What makes hot mustard hot? Readers frequently ask this question. I can understand their confusion. After all, the recipe for hot mustard is quite simple: dry mustard, cold water, perhaps some rice wine. What is it about this seemingly simple preparation that gives China's most popular table condiment its strong bite?
The answer lies in the chemical properties of mustard seeds. Mustard seeds come from the mustard plant, a member of the cabbage family. They contain two sulphur compounds, myrosin and sinigrin, as well as an enzyme, myrosinase. When the seeds are broken and water is added, the enzyme breaks down the sulphur compounds. The result is the sharp tasting oil that gives mustard its pungency, and helps explain why the name mustard comes from the Latin words mustum (much) and ardens (burning).
In the case of prepared mustards, the 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. For example, France's world famous Dijon mustard is made with strong brown or black mustard seeds, verjuice (the juice of unripened grapes) and/or a white wine or wine vinegar, cloves, cinnamon and other seasonings. This gives it a distinctive taste worlds apart from the plain yellow mustard you pour on your hotdog.
By contrast, Chinese hot mustard is made with dry mustard - mustard that has been dried sufficiently so that when crushed it forms a powder. Asian markets and online stores carry Chinese mustard powder which, like Dijon, is made with the stronger brown mustard seeds, called Brassica juncea. However, English Colman's dry mustard powder, made by blending the flavorful brown seeds with the less pungent white mustard seeds, is a perfectly acceptable substitute.
How do you transform mustard powder into hot mustard? If you prefer a hot, pungent mustard, all you need to do is add cold water, mix, and wait about fifteen minutes for the reaction to fully develop. The only thing to remember is that after the mustard reaches its peak strength at that point, it slowly begins to decline. If you're not using it immediately, adding an acid such as vinegar or rice wine will stop the reaction and prevent the mustard from losing its sharp edge. However, some people argue that the acid hides some of the mustard's flavor. While the effect is subtle, I do agree it exists, so as an alternative you may want to store the hot mustard in a sealed container in the refrigerator, as refrigeration also stops the reaction from progressing. If you want a hot mustard that's not quite as strong, adding salad or cooking oil to the mustard powder and water tones down the process somewhat. So does adding boiling water, but it also changes the taste.
Hot mustard's raw bite goes well with most Chinese appetizers, and is the perfect accompaniment for egg rolls. An added plus is that mustard is low in both fat and calories.
Hot Mustard - a basic recipe
Hot Mustard with Eggs and Sugar