Catalina offshore products did not have fresh tuna sashimi blocks for quite some time but, recently, it was back in stock. I ordered one pound along with other items. This is blue-fin tuna with “akami” and mostly “chu-toro” block which most likely came from a portion toward the tail.
The one pound block looks like you see below with the skin still attached. Top triangular part is mostly red meat or “akami” 赤身 and underneath is mostly moderately fatty or “chu-toro” 中トロ and only small amount of fatty part or “toro” トロ. We got a much better block of tuna from them in the past but given the long hiatus in availability, I am not complaining.
After I removed the skin and then the meat attached to the skin which was quite fatty (image above lower right). I decided to make “negitro” ネギトロ (“negi” means scallion and “toro” means fatty tuna) from this and other trimming or “scrap” parts. I then cut the akami by slicing horzontally (getting a triagular shaped akami block. I then divided the remaining rectangular blocks into slightly fatty (“ko-toro” and moderately fatty (“chutoro”). I wrapped each part in parchment paper, then paper towels and placed them in a Ziploc bag. I stored it in the meat drawer of the refrigerator, where it will keep up to 3 days if it is going to be used as sashimi. Any longer and it has to be cooked.
I am not sure where “negitoro” originally came from but I believe it was popularized by low-end shushi bars such as “Kaiten sushi” 回転寿司 place serving their customers utilizing scraps or low-quality tuna sashimi either as a roll or battle ship sushi or “gunkan maki” 軍艦巻き. Certainly, I did not have this while I lived in Japan. In any case, since I had thin but rather fatty meat (image above lower right) just off the skin, I made “negitoro”. Since the portion was not totally scrap or scrapings from the skin or bone, I cut it into small dices rather than making it almost like paste which is usually the consistency of negitoro.
I just mixed in finely chopped scallion and dressed it with a mixture of “real” wasabi (just defrosted) and soy sauce and garnished it with nori strips. This was our starter for the tuna feast evening. The only problem with this type of dish is that you tend to over indulge with sake.