A high-frequency alternating electromagnetic field assisted low-temperature salt solution spray freezing device and method

Abstract

This invention relates to the field of food freezing, and more particularly to a high-frequency alternating electromagnetic field-assisted low-temperature salt solution spray freezing device and method, comprising a continuous conveyor, a first single-mode resonant cavity, a first spray system, a second spray system, a second single-mode resonant cavity, and a third spray system. 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 maximum ice crystal zone, accelerating ice crystal nucleation in the food. This reduces the size of ice crystals formed 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.

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:

[0003] 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.

[0004] 2. In addition, maintaining a long-term low-temperature environment and the freezing process requires a large amount of energy;

[0005] 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.

[0006] 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

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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℃.

[0012] 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.

[0013] 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℃.

[0014] 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.

[0015] Preferably, the salt solution sprayed by the first, second, and third spray systems is a food-grade solution.

[0016] Preferably, the salt solution contains a food-grade antifreeze agent.

[0017] Preferably, both the first single-mode resonator and the second single-mode resonator are designed as vertically opposed beams to increase the penetration depth.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] The beneficial effects of this invention are:

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] A method for cryogenic salt solution spraying and freezing assisted by a high-frequency alternating electromagnetic field includes the following steps:

[0027] S1. Spray aquatic products with a salt solution at -10~-20℃ to pre-cool them;

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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℃.

[0032] 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.

[0033] 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

[0034] 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;

[0035] Figure 2 This is a schematic diagram of the method flow of the present invention.

[0036] 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

[0037] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0038] like Figure 1 and Figure 2As 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.

[0039] 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.

[0040] 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.

[0041] 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℃.

[0042] 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.

[0043] 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.

[0044] The salt solution contains a food-grade antifreeze agent to improve freezing quality and prevent cell damage.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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:

[0049] S1. Spray aquatic products with a salt solution at -10~-20℃ to pre-cool them;

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] Preferably, during 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, 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 allows the flexible film to move synchronously with the food along the tunnel to provide some protection for the food. The flexible film also reduces the direct impact of the salt solution on the food.

[0055] Comparison of the technical effects of this invention with existing technologies:

[0056] Case 1: Taking peony shrimp as an example, in order to avoid blackheads and ensure the quality of freezing, ultra-low temperature freezing, -70°C cold air freezing, or liquid nitrogen spraying are required, which are costly. Based on this technology, after being caught, the shrimp are immediately placed in 0°C polyphosphate ice water to anesthetize them and increase their water retention. Then, the peony shrimp are placed on the inlet horizontal conveyor 1a and sprayed directly in the rising tunnel spiral freezer 1b with propylene glycol as the refrigerant. The shrimp go through pre-cooling, a first-stage alternating electric field treatment, spiral tunnel freezing, a second-stage alternating electric field treatment, and freezing in the descending rising tunnel spiral freezer 1b in sequence. The freezing is completed quickly in 5 stages, and the freezing time can reach 5-10 minutes, reducing the core temperature to -18 to 30°C.

[0057] Case 2: Vacuum-packed large yellow croaker, 250-400g, after bleeding and evisceration, is vacuum-packed and then individually conveyed into the freezing system via horizontal conveyor 1a. Using 20% ​​propylene glycol + 15% CaCl2 as the refrigerant, it is pre-cooled (<5℃) and then enters the first single-mode resonant cavity 2 at 433MHz with a power of 200W and a processing time of 20S. Then, it is cooled to about -2℃ by the rising tunnel spiral freezer 1b and enters the second single-mode resonant cavity 5 at 433MHz with a power of 500W and a processing time of 40S. During this period, spray treatment is maintained, and then freezing is completed through the freezing tunnel.

[0058] Case 3: The tails of crayfish are directly fed into the first single-mode resonant cavity 2 after pre-cooling. The frequency of the resonant cavity is 915 MHz and the power is 300 W. A 30% calcium chloride (adjusted to neutral) solution is used as the refrigerant (-45°C) and is sprayed inside the ascending 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 low-temperature and puncture-resistant food-grade flexible film is laid above the product and moves synchronously with the conveyor belt. After passing through the high-frequency alternating electric field resonant cavity 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%.

[0059] The present invention provides a high-frequency alternating electromagnetic field-assisted low-temperature salt solution spraying freezing device and method. By subjecting food to two-stage high-frequency alternating electric field treatment, the first stage is pre-treatment to facilitate heat transfer and freezing, and the second stage is the latent heat release stage of the maximum ice crystal zone to accelerate ice crystal nucleation in the food, thereby reducing the size of ice crystals generated during the freezing process of aquatic products, improving the texture level, taste and water holding rate of aquatic products, and effectively increasing the frozen storage time of aquatic products.

[0060] The above are only the preferred examples of the present invention and are not used 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 perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall 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 apparatus, characterized by, The application relates to a continuous conveying machine, which comprises an inlet horizontal conveying machine, an ascending tunnel spiral freezer, an intermediate horizontal conveying section, a descending tunnel spiral freezer and an outlet horizontal conveying machine connected in sequence, and the intermediate horizontal conveying section is located at the top of the continuous conveying machine. A first single-mode resonant cavity is arranged on the inlet horizontal conveying machine and used for applying an alternating electric field with a frequency of 433 MHz or 915 MHz to aquatic products; A first spraying system is arranged on the inlet horizontal conveying machine and located before the first single-mode resonant cavity, and is used for spraying a salt solution with a temperature of-10 to-20 DEG C on the aquatic products to perform precooling treatment; A second spraying system is arranged in the ascending tunnel spiral freezer and used for spraying a salt solution with a temperature of-30 to-40 DEG C on the aquatic products to perform preliminary freezing; A second single-mode resonant cavity is arranged on the intermediate horizontal conveying section and used for promoting ice crystal nucleation in a maximum ice crystal generation zone, and the working frequency is 433 MHz or 915 MHz; A third spraying system is arranged in the descending tunnel spiral freezer and used for completing final freezing by spraying a salt solution with a temperature of-40 to-50 DEG C on the aquatic products; The first single-mode resonant cavity and the second single-mode resonant cavity both use a solid-state source with a power of 0 to 3 KW as a transmitting source of the high-frequency alternating electric field. The salt solutions sprayed by the first spraying system, the second spraying system and the third spraying system are food-grade solutions.

2. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spray freezing device according to claim 1, characterized in that: Food-grade antifreezing agents are added into the salt solutions.

3. The apparatus according to claim 2, wherein the apparatus is characterized in that: The first single-mode resonant cavity and the second single-mode resonant cavity are both designed as up-and-down radiation types to increase the penetration depth.

4. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spray 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 treatment time of the aquatic products is 5 to 30 seconds.

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

6. The high-frequency alternating electromagnetic field assisted low-temperature salt solution spray freezing device according to claim 1, characterized in that: The inlet horizontal conveying machine, the ascending tunnel spiral freezer, the intermediate horizontal conveying section, the descending tunnel spiral freezer and the outlet horizontal conveying machine of the continuous conveying machine are seamlessly connected, so that the continuous conveying machine forms a continuous conveying system.

7. The apparatus according to claim 1, wherein the apparatus is characterized by: The application further discloses a method for processing aquatic products, which comprises the following steps:

8. A method of high-frequency alternating electromagnetic field-assisted cryogenic salt solution spray freezing using the high-frequency alternating electromagnetic field-assisted cryogenic salt solution spray freezing apparatus according to claim 1, characterized by, S1, spraying a salt solution with a temperature of-10 to-20 DEG C on the aquatic products to perform precooling treatment; S2, feeding the precooled aquatic products into the first single-mode resonant cavity, generating a high-frequency alternating electric field with a frequency of 433 MHz or 915 MHz in the first single-mode resonant cavity by using a solid-state source with a power of 0 to 3 KW, and treating the aquatic products in the high-frequency alternating electric field for 5 to 30 seconds; S3, feeding the aquatic products treated by the first high-frequency alternating electric field into the ascending tunnel spiral freezer, spraying a salt solution with a temperature of-30 to-40 DEG C on the aquatic products by using the second spraying system, so that the temperature of the aquatic products is reduced to-1 to-5 DEG C and the aquatic products enter a phase change stage; S4, feeding the aquatic products through the ascending tunnel spiral freezer into the intermediate horizontal conveying section, applying a second high-frequency alternating electric field to the aquatic products in the phase change stage by using the second single-mode resonant cavity, and the frequency is 433 MHz or 915 MHz, and the treatment time is 30 to 120 seconds, so that the ice crystals in the aquatic products are uniformly nucleated; ​ S5, the water product treated by secondary electric field is sent into the descending tunnel spiral freezer of the continuous conveyor, and the deep freezing is completed by spraying salt solution at-40~-50℃ during the conveying process.

9. The method according to claim 8, wherein the method is characterized by: During the spraying of salt solution on the water product, direct contact spraying is adopted for the vacuum pre-packaged food, direct contact spraying is adopted for the unpackaged food, or a low-temperature-resistant and puncture-resistant flexible film is covered on the water product, and then spraying is conducted, and the flexible film moves synchronously with the food along the tunnel.

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