What is Ikekoshi?

A photo of fish rioting

When a fish is pulled from the sea, it is put into an extraneous environment with sunlight, temperature and hot human hands that it isn’t used to, so it starts to swim violently with all its might, trying to get away, in a perpetual state of tension. If cooked in this state, blood will still be running through all the cells of the body. There is no sense of transparency in the meat at this point, especially the white meat. The body also hardens. The entire body reeks of blood. In other words, the meat of white fish is full of blood, making it unsuitable for preparing as food.

Fish are placed in a tank with enough water and oxygen, only in numbers so that they do not rub up against each other. A lid is placed on the tank to create a temporary dark space. At this time, the temperature of the water is an ideal, low temperature. This keeps the fish from struggling. After being left for half a day, it will regurgitate anything undigested that was eaten prior to being caught, become acclimated to the dark space and settle down. The bloody tone from struggling fades throughout the body and the fish relaxes.

Creating this state is called “Ikekoshi”.

Ikekoshi methods differ depending on the species of fish, but the idea is to keep this state for only one day at most. When left for two or three days, the fish loses meat, starts to swim around the dark chamber that it has now grown accustomed to, and its body, tail and fins rub up against other fish or the sides of the tank, causing damage. This hurts the meat quality and appearance so it is something the fisherman must look out for.


We hope this information will be helpful.

Revision date: August 5, 2022

Do you know why canned crab is wrapped in paper inside the can?

a photo of crab canning

Crab protein has a high sulfur content. This sulfur can bind with the iron in the can, resulting in ferric sulfide that causes black spots in the meat. Black discoloration of the crab meat significantly mars the appearance and reduces the product value. In order to prevent this, parchment paper with superior water resistance and oil resistance is used to keep the crab meat from coming in contact with the can.

Meanwhile, the trace amounts of magnesium, ammonium and phosphoric acid contained in crab and fish meat sometimes bind to create magnesium ammonium phosphate glassy crystals. This chemical phenomenon is called struvite.

These crystals have no taste or odor and dissolve easily in the stomach so they are not considered to be an issue under the Food Sanitation Act. However, large crystals may hurt the oral cavity so efforts are made to improve production methods to prevent generation of crystals and keep any crystals that do form as small as possible. However, parchment paper does not reduce the struvite phenomenon.

In summary, do you now understand the truth of why crab meat is wrapped in white paper? Of course, nowadays the surfaces of cans are processed in a way that the iron doesn’t start to dissolve, so perhaps the correct theory is that the parchment continues to be used to give a sense of luxury.


We hope this information will be helpful.

Revision date: August 1 2022