Dried and powdered
Wasabi (わさび（山葵）?, originally 和佐比; Wasabia japonica or Eutrema japonica), is a member of the Brassicaceae family, which includes cabbages, horseradish, and mustard. It is also called Japanese horseradish, although horseradish is a different plant (which is often used as a substitute for wasabi). Its stem is used as a condiment and has an extremely strong flavor. Its hotness is more akin to that of a hot mustard than that of 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. The two main cultivars in the marketplace are W. japonica'Daruma' and 'Mazuma', but there are many others.
Wasabi is generally sold either as a stem, which must be very finely grated before use, as dried powder in large quantities, or as a ready-to-use paste in tubes similar to travel toothpaste tubes. Because it grows mostly submerged, it is a common misconception to
refer to the part used for wasabi as a root or sometimes even a rhizome, while it is
fact the stem of the plant, with the characteristic pock marks where old leaves fell off
or were collected.
In some high-end restaurants, the paste is prepared when the customer orders, and
is made using a grater to grate the stem; once the paste is prepared, it loses flavor in
15 minutes if left uncovered. In sushi preparation, sushi chefs usually put the wasabi
between the fish and the rice because covering wasabi until served preserves its
Fresh wasabi leaves can be eaten, having the spicy flavor of wasabi stems.
Because the burning sensations of wasabi are not oil-based, they are short-lived compared to the effects of chili peppers, and are washed away with more food or liquid. The sensation is felt primarily in the nasal passage and can be quite painful depending on the amount consumed.
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. 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 sprayed into his sleeping chamber. The 2011 Ig Nobel Prize in Chemistry was awarded to the researchers for determining the ideal density of airborne wasabi to wake people in event of an emergency.
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 bymyrosinase and occurs when the enzyme is released on cell rupture caused by maceration — e.g., grating — of the plant's rhizome.
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 of thioglucosides into glucose and methylthioalkyl isothiocyanates:
Research has shown that such isothiocyanates inhibit microbe growth, perhaps with implications for preserving food against spoilage and suppressing oral bacterial growth.
Preparation Wasabi on a metal oroshiganegrater
Wasabi is often grated with a metal oroshigane, but some prefer to use a more traditional tool made of dried sharkskin 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.