About the story of KUSAKABE’s signature sushi, Zuke Chutoro When I first came to the United States 1993, there was an established image that O-toro was of high quality, while medium-fatty tuna “Chu-toro”was of a lower rank than O-toro. Even if I got fresh and good quality tuna, no one will try the nice medium-fatty tuna Chu-toro. ZUKE Chu-toro was born with the desire to introduce the deliciousness of a new kind of medium fatty tuna. ZUKE means “marinated”with house sweet soy sauce. Traditionally, the Zuke technique uses “Akami”lean meat, but I tried it with medium-fatty meat. Many senior sushi chefs at the time said that marinating medium fatty tuna would lower its value. However, the American customers were very pleased with the taste, which was different from that of Toro. Furthermore, I use a cedar plate, grill it at the edge (corner) of the sushi with a cedar board and char it little. The cedar burns and the smoke rises, and the burned smell of soy sauce and the smell of smoke remain. Temperature is also half cold and half hot, so people can enjoy it with temperature difference. I'm also happy that many sushi restaurants in San Francisco now offer it. ****** About technique and idea It is a traditional technique used to preserve tuna (lean part or “akami”) when refrigerators did not exist. The idea is that it is keeping the activity of bacteria suppressed by immersing in soy sauce, which makes it long-term preserved without decaying. Traditionally, the tuna is marinated for a few days. However, currently we get fish in better freshness because of the established distribution, so KUSAKABE marinate the tuna (with soy sauce, mirin, and sake) for only 2-3 hours after soaking in hot water first to leave the taste and aroma of tuna. The purpose of soaking in hot water is to solidify the surrounding protein, drain moisture and leave the taste of Toro while adding the fragrance of soy sauce only in that part.
(If you marinate tuna for a long time, it will last for a long period of time, but the taste of tuna disappears.)