I'm trying to find out whether it's safe to eat cold-smoked salmon as I recently read that eating raw salmon may not be safe.

Potentially unwanted parasites can be found in a wide variety of raw fish. These fish include salmon, halibut, herring, flounder, sole, grouper, mullet, sablefish, turbot, and mackerel. Wild-caught salmon are among the species with the highest prevalence of potential parasites, and very often contain roundworm or tapeworm larvae.

Safety From Parasites in Cold-Smoked Fish - Basic Principles

Cold Smoking and Salting

Cold smoking is a process of preparing fish in which the fish is exposed to smoke and room-type temperatures (between 65˚-80˚F/18˚-27˚C) for a long period of time (typically 12-24 hours). This process is not sufficient to kill potentially unwanted parasites, including the larvae of ringworms or tapeworms. Heats of at least 140˚F/60˚C are needed to accomplish this task, and the innermost core of the fish must reach this temperature for at least one full minute.

Salting is sometimes combined with cold-smoking in the preparation of cold-smoked fish, and once again, this method is typically inadequate to assure safety. Most salt brines are not sufficiently concentrated, or used for a long enough period of time, to kill all larvae. In scientific studies, brine concentrations as high as 4.3% were insufficient to kill unwanted parasites after five weeks of marinating. At this salt concentration, seven full weeks of marinating were required. Other studies have show that a doubled concentration of 8-9% can lower this marinating time to 5-6 weeks at best. Since many cold-smoked, salted fish (including salmon) are not exposed to adequate salt concentrations for a sufficient period of time, they cannot be considered safe for consumption.

Freezing

Freezing is one of the most effective ways to kill unwanted parasites in raw fish. The Food and Drug Administration's Fish and Fishery Products Hazards and Controls Guide sets forth a temperature range of -31˚F/-35˚C for 15 hours or

-4˚F/-20˚C for 7 days as an effective way to kill potential parasites. Food industry standards for frozen fish take these safety issues into account, and many commercially sold fish have been previously frozen, intact and prior to any processing, at temperatures that meet FDA guidelines.

Practical Decisions About Cold-Smoked Fish

Ready-to-Eat Cold-Smoked Fish

Pre-packaged, ready-to-eat cold-smoked fish is safe for consumption provided it has been produced and packaged by a reliable manufacturer, is consumed by the "use by" date, and is kept properly refrigerated. In the case of ready-to-eat products, a variety of processing steps are available to the manufacturer to assure safety from parasites, and these include higher concentration salt marinating for seven or more weeks, as well as freezing of the entire, intact fish at very low temperatures prior to all processing.

Cold-Smoked Fish in Restaurants

Cold-smoked fish being served in a restaurant is most likely to have arrived at the restaurant pre-packaged by the supplier. If pre-packaged from the supplier, you can generally feel safe consuming cold-smoked fish from a high-quality restaurant with an outstanding safety rating. However, in some cases, the fish may have been prepared locally from scratch using fresh, raw fish. If your cold-smoked fish has not arrived at the restaurant pre-packaged, but instead has been prepared from scratch beginning with fresh, raw fish, the safety will depend on the preparation steps involved. In many cases, proper freezing of the fish will have removed the risk of unwanted parasites. If you are eating at a restaurant that cold smokes its own fish or purchases cold-smoked fish locally, you may want to ask what steps have been taken to ensure its safety from parasites, and you can feel safe if any of the guidelines described earlier have been met.

Do-It-Yourself Cold-Smoked Fish

In the case of fresh, raw fish that you are planning to cold-smoke yourself, prior freezing to kill parasites would be an effective step to take. You may be able to reach the -4˚F/-20˚C temperature requirement in your home freezer, depending on the model, year, working condition, etc. But you'll need to purchase an appliance thermometer that can be placed inside your freezer to determine if your freezer has reached this temperature level. If your freezer will allow freezing of the fish at -4˚F/-20˚C , you can store it for seven days and feel safe about the killing of unwanted parasites. Alternatively, you can follow the salt marinating concentration and duration requirements above to kill unwanted parasites.

References

• U.S. Food and Drug Administration (FDA). Processing Parameters Needed to Control Pathogens in Cold Smoked Fish Potential Hazards in Cold-Smoked Fish: Parasites. Center for Food Safety and Applied Nutrition, 2001. Available online at: http://www.foodsafety.gov/~comm/ift2para.html. 2001.

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