We have traveled to see wasabi grow in terraced river flowing pools made up of thousands of wasabi roots. These fields have a constant flow of icy fresh water passing over and around fresh wasabi. Fresh wasabi from the most famous region Shizuoka Japan is delicious and sold through Japan.
I am told that wasabi’s hotness varies according to the outside temperature and I somehow believe it. The one thing about wasabi which is true, it that at different times of the year it’s more hot or even more spicy. Sometimes it has a powerful bite but rarely close to what you get from powdered wasabi, or the tubular wasabi.
There is also no doubt that after grating it develops some more flavour and so oxidation plays a role, but more importantly as cell walls are split, friction occurs and its flavors are released. Fresh wasabi is in no way comparable to the chemical faux green wasabi sold outside of Japan.
So if you decide to buy wasabi, you’ll need to invest in a Oroshigane (a grater) that you see in the photos attached: this is the perfect tool for wasabi or ginger and will last you a life time.
One last thing, if you buy a grater, be very careful not to underestimate the little teeth on the surface as they will cut you much more than you think.