Fruit and vegetable fresh-keeping device and fruit and vegetable fresh-keeping method based on low-temperature plasma activated spray coating

Abstract

The invention discloses a fruit and vegetable fresh-keeping device and a fruit and vegetable fresh-keeping method based on a low-temperature plasma activated spray coating, and belongs to the technical field of fruit and vegetable fresh-keeping devices and methods. The device comprises an air plasma jet device, a water tank, a detection controller and an array low-temperature plasma generating device, the air plasma jet device consists of a copper electrode connected to a high-voltage power supply, a gas flowmeter and an air compressor; the air compressor is connected with the water tank through a pipeline; the bottom of the water tank is communicated with the array low-temperature plasma generating device; the detection controller controls the air plasma jet device, the colloid premixing device, the water tank and the array low-temperature plasma generating device through the electric power system. The device realizes stable and continuous production of plasma active components, can realize high-flux production of active substances and large-scale preparation work of active media, and meets the application requirements of large-scale popularization and demonstration in the field of modern agricultural foods.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fruit and vegetable preservation devices and methods, and particularly relates to a fruit and vegetable preservation device based on low-temperature plasma-activated spray coating and a fruit and vegetable preservation method. BACKGROUND

[0002] Fruits and vegetables have high water content and are not easy to store. After being picked, they are prone to lose freshness and quality due to respiration heat, mechanical damage, improper storage conditions, etc., and eventually rot and deteriorate, seriously affecting their nutritional value and commercial value. Currently, traditional fruit and vegetable preservation technologies have one or several outstanding problems such as high cost, chemical residue, damage to the flavor and nutrition of fruits and vegetables, and low antibacterial efficiency. Therefore, developing a new type of postharvest preservation technology for fruits and vegetables that is low in cost, safe and efficient, environmentally friendly, and widely applicable is a major problem that needs to be solved urgently.

[0003] In recent years, plasma-activated spray has been shown to have significant antibacterial properties, reducing the number of foodborne pathogens such as Listeria monocytogenes, Salmonella typhi, and Escherichia coli by 35.5 times, 166 times, and 266 times, respectively, within 15 seconds. During this process, the energy of free electrons in the plasma is increased through effective mass transfer between gas and liquid phases, significantly improving the bactericidal performance of plasma-activated spray. In a recent study, researchers found that plasma-activated spray treatment effectively reduced the amount of artificially inoculated Escherichia coli and Enterobacter aerogenes on the surface of strawberries and various leafy vegetables (lettuce, cabbage, and small spinach). Despite these impressive achievements in the field of food preservation, plasma-activated spray still needs to be adjusted flexibly in terms of processing mode in complex production environments and uncertain penetration depth. How to effectively retain active ingredients in the activated spray has been a "neck" problem in the application of plasma technology in the field of fruit and vegetable preservation.

[0004] Fruit and vegetable coating preservation technology is a method of prolonging the shelf life of fruits and vegetables by forming a protective film on their surface. This protective film can be made of various natural or synthetic materials such as polysaccharides, proteins, and lipids. These materials have good film-forming properties, antibacterial effects, and biocompatibility, and can effectively isolate fruits and vegetables from the external environment, reducing water evaporation and microbial infection, thereby prolonging the shelf life of fruits and vegetables.

[0005] Low-temperature plasma-activated coating is a technology that utilizes the process of ionizing the medium (liquid or semi-solid coating material) during plasma generation to achieve medium atomization (i.e., dispersing liquid or semi-solid into extremely fine particles) and spraying (i.e., spraying the atomized particles at high speed). The spray coating quickly forms an extremely thin film when it reaches the surface of the fruit and vegetable, and this coating can be completely washed off during normal fruit and vegetable cleaning before consumption.

[0006] A kind of ring around DBD low temperature plasma device, fresh-keeping storage vehicle and fresh-keeping method are disclosed in Chinese patent application document with publication number CN112155052A, device, including: container cover, container body, positive electrode, negative electrode, discharge medium, net partition, transformer and pulse power supply, wherein: positive electrode and negative electrode are arranged around the inside four sides of container body with interval;Discharge zone is formed between adjacent positive electrode and negative electrode;Positive electrode, negative electrode are connected with transformer and pulse power supply;Discharge medium covers the left and right sides of positive electrode;Insulating end cap is provided on the upper and lower ends of discharge medium;Container cover is located above container body, and can be separated from container body;Air inlet is uniformly arranged around container cover;Net partition is used to prevent fruits and vegetables from contacting positive electrode, negative electrode and discharge zone, to ensure discharge stability and equipment safety.The ring around DBD low temperature plasma device of the patent occupies small space, processing area is wide, and processing effect is uniform.But the active ingredient action time of the patent is still limited, and the fresh-keeping effect of fruits and vegetables is poor, so it still needs to be further improved. SUMMARY

[0007] The technical problem to be solved by the present application is how to solve the problem of poor preservation effect caused by the limited action time of existing active ingredients, and to provide a fruit and vegetable preservation device based on low temperature plasma activated spray coating and a fruit and vegetable preservation method.

[0008] The present application solves the above technical problems by the following technical means:

[0009] The present application provides a fruit and vegetable preservation device based on low temperature plasma activated spray coating, comprising an air plasma jet device, a water tank, a detection controller and an array low temperature plasma generating device.

[0010] The air plasma jet device is composed of a copper electrode connected to a high-voltage power supply, a gas flow meter and an air compressor;The air compressor is connected to the water tank through a pipeline;The bottom of the water tank is connected to the array low temperature plasma generating device;The detection controller controls the air plasma jet device, the colloid premixing device, the water tank and the array low temperature plasma generating device through the power system.

[0011] Preferably, the array low temperature plasma generating device is further provided with a conveying device below.

[0012] Preferably, one end of the conveying device is provided with a fruit and vegetable filling device;The other end of the conveying device is provided with a boxing system.

[0013] Preferably, the array low temperature plasma generating device is used to generate plasma activated spray.

[0014] Preferably, the water tank is further provided with a stirrer inside.

[0015] Preferably, the water tank is further provided with a liquid inlet and a liquid outlet on one side.

[0016] Preferably, the water tank is further provided with a colloid premixing device above the water tank, the colloid premixing device comprising a feeding inlet, a premixing tank and a discharging outlet, the feeding inlet being connected with the premixing tank through a pipeline; the bottom of the premixing tank is provided with the discharging outlet; the inside of the premixing tank is provided with a stirrer.

[0017] Preferably, the discharging outlet can directly discharge the material into the water tank or discharge the material into the water tank through a pipeline.

[0018] The application further provides a fruit and vegetable preservation method, comprising the following steps.

[0019] S1: the coating material is discharged into the water tank, and the air plasma jet device and the stirrer in the water tank are turned on;

[0020] S2: the array low-temperature plasma generating device is turned on, and the coating material is activated to generate a plasma-activated spray;

[0021] S3: the fruit and vegetable filling device and the conveying device are turned on, when the fruit and vegetable on the conveying device moves directly below the array low-temperature plasma generating device, the plasma-activated spray is uniformly coated on the surface of the fruit and vegetable to form a preservation coating, and the preservation of the fruit and vegetable is completed.

[0022] Preferably, when the coating material is two or more, the coating material is premixed by the colloid premixing device and then discharged into the water tank.

[0023] The application has the following beneficial effects:

[0024] 1. The application combines the air plasma jet device, the water tank, the detection controller and the array low-temperature plasma generating device to design a fruit and vegetable preservation device based on the low-temperature plasma-activated spray coating, realizes the stable and continuous production of the plasma active components, and can realize the high-throughput production of the active substances and the large-scale preparation of the active medium, and meet the application requirements of large-scale popularization and demonstration in the field of modern agricultural food.

[0025] 2. The efficient integration of the plasma technology and the colloid synthesis system solves the "neck" problem in the application process of the current plasma technology, i.e. the limited action time of the active components, greatly prolongs the residence time of the active components in the plasma, and improves the sterilization efficiency of the plasma. Through the low-temperature plasma-activated spray coating technology, the coating material can be covered on the surface of the fruit and vegetable passing through the conveying belt in a very thin and uniform manner, and a perfect coating effect is formed.

[0026] 3. Zein is used as a plasma activation carrier. Its excellent oxygen barrier performance, water retention and controlled release properties can effectively retain the active ingredients in the plasma-activated spray, prolong the bactericidal effect time and improve the bactericidal efficiency. At the same time, the plasma ionization activation of zein gives it better delivery efficiency and stronger biodegradability.

[0027] 4. The colloid premixing device of the present invention can flexibly replace the filling raw materials, realize the combined use of different types of colloids and plasma, and meet the complex and changing application needs of the market.

[0028] 5. The zein-based plasma-activated spray coating of the present invention can be completely cleaned by washing with water before consumption, which fully meets the current food industry's green and environmentally friendly food safety requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the low-temperature plasma activated spray coating fruit and vegetable preservation device in Example 1 of the present invention;

[0030] Figure 2 Graphs showing the effect of the low-temperature plasma-activated spray coating on the quality of cherry tomatoes during storage in Example 1 of the present invention; A: Photo of cherry tomatoes stored for 15 days; B: Graph showing the quality changes of cherry tomatoes after 15 days of storage;

[0031] Figure 3 These are diagrams showing the preservation effects of the low-temperature plasma-activated spray coating on fruits and vegetables in Example 1 of the present invention; A: Bayberry after one-week storage; B: Bayberry surface enrichment; C: Cherry tomato after one-week storage; D: Cherry tomato surface enrichment.

[0032] Figure 1 Among them, 1-air compressor; 2-feed port; 3-premixing tank; 4-water tank; 5-detection controller; 6-liquid inlet; 7-liquid outlet; 8-array low-temperature plasma generating device; 9-plasma activation spray; 10-fruit and vegetable filling device; 11-conveyor device; 12-packing system. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0034] In the description of the present application, it should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0035] The test materials and reagents used in the following examples, unless otherwise specified, can be obtained commercially.

[0036] Unless otherwise specified, the specific techniques or conditions in the examples can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. Unless otherwise specified, the quantitative tests in the following examples are set up with more than three repeated experiments, and the results are averaged.

[0037] Example 1:

[0038] A fruit and vegetable fresh-keeping device based on low-temperature plasma activated spray 9 coating, comprising an air plasma jet device, a water tank 4, a detection controller 5 and an array low-temperature plasma generating device 8;

[0039] The air plasma jet device is composed of a copper electrode connected to a high-voltage power supply, a gas flow meter and an air compressor 1 Outstanding, OTS-800. (This model of equipment uses high-efficiency full-bridge inverter topology structure, and the control circuit uses STM32 series high-performance control chip to intelligently control the reliable operation of the equipment. The equipment has stable performance, low energy consumption and potential for large-scale practical production)

[0040] The air compressor 1 is connected to the water tank 4 through a pipeline; the water tank 4 is also provided with a liquid inlet 6 and a liquid outlet 7 on one side; the bottom of the water tank 4 is in communication with the array low-temperature plasma generating device 8; the detection controller 5 controls the air plasma jet device, the colloid premixing device, the water tank 4 and the array low-temperature plasma generating device 8 through the power system; the detection controller 5 sets the plasma treatment parameters, and simultaneously monitors the stability of voltage, current and gas flow;

[0041] The array low-temperature plasma generating device 8 is used to generate plasma activated spray 9;

[0042] The array low-temperature plasma generating device 8 uses a high-frequency high-voltage power supply, with an output voltage range of 3-10kV and a frequency of 35kHz, and is grounded through an external electrode to ensure safety. The gas discharge process occurs between the pipeline and the copper electrode, passing through a dielectric barrier to generate uniform plasma in a discharge gap of 6mm, and flows out through a nozzle;

[0043] The array low-temperature plasma generating device 8 is further provided below with a conveying device 11 (specifically, a conveying belt); one end of the conveying device 11 is provided with a fruit and vegetable filling device 10 (for placing fruits and vegetables on the conveying device 11); the other end of the conveying device 11 is provided with a boxing system 12 (for packing and boxing the fruits and vegetables coated with the preservation coating).

[0044] A fruit and vegetable preservation method based on the above fruit and vegetable preservation device, comprising the following steps:

[0045] S1: Put the coating material zein into the water tank 4, and simultaneously start the air plasma jet device and the stirrer in the water tank 4; the air plasma jet device emits activated gas to preliminarily activate the coating material;

[0046] S2: Start the array low-temperature plasma generating device 8, and after the coating material is activated, the plasma activation spray 9 is stably generated; wherein the detection controller 5 sets the plasma activation parameters to 500 W, 15-30 L / min, and 10 min;

[0047] S3: Start the fruit and vegetable filling device 10 and the conveying device 11; when the fruits and vegetables (fresh fruits and vegetables after picking) on the conveying device 11 move directly below the array low-temperature plasma generating device 8, the plasma activation spray 9 uniformly coats the surface of the fruits and vegetables to form a layer of preservation coating, that is, the preservation of the fruits and vegetables is completed, and then the boxing system 12 is used to pack and box the fruits and vegetables coated with the preservation coating.

[0048] Through experiments: after the fruits and vegetables coated by the low-temperature plasma activation spray 9 are stored at room temperature 25℃, 55% RH for 15 days, compared with the control group without coating, the weight loss of the coating group is less than 10%, and the coating treatment effectively reduces the enrichment of natural fungal and bacterial colonies during the storage of fruits and vegetables by more than 90%.

[0049] As shown in Figure 1 , the picked fruits and vegetables are subjected to the treatment of zein plasma activation coating according to the embodiment, and the results show that the small tomatoes subjected to the coating treatment have lower weight loss than the control group without coating.

[0050] As shown in Figure 2 , after being stored at room temperature 25℃, 55% RH for 15 days, the weight of the control group decreases from 18.59 g to 14.02 g, and the weight loss is 24.6%; the weight of the coating group decreases from 18.75 g to 16.89 g, and the weight loss is 10%. In the control group, shrinkage caused by water loss can be obviously observed, which greatly affects the commodity nature of the fruits and vegetables. In addition, as shown in Figure 3The results confirmed that the plasma-activated coating not only has good water retention, but also has excellent antibacterial properties.

[0051] Water retention is measured by the simplest mass weighing method, measuring the initial mass, and then weighing again at 1, 3, 5, 7, 10, 15 days to determine the mass loss of fruits;

[0052] Antibacterial properties are measured by the classic CFU plate coating method, and the results are shown in Figure 3 In the table, a decrease in Log value indicates a decrease in the load of microorganisms on the surface of fruits and vegetables, and a lower decrease in Log value indicates a better sterilization effect of the coating material;

[0053] On red bayberries, the coating treatment can reduce the amount of fungi by at least 99%, and the amount of bacteria by 99.99%. On cherry tomatoes, the inhibition of microorganisms by the plasma-activated coating is slightly reduced, but still has at least 90% sterilization effect compared with the control. In summary, the plasma-activated coating has great application potential in the field of postharvest fruit preservation.

[0054] Example 2:

[0055] In addition to the components of Example 1, the fruit and vegetable preservation device of this embodiment is further provided with a colloid premixing device above the water tank 4, which includes a feed inlet 2, a premixing tank 3, and a discharge outlet. The colloid premixing device feed inlet 2 is connected to the premixing tank 3 through a pipeline; the bottom of the colloid premixing device premixing tank 3 is provided with a discharge outlet; the inside of the colloid premixing device premixing tank 3 is provided with a stirrer, and the discharge outlet can discharge the material into the water tank 4 through a pipeline.

[0056] A fruit and vegetable preservation method based on the above fruit and vegetable preservation device, comprising the following steps:

[0057] The two coating materials, zein and curcumin carbon nanodots, are placed in the colloid premixing device, the stirring function is turned on, and then they are delivered into the water tank 4. The remaining steps are the same as those of Example 1.

[0058] The above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent substitutions for some technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A fruit and vegetable preservation device based on low-temperature plasma activated spray (9) coating, characterized in that: It comprises an air plasma jet device, a water tank (4), a detection controller (5) and an array low-temperature plasma generating device (8); The air plasma jet device is composed of a copper electrode connected to a high-voltage power supply, a gas flow meter, and an air compressor (1); the air compressor (1) is connected to a water tank (4) through a pipeline; the bottom of the water tank (4) is connected to an array low-temperature plasma generating device (8); and the detection controller (5) controls the air plasma jet device, the colloid premixing device, the water tank (4), and the array low-temperature plasma generating device (8) through an electric power system.

2. The fruit and vegetable preservation device according to claim 1, characterized in that: A conveying device (11) is also provided below the array low-temperature plasma generating device (8).

3. The fruit and vegetable preservation device according to claim 3, characterized in that: One end of the conveying device (11) is provided with a fruit and vegetable filling device (10); the other end of the conveying device (11) is provided with a boxing system (12).

4. The fruit and vegetable preservation device according to claim 1, characterized in that: The array low-temperature plasma generating device (8) is used to generate plasma activated spray (9).

5. The fruit and vegetable preservation device according to claim 1, characterized in that: A stirrer is also provided inside the water tank (4).

6. The fruit and vegetable preservation device according to claim 1, characterized in that: A liquid inlet (6) and a liquid outlet (7) are also provided on one side of the water tank (4).

7. The fruit and vegetable preservation device according to claim 1, characterized in that: A colloid premixing device is also provided above the water tank (4), and the colloid premixing device comprises a feed port (2), a premixing tank (3), and a discharge port, wherein the feed port (2) is connected to the premixing tank (3) through a pipeline; a discharge port is provided at the bottom of the premixing tank (3); and a stirrer is provided inside the premixing tank (3).

8. The fruit and vegetable preservation device according to claim 7, characterized in that: The discharge port feeds the material into the water tank (4) through a pipeline.

9. A method for preserving fruits and vegetables, characterized in that: The following steps are involved: S1: Put the coating material into the water tank (4), and simultaneously start the air plasma jet device and the stirrer in the water tank (4); S2: Turning on the array low-temperature plasma generating device (8) to activate the coating material and generate a plasma activation spray (9); S3: The fruit and vegetable filling device (10) and the conveying device (11) are turned on. When the fruits and vegetables on the conveying device (11) move to the bottom of the array low-temperature plasma generating device (8), the plasma activated spray (9) is evenly coated on the surface of the fruits and vegetables to form a layer of fresh-keeping coating, thus completing the preservation of the fruits and vegetables.

10. The method for preserving fruits and vegetables according to claim 9, characterized in that: When there are two or more coating materials, they are first premixed by a colloid premixing device and then added into the water tank (4).

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