High-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device and method

Abstract

The invention relates to the related field of food freezing, in particular to a high-frequency alternating electromagnetic field assisted low-temperature saline solution spraying and freezing device and method, and the device comprises a continuous conveyor, a first single-mode resonant cavity, a first spraying system, a second spraying system, a second single-mode resonant cavity, a third spraying system and the like. According to the method, food is treated by adopting a two-section high-frequency alternating electric field, the first section is pretreatment for adjusting a water molecule structure in the food to facilitate heat transfer freezing, and the second section is a latent heat release stage of a maximum ice crystal band to accelerate ice crystal nucleation in the food, so that the size of ice crystals generated in the freezing process of aquatic products is reduced, and the freezing efficiency of the aquatic products is improved. The texture level, the taste and the water holding rate of the aquatic products are improved, and the freezing storage time of the aquatic products is effectively prolonged.

Description

Technical Field

[0001] This invention relates to the field of food freezing, and in particular to a high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing device and method. Background Technology

[0002] With the rapid development of cold chain logistics, low temperature has become an important technology for food preservation. Frozen foods, by freezing them to below -18°C, can be stored for extended periods. Traditional freezing technologies face challenges related to energy consumption and quality that need to be addressed. Traditional frozen storage technologies suffer from the following problems: 1. Low freezing rate can easily lead to the formation of large ice crystals inside food, which can easily puncture the cell membranes / walls of food, resulting in loss of juices, soft texture, and loss of flavor and nutrients after thawing. 2. In addition, maintaining a long-term low-temperature environment and the freezing process requires a large amount of energy; 3. Although many new physical technologies are currently being used to assist in the freezing process, such as electric field-assisted freezing, magnetic field-assisted freezing, and even ultrasonic-assisted freezing, most of these physical-assisted freezing technologies are still in the laboratory stage and require liquid nitrogen freezing, which presents a challenge for industrial scale-up. 4. Existing electric field assisted freezing has begun to be tested on shelves, but it requires a large number of upper and lower electrode plates to ensure contact with food in order to achieve the desired effect. It also has limitations on the size of the food. As for magnetic field assisted freezing, a strong magnetic field requires a large current electromagnetic coil, which consumes a lot of energy. Furthermore, the application of these technologies can only be used in cold storage and cannot be used for mobile products. Summary of the Invention

[0003] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device and method to solve the above-mentioned technical problems.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device, comprising a continuous conveyor, a first single-mode resonant cavity, a first spraying system, a second spraying system, a second single-mode resonant cavity, and a third spraying system. The continuous conveyor comprises an inlet horizontal conveyor, an ascending tunnel spiral freezer, an intermediate horizontal conveying section, a descending tunnel spiral freezer, and an outlet horizontal conveyor connected in sequence. The intermediate horizontal conveying section is located at the top of the continuous conveyor. The first single-mode resonant cavity is installed on the inlet horizontal conveyor and is used to apply an alternating electric field with a frequency of 433MHz or 915MHz to the aquatic products. The first spraying system is installed on the inlet horizontal conveyor and located before the first resonant cavity, and is used to spray the aquatic products with a salt solution at a temperature of -10~-20℃ for pre-cooling treatment. The second spraying system is installed inside the rising tunnel spiral freezer and is used to spray a salt solution at -30~-40℃ onto aquatic products for preliminary freezing, so that the temperature of the aquatic products enters the latent heat release stage of phase change at -1~-5℃. The second single-mode resonant cavity is located on the middle horizontal transport section and operates at a frequency of 433MHz or 915MHz. It is used to promote ice crystal nucleation in the maximum ice crystal formation zone. The third spraying system is installed inside the descending tunnel spiral freezer. It completes the final freezing by spraying a salt solution at -40~-50℃ onto the aquatic products, so that the core temperature of the products drops to below -18℃. Both the first and second single-mode resonant cavities use a 0~3KW solid-state source as the emission source for the high-frequency alternating electric field.

[0005] Preferably, the salt solution sprayed by the first, second, and third spray systems is a food-grade solution.

[0006] Preferably, the salt solution contains a food-grade antifreeze agent.

[0007] Preferably, both the first single-mode resonator and the second single-mode resonator are designed as top-to-bottom opposing beams to increase the penetration depth.

[0008] Preferably, the length of the first single-mode resonant cavity is 1 to 3 meters, and the processing time for aquatic products is 5 to 30 seconds.

[0009] Preferably, the length of the second single-mode resonant cavity is 1 to 5 meters, and the processing time for aquatic products is 30 to 120 seconds.

[0010] Preferably, the inlet horizontal conveyor, the rising tunnel spiral freezer, the intermediate horizontal conveyor section, the falling tunnel spiral freezer, and the outlet horizontal conveyor of the continuous conveyor are seamlessly connected, so that the continuous conveyor forms a continuous conveying system, realizing uninterrupted feeding, processing and discharging of aquatic products.

[0011] The beneficial effects of this invention are: 1. This invention employs a two-stage high-frequency alternating electric field treatment on food. The first stage is a pretreatment to adjust the water molecule structure in the food, making it more conducive to heat transfer and freezing. The second stage is the latent heat release stage of the largest ice crystal zone, which accelerates the nucleation of ice crystals in the food. This reduces the size of ice crystals generated during the freezing process of aquatic products, improves the texture, taste and water retention of aquatic products, and effectively increases the frozen storage time of aquatic products.

[0012] 2. The first and second single-mode resonant cavities of this invention employ a high-frequency alternating electric field with a frequency of 433MHz or 915MHz. Designing a single-mode resonant cavity at this frequency ensures a uniform electric field distribution, reduces energy reflection and loss, and further improves the penetration efficiency of the electric field for aquatic products of different thicknesses and shapes, ensuring the internal processing effect. The first and second single-mode resonant cavities adopt an up-and-down opposing design. This design, through bidirectional electric field superposition, can effectively enhance the penetration depth of the high-frequency alternating electric field for aquatic products, optimize the piercing depth of food, improve the uniformity of food freezing, and increase the freezing speed of food.

[0013] 3. The present invention uses a stepwise reduction in the salt solution used in the first, second and third spray systems, which complements the two high-frequency electromagnetic fields. This not only utilizes the electromagnetic fields to accelerate the microscopic changes inside the food, but also uses the low-temperature salt solution to quickly remove heat from the food, which helps to improve the freezing speed of the food and improve the stability of the food quality.

[0014] 4. The entire process of this invention is designed for continuous production, overcoming the current problem of small scale and inability to mass-produce various electromagnetically assisted freezing methods. The brine spray freezing method replaces the traditional air cooling, and the freezing speed is second only to liquid nitrogen. While significantly reducing costs, it improves the freezing rate and product quality. The freezing process does not require a high-current electromagnetic coil, which consumes a lot of energy. Furthermore, this invention is scalable and can meet the rapid freezing needs of different aquatic and livestock products by adjusting the high-frequency alternating electric field and application parameters, improving the flexibility of the device during use and expanding its application range.

[0015] A method for cryogenic salt solution spraying and freezing assisted by a high-frequency alternating electromagnetic field includes the following steps: S1. Spray aquatic products with a salt solution at -10~-20℃ to pre-cool them; S2. The pre-cooled aquatic products are sent into the first single-mode resonant cavity. A high-frequency alternating electric field of 433MHz or 915MHz is generated in the first single-mode resonant cavity through a 0~3KW solid source. The aquatic products are processed in the high-frequency alternating electric field for 5~30 seconds. S3. The aquatic products pretreated by the first high-frequency alternating electric field are sent into the rising tunnel spiral freezer. In the rising tunnel spiral freezer, the aquatic products are sprayed with a salt solution of -30~-40℃ through the second spray system, so that their temperature drops to -1~-5℃ and they enter the phase change stage. S4. The aquatic products pass through the rising tunnel spiral freezer and enter the intermediate horizontal conveying section. The second high-frequency alternating electric field is applied to the aquatic products in the phase change stage through the second single-mode resonant cavity. The frequency is 433MHz or 915MHz, and the processing time is 30~120 seconds, which promotes the uniform nucleation of ice crystals inside the aquatic products. S5. The aquatic products treated by the secondary electric field are sent to the outlet horizontal conveyor of the continuous conveyor. During this conveying process, they are deeply frozen by spraying a salt solution at -40~-50℃, so that the core temperature of the product drops to below -18℃.

[0016] Preferably, in the process of spraying salt solution onto aquatic products, if the food is vacuum pre-packaged, it can be sprayed directly into contact with the food; if the food is unpackaged, it can be sprayed directly into contact with the food. Alternatively, a flexible film that is resistant to low temperatures and punctures can be covered on the aquatic products, and then sprayed, with the flexible film moving synchronously with the food along the tunnel.

[0017] Preferably, in step S2, the first single-mode resonant cavity is used to adjust the water molecule structure to facilitate heat transfer and freezing. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device of the present invention; Figure 2 This is a schematic diagram of the method flow of the present invention.

[0019] Among them: continuous conveyor-1, inlet horizontal conveyor-1a, rising tunnel spiral chiller-1b, intermediate horizontal conveyor section-1c, descending tunnel spiral chiller-1d, outlet horizontal conveyor-1e, first single-mode resonant cavity-2, first spray system-3, second spray system-4, second single-mode resonant cavity-5, and third spray system-6. Detailed Implementation

[0020] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0021] like Figure 1 and Figure 2 As shown, the present invention provides a high-frequency alternating electromagnetic field assisted low-temperature salt solution spray freezing device, including a continuous conveyor 1, a first single-mode resonant cavity 2, a first spray system 3, a second spray system 4, a second single-mode resonant cavity 5, and a third spray system 6. The continuous conveyor 1 includes an inlet horizontal conveyor 1a, an ascending tunnel spiral freezer 1b, an intermediate horizontal conveying section 1c, a descending tunnel spiral freezer 1d, and an outlet horizontal conveyor 1e connected in sequence. The intermediate horizontal conveying section 1c is located at the top of the continuous conveyor 1. The continuous conveyor 1 is used for continuously conveying frozen products. The first single-mode resonant cavity 2 is set on the inlet horizontal conveyor 1a. It is equipped with a 0~3KW solid-state source as the source of high-frequency alternating electric field, which is used to apply an alternating electric field with a frequency of 433MHz or 915MHz to the aquatic products. Its length is 1~3 meters, and the processing time for the aquatic products is 5~30s. The first spraying system 3 is installed on the inlet horizontal conveyor 1a and located before the first resonant cavity, and is used to spray a food-grade salt solution with a temperature of -10~-20℃ onto aquatic products for pre-cooling treatment. The second spray system 4 is installed inside the rising tunnel spiral freezer 1b, and is used to spray a food-grade salt solution at -30~-40℃ onto aquatic products for preliminary freezing, so that the temperature of the aquatic products enters the latent heat release stage of phase change at -1~-5℃. The second single-mode resonant cavity 5 is set on the middle horizontal conveying section 1c, equipped with a 0~3KW solid-state source as the emission source of the high-frequency alternating electric field, so that the working frequency of the second single-mode resonant cavity 5 is 433MHz or 915MHz, the length of the second single-mode resonant cavity 5 is 1~5 meters, the processing time for aquatic products is 30~120S, and it is used to promote ice crystal nucleation in the maximum ice crystal formation zone inside the food. The third spraying system 6 is installed inside the descending tunnel spiral freezer 1d. It completes the final freezing by spraying aquatic products with a food-grade salt solution at -40~-50℃, so that the core temperature of the products drops to below -18℃. After the food is finally frozen, it is discharged to the outside through the outlet horizontal conveyor 1e of the continuous conveyor 1. The salt solution contains a food-grade antifreeze agent to improve freezing quality and prevent cell damage. Among them, the inlet horizontal conveyor 1a, the rising tunnel spiral freezer 1b, the intermediate horizontal conveying section 1c, the descending tunnel spiral freezer 1d, and the outlet horizontal conveyor 1e of the continuous conveyor 1 are seamlessly connected, so that the continuous conveyor 1 constitutes a continuous conveying system, realizing uninterrupted feeding, processing and discharging of aquatic products. In this embodiment, both the first single-mode resonant cavity 2 and the second single-mode resonant cavity 5 are designed as vertically opposed types to increase the penetration depth of food and improve the freezing speed of food. During operation, aquatic products are placed in the first spray system 3 for pre-cooling. After pre-cooling, the aquatic products enter the first resonant cavity for a first-stage high-frequency alternating electric field treatment. After the first-stage high-frequency alternating electric field treatment, the aquatic products enter the rising tunnel spiral freezer 1b and are conveyed upwards by the rising tunnel spiral freezer 1b. During the conveying process, the aquatic products are sprayed again by the second spray system 4, which lowers the temperature of the products to -1~-5℃. The aquatic products are continuously conveyed to the middle horizontal conveying section 1c, where the aquatic products undergo a second-stage high-frequency alternating electric field treatment by the second resonant cavity for 30~120 seconds to accelerate the nucleation of ice crystals inside the food. After the second-stage electromagnetic field treatment, the aquatic products are conveyed downwards by the descending tunnel spiral freezer 1d towards the outlet horizontal conveyor 1e. During the downward conveying process, the aquatic products undergo a third low-temperature salt solution spray freezing by the third spray system 6. At this time, the temperature of the aquatic products drops to below -18℃, and the frozen aquatic products are output through the outlet horizontal conveyor 1e, completing the freezing processing of the aquatic products.

[0022] A high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing method, using the aforementioned high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing device, includes the following steps: S1. Spray aquatic products with a salt solution at -10~-20℃ to pre-cool them; S2. The pre-cooled aquatic products are sent into the first single-mode resonant cavity 2. A high-frequency alternating electric field of 433MHz or 915MHz is generated in the first single-mode resonant cavity 2 by a 0~3KW solid source. The aquatic products are processed in the high-frequency alternating electric field for 5~30 seconds. S3. The aquatic products pretreated by the first high-frequency alternating electric field are sent into the rising tunnel spiral freezer 1b. The aquatic products are sprayed with a salt solution of -30~-40℃ through the second spray system 4 in the rising tunnel spiral freezer 1b, so that the temperature drops to -1~-5℃ and enters the phase change stage. S4. The aquatic products pass through the rising tunnel spiral freezer 1b and enter the intermediate horizontal conveying section 1c. The second high-frequency alternating electric field is applied to the aquatic products in the phase change stage through the second single-mode resonant cavity 5. The frequency is 433MHz or 915MHz, and the processing time is 30~120 seconds, which promotes the uniform nucleation of ice crystals inside the aquatic products. S5. The aquatic products treated by the secondary high-frequency alternating electric field are sent to the outlet horizontal conveyor 1e of the continuous conveyor 1. During this conveying process, the aquatic products are deeply frozen by spraying a salt solution at -40~-50℃, so that the core temperature of the products drops to below -18℃. The frozen aquatic products are then output through the outlet horizontal conveyor 1e of the continuous conveyor 1. Preferably, during the process of spraying the salt solution on aquatic products, for vacuum-prepacked foods, the salt solution can be directly sprayed onto the food in contact; for unpacked foods, direct-contact spraying can be used to more directly reduce the temperature of the aquatic products. Alternatively, a flexible film that is resistant to low temperatures and punctures can be covered on the aquatic products, and then the spraying design is adopted. The flexible film moves synchronously with the food along the tunnel, which is convenient for providing certain protection for the food. The setting of the flexible film reduces the direct impact of the salt solution on the food.

[0023] Comparison and explanation of the technical effects of the present invention and the prior art: Case 1: Taking the Peony Shrimp as an example, in order to avoid blackheads and ensure its frozen quality, ultra-low temperature freezing, -70°C cold air freezing, or liquid nitrogen spraying is required, which is costly. Based on this technology, after being caught, it is immediately placed in 0°C polyphosphate ice water to anesthetize it and increase its water retention. Then, the Peony Shrimp is placed on the inlet horizontal conveyor 1a and directly sprayed with propylene glycol as the refrigerant in the rising tunnel spiral freezer 1b; it passes through pre-cooling, first-stage alternating electric field treatment, spiral tunnel freezing, second-stage alternating electric field treatment, and freezing in the falling-rising tunnel spiral freezer 1b in sequence, and the freezing is completed quickly in 5 stages. The freezing time can reach 5 - 10 minutes, and the central temperature is reduced to -18 to -30°C. Case 2: Vacuum-packed large yellow croaker, 250 - 400g, after bleeding and evisceration, is vacuum-packed, and then the single body enters this freezing system through the oral horizontal conveyor 1a. Using 20% propylene glycol + 15% CaCl2 as the refrigerant, after pre-cooling (<5°C), it enters the first single-mode resonator 2 with a frequency of 433 MHz, the power is 200W, and the treatment time is 20S. Then, it is cooled to about -2°C by the rising tunnel spiral freezer 1b, enters the second single-mode resonator 5 with a frequency of 433 MHz, the power is 500W, and the treatment time is 40S. During this period, spraying treatment is maintained, and then it is frozen through the freezing tunnel. Case 3: The tails of crayfish, after pre-cooling, directly enter the first single-mode resonator 2 with a frequency of 915 MHz and a power of 300W. Using a 30% calcium chloride (adjusted to neutral) solution as the refrigerant (-45°C), it is sprayed inside the rising tunnel spiral freezer 1b. The crayfish conveyor belt is designed in a "convex" shape, with a raised conveyor belt in the middle and both sides lower than the middle. A flexible food-grade film that is resistant to low temperatures and punctures is covered above the product and moves synchronously with the conveyor belt. After passing through the high-frequency alternating electric field resonator and the freezing tunnel, the freezing is completed within 15 minutes, and the effect is the same as that of -80°C liquid nitrogen treatment, and the cost can be reduced by more than 40%.

[0024] This invention provides a high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing device and method. By treating food with a two-stage high-frequency alternating electric field, the first stage is a pretreatment to facilitate heat transfer and freezing, and the second stage is the latent heat release stage of the largest ice crystal zone, which accelerates the nucleation of ice crystals in the food, thereby reducing the size of ice crystals generated during the freezing process of aquatic products, improving the texture, taste and water retention of aquatic products, and effectively increasing the frozen storage time of aquatic products.

[0025] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing device, characterized in that, include: A continuous conveyor includes an inlet horizontal conveyor, an ascending tunnel spiral chiller, an intermediate horizontal conveyor section, a descending tunnel spiral chiller, and an outlet horizontal conveyor connected in sequence, with the intermediate horizontal conveyor section located at the top of the continuous conveyor. The first single-mode resonant cavity, which is set on the inlet horizontal conveyor, is used to apply an alternating electric field with a frequency of 433MHz or 915MHz to the aquatic products. The first spraying system, which is installed on the inlet horizontal conveyor and located before the first resonant cavity, is used to spray the aquatic products with a salt solution at a temperature of -10~-20℃ for pre-cooling treatment. The second spray system, which is installed inside the rising tunnel spiral freezer, is used to spray a salt solution at -30~-40℃ onto aquatic products for preliminary freezing; The second single-mode resonant cavity, which is located on the middle horizontal transport section, operates at a frequency of 433MHz or 915MHz and is used to promote ice crystal nucleation in the maximum ice crystal formation zone. The third spray system, located inside the descending tunnel spiral freezer, completes the final freezing by spraying a salt solution at -40 to -50°C onto the aquatic products. Both the first and second single-mode resonant cavities use a 0~3KW solid-state source as the emission source for the high-frequency alternating electric field.

2. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spray freezing device according to claim 1, characterized in that: The salt solution sprayed by the first, second, and third spray systems is a food-grade solution.

3. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device according to claim 2, characterized in that: The salt solution contains a food-grade antifreeze agent.

4. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device according to claim 1, characterized in that: Both the first and second single-mode resonant cavities are designed as top-to-bottom facing cavities to increase the penetration depth.

5. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device according to claim 1, characterized in that: The length of the first single-mode resonant cavity is 1 to 3 meters, and the processing time for aquatic products is 5 to 30 seconds.

6. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device according to claim 1, characterized in that: The second single-mode resonant cavity has a length of 1 to 5 meters and a processing time of 30 to 120 seconds for aquatic products.

7. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spraying and freezing device according to claim 1, characterized in that: The inlet horizontal conveyor, the rising tunnel spiral chiller, the intermediate horizontal conveyor section, the falling tunnel spiral chiller, and the outlet horizontal conveyor of the continuous conveyor are seamlessly connected, making the continuous conveyor a continuous conveying system.

8. A method for cryogenic salt solution spraying and freezing assisted by a high-frequency alternating electromagnetic field, using the high-frequency alternating electromagnetic field-assisted cryogenic salt solution spraying and freezing device of claim 1, characterized in that, Includes the following steps: S1. Spray aquatic products with a salt solution at -10~-20℃ to pre-cool them; S2. The pre-cooled aquatic products are sent into the first single-mode resonant cavity. A high-frequency alternating electric field of 433MHz or 915MHz is generated in the first single-mode resonant cavity through a 0~3KW solid source. The aquatic products are processed in the high-frequency alternating electric field for 5~30 seconds. S3. The aquatic products pretreated by the first high-frequency alternating electric field are sent into the rising tunnel spiral freezer. In the rising tunnel spiral freezer, the aquatic products are sprayed with a salt solution of -30~-40℃ through the second spray system, so that their temperature drops to -1~-5℃ and they enter the phase change stage. S4. The aquatic products pass through the rising tunnel spiral freezer and enter the intermediate horizontal conveying section. The second high-frequency alternating electric field is applied to the aquatic products in the phase change stage through the second single-mode resonant cavity. The frequency is 433MHz or 915MHz, and the processing time is 30~120 seconds, which promotes the uniform nucleation of ice crystals inside the aquatic products. S5. The aquatic products treated by the secondary electric field are sent to the outlet horizontal conveyor of the continuous conveyor. During this conveying process, they are deeply frozen by spraying a salt solution at -40~-50℃.

9. The high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing method according to claim 8, characterized in that: In the process of spraying salt solution onto aquatic products, if the food is vacuum-packed, it can be sprayed directly into contact with the food; if the food is unpackaged, it can be sprayed directly into contact with the food. Alternatively, a flexible film that is resistant to low temperatures and punctures can be covered on the aquatic products, and then sprayed, with the flexible film moving synchronously with the food along the tunnel.

10. The high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing method according to claim 8, characterized in that: In step S2, the first single-mode resonant cavity is used to adjust the water molecule structure to facilitate heat transfer and freezing.

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