JPH03240433A - Method for defrosting frozen fish meat - Google Patents

Abstract

PURPOSE:To defrost frozen fish meat without changing color and becoming watery by putting frozen fish meat in a bag in state immersed in a salt water, applying supersonic wave to the bag in the salt water having a specific salt concentration and temperature and then raising center temperature of the fish meat up to a specific temperature in air. CONSTITUTION:Frozen fish meat kept at -50 deg.C is cut into a prescribed size without defrosting and the cut fish meat is put in a bag in state immersed in a salt water having 2-6wt.% concentration and the bag is dipped in a salt water bath kept to about 10wt.% concentration and 5 deg.C temperature and supersonic wave is applied to the bag while stirring the salt water in the bag to raise the center temperature of the fish meat up to -2 to 0 deg.C and the fish meat is taken out of the bag and center temperature of the fish meat is raised up to 0-2 deg.C in air kept at 5-10 deg.C to carry out the aimed defrosting.

Description

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

"Conventional technology and its problems" Fish such as tuna caught in the distant sea are first transported on board a boat for 150 minutes.
It is quickly frozen to around 30°F, transported frozen to Japan, and then thawed in Japan before being provided to consumers.

Conventionally, in order to thaw such frozen fish, for example, the head and tail of the fish are first removed, and then the fish is cut longitudinally to produce frozen fish meat cut into quarters, and the frozen fish meat is heated at +5°C to
After immersing it in a water tank filled with tap water at around +10℃ and thawing mainly only the surface part in water to a relatively high temperature,
This was done by cleaning the frozen fish meat with a knife.

However, such conventional methods for thawing frozen fish meat have a problem in that the fish meat turns brown during surface thawing.

Additionally, the ice that forms inside the fish meat during rapid freezing on board the ship remains as residual water after the surface thaws, causing the fish meat to melt and become watery and elastic before it is delivered to consumers. There was a problem in that the quality of the meat would be impaired.

There was a problem in that the temperature of the surface part rose too high and it became susceptible to spoilage, while the temperature of the center part hardly rose from -50°C, making it impossible to thaw uniformly.

Another problem is that the tap water in the aquarium is easily affected by the outside temperature, making appropriate temperature control difficult.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a method for thawing frozen fish meat that does not change color or become watery. shall be.

[Means and effects for solving the problem] A method for thawing frozen fish meat according to the present invention to solve the above problem is to immerse frozen fish meat in salt water with a concentration of 2% to 6% and place it in a bag, The frozen fish meat is immersed in a bag of salt water maintained at +5°C with a concentration of approximately 10%, and ultrasonic waves are passed through both the inside and outside of the bag to raise the temperature of the frozen fish meat to a core temperature of -2°C to 0°C. a first step of heating the frozen fish meat to +5°C to +1°C;
It is characterized by comprising a second step of raising the temperature in air at 0°C to a core temperature of 0°C to +2°C.

In the above configuration, in the first step of thawing, the fish meat is immersed in salt water. At this time, due to the osmotic dehydration effect of the salt water in the bag, water is absorbed from the surface of the fish meat into the salt water, and the pigments and extracts from the fish meat are not extracted.

Also, as the temperature rises, the fish meat begins to respire, but the oxygen consumed by this respiration is replenished from the salt water inside the bag.
No discoloration due to oxygen deficiency. By passing ultrasonic waves through the salt water inside and outside the bag, the temperature at the center of the fish meat is efficiently raised, reducing the temperature difference between the surface temperature and the core temperature. Note that in the first step, a thawing machine, which will be described later, is used.

Next, in the second step of thawing, a thawing machine is not used, but the fish meat is brought into contact with air and the temperature is gradually raised. At this time, the fish meat becomes more active in respiration, but since there is plenty of oxygen in the air, the oxygen consumed through respiration is sufficiently replenished from the air, and discoloration due to lack of oxygen does not occur. Further, the thawing machine is not used in all the thawing steps, but is used only in the first step, thereby shortening the time required for thawing by the thawing machine and increasing the number of processes.

Prior to the present invention, the inventor investigated the cause of discoloration of fish meat. As a result, it was found that fish meat begins to respire when the temperature reaches -1.5° C. or below -E, and the oxygen in the fish meat is consumed for respiration, resulting in an oxygen-deficient state, and the fish meat changes color due to the oxygen deficiency.

The present invention was made after the above considerations.

Here, the thawing machine used in the method of thawing frozen fish meat of the present invention will be explained. FIG. 1(a) is a front view of the thawing machine, and FIG. 1(b) is a right side view.

The thawing machine 1 includes a liquid tank 2. Salt water is poured into the liquid tank 2, and the frozen fish meat 10 is thawed in the salt water. The frozen fish meat 10 is placed in a bag and suspended from a bar 9 placed on the upper edge of the liquid tank 2. Note that the frozen fish meat 10 may be continuously supplied to the liquid tank 2 by a conveyor line. The liquid tank 2 includes a spiral cooling heat exchanger 3 and an electric heater 4 provided at the center of the cooling heat exchanger 3.
The salt water injected into the liquid tank 2 is kept at a desired temperature. Three nozzles 5 are provided on the inner surfaces of both longitudinal walls of the liquid tank 2.

Air compressed by a compressor 7, which will be described later, is ejected from the nozzle 5 in the form of bubbles. The drive unit 6 includes a power source and a compressor 7 as shown in the diagram.

The operation panel 8 is used to set the temperature of the salt water in the liquid phase 2.

Next, FIG. 2 shows a process diagram. In the capture step 11, fish such as tuna are captured in the distant sea. In the quick-freezing step 12, the captured fish are quickly frozen to -50°C on board the ship. Frozen fish are transported domestically by air or other means while maintaining a temperature of -50°C. In Japan, fish are cut into 15 pieces in cutting process 13.
Frozen fish meat 10 is obtained by cutting the fish meat in a frozen state at 0° C. without thawing. Next, unzip. Thawing is performed in a first step 14 and a second step 15.

First, in the first step F1114, salt water with a concentration of about 10% is injected into the liquid tank 2 of the thawing machine 1 shown in Fig. 1 and kept at +5°C, and the frozen fish meat 10 is mixed with the salt water with a concentration of 2% to 6%. Put the frozen fish meat into a bag and package it with salt water.
Frozen fish meat 10 was immersed in salt water to bring the core temperature to -2°C to 0.
Raise the temperature to ℃. At this time, nozzle 3 of thawing machine 1
In addition to stirring the salt water by the flow of bubbles ejected from the
The ultrasonic waves generated by the collapse of the bubbles pass through the salt water, agitating the salt water and promoting heat exchange between the salt water and the frozen fish meat. Fish meat begins to breathe when the temperature drops to -1.5°C or lower, but the oxygen consumed during this respiration is replenished from the salt water in the bag, so it does not become oxygen deficient and turns brown. There's nothing to do. At this time, the surface temperature is +2℃~+3℃
When the temperature rises to 100%, the ice crystals that formed in the fish meat during rapid freezing on board the ship melt and become residual water, which has an osmotic pressure of 2% to 6% salt water in the bag. Due to the dehydration effect, the fish meat is discharged from the surface into the salt water inside the bag, so the fish meat does not become watery after thawing.

Next, in the second step 15, the fish meat is taken out of the bag and brought into contact with air to slowly raise the temperature to a core temperature of 0°C to 1°C. In this way, the temperature difference between the surface and center areas is made more uniform. After the first step 14 is completed, the water remaining inside the fish meat as a result of melting of the ice crystals 17 is completely drained out of the fish meat 17, and the surface of the fish meat is exposed to air and allowed to breathe. Ensuring that consumed oxygen is sufficiently replenished to bring the cell tissue closer to the state of raw meat.

Next, proceed to ice temperature storage step 16, where the thawed fish meat is wrapped in water-absorbing paper and temporarily stored in an ice temperature refrigerator, or proceed to ice temperature shipping step 17, where the thawed fish meat is stored in ice or a foamed sugar roll filled with a cold storage agent. Place in a container and ship at ice temperature.

“First Embodiment” Next, the first embodiment of the present invention will be explained in FIGS. 1(a) and (
b) will be explained with reference to FIG.

In this example, frozen fish meat is produced by rapidly freezing tuna caught in the distant sea to -50℃ on board a ship, removing the head and tail at -50℃ after transporting it to Japan, and then unfreezing it in the longitudinal direction. Use meat that is cut into quarters and made into approximately 3kg pieces of meat without skin.

In the first step 14 of thawing, salt water with a concentration of 10% is poured into the liquid tank 27- of the thawing machine 1, and the salt water is kept at +5°C. The frozen fish meat 10 is immersed in salt water with a concentration of 5% and placed in a plastic bag, and the plastic bag is immersed in the salt water in the liquid tank 2. In this state, ultrasonic waves are passed through both the inside and outside of the plastic bag to raise the temperature at the same time until the core temperature is within the range of -2°C to 0°C. Note that at this time, the surface temperature of the fish meat rises to +2°C to +3°C.

In the subsequent second step 15, the fish meat is first removed from the plastic bag, and the 5% concentration of salt water adhering to its surface is washed away.
Use a knife to remove the bones, blood (blackened parts of the meat), and unnecessary parts of the cap. Then, put the fish meat in a plastic bag with air, and keep it in the air outside the plastic bag, which is kept between +6℃ and +10℃ while keeping it away from the outside air, until the core temperature is within the range of 0℃~+1℃. Raise the temperature slowly for 3 hours. Here, the reason why the fish meat was not allowed to come into contact with the outside air outside the plastic bag was to prevent the air in contact with the surface of the fish from flowing and to avoid a sudden temperature rise, and to prevent the surface of the lump-shaped fish from drying out. This is to ensure that there is no such thing.

8 In this second step, the temperature decreases to +6°C/+10°C.
It can be done anywhere, such as in a refrigerator or at a fish processing plant, as long as it is kept within this range.

After thawing in this manner, it is stored at ice temperature in a plastic bag, or it is shipped at ice temperature by placing it in a foam box along with ice cubes or cold storage material placed in a plastic bag.

"Second Embodiment" Next, regarding the second embodiment of the present invention, FIGS. 1(a) and (b)
, will be explained with reference to FIG.

In this example, the frozen fish meat is made by rapidly freezing tuna caught in the distant sea at -50°C on board a ship, and cutting it without thawing at -50°C after transporting it to Japan to form 700g to 1000g rectangular parallelepipeds.
Use l ~ for so-called crispy frozen fish meat. This flaky frozen fish meat is finely divided into shapes and dimensions just before being cut by a final cook with a knife and cooked into sashimi or the like.

In the first step, salt water with a concentration of 10% is poured into the liquid tank of the thawing machine and maintained at +5°C, and the flaky frozen fish meat 10 is mixed with a salt water having a concentration of about 2 % of saline water and placed in a plastic bag, and the plastic bag is immersed in the salt water in the liquid tank 2. In this state, ultrasonic waves are passed through the warm water inside and outside the plastic bag, and the temperature is raised for about 25 minutes until the core temperature reaches about -1°C. Note that the surface temperature at this time rises to about +3°C. The reason why the concentration of salt water in the plastic bag is diluted to about 2% in the first step is as follows. In other words, since the surface of flaky fish meat is also edible, unlike meat chunks, the purpose is to prevent salt water adhering to the surface from becoming salty and spoiling the texture. The concentration of salt water has been lowered to the point where you won't even feel the salt.

In the second step, the flaky fish meat is first removed from the plastic bag, and the surface covered with salt water is wiped off with a clean towel, or absorbent paper. Then, while surrounding the fish meat with the towel or absorbent paper, the temperature is slowly raised in air at 5° C. to 10° C. until the core temperature reaches 0° C. to +2° C. for about 1 hour. At this time, the 2% salt water that had penetrated the surface is pushed out and absorbed into a towel or absorbent paper. Although some of the 2% salt water remains on the surface, the concentration is not so high that you can feel the salt, so it does not impair the texture when flaky fish meat is cut into pieces and cooked as sashimi.

As described above, in thawing the flaky frozen fish meat of this example, the time required for the first step of thawing is about 25 minutes, which is shorter than in the case of thawing the frozen fish meat in the form of chunks of meat. It is hygienic because there is little respiration, and the surface area
It has the advantage that there is no oxygen deficiency in any of the centers, resulting in a beautiful red color, and that it does not change color even at room temperature for about 3 hours after thawing.

"Effects of the Invention" As described above, the method for thawing frozen fish meat of the present invention involves placing the frozen fish meat immersed in salt water with a concentration of 2% to 6% in a bag, and adding the frozen fish meat together with the bag to a saline solution with a concentration of approximately 2% to 6%. A first step of raising the temperature of the frozen fish meat to a core temperature of -2°C to 0°C by immersing it in 10% salt water maintained at +5°C and passing ultrasonic waves into the warm water both inside and outside the bag. and a second step of raising the temperature of the frozen fish meat in air at +5°C to +10°C to a core temperature of 0°C to +2°C. In the first step, the use of salt water allows ultrasonic waves to pass through easily, allowing uniform thawing to occur quickly on the surface and center of the fish meat, and the osmotic dehydration action of the salt water removes residual water within the fish meat. The fish meat will not become watery and will not lose its elasticity. Furthermore, in the first step, the oxygen consumed by the respiration of the fish meat is replenished from the salt water to prevent oxygen deficiency, so the fish meat does not discolor. In the second step, the surface of the fish meat is brought into contact with air so that the oxygen consumed through respiration is sufficiently replenished to bring the cells of the fish meat closer to the state of raw meat. Therefore, there is an excellent effect of thawing the fish meat in a way that increases its commercial value.

12- 14, first step, 15. Second step.

[Brief explanation of drawings]

FIG. 1(a) is a front view of a thawing machine used for thawing frozen fish meat, FIG. 1(b) is a right side view thereof, and FIG. 2 is a process chart showing the method of thawing frozen fish meat of the present invention.

Claims (1)

[Scope of Claims] Frozen fish meat is immersed in salt water with a concentration of 2% to 6% and placed in a bag, and the frozen fish meat is immersed together with the bag in salt water with a concentration of about 10% maintained at +5°C, A first step of raising the temperature of the frozen fish meat to a core temperature of -2°C to 0°C by passing ultrasonic waves into the saline water inside and outside the bag, and core temperature of the frozen fish meat in air at +5°C to +10°C. Temperature 0℃
A method for thawing frozen fish meat, comprising: a second step of raising the temperature to ~+2°C.