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Served raw

Various species of tuna are often served raw in Japanese cuisine as sushi or sashimi.

Commercial sashimi tuna may have their coloration fixated by pumping carbon monoxide (CO) into bags containing the tuna, and holding it at 4 °C. For a 2-inch tuna steak, this requires 24 hours. The fish is then vacuum sealed and frozen. In Japan, color fixation using CO is prohibited.