Pretty good article on wasabi that completely threw me off. This whole time its just really horseradish. Real wasabi loses its flavor after 15 minutes of being prepared.
http://www.huffingtonpost.com/entry/fake-wasabi-horseradish_us_561bd666e4b0082030a33959
http://www.huffingtonpost.com/entry/fake-wasabi-horseradish_us_561bd666e4b0082030a33959