In most cases, even in Japan, a mixture of ground horseradish and green food coloring, flavored with Chinese mustard, is served with sushi. Much more economical and practical
The demand is too high
The reason lies in the unbalanced relationship between supply and demand. The authentic wasabi, known as Wasabia japonica, born from the most expensive crop in the world: wholesale is sold at around 160 dollars (142 euros) per kilo. The semi-aquatic grass, native to the mountain streams of central Japan, is notoriously difficult to grow: once planted, it takes several years before harvesting, and even then it does not germinate if the conditions are not perfect.
Here's what we really eat
If you are enjoying the true wasabi, you are consuming the stem of a grated and powdered plant in a spicy paste. But it must be eaten immediately: the grated root loses its flavor in 15 minutes. So what is served to us with sushi is a mixture of ground horseradish and green food coloring, flavored with a pinch of Chinese mustard. Experts believe that this mix is passed off as wasabi in about 99% of cases. Horseradish has a chemical composition similar to wasabi which allows it to imitate its spiciness: the much cheaper "wasabi" based on horseradish also has the advantage of preserving the taste longer.
The real taste of wasabi
The Japanese have been growing wasabi for more than four centuries. "The real one has a unique flavor that first of all hits the nose, Explains 75-year-old Shigeo Iida, who is part of a family that has been cultivating wasabi for eight generations, as told in the Edwin Lee documentary, Wasabia Japonica. "Then comes the sweetness, followed finally by a spicy note".
The film describes a sustainable farming technique known in Japan as tatamiishi. The farms that adopt it are built on hills near the rivers, and exploit the force of nature, without using chemicals or fertilizers: from these crops come the best wasabi in the world. According to Edwin Lee, Japanese food aficionados would be very surprised if they tasted real wasabi. "And they would struggle to go back and appreciate the fake again, just like I did."