Karasumi is a food product made from fish roe, which is first salted down and then sun-dried after some of the salt is removed in water. The Karasumi produced in Nagasaki Prefecture using mullet roe is famous in Japan, while the Karasumi produced in Kagawa Prefecture using roe of Spanish mackerel caught in the fishing grounds of Japan is also known. Besides Japan, Taiwan, Spain, Egypt and the Italian island of Sardinia also produce Karasumi. The roe of other ocean fish are also used in Europe.
Karasumi is often dubbed one of the three major Japanese delicacies, along with sea urchin and salted entrails of trepang. Its flavor, which is similar to sticky, salty cheese, is highly valued as a high-class accompaniment to drinks. Karasumi is served in various ways, including as an hors d'oeuvre by slicing it thinly and as Karasumi-vinegar by grating and mixing it with vinegar.
It is generally believed that the name "Karasumi" is derived from a block of sumi (ink stick) imported from China, based on the similarity of appearance.
Production method using mullet roe
The mullet's belly is carefully cut open so as not to incise the membrane covering the roe, and then the roe is removed.
After washing it with water gently, smear it with salt and pickle it in a barrel for three to six days.
Remove it from the barrel, and then place it in a large, flat-bottom tub filled with fresh water. Check the softness by hand in the water after an entire day and night. If every part of the roe has become soft, take it out of the water. It is said that the saltiness at this stage will ultimately affect the flavor.
Place the roe side by side on an inclined board, and then apply pressure by piling about five boards onto them. Sun-dry the partially dehydrated roe the next day, and when night arrives pile the boards on it again.
The Karasumi production process is complete after about ten days of sun-drying, during which the oil that rises to the surface should be wiped away.
Karasumi has been produced in Greece and Egypt since long ago, being salted down for consumption.
It is believed that Nagasaki was the first city in Japan to which Karasumi was imported from China; this occurred at the beginning of the Edo period.
As a historical document pertaining to Karasumi, there is a document that apparently states that Hideyoshi TOYOTOMI ate Karasumi. In the document, compiled in the early Edo period, there is a record stating that an official liaison (warimoto) Sagoemon-yoshishige SHINOZAWA in Iwamurata, Saku County, Shinano Province, donated materials (including dishes) to Munetoshi AOYAMA, Inaba no kami (the governor of Inaba Province), as well as the lord of Komoro Castle on the night of December 3, 1648. The record contains the word "Karasumi." Karasumi was served that day, being displayed on a four-legged wooden tray called "Oshiki." This document, which belongs to his descendant Akiyoshi SHINOZAWA, is currently open to public viewing at Saku Municipal Mochizuki City Museum of History and Folklore.
Karasumi had been made from Spanish mackerel roe since it was first imported from China. Yusuke TAKANO created the Karasumi production process in 1675 by using the roe of mullet, which were caught in large quantities in the Nomozaki district of Nagasaki Prefecture.
Karasumi in other countries
In Taiwan, Karasumi is called "U-yu-tsu" in the Beijing dialect of Chinese and "O-hi-ji" in Taiwanese. Stripping away the thin membrane covering the surface of the roe, the Taiwanese puts a small amount of sake on it and roasts both sides of the roe over a low flame for a few minutes until the surfaces become crispy and show white eruptions. After that, the roasted roe is served thinly sliced. Taiwanese often eat it with white radish or spring onion by piercing the pieces with a toothpick. The roasted roe is also sold at stands in the night stalls.
Karasumi is called "bottarga" or "enbotargo" in Italy. Bottarga is made not only from mullet roe but also from the roe of other ocean fish such as cod and tuna. Italians often eat bottarga by flaking it and then mixing it with pasta. Japan has a similar dish called "Tarako spaghetti" (spaghetti mixed with cod roe). Tarako spaghetti originated as spaghetti mixed with caviare instead of being mixed with bottarga.
In the eastern Mediterranean, Karasumi is popular as a dish of the meze.