How to extend the time that fish maintains its firmness

Abstract

To provide a novel method for extending the firmness retention time of a fish body capable of extending the firmness retention time of a fish body.SOLUTION: A method for extending the firmness retention time of a fish body comprises: a spinal cord destruction step of destroying the spinal cord of the fish body; an oxygen water conditioning step of placing the fish body in water in which the dissolved oxygen amount is 200% or greater relative to the saturated dissolved oxygen amount for four hours or longer after the spinal cord destruction step; a removal step of applying an anesthetic treatment using carbon dioxide to the fish body and removing the fish body from the water after the oxygen-water conditioning step; and a perfusion treatment step of performing a perfusion treatment that introduces supersaturated oxygenated water into blood vessels of the fish body after the removal step.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for extending the time for which the firmness of a fish is maintained. [Background technology]

[0002] In the culture of eating raw fish, sashimi is valued in some regions for its distinctive freshness (firmness or texture) immediately after the fish has been killed. For example, in the Kanto region, there is a culture of eating sashimi when it is "aged," while in the Kansai and Kyushu regions, there is a culture of eating sashimi when it is "firm" immediately after the fish has been killed.

[0003] In other words, in the Kanto region, fish meat that has been in the fishery for a certain amount of time after being slaughtered and has a relatively soft texture when the umami component IMP (inosinic acid) has been produced is eaten with dark soy sauce, whereas in the Kansai and Kyushu regions, the firm texture of fish meat immediately after being slaughtered is preferred, and there is a culture of eating firm fish meat (poor in IMP) with tamari soy sauce, which contains a lot of umami components.

[0004] However, since fish meat maintains its firmness for a relatively short time, firm sashimi can only be enjoyed in limited places, such as near the production area or in stores that handle live fish.

[0005] Specifically, the sense of freshness (firmness) has already disappeared when the fish's body becomes completely rigid after being killed (complete rigidity). Because the fish is completely rigid, it may seem at first glance that the sense of freshness (firmness) is maintained, but this is not the case.

[0006] There is little clear information on how long the firmness is maintained, and it is empirically known that this varies greatly depending on the fish species. Furthermore, literature describing the relationship between firmness and texture reports that the breaking strength rapidly decreases as the firmness progresses, but the scope of application is extremely limited. In other words, because the changes in the physical properties of muscle after slaughtering cannot be quantified in detail, it is currently not possible to determine when the firmness (hard texture) that exists during this change disappears.

[0007] For example, as an index of rigidity (rigor mortis), the rigidity index calculated by the method of Bito et al. (Report of the Tokai Regional Fisheries Research Institute, Vol. 109, pp. 89-96, 1983), as described in Patent Document 1, is commonly used; however, even using this method (Bito method), it is not possible to determine when the sense of rigidity disappears.

[0008] Specifically, the Bito method involves placing half of a round fish on a stand (horizontal platform), measuring the end of the body length as the measurement point, taking measurements at appropriate time intervals (for example, every hour), and calculating the rigor index (R) using the formula in Figure 1. In Figure 1, D0 is the measurement taken immediately after death, and D is the measurement taken thereafter. The round fish to be measured are sealed in a plastic bag and stored horizontally in a designated temperature refrigerator; each time a measurement is required, they are removed from the storage cabinet, removed from the plastic bag, and placed on the stand for measurement.

[0009] Figure 2 shows an example of measuring the rigor index of farmed yellowtail, red sea bream, and flounder using the Bito method. From the graph in Figure 2, it can be seen that the time it takes for the rigor index of yellowtail, red sea bream, and flounder to reach 100% (complete rigor time) is approximately 9, 16, and 28 hours, respectively, when stored at 0°C.

[0010] However, it is not possible to read from the graph when the sense of stiffness disappears before the time for complete stiffness is reached. Also, with the Bito method, the measurement subject (specimen) must be stored, moved, and set up each time it is measured, which increases the possibility of errors. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-159539 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention was completed in light of the current situation described above, as a result of various studies conducted by the inventor using a measurement method that can determine the time when the sense of hardness disappears, and aims to provide an unprecedented method for extending the time that the sense of hardness of a fish is maintained, which can extend the time that the sense of hardness of the fish is maintained. [Means for solving the problem]

[0013] The gist of the present invention will be described.

[0014] A method for extending the time during which the firmness of a fish body is maintained, a spinal cord destruction step of destroying the spinal cord of the fish; After the spinal cord destruction process, an oxygen water curing process is performed in which the fish is placed in water having a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content for 4 hours or more. After the oxygen water curing process, a removal process is performed in which the fish is anesthetized using carbon dioxide and removed from the water. After the harvesting step, a perfusion treatment step of introducing supersaturated oxygen water into the blood vessels of the fish body is performed; The present invention relates to a method for extending the time for which the firmness of a fish is maintained, comprising the steps of:

[0015] Furthermore, in the method for extending the time during which the firmness of fish body is maintained as described in claim 1, the oxygen water curing process relates to a method for extending the time during which the firmness of fish body is maintained, characterized in that it includes a first cooling process of cooling the fish body from room temperature to 6 to 9 degrees Celsius.

[0016] Furthermore, in the method for extending the time period during which the firmness of fish body is maintained as described in claim 2, the oxygen water curing process is characterized in that it includes a second cooling process of cooling the fish body to 5°C to 8°C after the first cooling process.

[0017] In addition, in the method for extending the time period during which the firmness of fish bodies is maintained as described in claim 1, the oxygen water curing process relates to a method for extending the time period during which the firmness of fish bodies is maintained, characterized in that the fish bodies are kept in the oxygen water for a period of 4 hours or more and 24 hours or less.

[0018] In addition, in the method for extending the time period during which the firmness of fish bodies is maintained as described in claim 2, the oxygen water curing process relates to a method for extending the time period during which the firmness of fish bodies is maintained, characterized in that the fish bodies are kept in the oxygen water for a period of 4 hours or more and 24 hours or less.

[0019] In addition, in the method for extending the time period during which the firmness of fish bodies is maintained as described in claim 3, the oxygen water curing process relates to a method for extending the time period during which the firmness of fish bodies is maintained, characterized in that the fish bodies are kept in the oxygen water for a period of 4 hours or more and 24 hours or less.

[0020] In addition, in the method for extending the time during which the firmness of fish bodies is maintained as described in any one of claims 1 to 6, the oxygen water curing process relates to a method for extending the time during which the firmness of fish bodies is maintained, characterized in that the fish bodies are placed in water in which the amount of dissolved oxygen is 200% or more and 350% or less of the saturated dissolved oxygen amount.

[0021] Also, a method for extending the time during which the firmness of a fish body is maintained, an anesthetizing step of placing the fish in water containing a predetermined concentration of dissolved carbon dioxide for a predetermined period of time; After the anesthesia process, the fish is placed in mixed water having a carbon dioxide concentration of 40 mg / L to 80 mg / L and a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content for 4 hours or more. After the mixed water curing step, a taking-out step of taking the mixture out of the mixed water; After the harvesting step, a perfusion treatment step of introducing supersaturated oxygen water into the blood vessels of the fish body is performed; The present invention relates to a method for extending the time for which the firmness of a fish is maintained, comprising the steps of:

[0022] Furthermore, in the method for extending the time during which the firmness of fish body is maintained as described in claim 8, the mixed water curing process is characterized in that it includes a first cooling process of cooling the fish body from room temperature to 6 to 9 degrees Celsius.

[0023] Furthermore, in the method for extending the time period during which the firmness of fish body is maintained as described in claim 9, the mixed water curing process is characterized in that it includes a second cooling process of cooling the fish body to 5°C to 8°C after the first cooling process.

[0024] In addition, in the method for extending the time period during which the fish body maintains its firmness described in claim 8, the mixed water curing process relates to a method for extending the time period during which the fish body maintains its firmness, characterized in that the fish body is stored for more than 4 hours and less than 24 hours.

[0025] In addition, in the method for extending the time period during which the fish body maintains its firmness described in claim 9, the mixed water curing process relates to a method for extending the time period during which the fish body maintains its firmness, characterized in that the fish body is stored for more than 4 hours and less than 24 hours.

[0026] In addition, in the method for extending the time period during which the fish body maintains its firmness as described in claim 10, the mixed water curing process relates to a method for extending the time period during which the fish body maintains its firmness, characterized in that the fish body is stored for a period of 4 hours or more and 24 hours or less.

[0027] In addition, in the method for extending the time during which the firmness of fish bodies is maintained as described in any one of claims 8 to 13, the mixed water curing process relates to a method for extending the time during which the firmness of fish bodies is maintained, characterized in that the fish bodies are placed in mixed water having a carbon dioxide concentration of 50 mg / L to 70 mg / L and a dissolved oxygen content of 200% to 350% of the saturated dissolved oxygen content.

[0028] In addition, in the method for extending the time for which the sense of firmness of a fish body is maintained as described in any one of claims 8 to 13, the anesthesia process relates to a method for extending the time for which the sense of firmness of a fish body is maintained, characterized in that the fish body is placed in water with a carbon dioxide concentration of 500 mg / L to 800 mg / L for 30 seconds to 1 minute and 30 seconds.

[0029] The method for extending the time period during which the firmness of fish body is maintained, as described in any one of claims 1 to 6 and 8 to 13, is characterized in that it includes a transportation step in which the fish body is kept at 5°C to 8°C and transported after the perfusion treatment step.

[0030] Furthermore, the method for extending the time period during which the firmness of a fish body is maintained, as described in any one of claims 1 to 6 and 8 to 13, relates to a method for extending the time period during which the firmness of a fish body is maintained, characterized in that the fish body is red sea bream, and the time period during which the firmness of a fish body is maintained is 30 hours or more.

[0031] Furthermore, the method for extending the time period during which the firmness of a fish body is maintained, as described in any one of claims 1 to 6 and 8 to 13, relates to a method for extending the time period during which the fish body is yellowtail, characterized in that the time period during which the firmness of a fish body is maintained is 20 hours or more. [Effects of the Invention]

[0032] As described above, the present invention provides a novel method for extending the time for which the firmness of a fish is maintained, which can extend the time for which the firmness of a fish is maintained. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a schematic diagram illustrating the Bito method. [Figure 2] 10 is an example of measurement results of the stiffness index. [Figure 3] FIG. [Figure 4] FIG. 1 is a schematic explanatory diagram of a photographing process. [Figure 5] 10 is a photograph showing the measurement state. [Figure 6] 1 is a graph showing the measurement results of the shrinkage degree of red sea bream. [Figure 7] 1 is a graph showing measurement results of the degree of shrinkage of yellowtail. [Figure 8] FIG. 1 is a schematic diagram illustrating five curve models of shrinkage curves. [Figure 9] 1 is a graph showing the measurement results of the shrinkage, hardness, and hardness sensation of red sea bream. [Figure 10] 1 is a graph showing the measurement results of the degree of shrinkage, hardness, and hardness sensation of yellowtail. [Figure 11] 1 is a graph showing a standard model of red sea bream. [Figure 12] 1 is a graph showing a standard model of yellowtail. [Figure 13] 10 is a graph showing the degree of shrinkage of red sea bream whose hardness maintenance time has been extended. [Figure 14] 1 is a graph showing the degree of shrinkage of yellowtail whose hardness retention time has been extended. [Figure 15] 10 is a graph showing the degree of shrinkage of red sea bream whose hardness maintenance time has been extended in another example. DETAILED DESCRIPTION OF THE INVENTION

[0034] A preferred embodiment of the present invention will be briefly described below, illustrating the operation of the present invention with reference to the drawings.

[0035] After the spinal cord of the fish is destroyed, the fish is placed in high-concentration oxygen water with a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content for at least 4 hours to cure, and the cured fish is then anesthetized and removed from the water. After that, the fish is subjected to a perfusion process in which supersaturated oxygen water is introduced into the blood vessels of the fish, thereby obtaining fresh fish that maintain their firmness for an extended period of time.

[0036] In addition, after paralyzing the fish with high-concentration carbon dioxide, the fish can be placed in a mixture of low-concentration carbon dioxide and high-concentration oxygen, with a carbon dioxide concentration of 40 mg / L to 80 mg / L and a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content, for four hours or more to cure.After removing the cured fish from the water, the fish can be perfused by introducing supersaturated oxygen water into the blood vessels of the fish, thereby obtaining fresh fish with an extended period of time to maintain its firmness.

[0037] By extending the time that the firmness is maintained, it will be possible to change the costly method of transporting live fish to transporting fresh fish (fresh fish distribution).In other words, transporting fresh fish is cheaper than transporting live fish, which is expected to promote the expansion of sales channels and contribute to the reduction of CO2 emissions, which has been much called for in recent years.If the time is within the set limit, it will also contribute to the expansion of sales channels not only domestically but also overseas. [Example]

[0038] Specific embodiments of the present invention will be described with reference to the drawings.

[0039] This embodiment is a method for extending the time for which the firmness of fish bodies such as red sea bream and yellowtail is maintained.

[0040] Specifically, the method includes a spinal cord destruction step of destroying the spinal cord of the fish, an oxygen water curing step of immersing the fish in water with a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content for four hours or more after the spinal cord destruction step, a removal step of anesthetizing the fish and removing it from the water after the oxygen water curing step, and a perfusion treatment step of introducing supersaturated oxygen water into the blood vessels of the fish after the removal step.

[0041] The oxygen water curing process may include either or both of a first cooling process in which the fish bodies are cooled from room temperature (20°C to 28°C) to 6°C to 9°C (preferably 8°C to 9°C) and a second cooling process in which the fish bodies are cooled to 5°C to 8°C (preferably 8°C) after the first cooling process. In addition, the second cooling process is preferably performed slowly at a rate of about 2°C per hour.

[0042] The storage time in the oxygen water curing step is preferably 24 hours or less, and the dissolved oxygen content is preferably 350% or less.

[0043] Furthermore, this embodiment includes a transporting step of transporting the fish body while keeping it at 5°C to 8°C after the perfusion treatment step.

[0044] In this embodiment, the hardness maintenance time can be measured using the hardness measurement method described below.

[0045] The stiffness measuring method includes a preparation step of cutting the head and tail of the fish body and removing one half to prepare a half body with a vertebrae attached; a placement step of placing the half body on a placement section in a temperature-controlled room (incubator) so that the tail side hangs down; a drooping degree acquisition step of acquiring the degree of drooping of the tail side; a recording step of recording the degree of drooping for each acquisition time; and a stiffness curve creation step of creating a stiffness curve based on the degree of drooping recorded in the recording step.

[0046] Although various means can be used to acquire the degree of sagging, this embodiment further includes a photographing step of photographing the body half placed on the mounting section from a fixed position at predetermined time intervals using a photographing means, and the degree of sagging is acquired from each image taken in the photographing step. The photographing in the photographing step is performed at fixed intervals of 1 minute to 60 minutes.

[0047] Figure 3 is a schematic diagram of the preparation process, and Figure 4 is a schematic diagram of the mounting and photographing processes. In the figures, reference numeral 1 denotes the fish body, 2 denotes vertebrae, 3 denotes neural spines, 4a and 4b denote half bodies, 5 denotes markers, 6 denotes a scale (a ruler with graduated scales along the vertical direction), 7 denotes a mount as a mounting part, and 8 denotes a camera as a photographing means.

[0048] As shown in Figure 3, the preparation process begins by cutting off the head and tail of the fish body 1 (Figure 3(a) → (b)), and then removing one half of the body 4b, leaving at least the vertebrae 2 (Figure 3(b) → (c)). In this example, the one half of the body 4b is removed, leaving only the vertebrae 2 and neural spines 3. Note that other bones such as vascular spines and ribs may or may not be removed.

[0049] The tail is then cut at the end of the body length (at the base of the caudal fin), and a marker 5 is attached to the (most rearmost) vertebra 2 exposed by cutting the tail (Fig. 3(c) → (d)). Specifically, a hole is drilled in the end face of the exposed vertebra 2, and one end of the marker 5 is inserted into this hole.

[0050] In this embodiment, the marker attachment work is performed after the removal of the body half 4b, but it may be performed before removal. Also, in this embodiment, the body half 4b is removed after the head and tail are cut, but it is also possible to cut the head, remove the body half 4b, and then cut the tail.

[0051] In the mounting step, the vertebra 2 and one half 4a (specimen) with neural spine 3 is placed on a stand 7 with the vertebra 2 facing downwards so that the marker 5 faces the scale 6, and the head side of the vertebra 2 is fixed to the stand 7 with a fixing screw 9 or the like. The tail side of the one half 4a is placed on the stand 7 so that it protrudes by a predetermined length (for example, 100 mm).

[0052] The photographing step, the acquiring step, the recording step, and the stiffness curve creation step are performed as follows.

[0053] Camera 8 is installed outside the temperature-controlled room and photographs body half 4a through the glass of the temperature-controlled room, including marker 5 and scale 6. As described above, photographs are taken at regular intervals (for example, every 10 minutes), and the value indicated by the scale markings on scale 6 corresponding to the vertical position of the tip of marker 5 (stiffness; hereinafter, also referred to as contraction) is obtained manually or automatically from the photographed images (the degree of sagging is obtained from the marker and scale markings in each photographed image), and the photographing time (obtaining time) and the value indicated by the scale at that time are plotted (recorded) manually or automatically to create a stiffness curve.

[0054] The obtained firmness curve confirmed a plateau, as described below, and because the firmness was rapidly lost after the end of this plateau, it was confirmed that the firmness was maintained at least until the end of the plateau. Therefore, by checking the firmness curves of fish bodies processed using different methods, it is possible to find a processing method that can extend the end of the plateau (a method that can extend the time that the firmness is maintained). In other words, by subjecting the same species of fish farmed under similar conditions to a similar extension process before shipping, it is possible to obtain fresh fish that retains its firmness for a longer period than conventional methods.

[0055] In this embodiment, a plateau refers to a temporary stagnant period in a stiffness curve (hereinafter also referred to as a contraction curve) where the increase in stiffness with time is small.

[0056] The reasons for adopting the above method (each step) and the effects of the above method will be explained below.

[0057] As mentioned in the background art, currently, because it is unknown when fish lose their firmness, efforts are made to maintain freshness (firmness) mainly by transporting live fish. Live fish are mainly transported by ship or truck, but in the case of truck transport, the transport density is about 10-15% of the seawater volume, and the cost is extremely high compared to transporting fresh fish. Furthermore, since aquaculture sites in Japan are mainly concentrated in areas south of Kansai, the main consumption areas for live fish that are specialized for freshness are in the production areas south of Kansai.

[0058] Furthermore, in market (consumer market) brokerage, prices are set based on the auctioneer's experience, using information such as the supplier, time since slaughter, the softness (limpness) of the fish, firmness, palpation with the toes, and whether the fish is wild-caught or farmed. Even in negotiated transactions, prices are mostly set based on experience. These pricing criteria also include information that is thought to be related to the time it takes for freshness to be maintained (the firmness or crunchiness of the texture after slaughter). However, there is no information that directly determines how long freshness will be maintained. It is empirically known that flounder (Paralichthys olivaceus) loses its firmness 10 to 16 hours after slaughter, but this is largely due to the fact that it is a species with a low metabolism. Yellowtail (Seriola quinqueradiata) is a species with an active metabolism that loses its firmness 4 to 8 hours after slaughter. Because it is unsuitable for live fish transportation, most flounders are shipped fresh on ice after slaughter. In other words, the areas where farmed yellowtail can be eaten are limited due to its firm texture. However, the amberjack, a related species of yellowtail, has a low metabolism, so live fish are also transported.

[0059] Furthermore, while wild-caught and farmed fish exist in the market, wild-caught fish tend to be more highly valued than farmed fish in the Kansai region. This is due to the fact that wild-caught fish retain their freshness (firmness) for a longer period of time. The shorter freshness retention period of farmed fish is thought to be the result of selective breeding of farmed fish seedlings since aquaculture first became popular, prioritizing growth rates that allow for rapid commercialization. As a result, the majority of farmed red sea bream are artificially grown, which have a high metabolic rate and shrink faster after death than wild-caught red sea bream, resulting in a faster decline in freshness (firmness). It is empirically known that farmed red sea bream (Pagrus major) lose their firmness 4 to 8 hours after being killed, and the areas where firm farmed red sea bream can be eaten are limited.

[0060] After a certain time has passed since death (after killing), the fish reaches the complete contraction stage (complete rigor stage), at which point the sense of firmness disappears. Therefore, in order to establish a method for understanding the detailed changes in the physical properties of the fish body (lateral muscles) that progress over time after killing (when body fluid circulation stops, after decapitation), we investigated whether a correlation could be found between the stiffness curve obtained using the following method and texture (hardness, sense of firmness).

[0061] Specifically, the objectives were to eliminate errors caused by sample movement, as in the Bito method, and to perform detailed measurements without contact up to the time of thawing, and measurements were conducted under the following conditions.

[0062] Condition 1: Assuming that the contraction changes of the round occur due to the contraction of both skeletal muscles (lateral muscles) centered on the vertebrae and gravity, and that the left and right skeletal muscles interfere with each other, we measure the contraction changes of the skeletal muscles of the skin-on half of the body with the vertebrae and neural spines attached (i.e., one half of the body, i.e., one lateral muscle removed).

[0063] Condition 2: To observe the shrinkage changes of the skinned half, once it is set on a stand in a temperature-controlled room, images are observed through a window without opening the window and without contact until it hardens.

[0064] Condition 3: By using an interval camera, the measurement interval time is shortened to a minimum of approximately 10 minutes, making it possible to detect minute changes.

[0065] Condition 4: The length of the tail hanging down from the stand (extending from the stand) is set to a constant 100 mm, a 20 mm marker is placed at the tip, and measurements are taken by setting a vertical scale to correspond to the marker. As a result of numerous preliminary tests, it was confirmed that the measurement unit should be 0.5 mm and the measurement interval should be 10 min.

[0066] As shown in Figure 3, the specimen's lateral muscles are blocked by the central septum at the vertebrae and neural spines. By removing half of the lateral muscles on both sides, the specimen is left with only half of the lateral muscles attached to the non-contractile vertebrae and neural spines. This allows for sensitive detection of postmortem lateral muscle contraction (using markers and a scale) as changes in the curvature of the vertebrae are converted into changes in the curvature of the vertebrae.

[0067] After decapitating the head and tail of the specimen, the lateral muscles on the side to be measured were removed, leaving only the vertebrae and neural spines in the lateral muscles on the opposite side. A narrow hole was drilled in the caudal vertebra (the first vertebra in the tail). A sharp-tipped marker was inserted into this hole, with a length (length protruding from the hole) of 20 mm. The specimen was wrapped in plastic wrap to prevent drying and prevent errors due to drying of the body surface during long-term measurements. The length hanging from the stand (the length of the tail extending from the stand) was standardized to 100 mm. This allowed for the mutual comparison of multiple measurements. While either a vertical or protractor-type scale was acceptable, a standardized measurement method was required to compare measurement results. Figure 5 shows the measurement setup, with the scale set vertically and two stands set on the left and right, allowing for simultaneous measurement of four specimens.

[0068] The shrinkage of farmed red sea bream and farmed yellowtail was measured using the above method. Red sea bream samples weighed approximately 800-1500g, and yellowtail samples weighed approximately 4-6kg. In this case, the shrinkage range was approximately 120mm at most. By enlarging the captured image on a display, the shrinkage (rigidity scale) could be easily read in 0.5mm increments, which is the scale unit. For the images, an interval camera or video camera, capable of fixed-point observation and continuous photography or video recording at regular intervals, could be used. The measurement interval could be freely set, but after careful consideration, we decided on a 10-minute interval, which clearly identifies each change point.

[0069] The measurement results for the shrinkage of red sea bream are shown in Figure 6, and the measurement results for the shrinkage of yellowtail are shown in Figure 7. The measurement time was set to 50 hours, although this was optional. The measurement accuracy was 0.5 mm.

[0070] If the scale value at the start of the measurement (0h) is taken as the reference (0mm), the degree of shrinkage was approximately -40 to +110mm for red sea bream and -30 to 120mm for yellowtail (negative values ​​indicate that the marker was lower than the reference, and positive values ​​indicate that the marker was higher than the reference).

[0071] The measurement results showed that the contraction curve (rigor curve) of both red sea bream and yellowtail is heavily dependent on how they were handled while alive. Furthermore, the measurement results also made it easy to predict at what point in the process of postmortem contraction physical property changes occur. When comparing the degree of contraction with the complete rigidity measured by the Bito method, the degree of contraction of the entire sarcomere is displayed as a real number, providing more information. Therefore, a database was created using the degree of contraction as an index, with measurements and change points recorded over time.

[0072] Regarding shrinkage, previous books and literature have described meat and livestock as having a phase where the degree of extensibility remains constant (delay phase per-rigor), a phase where the degree of extensibility rapidly decreases (rapid phase, onset of rigor), and a phase where extensibility is lost (full rigor phase) (Bate-Smith & Bendall 1947), but no literature has been found that describes relaxation.Furthermore, there are no known literature in the fisheries industry that describes these phases.

[0073] Therefore, the above measurement results were organized and summarized for red sea bream and yellowtail into five curve models (patterns 1 to 5) shown in Figure 8, and the points where the change points can be clearly read (A to F) were given stage names as follows.

[0074] A: Early relaxation This is the stage where relaxation occurs immediately after measurement, then changes to contraction and progresses to a plateau. Some specimens do not show initial relaxation (Pattern 1).

[0075] B: Plateau position (when plateau is reached) The position where the contraction reaches a plateau, where the contraction stagnates (the amount of increase in contraction is small). Depending on the specimen, relaxation may occur during the stagnation period (patterns 2 to 5).

[0076] C: End of plateau (start of rapid contraction at end of plateau) This is the point where rapid contraction occurs (the start of the rapid systole), but it can also occur gradually. The point can be difficult to read, but measurement is possible if the measurement interval is set to about 10 minutes. Specifically, after reaching the plateau, contraction begins from a stagnant state (Pattern 1), or if the heart enters a relaxed state after reaching the plateau, contraction begins in the middle of relaxation (Patterns 2 to 5). The point where this contraction begins is defined as the plateau end position (PE (Plateau End)). The period between B and C is the plateau period, and the period between C and D is the rapid systole period.

[0077] D: Full contraction (full rigor) This is the point where the rapid contraction phase ends and the full rigor phase begins, where the contraction rate stops changing.

[0078] E: Position reached at thawing stage The point where relaxation (rigor release) begins from a state where the degree of contraction remains unchanged (the point where the rigor release period begins).

[0079] F: End of measurement When the hardening is confirmed, the measurement is terminated.

[0080] Although there was a difference in the elapsed time of the pattern between red sea bream and yellowtail, both showed the same tendency of contraction pattern. It is assumed that similar contraction patterns will be observed not only in red sea bream and yellowtail but also in other fish species. In other words, this example can be applied not only to red sea bream and yellowtail but also to other fish species.

[0081] Next, a test was conducted to investigate the correlation between the degree of shrinkage, the hardness (pressure (KPa)) measured using a texturometer, which is a plunger test, and the texture (hardness, crunchyness) measured by tasting. The measuring device and measurement conditions for the hardness test (pressure) are as follows:

[0082] Measuring equipment: Japan Measurement Systems Co., Ltd. TEX-100N plunger (20mm diameter x 12mm cylinder) Measurement conditions: Test speed 120mm / min, pressure depth 3mm, output unit KPa

[0083] As with the specimens used for the shrinkage measurement described above, half of the body with the vertebrae attached was used as the specimen for the shrinkage measurement test, and for each measurement of hardness, the boneless back meat (the back meat excluding the ventral side of the vertebrae-free half removed from the half with the vertebrae that served as the shrinkage specimen) was sliced ​​into 1cm thick slices, and measurements were taken at three locations (some overlapping) along the horizontal diaphragm (the diaphragm separating the ventral and dorsal meat) for each specimen, and the average value was calculated. By setting the measurement displacement (pressure depth) to 3mm, the specimen was not destroyed by the hardness measurement test, and the specimen after hardness measurement was used for a texture test by tasting.

[0084] For the texture test by tasting, the sample after hardness measurement was roughly divided into three strips parallel to the horizontal diaphragm so that the distribution of hardness was uniform, and the testers (3 people) evaluated the food sensitivity (hardness, crunchy feeling) by choosing one of three options (3: hard, 2: slightly hard, 1: soft). After the hardness measurement, the texture test was conducted and the total score of the testers was used as the food sensitivity test. Therefore, the total score ranged from 9 points to 3 points.

[0085] Figures 9 and 10 show the test results. Figure 9 shows the shrinkage, hardness, and food sensitivity (texture judgment level) of red sea bream, along with the approximate lines calculated using polynomials. Figure 10 shows the shrinkage, hardness, and food sensitivity of yellowtail, along with the approximate lines calculated using polynomials.

[0086] When it comes to texture, two important aspects are considered to be hardness and crunchiness. The measured hardness is thought to express hardness, but by tracing the changes in the measurement, it is also thought possible to predict the crunchiness (breaking force), and a polynomial approximation of the measured hardness was used as a prediction line for the crunchiness.

[0087] The measurement results showed that the seven measurement points for red sea bream showed a change of 33 to 10 kPa over the elapsed time (50 hours), while the eight measurement points for yellowtail showed a change of 54 to 19 kPa over the elapsed time (42 hours). Therefore, there is a difference in the measured hardness between red sea bream and yellowtail.

[0088] The approximate line shows large changes at the position of each measurement point, but when expressed as an approximate line, it can be seen that the hardness of both red sea bream and yellowtail decreases rapidly after PE (rapid contraction period).

[0089] In the food sensitivity test, no significant changes were observed in the hardness of the texture until the end of the plateau (PE), and all participants unanimously rated it at 3 points for a total of 9. After the end of the plateau (PE) (rapid contraction phase), the hardness remained constant for a certain period of time, but the subsequent changes were sometimes gradual and sometimes rapid, resulting in variations in the taste evaluation at this point. Therefore, it was predicted that the PE was the starting point for changes in hardness.

[0090] In the same test, softening progressed over time from the beginning of the rapid contraction period after the plateau, with the softening rate being faster in yellowtail than in red sea bream. This was determined to match the texture, as the hardness measurement points were plotted as a polynomial approximation line, and the yellowtail showed a more rapid change than the red sea bream. The test was observed until the complete contraction period, but it was assumed that softening would continue after the hardening period.

[0091] From the above, it was found that the hardness and eating sensitivity of both red sea bream and yellowtail are in good agreement. As shown in Figures 6 and 7, there are various patterns of shrinkage curves, but it is presumed that the time when the hardness (feeling of hardness) begins to disappear is indicated by the end of the plateau (PE) (the start of rapid shrinkage).

[0092] As a result of each of the above treatments, the hardness in texture persists up to PE in the contraction curve. Furthermore, after PE, the hardness is maintained to a certain extent until a certain time period elapses at the beginning of the rapid contraction phase. For the contraction measurement, patterns 1 to 5 shown in Figure 8 were used as models. In each case, the change from PE to the full contraction phase mostly follows a sigmoid curve, so it is assumed that the softening process from the end of the plateau (rapid contraction phase) initially progresses slowly and then progresses rapidly. Therefore, it is assumed that the texture (hardness) remains good until the end of the plateau, but that softening then progresses due to changes in rapid contraction.

[0093] The method described above makes it possible to determine the time it takes for the firmness to disappear, and we conducted various studies to find a way to extend the time the firmness is maintained using this method. If it is possible to extend the time the firmness is maintained, it would be possible to transport firm farmed yellowtail (the number one farmed fish in Japan) and red sea bream (the second most farmed fish in Japan) more widely and broaden the range of consumer preferences by transporting fresh fish without relying on live fish transportation, thereby broadening the range of consumer preferences. In other words, the firmness of yellowtail and red sea bream, Japan's major farmed fish, could be maintained for a longer period of time by transporting fresh fish rather than transporting live fish, making it possible to enjoy the unique texture previously only available immediately after slaughtering in a wide range of regions, including not only the production area but also overseas.

[0094] To investigate how to extend the plateau end position (PE), we first created standard models of red sea bream and yellowtail.

[0095] The red sea bream samples were decapitated immediately after transport in a cage truck, and 20 other fish (1.8-2.2 kg) were placed in a 3.5 m isolated cage with a pre-prepared test tank. 3The fish were released into an offshore net cage, where they were then fed and satiation-fed for two weeks after they began feeding. The sample taken the day after the final feeding was designated as day 0 of feeding deprivation, and then samples taken on days 5 and 10 of feeding deprivation, totaling four fish, were used as the standard model. The seawater temperature during the curing period was kept between 22 and 23°C. The specimens were slowly guided one by one into a collection tank installed alongside the curing cage, and isolated. They were then picked up with a dip net, and immediately decapitated on site, in an effort to minimize stress upon picking.

[0096] Immediately after picking up, each specimen was decapitated (similar to the preparation process described above) to separate the body into halves with the vertebrae attached. A hole was drilled into the caudal vertebrae, and a 1.5 mm diameter, 30 mm long needle was inserted so that the tip was 20 mm exposed, which served as a marker. The specimen was placed head-side up on a stand so that 100 mm protruded from the tail end (the site of tail amputation), and with the marker protruding 20 mm beyond that, the vertical scale value corresponding to the horizontal was read.

[0097] The results of measuring the standard model of red sea bream using the above measurement method are shown in Figure 11.

[0098] The freshness (firmness) of red sea bream is generally maintained for approximately 4 to 8 hours after slaughter. However, as shown in Figure 11, the specimen immediately after transport in a cage truck showed a PE of 1.8 h and 24 mm, indicating a rapid contraction phase. Meanwhile, the specimen the morning after feeding (day 0 after feeding) showed a prolonged PE of 9.67 h and 29 mm, although the degree of PE contraction was nearly identical to that of PA. Furthermore, the specimen on day 5 of feeding curing showed a prolonged PE of 13.17 h and 13 mm, and the specimen on day 10 of feeding curing showed a decreased PE of 15 h and 7.5 mm. Therefore, the PE range was wide, from 1.8 h to 15 h. The average value of 9.91 h was used as the PE value for the red sea bream model. The deviation was large (5.14 h), and most of the contraction curves were positive. A common feature was that the degree of contraction was almost the same when the plateau was reached (PA) and when the plateau ended (PE), but in the sample taken on the 10th day after feeding was stopped, relaxation of 0.5 mm and 0.5 mm, totaling 1 mm, was observed 7 to 8 hours after the start of measurement.

[0099] The standard model of yellowtail is as follows:

[0100] After a four-day feeding period, 5.7–6.3 kg of fish per fish were brought into the live fish boat every day. After 18 hours of curing in a curing tank at 22–23°C with saturated oxygen water, the fish were then used for testing. For sample measurements, one fish per test was scooped up with a dip net 18 hours after delivery and decapitated on the spot. Similar to the red sea bream standard model, the specimen was separated into a half body with a vertebrae inserted into a marker, which was then mounted on a platform for measurement. Figure 12 shows the test results for the yellowtail standard model group. Most of the contraction curves were positive. Furthermore, the PE was 8.14 (h) and the standard deviation was 4.25 (h), showing a large variability similar to that of the red sea bream.

[0101] Based on the above results, the model PE values ​​were determined to be 9.91±5.04 (h) for red sea bream and 8.14±4.25 (h) for yellowtail.

[0102] The principle of extending the plateau end time is explained below.

[0103] ATP obtains energy from the accumulated Cr-P and maintains a homeostatic level until PE is reached. After blood flow stops, when ATP in the sarcoplasm decreases below the homeostatic level, Ca in the sarcoplasmic reticulum is released. ++ The pump becomes less effective, and Ca continues to be released to maintain metabolism. ++ As a result, muscle contraction progresses rapidly (reaching the rapid contraction phase). Therefore, what is required to extend PE is to maintain a homeostatic level of ATP for a longer period of time, thereby increasing Ca ++ Specifically, PE can be extended by maximizing the amount of Cr-P immediately after blood flow stops and minimizing the metabolism (excitability) of the fish meat.

[0104] Methods for reducing excitability and promoting ATP production include oxygenated water therapy and oxygenated water perfusion, which are discussed below. Specifically, after the spinal cord perforation procedure (described below), oxygen is passively transported from the interstitial fluid to cells via the bloodstream, and ATP continues to be produced in the electron transport system. If excess ATP is produced, creatine (Cr) is phosphorylated to store energy as a high-energy substance, Cr-P (creatine phosphate). The energy storage capacity of Cr-P is said to be approximately 3–10 times the homeostatic value of ATP. The purpose of oxygenated water therapy is to reduce excitability (sum of metabolic levels) due to oxygen and promote ATP production. Furthermore, oxygenated water perfusion is a final treatment step in which rapid oxygenated water perfusion is performed. This allows the excitatory hormone (cortisone) secreted by the interrenal gland due to excitability during removal to be diluted and excreted outside the body with the blood before it reaches the interstitial fluid. Furthermore, oxygen dissolved in the perfusion water is supplied to the interstitial fluid, providing oxygen to cells for some time after termination. The amount of oxygen dissolved in the perfusion water of this oxygenated water perfusion represents the physical dissolved amount, and it is possible to deliver a large amount of oxygen equivalent to the amount of oxygen that binds to hemoglobin in the blood to the interstitial fluid. The concentration of the perfusion oxygenated water promotes the conversion of ADP + Pi → ATP by the electron transport system in the fish's cells after slaughter, and a high oxygen concentration within the range that maintains and promotes each homeostasis is desirable.

[0105] In addition, blood flow stops after decapitation, and oxygen in the interstitial fluid is consumed in a relatively short time, eventually stopping the electron transport system and the TCA cycle. However, in the glycolytic system, lactic acid is produced by glycogenolysis in an anaerobic environment, and a small amount of ATP continues to be produced. ++ We believe that if the pump continues to function, postmortem muscle contractions will be suppressed, leading to prolonged postmortem contractions. Therefore, it is necessary to maintain a slowly changing environment (a non-excitable environment) that does not interfere with the glycolytic pathway. Although a decrease in pH (activation of proteolytic enzymes) seems unavoidable, CO2 anesthesia at the time of delivery is thought to be necessary to slow the activity of glycolytic enzymes and stabilize the rise in the minimum pH.

[0106] The types of agitation and their recovery are detailed below.

[0107] 1. Restores energy levels (for a few hours) The main cause of energy loss is the escape movement caused by the efferent nerves that occur when handled, which consumes a large amount of ATP, resulting in a decrease in Cr-P. Recovery is relatively short, but in the case of fish, in particular, the abnormal excitement caused by prolonged stress causes an underdeveloped regulatory function, and in addition to a decrease in Cr-P, lactic acid produced in the glycolysis pathway accumulates, so if it takes a long time for lactic acid levels to recover, it may be difficult to restore homeostasis and the fish may die.

[0108] 2. Recovery of hormone levels (they decline in about 24 hours) In fish, excitement during handling causes the release of cortisone and adrenaline into the blood, which act on the sympathetic nerves and cells, causing prolonged excitement. Therefore, it is thought that the majority of the variability in contraction test results is due to the secreted hormones.

[0109] 3. Recovery of muscle contractile proteins (16 to 48 hours) Excessive exercise causes damage to myofibrils.

[0110] 4. Neurological recovery (several days to 10 days or more) In the case of fish, they learn to adapt to stimuli below their threshold, making them easy to handle, but when they are repeatedly exposed to stimuli above their threshold, serotonin is secreted, causing them to become sensitized, and further prolonged exposure to stimuli leads to long-term memory. Sensitization and long-term memory are prone to cause abnormal excitement, and both release large amounts of neurotransmitters during processing, making them unsuitable for this processing method.

[0111] 5. In the case of fish, an increase in the temperature of the nurturing water is a factor in increasing the metabolic level.

[0112] In light of the above, the following steps (1. to 4.) are considered necessary to extend the plateau end time (the time during which the hardness sensation is maintained).

[0113] 1. Spinal Cord Drilling Spinal cord perforation involves using a sharp instrument such as an awl or ice pick to perforate and destroy the sacrum (nerve bundle) of the fish's spinal cord. This causes impairment of the conduction and transmission of nerves, including the afferent nerves, efferent nerves and autonomous sympathetic nerves, after the spinal cord perforation site. However, because the respiratory center remains normal, metabolism slows down, and this technique is used to transport live fish at higher densities than conventional live fish transportation.

[0114] 2.Oxygen water curing treatment In this example, spinal cord perforation is performed to reduce metabolic rate (α), followed by a period of curing to promote the reduction of excitatory hormones released into the blood. Curing in high-concentration oxygen water also allows the fish to take in oxygen through gill respiration, resulting in the accumulation of ATP as Cr-P. This high-concentration oxygen water curing is performed by placing the fish in water with a dissolved oxygen content of 200-350% of the saturated dissolved oxygen content (e.g., a dissolved oxygen concentration of approximately 20 mg / L-30 mg / L) for at least 3-4 hours before the end of the curing period. This results in a constant upper limit of pH of approximately 7.45. Note that a dissolved oxygen content of 400% or higher is undesirable, as the plasma pH will be 7.45 or higher, resulting in respiratory alkalosis, which will prevent oxygen dissociation from hemoglobin (Hb), reduce oxygen availability, and lead to oxygen deficiency in cells.

[0115] The oxygen water curing treatment requires a curing time of approximately 4 to 24 hours, depending on the state of stress hormones in the fish. The setting of this curing time is governed by habituation and sensitization, which are characteristics specific to living organisms. In the case of farmed fish, factors such as transportation from the source, water temperature, and type of stress interact in complex ways, making it practical to use an empirical method to determine the effects. Furthermore, in exceptional cases of fish that have been stressed for an extended period of time, their long-term memory causes them to react acutely the instant they are handled, accelerating the massive consumption of Cr-P and accelerating the changes that occur when ATP is reduced. Therefore, it is important to handle the fish in a way that prevents these conditions from occurring. (Fish that have been stressed for an extended period of time enter a state of long-term memory and require a long-term period of curing (10 days or more) to recover.)

[0116] For example, when transporting net cages by towing at a speed of 1.2 km / h or less, the curing time is approximately 4 hours, and when transporting by ship or truck, the curing time is approximately 24 hours.

[0117] Furthermore, by combining the cold acclimation treatment with the treatment 3-4 hours before removal during the oxygenated water curing period, the PE can be further extended. Cold acclimation is performed by cooling the fish to a temperature 8-9°C lower than room temperature (the same as or slightly higher than water temperature, 20-28°C) over a period of 2-4 hours (cooling is carried out all at once at a rate that does not cause cold shock). If necessary, it is also possible to further cool the fish slowly to around 8°C (for example, at a rate of 2°C per hour).

[0118] Low-temperature acclimation can be carried out, for example, by dividing the inside of a fish farm with movable fences or the like, maintaining different water temperatures in each section, and sequentially moving the fish to each section (from the section with the higher water temperature to the section with the lower water temperature) and storing them there for a predetermined period of time.

[0119] 3. Pick-up processing When removing fish from the sanitary environment, it is important to minimize stress during removal. In this example, the respiratory center of the fish after sanitary conditions is normal, and the sense of smell, vision, part of the hearing, and equilibrium receptors are also considered normal. Therefore, removal must be performed below the threshold of excitement. Care must be taken to prevent the release of excitatory hormones from the anterior lobe into the blood due to excitement. Specifically, the fish are anesthetized by being placed in water containing a predetermined concentration of dissolved carbon dioxide (carbon dioxide) for a predetermined period of time before removal. While it is possible to remove the fish without anesthesia and immediately decapitate them, anesthesia is preferred because this makes the subsequent oxygenated water perfusion difficult.

[0120] 4. Oxygenated Water Perfusion Treatment After blood flow is halted, oxygen in the interstitial fluid is absorbed and consumed intracellularly, resulting in a relatively short period of anoxic conditions, shutting down the electron transport system and subsequently the TCA cycle. However, the use of Ringer's solution (perfusion fluid) with an appropriate high oxygen concentration, suitable for bony fish, can prolong the duration of cellular respiration as a means of oxygen supply. In this example, after harvesting, the fish was perfused with oxygenated water (supersaturated oxygen water prepared by diluting seawater three times with tap water, with a dissolved oxygen concentration of 20 mg / L or more) for at least two minutes. This process involves pumping perfusion water into the arteries of the fish to remove blood, while simultaneously removing blood. This increases the dissolved oxygen concentration in the interstitial fluid even after fluid flow is halted. This allows oxygen to be absorbed into cells via passive transport, resulting in continued ATP production and maintaining high Cr-P concentrations. In addition, oxygenated water perfusion treatment quickly dilutes and excretes excitatory hormones released into the blood, bloodstream, and interstitial fluid from the body, while also excreting proteolytic enzymes such as cathepsin L present in red blood cells, preventing deterioration of meat quality.

[0121] After perfusion, the brain, medulla oblongata, and spinal cord are destroyed through the nasal cavity using a piano wire, and the fish are then stored in cold seawater with a salinity of about 2% at 7-10°C for at least 30 minutes to cool their body temperature and prepare them for shipping. The transport temperature is maintained at around 5-8°C, avoiding the rigor rigor temperature range. However, once complete contraction is achieved, they are promptly stored at 0°C.

[0122] The contraction curves of red sea bream and yellowtail after each of the above treatments are shown in Figures 13 (red sea bream) and 14 (yellowtail). Figures 13 and 14 confirm that PE was extended compared to the standard models shown in Figures 11 and 12. In Figures 13 and 14, the contraction model conformed to patterns 4 or 5 shown in Figure 8. Because the interval from plateau arrival (PA) to plateau end (PE) was significantly extended, the measured contraction curves were completely different from the standard model. Notably, there were many cases where relaxation continued after plateau arrival (PA), and it is thought that in some of these cases, metabolism was lower than the ATP produced by glycolysis, causing relaxation.

[0123] These test results confirmed that it is possible to achieve a texture (freshness and firmness) that could not be achieved with conventional fresh fish by combining measures to increase Cr-P with processes to minimize metabolism, starting from the time the fish is delivered.For red sea bream, as shown in Figure 13, all shrinkage values ​​were negative, and an average PE of 33.77±2.59 (h) was stably obtained, which is about three times longer than the PE value (12.55 h) in Figure 11, making it possible to maintain a firm texture for more than 30 hours.

[0124] Similarly, for yellowtail, the shrinkage in Figure 14 shows some negative values, but the PE is extended to more than 26.45 ± 3.14 (h), which is a better convergence than the average PE value of 8.14 ± 4.25 (h) in Figure 12. As with red sea bream, the time is extended by about three times, making it possible to maintain a firm texture for more than 20 hours.

[0125] In this example, the above steps 1 to 4 are performed to extend the plateau end time (the time the firmness sensation is maintained). However, as an alternative example, instead of step 1 (spinal tapping), an anesthesia treatment is performed in which the fish is placed in water with a predetermined concentration of dissolved carbon dioxide (carbon dioxide gas) for a predetermined time, and instead of the high-concentration oxygen water in step 2 (oxygen water curing), a treatment is performed using a mixture of low-concentration carbon dioxide and high-concentration oxygen with a carbon dioxide concentration of 40 mg / L to 80 mg / L and a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content. In this case, the anesthesia treatment in step 3 (harvesting) is not necessary (because the fish is already in a paralyzed state).

[0126] Specifically, the fish are placed in high-concentration carbon dioxide seawater with a carbon dioxide concentration of 500 mg / L to 800 mg / L for 45 seconds to 1 minute 30 seconds (preferably about 1 minute) (anesthesia treatment), and then placed in a mixed seawater of low-concentration carbon dioxide and high-concentration oxygen with a carbon dioxide concentration of 40 mg / L to 80 mg / L (preferably 50 mg / L to 70 mg / L) and a dissolved oxygen content of 200% to 350% of the saturated dissolved oxygen content (oxygen concentration 15 mg / L to 25 mg / L) for 4 hours to 24 hours (mixed water curing treatment), followed by removal treatment and then oxygen water perfusion treatment, thereby extending the plateau completion time (unless otherwise specified, the same as in this example).

[0127] The degree of shrinkage of the red sea bream processed in the above-mentioned other example is shown in Figure 15. The dissolved carbon dioxide concentration meter was calibrated each time a measurement was made (the measuring device used was the CGP-31 model manufactured by DKK-TOA). Figure 15 confirms that, as in this example, the firmness of the red sea bream can be maintained for 30 hours or more (PE was 34.14 ± 2.06 (h)).

[0128] Since the lateral muscles consume the most ATP instantaneously, not only spinal cord drilling but also any other procedure that allows breathing to continue while the lateral muscles are still (anesthesia procedure described above) can maximize Cr-P, stop the production of many excitatory hormones including cortisone, and extend the time that stiffness is maintained.

[0129] In the above-mentioned alternative example, it is necessary to control the carbon dioxide concentration in the seawater during the anesthesia treatment and mixed water curing treatment compared to this embodiment, but it is possible to send a large number of fish to the curing process in a short time compared to when spinal cord drilling treatment is performed (because spinal cord drilling must be performed for each fish and requires skill to perform it accurately).

[0130] In this embodiment, as described above, fresh fish can be obtained that retains its firmness for a longer period of time.

[0131] By extending the time that the firmness is maintained, it will be possible to change the costly method of transporting live fish to transporting fresh fish (fresh fish distribution).In other words, transporting fresh fish is cheaper than transporting live fish, which is expected to promote the expansion of sales channels and contribute to the reduction of CO2 emissions, which has been much called for in recent years.If the time is within the set limit, it will also contribute to the expansion of sales channels not only domestically but also overseas.

[0132] Furthermore, when shipping fresh fish, if information on the characteristics of changes in the fish's body, including its firmness, is written on the packaging box, consumers will be able to use this information to know the best time to consume the fish, making it possible to provide the fish to customers with higher preferences.

[0133] Therefore, this embodiment is an unprecedented method for extending the time for which the sense of hardness of a fish is maintained, which can extend the time for which the sense of hardness of the fish is maintained.

Claims

1. A method for extending the time during which the firmness of a fish body is maintained, a spinal cord destruction step of destroying the spinal cord of the fish; After the spinal cord destruction step, an oxygen water curing step is performed in which the fish is placed in water having a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content for 4 hours or more. After the oxygen water curing process, a removal process is performed in which the fish is anesthetized using carbon dioxide and removed from the water. After the harvesting step, a perfusion treatment step of introducing supersaturated oxygen water into the blood vessels of the fish body is performed; A method for extending the time that the firmness of a fish body is maintained, comprising:

2. A method for extending the time during which the firmness of fish body is maintained as described in claim 1, characterized in that the oxygen water curing process includes a first cooling process of cooling the fish body from room temperature to 6 to 9 degrees Celsius.

3. A method for extending the time during which the firmness of fish body is maintained as described in claim 2, characterized in that the oxygen water curing process includes a second cooling process in which the fish body is cooled to 5°C to 8°C after the first cooling process.

4. 2. The method for extending the time period during which the fish maintains its firmness as described in claim 1, wherein the oxygen water curing step comprises storing the fish for 4 hours or more and 24 hours or less.

5. 3. The method for extending the time period during which the fish maintains its firmness as described in claim 2, wherein the oxygen water curing step comprises storing the fish for 4 hours or more and 24 hours or less.

6. 4. The method for extending the time period during which the fish maintains its firmness as described in claim 3, wherein the oxygen water curing step comprises storing the fish for 4 hours or more and 24 hours or less.

7. A method for extending the time during which the firmness of a fish body is maintained, as described in any one of claims 1 to 6, characterized in that the oxygen water curing process involves placing the fish body in water in which the amount of dissolved oxygen is 200% or more and 350% or less of the saturated dissolved oxygen amount.

8. A method for extending the time during which the firmness of a fish body is maintained, an anesthetizing step of placing the fish in water containing a predetermined concentration of dissolved carbon dioxide for a predetermined period of time; After the anesthesia process, the fish is placed in mixed water having a carbon dioxide concentration of 40 mg / L to 80 mg / L and a dissolved oxygen content of 200% or more of the saturated dissolved oxygen content for 4 hours or more. After the mixed water curing step, a taking-out step of taking the mixture out of the mixed water; After the harvesting step, a perfusion treatment step of introducing supersaturated oxygen water into the blood vessels of the fish body is performed; A method for extending the time that the firmness of a fish body is maintained, comprising:

9. A method for extending the time during which the firmness of fish body is maintained as described in claim 8, characterized in that the mixed water curing process includes a first cooling process of cooling the fish body from room temperature to 6 to 9 degrees Celsius.

10. A method for extending the time during which the firmness of fish body is maintained as described in claim 9, characterized in that the mixed water curing process includes a second cooling process in which the fish body is cooled to 5°C to 8°C after the first cooling process.

11. 9. The method for extending the time period during which the fish maintains its firmness as described in claim 8, wherein the mixed water curing step comprises storing the fish for 4 hours or more and 24 hours or less.

12. 10. The method for extending the time period during which the fish body maintains its firmness according to claim 9, wherein the mixed water curing step comprises storing the fish body for 4 hours or more and 24 hours or less.

13. 11. The method for extending the time period during which the fish body maintains its firmness as described in claim 10, wherein the mixed water curing process comprises storing the fish body for 4 hours or more and 24 hours or less.

14. A method for extending the time during which the firmness of fish bodies is maintained, as described in any one of claims 8 to 13, characterized in that the mixed water curing process involves placing the fish bodies in mixed water having a carbon dioxide concentration of 50 mg / L to 70 mg / L and a dissolved oxygen content of 200% to 350% of the saturated dissolved oxygen content.

15. A method for extending the time that the sense of hardness of a fish body is maintained, as described in any one of claims 8 to 13, characterized in that the anesthesia process involves placing the fish body in water with a carbon dioxide concentration of 500 mg / L to 800 mg / L for 30 seconds to 1 minute and 30 seconds.

16. A method for extending the time during which the firmness of a fish body is maintained, as described in any one of claims 1 to 6 and 8 to 13, characterized in that it includes a transportation step in which the fish body is kept at 5°C to 8°C and transported after the perfusion treatment step.

17. A method for extending the time that the fish body maintains its sense of hardness according to any one of claims 1 to 6 and 8 to 13, wherein the fish body is red sea bream, and the time that the fish body maintains its sense of hardness is set to 30 hours or more. ...

18. A method for extending the time that the fish body maintains its firmness, as described in any one of claims 1 to 6 and 8 to 13, wherein the fish body is a yellowtail, and the time that the fish body maintains its firmness is set to 20 hours or more.

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