Salmon is one of the most popular and nutritious types of seafood. However, there are concerns about whether parasites like tapeworms can survive the freezing process and infect people who eat frozen salmon. This article will examine if it’s possible to get tapeworms from eating frozen salmon, looking at factors like:
- How tapeworms infect salmon
- If freezing kills tapeworms in salmon
- Proper storage temperatures for frozen salmon
- Recommendations for cooking frozen salmon
- Ways to tell if salmon contains tapeworms
Read on to learn the facts around tapeworms and frozen salmon so you can enjoy this healthy fish safely.
How Salmon Get Infected With Tapeworms
Salmon and other fish can become infected with a variety of worm parasites. One of the most concerning is the broad fish tapeworm, known scientifically as Diphyllobothrium.
This tapeworm goes through a complex life cycle that allows it to thrive in both marine environments and inside fish and mammal hosts. Here are the stages of the broad fish tapeworm life cycle:
- Adult tapeworms living in the intestines of infected marine mammals like seals or bears will release eggs into the water through the mammal’s feces.
- The eggs hatch into larvae called coracidia and are eaten by tiny crustaceans like copepods.
- These crustaceans are then eaten by small fish like herring or trout, and the larvae develop into the next stage called procercoid larvae.
- When larger fish prey on the smaller infected fish, they ingest the procercoid larvae which migrate into the muscles of the bigger fish.
- If an infected fish is eaten raw or undercooked by a marine mammal or human, the procercoid larvae can attach to the intestine and develop into adult tapeworms, completing the cycle.
This complex sequence allows the tapeworm larvae to work its way up the food chain into fish like salmon. When people eat the infected raw or undercooked fish, they can accidentally ingest the worm larvae and contract a tapeworm infection.
Symptoms of Tapeworm Infection in Humans
If someone eats infected salmon or other fish, and tapeworm cysts take hold in the digestive system, symptoms may include:
- Abdominal pain
- Loss of appetite
- Weight loss
- Bloating or increased gas
- Diarrhea or other digestive issues
- Weakness or fatigue from nutritional deficiencies
- Tapeworm segments passed in stool
Without treatment, tapeworm infections can cause complications like intestinal blockages or malnutrition. Some types of tapeworm larvae can also migrate outside the digestive system and impact other organs.
This demonstrates why proper freezing, cooking, and storage of fish is important to kill off any parasites before eating.
Does Freezing Salmon Kill Tapeworms?
Many people assume that freezing fish like salmon will kill off any parasites. But in fact, the temperature and length of freezing make a big difference in whether parasites are destroyed. Here are some key considerations on how freezing affects tapeworms:
- Quick freezing vs slow freezing – Flash freezing fish at very cold temperatures like -31°F or colder can destroy parasites. But slowly chilling fish to subzero temperatures allows worms to adjust and survive.
- Freezing duration – Tapeworm larvae need to be held at -4°F or below for at least 7 days to ensure they are killed by freezing. Colder temperatures will kill worms faster.
- Location of cysts – Tapeworm cysts embedded deep in the fish flesh take longer to reach deadly temperatures compared to cysts near the surface.
The FDA recommends flash freezing fish at -31°F or below until solid, and storing at -4°F or colder for 7 days to kill parasites. However, home freezers often can’t reach cold enough temperatures quickly enough to guarantee parasite destruction.
Proper Storage Temperatures for Frozen Salmon
To keep frozen salmon safe from parasites, bacteria, and other pathogens, follow these storage guidelines:
- 0°F or colder – Optimal long term storage temperature
- -4°F or colder – Required minimum temperature to kill parasites
- Prevent temperature fluctuations – Don’t allow the salmon to partly thaw then refreeze as this helps parasites survive.
- Keep freezer organized – Store frozen salmon well wrapped and dated so you know how long it’s been frozen.
- Monitor freezer temperature – Use a thermometer and adjust the temperature settings as needed.
Always check your freezer temperature periodically and do not refreeze thawed salmon. Follow the recommended guidelines for freezing and cooking fish to destroy any tapeworms or other pathogens.
Proper Cooking Methods for Frozen Salmon
Even if previously frozen salmon has been stored properly, it’s still important to cook it thoroughly before eating to kill any parasites. Follow these safe cooking methods:
- Raw frozen salmon – Do not eat raw lox, sashimi, sushi or other uncooked frozen salmon due to tapeworm risks.
- Heat to 145°F – Cook frozen salmon fillets or steaks to an internal temperature of at least 145°F.
- Poach, steam, or bake – These moist heat methods evenly cook salmon to kill parasites.
- Sautee or pan fry – Use a cooking thermometer to ensure the thickest part of the fish reaches 145°F.
- Boil or grill – Bringing salmon to a full boil kills parasites. Grill to 145°F, checking temperature carefully.
Proper cooking can destroy any worms or larvae surviving the freezing process. Take the internal temperature with a food thermometer to verify it reaches safe temperatures.
How to Tell if Salmon Contains Tapeworms
It can be difficult to tell if fresh or frozen salmon contains harmful tapeworm cysts. Here are some signs that may indicate the salmon is infected:
- White, fluid-filled cysts in the flesh – May indicate tapeworm larvae.
- Spots that look grainy or granular – Could be developing cysts.
- Small black dots on fillet – Can signal tapeworm larvae.
- Unpleasant ‘fishy’ odor – Potential spoilage and pathogens.
- Gaping fillets – Flesh separates unnaturally due to larvae.
- Sour taste when cooked – Sign of spoilage organisms.
However, a trained eye is often needed to identify parasite cysts with certainty. Always thoroughly cook your salmon to be safe.
Table: Signs Salmon May Contain Tapeworms
| Sign | Description |
|---|---|
| White cysts in flesh | Fluid-filled cysts may contain tapeworm larvae |
| Grainy spots | Could indicate developing tapeworm cysts |
| Black dots | May be tapeworm larvae |
| Fishy odor | Potential spoilage and pathogens |
| Gaping fillets | Flesh separates unnaturally due to larvae |
| Sour taste | Sign of spoilage organisms |
Conclusion
In summary, it is possible to get tapeworms from frozen salmon, but the risks are low if proper storage and cooking guidelines are followed. Flash freezing at very cold temperatures can destroy some parasites, but home freezers may not be cold enough to guarantee this. Store all frozen fish at 0°F or below, and cook to a minimum internal temperature of 145°F to kill any surviving worms or larvae. While the chances of getting tapeworms from properly handled frozen salmon are low, it’s impossible to fully inspect the raw fish, so caution is warranted. Use common sense purchasing, storage, thawing, and cooking methods for frozen salmon to enjoy this healthy seafood safely.
