It is quite incredible what happens to shellfish when it is subjected to salt and water and is agitated. This technique makes perfect sense, the activity of the fish is stimulated by the action and the fish rebounds.
Fish don’t have to support their body weight, so their muscle fibers are shorter and less tough than those in land animals.The same goes for the connective tissue holding the muscle fibers together.Their fibers are slim and shorter and react more quickly to change, and in effect the salt make a huge impact of the fibers.
An important factor in sushi is the salt, and it has various effects, it cooks, or it cures the fish, and when the fishes flesh is exposed to salt it develops a different texture. The idea is stimulation and you obtain revitalized fibers that spring back and gets new life and look.
It is all technique at the end of the day and the Japanese have developed techniques over thousands of years. Protection of foods from microbial spoilage using salt or sugar has ancient roots and is often referred to as salting, or corning. Rock salt used for curing are sometimes called corns, hence the name “corned beef.”
Salt or sugar attempts to reach equilibrium with the salt or sugar content of the food product with which it is in contact. This has the effect of drawing available water from within the food to the outside and inserting salt or sugar molecules into the food interior. The result is a reduction of the so-called product water activity (known as aw), a measure of unbound, free water molecules in the food that for microbial survival and growth. The aw of most fresh foods is 0.99 whereas the aw necessary to inhibit growth of most bacteria is roughly 0.91.