Many overseas visitors who are not accustomed to eating fish often find the fishy smell off-putting. This odor is mainly caused by a compound called trimethylamine, which forms when bacteria break down trimethylamine oxide, a substance abundant in fish that contributes to umami flavor. As time passes, ammonia is also generated, further intensifying the odor.
Trimethylamine begins to form after the fish dies. Therefore, the key to minimizing this smell is to process the fish as soon as possible after it is caught. Removing the slimy coating on the skin, as well as any decaying internal organs or blood, also helps reduce odor. It is essential to rinse the fish with water.
After cleaning, the fish is typically lightly salted and refrigerated. After some time, the salt is rinsed off using saltwater with a salinity of about 3%, similar to that of seawater. This step is crucial because rinsing with fresh water would cause the fish to reabsorb moisture through osmosis, making the previous dehydration process ineffective and leaving the fish with a watery texture.
Bacterial growth is further suppressed by refrigeration, which is why sushi toppings are kept cold. Additionally, since trimethylamine is alkaline, it can be neutralized by vinegar, which is acidic. Soaking fish in vinegar not only helps eliminate odor but also reduces surface bacteria.
In short, sushi restaurants take meticulous steps to prevent bacterial growth and eliminate fishy smells, ensuring that customers enjoy fresh, clean-tasting sushi.
We hope this information will be helpful.
Revision date: June 10, 2025
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