Wasabi (わさび,ワサビ , 山葵 (originally written 和佐比); Wasabia japonica , Cochlearia wasabi, or Eutrema japonica) is a member of the Brassicaceae family, which includes cabbages, horseradish and mustard. Known as "Japanese horseradish", its root is used as a spice and has an extremely strong flavor. Its hotness is more akin to that of a hot mustard than the capsaicin in a chili pepper, producing vapors that irritate the nasal passages more than the tongue. The plant grows naturally along stream beds in mountain river valleys in Japan. There are also other species used, such as W. koreana, and W. tetsuigi. The two main cultivars in the marketplace are W. japonica cv. 'Daruma' and cv. 'Mazuma', but there are many others.
Wasabi is generally sold either in the form of a root (real wasabi), which must be very finely grated before use, or as a ready-to-use paste (horseradish, mustard and food coloring), usually in tubes approximately the size and shape of travel toothpaste tubes. Once the paste is prepared it should remain covered until served to protect the flavor from evaporation. For this reason, sushi chefs usually put the wasabi between the fish and the rice.
Fresh leaves of wasabi can also be eaten and have some of the hot flavor of wasabi roots. They can be eaten as wasabi salad by pickling overnight with a salt-and-vinegar-based dressing, or by quickly boiling them with a little soy sauce. Additionally, the leaves can be battered and deep-fried into chips.
Wasabi is often served with sushi or sashimi, usually accompanied with soy sauce. The two are sometimes mixed to form a single dipping sauce known as Wasabi-joyu. Legumes (or peas) may be roasted or fried, then coated with a wasabi-like mixture (usually an imitation); these are then eaten as an eye-watering "in the hand" snack.
Recent studies have also shown that wasabi contains a natural chemical that can be used against certain cancer cells. This unique root vegetable can also be used for oral hygiene and infections. It has been suggested that Wasabi can help prevent cardiovascular diseases like stroke, heart attack, and hypertension. This root may also help with diarrhea, osteoporosis, asthma, arthritis, and allergies as well.
Research has shown that isothiocyanates have beneficial effects such as inhibiting microbe growth.
Few places are suitable for large-scale wasabi cultivation, and cultivation is difficult even in ideal conditions. In Japan, wasabi is cultivated mainly in these regions:
In North America, a handful of companies and small farmers are successfully pursuing the trend by cultivating Wasabia japonica. While only the Pacific Northwest and parts of the Blue Ridge Mountains provide the right balance of climate and water for natural cultivation of sawa (water grown) wasabi, the use of hydroponics and greenhouses has extended the range.
While the finest sawa wasabi is grown in pure, constantly flowing water, without pesticides or fertilizers, some growers push growth with fertilizer such as chicken manure, which can be a source of downstream pollution if not properly managed.
In Japanese, horseradish is known as ("Western wasabi").