The Frozen-Fish Topic

[BadRabbit]

Doesn't freezing kill the parasites/whatever that would make sushi 'dangerous'?

No. Freezing at very cold temperatures for an extended period of time will kill nematodes (regular freezing in a home unit might but might not) but a lot of dangerous stuff can survive freezing. I believe all the vibrio strains can survive freezing.

Vibrio vulnificus (often found in warm-water oysters) is killed by freezing.

Not according to this from the State of NC Dept of Public Health:

Does freezing kill Vibrio vulnificus?

No: any type of freezing - commercial or in your home freezer - does not kill these bacteria. If you are at high risk, do not eat shellfish iced or "on the half shell." Only thorough cooking - boiling, heavy steaming, frying, broiling or baking - will kill Vibrio vulnificus.

http://www.epi.state.nc.us/epi/gcdc/vibadvice.html

A WHO's risk assessment study was able to achieve 4 to 5 log reductions with freezing but only at -40C for 3 weeks (longer and colder than would be typical for treatment of seafood). This was from a study done in the early 90s. I could find an exerpt of it below but I've read the whole study (I used to run an oyster bar) and higher temps and shorter times were much less effective. This study was just on oysters but they are the most common vehicle for that type of Vib.

http://books.google.com/books?id=JLG5d6i3lVIC&pg=PA20&lpg=PA20&dq=Vibrio+vulnificus+freezing&source=bl&ots=FH5nqRbP4J&sig=NAUZKlwtEW9wpc3eXiEkuLjLHys&hl=en&ei=vQxMTczECMP_lgeHjp3WDw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CDMQ6AEwBA#v=onepage&q=Vibrio%20vulnificus%20freezing&f=false

EDIT: added WHO risk assessment information.

Edited February 4, 2011 by BadRabbit (log)

[BadRabbit]

Found the abstract from the study which contains a little more info:

Cold storage mild heat treatment as processing aids to reduce the numbers of Vibrio vulnificus in raw oysters.

Cook, D W | Ruple, A D

Journal of Food Protection. Vol. 55, no. 12, pp. 985-989. 1992

Pure cultures of Vibrio vulnificus held at temperatures of 4 and 0 degree C underwent a time-dependent decrease in number of recoverable cells. A similar pattern of decreasing numbers was observed with naturally occurring V. vulnificus in cold stored shellstock oysters and shucked oyster meats. The time required for the bacterium to reach undetectable levels (MPN < 3/g) may exceed the usual storage life of 14 d for oyster meats and 21 d for shellstock oysters. Freezing and storage of pure cultures of V. vulnificus at -20 degree C reduced the number of culturable cells more quickly than did holding the cultures at 0 degree C. However, the organism was cultured from oysters frozen at -20 degree C for 12 weeks. While cold storage reduced the numbers of V. vulnificus in oysters, such treatment cannot be relied upon to eliminate the organism. Exposure to temperatures above 45 degree C causes death of V. vulnificus . Decimal reduction times at 47 degree C for 52 strains averaged 78 s (SD plus or minus 30 s), and D sub(50) values for 18 of the hardiest strains averaged 39.8 s (SD plus or minus 12.2 s). Heating oysters for 10 min in water at 50 degree C proved adequate to reduce V. vulnificus to a nondetectable level. This treatment does not impart a noticeable cooked appearance or taste to the oysters and may be employed as a strategy to improve the safety of raw oysters.

http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=2007018130AN&q=&uid=1029868&setcookie=yes

[HungryC]

Thanks for providing the scientific source...I'd read in multiple places that freezing was sufficient.

[BadRabbit]

Thanks for providing the scientific source...I'd read in multiple places that freezing was sufficient.

No problem. It's a common belief. I once even had a health inspector tell me that you could kill vib by freezing.

If you want to be extra careful with oysters, you can stick them in an IC bath for ten minutes at 122F (a process covered in the study I linked). It doesn't really change the taste or texture and you can then recool them in ice water if you want.

I've only done it as an experiment. It is not part of my normal routine with oysters.

[budrichard]

I read all the Replies to the OP and most are probably due to an economic involvement or from lack of experience with fresh caught and properly processed fish.

First, there is NOTHING better than fresh caught and properly processed no matter what any interest will tell you as they try to promote their product or method. The best purveyor I know at the moment is Browne Trading and there is not anyhting I know of that is frozen that they sell.

Second if you haven't had the experience of truly fresh fish, then you have no standard to set the bar against.

Third, it doesn't take a genius to figure out that flash frozen will be better than fish that is in the processing chain for a while.

Fourth, more and more producers are using chemical preservatives to enhance the lifetime and add weight to fish. It started with scallops many years ago and I now I have found sellers that deal in 'fresh' fish, selling fish in chemicals. Now gases are added to protect from oxygen and make the product look better but in reality, you now can't tell if the product is bad. Anything that comes in vac packaging and bulges is off limits to purchase today for me.

Not all sashimi grade fish is previously frozen, you just have to know your purveyor.

Fifth, don't believe what any seller tells you about their fish or shellfish but verify yourself by look, smell and judgment.-Dick

[FauxPas]

Who out there is cooking with frozen fish? Is the argument true that when you freeze it on the boat the quality is as high or higher as fresh that has been sitting during transit? What are the necessary techniques for working with frozen fish? Do any particular fish freeze better than others?

I agree with others who recommend Trader Joe's for their frozen fish. I live about half of the year on the West Coast of Canada (lots of fresh seafood) but am currently in the Arizona desert for about 6 months. Trader Joe's and Costco are the two main places I go to here for good quality seafood.

Both have good to excellent quality Alaskan salmon. I also enjoy the halibut from either place, and Costco did have Chilean Sea Bass for a time (don't know if it was a special sustainable catch or not - does anyone else know and has anyone seen it recently?)Cooking Light has a Cumin encrusted or coated sea bass recipe that is simple, but delicious - one of my faves!

I usually allow my frozen fish to thaw overnight in the fridge in its original packaging before cooking. With salmon, I sometimes marinate for about an hour before cooking and then broil/BBQ. Or I poach it. Or cook on a cedar plank! With halibut, I often use a basic coating and use a combination of pan frying and baking (especially if the piece is large/thick).

I have read about thawing fish in milk to make it smell and taste fresher, but I have never tried that. Has anyone else?

Also, some people just cook from frozen without thawing. Here, for example, is the Alaska Seafood Marketing website which has cooking tips including cooking from frozen and also cooking on a plank:

http://www.alaskaseafood.org/recipes/tips/

Edited February 8, 2011 by FauxPas (log)

[Pierogi]

I read all the Replies to the OP and most are probably due to an economic involvement or from lack of experience with fresh caught and properly processed fish.

First, there is NOTHING better than fresh caught and properly processed no matter what any interest will tell you as they try to promote their product or method. The best purveyor I know at the moment is Browne Trading and there is not anyhting I know of that is frozen that they sell.

Second if you haven't had the experience of truly fresh fish, then you have no standard to set the bar against.

Third, it doesn't take a genius to figure out that flash frozen will be better than fish that is in the processing chain for a while.

Fourth, more and more producers are using chemical preservatives to enhance the lifetime and add weight to fish. It started with scallops many years ago and I now I have found sellers that deal in 'fresh' fish, selling fish in chemicals. Now gases are added to protect from oxygen and make the product look better but in reality, you now can't tell if the product is bad. Anything that comes in vac packaging and bulges is off limits to purchase today for me.

Not all sashimi grade fish is previously frozen, you just have to know your purveyor.

Fifth, don't believe what any seller tells you about their fish or shellfish but verify yourself by look, smell and judgment.-Dick

Couldn't agree more that nothing is better than fresh.

BUT----as I said in another thread (I think it was nickrey's eG food blog about eating in Australia....) in the roughly 300 miles of coastline between Santa Barbara and San Diego, that is considered the LA basin, where I live, there are two, count them TWO fresh fish mongers of repute. Both of them are about 35-40 miles away from my home, in LA traffic. That means a 2-3 hour round trip.

Yes, we have Whole Foods, and a very few other alternatives, but they are expensive, and they are not always the best choice. Not all of us have unlimited access to freshly caught, wild, not frozen, well handled seafood. For some of us, frozen is as close as we can get, and there are some, not many, but some outlets that offer a decent, not perfect, but acceptable alternative. Trader Joe's, IMO, is one of them. I happen to believe that Trader Joe's is more careful in sourcing, and choosing vendors, than the local MegaMart. On any given day in any of the chain megamarts in the area, your choice of fish is frozen/defrosted farmed salmon, frozen/defrosted cod, fresh farmed catfish, fresh farmed tilapia and fresh farmed "swai". Not gonna buy any of those. I'll take a carefully flash-frozen piece of wild halibut over those choices any day, regardless of cost.

[Luke]

Perceived quality can also depend on what species of fish you are eating frozen.

Some fish freeze well, and some don't. In Australia, fish like flake (fillets from a shark), or whiting freeze well.

Snapper (aka Red Snapper) does not, but Tuna is a definite no-go for freezing.

Interestingly, I catch calamari (squid) regularly, and it is one type of seafood that benefits from freezing, even if only for a few days, to help break down the rubbery nature of the protein.

Cheers

Luke

Edited February 8, 2011 by Luke (log)

[MarkIsCooking]

Re: Chilean Sea Bass - not long ago, I know Eric Ripert said he wouldn't sell CSB due to it's non sustainability.

Re: TJ's fish - would love to hear everyone's methods for slacking. Overnight in the refrigerator? Cold salt water??

[heidih]

Re: TJ's fish - would love to hear everyone's methods for slacking. Overnight in the refrigerator? Cold salt water??

Can you clarify "slacking" - I am not familiar with the term. If you mean the thaw process I just leave it in its packet in the fridge overnight. They are packed in single layers so even if a bit frosty when I need it, on the counter during prep it finishes up.

[MarkIsCooking]

Sorry about that. Yes, by "slacking" I meant "thawing".