Freshness-maintaining systems for seafood or seafood derivatives

Abstract

To provide a system and method for maintaining the freshness of fish and shellfish or derivatives thereof, which can maintain the freshness of caught and dead fish and shellfish or derivatives thereof such as sashimi by a simple method, and further prevent the disposal of the fish and shellfish or derivatives thereof. [Solution] The freshness preservation system for seafood or seafood derivatives comprises at least one coil (30) and an alternating current supply device (40) for passing an alternating current through the coil that continuously increases and decreases in frequency in at least a portion of the frequency range of 100 Hz to 10 kHz. The freshness of the seafood or seafood derivatives is maintained by passing the alternating current through the coil while maintaining or bringing the coil and the seafood or seafood derivatives close to each other.

Description

[Technical Field]

[0001] The present invention relates to a system and method for maintaining the freshness of seafood or seafood derivatives, and is suitable for use in maintaining the freshness of caught seafood or seafood derivatives such as sashimi after death. [Background technology]

[0002] Fresh fish shops and supermarket fresh fish sections offer a variety of seafood, including fillets, sashimi, and other seafood that have been caught and procured from markets. Sushi restaurants often store sashimi such as sashimi of tuna and octopus in a refrigerated space in front of the counter. Furthermore, conveyor belt sushi restaurants transport plates of nigiri sushi, consisting of vinegared rice topped with seafood, down a conveyor belt and serve them to customers. Supermarkets also offer nigiri sushi, either individually or pre-packaged.

[0003] In these stores, it is important to maintain the freshness of the caught seafood, fillets, slices, and sashimi.

[0004] Various technologies aimed at maintaining the freshness of caught fish have been proposed (e.g., Patent Documents 1 to 3). Patent Document 1 proposes a freshness-preserving device for captured fish in which a captured fish storage tank on a fishing boat is equipped with an electrodialysis device for desalination and a refrigerator for cooling the brine in the tank. Patent Document 2 proposes a freshness-preserving device for raw fish that includes a filter box and a germicidal lamp box installed parallel to the filter box, with multiple partition plates installed in multiple stages inside each box, and a communication port formed at one end of the partition plate in each box and the other end of the adjacent partition plate. In the filter box, a cylindrical filter is installed horizontally in each filtration space defined by the partition plates, with an inlet formed at one end of the lowest filtration space. In the germicidal lamp box, a germicidal lamp is installed in each sterilization space defined by the partition plates, an outlet is formed in the highest sterilization space, and a communication passage is provided between the highest filtration space and the lowest sterilization space. Patent Document 3 proposes a fish freshness preservation device that, when storing fish in ozone ice, places ozone ice and fish in a container, seals the container, changes the pressure inside the sealed container to permeate ozone water into the fish's internal organs, and sterilizes and disinfects the fish's internal organs with the permeated ozone water before storing them in a refrigerator.

[0005] However, the freshness preservation devices described in Patent Documents 1 to 3 are not only large-scale devices, but also difficult to maintain the freshness of slices, sashimi, and the like.

[0006] A liquid treatment device for preventing scale formation and / or scale adhesion is known, which involves winding a solenoid coil around a pipe through which a liquid flows and passing an alternating current whose frequency changes continuously and repeatedly in a frequency range of approximately 700 to 3000 Hz, thereby preventing scale formation on the inner wall of the pipe and removing scale that has adhered to the inner wall of the pipe (Patent Document 4). Another water treatment device for tap water is known, and has already been put to practical use, which involves winding a solenoid coil around a water pipe and passing an alternating current whose frequency changes continuously and repeatedly in a frequency range of 3.6 to 7.5 kHz, thereby preventing scale formation on the inner wall of the water pipe and removing scale that has adhered to the inner wall of the water pipe (Patent Document 5). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Utility Model Application Publication No. 53-34791 [Patent Document 2] Japanese Utility Model Application Publication No. 55-52988 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-45298 [Patent Document 4] U.S. Patent No. 5,074,998 [Patent Document 5] Utility Model Registration No. 3224220 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the problem that this invention aims to solve is to provide a system and method for maintaining the freshness of seafood or seafood derivatives, which can maintain the freshness of caught seafood and seafood derivatives such as sashimi after death using a simple method, and thereby prevent the disposal of seafood and seafood derivatives. [Means for solving the problem]

[0009] The present inventors conducted extensive research over many years to develop a technology that would solve the above-mentioned problems. As a result, they discovered a novel effect: maintaining the freshness of fish or fish derivatives by holding them in close proximity to each other while passing a similar alternating current through a coil similar to that used in the tap water treatment device described in Patent Document 5, or by bringing the coil and the fish or fish derivatives into close proximity to each other. As will be described in detail below, the freshness of fish or fish derivatives can be evaluated using the K value. Since the freshness of shellfish, cephalopods, crustaceans, etc. can also be evaluated using the K value, it can be reasonably concluded that the above method can maintain the freshness of seafood or seafood derivatives. Based on these findings and considerations, the present invention was conceived. To the best of the inventors' knowledge, no such effect has been reported to date. The reason for this effect is currently being elucidated, but it is believed to be due to the action of a special fluctuating electromagnetic field generated by the current flowing through the coil.

[0010] That is, in order to solve the above problems, the present invention provides: at least one coil; an alternating current supply device for supplying an alternating current whose frequency repeatedly increases and decreases continuously in at least a part of a frequency range of 100 Hz to 10 kHz to the coil; and This is a system for maintaining freshness of seafood or seafood derivatives by maintaining the coil and the seafood or seafood derivatives in close proximity to each other or by bringing them close to each other while passing the AC current through the coil.

[0011] The at least a portion of the frequency range is typically within a frequency range of 4.5 kHz to 8 kHz, for example, a frequency range of 4.5 kHz to 8 kHz. The frequency of the AC current is typically increased or decreased linearly, but is not limited to this and may be increased or decreased nonlinearly. The AC current typically repeats increasing or decreasing the frequency multiple times per second within the at least a portion of the frequency range. The AC current sweeps the frequency from 100 Hz to 10 kHz, for example. The waveform of the AC current is not particularly limited and can be selected as needed, but a square wave is typically used. The current value of the AC current can be selected as needed, but is generally 1 mA to 3 A, typically 100 mA to 3 A, more typically 1 to 3 A. The coil is generally wound around at least one location on the outer circumferential surface of a support (typically made of a non-magnetic material) such as a tube or rod, but a support is not necessarily required. The coil needs to be wound around at least one location on the outer circumferential surface of the tube, but may be wound around multiple locations. The number of turns in the coil is selected appropriately depending on the diameter of the pipe, etc., but since a better effect tends to be obtained when the strength of the fluctuating electromagnetic field generated by passing an AC current through the coil is relatively large, the number of turns in the coil is generally selected to be between 10 and 20.

[0012] Methods for holding or bringing the coil and seafood or seafood derivatives in close proximity to each other include fixing the coil and holding the seafood or seafood derivatives in close proximity to it, fixing the coil and bringing the seafood or seafood derivatives in close proximity to it, or fixing the seafood or seafood derivatives and bringing the coil in close proximity to it. Specifically, for example, the coil is placed below a stand on which the seafood or seafood derivatives are placed (e.g., a display stand in a supermarket or a stand in the refrigerated space in front of the counter at a sushi restaurant). Alternatively, in markets or various stores, where seafood or seafood derivatives are transported, the coil is placed below at least one location on the transport lane. In conveyor-belt sushi restaurants, the coil is placed below at least one location on the transport lane. Alternatively, if a tunnel is installed in part of the transport lane at a conveyor-belt sushi restaurant, the coil is placed on both sides or below at least one location on the tunnel.

[0013] The distance between the coil and the fish or seafood derivative is not particularly limited, but because the stronger the fluctuating electromagnetic field generated by passing an AC current through the coil, the shorter the processing time, the closer they are generally to a distance of 30 cm or less, typically 20 cm or less, and more typically 10 cm or less. Furthermore, to fully expose the fish or seafood derivative to the fluctuating electromagnetic field, the coil and the fish or seafood derivative are generally kept close to each other for at least 1 second, typically at least 5 seconds.

[0014] If the seafood or seafood derivative is contained in a container, the coil and the container containing the seafood or seafood derivative may be held or brought into close proximity to each other, or the seafood or seafood derivative may be threaded or inserted inside a tube having the coil wound around at least one portion of its outer periphery.

[0015] Seafood includes fish, shellfish, cephalopods, crustaceans, etc. Fish are not particularly limited, and can be either saltwater or freshwater fish, and any type can be used. Examples of saltwater fish include tuna, bonito, yellowtail, flounder, and saury. Examples of freshwater fish that spend their entire lives in freshwater include carp and crucian carp. Other examples include sweetfish, eels, and salmon that enter the sea at certain times of the year. Shellfish include scallops, clams, turban shells, oysters, and clams. Examples of cephalopods include squid and octopus. Examples of crustaceans include crab and shrimp. Seafood derivatives include fillets, slices, sashimi, raw processed seafood products, and refrigerated or frozen versions of these. Raw processed seafood products are not particularly limited, and any type can be used.

[0016] The present invention also provides: A method for maintaining the freshness of seafood or seafood derivatives by passing an alternating current through at least one coil that continuously increases and decreases in frequency in at least a portion of the frequency range of 100 Hz to 10 kHz, and maintaining or bringing the coil and seafood or seafood derivatives close to each other, thereby maintaining the freshness of the seafood or seafood derivatives.

[0017] In this invention of a method for maintaining the freshness of seafood or seafood derivatives, the matters explained in relation to the invention of a system for maintaining the freshness of seafood or seafood derivatives are applicable.

[0018] The freshness of seafood or seafood derivatives can be determined using the K value, an index for evaluating the freshness of seafood. The K value is calculated by measuring the content of ATP (adenosine triphosphate)-related substances, an energy component contained in fish muscle, which increases over time after the fish's death. The formula for calculating the K value is as follows:

[0019] (1)Fish K(%) =(HxR+Hx) / (ATP+ADP+AMP+IMP+HxR+Hx)×100 However, ADP is adenosine diphosphate, AMP is adenylic acid, IMP is inosinic acid, HxR is inosine, and Hx is hypoxanthine. The K value should be below 20% for raw sashimi and below 40% for boiled or grilled fish.

[0020] (2) Shellfish, cephalopods K(%) =(HxR+Hx) / (ATP+ADP+AMP+HxR+Hx)×100

[0021] (3) Crustaceans K(%) =(HxR+Hx) / (ATP+ADP+AMP+IMP+AdR+HxR+Hx)×100 However, AdR is adenosine.

[0022] Sample preparation and measurement for K value measurement is generally carried out as follows: After collecting the lateral muscles of caught seafood, the skin and blood are removed, crushed, and placed in an extraction container. An ice-cold dilute solution of perchloric acid is added to this extraction container, and the mixture is stirred with a homogenizer to extract ATP-related substances. The pH is adjusted, the mixture is cooled on ice, and then the protein is removed with a filter. The content of ATP-related substances is then measured using a high-performance liquid chromatograph. The K value of the sample is then calculated from the measured content of ATP-related substances. [Effects of the Invention]

[0023] According to this invention, the freshness of the seafood or seafood derivatives can be maintained by passing an alternating current through the coil that continuously increases and decreases in frequency in at least a portion of the frequency range of 100 Hz to 10 kHz, while the coil and the seafood or seafood derivatives are kept close to each other or brought close to each other. [Brief explanation of the drawings]

[0024] [Figure 1A] 1 is a perspective view showing a freshness preservation system for seafood or seafood derivatives according to a first embodiment of the present invention; [Figure 1B]1 is a plan view showing the internal configuration of the upper part of the housing of the freshness preservation system for seafood or seafood derivatives according to the first embodiment of the present invention. [Figure 1C] 1 is a side view showing the internal configuration of a housing of a freshness preservation system for seafood or seafood derivatives according to a first embodiment of the present invention. [Figure 1D] 1 is a side view showing the internal configuration of the lower part of the housing of the freshness preservation system for seafood or seafood derivatives according to the first embodiment of the present invention.

[0023] FIG. [Figure 1E] 1 is a side view showing one side of the housing of a freshness preservation system for seafood or seafood derivatives according to a first embodiment of the present invention. [Figure 2] 1 is a perspective view showing a power cable for connecting the seafood or seafood derivative freshness preservation system according to the first embodiment of the present invention to an AC 100V outlet. FIG. [Figure 3A] 3 is a schematic diagram showing an example of the waveform of an alternating current applied to a coil by an alternating current supply device in the freshness preservation system for seafood or seafood derivatives according to the first embodiment of the present invention. FIG. [Figure 3B] 3 is a schematic diagram showing an example of the frequency spectrum of an alternating current applied to a coil by an alternating current supply device in the freshness preservation system for seafood or seafood derivatives according to the first embodiment of the present invention; FIG. [Figure 3C] 3 is a schematic diagram showing an example of a measured frequency spectrum of an alternating current applied to a coil by an alternating current supply device in the freshness preservation system for seafood or seafood derivatives according to the first embodiment of the present invention; FIG. [Figure 4] 1 is a perspective view illustrating a method of using the system for preserving freshness of seafood or seafood derivatives according to a first embodiment of the present invention. FIG. [Figure 5] FIG. 10 is a schematic diagram showing a freshness preservation system for seafood or seafood derivatives according to a second embodiment of the present invention. [Figure 6] FIG. 4 is a cross-sectional view showing a processing stick of a freshness preservation system for seafood or seafood derivatives according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a perspective view illustrating a method of using the freshness preservation system for seafood or seafood derivatives according to the second embodiment of the present invention. [Figure 8A] FIG. 10 is a perspective view showing an example in which the freshness preservation system for seafood or seafood derivatives according to the third embodiment of the present invention is applied to the conveyor lane of a conveyor belt sushi restaurant. [Figure 8B] FIG. 10 is a side view showing an example in which the freshness preservation system for seafood or seafood derivatives according to the third embodiment of the present invention is applied to the conveyor lane of a conveyor belt sushi restaurant. [Figure 9] 1 is a photograph used as a drawing to show a simply configured freshness preservation system for seafood or seafood derivatives used in the K value measurement test in Examples 1 and 2. [Figure 10] 1 is a photograph used as a drawing to show a simply configured freshness preservation system for seafood or seafood derivatives used in the K value measurement test in Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, modes for carrying out the invention (hereinafter referred to as "embodiments") will be described.

[0026] First Embodiment [Freshness preservation system for seafood or seafood derivatives] 1A, 1B, and 1C show a freshness-preserving system for seafood or seafood derivatives according to a first embodiment. FIG. 1A is a perspective view, FIG. 1B is a plan view showing the internal configuration of the upper part of the housing with the top surface of the housing omitted, and FIG. 1C is a side view showing the internal configuration with one side surface of the housing omitted. As shown in FIGS. 1A, 1B, and 1C, in this freshness-preserving system for seafood or seafood derivatives, the interior space of a rectangular parallelepiped housing 10 is divided into upper and lower spaces by a magnetic shield plate 11. In the space above the magnetic shield plate 11, a tube 20 is installed parallel to one side of the housing 10 and is mounted on the magnetic shield plate 11 via support members 21 and 22 that support both ends of the tube 20. A solenoid coil 30 is wound around the outer periphery of the tube 20, excluding both ends. In the space below the magnetic shield plate 11, an AC current supply device 40 is installed on the bottom of the housing 10 to supply AC current to the coil 30. 1D shows the space below the magnetic shield plate 11 of the housing 10. The magnetic shield plate 11 can be made of a conventionally known material, such as soft magnetic iron, silicon steel, permalloy, or amorphous magnetic material.

[0027] The coil 30 wound around the outer periphery of the tube 20 is connected to the output terminal of the AC power supply device 40 by a cable 41 passing through holes 11a and 11b in the magnetic shield plate 11. The coil 30 is formed by spirally winding the cable 41. The power cable 42 of the AC power supply device 40 is connected to a power connector 60 attached to the side of the housing 10 via a rocker switch 50 attached to the side of the housing 10. FIG. 1E shows the side of the housing 10 with the rocker switch 50 and power connector 60 attached. The rocker switch 50 and power connector 60 may also be attached to other sides of the housing 10. As shown in FIG. 2, a plug 44 at one end of a power cable 43 for supplying 100V AC can be connected to the power connector 60. When using the seafood or seafood derivative freshness preservation system, a plug 45 at the other end of the power cable 43 is inserted into a 100V AC outlet.

[0028] The AC current passed through coil 30 sweeps its frequency from 100 Hz to 10 kHz and has a square waveform. In this case, the frequency is linearly increased and decreased multiple times per second, typically 2 to 5 times (e.g., 3.5 times), in at least a portion of the 4.5 kHz to 8 kHz frequency range (the f1 to f2 frequency range), and this is repeated. The f1 to f2 frequency range is typically 4.5 kHz to 8 kHz. Figure 3A shows an example of this AC current waveform. As shown in Figure 3A, the maximum current value in the f1 to f2 frequency range is higher than in the 100 Hz to f1 frequency range and the f2 to 10 kHz frequency range. The maximum current value in the f1 to f2 frequency range is, for example, 2 to 3 times higher than in the 100 Hz to f1 frequency range and the f2 to 10 kHz frequency range, but is not limited to this. Figure 3B shows an example of the frequency spectrum when AC current is passed through coil 30 in this manner. As shown in Figure 3B, the AC current flowing through coil 30 has approximately the same maximum current value in the frequency range from f1 to f2. Figure 3C shows an example of a measured frequency spectrum. The frequency range from f1 to f2 is 4.5 kHz to 8 kHz. The vertical axis of this frequency spectrum represents the sound pressure measured when a pickup for measuring sound pressure is attached to the side of tube 20 around which coil 30 is wound and the electromagnetic noise generated by the AC current flowing through coil 30 is measured, and corresponds to the maximum current value of the AC current.

[0029] A processing section 12 is provided on the upper surface of the housing 10 above the coil 30. The planar shape of the processing section 12 is, for example, square, but is not limited to this and can be selected as needed. The electromagnetic field generated by passing the above-mentioned alternating current through the coil 30 is mainly present in the processing section 12 and above it. Seafood or seafood derivatives to be kept fresh are placed on or held above the processing section 12. The seafood or seafood derivatives may be placed directly on the processing section 12, or may be placed on a plastic wrap or paper plate, or a container containing the seafood or seafood derivatives may be placed on the processing section 12.

[0030] The processing unit 12 is made of a non-magnetic material, such as plastic or aluminum. The housing 10 other than the processing unit 12 may be made of a non-magnetic material or a magnetic material.

[0031] [Method of using a freshness maintenance system for seafood or seafood derivatives] The method of using this system for preserving freshness of seafood or seafood derivatives is as follows. The plug 44 at one end of the power cable 43 shown in FIG. 2 is connected to the power connector 60 of the housing 10, the plug 45 at the other end of the power cable 43 is inserted into a 100V AC outlet, and the rocker switch 50 is turned on. While the AC current supply 40 is passing the AC current through the coil 30, the seafood or seafood derivative 70 to be preserved is placed directly on the processing section 12, placed in a container such as a cup or plate, or brought close to the processing section 12, as shown in FIG. 4. For example, the coil 30 and the seafood or seafood derivative 70 are brought close to each other, for example, within a distance of 10 cm, and maintained in this state for a certain period of time, for example, at least 1 second, typically at least 10 seconds. This allows the freshness of the seafood or seafood derivative 70 to be maintained.

[0032] As described above, according to the freshness preservation system for seafood or seafood derivatives of the first embodiment, the freshness of the seafood or seafood derivatives 70 can be maintained by applying a predetermined alternating current to the coil 30 wound around the tube 20 using the alternating current supply device 40, while the coil 30 and the seafood or seafood derivatives 70 are brought close to each other in the processing device 12 and processed in a fluctuating electromagnetic field. This eliminates the need to discard seafood or seafood derivatives 70 that have lost their freshness. Furthermore, this freshness preservation system for seafood or seafood derivatives can be easily configured using the coil 30 wound around the tube 20, the alternating current supply device 40, etc.

[0033] Second Embodiment [Freshness preservation system for seafood or seafood derivatives] FIG. 5 shows a freshness preservation system for seafood or seafood derivatives according to a second embodiment. As shown in FIG. 5, this freshness preservation system for seafood or seafood derivatives includes an alternating current supply device 40 and a stepped cylindrical stick 80 that can be held by a user's hand. The alternating current supply device 40 is the same as the alternating current supply device 40 used in the first embodiment. The alternating current supply device 40 and the stick 80 are connected to each other by a power cable 90. The stick 80 has a processing portion 81 at the front and a grip portion 82 at the rear. The diameter of the grip portion 82 is smaller than the diameter of the processing portion 81. The grip portion 82 is thick enough to be held by a user's hand.

[0034] A longitudinal cross section of the stick 80 is shown in Figure 6. As shown in Figure 6, a solenoid coil 30 wound around the outer surface of a tube 20 is installed inside the processing section 81 of the stick 80, similar to the freshness preservation system for seafood or seafood derivatives according to the first embodiment. Both ends of the tube 20 are supported by support members (not shown) provided on the inner wall of the processing section 81. The coil 30 is formed by spirally winding a cable 41. Both ends of the cable 41 are connected to two wires constituting a power cable 90 via rocker switches 50 attached to the side of the upper part of the gripping section 82.

[0035] [Method of using a freshness maintenance system for seafood or seafood derivatives] The method of using this system for preserving freshness of seafood or seafood derivatives is as follows. The plug 44 at one end of the power cable 43 shown in FIG. 2 is connected to the power connector 60 of the alternating current supply device 40, the plug 45 at the other end of the power cable 43 is inserted into a 100V AC outlet, and the rocker switch 50 on the side of the handle 82 of the stick 80 is turned on. Then, while applying an alternating current to the coil 30 using the alternating current supply device 40, the side of the processing section 81 of the stick 80 is brought close to the seafood or seafood derivative 70 whose freshness is to be preserved, as shown in FIG. 7 . For example, the processing section 81 and the seafood or seafood derivative 70 are brought close to each other, for example, within 10 cm, and this state is maintained for a certain period of time, for example, at least 1 second, typically at least 10 seconds, during which the seafood or seafood derivative 70 is processed by the fluctuating electromagnetic field generated by the alternating current flowing through the coil 30. This process preserves the freshness of the seafood or seafood derivative 70.

[0036] As described above, according to the freshness preservation system for seafood or seafood derivatives of the second embodiment, the freshness of the seafood or seafood derivatives 70 can be maintained by having the user hold the handle 82 of the stick 80 in their hand and bring the side of the processing section 81 close to the seafood or seafood derivatives 70 while a predetermined alternating current is applied by the alternating current supply device 40 to the coil 30 built into the processing section 81 of the stick 80. This eliminates the need to discard seafood or seafood derivatives 70 that have lost their freshness. Furthermore, this freshness preservation system for seafood or seafood derivatives can be easily constructed, as it can be made up of the stick 80 built into the coil 30 wound around the tube 20 and the alternating current supply device 40.

[0037] Third Embodiment [Freshness preservation system for seafood or seafood derivatives] In the third embodiment, a freshness preservation system for seafood or seafood derivatives is applied to the conveyor lanes of a conveyor belt sushi restaurant.

[0038] Figures 8A and 8B show a freshness-preserving system for seafood or seafood derivatives applied to a conveyor belt at a conveyor-belt sushi restaurant. Figure 8A is a perspective view of the conveyor belt seen from diagonally above, and Figure 8B is a side view of the conveyor belt. As shown in Figures 8A and 8B, a plate 102 carrying sushi 101 is placed on conveyor belt 100, which is moved in the direction of the arrow by a conveyor mechanism (not shown). Sushi 101 consists of vinegared rice 101a topped with seafood topping 101b. A solenoid coil 30 wound around the outer periphery of a tube 20 is installed parallel to conveyor belt 100 at at least one location below conveyor belt 100. Although not shown, an AC power supply device 40 for supplying AC power to coil 30 is installed, for example, in the open space below conveyor belt 100.

[0039] [Method of using a freshness maintenance system for seafood or seafood derivatives] The method of using this system for preserving the freshness of seafood or seafood derivatives will now be described. As in the first embodiment, an alternating current is passed through the coil 30 by the alternating current supply device 40. Then, the alternating current passing through the coil 30 generates a fluctuating electromagnetic field, which processes the sushi 101 placed on the plate 102. In this way, the freshness of the seafood topping 101b of the sushi 101 can be maintained.

[0040] As described above, according to the third embodiment of the freshness preservation system for seafood or seafood derivatives, a predetermined alternating current is applied to the coil 30 installed below the conveyor lane 100 in a conveyor belt sushi restaurant by an alternating current supply device 40, while a plate 102 carrying sushi 101 is conveyed along the conveyor lane 100, thereby bringing the seafood toppings 101b of the sushi 101 closer to the coil 30, thereby maintaining the freshness of the seafood toppings 101b.

[0041] An example will be described.

[0042] 9 and 10 show a simplified freshness-keeping system for seafood or seafood derivatives used in Examples 1 and 2 described below. Fig. 9 is a photograph taken obliquely from above, and Fig. 10 is a photograph taken from above. As shown in Figs. 9 and 10, this simplified freshness-keeping system for seafood or seafood derivatives consisted of a flat, rectangular, translucent plastic container approximately 28 cm wide, 20 cm deep, and 8 cm high. An AC power supply 40 (the outline of which could be seen through the translucent lid of the container) was installed at the bottom of one side of the container. A polyvinyl chloride pipe with an inner diameter of 10 cm and a height of approximately 8.5 cm was placed on the other side of the container through a hole in the lid. A coil 30 (the outline of which could be seen through the translucent lid of the container) was tightly wound around the outer periphery of the center of the polyvinyl chloride pipe for a length of approximately 5.5 cm, and connected to AC power supply 40 via cable 41. A commercially available Dollman Shock model MS-ST manufactured by Maxim Corporation was used as AC power supply 40. Coil 30 has 15 turns, with approximately 3 turns per unit length. The waveform of the AC current passed through coil 30 is shown in FIG. 3A, with a frequency range of f1 to f2 of 4.5 kHz to 8 kHz. The frequency spectrum of this AC current is shown in FIG. 3C. The maximum current value in the frequency range of f1 to f2 is 1.58 A. An AC current was passed through coil 20 by AC current supply device 40 to generate a fluctuating electromagnetic field.

[0043] As the sample for measuring the K value, red meat fillets of bigeye tuna were used in Example 1, and medium fatty tuna fillets were used in Example 2. The K value measurement test was carried out at the Yamaguchi Prefectural Industrial Technology Center (hereinafter simply referred to as the "Center"), a local independent administrative institution, using a high-performance liquid chromatograph (Model Prominence) manufactured by Shimadzu Corporation.

[0044] The red saku of bigeye tuna was purchased in a refrigerated state at 4pm one day from a fishmonger in Miyazaki City, Miyazaki Prefecture. The fishmonger purchased the bigeye tuna from the market at 3am that same day and processed it into saku in the store at 7am. A person in charge of measurement in Miyazaki City stored the tuna in his home refrigerator on the same day, then took it out at 6am the next day and brought it to the center at 2pm that same day to measure the K value. The tuna had never been frozen before being brought in.

[0045] The refrigerated medium fatty tuna fillets were purchased at 1pm one day from a fishmonger in Ube City, Yamaguchi Prefecture. The fishmonger purchased the tuna from the market at 3am that day and processed it into medium fatty tuna fillets in the store at 7am. The measurement staff member, who was in Ube City, brought the purchased medium fatty tuna fillets, placed them in an insulated bag and cooled with ice packs, to the center at 3pm that day for measurement. They had never been frozen before bringing them in.

[0046] Example 1 As shown in Figures 9 and 10, cut pieces of lean tuna fillet were placed in a beaker. This beaker was placed inside a PVC tube of a simple freshness-keeping system for seafood or seafood derivatives, as shown in Figure 10. Then, an AC current was applied to a coil 20 wound around the outer surface of the PVC tube using an AC current supply device 40 to generate a fluctuating electromagnetic field, and treatment using this fluctuating electromagnetic field (hereinafter referred to as "DS treatment") was performed. The treatment time was 30 seconds. An electromagnetic field measuring device was placed on the side of the PVC tube shown in Figure 9 to measure the electromagnetic field near the coil 30. The electric field strength was 352 V / m and the magnetic field strength (magnetic flux density) was 7.48 μT. For comparison, a sample without DS treatment was also prepared. Then, samples with and without DS treatment were prepared and measured according to the procedures previously described.

[0047] The K value measurement results for samples with and without DS treatment, along with the amount of ATP-related substances, are shown below.

[0048] ATP-related substances (μmol / g) Without DS treatment With DS treatment ATP 0.00 0.02 ADP 0.07 0.02 AMP 0.01 0.02 IMP 6.09 11.1 HxR 0.35 0.35 Hx 0.09 0.29 K value (%) 6.7 5.4

[0049] The K value with DS treatment was 1.3 lower than that without DS treatment.

[0050] Example 2 As in Example 1, cut fillets of medium-fatty tuna were placed in a beaker, and this beaker was then placed inside a polyvinyl chloride tube of a simple freshness-keeping system for seafood or seafood derivatives, as shown in Figure 10, for DS treatment. The treatment time was 30 seconds, as in Example 1. For comparison, a sample without DS treatment was also prepared. Then, samples with and without DS treatment were prepared and measured according to the procedure already described.

[0051] The K value measurement results for samples with and without DS treatment, along with the amount of ATP-related substances, are shown below.

[0052] ATP-related substances (μmol / g) Without DS treatment With DS treatment ATP 0.00 0.00 ADP 0.56 0.47 AMP 0.03 0.03 IMP 12.7 13.6 HxR 1.65 1.09 Hx 1.84 1.73 K value (%) 21 17

[0053] The K value with DS treatment was 4 points lower than that without DS treatment.

[0054] Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and examples, and various modifications based on the technical concept of the present invention are possible.

[0055] For example, the numerical values, configurations, shapes, materials, methods, etc. given in the above-described embodiments and examples are merely examples, and different numerical values, configurations, shapes, materials, methods, etc. may be used as needed. [Explanation of symbols]

[0056] 10...housing, 11...magnetic shielding plate, 12...processing section, 20...tube, 30...coil, 40...alternating current supply device, 41...cable, 42...power cable, 43...power cable, 50...rocker switch, 60...power connector, 70...seafood or seafood derivative, 80...stick, 81...processing section, 82...handling section, 100...conveyor lane, 101...sushi, 101a...vinegared rice, 101b...seafood toppings

Claims

1. at least one coil; an alternating current supply device for supplying an alternating current whose frequency repeatedly increases and decreases continuously in at least a part of a frequency range of 100 Hz to 10 kHz to the coil; and The coil is placed below at least one conveyor lane in a conveyor belt sushi restaurant, A system for maintaining freshness of seafood or seafood derivatives, which maintains the freshness of the seafood or seafood derivatives by transporting the seafood or seafood derivatives on the conveying lane while passing the alternating current through the coil and bringing the seafood or seafood derivatives close to the coil.

2. At least one coil; an alternating current supply device for supplying an alternating current whose frequency repeatedly increases and decreases continuously in at least a part of a frequency range of 100 Hz to 10 kHz to the coil; and The coil is placed on both sides or below at least one location of a tunnel provided in a part of a conveyor lane in a conveyor belt sushi restaurant, A system for maintaining freshness of seafood or seafood derivatives, which maintains the freshness of the seafood or seafood derivatives by transporting the seafood or seafood derivatives on the conveying lane while passing the alternating current through the coil and bringing the seafood or seafood derivatives close to the coil.

3. A freshness preservation system for seafood or seafood derivatives as described in claim 1 or 2, wherein at least a portion of the frequency range is included in the frequency range of 4.5 kHz to 8 kHz.

4. A freshness preservation system for seafood or seafood derivatives as described in claim 1 or 2, wherein at least a portion of the frequency range is 4.5 kHz to 8 kHz.

5. A system for maintaining the freshness of seafood or seafood derivatives as described in claim 1 or 2, wherein the seafood or seafood derivatives are caught seafood, fillets, slices, sashimi, raw processed seafood products, or refrigerated or frozen versions of these.

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