Shuto (salted and fermented bonito intestine) (酒盗)
Shuto is salted fish guts of a skipjack tuna, a bonito. It is one of local foods in the Tosa Province (Kochi Prefecture).
The name, Shuto, already appeared in the encyclopedia, "Wakan-sansai-zue" (an encyclopedia compiled in the Edo period) that is said to be published in around 1712.
It is said that, if you drink sake while eating Shuto as sakana (appetizers taken with alcoholic drinks), you run short of sake soon 'as if it is stolen by someone' or 'you want to drink it even if you steal it from someone.'
One theory is that its history started when the 12th lord of the Tosa Domain, Toyosuke YAMAUCHI, was served this appetizer in Tosashimizu and he named it Shuto, but this story lacks credibility as Toyosuke was born in 1794.
When you make Shuto, clean thoroughly bonito's stomach and intestines with water, and salt down in 20 % salt-water solution for salty one and 10 % salt-water solution for mild one. Shuto makers ship it, after seasoning it with sake, sakemirin (sweet cooking rice wine), and honey and maturing it for at least half a year to one year. It matures by digestive enzyme contained in guts, and well-matured Shuto almost melts when it is eaten with rice with tea poured on. Of course, it is good with rice, but still, it is the best appetizer when you drink sake.
Since a 4 to 5kg bonito has only about 50g of guts, Shuto is rarely made at home. It is believed that Shuto originally came from salted fish guts, made and eaten by fishermen and processors who made it from the large amount of guts removed when they made namaribushi (boiled and half-dried bonito).
Other than eaten as an accompaniment to a drink, recently various new recipes are invented by using it as a seasoning. It is used for aemono (chopped fish, shellfish or vegetables, dressed with [miso or other] sauce) as it is or, like anchovies, used for stir-fried dishes such as fried rice, or for food boiled and seasoned as it increases savory (rich) when used as a hidden flavor.
Other than Shuto product that uses bonitos, there are new products that use tuna, sake (Chum salmon), sea bream, or pike (fish) are now appearing on the market. There are many products that use not only guts but also fish meat, or seasoned with Yuzu citron or red peppers, and many makers are competing to sell various products.