Akami
赤身

What is Akami?

Akami (赤身, “red body”) is the lean red muscle of the Bluefin Tuna — and the cut that defines the fish. Serious sushi lovers judge a restaurant by its Akami before anything else. Other tuna species have Akami cuts too, but Bluefin’s is in a different category entirely: the depth, the complexity, the finish. There is no comparison.

Akami from our Goto Islands Bluefin is intense in umami and well balanced with a subtle, natural acidity. It is considered top-quality even in Japan — the standard against which other Akami is measured. The flavor needs no ornamentation. A proper piece of Akami tells you everything about the fish it came from.

Sub-cuts of Akami

Akami is not uniform across the fish. It yields from different blocks, each with its own texture and character. Sinews become progressively stronger toward the tail, and the block’s position on the fish changes how the cut feels and tastes.

Seasonal character — summer vs winter

Akami changes more dramatically across seasons than any other cut. The difference is real enough that it is worth understanding before you order.

Summer Akami has a lifted quality — bright aroma, lively acidity, a certain lightness. The flavor is vivid rather than deep. Think of it as a light roast coffee: immediate, aromatic, clean on the finish.

Winter Akami is the dark roast. The cold water concentrates the fish’s energy into the muscle. Umami becomes thick and layered, the texture denser, the finish longer and heavier. This is the Akami that connoisseurs plan around — peak season for Goto Bluefin is the winter months.

Color — what you should and should not see

When Akami is first cut from the block, it is a deep dark red-purple — almost maroon. As it is exposed to oxygen, myoglobin reacts and converts to oxymyoglobin, producing a darker ruby red. This is the natural color of properly handled sashimi-grade tuna. It is never vivid cherry-red or pink in its natural state.

CO treatment — what it is and why it matters

If you see bright cherry-red or pink tuna at a supermarket or fish counter in the US, it has almost certainly been treated with carbon monoxide gas — sometimes labeled “filtered wood smoke” or “tasteless smoke.” CO treatment is common in the US and banned in Japan.

The mechanism: CO reacts with the muscle pigment oxymyoglobin to form carboxy-myoglobin, a highly stable compound that permanently locks in a bright, watermelon-pink or cherry-red color. The fish looks vivid and fresh on the shelf for weeks rather than days. The color does not fade with age. The reaction is permanent.

Eating CO-treated tuna is not directly toxic. Breathing CO gas into your lungs is dangerous; eating meat where CO has bound to proteins is biologically harmless. The problem is different: CO treatment permanently strips away your ability to judge freshness by eye. A piece of CO-treated tuna three weeks old looks identical to one caught three days ago. If the fish was mishandled during transit — left at unsafe temperatures, bacterial buildup — it can carry dangerous toxins including histamine, which causes scombroid food poisoning, while looking completely picture-perfect. The visual signal that normally warns you of age has been chemically suppressed.

CO gas treatment is not unique to fish. In the US, beef, pork, and poultry are widely packaged using Modified Atmosphere Packaging (MAP) — a sealed tray flushed with a gas blend that includes up to 0.4% carbon monoxide. The same chemistry applies: CO binds to myoglobin and locks in a bright, stable red color. Meat can remain cherry-red for 20–30 days on the shelf while bacterial levels continue to rise. The FDA classifies CO at this concentration as Generally Recognized as Safe (GRAS). The EU, Canada, and Japan have banned it on consumer deception grounds. The US has not.

There is also an educational dimension worth considering. A child who grows up seeing only CO-treated fish — and only CO-treated beef — learns the wrong lesson: that bright, vivid red equals fresh. That is not how biology works. Myoglobin darkens naturally as it oxidizes. Color change is the body’s honest signal. CO treatment chemically suppresses that signal across the entire American meat supply. It is worth knowing.

How to eat it

Slice 10–12mm against the grain. A small amount of tamari, real wasabi. Nothing else is needed. The flavor does not require assistance.

For Zuke — the classic preparation of briefly marinating Akami in soy and mirin — this is the traditional cut for a reason. The soy’s polyphenols bind to the iron in the meat, deepening the umami while the salt pulls moisture and concentrates the flavor. Zuke Akami pairs exceptionally well with aged Pinot Noir. See the recipes page for guidance.

Where this fish comes from

Every piece of Bluefin Tuna at Sashimi DC comes from Hosei Suisan (宝生水産), a farm in the Kamishima Wakamatsu area of the Goto Islands, Nagasaki Prefecture — the westernmost islands of Kyushu, where the Pacific and East China Sea converge.

The Goto Islands maintain water temperatures that never fall below 13°C in winter and rarely exceed 29°C in summer — the stable, narrow range that Bluefin Tuna require for consistent growth and quality. Hosei Suisan operates in the Kamishima Wakamatsu area, one of the most environmentally favored zones for marine aquaculture within the islands.

Hosei Suisan uses wild-caught seed stock (天然種苗) rather than hatchery-bred fish. Feed is sourced fresh and locally, centered on fresh mackerel (生サバ) bought directly by their own trucks from local fishermen. Director Tsuneya Yamashita explains the choice: mackerel produces better fat marbling and color than sardines. As mackerel catches have declined and prices risen in recent years, they secured dedicated year-round supply agreements with their fishing partners to maintain the standard. Post-harvest handling — the initial processing and preparation after the fish is landed — is also a focus: Ikejime is performed in Nagasaki, at source.

After Ikejime processing in Nagasaki, the fish is transported to a specialist Miyazaki processor where it is broken down into saku blocks, then flown Fukuoka → Haneda → IAD.

Ikejime — the considered kill

Most harvested fish die by suffocation. Removed from water, they slowly asphyxiate. The stress hormones released during that process — combined with temperature mismanagement — degrade the flesh before it ever reaches a kitchen. Lactic acid accumulates. Texture deteriorates. The smell that people associate with “fishy” fish is, in large part, the smell of stress.

Ikejime (活け締め) is the opposite: a considered kill. The fish is dispatched instantly via a brain spike, stopping all stress signals immediately. This is followed by exsanguination (bleeding out) and spinal cord destruction — a technique called shinkei jime (神経締め) — which halts all neurological activity and prevents further ATP consumption in the muscle. The result is meat with superior texture, extended shelf quality, and the deep umami that makes sashimi-grade fish worth eating. Learn more at the Ikejime Federation.