It is the chemical reaction between two compounds, myrosin and sinigrin, that combines to turn up the heat when the cells of the seeds are broken and mixed with cold water. This combination results in mustard oil that can actually cause burning or blistering when it comes in contact with the skin, so be careful when making your own mustard.
The combination reaches its peak in fire and flavor about fifteen minutes after mixing and will quickly decline from that point on. The addition of an acidic element is added to prepared mustard to delay or stop the decline. However, the acidic agent often masks the true flavor of the mustard. Heat inhibits mustard's potency and flavor, so be sure the mixing liquid is unheated.
The white mustard seed variety is merely hot and tangy to the tongue, while the black and brown varieties carry their heat and pungency up to the nose, eyes, and forehead. The latter two have a more intense, longer-lasting flavor and pungency than the white. This is why the mild yellow mustard is made from the white seeds, and stronger mustards from darker seeds.
All parts of the plant are edible, including seeds, leaves, and flowers.
Mustard is the second most-used spice in the United States. Its usage is only exceeded by the peppercorn (usually in ground pepper form). And it's no wonder, since mustard works well with all types of meats, pork, poultry, and seafood. Most of us are used to standard yellow prepared mustard, but there are many wonderful varieties of seeds and prepared mustards to experiment with.
More about Mustard:
Mustard Substitutions and Cooking Tips
Mustard Seed Types
Mustard Selection and Storage
What makes mustard hot? FAQ
Mustard Legend and Lore
Mustard and Health
Mustard Seed and Mustard Recipes
Mustard Photo © 2009 Peggy Trowbridge Filippone, licensed to About.com, Inc.