According to Korean scientists, brass can be used to make shellfish a safer choice at the dinner table. “We showed that copper ions diffuse out from a brass plate into a fish tank filled with seawater, and within 40 hours the copper killed 99.99% of the Vibrio food poisoning bacteria contaminating the living fish and shellfish,” says Dr Jeong-Weon Huh from the Department of Health Research at the Gyeonggi-do Institute of Health and Environment.

When a brass plate is placed in a tank filled with seawater, copper ions will diffuse out from it and be absorbed by the Vibrio bacteria, causing them to die and fall of infested fish and shellfish. The copper will not only kill bacteria present on the outside of the animal, it will also get into the internal organs and kill Vibrio bacteria there. The dead bacteria will then be flushed out of the animal and sink to the bottom of the tank.

So, is this a safe method? According to Dr Huh¸ any remaining copper ions in the saltwater will be absorbed by sand and polyester filters and leave fish and shellfish suitable for consumption. “By being able to remove the copper ions, we can prevent people from consuming excess copper themselves, but let them safely enjoy any kind of fish, either raw or cooked.”

Raw fish and shellfish forms a major part of traditional Korean cuisine and finding a way of reducing the risk of food poisoning is high on the agenda for the Gyeonggi-do Institute of Health and Environment. Between 2003 and 2006, roughly 12 percent of food poisoning cases in Korea were caused by Vibrio bacteria. According to Korean tradition, the safest way to serve food is in a so called bangzza bowl – a bowl made from a 78% copper and 22% tin mixture. The researchers have now managed to show that this metal mixture emits enough copper ions to kill off nasty microbes like Vibrio bacteria. Using this traditional type of kitchenware might be a feasible way to prevent serious gastrointestinal infections in situations when it is difficult to uphold a high level of hygiene and sanitation.

Dr Jeong-Weon Huh revealed his findings at the Society for General Microbiology’s autumn meeting at Trinity College, Dublin.

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.