JP6675706B2 - Method for supplying sashimi of yellowtail fish, and method for suppressing discoloration of blood meat of yellowtail fish after frozen storage and thawing - Google Patents

Description

The present invention relates to how to suppress supply method sashimi fish yellowtail acids, as well as discoloration of Chiai meat fish yellowtail such after cryopreservation and thawing.

  The boom in Japanese food overseas has also increased the demand for sashimi used in sushi. Until now, sashimi of limited fish species such as tuna and salmon has been provided, but supply of sashimi of fish species such as Thailand and yellowtail that have not been consumed much outside Japan is also desired.

  Yellowtail is widely consumed as sashimi in Japan, but its distribution is chilled distribution. An attempt was made to supply yellowtail sashimi using a cold chain at -30 to -20 ° C, but it was difficult due to the problem of discoloration of blood meat. At present, in the frozen export to the United States, carbon monoxide treatment is performed in order to suppress discoloration of blood meat. By substituting carbon monoxide gas inside the fish meat packaging container, myoglobin is changed to carboxy myoglobin coordinated with carbon monoxide. The carbon monoxide treatment can prevent the myoglobin from becoming met and discolored. However, the color tone of carboxymyoglobin is bright red, which is different from the color tone of fresh blood meat. Also, the use of carbon monoxide has been banned in Japan, Europe, Australia and Asia.

  Discoloration of the blood meat, that is, methotzolization of myoglobin, can be suppressed by flowing at a low temperature of -35 ° C or lower. However, since the current cold chain has been developed for livestock meat, the temperature is -30 to -20C.

  Patent Literature 1 discloses a packaging material in which an antioxidant is supported on a base material containing a polymer compound. By wrapping fish meat with this film, oxidation of fish meat such as yellowtails is suppressed.

  Patent Literature 2 discloses that browning of blood meat during frozen storage and distribution of fish, including rapid freezing of fish meat obtained from fish immediately before stiffness after death and including blood meat in which ATP remains. A method of suppressing is disclosed.

  Non-Patent Document 1 discloses the relationship between the amount of ATP in muscle in frozen amberjack and the methotinization and browning of blood meat.

WO 2015/182791 JP 2012-196181 A

Kota Inohara, et al., “Suppression of Browning of Frozen Amberjack Meat by Intramuscular ATP,” Journal of the Japan Society of Fisheries Science, 2014, 80 (6), p. 965-972

The present invention has been made in view of the above circumstances, a method of supplying fish sashimi yellowtail compounds capable minimized discoloration of Chiai meat without carbon monoxide, as well as fish yellowtail such after cryopreservation and thawing and to provide a way to the suppressed discoloration of Chiai meat.

  The present inventors have found that, as described in Patent Document 2, freezing in a state where ATP in fish meat is not reduced can suppress methotification during thawing. However, when the fish meat comes into contact with air after thawing, the formation of the meth is relatively quickly progressed, and the meth can not be suppressed for a necessary time as a commercial product. As a result of further study on the methation after thawing, it was found that the methation after thawing was not a phenomenon that occurred in the whole blood meat but a phenomenon that occurred only on the surface of the blood meat that was exposed to the air.

  The blood meat of yellowtail fillets is mainly located on the skin side. Therefore, if the skin is peeled off, the blood meat after thawing proceeds to be met, but the present inventors show that if the skin covering the blood meat is maintained, it does not come into contact with air and does not discolor even after thawing. Found. It is the first time that both the freezing without lowering the ATP and the maintenance of the skin until the time of use and the inhibition of methoxide after thawing are satisfied, the yellowtails utilizing a cold chain at −30 to −20 ° C. It has been found that it is possible to supply fish sashimi, and the present invention has been completed.

A method for supplying sashimi of yellowtail fish according to the first aspect of the present invention,
A method for feeding sashimi of yellowtail fish using a cold chain at -30 to -20 ° C,
a) Immediately kill the landed fish, exsanguinate, cool to 10 ° C or less,
b) Wholesale the cooled fish into 3 or 2 pieces to make skinned fillet,
c) within 3 hours of immediate killing, freezing the fillet at a temperature of -30 ° C or less while keeping the skin on,
d) packaging the frozen fillet in a film,
e) transporting the fillet by a cold chain at -30 to -20 ° C;
f) 1 to 24 hours before use, thaw the fillet at -1 to 5 ° C,
g) Peel the fillet at the time of use and cut out the fence for sashimi,
It is characterized by the following.

In this case, in the above a) to c), the ATP concentration in the fish meat at the time of freezing is 0.5 mM or more.
It may be that.

A method for suppressing discoloration of blood meat of yellowtail fish meat after frozen storage and thawing according to the second aspect of the present invention,
The method is characterized in that the method for supplying sashimi of yellowtail fish according to the first aspect of the present invention is used.

  According to the present invention, discoloration of blood meat can be suppressed as much as possible without using carbon monoxide.

It is a figure which shows the time-dependent change of the metformation rate during preservation | save of the sample preserve | saved at -20 degreeC of Example 1. FIG. It is a figure which shows the time-dependent change of the metformation rate during preservation | save of the sample preserve | saved at -25 degreeC of Example 1. FIG. It is a figure which shows the cross section of the blood meat of the sample after the thawing of Example 2, and the time-dependent change of the internal methoxide rate. FIG. 9 is a diagram showing a change over time in the color tone of blood meat of a sample stored under the conditions of (1) to (3) in Example 3 as a / b values.

  In the overseas cold chains, livestock products are the main target, so that cold chains at −30 to −20 ° C. are developing. In the case of fish and shellfish, low-temperature freezing at −35 ° C. or less is preferable, but is not realistic at present. The method for supplying sashimi of yellowtail fish according to the present embodiment utilizes a cold chain at −30 to −20 ° C. It is not necessary for all steps of the present supply method to be at −30 to −20 ° C., and transport at a temperature of −30 ° C. or lower may be mixed.

  The target fish species for this supply method are those belonging to yellowtails such as yellowtail, amberjack, and gibberfish. Scientifically, it is a species of fish belonging to the genus Perciformes Carangidae Seriola. A characteristic of yellowtail fish meat is the presence of conspicuous red-brown bloody meat in the center of the side. Myoglobin is present at a high concentration in this blood meat, and its color is an important indicator that determines the freshness of the fish meat and thus determines the commercial value. Myoglobin combines with oxygen to form oxymyoglobin and shows a red color which is preferable as sashimi. However, oxidation progresses with time to form metmyoglobin (metomized), which turns brown and reduces commercial value.

  The sashimi is raw fish meat that is eaten as it is, specifically, cut into a size used for sushi, cut into bite-sized pieces, or sold in the form of a fence. is there. The sashimi is used not only for sushi but also for Western dishes such as carpaccio. In addition, not only completely raw ones, but also ones whose surfaces are burned with fire or grilled are included in sashimi if the center is raw.

This supply method includes the following seven steps as essential steps.
a) Immediately kill the landed fish, exsanguinate, cool to 10 ° C or less,
b) Wholesale the cooled fish into 3 or 2 pieces to make skinned fillet,
c) Within 3 hours of immediate killing, freeze the fillet at a temperature of -30 ° C or less while keeping the skin on,
d) packaging the frozen fillet with a film,
e) transporting the fillet by a cold chain at -30 to -20 ° C;
f) Thaw the fillet 1 to 24 hours before use at -1 to 5 ° C,
g) Peel the fillet in use and cut out the sashimi fence.

  In the step a), “landing” means raising fish on a ship or on land to supply fish that live underwater as commercial products. Landing refers to, for example, removing fish grown at a farm from a culture cage for shipping. Usually, fish raised from water are immediately killed and then left in water to remove blood. At that time, the fish is left in water containing ice, oxygen, or air to maintain freshness. The time of standing in water depends on the size of the fish, the size of the tank to be stored, the amount of water, and the like, but is at least 5 minutes or more, preferably 10 to 30 minutes. The water temperature is preferably about 5 to 30C lower than the water temperature at which the fish lived, and preferably about 10 to 15C.

  The method of cooling to 10 ° C. or lower is not particularly limited, but the fish after blood removal can be cooled to 10 ° C. or lower by storing it in a seawater ice solution at −1 to 5 ° C. for about 30 to 120 minutes.

  Step b) is a step of making fish filleted with skin. It is necessary to perform the process in a low temperature environment skillfully so that the temperature of the cooled fish does not rise. Usually, the head, gills, fins, and internal organs are removed, and the whole is cut into three pieces (without middle bone) or two pieces (with middle bone) to make a fillet. Do not peel at this time. The yellowtail meat of the yellowtail is located along the lateral line from the skin on the side of the fish body of the yellowtail. When the skin is peeled, the blood meat comes into direct contact with the air, but by holding the skin, the blood meat can be suppressed from coming into contact with the air. In the case of sashimi, skin is not required, so it is reasonable to remove the skin from the fillet for sashimi. Leaving without peeling is much more effective in retaining the skin than covering with a film as shown in the examples. It is for sashimi, but it is essential to leave the skin until it is processed as sashimi.

  In the step (c), the fillet with skin produced in the step (b) is frozen, preferably rapidly frozen, at a temperature of -30 ° C or less within 3 hours after the immediate killing. The freezing is performed at a temperature of -30C or lower, preferably -40C or lower, more preferably -50C or lower. Examples of the method include an air blast method, an ethanol brine immersion method, and a contact freezer freezing method. The time required for quick freezing is within about 2 hours, preferably within about 60 minutes.

  In step d), the frozen fillets are individually packaged in a film. Although it is a fillet with a skin, it is preferable that the side without the skin does not come into contact with the air as much as possible. Therefore, it is preferable to perform vacuum packaging with an oxygen-impermeable film or gas replacement packaging with an inert gas. A plurality of fillets may be packaged together, but preferably are individually packaged one by one.

  The step e) is a step of transporting the fillet by a cold chain at −30 to −20 ° C. It is important to transport from the frozen fillet manufacturing site to the use site while maintaining the temperature at -20 ° C or lower. If the temperature is −20 ° C. or lower, the temperature may be −30 ° C. or lower.

  Step f) relates to the thawing step. At the site where the sashimi is used, thaw at -1 to 5 ° C, preferably at low temperature, 1 to 24 hours before use. The color change of the blood fillet of the above fillet is suppressed, but the color tone naturally deteriorates if the temperature is too high or left for a long time during the thawing stage. To avoid that, thawing is started 1 to 24 hours, preferably 1 to 12 hours, more preferably 1 to 6 hours before the expected use time. In low-temperature thawing, thawing is performed while maintaining the temperature at -1 to 5 ° C. Specifically, the fillet is stored in a refrigerator at 5 ° C. or lower while being wrapped in a film, or immersed in a salt water ice solution.

  Step g) is a step of cutting out a sashimi fence at the time of use. At this stage, the fillet is peeled for the first time. When the skin is peeled and the blood meat comes in contact with the air, the blood meat starts to be met, but as long as it is protected by the skin, the blood meat is kept to a minimum. Also, there is a portion of my body that does not have skin, which has a large amount of myoglobin, and if there is some discoloration in that portion, it can be removed by thinning off the surface. Even if there is discoloration, if it is removed by about several mm, the inside of the meat has not discolored. As shown in Example 2, conditions such as vacuum packaging and shading were tried instead of holding the skin, but it was found that the method of holding the skin was the most reliable way to suppress the methoxide after thawing. Was.

  The sashimi fence prepared through the above-described steps maintains a lean reddish color tone of the blood meat. By performing steps a) to c) promptly, a decrease in the amount of ATP in fish meat can be suppressed. The ATP concentration in muscle immediately after killing is about 5 to 10 mM in normal muscle and about 2 to 3 mM in blood meat. When the fish are landed, the revitalization process is performed and the body temperature is lowered at the same time, but if the revitalization process and cooling are performed smoothly, the ATP concentration is maintained for several hours. Thereafter, the ATP concentration falls and stiffness begins after death. When stiffness occurs after death, ATP almost disappears. Therefore, it is important that the method of the present invention be completed to freezing before rigor after mortality. ATP remains in the blood meat muscle of the fish treated by this method, and specifically, ATP of at least 0.5 mM, preferably at least 1 mM is retained.

  The ATP content was determined by neutralizing the extract extracted from fish meat with 10% perchloric acid with an aqueous potassium hydroxide solution, determining the ATP concentration in the filtrate of the solution by the following method, and determining the ATP concentration in the muscle. The content was determined. The content of the ATP-related compound in the filtrate was analyzed by HPLC, that is, elution with an Asahipack GS-320 column and isocratic elution with a 0.1 M phosphate buffer (pH 3.0), monitoring at 250 nm, and a standard concentration of the ATP-related compound. (Yuko Murata, et al., "Extractive components in the skeleton metal from ten separate physic sessential physicist of the physician's physicist. Year, 60 (4), p.473-478).

  With the supply method according to the present embodiment, yellowtail fish meat can be transported by a cold chain at −30 to −20 ° C., and can be provided as sashimi that maintains the color tone of blood meat without using carbon monoxide or the like. . The supply method is a method suitable for the size of the fish body specific to the yellowtail fish and the position, shape and size of the blood meat. For example, when a fish is large like a tuna, it is necessary to divide it into several pieces, and it is difficult to transport it to a use site as a skinned fillet. Further, the blood supply of the tuna is widely distributed from the skin toward the middle bone, and even if the skin is left, the area of the blood contact with the air is too large, so the supply method is not suitable. In the case of tuna, the blood meat portion is not used for the sashimi, but in the case of yellowtail, fish meat containing the blood meat is often used for the sashimi. Therefore, the present supply method is particularly suitable for the fish sashimi of the yellowtail fish.

  As described above, only by strictly controlling the production process, it is possible to provide sashimi yellowtail fish meat that can be transported by a cold chain at −30 to −20 ° C. The yellowtail fish meat produced by this method can maintain its quality for about 3 months even at -20 ° C, and even longer at temperatures lower than that. In Example 2, the methoxide after 3 months at -20 ° C was about 50%. The metformation of about 50% was slightly brown as compared with fresh products, but was within a range acceptable for commercial products.

  Also, the formation of meth after thawing can be suppressed by maintaining the fillet skin. It seems that the problem is solved if the surface is cut off even if there is no skin, but the blood meat on the skin side is widely spread, so it is necessary to cut them out because the method after thawing is limited to the surface. The sashimi yield is greatly reduced and is not realistic. It has become a practical technique because it has been found that by leaving the skin, it is possible to suppress the formation of methoxide after thawing. Therefore, the above-described method is suitable for use in an overseas Japanese restaurant, a sushi restaurant, or the like, in which the skin is peeled off and used as a fence at the timing of use.

  The present invention will be further specifically described by the following examples, but the scope of the present invention is not limited by these examples.

(Example 1: Effect of freezing within 3 hours after death (prior to rigidity after death))
Immediately after killing the cultured yellowtail, they were exsanguinated and cooled in ice water, and after 60 minutes, they were wholesaled into three to obtain two fillets. The fillet was vacuum-packaged, and one fillet was rapidly frozen at -40 ° C. “sample immediately before stiffness” (2 hours after immediate killing) (sample A). The other sheet was kept in an aqueous ice solution for 7 to 8 hours and rapidly frozen in a similar manner "immediately after hardening after death" (sample B). These fillets were stored at −20 ° C. and −25 ° C. for 3 months, and the progress of metformation by frozen storage was measured.

  The methation ratio was measured as follows. First, myoglobin was prepared from each cryopreserved sample. Since the color change during thawing was rapid, blood meat was cut out in a frozen state, cut into small pieces, and myoglobin was quickly extracted with a 0.1 M KCl solution (pH 7.0). Since the centrifuged supernatant of the blood homogenized liquid homogenized solution contained lipid components and was turbid, ammonium sulfate fractionation was performed to obtain a clear solution. The 55-90% saturated ammonium sulfate fraction was analyzed as myoglobin.

  The methemolysis rate was determined according to the method of Inohara et al. (Kota Inohara, et al., Investigation of a method for measuring methemoglobin methionism of fish muscle myoglobin, Journal of the Japanese Society of Fisheries Science, 2015, 81 (3), pp. 456-464). Absorbance values at 548 nm and 524 nm were measured, and determined by the following formula for calculating the yellowtail methionization ratio.

  Methation ratio (%) = − 99.70 (A / B) +164.96 (Formula 1)

  Note that A and B in Equation 1 are the absorbance at 548 nm and the absorbance at 524 nm of the myoglobin solution, respectively.

(result)
FIG. 1 shows the result of storing the fillet at −20 ° C., and FIG. 2 shows the result of storing the fillet at −25 ° C. The ATP concentration in the blood meat at the time of freezing was about 1.00 mM (1.00 μmol / g) in sample A frozen immediately before stiffness after death, but in sample B frozen immediately after stiffness after death, The ATP concentration was 0.10 mM (0.10 μmol / g) or less. When stored at −20 ° C., the methodization of Sample B progressed rapidly, whereas the methodization of Sample A was suppressed. Even after storage for 3 months, the methodization rate was 50% or less. Furthermore, when the storage temperature was set to -25 ° C, it was recognized that the methotification rapidly progressed in Sample B, but hardly progressed in Sample A even after storage for 3 months.

  From the above results, the blood meat of yellowtail that was rapidly frozen in the fish “immediately after mortality” state was significantly suppressed in the formation of mets even when stored at a general frozen food distribution temperature such as −20 ° C. It became clear that. Up to a methionation rate of about 50%, the color tone is slightly brownish as compared with a fresh product, but it is within an acceptable range as a product.

(Example 2: Change of color tone after thawing of frozen fillet containing high ATP)
The frozen fillet containing high ATP was stored at -30 ° C for 95 days, and then the color tone change after thawing was observed using a freeze-thawed fillet that was thawed at low temperature. The fillet was halved at the blood meat portion and stored in a refrigerator at 2 ° C. so that the blood meat cross section was exposed to air. At each lapse of time, the methionization rate of myoglobin in the cross-section and inside (measured by cutting off the portion not in contact with air) of the blood meat was measured.

(result)
FIG. 3 shows the change of the methation ratio. It was confirmed that the progress of the methotization rate of the blood meat cross section in contact with the air was very fast. On the other hand, inside the blood meat, methation after thawing hardly proceeded. Even after 33 hours, it was about 2 mm from the surface that had been met. It has been newly discovered that metzation during freezing proceeds simultaneously on the surface and inside, whereas metzation after thawing occurs only on the surface, and that by maintaining the skin the metzation on the surface can be suppressed. Was.

  From the above results, it was inferred that, in the frozen fillet containing a high concentration of ATP, the progress of methotification during freezing was suppressed, and the methotification after thawing did not progress without touching air.

(Example 3: Change in color tone after thawing of frozen fillet containing high ATP)
After storing the high ATP-containing frozen fillet in the same manner as in Example 2 at −30 ° C. for 95 days, a change in color tone after thawing was observed under the following three conditions using a freeze-thawed fillet that was thawed at low temperature.
(1) The skin is removed from the fillet, and the blood meat portion is exposed to air to shield light (light shielding).
(2) The skin is removed from the fillet, the blood meat portion is exposed to air, and then vacuum-packed (vacuum).
(3) Do not allow the blood meat to come into contact with the air, leaving the skin of the fillet (with skin).

  These samples were stored at 2 ° C., and color tone changes were compared using a / b values as indices. A Minolta colorimeter was used for the measurement. What was measured was the surface of the blood meat portion for the samples (1) and (2), and the color tone of the blood meat under the skin for (3).

(result)
FIG. 4 shows the a / b values. The browning of the sample that was in contact with the air proceeded rapidly only by shading, and the browning of the vacuum-packed sample had a slightly delayed effect. It was shown that the samples that were left skinned and not exposed to air had the least browning.

  According to the method of the present invention, fish meat such as yellowtail can be transported using a cold chain at −30 to −20 ° C., so that yellowtail sashimi is provided even in an area where frozen transportation is indispensable, such as overseas. be able to.

Claims (3)

A method for feeding sashimi of yellowtail fish using a cold chain at -30 to -20 ° C,
a) Immediately kill the landed fish, exsanguinate, cool to 10 ° C or less,
b) Wholesale the cooled fish into 3 or 2 pieces to make skinned fillet,
c) within 3 hours of immediate killing, freezing the fillet at a temperature of -30 ° C or less while keeping the skin on,
d) packaging the frozen fillet in a film,
e) transporting the fillet by a cold chain at -30 to -20 ° C;
f) 1 to 24 hours before use, thaw the fillet at -1 to 5 ° C,
g) Peel the fillet at the time of use and cut out the fence for sashimi,
A method for supplying sashimi of yellowtail fish. In the above a) to c), the ATP concentration in the blood meat of the fish at the time of freezing is 0.5 mM or more,
A method for supplying sashimi of yellowtail fish according to claim 1. A method for supplying sashimi of yellowtail fish according to claim 1 or 2,
A method for suppressing discoloration of blood meat of yellowtail fish meat after frozen storage and thawing.