Method for producing frozen fish product

Abstract

This method for producing a frozen fish product includes: a dispatching / blood draining step for dispatching and blood-draining a landed fish; a trimming / processing step for trimming and processing the dispatched and blood-drained fish into loins; a vacuum packaging step for vacuum-packaging the loins obtained by the trimming and processing; a calcium chloride liquid freezing step for freezing a vacuum-packaged product of the loins, that is obtained by the vacuum-packaging, by putting the vacuum-packaged product into a tank of a calcium chloride liquid at -35°C or lower; a calcium chloride liquid removal step for removing the calcium chloride liquid adhering on the surface of the vacuum-packaged product taken out from the tank of the calcium chloride liquid; and a box-packing / wrapping step for box-packing and wrapping the vacuum-packaged product from which the calcium chloride liquid has been removed. In particular, by setting the time from the start of the trimming / processing step to the start of the calcium chloride liquid freezing step to 10 minutes or less for each roin, the K values of the loins are managed so as to become 5.0 or less.

Description

Manufacturing method for frozen fish products

[0001] The present invention relates to a method for producing frozen fish products by shaping and processing live fish to produce frozen products.

[0002] As a method for flash-freezing fish to produce a frozen product, Patent Document 1 discloses a freezing method in which the fish is temporarily removed from the calcium chloride brine at a relatively high product temperature during freezing, left for a certain period of time at a temperature higher than the brine temperature but lower than the freezing point of the fish, and then immersed in the brine again and frozen to a predetermined product temperature.

[0003] The calcium chloride flash freezing method is superior to other freezing methods in terms of cooling efficiency, freezing costs, etc. Furthermore, according to the freezing method disclosed in Patent Document 1, even when large fish such as tuna are flash-frozen using calcium chloride, frozen fish with good flesh color can be produced without cracking.

[0004] Special Publication No. 61-39008

[0005] However, two-stage freezing methods such as the one disclosed in Patent Document 1 slow the rate of passage through the ice crystal temperature range (-2°C to -4°C), making it difficult to prevent dripping to preserve flavor. When processing live fish to obtain frozen fish products, simply employing the common calcium chloride flash freezing method does not necessarily result in the production of frozen fish products with good freshness (low K value). The inventors of the present application arrived at the present invention after repeated trials and considerations regarding which steps should be managed and how when producing frozen fish products using the calcium chloride flash freezing method.

[0006] An object of the present invention is to provide a method for producing frozen fish products which can always produce frozen fish products with good freshness (low K value).

[0007] According to the present invention, the method for producing frozen fish includes a live-killing / bleeding step of killing and draining the blood of landed fish, a shaping step of shaping the live-killed / bleeded fish into loins, a vacuum packaging step of vacuum-packaging the shaped / processed loins, a calcium chloride solution freezing step of placing the vacuum-packaged loins in a bath of calcium chloride solution at −35°C or below and freezing them, a calcium chloride solution removing step of removing the calcium chloride solution adhering to the surface of the vacuum-packaged loins removed from the bath, and a boxing step of boxing the vacuum-packaged loins from which the calcium chloride solution has been removed. In particular, the time from the start of the shaping step to the start of the calcium chloride solution freezing step for each loin is controlled to be 10 minutes or less, so that the K value of the loin is 5.0 or less.

[0008] The production process includes a live-killing and bleeding process, a shaping process, a vacuum packaging process, a calcium chloride solution freezing process, a calcium chloride solution removal process, and a boxing process. The time from the start of the shaping process to the start of the calcium chloride solution freezing process for each loin is controlled to be 10 minutes or less, so that the loin's K value is 5.0 or less. When processing live fish to obtain frozen fish products, the time from the start of shaping the fish into loins to the time of immersion in calcium chloride solution is extremely important, and as in the present invention, it is essential that this time be 10 minutes or less for each loin. It has been confirmed that if this time exceeds 10 minutes, the K value cannot be maintained at 5.0 or less. Therefore, according to the present invention, frozen fish products with excellent freshness can be obtained without fail. Furthermore, since the shaped loins are vacuum-packaged and then immersed in a tank of calcium chloride solution, the loins are protected from the intense spiciness of the calcium chloride solution and food contamination and drying can be prevented. In this specification, the term "loin" refers to the four dorsal and ventral parts obtained by cutting each fillet obtained by filleting a fish into two pieces.

[0009] It is preferable that the shaping process is a process that starts within one hour of the live-killing and bleeding process, in a state where the live-killing and bleeding-drained fish is placed in a cold seawater tank at approximately -2°C or less.

[0010] It is also preferable that the calcium chloride solution freezing step is a step of allowing each vacuum package obtained in the shaping step to remain in a bath of calcium chloride solution for 10 minutes or more.

[0011] In this case, it is preferable that the calcium chloride solution removal step and the boxing step are completed within 5 minutes for each vacuum package.

[0012] Furthermore, in this case, it is more preferable that the live-killing and bleeding step is a step of live-killing and bleeding each landed fish within one minute of landing.

[0013] It is also preferred that the calcium chloride solution freezing step is a step of forcibly circulating calcium chloride solution in a calcium chloride solution tank into which the vacuum-packaged shaped body is placed.

[0014] It is also preferred that the vacuum packaging step is a step in which water adhering to the surface of the loin is removed with moisture-absorbing paper and then vacuum-packed.

[0015] It is also preferable that the method further comprises an ultra-low temperature storage step of storing the package obtained in the boxing step in an ultra-low temperature storage.

[0016] It is also preferred that the fish is yellowtail.

[0017] According to the present invention, the time from the start of the shaping process to the start of the calcium chloride solution freezing process for each loin is kept within 10 minutes, thereby controlling the K value of the loin to be 5.0 or less. As a result, frozen fish products with excellent freshness can be obtained without fail. Furthermore, since the shaping-processed loins are vacuum-packaged and then placed in a tank of calcium chloride solution, the loins can be protected from the intense spiciness of the calcium chloride solution and food contamination and drying can be prevented.

[0018] 1 is a flowchart showing each step in one embodiment of the method for producing frozen fish products of the present invention.

[0019] An embodiment of the method for producing frozen fish products of the present invention will be described below with reference to the drawings. The fish in this embodiment is yellowtail, and the production of frozen yellowtail products will be described below. Of course, the present invention can also be applied to other large fish, such as yellowtail, bonito, tuna, and others.

[0020] As shown in Figure 1, the method for producing frozen fish in this embodiment includes a live-killing bleeding process (step S1) in which landed yellowtail is killed and bled, a shaping process (step S2) in which the live-killed, bled yellowtail is shaped into loins, a vacuum packaging process (step S3) in which the shaped yellowtail loins are vacuum-packaged, a calcium chloride liquid freezing process (step S4) in which the vacuum-packaged loins are placed in a calcium chloride liquid bath at -35°C or below and frozen, a calcium chloride liquid removal process (step S5) in which the calcium chloride liquid adhering to the surface of the vacuum-packaged product is removed from the calcium chloride liquid bath, a boxing process (step S6) in which the vacuum-packaged product from which the calcium chloride liquid has been removed is boxed, and an ultra-low temperature storage process (step S7) in which the packaged product obtained by the boxing process is stored in an ultra-low temperature storage. These processes are described in detail below.

[0021] (Live-killing and bleeding process, step S1) Yellowtail caught from a yellowtail farm is killed individually on board a ship, for example by inserting a metal rod into the medulla oblongata. The live-killed yellowtail is immediately placed in a tank of cold seawater at around -2°C and bled. This is just one example, but in this case, 500 kg (100 fish) of yellowtail are added to 1 ton of cold seawater. The time from landing from the fish farm to live-killing and bleeding is within one minute. The K value of the yellowtail at the time of landing was 1.5, and this K value remained at 1.5 even in the cold seawater tank.

[0022] (Shaping and processing step, step S2) After returning to the port, 5 tons (1,000) of yellowtail that were killed and bled that day are transferred from the blood-containing cold seawater tank to a new cold seawater tank (around -2°C), transported to the processing plant, and the cold seawater tank is stored in a refrigerator. The cold seawater tank and refrigerator are maintained at around -2°C. Thereafter, a predetermined number (for example, 100) of yellowtail are transported to the processing plant in a cold seawater tank (around -2°C) at predetermined intervals (for example, every 13 minutes), and shaping and processing begins. The time from killing and bleeding to starting shaping and processing is within one hour. In a specific example, the time from killing and bleeding on board to returning to the port and starting shaping and processing at the processing plant is approximately one hour. The K value of the yellowtail at the start of shaping and processing was 2.0.

[0023] The shaping process is carried out, for example, as follows: (1) Yellowtail taken out of a cold seawater tank is cut into head, collar, flesh, organs, etc. by machine. 1,000 pieces are cut in 8,000 seconds (8 seconds per piece). (2) The obtained flesh is filleted into three pieces by machine, and then divided into two and cut into four loins (joints) on the dorsal and ventral sides. The processing time for 1,000 pieces is approximately 2 hours and 13 minutes, and for 100 pieces it is 800 seconds (approximately 13 minutes, 8 seconds per piece). (3) The skin is removed from the loins by machine and they are washed in cold water. The K value of the loins during and at the end of the shaping process was 5.0.

[0024] (Vacuum Packaging Process, Step S3) In a separate room, water adhering to the surface of the loin after shaping is removed using disposable moisture-retaining paper. The loin is then placed in a vacuum packaging bag using a backing sheet as a base and vacuum-packaged. Next, in a separate room, a metal detector is used to confirm the absence of metal foreign objects, and a weight-indicating sticker is affixed to each package. Vacuum-packaging the loin in this manner protects the loin from the intensely spicy calcium chloride solution and prevents food contamination and drying. For each loin, the time required for shaping and vacuum packaging (i.e., the time from the start of the shaping process to the start of the calcium chloride solution freezing process) is within 10 minutes, and in this specific example, 8 minutes. It is very important that the time from the start of this shaping process to the start of the calcium chloride solution freezing process is within 10 minutes for each loin; it has been confirmed that freshness decreases if the time exceeds 10 minutes. In this embodiment, the K value of the loin at the end of vacuum packaging was 5.0. Although this varies depending on the number of fish landed and the number of workers, the typical time required for shaping and vacuum packaging all loins was within three hours.

[0025] (Calcium chloride solution freezing step, step S4) Immediately after completion of vacuum packaging, the vacuum-packaged loins are placed into the entrance of the calcium chloride solution tank. In the calcium chloride solution tank, a portion of the calcium chloride solution cooled to a temperature of -35°C or below by a brine cooler pump is sprayed from above the entrance toward the exit, and a portion of this solution is poured diagonally downward in a shower-like fashion. As a result, the vacuum-packaged loins placed in the calcium chloride solution tank flow toward the exit, and the floating vacuum-packaged loins are also cooled. The calcium chloride solution is returned from the bottom of the tank to the brine cooler pump, where it is cooled and pressurized before being sprayed back into the calcium chloride solution tank, and this forced circulation is repeated. A conveyor is provided near the exit of the calcium chloride solution tank, and the vacuum-packaged loins flowing through the tank are successively removed from the calcium chloride solution tank by this conveyor. In this way, calcium chloride brine cooled to below -35°C is forcedly circulated in the calcium chloride bath, sprayed and poured, so the loins are continuously cooled and instantly frozen with seven times the cooling efficiency compared to air cooling. They pass through the "ice crystal temperature zone" that destroys the flavor of food in an extremely short time, thereby preserving excellent flavor. Furthermore, calcium chloride brine is inexpensive and easy to procure. Forced circulation significantly improves the freezing capacity relative to the volume of the calcium chloride bath, reducing capital investment. Each loin spends 10 minutes or more in the calcium chloride bath, e.g., approximately 15 minutes. In flowing calcium chloride brine at below -35°C, a loin weighing approximately 500g is cooled to a core temperature of below -30°C in 5 to 8 minutes. The K value of the loin during its stay in the calcium chloride bath and upon removal from the calcium chloride bath was 5.0.

[0026] (Calcium chloride solution removal step, step S5) The vacuum packaged loins were successively removed from the calcium chloride solution tank by the conveyor, and showered with fresh water at 15°C from above and below to remove the calcium chloride solution adhering to the surface of the vacuum packaged loins. The K value of the loins in this calcium chloride solution removal step was 5.0.

[0027] (Boxing process, step S6) The vacuum-packaged loins from which the calcium chloride solution has been removed are boxed and packed in units of the number required by the customer, for example, 20 loins per 10 kg cardboard box (20 loins per box). The work time for removing the calcium chloride solution from each vacuum-packaged loin and boxing it is within 5 minutes, and in this specific example, 3 to 4 minutes. The K value of the loins upon completion of boxing was 5.0. Note that, although this varies depending on the number of fish landed and the number of workers, the general time from the ikijime (killing) and bleeding process to the start of the ultra-low temperature storage process for all loins was within 6 to 8 hours.

[0028] (Ultra-low temperature storage step, step S7) The boxed packages are packed in groups of several, for example, 20 boxes (200 kg) of 10 kg cardboard boxes, which are placed on a pallet and transported by forklift to a -40°C ultra-low temperature storage facility for storage. For each vacuum-packaged loin, the time from removal from the calcium chloride solution bath to the start of ultra-low temperature storage is approximately 10 minutes. The K value of the loin at the time of transport to the ultra-low temperature storage facility was 5.0.

[0029] It has been confirmed that loins stored in an ultra-low temperature storage facility at -40°C do not lose their color even after 12 months, and that this condition is maintained even after three years.

[0030] As described in detail above, this embodiment includes the following manufacturing processes: a live-killing and bleeding process, a shaping process, a vacuum packaging process, a calcium chloride solution freezing process, a calcium chloride solution removal process, a boxing process, and an ultra-low temperature storage process. In particular, to maintain the loin's K value below 5.0, the time from the start of the shaping process to the start of the calcium chloride solution freezing process for each loin is limited to within 10 minutes. When processing live fish to obtain frozen fish products, the time from the start of shaping the fish into loins to the time of immersion in calcium chloride solution is extremely important. It has been confirmed that if this time exceeds 10 minutes, the K value cannot be maintained below 5.0. According to this embodiment, this time is controlled to within 10 minutes, ensuring the production of highly fresh frozen fish products. Furthermore, since the shaped loins are vacuum-packaged and then immersed in a tank of calcium chloride solution, the loins are protected from the intense spiciness of the calcium chloride solution and are also protected from food contamination and dried.

[0031] The relationship between the time from the start of the shaping process to the start of the calcium chloride solution freezing process and the K value for each loin was actually tested and confirmed. Specifically, live yellowtail (hamachi) landed at the port was received, and after being subjected to the same live-sealing process as in the embodiment, it was shaped into loins, immediately vacuum-packed, flash-frozen in calcium chloride solution, and stored in an ultra-low temperature storage facility at -45 ° C. The time from live-sealing to the start of the loin-shaping process was 5 minutes, and the live-sealed yellowtail was placed in a cold seawater tank at around -2 ° C for processing. The indoor temperature in the processing plant was 15 ° C.

[0032] A test was conducted to measure the K value for each of the flash-frozen samples, with the time from the start of the shaping process to the start of the calcium chloride solution freezing process being 4 minutes, 7 minutes, 10 minutes, 11 minutes, 15 minutes, and 25 minutes. This test was conducted on October 29, 2024, at the Japan Food Inspection Fukuoka Inspection Center, a general incorporated foundation registered with the Ministry of Health, Labor, and Welfare. The K value test method was high-performance liquid chromatography. The test results are shown in Table 1.

[0033]

[0034] From Table 1, it is clearly proven that when the time from the start of the shaping process to the start of the calcium chloride solution freezing process was 11 minutes (Sample 4), which was more than 10 minutes, the K value was 7, indicating a decrease in freshness, whereas when the time from the start of the shaping process to the start of the calcium chloride solution freezing process was 10 minutes or less (Samples 1, 2, and 3), the K value was maintained at 5 or less, indicating that freshness could be maintained.

[0035] The above-described embodiments are merely illustrative of the present invention and are not limiting, and the present invention can be embodied in various other modified and altered forms. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

[0036] It can be used in any industry that processes live fish to produce frozen fish products.

[0037] S1: Live-killing and bleeding process S2: Shaping and processing process S3: Vacuum packaging process S4: Calcium chloride solution freezing process S5: Calcium chloride solution removal process S6: Boxing process S7: Ultra-low temperature storage process

Claims

1. A method for producing frozen fish comprising the steps of: a live-killing and bleeding process in which landed fish are killed and the blood is drained; a shaping process in which the live-killing and bleeding fish are shaped and processed into loins; a vacuum packaging process in which the shaped and processed loins are vacuum-packaged; a calcium chloride liquid freezing process in which the vacuum-packaged loins are placed in a tank of calcium chloride liquid at -35°C or below and frozen; a calcium chloride liquid removal process in which the calcium chloride liquid adhering to the surface of the vacuum-packaged products removed from the tank is removed; and a boxing process in which the vacuum-packaged products from which the calcium chloride liquid has been removed are boxed; 2. A method for producing frozen fish products as described in claim 1, characterized in that the shaping process is started within one hour of the live-killing and bleeding process, with the live-killed and bled fish being placed in a tank of cold seawater at approximately -2°C or below.

3. A method for producing frozen fish products as described in claim 1, characterized in that the calcium chloride liquid freezing process is a process in which each vacuum packaged body obtained by the shaping processing process is allowed to remain in the tank of calcium chloride liquid for more than 10 minutes.

4. A method for producing frozen fish products as described in claim 3, characterized in that the calcium chloride liquid removal step and the boxing step are completed within 5 minutes for each vacuum package.

5. The method for producing frozen fish products according to claim 4, characterized in that the live-killing and bleeding process is a process in which each landed fish is live-killed and bleeding is performed within one minute after being landed.

6. A method for producing frozen fish products as described in claim 1, characterized in that the calcium chloride liquid freezing process is a process of forcibly circulating calcium chloride solution in the tank into which the vacuum-packaged shaped bodies are placed.

7. The method for producing frozen fish products according to claim 1, characterized in that the vacuum packaging step is a step of removing water adhering to the surface of the loin with moisture-absorbing paper and then vacuum packaging the loin.

8. The method for producing frozen fish products according to claim 1, further comprising an ultra-low temperature storage step of storing the packaged bodies obtained by the boxing step in an ultra-low temperature storage facility.

9. A method for producing frozen fish products as described in claim 1, characterized in that the fish is yellowtail.

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