Fresh wasabi is a rare and expensive delicacy that deserves proper handling. Like any vegetable, wasabi is at its best when served as close to harvest time as possible, but since the vast majority of wasabi is grown in Asia, gourmands lucky enough to get their hands on true fresh wasabi know to consume it timely. If necessary, wasabi rhizomes can be kept in a refrigerator for up to 30 days or so. For best results the cleaned rhizome should be wrapped in damp paper towels and stored in the crisper drawer of the refrigerator.
It is the process of grating and preparation before serving that optimizes wasabi's unique pungent flavor. Traditionally, the fresh wasabi rhizome is washed, the top end is cut off and it is then pressed tightly against an "Oroshi" grater, a piece of sharkskin mounted on a wooden or ceramic paddle. Using a tight circular motion, the rhizome is carefully grated to produce a small pile of mashed plant particles. While the traditional oroshi is considered ideal, a small toothed or nubbed stainless steel or ceramic grater may be used, the finer the better. Some chefs also use the back of a knife to further crush the wasabi particles to maximize the release of flavors. Photos thanks to wiki free images
The purpose of grating is to break open the cells of the plant so that the chemical compounds contained within can intermingle and transmute. Technically, it is the exposure of wasabi's glucosinolates with the enzyme myrosinase that releases isothiocyanates, the active compounds that produce wasabi's unique taste and are also nutritionally beneficial.
When a suitable amount of wasabi has been grated, gather and press it by hand into a small ball and let it relax at room temperature so that the chemical process can take place. Like a fine old wine, the grated wasabi needs some time to breathe, but not too much time, to maximize its flavor. The compounds released are quite volatile and the flavor will dissipate with too much exposure to air.
Timing is important. Generally, about ten minutes after preparation is the optimum time to serve the prepared Real Wasabi™ paste. Be advised however, the flavor will "peak" after about twenty to thirty minutes. If this occurs and the meal is still ongoing, you can re-invigorate the flavors by vigorously re-mixing it and again regrouping it back into a tight little pile. Some chefs suggest adding a pinch of sugar to re-ignite the enzyme reactions. Adding some freshly grated wasabi will also help it gain a second wind.
MAKING A PASTE
To make genuine reconstituted wasabi paste from Real Wasabi powder, vigorously mix a measure of dried ground Real Wasabi™ with an equal amount of water. When thoroughly blended to the right consistency a (slightly dry, not soupy, paste), cover the dish and set it aside for ten to fifteen minutes to allow the enzymatic action to activate the full flavors.
Authentic Real Wasabi™ paste is terrific served as a condiment to accompany sashimi or sushi, or used in a host of creative ways to lend an exciting kick to sauces or spreads.
TIP: If by some chance you find yourself with leftover wasabi paste at the end of a meal (unlikely), blend it with a small amount of olive oil before storing it in the fridge. This will help preserve the flavor, at least for a day or so, that would otherwise be lost.