Eutrema japonicum

Eutrema japonicum

Wasabi or Japanese radish (Eutrema japonicum (Miq.) Koidz.) Is a herbaceous species belonging to the Brassicaceae family.

Systematics –
From a systematic point of view it belongs to:
Eukaryota Domain,
Kingdom Plantae,
Magnoliophyta Division,
Magnoliopsida class,
Capparales Order,
Brassicaceae family,
Genus Eutrema,
E. japonicum species.
The terms are synonymous:
– Alliaria wasabi (Siebold) Prantl;
– Cochlearia wasabi Siebold;
– Eutrema japonicum f. terrestris (Makino) Nemoto;
– Eutrema japonicum var. sachalinensis (Miyabe & T.Miyake) Nemoto;
– Eutrema okinosimense Taken.;
– Eutrema wasabi (Siebold) Maxim.;
– Eutrema wasabi f. terrestris Makino;
– Eutrema wasabi var. sachalinensis Miyabe & T.Miyake;
– Lunaria japonica Miq.;
– Wasabia japonica (Miq.) Matsum.;
– Wasabia okinosimensis (Taken.) Hatus.;
– Wasabia pungens Matsum.;
– Wasabia tenue var. okinosimense (Taken.) Kitam.;
– Wasabia wasabi (Siebold) Makino.

Etymology –
The term Eutrema is of uncertain origin.
The specific epithet japonicum is related to its Japanese origin.

Geographic Distribution and Habitat –
Eutrema japonicum is a plant of Japanese origin that, in its natural state, grows spontaneously near rivers in cold areas of Japan, such as in the mountains or in high-altitude valleys.
It is a widespread and cultivated plant, as well as in Japan, in some areas of Asia.
Its habitat is that of humid places and along waterways, both in the plains and in the mountains.

Description –
Wasabi is a semi-aquatic herbaceous plant that can reach a height of 0.30 meters.
The roots are just over a cm thick and up to 18 cm long.
The leaves, which branch off from long stems from the level of the collar, are roundish ovate in shape, with an intense green color and clearly visible veins.
The flowers are small, composed of 4 petals and are separated forming a dialipetala corolla. There are also 4 sepals. There are 6 stamens, 4 of which cross like the petals and 2 shorter external ones.
The ovary is superior and bicarpellar.
The fruit is a dry and dehiscent siliqua.

Cultivation –
Eutrema japonicum is a perennial plant that is grown or harvested in nature for local use as a food and medicine.
The plant is native to Japan, where it grows wild along streams protected by large trees that provide abundant shade.
The plant can be grown provided the soil is moist enough or in shallow, shady water.
Plants grow with temperate temperatures as long as they do not exceed about 27 ° C.
The roots of this plant are used, for their spiciness, and those of the best quality are obtained from plants that grow in semi-shade in clear waters and spring currents at a temperature between 11 – 14 ° C.
This species is grown in East Asia for its edible root which is used in much the same way as horseradish.
The two most common cultivars on the market are E. japonicum var. Daruma and var. Mazuma but many others are cultivated.
Propagation occurs by seed. Sowing should be done in spring taking care to keep the soil moist.
The transplant must be carried out when the seedlings have reached a manageable size in the period from late spring to early summer.
It can also multiply by division in spring when the plant is in vegetation.
Larger divisions can be transplanted directly into the open field.

Customs and Traditions –
Eutrema japonicum is a plant from whose rhizomes wasabi is obtained, however all parts of the plant are edible, so both leaves and flowers can be eaten while waiting for the rhizome to develop to be harvested around 18 months.
The fleshy rhizomes are finely grated and prepared into an attractive fresh green paste that has been widely used as a condiment in Japan for over a thousand years.
A sauce is obtained, precisely wasabi (山葵), with a pasty consistency, so much so that it is distributed on the market in tubes similar to that of toothpaste.
Both the leaves and the rhizome of the plant are used: the former are dried and added to dishes as a seasoning; the second, a perennial shoot of the plant often confused with the root, is used to prepare the famous green sauce, with a deep and bold spiciness.
However, rhizomes of other species such as Cardamine pseudowasabi can also be used in the preparation of wasabi.
In fact, given its high cost, wasabi often lends itself to falsifications. In Japan, real wasabi is called hon-wasabi (本 山葵), which means “original wasabi”.
Wasabi is also nicknamed namida, meaning “tears”, because if used in excessive quantities it can cause tears. Unlike chilli, whose effect acts mainly in the mouth, wasabi strongly stimulates the nasal mucosa and a bite in which there is an overdose of wasabi can cause pain that leads to tearing. However, the pain is short-lived and does not persist like that of hot peppers. It is said to have an antibacterial and digestive function which would make it indispensable when eating raw fish.
According to the work of a group of researchers from the Faculty of Medicine of the University of Florence, published by the US journal Proceedings of the national academy of sciences (Pnas), the regular consumption of wasabi would be able to raise the pain perception threshold, thanks to the effect of wasabi receptor (Trpa1).
From the biochemical point of view, the leaves contain about 6.1% of proteins, 0.2% of fats, 22.3% of carbohydrates, 1.3% of ashes.
The molecules that also give wasabi its unmistakable aroma are isothiocyanates including: 6-methylthiohexyl isothiocyanate, 7-methylthioeptyl isothiocyanate and 8-methylthioctyl isothiocyanate.
Among the other uses of this plant it should be remembered that the leaves of Eutrema japonicum are used dry as a flavoring to flavor salads, cheese or simply bread. A wine and a strong liqueur sold in Japan by local specialty shops are also obtained from the same plant.
In Japanese-style cheap restaurants as well as in supermarkets and markets there are almost always pastas similar to wasabi, in fact a substitute: the most frequent are made with colored horseradish powder, often with Spirulina microalgae.

Preparation Method –
The fleshy rhizomes are finely grated and prepared into an attractive fresh green paste that is widely used as a condiment in Japan. This paste has a notable spiciness which, when fresh, deteriorates rapidly once the root is cut. 15 – 24 month old plant roots are best.
You can use the leaves, flowers and petioles of this plant, cooked.
The leaves, flowers, leaf stems and freshly sliced ​​rhizome are soaked in salted water and then mixed with saki lees to make a popular Japanese pickle called ‘wasabi-zuke’.
Wasabi is available in paste and powder form. Wasabi loses its aroma when dried, so wasabi powders do not retain its aroma. Horseradish, along with other spices, is usually added to real wasabi to reproduce the typical smell of fresh product that is lost with drying.
Wasabi paste is often used to accompany raw fish and, in particular, sushi and sashimi, sometimes dissolved in soy sauce. In sushi, a small amount is spread between the fish and the rice; in sashimi it dissolves in soy sauce, in which raw fish is then dipped.

Guido Bissanti

Sources
– Acta Plantarum – Flora of the Italian Regions.
– Wikipedia, the free encyclopedia.
– GBIF, the Global Biodiversity Information Facility.
– Useful Tropical Plants Database.
– Conti F., Abbate G., Alessandrini A., Blasi C. (ed.), 2005. An annotated checklist of the Italian vascular flora, Palombi Editore.
– Pignatti S., 1982. Flora of Italy, Edagricole, Bologna.
– Treben M., 2000. Health from the Lord’s Pharmacy, Advice and experiences with medicinal herbs, Ennsthaler Editore.
Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/84486999/original.jpeg

Warning: Pharmaceutical applications and alimurgical uses are indicated for informational purposes only, they do not represent in any way a medical prescription; therefore no responsibility is taken for their use for curative, aesthetic or food purposes.