Horseradish (Armoracia rusticana, syn. Cochlearia armoracia) is a perennial plant of the Brassicaceae family, which also includes mustard, wasabi, and cabbages. The plant is probably native to southeastern Europe and western Asia, but is popular around the world today. It grows up to 1.5 metres (five feet) tall and is mainly cultivated for its large white, tapered root.
The horseradish root itself has hardly any aroma. When cut or grated, however, enzymes from the damaged plant cells break down sinigrin (a glucosinolate) to produce allyl isothiocyanate (mustard oil), which irritates the sinuses and eyes. Once grated, if not used immediately or mixed in vinegar, the root darkens and loses its pungency and becomes unpleasantly bitter when exposed to air and heat.
Both root and leaves were used as a medicine during the Middle Ages and the root was used as a condiment on meats in Germany, Scandinavia, and Britain. It was brought to North America during Colonial times.
William Turner mentions horseradish as Red Cole in his "Herbal" (1551-1568), but not as a condiment. In "The Herball, or Generall Historie of Plantes" (1597), John Gerard describes it under the name of raphanus rusticanus, stating that it occurs wild in several parts of England. After referring to its medicinal uses, he says: "the Horse Radish stamped with a little vinegar put thereto, is commonly used among the Germans for sauce to eate fish with and such like meates as we do mustarde."
In the USA, prepared horseradish is commonly used as an ingredient in Bloody Mary cocktails, in cocktail sauce, as a sauce or spread on meat, chicken, and fish, and in sandwiches. The American fast-food restaurant chain Arby's uses horseradish in its "Horsey Sauce", which is provided as a regular condiment, alongside ketchup, mustard, and mayonnaise. This is not a common practice at its major competitors. There are several manufacturers of prepared horseradish in the United States. The largest is Gold's Horseradish in New York which sells about 2.5 million jars each year.
Horseradish sauce made from grated horseradish root and cream is a popular condiment in the United Kingdom. It is often served with roast beef, but can be used in a number of other dishes also. Also popular in the UK is Tewkesbury mustard, a blend of mustard and grated horseradish originally created in medieval times and mentioned by Shakespeare. In the U.S., the term Horseradish Sauce refers to grated horseradish combined with mayonnaise or Miracle Whip salad dressing (such as Arby's "Horsey Sauce"). Kraft and other large condiment manufacturers sell this type of Horseradish Sauce.
In Eastern European Jewish cuisine, a sweetened horseradish-vinegar sauce called chrain in Yiddish traditionally accompanies gefilte fish. There are two varieties of chrain. "Red" chrain is mixed with red beet (beetroot) and "white" chrain contains no beet. It is also popular in Poland (under the name of chrzan), in Russia (хрен), in Hungary (torma), in Romania (hrean), and in Bulgaria (хрян). Having this on the Easter table is a part of Easter tradition in Eastern and Central Europe. A variety with red beet also exists and it is called ćwikła z chrzanem or simply ćwikła in Poland. Horseradish (often grated and mixed with cream, hardboiled eggs, or apples) is also a traditional Easter dish in Slovenia and in the adjacent Italian region of Friuli Venezia Giulia.
Horseradish is also used as a main ingredient for soups. In Polish Silesia region, horseradish soup is a main Easter Sunday dish.
Horseradish dyed green is often substituted for the more expensive wasabi traditionally served with sushi, even in Japan. The Japanese botanical name for horseradish is , or "Western wasabi".
The enzyme horseradish peroxidase, found in the plant, is used extensively in molecular biology for antibody detection, among other things. It is increasingly important in biochemical research fields.
Horseradish peroxidase (HRP) is commonly used for specifically coloring of thin (~5 micrometer) slices of tissue biopsies from patients suspected to have cancer. This is an area of human pathology called immunohistochemistry (IHC). Many molecules of HRP are bound to a polymer together with immunoglobulins that will bind to a primary immunoglobulin that recognizes a specific biomarker in cells in the tissue slices. The HRP will convert 3,3-diaminobenzidin (DAB) to a yellowish brown insoluble compound. This compound is visible in a microscope and helps the pathologist to diagnose the cancer. For more information see Histochemistry. Horseradish peroxidase has been employed in materials used to test for the presence of glucose in blood or urine .