Parasites in the Wild

• Salmon in the wild can have two kinds of parasites harmful to humans: anisakid nematodes and tapeworms. Anisakis simplex can be found in both freshwater fish and in species that are anadromous, meaning fish that are born in fresh water, migrate to saltwater bodies, and return to fresh water for spawning. Wild salmon are anadromous. Eating raw fish with these nematodes results in an illness called anisakisitis, an inflammation of the digestive tract. Tapeworms, which originate in land mammals, such as bears, are typically found in fish caught in waters near wildlife habitats. Tapeworms inhabit the human intestine. Regular testing by government food safety agencies has shown that farm-raised salmon have neither of these parasites common to wild salmon, so they're a safer choice.

First Safeguard: Freezing

• Processing salmon properly also lowers the risk of parasites. The U.S. Food and Drug Administration requires that salmon and all fish potentially harboring parasites must be frozen before raw consumption. Freezing fish to minus 4 degrees Fahrenheit for seven days kills parasites. A faster technique is to freeze the salmon at minus 35 F for 15 hours. Besides these processing techniques, grocery stores typically keep fish frozen to ensure safety. To avoid parasites, make sure you choose fish the grocer has frozen.

Final Safeguard: Cooking

• Cooking is the final safeguard against any parasites in supermarket salmon that may somehow have survived the freezing process. All fish should be cooked to an internal temperature of 145 F. A standard for cooking fish to correct temperature is to plan for 10 to 15 minutes of cooking per 1 inch of thickness at a temperature exceeding 350 F. It's best to check for this temperature with a thermometer. If you don't have a thermometer, fish is considered thoroughly cooked if it's opaque and flakes easily with a fork. Another doneness method used by restaurant chefs avoids cutting into the fish and ruining its presentation. Here's the trick: stick a small, sharp knife into the thickest part of the fish. Hold the knife there from 5 seconds, then remove and touch the flat side of the blade to the lower lip, which is sensitive to temperature. If the knife feels warm, then the fish is done. If the knife is cold, the fish needs to cook longer.

Cook, Exchange or Return

• If you choose to eat raw salmon, such as sushi or sashimi made from it, the best safeguards are to choose farm-raised salmon that has been previously frozen. Should you find parasites in the fish, you can remove the visible worms and cook the fish, or you can notify the supermarket where you bought it and ask to return or exchange it.