Picture Japanese sushi, and the first fish that comes to mind is likely tuna. From lean akami to buttery chutoro, tuna is broken down into various cuts. This isn’t filleting — to butcher such a large fish requires technique and the right tools. To learn more, we reached out to Las Vegas sushi chef Winston Matsuuchi of Omakase Kyara Sake Bar. Matsuuchi is known in Las Vegas for his tuna cutting ceremony, where he breaks down a whole bluefin tuna with traditional Japanese knives. “Every time I cut a tuna, it teaches me something new,” says Matsuuchi.
How to break down a whole tuna
First, because of its size, butchering tuna is comparable to beef butchery. The biggest tuna Matsuuchi ever cut was 285 pounds, although many can reach twice that weight. Matsuuchi prefers that range because the bones and skin are easier to handle while still having good marbling. The first step is cutting through the spine and removing the head, allowing the fish to be moved more easily. Then, the collar before Matsuuchi starts shaving off some of the skin. Finally, he cuts down the middle of the fish, revealing the bloodline. “An early mistake was misjudging the major incision for the bloodline,” said Matsuuchi. “If you get that wrong, the loins do not come out correctly. They end up off. It matters where your knife goes. I can be just a little off and cut away a large piece of meat that I did not mean to remove.”
Because of the size, Matsuuchi breaks tuna down into quarters instead of halves. Essentially, there are three main parts of tuna: akami, lean and closest to the spine; chutoro, the flesh close to the skin with good fat and flavor; and otoro, the fattiest and most marbled. This is only the beginning, as these main parts can be butchered into various subparts. “There is chiai chutoro, which is by the bloodline of the tuna, so it’s a little richer in flavor, explains Matsuuchi. Then there is shimofuri chutoro, which is closer to the belly and sits between chutoro and otoro. There’s also kamatoro, which is by the collar and is the richest, fattiest piece. Noten is next, which is meat from the head. It has a different texture, more muscular, but it has a distinct flavor. Lastly, we have nakaochi, which is the bone scraping from the spine, as well as the spine jelly.”
Japanese Knives
Three knives are used for tuna cutting. “The first is the deba bocho,” explains Matsuuchi. “The deba is a thick, wide knife meant for cutting fish bones. It’s the go-to knife for chefs breaking down fish, from small to big. Obviously, the size of the deba changes depending on the size of the fish. There are different classifications: ko-deba is a small one, deba is the regular one, and dai-deba is the big one. I use the biggest deba from Japan.” The second knife is the maguro kiri bocho. “It resembles a katana (samurai sword),” says Matsuuchi. “The reason we use it is because it’s long and thin, which gives us a nice, clean cut through the loins instead of using a shorter knife that would force you to saw through the meat. It makes one long, uninterrupted cut.” Lastly, there’s yanagi bocho, which is used for sashimi. Long and thin, this knife is single-beveled and easy to wield for precise slicing.
There are two Japanese brands that Matsuuchi prefers: Artisugu and Masamoto, both composed of White Carbon Steel No. 1. “You want a knife that stays sharp for a very long time,” explains Matsuuchi. “White carbon steel is one of the hardest metals used for Japanese knives. The only drawback is that it’s hard to sharpen. But it doesn’t rust too much, and it stays super sharp, which is why I like it.”
