My japanese girlfriend dont believe me when I say that most....say 90% of the maguro in Japan has been frozen at some point before you get it to eat ..... she watched something on Nippon tv and they said that there is unfrozen maguro available.... well where is that ? Ive caught Tuna [not off japan], and it needs freezing to kill bacteria and makes the meat better to eat .. otherwise ..straight after catching a Tuna ....day 1 meat is crunchy ..yes cruchy.!! day 2, softer texture , day 3 is perfect .. I believe that all tuna has some frozen time..lets face it they are caught way out to sea and are put straight into ice slurry after the ikijimi death spike.... please tell me otherwise ..I cant see anywhere online about how much is frozen ...too much wording abiguieties.. like the word "fresh "... still might imply its been snap frozen .. have you ever seen Tsukiji fish markets in Tokyo where they deal with frozen tuna daily ??? hmmmm I need to hear your facts ..cheers
Lots of frozen tuna at Tsukiji. Lots of tuna sushi matured for weeks until served, in a way like maturing beef.
I don't know the percentage breakdown but a lot of the bluefin is raw, unfrozen. They are caught, killed, bled, headed and gutted and then chilled on the vessel before being sent to Tsukiji- in some cases air freighted in from overseas.
Regarding frozen maguro, yes, most of it has been frozen. All the farmed maguro is delivered frozen, and that is perhaps half of what is sold at Tsukiji every day (it comes mostly from Australia or Viet Nam). Most of the caught Indo maguro (from the Indian Ocean) as well has been frozen. A friend of mine's shop has a sign posted saying none of the fish served has been frozen with the exception of maguro. If you want maguro that has not been frozen I suggest finding some from Oma, in Aomori Prefecture. If you visit Tsukiji jonai, the wholesale market, you will see a lot of shops cutting tuna with bandsaws.
Regarding Asomaniac's comments regarding aging maguro, that is true. Maguro is the only warm blooded fish and so like beef, is best when aged for a week or so; the fish needs time for certain amino acids to develop as muscle fiber proteins breakdown. Otherwise it would be very tough and lacking in fully developed flavors.
As for the comment regarding finding gutted and headless tuna at Tsukiji, no way. All maguro are auctioned whole, the exception being that the tail has been cut off. Perhaps he was thinking of the Honolulu wholesale fish market where fish are displayed for auction opened up, but not Tsukiji. That is why there is the "Tuna Court," a place where disputes regarding large fish (maguro and kajiki) with serious defects can be resolved.
Parasites are more of an issue with fatty fish like salmon so there's not as much of a need for freezing tuna for that reason, however, the freezing methods are much better today and you do preserve freshness.
The frozen tuna auction is bigger than the fresh tuna auction at tsukiji, but both are big. There is fresh tuna there from all over the world. The fresh auction is more than 10% of all the tuna sold at auction at Tsukiji, but I imagine that for all of Japan the large majority of bluefin tuna is frozen. You can see the sales figures somewhere on the Tsukiji website. Tuna does not need to be frozen for any reason. Freezing doesn't kill bacteria, and there are no dangerous parasites in tuna like there are in freshwater fish. Tuna is sold gutted with the head on.