What exxactly does the mustard/goop do?

Seth

I have cooked many Butts with just rub on them and they have for the most part turned out great. I have never done the mustard/goop thing. Why do it? I am not opposed, just don't understand the need?
Thanks,
Seth

mike

Seth ,
The mustard helps adhere the rub to the butt, it also helps the butt form a slight crust on the outside with the rub, and it does not add any flavor. I've also noticed that the rub sort of dissolves into the mustard making the whole thing a bit more flavorful. In general I use the mustard on butts and ribs because it seems to make the process easier and the results just a bit better. But it is by no means a critical step and you will find holy wars on both sides of this question.

BluesnBBQ

Mustard also gives you an idea of how much rub to use. My rule of thumb is, when you can't see any more yellow, you've added enough rub.

SouthJerseyGrEGG

Seth ,[p]I made ribs with the same rub, once with and once without
yellow mustard. Both were such crowd pleasers that I did
not pay attention to which was better. [p]Since mustard is moist, I would venture to guess that it helps to keep the meat more moist as well.[p]

Banker John

Seth ,
As others have mentioned, this topic can start another civil war. I guess it is a personal preference.[p]For me, I have noticed that the mustard is moist and provides something for the rub to adhere to. Before mustard for me, I went through an awful lot of spices in rubs. Now, however, I mix up a rub and use a shaker to apply directly to the mustard.[p]Overall, for me as a preference, it saves quite a bit of rub and has less mess & clean up after preparation.[p]As for a difference in flavors, I'll leave this answer to someone else.