Fruit and vegetable modified atmosphere packaging equipment based on plasma technology and fresh-keeping method

Abstract

The invention discloses fruit and vegetable modified atmosphere packaging equipment based on a plasma technology and a fresh-keeping method. The method comprises the following steps: pre-cooling fruits and vegetables, and putting the pre-cooled fruits and vegetables into a packaging bag with a one-way valve; oxygen, carbon dioxide and nitrogen are mixed according to a specific proportion through a gas distribution system; introducing the mixed gas into a plasma generating device to generate low-temperature plasma; and finally, injecting the plasma gas into a packaging bag to finish modified atmosphere packaging. According to the method, modified atmosphere packaging and plasma sterilization are combined, respiration of fruits and vegetables can be effectively inhibited, enzyme activity can be reduced, microorganisms can be killed, the fresh-keeping period is prolonged, and the quality is kept. The equipment for realizing the method comprises a gas distribution system for mixing gas; the plasma generation device is communicated with the gas distribution system and is used for converting the mixed gas into low-temperature plasma; the air blowing gun is used for injecting the plasma gas into the packaging bag; and the control device is used for controlling the operation of the whole equipment. The equipment is high in integration level, convenient to operate and suitable for household and industrial production.

Description

Technical Field

[0001] This invention relates to the field of fruit and vegetable preservation technology, and in particular to a modified atmosphere packaging device and preservation method for fruits and vegetables based on plasma technology. Background Technology

[0002] Fruits and vegetables continue to respire and metabolize after harvest, consuming their own nutrients and releasing ethylene, accelerating aging. Simultaneously, surface microbial contamination easily leads to spoilage. Traditional preservation technologies such as physical, chemical, or biological methods have limitations in terms of timeliness, environmental friendliness, and applicability. Modified atmosphere packaging, by adjusting the oxygen and carbon dioxide concentrations within the packaging, can inhibit respiration and microbial growth, but its sterilization effect is limited when used alone. Low-temperature plasma technology is an emerging non-thermal sterilization technology that can generate a large number of active particles, effectively killing microorganisms with minimal impact on fruit and vegetable quality; in particular, dielectric barrier discharge is widely used.

[0003] However, there is currently a lack of dedicated methods and equipment for efficiently integrating modified atmosphere packaging (MAP) with low-temperature plasma technology to achieve synergistic preservation effects. Existing technologies typically treat these two processes as separate steps, resulting in cumbersome procedures and dispersed equipment, which hinders widespread adoption and application. Therefore, developing a method and equipment that integrates gas preparation, plasma activation, and packaging injection is of great significance for improving the preservation effect and efficiency of fruits and vegetables. Summary of the Invention

[0004] The purpose of this invention is to provide a modified atmosphere packaging device and preservation method for fruits and vegetables based on plasma technology, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a modified atmosphere packaging device for fruits and vegetables based on plasma technology, comprising: A gas mixing system is used to prepare a mixture of oxygen, carbon dioxide, and nitrogen in a predetermined ratio. A plasma generating device, the input end of which is connected to the output end of the gas distribution system, is used to convert the mixed gas into low-temperature plasma gas; An air gun, connected to the output end of the plasma generating device via a conduit, is used to inject the low-temperature plasma gas into fruit and vegetable packaging bags; A control device is electrically connected to the gas distribution system and the plasma generation device. The control device is used to control the gas distribution system to prepare a mixed gas of oxygen, carbon dioxide and nitrogen in a predetermined ratio, and to control the plasma generation parameters of the plasma generation device.

[0006] Preferably, the gas mixing system includes an oxygen tank, a nitrogen tank, a carbon dioxide tank, a gas mixing tank, and a control system; the oxygen tank, nitrogen tank, and carbon dioxide tank are respectively connected to the gas mixing tank via pipelines, and each pipeline is equipped with a solenoid valve; a pressure sensor is installed on the gas mixing tank; the pressure sensor and the solenoid valve are both electrically connected to the control system; a flow control valve is installed on the connecting pipeline between the gas mixing tank and the plasma generating device, and the flow control valve is electrically connected to the control device.

[0007] Preferably, the control device includes a power supply, a transformer, a digital pulse regulator, and a control terminal; the power supply provides power to the transformer, the plasma generation device, and the digital pulse regulator, and the transformer and the digital pulse regulator are used to adjust the voltage and frequency of plasma generation, respectively; the power supply, the transformer, the digital pulse regulator, and the gas distribution system are all electrically connected to the control terminal.

[0008] Preferably, the plasma generating device is a coaxial dual dielectric barrier discharge device.

[0009] Preferably, it also includes a housing, in which the gas distribution system, the plasma generation device, and the control device are all housed; the housing is provided with a partition, which divides the internal space of the housing into installation compartments for installing different devices.

[0010] Preferably, the bottom of the housing is provided with several casters.

[0011] This invention provides a modified atmosphere packaging method for fruits and vegetables based on plasma technology. Using the aforementioned modified atmosphere packaging equipment for fruits and vegetables based on plasma technology, the method includes the following steps: Pre-cool the harvested fruits and vegetables; The pre-cooled fruits and vegetables are placed in a packaging bag equipped with a one-way valve. The control device controls the gas distribution system to prepare a mixed gas of oxygen, carbon dioxide and nitrogen in a predetermined ratio; The mixed gas is introduced into the plasma generating device, and the plasma generating parameters of the plasma generating device are controlled by the control device to generate low-temperature plasma gas. The low-temperature plasma gas is injected into the packaging bag via the one-way valve using the air gun, thus completing the modified atmosphere packaging. After the modified atmosphere packaging is completed, the packaging bags should be stored in a low-temperature environment.

[0012] Preferably, the pre-cooling treatment is performed at a temperature of 4°C for 12 hours.

[0013] Preferably, the storage temperature is 1℃±0.5℃.

[0014] Preferably, the concentration ratio of the mixed gas is: oxygen concentration of 2%-5%, carbon dioxide concentration of 4%-8%, and nitrogen concentration of 87%-94%. The conditions for the plasma generation device to generate low-temperature plasma gas are: voltage of 100V-120V, frequency of 120Hz-140Hz, and processing time of 60-80 seconds.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: 1. This invention creatively combines the physiological inhibition function of modified atmosphere packaging with the physical sterilization function of plasma in one step. The low-temperature plasma gas not only has a strong sterilization effect, but its injection process also simultaneously regulates the gas environment inside the packaging bag. The synergy of the two is significantly superior to single technologies, and can more effectively inhibit respiration intensity, reduce enzyme activity, and kill microorganisms, thereby maximizing the preservation of the color and nutritional components (such as vitamin C and TSS) of fruits and vegetables and extending their shelf life.

[0016] 2. This invention highly integrates modules such as gas storage, mixing, plasma conversion, and control, resulting in a compact structure. It achieves automated or semi-automated operation through control devices, reducing operational difficulty and human error, and improving production efficiency.

[0017] 3. The device of this invention can be flexibly designed in size, and the universal wheels at the bottom make it easy to move. It is suitable for continuous industrial production, as well as for use in small-scale scenarios such as supermarkets, restaurants or homes, and has great potential for promotion and application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the modified atmosphere packaging equipment for fruits and vegetables based on plasma technology according to the present invention. In the diagram: 1. Oxygen tank; 2. Nitrogen tank; 3. Carbon dioxide tank; 4. Control system; 5. Pressure sensor; 6. First solenoid valve; 7. Second solenoid valve; 8. Third solenoid valve; 9. Mixing tank; 10. Flow control valve; 11. Transformer; 12. Power supply; 13. Plasma generation device; 14. Air gun; 15. Digital pulse regulator. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] like Figure 1 As shown, the present invention provides a modified atmosphere packaging device for fruits and vegetables based on plasma technology, comprising: A gas mixing system is used to prepare a mixture of oxygen, carbon dioxide, and nitrogen in a predetermined ratio. The plasma generating device 13 has its input end connected to the output end of the gas distribution system and is used to convert the mixed gas into low-temperature plasma gas. The air gun 14 is connected to the output end of the plasma generating device 13 via a conduit and is used to inject low-temperature plasma gas into the fruit and vegetable packaging bag. The control device is electrically connected to the gas distribution system and the plasma generation device 13. The control device is used to control the gas distribution system to prepare a mixture of oxygen, carbon dioxide and nitrogen in a predetermined ratio, and to control the plasma generation parameters of the plasma generation device 13.

[0022] The scheme is further optimized. The gas distribution system includes an oxygen tank 1, a nitrogen tank 2, a carbon dioxide tank 3, a gas mixing tank 9, and a control system 4. The oxygen tank 1, nitrogen tank 2, and carbon dioxide tank 3 are connected to the gas mixing tank 9 through pipelines, and each pipeline is equipped with a solenoid valve. A pressure sensor 5 is installed on the gas mixing tank 9. The pressure sensor 5 and the solenoid valve are electrically connected to the control system 4. A flow control valve 10 is installed on the connecting pipeline between the gas mixing tank 9 and the plasma generation device 13. The flow control valve 10 is electrically connected to the control device.

[0023] Based on the feedback from the pressure sensor 5, the control system 4 controls the opening and closing of each solenoid valve and uses the pressure method to complete the automatic gas proportioning.

[0024] The scheme is further optimized. The control device includes a power supply 12, a transformer 11, a digital pulse regulator 15, and a control terminal. The power supply 12 supplies power to the transformer 11, the plasma generation device 13, and the digital pulse regulator 15. The transformer 11 and the digital pulse regulator 15 are used to adjust the voltage and frequency of plasma generation, respectively. The power supply 12, the transformer 11, the digital pulse regulator 15, and the gas distribution system are all electrically connected to the control terminal.

[0025] Further optimization of the scheme: the plasma generation device 13 is a coaxial dual dielectric barrier discharge device, which can efficiently convert the flowing mixed gas into low-temperature plasma gas rich in active particles.

[0026] The design is further optimized to facilitate movement and integration. It also includes a housing, a gas distribution system, a plasma generation device 13, and a control device, all housed within the housing. The housing is equipped with partitions that divide the internal space into mounting compartments for different devices.

[0027] To further optimize the design, several casters are installed at the bottom of the housing. The casters are arranged symmetrically in pairs at the bottom of the housing, with four casters being the preferred number. The casters enable the device to move.

[0028] This invention provides a modified atmosphere packaging method for fruits and vegetables based on plasma technology. Using the aforementioned modified atmosphere packaging equipment for fruits and vegetables based on plasma technology, the method includes the following steps: Pre-cool the harvested fruits and vegetables; The pre-cooled fruits and vegetables are placed in packaging bags equipped with one-way valves. A gas mixture of oxygen, carbon dioxide, and nitrogen in a predetermined ratio is prepared by controlling the gas distribution system using a control device. The mixed gas is introduced into the plasma generating device 13, and the plasma generating parameters of the plasma generating device 13 are controlled by the control device to generate low-temperature plasma gas. Low-temperature plasma gas is injected into the packaging bag via a one-way valve using a blow gun 14 to complete modified atmosphere packaging. After the modified atmosphere packaging is completed, the packaging bags should be stored in a low-temperature environment.

[0029] The solution was further optimized, with the pre-cooling temperature set at 4°C and the pre-cooling time set at 12 hours.

[0030] The storage temperature was further optimized to 1℃±0.5℃.

[0031] The scheme was further optimized, with the following gas concentration ratios: oxygen concentration 2%-5%, carbon dioxide concentration 4%-8%, and nitrogen concentration 87%-94%. The conditions for generating low-temperature plasma gas by plasma generating device 13 are: voltage of 100V-120V, frequency of 120Hz-140Hz, and processing time of 60-80 seconds.

[0032] Example 1 The daylilies, known as "Dawuzui," were harvested when they were 80% ripe, had a good color, and were free from mechanical damage. They were then quickly transported back to the laboratory and pre-cooled in a 4°C cold storage for 12 hours.

[0033] Weigh 200g of pre-cooled daylily and pack it into a polypropylene bag with a one-way valve.

[0034] The mixed gas is filled with a volume ratio of 3% oxygen, 6% carbon dioxide, and 91% nitrogen.

[0035] A coaxial dual-dielectric barrier discharge plasma generator was used, with a discharge voltage of 111V and a frequency of 130Hz. The ionized low-temperature plasma gas was injected into a sealed bag through a one-way valve on the packaging bag, and the treatment lasted for 70 seconds. After treatment, the one-way valve on the packaging bag automatically closed to maintain the internal gas environment.

[0036] The treated packaging bags were stored in a cold storage at 1℃±0.5℃.

[0037] Example 2 The procedure is essentially the same as in Example 1, except that the mixed gas ratio is set to: 5% oxygen, 8% carbon dioxide, and 87% nitrogen. Other operations and conditions are the same as in Example 1.

[0038] Example 3 The procedure is essentially the same as in Example 1, except that the plasma treatment parameters are set as follows: voltage 100V, frequency 120Hz, and treatment time 80 seconds. Other operations and conditions are the same as in Example 1.

[0039] Example 4 The procedure is essentially the same as in Example 1, except that a polyethylene food storage bag with a one-way valve is used for packaging. All other operations and conditions are the same as in Example 1.

[0040] Comparative Example 1 The pre-cooled daylily was processed according to the steps in Example 1, and a mixed gas (3% oxygen, 6% carbon dioxide, and 91% nitrogen) was introduced, but no plasma treatment was performed. It was then directly stored in a cold storage at 1℃±0.5℃.

[0041] Comparative Example 2 The pre-cooled daylily buds were packed into a bag with a one-way valve, without being filled with mixed gas. Other steps were carried out directly using the processing steps of Example 1, including plasma treatment (voltage 111V, frequency 130Hz, processing time 70 seconds), and then stored under the same conditions.

[0042] Comparative Example 3 The pre-cooled daylily buds were first subjected to conventional plasma treatment under the conditions of Example 1, then filled with a mixed gas (3% oxygen, 6% carbon dioxide, 91% nitrogen), and then stored under the same conditions.

[0043] Comparative Example 4 The pre-cooled daylily was packaged in a low-barrier packaging material (25μm thick PVC film) under normal pressure and then placed between the electrode plates of a low-temperature plasma generator. It was then treated for 15 seconds at a voltage of 50kV and a frequency of 50Hz, and finally stored under the same conditions.

[0044] Preservation effect test During storage, the quality indicators of daylilies in each example and comparative example were periodically measured. The measurement methods are as follows: 1. Color Measurement The colorimeter was used to measure the epidermis of each daylily petal at its midpoint. Each daylily was measured three times, and the values ​​were recorded. Value. a The value represents the red-green tint, a The lower the value, the better the green color is preserved. Six samples were randomly selected for each treatment, and the average value of the results was taken.

[0045] 2. Weight loss rate determination The weight loss rate (%) was determined by weighing and calculated using the following formula: (Initial storage mass - Actual storage time mass) / Initial storage mass × 100%.

[0046] 3. Determination of Vitamin C (Vc) Content Take 10g of daylily, crush and homogenize it, then use a vitamin C analyzer to determine the vitamin C content. Repeat the measurement three times and take the average value.

[0047] 4. Total bacterial count determination Record the total number of colonies according to the method in GB4789.2-2016.

[0048] Table 1 shows the a content of fruits and vegetables under different treatment conditions. Values, total bacterial count, respiration rate, peroxidase activity, soluble solids content, and vitamin C content—taking daylily as an example.

[0049] Table 1 compares the a of fruits and vegetables under different treatment conditions. The values ​​of total bacterial count, respiration rate, POD activity, TSS content, and VC content show that Example 4, which uses modified atmosphere packaging based on plasma technology, exhibits lower total bacterial count, respiration rate, and POD activity, as well as higher TSS and VC content. This indicates that plasma technology combined with modified atmosphere packaging can inhibit the respiration of fruits and vegetables, reduce enzyme activity, and thus benefit the preservation of fruits and vegetables and extend their shelf life, while maintaining their original nutritional quality. Meanwhile, due to a... The values ​​show that the color of fruits and vegetables will be preserved better.

[0050] This invention avoids the physical and thermal damage to daylily tissue caused by direct plasma discharge. Daylilies treated with this method, after being stored at 1℃±0.5℃ for 30 days, show the following results: The value is more than 40% lower than that of the "pre-treatment, post-packaging" process, the color is well maintained, and there is no cold damage or discharge damage.

[0051] This invention achieves a deep synergistic effect between modified atmosphere packaging and low-temperature plasma. Daylilies treated with this method have a good flower rate of ≥68% after 30 days of storage, a vitamin C loss rate that is reduced by about 30% compared to modified atmosphere packaging alone, a weight loss rate controlled within 2%, and a total bacterial count that is reduced by 1-2 orders of magnitude compared to the control group.

[0052] This invention employs a process of packaging first and then processing. The processed products directly enter the cold chain storage and transportation, and are sealed throughout the process, eliminating the risk of secondary contamination and extending the shelf life to more than 30 days.

[0053] The process parameters of this invention are precise and controllable, and the operation is simple. The processed product can be directly put into cold chain storage and transportation, providing an efficient, safe and economical solution for the industrial preservation of fresh daylilies, and has broad application prospects.

[0054] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified atmosphere packaging device for fruits and vegetables based on plasma technology, characterized in that, include: A gas mixing system is used to prepare a mixture of oxygen, carbon dioxide, and nitrogen in a predetermined ratio. The plasma generating device (13) has its input end connected to the output end of the gas distribution system, and is used to convert the mixed gas into low-temperature plasma gas. The air gun (14) is connected to the output end of the plasma generating device (13) through a conduit and is used to inject the low-temperature plasma gas into the fruit and vegetable packaging bag; The control device is electrically connected to the gas distribution system and the plasma generation device (13). The control device is used to control the gas distribution system to prepare a mixture of oxygen, carbon dioxide and nitrogen in a predetermined ratio, and to control the plasma generation parameters of the plasma generation device (13).

2. The modified atmosphere packaging equipment for fruits and vegetables based on plasma technology according to claim 1, characterized in that, The gas distribution system includes an oxygen tank (1), a nitrogen tank (2), a carbon dioxide tank (3), a gas mixing tank (9), and a control system (4); the oxygen tank (1), nitrogen tank (2), and carbon dioxide tank (3) are connected to the gas mixing tank (9) through pipelines, and each pipeline is equipped with a solenoid valve; a pressure sensor (5) is installed on the gas mixing tank (9); the pressure sensor (5) and the solenoid valve are electrically connected to the control system (4); a flow control valve (10) is installed on the connecting pipeline between the gas mixing tank (9) and the plasma generating device (13), and the flow control valve (10) is electrically connected to the control device.

3. The modified atmosphere packaging equipment for fruits and vegetables based on plasma technology according to claim 1, characterized in that, The control device includes a power supply (12), a transformer (11), a digital pulse regulator (15), and a control terminal; the power supply (12) supplies power to the transformer (11), the plasma generation device (13), and the digital pulse regulator (15), and the transformer (11) and the digital pulse regulator (15) are used to adjust the voltage and frequency of plasma generation, respectively; the power supply (12), the transformer (11), the digital pulse regulator (15), and the gas distribution system are all electrically connected to the control terminal.

4. The modified atmosphere packaging equipment for fruits and vegetables based on plasma technology according to claim 1, characterized in that, The plasma generation device (13) is a coaxial dual dielectric barrier discharge device.

5. The modified atmosphere packaging equipment for fruits and vegetables based on plasma technology according to claim 1, characterized in that, It also includes a housing, in which the gas distribution system, the plasma generation device (13) and the control device are all housed; the housing is provided with a partition, which divides the internal space of the housing into installation compartments for installing different devices.

6. The modified atmosphere packaging equipment for fruits and vegetables based on plasma technology according to claim 5, characterized in that, The bottom of the box is equipped with several casters.

7. A method for modified atmosphere packaging and preservation of fruits and vegetables based on plasma technology, characterized in that, Using the modified atmosphere packaging equipment for fruits and vegetables based on plasma technology as described in any one of claims 1-6 includes the following steps: Pre-cool the harvested fruits and vegetables; The pre-cooled fruits and vegetables are placed in a packaging bag equipped with a one-way valve. The control device controls the gas distribution system to prepare a mixed gas of oxygen, carbon dioxide and nitrogen in a predetermined ratio; The mixed gas is introduced into the plasma generating device (13), and the plasma generating parameters of the plasma generating device (13) are controlled by the control device to generate low-temperature plasma gas; The low-temperature plasma gas is injected into the packaging bag through the one-way valve via the air gun (14) to complete the modified atmosphere packaging; After the modified atmosphere packaging is completed, the packaging bags should be stored in a low-temperature environment.

8. The modified atmosphere packaging method for fruits and vegetables based on plasma technology according to claim 7, characterized in that, The pre-cooling treatment was performed at a temperature of 4°C for 12 hours.

9. The modified atmosphere packaging method for fruits and vegetables based on plasma technology according to claim 7, characterized in that, The storage temperature is 1℃±0.5℃.

10. The modified atmosphere packaging method for fruits and vegetables based on plasma technology according to claim 7, characterized in that, The concentration ratio of the mixed gas is: oxygen concentration of 2%-5%, carbon dioxide concentration of 4%-8%, and nitrogen concentration of 87%-94%. The conditions for generating low-temperature plasma gas by the plasma generating device (13) are: voltage of 100V-120V, frequency of 120Hz-140Hz, and processing time of 60-80 seconds.

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