Dear Chef,

Hi! I have a beautiful ahi steak, but it’s not sashimi grade. How well should I cook it to be safe, without ruining it? Thanks!

Kate from Pittsburgh

Tuna is graded the way beef is graded. The whole fish is subjectively examined for fat and color and then given a rating of #1 (sashimi or sushi grade), #2, or #3. The grade does not indicate freshness or how long the tuna has been out of the water or how it has been handled after grading. A higher fat content in the tuna is preferred for tuna that is eaten raw. A deep red color, not bruised flesh, is also desired for sushi preparations.

Tuna does not have to be sashimi grade to be safely eaten, but the tuna should be fresh. The nose knows if the fish is fresh. If the tuna is fully cooked by a dry heat method, it will be dry and inedible, so tuna is usually cooked rare or medium-rare (with a 1/2-inch line of red still in the middle of the fish fillet). The only way to fully cook tuna and have it stay moist, is to gently poach it on low heat in olive oil (which is how canned tuna fish is made).

Some tuna is treated with carbon monoxide to improve shelf life and fix the color. That tuna has a rosier color than the deep red of fresh tuna and is usually available in supermarkets. Treated tuna can still be eaten rare, but is not the preferred choice for sushi preparations.

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