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

Ending a fish’s life without stress is the key to delicious flavor. When fish are left out in air, and die in agony it promotes rapid Adenosine triphosphate (ATP) degradation and increase 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 oxygen supply is cut off after death, energy required for muscles to move is no longer supplied, so 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 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 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 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 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 results 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 to “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

http://fr.gaultmillau.com/news/premiere-poissonnerie-ikejime-a-paris

https://elisabethscotto.com/2016/02/27/ikejime/

https://www.huffingtonpost.fr/2018/12/18/le-poisson-ikejime-la-technique-ancestrale-venue-du-japon_a_23617381/

https://www.lemonde.fr/m-gastronomie/article/2017/04/27/l-ikejime-cet-art-japonais-qui-sublime-le-poisson_5118590_4497540.html

https://guide.michelin.com/sg/en/article/dining-out/what-is-ike-jime

https://www.1843magazine.com/food-drink/ikejime-a-humane-way-to-kill-fish-that-makes-them-tastier


We hope this information will be helpful.

Revision date: May 1, 2020

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.


We hope this information will be helpful.

Revision date: December 17, 2019

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.

 

 

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.


We hope this information will be helpful.

Revision date: March 27, 2018