When Japanese Horseradish or Wasabi is purchased in powdered form, it is mixed with water to produce a thick paste-like condiment. The ground version of Wasabi typically contains very little of the Wasabi plant, but may contain dried Wasabi leaves. Most often, ground Wasabi is basically a powder made from horseradish, mustard powder, cornstarch, food coloring, and possibly a little fresh Wasabi. Since fresh Wasabi is difficult to keep, it is not uncommon to find that a blend of horseradish and green food coloring has been combined that is referred to as "Wasabi" or Wasabi Paste on a menu or ingredient listing. Wasabi Paste labeled as "Prepared" Wasabi is a mixture of horseradish, artificial flavor, artificial coloring, and miscellaneous ingredients. Wasabi Paste labeled as "100% Real Wasabi" will typically be the genuine ingredients using Wasabi root and no horseradish. However, to be sure, check the listing of ingredients on the product label.
Japanese Horseradish products are most often used in raw fish dishes, such as sushi or sashimi as well as for serving with various varieties of cooked fish, noodle dishes, salads, and for making into sauces, dips or marinades. It is a common flavoring for soba and udon noodle dishes as well as for meats, seafoods, and dim sum. Other ingredients such as soy sauce (Wasabi-joyu) or rice wine may be blended with fresh Wasabi or Wasabi paste to provide added flavor.