The terms dry mustard, ground mustard, mustard flour, ground mustard seed and dry mustard powder all refer to the same thing. They refer to the ground seeds of any one of several species of mustard plant.
Mustard powder has a hot flavor of varying strengths and is a versatile spice used in many meat, fish, chicken and vegetable dishes. The various types of mustard come from the different kinds of mustard plant.
- White or yellow mustard seeds are relatively large and the mildest in flavor. These are used in typical ballpark, yellow mustards.
- Brown or Asian mustard seeds are smaller and sharper in flavor; they are used in pickling and in producing European and Chinese mustards.
- Black mustard seeds are small and the most pungent of the three; they are not often seen since they are hard to grow and have been largely replaced in the market with the brown variety.
Mustard seeds may also be blended together. English mustards, for example, typically use a combination of white and brown mustard seeds. The leaves of the mustard plant are called mustard greens and are used in some recipes.
Mustard seeds may be stored for up to a year in a cool, dry place. Ground mustard or powdered mustard can be stored for up to six months.