Freezing fish can indeed help eliminate parasites if done correctly and for a sufficient amount of time. Freezing fish at low temperatures is a widely recognized method for parasite control, and it is commonly used in the seafood industry to ensure the safety of fish intended for raw consumption, such as in sushi and sashimi.
The freezing process kills or renders inactive most parasites that may be present in the fish. The low temperatures cause ice crystals to form within the fish's tissues, which can destroy the parasites' cells and structures. However, it's important to follow some guidelines to ensure the freezing process is effective:
Temperature: Set your freezer to the coldest possible temperature, ideally at or below -4°F (-20°C). The faster the fish freezes, the smaller the ice crystals will be, which is more effective in killing parasites.
Time: The amount of time needed to kill parasites depends on the thickness of the fish. As a general rule, the FDA (U.S. Food and Drug Administration) recommends freezing fish for:
- 7 days at -4°F (-20°C) or below, OR
- 15 hours at -31°F (-35°C) or below
These guidelines are sufficient to kill most common parasites found in fish, such as Anisakis and Diphyllobothrium.
Preparation: It's essential to freeze the fish as soon as possible after catching or purchasing it to minimize the risk of parasite development. Clean the fish thoroughly before freezing, removing any internal organs, and rinse it under cold water.
Packaging: Use airtight and moisture-resistant packaging to prevent freezer burn and ensure the fish stays in the best possible condition during freezing.
By following these guidelines, you can significantly reduce the risk of parasites in the fish. However, it's worth noting that freezing may not eliminate all types of parasites or kill their eggs. For certain species, such as some types of flatworms, freezing might not be as effective. If you have specific concerns or want to ensure the safety of raw fish, you may want to consider purchasing fish that is specifically labeled as "sushi-grade," as it has undergone specific parasite control measures.