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What is sushi or sashimi grade fish?

sushi or sashimi grade fish photo — Do you know when this fish was caught?

Fish is not only cooked and eaten as grilled or boiled fish but also eaten raw as sushi or sashimi. Naturally, the way to eat fish depends on individual tastes. But in fact, the way we eat fish depends on the time frame after we catch it.

Fish that is still alive or freshly dead is ideal for sashimi. In this case, you should enjoy the elasticity of the flesh, or texture, rather than the umami of the fish. Only the freshest fish is suitable for sashimi. The fish will go rigor mortis within a few hours at the earliest, and within a few days at the latest. The period leading up to rigor mortis is the time when the umami component increases, making it ideal for sushi.

On the other hand, the flesh becomes softer, so it is the sushi chef’s job to find the right balance between the umami and the chewiness of the fish. Of course, for those who prefer fish with more umami, it can also be served as sashimi. The rigor mortis of the fish is eventually dissipated and it gradually begins to decompose, so it is consumed as sashimi or sushi until a certain point in time.

The chef’s job is to determine when the fish cannot be used as sashimi or sushi. After that, the fish will be consumed as grilled or boiled fish. Eventually, the color, taste, and aroma of the fish will change dramatically, and it will reach the so-called putrefied state, making it inedible. The chef’s job is to determine when the fish cannot be used as sashimi or sushi. After that, the fish will be consumed as grilled or boiled fish. Then the color, taste, and aroma change dramatically, and the fish reaches the so-called putrefied state and becomes inedible.

A variety of conditions exist before rigor mortis sets in. Ideally, the fish should be properly processed and cooled as soon as possible after it is caught. Without this, rigor mortis will set in immediately, shortening the time until the rigor mortis is dissipated and speeding up the decomposition process. In other words, it will affect the length of time the fish can be enjoyed.

It is difficult to judge whether fish can only be used for grilled or boiled fish. It is not a simple matter of how many hours after the fish has died. Even if the fish is in sushi or sashimi grade, you can imagine that some are in good condition, and others can only be used almost exclusively for grilling or boiling.

Look around the world and you will see fish being sold around fishing ports as soon as they return from fishing. The fish is truly freshly caught and could not be fresher. Usually, the fish is cooked by dinner at the latest, so the loss of freshness is not a concern at all. People call fish in this state very fresh. To be more precise, it takes a few hours from the time the fisherman catches the fish to the time it is on the market, or at most 12 hours before it is served for dinner. This is what we call sushi or sashimi grade. However, because the fish is not caught in large quantities, it is not distributed to supermarkets in urban areas. This is limited to fishing with small boats.

Large vessels use large nets and other equipment to catch large numbers of fish. When the nets are raised on deck, many of the fish are live. They are quickly sorted, cooled with ice or other means, and placed in refrigerated or frozen storage. Some of the larger fish are stored after Ikejime, etc. Once fishermen go out to fish, they are not allowed to return for at least three days and as long as several months.

Although refrigeration and freezing technology have advanced considerably, freshness is not the same when the fish is caught as it is when it returns to the fishing port. And by the time the fish reaches the supermarket, which is a long way from the fishing port, it is arguably even less fresh. It has already been almost 24 hours since the fishermen caught the fish. It will then spend several days in the supermarket enduring temperature changes and drying out. One wonders if this can be called sushi or sashimi-grade fish.

So far, we think you can understand that this is a typical situation in countries other than Japan.

The situation in Japan is a bit different.

Regardless of the size of the boat, the fish are not allowed to get out of control, Ikejime and other processing is done. And cooling is always done. That is what even the average fisherman does as a matter of course. In other words, it is recognized that keeping fish fresh means delaying the time until rigor mortis.

On top of that, a distribution system has been established to deliver the caught fish to markets and restaurants while keeping them alive. Not only are the fish kept alive, but the know-how to reduce stress during fishing and transportation is shared among fishermen. For example, fish are transported by truck to the consumption area in a state of suspended animation to prevent them from getting out of control. In other cases, fish are not shipped immediately from the fishing port, but are allowed to calm down in a fish tank. By trying to keep the fish as close as possible to the state in which they were swimming in the sea, the fish can recover their original amount of adenosine triphosphate. This is because adenosine triphosphate is the source of umami, which eventually converts to inosinic acid.

In other words, a system is in place to distribute fresher and tastier fish. As a matter of course, it is safe to say that the fish is delivered from the fishing port to the place of consumption and then displayed in supermarkets within 12 hours.

The minimum requirement is that the fish must be usable for sashimi. The words sushi or sashimi grade do not exist in the market. Who caught the fish? What time and minute it was caught? How was it processed? Whether the fish was caught by fishing or by netting, and other details are required. These things change the price of the fish in the market.

In summary, there is no legal definition of sushi or sashimi-grade fish. When seafood is labeled as sashimi grade, it means that the seller, such as a supermarket, has determined that the fish is suitable for sushi or sashimi, based on its evaluation of criteria such as bacteria levels, temperature, parasites, appearance, odor, taste, display method, and time since catch. It is very vague and does not state that they are responsible for any problems that may occur, such as food poisoning. In the extreme, it is merely a marketing term for sales promotion purposes. Above all, they say nothing about actual quality or taste.

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Revision date: March 1, 2024

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What is traditional Ikejime?

a photo of Ikejime Madai — In order to fully drain the blood from the red seabream, the spinal cord at the base of the tail is also cut off.

Articles related to Sushi are now filled with jargon such as Shinkeijime, Chinuki, Noujime, Ikekoshi, and Korijime. That much confirms the fact that opportunities to eat fish are increasing all over the world. And it has also become a common occurrence to find articles written by people who have heard Ikejime in bits and pieces. According to what we have heard, Ikejime processing is one of the reasons why red seabream from Akashi, which is said to be the best in Japan, is so tasty, and the technology has been around since the Edo period (1603-1868).

The Ikejime procedure consists of four parts or some of them, and the point of Ikejime is to kill the fish in a relaxed state.

The first step is a brain-dead the fish by stabbing it in the head with a sharp object. This process is called Noujime (Nou means brain and jime means kill).

After the fish is out of the water and before it gets out of control, it is stabbed in the head with a hook called a Tegaki (手鉤). If the brain is not destroyed by one blow, the fish will struggle. When this happens, a large amount of ATP, which is the source of umami, is consumed. As a point of caution, the right side of the head is stabbed so that the puncture wound is not on the upper side, as the fish will be handled later in the distribution process with the belly facing forward and the head facing to the left.

Next, use a knife to quickly kill the live fish.

Place the fish with its head facing left, open the gill cover, and cut a spinal cord below the lateral line that is visible on the fish’s body. Since bones have hard parts, move the cutting edge slightly to the left and right if it is difficult to cut. If you don’t cut it completely, you have not killed the fish, and the blood will not drain well. To drain the blood sufficiently, the spinal cord at the base of the tail is also cut off. Place the fish’s head to the right and cut the front part of the tail so that the spinal cord is visible. At this point, the knife should be placed at a right angle to the spinal cord so that the cut surface is not at an angle.

The next step is to remove the nerves and delay rigor mortis. This process is called Shinkeijime (Shinkei means nerve).

Shinkeijime is a technique to delay rigor mortis in fish. A wire is inserted into a small hole in the upper part of the spinal cord. When the wire hits the nerve, the fish will act violently, so hold it down. The nerve hole tapers from the head side to the tail, so when stabbing in from the tail side, make sure to insert the wire securely first, so that the wire does not pierce through the nerve hole and pierce the body. Once you have securely inserted the wire, repeatedly pull out and insert the wire to completely destroy the nerve in the hole. When the nerve is destroyed, the body color quickly changes to white. The destroyed nerve appears as a white, sludgy fluid.

Any wire can be used for this purpose as long as it is straight, but a piano wire that does not bend easily can be used many times. The diameter of the nerve hole differs depending on the fish. Use a thick wire for Tai and Suzuki, which have large nerve holes, and a thin wire for Aji and Anago, which have small nerve holes. Several types between 0.8mm and 1.5mm should be enough. As you get used to it, you will be able to stick the wire in without visually seeing the nerve hole. If you remove a few scales from the upper part in front of the tail, insert the wire along the spinal cord, probe the nerve hole, pierce it, and destroy it, you can remove the nerve without making any cuts on the fish’s body. The same applies to the head side. The nerve hole is probed and pierced from the head side, but the key is to keep the head and body straight so that the nerve hole is not misaligned by the spinal cord severed behind the gills. In any case, it takes experience and familiarity to pierce the nerve hole without seeing it.

The final step is to perfectly remove the blood from the fish’s body. In Japanese, it is called Chinuki (Chi means blood and nuki means remove).

The blood is removed by cutting the spinal cord and immersing the fish’s body in seawater. At this time, running water is more reliable to remove blood. In the case of stored water, leave it for a while and then replace it with other stored water. If the water does not turn red with blood, the fish has already been drained. Blood has a tendency to clot, so it is important to wash off any blood that has clotted on the gills or other parts of the body. The body temperature of the fish is raised by the Ikejime process and by human hands. Since the fish were originally in the sea, which has a lower temperature range than that of the ground, the higher temperature increases the speed of deterioration, so the fish is soaked in ice water to lower the temperature of the fish’s body. If the fish is soaked too long, its body surface will turn white, so remove it from the water when it cools down.

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Revision date: August 18, 2023

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The pros know that stress-free killing (Ikejime) is the key to good flavor!

Ending a fish’s life without stress is the key to the delicious flavor. When fish are left out in air, and die in agony it promotes rapid Adenosine triphosphate (ATP) degradation and increases in Inosinic acid. This is the worst way to kill a fish.

So what method can control the fish’s flavor or “umami”?

The delicious flavor of fish comes from the postmortem breakdown of ATP, which is the source of biological energy, and the generation of Inosinic acid, which is the component of the umami. Rigor mortis after the fish has died, progresses with the decomposition of ATP. When the oxygen supply is cut off after death, the energy required for muscles to move is no longer supplied, so the flexibility of the muscles is lost and the body starts to contract. This is postmortem rigidity. This state depends on the fish, but it is the lowest point for flavor and after that, the fish is managed at an appropriate temperature to increase the Inosinic acid.

This method has been the norm among sushi chefs who didn’t know about the mechanism that produces umami. Since long ago, the daily routine was to purchase fish that were killed first thing in the morning in the market, then increase the umami by keeping the fish in a refrigerator with a controlled temperature for 12 to 48 hours. Nowadays, the method has become a common practice among fisherman, distributors and fish handlers at the market.

Now I will explain a number of methods that maintain peak flavor.

Ikezukuri means to take a fish that’s swimming in a tank at the restaurant, and immediately making sashimi after killing it, while the meat is still super fresh. In this state, there is no Inosinic acid, but there is quite a show with movement still in the fish and this preparation method gives the best-tasting texture.

Nojime* means using a massive amount of ice to suddenly reduce the temperature, resulting in the death of the fish, either at the fishing site or at the local market. This method is used for small, cheaper mass-market fish that are caught in large amounts. Nojime starts with a reverse calculation for flavor from the day after fishing, but if the process isn’t thorough or there are any deficiencies, the fish won’t stay as fresh, so detailed care must be taken in temperature management.

Hamajime* means to cut the spinal cord at the production site, drain blood and spinal fluid, then pack in ice from the afternoon the next day and wait for the peak flavor, which will be about two days later. That’s when the seafood is shipped to make it to the consumer auction the next day. As time passes, inosinic acid is generated and the aim is to use the fish in sushi at peak flavor.

Ikejime is used so that the peak flavor will be reached during afternoon and evening business hours. The spinal cord of the live fish is cut and spinal fluid drained at the early morning market. This result is a firmness from the remaining ATP, and delicious flavor from the Inosinic acid that is generated as time passes. After some time has passed, even fish for which Ikejime is applied, can reach the same state as Hamajime if used after being refrigerated for one to two days, in order to maximize the Inosinic acid generated. Of course, sushi chefs find their own balance of firmness in meat or added flavor, and incorporate this balance for the optimum combination with their shari in each piece of sushi.

Finally, maintaining freshness by using Ikejime, has become common practice overseas, and the term “Ikejime” has also become standard among the fishing industry. There are many websites that go into further detail on Ikejime, which you can reference from the links below.

*At markets in Japan, the term “kill” is not used for living fish, instead the word “shimeru” meaning “close” or “tighten” is used. This expression is thought to have come from the sentiment of showing respect and appreciation for all living beings, not only humans.

Related Contents:
Première poissonnerie ikejime à Paris

Le poisson ikejime, la technique ancestrale venue du japon

L’ikejime, cet art japonais qui sublime le poisson

Technique Thursdays: Ike Jime, The Japanese Slaughter Method For Tastier Fish

Ikejime: a humane way to kill fish that makes them tastier

TYPES OF EDO-STYLE PREPARATIONS

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Revision date: May 1, 2020

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Why do they say that the quality and price of tuna is determined by the processing after the fish is caught?

Why is only tuna brought into certain ports high-priced, even though all of the tuna is caught in the seas near Japan? This is because the level of stress caused to the fish when it is caught has a huge impact on the quality, including taste, color and texture. In other words, the same fish may be delicious or taste unpleasant depending on how the fisher handles the fish directly after catching it. Naturally, everyone ends up wanting the fish from the ports with fisherman who are skilled in this practice*. Furthermore, it is individuals who process the fish. The quality changes drastically depending on who caught it.

*This is a method of cutting off the medulla oblongata and aorta of a fish, essentially keeping the body alive while killing the fish. There is also a method of inserting a thin wire, like a piano wire, into the backbone. This technique paralyzes the nerves while at the same time suppressing the putrefied substance that comes from the spinal cord. Using the ikejime method extends the time until rigor mortis starts, and makes it easier to maintain freshness, while at the same time preventing raw fish odor and damage to the body by inserting a butcher knife into the base of the tail to drain the blood and keep oxidized blood from running throughout the body.

What are “Ikejime” and “Nojime”?

How the fish is butchered also changes the taste. If the fish suffers and struggles, the body wears and may be damaged, circulating oxidized blood throughout the body, which makes it lose flavor. For fish of high value such as sea bream, flounder, yellowtail, rudderfish and tuna, a method called “ikejime” is used.

The taste of tuna is said to be determined based on the preparations after being caught. The tuna is caught with as little suffering as possible and the nerves are killed immediately for an instant death. Generally, blood is then drained perfectly, entrails and gills are removed, the tail cut off and then the fish is placed in ice-water to lower the body temperature.

The medulla oblongata and main artery of the fish are cut and a kitchen knife is inserted into the base of the tail to drain the blood. A thin metal rod is inserted into the backbone to paralyze the nerves and at the same time controls the putrefied materials that come out of the spinal cord.

This extends the time until rigor mortis sets in, making it easier to maintain freshness and simultaneously preventing blood from circulating in the body, which also prevents the fishy smell.

Freezing the fish to death in ice water is called “nojime”. This method is generally used for small fish such as sardines, horse mackerel and mackerel that are fished in large volume. Although the freshness of the fish deteriorates more quickly than in the case of “ikejime,” it can be done in large quantities without a lot of labor and maintains a certain level of freshness afterwards.

At fish markets, the term “kill” is not used for living fish, instead the word “shimeru” meaning to close or tighten. The term “dead fish” is also not used. Instead the term “nojime” is used for fish that died naturally en route to the market. This stems from the awe of precious life and turning that life into food.

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Revision date: January 13, 2023

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