Buying sushi-grade fish
Can someone give me a short primer on how fish is "graded"? For example, what is the difference between sushi grade fish and non-sushi grade fish? How hazardous is it to use high quality, non-sushi grade fish for sushi?
I am often in Spain for an extended stay and sometimes I go to the fish market, which has incredibly fresh, to buy fish to prepare sushi at home. Things are never labeled as "sushi grade" and I don't think most would know what that was if I ask. So are there some basic questions that I can ask to determine whether the fish I get can be used for sushi/sashimi?
My understanding is that "sushi grade" is either immaculately fresh or has been frozen at very cold temperatures, dry ice or lower, for a longish period of time (maybe a week or so, to kill parasites). So, I've read that most all sushi in restaurants has been previously frozen, but maybe this isn't true at some very high quality restaurants.
Notice that even the frozen fish must be quickly eaten upon thawing to maintain quality and taste good. "Sushi grade" fish at markets can sit out for some time before someone is willing to pay the higher price. When I buy fish to make sushi at home I usually go to a Japanese market (I'll add that I try to live in towns that have Japanese markets for this reason). I'd order over the web if you don't have a market in town.
On the other hand, I've know people who buy salmon from the local chain market and make sushi with it. The argument against this is that the ice displays at markets is a great place for parasites to travel around and sample the fish! Swordfish, for instance, is famous for giant worms... once I learned this I've never had swordfish again.
I believe that the only fish that needs to be frozen and is still considered sushi grade is salmon. Salmon contains parasites and i understand that any salmon anyone has ever eaten at a sushi bar, has been frozen. As far as the other fish are concerned, i think that if it is very fresh and caught from clean (relatively) waters, it should be fine.
There are no government regulations in the U.S. regarding the grading of fish -- vendors are free to call it "sushi grade" or whatever. It's strictly buyer beware, so know your fishmonger and trust your eyes/nose. It's my understanding that the only fish that are parasite safe are tuna and everything else that's been frozen.
No, actually you are wrong -- the United States FDA (Food and Drug Administration) has passed regulations on what is "sushi grade" fish. It is required to be flash frozen at -35 degrees for 15 hours, or to be frozen for one week's time at -4 degrees (Farenheit). This requirement is to kill parasites that can be found in all types of fish used for sushi. Also the fish must be oceanic -- fresh water fish is NEVER used for sushi.
No, actually, I'm not. The FDA has never created a category of "sushi grade fish." It's a marketing gimmick. The FDA has created regulations governing fish that is to be served raw:
# (A) Except as specified in ¶ (B) of this section, before service or sale in ready-to-eat form, raw, raw-marinated, partially cooked, or marinated-partially cooked fish other than molluscan shellfish shall be:
* (1) Frozen and stored at a temperature of -20°C (-4°F) or below for 168 hours (7 days) in a freezer; or
* (2) Frozen at -35°C (-31°F) or below until solid and stored at -35°C (-31°F) for 15 hours.
# (B) If the fish are tuna of the species Thunnus alalunga, Thunnus albacares (Yellowfin tuna), Thunnus atlanticus, Thunnus maccoyii (Bluefin tuna, Southern), Thunnus obesus (Bigeye tuna), or Thunnus thynnus (Bluefin tuna, Northern), the fish may be served or sold in a raw, raw-marinated, or partially cooked ready-to-eat form without freezing as specified under ¶ (A) of this section.
As pointed out above, "Sushi-quality" is a marketing term. Unlike other meats where "Prime" and "Choice" actually have standards and meaning, if Stop and Shop (not to pick on them) wants to call fish "sushi-grade" they are free to do so.
Very fresh fish will have a crisp, more desirable texture and no offensive odors, making it better for eating raw. Frozen and thawed fish has a much less desirable texture.
Parasites are another matter. They are found in most fish in the market, and fish isn't routinely screened. Even frozen fish can have parasites, unless it has been frozen with a process designed to kill them (very cold for a long time). Most won't cause you any harm, but some can. This is part of the risk with eating anything raw.