I asked one Japanese guy who offered citrus seeds about Yuko and he answered me this:
I just found there are 2 cultivars in Japan
Yukkou - ゆうこう
ja.wikipedia.org/wiki/%E3%82%86%E3%81%86%E3%81%93%E3%81%86 Yuko - ユコウ
ja.wikipedia.org/wiki/%E3%83%A6%E3%82%B3%E3%82%A6 Do you know what fruit you will have? Yuko - ユコウ or Yukkou - ゆうこう ?
There is info from Japanese wiki page (Translated with
www.DeepL.com/Translator (free version))
Yuukou
The yukou is a small, evergreen, evergreen tree in the family Tangerineidae, a member of the same fragrant acid citrus family as the yuzu and daiji. Its name suggests a relationship with the yukou, a close relative of the yuzu grown in Tokushima Prefecture, but it is a
different species and is a unique native species that grows only in some
areas of Nagasaki, Nagasaki Prefecture [1].
Features
It resembles a yuzu in appearance, and as it matures, both the skin and flesh turn bright yellow, and the
skin has a sweet smell similar to that of a yuzu or pomelo. The flesh has a pleasantly sour taste, with lots of water and seeds, and the
white part of the rind is edible[2]
Distribution
It grows in the Doinokubi and Sotomi districts of Nagasaki City, Nagasaki Prefecture. According to the National Agricultural Research Institute, it is assumed to be an
accidental cross between yuzu and pomelo,[3] but its history is not known. Several seedling trees over 100 years old are known to exist, which suggests that they may have already existed in the late Edo to early Meiji periods[4].
However, no Yukkou trees have been found in other villages of Christians in hiding, so the causal relationship between them is unknown. Many people believe that it was spread in the Gaihai area, where many Christians still live today, by the French priest (or priest) Marc-Marie de Roe (1840-1914), who worked hard to improve the lives of the villagers in those days,[4][5] who was unable to see the poverty of the villagers.
In the settlements of Dezu and Ohno in Sotomi, which have been inscribed on the World Heritage List as a heritage site related to latent Christians in the Nagasaki and Amakusa regions, Yuhkoh's agricultural landscape is also considered a cultural landscape as an important cultural landscape under the Cultural Properties Protection Law.
Usage
Some of them measure more than
12 degrees of sugar, the highest among citrus fruits, and can also be
enjoyed as a fresh fruit. In addition, it is not limited to edible uses such as vinegar, seasoning, flavoring, condiments, snacks, and beverages, but is also used by a wide range of people as a substitute for lotion and throat remedies, and to float in baths, etc. [6].
A Japanese restaurant "Kappo Restaurant Toshi" in Nagasaki City developed its own ponzu with "Yuuko" vinegar, which won the International Taste Award by the International Taste Testing Institute (iTQi) from 2013 to 2017 in succession [7]. Since 2014, it has also been certified by the Nagasaki Prefecture's branded agricultural products certification system, "Nagasaki Shikibata" [8].
Other
Recognized on October 31, 2008 by Slow Food, a global non-profit organization that works to revise traditional food culture and ingredients, the Ark of Taste, a project to protect rare ingredients [9].
YUKO
The yukou (Citrus yuko) is a small evergreen evergreen tree in the citrus family. A fragrant acid citrus fruit, the f
ruit is larger and more fragrant than yuzu,[2] and is also spelled yuzhuang[1].
Distribution
It is a
variant of the yuzu tree born by natural hybridization and is native to Japan[1]. It has long been cultivated in Tokushima and Kochi prefectures, and before the great cold wave of 1981 (1981), old trees estimated to be over 150 years old were scattered throughout Tokushima Prefecture [1].
Domestic production areas
While Tokushima Prefecture is known throughout the country for its sudachi (Castanopsis cuspidata var. sudachi), this yukou also accounts for more than 99% of national production. (The 2010 harvest in Japan was 397.5 tons, of which 395 tons were produced in Tokushima Prefecture [3]). Kamikatsu-cho accounts for the majority of this. Because of its
poor cold resistance compared to yuzu and sudachi,
the great cold wave of 1981 resulted in a decrease in the area of the plantation. In addition, it is often used as a substitute for sudachi, and in recent years the production volume has been decreasing year by year, falling to about 40% of its peak due to the sluggish demand for processed products and the lack of expected transaction prices due to its inferiority to sudachi in terms of name recognition.
However, towns, agricultural cooperatives, and the venture company "Irodori" have developed and sold seasonings and confectionery products, and as a result of their steady efforts to spread the use of the vinegar, its name recognition has gradually spread, and demand for it has increased in the Keihanshin area. In addition, production in Kamikatsu-cho has remained unchanged since 2006, due to its
resistance to disease and the lack of spines on its branches, which makes it easier to pick fruit than yuzu.
Utilization
Because of its
strong aroma and mild taste, the fruit is pressed and used for processing. In addition to being sold as a fruit vinegar, it is
often combined with yuzu juice and sudachi juice to make ponzu (citrus fruit juice). In the local Kamikatsu town, it is also a valuable ingredient in home-style cooking, and has been used in some cases, such as in brewing vinegar to accompany sushi rice.
The fruit is
not commercially available as of 2017. In the past, the fruit was allowed to overstay its welcome
after the fruit was harvested, and the following spring, when the acidity was removed and the sugar content increased to the point where it was sticky to the touch, the sweetened fruit was eaten as a snack. There was also a method of harvesting the blue berries(fruit with green rind?) and burying them in the soil covered with kawashoubu leaves to make them fully mature[4].
Other Features
It is very
similar to a yuzu in appearance and skin color, but the
surface is smoother than a yuzu. Also, the apex of the fruit has no oil vacuoles and is slightly concave.Translated with
www.DeepL.com/Translator (free version)