Mustard powder is used to season and marinate a variety of dishes. It usually contains about 80 % ground white mustard seeds, along with herbs, spices, and grains. When you add water to the mustard powder and combine to make a paste, it is much like table mustard. This paste is also used as an ingredient in sauces, salads, and vegetable dishes.
General information about mustard:
From Wikipedia: “Mustard is a condiment made from the seeds of a mustard plant (white/ yellow mustard, Sinapis alba; brown/ Indian mustard, Brassica juncea; or black mustard, B. nigra).
The whole, ground, cracked, or bruised mustard seeds are mixed with water, vinegar, lemon juice, wine, or other liquids, salt, and often other flavorings and spices, to create a paste or sauce ranging in color from bright yellow to dark brown. The taste of mustard ranges from sweet to spicy. ...
It is also used as an ingredient in many dressings, glazes, sauces, soups, and marinades. As a cream or as individual seeds, mustard is used as a condiment in the cuisine of India and Bangladesh, the Mediterranean, northern and southeastern Europe, Asia, the Americas, and Africa, making it one of the most popular and widely used spices and condiments in the world.”
“Mustard is most often used at the table as a condiment on cold meats. It is also used as an ingredient in mayonnaise, vinaigrette, marinades, and barbecue sauce. Mustard is also a popular accompaniment to hot dogs, pretzels, and bratwurst. In the Netherlands and northern Belgium it is commonly used to make mustard soup; which includes mustard, cream, parsley, garlic and pieces of salted bacon. Mustard as an emulsifier can stabilize a mixture of two or more immiscible liquids, such as oil and water. Added to Hollandaise sauce, mustard can inhibit curdling.”
“Hot table mustard may easily be prepared by the home cook by mixing "powdered mustard" (ground mustard seed, turmeric and wheat flour) to the desired consistency with water or an acidic liquid such as wine, vinegar, or beer, and leaving to stand for ten minutes. It is usually prepared immediately before a meal; mustard prepared with water, in particular, is more pungent but deteriorates rapidly.”
“The amounts of various nutrients in mustard seed are to be found in the USDA National Nutrient Database. As a condiment, mustard averages approximately 5 calories per teaspoon. Some of the many vitamins and nutrients found in mustard seeds are selenium and omega 3 fatty acid.”
“The many varieties of prepared mustards have a wide range of strengths and flavors, depending on the variety of mustard seed and the preparation method. The basic taste and "heat" of the mustard are determined largely by seed type, preparation and ingredients. Preparations from the white mustard plant (Sinapis alba) have a less pungent flavor than preparations of black mustard (Brassica nigra) or brown Indian mustard (Brassica juncea). The temperature of the water and concentration of acids such as vinegar also determine the strength of a prepared mustard; hotter liquids and stronger acids denature the enzymes that make the strength-producing compounds. Thus, "hot" mustard is made with cold water, whereas using hot water produces a milder condiment, all else being equal.
Mustard oil can be extracted from the chaff and meal of the seed.”
“The mustard plant ingredient itself has a sharp, hot, pungent flavor.
Mixing ground mustard seeds with water causes a chemical reaction between two compounds in the seed: the enzyme myrosinase and various glucosinolates such as sinigrin, myrosin, and sinalbin. The myrosinase enzyme turns the glucosinolates into various isothiocyanate compounds known generally as mustard oil. The concentrations of different glucosinolates in mustard plant varieties, and the different isothiocyanates that are produced, make different flavors and intensities.”
Mustard seeds and mustard powder:
“Mustard seeds contain about 20 to 36 % nutty, mild mustard oil, 28 % protein, and the glycosides sinalbin (white mustard) and sinigrin (brown and black mustard), which are responsible for the spicy taste and also help to stimulate the appetite and digestion.*”
“Crushed, an enzyme is activated that releases pungent sulphurous compounds; but they quickly evaporate. An acidic liquid, such as wine or vinegar, produces a longer-lasting paste. However, even then prepared mustard loses its pungency over time; the loss can be slowed by keeping a sealed container (opaque or in the dark) in a cool place or refrigerator.”
Note (italics): * = Translation from a German Wikipedia entry