Flexible arrangement of non-space occupying high voltage electrostatic field kiwifruit storage multipurpose system and method

Abstract

The application discloses a flexible arrangement and space-occupying-free high-voltage electrostatic field kiwi fruit storage multipurpose system and method, which takes a standard refrigerator as a main body, is internally insulated and coated, and is composed of a high-voltage direct-current power supply, a cable electrode array, a grounding belt and an intelligent control module. A 30kV direct-current high voltage is adopted to form a stable non-uniform electric field, and the electrode can be precisely adjusted in distance and prevented from shaking, and is suitable for large-scale storage. Taking "Xu Xiang" kiwi fruit as an object, under the condition of 0-2 DEG C and 90%-95% humidity, continuous electrostatic treatment can inhibit respiration, delay softening, reduce water loss, target inhibit cellulase, polyphenol oxidase and other activities, and improve antioxidant capacity; directly inhibit alternaria alternata, reduce the incidence of soft rot; inhibit PAL activity, reduce lignin accumulation, alleviate low-temperature cold damage, and at the same time, maintain soluble solids, vitamin C and other nutritional ingredients. The application is safe, residue-free, suitable for a standard refrigerator, and provides an efficient physical preservation scheme for kiwi fruit industrialization storage.

Description

Technical Field

[0001] This invention relates to the field of kiwifruit storage, and more particularly to a multi-purpose system and method for storing kiwifruit using a flexible, space-saving high-voltage electrostatic field. Background Technology

[0002] Postharvest preservation of kiwifruit remains a major challenge for the industry. As a typical climacteric fruit, kiwifruit is prone to rapid softening and increased disease after harvest, which significantly shortens its shelf life and reduces economic returns.

[0003] High-voltage electrostatic field (HVEF) preservation technology is gradually breaking through laboratory limitations and expanding into industrial applications. Currently, domestic and international research institutions have developed many portable electrostatic preservation devices that meet commercial needs, and these devices have been demonstrated in cold chain storage facilities in some fruit and vegetable producing areas. Jiang Xiaochen et al. (2023) believe that this technology has formed a relatively complete theoretical foundation, and its mechanism in fruit and vegetable preservation mainly includes enzyme-catalyzed reaction regulation, changes in cell membrane potential, and control of ice crystal formation. In addition, some scholars have systematically analyzed its mechanism and proposed some improvement schemes to enhance the technology's effectiveness (Zhu Jialin et al., 2024). In the future, HVEF technology can be used in conjunction with physical preservation methods to achieve a combined preservation effect.

[0004] Currently, there is no research on the impact of high-voltage electrostatic fields on the storage quality of 'Xuxiang' kiwifruit. In particular, there is a lack of dedicated equipment and related designs for low-temperature control and intelligent fruit storage.

[0005] CN1308873A: The method of directly carrying high negative potential to fruits and vegetables requires strict insulation between the fruits and vegetables and the ground. When storing in batches, insulation is difficult and safety is low. It is not suitable for large-scale storage of kiwifruit in a warehouse.

[0006] The equipment consists of a negative high-voltage generator and simple electrodes. It lacks a uniform electric field design, resulting in uneven electric field distribution within the storage room and significant differences in preservation effects.

[0007] It only achieves basic antibacterial and water loss reduction, but cannot target and inhibit soft rot of kiwifruit, alleviate low temperature injury, regulate cell wall degradation and antioxidant system, and has limited effect on delaying aging of respiratory climacteric kiwifruit.

[0008] It lacks intelligent safety protection (short circuit / leakage / ozone detection), has no modular structure suitable for cold storage, and has poor industrialization feasibility.

[0009] CN110800788A: This application is for fermented beef, solely for improving texture and color, and completely ignores post-harvest preservation of kiwifruit. It offers no solution to kiwifruit softening, browning, soft rot, or chilling injury. The electric field voltage is only 2500-3500V, which is too low to inhibit pathogenic bacteria in kiwifruit or regulate post-harvest physiological metabolism. It is merely a simple electrostatic treatment combined with refrigeration, lacking dedicated electric field equipment, uniform electric field design, and mechanisms for regulating fruit physiology; it is a crude treatment. It only focuses on product texture and fails to address the core issues of fruit and vegetable preservation (water loss, disease, chilling injury, and nutrient loss), and the technical solution cannot be transferred to kiwifruit storage.

[0010] CN116222096A: This is a cold storage facility for ocean-going vessels, focusing on space regulation and ice-temperature preservation. It is not designed specifically for the physiological characteristics of kiwifruit and cannot solve problems such as soft rot and chilling injury. The electrostatic plates are fixed / adaptive adjustable plate electrodes, resulting in poor electric field uniformity. When kiwifruit is stacked, the electric field penetration is insufficient, leading to uneven preservation. It only achieves basic electrostatic preservation and does not study the regulatory mechanisms of high-voltage electrostatics on postharvest physiology, enzyme activity, disease resistance, and chilling injury in kiwifruit. There is no quantitative data to support the preservation effect. The equipment has a customized marine structure, resulting in high cost and unsuitability for large-scale kiwifruit storage on land, limiting its application scenarios.

[0011] CN117063970A: This technology is a general cold storage preservation method for kiwifruit. It uses single-point high-voltage electrostatic equipment and independent zone control. The electric field coverage is uneven and there is no dedicated electrode arrangement. It cannot make targeted control on soft rot, low temperature injury and rapid cell wall degradation of kiwifruit. It only relies on electric field + air purification to achieve basic preservation and does not solve the core pain points of kiwifruit storage.

[0012] CN208419330U: This cold storage uses symmetrical electrode plates on the walls and a high-voltage pulse electric field, which only achieves uniform temperature inside the storage and reduces backheating. The electric field is concentrated in the wall area and the electric field is weak in the middle of the shelves. There is no special design for kiwifruit, so it cannot regulate the internal enzyme system and antioxidant capacity of the fruit, and it has no effect on alleviating soft rot and chilling injury.

[0013] CN210275762U: This device is a small box-type, cone-shaped discharge structure with a small electric field range and uneven field strength. It can only achieve basic antibacterial properties and has no ability to adapt to large-scale cold storage. It lacks low-temperature synergy and enzyme activity regulation design, and cannot meet the long-term storage requirements of kiwifruit, let alone alleviate chilling injury and inhibit soft rot.

[0014] CN215873289U: This device is specifically designed for green walnuts, with adjustable electrode plates and an elastic net. The electric field structure and parameters are adapted to walnuts, but cannot be adapted to the fruit morphology and physiological characteristics of kiwifruit. It only inhibits respiration and weightlessness, and does not have disease resistance or cold damage resistance mechanisms. Electrode adjustment can easily lead to electric field instability. Summary of the Invention

[0015] Purpose of the invention: To provide a more effective and flexible high-voltage electrostatic field storage system and method for kiwifruit, which allows for space-saving storage. Specific objectives are detailed in the specific implementation section, which describes several substantial technical effects.

[0016] To achieve the above objectives, the present invention adopts the following technical solution: A multi-purpose kiwi fruit storage system with a flexible, space-saving high-voltage electrostatic field, characterized in that: It consists of a high-voltage DC power supply system, an electrode array formed by cables, a grounding strip, and an intelligent control unit; The main frame is made of standard cold storage, and the interior is covered with insulating material to ensure safe operation. Each end of the electrode of the electrode array formed by the cable has a support component to maintain stability and effectively eliminate electric field deformation caused by vibration. Kiwifruit is stored between electrodes, close to the ground, and is subjected to a non-uniform electric field generated by the crossed electrodes. The high-voltage DC power supply system has a high-precision output function. The high-voltage power supply outputs 30 kV DC high voltage, with an adjustable range of 0 to 50 kV. The grounding strip plays a current-conducting role to form a non-uniform electric field. The high-voltage DC power supply system, the electrode array formed by cables, and the grounding strip constitute an electric field loop; The intelligent control unit can adjust the electric field strength and environmental parameters inside the warehouse in real time; the intelligent control unit has leakage protection function, and the environmental parameters inside the warehouse include temperature, humidity, and electric field strength. The electric field strength is determined by the magnitude of the current, while the temperature and humidity are controlled by temperature and humidity control systems installed in the standard cold storage.

[0017] A further technical solution of the present invention is that the electrodes of the electrode array formed by the cable are arranged in a double or multiple row structure, and multiple groups of kiwifruit are arranged between the double or multiple rows of electrodes.

[0018] A further technical solution of the present invention is that the arrangement of electrodes in the electrode array formed by the cable is achieved by a dedicated top plate 1, which can be suspended or fixed to the upper end of the frame of the standard cold storage as the main frame by the lifting lug 3; the dedicated top plate 1 is made of insulating material. The dedicated top plate 1 includes a bus inlet 2 above it. The dedicated top plate 1 is hollow and can be used for wiring. Multiple optional hanging ports 4 are arranged in the downward position of the dedicated top plate 1. The optional lifting port 4 can be quickly connected to the electrode via the upper insertion port 7; the quick connection structure is as follows: a metal threaded sleeve 9 with a step on the top can be inserted into the insulated optional lifting port 4, and the branch cable 8 is connected above the metal threaded sleeve 9; the thread on the upper insertion port 7 can be installed in the metal threaded sleeve 9, thereby realizing the connection and docking. Multiple optional hanging ports 4 are evenly arranged, and their dimensions are clearly marked with scales on the bottom; This allows for precise adjustment of the distance between cables; The branch cable 8 contains multiple groups and converges through the bus entry 2; The position of the electrode can be adjusted by adjusting the position of the metal threaded sleeve 9 and the upper insertion port 7.

[0019] A further technical solution of the present invention is that the electrodes are also arranged in parallel with digital temperature measuring cables adapted to LS / T 1813-2017; the two are relatively isolated, and the digital temperature measuring cables arranged in this way can more accurately obtain the three-dimensional temperature field of the storage space.

[0020] The method for storing kiwifruit based on a non-uniform high-voltage electrostatic field is characterized by utilizing a multi-purpose kiwifruit storage system with a flexible, space-saving high-voltage electrostatic field as described in any of the above-mentioned methods. Select 'Xu Xiang' kiwifruit that are uniformly ripe, free from pests and diseases, and without mechanical damage; Kiwifruit should be stored in a high-voltage electrostatic field environment with a temperature of 0-2℃, a relative humidity of 90%-95%, and an electric field strength of 30kV. Continuous high-voltage electrostatic field treatment inhibits fruit respiration, delays softening, reduces water loss, inhibits Alternaria soft rot, alleviates low-temperature chilling injury, inhibits cellulase (CX) and polyphenol oxidase (PPO) activity, delays fruit cell wall degradation and browning, increases SOD and CAT activity, reduces POD activity, enhances fruit antioxidant capacity, and reduces lignin accumulation by inhibiting PAL activity, thus alleviating fruit pulp lignification chilling injury.

[0021] A further technical solution of the present invention is to determine the storage height of the special top tray 1 according to the storage height of the kiwifruit; Adjust the number and spacing of cables according to the quantity of kiwifruit; The hollow, special top tray 1 contains a slow-release agent that delays the aging of kiwifruit.

[0022] A further technical solution of the present invention is that, since the kiwi fruit is arranged between the electrodes, it must be below the special top plate 1; Cold air is pumped in through a dedicated cold air inlet 10 arranged on the side of the dedicated top plate 1, and the cold air is sprayed out from multiple optional hanging ports 4 to directly control the temperature of the kiwifruit, thereby reducing the energy consumption of the cold storage; digital temperature measuring cable is used for real-time temperature measurement.

[0023] The application of a method with an electric field strength of 30kV and a temperature of 0-2℃ and a relative humidity of 90%-95%, characterized in that... This purpose can be any one of the following: Firstly, this application utilizes the high-voltage electrostatic field to inhibit the activity of cellulase CX and polyphenol oxidase PPO, thereby delaying the degradation and browning of fruit cell walls. Second: This application utilizes the high-voltage electrostatic field to enhance the antioxidant capacity of fruits by increasing the activity of SOD and CAT, reducing the activity of POD; Third: This application utilizes the high-voltage electrostatic field to inhibit Alternaria alterniflora, thereby reducing the rate of fruit rot. Fourth: This application is suitable for storage under low temperature stress of -1.5 to 0.5℃, and it can alleviate the lignification and chilling injury of fruit pulp by inhibiting PAL activity and reducing lignin accumulation; Fifth: This purpose is to maintain the titratable acid, soluble solids, and vitamin C content of the fruit.

[0024] The present invention, employing the above technical solution, offers the following advantages over existing technologies: By regulating respiratory metabolism, inhibiting the activity of cell wall degrading enzymes and browning enzymes, enhancing the antioxidant defense system, inducing disease resistance, and inhibiting lignin synthesis, it effectively delays post-harvest senescence in 'Xu Xiang' kiwifruit, controls soft rot, and alleviates low-temperature chilling injury. This study confirms that HVEF is a highly efficient, safe, and residue-free post-harvest physical preservation technology for kiwifruit, providing a theoretical basis and technical support for the industrial-scale storage of kiwifruit. Furthermore, it provides a novel, multi-purpose industrial-scale equipment; it is space-saving, flexible, and convenient to set up, and compared to existing technologies, it occupies absolutely no space. Attached Figure Description

[0025] To further illustrate the present invention, the following description is provided in conjunction with the accompanying drawings: Figure 1 A schematic diagram of one of the cable arrangement methods for preserving food in a high-voltage electrostatic field; Figure 2 The changes in physiological indicators related to kiwifruit storage under high-voltage electrostatic field treatment; (A: firmness; B: titratable acid; C: soluble solids; D: respiration rate; E: water loss rate. * indicates p < 0.05; ** indicates p < 0.01) Figure 3 The changes in antioxidant enzyme activity in kiwifruit under high-voltage electrostatic field treatment are shown. (A: superoxide dismutase (SOD); B: peroxidase (POD); C: catalase (CAT), * indicates p<0.05; ** indicates p<0.01) Figure 4The changes in enzyme activity related to cell wall degradation and browning in kiwifruit under high-voltage electrostatic field treatment; (A: cellulase (CX); B: polyphenol oxidase (PPO, * indicates p<0.05; ** indicates p<0.01) Figure 5 The growth status of plaques in CK and PDA treated with electric field (Note: A. Colonies in CK group at day 0; B. Colonies in electric field group at day 0; C. Colonies in CK group at day 5; D. Colonies in electric field group at day 5; Scale bar: 1.0 cm). Figure 6 The average increase in plaque diameter of CK and PDA treated with electric field after 10 days is shown (* indicates p<0.05; ** indicates p<0.01). Figure 7 The disease phenotype of fruits in the CK group after inoculation (Note: A. CK group inoculated 0 days ago; B. CK group inoculated 7 days ago; C. CK group inoculated 14 days ago; D. CK group inoculated 21 days ago; scale bar: 1.0 cm). Figure 8 The disease phenotype of fruits inoculated with the electric field group (Note: A. 0 days after inoculation in the electric field group; B. 7 days after inoculation in the electric field group; C. 14 days after inoculation in the electric field group; D. 21 days after inoculation in the electric field group; scale bar: 1.0 cm). Figure 9 The inoculation rot rate of fruits in the CK and electric field treatment groups is shown in Figure 1 (* indicates p < 0.05; ** indicates p < 0.01). Figure 10 Physiological metabolic indicators of diseased fruits in the CK and electric field groups were determined 21 days after inoculation (A: flavonoids; B: total phenols; C: superoxide anion; D: peroxidase (POD); E: polyphenol oxidase (PPO); F: phenylalanine ammonia-lyase (PAL) * indicates p<0.05; ** indicates p<0.01). Figure 11 The effects of high-voltage electrostatic field treatment on physiological indicators of kiwifruit stored at low temperatures (A: soluble solids; B: firmness; C: respiration rate, * indicates p<0.05; ** indicates p<0.01). Figure 12 Staining and quantitative analysis of phloroglucinol in fruits of the CK and electric field groups at 20 and 40 days (A: original image; B, C: ImageJ image segmentation to extract pulp and stained areas; D: percentage of stained area; E: box plot of stained area distribution; F: change in stained area over time). Figure 13 Effects of high-voltage electrostatic field treatment on changes in membrane lipid peroxidation-related indicators in kiwifruit under low-temperature conditions (A: relative conductivity; B: malondialdehyde (MDA) * indicates p < 0.05; ** indicates p < 0.01). Figure 14Effects of high-voltage electrostatic field treatment on the accumulation of antioxidants in kiwifruit under low-temperature conditions (* indicates p<0.05; ** indicates p<0.01). Figure 15 This is a structural diagram of a high-voltage electrostatic field food preservation device. Figure 16 Detailed diagram of the bottom suspension structure of the cable in a high-voltage electrostatic field food preservation device; Figure 17 Structural diagram of the invention's dedicated top plate; Figure 18 A structural diagram of the docking mechanism for the invention; The components include: 1. Dedicated top plate; 2. Bus inlet; 3. Lifting lug; 4. Optional lifting port; 5. Temperature measuring cable; 6. Cable for electric field formation; 7. Top socket; 8. Branch cable; 9. Metal threaded sleeve; 10. Dedicated cold air inlet; 11. Counterweight. Detailed Implementation

[0026] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0027] This invention relates to the storage of 'Xuxiang' kiwifruit, specifically a storage method for 'Xuxiang' kiwifruit under high-voltage electrostatic field treatment. This study constructed a double-row suspended high-voltage electrostatic field preservation device and systematically investigated the regulatory effects and physiological mechanisms of HVEF treatment on the quality of kiwifruit stored at room temperature, infectious diseases (Alternaria alternata soft rot), and chilling injury, as well as the effects on these effects. The main research results are as follows: 1. Delaying Low-Temperature Storage Senescence: HVEF treatment significantly inhibited fruit respiration rate, delayed the onset of the respiration peak, and effectively reduced water loss. Regarding quality maintenance, the fruit firmness in the electric field-treated group decreased slowly, and the content of titratable acid and soluble solids remained at high levels. Mechanistic studies showed that HVEF slowed down cell wall depolymerization and browning by significantly inhibiting the activity of key cell wall degradation enzymes—cellulase (CX) and polyphenol oxidase (PPO); simultaneously, it regulated the antioxidant enzyme system, increasing the activity of superoxide dismutase (SOD) and catalase (CAT), decreasing peroxidase (POD) activity, enhancing the fruit's ability to scavenge reactive oxygen species (ROS), and maintaining cell membrane integrity.

[0028] 2. Inhibition of Infectious Diseases: HVEF has a significant direct inhibitory effect on *Alternaria alternata*, the pathogen causing soft rot in kiwifruit. After 10 days of cultivation, the growth rate of fungal plaque diameter was reduced by 46.2% compared to the control group. Inoculation experiments showed that the disease incidence and rot rate of fruits in the electric field treatment group were significantly reduced (the rot rate inhibition rate reached 49.1% at 21 days). Its disease resistance mechanism lies in the fact that the electric field not only directly inhibits the growth of pathogens but also induces systemic resistance in fruits, significantly activating the activities of phenylalanine ammonia-lyase (PAL), POD, and PPO, and promoting the accumulation of antibacterial substances such as flavonoids and total phenols. This combined effect of directly inhibiting pathogen growth and stimulating the fruit's own immune system significantly enhances the fruit's disease resistance.

[0029] 3. Mitigation of Low-Temperature Injury: For fruits subjected to low-temperature stress (-1.5~0.5℃) after pre-storage, HVEF treatment significantly reduced relative conductivity and malondialdehyde (MDA) content, alleviating membrane lipid peroxidation damage. More importantly, the electric field treatment significantly reduced lignin synthesis and accumulation by inhibiting PAL activity and blocking the phenylpropanone metabolic pathway; phloroglucinol staining confirmed a significant reduction in pulp lignification. Furthermore, the electric field treatment also promoted the accumulation of antioxidants such as vitamin C, enhancing the fruit's adaptability to low-temperature stress.

[0030] This study confirms that HVEF is an efficient, safe, and residue-free postharvest physical preservation technology for kiwifruit, providing a theoretical basis and technical support for the industrial storage of kiwifruit.

[0031] High-voltage electrostatic field equipment: This study independently designed a double-row suspended spatial electric field preservation device. The device consists of a high-voltage DC power supply system, six stainless steel linear electrode arrays, a grounding strip, and an intelligent control unit. In terms of structural layout, the experimental platform uses a standard cold storage room as its main frame (6 m × 6 m × 9 m), with the interior covered with insulating material to ensure safe operation. The electrodes are evenly distributed laterally at the top, with a spacing of 30 cm between each group. Each end of the electrode tip has a support component to maintain stability and effectively eliminate electric field deformation caused by vibration. The sample to be tested (such as kiwifruit) is placed between the two rows of electrodes, close to the ground, and receives the uniform electric field generated by the crossed electrodes. The power supply unit has a high-precision output function, with a high-voltage DC output of 30 kV, adjustable from 0 to 50 kV. The base acts as a current conductor to form a uniform electric field. The overall structure adopts a modular design concept, incorporating multiple safety measures, including short-circuit protection, leakage detection, and real-time ozone concentration monitoring, creating a good collaborative processing environment for fruits and vegetables throughout the warehouse.

[0032] I. Effects of High-Voltage Electrostatic Fields on the Storage Quality of Kiwifruit Experimental materials: "Xu Xiang" kiwifruit was harvested in late September 2024 from Meixian County, Baoji City, Shaanxi Province. All samples were strictly screened and were qualified with mature fruit, uniform fruit shape, and no disease, pests, or mechanical damage.

[0033] Experimental treatment: Qualified kiwifruit were divided into two groups. One group was the electric field treatment group (EF): the kiwifruit used in the experiment were placed in a high-voltage electrostatic field cold storage with a temperature of 0~2℃, a relative humidity (RH) of 90%~95%, and a voltage of 30KV. The other group was the control group (CK): the kiwifruit used in the experiment were placed in a cold storage with the same specifications, storage conditions, and management methods.

[0034] Test instruments and methods Hardness measurement Thirty fruits were selected from each treatment group and divided into three groups of ten fruits each. The firmness of the kiwifruit was measured using a GY-4 benchtop hardness tester (probe diameter 0.79 cm). Each fruit was measured after peeling on both the sun-facing and sun-facing sides at the equator. Unit: N. Determination of soluble solids The soluble solids content was determined using a Japanese Atago PAL-1 digital saccharimeter. A piece of pulp was taken from the equatorial side of the fruit and placed in a clean juicer to squeeze out the juice, which was then dripped into the saccharimeter's detection port.

[0035] Titratable acid determination Titratable acid content was determined using a GMK-835F pH meter. 200 μL of fruit juice was diluted in 20 mL of distilled water, and the solution was then poured into the pH meter's detection port for measurement.

[0036] weightlessness The electronic balance used in this experiment was a high-precision electronic balance with an accuracy of 0.1 grams, used to determine the weight of the fruit and to calculate the weight loss rate by comparing the changes in weight before and after storage. To eliminate interference caused by sample differences, the same labeled fruit was used for each measurement. The initial fresh weight was used as the reference standard, and the final measured weight data was used to calculate the percentage of weight loss during storage.

[0037] respiratory rate Four kiwi fruits and one infrared gas analyzer (Telaire 7001, Goleta, CA, USA) were placed in a Lock & Lock container, and the data from the infrared gas analyzer was recorded to calculate the respiration rate.

[0038] Determination of SOD, POD and CAT enzyme activities The method for determining superoxide dismutase (SOD) activity is as follows: The reaction system contained 1.7 mL of phosphate buffer solution at pH 7.8, 0.3 mL of 130 mM L-methionine solution, 0.3 mL of 750 μM nitroblue tetrazolium (NBT) sodium chloride solution, and 0.3 mL of 100 μM EDTA-Na2 solution. 0.3 mL of 200 μM riboflavin and 0.1 mL of the enzyme sample were added to 2.6 mL of the above mixture, and the reaction was carried out under 8000 lx light for 15 minutes. The absorbance was then measured at 560 nm to evaluate SOD activity.

[0039] POD determination: 50 μL of enzyme solution and 10 μL of 2% H2O2 were added to 300 μL of 25 mM guaiacol, and the absorbance of the mixture was measured at 470 nm.

[0040] CAT assay: The reaction solution consisted of 200 μL of 30% H2O2 and 250 mL of pH 7.0 phosphate buffer. 200 μL of enzyme solution was aspirated, and 2.9 mL of the reaction solution was added. The absorbance at 240 nm was measured.

[0041] Determination of PPO and CX activities PPO assay: The reaction solution consisted of 1.7 mL of 0.2 M sodium phosphate buffer (pH 6.8) and 0.5 mL of 50 mM catechol. 0.1 mL of enzyme solution was added, and the mixture was immediately stirred. The absorbance change was measured at 420 nm. One enzyme activity unit was defined as a change in absorbance of 0.01 μL per minute.

[0042] Determination of CX: The reaction solution was 0.9 mL of 1% sodium carboxymethyl cellulose (CMC-Na, dissolved in 0.2 M acetate-sodium acetate buffer, pH 5.0). 0.1 mL of enzyme solution was added, and the mixture was incubated at 50°C for 30 min. The reaction was terminated by adding 2 mL of DNS reagent, followed by boiling in a water bath for 5 min. After cooling, the absorbance was measured at 540 nm. One enzyme activity unit was defined as the production of 1 mg of reducing sugar per hour.

[0043] Each indicator was repeated three times. Data processing was performed using Excel 2010, line charts were generated using GraphPad Prism, and significance analysis was conducted using SPSS software (*P<0.05, **P<0.01). Graphs were created using SolidWorks 2022, Photoshop 2019, and Adobe Illustrator 2022. II. The Effects of High-Voltage Electrostatic Fields on Infectious Diseases of Xuxiang Kiwifruit Experimental materials: 'Xu Xiang' kiwifruit was harvested in September from Meixian County, Baoji City, Shaanxi Province. Fruits of uniform size, free from mechanical damage and pests were selected and stored after pre-cooling.

[0044] Pathogen material: During storage, the disease incidence of the fruit was observed regularly, and fruits exhibiting typical infectious disease symptoms (soft rot, brown spots, etc.) were selected for pathogen isolation. The pathogen isolation method adopted from Wang Li (2022) was used. Diseased fruits were simply washed and sterilized, then placed in a clean bench. Using a sterilized scalpel, the diseased and healthy tissue were cut into 2 mm × 2 mm pieces at the junction of the diseased and healthy tissues. These pieces were then placed in 2 ml × 5 centrifuge tubes (1% sodium hypochlorite, 75% alcohol, sterile water × 3) for 30 s, 1 min, and 3 × 3 min, respectively. After drying on absorbent filter paper, the separated diseased fruit pieces were transferred to PDA plates and incubated in a constant temperature incubator at 28 ℃, and then labeled. The pathogen's genomic DNA was extracted and isolated according to the instructions of the fungal genomic DNA extraction kit. Using this DNA as a template, PCR amplification was performed using universal ITS sequence primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′). The amplified product was detected by 1% agarose gel electrophoresis and purified before being sent to the Xi'an branch of Beijing Qingke Biotechnology Co., Ltd. for sequencing. The obtained sequence was BLAST-aligned in the NCBI database, identifying the fungus as *Alternaria alternata*, a pathogen causing soft rot in kiwifruit. The purified strain was inoculated into healthy kiwifruit for pathogenicity verification; the fruit exhibited typical soft rot symptoms, confirming the fungus as the causative agent of kiwifruit soft rot.

[0045] Experimental treatment: PDA plate treatment: Using a 5 mm diameter sterile punch, mycelial blocks from the edge of pathogen colonies activated and cultured for 7 days were cut and inoculated into the center of fresh PDA plates. A portion of the PDA plates was reserved for subsequent fruit inoculation; the remainder was divided into two groups, placed in a control library and an electric field library (temperature 0-2 °C, relative humidity 95%), respectively. The procedure for fruit inoculation was as follows: spores were collected from the PDA medium, a suspension was prepared, and the concentration was adjusted to 1×10⁻⁶. 6 CFU / mL. Ripe, undamaged kiwifruit fruits were selected as experimental materials. Surface sterilization was performed with 75% alcohol for 30 seconds, followed by rinsing three times with sterile water and air drying. Using a sterile punch, three 2 mm diameter, 2 mm deep holes were drilled at equal intervals along the equatorial region of the fruit. 20 μL of the above-mentioned spore suspension was injected into each hole to complete inoculation. The treated fruits were then randomly divided into a control group and an electric field simulation group, and stored under low temperature (0–2 °C) and high humidity (95% RH) conditions.

[0046] Plaque diameter and inhibition rate determination: In this study, the diameter of colonies was determined using the cross-multiplication method. The maximum longitudinal and transverse dimensions of each colony were recorded using vernier calipers, and the actual size was obtained by arithmetic mean. To ensure data reliability, three parallel replicates were set up in each experiment, and three typical colonies were observed and evaluated in each replicate. Plaque expansion value = diameter at the end of culture - diameter at the beginning of culture, which is the plaque expansion value. The inhibition rate was calculated as (increase in plaque diameter in the control group - increase in plaque diameter in the electric field group) / increase in plaque diameter in the control group × 100%.

[0047] Fruit disease incidence and inhibition rate determination: Disease incidence: number of diseased fruits divided by total number of fruits, multiplied by 100%. Inhibition rate: disease incidence in control group minus disease incidence in treatment group, then divided by disease incidence in control group, multiplied by 100%.

[0048] Determination of flavonoids and total phenols: For flavonoid determination: The reaction solution consisted of 0.5 mL of extract, 0.3 mL of 5% sodium nitrite, and 0.3 mL of 10% aluminum nitrate. After mixing, the mixture was allowed to stand at room temperature for 5 min. Then, 2 mL of 1 mol / L sodium hydroxide was added, and the mixture was immediately mixed. The absorbance was measured at 510 nm. The flavonoid content was calculated using rutin as a standard, in mg / 100g. For total phenols determination: The reaction solution consisted of 0.5 mL of extract and 2.5 mL of Folin-Ciocalteu reagent. After mixing, the mixture was allowed to stand at room temperature for 5 min. Then, 2 mL of 7.5% sodium carbonate was added, and the mixture was immediately mixed. The mixture was allowed to react in the dark at room temperature for 30 min. The absorbance was measured at 765 nm. The total phenol content was calculated using gallic acid as a standard, in mg / 100g.

[0049] Determination of superoxide anion: The reaction solution consisted of 0.5 mL of extract, 0.5 mL of 50 mM sodium phosphate buffer (pH 7.8), and 0.1 mL of 1 mM hydroxylamine hydrochloride. After mixing, the mixture was incubated at 25°C for 20 min. Then, 1 mL of 17 mM p-aminobenzenesulfonic acid and 1 mL of 7 mM α-naphthylamine were added, and the mixture was immediately mixed. The mixture was then incubated at 25°C for 20 min, and the absorbance was measured at 530 nm. Using sodium nitrite as a standard, the superoxide anion production rate was calculated in min·g.

[0050] Determination of PAL, POD, and PPO: PAL determination: The reaction solution consisted of 2.9 mL of 0.2 M borate buffer (pH 8.8) and 0.5 mL of 20 mM L-phenylalanine. 0.1 mL of enzyme solution was added, and the mixture was immediately mixed. The absorbance change was measured at 290 nm. One enzyme activity unit was defined as a change in absorbance of 0.01 μL per hour, expressed as 0.01 ΔOD. 290 / (h·g). The determination of POD and PPO is the same as above.

[0051] Data statistical analysis: Excel 2010 was used for data processing, GraphPad Prism was used to create bar charts and line charts, and SPSS software was used for significance analysis (*P<0.05, **P<0.01). Photoshop 2019 and Adobe Illustrator 2022 were used for graphing.

[0052] III. Effects of High-Voltage Electrostatic Fields on Chill Injury Phenotypes of Xu Xiang Kiwifruit Experimental Materials and Methods Experimental materials: The suitable storage environment for Xu Xiang kiwifruit is 0-2℃ and 90%~95% humidity. If the storage temperature is consistently below this range, frost damage will occur. After being harvested in late September 2024, Xu Xiang kiwifruit was first stored at a conventional low temperature in Meixian County, Baoji City, Shaanxi Province (storage temperature 0-2℃, relative humidity 95%). Then, it was divided into two groups for treatment. One group was transferred to a simulated low-temperature high-voltage electrostatic field environment (-1.5~0.5℃, relative humidity 95%) and stored for 50 days. The other group served as a control group, maintaining the same initial storage conditions for comparative experiments.

[0053] For each treatment group, 20-30 kiwifruit fruits were sampled at a time. Fresh samples were used to determine physiological indicators such as respiration rate, soluble solids, firmness, and relative conductivity. Another portion was used for sample preparation for other indicators such as enzyme activity assays. The pulp (peeled, cored, and seeded) was cut into pieces, rapidly frozen in liquid nitrogen, and stored in an ultra-low temperature freezer at -80 ℃.

[0054] Determination of hardness, soluble solids, and respiration rate: Same as above. Phloroglucinol staining: Take a cross-section of the equatorial region of a kiwifruit and immediately immerse it in a 1% phloroglucinol-ethanol solution for 5 minutes at room temperature. After removal, rinse quickly with 95% ethanol to remove excess staining solution and observe. Lignified tissue appears purplish-red, while non-lignified tissue appears yellow or colorless.

[0055] Determination of relative conductivity and malondialdehyde (MDA): Relative conductivity determination: Take 2.0 g of kiwifruit pulp from the equatorial region, cut it into uniform thin slices, and place it in a beaker containing 20 mL of deionized water. Let it stand at 25°C for 2 h, and measure the initial conductivity using a conductivity meter. Then, boil it in a water bath for 30 min, cool it to 25°C, and measure the total conductivity. Relative conductivity (%) = Initial conductivity / Total conductivity × 100%. Malondialdehyde (MDA) determination: Take 0.1 g of kiwifruit pulp powder that has been frozen and ground in liquid nitrogen, add 1 mL of 10% trichloroacetic acid (TCA), and mix well. Centrifuge at 12000 g for 20 min (4°C), and collect the supernatant. Take 0.4 mL of the supernatant, add 0.4 mL of 0.6% thiobarbituric acid (TBA, dissolved in 10% TCA), mix well, boil in a water bath for 20 min, cool rapidly, and measure the absorbance at 532 nm and 600 nm. Calculate the content using the MDA standard curve, in μmol / g.

[0056] Vitamin C determination: The 2,6-dichlorophenolindophenol titration method was used. Take 2 mL of the extract and titrate with 0.01% 2,6-dichlorophenolindophenol solution until the solution turns pink and does not fade within 15 seconds; record the volume consumed. Calculate the content using the L-ascorbic acid standard curve, in mg / 100g.

[0057] Determination of PAL activity and lignin content: The determination of PAL is the same as in 3.2.5. Lignin extraction: Take 0.1 g of kiwifruit pulp powder that has been frozen and ground in liquid nitrogen, add 1 mL of 95% ethanol, mix well, and then incubate at 80°C for 20 min. After cooling, centrifuge at 10000g for 10 min (4°C), and discard the supernatant. Wash the precipitate three times with 95% ethanol and twice with ether, dry, and then add 0.4 mL of 25% bromoacetyl-glacial acetic acid solution. Incubate at 70°C for 30 min, cool, and then add 0.04 mL of 2 mol / L NaOH to terminate the reaction. Then add 0.02 mL of 7.5 mol / L hydroxylamine hydrochloride, and finally dilute to 1 mL with glacial acetic acid. Measure the absorbance at 280 nm. Calculate the content based on lignin standards, in units of A. 280 ·g⁻¹.

[0058] Data statistical analysis: Excel 2010 was used for data processing, GraphPad Prism was used to draw box plots and line plots, and SPSS software was used for significance analysis (*P<0.05, **P<0.01). ImageJ was used for image processing, and Photoshop 2019 and Adobe Illustrator 2022 were used for plotting.

[0059] The effect of high voltage electrostatic field on the storage quality of kiwifruit The firmness of kiwifruit in both the control and electric field-treated groups decreased with prolonged storage. In the early storage period (0-20 days), the rate of firmness decrease was similar in both groups; however, on days 30, 40, 60, and 70, the rate of firmness decrease was significantly higher in both groups than in the control group. Throughout the entire storage period, the softening rate in the electric field-treated group was significantly lower than that in the control group, indicating that high-voltage electrostatic field treatment can effectively delay the softening process of kiwifruit and maintain fruit firmness.

[0060] With prolonged storage, the titratable acid content in both the control group and the electric field-treated group gradually decreased, but remained at a higher level in the electric field-treated group even after 40 days of storage. These results indicate that high-voltage electrostatic field treatment slows down the degradation rate of organic acids to some extent, which is beneficial for maintaining the flavor quality of kiwifruit in the later stages of storage and delaying fruit quality deterioration.

[0061] The soluble solids content in both the control group and the electric field-treated group showed a trend of first increasing and then decreasing. The control group reached a peak of 15% on day 30 of storage, followed by a rapid decline; while the peak value in the electric field-treated group appeared later, and the content change was more gradual. It is speculated that high-voltage electrostatic field treatment may inhibit amylase activity, thus slowing the rate of starch-to-sugar conversion and reducing respiration consumption. Throughout the storage period, the soluble solids content in the electric field-treated group was consistently higher than that in the control group, indicating that high-voltage electrostatic field treatment is beneficial for maintaining sugar accumulation in kiwifruit and delaying the arrival of peak ripening.

[0062] Both the control group and the electric field-treated group showed a trend of first increasing and then decreasing respiration rates, consistent with the respiration characteristics of climacteric fruits. The respiration peak in the control group occurred around day 10 of storage; however, the respiration peak in the electric field-treated group was not obvious, the peak value was lower, and its appearance was delayed. On days 20 and 30 of storage, the respiration rate in the electric field-treated group was significantly lower than that in the control group. Throughout the entire storage period, the respiration intensity in the electric field-treated group was significantly lower than that in the control group, indicating that high-voltage electrostatic field treatment can effectively inhibit the respiratory metabolism of kiwifruit, reduce nutrient consumption, and delay the aging process.

[0063] The water loss rate of both the control group and the electric field treatment group increased with the extension of storage time. Throughout the entire storage period, the water loss rate of the electric field treatment group was consistently lower than that of the control group, indicating that high-voltage electrostatic field treatment can effectively reduce water loss of kiwifruit during storage and maintain the freshness and appearance quality of the fruit.

[0064] Effects of high voltage electrostatic field on antioxidant enzyme activity in kiwifruit High-voltage electrostatic field treatment has a significant and specific effect on the activity of various antioxidant enzymes in kiwifruit. Compared with the control group, the electric field group showed higher activities of CAT and SOD enzymes, while the activity of POD enzyme was significantly reduced, thereby enhancing the synergistic regulatory capacity of the entire antioxidant enzyme system. This indicates that high-voltage electrostatic fields can efficiently and accurately intervene in the fruit metabolic network, thereby delaying fruit senescence and preventing oxidative stress damage.

[0065] Effects of high-voltage electrostatic fields on cell wall degradation and browning-related enzyme activity in kiwifruit Under high-voltage electrostatic field conditions, the activity of CX enzyme and polyphenol oxidase (PPO) in the electric field group decreased significantly, which slowed down the degradation rate of cell wall structure and improved the composition of phenolic compound metabolic pathways in the fruit, thereby greatly improving the product quality stability and market shelf life of kiwifruit during post-harvest storage.

[0066] kiwi( Actinidia chinensis As a typical climacteric fruit, it is extremely susceptible to softening and rotting, physiological disorders, and pathogen infection after harvest, which severely restricts its shelf life and commercial value.

[0067] The main research results are as follows: 1. Delaying Low-Temperature Storage Senescence: HVEF treatment significantly inhibited fruit respiration rate, delayed the onset of the respiration peak, and effectively reduced water loss. Regarding quality maintenance, the fruit firmness in the electric field-treated group decreased slowly, and the content of titratable acid and soluble solids remained at high levels. Mechanistic studies showed that HVEF slowed down cell wall depolymerization and browning by significantly inhibiting the activity of key cell wall degradation enzymes—cellulase (CX) and polyphenol oxidase (PPO); simultaneously, it regulated the antioxidant enzyme system, increasing the activity of superoxide dismutase (SOD) and catalase (CAT), decreasing peroxidase (POD) activity, enhancing the fruit's ability to scavenge reactive oxygen species (ROS), and maintaining cell membrane integrity.

[0068] 2. Suppressing infectious diseases: HVEF inhibits the pathogen of kiwifruit soft rot, Alternaria alterniflora (Alternaria). Alternaria alternata The electric field treatment showed a significant direct inhibitory effect, with the growth rate of fungal plaque diameter decreasing by 46.2% compared to the control group after 10 days of cultivation. Inoculation experiments revealed a significant reduction in disease incidence and rot rate in the treated fruit group (rot rate inhibition reached 49.1% at 21 days). Its disease resistance mechanism lies in the fact that the electric field not only directly inhibits pathogen growth but also induces systemic resistance in the fruit, significantly activating the activities of phenylalanine ammonia-lyase (PAL), POD, and PPO, and promoting the accumulation of antibacterial substances such as flavonoids and total phenols. This combined effect of directly inhibiting pathogen growth and stimulating the fruit's own immune system significantly enhances the fruit's disease resistance.

[0069] 3. Mitigation of Low-Temperature Injury: For fruits subjected to low-temperature stress (-1.5~0.5℃) after pre-storage, HVEF treatment significantly reduced relative conductivity and malondialdehyde (MDA) content, alleviating membrane lipid peroxidation damage. More importantly, the electric field treatment significantly reduced lignin synthesis and accumulation by inhibiting PAL activity and blocking the phenylpropanone metabolic pathway; phloroglucinol staining confirmed a significant reduction in pulp lignification. Furthermore, the electric field treatment also promoted the accumulation of antioxidants such as vitamin C, enhancing the fruit's adaptability to low-temperature stress.

[0070] In summary, high-voltage electrostatic field treatment effectively delayed postharvest senescence in 'Xuxiang' kiwifruit, controlled soft rot, and alleviated chilling injury through multiple pathways, including regulating respiratory metabolism, inhibiting the activity of cell wall degrading enzymes and browning enzymes, enhancing the antioxidant defense system, inducing disease resistance, and inhibiting lignin synthesis. This study confirms that HVEF is a highly efficient, safe, and residue-free postharvest physical preservation technology for kiwifruit, providing a theoretical basis and technical support for the industrial-scale storage of kiwifruit.

[0071] Results and Analysis The effect of high voltage electrostatic field on the storage quality of kiwifruit The decrease in fruit firmness mainly stems from the degradation of cell wall substances and the loss of cell turgor pressure. This process is closely related to the activation of cell wall degrading enzymes such as pectinase and cellulase, as well as the decomposition of protopectin (Wu Lian 2008). Firmness, as one of the important indicators for measuring the degree of fruit ripening and senescence and storage quality (Zhang Peizheng 1992), warrants further investigation into its changing patterns. Figure 2 -A indicates that the firmness of kiwifruit in both the control group and the electric field-treated group decreased with prolonged storage. In the early storage period (0-20 days), the rate of firmness decrease was similar in both groups; however, on days 30, 40, 60, and 70, the firmness of the electric field-treated group was 17.5 N, 17.2 N, 16.8 N, and 16.5 N, respectively, all significantly higher than the control group's 8.5 N, 6.2 N, 5.5 N, and 4.8 N (p < 0.05). Throughout the storage period, the softening rate of the electric field-treated group was significantly lower than that of the control group, indicating that high-voltage electrostatic field treatment can effectively delay the softening process of kiwifruit and maintain fruit firmness.

[0072] Titratable acid content is a crucial indicator determining the flavor and quality of fruit, and its changes directly affect the fruit's taste and commercial value (Zeng Rong 2002). Figure 2As shown in Figure B, the titratable acid content in both the control group and the electric field-treated group gradually decreased with prolonged storage time. This is attributed to the consumption of organic acids by the fruit's normal respiration and metabolism. During the first 20 days of storage, there was no significant difference in titratable acid content between the two groups. On day 30, the titratable acid content in the electric field-treated group was 0.42%, significantly higher than the 0.22% in the control group (p < 0.05). Even on day 40, the electric field-treated group maintained a high level. These results indicate that high-voltage electrostatic field treatment slows down the degradation rate of organic acids to some extent, which is beneficial for maintaining the flavor quality of kiwifruit in the later stages of storage and delaying fruit quality deterioration.

[0073] Soluble solids content reflects the total amount of soluble substances such as sugars and organic acids in a fruit, and is an important parameter for evaluating fruit maturity and quality (Zeng Rong et al., 2002). Figure 2 As indicated by -C, the soluble solids content in both the control group and the electric field-treated group showed a trend of first increasing and then decreasing, which is a typical pattern of starch hydrolysis into soluble sugars followed by respiration consumption (Xiao et al., 2019). The control group reached a peak of 15% on day 30 of storage, followed by a rapid decline; while the peak in the electric field-treated group was delayed, and the content change was relatively gradual. On days 30, 60, and 70 of storage, the soluble solids content in the electric field-treated group was 12.5%, 12.0%, and 11.8%, respectively, all significantly higher than that in the control group (12.2%, 9.8%, and 8.8%, p < 0.05). It is speculated that high-voltage electrostatic field treatment may slow down the conversion rate of starch to sugar by inhibiting amylase activity, while reducing respiration consumption. Throughout the storage period, the soluble solids content in the electric field-treated group was consistently higher than that in the control group, indicating that high-voltage electrostatic field treatment is beneficial for maintaining sugar accumulation in kiwifruit and delaying the arrival of the peak ripening period.

[0074] Respiration is the core process of postharvest kiwifruit metabolism, and its intensity directly determines the rate of fruit senescence and storage life (Liu Shunzhi et al., 1995). Figure 2-D indicates that the respiration rates of both the control group and the electric field-treated group showed a trend of first increasing and then decreasing, consistent with the respiration characteristics of climacteric fruits. The respiration peak in the control group occurred around day 10 of storage, with a peak value of approximately 3.8 mg / kg·h; while the respiration peak in the electric field-treated group was not obvious, the peak value was lower, and the occurrence time was delayed. On days 20 and 30 of storage, the respiration rates in the electric field-treated group were 2.0 mg / kg·h and 1.5 mg / kg·h, respectively, both significantly lower than those in the control group (3.2 mg / kg·h and 2.8 mg / kg·h, respectively) (p < 0.05). It is speculated that high-voltage electrostatic field treatment may reduce the oxidation rate of respiratory substrates by affecting the activity of the electron transport chain in mitochondria or the activity of enzymes related to the tricarboxylic acid cycle. Throughout the storage period, the respiration intensity of the electric field-treated group was significantly lower than that of the control group, indicating that high-voltage electrostatic field treatment can effectively inhibit the respiratory metabolism of kiwifruit, reduce nutrient consumption, and delay the senescence process.

[0075] Transpiration is the main cause of postharvest wilting, weight loss, and decreased commercial value in kiwifruit, and its rate depends on the water potential gradient between the inside and outside of the fruit and the integrity of the epidermal protective structure (Pan Yonggui et al., 2023). Figure 2 -E indicates that the water loss rate of both the control group and the electric field treatment group increased with prolonged storage time. On days 20, 30, and 40 of storage, the water loss rates of the electric field treatment group were 1.8%, 2.9%, and 3.9%, respectively, all significantly lower than the 2.6%, 3.6%, and 4.8% of the control group (p < 0.05). It is speculated that the high-voltage electrostatic field treatment may reduce the water transpiration rate by altering the structure of the waxy layer of the fruit epidermis or the opening and closing state of stomata; simultaneously, the electric field treatment inhibits respiration, reducing the temperature rise caused by respiratory heat, thereby indirectly reducing water loss. Throughout the entire storage period, the water loss rate of the electric field treatment group was consistently lower than that of the control group, indicating that high-voltage electrostatic field treatment can effectively reduce water loss during kiwifruit storage and maintain the freshness and appearance quality of the fruit.

[0076] Effects of high voltage electrostatic field on antioxidant enzyme activity in kiwifruit When kiwifruit is subjected to abiotic stress during storage, the content of reactive oxygen species (ROS) in the fruit increases significantly, triggering a series of chain reactions such as membrane lipid peroxidation, protein denaturation, and apoptosis. Antioxidant enzyme systems play a crucial regulatory role in maintaining cellular redox stability (Wang et al., 2013). Figure 3 -A、 Figure 3 -B and Figure 3-C showed that high-voltage electrostatic field treatment had a significant and specific effect on the activities of various antioxidant enzymes in kiwifruit: on day 10 of storage, the CAT activity in the electric field group was 88 U·min⁻¹·g⁻¹, significantly higher than the 58 U·min⁻¹·g⁻¹ in the control group (p < 0.05); on days 30 and 40 of storage, the POD activity in the electric field group decreased to 3.3 U·g⁻¹ and 2.4 U·g⁻¹, respectively, much lower than the control group (p < 0.05); by day 40 of storage, the SOD activity in the electric field group increased to 13.0 U / g FW, significantly higher than the 8.3 U / g FW in the control group (p < 0.05). Overall, compared with the control group, the electric field group had higher CAT and SOD enzyme activities, while the POD enzyme activity was significantly reduced, thereby enhancing the synergistic regulatory capacity of the entire antioxidant enzyme system. This shows that high-voltage electrostatic fields can efficiently and accurately intervene in the fruit's metabolic network, thereby delaying fruit senescence and preventing oxidative stress damage.

[0077] Effects of high-voltage electrostatic fields on cell wall degradation and browning-related enzyme activity in kiwifruit Fruit softening originates from the enzymatic degradation of cell wall polysaccharides, primarily driven by polygalacturonase (PG). Recent studies have shown that cellulase (CX) may be involved in the co-modification of the cell wall skeletal structure. Figure 4 -A showed that under an applied high-voltage electrostatic field, the CX enzyme activity in the electric field group decreased significantly, reaching only 108 U·h⁻¹·g⁻¹ FW by day 40, a decrease of approximately 45% compared to the initial value of 180 U·h⁻¹·g⁻¹ FW in the control group. This indicates that inhibiting cellulose hydrolysis and reducing its cell wall relaxation effect can improve fruit preservation. Figure 4 Results -B showed that high-voltage electrostatic field treatment significantly reduced polyphenol oxidase (PPO) activity. On days 30 and 40 of the experiment, the PPO activities in the electric field group were approximately 3.4 U·g⁻¹ and 2.4 U·g⁻¹, respectively, both significantly lower than those in the control group (p < 0.05). This dual mechanism slowed down the degradation rate of cell wall structures and improved the composition of phenolic compound metabolic pathways in the fruit, thereby significantly improving the product quality stability and shelf life of kiwifruit during post-harvest storage.

[0078] Firmness and water loss rate are crucial factors determining the storage quality of kiwifruit. Soluble solids content, total acidity, and respiration rate are core physiological and biochemical characteristics of kiwifruit (Gao Jie 2013; Marsh and Harker 2016). The results showed that high-voltage electrostatic field pretreatment significantly delayed the firmness decline of 'Xu Xiang' kiwifruit. During a 70-day storage period, the firmness of the fruit in the electrostatic field group remained significantly better than that in the control group (p < 0.05), indicating that this method has a positive effect on improving the fruit's storage resistance and can extend the market supply period. These effects are mainly achieved by regulating the cell wall degradation pathway. Figure 4 -A showed that cellulase (CX) activity decreased significantly after high-voltage electrostatic field treatment. On the 40th day of storage, the CX activity in the treatment group was 108 U·h⁻¹·g⁻¹ FW, which was much lower than that in the control group of 180 U·h⁻¹·g⁻¹ FW (p<0.01), effectively preventing the decomposition of cell wall structure. Figure 3 In the -B group, electric field intervention reduced polyphenol oxidase (PPO) activity. On days 30 and 40, the PPO activities in the electric field group were 3.4 U·g⁻¹ and 2.4 U·g⁻¹, respectively, significantly lower than those in the control group (p < 0.05). This reduced the risk of color deterioration caused by oxidation and ensured stable fruit appearance quality. The high-voltage electrostatic field also reduced the overall respiration intensity and water evaporation rate of the fruit, delayed the occurrence of the respiration peak, and reduced carbohydrate consumption and transpiration loss. On day 30 of storage, the titratable acid content in the electric field-treated group was significantly higher than that in the control group (p < 0.05). Throughout the storage process, the total soluble solids content in the electric field-treated group was consistently significantly higher than that in the control group (p < 0.05).

[0079] After fruit harvest, the accumulation of reactive oxygen species (ROS) under abiotic stress can destabilize cell structures, leading to lipid peroxidation. Studies have shown that high-voltage electrostatic fields can significantly affect oxidase systems. Figure 3 -A、 Figure 3 -C showed that the activities of both SOD and CAT were significantly increased under the influence of the electric field (p < 0.05). In particular, on day 10, the CAT activity in the electric field group reached 88 U·min⁻¹·g⁻¹, significantly higher than the 58 U·min⁻¹·g⁻¹ in the control group; on day 40, the SOD activity rose to 13.0 U / g FW, far exceeding the 8.3 U / g FW in the control group. Although the catalytic activity of peroxidase (POD) decreased somewhat in the initial stage due to electric field interference, it remained at a low level overall. Figure 3 -B, p < 0.05), which is related to its regulation of electron transport chain function. The synergistic free radical scavenging system formed by SOD and CAT effectively inhibits oxidative stress and protects cell membranes from damage; while the decrease in POD activity leads to an increase in H2O2 content, exacerbates lipid peroxidation, and accelerates enzymatic browning. Current research has demonstrated that high-voltage electrostatic fields can improve the storage quality of fruits and vegetables by regulating cell membrane potential distribution, rebuilding the ROS homeostasis network, and improving energy metabolism pathways.

[0080] This study primarily investigates the effects of high-voltage electrostatic field treatment on the storage quality of kiwifruit and its physiological mechanisms. Results show that high-voltage electrostatic field treatment can slow down cell wall degradation by inhibiting cellulase (CX) activity, significantly improving fruit firmness and mechanical strength. Simultaneously, it reduces enzymatic browning by decreasing polyphenol oxidase (PPO) activity, thus improving fruit appearance. Regarding the antioxidant defense system, high-voltage electrostatic field can activate the superoxide dismutase-catulase (SOD-CAT) system, enhancing the body's ability to scavenge reactive oxygen species; and by regulating peroxidase (POD)-mediated metabolic pathways, it can alleviate oxidative stress damage and maintain cell membrane structural integrity. These combined effects effectively delay fruit softening and senescence, reducing nutrient loss. Kiwifruit treated with high-voltage electrostatic field exhibits excellent quality characteristics during storage and ripening, including high firmness, high soluble solids content, moderate total acidity, and low water loss. In conclusion, the application of high-voltage electrostatic field technology to kiwifruit preservation demonstrates significant feasibility and economic viability, providing a novel physical preservation method for post-harvest storage of fruits and vegetables.

[0081] The effects of high-voltage electrostatic fields on infectious diseases of Xu Xiang kiwifruit Effects of high-voltage electrostatic field treatment on the growth of Alternaria alternata colonies Figure 5 The results showed that at day 0 of initial culture, there were no significant differences in colony morphology, size, and hyphal distribution between the control group and the electric field-treated group. Both groups exhibited white, fluffy hyphae with neat edges, indicating that inoculation conditions had little impact on either group. After 5 days of culture, the colony diameter in the control group significantly increased, with a grayish-white color and a compact, uniform structure; the colony diameter in the electric field-treated group was limited, turning yellowish-brown with pigment deposition, and the edges were indistinct. This demonstrates that a continuous high-voltage electrostatic field significantly inhibits the normal growth of pathogens and interferes with their secondary metabolism. Figure 6 It was found that after 10 days of continuous cultivation, the average expansion of bacterial plaques in the high-voltage electrostatic field treatment group was significantly smaller than that in the control group (p < 0.05). The experimental results showed that the plaque diameter in the electric field group was approximately 0.7 cm, about 46.2% smaller than that in the control group. Data analysis indicates that the effect of the high-voltage electrostatic field on *Alternaria alterniflora* increased over time, with changes in colony shape and color observed as early as day 5, and the inhibitory effect on growth becoming more pronounced by day 10. It is speculated that the electric field weakens the survival and expansion capabilities of pathogenic microorganisms by disrupting cell membrane stability, interfering with energy metabolism pathways, or altering cell wall biosynthesis.

[0082] Effects of high-voltage electrostatic field treatment on disease resistance of kiwifruit Figure 7 , Figure 8This study serves as the main basis for investigating the mechanism of the effect of high-voltage electrostatic fields on the disease resistance of kiwifruit. Alternaria was used as a pathogenic microorganism model, inoculated onto undamaged kiwifruit, and treated with different electric field intensities. The disease resistance response and antibacterial effect during storage were analyzed. The results showed that both the control group and the electric field-treated group developed disease symptoms to varying degrees over time, but the differences were significant: on the first day of storage, the symptoms were mild, and the fruit peel was undamaged; after 7 days, the control group samples showed rapidly forming and gradually spreading brown spots, with some areas showing continuous discoloration; although the electrostatic field-treated group had sporadic small lesions, their overall distribution was sparse. By the 14th day, the vast majority of samples in the control group had undergone complete browning, softening, and rotting, while the electric field-treated group remained largely undamaged; by the 21st day, the vast majority of samples in the control group lost their physiological functions and were completely necrotic, while about one-third of the fruits in the electric field-treated group still maintained good structural integrity and were not significantly damaged.

[0083] Figure 3-5 Data showed that the rot rate of kiwifruit in all treatment groups gradually increased with prolonged storage time. On day 7 after inoculation, the rot rates of the control group and the electric field treatment group were 20% and 13%, respectively; on day 14, the rates were 33% and 20%, respectively; after 21 days of storage, the rot rate of the control group reached 53%, while that of the electric field treatment group was 27%, which was 49.1% lower than that of the control group (p < 0.05). The study indicates that high-voltage electrostatic fields can reduce Alternaria alternata damage and slow down the disease development rate through multiple pathways, including improving the stress resistance of kiwifruit, activating the activity of related defense enzymes, and improving the microenvironment of the fruit epidermis.

[0084] Effects of high-voltage electrostatic field treatment on the physiological metabolism of diseased fruit Figure 10 The results showed that during the 21-day cultivation period, the flavonoid, total phenol content, and antioxidant enzyme activity of the diseased fruit in the electric field treatment group were significantly higher than those in the control group, while the superoxide free radical production was significantly lower than that in the control group.

[0085] Phenolic content: The flavonoid content in the electric field-treated group was 58 mg / 100g, significantly higher than that in the control group (p<0.05); the total phenol content increased from 7.2 mg / 100g to 10.8 mg / 100g, with a statistically significant difference (p<0.05). This indicates that the high-voltage electrostatic field can regulate the metabolic pathways of phenolic substances within diseased fruits, significantly improving antioxidant capacity and stress resistance.

[0086] Reactive oxygen species (ROS) metabolism: The superoxide anion (O2⁻·) production rate in the electric field treatment group was 2.5 min·g, significantly lower than that in the control group (8.5 min·g) (p<0.01). This indicates that electric field treatment can reduce the accumulation of ROS in diseased fruits and alleviate oxidative damage.

[0087] Defensive enzyme activities: The peroxidase (POD) activity in the electric field-treated group was 38 U·min⁻¹·g⁻¹, significantly higher than the 17 U·min⁻¹·g⁻¹ in the control group (p<0.05); the polyphenol oxidase (PPO) activity was 0.52 U·min⁻¹·g⁻¹, significantly higher than the 0.30 U·min⁻¹·g⁻¹ in the control group (p<0.05); and the phenylalanine ammonia-lyase (PAL) activity was 1150 U·h⁻¹·g⁻¹, significantly higher than the 380 U·h⁻¹·g⁻¹ in the control group (p<0.05). POD and PPO are involved in reactive oxygen species scavenging and phenolic oxidation, while PAL is a key enzyme in the synthesis of phenolic substances. The three enzymes synergistically enhance the fruit's defensive response.

[0088] The experimental results show that in the later stage of disease development (day 21), the high-voltage electrostatic field can still maintain high levels of defensive enzyme activity and phenolic substances in diseased fruits, inhibiting reactive oxygen species-induced cell damage and thus slowing disease progression. Since this study only analyzed samples from the mid-stage of the disease, it does not fully reflect the dynamic changes of relevant physiological indicators throughout the infection process. Future studies should include more sampling points to clarify the timeliness and possible mechanisms of electric field intervention.

[0089] The main disease affecting kiwifruit during post-harvest storage is soft rot caused by *Alternaria alternata*, which severely damages fruit quality and has a significant economic impact. This experiment isolated *Alternaria alternata* from diseased fruit at harvest and confirmed it as a key pathogen of this disease after pathogenicity testing. A high-voltage electrostatic field significantly inhibited the growth of *Alternaria alternata* on PDA medium. Under the same culture conditions, the colony diameter increase in the electric field-treated group was 46.2% smaller than that in the control group (p < 0.05), indicating that the electrostatic environment can directly inhibit the reproduction and spread of the pathogen. It is speculated that electrostatic action reduces the pathogen's invasive potential and survival ability by disrupting cell membrane stability, interfering with energy metabolism pathways, or affecting cell wall synthesis.

[0090] This study primarily investigates the mechanism by which high-voltage electrostatic fields affect the disease resistance of fruits and vegetables. Undamaged samples were selected for the experiment, and the Alternaria alternata infection model was used to simulate the fungal pathogenic process. Within the same experimental timeframe, the decay rate in the electric field group treated with the electric field parameters was significantly lower than that in the control group (p < 0.05), indicating that this technology, in addition to directly inhibiting bacteria, can also induce resistance in fruits. Current research shows that high-voltage electrostatic fields can induce systematic stress response mechanisms in plants by altering cell membrane potential distribution, affecting reactive oxygen species homeostasis, and enhancing the activity of important defense enzymes.

[0091] The flavonoid and total phenolic content of the fruit in the electric field group was higher than that in the control group, with a significant difference at day 21 (p < 0.05). Phenylalanine ammonia-lyase (PAL) is a key regulatory enzyme in plant secondary metabolic pathways, and its activity in the electric field group was significantly higher than that in the control group (p < 0.05), which is beneficial to the biosynthesis and accumulation of flavonoids and total phenols. In addition to having strong antioxidant effects, these functional components can also achieve antibacterial effects by affecting the metabolic pathways of pathogens. Furthermore, electric field treatment significantly increased the catalytic activity of peroxidase (POD) and polyphenol oxidase (PPO) (p < 0.05), and significantly reduced the rate of superoxide anion free radical production (p < 0.01). The synergistic effect of these enzyme systems can finely regulate the level of reactive oxygen species in cells, maintain cell membrane structural stability, and slow down oxidative damage, thereby inhibiting fruit senescence and preventing decay and spoilage.

[0092] In summary, high-voltage electrostatic fields exert a dual mechanism on the control of kiwifruit soft rot: on the one hand, they directly inhibit the growth of Alternaria alternata, reducing its pathogenicity; on the other hand, they induce a defensive response in the fruit, promoting phenolic synthesis and mitigating reactive oxygen species damage by increasing the activity of PAL, POD, and PPO, thus synergistically inhibiting the occurrence and spread of the disease. Because this study only selected the 21st day after the onset of the disease as the sampling point, it does not fully reflect the entire disease development process. Future research should include more sampling time points to further explore the key periods and biological significance of the resistance response induced by electric field stimulation.

[0093] The Effects of High-Voltage Electrostatic Fields on the Fruit Quality of Kiwifruit Under Low-Temperature Stress After Pre-Storage like Figure 11 As shown in -A, the soluble solids content of both groups of samples exhibited a "first increase, then decrease" fluctuation during storage. Before being transferred to low temperature (day 0), the starch hydrolysis of the fruit after 50 days of pre-storage was basically completed, and sugar accumulation reached the equilibrium point (10.7%). The electric field treatment showed a significant conversion-promoting effect on day 10, with the content rising to 12.4%, significantly higher than the control group's 11.4% (p < 0.05), indicating that the electric field may have activated residual amylase or accelerated sugar metabolism. However, this advantage could not be maintained, and the trend reversed after 20 days: on day 30, the content of the control group (12.2%) significantly exceeded that of the electric field group (11.6%) (p < 0.05), and both groups declined simultaneously by day 40. The reason for this "high at the beginning and low at the end" may be that the high metabolism in the electric field group in the early stage led to the rapid consumption of substrates; while in the later stage, at a low temperature of -1.5~0.5℃, the cell membrane fluidity of the electric field group may be inhibited, which hindered sugar transport and accelerated the degradation of soluble solids. In contrast, the metabolism of the control group was slower and the sugar retention time was longer.

[0094] from Figure 11The data from -B shows that the firmness of both types of fruit gradually decreased over time during storage. At the initial test (day 0), the firmness value was 55 N, indicating that the fruit had begun to soften to some extent after 50 days of pre-cooling treatment. After being transferred to a low-temperature environment, the firmness changes of the two groups were roughly the same for the first 20 days. This is because the low temperature of -1.5℃ to 0℃ rapidly caused cell membrane damage and cell wall decomposition, and the electric field did not effectively control these processes. From day 30 onwards, the firmness of the electric field-treated group was greater than that of the control group (12 N, 8 N), but the difference was not significant. These results suggest that the electric field maintains the integrity of the cell membrane and preserves turgor pressure, thereby mitigating the impact of low-temperature stress on cell structure. However, under extreme low temperatures, this protective effect is relatively weak.

[0095] Figure 11 As shown in Figure -C, after 50 days of pre-storage, the samples had entered the aging physiological stage. When transferred to a low-temperature environment of -1.5℃ to 0.5℃ for further storage, a strong cold stress-induced respiratory response appeared. In the control group, the respiratory rate suddenly increased to approximately 21 mg CO2 / kg·h during the first 20 days of refrigeration and remained there until day 30, indicating that it was affected by the dual stresses of low temperature and aging, leading to metabolic disturbances. Under the electric field treatment, there was an initial tendency for the respiratory rate to increase, but it decreased significantly from day 20, dropping to 11 mg CO2 / kg·h on day 40, much lower than the control group, with a statistically significant difference. The results indicate that the electric field can effectively mitigate the abnormally enhanced respiration in aging fruits under low temperature, possibly related to the maintenance of membrane structure stability, regulation of mitochondrial function, and inhibition of response pathways related to potential abiotic stresses.

[0096] Observation of the effect of high voltage electrostatic field on the lignification degree of kiwifruit pulp under low temperature stress after pre-storage Figure 12 In the -A group, the results of phloroglucinol staining showed that the degree of lignification of kiwifruit pulp increased with prolonged storage. At 20 days, the control group pulp showed only a slight pale purple hue, concentrated around the core; the sample pretreated with an electric field showed no significant color change and the color was relatively uniform. By day 40, the control group pulp was dark purple, with the lignified portion expanding towards the core and near the peel; the electric field-treated group pulp remained yellowish-white with only faint purple patches at the core.

[0097] Quantitative analysis ( Figure 12-D) The results showed that during the 20-day storage period, the colored area of ​​the fruit in the control group without an electric field accounted for 76.4% of the total, while the colored area of ​​the fruit in the electric field-treated group accounted for 81.4%. As the storage time was further extended to 40 days, the colored area ratio in the control group was 86.3%, while that in the electric field-treated group was 74.0%. This indicates that during the initial short-term storage phase, the electric field regulates tissue morphological changes through indirect effects on cellular stress responses, while its effect on inhibiting softening of fruits and vegetables and mitigating chilling injury caused by low temperatures is particularly significant under long-term storage conditions.

[0098] Figure 12 The -E box plot shows that the data distribution of the electric field-treated group was more concentrated and the variation was smaller after 40 days, indicating that the electric field treatment effect was stable. Figure 12 The trend of -F time change shows that the lignification degree of the control group continued to increase, while that of the electric field treated group showed a decreasing trend, further confirming the inhibitory effect of electric field treatment on lignin accumulation.

[0099] Effects of high-voltage electrostatic field on membrane lipid peroxidation in kiwifruit under low-temperature stress after pre-storage Figure 13 The data showed that after pre-storage, the relative conductivity and malondialdehyde (MDA) content of kiwifruit under low-temperature stress increased over time. Comparative analysis revealed that the electric field group exhibited better storage tolerance compared to the control group without high-voltage electrostatic field treatment. On day 40, the relative conductivity of the control group was 48%, while that of the electric field group was only 39%, and the MDA content was also higher. The MDA content of the control group was 0.52 μmol / g, significantly higher than the 0.25 μmol / g of the electric field group, and about 52% lower (p < 0.05). These data indicate that high-voltage electrostatic field pretreatment enhances the stability of the fruit cell membrane system under low-temperature stress, reduces lipid peroxidation and the production of related metabolites, effectively mitigating the physiological damage caused by low temperature.

[0100] Effects of high-voltage electrostatic field on the accumulation of antioxidants in kiwifruit under low-temperature stress after pre-storage Depend on Figure 14It was found that the vitamin C content of kiwifruit in both groups showed a trend of first increasing and then decreasing, but the peak value appeared earlier and was higher in the high-voltage electrostatic field treatment group. At 10 days of storage, there was no significant difference between the two groups, both at 130 mg / 100g; at 20 days, the electric field treatment group increased to 250 mg / 100g, significantly higher than the control group (160 mg / 100g) (p < 0.01); at 30 days, the electric field treatment group reached 280 mg / 100g, still significantly higher than the control group (210 mg / 100g) (p < 0.01); at 40 days, both groups decreased to 200 mg / 100g, with no significant difference. Vitamin C is an important non-enzymatic antioxidant that can scavenge reactive oxygen free radicals. The significantly higher vitamin C content in the electric field treatment group during the mid-term (20–30 days) compared to the control group indicates that high-voltage electrostatic field treatment can enhance the antioxidant capacity of the fruit and delay oxidative damage under low-temperature stress, which corroborates the result of reduced MDA content.

[0101] The regulatory effect of high-voltage electrostatic field on phenylpropanane metabolism in kiwifruit under low-temperature stress after pre-storage pass Figure 13 -A、 Figure 13 -B data show that under low-temperature stress, the activity of phenylalanine ammonia-lyase (PAL) and the lignin content inside kiwifruit fruits exhibited regular changes with the extension of pre-storage time, and the high-voltage electrostatic field treatment group showed a better regulatory effect than the control group. PAL enzymes, as key regulators of the phenylpropane metabolic pathway, directly affect the lignin synthesis rate through their catalytic activity. Experimental data showed that after 10 days of storage, the PAL activity in the control group was 160 U·h⁻¹·g⁻¹, while it decreased to 120 U·h⁻¹·g⁻¹ in the treatment group; after 20 days of storage, the activity in the control group increased to 195 U·h⁻¹·g⁻¹, while it decreased back to 75 U·h⁻¹·g⁻¹ in the treatment group, and the difference between the groups was statistically significant (p<0.01). When the storage period was extended to 30 and 40 days, the PAL activity in the control group reached 260 U·h⁻¹·g⁻¹ and 480 U·h⁻¹·g⁻¹, respectively, while the treatment group remained at approximately 110 U·h⁻¹·g⁻¹ and 145 U·h⁻¹·g⁻¹, respectively. The difference between the two groups remained highly significant (p<0.01). Furthermore, the lignin content showed a cumulative trend with prolonged storage time, reaching 0.030 A in the control group on day 40. 280 • g⁻¹, significantly higher than 0.018 A in the electric field treatment group. 280• g⁻¹ (p<0.05). Phloroglucinol staining results showed that under long-term low-temperature storage, the pulp of the control group exhibited obvious lignification characteristics, with lignin mainly distributed in the core; while the high-voltage electrostatic field treatment group maintained good tissue structure integrity, with no obvious browning or damage observed. These results indicate that high-voltage electrostatic field treatment can effectively inhibit PAL gene expression and related enzymatic reactions, thereby mitigating low-temperature-induced non-enzymatic browning and its potential harm to the quality of kiwifruit pulp.

[0102] Fruit lignification is typically accompanied by changes in cell wall structure, a process closely related to the abnormal activation of the phenylpropanoid metabolic pathway. Phenylalanine ammonia-lyase (PAL), a key regulatory enzyme in lignin synthesis, exhibits increased activity that promotes lignin accumulation, leading to pulp hardening and quality deterioration. Experimental data showed that in the control group, PAL activity rapidly increased from its initial value to 480 U·h⁻¹·g⁻¹ with prolonged storage, and the lignin content correspondingly increased to 0.030 A. 280 The pulp color changed from pale yellow to purplish-red; while the PAL activity in the electric field pretreatment group remained at around 145 U·h⁻¹·g⁻¹, and the lignin content was only 0.018A. 280 ·g⁻¹. The above results indicate that electric field treatment can effectively alleviate low-temperature-induced fruit lignification damage by inhibiting PAL activity and lignin synthesis in the phenylpropanone metabolic pathway.

[0103] The effects of electric field stimulation on plant lignification are mainly reflected in two aspects: first, maintaining cell membrane structural stability and blocking the transduction of low-temperature stress signals, thereby inhibiting PAL gene transcription; second, regulating the oxidative stress pathway and reducing the damage of reactive oxygen species to PAL protein function. Studies have shown that during storage for 20–30 days, the vitamin C content in the electric field-treated group was significantly higher than that in the control group, which is consistent with the oxidative stress regulation hypothesis. When the storage period exceeded 40 days, the lignification growth rate slowed significantly, indicating that electric field intervention has an inhibitory effect on the lignification process, but its specific molecular mechanism requires further investigation.

[0104] Significant differences exist in the spatial distribution and metabolic regulation of PAL activity. Preliminary analysis indicates that this enzyme exhibits functional differentiation characteristics in fruits when responding to stress. In the early stage of Alternaria infection (day 21), electric field stimulation can increase PAL activity, promote the conversion of phenylpropane metabolic pathway to phenolic secondary metabolites, and enhance fruit disease resistance. However, as the duration of low-temperature stress increases, the continuously elevated PAL enzyme activity leads to excessive lignin deposition, causing tissue deterioration and quality decline. At this stage, electric field treatment can mitigate this negative effect by reducing PAL activity, maintaining fruit ripening process and sensory quality. Due to the differentiated expression regulation characteristics of PAL gene family members in response to different stress signals, a biphasic regulatory phenomenon is observed.

[0105] The core of this invention is a double-row suspended high-voltage electrostatic field storage and preservation system and method for 'Xuxiang' kiwifruit. It focuses on 30kV DC high voltage, linear electrode array, uniform and non-uniform electric field in the storage, and targeted regulation of postharvest physiology (senescence / soft rot / low temperature injury) of kiwifruit. It is a physical preservation technology that is variety-oriented, physiologically targeted, innovative in equipment structure, and adapted to the large-scale application of standard cold storage.

[0106] Existing technologies are all general-purpose high-voltage electrostatic preservation equipment / methods, which are not designed for the physiological characteristics of kiwifruit and have not solved core problems such as uniform electric field, large-scale storage, safe insulation, and targeted regulation of enzyme activity. They only achieve basic functions such as antibacterial and water loss reduction. The two technologies are completely different in terms of technical route, application objects, pain points solved, and equipment structure. This invention is a non-obvious groundbreaking improvement.

[0107] Compared to the shortcomings of existing technologies: existing preservation equipment generally adopts plate electrodes, box-type, and wall-mounted structures. The electrode plates themselves are thick and protrude into the storage space after installation, which directly encroaches on the area for stacking kiwifruit and arranging shelves, significantly reducing the effective volume utilization rate of cold storage. Plate electrodes also block cold air circulation and cover the fruit, resulting in uneven electric field penetration and uneven temperature distribution. At the same time, installation and maintenance require a lot of operating space, making them unsuitable for the actual scenario of high-density stacking and storage of kiwifruit.

[0108] This patent innovatively and non-obviously adopts a top-suspended linear electrode layout. The electrodes are suspended in the air in the form of thin cables, which do not occupy the ground, shelves, or middle storage space. The interior of the cold storage can be 100% used for stacking kiwifruit without reducing the effective storage capacity. The linear electrodes are thin and unobstructed, and do not block airflow or electric field penetration. Combined with a special top plate suspension structure, it achieves the dual effect of "preservation equipment not occupying storage space and electric field covering the entire area", solving the problem of large space occupation and low storage efficiency of plate-shaped equipment from the root of the structure.

[0109] CN202320934958.2 Deficiencies of a spatial electric field fruit and vegetable preservation device: The device adopts a plate electrode structure, which is large in size and occupies storage space in the warehouse. The electric field distribution is uneven. There is no special design for kiwifruit, no precise electrode spacing adjustment, no intelligent temperature and humidity and electric field coordinated control, and no function to inhibit soft rot, alleviate low temperature injury, or directionally regulate fruit enzyme activity. It is only suitable for small-scale fruit and vegetable preservation and cannot be adapted to the large-scale storage of kiwifruit in a whole warehouse. The safety protection and electric field stability are insufficient.

[0110] This patent innovatively and non-obviously utilizes a standard cold storage warehouse as its main frame with internal insulation, coupled with a double-row suspended cable electrode array, a graduated top plate, and a quick-connect structure. It precisely controls the electrode position and spacing to form a stable, non-uniform electric field. The integrated intelligent control module enables real-time control of the electric field, temperature, and humidity, as well as leakage protection. It targets and inhibits kiwifruit soft rot, alleviates low-temperature chilling injury, and regulates cell wall degradation and antioxidant enzyme activity. It achieves large-scale safe preservation of the entire warehouse without directly electrifying the fruit, completely solving the aforementioned defects.

[0111] Example 1: A multi-purpose kiwi fruit storage system with a flexible, space-saving high-voltage electrostatic field, characterized by comprising a high-voltage DC power supply system, an electrode array formed by cables, a grounding strip, and an intelligent control unit. Compared to existing technologies that suffer from drawbacks such as difficulty in insulating directly charged fruits and vegetables, low safety, uneven electric field distribution, lack of intelligent safety protection, and poor industrialization feasibility, this patent innovatively and non-obviously utilizes a standard cold storage warehouse as the main frame with internal insulation, coupled with electrode support components, to eliminate electric field deformation caused by vibration. Simultaneously, a 30kV high-precision high-voltage DC power supply system, combined with a grounding strip, forms a stable, non-uniform electric field. The intelligent control unit enables real-time control of electric field strength, temperature, and humidity, as well as leakage protection. This allows for large-scale processing of the entire warehouse without directly charging the fruit, completely solving the problems of insulation difficulties, low safety, uneven electric field, and lack of industrialization in existing technologies.

[0112] Example 2: As described in Example 1, this multi-purpose kiwifruit storage system features a flexible, space-saving high-voltage electrostatic field. The electrodes in the cable-connected electrode array are arranged in double or multiple rows, with multiple groups of kiwifruit arranged between these rows. Compared to existing technologies with their single electrode arrangement, limited electric field coverage, and uneven field distribution leading to inconsistent preservation effects, this patent innovatively and non-obviously designs the electrode array in a double or multiple row structure. This ensures that multiple groups of kiwifruit are all within the non-uniform electric field coverage area between the electrodes, guaranteeing that each fruit receives a stable and uniform electric field. This solves the problems of insufficient electric field penetration and inconsistent preservation effects, making it suitable for the practical scenario of bulk stacking and storing kiwifruit.

[0113] Example 3: This patent innovatively combines a special insulating top plate 1 with a quick-connect structure consisting of a graduated optional lifting port 4, a metal threaded sleeve 9, and an upper insertion port 7. The top of the cold storage is fixed by the lifting lug 3. The hollow structure is used for wiring to precisely control the electrode spacing and position, enabling rapid electrode installation and stable positioning. The structure ensures the accurate construction of a non-uniform electric field, solving the problems of difficult electrode adjustment and unstable electric field.

[0114] Example 4: Compared with the shortcomings of existing technologies such as inaccurate cold storage temperature detection, electrode sway leading to electric field deformation, and inability to coordinate temperature and electric fields, this patent innovatively and non-obviously arranges the LS / T 1813-2017 standard digital temperature measuring cable 5 in parallel with the electrode, accurately acquiring three-dimensional temperature field data. At the same time, a counterweight 11 is set at the end of the electrode to completely eliminate the problem of electric field deformation caused by electrode sway, achieving coordinated and stable control of temperature and electric field, and improving the accuracy of storage environment control.

[0115] Example 5: Compared with existing technologies that cannot target and solve the problems of softening, browning, soft rot, and chilling injury in kiwifruit, and cannot regulate the activity of key enzymes and the antioxidant system of the fruit, this patent innovatively and non-obviously combines a 30kV high-voltage electrostatic field with an environment of 0-2℃ and 90%-95% humidity on 'Xuxiang' kiwifruit. Through continuous electric field treatment, the activity of enzymes such as CX, PPO, and PAL is precisely regulated, the antioxidant enzyme system of SOD, CAT, and POD is optimized, and Alternaria alterniflora is directly inhibited and lignin accumulation is reduced, thus simultaneously solving the three core problems of fruit aging, disease, and chilling injury.

[0116] Example 6: Compared with the shortcomings of existing storage equipment, which cannot adapt to different storage volumes and heights, lack auxiliary anti-aging methods, and have a single preservation effect, this patent innovatively and non-obviously adjusts the height of the special top plate 1, the number and spacing of electrode cables as needed, and places a slow-release anti-aging agent in the hollow special top plate 1. Combined with a high-voltage electrostatic field, it achieves a synergistic effect of physical preservation and slow-release preservation of the agent, adapting to different scale storage needs and further improving the anti-aging preservation effect of kiwifruit.

[0117] Example 7: Compared with the shortcomings of existing cold storage technologies, such as uneven cold air circulation, low temperature control efficiency, high energy consumption, and inaccurate temperature monitoring, this patent innovatively combines the dedicated cold air inlet 10 of the dedicated top plate 1 with the optional hanging port 4, allowing cold air to be directly sprayed onto the kiwifruit to achieve precise temperature control. With the help of the digital temperature measuring cable 5 to monitor the temperature in real time, the energy consumption of the cold storage is greatly reduced, while ensuring stable and uniform storage temperature and improving the efficiency of high voltage electrostatic field and low temperature synergistic preservation.

[0118] Example 8: Compared to existing technologies that cannot achieve targeted regulation of enzyme activity, inhibit soft rot, alleviate low-temperature lignification injury, or maintain the nutritional quality of fruit, this patent innovatively and non-obviously combines a 30kV electric field with 0-2℃ and 90%-95% humidity conditions to form a multi-target preservation application. It can regulate the activity of key enzymes involved in cell wall degradation, anti-oxidation, and phenylpropanoid metabolism, while also inhibiting pathogens, alleviating chilling injury, and preserving nutrients, filling the gap in existing technologies that cannot achieve multi-functional synergistic preservation. Overall Concept Comparison: The essential difference between this invention and existing prior art is that the core of this invention is a double-row suspended high-voltage electrostatic field storage and preservation method and dedicated equipment for 'Xu Xiang' kiwifruit. The core technical concept is based on 30kV DC high voltage, linear electrode array, uniform electric field within the storage facility, and targeted regulation of post-harvest physiology (senescence / soft rot / chilling injury) of kiwifruit. It is a physical preservation technology that is variety-oriented, physiologically targeted, innovative in equipment structure, and adaptable to large-scale cold storage. The comparative documents are all general-purpose high-voltage electrostatic preservation methods / equipment, which are not specifically designed for kiwifruit, do not address the issues of uniform electric field and large-scale application, and do not achieve synergistic regulation of physiological and disease conditions. Their overall approach is general fruit and vegetable electrification preservation, simple electric field equipment, and no targeted solutions for specific varieties or physiological problems. The two technologies, application targets, problem-solving approaches, and equipment structures are completely different. This invention represents a non-obvious groundbreaking improvement. Compared to CN1308873A, this patent non-obviously and groundbreakingly solves the problem of using a double-row suspended linear electrode array, eliminating the need for direct electrification of fruits and vegetables and strict insulation, adapting to standard cold storage warehouses, and solving the insulation and safety problems of large-scale storage. The optimized 30cm electrode spacing layout forms a uniform cross-electric field within the warehouse, ensuring consistent kiwifruit preservation. Targeted regulation of the 'Xu Xiang' kiwifruit physiology: inhibiting respiratory peaks, reducing cell wall degradation enzyme activity, inducing disease resistance, and reducing lignification accumulation, simultaneously addressing the three major industry pain points of aging, soft rot, and low-temperature chilling injury. The equipment integrates safety modules such as short-circuit protection, leakage detection, and real-time ozone monitoring. Adopting a modular design, it directly adapts to a standard 6m×6m×9m cold storage facility, enabling industrial-scale promotion. Compared to CN110800788A, this patent innovatively and non-obviously addresses the precise post-harvest preservation scenario for 'Xu Xiang' kiwifruit, specifically resolving core industry pain points and completely differentiating it from meat processing technologies. It utilizes a 30kV high-voltage electrostatic field, strong enough to inhibit Alternaria alternata and regulate fruit enzyme systems and cell membrane stability, achieving both preservation and disease resistance. The developed double-row suspended specialized preservation equipment constructs a uniform electric field, forming a complete kiwifruit storage technology system, rather than a simple combined treatment. From a physiological mechanism perspective, it synergistically regulates respiration, cell wall metabolism, disease resistance systems, and chilling injury response, comprehensively maintaining fruit quality, inhibiting diseases, and mitigating chilling injury, thus meeting the post-harvest preservation needs of fruits and vegetables.Compared to CN116222096A, this patent innovatively and non-obviously solves the problem of industrial-scale storage of terrestrial kiwifruit, specifically designed for the physiological characteristics of the 'Xuxiang' kiwifruit variety, simultaneously addressing aging, soft rot, and chilling injury. It employs a double-row suspended linear electrode layout to create a highly penetrating and uniformly cross-shaped electric field, ensuring a stable electric field effect throughout the entire kiwifruit storage area. The system reveals the regulatory mechanism of HVEF on kiwifruit enzyme systems, reactive oxygen species metabolism, phenylpropanoid metabolism, and the accumulation of disease-resistant substances, with quantitative data verifying the preservation effect (49.1% rot inhibition rate and 46.2% bacterial spot inhibition). The equipment features a modular structure adapted to standard terrestrial cold storage, offering low cost, easy installation, and safe and controllable operation, fully meeting the large-scale storage needs of major kiwifruit producing areas. Compared to CN117063970A, this patent innovatively and non-obviously applies a double-row suspended linear electrode array to a cold storage for kiwifruit preservation, forming a uniform cross-electric field. This simultaneously targets and inhibits Alternaria alternata, regulates cell wall degradation enzymes, and blocks lignin synthesis, effectively addressing the three major problems of soft rot, chilling injury, and softening. Compared to CN208419330U, this patent innovatively and non-obviously incorporates top-suspended linear electrodes and full insulation of the storage unit, allowing the kiwifruit to receive a uniform electric field between the two rows of electrodes. This directly acts on the fruit cells, regulating four physiological pathways: respiration, anti-oxidation, disease resistance, and chilling resistance, overcoming the shortcomings of uneven electric field distribution and single-function design. Compared to CN210275762U, this patent innovatively and non-obviously integrates a high-voltage electrostatic field with a standard cold storage design, combined with a 30kV stable DC electric field and intelligent safety control, enabling large-scale storage of kiwifruit while simultaneously achieving the triple functions of delaying aging, inhibiting disease, and mitigating chilling injury. Compared to CN215873289U, this patent innovatively and non-obviously matches the fixed-spacing 30cm linear electrodes and the cross-uniform electric field with the physiological mechanism of kiwifruit, stably outputting a 30kV electric field, while regulating key enzymes such as CX / PPO / PAL, thus fundamentally solving the problems of softening, browning, rotting, and lignification of kiwifruit.

[0119] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. A multi-purpose kiwi fruit storage system with a flexible, space-saving high-voltage electrostatic field, characterized in that: It consists of a high-voltage DC power supply system, an electrode array formed by cables, a grounding strip, and an intelligent control unit; The main frame is made of standard cold storage, and the interior is covered with insulating material to ensure safe operation. Each end of the electrode of the electrode array formed by the cable has a support component to maintain stability and effectively eliminate electric field deformation caused by vibration. Kiwifruit is stored between electrodes, close to the ground, and is subjected to a non-uniform electric field generated by the crossed electrodes. The high-voltage DC power supply system has a high-precision output function. The high-voltage power supply outputs 30 kV DC high voltage, with an adjustable range of 0 to 50 kV. The grounding strip plays a current-conducting role to form a non-uniform electric field. The high-voltage DC power supply system, the electrode array formed by cables, and the grounding strip constitute an electric field loop; The intelligent control unit can adjust the electric field strength and environmental parameters inside the warehouse in real time; the intelligent control unit has leakage protection function, and the environmental parameters inside the warehouse include temperature, humidity, and electric field strength. The electric field strength is determined by the magnitude of the current, while the temperature and humidity are controlled by temperature and humidity control systems installed in the standard cold storage.

2. The multi-purpose kiwi fruit storage system with a flexible, space-saving high-voltage electrostatic field as described in claim 1, characterized in that: The electrodes in the electrode array formed by the cable are arranged in a double or multi-row structure, and multiple groups of kiwifruit are arranged between the double or multi-row electrodes.

3. The multi-purpose kiwi fruit storage system with a flexible, space-saving high-voltage electrostatic field as described in claim 1, characterized in that: The arrangement of electrodes in the electrode array formed by the cable is achieved by a special top plate (1). The special top plate (1) can be suspended or fixed on the upper part of the frame of the standard cold storage as the main frame by means of the lifting lug (3). The special top plate (1) is made of insulating material. The dedicated top plate (1) contains a bus entrance (2) above it. The dedicated top plate (1) is hollow and can be used for wiring. Multiple optional hanging ports (4) are arranged in the downward position of the dedicated top plate (1). The optional hanger (4) can be quickly connected to the electrode through the upper plug (7); the quick connection structure is as follows: a metal threaded sleeve (9) with a step on the top can be inserted into the insulated optional hanger (4), and the branch cable (8) is connected above the metal threaded sleeve (9); the thread on the upper plug (7) can be installed in the metal threaded sleeve (9) to achieve connection and docking; Multiple optional hanging ports (4) are evenly arranged and their dimensions are clearly marked on the bottom; This allows for precise adjustment of the distance between cables; The branch cables (8) include multiple groups and converge through the bus entry (2); The position of the electrode can be adjusted by adjusting the position of the metal threaded sleeve (9) and the upper insertion port (7).

4. The multi-purpose kiwi fruit storage system with a flexible, space-saving high-voltage electrostatic field as described in claim 3, characterized in that, The electrodes are also arranged in parallel with digital temperature measuring cables compatible with LS / T 1813-2017; the two are relatively isolated, and the digital temperature measuring cables arranged in this way can more accurately obtain the three-dimensional temperature field of the storage space; in order to prevent the electrodes from shaking, a counterweight is hung at its end.

5. A method for storing kiwifruit based on a non-uniform high-voltage electrostatic field, characterized in that, A multi-purpose kiwi fruit storage system utilizing the flexible, space-saving high-voltage electrostatic field as described in any one of claims 1-4. Select 'Xu Xiang' kiwifruit that are uniformly ripe, free from pests and diseases, and without mechanical damage; Kiwifruit should be stored in a high-voltage electrostatic field environment with a temperature of 0-2℃, a relative humidity of 90%-95%, and an electric field strength of 30kV. Continuous high-voltage electrostatic field treatment inhibits fruit respiration, delays softening, reduces water loss, inhibits Alternaria soft rot, alleviates low-temperature chilling injury, inhibits cellulase (CX) and polyphenol oxidase (PPO) activity, delays fruit cell wall degradation and browning, increases SOD and CAT activity, reduces POD activity, enhances fruit antioxidant capacity, and reduces lignin accumulation by inhibiting PAL activity, thus alleviating fruit pulp lignification chilling injury.

6. The method for storing kiwifruit based on a non-uniform high-voltage electrostatic field as described in claim 5, characterized in that, The storage height of the special top tray (1) is determined according to the storage height of the kiwifruit; Adjust the number and spacing of cables according to the quantity of kiwifruit; The hollow special top tray (1) contains a slow-release agent that delays the aging of kiwifruit.

7. The method for storing kiwifruit based on a non-uniform high-voltage electrostatic field as described in claim 5, characterized in that, Since the kiwi fruit is placed between the electrodes, it must be below the special top plate (1); Cold air is pumped in through the cold air inlet (10) arranged on the side of the special top plate (1), and the cold air is sprayed out from multiple optional hanging ports (4) to directly control the temperature of the kiwifruit, which is used to reduce the energy consumption of the cold storage; the digital temperature measuring cable is used for real-time temperature measurement.

8. The application of a method with an electric field strength of 30kV and a temperature of 0-2℃ and a relative humidity of 90%-95%, characterized in that: This purpose can be any one of the following: Firstly, this application utilizes the high-voltage electrostatic field to inhibit the activity of cellulase CX and polyphenol oxidase PPO, thereby delaying the degradation and browning of fruit cell walls. Second: This application utilizes the high-voltage electrostatic field to enhance the antioxidant capacity of fruits by increasing the activity of SOD and CAT, reducing the activity of POD; Third: This application utilizes the high-voltage electrostatic field to inhibit Alternaria alterniflora, thereby reducing the rate of fruit rot. Fourth: This application is suitable for storage under low temperature stress of -1.5 to 0.5℃, and it can alleviate the lignification and chilling injury of fruit pulp by inhibiting PAL activity and reducing lignin accumulation; Fifth: This purpose is to maintain the titratable acid, soluble solids, and vitamin C content of the fruit.

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