Wasabi is a culinary condiment of Japanese origin most closely associated with sushi, a dab of it smeared between a slice of raw seafood and a morsel of vinegar flavored rice. Made fresh, it is the root of the commonly called Japanese horseradish plant grated into a wet paste. The plant, however, is very difficult to commercially cultivate and to freshly transport. As a result, wasabi powder is the most widely distributed form of the product. Furthermore, it is usually not even made from real wasabi.
Even in Japan, or in a few other countries which have successfully farmed the plant, fresh wasabi root is rarely available, and very expensive where sold. A squeeze tube of wasabi is more common, but once the root is grated, wasabi quickly starts to lose its signature pungency. Any commercial “fresh pastes” will, therefore, have been re-formulated with preservatives and flavorings. You are most likely to find wasabi powder instead, packaged in small tins, at your local ethnic markets, and the only advice for choosing the best one is to read its ingredients list.
Fresh wasabi is pale green in color, but it oxidizes very quickly, turning more brown. Its taste is hard to describe, somewhat earthy and grassy. Closely related to the common horseradish root vegetable, the scientifically named Wasabia japonica also contains so-called mustard oils that irritate the nasal and sinus passages of your head when eaten. Some people wince and complain that its effect is painful.
When choosing your wasabi powder, it is important to keep in mind that most preparations sold at public markets are not actually made with wasabi. They are a powder of the more common horseradish made green with artificial food-coloring. Sometimes, they are mustard powder, also colored green. This shouldn’t dissuade you, however, from purchasing it. Except at the most expensive Japanese sushi restaurants, the majority of establishments uses this wasabi powder.
If you can find wasabi powder whose packaging container only lists its ingredient as “Japanese horseradish,” with perhaps a bit of cornstarch to keep the powder dry, you are in luck. Another indication of true wasabi will be whether the origin of manufacture is listed as Japan, New Zealand, China or Taiwan. This is your absolute best choice.
Again by inspecting the ingredients list, your second best choice will be a mixture of Japanese horseradish with either mustard or regular horseradish powder. The latter tends to be the combination that is more potent in taste. Both will likely list the addition of green, and perhaps yellow, food coloring. Lastly, if the package does not contain real wasabi, your better choice is horseradish instead of mustard powder as the substitute.
To make wasabi, water is added and mixed a little bit at a time with the powder until it forms into a thick, somewhat sandy paste. It is a proven complement to soy sauce and many kinds of seafood. Creative cooks have discovered other uses for wasabi, such as in sauces and dressings, treating the condiment similarly to mustard paste. If you are going to use wasabi in your kitchen, there is one very important precautionary rule; almost never should you use or serve a large quantity of it.