Snow crab nigiri

Snow crab (Zuwaigani)

【Nigiri sushi: Ebi/Kani】
What is Zuwaigani?
Zuwaigani live in the Japan Sea and the Sea of Okhotsk. The shells of males are about 15 cm in width, and the females’ shells are 7 to 8 cm wide. The names of these crabs differ depending on region. Males are called Matsuba-gani or Echizen-gani while females are called Seiko-gani or Kobako-gani.

What does Zuwaigani (Snow crab) nigiri sushi taste like?
Since Zuwaigani is not regular Edomae sushi material, it isn’t always chosen by sushi chef. Although the leg part of male crab is preferred as sushi ingredient because it has tender yet fine texture and distinctive sweet taste. On the other hand, the female snow crab can be enjoyed for its internal (Uchiko) and external roe (Sotoko), which are not part of the meat. Enjoy the interesting texture of Sotoko, eggs in the belly, and the rich flavor of Uchiko, eggs inside the shell.

Zuwaigani contains high levels of free amino acids. There are sweet taste component in glycine or alanine, umami taste component in glutamic acid, and bitter taste component in arginine. Because all these are balanced well, they produce such unique delicious taste.

The voracious appetite of crab-loving Japanese cannot be satisfied only with zuwaigani caught in Japan. Therefore, large quantities of zuwaigani are imported from Russia, the east coast of Canada, and Alaska. The state of Alaska, one of the major producers of zuwaigani, is known for its strict fishing regulations to protect the resource. There are size regulations, and small fish must be released. As a result, Alaska caught fish are generally regarded as large and plump. Even if female crabs, which are highly prized in Japan, are caught, they must be released to protect the resource.

The black grains on the shell, incidentally, are the eggs laid by Notostomum cyclostomum (Kanibiru). Kanibiru is a type of leech that attaches itself to fish and sucks their body fluids. They do not attach to crabs to suck their body fluids, but simply choose the shell as a place to lay their eggs instead of a rocky place. Notostomum cyclostomum itself will die if boiled or frozen. And the abundance of Notostomum cyclostomum eggs is a sign that the crab has been molting for a long time, which is a sign that the crab is tasty.

Sekogani is the name for female snow crabs that have eggs and is mainly used in Fukui, Hyogo, and Tottori prefectures. Koppe-gani is also the name for female snow crabs that have eggs and is only used in the Tango region of Kyoto. Kobako-gani is also the name for female snow crabs that have eggs and is heard mainly in Kanazawa in the Hokuriku region. Uchiko refers to the red ovaries attached to the inside of the shell, and Sotoko refers to the fertilized eggs held in the abdomen.

ATP is broken down as follows, but in living fish, only the reaction up to AMP occurs. Once broken down to AMP, it is regenerated as ATP.

ATP→Adenosine diphosphate (ADP)→Adenosine monophosphate (AMP)→inosinic acid (IMP)→hypoxanthine riboside (HxR)→Hypoxanthine (Hx)

In fish after death, inosine monophosphate (IMP) is produced from AMP by an enzyme called adenosine deaminase (ADA). This is called maturation.Inosine monophosphate is not found in cells immediately after death. Maturation is required for the production of inosine monophosphate. If it goes further, it will go bad and HxR (inosine) and Hx (hypoxanthine) will be produced.

After snow crabs die, AMP is broken down to inosine acid in the same way as fish. Boiling or roasting also accelerates the breakdown of ATP and increases the amount of inosine acid.

When eating snow crab, it is best to leave some parts slightly raw, as this allows the umami flavor to concentrate and intensify. When cooking snow crab in a pot, it is best to eat it with a special broth that is full of the umami flavor of kelp (glutamate) and bonito (inosinate), as this combines with the umami flavor of the crab to make it taste even better. When freezing crab, the reason for the loss of umami flavor is the disappearance of ATP during the defrosting process. In other words, it means that eating a live crab that has been cooked is delicious.

Also called Tanner crab or Queen crab.

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(Revision date: March 17, 2025)