Week 2: Wasabi

Wasabi rhizome

Sushi wouldn’t be complete without a traditional mound of wasabi, but sushi lovers rarely ever get real wasabi.


The pistachio-green paste is often just a blend of European horseradish, mustard, and food coloring. Even in Japan authentic wasabi is in short supply.


The discovery of real wasabi dates back to the 10th century when a farmer first cultivated it and showed it to a Japanese warlord who later became Shogun. The warlord liked it so much he declared it a treasure only to be grown in the Shizuoka area.

Wasabia japonica plants are slow growing perennials with a thick stem or rhizome, long petioles and large leaves. All parts of the wasabi japonica plant, including rhizomes, roots, stems and leaves are harvested, processed and valued for use. The rhizome looks a lot like a brussel sprout stalk after the sprouts are removed. It is a member of the Brassicaceae family, which also includes cabbages, horseradish, and mustard. Because the burning sensations of wasabi, which are felt primarily in the nasal passage, are not oil-based, they dissipate quickly and are diluted with additional food or liquid. The flavor is affected by how finely the wasabi is grated. The traditional way to grate wasabi is with a sharkskin grater, called an oroshi, which resembles fine sandpaper.

During a trip to Japan a few years ago, my husband and I took a side trip to the Daioo Wasabi Farm to learn more about the commercial cultivation of wasabi. We took a local train east from Matsumoto (Nagano Prefecture) to Hotaka, a small farming town, where we rented bikes.  Having been at the mercy of trains and buses for several days, the freedom of biking through the countryside on three-speed bikes with baskets was a joy.

Daioo is an old-style wasabi farm with rickety water mills used for grinding the wasabi root into that green paste we all know and fear. Wasabi is very temperamental to grown because it needs a special balance of soil minerals and cold, clear water. It’s growing practices are carefully-guarded secrets and the supply of genuine wasabi japonica is limited. The wasabi at Daioo is grown in screen-shaded gravel beds (to simulate the conditions under a natural forest canopy) and fed with a constant supply of fresh water from a river that fed into the larger Saigawa River.

Screen-shaded wasabi beds

Screen-shaded wasabi beds

Wasabia japonoica plants are usually harvested two years after planting but can take as much as three years to reach maturity. Normally the rhizome will is approximately six to eight inches in length and an inch or so in diameter when it is harvested.

The wasabi harvest

The wasabi harvest

Culinary Uses

Wild wasabi was first used to season raw trout, raw venison and pickled vegetables. Tasting at Daioo included a variety of products made from wasabi – including ice cream!  My favorite were the potato cakes (similar to McDonald’s hash browns) served with squeeze bottles of wasabi mayonnaise.

Cleaning the wasabi rhizomes

Cleaning the wasabi rhizomes

Health Benefits

Wasabia japonica has powerful anti-bacterial properties and also kills some forms of E-Coli and Staphylococcus.  Studies also indicate it helps reduce mucous, which has made it the focus of experiments relating to its use in combating asthma and congestive disorders.  It is very low in Saturated Fat, Cholesterol and Sodium.  It is a good source of Vitamin B6, Calcium, Magnesium, Potassium and Manganese, and an excellent source of Dietary Fiber and Vitamin C.


Nutrition Data. http://www.nutritiondata.com

Real Wasabi. http://www.realwasabi.com

Arnaud, Celia Henry. “Wasabi: In condiments, horseradish stands in for the real thing.” Chemical & Engineering News.

Wikipedia. http://www.wikipedia.com

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