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What exactly makes some fish "Sushi Grade"?

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3 Answers 3

up vote 33 down vote accepted

"Sushi grade" means that it is safe to prepare and eat raw. In order to do that, it must be frozen to kill any parasites. That means it either has to be:

  • Frozen at -20° C (-4° F) for 7 days; or
  • Frozen at -35° C (-31° F - "flash frozen") for 15 hours.

There aren't any official regulations about the fish itself or its quality, and most sushi/sashimi distributors have much more stringent rules of their own beyond the freezing guarantee.

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Interestingly (if you'll accept anecdotal evidence), the few sushi chefs that I've gotten a chance to ask this question told me they buy most fish fresh with no freezing involved. –  I. J. Kennedy Mar 7 at 20:03
@I.J.Kennedy: That might imply that they freeze it themselves, since it's not always easy to find fish that's been properly flash-frozen. Or, maybe some chefs don't trust the distributors to do it properly. There are definitely sushi chefs who just order fish from distributors though - almost all of the small-time sushi joints (and in this area, there are 5 on every block) do it. –  Aaronut Mar 8 at 4:30
No, they were very clear that there was no freezing involved, by them or anyone else. –  I. J. Kennedy Mar 8 at 16:00

There is no real definition of 'sushi grade' fish. It's purely a marketing term to imply a higher quality piece of fish.

There are some actions that should be done for tuna (really for all fish, but especially for tuna) when they are caught, such as bleeding them immediately, destroying the neural canal, reducing the temperature of the fish immediately, etc.

Here's a blog post on the seven different ways to kill/fillet fish and how those ways affect the taste of the meat.

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This FAQ will probably help http://www.sushifaq.com/sushi-grade-fish.htm

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Needs more than just a link - if that site goes away, we're left with just a dead URL. –  mskfisher Sep 23 '10 at 2:49

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