【Reading】ちあいとり

【English Name】Bloodline removal

In the process of preparing sushi and sashimi, a preparation step that greatly affects the flavor and appearance of the neta is chiai-tori (removal of the bloodline). The dark reddish-brown muscle running through the flesh of the fish body—this is the bloodline meat (chiainiku), and the skill of accurately trimming it away is required.

Centered on myoglobin and hemoglobin, pigment proteins responsible for oxygen transport are densely concentrated in the bloodline meat. It also has high contents of B-group vitamins, iron, and glycogen, making it a nutritionally excellent part. On the other hand, because blood components and iron gather there, it tends to be a cause of fishy odor, and for sushi and sashimi served raw, the step of removing it is indispensable.

The proportion of bloodline meat in the whole flesh varies greatly by fish species. In ocean-migrating fish such as katsuo (bonito), maguro (tuna), and saba (mackerel), there are cases exceeding 20% of total meat mass, whereas in white-flesh fish such as tai (sea bream) and karei (righteye flounder) it is no more than a few percent. This is because the more constantly a fish swims the open ocean, the more pronounced the development of the bloodline muscle that supports its endurance.

In making katsuobushi (dried bonito) as well, the "chiai-nuki" type, with the bloodline removed, has a delicate and refined flavor and is classified as a high-grade product. In cooking fish scraps (ara), the procedure of shimofuri—briefly passing them through boiling water and then immersing them in cold water—is widely used to remove odor and sliminess.