You’re eating a sushi place and notice a little nub of green paste on your plate. Be cautious: it’s really hot. Most of us experience wasabi either at Asian food places or as a spicy coating for peas or peanuts. However, that “wasabi” is probably not the real deal.
First, let’s get into what real wasabi actually is. It comes from a family of flowering plants. Other members of that family include cabbage and horseradish. Known officially as Wasabia Japonica, you can find real wasabi growing in Japan. The stems are the spicy part. How spicy? Pretty spicy, though it’s more of a “hot” sensation than a long-lasting, lingering spice. If you eat a big serving, it will feel like eating a habanero pepper, but wasabi heat is a short experience. To quell the burn, drink water, which is something that doesn’t really work with chili peppers. Wasabi gets its heat from isothiocyanates, which produce a vapor. That’s why you feel wasabi strongly in your nose.
When buying wasabi in Japan, the stems are often sold and then you grate them in your food yourself. You can buy them fresh and then grate them, or in powder or paste form. However, if you’re outside of Japan, the “wasabi” you’re eating is actually horseradish mixed with dry mustard and green food coloring. While from the same family, there’s a slight difference in their taste. Real wasabi is earthier, but less stinging than horseradish.
Why aren’t people using the real thing? Practicality is a big reason. Real wasabi is best when fresh and starts to lose its heat and spice very quickly. If you were to use the stems and grate them, the flavor starts to fade within mere minutes. The plants are also expensive to grow and buy, though if you do get your hands on a rhizome (the stem), it will last in the fridge for a month. Horseradish, however, is cheap and lasts a long time. The fake wasabi paste in tubes has a long expiration date, too, so it’s just easier for restaurants.