August, 2023 | Sushiblog－Sushiuniversity

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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a photo of making nigiri sushi — A sushi chef adds wasabi to sushi topping.

Sushi continues to spread throughout the world. Nowadays, not only sushi rolls but also Nigiri sushi can be eaten all over the world. But if you have the opportunity to come to Tokyo, we want you to go home with sushi toppings that you can only eat in Tokyo. Not seafood exported from your country, but sushi made from natural seafood caught in the seas around Japan.

First of all, what kind of sushi do you think of when you hear the word “Nigiri sushi”? Most people think of sushi with Hamachi or Salmon on top of vinegared rice.

This is correct if you only look at the appearance. However, from the essence of Nigiri sushi, it is clearly wrong. In order to make your understanding perfect, we dare to confuse you, but we would like to understand the term “Edomae sushi” as well.

What is Edomae sushi?

Nigiri sushi and Nigiri are words you may have heard before. However, “Edomae sushi” is a word you may not be familiar with, so it is important to understand exactly what it is.

It is quite simple.

Edomae sushi consists of Nigiri sushi and Nori maki. Nigiri sushi originated in Edo (now Tokyo) about 200 years ago, while Nori maki is said to have originated 50 years earlier. And Edomae sushi has remained almost in its original form to the present day. We will skip the explanation of Nori maki here, so you can just assume that “Edomae sushi” and “Nigiri sushi” refer to the same thing.

Now let’s dig deeper into the story of Nigiri sushi. You have probably seen Nigiri sushi and Nori maki before. If you do not like fish and nori, you have probably eaten them.

However, many people, including the Japanese, misunderstand Nigiri sushi.

They think that Nigiri sushi is sushi with sashimi such as salmon on top of vinegared rice. Many cookbooks and other books say this as well, so it is no wonder they understand it incorrectly.

To correct here, nigiri sushi consists of prepared fillets on a bed of vinegared rice. Preparation means sprinkling salt on the seafood, soaking it in vinegar or soy sauce, boiling it, simmering it, etc. This preparation is called Edomae shigoto (Edo-style preparation) in Edomae sushi restaurants. To confirm, sashimi is unheated seafood or other ingredients cut into small pieces.

Why do they dare to prepare super-fresh seafood?

The reason is said to be that in the Edo period, there was no such thing as a refrigerator, and people had to devise ways to keep seafood from spoiling even a little.　Then it seems that it is not necessary now. However, this preparation process helps to make seafood more delicious (to give an example, inosinic acid is produced, which, combined with the glutamic acid and other substances that seafood originally contains, produces a synergistic effect of umami). This is why they still use prepared seafood today.

On the other hand, salmon nigiri sushi found overseas uses sashimi. Even in Japan, in regions where fresh seafood is available, sashimi is used. This is because the priority is not the synergy of umami, but rather the texture and security of freshness. And there is no way to know that this is clearly different from Edomae sushi (Nigiri sushi) on the main road.

If you make nigiri sushi with sashimi, you don’t have to be a sushi chef to do it. In fact, to put it bluntly, anyone can do it. There is an experience to make Nigiri sushi for tourists, but you understood that this is only to make Nigiri sushi in appearance, right? And to learn Edomae shigoto (Edo-style preparation), the sushi chefs need a long period of training.

Let’s get to the point here.

Here are 8 sushi toppings you should try in Tokyo. We divided it into 4 so that you can see the opportunity to eat.

The first is the typical sushi toppings at Edomae sushi. It is a sushi topping that can be eaten regardless of the season (of course, there is a season), but it shows the characteristics of the sushi restaurant. The boiled Kuruma ebi, with its beautiful red color, aroma of the sea, and complex umami, is a must-try. Next is not eel but Anago (Japanese conger). The soft- simmered anago instantly falls apart in your mouth, spreading the ummai of the fish, and the restaurant’s unique sauce, called Nitsume, is not to be missed.

Second, sushi toppings are only available at certain times of the year. The season is short, so even if you want to eat it, you will have to wait until the next year when the season is over. For example, don’t you think you can eat Bluefin tuna all the time? The season for fresh bluefin is from around September to early January. This is the time when all parts of the fish are at their best. Shinko, the juvenile kohada, can cost as much as $2,000 per kilogram at the beginning of the season, and sushi chefs are forced to pay a premium for this fish because sushi lovers compete to be the first to eat it. The taste is not as good as kohada, but the aroma may be a cut above.

Chum salmon is not eaten raw in Japan. This is because of problems such as anisakis. Even so, you should definitely try Keiji (young Chum salmon) nigiri, which has a completely different quality of fat. It is very rare and costs more than US$1000 per fish. Then there is Hoshigarei, the king of flounder. The moderate fat and fresh aroma will fascinate you. Next, the Red sea urchin is caught in Kyushu and other parts of Japan. Sea urchin has a rather complex flavor. However, red sea urchin has a refreshing aftertaste. It is a mysterious sushi material.

The fourth is the sushi items that you should eat without grumbling. You should be happy to eat these items in season. Ezobafununi, caught in Hokkaido during the summer, is exceptional. Many people say they can’t eat sea urchin, but if you eat this, you’ll become a sea urchin lover. And then there is Akagai (Ark shell). Many shellfish enjoy the delicate balance of sweetness and bitterness, but Ark shell is a great ingredient to enjoy the scent of the sea.

If you want to eat Hamachi or Salmon, which you often eat as Nigiri sushi, you have to go to a conveyor belt sushi restaurant. Buri, which is farmed, is called Hamachi. Salmon is also mostly farmed, with Norway and Chile being the world’s leading producers. There is no point in going all the way to Tokyo to eat them.

Finally, sushi chefs tend to avoid farmed fish. And the same goes for frozen fish. Some fish can only be used for Nigiri sushi if they are live. The chef cooks fish deliciously, but sushi chef is only trying to bring out the true flavor of the fish. In other words, there is no compromise in the selection of seafood. If the fish is too expensive, sushi chefs may not buy it. And sometimes they have to buy it even if it is too expensive. For your information.

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We hope this information will be helpful.

Revision date: August 12, 2023