JPH03180140A - Thawing of frozen fish meat - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] "Technical field" The present invention relates to a method for thawing frozen fish meat.

"Prior art and its problems" Many large fresh fish, including those used for sushi, are immediately frozen at an ultra-low temperature of around 160 degrees Celsius after having their gills and internal organs removed and blood drained. .

These frozen fish go through some kind of thawing process and are sold in the form of shells weighing several hundred grams or as sashimi made by slicing the fish shells.

The quality of thawed fish meat is generally evaluated by its color and freshness. Among them, the red color of red fish meat such as tuna and cutlet is mainly due to the muscle pigment myoglobin (Mb) and the blood pigment hemoglobin (Hb), but since blood has been removed, most of the pigment is Mb. Mb is originally dark purple-red (reduced form), but it is known that when it combines with oxygen in the air to produce oxymyoglobin (MbOx), a beautiful bright red color is obtained. However, Mb
When MbOz and MbOz are further oxidized, metmyoglobin (m
etMb) is produced, which exhibits a brown or blackish brown color.

If the tuna has changed color, it means that Mb and MbO□ are ffl.
This means that it has changed to etMb. Such autoxidation reactions have been well-studied because they have a direct effect on meat color.Furthermore, it has been shown that the rate of autooxidation increases as the temperature increases, and that the rate of autooxidation increases as the partial pressure of oxygen in beef cattle decreases. It is known that the oxidation rate increases.

Therefore, in order to obtain bright red tuna by thawing frozen tuna, it is necessary to suppress the oxidation of Mb to MbO and prevent the production of metMb, but this has been difficult with conventional thawing methods. In addition, during the thawing process, a large temperature difference occurs between the surface and the center, which makes it difficult to obtain fish meat that is bright red throughout. When the fish meat is thawed, the temperature of the surface layer of the meat increases until the center of the fish meat is thawed, promoting the production of metMb and turning it brown. In addition, when slowly thawed in still air in a refrigerator (0 to 4 degrees Celsius),
As a result of being exposed for a relatively long time to the temperature range where metMb is most likely to be produced (around -3°C to -8°C), it becomes brown. Furthermore, as mentioned above, the lower the partial pressure of oxygen in beef cattle, the more accelerated the autooxidation reaction is, but when the meat is thawed in block form, sufficient oxygen is supplied to the surface area of the meat, while the center Oxygen supply is extremely insufficient in these areas, and as a result, even if the surface is bright red, the center becomes brown. Therefore, m
There has been a desire for a thawing method in which etMb quickly passes through the temperature body where it is most likely to be produced, and which combines sufficiently with oxygen in the air to exhibit a bright red color.

Also, adenosine diphosphate (ATP) contained in fish muscles.
) becomes adenosine diphosphate (
It is known that the decomposition changes sequentially to ADP), adenosine-phosphate (AMP), inosinic acid (IMP)% inosine (HxR), and hypoxanthine (Hx).

In other words, inosine (HxR) and hypoxanthine (Hx
) means that the freshness has decreased. The decomposition changes caused by these enzymes can be suppressed by keeping the fish at as low a temperature as possible; however, in conventional thawing methods, such as natural thawing, a large temperature difference occurs between the surface and center of the fish meat. It was difficult to maintain freshness.

``Object of the Invention'' Based on this theoretical understanding of color and freshness, the present invention aims to develop thawing conditions that suppress the temperature difference between the surface and the center as much as possible during the thawing process, and that make it difficult for metMb to occur. The purpose of the present invention is to obtain a method for thawing frozen fish meat that achieves this and also allows sufficient bonding with oxygen.

"Summary of the Invention" The present invention is based on the idea of suppressing the temperature difference between the surface and the center as much as possible during the thawing process, and quickly reducing the temperature range (maximum color zone) where metMb is most likely to occur in red fish meat. It was completed as a result of research to satisfy both ideas. According to previous research, a+etMb is -3 to -4℃ in the surface layer and -3℃ in the center.
It has been found that this phenomenon is most likely to occur at 6 to -8°C.

In thawing frozen fish meat stored at temperatures below -35°C, preferably at about -50°C, where metMb is less likely to occur, the present invention rapidly raises the temperature to just before the maximum color band while balancing the surface temperature and center temperature. This method was based on the idea of rapidly passing through the largest colored skin zone and actively contacting the air.
The contents include both methods of making blocks of ~ several kg and then thawing them, and methods of suddenly making blocks of several hundred grams each and then thawing them.

First, the former block decompression method will be explained.

This first invention (block thawing method)
Store g of frozen fish meat in a block shape in a closed container,
A block thawing step in which the block is left to stand until the center temperature reaches approximately -12 to -6 degrees Celsius; and a scooping step in which blocks weighing several hundred grams are cut out from this block whose center temperature has reached approximately -12 to -6 degrees Celsius; It is characterized by including.

The scooped saku can be eaten as sashimi by waiting for it to thaw, but after leaving it until the core temperature reaches about -3 to -1℃, store it in a cold storage at -i to 4℃. It can also be stored and aged before being eaten.

The latter thawing method involves directly cutting shells weighing several hundred grams from frozen fish meat; and immersing the shelled fish meat in salt water until the center temperature reaches approximately -12 to
It is characterized by including a step of thawing in salt water, which is taken out after reaching -6°C.

Once the center temperature has reached -12~-6℃, you can wait for it to thaw and eat it as sashimi, but if you leave it until the center temperature reaches -3~-1℃, then -
It can also be stored in a refrigerator at 1 to 4°C to ripen and then eaten.

When the method of the present invention is applied to thawing red fish meat such as tuna and cutlet, it is particularly effective because it can solve the above color problem. The same applies to .

"Embodiments of the Invention" The present invention will be described in more detail below. This example deals with tuna as the frozen fish meat. First, a block decompression method will be explained with reference to FIG.

a, f Disassembly process 1 This process consists of frozen tuna 11 frozen at about -50°C.
This is a process of cutting out tuna blocks 12 weighing from several hundred grams to several kilograms. A knife won't fit, so cut it with a saw-like electric cutter. The block 12 is cut out in the shape of a rectangular parallelepiped between the legs, but its shape is not limited.

b, r Block Thawing Step 1 This step is a step in which the tuna block 12 is placed in a sealed container 13 made of, for example, stainless steel, and thawed in a sealed state. Tuna block 1 cut out during the dismantling process
Since the surface of the container 2 is dirty, it is preferable to wash away dirt and debris adhering to the surface with running water and place it in the closed container 13. What is important in this step is that since the tuna block 12 cools the air inside the closed container 13, the closed container 13 becomes like a refrigerator with the tuna block 12 as a cold source.
is the point at which the temperature at the surface and center increases almost uniformly. That is, only the surface of the tuna block 12 is not thawed excessively, and the increase in surface temperature is absorbed by heat exchange with the inside, and as a result, thawing occurs with an extremely small temperature difference between the surface and the center. It's about moving on. In order to speed up this block thawing process, the outside of the sealed container 13 can be exposed to wind with an electric fan or with running water.

In the conventional thawing method, since the outside of the tuna block 12 is always in contact with the outside air, the surface portion thaws much faster than the inside. As a result, as thawing progresses, the temperature difference between the surface area and the center area increases.

This tuna block 12 has a center temperature of approximately −12 to
When the temperature reaches -6°C, it is taken out from the closed container 13.

Preferably, it is best to take it out when the temperature reaches -10 to -8°C.The temperature range in which metMb is likely to occur is -3 to -4°C on the surface and -6 to -6 in the center.
Since the temperature is 8° C. (maximum color zone), the tuna block 12 is taken out from the closed container 13 before reaching the maximum color zone. Also, if the temperature reaches -10°C, it can be cut with a knife.

Note that "1-sealing the container 13" does not mean that air cannot enter or exit at all. Even if some air enters and exits, the above effects can be obtained.

C, f cutting process” From the tuna block 12 taken out from the closed container 13,
Weight several hundred grams (1 (1~20ma+X 40~55mm)
This is a step of cutting out one piece J14 of approximately X10a to 250 mm and bringing it into contact with air. As is well known, r-saku1 refers to the shape of sashimi before slicing it.

MbO quickly passes through the maximum color band and Mb.

In this process, tuna blocks 12
Then, cut out the fins 14 to increase the surface area and actively bring the tuna meat into contact with the air. When the tuna block 12 that has reached just before the maximum color band is cut out as a block 14, the surface of the block 14 is brought into sufficient contact with the outside air and its temperature rises, and the block 14 quickly passes through the maximum color band. At this time, it is desirable to immerse the stake 14 cut out from the block in salt water with a concentration of 3 to 3.5% to remove free water from the beef cow, and after taking it out from the salt water, wipe the surface with a dry paper towel. By removing free water in advance due to the difference in osmotic pressure between tuna and tuna, which usually has a salinity of around 1%, it is possible to suppress the occurrence of drips. In addition, it is preferable that the baskets 14 are arranged on a tray 16 covered with a dry cloth or a cloth 15 moistened with salt water with a concentration of 3 to 3.5%, so that they do not touch each other. Then, the contact area becomes oxygen-deficient, and the production of metMb is promoted, resulting in a brown color. When the cloth 15 is laid, the lower surface of the fence 14 can also be brought into contact with the air. The size of the fence 14 is 10~20mm x 40~55m.
Since the aIX is about 100 to 250ffl111, thawing can proceed with a small temperature difference between the surface and the center and with sufficient oxygen supplied to the center.

The sashimi 14 thawed in this way can be cut into sashimi and eaten as is.

When storing the cage 14 for further storage, the center temperature of the cage 14 is -3 to -1°C, preferably -2 to -1.3°C.
When the temperature reaches around ℃, put it in a cold storage at around -1 to 4℃. If the center temperature is lower than 13 degrees Celsius, it will be in the temperature range of the maximum color band, so metMb will occur and discoloration will occur easily, -1 degrees Celsius
When the temperature is higher, the surface temperature rises rapidly, and metMb formation is promoted, resulting in discoloration. Furthermore, -1.3°C is said to be the temperature at which tuna develops its brightest red color (the freezing point of tuna).

When the tuna is placed in a cold storage for about a day or night, the box 14 is further exposed to air, and the conversion of Mb to MbO is promoted, resulting in bright red tuna. Also, during this storage, ATP is sequentially decomposed into IMP and HxR.

It becomes Hx and the flavor comes out. Furthermore, a storage temperature of about -1 to 4°C suppresses the growth of mesophilic bacteria that cause food poisoning.

Next, FIG. 2 schematically shows the single-pack thawing method 1 of the present invention. This thawing method is as follows: 1.
and 1 salt water thawing step 1, and is useful when thawing is desired to be done more quickly and easily than the above-mentioned block thawing method.

a, r Cutting process 1 This process is a process in which pieces 21 each weighing several hundred grams are directly cut out from frozen tuna chunks 11 that have been frozen to about -50°C. The size of the fence 21 is approximately 10 to 20 mm x 40 to 55 layers x 100 to 250 mm. Since a knife cannot fit into the frozen tuna 11, it is cut with a saw-like electric cutter, for example.

b. "Salt water thawing step 1 This step is about 2 to 4%, preferably 3 to 4%, of the cage 21.
This is a step of thawing by immersing it in about 3.5% salt water 22. Salt water at this level of concentration is effective in removing excess water from the cage 21 without leaving behind a salty taste. In other words, the salt concentration of tuna meat is approximately 1%. Add this to 3-3.5
When immersed in salt water of about 100%, free water will be extracted from the tuna beef due to the principle of osmotic pressure. This is effective in producing fresh tuna with less drips after thawing. In addition, since the salt water 22 has a much larger heat capacity than air, the cube 21 can be thawed quickly without creating a temperature difference between the surface and the center of the cube 21. In addition, during thawing, it is preferable to circulate the salt water 22 at an appropriate speed so that fresh salt water 22 is always in contact with the sill 21, because the temperature of the salt water 22 decreases as it comes into contact with the frozen sill 21. It is best to move slowly at all times.

In addition, the salt water 22 can be heated to about 20 to
When using warm salt water at 30°C, it can be thawed quickly.

The boll 21 thawed in this way is removed from the brine 22 when its core temperature reaches approximately -10 to -5°C. Preferably, it is taken out when the temperature reaches -8 to -5°C. This temperature range is higher than the temperature range described in the block thawing method, but this is because it was taken into consideration that the temperature of the slag increases more easily than that of the block.

After removing the sachets 21 from the salt water 22, wipe off the salt water on the surface with a paper towel or the like, and place them together on a tray 16 on which a dry cloth or a cloth 15 moistened with salt water with a concentration of 3 to 3.5%, for example, is spread. Arrange them so they don't touch.

The reason for non-contact and placing a cloth is the same as that described in the r-block thawing method.

The saku 21 thawed in this way can be cut into sashimi and eaten as is.

In addition, when storing the box 21 for further storage, the center temperature of the box 21 should be -3 to -1℃, preferably -2 to -1.3℃.
When the temperature reaches around ℃, put it in a cold storage at around -1 to 4℃. This point is similar to that described in the r-removal step j in the block decompression method.

"Effects of the Invention" As described above, the inventions of claims 1 and 2 first cut into blocks when thawing frozen fish meat, and then thaw them in a closed container. Temperature differences are less likely to occur. Then, just before reaching the maximum white discoloration zone, it is scraped off to make it smaller, increasing the surface area and allowing not only the surface but also the center to come into sufficient contact with air, which allows the temperature of the product to rise rapidly. Therefore, the maximum white discoloration zone can be quickly passed through, and in the case of red fish meat, the muscle pigment myoglobin (Mb) can be converted to oxymyoglobin (MbO□).
A beautiful bright red thawed red fish meat can be obtained. After scooping, the color and freshness can be maintained for a longer period of time if you leave it until the center temperature reaches about -3 to -1℃, and then store it in a refrigerator at -1 to 4℃. .

Furthermore, in the inventions of claims 3 and 4, since a piece of frozen fish meat is first taken and thawed in salt water, similarly,
Rapid thawing can proceed with a reduced temperature difference between the surface and the center. The fish is then taken out just before reaching the maximum whitening zone and brought into contact with air to quickly pass through the maximum whitening zone.
O □), beautiful bright red thawed red fish meat can be obtained. After taking it out from the salt water, let it stand until the center temperature reaches about -3 to -1℃, then -1 to -1℃.
If stored in a refrigerator at 4°C, both color and freshness can be preserved for a longer period of time.

The thawing methods according to claims 1 and 2 proceed with thawing relatively slowly, and the thawing methods according to claims 3 and 4,
This is effective when you want to defrost more quickly.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing the block decompression method of the present invention. FIG. 2 is an explanatory diagram schematically showing the thawing method of the present invention. 11...Frozen tuna lump (fish meat lump), 12...Tuna block, 13...Airtight container, 14.21...Fill, 22...Brine.

Claims (4)

[Claims] (1) A block thawing process in which several hundred grams to several kilograms of frozen fish meat is stored in a closed container and left until the center temperature reaches approximately -12°C to -6°C; and ℃
A method for thawing frozen fish meat, comprising: a step of removing the shells from the block that has reached ~-6°C and bringing them into contact with air; (2) In claim 1, the frozen fish meat is further left until the core temperature reaches about -3°C to -1°C, and then stored in a cold storage at -1°C to 4°C. How to unzip. (3) A scooping process in which the shells are directly cut from the frozen fish meat; and the scooped fish meat is immersed in salt water until the center temperature is about -
A method for thawing frozen fish meat, comprising: a step of thawing frozen fish meat in brine, which is taken out and brought into contact with air after the temperature reaches 12°C to -6°C. (4) In claim 3, the bale whose center temperature has reached -12°C to -6°C is further left until the center temperature reaches about -3°C to -1°C, and then the block has a temperature of -1°C to 4°C. How to thaw frozen fish stored in a refrigerator.