The flavor of ground mustard develops when soaked in liquid to bring out the pungent compounds. It is commonly used in spice rubs, salad dressings, soups, and to add an acidic component to cut through rich sauces like for macaroni and cheese.
Dry mustard works in a variety of spice rubs. Because its essentially yellow mustard, you can use it to flavor meat and seafood items that take to the condiment well. Salmon, for example, can be crusted using dry mustard powder, salt, brown sugar and dill. Beef spice rubs, such as those containing paprika, rosemary, thyme, salt and pepper and dry mustard are also ideas. Dry mustard can also be used on chicken and pork.
Mustard seeds are an excellent source of selenium and a very good source of omega-3 fatty acids and manganese. They are also a good source of phosphorus, magnesium, copper and vitamin B1.
1 1/4 teaspoon of dry mustard = 1 teaspoon mustard seed