For fans of sushi, nothing beats Edo made with orhonmaguro "black diamond" tuna. Edo, the simplest type of sushi, is made with an oblong of sticky rice atop which a piece of raw fish is wrapped with a bit of seaweed. As the fish is eaten raw, it absolutely must be sushi grade and utterly fresh. The best tuna for sushi should have been caught very recently from cold fishing waters and wear a uniquely cobalt blackish-blue skin.
Orhonmaguro tuna, also called bluefin, makes its home in cold oceans in far northern and southern waters. This gives its flesh greater flavor due to a reduced fat content and strong muscles. It also makes the flesh firmer and gives the highly treasured belly section a delectable flavor.
So certain are fishers and cooks of orhonmaguro’s almost sacred work as the best tuna for sushi that it is nearly always consumed in its uncooked state. The belly meat, which is called toro, is especially cherished. While the rest of a bluefin has a full-bodied flavor, the buttery toro has the feel of silk on the tongue.
When bluefin isn’t available fresh from the docks, the next best place to get tuna for sushi is from a reputable fish monger who sells sushi-grade fish. Tuna steaks can also be purchased flash frozen if nothing else is available. This type of tuna is not, however, available in cans. Woe to any naïve home cook who doesn’t understand bluefin’s mystic appeal and fries, broils, or grills it as sushi aficionados will be tempted to report the crime to the food police.
Anyone who loves sushi knows the inherent danger of food poisoning from consuming raw meat of any kind. Sushi-grade orhonmaguro that is sufficiently fresh will show off a deep, rich, red flesh. The meat of bluefin tuna for sushi should appear firm to the eye and be firm to the touch. If the flesh retains the indention of a finger, it should be returned to the kitchen and tossed out.
Sushi is often eaten in a specific order. The first offering is typically sushi that features white, mild fish. Next comes sushi made with black diamond tuna. Following this, the palate is ready for the deeper flavors of sea urchin and Spanish mackerel. The whole point of sushi is simplicity and freshness. A little wasabi, which has been mixed with some tamari and perhaps some pickled ginger, are the only accompaniments.
Ahi tuna, also called yellowfin, swims in milder currents that are closer to the equator. While plenty of folks enjoy a yellowfin fillet or steak, its flesh lacks the firm presence of orhonmaguro tuna. While it isn't prized for Edo sushi, plenty of cooks use it for Nigiri sushi. In nonsushi recipes, yellowfin tuna is often breaded, fried, and served with salsa or chutney generously flavored with hot sauce.