All our Tuna items are (super) frozen at ultra low temperature of -60°C. They are directly stored onboard in super-freezer, so the quality does not deteriorate as in fresh or standard frozen condition. As the Japanese sashimi markets have understood for a long time, super frozen tuna is the best quality tuna that money can buy.
Comparing to regular frozen process, super frozen fish is infinitely much fresher as it usually takes days until those fish treated with regular frozen process are served to your table.
So called 'fresh fish' can be 11 to 14 days old and deteriorating all the while before it is ultimately consumed., so super frozen tuna is more value for less catch.
Besides that, the most commonly retailed tuna in USA are treated with CO (Carbon Monoxide) process which prevent oxidation, so that the color keeps remaining fresh.
However, the color remains unchanged even after the fish has gone off.
Due to this huge potential risk of food-poisoning, almost all the countries are legally banning CO processed fishes, while there is no strict rule in USA for this, which is basically because there is no custom to have raw fishes meaning USA doesn’t have specific benchmark rule of bacterial count.
More information about CO process, please refer to the article below: