Horseradish is a vegetable which is cultivated for its distinctively flavored root, which in no way resembles a horse. If you're wondering about the inclusion of “horse” in horseradish, it dates to the late 1500s, when “horse” was used to infer that something was extremely strong or coarse. Horseradish root is certainly powerful in flavor, and it was a common condiment among the lower classes, who are often considered coarse. Horseradish root is a very popular condiment in many parts of the world, including the United States, Japan, and Eastern Europe. Many stores sell prepared horseradish root, consisting of the ground or grated root pickled in vinegar. In some regions of the world, it is also possible to find whole roots at the market.
The formal name for horseradish is Armoracia rusticana. The plant is a crucifer, meaning that it is in the mustard family, along with an assortment of similarly flavored vegetables. The peppery, biting flavor of mustard is very strong in horseradish root, and it can sometimes be almost caustically spicy. Above ground, the plant has small clusters of open flowers and large roughly lobed leaves, causing it to look much like mustard or wild radish.
A whole horseradish root is actually relatively inert. When the cells in the root are crushed and broken, however, they release volatile oils in a chain reaction. Vinegar will stop the reaction, which is why horseradish root is traditionally prepared with vinegar when it is served fresh. Depending on the strength desired, cooks may grate the root and wait a few minutes before adding vinegar, or they may add vinegar right away.
Once grated, horseradish root will quickly lose potency. Storing it in the fridge or freezer can help to preserve the flavor, while cooks who like their horseradish spicy usually keep whole roots on hand. The whole root vegetable has snowy white flesh and a flaky brown exterior. It can be stored in a cool dry place, well wrapped, for several months.
Several commercial preparations of horseradish are available. Grated horseradish root can be pickled in vinegar so that it will remain shelf stable for several months, although the older the package, the less strong it will be. Horseradish root is also ground into a powder which can be reconstituted with water. In addition, fresh roots may be mixed with mustard to give it a particularly powerful bite. The spicy condiment pairs well with a number of foods, including roast meats and sandwiches.