Translation: Elizabeth Aveling
Illustration: Takayuki Ishikawa
Seawater contains bacteria so it is important to remember that regardless of its freshness, fish will often be contaminated with bacteria because of this. There are many ways of ridding the fish of bacteria. Vibrio parahaemolyticus, for example, which can cause gastroenteritis, cannot survive in fresh water, so it can be washed away by thoroughly rinsing the skin and scales of the fish under cold running water. However, washing was not the only technique available: 200 years ago, when nigirisushi first appeared, there was no such thing as a refrigerator, and so many techniques were developed to keep raw fish fresh and safe to eat. Let us take a look at some of these.
This technique involves pouring boiling water over the cleaned fish, then rinsing it in cold water. It is used for fish such as sea bass and red snapper, which have particularly tasty skin and are better enjoyed with the skin left on. However, since fish skin can harbour bacteria from seawater, scalding is used to kill it and wash it off.
Searing is often used with fish such as bonito, and involves searing the whole fish then rinsing in cold water. This not only rids the fish of bacteria but allows it to retain the delicious fatty flesh found under the skin.
Washing has long been used as a means of preparing fish such as freshwater carp and sea bass, whose flesh gains a fatty texture over the summer months. Live fish are sliced very thinly and washed in cold water, to remove both bacteria and excess fat. The slices are then served with a dipping sauce such as miso (fermented soy bean paste) and vinegar.
Sujime (Marinating in vinegar)
This is often used for small bony fish, or fish with shiny skin. After removing the bones, the fish are sprinkled with salt which tightens the flesh. The fish are then rinsed and marinated in vinegar, which softens the small bones and makes them easier to swallow. Using vinegar is a particularly good means of ridding fish of vibrio parahaemolyticus, a bacterium which causes gastroenteritis and is prevalent in fish caught in relatively warm seas off the shores of Japan.
A range of methods are used to prepare the fish and to bring out its taste, and these are a vital part of making sushi. Bacteria also live in implements such as chopping boards, knives and cloths, and further contamination can be caused by bringing the fish into contact with these foreign bacteria during preparation. Bacteria are also present on the sushi chef’s hands of course. It is therefore vital to wash and keep everything thoroughly clean. Sushi also has various accompaniments, such as wasabi, soy sauce, vinegar, gari, bamboo leaves and green tea, all of which have strong antibacterial properties and are an integral part of enjoying delicious and safe sushi.