Packaged fresh tuna meat, method for producing packaged fresh tuna meat, method for preventing cut of fresh tuna from discoloring, cut of fresh tuna, and method for providing cut of fresh tuna

Abstract

To provide a packaged fresh tuna meat in which discoloration of fresh tuna meat is suppressed while being packaged.SOLUTION: In one aspect, the present disclosure provides a packaged fresh tuna meat comprising an oxygen-impermeable packaging member and a cut of fresh tuna packaged by the packaging member along with a gas having an oxygen concentration of 1 vol.% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a packaged raw tuna meat product, a method for producing a packaged raw tuna meat product, a method for inhibiting discoloration of a block of raw tuna meat, a block of raw tuna meat, and a method for providing a block of raw tuna meat. [Background technology]

[0002] In recent years, consumers have become more interested in taste and safety, and there is an increasing demand for fresh and tasty fish meat. Packaged fish meat is widely known as a product that prolongs the freshness and tastyness of fish meat. In order to prolong the freshness of fish meat, a method of replacing the gas inside the package with a predetermined gas is known.

[0003] For example, Patent Document 1 discloses a gas composition for extending the shelf life of seafood, which comprises a mixture of nitrogen gas and carbon dioxide gas in a ratio of 7:3 to 4:6 (volume ratio) and allyl isothiocyanate gas at 10 to 300 ppm relative to the total of nitrogen gas, carbon dioxide gas, and allyl isothiocyanate gas. Patent Document 1 describes that the use of such a gas composition for extending shelf life can suppress the generation of odors in packaged seafood for 10 to 14 days, and can effectively suppress the generation of psychrophilic bacteria, which are particularly problematic when storing seafood.

[0004] In particular, in the case of large fish such as tuna, the fish is sometimes processed into chunks of meat of a certain size, such as blocks, after being landed, rather than the whole fish itself, and then distributed as a processed product. For this reason, even in such processed products, it is necessary to maintain freshness.

[0005] For example, Patent Document 2 discloses a thawing method in which highly fresh frozen meat frozen just before rigor mortis is thawed in oxygen-exchange packaging or oxygen-exchange storage. Patent Document 2 also discloses a method for frozen tuna muscle in oxygen-exchange packaging or oxygen-exchange storage to produce bright red oxymyoglobin and prevent myoglobin autoxidation, metmyoglobin formation, browning of meat color, and deterioration of meat quality. Patent Document 2 describes an investigation into storage conditions that suppress metmyoglobin formation, and as a result, describes that these methods improve and maintain the color tone of tuna and other muscle over a long period of time, promote muscle restoration, suppress drip formation, and improve texture.

[0006] On the other hand, from the perspective of securing marine resources, aquaculture (including livestock farming, hereafter referred to simply as aquaculture) is actively carried out for tuna and other fish. In aquaculture, fish are raised under controlled environments and feeding conditions, which means that they have more fat (fat) than wild fish, making it possible to provide high-quality processed fish meat. Unlike wild tuna, which can only be obtained by traveling to distant oceans, farmed tuna is raised in relatively nearby waters, so it is processed and shaped into blocks relatively soon after being caught, and is sometimes shipped as a packaged product in a raw state without being frozen.

[0007] The blocks obtained by processing are sometimes tightly packed in plastic film and distributed. In this case, it has been pointed out that the amount of dripping increases with time after packaging. To solve this problem, Patent Document 3 proposes cooling the blocks to a temperature of 10°C or less after tightly packing them in plastic film. The technology disclosed in Patent Document 3 is said to reduce drip loss during storage and distribution and improve the yield of edible tuna. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 08-070764 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-015946 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-014630 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the case of raw tuna, even if it is processed into blocks and then packaged, the fish meat may discolor if exposed to air for a long period of time. Furthermore, in recent years, supermarkets and other stores have begun to receive processed products such as blocks, and then open the packages at the store to further prepare products such as sashimi from the processed products. However, if discoloration has already occurred in the processed product when the package is opened, this portion cannot be used as a product. This makes it necessary to remove the discolored portion, and if there is a large amount of discolored portion, the product utilization rate, i.e., yield, decreases.

[0010] The present disclosure provides a method for inhibiting discoloration of raw tuna chunks while they are packaged, and in some cases even after they have been opened. [Means for solving the problem]

[0011] The present disclosure provides the following: [1] A packaged raw tuna meat product comprising an oxygen-impermeable packaging material and raw tuna meat packaged in the packaging material together with a gas having an oxygen concentration of 1% by volume or less. [2] The packaged raw tuna meat product according to [1], wherein the gas contains an inert gas. [3] The packaged raw tuna meat product according to [2], wherein the inert gas contains at least one gas selected from the group consisting of nitrogen gas, carbon dioxide gas, helium gas, and argon gas. [4] A packaged raw tuna meat product according to any one of [1] to [3], further comprising a water-absorbent member, with the raw tuna meat being in contact with the water-absorbent member in part or in whole. [5] The oxygen permeability of the packaging material is 1000 cm 3 / m 2A packaged raw tuna meat product according to any one of [1] to [4], which is 24hr·atm or less. [6] The oxygen permeability of the packaging material is 50 cm 3 / m 2 A packaged raw tuna meat product according to any one of [1] to [5], which is 24hr·atm or less. [7] A method for producing a packaged raw tuna product, comprising: cutting up tuna after landing to obtain raw tuna chunks; packaging the raw tuna chunks in an oxygen-impermeable packaging material; subjecting the packaging material to a gas replacement process until the oxygen concentration in the gas inside the packaging is 1% by volume or less; and sealing the packaging material after the gas replacement process. [8] The method for producing a packaged raw tuna meat product according to [7], wherein the gas substitution treatment is carried out using an inert gas. [9] The method for producing a packaged raw tuna meat product according to [8], wherein the inert gas contains at least one gas selected from the group consisting of nitrogen gas, carbon dioxide gas, helium gas, and argon gas.

[10] A method for producing a packaged raw tuna meat product according to any one of [7] to [9], further comprising refrigerating the raw tuna block until it is packaged in the packaging material.

[11] A method for inhibiting discoloration of raw tuna meat, comprising: cutting up tuna after landing to obtain raw tuna meat; packaging the raw tuna meat in an oxygen-impermeable packaging material; and subjecting the packaging material to a gas replacement process until the oxygen concentration in the gas inside the packaging is 1% by volume or less; and sealing the packaging material after the gas replacement process to obtain a packaged raw tuna meat product.

[12] The method for inhibiting discoloration of raw tuna meat described in

[11] , further comprising storing the packaged raw tuna meat in a refrigerator.

[13] The method for inhibiting discoloration of raw tuna block meat according to

[12] , wherein the refrigerated storage period is at least one week.

[14] The method for inhibiting discoloration of raw tuna block meat according to

[12] , wherein the refrigerated storage period is at least 4 weeks.

[15] A packaged raw tuna meat product comprising an oxygen-impermeable packaging material and raw tuna meat tightly packed by the packaging material, wherein the amount of gas in the package is 21 mL or less per 1 kg of raw tuna meat.

[16] The oxygen permeability of the packaging material is 1000 cm 3 / m 2

[15] A packaged raw tuna meat product having a temperature of 24hr·atm or less.

[17] The oxygen permeability of the packaging material is 200 cm 3 / m 2 A packaged raw tuna meat product according to

[15] or

[16] , which is 24hr·atm or less.

[18] The packaged raw tuna meat product according to any one of

[15] to

[17] , wherein the tensile strength of the packaging member is 80 MPa to 250 MPa.

[19] A packaged raw tuna meat product according to any one of

[15] to

[18] , wherein the tensile modulus of the packaging member is 500 MPa to 900 MPa.

[20] A method for producing packaged raw tuna meat, which includes cutting up tuna after landing to obtain raw tuna chunks, and tightly packaging the raw tuna chunks in oxygen-impermeable packaging materials to reduce the amount of gas in the package to 21 mL or less per 1 kg of raw tuna chunks.

[21] A method for producing a packaged raw tuna meat product according to

[20] , further comprising refrigerating the raw tuna block meat until it is packaged in the packaging material.

[22] A method for inhibiting discoloration of raw tuna chunks, comprising: cutting up tuna after landing to obtain raw tuna chunks; and tightly packaging the raw tuna chunks in an oxygen-impermeable packaging material, reducing the amount of gas in the package to 21 mL or less per 1 kg of raw tuna chunks, thereby obtaining packaged raw tuna meat.

[23] The method for inhibiting discoloration of raw tuna meat described in

[22] , further comprising storing the packaged raw tuna meat in a refrigerator.

[24] The method for inhibiting discoloration of raw tuna block meat according to

[23] , wherein the refrigerated storage period is at least 4 days.

[25] Raw tuna meat taken out of a package that has been packaged for more than four days and measured with a color difference meter. * Raw tuna meat with a value of 14.05 or more and 19 or less 0.5 hours after opening the package of raw tuna meat.

[26] Raw tuna meat chunks removed from a packaged product, as measured by a color difference meter * / b* The value of a is 0.5 hours after opening the package of raw tuna meat. * / b * Raw tuna chunks with a value of 99% or more.

[27] Raw tuna meat taken out of a package that has been packaged for more than four days and measured with a color difference meter. * / b * However, the saturation index of raw tuna meat is 1.29 or higher 0.5 hours after opening the package.

[28] A method for providing raw tuna meat, comprising a step of opening a package of raw tuna meat, wherein the color difference of the raw tuna meat measured with a color difference meter is a * The method of providing the raw tuna meat product, wherein the value is 17.05 or more 8 hours after opening the packaged product. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a packaged raw tuna meat product and a method for inhibiting discoloration of raw tuna meat, in which discoloration is inhibited while the product is packaged and, in some cases, even after the package is opened. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a graph showing the change in the a* value of tuna meat seven days after packaging according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a graph showing the change in the a* / b* value of tuna meat seven days after packaging according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present disclosure will be described below, although the present disclosure is not limited to the following embodiments.

[0015] In this specification, unless otherwise specified, the color change over time of raw tuna block meat, which follows a specific pattern as described below, is simply referred to as "discoloration." Furthermore, slowing the rate of this "discoloration" may also be referred to simply as maintaining the color, delaying discoloration, or inhibiting discoloration (discoloration inhibition). As described below, this "discoloration" refers to a color change that occurs irreversibly and in a specific manner under normal temperature and pressure in air (oxygen concentration: 21.0% by volume) from a low-saturation red (e.g., dark red) at the time of cutting to a bright red (e.g., crimson) and then to a red with low brightness and saturation (e.g., dark brown). "Discoloration" does not include temporary color changes in tuna block meat that occur, for example, when exposed to nitrogen gas. In this specification, the bright red color may be referred to as "bright red" or "light pink" based on the intensity of the red color.

[0016] In the first embodiment of this specification, when the concentration or amount of a gas is mentioned, the concentration or amount is based on the volume of the gas at room temperature (1 atmosphere) and a temperature of 0°C to 10°C. In the second embodiment of this specification, when the concentration or amount of a gas is mentioned, the concentration or amount is based on the volume of the gas at room temperature (1 atmosphere) and a temperature of 18°C ​​to 20°C.

[0017] As used herein, the term "process" refers not only to an independent process, but also to processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after the range as the minimum and maximum values, respectively. In this specification, when multiple substances corresponding to each component are present in the composition, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified. In this specification, the terms "equal to or less than" and "less than" in relation to percentages include 0%, i.e., "not contained," unless a lower limit is specifically stated, or refer to a range that includes values ​​that are undetectable by current means.

[0018] In the present disclosure, when a numerical range specifying only one or more upper limits and a numerical range specifying only one or more lower limits are described for the same subject, unless otherwise specified, a numerical range formed by combining an upper limit arbitrarily selected from one or more upper limits with a lower limit arbitrarily selected from one or more lower limits is also included in one embodiment of the present invention. The present disclosure will be described below.

[0019] First Embodiment A first embodiment of a packaged raw tuna meat product according to the present disclosure is a packaged raw tuna meat product having an oxygen-impermeable packaging member and a block of raw tuna meat packaged in the packaging member together with gas having an oxygen concentration of 1% by volume or less.

[0020] A first embodiment of the method for producing a packaged raw tuna meat product according to the present disclosure is a method for producing a packaged raw tuna meat product, which includes cutting up tuna after landing to obtain a block of raw tuna meat, packaging the block of raw tuna meat in an oxygen-impermeable packaging material and performing a gas replacement process until the oxygen concentration in the gas inside the packaging becomes 1% by volume or less, and sealing the packaging material after the gas replacement process.

[0021] A first embodiment of the method for inhibiting discoloration of a raw tuna block according to the present disclosure is a method for inhibiting discoloration of a raw tuna block, comprising: cutting up tuna after landing to obtain a raw tuna block; packaging the raw tuna block in an oxygen-impermeable packaging material; and performing a gas replacement process until the oxygen concentration in the gas inside the packaging is 1% by volume or less; and sealing the packaging material after the gas replacement process to obtain the packaged raw tuna meat product.

[0022] According to the present disclosure, cut raw tuna chunks are packaged in the above-mentioned packaging material together with a gas having an oxygen concentration of 1% by volume or less, thereby providing a packaged raw tuna meat product in which discoloration is suppressed while it is packaged, and in some cases even after the package is opened.

[0023] First, let's look at changes in the color of fish meat. In general, the color of fish meat varies depending on the state of myoglobin. Fresh tuna meat immediately after landing is dark red due to reduced myoglobin. When the tuna is cut after landing, the reduced myoglobin near the cut surface binds with oxygen in the air. This causes the reduced myoglobin to change to oxymyoglobin, and the color of the raw tuna meat changes from dark red to bright red. It is thought that as the oxidation of oxymyoglobin progresses further, it becomes metoglobin, which turns dark brown.

[0024] Furthermore, it is believed that the color tone of fish meat is determined not only by changes in myoglobin but also by various other factors, such as those caused by lipid oxidation and metabolic products.

[0025] It is known that the color tone of raw tuna block meat varies depending on, for example, the part of the tuna, the individual tuna, etc. However, the color tone of raw tuna block meat after cutting is generally common in that it shows a low-brightness red (e.g., dark red) when cut, then a bright red (e.g., bright crimson), and as time passes, it tends to show a red with lower brightness and saturation (e.g., dark brown).

[0026] As mentioned above, it is known that the color of raw tuna meat changes over time according to a certain pattern, but the reason for this has not been clearly elucidated.

[0027] According to one aspect of the present disclosure, raw tuna chunks obtained by cutting after landing are packaged together with a gas having a predetermined oxygen concentration, and although the detailed mechanism is not clear, the progress of the aforementioned change in color tone of the raw tuna chunks over time can be delayed. In other words, according to one aspect of the present disclosure, it is possible to provide a so-called packaged raw tuna meat product that retains its color well. This tendency for delay in color tone change can be confirmed in the packaged product, and can also be confirmed after the package is opened.

[0028] Furthermore, in the first embodiment of the packaged raw tuna meat according to the present disclosure, the raw tuna chunk is packaged together with a gas having a predetermined oxygen concentration, so that the change in color tone of the raw tuna chunk can be delayed for a longer period of time than in conventional packaged raw tuna meat during packaging, and in some cases even after the packaging has been opened, although the details are not clear. Also, in the first embodiment of the packaged raw tuna meat according to the present disclosure, a good color tone can be maintained for a longer period of time than in conventional products.

[0029] Furthermore, in the first embodiment of the method for inhibiting discoloration of raw tuna blocks according to the present disclosure, the raw tuna blocks are packaged together with a gas having a predetermined oxygen concentration, and therefore, compared to conventional products, color change in the packaged raw tuna blocks is delayed for a longer period of time, and in some cases, good color can be maintained for a longer period of time even after the package is opened.

[0030] Furthermore, in particular, conventional packaged raw tuna meat can discolor not only the surface but also the interior of the raw tuna. In contrast, in one embodiment of the packaged raw tuna meat according to the present disclosure, even if discoloration occurs in the raw tuna, the discoloration can be limited to a shallower portion (surface layer) of the surface compared to conventional products. Therefore, when preparing a final product from the raw tuna, the amount of discolored portion that needs to be removed can be reduced, and the yield of the final product can be higher than conventional products.

[0031] [Packaged raw tuna meat] One embodiment of a packaged raw tuna meat product according to the present disclosure comprises an oxygen-impermeable packaging member and a raw tuna block packaged in the packaging member together with a gas having an oxygen concentration of 1% by volume or less.

[0032] Examples of tuna that can be used in the packaged raw tuna meat include those belonging to the genus Thunnus. Among the tuna species, relatively large tuna species are preferably used, such as Pacific bluefin tuna, southern bluefin tuna, and Atlantic bluefin tuna. Because the tuna species mentioned above are relatively large, they are often distributed as processed products, and are therefore preferably applicable to the packaged raw tuna meat of the present disclosure. The tuna species mentioned above are generally known to contain relatively high amounts of functional unsaturated fatty acids such as docosahexaenoic acid (DHA). The packaged raw tuna meat may contain chunks of other fish in addition to chunks of raw tuna. Examples of such other fish include swordfish.

[0033] The tuna used in the packaged raw tuna meat product may be farmed tuna or wild tuna. Farmed tuna contains more fat than wild tuna (so-called fatty), and therefore tends to discolor more easily than wild tuna, but it can be used in the packaged raw tuna meat product of the present disclosure. When the raw tuna block contains farmed tuna, the discoloration suppression effect of the present disclosure is more pronounced.

[0034] As used herein, "farmed tuna" refers to tuna that have been raised for a specified period on compound feed, moist pellets, or live bait. In this specification, "farming" includes not only artificial seedlings or 0-1-year-old juvenile fish weighing between several hundred grams and 5 kg that are caught and raised for 3-5 years, but also "livestock farming," in which juvenile fish weighing between 5 kg and 300 kg are caught and raised for a short period, such as 6 months to 1 year.

[0035] In this specification, "raw tuna meat" refers to fish meat obtained by cutting up a tuna fish (tuna meat after cutting up). In this specification, "raw" means that the fish has not been heated or frozen from the outside, or has not been stored frozen. The tuna used in packaged raw tuna meat products may be tuna that has not been heated or frozen, or stored frozen, after being landed.

[0036] Cutting conventionally refers to the process of cutting a tuna fish at the time of landing into the following order: GG, which is the tuna fish with the gills and internal organs removed; "dress" (also called headless), which is the GG with the head and tail cut off; "fillet", which is the fillet cut into three pieces and the spine removed; and "loin (fourth section)", which is the fillet further cut into male and female sections. In this specification, "tuna whole meat" includes not only the above-mentioned dress, fillet, and loin, but also "block" (also called koro), which is obtained by further cutting the loin into, for example, two to four pieces perpendicular to the length of the body.

[0037] The above-mentioned "chunk of tuna meat" does not, for example, refer to the tuna itself at the time of landing, but rather to fish meat in an intermediate form from which at least a portion of the fish has been removed, and in some cases, may also include fish meat in the form in which it is finally eaten. However, tuna meat does not include the so-called "GG" form from which the gills and internal organs have been removed. "Chunk of tuna meat" may, for example, refer to a part of an individual fish that is in the conventional processed form for cutting (for example, the above-mentioned dress, fillet, loin, etc.), or may include tuna meat that has been processed into a different shape. There are no particular restrictions on the shape of tuna meat that is different from the conventional processed form, and it may be a shape derived by further removing a portion of the dress, fillet, loin, etc., or any shape cut from an individual fish without depending on the processed form such as dress, fillet, loin, etc.

[0038] More specifically, the raw tuna block may be, for example, a block of tuna. By forming the raw tuna block into a block, a packaged raw tuna meat product that is easy to handle can be obtained.

[0039] The raw tuna chunk can be any part of the tuna body, such as the lean part of the back meat, the medium fatty part of the back meat, the lean part of the belly, the medium fatty part of the belly, or the fatty part of the belly.

[0040] The parts of raw tuna meat where discoloration has been suppressed can be used as is in final products such as sashimi, so by first turning the landed tuna fish into the packaged raw tuna meat product of the present disclosure, discoloration can be suppressed, minimizing the effort required to remove discolored parts and increasing the yield of the final product.

[0041] There are no particular restrictions on the size of the raw tuna block. The size can be appropriately set depending on the purpose of use. When the raw tuna block is a loin, for example, it may be 65 cm to 90 cm in length and 25 cm to 35 cm in width, and when the raw tuna block is a block, for example, it may be 25 cm square. The thickness of the raw tuna block may be, for example, 1 cm or more, 3 cm or more, 5 cm or more, 10 cm or more, or 20 cm or more. The size of the raw tuna block may be small, for example, 5 cm x 7 cm x 1 cm square, and it can weigh about 200 g, or even about 1 kg. The shape of the raw tuna block may also be any shape as long as it can be packaged in a packaging material.

[0042] Immediately after cutting, raw tuna meat retains its natural color. "Immediately after cutting" refers to, for example, within 30 minutes, 10 minutes, or 5 minutes after cutting. Because cutting exposes the surface of the raw tuna meat to the surrounding environment, prolonged exposure to the surrounding environment, such as air, can significantly change the color. Therefore, it is preferable to package the raw tuna meat immediately after cutting. However, the raw tuna meat can maintain its natural color for a longer period by, for example, packaging the raw tuna meat to block out the surrounding environment after cutting and storing it in a refrigerator. In this case, raw tuna meat within 24 hours or 12 hours after cutting can also maintain its natural color and can be used to produce packaged raw tuna meat products. Within this range, much of the reduced myoglobin in the fish meat is retained, allowing it to exhibit a dark red color. The dark red color is a color that can be distinguished from the bright red color of oxymyoglobin or the dark brown color of metmyoglobin.

[0043] According to one embodiment of the packaged raw tuna meat of the present disclosure, the packaged raw tuna meat can maintain almost the same color tone (raw color tone) of the tuna meat immediately after cutting for a long period of time. Whether or not the packaged raw tuna meat of the present disclosure is the one can be confirmed, for example, by measurement using a color difference meter. Examples of confirmation methods include, but are not limited to, the following method.

[0044] First, a packaged raw tuna meat product packaged with air is prepared as a standard product. The packages of both the measurement target raw tuna meat package and the standard product are opened, and the color change on the surface of the raw tuna block meat that was packaged in the packaging material is measured using an appropriate color difference meter or the like. The measurement target result is compared with the result of the standard product to determine whether the progression of discoloration according to the color change pattern is fast or slow. If the progression of discoloration according to the color change pattern is slow, it can be determined that the product is a packaged raw tuna meat product according to the present disclosure.

[0045] The leakage of moisture from a raw tuna block is generally referred to as dripping. In the packaged raw tuna meat according to the present disclosure, the exposure of moisture from the raw tuna block tends to be suppressed, and the amount of dripping is reduced.

[0046] The packaged raw tuna meat may further have a water-absorbing member. That is, the raw tuna block may be packaged together with the water-absorbing member. In the packaged raw tuna meat, part or all of the raw tuna block may be in contact with the water-absorbing member. For example, only one side of the raw tuna block may be in contact with the water-absorbing member, or the entire raw tuna block may be in contact with the water-absorbing member (the raw tuna block may be wrapped in the water-absorbing member). By bringing the water-absorbing member into contact with the raw tuna block, dripping from the raw tuna block can be further suppressed. Furthermore, by bringing the water-absorbing member into contact with the raw tuna block, discoloration of the surface and outer layer (for example, a layer several mm from the surface) of the raw tuna block due to blood or the like can be more reliably prevented, and a decrease in yield when preparing a final product from the raw tuna block can be more effectively suppressed.

[0047] The water-absorbent member is not particularly limited as long as it is suitable for this purpose, and examples thereof include materials typically used for water absorption. Examples of the shape of the water-absorbent member include a sheet and a tray. Specific examples of the water-absorbent member include a water-absorbent sheet (product name: "Shinsen Plate", manufactured by Kinboshi Seishi Co., Ltd.).

[0048] The packaging material used for the packaged raw tuna meat product is an oxygen-impermeable packaging material. For example, a packaging material having an oxygen permeability of a predetermined value or less can be used as the oxygen-impermeable packaging material. The oxygen permeability of such a packaging material is, for example, 1000 cm 3 / m 2 24hr·atm or less, 500cm 3 / m 2 ·24hr・atm or less, 400cm 3 / m 2 ·24hr・atm or less, 320cm 3 / m 2 ·24hr・atm or less, 300cm 3 / m 2 ·24hr・atm or less, 200cm 3 / m 2 ·24hr・atm or less, 100cm 3 / m 2 ·24hr・atm or less, 50cm 3 / m 2 ·24hr·atm or less, 30cm 3 / m 2 ·24hr・atm or less, 25cm 3 / m 2 ·24hr・atm or less, 20cm 3 / m 2 24hr atm or less, and 10cm 3 / m 224hr·atm or less. Packaging materials with the above oxygen permeability can be used alone or in combination of two or more. Using packaging materials with lower oxygen permeability is preferable from the viewpoint of controlling the oxygen concentration of the gas inside the package, and when used alone, it may be advantageous to select a packaging material with lower oxygen permeability. The oxygen impermeability is a value measured according to the conditions of JIS K 7126 (23°C, 65% RH).

[0049] Examples of packaging materials include films vapor-deposited with silicon oxide, aluminum oxide, aluminum, etc., aluminum foil, and materials containing resin films such as polyamide (nylon), polyethylene naphthalate, polyvinylidene chloride, ethylene vinyl copolymer, and polyvinyl alcohol.

[0050] The shape of the packaging material is not particularly limited and can be appropriately selected depending on the shape of the raw tuna block. The shape of the packaging material may be, for example, a bag-like or box-like shape that is normally used for this purpose. More specifically, packaging materials include those normally used for this purpose, such as bag-like packaging materials made of soft materials and box-like packaging materials made of hard materials.

[0051] The packaging member may have a sealable mechanism to retain the gas inside the packaged product. The sealable mechanism of the packaging member may be integrated with the packaging member or may be separable. Examples of packaging members having a sealable mechanism include packaging members consisting of a box-shaped main body and a sealable lid, and packaging members having a meshable zipper mechanism, adhesive member, etc., as part of the packaging member. The packaging member does not need to be pre-equipped with a sealable mechanism. In this case, it can be sealed using a separate, physically sealable mechanism. Examples of such sealable mechanisms include thermocompression (heat sealing), rubber fasteners, adhesives, pressure-sensitive adhesive sheets, and clips.

[0052] Specific examples of packaging materials include bags made of composite films of nylon and polyethylene, and boxes made of polypropylene.

[0053] In a packaged raw tuna meat product, the oxygen concentration of the gas inside the package packaged together with the raw tuna chunk is 1% by volume or less. The gas inside the package may contain oxygen below the detection limit, or it may be a gas that is completely oxygen-free. By keeping the oxygen concentration of the gas inside the packaged raw tuna meat within the above range, discoloration of the raw tuna chunk after cutting can be suppressed, and the progression of discoloration of the raw tuna chunk after opening the package can be suppressed.

[0054] From the viewpoint of further suppressing discoloration, the oxygen concentration in the gas inside the packaged raw tuna meat may be, for example, 0.8% by volume or less, 0.5% by volume or less, 0.4% by volume or less, 0.3% by volume or less, 0.2% by volume or less, or 0.1% by volume or less. A predetermined gas with an oxygen concentration of 1% by volume or less can be obtained by a conventionally known method, which will be described later.

[0055] The oxygen concentration in the gas inside the package can be confirmed by a method normally used for this purpose. For example, the oxygen concentration in the gas inside the package of packaged raw tuna meat can be confirmed by taking a predetermined amount (e.g., 10 mL) of the gas inside the package using a syringe or the like and measuring it using an oxygen analyzer.

[0056] In a packaged raw tuna meat product, as long as the oxygen concentration of the gas packaged together with the raw tuna block is 1% by volume or less, there is no particular limit to the amount of gas inside the package; for example, the amount of gas per 1 kg of raw tuna block can be 10 L (liters) or less. The amount of gas inside the package may also be adjusted depending on the type of gas. By keeping the amount of gas inside the package within the above range, the color tone of the packaged raw tuna block can be made more desirable, and the packaged raw tuna meat can be produced in such a way that discoloration is suppressed for a longer period of time and the color tone is maintained.

[0057] The gas packaged together with the raw tuna block may contain an inert gas. By including an inert gas in the gas, the progression of discoloration of the raw tuna block can be further suppressed not only during packaging but also after the package is opened. Examples of inert gases include inert gases that can maintain the oxygen concentration inside the package at 1% by volume or less. Examples of such inert gases include at least one gas selected from the group consisting of nitrogen gas, carbon dioxide gas, helium gas, and argon gas.

[0058] As the inert gas, nitrogen gas is particularly preferred. By including nitrogen gas as the inert gas, discoloration can be suppressed for a longer period of time compared to conventional products, both in the packaged product and even after the package has been opened. Furthermore, even if discoloration occurs in the raw tuna block after the package has been opened, the discoloration can be limited to a thinner surface layer compared to conventional products. Note that the inclusion of nitrogen gas may temporarily change the color of the surface layer of the raw tuna block that comes into contact with the nitrogen gas, but this color change is reversible, and by opening the package and exposing it to air, the surface layer of the raw tuna block can return to a color close to the color at the time of cutting, i.e., dark red or bright red.

[0059] The packaged raw tuna meat may contain, for example, other components and food materials, etc., as long as the effects of the present disclosure are not impaired. Examples of such other components include waterproof paper and non-absorbent trays. Examples of such food materials include meat.

[0060] The packaged raw tuna meat according to the present disclosure can also be a packaged raw tuna meat in which raw tuna chunks are packaged in an oxygen-impermeable packaging material together with gas having an oxygen content of 21 mL or less per 1 kg of raw tuna chunks.

[0061] In this specification, the above-mentioned packaged raw tuna meat in which raw tuna meat is packaged together with a gas having an oxygen concentration of 1% by volume or less will be referred to as a "first packaged raw tuna meat," and the packaged raw tuna meat in which raw tuna meat is packaged together with a gas having an oxygen content of 21 mL or less per 1 kg of raw tuna meat will be referred to as a "second packaged raw tuna meat," and when these are not to be distinguished from each other, they may be simply referred to as a "packaged raw tuna meat."

[0062] In the second packaged raw tuna meat, the raw tuna is packaged with a gas containing 21 mL or less of oxygen per 1 kg of raw tuna, so that, similar to the first packaged raw tuna meat, discoloration of the surface or interior of the raw tuna is suppressed over the packaging period and even after the packaging is opened, and the color tone can be maintained for a long period of time.

[0063] In the second packaged raw tuna meat, the raw tuna meat is packaged with a gas having an oxygen content of 21 mL or less per 1 kg of raw tuna meat. By packaging the raw tuna meat with a gas having an oxygen content within the above range, discoloration of the raw tuna meat can be effectively suppressed and the color tone can be maintained for a long period of time.

[0064] The amount of oxygen in the gas in the package can be, for example, 15 mL or less, 10 mL or less, 8 mL or less, 6 mL or less, 4 mL or less, 3 mL or less, 2.5 mL or less, 2 mL or less, 1.5 mL or less, 1 mL or less, 0.5 mL or less, 0.3 mL or less, 0.2 mL or less, etc. per kg of raw tuna whole meat. The amount of oxygen can be confirmed using, for example, an oxygen analyzer, as described in relation to the first packaged raw tuna whole meat.

[0065] As described above, there are no particular restrictions on the amount of gas inside the package, as long as the gas inside the package satisfies the oxygen content of 21 mL or less per 1 kg of raw tuna meat; for example, the amount of gas inside the package can be 10 L (liters) or less per 1 kg of raw tuna meat. The amount of gas inside the package can also be adjusted depending on the type of gas. The amount of air inside the package can be, for example, 100 mL or less per 1 kg of raw tuna meat inside the package. The gas inside the package may contain an inert gas. The contents described for the first raw tuna meat package can be applied to the inert gas applicable to the second raw tuna meat package.

[0066] In the second packaged raw tuna meat, the raw tuna meat may be packaged together with a gas having an oxygen concentration of 1% by volume or less and an oxygen amount of 21 mL or less per 1 kg of raw tuna meat. In this case, the oxygen concentration may be other concentrations described in the first packaged raw tuna meat, and the oxygen amount per 1 kg of raw tuna meat may be other oxygen amounts described above, and any combination thereof may be used within the possible range.

[0067] The contents explained in relation to the first packaged raw tuna meat can be applied to the raw tuna chunks and oxygen-impermeable packaging member in the second packaged raw tuna meat. The contents explained in relation to the first packaged raw tuna meat can also be applied to other matters related to the second packaged raw tuna meat.

[0068] [Manufacturing method for packaged raw tuna meat] A first embodiment of the method for producing a packaged raw tuna meat according to the present disclosure includes cutting up tuna after landing to obtain a raw tuna block (hereinafter also referred to as the cutting step), packaging the raw tuna block in an oxygen-impermeable packaging material and subjecting it to a gas replacement treatment until the oxygen concentration in the gas inside the packaging is 1% by volume or less and / or until the amount of oxygen in the gas inside the packaging is 21 mL or less per kg of raw tuna block (hereinafter also referred to as the packaging step), and sealing the packaging material after the gas replacement treatment (hereinafter also referred to as the sealing step). The method for producing a packaged raw tuna meat according to the present disclosure may include other steps as necessary.

[0069] According to this production method, the above-mentioned packaged raw tuna meat product can be obtained efficiently.

[0070] In the cutting process, the landed tuna is cut using, for example, a cutting tool. When the tuna is landed, it may be subjected to ikijime (killing by killing the fish alive). In this specification, "ikijime" refers to a process in which the caught tuna (live fish) is paralyzed to a brain-dead state and then further bled. When the tuna is landed, it may be paralyzed by a commonly used method. Examples of methods that can be used for paralyzing include carbon dioxide gas, immersion in cold water, and an electric shocker. Of these methods, the method using an electric shocker is preferred because it avoids excessive muscle movement when the tuna is landed and can suppress the occurrence of so-called burnt meat.

[0071] In order to maintain the fresh state of the tuna, it is preferable to store it in a refrigerator between landing and cutting. That is, the cutting step may further include storing the tuna in a refrigerator after landing. The temperature for refrigerated storage may be cold, for example, 10°C or below, 4°C or below, 2°C or below, or 0°C or below, and above the freezing temperature.

[0072] The tuna provided to the cutting process may be either wild-caught tuna or farmed tuna. Wild-caught tuna and farmed tuna may be fish in their natural form, or may be fish in the so-called GG form. In the case of farmed tuna, it is preferable that the tuna is an individual that has gained weight and fatness during the growing period. The weight of the tuna provided to the cutting process is preferably 40 kg or more, more preferably 60 kg or more, and even more preferably 80 kg or more.

[0073] The fatness index of the tuna provided to the cutting process is preferably 20 or higher, more preferably 22 or higher, and even more preferably 24 or higher. Such tuna is a fatty fish, with abundant fat throughout the fish, and is highly commercially valuable when processed into food products, making it preferable. In this specification, "fatness index" refers to the value calculated from the total body weight and fork length of the tuna according to the following formula: Obesity index = {total weight (g) / [fork length (cm)] 3}×1000

[0074] The cutting can be carried out at room temperature, for example, in an environment of 18 to 20° C. From the viewpoint of maintaining the freshness of the raw tuna block meat and preventing discoloration, the cutting is preferably carried out soon after landing, for example, within 24 hours or within 12 hours after landing.

[0075] The cutting can be carried out using a cutting tool capable of cutting fish into predetermined sizes. There are no particular limitations on the cutting tool, and examples include a kitchen knife, a cutter, a knife, and a cutting machine. A relatively short kitchen knife is preferable as the cutting tool. The blade length of such a knife is preferably 50 cm or less, more preferably 20 cm or more but less than 30 cm, and even more preferably 20 cm or more but less than 28 cm. By using such a cutting tool, it is possible to reliably cut up relatively soft fish, such as fish immediately after landing, and even farmed tuna immediately after landing.

[0076] It is preferable to securely fix the fish during cutting. The fixing method can be, for example, a method in which the fish is held down by personnel or a method in which the fish is held down using a fixing device, without any particular limitation. The fixing method can be selected appropriately taking into consideration the size of the fish, efficiency, etc.

[0077] The cutting step may further include trimming the raw tuna block obtained by cutting. Trimming adjusts the shape of the raw tuna block, thereby improving the efficiency of subsequent processing. For trimming, any tool can be used without limitation as long as it can adjust the shape of the raw tuna block. Such trimming tools may include, for example, the cutting tool used during cutting, scissors, etc.

[0078] From the viewpoint of maintaining the freshness of the raw tuna and preventing discoloration, the raw tuna block obtained by cutting is preferably stored in a refrigerator until it is packaged in a packaging material. That is, the method for producing a packaged raw tuna meat according to the present disclosure may further include storing the raw tuna block in a refrigerator. When storing the raw tuna block in a refrigerator, it is possible to maintain the color tone immediately after cutting until it is packaged, and it is not necessary to package the raw tuna block immediately after the cutting step.

[0079] The refrigerated storage temperature is preferably a cold temperature, for example, 10°C or below, 4°C or below, 2°C or below, or 0°C or below, and above the freezing temperature, for example, a temperature of 0°C ± 2°C. If the refrigerated storage temperature is within the above range, the raw tuna block can be stored without freezing and the raw color tone can be more sufficiently maintained. Note that, as long as discoloration of the raw tuna block can be suppressed, it may be stored at a temperature higher than the above-mentioned example temperatures.

[0080] In the packaging process, the cut raw tuna block is packaged in oxygen-impermeable packaging material and subjected to a gas replacement treatment until the oxygen concentration of the gas inside the package reaches 1% by volume. In this specification, "gas replacement" means changing the gas inside the package, and includes introducing a different type of gas into the package to replace the gas inside the package, and removing the gas that makes up the gas inside the package to a desired amount.

[0081] The packaging method is not particularly limited and can be appropriately selected depending on, for example, the shape of the packaging material, the packaging mechanism, etc. Packaging can be carried out at room temperature, for example, in an environment of 18 to 20°C. Furthermore, the packaging material can be the same as that described above for the packaged raw tuna meat product, and multiple types of packaging material may be used to more reliably maintain the type and composition ratio of the gas inside the packaged product.

[0082] From the viewpoint of preventing discoloration of the raw tuna block, the packaging step is preferably carried out within 24 hours or 12 hours after cutting, and may be carried out immediately after the cutting process. If the raw tuna block is refrigerated after cutting, the packaging step may be carried out immediately after the refrigerated storage ends. If the raw tuna block is refrigerated after cutting, the packaging step does not need to be completed within about 24 hours after landing, as long as it is carried out after cutting, and may be completed, for example, within 5 days, 4 days, 3 days, or 2 days after landing. If packaging is not carried out immediately after cutting, a processing step may be further included before packaging, and the tuna may be further processed into a desired shape appropriate for a packaged product.

[0083] The gas substitution treatment may be performed by any method as long as it is a treatment that can reduce the oxygen concentration of the gas inside the packaging material to a predetermined value or less. Examples of the gas substitution treatment method include a degassing treatment, a gas filling treatment, and a combination of these. More specific examples of the gas substitution treatment method include a method of degassing the inside of the package to a desired gas amount, a method of filling the inside of the packaging material with an inert gas, a method of degassing the inside of the package and then filling it with an inert gas, and a method of performing these treatments multiple times in succession. The degassing treatment may be performed, for example, using a vacuum packaging machine or by applying pressure from the outside.

[0084] The gas replacement treatment is preferably carried out by repeating a set of filling with an inert gas and degassing a plurality of times, and by carrying out the gas replacement treatment in this manner, the oxygen concentration of the gas inside the package can be more reliably reduced to a predetermined value or less. In addition to the above, other methods of gas replacement treatment may also be used, such as a method using an oxygen scavenger.

[0085] As explained above for the packaged raw tuna meat, the inert gas used in the gas substitution treatment can be at least one gas selected from the group consisting of nitrogen gas, carbon dioxide gas, helium gas, and argon gas. The inert gas preferably contains nitrogen gas, and more preferably consists of nitrogen gas.

[0086] In the sealing step, the packaging member is sealed after the gas replacement treatment. That is, the sealing step is a step in which a gas with an oxygen concentration of 1% by volume or less and the cut raw tuna block are sealed in the packaging member. The sealing method can be selected appropriately depending on the type of packaging member. From the viewpoint of maintaining the gas inside the package, a preferred sealing method is, for example, heat sealing. The sealing step makes it possible to obtain the above-mentioned packaged raw tuna meat product in which the raw tuna block is packaged together with a predetermined gas.

[0087] The method for producing a packaged raw tuna meat product may further include refrigerating the packaged raw tuna meat product obtained after the sealing step. By further including refrigerating the packaged raw tuna meat product, discoloration of the raw tuna meat can be suppressed for a longer period of time.

[0088] [Method for preventing discoloration of raw tuna meat] A first embodiment of the method for inhibiting discoloration of a raw tuna block according to the present disclosure includes cutting up a landed tuna to obtain a raw tuna block (hereinafter also referred to as the cutting process), packaging the raw tuna block in an oxygen-impermeable packaging material and performing a gas replacement process until the oxygen concentration of the gas inside the packaging is 1% by volume or less and / or the amount of oxygen in the gas inside the packaging is 21 mL or less per kg of raw tuna block (hereinafter also referred to as the packaging process), and sealing the packaging material after the gas replacement process to obtain the above-mentioned packaged raw tuna meat (hereinafter also referred to as the sealing process). The above method for inhibiting discoloration of a raw tuna block may further include refrigerating the obtained packaged raw tuna meat (hereinafter also referred to as the refrigerated storage process). The above method for inhibiting discoloration of a raw tuna block may include other processes as necessary.

[0089] That is, the method for suppressing discoloration of a raw tuna block according to the present disclosure includes a cutting step, a packaging step, and a sealing step, similar to the above-described method for producing a packaged raw tuna meat. Therefore, the change in color of the raw tuna block in the packaged raw tuna meat is delayed to maintain the color, and discoloration of the raw tuna block is suppressed to maintain the color during packaging, and in some cases even after the package is opened, so that a good color can be maintained for a longer period of time than conventional products. The above-described method for suppressing discoloration of a raw tuna block may further include refrigerating the obtained packaged raw tuna meat. By refrigerating the packaged raw tuna meat, the change in color of the raw tuna block in the packaged raw tuna meat is further delayed to maintain the color more satisfactorily, and discoloration of the raw tuna block is suppressed to maintain the color more satisfactorily during packaging, and in some cases even after the package is opened, so that a good color can be maintained for a longer period of time than conventional products.

[0090] According to the method for inhibiting discoloration of raw tuna block meat of the present disclosure, the progression of discoloration of raw tuna block meat can be delayed and the color tone can be maintained, thereby inhibiting the occurrence of discolored areas in the raw tuna block meat. Furthermore, even if areas of the raw tuna block meat that change color are formed, the distance from the surface of the discolored areas can be made smaller compared to packaged products packaged with air. For these reasons, the method for inhibiting discoloration of raw tuna block meat can increase the product yield.

[0091] Up to the sealing step in the method for inhibiting discoloration of raw tuna meat, the entire contents already described in relation to the method for producing a packaged raw tuna meat product can be applied.

[0092] In the refrigerated storage step, the packaged raw tuna meat obtained after the sealing step is stored in a refrigerator. The temperature in the refrigerated storage step is preferably a cold temperature, for example, 10°C or below, 4°C or below, 2°C or below, or 0°C or below, and a temperature above the freezing temperature, for example, a temperature of 0°C ± 2°C. If the temperature in the refrigerated storage step is within the above range, discoloration of the raw tuna block can be more effectively suppressed and the color can be more fully maintained until the package is unpackaged, and in some cases even after the package is unpackaged, allowing the good color to be maintained for a longer period of time compared to conventional products.

[0093] The refrigerated storage step can be continued until the package is unwrapped and the raw tuna block is used or eaten. From the viewpoint of maintaining the freshness, color, texture, etc. of the raw tuna block, the refrigerated storage period can be, for example, at least one week, or at least four weeks. The refrigerated storage period can be ended within a range that allows the color, etc. of the raw tuna block to be maintained.

[0094] The method for inhibiting discoloration of raw tuna meat may further include a step of unpacking the packaged raw tuna meat that has been stored in a refrigerator. The unpacking method may be selected depending on the packaging method, and may include, without limitation, opening, cutting, peeling, and removing fasteners.

[0095] In a packaged raw tuna meat product obtained through the method for inhibiting discoloration of raw tuna meat, discoloration of the raw tuna meat is inhibited even after the package is opened, and the color tone of the raw tuna meat can be maintained for a longer period than conventional products. In a packaged raw tuna meat product obtained through the method for inhibiting discoloration of raw tuna meat, the occurrence of discolored areas in the raw tuna meat is also inhibited, and if discolored areas occur, the area is small, preferably limited to the shallow surface area, so that even after long-term storage, the yield can be increased when preparing the final product. When an inert gas is used during packaging, discoloration can be inhibited for an even longer period than conventional products, not only in the packaged product but also after opening the package.

[0096] The raw tuna meat packaged product and the raw tuna meat discoloration suppression method according to the present disclosure are raw tuna meat that maintains the color tone of raw tuna meat well and retains its freshness well.

[0097] The raw tuna block meat according to the present disclosure can be confirmed by the following evaluation method.

[0098] (Check for discolored areas) In the raw tuna chunk obtained from the packaged raw tuna meat according to the present disclosure, there are fewer discernible discolored areas on the surface or inside of the meat compared to the raw tuna chunk obtained from a conventional package packaged with air. Therefore, whether or not the target packaged raw tuna meat is the packaged raw tuna meat according to the present disclosure can be confirmed by examining the discolored areas of the obtained raw tuna chunk.

[0099] The evaluation method involves unwrapping the packaged product, removing the raw tuna block, and cutting out a portion to use as an evaluation sample. The evaluation sample is then cut down the center and the cut surface is observed. Since the color changes from dark red when cut to bright red and then dark brown, it is possible to determine whether the sample is a raw tuna block from the packaged raw tuna meat product according to the present disclosure or a comparative product packaged in air based on the presence or absence of discoloration from the color when cut, the presence or absence of discoloration on the surface or inside, and the thickness of the discolored portion.

[0100] Specifically, the packaged product is placed under conditions of room temperature 18°C ​​and relative humidity 60-90%, and the raw tuna block removed from the package is cut in the center and the thickness of the discolored part from the surface is measured every predetermined time. If multiple layers with distinguishable different color tones are formed in the thickness direction, the thickness of each can be measured. If the thickness of the discolored part is smaller than that of a conventional product packaged with air, it can be confirmed that the raw tuna block according to the present disclosure is the one disclosed.

[0101] The raw tuna block contained in the packaged raw tuna meat according to the present disclosure is prevented from discoloring while packaged, and in some cases even after opening the package, and can maintain a good color tone for a long period of time compared to conventional products. As a result, raw tuna block with a good color tone obtained after landing and cutting can be obtained for a long period of time. Furthermore, raw tuna block with a good color tone obtained after landing and cutting can be stored for a long period of time and then further processed to provide a tuna processed food with high commercial value.

[0102] Second Embodiment A second embodiment of the packaged raw tuna meat according to the present disclosure is a packaged raw tuna meat that includes an oxygen-impermeable packaging member and a piece of raw tuna meat tightly packed by the packaging member, and the amount of gas inside the package is 21 mL or less per 1 kg of the raw tuna meat.

[0103] A second embodiment of the method for producing a packaged raw tuna meat according to the present disclosure is a method for producing a packaged raw tuna meat, which includes cutting up tuna after landing to obtain a raw tuna block, tightly packaging the raw tuna block in an oxygen-impermeable packaging material, and setting the amount of gas inside the package to 21 mL or less per 1 kg of raw tuna block.

[0104] A second embodiment of the method for inhibiting discoloration of a raw tuna block according to the present disclosure is a method for inhibiting discoloration of a raw tuna block, which includes cutting up tuna after landing to obtain a raw tuna block, and tightly packaging the raw tuna block in an oxygen-impermeable packaging material, reducing the amount of gas inside the package to 21 mL or less per 1 kg of the raw tuna block, thereby obtaining the packaged raw tuna meat.

[0105] The second embodiment will be described below, but the same descriptions can be applied to the disclosure according to the second embodiment and the disclosure according to the first embodiment described above with respect to common configurations and optional configurations. The second embodiment will be described mainly with respect to the parts that are different from the first embodiment described above.

[0106] According to one aspect of the present disclosure, the raw tuna chunk is tightly packed in the above-mentioned packaging member, and the amount of gas inside the package is 21 mL or less per 1 kg of raw tuna chunk, so that it is possible to provide a packaged raw tuna meat product that is inhibited from discoloring while it is packaged and even after it has been opened.

[0107] According to one aspect of the present disclosure, raw tuna chunks obtained by cutting after landing are tightly packaged in a substantially vacuum or vacuum state with a predetermined gas volume or less, which makes it possible to delay the progression of the aforementioned change in color tone of the raw tuna chunks over time. In other words, according to one aspect of the present disclosure, it is possible to provide a packaged raw tuna meat product that retains its color well. This tendency for delay in color tone change can be confirmed in the packaged product, and can also be confirmed after the package is opened.

[0108] Furthermore, in the second embodiment of the packaged raw tuna meat according to the present disclosure, the raw tuna chunk is tightly packed in a substantially vacuum or vacuum state as described above, so that the change in color tone of the raw tuna chunk can be delayed for a longer period of time than in conventional packaged raw tuna meat during the packaging, and in some cases even after the packaging has been opened. Also, in the second embodiment of the packaged raw tuna meat according to the present disclosure, a good color tone can be maintained for a longer period of time than in conventional products.

[0109] Furthermore, in the second embodiment of the method for inhibiting discoloration of raw tuna blocks according to the present disclosure, the raw tuna blocks are tightly packed in a substantially vacuum or vacuum state as described above, and therefore, compared to conventional products, color change in the packaged raw tuna blocks is delayed for a longer period, and in some cases, good color can be maintained for a longer period even after the packaging is opened.

[0110] [Packaged raw tuna meat] A second embodiment of the packaged raw tuna meat according to the present disclosure is a packaged raw tuna meat that includes an oxygen-impermeable packaging member and a piece of raw tuna meat tightly packed by the packaging member, and the amount of gas inside the package is 21 mL or less per 1 kg of the raw tuna meat.

[0111] The packaging material used for packaged raw tuna meat is preferably a film material with mechanical properties of low elongation and high flexibility. When raw tuna meat is tightly packaged while it is still highly fresh, a so-called bulging phenomenon may occur after packaging due to rigor mortis of the raw tuna meat. When a packaging material with high elongation is used, the bulging may cause a gap between the raw tuna meat and the packaging material. Gas inside the packaging may collect in this gap, and contact with the collected gas may cause discoloration around the bulged portion of the raw tuna meat. Packaging materials with low elongation are less likely to cause gaps due to the bulging, and therefore tend to be able to better suppress discoloration around the bulged portion. Furthermore, when packaging raw tuna meat, highly flexible packaging materials can accurately conform to the shape of the raw tuna meat without crushing it, thereby uniformly enveloping the raw tuna meat. In other words, highly flexible packaging materials can increase the degree of adhesion to the raw tuna meat. In this way, by using a packaging member having mechanical properties of small elongation and high flexibility, it is possible to tightly package raw tuna chunks at a higher degree of vacuum.

[0112] The elongation of the packaging material can be evaluated using the tensile strength or elongation at break as an index. The tensile strength and elongation at break are values ​​measured in accordance with JIS K 7127 under conditions of 23°C and 50% RH.

[0113] The tensile strength of the packaging material may be, for example, 250 MPa or less, and may be 80 MPa to 250 MPa, or 100 MPa to 200 MPa. The tensile strength of the packaging material may differ between the longitudinal and transverse directions, and the tensile strengths in the longitudinal and transverse directions can be adjusted, for example, depending on the shape and material of the packaging material. For example, when the packaging material is a film material prepared by extrusion molding, and the longitudinal direction during extrusion molding is the longitudinal direction of the packaging material and the width direction is the transverse direction of the packaging material, the tensile strength in the longitudinal direction can be 80 MPa to 200 MPa, or 100 MPa to 150 MPa, and the tensile strength in the transverse direction can be 100 MPa to 250 MPa, or 130 MPa to 200 MPa. The tensile strength in the longitudinal direction and the tensile strength in the transverse direction can be adjusted by controlling the extrusion speed and winding speed of the film material during extrusion molding, respectively.

[0114] The elongation at break of the packaging member may be, for example, 200% or less, or may be 110% to 200%, or 120% to 180%. The elongation at break of the packaging member may differ between the longitudinal direction and the transverse direction, depending on, for example, the shape and material of the packaging member. For example, when the packaging member is a film member prepared by extrusion molding, and the longitudinal direction during extrusion molding is the longitudinal direction of the packaging member and the width direction is the transverse direction of the packaging member, the elongation at break in the longitudinal direction can be 120% to 200%, or 130% to 180%, and the elongation at break in the transverse direction can be 110% to 180%, or 110% to 150%. The tensile strength in the longitudinal direction and the elongation at break in the transverse direction can be adjusted by controlling the extrusion speed and winding speed of the film member during extrusion molding, respectively.

[0115] The flexibility of a packaging material can be evaluated using Young's modulus (tensile modulus), which is a value measured in accordance with JIS K 7127 at 23°C and 50% RH.

[0116] The tensile modulus of the packaging material may be, for example, 900 MPa or less, 500 MPa to 900 MPa, or 650 MPa to 850 MPa. The tensile modulus of the packaging material may differ between the longitudinal and transverse directions, and the tensile strength in the longitudinal and transverse directions can be adjusted, for example, by the shape and material of the packaging material. For example, when the packaging material is a film material prepared by extrusion molding, and the longitudinal direction during extrusion molding is the longitudinal direction of the packaging material and the width direction is the transverse direction of the packaging material, the Young's modulus in the longitudinal direction can be 500 to 800 MPa, or 650 to 700 MPa, and the Young's modulus in the transverse direction can be 550 MPa to 850 MPa, or 650 MPa to 850 MPa. The tensile strength in the longitudinal direction and the tensile modulus in the transverse direction can be adjusted by controlling the extrusion speed and winding speed of the film material during extrusion molding, respectively.

[0117] In order to preferably exhibit the above-mentioned mechanical properties, the thickness of the packaging member is preferably, for example, 15 μm to 80 μm, 20 μm to 70 μm, 30 μm to 60 μm, or 35 μm to 50 μm.

[0118] Packaging materials having the above-mentioned oxygen permeability and mechanical properties are preferred from the viewpoint of more fully and tightly packaging raw tuna chunks, and any material that satisfies the above-mentioned conditions can be used without particular restrictions. Examples of packaging materials having the above-mentioned oxygen permeability and mechanical properties include co-extruded multilayer films containing ethylene vinyl alcohol (EVOH). Examples of co-extruded multilayer films containing EVOH include "Krehalon ML40G" (trade name, manufactured by Kureha Corporation). Krehalon ML40G has a multilayer structure (PET / PA / EVOH / PO multilayer structure) in which polyethylene terephthalate (PET), polyamide (PA), EVOH, and polyolefin (PO) are laminated in this order, and is 40 μm thick.

[0119] The sealable mechanism in the packaging member may be integrated with the packaging member or may be separable. Examples of packaging members having a sealable mechanism include packaging members that have a meshable zipper mechanism, adhesive member, or the like as part of the packaging member. The packaging member does not need to be pre-equipped with a sealable mechanism. In this case, the packaging member may be sealed using a separate, physically sealable mechanism. Examples of such sealable mechanisms include thermocompression (heat sealing), rubber fasteners, adhesives, pressure-sensitive adhesive sheets, and clips.

[0120] Specific examples of packaging materials include bags made of composite film of nylon and polyethylene, and boxes made of polypropylene.

[0121] In a packaged raw tuna meat product, the amount of gas inside the package is 21 mL or less per 1 kg of raw tuna meat. By keeping the amount of gas inside the packaged raw tuna meat within this range, discoloration of the raw tuna meat after cutting can be suppressed, and the progression of discoloration of the raw tuna meat after opening the package can also be suppressed.

[0122] The amount of gas inside a package can be confirmed, for example, by the following method. After packaging, the package is left to stand for 10 minutes, and then placed in a container filled with water or other liquid, thereby applying pressure to the entire package and collecting air bubbles in one location on the upper surface of the tuna block inside the package. The air bubbles that have collected on the surface are sucked out into a syringe while visually checking, and the amount collected in the syringe is measured, and the obtained amount is taken as the gas amount. Measurement is carried out at room temperature (18°C to 20°C).

[0123] The amount of gas in the package may be, for example, 15 mL or less, 10 mL or less, 8 mL or less, 6 mL or less, 4 mL or less, 3 mL or less, 2.5 mL or less, 2 mL or less, 1.5 mL or less, 1 mL or less, 0.5 mL or less, 0.3 mL or less, or 0.2 mL or less per 1 kg of raw tuna, or may be below the detection limit, for example, 0 mL. The smaller the amount of gas in the package, the more effectively discoloration can be suppressed.

[0124] The type of "gas" in the second embodiment is not particularly limited, and examples thereof include air, oxygen gas, inert gas, and mixtures thereof. Examples of inert gases include nitrogen gas, carbon dioxide gas, helium gas, and argon gas.

[0125] [Manufacturing method for packaged raw tuna meat] A second embodiment of the method for producing a packaged raw tuna meat according to the present disclosure includes cutting up tuna after landing to obtain a raw tuna block (hereinafter also referred to as the cutting step), tightly packaging the raw tuna block in an oxygen-impermeable packaging material and reducing the amount of gas inside the package to 21 mL or less per kg of raw tuna block (hereinafter also referred to as the packaging step), and may include other steps as necessary. According to this production method, the above-mentioned packaged raw tuna meat can be obtained efficiently.

[0126] In the packaging process, the raw tuna block is tightly packaged in an oxygen-impermeable packaging material, and the amount of gas inside the package is set to 21 mL or less per 1 kg of raw tuna block. There are no particular restrictions on the packaging method, and it can be carried out appropriately depending on the shape of the packaging material and the packaging mechanism, etc. Furthermore, multiple types of packaging material may be used to more reliably maintain the type and composition ratio of the gas inside the package. Packaging can be carried out at room temperature, for example, in an environment of 18 to 20°C.

[0127] The tightly sealed packaging can be carried out by wrapping the raw tuna block in the packaging member so that the packaging member conforms to the shape of the raw tuna block. In this case, it is preferable to pack the raw tuna block so that no gas remains between the raw tuna block and the packaging member. By tightly sealing the raw tuna block, the amount of gas inside the resulting packaged raw tuna meat can be reduced.

[0128] The amount of gas inside a packaged raw tuna meat product can be kept to 21 mL or less per 1 kg of raw tuna meat by, for example, tightly packaging as described above. Furthermore, a method for reducing the amount of gas inside the package can be used to more reliably keep the amount of gas below a predetermined level. The method for reducing the amount of gas inside the package to a predetermined level or less may be any method known in the art for this purpose, such as degassing. Degassing may be performed, for example, using a vacuum packaging machine or by applying external pressure. In addition to the above, a method for reducing the amount of gas inside the package to a predetermined level or less may also be a method using an oxygen absorber.

[0129] The method for producing a packaged raw tuna meat product may further include sealing the packaging material after tightly packaging (hereinafter also referred to as a sealing step) in order to maintain the amount of gas inside the packaged product after tightly packaging for a long period of time. The sealing method can be selected appropriately depending on the type of packaging material. From the viewpoint of maintaining the gas inside the package, a preferred sealing method is, for example, heat sealing. By the sealing step, the packaged raw tuna meat product according to the present disclosure, in which the raw tuna meat is packaged so that the amount of gas inside the package is equal to or less than a predetermined amount, can be stored for a longer period of time.

[0130] The method for producing a packaged raw tuna meat product may further include refrigerating the packaged raw tuna meat product obtained after the packaging step or the sealing step. By further including refrigerating the packaged raw tuna meat product, discoloration of the raw tuna meat block can be suppressed for a longer period of time.

[0131] [Method for preventing discoloration of raw tuna meat] A second embodiment of the method for inhibiting discoloration of raw tuna blocks according to the present disclosure includes cutting and dicing tuna after landing to obtain raw tuna blocks (hereinafter also referred to as the cutting step), and tightly packaging the cut raw tuna blocks in oxygen-impermeable packaging materials to reduce the amount of gas in the packaging to 21 mL or less per kg of raw tuna blocks, thereby obtaining the above-mentioned packaged raw tuna meat (hereinafter also referred to as the packaging step). The above-mentioned method for inhibiting discoloration of raw tuna blocks may further include refrigerating the obtained packaged raw tuna meat (hereinafter also referred to as the refrigerated storage step). The above-mentioned method for inhibiting discoloration of raw tuna blocks may include other steps as necessary.

[0132] The entire contents already described regarding the method for producing a packaged raw tuna meat product can be applied up to the packaging step in the method for inhibiting discoloration of a raw tuna block.

[0133] The refrigerated storage step can be continued until the packaged product is unpacked and the raw tuna block is used or eaten. From the viewpoint of maintaining the freshness, color, texture, etc. of the raw tuna block, the refrigerated storage period can be, for example, at least 3 days, at least 4 days, at least 5 days, at least 6 days, at least 1 week, at least 2 weeks, at least 3 weeks, or at least 4 weeks. The refrigerated storage period can also be ended within a range in which the color, etc. of the raw tuna block can be maintained.

[0134] The raw tuna meat packaged product and the raw tuna meat discoloration suppression method according to the present disclosure are raw tuna meat that maintains the color tone of raw tuna meat well and retains its freshness well.

[0135] The raw tuna block meat according to the present disclosure can be confirmed by the following evaluation method.

[0136] (1) Color tone evaluation The raw tuna block meat according to the present disclosure is tightly packed, and the amount of gas inside the package is very small or it is a vacuum, so the transition from bright red to dark brown is delayed and color change is well suppressed. This color change can be measured with a color difference meter, for example, to measure the change over time from processing to unpacking, and the change over time from opening the sealed package until a predetermined time has passed. * value, and a * / b * It can be evaluated and confirmed based on values, etc.

[0137] The a of raw tuna meat measured with a color difference meter * In the case of the packaged raw tuna meat that has been packaged for 4 days or more (for example, 4 days, 5 days, 6 days, or 7 days, etc.), the value may be, for example, 14.05 or more, 15.00 or more, 16.00 or more, 17.00 or more, 17.30 or more, 17.50 or more, or 17.7 or more immediately after opening the packaged raw tuna meat, 0.5 hours, 2 hours, 4 hours, or 8 hours after opening. * There is no particular upper limit to the value, and it can be, for example, 20 or less, or 19 or less.

[0138] The a of raw tuna meat measured with a color difference meter * / b * The values ​​are measured immediately after opening the above-mentioned raw tuna meat package that has been packaged for 4 days or more (for example, 4 days, 5 days, 6 days, or 7 days), 0.5 hours after opening, 2 hours after opening, 4 hours after opening, or 8 hours after opening, and the a value is measured 0.5 hours after opening the above-mentioned raw tuna meat package. * / b * The standard value may be, for example, 96% or more, 99% or more, 100% or more, 101% or more, or 102% or more, and may be 120% or less, 110% or less, or 105% or less.

[0139] The a of raw tuna meat measured with a color difference meter * / b *In the packaged fresh tuna meat product for which 4 days or more have passed since packaging (for example, 4 days, 5 days, 6 days, or 7 days have passed), the RI may be 1.46 or more, 1.48 or more, 1.50 or more, 1.60 or more, or 1.70 or more immediately after opening the packaged fresh tuna meat product, and may be 1.29 or more, 1.30 or more, 1.31 or more, 1.34 or more, 1.40 or more, or 1.45 or more 0.5 hours, 2 hours, 4 hours, or 8 hours after opening the packaged fresh tuna meat product. * / b * There is no particular restriction on the upper limit, and it can be, for example, 1.90 or less, or 1.80 or less.

[0140] (2) K value The K value is an index expressed by the following formula (1), which measures the degree of decomposition of ATP (adenosine triphosphate) and quantifies the freshness assessment.

[0141] K value =(HxR+Hx) / (ATP+ADP+AMP+IMP+HxR+Hx)×100...(1) In the above formula, ATP represents the content of adenosine triphosphate, ADP represents the content of adenosine diphosphate, AMP represents the content of adenosine monophosphate, IMP represents the content of inosinic acid, HxR represents the content of inosine, and Hx represents the content of hypoxanthine.

[0142] ATP in fish meat is broken down after death and gradually decomposes into ADP, AMP, IMP, HxR, and Hx. ADP, AMP, IMP, HxR, and Hx are compounds produced during the decomposition process of ATP and are also called ATP-related substances. A smaller K value indicates a smaller ratio of the total amount of HxR and Hx to the total amount of ATP and ATP decomposition-related substances in the measurement sample, meaning that the decomposition from IMP to HxR or Hx has not progressed sufficiently. In other words, the smaller the K value, the more ATP decomposition-related substances (i.e., ATP, ADP, AMP, and IMP) remain, indicating that the fish meat is fresher.

[0143] The K value of the raw tuna block obtained by the above-mentioned method for inhibiting discoloration of the raw tuna block can be, for example, 35% or less, preferably 15% or less, and more preferably 10% or less.

[0144] One embodiment of the method for providing raw tuna chunks according to the present disclosure is a method for providing raw tuna chunks, which includes a step of opening a package of raw tuna. * The K value may be 17.05 or more or 17.38 or more 8 hours after the packaged raw tuna meat is opened, and the K value of the raw tuna meat represented by the above formula (1) may be 35% or less.

[0145] Although several embodiments have been described above, the descriptions of the common configurations can be applied to each other, and the present disclosure is not limited to the above-described embodiments. [Example]

[0146] The present disclosure will be described in more detail below with reference to examples and comparative examples, although the present disclosure is not limited to the following examples.

[0147] <First aspect> [Exam Preparation] (1) Tuna farming The breeding began with 1,500 tuna weighing approximately 3 kg and measuring approximately 55 cm in length, housed in a 40 m x 45 m Aba-style fish pen. Mackerel and sardines were used as feed, and the fish were normally fed satiation once a day, and once every two days during the winter. The breeding began in July and continued for over three years, with the fish paralyzed using an electric shocker and then landed. Immediately after landing, the fish were bled and killed, and the gills and internal organs were removed using standard methods to obtain GG tuna. The GG tuna weighed more than 80 kg and had a fatness index of 24 or higher.

[0148] (2) Juwari The cutting was carried out in a cutting room with a room temperature of 18-20°C. A cutting board known to be non-slip was selected. The fish was held in place by hand, with no special fixing devices used. The workers wore vinyl gloves on both hands, and also wore cut-resistant gloves on the hand not holding the knife.

[0149] Immediately after obtaining the tuna GG obtained as described above, first, the head and tail were cut off from the tuna GG using a knife with a blade length of 20 cm to 28 cm, and then, according to the usual procedure, the fish meat was cut into loins by cutting the dorsal side and then the ventral side.

[0150] When cutting, the first cut was made on both sides of the center line on the dorsal side of the GG, cutting the surface of the GG a few millimeters deep. Then, the knife was angled at about 10-30 degrees to the body of the fish, and the blade was carefully inserted little by little until the neural spines were visible. When cutting, the separated flesh was gently pinched to prevent tearing, and the process was carried out carefully. The ventral side was cut in the same way. Because the flesh was still elastic within a few hours of being caught, careful cutting with a relatively short knife allowed us to reliably obtain each of the four loins.

[0151] Next, the loin was trimmed to adjust its shape. When trimming, the knife was operated so that it was almost parallel to the flesh of the tuna, cutting at an angle of 5° or less. As described above, the loin was obtained 3 hours after ikijime. The length of the loin was 65 cm to 90 cm, and the thickness was 15 cm to 23 cm.

[0152] When storing the obtained loins, they were wrapped in absorbent paper and then placed directly in a plastic bag. The entire loin was then submerged in a 500 L polyethylene container box filled with ice water (water temperature 0°C ± 2°C) so that the entire plastic bag containing the loin was submerged in ice water, and stored in this state in a refrigerator until use.

[0153] When preparing blocks from the obtained loin, roughly cubic blocks weighing approximately 200 g to 3.5 kg and measuring approximately 5 cm to 25 cm thick were cut out from the cut loin or from the loin that had been refrigerated using a knife with a blade length of 20 cm to 28 cm.

[0154] (3) Packaging materials and absorbent sheets, etc. The following tests were carried out using the loins or blocks prepared as described above. When preparing sashimi as the evaluation sample pieces, slices measuring approximately 4 cm to 10 cm x approximately 5 cm to 20 cm x approximately 1 cm to 2 cm were prepared from the lean or medium-fatty part on the back side of the loin or block, and then fillets approximately 0.5 cm to 1.0 cm thick were prepared to serve as the evaluation sample pieces.

[0155] The packaging types used in the evaluation are shown in Table 1. The oxygen permeability of each packaging material is also shown in Table 1. In Table 1, "*1" means that there is almost no oxygen permeation, and "*2" means that samples of 40.0 cm x 20.0 cm, 40.0 cm x 30 cm, or 40.0 cm x 50.0 cm were appropriately selected based on the sample size. In Table 1, PE is an abbreviation for polyethylene, and NY is an abbreviation for nylon.

[0156] In Table 1, the products used are as follows: Plastic container: "Keep Lock Easy Clean" (deep airtight container, product name, manufactured by Pearl Metal Co., Ltd.) Freezer bag: "Ziploc (registered trademark)" (product name, manufactured by Asahi Kasei Home Products Co., Ltd.) Nylon plastic bag: "Shinjumon" (product name, manufactured by Chlorine Chemical Co., Ltd.) Absorbent sheet: "Fresh Plate" (product name, manufactured by Kinsei Paper Co., Ltd.) Cooking sheet: "Fuji Cooking Paper" (product name, manufactured by Fujinap Co., Ltd.) Waterproof paper: "Sanproof (registered trademark) G" (cutting paper) (product name, manufactured by Asahi Kasei Home Products Corporation)

[0157] [Table 1]

[0158] [Example 1-1] (1) Preparation of Sample 1 and Control Sample Within 24 hours after landing, the GG tuna was cut and processed into blocks, creating six blocks of approximately 1 kg each. These were then divided into three blocks for preparing sample 1 and three blocks for preparing the control sample.

[0159] The blocks for preparing Sample 1 (weight: 1.14 kg, 1.14 kg, and 1.26 kg) obtained as described above were divided into smaller blocks (size: length 7 cm, width 7 cm, thickness approximately 1 cm to 2 cm) and packaged using Type I packaging material and a water-absorbent sheet as follows to obtain Sample 1.

[0160] The block was sandwiched between absorbent sheets and then placed in a plastic container with a lid, and the plastic container was then placed in a freezer bag. Next, with the zipper of the freezer bag mostly closed, a plastic pipette for gas injection was inserted between the plastic container and the lid of the plastic container, and nitrogen gas was injected. When the freezer bag expanded due to the nitrogen gas leaking from the plastic container, the freezer bag was manually compressed to release the gas inside the freezer bag while the nitrogen gas was still being released, and the freezer bag was allowed to expand again due to the nitrogen gas leaking from the plastic container. This operation was repeated four times to replace the gas inside the plastic container and the freezer bag.

[0161] Finally, when the freezer bag had inflated with nitrogen gas, the pipette was removed from the plastic container and the lid was closed. Next, the freezer bag was slowly compressed to release the gas, while the pipette was also removed from the freezer bag, and the freezer bag was then closed and sealed. In this way, Sample 1, a packaged raw tuna meat product containing a block of raw tuna meat, was prepared. The oxygen concentration of the gas inside the package of Sample 1 was 0.1% by volume or less, and the amount of oxygen was 0.2 mL to 1.5 mL per kg of raw tuna meat. It was also confirmed that the amount of gas inside the package of Sample 1 was 5 L or less per kg of raw tuna meat. The prepared Sample 1 was placed in a polystyrene storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0162] Control samples were also prepared using Type IV packaging materials and absorbent sheets for the blocks (weights: 0.92 kg, 1.24 kg, and 1.58 kg). The blocks were wrapped in parchment paper, then wrapped in waterproof paper, and then placed in a plastic bag. The plastic bag was then filled with air instead of nitrogen gas, and the bag was sealed with a rubber band to obtain the control samples. The oxygen concentration of the gas inside the packaging for the control samples was 0.1% by volume or higher, and the amount of oxygen was 200 mL per kg of raw tuna. The amount of gas inside the packaging for the control samples was also confirmed to be 1,000 mL per kg of raw tuna. The prepared control samples were placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0–2°C until evaluation.

[0163] (2) Evaluation For Sample 1 and the control sample prepared as described above, one package of raw tuna meat was opened for each of the following five and eight days after landing, and sashimi was prepared from the removed raw tuna meat. The color tone of the surface or interior of the sashimi and its change over time were then confirmed and evaluated.

[0164] In Sample 1, packaging using nitrogen gas caused the surface in contact with nitrogen to turn dark purple or reddish purple during packaging, but when the package was opened and exposed to air, this discolored surface turned to the same reddish purple or bright red as when it was cut. Five and eight days after landing, no discoloration was observed on the surface or inside of the sashimi prepared by opening the packaged raw tuna meat of Sample 1. In contrast, in the control sample, dark red discoloration was observed on the surface and about 5 mm from the surface of the sashimi prepared by opening the package five days after landing, and dark brown discoloration was observed on the surface and about 15 mm from the surface of the sashimi prepared by opening the package eight days after landing.

[0165] As shown in the results above, the raw tuna meat obtained from Sample 1 had fewer discolored areas than the raw tuna meat obtained from the control sample, both during the period from preparation of the package to unsealing the package, and even after unsealing the package. Therefore, discoloration of the raw tuna meat was suppressed in Sample 1 compared to the control sample, and even if discoloration was present, it was kept to a smaller area on the surface than in the control sample. This means that when preparing a final product such as sashimi from the raw tuna meat package using Sample 1, fewer discolored areas can be removed compared to the control sample, resulting in a higher yield. Furthermore, when sashimi obtained from Sample 1 was eaten, it was confirmed to have a good taste.

[0166] For sample 1, the storage period was further extended, and the package was opened 11 days after landing, and sashimi was prepared as described above, and the surface and internal color of the sashimi was checked. Even in the sashimi prepared from the package 11 days after landing, only the surface layer about 1 mm from the surface had irreversibly discolored, but no discoloration was observed inside.

[0167] [Implementation 1-2] (1) Preparation of Sample 2 and Control Sample Within 24 hours of landing, the GG tuna was cut and processed into blocks, creating two blocks of approximately 2 kg each. Each block was then cut in half to create two blocks for preparing sample 2 and two blocks for preparing the control sample.

[0168] The block for preparing Sample 2 obtained as described above was packaged using a Type II packaging material and a water-absorbent sheet as follows to obtain Sample 2.

[0169] A water-absorbent sheet was attached to the surface of the block used to prepare Sample 2, and then the block was placed in a Type II nylon plastic bag. Next, after removing as much gas as possible from the nylon plastic bag, a plastic pipette for gas injection was inserted into the nylon plastic bag, and nitrogen gas was injected into the bag with the opening of the bag squeezed. Once the nylon plastic bag expanded, the opening of the bag was loosened while still allowing nitrogen gas to pass through, and the nylon plastic bag was compressed by hand to push out as much gas as possible from the nylon plastic bag. The opening of the nylon plastic bag was then squeezed again, and the nylon plastic bag was left to expand. This procedure was repeated four times to replace the gas inside the nylon plastic bag.

[0170] After that, with a certain amount of nitrogen gas remaining in the nylon plastic bag, the plastic pipette was removed and the constricted part of the nylon plastic bag was sealed with a rubber band. In this way, Sample 2, a packaged raw tuna product containing a block of raw tuna, was prepared. The oxygen concentration of the gas inside the package for Sample 2 was 0.1% by volume or less, and the amount of oxygen was 0.2 mL to 1.5 mL per kg of raw tuna. It was also confirmed that the amount of gas inside the package for Sample 2 was 5 L or less per kg of raw tuna. The prepared Sample 2 was placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0171] In addition, a control sample was prepared using Type IV packaging materials and a water-absorbent sheet. The block was first wrapped entirely in parchment paper, then wrapped in waterproof paper, and then placed in a plastic bag. The plastic bag was then filled with air instead of nitrogen gas, and the opening of the bag was sealed with a rubber band to obtain a control sample. The oxygen concentration of the gas inside the package for the control sample was 0.1% by volume or higher, and the oxygen volume was 200 mL per kg of raw tuna. It was also confirmed that the volume of gas inside the package for the control sample was 1,000 mL per kg of raw tuna. The prepared control sample was placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0172] (2) Evaluation For Sample 2 and the control sample prepared as described above, one package of raw tuna meat was opened after landing, four days, and six days (corresponding to three days and five days after packaging, respectively), and sashimi was prepared from the removed raw tuna meat. The color tone of the surface or interior of the sashimi and its changes over time were then confirmed and evaluated.

[0173] As a result, for Sample 2, packaging with nitrogen gas caused the surface that came into contact with nitrogen during packaging to turn dark purple or reddish purple; however, when the package was opened and exposed to air, this discolored surface turned to the same reddish purple or bright red as when it was cut. Furthermore, for Sample 2, no discoloration was observed on the surface or inside of the sashimi prepared by opening the packaged raw tuna meat, either 4 or 6 days after landing. In contrast, for the control sample, discoloration was observed on the surface and in the top 5 to 10 mm of the sashimi prepared by opening the package 4 days after landing, and discoloration was also observed on the surface and in a portion of the top 5 to 10 mm of the sashimi prepared by opening the package 6 days after landing.

[0174] As shown in the results above, Sample 2 showed better results, with dark brown discoloration being suppressed than the control sample. This shows that similar effects can be achieved with packaging materials with low oxygen permeability, regardless of their shape.

[0175] [Examples 1-3] (1) Preparation of Sample 3-1, Sample 3-2, and Control Sample Within 24 hours of landing, the GG tuna was cut and processed into blocks weighing approximately 1.4 kg to 1.7 kg. The blocks were stored at 0°C for several hours and then packaged using Type III packaging materials and absorbent sheets as follows to obtain Sample 3-1 (a packaged raw tuna meat containing a block weighing 1.72 kg) and Sample 3-2 (a packaged raw tuna meat containing a block weighing 1.74 kg).

[0176] First, the entire block was wrapped in parchment paper, then wrapped in waterproof paper, and placed in a nylon plastic bag. For Sample 3-1, the nylon plastic bag was degassed using a vacuum packaging machine (V610G series, Fuji Impulse Co., Ltd.) and then nitrogen gas was injected into it. This degassing and nitrogen gas injection process was repeated two to four times, until only a small amount of gas remained in the nylon plastic bag. The nylon plastic bag was then sealed using the vacuum packaging machine's sealer, thereby preparing Sample 3-1. For Sample 3-2, the degassing and nitrogen gas injection process was repeated two to four times in the same manner as for Sample 3-1. The inside of the nylon plastic bag was then degassed as much as possible using the vacuum packaging machine, and the nylon plastic bag was then sealed using the vacuum packaging machine's sealer, thereby preparing Sample 3-2.

[0177] Samples 3-1 and 3-2 contained gas with an oxygen concentration of 0.1% by volume or less, with the amount of oxygen being 0.2 mL to 1.5 mL per 1 kg of raw tuna. It was also confirmed that the amount of gas inside the packaging for each of Samples 3-1 and 3-2 was 5 L or less per 1 kg of raw tuna. Each prepared sample was placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0178] The control sample was prepared using Type IV packaging materials and a water-absorbent sheet for the block (weight: 1.46 kg). First, the block was completely wrapped in parchment paper, then wrapped in waterproof paper, and then placed in a plastic bag. Next, the plastic bag was filled with air instead of nitrogen gas, and the opening of the plastic bag was sealed with a rubber band to obtain the control sample. The oxygen concentration of the gas inside the package for the control sample was 0.1% by volume or higher, and the oxygen volume was 200 mL to 600 mL per 1 kg of raw tuna. It was also confirmed that the volume of gas inside the package for the control sample was 1000 mL to 3000 mL per 1 kg of raw tuna. The prepared control sample was placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0179] (2) Evaluation For Sample 3-1, Sample 3-2 and the control sample prepared as described above, the packages of raw tuna meat were opened 5 days after landing (corresponding to 4 days after packaging), and sashimi was prepared from the removed raw tuna meat.The sashimi was stored at 0°C to 2°C, and the color tone was checked 6 hours and 72 hours after preparation of the sashimi.

[0180] As a result, in Samples 3-1 and 3-2, the surfaces that came into contact with nitrogen gas during packaging turned dark purple or reddish purple. However, when the packages were opened and exposed to air, the discolored surfaces changed to the same reddish purple or bright red (bright red) as when cut. When opened, both Samples 3-1 and 3-2 were brighter red (bright red) than the control sample. Comparing Samples 3-1 and 3-2, Sample 3-1 was brighter red. Furthermore, Sample 3-1 maintained a brighter red color for a longer period after opening the package compared to the control sample.

[0181] Furthermore, sample 3-1 was brighter red than the control sample both 6 and 72 hours after the sashimi was prepared. In contrast, the surface of the control sample was already discolored when the package was opened, and it was confirmed that the color gradually turned dark brown starting from the area near the surface of the sashimi as time passed 6 and 72 hours after the sashimi was prepared. Similarly to sample 3-1, sample 3-2 was also brighter red than the control sample.

[0182] As shown by the results above, it was found that packaged products stored in a gas with a low oxygen concentration can suppress discoloration during storage. It was also found that gas-flushed packaging using nitrogen gas can extend the color retention period compared to control samples filled with air.

[0183] [Examples 1-4] (1) Preparation of Samples 4-1, 4-2, 4-3, 4-4, and Control Sample Within 12 hours after landing, the GG tuna was cut into pieces and processed into loins. The loins were then placed in plastic bags, cooled in ice water, and stored. After several hours, the loins were removed from the ice water and cut into blocks, each weighing approximately 1 kg. The blocks were packaged using Type II packaging materials and absorbent sheets in the same manner as Sample 2 in Example 1-2, to obtain Sample 4-1.

[0184] The blocks prepared as described above were packaged in nylon plastic bags using Type III packaging materials and a water-absorbent sheet, in the same manner as in Sample 3-2 of Example 1-3. The interior of the nylon plastic bags was degassed as much as possible, and the nylon plastic bags were sealed using a sealer attached to a vacuum packaging machine to obtain Sample 4-2. The blocks prepared as described above were packaged in the same manner as in Sample 4-1, except that helium gas was used instead of nitrogen gas, to obtain Sample 4-3. The blocks prepared as described above were packaged in the same manner as in Sample 4-1, except that carbon dioxide was used instead of nitrogen gas, to obtain Sample 4-4.

[0185] For Samples 4-1, 4-2, 4-3, and 4-4, the oxygen concentration of the gas inside the packaging was 0.1% by volume or less, with the amount of oxygen being 0.2 mL to 1.5 mL per 1 kg of raw tuna. It was also confirmed that the amount of gas inside the packaging for each of Samples 4-1, 4-2, 4-3, and 4-4 was 5 L or less per 1 kg of raw tuna. The prepared samples, Samples 4-1, 4-2, 4-3, and 4-4, were placed in polystyrene foam storage boxes and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0186] A portion of the block prepared as described above was used as a control sample preparation block, and a control sample was prepared using Type IV packaging materials and a water-absorbent sheet. First, the entire block was wrapped in parchment paper, then waterproof paper was wrapped around it, and the whole was placed in a plastic bag. Next, the plastic bag was filled with air instead of nitrogen gas, and the opening of the plastic bag was sealed with a rubber band to obtain a control sample. For the control sample, the oxygen concentration of the gas inside the package was 0.1% by volume or higher, and the oxygen amount was 100 mL to 200 mL per 1 kg of raw tuna meat. It was also confirmed that the gas amount inside the package for the control sample was 500 mL to 1000 mL per 1 kg of raw tuna meat. The prepared control sample was placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0187] (2) Evaluation For Samples 4-1, 4-2, 4-3 and the control sample prepared as described above, each block was opened 5 days after landing, and the color of the removed raw tuna block was checked.

[0188] As a result, in the control sample, the surface and the outermost layer of the block were discolored dark brown within a range of about 5 mm to 8 mm. In contrast, no change was observed in samples 4-1 and 4-2. In sample 4-3, discoloration was observed on the surface and the outermost layer of the block within a range of about 5 mm, but it was less than that of the comparison product. Sample 4-4 was also evaluated in the same way as sample 4-1, and it was confirmed that the color tone was maintained.

[0189] [Examples 1-5] (1) Preparation of Sample 5 and Control Sample Within 24 hours of landing, the GG tuna was cut and processed into loins, which were then placed in plastic bags and stored in a refrigerator set at 0°C. Two days after landing, the loins were removed from the plastic bags and cut into two blocks of approximately 1 kg each. These blocks were then divided into one block for preparing sample 5 and one block for preparing the control sample.

[0190] The block for preparing Sample 5 obtained as described above was packaged using Type II packaging material and a water-absorbent sheet in the same manner as Sample 2 in Example 1-2 to obtain Sample 5. For Sample 5, the oxygen concentration of the gas inside the package was 0.1% by volume or less, and the amount of oxygen was 0.2 mL to 1.5 mL per 1 kg of raw tuna block. It was also confirmed that the amount of gas inside the package for Sample 5 was 5 L or less per 1 kg of raw tuna block. The prepared block of Sample 5 was placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0191] The control sample was prepared using Type IV packaging materials and a water-absorbent sheet. The block was wrapped in parchment paper, then wrapped in waterproof paper, and then placed in a plastic bag. The plastic bag was then filled with air instead of nitrogen gas, and the opening of the bag was sealed with a rubber band to obtain a control sample. The prepared control sample was placed in a polystyrene foam storage box and stored in a refrigerator kept at approximately 0°C to 2°C until evaluation.

[0192] (2) Evaluation For Sample 5 and the control sample prepared as described above, one package of raw tuna meat was opened after five days (corresponding to three days after packaging) and eight days (corresponding to six days after packaging) had passed since landing, and the removed blocks of raw tuna meat were cut in the middle to check and evaluate the color of the cross section.

[0193] As a result, the control sample was opened five days after landing, and sashimi was prepared from the removed block of raw tuna. Five hours after preparation, discoloration was confirmed on the surface of the sashimi and within a 5-10 mm depth of the surface. Furthermore, the control sample was opened eight days after landing, and the raw tuna block was removed and cut in the middle. The cut surface of the block was separated into three layers based on color. Specifically, the block surface turned light pink from the top 7-8 mm, and the layer below that turned light green over a thickness of approximately 3-10 mm. No discoloration was observed further inside. The light green discoloration indicates that discoloration had progressed further than the light pink discoloration.

[0194] In contrast, Sample 5 was opened five days after landing, and the block of raw tuna meat was removed and cut in the middle. Similar to the control sample, the top 7-8 mm of the block had turned a light pink color, but no discoloration was observed below that. Sample 5 was also opened eight days after landing, and the block of raw tuna meat was removed and cut in the middle. Discoloration was only observed within the top 7-8 mm of the block, with no significant change in the thickness of the discoloration on the surface, nor was any discoloration observed internally. This confirms that Sample 5 showed more suppressed color change than the control sample.

[0195] As shown by the results above, even when packaging approximately 24 hours after cutting, refrigerating the product after cutting yields favorable results, similar to packaging immediately after cutting. In other words, Sample 5 tended to have a better color tone than the control sample. Furthermore, once discoloration occurred, it was confirmed that the discoloration accelerated and expanded over time, centered on the discolored area. Therefore, it is expected that the discolored area will expand more quickly in the control sample compared to Sample 5, potentially resulting in a significant decrease in yield. In the case of Sample 5, even if the discolored area is removed, the amount removed can be reduced to about half of that of the control sample, resulting in a significantly higher yield than the control sample.

[0196] [Examples 1-6] (1) Preparation of Sample 6 and Control Sample Within 12 hours of landing, the GG tuna was cut into loins, which were then placed in plastic bags and stored in a refrigerator at approximately 0-2°C. Approximately 24 hours after landing, the loins were removed from the plastic bags and cut into 200g blocks. These blocks were then divided into blocks for preparing Sample 6 and blocks for preparing the control sample.

[0197] The block for preparing Sample 6 obtained as described above was packaged in the same manner as in Example 2 using Type II packaging material and a water-absorbent sheet to obtain Sample 6. For Sample 6, the oxygen concentration of the gas inside the package was 0.1% by volume or less, and the amount of oxygen was 0.2 mL to 1.5 mL per 1 kg of raw tuna block. It was also confirmed that the amount of gas inside the package for Sample 6 was 5 L or less per 1 kg of raw tuna block. Prepared Sample 6 was stored in a refrigerator set at a relatively high temperature of 5°C until evaluation.

[0198] The control sample was prepared using Type IV packaging materials and a water-absorbent sheet. The block was wrapped in parchment paper, then wrapped in waterproof paper, and then placed in a plastic bag. The plastic bag was then filled with air instead of nitrogen gas, and the opening of the bag was sealed with a rubber band to obtain the control sample. The prepared control sample was placed in a polystyrene foam storage box and stored in a refrigerator set at a relatively high temperature of 5°C until evaluation.

[0199] (2) Evaluation For Sample 6 and the control sample prepared as described above, one package of raw tuna meat was opened four days after landing (corresponding to three days after packaging), and sashimi was prepared from the removed block of raw tuna meat, and the color of the sashimi was confirmed and evaluated.

[0200] As with the other evaluation results, when the color tones of the surface and the outermost layer 3 mm to 5 mm deep of Sample 6 and the control sample were compared with the color tones of the layers below, it was confirmed that Sample 6 exhibited a relatively brighter color tone in both cases. It was confirmed that Sample 6 did not show a significant change in color even one day after preparation as sashimi. It was found that the color change was delayed in Sample 6. From the above results, it was confirmed that by storing the sample in a refrigerator before packaging, Sample 6 tends to have a better color tone than the control sample, even when the refrigerator temperature after packaging is set at a relatively high temperature (e.g., 5°C).

[0201] [Examples 1-7] (1) Preparation of Sample 7 and Control Sample Within 72 hours of landing, the GG tuna was cut and processed into loins, which were then placed in plastic bags and stored in a refrigerator set at 0°C. Approximately 96 hours (4 days) after landing, the loins were removed from the plastic bags and cut into 100g-200g blocks. The blocks were then divided into blocks for preparing Sample 7 and blocks for preparing the control sample.

[0202] The block for preparing Sample 7 obtained as described above was packaged using Type I packaging material and a water-absorbent sheet in the same manner as in Test 1 of Example 1 to obtain Sample 7. The oxygen concentration of the gas inside the package of Sample 7 was 0.1% by volume or less, and the amount of oxygen was 0.2 mL to 1.5 mL per 1 kg of raw tuna block. It was also confirmed that the amount of gas inside the package of Sample 7 was 5 L or less per 1 kg of raw tuna block. The prepared Sample 7 was stored in a refrigerator maintained at approximately 0°C to 2°C.

[0203] The control sample was prepared using Type IV packaging materials and a water-absorbent sheet. The block was first wrapped in parchment paper, then wrapped in waterproof paper, and then placed in a plastic bag. The plastic bag was then filled with air instead of nitrogen gas, and the opening of the bag was sealed with a rubber band to obtain the control sample. The prepared control sample was placed in a polystyrene foam storage box and stored in a refrigerator maintained at approximately 0°C to 2°C until evaluation.

[0204] (2) Evaluation For Sample 7 and the control sample prepared as described above, 25 days after landing (corresponding to 21 days after packaging), one package of raw tuna meat was opened for each sample, and sashimi was prepared from the removed block of raw tuna meat, and the color of the sashimi was confirmed and evaluated.

[0205] As a result, in sample 7, only the surface and approximately 1 mm of the outermost layer of the sashimi had irreversibly discolored, but no discoloration was observed inside. In contrast, in the control sample, the discoloration of the sashimi had spread to the inside, resulting in the flesh being separated into three layers, with only the center remaining undiscolored. Furthermore, when each piece of sashimi was stored in a refrigerator maintained at 0°C to 2°C and monitored for changes over time, sample 7 maintained good color even 48 hours after opening, confirming that its quality could be maintained for up to 27 days after landing.

[0206] The outline of Examples 1-1 to 1-7 is summarized in Table 2 below.

[0207] [Table 2]

[0208] In addition, compared to the control sample, Samples 1 to 7 tended to reduce the amount of dripping that occurred from the raw tuna block taken out after opening the package.

[0209] As shown in the above examples, according to the present disclosure, it is possible to obtain a packaged raw tuna meat product containing raw tuna chunks in which discoloration is suppressed and color change is delayed during packaging, and in some cases even after the packaging is opened. Furthermore, the color tone of the raw tuna chunks can be well maintained during packaging, and in some cases even after the packaging is opened. Furthermore, when preparing products such as sashimi from the packaged product, it is possible to reduce the amount of discolored portions that need to be removed, thereby improving the product yield compared to conventional products. Therefore, according to the present disclosure, it is possible to provide a packaged raw tuna meat product in which discoloration is suppressed and a method for suppressing discoloration of raw tuna chunks.

[0210] <Second mode> [Example 2-1] Three farmed bluefin tuna were caught, immediately killed, their gills and internal organs removed, and placed in ice water. The GG weights of the resulting tuna were 68.4 kg, 74.8 kg, and 82.0 kg, respectively, and their fatness indexes were 20.3, 22.6, and 23.3, respectively.

[0211] The farmed tuna was cut into pieces 24 to 28 hours after being processed into GG. The cutting was carried out in a cutting room at a room temperature of 18 to 20°C. The head and tail were cut off from the GG tuna, and then, following the usual procedure, the fish meat was cut into the dorsal and then ventral sides with a knife to obtain a 9 kg back loin. The back loin was then divided into five blocks weighing 1 kg to 2 kg (designated A, B, C, D, and E from the head side), of which A to D, corresponding to the dorsal chu-toro, were used for the test. Each block was further processed into 20 cm x 8 cm x 2.5 cm fillets as test samples.

[0212] The packaging has an oxygen permeability of 20cm at a temperature of 23°C and a humidity of 80%. 3 / m 2 Plastic film pouches (Kureha Corporation, product name: Krehalon ML40G) with a 24-hour saturation temperature were used. Each sample was placed in a film pouch and vacuum-packed to 10 mbar or less using a chamber-type vacuum packaging machine (product name: C-200, MULTIVAC), and then sealed by heat sealing. The pouches were then packed with ice in a polystyrene foam box and stored for one day, and from the second day onwards, they were stored in a refrigerator set at 5°C.

[0213] The Krehalon ML40G used had the following properties: Resin composition: PET / PA / EVOH / PO (PET: polyethylene terephthalate, PA: polyamide, EVOH: ethylene-vinyl alcohol copolymer, PO: polyolefin) Total thickness: 40 μm Tensile strength (JIS K 7127 (23℃-50%RH): 130MPa / 160MPa (vertical / horizontal) Elongation at break (JIS K 7127 (23℃-50%RH): 160% / 130% (vertical / horizontal) Tensile modulus (JIS K 7127 (23℃-50%RH): 650MPa / 700MPa (vertical / horizontal)

[0214] After packaging, the amount of gas inside the package was measured and found to be less than 5 mL. This packaged product will hereinafter also be referred to as a "vacuum product."

[0215] As a comparative control, a packaged product (hereinafter referred to as the "normal product") was used, which was obtained in the same manner as the vacuum-sealed product, except that it was wrapped in a moisture-absorbing sheet, packaged in "CANS FILM (registered trademark) Barrier 7" (product name, manufactured by Shikoku Kako Co., Ltd.), and sealed.

[0216] (Color evaluation) Three days after packaging (corresponding to four days after harvesting), both standard and vacuum-packed sashimi, prepared from the same left and right regions of the same fish, were opened simultaneously. Two 10 mm-thick sashimi slices, cut perpendicular to the vertebrae, were placed in an airtight container, arranged with the cut surface facing up, and stored at 4°C. The color of one point in the center of each of the two sashimi slices was measured using a colorimeter (product name: CR-400, manufactured by Konica Minolta Japan, Inc.) at 0 hours (immediately after opening), 0.5 hours, 2 hours, 4 hours, and 8 hours after storage. Standard and vacuum-packed sashimi, stored unopened at 4°C for seven days after packaging (corresponding to eight days after harvesting), were also evaluated in the same manner.

[0217] The results are shown in Tables 3 and 4, and Figures 1 and 2. In Tables 3 and 4, Figures 1 and 2, "D+3" and "D+7" mean samples that were 3 days and 7 days old after packaging, respectively. Also, in Tables 3 and 4, Figures 1 and 2, "regular" means a regular product, and "vacuum" means a vacuum-packed product.

[0218] [Table 3]

[0219] [Table 4]

[0220] As shown in Tables 3 and 4, Figures 1 and 2, for both the regular product and the vacuum product, the samples 3 days after packaging showed a * While the value is rising, a * / b * The value drops, but then remains relatively constant. This result indicates that the color changes from dark red, which indicates high freshness, to bright red, and that the condition is well maintained. Even after 7 days from packaging, both the regular product and the vacuum-packed product showed a * value and a * / b *Although the values ​​immediately after unpacking were different, a similar trend was observed as in the samples three days after packaging.

[0221] On the other hand, when comparing the samples that were packed for 3 days and 7 days, the normal product had a * value and a * / b * It was confirmed that the sample left for 7 days had a larger decrease in both values ​​than the sample left for 3 days. This means that the redness has become duller and the yellowness has become slightly stronger with the passage of time after packaging, meaning that the sample has shifted to dark brown. In particular, a * The value is the a of the sample that has been left for 7 days immediately after unpacking. * The value of a for the sample aged for 3 days * This means that the color of the raw tuna meat changed even when it was packaged.

[0222] In contrast, in vacuum products, a * value and a * / b * In both cases, the a value of the sample immediately after unpacking was higher than that of the sample after 3 days. * value and a * / b * a of 7-day-old samples against the value * value and a * / b * The decrease in the value is small, especially a * It can be seen that the value of the sample hardly decreased even after 7 days. * value and a * / b * Both values ​​remained relatively high even after the packaging was opened, and did not decrease to the same extent as with the regular product. These findings indicate that the vacuum-sealed product is able to delay color changes not only while it is packaged, but also after it has been opened.

[0223] (Drip evaluation) Three days after packaging (corresponding to four days after landing), both standard and vacuum-packed saku (sashimi) made from the same left and right regions of the same individual were simultaneously opened. Two 10 mm-thick sashimi slices were prepared from each of the standard and vacuum-packed saku by cutting perpendicular to the vertebrae. These slices were then placed in a pre-weighed container and weighed. The weight of the container was subtracted from the measured value to calculate the weight of the sashimi before storage. The two sashimi slices were then placed in a container with the cut side facing up, sealed, and stored at 4°C. After six hours of storage, each sashimi slice was removed from the container, and the total weight of the container and the drip remaining in the container was measured. The drip amount was calculated by subtracting the weight of the container from the measured value to evaluate the drip amount from the two sashimi slices. The drip amount was calculated using the following formula. The same measurement was performed on saku obtained from three farmed bluefin tuna. The results are shown in Table 5. Drip volume [%] = [Drip weight] / [Sashimi weight before storage] x 100

[0224] [Table 5]

[0225] As shown in Table 5, it was confirmed that the amount of dripping was less for the vacuum-sealed product than for the regular product. This means that the vacuum-sealed product can delay the deterioration of the quality of the raw tuna block compared to the regular product, not only while it is packaged but also after it has been opened.

[0226] Furthermore, when compared to regular tuna, the raw tuna meat from the vacuum-sealed package was softer and easier to cut when processed. The vacuum-sealed product also tended to absorb less of the odor commonly found in farmed fish compared to regular tuna.

[0227] These results demonstrate that the present disclosure can provide a packaged raw tuna meat product and a method for inhibiting discoloration of raw tuna meat, in which the change in color tone is delayed while the product is packaged and even after the package is opened, and discoloration is inhibited.

Claims

1. an oxygen-impermeable packaging material; A raw tuna block packaged in the packaging member together with a gas having an oxygen concentration of 1% by volume or less; A packaged raw tuna meat product comprising:

2. 2. The packaged raw tuna meat product of claim 1, wherein the gas comprises an inert gas.

3. 3. The packaged raw tuna meat product according to claim 2, wherein the inert gas comprises at least one gas selected from the group consisting of nitrogen gas, carbon dioxide gas, helium gas, and argon gas.

4. Further comprising a water-absorbent member, The packaged raw tuna meat product according to any one of claims 1 to 3, wherein a part or all of the raw tuna meat is in contact with the water-absorbent member.

5. The packaging material has an oxygen permeability of 1000 cm ３ / m ２ The packaged raw tuna meat product according to any one of claims 1 to 4, which has a storage life of 24 hr·atm or less.

6. The oxygen permeability of the packaging material is 50 cm ３ / m ２ The packaged raw tuna meat product according to any one of claims 1 to 5, which has a storage life of 24 hr·atm or less.

7. After landing, the tuna is cut into pieces to obtain raw tuna chunks. The raw tuna block meat is packaged in an oxygen-impermeable packaging material and subjected to a gas replacement treatment until the oxygen concentration in the gas inside the package becomes 1% by volume or less; and sealing the packaging member after the gas replacement treatment; A method for producing a packaged raw tuna meat product, comprising:

8. The method for producing a packaged raw tuna meat product according to claim 7, wherein the gas substitution treatment is carried out using an inert gas.

9. The method for producing a packaged raw tuna meat product according to claim 8, wherein the inert gas contains at least one gas selected from the group consisting of nitrogen gas, carbon dioxide gas, helium gas, and argon gas.

10. The method for producing a packaged raw tuna meat product according to any one of claims 7 to 9, further comprising refrigerating the raw tuna block until it is packaged in the packaging member.

11. After landing, the tuna is cut into pieces to obtain raw tuna chunks. The raw tuna block meat is packaged in an oxygen-impermeable packaging material and subjected to a gas replacement treatment until the oxygen concentration in the gas inside the package becomes 1% by volume or less; and After the gas replacement treatment, the packaging member is sealed to obtain a packaged raw tuna meat product. The method for inhibiting discoloration of raw tuna chunks includes the steps of:

12. The method for inhibiting discoloration of raw tuna meat according to claim 11, further comprising refrigerating the packaged raw tuna meat.

13. The method for inhibiting discoloration of raw tuna meat according to claim 12, wherein the refrigerated storage period is at least one week.

14. The method for inhibiting discoloration of raw tuna meat according to claim 12, wherein the refrigerated storage period is at least 4 weeks.

15. an oxygen-impermeable packaging material; and a raw tuna block tightly packed by the packaging member, The packaged raw tuna meat product has a gas amount in the package of 21 mL or less per 1 kg of the raw tuna meat.

16. The packaging material has an oxygen permeability of 1000 cm ３ / m ２ The packaged raw tuna meat product according to claim 15, wherein the storage temperature is 24 hr·atm or less.

17. The oxygen permeability of the packaging material is 200 cm ３ / m ２ The packaged raw tuna meat product according to claim 15 or 16, which has a storage life of 24 hr·atm or less.

18. The packaged raw tuna meat product according to any one of claims 15 to 17, wherein the packaging member has a tensile strength of 80 MPa to 250 MPa.

19. The packaged raw tuna meat product according to any one of claims 15 to 18, wherein the tensile modulus of the packaging member is 500 MPa to 900 MPa.

20. After landing, the tuna is cut into pieces to obtain raw tuna chunks; and The raw tuna block is tightly packed in an oxygen-impermeable packaging material, and the amount of gas in the package is 21 mL or less per 1 kg of the raw tuna block. A method for producing a packaged raw tuna meat product, comprising:

21. The method for producing a packaged raw tuna meat product according to claim 20, further comprising refrigerating the cut raw tuna block until it is packaged in the packaging member.

22. After landing, the tuna is cut into pieces to obtain raw tuna chunks; and The raw tuna block is tightly packed in an oxygen-impermeable packaging material, and the amount of gas in the package is set to 21 mL or less per 1 kg of the raw tuna block, thereby obtaining a packaged raw tuna meat product. The method for inhibiting discoloration of raw tuna chunks includes the steps of:

23. The method for inhibiting discoloration of raw tuna meat according to claim 22, further comprising storing the packaged raw tuna meat in a refrigerator.

24. The method for inhibiting discoloration of raw tuna meat according to claim 23, wherein the refrigerated storage period is at least 4 days.

25. A raw tuna block taken out of a raw tuna package that has been packaged for four days or more, Measured with a colorimeter ＊ The raw tuna meat package has a value of 14.05 or more and 19 or less 0.5 hours after opening the package.

26. A raw tuna chunk taken out from a raw tuna meat package, Measured with a colorimeter ＊ / b ＊ The value of a is 0.5 hours after opening the package of raw tuna meat. ＊ / b ＊ Raw tuna chunks with a value of 99% or more.

27. A raw tuna block taken out of a raw tuna package that has been packaged for four days or more, Measured with a colorimeter ＊ / b ＊ is 1.29 or more 0.5 hours after opening the packaged raw tuna meat.

28. A method for providing raw tuna meat, comprising the step of opening a package of raw tuna meat, The color difference of the raw tuna meat measured with a color difference meter ＊ The method for providing raw tuna meat, wherein the value is 17.05 or more 8 hours after the packaged raw tuna meat is opened.

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