power supply 11. The discharge area 9 is composed of a plurality of parallel and parallel columnar spaces with the same structure, and the outermost structure of each columnar space is a hollow columnar glass tube. , the low-voltage mesh electrode 14 is close to the inner wall of the hollow cylindrical glass tube, the center of the cylindrical space is a high-voltage wire electrode 7, the two ends of the hollow cylindrical glass tube are closed by a cover plate 15, and the cover plate 15 is left with air holes 8. The high-voltage wire electrode 7 of each columnar space in the discharge area 9 is connected to one end of the transformer 10 and the pulse power supply 11 through the electrode lead-out line 6, and the low-voltage mesh electrode 14 of each column-shaped space is connected to the transformer 10 and the pulse power supply 11 through the electrode lead-out line 6. The other ends are connected to form a closed loop.

In a preferred embodiment, the discharge area 9 is composed of three parallel and parallel columnar spaces with the same structure, and the distance between each columnar space is 10 mm.

The output voltage of the pulse power supply is 0-15kV, the pulse width is 1-20μs, and the frequency is microsecond pulse power supply of 10-50kHz.

The hollow cylindrical glass tube has an outer diameter of 40 mm, an inner diameter of 30 mm and a length of 150 mm. The mesh diameter of the low-voltage mesh electrode is 3 mm, the length is 130 mm, and the thickness is 1 mm. The outer diameter of the high-voltage wire electrode is 0.5mm and the length is 150mm.

Both the low-voltage mesh electrode and the high-voltage wire electrode are made of steel or brass. The cover material is polyethylene or polypropylene.

The working principle of the corona discharge low-temperature plasma device is: after starting the pulse power supply 11, the air entering the columnar space of the discharge area 9 through the air hole 8 is ionized near the high-voltage wire electrode 7 and the low-voltage mesh electrode 14, producing high-energy active particles, and then The high-energy active particles gradually diffuse through the stomata 8 and come into contact with the lychee. The low-temperature plasma acts on the surface of the lychee, causing irreversible structural changes to the PPO and POD in the peel, which fundamentally solves the problem of enzymatic browning. Degrades ethylene, resists softening and lignification, kills microorganisms, deodorizes and removes agricultural residues, and plays a role in preservation.

In one embodiment, the voltage range of the corona discharge plasma device is 0-15kV, the frequency is controlled at 10-50kHz, and the power is controlled at 50-500W. Corona discharge plasma device treatment for 8-10min can achieve good fresh-keeping effect of litchi.

Example 2

A corona discharge low-temperature plasma litchi fresh-keeping device, comprising: a fresh-keeping container and a corona discharge low-temperature plasma device, the fresh-keeping container comprises a container body and a container cover, the container cover is equipped with a corona discharge low-temperature plasma device, and the container body and the container cover Snap closure.

One or more cubic protrusions, preferably four cubic protrusions, are distributed along the circumference of the container on the upper end of the container body, and are used for snap closure with the container cover.

The container cover is a double-layer hollow structure, and the two layers are separated by a perforated plastic plate, and the plastic plate can be disassembled. The upper layer is used to store the pulse power supply and the transformer, the lower layer is used to store the discharge area, and the hole is used to place the electrode lead wire. There is an opening on the upper end of the container cover for power supply replacement. The outer lower end of the container cover is provided with a buckle at a position corresponding to the cube protrusion of the container body, and the buckle is used for buckle closure with the container body.

Fresh-keeping containers include fresh-keeping buckets, fresh-keeping boxes, fresh-keeping boxes, and the like.

In a preferred embodiment, the fresh-keeping container is a fresh-keeping bucket. A corona discharge low temperature plasma lychee fresh-keeping barrel, as shown in Figures 1-4, includes a barrel body 2, a plasma generating device and a barrel cover 1.

The barrel body 2 is a cylindrical body, and one or more cubic protrusions 4, preferably four cubic protrusions, are distributed along the circumference on the upper end of the barrel body 2, which are used for snap closure with the barrel cover 1 . The barrel is made of insulating material, preferably polyethylene or polypropylene.

The barrel cover 1 is a double-layer hollow structure, and the two layers are separated by a plastic plate 13 with a hole 12, and the plastic plate 13 can be disassembled. The upper layer is used to store the pulse power supply 11 and the transformer 10 , the lower layer is used to store the discharge area 9 , and the hole 12 is used to place the electrode lead wires 6 . The upper end of the barrel cover 1 has an opening 5 for power replacement. The outer lower end of the barrel cover is provided with a snap 3 along the circumference at a position corresponding to the cubic protrusion of the barrel body, for snapping closure with the barrel body 2 .

Example 3

A corona discharge low-temperature plasma litchi preservation method, comprising:

(1) Litchi is placed in the container body, and the container cover that is equipped with corona discharge low-temperature plasma device is covered;

(2) Start the corona discharge plasma device in the container cover, set the voltage range of the corona discharge plasma device to 0-15kV, control the frequency to 10-50kHz, control the power to 50-500W, and treat the lychee sample for 8- 10min, can achieve lychee source preservation, can extend the shelf life of lychee by 2-3 days.

Example 4

A corona discharge low-temperature plasma litchi preservation method, comprising the following steps:

(1) in the fresh-picked lychee fresh-keeping barrel, cover with a barrel cover equipped with a corona discharge low-temperature plasma device;

(2) Start the corona discharge low temperature plasma device in the barrel cover, set the voltage of the corona discharge low temperature plasma device to 10kV, control the frequency to 20kHz, control the power to 100W, and treat the lychee sample for 10min.

Litchi preservation experiment: After the above-mentioned corona discharge low-temperature plasma litchi preservation barrel was assembled, a certain amount of fresh lychees was selected as the control group, and an equal amount of fresh lychees was selected as the experimental group. Treated in a fresh-keeping bucket for 10 min, the control group did not undergo any treatment, the two groups of lychees were placed at room temperature, and the browning index of the peel was calculated by the grading method. Mild browning appeared on the surface, and the red area on the fruit surface was still more than 3/4 of the surface area of the peel; the third-grade fruit was moderately browned, and the browning area and the bright red area basically accounted for half of the fruit surface; the fourth-grade fruit was severe browning The surface of the fruit is basically occupied by the browning area, and the red area is less than 1/4 of the surface area of the peel; the fifth-level fruit is completely brown. Browning index BI = Σ (number of browning stages×number of browning fruits at each level)/total number of investigated fruits. Higher BI values indicate more severe browning. As shown in Figure 5, it was found that the BI value of litchi in the control group increased sharply with time, while the BI value of the experimental group increased slowly with time, which can prove that the corona discharge low-temperature plasma litchi fresh-keeping barrel can effectively inhibit the browning of litchi and achieve Lychee source preservation.

Example 5

The lychee preservation method adopted in the present embodiment is the same as that in Example 1. Specifically include the following steps:

(1) in the fresh-picked lychee fresh-keeping barrel, cover with a barrel cover equipped with a corona discharge low-temperature plasma device;

(2) Start the corona discharge low temperature plasma device in the barrel cover, set the voltage of the corona discharge low temperature plasma device to 10kV, control the frequency to 20kHz, control the power to 100W, and treat the lychee sample for 10min.

Litchi skin enzyme activity change experiment: After the above-mentioned corona discharge low-temperature plasma litchi fresh-keeping barrel was assembled, a certain amount of fresh litchi was selected as the control group, and an equal amount of fresh litchi was selected to set up 5 experimental groups. The lychees in the experimental group were placed in a low-temperature plasma fresh-keeping barrel for 2, 4, 6, 8, and 10 min under the conditions of 20 kHz and 10 kV, respectively. The enzyme activities of peroxidase and polyphenol oxidase in the control group and the experimental group were determined. As shown in Figure 6, it was found that the peroxidase was inactivated when treated for 8 min; the polyphenol oxidase was inactivated when treated for 10 min, which can prove that low temperature plasma can effectively inhibit lychee peroxidase and polyphenol oxidase The activity of lychee source can be realized.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the described embodiments, and any other changes, modifications, substitutions, and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement modes, and are all included in the protection scope of the present invention.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (10)

1. A corona discharge low temperature plasma apparatus, comprising: discharge area, transformer and pulse power supply, wherein: the discharge area is composed of a plurality of parallel columnar spaces with the same structure, the outermost layer of each columnar space is a hollow columnar glass tube, the low-voltage reticular electrode is tightly attached to the inner wall of the hollow columnar glass tube, the center of the columnar space is a high-voltage linear electrode, two ends of the hollow columnar glass tube are sealed by cover plates, and air holes are reserved on the cover plates; the high-voltage linear electrode of each columnar space in the discharge area is connected with one end of the transformer and one end of the pulse power supply through the electrode outgoing line, and the low-voltage reticular electrode of each columnar space is connected with the other end of the transformer and the other end of the pulse power supply through the electrode outgoing line to form a closed loop.

2. The corona discharge low temperature plasma device according to claim 1, wherein the pulsed power supply has an output voltage of 0 to 15kV, a pulse width of 1 to 20 μ s, and a frequency of 10 to 50 kHz.

3. The corona discharge low temperature plasma device according to claim 1, wherein the hollow cylindrical glass tube has an outer diameter of 40mm, an inner diameter of 30mm, and a length of 150 mm; the mesh aperture of the low-voltage mesh electrode is 3mm, the length is 130mm, and the thickness is 1 mm; the outer diameter of the high-voltage linear electrode is 0.5mm, and the length of the high-voltage linear electrode is 150 mm.

4. The corona discharge cryogenic plasma device of claim 1 wherein the low voltage mesh electrode and the high voltage wire electrode are steel or brass.

5. The corona discharge low temperature plasma device of claim 1, wherein the corona discharge low temperature plasma device operates on the principle of: after the pulse power supply is started, air entering the columnar space of the discharge area through the air holes is ionized near the high-voltage linear electrode and the low-voltage mesh electrode to generate high-energy active particles, and then the high-energy active particles are gradually diffused through the air holes and are contacted with litchi to realize litchi preservation.

6. The corona discharge low temperature plasma device according to claim 1, wherein the voltage range of the corona discharge plasma device is 0-15kV, the frequency is controlled to 10-50kHz, and the power is controlled to 50-500W; the corona discharge plasma device is used for treating for 8-10min to achieve a good litchi fresh-keeping effect.

7. The utility model provides a corona discharge low temperature plasma litchi device that keeps fresh which characterized in that includes: the fresh-keeping container comprises a container body and a container cover, the container cover is provided with the corona discharge low-temperature plasma device, and the container body and the container cover are closed in a buckling mode;

one or more cubic protrusions are distributed on the upper end of the container body along the periphery of the container and used for being closed with the container cover in a buckling mode;

the container cover is of a double-layer hollow structure, the two layers are separated by a plastic plate with holes, and the plastic plate can be detached; the upper layer is used for storing a pulse power supply and a transformer, the lower layer is used for storing a discharge area, and the hole is used for placing an electrode lead-out wire; the upper end of the container cover is provided with an opening for power supply replacement; the periphery of the lower end of the outer part of the container cover is provided with a buckle at a position corresponding to the cubic bulge of the container body, and the buckle is used for being closed in a buckling mode with the container body.

8. The device for litchi preservation by corona discharge low-temperature plasma according to claim 7, wherein the preservation container comprises: a fresh-keeping barrel, a fresh-keeping box and a fresh-keeping box.

9. The utility model provides a corona discharge low temperature plasma litchi fresh-keeping bucket which characterized in that includes: the device comprises a barrel body, a plasma generating device and a barrel cover;

the barrel body is a cylinder, and one or more cubic bulges are distributed at the upper end of the barrel body along the circumference and used for being closed with the barrel cover in a buckling manner;

the barrel cover is of a double-layer hollow structure, the two layers are separated by a plastic plate with holes, and the plastic plate can be detached; the upper layer is used for storing a pulse power supply and a transformer, the lower layer is used for storing a discharge area, and the hole is used for placing an electrode lead-out wire; the upper end of the barrel cover is provided with an opening for power supply replacement; the lower end of the outer part of the barrel cover is provided with a buckle at a position corresponding to the cubic bulge of the barrel body along the circumference, and the buckle is used for being closed with the barrel body in a buckle mode.

10. A litchi preservation method by corona discharge low-temperature plasma is characterized by comprising the following steps:

(1) placing litchi in a container body, and arranging a container cover with a corona discharge low-temperature plasma device on the cover;

(2) starting corona discharge plasma equipment in the container cover, setting the voltage range of a corona discharge plasma device to be 0-15kV, controlling the frequency to be 10-50kHz and controlling the power to be 50-500W, and treating the litchi sample for 8-10min to realize litchi preservation.

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