【Reading】しんけいじめ

【English Name】Shinkeijime (spinal cord destruction)

Ike-jime has several stages, and shinkei-jime (nerve destruction) is the key processing among them for maintaining freshness. The essence of this technique is to instantly brain-kill the fish by piercing the vital point in the head with a hand gaff, then to pass a wire or dedicated needle through the spinal cord to physically destroy the nervous tissue.

The significance of this process lies in preserving ATP (adenosine triphosphate). In the fish's body, umami is produced in the process of ATP breaking down into inosinic acid, but if the muscles thrash and convulse after death, ATP is wasted. By cutting off this depletion with shinkei-jime, the amount of umami components produced can be maximized. Furthermore, when bloodletting is performed together, the blood that causes internal bleeding and microbial growth can be removed, also yielding an effect of suppressing the decline of freshness. Since the accumulation of fatigue substances such as lactic acid can also be prevented, deterioration of taste can be minimized.

The procedure differs by fish species: while flounder and red sea bream are dispatched by piercing the vital point behind the eye, for large fish such as tuna a spiral needle is inserted into the medulla to sever the nervous system. This ike-jime technique is said to have originated in Edo-period Japan, and in the 2010s, against the backdrop of the global spread of Japanese cuisine, it gained international recognition under the name "ikejime." In the sushi setting, it is an indispensable basic technique for maximizing the umami and freshness of the toppings.