Parasites in Our Salmon and What to Do … For Real

Sushi, it seems, has become more and more fashionable here in the U.S.  When we say sushi grade fish, most people presume it is fresh, raw fish. This is probably one of the best misconceptions in the sushi world. The fish you are eating raw is not fresh and has been previously frozen.
U.S. law states that fish intended to be served raw as sushi or sashimi has to be bought by an approved supplier and has to be previously frozen.  The purpose of the freezing process is to kill any parasitic contamination that might be found in the fish.  Parasites need a host body, animal including humans or fish to live and can be destroyed with heat or freezing.  Please note that freezing will not kill the other pathogens responsible for foodborne illnesses, i.e. viruses, bacteria, fungi and toxins.
Recent news reported a Japanese broad tapeworm was found in salmon from U.S. Alaskan Pacific waters.  This tapeworm has normally been associated with fish found in Japan, South Korea and Russia.  This tapeworm can grow to 30 feet long in human bodies.  The Center for Disease Control reports that most infected people have no symptoms, but some can suffer from diarrhea, stomach pain, weight loss and vitamin B-12 deficiency.  The CDC reports that treatment of praziquantel and niclosamide are two drugs used for treatment.
In our Food Service Manager certification classes, we teach that sushi — raw fish — can be eaten because it is so fresh and has been previously frozen. My initial reaction to the news story of parasites being found in salmon was, “Why would there still be parasites found in the salmon? It’s been pre-frozen, no?”  Then I realized that not all fish is sold pre-frozen because not all fish will be served in its raw state as sushi or sashimi.
Heat, in the form of proper cooking temperatures, kills the parasites as well.  The Food and Drug Administration recommends cooking fish to a minimal internal temperature of 145°F for at least a duration of 15 seconds.
Herein lays the problem. Many chefs don’t like to cook salmon according to FDA recommendations, as they consider it overcooked. Many chefs actually cook salmon to 135°F, 130°F or even 125°F so the center of the fish is opaque. Chefs have found overall that guests consider fish overcooked when it is cooked to the proper internal temperature of 145°F.Here are some ways around this if a chef wants to continue under-cooking salmon to the guests’ preference. Research shows that tapeworm parasites are usually unlikely to be found in fish from cold salt waters. Salmon is a strange fish as it travels and can live in fresh water as well as salt water. Purchasing salt water fished salmon or farm raised salmon can help versus purchasing fresh water salmon. Note that nothing is guaranteed to be parasite free.
Consider freezing your “fresh’ and not pre-frozen bought salmon onsite for at least seven days with a freezer that is capable of freezing at -4°F.  Commercial freezing is done at -35°F so it does not have to be frozen for as long a period of time. At least 15 hours should be sufficient at that very cold temperature. When you freeze fresh salmon at home or on site, because our freezers are not as cold as commercial freezers, at least seven days at -4°F is required. At this point it is unlikely that parasites will survive and you would thus diminish the risks associated with under-cooking the fish.
Again, please note, that bacteria will not be destroyed by freezing and that reinforces the needs to follow the guideline of properly cooking fish to an FDA recommended internal temperature of 145°F for a duration of 15 seconds.
I would recommend that you add salmon or undercooked and raw fish to your consumer advisory to allow your guests to know this, just as you would add rare, medium rare undercooked meat to your consumer advisory.

About the Author

Juliet Bodinetz is executive director of Bilingual Hospitality Training Solutions and has over 30 years industry and training experience. She and her team of instructors specialize in food safety, alcohol training and ServSafe training in English or in Spanish and writing HACCP Plans in the Baltimore and Washington D.C. area., or 443-838-7561. For latest food safety tips: Become a fan on Facebook or Twitter: @BHTS

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