What Is Wasabi?

Wasabi (Eutrema japonicum), also known as Japanese horseradish, is a plant in the mustard family (Brassicaceae) that is made from the ground rhizomes of a hot paste. The plant is native to Japan, Korea, and Sakhalin, Russia, and its cultivation is restricted due to its specific growing requirements. Given that real wasabi rhizomes are expensive and in limited supply, Western restaurant mustard sauces are often made from Armoracia rusticana, another plant in the mustard family.

Mustard plants grow in mountain and valley streams. It can be difficult to grow even in ideal conditions similar to creek banks, as the plants require cool, moist and shady conditions and are susceptible to disease. The rhizomes can take up to three years to mature, and any damage to the brittle leaves by farm workers or animals will slow their growth. Due to strict environmental regulations, wasabi is mainly grown commercially in Shizuoka Prefecture, Japan, particularly the Izu Peninsula, as well as Iwate and Nagano prefectures. There are different types of wasabi grown in Japan, each associated with a different quality of wasabi rhizomes. Traditional methods tend to use small amounts of fertilizer, rely on mineral-rich springs and manual labor with minimal impact on the environment. Fields are carefully landscaped with stone and gravel to replicate the plants’ natural habitat and accommodate mild flooding, and some have been producing continuously for hundreds of years.

Mustard has also been successfully grown in China, Korea, Taiwan, New Zealand and the United States, albeit usually on a smaller scale. Growing plants in a greenhouse or using hydroponics has had limited success, and these operations are expensive.

What is wasabi and how should you use it?

Wasabi is best known as a spicy green paste used as a condiment for all kinds of sushi. But you can spice up any recipe with mustard, like these mustard beef fajitas. Real wasabi is made from the rhizome of the wasabi plant (like a plant stem that grows underground, you would expect roots).

Its characteristic clean spiciness comes from allyl isothiocyanate, not the capsaicin in chili peppers. (How does your favorite chili rank on the Scoville Spicy Scale?) As a result, people sometimes describe a mustard-spiced sensation that “gets into their noses” when they take a bite. Mustard’s smell receptors are tightly packed in our nostrils!

How does the mustard taste?

Really freshly grated mustard tastes bright green with a hint of heat that disappears quickly. It was spicy but tender enough to bring out the flavor of the raw fish. The heat of the wasabi served with the sushi is to bring out the flavor of the fish, not mask it.

At the best sushi restaurants, chefs will distribute wasabi onto each piece of sushi (usually nigiri) to balance out the rich flavor of the fish.

Fake “mustard” burns hotter and longer because it’s made from horseradish and sometimes mustard. Too much of this imitation wasabi can completely mask the delicate taste of the sushi.

What is the most “mustard” made of?

True mustard plants belong to the cruciferous family. Horseradish, radish, and mustard are also part of this family and have a pungent taste similar to mustard. Because authentic wasabi is expensive, most wasabi found in grocery stores and in prepackaged sushi is made with horseradish powder and artificial coloring. It may also contain mustard powder and thickeners such as flour or cornstarch. If you like horseradish zip, try these horseradish recipes.

How to distinguish real and fake mustard?

To identify fake mustard, first look at the texture. A mushy and thick consistency is a hallmark of mustard-mimicking (horseradish is usually pureed until smooth). Real mustard has a grated grainy texture.

To capture the greatest possible flavor, real mustard is always freshly grated. The traditional method of rubbing is to rub the roots in a circle around the shark skin, which acts like sandpaper, and cut very fine pieces of mustard from the roots.

What makes real wasabi so expensive?

The Wasabia japonica plant is very difficult to grow because it requires partial submersion in running water, which is not a common agricultural structure. In Japan, wild wasabi grows on rocky river beds. According to the BBC, it is also a delicate plant that will die from small changes in the environment or humidity.

Most wasabi is grown in Japan, although a few farms have popped up in North America. Why grow such delicate plants? Because rhizomes can fetch upwards of $75 a pound. This extreme cost is also why you’ll see the original in most restaurants rather than grocery stores.