What Is Wasabi?
If you've ever had sushi, chances are you've come across the spicy green paste known as wasabi. Usually, it shows up next to pickled ginger on a tray of sashimi or sushi rolls. So what is wasabi? Wasabi, or Wasabi japonica, is part of the Brassicaceae family. While we sauté or roast other cruciferous vegetables, like Brussels sprouts and kale, wasabi is most commonly used as a condiment or seasoning.
Related Recipe: Ginger-Wasabi Sauce
How Wasabi Is Prepared
The leaves of the plant are trimmed down to the stem by hand. The stem (or rhizome—a stem that extends underground) is then gently rubbed or grated with a fine grater, traditionally made of shark skin, into a paste. The fresh wasabi is then served raw as a condiment or is used to season sauces and other dishes. (Check out: Eight of the World's Healthiest Spices & Herbs You Should Be Eating.)
Related Recipe: Grilled Flank Steak Salad with Ginger-Wasabi Dressing
Horseradish or Wasabi?
The wasabi plant is considered one of the hardest plants to grow commercially in the world. It thrives under very specific growing conditions which are difficult to meet outside of Japan. There are only a few wasabi farms in North America. In the United States, there are farms in Oregon, North Carolina and Northern California. So, while we call the green paste served at most sushi restaurants "wasabi," it's probably not real wasabi; it's likely a horseradish paste combined with mustard and green food coloring. Wasabi is in the same family as horseradish and mustard and there are similarities in their flavor. They all contain a compound called allyl isothiocyanate (AITC). It's responsible for the sharp taste and smell. However, in wasabi, it only forms when it's rubbed into a paste. The full flavor of true wasabi only lasts for a few minutes and then it's gone, while horseradish holds the heat for much longer.
Most wasabi that you find in the grocery store is a mixture of several ingredients, some that include real wasabi, but only a small percentage. You can buy pastes and powders that can be reconstituted by adding water. And yes, if you can find it, you can buy real wasabi—in the form of a full, fresh rhizome straight from the farm—but it's very expensive. Your best bet for experiencing the real thing is finding a Japanese restaurant that offers it on their menu. Until then, our Western version of wasabi will have to do.