Fish bleeding treatment method and bled fish production method

Abstract

A fish bleeding treatment method according to the present invention includes: an insertion step ST2 for inserting a tubular instrument that is a tubular member into a blood vessel system of fish; and a gas injecting step ST4 for injecting a freshness-maintaining gas into the blood vessel system of the fish through the tubular instrument that has been inserted in the insertion step ST2. The fish bleeding treatment method according to the present invention may include, between the insertion step ST2 and the gas injection step ST4, a liquid injection step ST3 for injecting an injection liquid into the blood vessel system of the fish through the tubular instrument that has been inserted in the insertion step ST2.

Description

Method for draining blood from fish and method for producing drained fish

[0001] The present invention relates to a method for bleeding fish to maintain the freshness of the fish and a method for producing bled fish.

[0002] Fish blood is the source of the fishy smell and one of the causes of a decrease in freshness. Therefore, removing the blood from the fish body (bleeding) is a very important process for maintaining the quality of the fish.

[0003] A common method for bleeding fish is to cut the gills or tail fin and allow the blood to drain from the blood vessels, but this method leaves blood in the vascular system, making it difficult to remove all of the blood.

[0004] To address this issue, for example, Patent Document 1 discloses a method of injecting an injection liquid containing fine bubbles into the vascular system of a fish. This method uses the injection liquid containing fine bubbles to more reliably remove blood while minimizing damage to the fish's muscle tissue, thereby reducing the fish's odor without weakening its flavor.

[0005] JP 2023-044743 A

[0006] However, recently, there has been a demand for not only preventing the fish from spoiling from an organoleptic or microbiological standpoint after bleeding, but also for further improving its vitality, particularly from a chemical standpoint.However, to meet such demands, it has been insufficient to simply inject an injection liquid containing fine bubbles into the vascular system of the fish, as has been done in the past.

[0007] The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to further improve the vitality of fish after bleeding. Means for solving the problem and effects of the invention

[0008] A method for bleeding fish according to a first aspect of the present invention can be configured to include an insertion step of inserting a tubular instrument that is a tubular member into the vascular system of a fish, and a gas injection step of pressurizing a freshness-preserving gas into the vascular system of the fish via the tubular instrument inserted in the insertion step. The freshness-preserving gas is a gas that prevents the progression of oxidation of the fish, and examples of this gas include a reducing gas and an inert gas.

[0009] With this configuration, the freshness-preserving gas is injected into every corner of the fish's internal tissues via the fish's vascular system, suppressing oxidation of the fish's internal tissues and lowering the K value, an objective indicator of fish freshness, thereby further improving the vitality of the fish after bleeding.

[0010] In addition, a method for draining blood from fish according to a second aspect of the present invention can be configured to include an insertion step of inserting a tubular instrument, which is a tubular member, into the vascular system of the fish, a liquid injection step of pressurizing an injection liquid into the vascular system of the fish through the tubular instrument inserted in the insertion step, and a gas injection step of pressurizing a freshness-preserving gas into the vascular system of the fish after the liquid injection step through the tubular instrument inserted in the insertion step.

[0011] With this configuration, the blood inside the body can be removed more reliably by the pressurized liquid, and the freshness of the fish can be further maintained.

[0012] Furthermore, the method for bleeding fish according to the third aspect of the present invention can be configured so that the gas for preserving freshness is hydrogen gas.

[0013] Furthermore, a fourth aspect of the present invention relates to a method for producing bleed-free fish, which method produces bleed-free fish by subjecting fish to a bleeding process, and the bleeding process can be configured to include an insertion step of inserting a tubular instrument, which is a tubular member, into the vascular system of the fish, and a gas injection step of pressurizing a gas for preserving freshness into the vascular system of the fish through the tubular instrument inserted in the insertion step.

[0014] Furthermore, a method for producing bled fish according to a fifth aspect of the present invention is a method for producing bled fish by subjecting fish to a bleeding process, and the bleeding process can be configured to include an insertion step of inserting a tubular instrument, which is a tubular member, into the vascular system of the fish, a liquid injection step of pressurizing an injection liquid into the vascular system of the fish through the tubular instrument inserted in the insertion step, and a gas injection step of pressurizing a freshness-preserving gas into the vascular system of the fish through the tubular instrument inserted in the insertion step after the liquid injection step.

[0015] Furthermore, the method for producing bled fish according to the sixth aspect of the present invention can be configured so that the freshness-preserving gas is hydrogen gas.

[0016] 1 is a flowchart of a method for bleeding fish according to a first embodiment of the present invention. FIG. 2 is a flowchart of a method for bleeding fish according to a second embodiment of the present invention. FIG. 3 is a diagram showing the change characteristics of the K values ​​of specimens 1 to 3. FIG. 4 is a photograph showing the state of specimens 1 to 4 on the second day after bleeding. FIG. 5 is a photograph showing the state of specimens 1 to 4 on the fourth day after bleeding. FIG. 6 is a photograph showing the state of specimens 1 to 4 on the sixth day after bleeding. FIG. 7 is a photograph showing the state of specimens 1 to 4 on the eighth day after bleeding. FIG. 8 is a photograph showing the state of specimens 1 to 4 on the tenth day after bleeding.

[0017] The following describes embodiments of the present invention with reference to the drawings. However, the embodiments described below exemplify a method for bleeding fish and a method for producing bled fish to embody the technical concept of the present invention. The present invention does not limit the method for bleeding fish, the method for producing bled fish, the bled fish, or the device for bleeding fish to those described below. Furthermore, this specification does not in any way limit the components described in the claims to those described in the embodiments. The dimensions, materials, shapes, and relative positions of components described in the embodiments, unless otherwise specified, are not intended to limit the scope of the present invention and are merely illustrative examples. The size and relative positions of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, identical names and symbols indicate identical or similar components, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present invention may be configured with the same components, with one component serving multiple functions, or the functions of one component may be shared among multiple components. (First Embodiment)

[0018] As shown in Figure 1, the method for bleeding fish according to the first embodiment of the present invention mainly comprises a live-tightening step ST1, a piercing step ST2, a liquid injection step ST3, and a gas injection step ST4. The method for bleeding fish according to this invention can be used for a wide range of fish, and is suitable for use with farmed fish such as red sea bream, amberjack, yellowtail, and yellowtail.

[0019] In the live-killing process ST1, live fish are killed immediately so as not to struggle as much as possible in order to preserve the freshness of the fish. To achieve this, a pick is inserted between the eyebrows of the live fish to destroy its brain, or a wire is passed through the spine to destroy its nerves. However, in this live-killing process ST1, the gills are not removed and the blood vessels at the base of the caudal fin are not severed. Furthermore, even though the live fish are killed immediately, this does not mean that the heart or internal organs are deprived of their functions. In this bleeding method, it is desirable to complete the processes after the live-killing process ST1 as quickly as possible to minimize damage to the heart, internal organs, etc.

[0020] In the insertion step ST2, a tubular instrument, which is a tubular member, is inserted into the vascular system of the fish. In this embodiment, a syringe needle is used as the tubular instrument, and the syringe needle is inserted from the caudal surface of the ventricle of the fish's heart toward the bulbus arteriosus. The part of the bulbus arteriosus through which the syringe needle is inserted is pinched with a pinch to prevent the syringe needle from being pulled out after insertion.

[0021] In the liquid injection step ST3, the injection liquid is injected into the vascular system of the fish through the injection needle inserted in the insertion step. The injection liquid may be, for example, sterilized seawater or a liquid containing physiological saline as its main component. The injection liquid is pressurized to a predetermined pressure and then supplied to the injection needle so that it can be injected into the vascular system of the fish.

[0022] In this embodiment, the injected liquid can contain fine bubbles to suppress the fishy odor regardless of the passage of time and enhance the umami flavor. In this case, if a liquid containing gas, such as carbonated water, is used, the process of mixing the gas can be omitted when generating the fine bubbles.

[0023] Here, fine bubbles are bubbles with a diameter of less than 100 μm, and are standardized by the International Organization for Standardization (ISO). Furthermore, among fine bubbles, bubbles with a diameter of 1 μm or more and less than 100 μm are defined as microbubbles, and bubbles with a diameter of less than 1 μm are defined as ultrafine bubbles. Bubbles generally called nanobubbles (not a term standardized by ISO) belong to the ultrafine bubbles category.

[0024] Fine bubbles are generated using a known fine bubble generator. Fine bubbles, for example, containing carbon dioxide, are generated in this fine bubble generator over a period of 20 to 60 minutes until saturation is reached. Since the concentration of oxygen dissolved in the water is maintained at a constant value once the fine bubbles are saturated, the saturation of the fine bubbles can be determined when this constant oxygen concentration is reached. For example, at 15°C, the oxygen concentration in the injection liquid is 5.0 to 6.0 mg / L without fine bubble generation. However, as the amount of fine bubble generation increases, the oxygen concentration decreases, and even if fine bubble generation continues, the oxygen concentration stops decreasing at 0.05 mg / L. The density of fine bubbles in a saturated state is 5.0 x 10 at temperatures between 0 and 25°C. ８ ~2.0 x 10 ９ It is estimated to be 1 / mL.

[0025] The gas that composes the fine bubbles may be air, nitrogen gas, carbon dioxide gas, or a mixture of nitrogen gas and carbon dioxide gas. By eliminating the oxygen content of the fine bubbles, lipid oxidation in the fish meat and metmyoglobin formation due to the gas components contained in the injection liquid can be prevented.

[0026] The injection fluid injected into the vascular system of the fish flows from the aorta, circulates through the body tissues, and returns to the heart via the vena cava, and is expelled from the insertion point of the fish's heart, i.e., the gap between the insertion point of the injection needle and the outer surface of the needle, and from weak parts of the capillaries in the gills, internal organs, etc. As a result, the fish's blood is pushed out by the injection fluid and replaced with the injection fluid. Normally, the heart of a fish that has been killed while alive is still functioning at the time the injection fluid is injected, so the heart's function also promotes the return of the injected injection fluid to the heart.

[0027] Whether or not the blood in the fish's body has been replaced by the injected fluid can be determined by the color of the fluid discharged from the puncture point of the fish's heart and from weak points in the capillaries of the gills. The discharged fluid is initially red, but the red color gradually fades. When the discharged fluid becomes almost colorless, it is considered that the blood in the fish's body has been replaced by the injected fluid.

[0028] In this embodiment, the injection needle is provided in a fish bleeding device (not shown), and the worker operates this fish bleeding device at any time as needed, so that the injection needle is selectively supplied with the pressurized liquid and the freshness-preserving gas used in the gas injection process ST4.

[0029] In the gas injection step ST4, after the liquid injection step ST3, the injection needle inserted in the insertion step ST2, i.e., the injection needle used in the liquid injection step ST3, is not removed from the vascular system, and freshness-preserving gas is injected into the vascular system of the fish through the injection needle.

[0030] The freshness-preserving gas injected into the vascular system, like the injected liquid in the liquid injection step ST3, flows from the aorta of the fish, circulates through the body tissues, and returns to the heart via the vena cava, and is discharged from the puncture point of the fish's heart and weak parts of the capillaries in the gills, internal organs, etc. Accordingly, the injected liquid injected into the vascular system of the fish in the liquid injection step ST3 is pushed out by the injected freshness-preserving gas and replaced by the freshness-preserving gas.

[0031] Whether or not the injected liquid in the liquid injection step ST3 has been replaced with gas for preserving freshness is determined by determining whether or not bubbles are coming out from the puncture point of the fish's heart and from weak parts of the capillaries in the gills and internal organs.

[0032] In this embodiment, the gas for preserving freshness is hydrogen gas, and when an operator operates the fish bleeding device, hydrogen gas pressurized to a predetermined pressure is supplied to the injection needle (Second Embodiment).

[0033] As shown in Figure 2, the method for bleeding fish according to the second embodiment of the present invention mainly comprises a live-killing step ST1, a piercing step ST2, and a gas injection step ST4. That is, the method for bleeding fish according to the second embodiment of the present invention differs from the first embodiment of the present invention in that the liquid injection step ST3 shown in Figure 1 is omitted, and freshness-preserving gas is injected into the vascular system of the fish immediately after the piercing step ST2 via the tubular instrument inserted in the piercing step ST2. The freshness-preserving gas injected in the gas injection step ST4 pushes blood and other substances from the blood vessels through weak parts of the capillaries in the fish's heart, gills, internal organs, etc., and then the freshness-preserving gas leaks out from the fish's heart, gills, internal organs, etc. When bubbles are confirmed to emerge from the fish's heart, gills, internal organs, etc., it is considered that the blood in the blood vessels has been replaced with freshness-preserving gas.

[0034] Next, an example of the method for bleeding fish according to the present invention will be described.

[0035] In order to verify the effectiveness of the present invention, four live yellowtails weighing approximately 5 kilograms (error range: plus or minus 0.1 kilograms) were taken out of a curing pen, and these four yellowtails were designated as individual specimens 1 to 4.

[0036] In Example 1, a bled fish was produced from a specimen 1 using the method for bleeding fish according to the first embodiment of the present invention shown in FIG.

[0037] In the liquid injection step ST3, sterilized seawater was used as the injection liquid. This injection liquid was pressurized to a pressure of 0.1 MPa and supplied to the injection needle for 8 minutes. During this time, the amount of pressurized liquid supplied to the injection needle reached approximately 4 liters. It was then confirmed that the color of the liquid discharged from the puncture point of the fish's heart and the weak points of the capillaries in the gills became almost colorless. At this time, the color of the gills also changed from red to whitish.

[0038] In the gas injection step ST4, hydrogen gas at a pressure of 0.2 millipascals was supplied to the injection needle as a freshness-preserving gas for 4 minutes, and it was confirmed that the injected liquid inside the fish's body had been replaced with hydrogen gas.

[0039] As Comparative Example 1, specimen 2 was subjected to the live-killing step ST1, the piercing step ST2, and the liquid injection step ST3 shown in Figure 1, and a bled fish was produced without performing the gas injection step ST4. As Comparative Example 2, specimen 3 was subjected to only the live-killing step ST1 shown in Figure 1, and a bled fish was produced.

[0040] Furthermore, in Example 2, a bleed-out fish was produced from specimen 4 using the fish bleeding method according to the second embodiment of the present invention shown in Figure 2. In the gas injection step ST4 shown in Figure 2, immediately after piercing the specimen 4 with the injection needle, hydrogen gas at a pressure of 0.2 millipascals was supplied as a freshness-preserving gas into the injection needle for 4 minutes, as in Example 1. It was then confirmed that bubbles were coming out from the injection hole in the fish's heart, gills, and internal organs.

[0041] Next, each of the bled fish samples 1 to 4 was cooled to a core temperature of approximately 5°C, and then prepared into sashimi. The sashimi samples 1 to 4 were stored in cold air at 5°C for 10 days, and the K values ​​of the sashimi samples 1 to 3 were calculated every other day using high-performance liquid chromatography to objectively assess their viability from a chemical perspective during this 10-day storage period. The results are shown in Table 1 and Figure 3. In Figure 3, the horizontal axis corresponds to the number of days elapsed, and the vertical axis corresponds to the K value.

[0042]

[0043] A K value of 20% or less is considered a guideline for whether or not yellowtail, such as sashimi, can be eaten raw. Furthermore, if bled fish is to be delivered within Japan, for example, a transportation period of 10 days is sufficient. As shown in Figure 3, the K values ​​of Sample 1 of Example 1, Sample 4 of Example 2, and Sample 2 of Comparative Example 1 on the 10th day were all below 20%, indicating that Samples 1, 1, and 2 could be eaten raw even after 10 days. In contrast, the K value of Sample 3 of Comparative Example 2 on the 10th day exceeded 20%, indicating that Sample 2 was not suitable for raw consumption after 10 days. Furthermore, the K values ​​of Sample 1 of Example 1 and Sample 4 of Example 2 on the 10th day were lower than the K value of Sample 2 of Comparative Example 1 on the 10th day. This demonstrates that the fish bleeding method of the present invention can further enhance the vitality of fish after bleeding compared to the treatment in Comparative Example 1.

[0044] In order to promote the consumption of fish that can be eaten raw, it is important not only to objectively understand the viability of the fish after bleeding from a chemical perspective, but also to understand it sensorily. Therefore, for sashimi samples 1 to 4, sensory tests were conducted every day over the 10-day storage period to determine the K value as well as the texture, color, flavor, texture, odor, and drip.

[0045] The sensory test for meat quality involves tactile and, in some cases, visual evaluation of the firmness of the sashimi. The sensory test for color involves visual evaluation of the discoloration of the sashimi. The sensory test for umami involves tasting the umami of the sashimi. The sensory test for texture involves evaluating the chewiness and texture of the sashimi when placed in the mouth. The sensory test for odor involves olfactory evaluation of the odor of the sashimi. The sensory test for drip involves visual evaluation of the presence or absence of juice flowing from the sashimi. In these sensory tests, each evaluation item was rated on a five-point scale, with "1" representing the lowest rating and "5" representing the highest rating. The evaluation scores for each evaluation item for Samples 1 to 4 were then summed for each sample to obtain a total score. The results of these sensory tests are shown in Table 2. Figures 4 to 8 show the changes in appearance of Samples 1 to 4 used in the sensory tests.

[0046]

[0047] As shown in Table 2, the total values ​​of the test items for sample 1 of Example 1 and sample 4 of Example 2 changed similarly with the number of days that had passed, and from the sixth day onwards, both values ​​were greater than the total values ​​of the test items for sample 2 of Comparative Example 1. Therefore, it can be said that the method for bleeding fish according to the present invention has the effect of further improving the vitality of the fish after bleeding not only from a chemical standpoint but also from a sensory standpoint.

[0048] ST1: Live tightening process ST2: Insertion process ST3: Liquid injection process ST4: Gas injection process

Claims

1. A method for draining blood from fish, comprising: an insertion step of inserting a tubular instrument, which is a tubular member, into the vascular system of a fish; and a gas injection step of pressurizing a gas for preserving freshness into the vascular system of the fish through the tubular instrument inserted in the insertion step.

2. A method for draining blood from fish, comprising: an insertion step of inserting a tubular instrument, which is a tubular member, into the vascular system of the fish; a liquid injection step of pressurizing an injection liquid into the vascular system of the fish through the tubular instrument inserted in the insertion step; and a gas injection step of pressurizing a freshness-preserving gas into the vascular system of the fish after the liquid injection step, through the tubular instrument inserted in the insertion step.

3. A method for draining blood from fish as claimed in claim 1 or 2, wherein the gas for preserving freshness is hydrogen gas.

4. A method for producing bleed-out fish, comprising the steps of: (a) bleeding fish to produce bled fish; (b) bleeding the fish by subjecting the fish to a bleeding process comprising: an insertion step of inserting a tubular instrument which is a tubular member into the vascular system of the fish; and (c) injecting a gas for preserving freshness by pressurizing the gas into the vascular system of the fish through the tubular instrument inserted in the insertion step.

5. A method for producing bled fish, comprising the steps of: inserting a tubular instrument, which is a tubular member, into the vascular system of the fish; a liquid injection step of injecting an injection liquid into the vascular system of the fish through the tubular instrument inserted in the insertion step; and, after the liquid injection step, pressurizing a gas for preserving freshness into the vascular system of the fish through the tubular instrument inserted in the insertion step.

6. A method for producing bled fish according to claim 4 or 5, wherein the freshness-preserving gas is hydrogen gas.

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