Food freezing system based on electrode coupling and multi-stage electric field and freezing method thereof

Abstract

The invention discloses a food freezing system based on electrode coupling and a multi-stage electric field and a freezing method thereof. The system comprises an electric field generating device (1), a refrigeration house (2), a space plate type discharge electrode (3), a metal frame discharge electrode (4) and the like. According to the freezing method, a discharge electrode is used for being coupled with an electric field, a special'superposed electric field effect 'is generated, the freezing efficiency is remarkably improved, heat conduction inside and on the surface of food can be accelerated, uniform and rapid crystallization of water is promoted, large ice crystals are effectively prevented from being formed, and therefore damage to cell structures is reduced. Compared with a traditional freezing method, the freezing time can be shortened by 15%-30%, and the juice loss rate is reduced by 3%-6%. Due to the synergistic effect of the double electric fields in different stages, the food can be quickly frozen under lower voltage, and the comprehensive energy consumption can be reduced by 15-30% while the safety is ensured. The method is suitable for large-scale food freezing application, and remarkable technical progress and economic benefits can be brought to the food freezing industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of food freezing, and in particular, relates to a food freezing system and a freezing method thereof based on electrode coupling and multi-stage electric field. Background Art

[0002] Freezing is one of the important methods of food preservation. It can effectively extend the shelf life of food and maintain the nutritional value and quality of food. However, there are many problems with traditional freezing methods. These problems are mainly manifested in slow freezing speed, serious loss of food quality, and high energy consumption. Traditional freezing methods mainly rely on heat conduction or convection heat transfer. Due to the limitation of heat transfer efficiency, there is a temperature gradient from the surface to the inside of the food, resulting in a relatively slow freezing process. This slow freezing process is prone to form larger ice crystals, destroying the cell structure of the food, which in turn leads to more juice loss during thawing, affecting the texture, nutrients and flavor of the food. At the same time, long-term operation of refrigeration equipment also leads to high energy consumption and increases production costs.

[0003] To solve these problems, researchers have been exploring new freezing technologies. In recent years, electric field-assisted freezing technology has attracted widespread attention due to its unique advantages. Electric field freezing technology affects the orientation and movement of water molecules by applying an electric field, promotes the uniform nucleation of ice nuclei, and forms small and uniform ice crystals, thereby increasing the freezing rate. However, existing electric field freezing technologies still have some limitations. For example, most electric field freezing technologies use higher voltages, usually in the range of 6 to 10 kV. This higher voltage not only increases the complexity and cost of the equipment, but also brings potential safety hazards. High-voltage equipment requires more stringent safety measures and operating procedures, which increases the difficulty of implementation and operating costs. In addition, high voltage may cause unstable local discharge, which not only affects the freezing effect, but also leads to high energy consumption. Therefore, there is an urgent need for a new food freezing method that can achieve fast and uniform freezing effects at lower voltages, while having wide applicability and good safety. The ideal method should be able to significantly increase the freezing speed, improve the freezing effect, reduce energy consumption, and be suitable for the production of various types of food and the food industry. Summary of the invention

[0004] The present invention aims to solve the above technical problems and proposes a food freezing system and freezing method based on electrode coupling and multi-stage electric field. The method uses a relatively low voltage and achieves efficient, uniform and energy-saving food freezing through innovative discharge electrode coupling design and control strategy, while maintaining high food quality.

[0005] First, the present invention provides a food freezing system based on electrode coupling and multi-stage electric field, comprising:

[0006] Electric field generating device (1): capable of generating and cooperatively controlling DC electric fields of different intensities and realizing real-time optimization of electric field parameters;

[0007] Cold storage (2): has precise temperature control and air cooling circulation system; further, a fan (22) is provided on the cold storage (2).

[0008] A space plate type discharge electrode (3) and a metal frame discharge electrode (4), wherein the metal frame discharge electrode (4) and the space plate type discharge electrode (3) are connected to an electric field generating device (1) via an insulated wire;

[0009] The portion of the metal frame discharge electrode (4) in contact with the cold storage floor is provided with an insulating base (42);

[0010] A shelf plate (41) is arranged on the metal frame discharge electrode (4), and the frozen food is placed in a perforated plastic container and placed on the shelf plate (41);

[0011] The electric field generating device (1) comprises: an electric field control system power supply / emergency brake device, a main electric field generating unit, a main electric field voltage regulating device, an auxiliary electric field generating unit, and an auxiliary electric field voltage regulating device; and they correspond to the electric field control system power supply / emergency brake switch (11), the main electric field control switch (12), the main electric field voltage regulating knob (14), the auxiliary electric field control switch (13), and the auxiliary electric field voltage regulating knob (15) in sequence. The electric field generating device (1) is also provided with a digital display screen (16) which can display real-time voltage (kV) and real-time current (mA).

[0012] The main electric field generating unit has an operating voltage range of 1 to 12 kV. This unit can generate a sufficient main electric field and is a key component for achieving rapid freezing; the auxiliary electric field generating unit has an operating voltage range of 1 to 12 kV. The auxiliary electric field works in conjunction with the main electric field to optimize the electric field distribution and improve freezing uniformity; the voltage regulating unit can achieve fine adjustment of 0.1 kV. This system can simultaneously generate and accurately control the voltage relationship between the main electric field and the auxiliary electric field. Through a unique coupling mechanism, the synergistic effect of the two electric fields is achieved, significantly enhancing the effect of the electric field in accelerating the freezing of food.

[0013] Furthermore, the perforated plastic container is made of food-grade plastic material, which has excellent low-temperature resistance and electrical insulation. The pore size and distribution are optimized through CFD (computational fluid dynamics) and FEM (finite element method) joint simulation, which not only optimizes the penetration effect of the electric field, but also significantly improves the uniformity of the cold air flow.

[0014] The cold storage (2) is controlled by a cold storage control system (21). The cold storage control system (21) is provided with a cold storage main power switch (211), a temperature adjustment knob (212) and a display screen (213); the display screen (213) can display the real-time temperature in the cold storage.

[0015] The electric field generating device (1) is installed on the outer wall of the cold storage.

[0016] Furthermore, the insulated wires connecting the electric field generating device (1) with the metal frame discharge electrode (4) and the space plate discharge electrode (3) are made of cold-resistant silicone rubber insulation material, the thickness of the insulation layer is not less than 3 mm, and the cross-sectional area of ​​the wire is 0.5~4 mm². Inside the cold storage, the wires are laid along a specific path and fixed every 50 cm using insulating fixtures.

[0017] Furthermore, the area of ​​the spatial plate-type discharge electrode (3) is one third to one half of the cross-sectional area of ​​the metal frame discharge electrode (4).

[0018] Furthermore, the angle of the spatial plate-type discharge electrode (3) is an adjustable structure, and a fine-tuning hinge and an integrated micro-motor are provided, allowing the spatial plate-type discharge electrode to automatically adjust its angle within a range of ± 10°.

[0019] Furthermore, the automatic adjustment structure of the spatial plate discharge electrode angle is composed of a fine-tuning hinge structure and a micro-motor structure. The fine-tuning hinge structure is used to achieve precise angle adjustment of the spatial plate discharge electrode, so that the electric field can evenly cover the processed food of different specifications; the micro-motor structure provides power drive for the spatial plate discharge electrode, with a control accuracy of ± 0.5° and an adjustment range of ± 10°, and can adjust the spatial plate discharge electrode angle in real time according to the size and position of the food, thereby optimizing the electric field distribution.

[0020] The structure of the present invention is set as a multi-level, three-dimensional electric field distribution structure. The combination of the space plate discharge electrode and the metal frame discharge electrode designed above is conducive to forming a relatively uniform electric field distribution and improving the penetration ability of the electric field. The space plate discharge electrode adopts a metal plate with a smooth surface inside, which improves the uniformity and stability of the electric field and has better conductivity. The upper side is wrapped with an acrylic plate with a thickness of 1 to 3 mm, and the lower side is wrapped with a perforated acrylic plate of the same thickness, which improves its safety performance. The metal frame discharge electrode is an adjustable structure, and the layer spacing can be adjusted according to the size of the food, ensuring the uniformity of the electric field effect during the freezing process of large quantities of food.

[0021] Furthermore, the connection point between the insulated wire and the metal frame discharge electrode (4) adopts an adaptive connection structure. The adaptive connection structure includes: an elastic alloy contact: capable of maintaining good conductivity and elasticity within a temperature range of -40°C to 20°C, having good conductivity and elasticity; a micro pressure sensor: real-time monitoring of the contact pressure of the connection point, the system can timely detect and adjust unstable connections; an automatic adjustment mechanism: according to the feedback of the pressure sensor, the contact pressure is adjusted by a micro motor to ensure a stable connection under temperature changes and mechanical vibration conditions.

[0022] Furthermore, the present invention also includes multiple safety protection mechanisms, which are overload protection, leakage protection, ground fault detection and emergency cut-off. The response time is less than 5 ms. If the system detects excessive current, the electric field system automatically shuts down to ensure safety.

[0023] Furthermore, overload protection can prevent the system from being damaged due to excessive current. This mechanism can cut off the power supply within milliseconds to ensure the safety of the system to the greatest extent. The leakage protection system is equipped with a highly sensitive current monitoring device that can detect tiny leakage currents, thereby effectively avoiding the risk of electric shock to operators. Ground fault detection can ensure that the system is always in a safely grounded state. The emergency cut-off system can quickly shut down all electric fields in an emergency, with a response time of less than 5 ms.

[0024] Furthermore, the present invention also includes a real-time monitoring network, which mainly includes a temperature sensor and an electric field strength sensor. The temperature sensor monitors the real-time temperature changes on the surface and inside of the food; the electric field strength sensor monitors the real-time electric field distribution.

[0025] Furthermore, the present invention also includes an intelligent electric field parameter dynamic control system, which can monitor key parameters such as food center temperature, surface temperature, and ambient humidity in real time, and can automatically adjust the voltage and action time of the main electric field and the auxiliary electric field in combination with the real-time temperature during freezing. The system can control the food center temperature within the range of ± 1°C of the target temperature according to the freezing characteristics of different types and volumes of food, realize precise control of the freezing process, and ensure the optimization of the freezing effect.

[0026] The present invention also provides a freezing method for a food freezing system based on electrode coupling and a multi-stage electric field, the steps of which are as follows: first, the cold storage refrigeration system is turned on, and after the temperature in the cold storage is stabilized at a preset value (e.g., below -18°C), the food is placed on a shelf (41) of a metal rack discharge electrode in the cold storage, and then the electric field generating device (1) is started.

[0027] The specific operation is as follows: start the cold storage and adjust the temperature to the preset value, usually in the range of -25℃ to -40℃. After the temperature of the cold storage drops to the preset value, select a suitable plastic basket with holes according to the frozen object, place the food evenly in the plastic basket, and then place it on the metal frame discharge electrode; connect the space plate discharge electrode and the metal frame discharge electrode to the same electric field generating device; start the electric field equipment after the food is pre-cooled for 5~10 minutes, and set the initial electric field parameters according to different types of food; monitor key parameters such as the center temperature of the food, ambient humidity, and electric field strength through a multi-parameter real-time sensor network. The control system performs multi-stage parameter regulation to adjust the electric field voltage, dynamically adjusts the electric field strength, the angle of the space plate discharge electrode, and the cold air speed according to the monitoring data, and realizes precise control of the freezing process.

[0028] The multi-stage parameter control to adjust the electric field voltage is divided into the following steps:

[0029] (1) Initial stage (above 0℃ to 0℃), main electric field voltage: 3.0~4.0 kV, auxiliary electric field voltage is set to: 2.0~3.0 kV;

[0030] (2) Ice crystal growth stage (0℃ to -5℃), the main electric field voltage increases to 4.0~6.0 kV, and the auxiliary electric field voltage increases to 3.0~4.0 kV;

[0031] (3) Rapid freezing stage (-5℃ to -18℃), the main electric field voltage is reduced to 2.0~3.0 kV, and the auxiliary electric field voltage is reduced to 1.0~2.0 kV;

[0032] (5) When the center temperature of the frozen object reaches the preset end temperature, the system automatically enters the holding stage, and the main electric field and the auxiliary electric field are automatically turned off;

[0033] (6) After freezing is completed, the system enters the equilibrium stage, which lasts for 20 to 40 minutes to ensure uniform temperature distribution. Wait for subsequent processing.

[0034] During the whole process, the system automatically adjusts the angle of the spatial plate discharge electrode (3) by 1 to 2° through the fine-tuning hinge every 5 to 10 minutes to ensure that the food surface is evenly affected by the electric field.

[0035] Beneficial effects of the present invention:

[0036] (1) Through multi-stage DC electric field technology, a unique "electric field gradient effect" is formed. This effect can affect the orientation and movement of water molecules, accelerate the formation and growth of ice nuclei, and significantly improve the freezing speed and uniformity. By designing the electric field formed by the space plate discharge electrode and the metal frame discharge electrode for coupling, a special "superposition electric field effect" is produced. This superposition effect enables a freezing effect equivalent to that of a higher voltage to be achieved at a lower voltage. This innovative electric field superposition mechanism not only enhances the effect of the electric field on food, but also reduces energy consumption and safety risks.

[0037] (2) Dynamic regulation of electric field parameters is achieved through a precise control system. During the freezing process, the system adjusts the electric field strength based on real-time monitoring data, allowing the migration of water inside the food and the formation of ice crystals to be precisely regulated, effectively reducing the formation of large ice crystals and minimizing damage to the cell structure.

[0038] (3) Through the design of modular storage units, the present invention can flexibly adjust the spacing and layout of the metal frame discharge electrodes, optimize the penetration effect of the electric field, adapt to foods of different volumes and shapes, and avoid the problem of material extrusion and stacking. The special container has a suitable pore size and distribution, which improves the uniformity of the electric field, further reduces the shielding effect between foods, significantly improves the distribution of cold air flow, avoids local overcooling, and enables each food to be evenly frozen.

[0039] (5) Multiple safety protection mechanisms ensure the stable operation of the system in extremely low temperature environments. In particular, the adaptive wire connection structure solves the problem of unstable connection in low temperature environments and ensures the continuous stability of the electric field distribution.

[0040] (6) The present invention achieves efficient freezing at a relatively low voltage by coupling the discharge electrode to a DC electric field to produce a special "superposition electric field effect". This technology is not only suitable for the freezing processing of various types of meat, aquatic products, and fruits and vegetables, but can also be extended to the fields of medicine and biological sample preservation, with broad application prospects and significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0042] Figure 1 The schematic diagram of the multi-stage, electrode-coupled DC electric field high-efficiency food freezing system of the present invention.

[0043] Figure 2 A comparison of the time-temperature curves of the whole chicken electric field group and the control group provided by the method of the present invention

[0044] Figure 3This is a comparison diagram of the time-temperature curves of the large yellow croaker electric field group freezing and the control group provided by the method of the present invention.

[0045] In the figure:

[0046] Electric field generating device (1); power supply / emergency brake switch (11); main electric field control switch (12); auxiliary electric field control switch (13); main electric field voltage adjustment knob (14); auxiliary electric field voltage adjustment knob (15); digital display screen (16);

[0047] Cold storage (2); cold storage control system (21); cold storage main power switch (211); temperature adjustment knob (212); digital display screen (213); fan (22);

[0048] A space plate type discharge electrode (3); a metal frame discharge electrode (4); a shelf plate (41) and an insulating base (42). DETAILED DESCRIPTION

[0049] It should be noted that the various embodiments and features of the food freezing system based on electrode coupling and multi-stage electric field of the present invention can be combined without conflict. The specific implementation of the present invention will be described in detail below with reference to the accompanying drawings, especially the cooperative working mode of electrode coupling, multi-stage electric field generating device, precise control system and modular storage unit.

[0050] In the present invention, except for special explanations, the professional and technical terms used should be interpreted according to the common understanding of technicians in the field of cryotechnology and electric field application. For example, the terms "electric field gradient effect", "ice nucleation", "superimposed electric field effect" and the like have the common meanings in these fields.

[0051] When describing the present invention, unless otherwise stated, the terms used in the text such as "main electric field" and "auxiliary electric field" are relative to the mode of action of the discharge electrode coupling DC electric field. It is generally believed that the "main electric field" is the "metal frame discharge electrode" and the "auxiliary electric field" is the "space plate discharge electrode". "Multi-stage" is mainly relative to the voltage precision control strategy. "Inside" and "outside" are defined relative to the boundaries of the freezing chamber or each component itself. It should be noted that the use of these descriptive words is only for the convenience of explaining the structure and working method of the present invention, and is not used to limit the scope of protection of the present invention. In different embodiments, the method of using the electric field and the voltage intensity may be adjusted according to specific needs.

[0052] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can implement the invention with reference to the description.

[0053] Example 1

[0054] like Figure 1 As shown, this embodiment provides a food freezing system based on electrode coupling and multi-stage electric field, including:

[0055] Electric field generating device (1): capable of generating and cooperatively controlling DC electric fields of different intensities and realizing real-time optimization of electric field parameters;

[0056] Cold storage (2): having precise temperature and humidity control and air cooling circulation system, and a fan (22) is provided on the cold storage (2);

[0057] A space plate type discharge electrode (3) and a metal frame discharge electrode (4), wherein the metal frame discharge electrode (4) and the space plate type discharge electrode (3) are connected to an electric field generating device (1) via an insulated wire;

[0058] The portion of the metal frame discharge electrode (4) in contact with the cold storage floor is provided with an insulating base (42);

[0059] A shelf plate (41) is arranged on the metal frame discharge electrode (4), and the frozen food is placed in a perforated plastic container and placed on the shelf plate (41);

[0060] The spacing between the shelf plates (41) is 5 to 50 cm;

[0061] A space plate discharge electrode (3) is arranged 0.2 to 0.8 m above the metal frame discharge electrode (4).

[0062] Specifically, the electric field generating device (1) provided in this embodiment is a discharge electrode coupled direct current electric field generating device.

[0063] The electric field generating device (1) comprises: an electric field control system power supply / emergency brake device, a main electric field generating unit, a main electric field voltage regulating device, an auxiliary electric field generating unit, and an auxiliary electric field voltage regulating device; and they correspond in sequence to the electric field control system power supply / emergency brake switch (11), the main electric field control switch (12), the main electric field voltage regulating knob (14), the auxiliary electric field control switch (13), and the auxiliary electric field voltage regulating knob (15).

[0064] The electric field generating device (1) is also provided with a digital display screen (16) which can display key information such as real-time voltage (kV) and real-time current (mA).

[0065] The working voltage range of the main electric field generating unit is 1~12 kV; the working voltage range of the auxiliary electric field generating unit is 1~12 kV, and the main electric field generating unit and the auxiliary electric field generating unit can achieve fine adjustment of 0.1 kV.

[0066] The cold storage (2) is controlled by a cold storage control system (21). The cold storage control system (21) is provided with a cold storage main power switch (211), a temperature adjustment knob (212) and a digital display screen (213); the digital display screen (213) can display the real-time temperature in the cold storage.

[0067] The metal frame discharge electrode (4) is made of stainless steel and has 3 to 6 layers, with a spacing of 10 to 60 cm between each layer. The single-layer load-bearing capacity of the metal frame discharge electrode is not less than 100 kg, and the total load-bearing capacity is not less than 500 kg. The columns and beams of the metal frame discharge electrode are designed to be detachable, so that the number of layers and the spacing can be adjusted according to the volume of different foods.

[0068] The electric field generating device (1) is installed on the outer wall of the cold storage.

[0069] The insulated wires connecting the electric field generating device (1) with the metal frame discharge electrode (4) and the space plate discharge electrode (3) are made of cold-resistant silicone rubber insulation material, the thickness of the insulation layer is not less than 3 mm, and the cross-sectional area of ​​the wire is 0.5-4 mm². Inside the cold storage, the wires are laid along a specific path and fixed every 50 cm using insulating fixings.

[0070] The food freezing system provided in this embodiment also includes a real-time monitoring network, which mainly includes humidity, temperature sensors and electric field strength sensors. The temperature sensor monitors the real-time temperature changes on the surface and inside of the food; the electric field strength sensor monitors the real-time electric field distribution and transmits the data to a display in real time, which is shared by the display and the digital display screen (16) set on the electric field generating device (1).

[0071] The food freezing system provided in this embodiment also includes an intelligent electric field parameter dynamic control system, which can monitor key parameters such as food center temperature, surface temperature, and ambient humidity in real time, and transmit the parameters to a display in real time, which is shared by the display and the digital display screen (16) set on the electric field generating device (1). It can also automatically adjust the voltage and action time of the main electric field and the auxiliary electric field in combination with the real-time temperature during freezing. The system can control the food center temperature within the range of ± 1°C of the target temperature according to the freezing characteristics of different types and volumes of food, thereby achieving precise control of the freezing process and ensuring the optimization of the freezing effect.

[0072] In this embodiment, the spatial plate-type discharge electrode (3) has the following specially designed structure:

[0073] (1) The upper side of the space plate discharge electrode (3) is wrapped with an acrylic plate with a thickness of 1 to 3 mm, and the lower side is wrapped with a perforated acrylic plate of the same thickness.

[0074] (2) The area of ​​the space plate type discharge electrode (3) is one third to one half of the cross-sectional area of ​​the metal frame discharge electrode (4).

[0075] (3) The angle of the spatial plate discharge electrode (3) is an adjustable structure, and a fine-tuning hinge and an integrated micro motor are provided to allow the spatial plate discharge electrode to automatically adjust the angle within the range of ± 10°.

[0076] In this embodiment, the installation height of the insulating base (42) is 50-200 mm. The connection point between the insulated wire and the metal frame discharge electrode (4) adopts an adaptive connection structure. The adaptive connection structure includes:

[0077] Elastic alloy contacts: can maintain good conductivity and elasticity in the temperature range of -40℃ to 20℃;

[0078] Micro pressure sensor: real-time monitoring of contact pressure at the connection point;

[0079] Automatic adjustment mechanism: Based on the feedback from the pressure sensor, the contact pressure is adjusted by a micro motor to ensure a stable connection under conditions of temperature changes and mechanical vibration.

[0080] This combined action mechanism ensures a stable connection of the electric field under conditions of temperature changes and mechanical vibrations.

[0081] The food freezing system of this embodiment also includes multiple safety protection mechanisms, including overload protection, leakage protection, ground fault detection and emergency cut-off system. Among them, overload protection can prevent the system from being damaged due to excessive current. This mechanism can cut off the power supply within milliseconds to maximize the safety of the system; the leakage protection system is equipped with a highly sensitive current monitoring device that can detect tiny leakage currents, thereby effectively avoiding the risk of electric shock to operators; ground fault detection can ensure that the system is always in a safe grounding state; the emergency cut-off system can quickly shut down all electric fields in an emergency, with a response time of less than 5 ms.

[0082] This embodiment also provides a special perforated plastic basket for food freezing, which is made of food-grade plastic material and has excellent low-temperature resistance and electrical insulation. The aperture and distribution are optimized by CFD (computational fluid dynamics) and FEM (finite element method) joint simulation, which not only optimizes the penetration effect of the electric field, but also significantly improves the uniformity of the cold air flow.

[0083] The food freezing system of this embodiment is a multi-level, three-dimensional electric field distribution structure. The combination of specially designed space plate discharge electrodes and metal frame discharge electrodes is conducive to forming a more uniform electric field distribution and improving the penetration ability of the electric field. The space plate discharge electrode uses a smooth metal plate inside to improve the uniformity and stability of the electric field, and has better conductivity. The upper side is wrapped with an acrylic plate with a thickness of 1 to 3 mm, and the lower side is wrapped with a perforated acrylic plate of the same thickness, which improves its safety performance. The metal frame discharge electrode is an adjustable structure, and the layer spacing can be adjusted according to the size of the food, ensuring the uniformity of the electric field effect during the freezing process of large quantities of food.

[0084] Example 2

[0085] This embodiment provides a freezing experiment of a specific food material using the freezing system provided in Embodiment 1, taking a whole chicken weighing 1.0-3.0 kg as the object, and describes in detail the specific operation steps and effects of the method of the present invention.

[0086] Raw material preparation: Select fresh whole chickens that have been slaughtered for no more than 3 hours. Each chicken is wrapped in a food-grade PE plastic bag. The weight of each chicken is about 1.5-2.2 kg. Precool the whole chicken to about 6 ± 1°C during the slaughter process. Put the wrapped whole chicken into a special perforated plastic basket with a size of 40 cm × 30 cm × 30 cm. Install a micro temperature sensor (accuracy ± 0.1°C) on the chicken breast and a humidity sensor (measurement error ± 0.5% RH) on the surface of the whole chicken.

[0087] Cold storage preparation: Start the cold storage system and set the temperature to -30 ± 2°C. Set the circulation fan speed to 3~6 m / s. When the cold storage temperature reaches the preset value, place the experimental group in the middle layer of the multi-layer metal rack discharge electrode, ensuring that the distance between the upper layer of food and the lower layer of the rack is 5~15 cm.

[0088] For the electric field group, the electric field system settings are as follows: start the electric field control system, and the initial parameters are set as follows: the main electric field voltage is set to 3.0~4.0 kV, the auxiliary electric field voltage is set to 2.0~3.0 kV, and the angle of the spatial plate discharge electrode is adjusted to the horizontal position (0°).

[0089] Freezing process control: Based on the multi-stage parameter control strategy and real-time monitoring data, the system automatically performs the following adjustments: During the entire process, the system automatically adjusts the angle of the spatial plate discharge electrode by 1~2° through the fine-tuning hinge every 5~10 minutes to ensure that the surface of the whole chicken is evenly affected by the electric field. When the internal temperature of the whole chicken is between 5℃ and 0℃, the main electric field voltage is set to 3.0~4.0 kV, and the auxiliary electric field voltage is set to 2.0~3.0 kV; when the internal temperature of the whole chicken is between 0℃ and -5℃, the main electric field voltage increases to 4.0~6.0 kV, and the auxiliary electric field voltage increases to 3.0~4.0 kV; when the internal temperature of the whole chicken is below -5℃, the main electric field voltage is reduced to 2.5~3.5 kV, and the auxiliary electric field voltage is reduced to 1.0~2.0 kV; when the center temperature of the whole chicken reaches the preset value, the system automatically enters the holding stage, the angle of the spatial plate discharge electrode returns to the initial position, the main electric field and the auxiliary electric field are turned off, and the circulation fan speed is reduced to the minimum value (about 0.5 m / s), waiting for the whole chicken to be shipped out.

[0090] For the control group, except for not turning on the electric field, the rest of the steps were the same as the electric field group. The control group and the electric field group were placed in the same space and frozen at the same time. An insulating partition was placed between the control group and the electric field group, and the changes in the voltage parameters of the control group were detected to ensure that the control group was not affected by the electric field.

[0091] Experimental data and analysis:

[0092] Table 1. Freezing time of whole chicken at different stages

[0093] 5℃~0℃ 0℃~-5℃ -5℃~-10℃ -10℃~-18℃ 5℃~-18℃ Control group time (min) 66.67 ± 32.15 384.33 ± 57.95 160.00 ± 31.23 215.00 ± 10.00 808.33 ± 32.15 Electric field group time (min) 36.67 ± 5.77 295.00 ± 10.00 123.33 ± 10.41 128.33 ± 24.66 596.67 ± 23.63

[0094] The temperature data of each part is recorded every 5 minutes. The specific data are shown in Table 1. Figure 2 It can be seen that the freezing rate of whole chickens in the electric field group increased by 44.99% in the 5°C to 0°C stage, 23.24% in the 0°C to -5°C stage, 22.92% in the -5°C to -10°C stage, 40.31% in the -10°C to -18°C stage, and 26.18% in the overall range (5°C to -18°C stage). In addition, the standard deviation shows that the temperature fluctuations in the electric field group during the freezing process at different stages are small.

[0095] Embodiment 3:

[0096] This embodiment takes 200 g of large yellow croaker as the object, and the specific freezing method steps are as follows:

[0097] The refrigeration equipment is a self-assembled freezer, the lowest temperature of the freezer can be set to -35°C, the freezing method is air cooling, and other devices and methods are referred to Example 2. The following steps describe in detail the application method and effect of the present invention in quick freezing of aquatic products.

[0098] Raw material preparation: Select fresh large yellow croaker, remove the scales and internal organs, take out the dorsal and ventral muscles, and cut into fish pieces with a size of 10 cm × 7 cm × 5 cm. The weight of each piece is controlled at 200 ± 5 g, and there are 6 pieces in total. Insert the temperature probe into the center of the fish piece.

[0099] Freezer precooling preparation: First, install the metal frame discharge electrode and the space plate discharge electrode inside the freezer, and connect the discharge electrode coupling DC electric field device through a wire. The space plate discharge electrode is one-half to two-thirds of the cross-sectional area of ​​the metal frame discharge electrode. Then start the freezer and set the temperature to -25~-30°C. Set the circulation fan speed to 0.4~0.6 m / s.

[0100] When the freezer temperature reached the preset temperature, the center temperature of the fish was ensured to be 15 ± 0.5°C, and the fish was placed in a small perforated plastic basket, which was then placed on a small detachable metal frame discharge electrode with a smooth surface. The electric field device was turned on 2 min after the fish was placed in the electric field group, and the control group was not turned on.

[0101] The electric field control system was started, and the initial parameters were set as follows: the main electric field voltage was 3.5-4.5 kV, and the auxiliary electric field voltage was 2.0-3.0 kV. The error range of the temperature sensor was ± 0.1°C.

[0102] After the system starts running, a segmented control strategy is adopted according to the real-time parameters displayed by the temperature sensor. During the whole process, the system automatically adjusts the angle of the spatial plate discharge electrode by 1~2° through the fine-tuning hinge every 2 minutes to ensure that the surface of the fish block is evenly affected by the electric field. In the 10°C to 0°C stage, the initial electric field parameters are kept unchanged. In the 0℃ to -5℃ stage, the main electric field voltage is increased to 4.5~5.5 kV, and the auxiliary electric field voltage is increased to 2.5~3.5 kV to accelerate the formation of internal ice crystals; in the -5℃ and below stage, the main electric field voltage is reduced to 2.0~3.0 kV, and the auxiliary electric field voltage is reduced to 1.0~2.0 kV; when the center temperature of the fish block is below -15℃, the system automatically enters the holding stage, the spatial plate discharge electrode angle is restored to the initial position, the main electric field and the auxiliary electric field are turned off, and wait for the next step of processing. The temperature data of each fish block is recorded every 2 minutes.

[0103] Experimental data and analysis:

[0104] Table 2. Freezing time of large yellow croaker at different stages

[0105] 10℃~0℃ 0℃~-5℃ -5℃~-10℃ -10℃~-15℃ 10℃~-15℃ Control group time (min) 22.67 ± 1.16 70.67 ± 1.16 20.00 ± 2.00 14.00 ± 2.00 125.33 ± 3.06 Electric field group time (min) 17.33 ± 1.16 52.67 ± 1.16 16.67 ± 1.16 12.67 ± 1.16 101.33 ± 2.31

[0106] Table 3. Juice loss rate and texture analysis of large yellow croaker after freezing

[0107] index Control group Electric field group Juice loss rate (%) 7.67 ± 0.76 2.33 ± 0.58 Hardness (N) 29.41 ± 1.42 21.69 ± 0.74 Cohesion (Ratio) 0.318 ± 0.016 0.184 ± 0.025 Elasticity (mm) 0.654 ± 0.072 0.505 ± 0.014 Adhesiveness (N) 6.63 ± 0.22 4.90 ± 0.47 Chewing property (mj) 4.47 ± 0.40 3.17 ± 0.78

[0108] The system records the temperature data of each part every 2 minutes. The specific data are shown in Table 2. Figure 3 It can be seen that the freezing rate of large yellow croaker in the electric field group increased by 23.56% in the 5°C~0°C stage, 25.47% in the 0℃~-5℃ stage, 16.65% in the -5℃~-10℃ stage, 9.5% in the -10℃~-18℃ stage, and 19.15% in the overall range (5℃~-10℃ stage). In addition, it can be seen from the standard deviation that the temperature change fluctuations in the electric field group during the freezing process at different stages were small.

[0109] As shown in Table 3, the juice loss rate of large yellow croaker in the electric field group was significantly lower than that in the control group. This was mainly due to the effect of the electric field on the mobility and hydrogen bonding pattern of water molecules, which restricted the migration of free water and prevented water loss. The texture parameters of large yellow croaker in the electric field group were all higher than those in the control group. This showed that the structural integrity of large yellow croaker was well protected. Especially in terms of hardness, viscosity and chewiness, it was shown that the electric field could stabilize myofiber proteins better and inhibit enzyme degradation more effectively than the ordinary freezing method. This stabilizing effect emphasized the role of the electric field in maintaining the recovery ability of muscle after deformation and maintaining its structural cohesion.

[0110] Energy consumption analysis: The operating power of the electric field equipment is about 100 W, which is negligible compared to the operating power of the freezer compressor of about 3000 W. The operating time of the freezer compressor in the electric field group is 63 minutes, and the operating time of the freezer compressor in the control group is 85 minutes. It can be seen that the energy consumption is reduced by about 25.9%.

[0111] Although the system and method of the present invention have been disclosed, they are by no means limited to the scope of application presented in the specification and implementation. They have the potential to be applied in various fields suitable for the present invention. For professionals who are well versed in this field, additional modifications and improvements can be easily achieved. Therefore, without departing from the general concept defined by the claims and equivalents, the present invention is by no means limited to the specific details and the illustrations shown and described herein.

[0112] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A food freezing system based on electrode coupling and multi-stage electric field, characterized in that: include: An electric field generating device (1), a cold storage (2), a space plate type discharge electrode (3) and a metal frame discharge electrode (4); the metal frame discharge electrode (4) and the space plate type discharge electrode (3) are connected to the electric field generating device (1) via an insulated wire; The portion of the metal frame discharge electrode (4) in contact with the cold storage floor is provided with an insulating base (42); A shelf plate (41) is arranged on the metal frame discharge electrode (4), and the frozen food is placed in a perforated plastic container and placed on the shelf plate (41).

2. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: The spacing between the shelf plates (41) is 5 to 50 cm.

3. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: A space plate discharge electrode (3) is arranged 0.2 to 0.8 m above the metal frame discharge electrode (4).

4. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: The electric field generating device (1) is a discharge electrode coupled direct current electric field generating device.

5. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: The electric field generating device (1) comprises: an electric field control system power supply / emergency brake device, a main electric field generating unit, a main electric field voltage regulating device, an auxiliary electric field generating unit, and an auxiliary electric field voltage regulating device; and they correspond in sequence to the electric field control system power supply / emergency brake switch (11), the main electric field control switch (12), the main electric field voltage regulating knob (14), the auxiliary electric field control switch (13), and the auxiliary electric field voltage regulating knob (15).

6. The food freezing system based on electrode coupling and multi-stage electric field according to claim 5, characterized in that: The electric field generating device (1) is also provided with a digital display screen (16) which can display real-time voltage (kV) and real-time current (mA).

7. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: The working voltage range of the main electric field generating unit is 1~12 kV; the working voltage range of the auxiliary electric field generating unit is 1~12 kV, and the main electric field generating unit and the auxiliary electric field generating unit can achieve fine adjustment of 0.1 kV.

8. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: The cold storage (2) is controlled by a cold storage control system (21). The cold storage control system (21) is provided with a cold storage main power switch (211), a temperature adjustment knob (212) and a digital display screen (213); the digital display screen (213) can display the real-time temperature in the cold storage.

9. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: The metal frame discharge electrode (4) is made of stainless steel and has 3 to 6 layers, with a spacing of 10 to 60 cm between each layer. The single-layer load-bearing capacity of the metal frame discharge electrode is not less than 100 kg, and the total load-bearing capacity is not less than 500 kg. The columns and beams of the metal frame discharge electrode are designed to be detachable, so that the number of layers and the spacing can be adjusted according to the volume of different foods.

10. The food freezing system based on electrode coupling and multi-stage electric field according to claim 1, characterized in that: The electric field generating device (1) is installed on the outer wall of the cold storage.

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