Hot Chinese Mustard
from http://chinesefood.about.com/

Many Chinese appetizers are accompanied by Chinese hot mustard, a condiment that will provide a real bite. It is the mustard that Chinese take-out restaurant gives you in those little packets. You'll definitely feel the sinus-clearing heat with just a touch of this potent spice. You'll find this mustard served at Chinese restaurants both in the U.S., China, and Taiwan.

Chinese hot mustard can be bought premade or made fresh for each use by mixing a dry mustard powder with water, causing a chemical reaction that produces a sharp, spicy taste. Some recipes call for the addition of cooking or vegetable oil, which reduces the effect somewhat; sesame oil and rice vinegar may also be added.

Hot mustard's raw bite goes well with most Chinese appetizers and is the perfect accompaniment for egg rolls and spring rolls. It is also an ideal condiment for Chinese shrimp balls and deep-fried wontons, any appetizer which is deep-fried which mustard would compliment.

You may be surprised to learn what gives China's most popular table condiment its strong bite, especially considering its seemingly simple preparation. The answer lies in the chemical properties of mustard seeds. Mustard seeds come from the mustard plant, a member of the cabbage family, and contain two sulfur compounds—myrosin and sinigrin—as well as an enzyme, myrosinase. When the seeds are broken and water is added, the enzyme breaks down the sulfur compounds. The result is the sharp tasting oil that gives mustard its pungency.

If you can't find Chinese mustard powder, you can use English Colman's dry mustard powder as a perfectly acceptable substitute; it is made by blending the flavorful brown seeds with the less pungent white mustard seeds. In 1866, Colman perfected the technique of grinding mustard seeds into a fine powder without creating the heat which brings out the oil. The oil must not be exposed or the flavor evaporates with the oil.

Chinese Hot Mustard vs. Prepared Mustards

You may wonder how regular mustards are not just as spicy as Chinese hot mustard. In the case of prepared mustards, the enzyme reaction is toned down by using additives such as flour. The actual flavor of prepared mustard will depend on a number of factors, including the type of seeds used, how they are processed, and what spices are added. The brown mustard seeds used in Chinese hot mustard are stronger than the black and white mustard seeds used in some other types of mustard. By comparison, Dijon mustard is made with strong brown or black mustard seeds, verjuice (the juice of unripened grapes) and/or white wine or wine vinegar, cloves, cinnamon, and other seasonings.

Chinese Hot Mustard is one of those condiments you might not think of making yourself, but it’s quick and easy to prepare at home with mustard powder and water. That intense heat can be preserved to some point either by refrigerating the mustard at its peak, or adding a little vinegar to stabilize it, but this mustard is so quick and easy to put together; just equal parts mustard powder and cold water. I'd recommend making as much as you need when you need it and forget about trying to store it.