is small seafood, meat or seaweed

Seaweed

Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...

 that has been simmered in soy sauce

Soy sauce

Soy sauce is a condiment produced by fermenting soybeans with Aspergillus oryzae or Aspergillus sojae molds, along with water and salt...

 and mirin

Mirin

is an essential condiment used in Japanese cuisine, consisting of 40%–50% sugar. It is a kind of rice wine similar to sake, but with a lower alcohol content—14% instead of 20%. There are three general types. The first is hon mirin , which contains alcohol. The second is shio mirin, which contains...

. High osmotic pressure

Osmotic pressure

Osmotic pressure is the pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane....

 preserves the ingredients. Its name originates from Tsukudajima, the island (in present-day Chūō, Tokyo

Chuo, Tokyo

is one of the 23 special wards that form the heart of Tokyo, Japan. The ward refers to itself as Chūō City in English.Its Japanese name literally means "Central Ward," and it is historically the main commercial center of Tokyo, although Shinjuku has risen to challenge it since the end of World War II...

) where it was first made in the Edo period

Edo period

The , or , is a division of Japanese history which was ruled by the shoguns of the Tokugawa family, running from 1603 to 1868. The political entity of this period was the Tokugawa shogunate....

. Many kinds of tsukudani are sold. Traditionally made tsukudani is preservable and has been favored as a storable side dish in Japanese kitchen since the Edo period.

Tsukudani can be made with kombu

Kombu

Kombu or konbu , also called dashima or haidai , is edible kelp from the family Laminariaceae widely eaten in East Asia....

 or wakame

Wakame

, Undaria pinnatifida, or Miyeok in Korean, is a sea vegetable, or edible seaweed. It has a subtly sweet flavour and is most often served in soups and salads....

 seaweeds. It is usually eaten with steamed rice

Rice

Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 as a flavoring agent since the flavor is very intense (approximately 1 Tbsp for one bowl of rice). Finished tsukudani is served chilled from the refrigerator

Refrigerator

A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...

 where it takes on a gelatinous texture.