Horseradish

Horseradish is a perennial plant 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, tapering root. The horseradish root itself has hardly any aroma. When cut or grated, however, enzymes from the damaged plant cells break down sinigrin 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.