Why you should always freeze fish before serving it raw

Raw fish, such as sushi and salmon tartar, is considered a delicacy and is served in restaurants all over the world. Before you decide to make your own raw fish dishes, it is however important to store the fish in the freezer for at least 72 hours prior to preparation. The recommended freezer temperature is -18°C / -0.5° F or colder. A quicker method is to store the fish at – 35°C / -31°F for 15 hours.

If the fish is really large, ideally keep it in the freezer even longer than the recommendations above since it can take some time for the cold temperature to reach all the way into the fish. For really thin fish, e.g. a slice of salmon, a shorter period can be acceptable. The important thing is that the entire fish is deep frozen all the way through.

By freezing the fish, you will kill potentially harmful parasites that may be present inside the flesh. The popular salmon can for instance be infested with Diphyllobothrium latum, a tapeworm capable of taking up residence in the human digestive tract. You don’t want this tapeworm inside you because it will deprive you of nutrients and can for instance cause vitamin B12 deficiency.

Some connoisseurs dislike freezing fish prior to serving it raw and will instead pay meticulous care when preparing the fish. The fish is carefully cleaned out and all specimens that show signs of parasite attacks, e.g. the presence of tiny worms, are discarded. It is also common to slice the fish into really thin slices since this makes it easy to spot parasites. This method should however only be considered by those who have received proper training in spotting parasites and is not as reliable as freezing the fish.