Induced electric field generating device and aquatic product preservation method

Abstract

The invention discloses an induced electric field generation device and an aquatic product preservation method, and belongs to the technical field of aquatic product processing and storage. The induced electric field generating device comprises a discharge plate and a fresh-keeping container; the discharge plate comprises a plate electrode, the upper surface of the plate electrode is connected with a plurality of conical electrodes, and the bottom surface ends of the conical electrodes are connected to the plate electrode; an induction coil corresponding to the discharge plate is laid on the inner bottom surface of the fresh-keeping container; the fresh-keeping container is arranged on the plate electrode, and a distance is reserved between the top end of the conical electrode and the induction coil. According to the device, the conical electrode is welded on the plate electrode to change the plate electrode into a barb electrode, so that the intensity of an electric field is effectively increased, and the induction coil is additionally arranged, so that induction current is formed while the intensity of the electric field is increased, and the storage and fresh-keeping effects of a high-voltage alternating-current electric field are effectively enhanced. The device is particularly suitable for storage and fresh-keeping of prawns, and the blackening phenomenon of the prawns can be effectively inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of aquatic product processing and storage, and specifically relates to an induced electric field generating device and a method for preserving aquatic products. Background Art

[0002] High-voltage electric field technology is a non-thermal processing technology with the characteristics of green energy saving, enhanced heat and mass transfer, and basically no damage to the nutrients in the food itself. It has certain application potential and prospects in the field of food preservation. High-voltage electric field technology mainly includes high-voltage direct current electric field and high-voltage alternating current electric field. High-voltage alternating current will generate a changing magnetic field while generating an electric field. The electromagnetic induction phenomenon shows that changes in the magnetic field cause changes in the magnetic flux through the closed conductor loop. Charged substances undergo charge migration under the action of electromotive force and magnetic field, and induced current and induced electric field are generated in the loop. Studies have shown that induced electric fields have an inhibitory effect on the growth of microorganisms and the activation of endogenous enzymes in food, thereby effectively extending the storage period of food. Therefore, induced electric field technology will be a new food processing technology with high efficiency and a wide range of applications.

[0003] Among aquatic products, shrimps are favored by consumers because of their tender meat, delicious taste and large amount of nutrients needed by the human body. However, the high water and protein content in shrimp meat is very suitable for the growth and reproduction of microorganisms. At the same time, the activity of its own endogenous enzymes increases rapidly after the death of shrimps, resulting in a sharp decline in its freshness and corruption, which is mainly manifested as the blackening of the shrimp heads. This not only causes economic losses, but also seriously affects the food safety of consumers. The commonly used preservation methods for shrimps are mainly low-temperature preservation and chemical preservatives. However, low-temperature preservation has high requirements for the external environment and the cost of use. Excessive use of chemical preservatives will have a certain impact on the health of consumers. Therefore, it is very necessary to develop a safe, efficient and green method for preserving shrimps. Existing studies have confirmed that applying high-voltage electric field treatment can effectively extend the shelf life of shrimps and improve the quality of shrimps during storage.

[0004] However, although many studies have shown that high-voltage electric field technology is a new and effective food preservation technology, its application still has certain limitations. First, the discharge plate of the electric field must be wrapped with insulating materials, which greatly attenuates the preservation effect of the electric field. Secondly, the electrode plates of the electric field device are usually located at the top of the refrigerated space and have a certain spatial distance from the preserved food. A higher voltage (5kV and above) needs to be applied to ensure the preservation effect, which poses a great safety hazard. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the present invention provides an induced electric field generating device and a method for preserving aquatic products. The induced electric field generating device forms a contact induced electric field in a certain space. The aquatic products do not need excessively high voltage or direct contact with the discharge electrode to be preserved. The preservation effect can be achieved or enhanced, and the method is safer and more reliable.

[0006] The specific technical solutions are as follows:

[0007] One of the purposes of the present invention is to provide an induced electric field generating device, which comprises a discharge plate and a fresh-keeping container;

[0008] The discharge plate comprises a flat plate electrode, the upper surface of the flat plate electrode is connected to a plurality of conical electrodes, and the bottom end of the conical electrode is connected to the flat plate electrode;

[0009] The inner bottom surface of the fresh-keeping container is provided with an induction coil corresponding to the discharge plate;

[0010] The fresh-keeping container is arranged on the flat electrode, and a distance is left between the top of the conical electrode and the induction coil.

[0011] The above device effectively increases the intensity of the electric field by welding a conical electrode on a flat electrode to turn it into a thorn electrode; by adding an induction coil, an electric field and a magnetic field can be generated simultaneously after applying high-voltage alternating current, so that an electric field and an enhanced electric field can be formed by electromotive force on the induction coil, and an induced current is formed by cutting the magnetic flux lines through the induction coil forming a closed loop, which effectively enhances the storage and preservation effect of the high-voltage alternating current electric field. When using the above device, the aquatic product is placed in a fresh-keeping container, in direct contact with the induction coil, and the discharge plate is connected to the high-voltage alternating current. The synergistic effect of the induced electric field and the induced current is achieved through the induced electric field generating device, which is particularly suitable for the storage and preservation of shrimps and can effectively inhibit the blackening phenomenon of shrimps. In addition, the discharge plate is placed in the bottom space of the induced electric field generating device, which is not easy to be touched and has high safety.

[0012] Furthermore, the discharge plate is connected to an AC power source via a wire to generate an induced current and an induced electric field.

[0013] Furthermore, the induction coil is a closed coil, forming a closed path connected head to tail. The induction coil is preferably embedded in the inner bottom surface of the fresh-keeping container, and its layout has little effect on the fresh-keeping effect, and can be set as a wavy single-turn coil. The portion of the discharge plate with the conical electrode needs to cover the entire induction coil, that is, the orthographic projection of the induction coil on the discharge plate is completely covered by the portion with the conical electrode.

[0014] Furthermore, the conical electrodes are evenly distributed on the upper surface of the flat electrode, preferably arranged in a square array with aligned rows and columns to form a uniform and high-intensity electric field. The spacing between adjacent conical electrodes is preferably 1 to 5 cm. The height of the conical electrodes is preferably 0.5 to 1 cm; the conical electrodes are preferably conical, and the bottom diameter is preferably 0.5 to 1 cm. Preferably, 100 to 300 conical electrodes are arranged on the flat electrode.

[0015] Furthermore, the conical electrode is preferably welded to the upper surface of the flat electrode.

[0016] Furthermore, the lower surface of the flat electrode is covered with an insulating material, such as an acrylic plate; the portion of the upper surface connected to the conical electrode is not covered with an insulating material and is exposed to the air. The bottom of the discharge plate is insulated and placed in the bottom space of the electric field generating device, which is not easily touched, which effectively avoids the danger caused by high voltage electricity.

[0017] Furthermore, the flat electrode and the conical electrode are made of metal or alloy, preferably aluminum alloy, such as 5052 aluminum alloy and 6061 aluminum alloy.

[0018] Furthermore, the material of the induction coil is preferably copper wire.

[0019] Furthermore, the fresh-keeping container is made of insulating material, such as resin, silica gel or glass; preferably resin material, such as PC, PP, PE, etc. The fresh-keeping container is preferably sealed on all sides and at the bottom to prevent the juice of the aquatic product from flowing out to the discharge plate, thereby improving safety.

[0020] Furthermore, the fresh-keeping container is supported on the flat electrode by an insulating bracket so that a proper distance is left between the induction coil and the conical electrode.

[0021] Furthermore, the distance between the plane where the induction coil is located and the top of the conical electrode is preferably 1 to 5 cm.

[0022] The second object of the present invention is to provide a method for preserving aquatic products using the above-mentioned induction electric field generating device, which comprises the following steps:

[0023] Place the aquatic product in a fresh-keeping container so that the aquatic product is in direct contact with the induction coil; connect the discharge plate to an AC power source.

[0024] The aquatic product is preferably prawns. The test results show that the prawns preserved by the above method have significantly reduced blackening, significantly reduced protein degradation and fat oxidation, and effectively inhibited microbial reproduction.

[0025] Furthermore, in the above-mentioned preservation method, the output voltage of the AC power supply is preferably 1-5 kV, so that an induced current and an induced electric field are generated on the induction coil.

[0026] Furthermore, in the above-mentioned preservation method, the preservation temperature is 0-4° C. Specifically, the induction electric field generating device containing the aquatic product can be placed in a closed low-temperature environment of 0-4° C. for storage.

[0027] The beneficial effects of the present invention are as follows:

[0028] The invention welds a cone electrode on a flat electrode to make it a thorn electrode, thereby effectively increasing the intensity of the electric field. In addition, the electric field formed by the cone electrodes arranged closely and regularly is more uniform.

[0029] The present invention forms an induced current while increasing the electric field strength by adding a closed induction coil, which effectively enhances the storage and preservation effect of the high-voltage AC electric field. In addition, the induced electric field generating device of the present invention has good safety. On the one hand, the thorn discharge plate is insulated at the bottom and is placed in the bottom space of the electric field generating device, which is not easy to be touched, which effectively avoids the danger caused by high voltage electricity; on the other hand, the thorn discharge plate does not directly contact the induction coil, and the induced current formed on the induction coil is relatively weak, which will not cause potential harm to the human body.

[0030] The present invention realizes the synergistic effect of the induced electric field and the induced current through the induced electric field generating device, and applies it to the storage and preservation of shrimps, which can effectively inhibit the blackening phenomenon of shrimps and improve their storage quality. The application of the present invention has a good effect on extending the shelf life of aquatic products, especially shrimps. This result provides a new direction and a certain theoretical basis for electric field technology in the field of aquatic product preservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic structural diagram of the induced electric field generating device in Example 1 of the present invention;

[0032] Figure 2 The blackening area ratio test results of the shrimps after the preservation treatment of Example 2, Comparative Example 1 and Comparative Example 2 in the test;

[0033] Figure 3 The pH test results of the shrimps after the preservation treatment of Example 2, Comparative Example 1 and Comparative Example 2 in the test;

[0034] Figure 4 The TBARS test results of the shrimps after the fresh-keeping treatment of Example 2, Comparative Example 1 and Comparative Example 2 in the test;

[0035] Figure 5The volatile basic nitrogen test results of the shrimps after the preservation treatment of Example 2, Comparative Example 1 and Comparative Example 2 are shown in the test;

[0036] Figure 6 The total colony count test results of the shrimps after the fresh-keeping treatment of Example 2, Comparative Example 1 and Comparative Example 2 are shown in the test.

[0037] Figure 1 In: 1. Induction coil; 2. Flat electrode; 3. Conical electrode; 4. Fresh-keeping container; 5. Insulating bracket; 6. Acrylic plate; 7. Wire. DETAILED DESCRIPTION

[0038] The principles and features of the present invention are described below in conjunction with examples. The examples are only used to explain the present invention and are not used to limit the scope of the present invention.

[0039] Example 1

[0040] An induced electric field generating device, such as Figure 1 As shown, it includes a discharge plate and a fresh-keeping container 4;

[0041] The discharge plate comprises a flat electrode 2, a plurality of conical electrodes 3 are welded on the upper surface of the flat electrode 2, and the bottom end of the conical electrode 3 is connected to the flat electrode 2;

[0042] The inner bottom surface of the fresh-keeping container 4 is inlaid with an induction coil 1 arranged corresponding to the discharge plate;

[0043] The fresh-keeping container 4 is supported on the flat electrode 2 through the insulating bracket 5, and a distance is left between the top of the conical electrode 3 and the induction coil 1.

[0044] The flat electrode 2 and the conical electrode 3 are both made of 5052 aluminum alloy; there are 300 conical electrodes 3 in total, which are conical in shape, with a bottom diameter of 0.5 cm and a height of 0.5 cm. The distance between two adjacent conical electrodes is 1 cm and they are arranged neatly to form a 20×15 square array.

[0045] The fresh-keeping container 4 is made of PE material, has an open top, a flat bottom surface parallel to the flat electrode 2, and is sealed around the periphery and the bottom.

[0046] The induction coil 1 is a closed coil made of copper wire; the distance between the plane where the induction coil 1 is located and the top of the conical electrode 3 is 1 cm; the layout of the induction coil 1 is a wavy single-turn coil, and the part of the discharge plate where the conical electrode 3 is provided covers the entire induction coil 1.

[0047] The bottom of the flat electrode 2 is covered by an acrylic plate 6; the portion of the upper surface of the flat electrode 2 connected to the conical electrode 3 is not covered with insulating material and is exposed to the air.

[0048] The discharge plate can be connected to a high voltage AC power source via a wire 7 .

[0049] The steps of using the above-mentioned induction electric field generating device to preserve the shrimp Penaeus vannamei are as follows:

[0050] S1. Pretreatment: Select fresh live shrimps, kill them suddenly with crushed ice, wash them with sterile ice water at a low temperature below 18°C ​​and drain the water;

[0051] S2. Induction electric field preservation: The pre-treated shrimps are placed in a preservation container 4 so that the shrimps are in direct contact with the induction coil 1; the induction electric field generating device containing the shrimps is loaded into a refrigerator for storage; the discharge plate is connected to a high-voltage AC power supply through a wire 7; the refrigerator temperature is 2°C, and the output voltage of the discharge plate is 1000V.

[0052] Example 2

[0053] Referring to Example 1, the difference from Example 1 is that in step S2, the output voltage of the discharge plate is 3000V.

[0054] Other technical features are the same as those of Example 1.

[0055] Example 3

[0056] Referring to Example 1, the difference from Example 1 is that in step S2, the output voltage of the discharge plate is 5000V.

[0057] Other technical features are the same as those of Example 1.

[0058] Example 4

[0059] Referring to Example 1, the difference from Example 1 is that in step S2, the temperature of the refrigerator is 4°C, and the output voltage of the discharge plate is 3000V.

[0060] Other technical features are the same as those of Example 1.

[0061] Comparative Example 1

[0062] Referring to Example 1, the difference from Example 1 is that step S2 is replaced by: placing the pretreated prawns in a fresh-keeping box and storing them in a refrigerator at 2°C.

[0063] Other technical features are the same as those of Example 1.

[0064] Comparative Example 2

[0065] Referring to Example 1, the difference from Example 1 is that: the induction electric field generating device in step S2 is replaced by a loading space type electric field generating device; the loading space type electric field generating device comprises a discharge plate located on the top of the refrigerator and a fresh-keeping container (without an induction coil) arranged below the discharge plate corresponding to the discharge plate; the discharge plate is the same flat electrode as in Example 1; the discharge plate is 10 cm away from the shrimp. The refrigerator temperature and output voltage are the same as in Example 2.

[0066] Other technical features are the same as those of Example 1.

[0067] test

[0068] On the 0th day, 2nd day, 4th day, 6th day and 8th day, the shrimps in each embodiment and each comparative example were randomly sampled after the preservation treatment to measure the changes in their freshness indexes, including the blackening area, pH value, lipid oxidation value, volatile basic nitrogen and total bacterial count. Each treatment group was measured three times in parallel, and the average value was taken as the measured value of the sample. The test method and results are as follows:

[0069] 1. Determination of blackening area

[0070] The shrimps were placed under a light source and the lighting conditions of the images were kept consistent. Six identical shrimps in each group were selected for photographing, and the blackening area ratio of the shrimps was calculated using Image J software. The test results of Example 2, Comparative Example 1 and Comparative Example 2 are shown in Figure 2 . Figure 2 In the figure, the control group corresponds to Example 1, the space electric field group corresponds to Example 2, and the induced electric field group corresponds to Example 2.

[0071] The blackening of the shrimp head is the most direct sign of deterioration in shrimp quality. Figure 2 As shown in the figure, the blackening area of ​​the shrimp increases rapidly with the increase of storage time. The blackening area ratio of the shrimp in the induction electric field treatment group is significantly lower than that in the control group and the space electric field group, which is only 15.24% on the 8th day, indicating that the induction electric field treatment can effectively slow down the degree of blackening of the shrimp.

[0072] The blackening area ratios of the embodiments and the comparative examples on the 8th day are shown in Table 1.

[0073] Table 1 Blackening area ratio on the 8th day of storage

[0074] Group Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Black area ratio 32.74％ 15.24％ 13.25％ 26.41％ 52.97％ 35.66％

[0075] 2. pH value determination

[0076] The pH value of food was measured according to GB 5009.237-2016 "National Food Safety Standard for Food pH Value". Figure 3 . Figure 3 In the figure, the control group corresponds to Example 1, the space electric field group corresponds to Example 2, and the induced electric field group corresponds to Example 2.

[0077] The pH value can reflect the degree of spoilage of aquatic products and is an important indicator for evaluating the freshness of aquatic products. Figure 3 As shown, the results showed that the pH values ​​of the three groups of shrimp increased significantly during storage, while the increase in pH value of shrimp in the induced electric field treatment group was significantly lower than that in the control group and the space electric field group, indicating that the induced electric field treatment can effectively slow down the increase in pH value and spoilage during shrimp storage.

[0078] 3. Determination of lipid oxidation value (TBARS)

[0079] The spectrophotometric method described in GB 5009.181-2016 "National Food Safety Standard for Determination of Malondialdehyde in Food" was used for determination. Figure 4 . Figure 4 In the figure, the control group corresponds to Example 1, the space electric field group corresponds to Example 2, and the induced electric field group corresponds to Example 2.

[0080] TBARS value is a key indicator reflecting the degree of lipid oxidation in aquatic products. Figure 4 As shown in the figure, the results showed that the TBARS values ​​of the three groups increased over time, but during the whole storage process, the TBARS values ​​of the shrimp in the induction electric field treatment group were significantly lower than those in the control group and the space electric field group. On the 8th day of storage, the TBARS values ​​of the control group and the space electric field group were 0.33±0.04 and 0.32±0.01 mg MDA / kg, respectively, while the TBARS values ​​of the induction electric field group were only 0.28±0.03 mg MDA / kg, indicating that the induction electric field treatment can effectively inhibit the lipid oxidation of shrimp and improve the freshness of shrimp.

[0081] 4. Determination of Volatile Basic Nitrogen (TVB-N)

[0082] The microdiffusion method described in GB 5009.228-2016 "National Food Safety Standard Determination of Volatile Basic Nitrogen in Food" was used for determination. The test results of Example 2, Comparative Example 1 and Comparative Example 2 are shown in Figure 5 . Figure 5 In the figure, the control group corresponds to Example 1, the space electric field group corresponds to Example 2, and the induced electric field group corresponds to Example 2.

[0083] TVB-N is widely used as an evaluation index for the freshness of aquatic products. Figure 5As shown in the data, the TVB-N values ​​of the three groups were on an upward trend during the storage period. The TVB-N value of the control group exceeded the national standard limit (≤15 mg / 100 g) after the 8th day of storage, which was 16.05±2.25 mg / 100 g. The TVB-N value of the induction electric field treatment group was 10.64±1.37 mg / 100 g after 8 days of storage, which was significantly lower than that of the control group and the space electric field group (P<0.05). This indicates that the induction electric field treatment can effectively delay the corruption of shrimp and extend the shelf life.

[0084] 5. Determination of total colony count

[0085] The test was performed using the method described in GB 4789.2-2016 "National Food Safety Standard for Microbiological Examination of Food Colony Count". Figure 6 . Figure 6 In the figure, the control group corresponds to Example 1, the space electric field group corresponds to Example 2, and the induced electric field group corresponds to Example 2.

[0086] The total number of colonies is a key indicator for evaluating the freshness of aquatic products. Figure 6 As shown in the figure, with the extension of storage time, the total colony counts of the three groups increased significantly, while the total colony counts of shrimp in the induced electric field treatment group were significantly lower than those in the control group and the space electric field group. The value was only 5.95±0.19lg CFU / g on the 8th day of storage, indicating that the induced electric field treatment can effectively inhibit the growth of microorganisms.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An induced electric field generating device, characterized in that: It includes a discharge plate and a fresh-keeping container (4); The discharge plate comprises a flat plate electrode (2), the upper surface of the flat plate electrode (2) is connected to a plurality of conical electrodes (3), and the bottom end of the conical electrode (3) is connected to the flat plate electrode (2); The inner bottom surface of the fresh-keeping container (4) is provided with an induction coil (1) arranged corresponding to the discharge plate; The fresh-keeping container (4) is arranged on the flat electrode (2), and a distance is left between the top of the conical electrode (3) and the induction coil (1); The induction coil (1) is a closed coil.

2. The induced electric field generating device according to claim 1, characterized in that: The discharge plate is connected to an AC power source via a wire (7).

3. The induced electric field generating device according to claim 1, characterized in that: The conical electrodes (3) are evenly distributed on the upper surface of the flat electrode (2).

4. The induced electric field generating device according to claim 1, characterized in that: The lower surface of the flat electrode (2) is covered with insulating material.

5. The induced electric field generating device according to claim 1, characterized in that: The flat electrode (2) and the conical electrode (3) are both made of aluminum alloy; The induction coil (1) is made of copper wire; The fresh-keeping container (4) is made of insulating material.

6. The induced electric field generating device according to claim 1, characterized in that: The fresh-keeping container (4) is supported on the flat electrode (2) via an insulating bracket (5).

7. A method for preserving aquatic products, using the induction electric field generating device according to any one of claims 1 to 6, characterized in that: The steps include: The aquatic product is placed in a fresh-keeping container (4) so ​​that the aquatic product is in direct contact with the induction coil (1); and the discharge plate is connected to an AC power source.

8. The method for preserving aquatic products according to claim 7, characterized in that: The aquatic product is prawns.

9. The method for preserving aquatic products according to claim 7 or 8, characterized in that: The output voltage of the AC power supply is 1~5kV.

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