Funazushi
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Funazushi is a type of nare-zushi, an ancient Japanese type of sushi. It is a local dish of Shiga Prefecture (formerly Ōmi Province), where it has been made since ancient times using Lake Biwa's nigorobuna (Carassius auratus grandoculis) and other fish as the main ingredients.
Funazushi is a type of nare-zushi.[1] Nare-zushi is a food made by salting raw fish for several months, removing the salt, and then mixing it with cooked rice and fermenting it with lactic acid bacteria. Generally, the rice used for fermentation is discarded and only the fish is eaten. [2] Modern sushi is made with rice mixed with vinegar, but this has been around since the 17th century; until then, the word sushi meant nare-zushi.[3]
Many literature claim that nare-zushi originated from a fish storage method found in the mountainous region of Yunnan in Southeast Asia, but there are also different theories.[4]
Today, crucian carp with the ovaries is generally used for funazushi. However, until the 19th century, the ovaries were often absent. [5] The egg part smells similar to cheese.[2]
Often cut into thin slices before eating. Often eaten as a snack with sake. It is sometimes made into chazuke.
In 1998, it was selected as one of Shiga Prefecture's Intangible Folk Cultural Assets as food.[1]
Nigorobuna (Carassius auratus grandoculis) is used to make funazushi. The lactic acid softens the bones so that the fish can be eaten down to the bones.[1] Until the Edo period, many documents stated that gengorobuna (Carassius cuvieri) was used as the raw material, but it is now believed that these were actually nigorobuna.[5]
Funazushi was eaten as a substitute for medicine in the past because it contains lactobacillus, which helps to improve intestinal health.[1]
In recent years, due to the deterioration of the spawning environment in Lake Biwa and feeding damage by invasive fishes, the number of nigorobuna has decreased, and the number of households making funazushi is decreasing.[1]
Method of manufacture

Funazushi is a specialty of Shiga Prefecture and is believed to be the oldest form of nare-zushi existing in Japan.[4]
Generally, nigorobuna with eggs are used as a raw material, but gengorobuna are also used.[6]
Its manufacturing process varies from vendor to vendor and home to home.[4][7]
In most modern times, the fish is salted in early spring. That is, after the scales, gills, and internal organs except for the ovaries of the raw fish are removed, the belly cavity is stuffed with salt and stored in layers in wooden vats until summer.
In summer, the fishes are rinsed for desalt, dried, and placed in a wooden bucket on a bed of cooked rice. On top of that, more rice is spread, and fishes are placed again. After several layers, a drop-lid is placed on top, and a weight is placed on the lid. After this, it is stored for several months until winter to ferment.[7]
It is believed that the flavor and shelf life of funazushi is mainly imparted during this rice pickling process.[4] The process of salting in the preliminary stage is also thought to inhibit the growth of spoilage bacteria, inhibit the progress of autolysis, and dehydrate, harden, and bleed the meat.[4]
Funazushi is a fermented food that uses the action of lactic acid bacteria and yeast.[4]
Air deprivation is important for lactic acid fermentation, and water has been used to cover the top of the drop-lid. Currently, a plastic bag is placed over the bucket, the bag is filled with fishes and rice, the mouth of the bag is closed, and a drop-lid and weight are placed on the bag to keep out air without water.
To make it with 1 kg per fish, one barrel contains 40 to 50 fish, 27 kg of rice and 15 kg of salt.[8]
In Shiga Prefecture, in addition to funazushi made from nigorobuna, nare-zushi is also made from freshwater fish such as ugui, hasu, moroko, Ayu Biwa trout, koi, and dojo. Nare-zushi has been designated as Shiga's food cultural asset in Shiga Prefecture's Intangible Folk Cultural Assets in 1998.[7]。
The decline of nigorobuna, the fish used to make funazushi, has become a problem, and Shiga Prefecture is working to release young fish into Lake Biwa and to conserve the reed community along the lake's shores.[4]
Biochemistry
Funazushi contains organic acids such as lactic acid, formic acid, acetic acid, propionic acid, and butyric acid.[4] These organic acids lower the pH, which also imparts preservative properties.[4]


