Whole grain mustard is a variation of the more traditional mustard condiment in which the mustard seeds are not powdered, but are left whole or only partially broken so grains of the seeds are still present in the mustard. In general, whole grain mustard has a slightly less harsh taste than smooth mustard, although this can easily be changed through the use of different combinations of mustard seeds. When eaten, the individual whole grains pop when chewed, releasing small amounts of intense, spicy mustard flavor. It is relatively easy to make whole grain mustard in a home kitchen, although great care must be taken to control the amount of spice and heat that develops as the mustard ages. In both commercial and homemade varieties, a number of additional ingredients can be added to change the character of the mustard, including apple cider, beer or wine, nuts, dried fruit, or even other spicy foods such as horseradish.
As with nearly all mustards, there are three types of mustard seeds that can be used to make the whole grain variety. Brown mustard seeds are used to provide a low spiciness that is released in the mouth over time. Yellow mustard seeds are much more intense than brown seeds and provide immediate heat that dissipates quickly. Black mustard seeds have a more subtle taste than the other two types, although they release a good amount of heat the longer they are allowed to age in the mixture. Most whole grain mustard is made from blending different seeds to achieve a distinctive taste.
In the most basic preparations, whole grain mustard can be made by soaking mustard seeds in vinegar and water, along with any other flavoring ingredients. Most often, a sweet element such as honey, cider or sugar is added, along with some salt to enhance the flavor. The mixture is either partially ground with a mortar and pestle or in a food processor until some — but not all — of the seeds have been cracked. The mustard is then placed in a non-reactive container and allowed to age at room temperature until the desired level of heat has been achieved. The longer the mustard ages at room temperature, the hotter it will become; refrigeration will stop the heat from developing any further.
In cooking, whole grain mustard can be used for aesthetic purposes to give sauces a more rustic appearance. It can be used as a rub on meats, and the mustard seeds will roast when fried or grilled. The whole grains also can provide a unique mouth feel when used in salad dressings or sauces.