informational desert: Wasabi

Wasabi

Wasabi crop growing on Japan's Izu peninsula
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Brassicales
Family:	Brassicaceae
Genus:	Wasabia
Species:	W. japonica
Binomial name
*Wasabia japonica* Matsum.

Wasabi (ワサビ（山葵）^?, originally 和佐比; Wasabia japonica, Cochlearia wasabi, or Eutrema japonica), also known as Japanese horseradish^[1] is a member of the Brassicaceae family, which includes cabbages, horseradish, and mustard. Its root is used as a condiment and has an extremely strong flavor. Its hotness is more akin to that of a hot mustard rather than the capsaicin in a chili pepper, producing vapors that stimulate 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.^[2]

1 Uses
2 Chemistry
3 Cultivation
4 Preparation
5 Etymology
6 Gallery

Uses

Fresh wasabi root for sale at Nishiki Market in Kyoto

Wasabi is generally sold either in the form of a root which is very finely grated before use, or as a ready-to-use paste (either real wasabi or a mixture of horseradish, mustard, and food coloring), usually in tubes approximately the size and shape of travel toothpaste tubes.^[3] In some restaurants the paste is usually prepared as needed by the customer using the root and a grater directly; once the paste is prepared, it will lose flavor within 15 minutes.^[4] In sushi preparation, covering wasabi until served preserves flavor, and 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.
Because the burning sensations of wasabi are not oil-based, they are short-lived compared to the effects of chili peppers, and are easily washed away with another bite of food or liquid. The sensation is felt primarily in the nasal passage and can be quite painful depending on amount taken.
Inhaling or sniffing wasabi vapor has an effect like smelling salts, a property exploited by researchers attempting to create a smoke alarm for the deaf. One deaf subject participating in a test of the prototype awoke within 10 seconds of wasabi vapor being sprayed into his sleeping chamber.^[5]
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. Due to the expense and difficulty of cultivating wasabi, a very widely used substitute (imitation wasabi) is a mixture of (western) horseradish, mustard, and green food coloring; in American sushi restaurants this is generally referred to as "wasabi", while genuine wasabi, which is rarely available, is referred to as "fresh wasabi". Similarly, when wasabi is sold in tubes, the contents may be genuine wasabi, or it may be horseradish, mustard, and green food coloring, or it may be a mixture of the two. In Japan, horseradish is referred to as seiyō wasabi (西洋わさび^?, "western wasabi").^[6]
Legumes (peanuts, soybeans, or peas) may be roasted or fried, then coated with wasabi powder mixed with sugar, salt, or oil and eaten as a crunchy snack.

Chemistry

The chemical in wasabi that provides for its initial pungency is the volatile allyl isothiocyanate, which is produced by hydrolysis of natural rhizome thioglucosides (conjugates of the sugar glucose, and sulfur-containing organic compounds); the hydrolysis reaction is catalyzed by myrosinase and occurs on when the enzyme is released on cell rupture caused by maceration—e.g., grating—of the plant's rhizome.^[7]^[8]^[9]
The unique flavor of wasabi is a result of complex chemical mixtures from the broken cells of the rhizome, including those resulting from the hydrolysis—glucose, and other methylthioalkyl isothiocyanates:^[10]^[11]^[12]

6-methylthiohexyl isothiocyanate,
7-methylthioheptyl isothiocyanate, and
8-methylthiooctyl isothiocyanate.

Research has shown that such isothiocyanates inhibit microbe growth, perhaps with implications for preserving food against spoilage and suppressing oral bacterial growth.^[13]

Cultivation

A drawing of a wasabi plant, published in 1828 by Iwasaki Kanen

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:

There are also numerous artificially cultivated facilities as far north as Hokkaidō and as far south as Kyūshū. As the demand for real wasabi is very high, Japan has to import a large amount of it from Mainland China, Ali Mountain of Taiwan, and New Zealand.
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.

British Columbia, Canada
North Carolina, United States

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.

Preparation

Wasabi is often grated with a metal oroshigane, but some prefer to use a more traditional tool made of dried sharkskin (鮫皮) with fine skin on one side and coarse skin on the other. A hand-made grater with irregular teeth can also be used. If a shark-skin grater is unavailable, ceramic is usually preferred.^[14]

Etymology

The two kanji characters "山" and "葵" do not correspond to their pronunciation: as such it is an example of gikun (meaning, not sound). The two characters actually refer to the mountain Asarum, as the plant's leaves resemble those of a member of Asarum species, in addition to its ability to grow on shady hillsides. The word, in the form 和佐比, first appeared in 918 in The Japanese Names of Medical Herbs (本草和名 Honzō Wamyō). Spelled in this way, the particular kanji are used for their phonetic values only, known as ateji (sound, not meaning – opposite of gikun).