The oldest barbecue sauces are largely butter. This is part of a tradition of "saucing" meats that goes back centuries in European cooking history. As time went by, in the development of the barbecue of the Carolinas, vinegar became a more and more important ingredient until it was the principle base of this style of barbecue. Then the Germans began migrating to the region at the end of the 18th century, particularly the central portion of South Carolina and parts of Northern Georgia.
With them came mustard. Germans love the combination of mustard and pork and in the Carolinas, barbecue means pulled pork. Slowly, mustard began to become an ingredient in the sauces served with and on barbecue produced in this region, growing in popularity and complexity.
Mustard barbecue sauces are the newest style and today they are almost always made from prepared mustard out of a bottle. Just as bottle ketchup has become the base for tomato-based sauces, so has the standard grocery store mustard for this style of sauce. Typical prepared yellow mustard contains Vinegar, Mustard Seed, Salt, Turmeric, Paprika, and Garlic Powder, as well as other spices. Considering that Carolina sauces started with vinegar and frequently added herbs and spices, all that a mustard sauce really picks up is the mustard seed. Of course, this isn't to say that a mustard sauce cannot be started with any type of mustard, just that the standard yellow stuff is what most people start with.
Try a good brown mustard or a Dijon, or any other kind of mustard you happen to like best.
From the mustard, it is time to add the sweet. There are brown mustard sauces that add molasses, but in general, the sweetness added to these types of sauces is sugar, particularly brown sugar. This adds the sweetness and a hint of the molasses without dramatically changing the golden color, which is actually a prized element of mustard barbecue sauces.
Add a little to offset the tanginess of the vinegar or a lot to make it a sweeter sauce. Tradition dictates that mustard sauces should be tangy, but there are no real rules here. I have a Sweet Mustard Sauce that not only includes a good dose of sugar but apricot preserves as well.
While prepared mustard starts with vinegar, a good mustard sauce adds more. This brings up the tanginess and adds the depth of flavor that goes so perfectly with pork in particular. While most of these sauces add apple cider vinegar because of the superior flavor, any vinegar will do. I have a recipe for a Mustard Sauce with Balsamic Vinegar which is excellent so the kinds of vinegar used are not set in stone either. The trick with the vinegar is to balance it with the sweet depending on your preference.
Now the question of heat arises. Mustard sauces can be sweet and savory, tangy, or they can be any of these as well as spicy hot. To accomplish the addition of heat we want to add pepper. This can be simple black pepper or hot chili peppers, typically in the form of cayenne powder or chili powder, though hot sauces work well.
What I find works best is a balance of the three peppers, meaning white, black, and red. These different types of heat hit different parts of the tongue giving a well-rounded heat. Add to this the natural pungent heat of mustard and you have a sauce that has a complete spiciness that is perfect for some great barbecue. My Golden Carolina BBQ Sauce includes all these types of pepper for a perfect balance of flavor.
Lastly, a great mustard sauce can include most any herbs and spices. In fact, most anything can be added to boost the flavor. Mustard sauces should, first and foremost, be savory, with deep, rich flavors. Certainly, this means garlic and onion, but also consider herbs like oregano, thyme, or marjoram and spices like cumin, celery seed, and yes, nutmeg. Nutmeg, in particular, makes flavors pop out and adds depth to anything it is added too. Use these spices in moderation so that they don't overpower, but enhance. From here you will want to try any or all of my favorite Mustard Barbecue Sauce Recipes.